Specification
[Title of the Invention] AI-BASED ALLOY-PLATED STEEL HAVlNG HAlRLINE
APPEAIWNCE
[Technical Field of the Invention]
[OOOl]
The present invention relates to Al-bascd alloy-plated steel having a hairline
appearance which is used for surface layer materials of electrical equipment, interior
materials or exterior matcriais for buildings and vehicles, and the like.
Priority is claimed on Japanese Patent Application No. 2012-1 17284, filed on
May 23,2012, the content of which is incorporated herein by reference.
[Related Art]
[OO02]
Stainless steel is well lcnown as a steel having a hairline appcarance of the
related art. That is, as a method for surface finishing of stainless steel, hairline
finishing (HI, finishing) is regulated in JIS-G4305. In this regulation, the hairline
finishing refers to surface finishing through which a surface is polished to appear like
long and continuous hail. strands as defined as "a surface finished through polishing
using a polishing agent having an appropriate grain size so as to obtain continuous
polishing lines". FIG. 1 is a view showing an overview of the hairline finishing.
[O003]
It is well known that an ordinary hairline finishing method is a processing
method in which an endless paper polishing belt 3 supported by a contact wheel 1 and
an idler roll 2 is rotated at a high speed by rotating the contact wheel 1, and thc surface
of a metal strip 6 moving fiom an uncoiler 4 to a coiler 5 is polished using the
polishing bclt as shown in Y1G 1 (for example, rel'er to Patent Documents 1 and 2)
Hairline-finished stainless steel has corrosion resistance and a unique surTace pattern,
and thus is widely used Tor surface layer materials of electrical equipment, interior
materials or exterior materials for buildings and vehicles, and the like in which the ease
of design mattcrs.
LOO041
However, stainless steel is very expensive, and thus there is a dcmand for stccl
which is a ncw inexpensive material replacing stainless stcel, has ease of design and
corrosion resistance as favorable as stainless steel, and has a hairline appearatice
suitable for electrical equipment, construction materials, and the like.
[OOOS]
Therelore, the present inventors have paid attention to Al-bascd alloy-plated
steel which has as excellent corrosion resistance as that of stainless steel and is
inexpensive, and have studied to carry out the hairline finishing on the Al-based alloyplated
steel.
[OOO6]
When a plate-coated layer is formed on the surface of a lightweight Mg-based
member, and a hairline pattern is formed on thc surface oTtbe plate-coatcd layci
through the hairline finishing, there is a problem in that the basc of the plate-coated
layer appears and thus the corrosion resistance deteriorates, and a high-quality member
cannot be stably obtained. A technique solving the above-described problem has
been proposed as a technique of the relatcd art in which the hairline finishing is carried
out on a plated layer. That IS, in this technique, the hairlinc finishing is canied out on
the surface of a Mg-based component including a layer (1) coated with a plate of any
one selected from Cu, a Cu alloy, An, an Au alloy, Al, and an Al alloy formed by a dry
plating method, and furthernioie, on the plate-formed layel (I), a layer (2) coated with
a plate of any one selectrd from Cu, Ni, Au, Cr, Zn, Pa, Pt, Rh, Fe, Co, Sn, Cd, Ru, and
alloys thereof formed by a wet plating method (lor example, refer to Patcnt Document
3). Howcver, in this technique, it is necessary to provide two thick plate-coated
layers, and to combine a dry plating method and a wet plating mcthod, and therefore it
is difficult to apply this technique to Al-based alloy-plated steel with no change.
[0007]
Tn addition, there has been proposed another technique for creating a hairline
appcarance on a highly corrosion-resistant Zn-based plated steel shcet, but it is not
possible to obtain high-class ease of design as that of stainless steel (for example, refer
to Patcnt Documents 4 and 5).
[Prior Art Document]
[Patent Document]
[0008l
[Patent Document 11 Japanese Unexamined Patent Application, First
Publicat~onN o. NO1 -3061 62
[Patent Document 21 Japanese Patent No. 2055570
[Patent Docun~cn3t 1 Japanese Patent No. 3934810
[Patent Document 41 Japanese Patent No. 4546848
[Patent Document 51 Japanese Patent No. 4757608
[Disclosure of the Invention]
[Problems to be Solved by the Invention]
100091
An object of the present invent~onis to provide Al-based alloy-platcd steel
having a hairline appearance which can be sinlilarly applied to the same uscs as the
uses oT stainless steel having a hairline appcarance.
