FIELD
The present invention relates to an apparatus, method, and prograln for monitorkg an
operation of high kequency resistance welding and induction heating welding of an electric
resistance welded steel pipe (below, refelred to as "electric resistance welding") &ere a metal
plate is continuously formed into a tubular shape by a group of rolls while being conveyed and
two end parts in its circumferential direction made to converge to a V-shape are heated to melt
15 and made to abut against each other.
BACKGROUND
[@O@Z]
Electric resistance welded steel pipes are being used in a broad range of fields such as
20 line pipes for oil or natwal gas, oil well pipes, nuclear power use, geothermal use, chemical plant
use, mechanical structure use, and general piping use. In a manufacturing facility for an electric
resistance weMed steel pipe, a strip of steel plate is cont'muously formed into a tubular shape by
a group ofrolls while being conveyed and two end parts in the circumferential dkection made to
converge to a V-shape are heated to melt and made to abut against each other.
25 [0003]
When a strip of steel plate is continuously formed into a tubular shape by a group of rolls
while being conveyed in this way, sometimes a step difference is formed between one end part of
the steel plate and the other end part, that is, an abnormality called ""misalignment" occurs. This
misalignment leads to insufficient strength and other defective aspects of quality ofthe electric
30 resistance welded steel pipe, so monitorhg of electric resistance welding to detect misalignment
has been sought.
[O0041
As this type of art, PTL 1 dlscboses a method sf monitoring the state of weldhg when
bending a strip of metal plate and continuous butt welding the facing end faces to pa-oduce
35 welded metal pipe comprising simultaneously detecting from the inlet side direction ofthe Vshape
the edge parts in the plate thickness direction at the welded pal? at both facing eaad faces
and the temperature profile of the center part in the plate thickness direction and estimating the
state of input heat to the butt welded part based on the detected temperature profile. Further,
according to this method, it is considered possible to also detect a state where the left and right
abutting faces are offset to the top and bottom, that is, misalignment.
5 [OOOS]
PTL 2 discloses a method of monitoring electric resistance welding comprisillg
monitoring a weld zone in electric resistance welding continuously forming steel plate into a
tubular shape while heating, then pressing together and welding the two end parts of the steel
plate made to abut against each other. The method of monitoring electric resistance welding
10 comprises detecting starting positions of discharge of molten steel, judging if the startkg
positions of disctharge of molten steel detected at the two end parts are symmdric with respect to
the abuMing line of the two end parts, and, when it is judged that the starling positions of
discharge of lnolten steel detected at the two end pa1-l-s are not symmetric, outputting information
indicating this effect. Further, using this method, it is considered possible to detect asymmetry in
15 the heated states of the two end parts of the steel plate made to abut against each other during
welding.
[0006]
PTL 3 discbses a method of monitorig an electric resistance weldkg operdiola
continuously for~ninga strip of steel plate into a tubular shape by a group of rolls while
20 conveying it, and hating and meltiq the two ends of the steel plate in the clrcum.ferential
direction made to converge to a V-shape so as to make them abut agahst each other. The method
of monitoring the electric resistance wldhg operation coqrises seMing a temperature
measurement region including the weld zone where the melted portion at the inside of the plate
thicki~esso f the steel plate starts to be discharged to the surface due to upset of the squeeze rolls,
25 calculating the level of luminance of the temperature measurement region, coi~verthgth e level
of luminance to the temperature of the temperature measurement region based on preset
temperature conversion data, and judging if the temperature of the temperature measurement
region is a predeter~nined lower limit value or more. Further, using this neth hod, it is considered
possible to prove melting to avoid welding conditions where there is a possibility of melting
30 failure and suppress the occurrence of defects due to melting failure.
[CITATIONS LIST]
[PATENT LITEMTUW]
[0007]
3 5 [PTL W lg Japanese Unexarnined Patent Publication No. 62-203680
[PTL 21 Japanese Unexarnined Patent Publication No. 201 5-217420
[PTL 31 Japanese Patent No. 5549963
SUMMARY
[TECHNICAL PROBLEM]
[OOOSl
In PTE I, the regions VIihich melt and emit light at the t w end faces which are but&
welded together change into liquid to thereby become low in roughness or be cleared of
irregularities thus leading to becoming mirror surfaces. Further, sometimes the end faces are
treated to remove oxides at the upstream side of the abuuing parts. In this case, the majorities of
the two end faces become mlrror surfaces. If in this way the two end faces to be butt welded
together beco~nem irror surfaces, the light emission profiles of the two end faces become
unifor~na nd further in principle it is not possible to separate the original emitted light and the
reflected emiued light. For this reason, if measuring the temperature profiles of the two end faces
as optical images like in PTL I, the mirror images resulting from multiple reflection are
measured as superposed images and it is not possible to precisely detect the temperature profiles
at the welded parts af both the facing end faces. In paaicular, sometimes it is not possible to
detmt mkalivrmed with small dep diPEerences.
[00091
In the method described in PTL 2, just the difierence in sta&kg points of discharge of
rnolLen steel is detected, so there is Be problem that if molten metal happens to be discharged to
the upper side of the misalignment, it will directly lead to mistalten detection. Furthermore,
sometimes the WS ( w r k side)/DS (drive side) balance of the V-convergence angle formed by
the two edges of the steel material collapses during shaping, that is, so-called ""rolling" occurs,
but in this case, the reference axis between the horizontal axis of the captured image and the
shaping becomes off and again there was the problem that the possibility of mistaken detection
became higher.
[OOlO]
In the method described in PTL 3, the temperature of the weld zone where the melted
portion of the inside of the steel plate in the plate thickness starts to be discharged to the surface
due to upset of the squeeze rolls is measured, so it is possible to prove melting to avoid welding
conditbns whicl~m ight lead to melting failure, but it is not possible to precisely detect
misalignment.
[SOll]
The present invention was made in consideration of the above such point and has as its
object to enable precise detection of ~nisalignmentin electric resistance welding.
[SOLUTION TO PROBLEM]
[OOlZ]
The gist of the present invention is as follows:
( 1 ) An apparatus for monitoring an operation of high frequency resistance welding
5 and induction heating welding of an electric resistance welded steel pipe where a drip of metal
plate is continuously formed into a tubular shape by a group of rolls vvhile being conveyed from
an upstream side to a downstrean1 side and two end parts of said metal plate in its circumferential
direction made to converge to a V-shape are heated to melt and made to abut against each other,
characterized in that
10 said apparatus detects misalign~nentb y obtaining a grasp of unevenness of Iight
emi@ing regions of metal parts at two sides in the circumferential direction at abusing positions
at an outside surface or inside surface of said metal plate based on an image, captured by an
imaging device from the outside surface side or inside surface side of said metal plate being
formed into the tubular shape, of a region including a V-convergence portion where said two end
15 parts in the ckcumferential direction collverge to a V-shape and said metal parts Rowing out to
the surfacre ofsaid metal plate by electromagnetic force at a downstream side &om said Vcsasvergence
ipodbn.
(2) The qpamtus for m-onitor'lng an operdion of high &equency resistance weldhg
and induction heatir~gw elding of an electric resistance welded steel plpe according lo (I),
20 chamcterlzed in that the apparatus co~nprises
an hput nleans to which an image having a conveyance direction of said metal
plate as an X-direction and a ckcumferential direction of said metal plate as a Y-dkection is
input from said imaging device,
an lmage processing means for performing image processing on the image input
25 to said input means,
a V-convergence point detectkg means for detecting a geometric V-convergence
point h e r e said two end parts in the circumferential direction converging to the V-shape
geometrically intersect by linearly approximating said two end parts in the circumferential
dkection and fmding the intersecting point of the approximation lines of said two end parts in the
30 ckcumferential direction in the image processed by said image processing means,
an area calculating means for findillg a line passing through the geometric Vconvergence
point detected by said V-convergence point detecting means and parallel to the Xdirectior~
o f the image in the image processed by said i~nagep rocessing means, using said line as
the abutting position, and calculating an area SI of the light emitting region of said metal part at
35 the downstream side from said geoanetric V-convergence pointat one side divided by said line
and an area $2 of the light emitting region of said metal part at the downstream side &om said
geometric V-convergence point at the other side divided by said line, and
a judging means for comparing the areas S 1, S2 ofthe light emitting regions at the
two sides of the abutting position calculated by said area calculating means to judge the
occurrence of inisalignment.
(3) The apparatus for monitoring an operation of high fieque~~creys istance welding
and induction heating welding of an electric resistance welded steel pipe according to (I),
characterized in that the apparatus comprises
an input means to which an image having a conveyalice direction of said metal
plate as an X-dkection and a circumferential direction of said metal plate as a U-direction is
input fiom said imaging device,
an image processing means for perforlning image processing on the image input
to said input means,
a V-convergence point detecting means for detecting a geometric V-convergence
point where said two end parts in the circumferential direction converging to a V-shape
geometrically itersect by linearly approximathg said tvvo end parts in the circumferential
direction and fmding the intersecting point of the approximdion lines of said two end parts in the
clrcum"Eerential dlrmtion in the image processed by said im;age processing means,
an area calculati~~mg ans for e~endingth e approximation Lines linearly
approximating the two end parts in the circumferential direction to the downstream side over
said geonnetric V-convergence point and calculating an area S 1" ofthe light emitting region of
said metal part at the outside from one of said e~endedap proximation lines and an area ~ 2o"f
the light em&ig regloll of said metal part at the outside from the other of the e&ended
approximation lines, and
a judging means for comparing the areas ~ 1 'S'2~" o f the light emitting regions
calculated by said area calculatillg means Lo judge the occurrence of misalignment.
