JPH09155404A - Stainless steel plate excellent in polishability and its manufacturing method - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To reduce the number of times of polishing for finishing the surface of a steel plate to the target surface texture by polishing it with a cloth or the like, and to improve the polishing efficiency. And a method of manufacturing the same. SOLUTION: The center line average roughness (R
a) is 0.15 μm or less, the ratio of center line peak height (Rp) to center line valley depth (Rv) (Rv / Rp) is 1.0 or less, and center line valley depth is 0.5 μm or less. As a stainless steel plate having excellent polishing property, which is characterized by being a work roll used in at least the final rolling pass of a cold rolling mill and a roll in contact with the work roll, the polishing marks on the roll surface are in the roll axial direction. The center line average roughness (Raθ) in the roll circumferential direction is 0.05 to 0.3 μm, and the work roll diameter is less than 150 mm. A method for producing a stainless steel sheet having excellent polishing properties, which comprises pickling and further temper rolling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stainless steel sheet having excellent abrasiveness and a method for producing the same, and more specifically, it can efficiently polish a surface of a cold rolled stainless steel sheet to a target surface texture. The present invention relates to a stainless steel plate and a method for manufacturing the same.

[0002]

2. Description of the Related Art As stainless steel sheet products, JIS products include BA products, 2B products, and polishing products. Abrasive products are made of BA products or 2B products, and are grinded or draped to be used for hairline processing and various surface finishing counts. In this case, if the cold-rolled steel sheet to be polished has poor smoothness, and if there are many surface defects, uneven polishing occurs. Therefore, it is necessary to increase the number of times of polishing to obtain the target surface quality. Among them, it was not easy to finish it to a mirror surface, which requires extremely high gloss.

[0003] In the work of polishing the quilt, if a coarse quilt having a small count is used, abrasions are caused by the quilt.
It is performed using a fine cloth such as No. 0 or No. 2000. Therefore, the polishing amount in the thickness direction of the steel sheet is extremely small, and is up to about 0.5 μm. On the other hand, the surface of the stainless steel plate to be polished has an average roughness Ra of 0.05 to 0.2 μ.
m, and the maximum roughness Rmax is 0.5 to 2.0 μm. Such roughness is due to residual surface irregularities during pickling of hot-rolled steel strip before cold rolling, oil pits (fine oil pools) during cold rolling, and roll transfer flaws (transfer flaws of roll polishing eyes, Indentation),
It is caused by a flaw defect such as a scratch, an etch pit due to annealing / pickling after cold rolling, and a recess mainly. Therefore,
In order to remove these defects by polishing, it is necessary to polish and remove all the convex portions (trapezoidal flat surface portions) that occupy most of the surface, which increases the number of times of polishing and the time required for polishing becomes enormous.

Therefore, various measures have been taken to reduce the irregularities on the surface of the steel sheet. Japanese Unexamined Patent Publication (Kokai) No. 6-170432 discloses a method for reducing surface irregularities during pickling of hot-rolled steel strip before cold rolling, and Japanese Unexamined Patent Publication (Kokai) No. 7-1001 and No.
Japanese Patent Publication No. 96309 discloses a method of reducing the oil pit during cold rolling.

[0005]

However, Japanese Patent Application Laid-Open No.
The method disclosed in Japanese Patent No. 70432 requires a major facility remodeling, and the surface finish state considerably affects the rolling conditions in the subsequent cold rolling. On the other hand, in the case of the method disclosed in Japanese Unexamined Patent Publication No. HEI 7-1001, fine concave defects on the surface are reduced and the image clarity is improved, but the depth of the concave is still large and the reduction in the number of polishing is slight. , Not satisfied. In addition, JP-A-5-963
No. 09 publication, the method of rolling with a roll in which the direction of the grain on the roll surface is the roll axis direction on average is
Originally, when rolling with a large roll diameter where no gloss is obtained, this is a rolling method to obtain a gloss equivalent to that of rolling using a small diameter roll, but the gloss and smoothness are better than when using a small diameter roll. The absolute value of is not necessarily high.