[Measures for Solving the Problem]
[00 1 01
The present invention employs the following measures to achieve the object
by solving the above-described problems. That is,
(1) According to as aspect of the present invention, there is provided Al-based
alloy-plated steel having a hairline appearance in which hairlines are formed on a
surlace of a plated layer made up of Si and a remainder being Al and impurities, in
which, in the plated layer, a plated amount per single surrace of the plated layer is in a
range of 20 g/m2 to 100 g/m2; an amount of the Si in the entire plated layer is in a
range of 5 mass% to 12 mass%; a maximum amount olthe Si in a 2 pm-thick region in
a surface layer of the plated layer is in a range of 12 mass% to 24 mass%; and, in the
hairlines, a surface roughness Ra at a right angle to the hairlines is in a range of 0.3 pm
to 2.0 pm; PPI at a relerence level of 300 pin is 0; the PPI at a rekrence level or200
pin is less than 10; and thc lJPI at a reference level of 30 pin is 50 or more.
[0011]
(2) In the Al-based alloy-plated steel having a hairline appearance according
to the above-described ( I ), in a case in which the surface roughness Ra at a I ight a11glc
to the hairlines is in a range of 0.3 pm to 1.0 klm, the PPI at a reference level of 300 pin
may be 0; the PPI at a reference level of 200 pin may be 0; the PPI at a reference level
of 100 pin may be less than 10; and the PPI at a relerence level of 30 in may be 50 or
more.
100 121
(3) 111 the Al-based alloy-plated steel having a hairline appearance according
to the above-described (1) or (2), 1 nlg/m2 to 1000 mg/m2 ol a chemical conversion
trcatlnent layer may be present on the surface of the plated layer.
(4) 111 the Al-based alloy-plated steel having a hairline appearance according
to the above-describcd (1) or (2), a transparent film layer having a ihiclmess in a range
of 0.5 pm to 100 pm may bc prcsent on the surface of the plated laycr.
( 5 ) In the Al-based alloy-plated steel having a hairline appearance according
to the above-described (3), a transparent film layer having a thickness in a range of 0.5
pm to 100 pm may be formed on a surface of the chcmical conversion treatment laycr.
[Effects of the Invcntion]
100 131
The Al-based alloy-plated steel having a hairline appearance according to thc
above-described aspect has a favorable hairline appearance, and also has excellent
corrosion resistance and discoloration resistance, and thus can bc applied to the same
uses as the uses of stainlcss steel having a hairline appearance of the related art.
Furthermore, it becomes possible to supply the Al-based alloy-plated steel at a lower
price than expensive stainless steel.
[Brief Description of the Drawing]
[0014]
FIG. 1 is a view showing an overview of hairline finishing.
FIG. 2 is a view showing a relationship between a depth from a surface of a
plated layer and a concentration of Si.
[Embodiments of the Invention]
1001 51
Hereinafter, an embodiment of the present invention will be described in
detail.
[00 161
As steel having a hairline appearance, there is stainless steel that has been
subjected to hairline fini~hingb, ut stainless steel is expensive. Therefore, the prcsent
inventors paid attention to plated steel fiom the viewpoint of ensuring corrosion
resistance at a low cost. In addition, stainless steel has a high-class metal impression,
but has unsatisfactory brightness. Therefore, Al-based alloy plating was studied as a
plating type. A1 is an achromatic metal having a uniform hue and a high reflectivity.
In addition, Al is an active metal, but forms an extremely thin oxide film, and thus does
not immediately generate white rust unlike, for example, Zn. Therefore, the same
achromatic color as stailllcss steel can be attained at a low cost through the application
of the Al-based alloy-plated steel. While the rellectivity of stainless steel after mirror
finishing is approximately 70%, the reflectivity of the Al-based alloy-plated steel after
mirror finishing reaches 75% to 90%, and a bright achromatic color can be obtained
from thc Al-based alloy-plated steel rather than stainless steel.
[0017]
As the method for the surface treatment ofthe Al-based alloy-plated steel,
there are electroplating, hot dip plating, deposition, and the like. However, A1
electro-crystallizes only from a non-aqueous solvent, and thus electroplating is
industrially unsuitable. Deposition also has a problem oTa slow film-fornl~r~sgp eed,
and is thus industrially unsuitable. The method for the surface treatment of thc Albased
alloy plated steel is not particularly limited, but hot dip plating, which is a more
industrially-suitable method, is preferably used.