(4) The apparatus for monitoring an operation of high fiequency resistance welding
and hduction heating welding of an electric resistance welded steel pipe according to (2),
characterized in that said Judgiilg means finds a ratio of either of said area S 1 of the light
emieing region at the one side and said area S2 of the light emitting region at the other side with
respect to the sum of said area S1 of the light emiMing region at the one side and said area S2 of
the light emitting region at the other side and Judges whether said ratio is within predetermined
upper and lower limit values.
(5) The apparatus for monitoring an operation of high fiequency resistance welding
and induction heating welding of an electric resistance welded steel pipe according to (3),
characterized in that said judging means finds a ratio sf ea"cher of said area S I '' of the light
emitting region at the one side and said area ~ 2 ' o' f the light emitting region at the other side
with respect to the sum of said area s1" of the light emitting region at the one side and said area
s2" of the light emitting region at the other side and judges whether said ratio is within
predetermined upper and lower limit values.
(6) The apparatus for monitoriilg an operation of high frequency resistance welding
5 and induction heating welding of an electric resistance welded steel pipe according to any one of
(2) to (S), characterized in that said Judging means judges whether said geometric V-convergence
point is at ail upstream side from a predetermined X-direction position in the image processed by
said image processing means.
(7) The apparatus for monitoring an operation of high frequency resistance welding
10 and inductioil heating welding of an electric resislance welded steel pipe according to (2),
characterized in that said area calculating means fillds a bisector of an angle of intersection of the
approximation lines of said two end parts in the circumferential direction converging to the Vshape
or a median line passing through said geometric V-convergence point in a triangular shape
formed by the approximation lines of said end pai-ts in the circumferential direction converging
15 to the V-shape and the end part at the upstream side in the X-direction of said image in the image
processed at said image processing means and corrats said area S 1 of the light emigig region
at the one side and said area S2 of the EglaL em&hg region at the other side calculald by said
ma calculatimg rnealls-
(8) A neth hod for monitoring an operdion of high kequency resistance welding and
20 induction heating welding of an electric resistance welded steel pipe conthuously forming a strip
of metal plat,e into a tubular shape by a group of rolls while conveying the strip of metal plate
gem an upstream side to a downstream side and heating two end parts of said metal plate in its
ckcumferential direction made to converge to a V-shape to melt and making the two end parts of
said metal plate abut against each other, characterized in that:
25 said n~ethodc omprises capturing an image, by an imaging device fiom an outside
surface side or inside surface side of said metal plate being formed into the tubular shape, of a
region including a V-convergence portion where said two end parts in the circumferential
directio~cl onverge to a V-shape and metal parts Rowing out to the surface of said metal pIate by
electromagnetic force at a downstream side from said V-convergence portion, and detectkg
30 misalignment by obtaining a grasp of unevenness of light emitthg regions of said metal part at
two sides in the ckcumferential direction at abusing positions at the outside surface or inside
surface of said rnetal plate based on said image-
(9) The method ifor monitorhg an operation of high &equemcy resistance welding and
induction heating welding of an electric resistance welded steel pipe according to (81,
35 characterized by:
capturing an image having a conveyance direction of said metal plate as an Xdirection
and a circumferential direction of said inetal plate as a Y-direction by said imaging
device,
performing image processing on said captured image,
detecting a geometric V-convergence point where said two end parts in the
5 circumferential direction collverging to the V-shape geo~netricallyi ~tersecbt y tinearly
approximating said two end parts in the circu~nferentiald irection and findi~igth e intersecting
point of the approximation lines of said two end parts in the circumferential direction in the
processed image,
finding a line passing through the detected geometric V-convergence point and
10 parallel to the X-dkectiol~o f the i~nagein the processed itnage, using said line as the abulting
position, and calculating an area S 1 of the light emitting region of said inetal park at the
domstream side fiom said geometric V-convergence point at one side divided by said line and
an area S2 of the light emifiing region of said metal part at the downstream side fi-om said
geometric V-convergence point at the other side divided by said line, and
15 comparing the areas Sl, S2 of the light emifiing regions at the two sides of the
abuttkg position to judge the occurrence of misalignment.
(10) The neth hod for mnitorirng m opemtion of high fieglrency resishme welding and
Illduction heatl-mg weldhg of m electric ~sistancew lded steel pipe accordi~~tog 3 86,
characterized by:
20 capturing an image having a eonveyallce dkection of said metal plate as an Xdirection
and a ckcumferential direction of said metal plate as a U-dkection by said imaging
device,
perfor~ning image processing on said captured image,
detecting a geometric V-convergence point where said two end parts in the
25 ckcumferential direction converging to the V-shape geometrically intersect by linearly
approxiinating said two end parts in the ckcurnferential direction and finding the intersecthg
point of the approximation lines of said two end pads in the circumferential direction in the
processed image,
e&ending the approximation lines linearly approxilnating said two end parts in
30 the circumferential direction to the downstream side of said conveyance dkection over said
geomtl-ic V-convergence poillk and calculating an area S 1 " ofithe light emitting region of said
metal part at tile outside &om om of said extended approximation lines and an area s;?" of the
light erniukg region of said metal part at the outside fiorn the other of the extended
apprsxia-anation lines, and
35 comparing said areas s~"~, 2o"f t he light emitting regions calculated to judge the
occurrence of misalignment.
(1 1) The method for monitoring an operation of high 16-equency resistance welding and
illduction heating welding of an electric resistance welded steel pipe according to (9),
characterized by, in said judgment, finding a ratio of either of said area S1 of the light emitting
region at the one side and said area S2 of the light emitting region at the other side with respect
to the sum of said area S1 of the light einitting region at the one side and said area S2 of the light
emilting region at the other side, and judging whether said ratio is within predetermined upper
and lower limit values.
(12) The method for monitoring an operation of high frequency resistance welding and
induction heating wlding of an electric resistance welded steel pipe according to (lo),
characterked by, in said judgment, finding a ratio of either of said area SI" of the light elnilting
region at the one side and said area ~ 2o"f t he light emilting region at the other side with respect
to the sum of said area Sl'hfthe light einilting region at the one side and said area ~ 2 o"f the
light emitting region at the other side, and judging whether said ratio is within predeterinined
upper and lower limit values.
(13) The lnethod for monitoring an operation of high frequency resistance welding and
induction heating welding of an electric resistance welded steel pipe according to any one of (9)
to (12), ehmctenzed by, in said judgment, jdglng whether said geometric V-convergence point
is at an upstrea~ns ide from a predetemlrned X-direction position 111 said processed image-
(14) The mthod for monitoring an operation of high frequency resistance welding and
illduction heating welding of an electric resistance welded steel pipe according to (9),
characterized by, in said calculation of the areas S 1, S2, finding a bisector of an angle of
intersection of the approximation llnes of said two end parts in the circumferential direction
converging to the V-shape or a median line passing through said geometric V-convergence point
in a triangular shape formed by the approxhation lines of said end parts in the circumferential
dkection converging to the V-shape and the end part at the upstream side in the X-dkection of
said image in said processed image and correcting said area Sl of the light emitting region at the
one side and said area S2 of light emittkg region at the other side.
(15) A program for ~nonitonnga n operation of high frequency resistance welding and
induction heating welding of an electric resistance welded steel pipe continuously forming a strip
of metal plate into a tubular shape by a group of rolls while conveying the strip of metal plate
from an upstream side to a downstream side and heating two end parts of said metal plate in its
ckcumferential dkection made to converge to a V-shape to melt and ll~akingtw o end parts of
said metal plate abut against each other, cl~aractenzedi n that:
said prograln rnaltes a computer run processing for detecting misalignment by
obtaining a grasp of unevenness of light emitting regions of metal pants at two sides in the
circumferential direction at abutting positions at an outside surface or inside surface of said metal
plate based on an image, captured by an imaging device fi-orn the outside surface side or inside
surface side of said metal plate being formed into the tubular shape, of a region including a Vconvergence
portion where said two end parts in the circumferential direction converge to a Vshape
and said metal parts flowing out to the surface of said inetal plate by electromagnetic ibrce
5 at a dowi~streams ide from said V-convergence portion.
(16) The program for monitoring an operation of high frequency resistance welding
and induction heating welding of an electric resistance welded steel pipe according to (151,
characterized in that said prograin makes said computer hnction as
an input means to which an image having a conveyance direction of said metal
10 plate as an X-direction and a circumferential direction of said metal plate as a U-direction is
input fiom said imaging device,
an image processing means for performing image processing on the in~agein put
to said input means,
a V-convergence point detecting means for detecting a geometric V-convergence
15 point where said two end parts in the circumferential direction converging to the V-shape
geometri~allyl lltersect by linearly approximating said two end parts in the circumferential
cltection and f-mdiw the intersecting point of the approximation lines of said two elld parts Irr the
ckcumferential dkection in the imwe pmcessed by said image processig means,
an area calculating means for fillding a line passing through the geornetri~V -
20 convergence point detected by sald V-convergence point detecting means and parallel to the Xdirection
of the image in the image processed by said image processing means, using said line as
the abuMlng position, and calculating an area S 1 of the light emiMing region of sald metal part at
the downstream side om said geometric V-convergence point at one side divided by said line
and an area S2 of the light emitting region of said metal part at the downstream side fiom said
25 geomtric V-convergence polllt at the other side divided by said line, and
a judging means for comparing the areas S1, S2 of the light emitting regions at the
two sides of the abuMing position calculated by said area calculating means to judge the
occurrence of misalignment.