As described above, various improvements have been made in the past, but all of them have the effect of reducing the surface roughness and increasing the smooth surface, but have not significantly improved the polishing property. Further improvement was needed.

The present invention is capable of reducing the number of times of polishing for polishing the surface of a steel sheet with a cloth or the like to finish it to a target surface texture, and is capable of improving the polishing efficiency, and a stainless steel sheet having excellent polishability. It is intended to provide a manufacturing method.

[0008]

Means for Solving the Problems The present inventor has obtained the following findings as a result of repeated experimental studies on a method of reducing surface recess defects of a stainless steel plate before polishing during cold rolling.

1) When cold rolling is performed by using a small-diameter roll having a diameter of less than 150 mm, which is oriented in the axial direction of the roll surface, as a work roll, cold rolling is carried out, as compared with the case where a normal roll is used. The number of defects in the recesses is reduced and the depth of defects is reduced.

2) The life of the abrasive grain in the axial direction of the work roll is influenced by the surface condition of the roll in contact with the work roll, and the polishing surface is extended in the axial direction on the roll surface in contact with the work roll. can do.

3) When cold rolling is performed with a work roll having a grain in the axial direction, the amount of plastic deformation in the extremely surface layer of the steel sheet becomes large, and the number of recrystallization starting points during annealing performed after cold rolling increases. Since the crystal grains in the extreme surface layer are small, the increase in roughness due to acid roughening such as grain boundary groove corrosion that occurs during the subsequent pickling is reduced.

The present invention has been completed on the basis of such findings, and the gist is that "the center line average roughness (Ra) of the surface of the stainless steel plate is 0.15 μm or less and the center line peak height (Rp).
And a centerline valley depth (Rv) ratio (Rv / Rp) of 1.0 or less, and a centerline valley depth of 0.5 μm or less, and a stainless steel plate with excellent polishability, and As a work roll used for at least the final rolling pass of the rolling mill and a roll that is in contact with the work roll, the polishing marks on the roll surface are in the roll axis direction, and the centerline average roughness (Raθ) in the roll circumferential direction is Polishing characterized by cold rolling, annealing, if necessary pickling, and temper rolling of a stainless steel plate using a roll having a diameter of 0.05 to 0.3 µm and a work roll diameter of less than 150 mm. The method of manufacturing a stainless steel sheet having excellent properties ”.

Here, the center line average roughness (Ra), center line peak height (Rp) and center line valley depth (Rv) are JISB.
0601.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The stainless steel sheet of the present invention and the limiting conditions of the method for producing the same will be described in detail below.

Generally, a surface-polished stainless steel plate is obtained by cold rolling a hot-rolled steel plate into a thin steel plate and annealing it.
When scale is generated on the surface of the steel sheet, it is pickled to remove it, and then to impart mechanical properties 1
The temper rolling is performed at a light reduction rate of about 10%, and the surface is polished as the final step to finish to the target surface properties for manufacturing. Note that the surface polishing is performed by the steel plate manufacturer and may be shipped as a polished product, but in many cases the user finishes polishing.

The stainless steel sheet of the present invention defines the surface roughness of the stainless steel sheet before polishing, that is, the steel sheet after temper rolling. In addition, the manufacturing conditions are those that stipulate the conditions in cold rolling, and after cold rolling under the conditions, the steel sheet is subjected to normal annealing, if necessary, pickling, and temper rolling. The surface roughness of the steel sheet can be obtained.

The reasons for limitation in the stainless steel sheet and the method for producing the same according to the present invention will be described below.

Center line average roughness (Ra), center line peak height (Rp), center line valley depth (R
v) ratio (Rv / Rp) and center line valley depth: In order to reduce the number of polishing times during polishing, it is most important to set the center line valley depth Rv to 0.5 μm or less. 0.
By setting the thickness to 15 μm or less, it is possible to reduce the number of polishing times of the conventional steel sheet by more than 1/2. For example, the Rv of the conventional steel sheet is 0.8 to 1.5 μm, but the polishing depth per time is about 0.2 μm, and the target gloss (Gs 20 °) is 100.
When it was set to 0, polishing was required 4 to 5 times. However, if Rv is 0.5 μm or less, the number of polishing can be set to 2 times.