[0018]
Next, the reasons for lim~tingth e composition of the plated layer of thc Albased
alloy-plated steel will be described
YO0 191
Whcn hairline kinishing for stainless steel was cailied out on pure Al-plated
steel containing no Si, the ridge portions of hairlines were worn, or the hairlines
collapsed, and thus hairlines having a favorable appearance could not be obtained, and
there were portions through which an AI-Fe alloy layer was exposed. In addition,
therc was a problem of the occurrence of clogging in a grinding belt for hairline
finishing. The reasons for failing to obtain Savorable hairlines as described above can
be considered that the pure Al plated steel has a Vickers hardness of approximately 120
Hv, and is a soSt metal, and, in the case of the pure Al-plated steel, a hard and brittle
intermetallic compound (Al-Fe alloy layer) significantly grows between a base metal
(steel plate) and the plated layer. Sincc Si is a hard element having a Viclcers
hardness of approximately 1050 Hv, when an appropriate amount of Si is included in
the plated layer, the hardness of the plated layer increases. In addition, the addition of
Si until an eutectic composition is obtained decreases the liquidus-line temperature of a
A1-Si system, and is thus effective for the control of the growth of an AI-Fe alloy layer.
To increase the hardness of the plated layer and exhibit an effect that supprcsscs thc
growth of the A1-Fe alloy layer, the lower limit of thc amount of Si in the entire plated
layer is preferably 5 mass%.
[0020]
When Si is added to the plated layel; the chromaticity and brightness of the
Al-based alloy-plated steel changes, and the appearance gradually becomes more dull
aq the amount of Si in the platcd layer increases. The reason therefor is that AI-Si is
an eutectic alloy, and, in particulal; whcn the composition exceeds an cutectic
composition oSAI-12.6 mass% Si, the reflectivity is lower than that ofAl, and p~imary
Si crystallizes, and thus the brightness significantly decreases. Furthermore, when the
composition exceeds the cutectic composition, the liquidus-line temperature increases,
and thus the growth of an Al-Fc alloy layer is, inversely, accelerated. Therefore, the
upper limit of the amount of Si in the entire plated layer is preferably 12 mass% in
consideration of changes in an actual operation as well. Furthermore, since it is
confirmed from the measurement results that the chromaticity tends to shift toward the
blue side as the amount of Si in the platcd layer increases, the amount of Si in the
entire plated layer is preferably set to 12 mass%.
[0021]
Amount of ihe plated layer suitable for carrying out the hairline finishing is
preferably in a range oC 20 girn2 to 100 g/m2 per single surface of thc base mctal (stcel).
Particularly, amount of the plated layer is preferably in a range of 40 g/m2 to 80 g/m2
per single surface of the base metal. 111 a case in which amount of the plated layer is
less than 20 g/m2, the plated layer is thin, and therefore the corrosion resistance is
insufficient, and unprocessed steel is easily cxposed during the hairline finishing. Jn
a case in which amount of the plated layer exceeds 100 g/m2, the plated layer becomes
too thick, and therefore a plated laycr having a uniform appearance cannot be obtained,
and the plated layer becomes easily peelable, which is not preferable Trom the
viewpoint of cost. Thcrefore, amount of the plated layer is preferably in a range of 20
g/m2 to 100 g/in2.
[0022]
The maximum amount of Si in a 2 pm-thick region in a surface layer of the
platcd layer is preferably in a range of 12 mass% to 24 mass%. Hereinafter, the
reasons therefor will bc described.
To form beautiful hairlines on thc sluface of the plated layer, it is necessary to
reinove a solidified pattern (so-called spangle) remaining on the surfacc of thc plated
laycr in a process [or form~ngth e plated layel ?'hcrcfore, it is necessary to cany out
a flattening treatment on the plated layer before the formation of the hairhnes so that
the surface roughness RR ofthe plated layer reaches 0.5 pm or less.
The present inventors encountered a problem in that, when the flattening
treatment is carried out on the plated laycr; in a case in which hairlines are formed after
the surface layer of the plated laycr is ground up to a depth of approximately 2 pm
'~ from the surface, the surrace of the plated layer discolors (that is, the discoloration
resistance degrades) as time elapses.
[0023]
As a result of intensive studies regarding the cause therefor, the present
inventors found that, in thc surface layer (an area up to a depth of approximately 2 pm
from thc surface) of the plated layer, the concentration of Si reaches a maximum of
approximately double thc bulk concentration of Si (the concentration of Si in an area
deeper than 2 pm from the surface) as shown in FIG. 2. FIG. 2 shows an example of a
curvc of the concentration of Si in a casc in which the bulk concentration of Si (the
base concentration of Si) is 10%. That is, it is considered that, when a Siconcentrated
layer (the 2 pm-thick region in the surfacc layer of thc plated layer) as
described abovc is removed during the flattening treatment of the plated layel; the
discoloratio~ri esistance tlcgrades.