(17) The program for monitoring an operation of high frequency resistance welding
30 and induction heating welding of an electric resistance welded steel pipe according to (151,
characterized in that said program makes said computer hnction as
an input means to which an irnage having a conveyallce direction of said metal
plate as an X-direction and a circumferential direction sf said metal plate as a U-dkectisn is
illput fiom said imaging device,
3 5 an image processing means fir performisag image processing on the image input
$0 said input means,
a V-convergence point detecting means for detecting a geometric V-convergence
point where said two end parts in the circumferential direction converging to a V-shape
geometrically intersect by linearly approximating said two end parts in the circumferential
direction and frnding the intersecting point ofthe approximation lines of said two end parts in the
5 circumferential direction in the image processed by said iinage processing means,
an area calculating ineans for extending the approxlmation lines linearly
approximating the two end parts in the circuinferential direction to the domsh-eam side over
said geometric V-convergence point and calculatkg an area s 1'' of the light emitting region of
said metal pad at the outside &om one of said exlended approximation lines and an area ~ 2o"f
10 the light em&ing region of said metal part at the outside from the other of the extended
approximation lines, and
a judging means for comparing the areas ~1"",2'\f the light emitting regions
calculated by said area calculating meails to judge the occurrence of misalignment.
(18) The program for ~nonitoring an operation of high fi-equency resistance welding
15 and hduction heating welding of an electric resistance welded steel pipe acmrding to (161,
characterlzed in that said judging means finds a ratio of either of said area S I of the light
em&ing regbn at the one side and said wea S2 sf the light eemieing region at the other side with
respect to the sum of said wea S 1 of the light emiging region at the one side and said area S2 of
the light eemitthg regloll at the other side and Judges whether said ratio is with'm predetermhed
20 upper and lower limit values.
(19) The program for monitoring an operation of high frequency resistance welding
and induction heating welding of an electric resistance mlded steel pipe according to (1 7),
characterlzed in that said judging means finds a ratio of either of said area Slqf of the light
emitting region at the one side and said area ~ 2 o"f t he light emitting region at the other side
25 with respect to the sum of said area SI" of the light ein&ing region at the one side and said area
S2" of the light emifiing region at the other side and judges whether said ratio is within
predetemined upper and lower Limit values.
(20) The program for monitoring an operation of high frequency resistance welding
and induction heating welding of an electric resistance welded steel pipe according to any of (16)
30 to (19), characterized in that said judging means judges whether said geometric V-convergence
point is at an upstream side from a predetermined X-direction position in the image processed by
said image processing means.
(21) The program for monitoring an operation of high frequency resistance welding
and induction heating welding sf an electric resistance welded steel pipe according to (161,
35 characterized in that said area citBcealating means finds a bisector ofan angle of intersection of the
approximation lines sf said two end parts in the ckcun-nferential direction converging to the Vshape
or a median line passing through said geometric V-convergence point in a triangular shape
formed by the approximation lines of said end parts in the circumferential direction converging
to the V-shape and the end part at the upstream side in the X-direction of said image in the image
processed at said image processing means and corrects said area S1 of the light emiMi11g region
5 at the one side and said area S2 of the light emitting region at the other side calculated by said
area calculating means. .
[ADVANTAGEOUS EFFECTS OF INVENTION]
[0013j
10 According to the present in veil ti or^, inisalignment is detected by obtaining a grasp of the
unevenness of the light emitting regions at the tm sides of an abuMing position at the outside
surface or inside surface of the metal plate for~nedin to a tubular shape, so it is possible to
precisely detect misaligninent in electric resistance welding without being afFected by the end
faces becomlng mirror surfaces.
15
BNEF DESCRIPTION OF DMWNGS
[@@I41
FIG- 1 is a view showkg the configuration of a manufacturing facilty ofan electric
resistance welded steel pipe and an apparatus for tnonitoring an operation of electric resistance
20 welding accordkg to a fist embdiment.
FIG. 2 is a flow chai% showing a method for monitoring an operation by an apparatus for
mn&oringa n operation of electric residance welding aceordi~lgto the first ernbodinnent.
FIG- 3 is a flow chart showing processing for detection of a V-convergence point of the
flow chari of FIG. 2.
2 5 FIG. 4 is a view showing a state of occurrence of misalignment.
FIG. 5 is a schematic view showing an image captured by an imaging device.
FIG. 6 is a view for explaining a V-convergence point.
FIG. 7 is a schematic view showing images on which i~nagep rocessing has been
performed and for which the V-convergence point has been detected.
3 0 FIG. 8 is a schematic view showing an exarnple of a binary image in which a blob at a Vconvergence
portion is not extracted.
FIG. 9 is a schematic view showing images for which the area has been calculated in the
first embodiment.
FIG. I0 are gaphs finding the area in actual operation and plotting it along with the
35 elapse of time.
FIG. I I is a flow chart slacswing a method for monitoring operation of an apparatus for
monitoring operation of electric resistance welding according to a second embodimeilt.
FIG. 12 gives views for explaining the reason why the V-convergence point V1 shifts to
the upstream side in the case where misalignment occurs compared to when misalignment does
not occur.
5 FIG. 13 gives schematic views showing images for which the area is calculated in the
second embodiment.
FIG. 14 is a view showing the configuration of a manufacturing facility of an electric
resistance welded steel pipe and an apparatus for l-nonitoring operation of electric resistance
welding accordii~gto a thud embodiment.
10 FIG. 15 gives schematic views showil~gim ages -forw l~ichth e area is calculated in the
thbd embodiment.
FIG. 16 is a graph finding the area ratio in actual operation and pbtting it along with the
elapse of time.
FIG. 14 is a Row chart showing a method for monitoring operation of an apparatus for
15 monitoring operation of electric resistance welding according to a fourth embodiment.
FIG. 18 gives schematic views showing images for which the area is calculated in the
fou&h embodhe~~t.
FIG. 19 is a cross-%ctio~~sacl l~ematicv iew showing the direlions of the high &quency
current, the outflow of the melted portions due to electromagnetic force, and the dlschasge of the
20 melted podions due to upset,
DESCRIPTION OF EMBODIMENTS
[0015]
Below, referring to the aaached drawings, prefewed e~nbodilnentso f the present
25 hventbn will be explained.
First Embodllnent
Referring to FIG. I, a manufacturhg facility of an electric resistance welded steel pipe
will be explained in brief. As shown in FIG. I, a strip of steel plate I is continuously formed into
a tubular shape by a group of rolls (not shown) while being conveyed from an upstream side to a
30 downstream side toward a direction 3. Further, an lmpeder 6 is arranged inside of the steel plate
I being fomed into the tubular shape alld a pair of contact tips 7 (high kequency resistance
welding) or induction coils (not shown) (induction heating welding) are used to supply high
fiequeney current 5 while applykg upset by the squeeze rolls 2. Due to tlais, two end parts 4, 4 of
the steel plate 1 in the circumfereratia8 direction (below, also simply referred to as the ""end
35 parts") can be heated to melt to make them abut and melt bond the steel plate % while being made
to converge to a V-shape (electric resistance welding QERW).
[0016]
Above the steel plate 1, an imaging device 8 is arranged. This captures the pattern of
natural light (radiant pattern) of the region including the V-convergence portion where the
outside surface of the steel plate I being formed into a tubular shape converges to a V-shape. The
V-convergei~ce pontion includes a geometric V-convergellce point VI explained below a portion
where the two end parts 4,4 of the steel plate I converge toward the geol~etricV -convergence
point V1, and an abutme~lpt oint V2 where the two end parts 4,4 physically abut (contact). The
"portion where the two end parts 4, 4 of the steel plate 1 converge toward a geometric Vconvergence
point V19' preferably includes a region of 5 mm to 30 mrn fi-om the V-convergence
point VI tolvard the upstream side. The imaging device 8, for example, uses a 1600x 1200 pixel
3CCD type color camera to capture images by an imagillg field of a width of 30 rnm or more and
a len@h of 50 to 100 mm, an imaging resolution of 50 to 100 pdpixel, an imaging rate of 30 @s
or more, and an exposure time of 115000 sec or less. The image data captured by the imaging
device 8 is input to an apparatus 100 for monitoring an operation of electric resistance welding.
[0017j
When a strip of steel plate 1 is continuousiy formed into a tubular shape by a group of
rolls whik being conveyed, sorraetirnes a step diifSerenm occurs &tween one end part and the
other end part of the steel plate, that is, ""misalignment9' occurs, as explained abve. If
rnisalignrnela occurs, as sbvvn in FIG. 4, high frequency current 5 concentrates at the fxlng
locatio~~ofs the abuging end faces of the two end parts 4, 4 of the steel plate 1 (actual
thicknesses "W9 of abutting end faces). As a result, at the end part 4 offset upward (end part at
left slde in FIG. 4)' the tel-nperature rises at the inside surfae side ofthe steel plate 1 and the
degree of melting becomes higher. As opposed to this, at the end part 4 offset downward (end
part at right side in FIG. 41, the temperature rises at the outside surface side of the steel plate I
and the degree of melting becomes higher. Therefore, when misalignment occurs, unevenness
occurs in the light emieing regions due to the melting or red heat at the two sides of the abutting
position at the outside surface side and inside surface side of the steel plate I. The misalignment
is prefel-ably within 10% of the plate thickness. For example, when the plate thickness is 10 mm,
the misalignment is preferably made within 1 .O min. Therefore, as explained in detail below, the
imaging device 8 is used to capture the image of the region lncludiilg "re V-convergence portion
and the metal parts Rowillg out to the surface of the metal plate due to the electromagnetic force
at the downstream side from the V-converge~~cpeo rtion from the outside surface slde of the steel
plate I formed into a tubular shape, The inventors discovered that by oobbajnhg a grasp of the
unevenness of the light emitting regions ofthe metal parts at the two sides of the abutting
position at the outside surface of the steel plate I based on that iiansage, misalignment is detected.
