The present invention relates to improved stripper guard system for rolling
joist which is useful in section rolling to ensure separation of material from the
roll mainly at close passes during rolling. This helps in preventing ring
formation of the material and avoid roll breakage. The above system of the
invention also includes improved stripper flange guard and improved bottom
web guards for rolling joist.
The conventional guards consist of a pair of left and right flange guards and a
web guard in between. The guards are made of mild steel plate and often the
thickness of the plate is not governed by pass width. The front radius of the
pass is cut by gas cutting making the contour rough and uneven even after
manual grinding. Moreover, only one set of stripper guards are used for rolling
a particular section inspite of the reduction of roll radius by merely adjusting
the legs with the help of gas cutting and welding. Additionally, frictional
condition of guards at nose aggravates the deformation of the guards which
call for frequent change of guards. All this resulted in loss of precious time
and loss in production.
Thus the conventional existing guards presently available are found to suffer
from the following inherent drawbacks/disadvantages :
i) Fast wearing out of the guards
ii) Deformation of guard nose
iii) Ring formation of the material due to guard failure
iv) Tearing of flange
v) Roll breakage
vi) Rejection due to guard mark
vii) High operational delay time
It is thus the basic object of the present invention to provide improved stripper
guard system for rolling joist which would avoid the above discussed
problems of existing stripper guards.
Another object of the present invention is to provide improved flange and web guards
which would avoid the problem of knocking and provide perfect matching of contact
surface of stripper guard with the roll thereby avoid thrusting of material.
Yet another object is to provide an improved stripper guard system which would have
optimum clearance in the thickness in the pass for avoiding choking of the guard in
the pass.
Yet further object is directed to provide improved bottom web guard heavier than the
existing guard with the tapering of front leg for better stable sitting on the cramp bar.
Yet another object is to provide improved web guard which would favour easy handling
of the web guards.
Yet further object is to provide the improved guards for rolling joist with improved
wear resistance and having superior mechanical properties than the existing guard.
Thus according to one aspect of the present invention there is provided an improved
stripper guard system for rolling joist comprising :
Left and right flange guards and web guard in between, the front end of each said
guard lowered than the rear end, the contact surface of the guard with roll adapted to
be perfectiy matched with said roll surface, each said guard nose adapted to absorb
impact at nose and facilitate smooth separation of bar from the roll surface.
In accordance with another aspect the present invention provides for an improved
flange guard for use in rolling joist comprising a front end having a tip/nose portion
and a rear end, said front end being lower than the rear end, the contact surface of
said guard adjacent its front end with roll adapted to be matched with said roll
surface, the tip /nose portion adapted to absorb impact at nose end facilitate smooth
separation of bar from the roll surface. The guard tip/nose is given any suitable shape
in order to make it more impact resistant. For example the fillet type shape at the tip
is more impact resistant to deformation because of more area involved in the fillet type
tip compared to the sharp tip.
matched with said roll surface, the tip/nose portion adapted to absorb impact at nose
and facilitate smooth separation of bar from the roll surface.
In accordance with yet another aspect the present invention provides an improved
bottom web guard for use in rolling joist comprising a front end having a nose portion,
a rear end and leg portion said front end being lower than the rear end, the contact
surface of said guard its front end with roll adapted to be matched with said roll
surface, said nose portion adapted to absorb impact at nose and facilitate smooth
separation of bar from the roll surface.
Preferably, according to the invention optimum clearance is provided in the thickness
of the stripper guard in the pass to avoid choking of the guard in the pass. Also, the
contact surface of the stripper guard with the material is adapted to prevent twisting
of the material. The contact surface of the stripper guard may be given any shape as
known in the art such that twisting of the material is avoided. Advantageously, in the
improved stripper guard system the bottom web guard is provided with tapering front
legs. Moreover, the bottom web guard is made heavy for stability.
Also, to facilitate easy and comfortable handling, in the improved stripper guard there
is provided means for easy handling of the web guard, preferably in the form of a
grooved portion in the body portion of the web.
The details of the present invention, its objects and advantages will be apparent from
the following description made in relation to the accompanying figures wherein :
Fig. 1A is an illustration of a conventional flange stripper guard;
Fig. 1B is an illustration of a conventional web guard;
Fig.2 is an illustration of the position of flange guards of conventional strippers in the
pass groove;
Fig.3 shows the possible variation in the thickness for different passes;
Fig.4 is a sectional illustration of the improved flange stripper guard of the invention;
Fig. 5 is a sectional illustration of improved bottom web guard of the system of
the invention.
Fig. 6 illustrates the variation in the cramp bar of the guard of the invention
from that of existing guards.