Therefore, based on thc results from the above-described studies, the present
inventors round that, when hairlines are formed in a statc in which the Si-concentrated
layer remains, the discoloration resistance improves as long as the maximum amount
of Si in the Si-concentrated layer is in a range ol' 12 mass% to 24 mass% (refer to
examples described below for thc details).
Thererore, the maximum amount of Si in the 2 pm-thick region (the Siconcentrated
layer) in the surface laycr ol'the plated laycr is preferably in a range of 12
mass% to 24 mass%. Meanwhile, to let the Si-concentrated layer remain, a
preliminary skin pass (mild rolling carried out using a roll having a low degree of
roughness) is preferably employed as the flattening treatment of the plated layer.
100241
To form hairlines having an excellent appearance on the surface of the Albascd
alloy-plated steel (that is, the surface of the plated layer), the surface roughness
Ra at a right angle (in a C direction) to the hairlines is set in a range of 0.3 pm to 2.0
pm, and is preferably set in a range of 0.3 pm to 1.0 pm. When the surface roughness
Ra in the C direction is less than the lower limit, the hairlines become invisible, and the
hairline finishing becomes useless. In addition, inversely, when the surface roughness
Ra exceeds the upper limit, the hairlines become too coarse, and thus beautiful
hairlines are not obtained, the ease of design of the hairlines is impaired, and thus the
commercial value decreases. The surface roughness Ra was measured with a
refcrence length ol0.8 mm according to the measurement method regulated in JIS
B060 (1997).
[0025]
In a case in which the surface roughness Ra at a right angle to the hairline is
in a range of 0.3 pm to 2.0 pm, it is preferable to set the number of pealcs (P1'1: pealts
per inch) at a reference level of 300 pin to 0; to set the PPI at a reference level of 200
pin to less than 10; and to set the PPI at a reference level of 30 pin to 50 or more. For
the reference level, a method was elnploycd in which, on the basis of SAEJ 91 1, one
peak is added when ihe peak exceeds a negative rcference level -H and then exceeds a
positive reference level -1-13.
[0026]
In a case in which the reference level is 200 pin or more, wllcn thc IJQI
exceeds the above-described numeric valuc, the bare steel is exposcd in some portions,
or the plated layer becomes locally thinner in some portions, and it is likely that the
corrosion resistance is adversely arfected. Meanwhile, in a case in which the PPI at a
reference level of 30 pin is less than 50, the hairlines become invisible.
[0027]
In a case in which the surface roughness Ra at a right angle to the hairline is
in a range of 0.3 pm to 1.0 pm, it is preferable to set the PPI at a refcrence level of 300
pin to 0; to set the PPI at a reference level of 200 pin to 0; to set the PPI at a reference
level of I00 pin to less than 10; and to set the PPJ at a reference level of30 pin to 50 or
more. This is for the same reasons as the case in which the surface roughncss Ra is in
a range of0.3 pm to 2.0 pm. That is, in a case in which the reference level is 100 pin
or morc, when the PPI exceeds the above-described numeric value, the bare steel is
exposed in some portions, or the plated layer becomes locally thinner in some portions,
and it is likely that the corrosion resistance is adversely affected. Meanwhile, in a
case in which the PPI at a reference level of 30 pin is less than 50, thc hairlines become
invisible. Hairlines regulated by the above-described surface roughness Ra and PPI
have a hairline appearance imparting a soft impression. in addition, the amount of the
hairlines ground is declcased, and therefore the Al-based alloy-plated steel bccomes
superior in terms of continuous operability such as the mitigation of clogging in the
polishing belt. The number of peaks (PPI) was measured according to the regulation
of SAEJ 91 1-1986, and the measured lengths were expressed in inches
To form hairlines satisfying the above-described requirements of the surface
roughness Ra and the numbcr of pealis (PPI), the hairline finishing is preferably carried
out using a belt sander (polishing belt) of approximately #l50 to #320. Alternatively,
a method in which hairlines are transferred from a roller having a hairline pattern
formed on the surface may be employed. The hairline processing is only required on
a surface of the Al-based alloy-plated stcel which forms the surface of a processed
product from the viewpoint of the ease of design, but the hairline processing may be
carried out on both surfaces.