It is also possible to place the ianaging device 8 at the inside surface side ofthe steel plate 1
formed into a tubular shape and, in the same way as the case of placing the imaging device 8 at
the outside surface side of the steel plate 1, capture an image from the inside surface side of the
steel plate 1 to detect misalignment. The "metal parts flowing out to the surface ofthe metal
plate due to the electromagnetic force at the downstl-eam side fkom the V-convergence portion"
5 preferably include the metal parts at regions of 0 mm to 20 rnln fiom the V-convergence portion
toward the downstream side in the horizontal dkection of the image obtained by the imaging
device.
[oolel
Returning the explanation to FIG. I, in the apparabs 100 for monitoring an operation of
10 electric resistance welidhg, 101 kdicates an input part by which image data captured by the
imaging device 8 is input. From the imaging device 8, an image having the conveyance direction
of the steel plate 1 as the X-direction and the abutment dkection of the steel plate 1 as the Vdkection
is input. FIG. 5 is a sche~naticv iew illustrating the image captured by the imaging
device 8. In the image captured by the imaging device 8, a light emitting region 51 (high heat
15 region with high luminance level) appears along the two end parts 4,4 of the steel plate 1. At the
downstream side of the conveyance direction (X-direction), the melted portions of the two end
p ~4,4s f% Bwo ut to the surfa~eo f the mebl gl&e due to the electromagnetic b r a r esulting in
wave-like pal.lerns. As show in FIG. 1 and FIG. 19, the h'lgh eequency currrent 5 flows in
opposite directions at facing locations of the abuMlng end faces of the two end parts 4,4 of the
20 steel plate 1, so repulsive force is generated bemeen the two end pads 4,4. The meked portions
of the two end parts 4, 4 Row out to the surface of the metal plate due to the electromagnetic
force. Afier that the mlten steel is pushed out in the upward and downward directions due to
the upset of the strong pressure applied &om the left and right. In the present invention, the
uilevenness of the light e~nittingr egions of the metal parts Rowing out to the surface of the metal
25 plate due to this electromagnetic force is grasped to detect the misalignment. Ifmisalignment
occurs, current concentrates and melting is accelerated at the outside surface side of the steel
plate I at the end part (end part at right side of FIG. 4) 4 offset downward, while current is
reduced and melting becomes more difficult at the outside surface side of the end part 4 offset
upward (end part at left side of FIG. 4), so the areas of outflow of molten metal to the outside
30 surface of the metal plate at the two end parts 4,4 differ. Similarly, if misalignment occurs,
cuwent concentrates and melting is accelerated at the inside surface side of the steel plate 1 at the
end part 4 offset upward (end part at right side of FIG. 4), while current is reduced and mlting
becomes more difficult at the inside surface side of the end part 4 oficset downward (end part at
leA side of FIG. 4), so the areas of outflow of molten metal to the inside surface ofthe metal
35 plate at tlae two end parts 4, 4 differ. The change can be clearly discrimhated even wit"e&asmall
misaBignmenh of less than 5% of the plate thickness, so it is possible to obtain a grasp of the
unevenness of the light emitting regions ofthe metal parts flowing out to the surface of the metal
plate due to the electromagnetic force so as to detect misalignment more precisely than in the
past.
100191
5 102 is an image processing part which processes the image input to the input part 101 by
red component e~ractionb, inarkation, and other image processing.
[0020]
103 is a V-convergence point detecting part which detects the geometric V-convergence
point VI on the lmage processed by the image processing part 102. The geometric V-
10 convergence point VI, as shown in FIG. 6 by the broken line, is the point where the two end
parts 4,4 converging to a V-shape geometrically intersect. By capturing the paMern of natural
light of the portion where the two end parts 4, 4 of the steel plate I coilverge toward the
geometric V-coilvergence point Vl (radiant pagerns), it is possible to detect the geometric Vconvergence
point VI based on the approximation lines of the two edges of the two end parts 4,
15 4. Note that in actuality, as shown in FIG. 6, a tm-stage convergence phenolnenon is observed
of there being an abutment point V2 where the two end parts 4, 4 physically abut (contact each
otkr) at &e downsl-rem side of the geometric V-convergence pokt V 1, inded sf the tvvo end
pats 4,4 abusing d the geometric V-convergence p i n t VI. Further, the weldkg point (pok~t
where solidification stads) is present at the h ~ h edro wnstream side eon? the abutment point V2.
20 Note that in the followkg explanation, the geometric V-convergence point V1 will sometimes be
simply called the "V-convergence point V1".
[ooall
104 is an area calculating par& vvlnich finds the line L1 passing through the V-convergence
point V1 detected by the V-convergence point detecting part 103 and parallel to the X-direction
25 of the image on the image processed at the linage processing part 102. The imaging device 8 is
set so that the horizontal direction of the image obtained by the imaging device 8 becomes
parallel to the conveyance direction (X-direction) of the steel plate 1. The line passing through
the V-convergence point V1 and parallel to the horizontal direction of the image obtained at the
imaging device 8 is defined as the ""line L1". Further, this line L1 is deemed as the abuaing
30 position and an area S1 of the light elnitting region of the metal part flowing out to the surface of
the ~netapl late due to the electromagnetic force at the downstream side from the V-convergence
point V1 at one side divided by the line L1 and an area S2 of the light emitting region of the
metal part flowing out to the surface of the metal plate due to the electromagnetic force at the
downsbeam side from the V-convergence point VI at the other side divided by the line Li are
35 respectively calculated The ""metal parts flowing out to the surface ofthe metal plate due to the
electromagnetic force at the downstream side 501-nth e V-convergence point V19'p referably
include the metal parts at regions of 0 min to 20 mm fiom the V-convergence point V1 toward
the downstream side in the horizontal direction of the iinage obtained at the imaging device.
Note that details of the calculation of the areas S1, S2 will be explained at the later explained
FIG. 9.
5 [0022]
105 is a judging part vvhlch colnpares the areas S 1, S2 of the light emitting regions at the
two sides ofthe abutting position calculated at the area calculating part 104 to Judge the
occuwence of any misalignmel.nl.
100231
10 106 is an output part which, for example, displays the images handled by the pads 10 1 to
105 and the results of comparison of the areas S 1, S2 at the judging part 105 on a not shown
display device. Fu~$herw, hen the judging part 105 judges misalignment, for example, it outputs
an alarm.
[0024j
15 Ned, referring to FIG. 2, the method for monitoring operation according to the apparatus
100 for monitorkg an opemtion of electric resistan= welding according to the Pist embodiment
will be explakd in ddail. The image capture opemtbn by the imaging device 8 is perfomed
continuowly at cedztin time intexlrals. One image captured at the sam timing is called a "hme5'.
I f t k image data is input &om the imaging device 8 through the input part 101 (step SI), the
20 image gro~essingp art 102 earacts the red component (wavelen@h 590 to 680 nm) from the
ilnage data to clarify the contrast (step S2).
10025 J
The image processi~lgp art 102 bi~~ariz(eksv efis) the image data &om which the red
component has been e~ractedat step S2 (step S3). Here, ""O'is entered for a pixel with a
25 luminance level of a predetermined threshold value or more and ""I'is entered for a pixel of less
than a cedain value. The areshold value here is made the level of a disturbance factor, such as
the noise level of the camera or reflection fiom the top roll, or more and is adjusted in the range
where the shapes of the melted parts or end parts of the steel material can be grasped. For
example, if a melted region is the 160 level by 255 gradations and the disturbance factor is the 30
30 level, about the 40 level is selected. By setting this threshold value, the range of a light emitting
region for which the area is calculated in the present application is determined. FIG. '-/(a) is a
schematic view illustrating a binary image.
[0026]
The V-convergence point detecting part 103 detects the geometric V-colavergence point
35 Vp on the binary image generated at step S3 (step $4). FIG. 3 shows a specific example of the
processing for detection ofthe V-convergence point of step S4. First, as shown in FIG. 7(b),
labeling is performed for labeling each blob (step S41), then it is judged if a blob matching
predetermined conditions has been extracted (step S42). The "blob referred to here means a
region forming a clump at the 255 level in a binary image (at 8 bit, 0 or 255 level), more
specifically means an individual region where any of the eight pixels adjoining a pixel of "I",
5 including the four pixels to the top, bottom, lee, and right and the four pixels in the diametrical
directions, is "I9a' nd are connected to form a clump. Further, '"abeling" indicates assigning the
same label numbers to individual blobs to extract specific blobs and perform processing for
e~ractingpo sitions inside the image (maximum points and minimum points of X-coordinates
and maximum points and minimum points of Y-coordinates) and widths, lenghs, areas, etc.
10 together. For example, at FIG. 7(b), the three blobs are labeled ""1" "Z9, and "3'" If at step S42
there is a blob matching predetermined conditions, that blob (here, the label "'2") is extracted as
the blob 52 of the V-convergence portion of the portion where the two end parts 4,4 converge in
a V-sllape (see FIG. 7(c)) and its coordinates, area, or other shape information is acquked. For
example, in the binary image shown in FIG. 7(a), if there is a blob contiguous with the left end
15 and having a predetemi~leda rea condition, that is extracted as the blob 52 of the V-convergence
podion. As the condition of the predetermined area, for example, the condition of the actual
dimension of the area of the bhb king 15 to 150 mm2 andor the condition of the actual
dimension of the ck~umscrlblngre ctangular shape being 25 to 320 mm 2 may be set.