Reference is first invited to Figs. 1A and 2 which show the conventional flange
stripper guard which can be left (A1) or the right (B1) flange stripper guard
and web guard (C1) inbetween. As shown in said figure such conventional
stripper guard comprise a substantially flat top (D) with its front end (I) and
rear end (II) having a same height from the base. Also as shown in said figure
the front end (FE) of the said stripper guard is provided with a sharp end. The
front contour is indicated by reference (2). Also, shown in said figure is a
cross-sectional view of the front portion of the stripper guard when the tip
configuration (8 & 9), side walls (4 & 5), thickness of the guard (12) obtained
of either 0.5 or 1 inch plate and the groove (10) is illustrated. It is to be noted
that due to the straight (same level) of the front end (I) and the rear end (II) of
the conventional stripper guard, knocking of the guard and cobble formation
was experienced in use of said conventional guards. Moreover, the tip portion
of the front end was not suitably configured to favour smooth separation of the
roll from the bar surface. Moreover, the contact surface of the guard with the
roll was also improper resulting in additional problems.
Reference is now invited to Fig. 1B which is a sectional illustration of a
conventional bottom web guard. As shown in said figure, the conventional
bottom web guard is comprised of a front end (1) and a rear end (6) which are
on a substantially flat surface. Also, as shown in said figure the web guard
has a front contour (2) and front legs (4). Likewise that in case of the
conventional flange guard, the conventional web guard due to such provisions
of front end (1) and rear end (6) at same level and sharp tip portion suffer
from problems/disadvantages as discussed above in relation to the flange
guards.
The flange guards (F) sit in the pass groove (U) as shown in Fig. 2. The
contour as well as thickness of the passes are different for different passes as
would be evident from Fig. 3 as per pass configuration of joist.
Also, such conventional guards are made of mild steel plate (IS : 2062/1994)
which basically comprise of C 0.20-0.24, Mn 1.50, S 0.040-0.050, P 0.040-
0.050, Si 0.40. The thickness of such conventional guard are not governed by
the pass width rather it is governed by the availability of the plate. Moreover,
the other variable parameters of the pass grooves (like rr (Fillet radius
between flange and web), x2 (Thickness of the flange before the web of the
pass (3)), L (Diameter at web (2)), rt (Fillet radius at the tip in the outer side of
the flange (8)), rs (Fillet radius at the tip in the outer side of the flange (9)), h1
(Height of the flange in the pass), Db (Diameter of top roll (2)) & Dt (Diameter
of bottom roll (2)) etc. are also not taken into account for making guard. All
these lead to guard failure by choking of the pass and even sometimes result
into roll breakage. Nose geometry is mostly convergent and prone to damage.
Also causes the quality problem of the rolled material like guide mark.
The contour of the conventional guard is basically cut by gas cutting making
the contour rough and uneven even after manual grinding. Additionally, the
friction condition guards (poor wear resistant property as it is made of mild
steel IS:2062 quality) at front radius calls for frequent change of guards. All
this cost precious time by increasing operation delay time and loss of
production. Thus, the existing guards essentially suffer from the following
drawbacks/disadvantages :
a) Fast wearing out of the guards.
b) Deformation of guard nose.
c) Ring formation of the material due guard failure.
d) Tearing of flange.
e) Roll breakage.
f) Rejection due to guard mark.
g) High operational delay time.
Reference is now invited to Figs. 4 and 5 which illustrate the improved stripper
flange guard and the web guard of the invention developed to overcome the
earlier mentioned limitation of existing guards. As shown in Fig 4, the front
end (I) of the stripper guard is lowered than the rear end (II). Also, the tip
portion (nose) of the stripper flange guard is provided with a modified
downwardly protruding portion (DP) which is adapted to avoid shaft edge and
favour smooth separation of the roll form the bar surface.
Likewise that of the flange guard, the improved web guard is provided with a
lowered front (I) as compared to the rear portion (6). Also, the tip portion
(nose) of the web guard of the invention is provided with a downwardly
protruding (dp) portion to avoid sharp edges.
The bottom web guard (Fig. 5) is preferably made four times (30-35 kg)
heavier than that of existing bottom web guard with the tapering front leg (4)
as shown in Fig. 5. Earlier the cramp bar (E) was square in shape as shown
by dotted line in Fig. 6 and the leg (10) of the web guard (Fig. 1A) was not
tapered which resulted in coming out of the guard. Thus the modified web
guard has been developed to avoid such existing problems of web guards.
Additionally, suitable groove (E) is provided as shown in Fig. 5 for easy
handling of the web guard. In the conventional guards no such handling
facility was available which resulted in frequent dropping and wastage of the
web guard in the water trench lying just below the mill housing.
The contact surface (2) of the guard (both flange and web) with the roll (2A) is
made in such a way that it perfectly matched with the roll surface. This would
be evident from Figs. 4 and 5. Optimum clearance (2 mm) is provided in the
thickness (X1 & X2) in Fig. 3 of the stripper guard in the pass to avoid choking
of the guard in the pass. The contact surface (D) of the stripper flange guard
with the material is made in such a way that it prevents twisting of the
material.