100291
It is preferable to carry out a primary anti-rust treatment by carrying out a
chromate treatment or a chromate-free trcatment on the plated layer after the hairline
processing is carried out. Tne primary anti-rust trcatment, through which an anti-rust
film layer is formed by a chromate treatment or a chromate-free treatment, is carried
out after the hairline finishing is carried out on the platcd layer for the purposc of
preventing discoloration and improving the adhesion of a transparent film layer
described above. In the case of the chromate treatment, for example, a chromate
treatment in which a chromate treatment solution including chromic acid and a reaction
accelerator as main components is used can be applied, and the chromate plated
amount is set in a range of 1 mg/m2 to 200 mg/m2. In a case in which the chromate
plated amount is less than 1 mg/m2, a sufficient anti-rust cffcct cannot be obtaincd. In
addition, in a case in which the chromate plated amount exceeds 200 mglm', the
hairline finishing becomes less prominent, the anti-rust effect is saturated, and thus the
cost increases in an economic sense. In addition, similar to the chromate treatment, in
the chromate-free treatment (non-chromate treatmcnt) as well, it is possible to carry
out the primary anti-rust treatment.
[0030]
Examples of the treatment solution that can be used for the chromate-free
treatmcnt (non-chromate treatment) includc trcatment sol~itionsc ontaining no
hexavalent chomiusn, which is harmful to the cnvirollment, such as trcatment
solutions containing salt? of ZI; l i , or the like, treatment solutions containing a silane
coupling agent, and the like. In this chromate-frce treatmcnt, a chromate-free
treatment layer (chcmical conversion layer) which contains Ti, Zr, P, Cc, Si, Al, Li, and
the like as main components, but does not contain chromium is formed. The plated
amount of the chromate-frec treatmcnt layer is preferably set in a range of 1 mg/m2 to
1000 rng/m2. In a case in which tl~ep lated amount of the chromate-free treatment
layer is lcss than 1 mg/m2, a sufficient anti-rust effect cannot be obtained. In addition,
in a case in which the platedamount of the chromate-free treatment layer exceeds 1000
mg/rn2, the hairline finishing becomes less prominent, the anti-rust effcct is saturated,
and thus the cost increases in an economic sense.
[003 11
In addition, when the Al-based alloy-plated steel is subjected to the hairline
finishing, and then is left to stand in the atmosphere, the plated surrace is oxidized and
discolored. When the plated surface is discolored, the hairline finishing becomes less
promincnt, and thus the appearance of the hairlines is impaired. Furthermore, the Albased
alloy-plated layer is lilcely to be scratched when the layer collides with a hard
substance. Therefore, when a transparent resin film layer is formed in a thrclmess in a
I
langc of 0.5 pm to 100 pm on the plated surface that has been subjected to the hairline
finishing, it is possible to improve the discoloration resistance or the scratch resistance.
The transpalent resin film layer can bc formed using a well-lcnown painting method
such as the use of an organic clear paint. Specific examples of the organic clear paint
includc alkali-based printing clear paints, urethane-based clear paints, epoxy-based
clear paints, polyester-bascd clcar paints, polyethe1 sulfo~ie-basedc lear paints,
melamine alkyd-based clear paints, and the lilie. A mixture of' the above-described
palnts may also be used. Specific exanples of the method Tor painting the organic
clear paint include a roll coating method, a curtain coating method, a spray gun method,
an elcctroslatic method, and the like. Among the above-described methods, the roll
coating method and the curtain coating method arc preferred.
Meanwhile, the above-described transparent resin film layer may be directly
formed on the surface of the plated layer, or may bc formed on the surface of a
chemical conversion treatment layer (lor example, a chromate-free treatment layer or
the like) that is formed on the surface of the plated layer.
[Example]
[0032]
Irereinafter, the present invention will bc described in detail with the use of
cxampies.
[0033]
A low-carbon steel sheet having a sheet thickness of 0.6 mm was used as a
raw plating sheet. A heat treatmcnt, an annealing treatmcnt, and a plating trcatment
are carried out on the raw plating sheet in a non-oxidizing furnace-type continuous hot
dip plating line, thereby forming a plated layer on the raw plating sheet. The
annealing atmosphere contains 10% of hydrogen and 90% of nitrogen, and thc dew
point was set to -30°C. The annealing tcmperature was 730°C and the annealing
time was three minutes. The plating bath composition was adjusted hy adding Si to
Al. The plating bath tcmperature was set to the liquidus-line temperature of each
plating composition+20"C. The raw plating sheet was immerscd in thc plating bath
for two seconds, and then the platedamount was controlled using a nitrogen gas wiping
method.