I00271
20 If at step S42 a blob matching predetermined conditions is exlracted, t k two end parts 4,
4 ofthe steel plate 1 are searched for at the extracted blob 52 of the V-convergence pol-tion (step
S43). As shown in FIG. 7(d) enlarging FIG. 7(c), points where 6c"Ib' ecomes ""0, are searched for
in the +Y-dkection and -Y-direction from the line passing through the downstream most point of
the blob 52 of the V-convergence portion in the conveyance direction and parallel to the X-
25 dkection (shown by one-dot chain line in figure) and the points are deemed end parts 4 of the
steel plate I. This is performed in a predetemined range in the direction converging to the Vshape
(X-direction), for example, in a range of 213 @om the left end of the range .from the left
end of the binary image (downstream side of col~veyanced irection) to the eont end of the blob
52 ofthe V-convergence po~ionF. urther, the end parts 4, 4 of the steel plate I are linearly
30 approximated in this predetermined range (step S44) and the intersecting point of approximation
lines of the same is detected as the geometric V-convergence point VI (step S4.5). Note that, the
above predetermined range is not always made ""a range of 213 from the left end". If the position
of the V-convergence point Vl moves to the upstream side of the conveyance direction due to
the operating conditions, it is preferable to set this to a sn-naller value, fir example, 112, or other
35 suitable value.
[ooas]
When searching for the end pailts 4 of the steel plate 1 , for example, it is also possible to
search for the points where "0" becomes "1" fiom the top and bottom positions of the image
shown in FIG. 7(d) in the Y-direction toward the inside. However, it is learned that the blob 52
of the V-convergence portion appears near the center of the image in the Y-direction. Ifthe
5 search is started from the topinost position and boMolnrnost position of the image, the processi~lg
becomes wastehl. Tlnerefore, as explained above, the points where "'I" becoines "0" are
searched for fiom the inside of the blob 52 of the V-convergence podion in the +U-direction and
-Y-direction to thereby shorten the processing time. FuPcher, even if searching for the points
where "0" becomes ""13-om the top and bottom positions of the irnage toward the inside, it is
10 possible to learn the Y-direction position of the broad part (left end of image) of the blob 52 at
the V-convergence poaion by labeling, so if searching for the points where "0" becomes ""I"
fiom the U-dkection position or near it toward the inside, it is possible to shorten the pmcessing
time.
[0029]
15 If at step S42 a blob matching predetermined conditions is not e~racteda,n abnormal
flag is set (step S46). For example, ifthe amount of hput heat is low, as shown in FIG. 8, a blob
at the Vanvergeance podion is not e&racted, so the mutilc: proceek to step S46. Fudker, it is
judged if the abmnnal flag has been co~ltinuornIys et for exactly a predetermimed number of
hmes (step S47). If the abnorml flag has been continuously set for exactly a predetermked
20 n u d e r of frames, an ablmrmality alarm is output (step S48).
[0030j
Returning the explanation to FIG. 2, the area calculating part 104, as shown 141 FIG. 9(a),
finds the line LI passil~gt hough the V-convergence point V1 detected at step S4 and parallel to
the X-direction of the image on the binary image genemted at step S3 (step S5). Note that, in
25 FIG. 9, considering ease of viewhg, the black and white such as shorn k FIG. 7 is omiued.
Fuaher, the area calculating part 104 uses the line LI as the abuttlng position and, by labelkg,
respectively calculates the area S1 of the light emitting region of the metal part flowing out to the
surface of the metal plate due to the electromagnetic force at the downdream side &om the Vconvergence
point V1 at one side divided by the line L1 and the area S2 of the light emitting
30 region of the metal part Rowing out to the surface of the metal plate due to the electromagnetic
force at the downstream side from the V-convergence poil?t V1 at the other side divided by the
line L1 (step S6).
[oo3ag
The judging part 105 judges if the ratio sf the area S 1 or S2 of the light emitting region of"
35 either side designated in advance with respect to the sum of "he area S1 of the Bight emitting
region at one side and the area S2 of Bight emitting region at the other side calculated at step S6 ns
within the upper and lower liinit values (step S7). If as a result the area ratio SI/(SI+S~o)r
S2/(Sl+S2) is within the upper and lower limit values, it is judged that misalignment is not
occurring, while if it is over the upper limit value or lower limit value, it is judged that
misalignment is occurring. As explained in FIG. 4, when misalignment occurs, unevenness
5 occurs in the light emitling regions at the two sides of the abutling position at the oukide surface
side or inside surface side of the steel plate 1 and the state bemmes one shown in FIG. 9(b).
Therefore, it may be judged that misalignment has not occurred if the area ratio is near 112, that
is, for example, is in a range of 40% to 60%, and that misalignment has occurred if it is under
40% or over 60%. FulZher, it is also possible to judge nomalitylmisalignment based on a
10 calibration curve correlatii~gth e step difference with an area ratio detemined by changing the
misalignment. If the area ratio is over the upper limit value or lower limit value, an alarm is
output or other indication of abnormality is output (step S8).
[0032]
At step S7, it is also possible to calculate the ratio of the area S1 and the area S2 or the
15 absolute value of the difference of the area S I and the area S2 and judge if this exceeds a
predetemined threshold value. Howver, if swingil~go r misting etc. of the steel plate 1 at the
tinre of wnwymce causes one area of tlne sue% S 1, Sa to fluctuate, that fictuatisn aEeds the
other area as is, so if just finding the ratio or difference of the area S 1 and area S2, the j u d w e ~ ~ t
will tend to become excessively sensitive. As opposed to this, as show in the present
20 embodiment, by making the judg~nentb ased on the ratio of one area to the overall area
(S 1/(S l+S2) or S2/(S l+S2)), more stable Judgment becomes possible.
f00331
FIGS. I O(a) and (b) are graphs finding one area ratio with respect to the overall area in
actual operation (Sl/(Sl+S2) or S2I(Sl+S2)) and ploMing it along with the elapse of time. As
25 shown in FIG. I0(a), as a result of plotting while monitorkg it constantly during operation, at the
time 15:03:21 on, the state of the area ratio exceeding the upper limit value continues. After that,
if tracing and inspectkg an actual material, it was confirmed that misalignment actually occurred
at that point of time. From this result as well, it is learned that the techique of detecting
misalignment using the present invention is effective.
30 [0034]
FIG. 10(b) is a view replo~ingth e data of FIG. IO(a) by obtaining the movtllg average of
seven points by a time series. In FIG. IO(a), even before 15:03:21, sometl~nesth e area ratio
te~laporarllye xceeds the lower limit value, but there is a high possibility of this being a noise
component. Therefore, by taking the emoving average sf several points or so of data to smooth
45 the graph and rernoTvet he noise component, it is possible to more ckar:s-lyju dge the occurrence of
rnisaligna-aaent.
LO0351
As explained above, misalignment is detected by obtaining a grasp of the unevenness of
the light emitting regions of inetal parts flowing out to the surface of the metal plate due to
electro~nagneticfo rce at the two sides of an abutting position at the outside surface or inside
5 surface of a steel plate 1 formed into a tubular shape, so it is possible to precisely detect
misaligntnent in electric resistance welding without being affected by the end faces becoming
mirror surfaces. By applying the present invention, it becomes possible to detect misalignment
even if a step differei~ceo f a small step difference of about 2 to 3 mm occurs.
LO0361
10 Second Embodiment
The second embodiinent is an example configured to compare at the judging part 105 the
areas S1, S2 ofthe light emitting regions of the metal parts flowing out to the metal plate due to
the electromagnetic force at the two sides of the abugi~lgp osition as explained in the first
einbodiment and also judge if the V-convergence point VI is at the upstrean1 side fiom a
15 predetermined X-direction position on the image processed by the image processing part 102 to
judge if any misalignment has occurred. Note that, below, the points of difference fkoin the first
ernhdiment will be f o c u ~odn in the ewlanation ;Pnd sverlqping explanatiofas will be orniud.
[0037]
In the process of conveyance of the steel plate I, the steel plate 1 so~netlrness wings or
20 twists to the t f i and right of the conveyance direction. As explained in tlne fist embodiment, the
line L1 passing through the V-convergence point V1 and parallel to the X-direction of the image
is found to calculate the areas S 1, S2 ofthe light emitting regions at the two sides of this line Lj,
but if the steel plate 1 swings or twists to the leR and right of the conveyallce dkection,
sometimes the actual abuMing position becomes slanted with respect to the line L1 (see FIG.
2 5 15(a)). In this case, regardless of the occurrence of any misalignment, a difference ends up
occurring in the areas S 1, S2 of the light emitting regions at the two sides of the line LI.
[0038]
It was learned that if misalignment occurs, compared to if misalignment does i~oot ccur,
the V-convergence point V1 detected by the V-convergence point detectiilg part 103 shifts to the
30 upstream side. If misalignment does not occur, drawn to show the e&rerne case, as shown in
FIG. 12(a), the inside surface sides and outside surface sides of the t m end parts 4,4 melt
substantially evenly. On the other hand, if misalignment occurs, drawn to show the extreme case,
as shown in FIG. 12(b), the degree sf melti~~bgec omes higher at the inside surface side of the
steel plate 1 at the end part 4 offset upward (end part at IleA side of FIG. 12), while the degree of
35 melting becomes higher at the outside surface side ofthe steel plate A at the elad pa11 4 offset
downward (end part ah right side of FIG. 12). For this reasoa-a, as shown in FIGS. 12(a) and (b),
even in the state where the distances between the two end parts 4, 4 are equal, if the melted
portioils 120 flow out to the surface of the metal plate due to the electromagnetic force, when
observed froin the arrow Z-direction, the distance 11 of viewing when misalignment occurs
becomes shorter cotnpared with the distance 12 of viewing when no misalignment occurs. In
5 other words, when observed &om the arrow Z-direction, if misalignment occurs, compared to if
no misalignment occurs, the V-convergence poiilt V1 is detected at an early stage, that is, at the
upstream side. Therefore, in the present embodiment, it is also judged if the V-convergence point
V1 is at the upstream side from a predetermined X-direction position.