Preferably, the guards are made of cast steel IS:4896:1992 which is more
wear resistant and having superior mechanical strength than the existing
guard material l,e,IS:2062 as detailed hereunder in TABLE - I.
Reference is now invited to Fig. 3 which illustrates the conditions of matching
based on the various dimensions of the different passes in 300 x 140 mm
joist (4,5,6,7,8,9) taken into consideration to match all the stripper guard for all
passes of the section in case of the improved construction of guard according
to the invention. The various pass nos and the dimensions detailed in relation
to Fig. 3 are provided hereunder:
It is thus possible by way of the present invention to provide for improved and
modified stripper guard having the following special characteristics :
i) matching of the front contour with the pass profile to avoid choking of
the guard in the pass ;
ii) modification of nose geometry to take care of impact at nose and
smooth separation of bar from roll surface ;
iii) increase of weight for web guard for better stability and rigidity ;
iv) providing better handling facility of heavier guards,
v) change of material from IS ; 2062 to IS : 4896 for improved wear
resistance.
WE CLAIM :
1. An improved stripper guard system for rolling joist comprising :
left and right flange guards and web guard connecting said, the front end of each said
guards being lower than the rear end, the contact surface of each said guard with roll
adapted to be perfectly matched with said roll surface, each said guard tip/nose adapted to
absorb impact at tip/nose and facilitate smooth separation of bar from the roll surface.
2. An improved stripper guard system as claimed in claim 1 wherein optimum clearance is
provided in the thickness of the stripper guard in the pass to avoid choking of the guard in
the pass.
3. An improved stripper guard system as claimed in anyone of claims 1 or 2 wherein the
contact surface of the stripper guard with the material is adapted to prevent twisting of the
material.
4. An improved stripper guard system as claimed in anyone of claims 1 to 3 wherein said web
guard comprise bottom web guard provided with tapering front legs.
5. An improved stripper guard system as claimed in claim 4 wherein the bottom web guard is
made heavy for stability.
6. An improved stripper guard system as claimed in anyone of claims 1 to 5 comprising means
for easy handling of the bottom web guard comprising a groove portion to facilitate said easy
handling.
7. An improved stripper guard system as claimed in claim 7 wherein a grooved portion is
provided to facilitate handling of the web.
8. An improved stripper guard system as claimed in anyone of claims 1 to 7 which is obtained
of cast steel.
9. An improved stripper guard system as claimed in claim 8 wherein the cast steel comprise
C 0.45 - 0.55, Mn 0.50 - 1.00, S 0.040, P 0.040, Si 0.75, Cr 0.80 - 1.50.
10. An improved flange guard for use in rolling joist comprising a front end having a tip/nose
portion and a rear end, said front end being lower than the rear end, the contact surface of
said guard adjacent its front end with roll adapted to be matched with said roll surface, the
tip/nose portion adapted to absorb impact at nose and facilitate smooth separation of bar
from the roll surface.
11. An improved web guard for use in rolling joist comprising :
a front end having a tip/nose portion, a rear end and bottom leg portion, said front end being
lower than the rear end, the contact surface of said guard its front end with roll adapted to
be matched with said roll surface, said tip/nose portion adapted to absorb impact at tip/nose
and facilitate smooth separation of bar from the roll surface.
12. An improved web guard as claimed in claim 11 wherein said bottom leg portion comprise
tapering front leg.
13. An improved web guard as claims in anyone of claims 11 and 12 comprising means for easy
handling of the bottom web guard comprising a groove portion to facilitate said easy
handling.
14. An improved web guard as claimed in claim 13 wherein said means for easy handling
comprise a grooved portion in the body.
15. An improved web guard as claimed in anyone of claims 11 to 14 wherein it is obtained of
cast steel comprising C 0.45-0.15, Mn 0.50-1.00, S 0.040, P 0.040, Si 0.75 and Cr 0.80-
1.50.

An improved stripper guard system for rolling joist comprising left and right flange guards
and web guard connecting said left and right flange guards, the front end of each said guard
lowered than the rear end, the contact surface of the guard with roll adapted to be perfectly
matched with said roll surface, each said guard nose adapted to absorb impact at nose and
facilitate smooth separation of bar from the roll surface. The improved stripper guard system
for rolling joist would avoid the problems of existing stripper guards such as (i) Fast wearing
out of the guards, (ii) Deformation of guard nose, (iii) Ring formation of the material due to
guard failure, (iv) Tearing of flange, (v) Roll breakage, (vi) Rejection due to guard mark, (vii)
High operational delay time. Also, provided is an improved flange guard and improved
bottom web guard for use in rolling joist.