100341
After the formation of the plated layel; the surface roughness Ra was set to 0.5
pm by carrying out a flattening treatment using preliminary rolling, and then hairline
finishing was carried out under conditions of a threading speed of0.25 mtsecond and a
polishing time of three seconds using belt sanders having different polishing paper
numbers. Jn addition, the influcnces on the PPIs at the reference levels of 300 pm
and 200 pm were investigated by changing the press pressure for the polishing paper
numbers #I20 and #150. The surface roughness (Ra) at a right angle to the hairlines
and the number of peaks (PPI) were investigated using a roughness gauge. When the
1'PI failed to satisfy the present invention example at a certain rererence level, the
measurement was not carried out for other referencc levels, and "-" was given in the
table. The damage state of the plated layer was investigated on the basis of the antirust
state after 24 hours of a salt splay test of JlS 2233 1, and a case in which lust was
observed in recess portions betwccn the hairlines was evaluated as Fail. The results
are described in Table 1.
[0035]
As described in Table 1, Nos. 4 to 7 formed highly corrosion-resistant plated
steel which satislied the conditions of thc surface roughness (Ra) and the lnunber of
peaks (PPI), and had a bcautiCu1 hairline appearance. Nos. 4 and 5 are suitahlc for a
case in which sharp sharpness is desired, and Nos. 6 and 7 are suitable for a case in
which a slightly soft appearance is desired. In addition, in Nos. 4 and 5, the belt
sander was gradually clogged whcn the threading distance exceeded 500 n ~a,n d a
slight attention was required during a continuous operation.
100361
On the contrary, Nos. 1 and 2 in which the hairline treatment was carried out
using the belt sander of #120, and No. 3 in which the hairline treatment was carried out
using the belt sander of #I50 at a high press pressure included deep hairline scratches,
and rust was observed in hairline recess portions. For No. 8, while the hairline
finishing was carried out, the belt sander (#500) was too fine, and thus the requirement
of hairlines regulated by the present invention was not satisfied, and it was not possible
to clearly observe hairlines in the appearance. The above-described test results show
that only the plated steel satisfying the requirements regulated by the present invention
formed plated steel having a beautiful hairline appearance.

[0038]
Next, plated steel sheets including plated laycrs having a variety of
compositions were produced, plated, and then flattened using preliminary rolling so as
to obtain a surlace roughness Ra of 0.5 pm. Then, hairline finishing was carried out
under conditions of a threading speed of 0.25 mtsecond, a polishing time olthree
seconds, and a press pressure of 0.2 Ml'a using a belt sander having a polishing paper
number #180. At this time, the hairline appearance and thc dcposition state of
grounds were investigated. The results are described in Table 2. Nos. 8 to 15 had
the plating composition regulated by the present invention, and favorable results were
produced in both the hairline appearance and the glounds on the belt sander, that is,
corrosion resistance. On the other hand, Nos. 7 and 16 were plates having a
composition dilferent from the composition regulatcd by the plesent invention, and the
value of the surface roughness satisfied the value regulated by the present invention,
but it was not possible to clearly observe the appearance of the hairlines, and the
generation of grounds and the corrosion resistance were poor. Thc rcasons for the
appearance of the hairlines not being clearly observed are considered to be the
generation of the grou~idsa nd the shear drop olthe belt sander.

[0040]
Next, plated steel sheets having a variety of amounts of the plated layer wcre
produced, plated, and then flattcned using preliminary rolling so as to obtain a surface
roughness Ra of 0.5 pm. Then, hairline finishing was carried out under conditions of
a sheet threading speed of 0.25 m/sccond, a polishing time of thrcc seconds, and a
press pressure oS0.2 MPa using a belt sander having a polishing paper number #180.
The rcsults are dcscribed in Table 3. Nos. 18 to 24 had the plated amount regulated
by the present invention, and favorable results were produced in both the haitline
appearance and the grounds on the belt sandcl; that is, corrosion resistance. On the
other hand, No. 17 was a plate having a plated amount less than that of amount
rcgulated by the present invention, and the value of the surface roughness sat~sfiedth e
value regulated by the prcsent invention, but the corrosion resistance thereof was poor.
No. 25 had a great plated amount, and a poor appearance.
SST: Salt Spray Test
[0042]
Furthennore, a chromate treatment, a chromate-free treatment, a clear painting
treatment, and a corrosion resistance evaluation were carried out using a plated steel
sheet having a composition of A1 and 10 mass% Si. The results are described in
Tables 4 and 5. In the chromate treatment, a solution of 100 gll of chromic acid was
applied, and then was dried in an air-heating furnace (60°C) for 30 seconds. In the
chromate-free treatment, a chemical agent made up of ammonium zirconium carbonate,
cobalt nibate, silica, and ammouiuin phosphate was applied, and then was dried in an
air-heating furnace (60°C) for 30 seconds. Furthemlore, a melamine alkyd-based
clear paint (solvent-based) and a urethane-based clear paint (water dispersion-based)
were applied, and were heated to sheet temperatures of 220°C (melamine alkyd-based)
and 150°C (urethane-based).