100391
10 Nex%,r efe~~intog F IG. I I, a method for mollitori~lga n operation according to an
apparatus 100 lfor monitoring an operation of electric resistance wlding according to the second
embodiment will be explained in detail. Steps SI to S6 and S8 are similar to FIG. 2 of the first
embodiinent. Here, the explanation will be omitted. At step S17, the judging part 105 judges if
the ratio of the area Sl or S2 of the light emitting region of either side designated in advance with
15 respect to the sum of the area S1 of the light emitting region at one side and the area S2 of Iight
emitting region at the other side calculated at step S6 is within the upper and lower limit values.
In addition, it judges ifthe V-convergence point V1 detected at step S4 is at the upstream side
&om the grdetemilled X-dkection position XS. As a result, if the area ratio SI/(SI+S~o)r
S~/(SI+Si~s )o ver the upper limit value or lower limit value and the V-convergence point V1 is
20 at the up~reamsi de ii-om a predetemined X-direction position XS, it is judged that
misalignment is occurring (see FIG. 13(b)), pjvhile othewise, it is Judged that misaligllment is not
occurring (see FIG. 13(a)). For example, even ifthe area ratio Si/(Sl+S2) or S~/(SI+Se~x)ce eds
the upper limit value or lower limit value, unless the V-convergence point Vl is at the upstream
side of the predetermined X-diuection position XS, it is deemed that there is a high possibility
25 that this is caused by swinging or twisting etc. of the steel plate 1 and it is judged that no
misalignment has occuwed. By setting the poshion of the geometric V-convergence point VI as
the condition for judgment of normalitylabnormality, it is possible to obtain broader upper and
lower limit values of the area ratio than the frrst e~nbodiment, so, as explained above, even ifthe
steel plate I swings or mists to the left and right in the conveyance direction, a high precision,
30 stable Judgment becomes possible.
100401
As explained above, it is possible to eliminate the effect of swinging or twisting of the
steel plate 1 etc. to detect misalignment, so id- is possible to precisely detect misalignment in
electric resistance welding.
3 5 [0041]
Third E~nbodin~ent
The third embodiment, as sl~own in FIG. 14, is an example where the area calculating
part 104 is provided with a correcting part 104a and has the function of correcting the calculated
areas S1, S2. Note that, below, the points of difference from the first eiubodiment will be focused
on in the explanation and overlapping explanations will be omitted.
5 100421
As stated in the second embodiment as well, in the process of conveyance of steel plate 1,
if the steel plate I swings and twists to the left and right of the conveyance dkection, the actual
abutting position will become slanted with respect to the line LI. For this reason, as shown in
FIG. 15(a), whhout regard as to occurrence of any misalignment, sometimes a difference will
10 arise in the areas S1, S2 of the light eemiakg region at the two sides of the line L1.
100431
Therefore, the area calculating part 104, as show11 in FIG. 15(a), first, in the same way as
the first embodiment, fii~dtsh e line L1 passing though the V-convergence point V1 and parallel
to the X-direction of the image and calculates the area SI of the light emitting region ofthe metal
15 part flowing out to the surface of the metal plate due to the electromagnetic force at the
dowstream side &om the V-convergence point V1 at one side divided by the line L1 and the
area S2 of the light emiuing reghn of the metal part Bowing out to the surface of the metal plate
due to the elec&osnagnetic force at the dowstrea~ns ide fiorn the V-convergence poid V1 at the
other side divided by the line LI.
20 I00441
Ned, the correcting part 104a, as shown in FIG. I5(b), finds the bisector L2 ofthe angle
formed by the ilersection of approximation lines of the two end parts 4,4 of the steel plak I
found at step S44 of FIG. 3. Further, the region surrounded by the line L1 and the bisector L2 in
the light e m i ~ b gre gion of the metal part Rowing out to the surface of the metal plate due to the
25 electromagnetic force at the domslream side om the V-convergence point VI is used as the
correction region and an area S3 ofthe correction region is calculated.
/0045)
Next, the correcting part 104a, as shown in FIGS. 15(b) and (c), adds the area S3 to the
area of the region which the bisector L2 does not pass through in the light emitthg region at the
30 dowstream side fiorn the V-convergence point V1 (in the case of the illustrated example, the
area S1) and subtracts the area S3 from the area of the region which the bisector L2 passes
thsough to calculate the eowected area s~'(=sI+s~)s,~ '(=sz-s~)I.n other words, the area SI' of
the light emitting region at the downstream side di-om the V-convergence point V1 at one side
divided by the bisector &2 and an area ~2o'ff he light emitting region at the downstream side
35 from the V-convergence point Tail at the other side divided by the bisector. L2 are respectively
ca%cuIateed.
[0046]
After that, in the same way as the first embodiment, it is judged if the ratio of the
corrected area s I' or S2' of the light emitting region of either side designated in advance with
respect to the sum of the corrected area s 1' of the ligl~et mitting region at one side and the
5 corrected area S2\fthe light emi~ingre gion at the other side is within the upper md Lower limit
values. If as a result the area ratio S 1 'I(§ lq+s2') or s~'/(sI'+s~') is within the upper and lower
limit values, it is judged that no misalignment has occurred, bile if it is over the upper llinit
value or lower limit value, it is judged that misalignment has occuwed.
100471
10 As explained above, it is possible to detect ~nisalignmentw hile eliminating the effect of
swinghg or misting etc. of the steel plate I, so it is possible to precisely detect misalignment in
the electric resistance welding.
10048)
FIG. 16 is a graph finding the "uncorrected area ratio (SI/(S~+So~r) S 2/(Si+S2)) and
1 5 the "corrected" area ratio (S I'/(s1 '+~2')o r s~'/(sl f+S2')) when twisting actually occurs in steel
plate 1 in actual operdion and plotting it along with the elapse of time. In the figure, the fine line
shows the ""lanmmececl" characteristic, d i l e the bold line shows the "csrrecteP ehamcteristic.
It is confwmed that up to the time tl, no misalignment occurs, but with "no correction", the result
becomes lower than the lowr limit value, while with "correction9', the result is kept wkhin the
20 upper and lower limit values after reiov'mg the noise component. It was confirmed that
misalignment can be precisely detected even in the state where misting occurs in the steel plate
1.
100491
In the present embodiment, the bisector L2 of the angle formed by the intersection of the
25 approxhation lines of the two end parts 4, 4 of the steel plate 1 is found, but the invention is not
limited to this. For example, it is also possible to find the median line passing through the Vconvergence
point Vl at the triangular shape fomed by the approximation lines of the two end
pasts 4, 4 of the steel plate I and the X-direction end part of the image Xg.
[0050]
3 0 Foufih Embodiment
In the first embodl~nentto the third embodiment, to detect the unevenness of the area at
the downstream side ko~nth e geometric V-co~avergencep oint V1, a horkontal line passing
through the geo~netrlcV -convergence point V1 and hfiher a bisector of the angle formed by the
intersection of the approximation lines were used. AS opposed to this, in the present
35 embodiment, the example is shown of using just the approximation lines for finding the
geometric "6-convergence point V1 to try to detect unevenness of the area. Note that, below, the
points of difference from the first einbodimel~tw ill primarily be explained and overlapping
explanations will be omitted.
[OOSl]
Referring to FIG. 17, a method for monitoring a11 operation according to the apparatus
5 100 for monkoring an operation of electric resis(ance welding accoding to the fourth
embodirnelll will be explained in detail. Instead of step S5, the processing of step S15 is
performed. Steps S1 to S4 and S6 to S8 are slnlilar to FIG. 2 of the first embodiment, so here the
explanation will be omitted. At step S 15, the approximation lines of the end parts 4, 4 of the steel
plate I obtained at step S4 (step S44) are extended to the downstream side of the V-convergence
10 point V1. Further, at step S6, the area calculati~lgp art 104, as shown in FIG. 18(a), calculates the
arca S1" at the outside of the extended approximation line in the circumferential direction in the
light emitting region ofthe metal part flowing out to the surface of the metal plate due to the
electromagnetic force at one side at the downstream side &om the V-convergence point V1 and
the area S2" at the outside of the extended approximation line in the circumferential direction in
15 tile light elniMing regloll ofthe metal part flowing out to the surface of the metal plate due to the
electromagnetic force at the other side at the dowstrearn side &om the V-convergence point VI.
The ''nnebl pws flowing out .to the surfare of the mebl plate due to the elatrosnagnetie fore at
the dowstrem side @om the V-convergence point V19' preferably include the metal parts at
regions of 0 mm to 20 mm &om the V-convergence point V1 toward the downstream side in the
20 horkontal dkection of the iinage obtaied at the iinagil~gd evice.
loosal
At step S7, the judging part 105, in the satne way as the first embodhent, judges if the
area ratio (S 1"/(Sln+S2") or S2"/(S1 "+S2")) or the absolute value of the difference of areas (IS1 "-
S27) is within the upper and lower limit values. When inisalignment occurs, unevenness occurs
25 in the light emietling regions bemeen the two sides of the abutting position at the outside surfxe
side or inside surface side of the steel plate 1 and the state becomes one such as shown in FIG.
18(b). By doing this, even if the steel plate 1 swings or twists to the left and right of the
conveyance dkection, misalignment can be precisely and stably detected. Further, it is also
enough to just extend the approximation lines of the two end parts in the circumferential
30 dkection converging to a V-shape, so it is not necessary to calculate the horkontal line passing
through the geometric V-convergence point VI and, fufiher, the bisector of the angle formed by
intersection sf the approximation lines, and the processing becomes simpler.
[OS53]
Even iffinding the areas SB "', Sz" like in this embodiment, as explained in the second
3 5 embodiment, it is also possible to together judge if the geometric V-convergeaxe point -8$bis at
the upstream side ofa predetermined X-direction position.
[0054]
Above, the present invention was explained together with various embodiments, but the
present invention is not limited to these embodiments. Changes etc. are possible within the scope
of the present invention. For example, in the above embodiments, a 3CCD type camera was
5 used, but even if aMaching an optical filter passing 570 to 740 nm or so to a monochrome
camera, an image equivalent to the R-component of a color camera is obtained. For example, if
using a camera provided with a 113 type CCD (XGA size) and the distance up to the Vconvergence
portion is 1.2 m, a lens with a focal distance e75 mm and a brightness FS is set
above the V-convergence portion to capture an image. Preferably y-correction is performed to
10 enable regions with low luminance at the end parts 4 of the steel plate I to be accurately
detected.
[OOSS]
The apparatus for monitoring an operatio11 of electric resistance weldiilg of the present
invention specifically can be achieved by a computer system provided with a CPU, ROM, RAM,
15 etc. and is realized by a CPU running a program. The apparatus for monitoring an operation of
electric resistance welding of the present invention may be comprised of a single apparatus or
may be comprixd of a plurality of pieces of equlpmernt.
[Or0561
Fu&he[; the object of the present kvention is also achieved by providing a aorage
20 medium storing program codes of sofiware for realizing the above-mentioned function of
monitoring an operation of electric resistance welding in a system or an apparatus. In this case,
the progrm codes read out from the storage lnedium t'hemselves realize the knctions of the
above-mentioned embodiment, and the program codes themselves and the storage mediu~n
storing the program codes constitute the present invention. As the storage medium for providing
25 the program codes, for example, a flexible disk, hard disk, optical disk, magneto optical disk,
CD-ROM, CD-R, magnetic tape, nonvolatile memory card, ROM, etc. can be used.
REFERENCE SIGNS LIST
[0057]
30 1: steel plate
2: squeeze roll
3: conveyance direction
4: circunnfesential direction end part
5: high 6equency current
35 6: impeder
7: contact tip
8: imaging device
100: apparatus for monitoring operation of electric resistance welding
10 1 : input past
102: image processing part
103 : V-convergence point detecting part
104: area calculating part
104a: correcting part
105: judging part
106: output past
1.1: actual thickness of abuwing end faces
L1: line parallel to X-direction of image
L2: bisector of angle formed by intersection of approximation lines of two end parts of steel plate
11: distance of viewing when misalignment occurs
12: distance of viewing when no misalignment occurs
t: thickness of steel plate
S1: area of light emi~ingre gion at one side
S2: area of light emigl-llmg region at otkr side
S3: correction region surrounded by line L1 and bisector d2
SI!: S1+S3
~ 2 ' S: 2 -S3
VI : V-convergence point
V2: abutment point
Xo: X-direction end part of image
XS: predetermined X-direction position

CLAIMS
[Claim 11
An apparatus for monitoring an operation of high frequency resistance welding and
induction heating welding of an electric resistance welded steel pipe where a strip of metal plate
5 is continuously formed into a tubular shape by a group of rolls while beiilg conveyed h m an
upstream side to a downstrea~ns ide and two end parts of said metal plate in its ckcumferential
direction made to converge to a V-shape are heated to melt and made to abut against each other,
characterlzed in that
said apparatus detects misalignment by obtailling a grasp of unevenness of light
10 emiaing reglolls of lnetal parts at two sides in the circumferential direction at abutting positions
at an outside surface or inside surface of said metal plate based on an image, captured by an
imaging device from the outside surface side or inside surface side of said metal plate being
formed into the tubular shape, of a region including a V-convergence portion vvhere said two end
parts in the circumferential direction converge to a V-shape and said metal parts flowing out to
15 the surface of said metal plate by electromagnetic force at a downstream side &om said Vconvergence
portion.
[Glalln 23
The apparatus for mnitoring an operation of high &equency resistance wlding and
20 induction heating welding of an electric resistance welded steel pipe according to claim I,
characterlzed in that the apparatus comprises
an input lneans to which an image having a conveyance directhn of said metal
plate as an X-direction and a circumferential direction of said metal plate as a Y-dkection is
input fiom said imaging device,
25 an image processing means for performillg i~nagep rocessing on the image input
to said input means,
a V-convergence point detecting nleans for detecting a geometric V-convergence
point where said two end parts in the ckcumferential dkection converging to the V-shape
geometrically intersect by linearly approximating said two end parts in the circumferential
30 direction and finding the intersecting point of the approximation lines of said two end parts in the
ckcumferential dkection in the image processed by said image processing means,
an area calculating meal?$ for finding a line passing through the geo~netricV -
convergence point detected by said $I-convergence point detecting means and parallel to the Xdirection
of the image iaa the image processed by said image processing means, using said line as
35 the abutting position, and calculating an area Sg of the light emitting region of said metal park at
the downstream side fsom said geometric V-convergeaace point at one side divided by said line
and an area S2 of the light emitting region of said inetal part at the downstream side from said
geometric V-convergence point at the other side divided by said line, and
a judging means for comparing the areas S1, S2 ofthe light emitting regions at the
two sides of the abutLing position calculated by said area calculating means to judge the
5 occurrence of misalignment.
[Claim 31
The apparatus for monitoring an operation of high fi-equency resistance welding and
induction heatkg welding of an electric resistance welded steel pipe according to claim I,
10 characterized in that the apparatus comprises
an input mans to which an image having a conveyance direction of said metal
plate as an X-direction and a circumferential dkection of said metal plate as a U-direction is
illput from said imaging device,
an image processing means for performing image processing on the image input
I5 to said input mans,
a V-convergence point detectil~gm eans for detectil~ga geometric V-convergence
poi& where said mo errd pa& in the ckcumferential dkation converging to a V-shape:
geolnetrically htersect by linearly approximating said two end parts in the ckcumferential
dkection and fmding the intersecting point ofthe approximation lines of said two end parts in the
20 ckcumferential dkection in the image processed by said image processing means,
an area calculating means for extending the approximation lines li~~early
approximating the two end p a ~isn the ckcumferential direction to the dowstream side over
said geometric V-convergence point and calculating an area SI" of the light ernitting region of
said metal part at the outside from one of said eiil-ended approximation lines and an area ~ 2 o"f
25 the light em~tingre gion of said mtal part at the outside fkom the otkr of the ex(ended
approximation lines, and
a judging means for comparing the areas SI"> $2'' of the light emitting regions
calculated by said area calculating means to judge the occurrence of misalignment.
30 [Claim 41
The apparatus for monitoring an operation of high frequency resistance welding and
illduction heating welding of an electric resistance welded steel pipe according to claim 2,
characterized in that said judging means finds a ratio of either of said area S 1 of the light
emitting region at the one side and said area S2 sfthe light emitting region at the other side with
35 respect to the sum of said area S 1 of the light emitting region at the one side and said area $2 of
the light emitting region at the other side and judges whether said ratio is within predetermined
upper and lower limit values.
[Claim 51
The apparatus for inonitoring an operation of high frequency resistance welding and
5 inductioi~h eating welding of a11 electric resistailce welded steel pipe according to claim 3,
characterized in that said judgi~~mge ans finds a ratio of either of said area S 1" of the light
emitting region at the one side and said area ~ 2 o"f the light emiging region at the other side
with respect to the sum of said area S 1 '\of the light emitling regiol~a t the one side and said area
S2" of the light emiQing region at the other side and Judges whether said ratio is within
10 predetermined upper and lower limil- values.
[Claim 61
The apparatus for monitoring an operation of high ti-equency resistance welding and
induction heating welding of an electric resistance welded steel pipe according to any one of
15 claims 2 to 5, characterized in that said judging means judges whether said geometric Vconvergence
point is at an upstream side from a predetemked X-dkection position in the image
processed by said image processhg means.
[ e l a i ~ l l ~ j
20 The apparatus for monitoring an operation of high frequency resistance welding and
kduction heating welding of a11 electric resistance welded steel plpe according to claim 2,
characterized in that said area calculating mans finds a bisector of an angle of intersection of the
approxinnatior~li nes of said two end parts in the circumferential direction converging to the Vshape
or a media11 line passing through said geometric V-convergence point in a triangular shape
25 formed by the approximation lines of said end parts in the clrculnferentkl dkection converging
to the V-shape and the end part at the upstream side in the X-direction of said image in the image
processed at said lrnage processing means and corrects said area S1 of the light emiHhg region
at the one side and said area S2 of the light emitting region at the other side calculated by said
area calculating means.
3 0
[Claim $1
A neth hod for monitoring an operation of high frequency resistat~cew elding and
induction heating welding of an electric resistal~cew elded steel plpe continuously forlnilag a strip
of metal plate into a tubular shape by a group sf rolls while conveying the strip sf metal plate
35 &om an upstream side to a downstream side and heating two end parts of said metal plate in ?ts
clcurnfere~atiald irection made to converge to a V-shape to melt and making the two end parts of
said metal plate abut against each other, cl~aracterized in that:
said method comprises capturing a11 image, by an imaging device fiom an outside
surface side or inside surface side of said metal plate being formed into the tubular shape, of a
region including a V-convergence portion where said two end parts in the circumferential
5 direction converge to a V-shape and metal parts flowing out to the surface of said inetal plate by
electromagnetic force at a downstream side fiom said V-convergence porlion, and detecting
misalignment by obtaini~lga grasp of unevenness of light emitting regions of said metal part at
two sides in the circumferential direction at abuMing positions at the outside surface or inside
surface of said metal plate based on said image.