[0043]
The corrosion resistance of a flat surface portion and the discoloration
resistance were evaluated on the basis of the amount or white rust generatcd after 240
hours of a salt spray test of JIS 22331 to be A (discolored, the generation of white rust:
1% or less) and B (the generation of white rust: 10% or more). A crosscut portion
was evaluated on the basis of a swollen fabric after 240 hours of a salt spray tcst, and
was determined to be AA: less than 2 mm, A: less than 5 mm, and B: 5 mm or more.
[0044]
'The scratch resistance was evaluated using the pencil hardness of JIS K5600.
The test was repeated twice, and, in a casc in which the determinations wcre diffcrcnt
in the two-time tests, the test was carried out again, the hardness scale was decreased
up to a hardness at which the steel sheet was not scratched, and the steel sheet that was
not sclatchcd at 2 H or more was detelmined as Pass Meanwhile, the orde~o f the
pencil hardness is (son) 6B-HB-6H (hard).
[0045]
At levels satisfying the chemical conversion treatment and the painting
requirements regulated by thc present invention, the corrosion resistance, thc
discoloration resistance, and the scratch resistance wcre favorable in both the flat
surface portion and the crosscut portion.
1
Note I
-
-
-
No.
26
27
-
28
29
3 0
3 1
32
33
34
Hairlines
Polishing
paper
number
#I80
#I 80
#I80
#I80
#I80
#I80
#I 80
#I80
#I80
SST
Flat
surface
portion
B
A
A
A
A
A
B
A
A
Scratch
resistance
pencil test
----
--
24011
crosscut
B
A
A
A
A
A
B
A
A
[Table 41
Present
Invention
Example
Present
Invention
Example
Preseiii
Invention
Example
Present
Invention
Example
Present
Invention
Example
Present
Invention
Example
Present
Invention
Example
Present
Invention
-Exam-ple
~ ~ ~ , ~ ~ t i ~ Present
'Iated
amount
g/m2
50
50
50
50
50
1
50
50
50
--
50
Chemical
Type
Chromate
Chromate
----
Chromate
Chromate
Chromate
Chromate
Cliromatefree
Chrsmatefree
fraa
Chromate-
Plate
Composition
Si mass%
10
---
10
10
10
10
10
10
---
10
10
Transparent
Type
. ~
---
--------
treatment layer
Plated
amount
mg/m2
0.8
1
5
10
15
20
-------
0.8
I
5
film layer
Thickness
Pm
----
--------

SST: Salt Spray Test

[0048]
Next, plated steel sheets for which the concentration of Si in the bath was
changed in a range of 5% to 12% were produced, plated, and then flattened using
preliminary rolling. At this time, the surface roughness Ra was changed in a range of
0.3 pm to 1 pm by changing the rolling force. After that, conditions under which a
beautiful hairline appearance was obtained were searched by setting the sheet
threading speed to 0.25 mtsecond, and changing the polishing time in a range of 3
seconds to 30 seconds using a belt sander having a polishing paper number HI 80. In
a case in which the surface roughness after the flattening treatment was great, beautiful
hairlines were not obtained until the steel sheet was polished for a long period oC time.
In addition, the thicltness of the plate ground during the hairline trcatment was
obtained by measuring the weights per unit area before and after the hairline treatment.
The results are described in Table 6. In Nos. 64 to 66, 68,69,71, and 72, the surlace
roughness after the flattening treatment was 0.5 pm or less, and the thickness of the
plated layer ground to obtain beautiful hairlines was as small as 0.5 pm, and therefore
the above-described specimens were plated steel sheets including a Si-concentrated
layer having a maxinlr~ilai mount (12 mass% to 24 mass%) of Si rcgulated by Lhe
present invention, and the specimens were not discolored over time (passed
discoloration resistance). On the other hand, Nos. 61 to 63, 67, and 70 were plated
steel sheets including a Si-concentrated layer having a maximum amount (less than 12
mass%) of Si that is outside the regulation by the present invention, and the specimens
were discolored over time (failed discoloration resistance).
Whether the discoloration passes or fails was determined on the basis of the
color dilference measurement AE. The color difference measurement AE is a value
defined by the following equation (1).