10
[Claim 91
The method for monitorkg an operation of high frequency resistance welding and
induction heating welding of an electric resistance welded steel pipe according to claiin 8,
characterized by:
15 capturing an linage having a conveyance direction of said metal plate as an Xdkection
and a clrcumfere~ltiald irection of said metal plate as a Y-direction by said imaging
device,
pedomming i~magep rocessing on said captured image,
detectkg a geometric V-converge~~cpeo ht where sald tvvo end pads in the
20 circumferential direction converging to the V-shape geometrically i(ersect by linearly
approximating said two end parts in the ckcumferential direction and finding the intersecthg
po111t of the approximation llnes of said two end parts in the circumferential direction in the
processed image,
finding a line passing through the detected geometric V-convergence point and
25 parallel to the X-dkection of the image in the processed image, using said line as the abuMl~lg
position, and calculating an area S 1 of the light emitting region of said metal part at the
downstream side from sald geo~netricV -convergence point at one side divided by said line and
an area S2 of the light emitting region of said metal part at the downstream side from said
geometric V-convergence point at the other side divided by said line, and
30 comparing the areas S 1, S2 of the light emitting regions at the hvo sides of the
abutting position to judge the occurrence of misalignment.
[Claim l O]
The method for monitoring an operation of high frequency resistance welding and
3 5 induction heating welding of an electric resistance welded steel pipe according to claim 8,
characterized by:
capturing an image having a conveyance direction of said metal plate as an Xdirection
and a circumferential direction of said metal plate as a Y-direction by said imaging
device,
performii~gim age processing on said captured image,
5 detecting a geometric V-convergence point where said two end parts in the
ckcumferential direction converging to the V-shape geometrically intersect by linearly
approximating said two end parts in the circun~ferentiadl irection and finding the intersecting
point of the approximation lines of said two end parts in the circumferential direction in the
processed image,
10 extending the approximation lines linearly approximating said two end parts in
the ckcumferential direction to the downstream side of said conveyance direction over said
geometric V-convergence point and calculating an area s 1 '' of the light emitting region of said
metal part at the outside from one of said edended approximation lines and an area S2" of the
light emiaing region of said metal part at the outside from the other of the extelided
15 approximation lines, and
comparing said areas ~ 1 ~ 3of~the' li'gh t emitting regions calculated to judge the
smurrence sf mislignment.
[Claim I L ]
20 The mthod for monitoring an operation of high frequency resistance welding and
induction heating welding of an electric resistance welded steel pipe according to claim 9,
chamcterked by, in said judgment, finding a ratio of either of said area S 1 of the light erniakg
regbn at the one side and said area S2 of the light emiaing region at the other side with respect
to the sum of said area S1 of the light emiaing region at the one side and said area S2 of the light
25 emigiilg region at the other side, and judging whether said ratio is within predetermined upper
and lower limit values.
[Claim 121
The lnethod for monitoring an operation of high ~equencyre sistance welding and
30 induction heating weldiilg of an electric resistance welded steel pipe according to claim 10,
characterized by, in said judgment, finding a ratio of either of said area Slf\of the lighkemitting
region at the one side and said area ~ 2o"f t he light emitting region at the other side with respect
to the sum of said area S1" of the light emittkg region at the one side and said area ~ 2 'o' f the
Bight emitting region at the other side, and judging whether said ratio is within predetermined
35 upper and Bower limit values.
[Claim 131
The method for inonitorii.~gan operation of high frequency resistance welding and
induction heating welding of an electric resistance welded steel pipe according to any one of
claims 9 to 12, characterized by, in said judgment, judging whether said geometric V-
5 convergence point is at an upstream side fiom a predetermined X-direction position in said
processed image.
[Claim 141
The method for monitoring an operation of high &equency resistance welding and
10 induction heating welding of an electric resistance wlded steel pipe according to claim 9,
characterked by, in said calculation of the areas S1, S2, finding a bisector of an angle of
intersection of the approxiination lines of said two end parts in the circumferential direction
converging to the V-shape or a median line passing tl~roughs aid geometric V-convergence point
in a triangular shape formed by the approximation lines of said end parts in the circumferential
15 dkection converging to the V-shape and the end part at the upstream side in the X-direction of
said image in said processed image and correcting said area S1 ofthe light emi@ing region at the
one side and said area S2 of Iight erana&-tlngr egion at the &her side.
[Claim 151
20 A program for monitoring an operation of high 16requency resistance welding and
induction heating welding of an electric resistance welded steel pipe con"cnuously forming a strip
of metal plate into a tubular shape by a group of rolls while conveying the strip of lnetal plate
fiorn an upstream side to a downstream side and heating two end parts of said metal plate in its
circumferential direction made to converge to a V-shape Ito melt and making two end parts of
25 said metal plate abut against each other, characterized in that:
said program makes a computer run processing for detecting misalignment by
obtaining a grasp of unevenness of light emitting regions of metal parts at two sides in the
circumferential direction at abutting positions at an outside surface or inside surface of said lnetal
plate based on an image, captured by an imaging device fiorn the outside surface side or inside
30 surface side of said metal plate being formed into the tubular shape, oEa region including a Vconvergence
portion where said two end parks 111 the ckcumferential direction converge to a Vshape
and said metal parts Rowing out to the surface of said metal plate by electromagnetic force
at a downstream side from said V-convergence gottiola.
3 5 [Claim 1 61
The program fir monitoring an operation of high fieqmency resistance welding and
induction heating welding of an electric resistance welded steel pipe according to claim 15,
characterized in that said program makes said computer function as
an input means to which an image having a conveyance direction of said metal
plate as an X-direction and a circumferential direction of said inetal plate as a Y-direction is
5 illput om said imaging device,
an hage processing means for performing image processing on the image input
to said input means,
a V-convergence point detecting means for detecting a geometric V-convergence
point where said two end parts in the circumferential direction converging to the V-shape
10 geometrically intersect by linearly approximating said two end parts in the circumferential
dkection and fiMding the i~~tersectinpgo int ofthe approximation lines of said two end pa&s in the
ckcuinferential direction in the image processed by said image processing means,
an area calculating means for finding a line passing through the geo~netricV -
convergence point detected by said V-convergence point detecting means and parallel to the X-
15 dkection of the image in the image processed by said image processing means, using said line as
the abuMing position, and calculating an area S1 of the light emiMing region of said metal part at
the downstream side &om said geometric Vanverger~eepo il?Z at one side divided by said line
and an area S2 of the light em&ing region of said metal part at the downstream side ]From sald
geometric V-cot~vergencep oint at the otl~esri de divided by said Ihe, and
20 a judgil: means for coqarlng the areas SI, S2 of the light emiging regions at the
two sides of the abutting position calculated by said area calculating means to judge the
occurrence of misalignment.
[Claim 171
,
25 The program for mnitonng an operation of high 6equency resistance welding and
induction heating wlding of an electric resistance welded steel pipe according to claim 15,
characterked in that said program makes said computer function as
an input means to which an image having a conveyance direction of said metal
plate as an X-direction and a circumferential direction of said metal plate as a U-direction is
30 input konn said imaging device,
an bnage processing means for performing image processing on the image input
to sald input means,
a V-convergence point detecting means for detecting a geometric V-convergence
point ahwhere said two end parts in the chcumferential direction converging to a V-shape
35 geo~netrically intersect by linearly approxia?nating said two end parts in the circumferential
direction and finding the intersectkg point of the approximation lines of said two end parts in tBae
circun~ferential direction in the image processed by said iinage processing means,
an area calculating means for extending the approximation lines linearly
approximating the two end parts in the circumferential direction to the downstream side over
said geometric V-convergence point and calculating an area S l ' h f the light emitting region of
5 said mehl part at the outside from one of said extended approximation Iines and an area S2" of
the light emitting region of said metal part at the outside from the other of the edended
approximation Iines, and
a judging means for coqaring the areas SI", ~ 2 o"f t he light emitting regions
calculated by said area calculating means to judge the occurrence of misalignment.
10
[Claim 181
The program for monitoring an operation of high frequency resistance welding and
induction heating welding of an electric resistance welded steel pipe according to claim 16,
characterized in that said Judging means finds a ratio of either of said area S1 of the light
15 emitting region at the one side and said area S2 of the light emitting region at the other side with
respect to the sum of said area S 1 of the light emitting region at the one side and said area S2 of
the Eght eem&ing region at tk other si& and judges whether said r&io is w&hin p ~ d e t e m i n d
upper and lower limit values.
20 [Claim 191
The program for monitoring an operation of high Erequency resistance welding and
induction heating welding of an electric resistance welded steel pipe according to claim 17,
characterized in that said judging means finds a ratio of either of said area S 1'' of the light
emitting region at the one side and said area ~ 2 'o' f the light emitting region at the other side
25 with respect to the sum of said area SI" of the light emitting region at the one side and sald area
s2" of the light emitting region at the other side and judges whether said ratio is witkin
predetermined upper and lower limit values.
[Claim 201
30 The program for monitoring an operation of high frequency resistance welding and
induction heating welding of an electric resistance welded steel pipe according to any of clalms
16 to 19, characterized in that said judging means Judges whether sald geometric V-convergence
point is at an upstream side from a predetermined X-direction position in the image processed by
said image processing means.