AE={(AL)~+(A~)~+'(I2A .,~. ()1~)}
Here, AL, Aa, and Ab indicate the difference in the CIE1976 brightness L
between two object colors in the Lab expression system regulated by J1S Z 8729 and
the difference in the color coordination a and b before and after the test. The
evaluation criteria are as described below.
Pass: AEi2, No change or variation in hue is visually observed.
Fail: AE>2, A change or variation in hue is visually observed.
30 pin
170
160
150
130
110
90
150
130
110
I 50
Grinding
thickness
(pm)
4
2
1
0.5
0.3
0.2
1
0.5
-
0.3
1
[Table 61
Discoloration
resistance
Fail
Fail
-
Fail
Pass
Pass
Pass
Fail
Pass
Pass
Fail
Surfaces
roughness
after
flattening
treatment
( ~ m )
1
0.8
0.6
0.5
0.4
ppp
0.3
0.6
No.
61
62
63
Comparative
Example
Comparative
Example
Comparative
Example
Present
Invention
Example
Present
Invention
Example
Present
Invention
Example
Comparative
Example
Present
Invention
Example
Present
Invention
Example
Comparative
Polishing
paper
number
#I80
#I80
#I80
#I80
#I80
#I80
#I80
#I80
#I80
#I80
Mass of Si
in Siconcentrated
layer %
(maximum
value)
10
11
-
11.5
12
18
24
11.5
Concentration
of Si
(%I
10
10
10
Ra
( ~ m )
0.8
0.8
-
0.8
0.8
0.8
----
0.8
0.8
0.8
0.8
0.8
Plated
amount
(g'm2)
50
50
50
A I
50
50
50
50
50
50
50
64) 10
0.4
0.6
300
pin
0
0
0
0
0
0
0
0
0
0
65
-
I 66
67
68
69
70
18
11.5
200
pin
E
8
-
8
7
7
6
8
7
----
7
8
10
10
12
12
12
5

[OOSO]
Rased on the above-described results, it was contirmcd that the present
invention example has a beautiful hairline appearance, and has excellent corrosion
resistance, discoloration resistance, and scratch resistance.
[Industrial Applicability]
100s 11
The Al-based alloy-plated steel of the prcscnt invention having a hairline
appcarancc enables to provide a low-cost material having excellent corrosio~r
resistance, discoloration resistance, and ease of design to uses such as surkce layer
materials for electrical devices, interior materials or exterior materials for buildings
and vehicles, and the like.
[Brief Description of the Reference Symbols]
[OOSZl
1 : CONTACT WHEEL
2: IDLERROLL
3: POLlSHING BELT
4: UNCOIL1:It
5: COILER
6: METAI, STRIP
[Document Type] CLAIMS
[Claim I]
Al-based alloy-plated steel having a hairline appearance in which a hairline is
formed on a surface of a plated laycr made up of Si and a remainder being Al and
impurities,
wherein, in the plated layer,
a plated amount per single surface of the plated layer is in a range of 20 g/m2
to 100 g/m2;
an amount of thc Si in the entire plated layer is in a range oS5 mass% to 12
mass%;
a maximum amount of the Si in a 2 pm-thick region in a surface layer of the
plated layer is in a range of 12 mass% to 24 mass%; and,
in the hairline,
a surface roughness Ra at a right angle to the hairline is in a range of 0.3 pm
to 2.0 pm;
PPI at a reference level of 300 pin is 0;
the PPI at a rcfcrrencc lcvcl of 200 pin is less than 10; and
the PPI at a reference level of 30 pin is 50 or more.
[Claim 21
The Al-based alloy-plated steel having a hairline appearance according to
Claim 1,
wherein, in a case in which the surface roughness Ra at a right angle to the
hairline is in a range of 0.3 pm to 1 .0 pin,
the PPT at a reference level of 300 pin is 0;
the PPI at a reference level of 200 pin is 0;
the PPI at a reference level of 100 ,sin is less than 10; and
the PPI at a reference level of 30 pin is 50 or more.
[Claim 31
The Al-based alloy-plated steel having a hairline appearance according to
Claim 1 or 2,
wherein 1 mg/m2to 1000 mg/m2 of a chemical co~lversiontr eatment layer is
present on the surface of the plated layer.
[Claim 41
The Al-based alloy-plated steel having a hairline appearance according to
Claim 1 or 2,
wherein a transparent film layer having a thickness in a range of 0.5 pm to
100 pm is present on the surface of the plated layer.
[Claim 51
The Al-based alloy-plated steel having a hairline appearance according to
Claim 3,
wherein a transparent film layer having a thickness in a range of 0.5 pm to
100 LLrn is formed on a surface of the chemical conversion treatment layer.