The reason why Rv / Rp ≦ 1 is set is to reduce the polishing allowance required for removing the recess, and when it exceeds 1, it becomes difficult to reduce the number of polishing steps. By setting the roll mesh in the roll axial direction, Rv / Rp ≦ 1 is obtained.

Using an axially polished roll, Rv of 0.
When the thickness is 5 μm, the range of Ra is 0.1 to 0.15, so the upper limit of Ra is set to 0.15 μm.

FIG. 1 is a diagram showing the surface roughness of a steel plate.
FIG. 7A is a diagram showing a surface roughness state in the case of Rv / Rp ≦ 1, and FIG. 8B is a diagram showing a surface roughness state in the case of conventional Rv / Rp ≧ 1.

Centerline average roughness (Ra), centerline mountain height (R
p) and the center line valley depth (Rv) are as shown in FIG.

Polishing is carried out from the surface layer of the steel plate, and the convex portions are ground and worn away faster. Therefore, even if the surface roughness is the same, the volume required for polishing and removing until the recesses disappear is (a)
As shown in, the surface with many protrusions, that is, the height of the center line peak (Rp)
And the ratio of center line valley depth (Rv) (Rv / Rp) is smaller,
It is smaller than the conventional surface with large Rv / Rp shown in (b).

Further, the smaller the center line average roughness (Ra) and the center line valley depth (Rv) of the polishing volume, the easier the polishing.

Direction and Surface Roughness of Polished Grains of Work Roll Used for Cold Rolling: FIG. 2 is a view for explaining the direction of roll-polished grain (roughness of roughness), and FIG. The figure which shows the direction of the grind of a roll, (b) is a figure which shows the direction of the grind of the roll used for the manufacturing method of this invention. The steel plate 2 is rolled by the roll 1 having the polishing marks 4.

As shown in FIG. 2A, in the conventional roll, the angle α between the polishing grain and the roll circumferential direction (the direction perpendicular to the roll axis) is approximately 0 °, and the roll polishing grain is in the roll circumferential direction. Parallel. On the other hand, in the roll used in the manufacturing method of the present invention, α is approximately 90 ° as shown in FIG. That is, the roll polishing meshes are parallel to the roll axis direction.

The reason why the roll-polished grain is in the roll axial direction will be described below.

FIG. 3 is a cross-sectional view of a roll bite portion for explaining that there is slippage between the roll surface and the steel sheet surface in cold rolling. As shown in FIG. 3, when the steel plate 2 is rolled from the thickness t ₁ to t ₂ in the X direction by the work roll 1, the point where the rolling speed v ₁ of the steel plate 2 is the same as the roll peripheral speed V is the neutral point. It is called (N point) and forward from N point (
The roll-out side) indicates the advanced region, that is, the region where the steel plate speed is faster than the roll peripheral speed where V <V ₂ . Further, the area from the point N to the rear (roll-in side) is referred to as the reverse travel area. That is, it indicates a region where the steel plate speed is slower than the roll peripheral speed where V ₁ <V. In either case, relative rolling occurs between the roll and the rolled material during rolling except for a moment at point N.

FIG. 4 shows the contact state of the steel plate surface with the roll-polished eyes and the change of the steel plate surface due to relative sliding when cold rolling was performed using a conventional roll whose polishing eyes were in the roll circumferential direction. It is a figure for explaining. (A) is a cross-sectional view showing a contact state between the roll and the steel plate in the width direction,
(B) is a figure which shows the roughness curve of the rolling direction of the steel plate surface after rolling. (C) is a figure which shows the roughness curve of the plate width direction of the steel plate surface after rolling.

As shown in FIG. 4 (a), since the recessed portion of the work roll is not in contact with the steel plate, an oil pit is generated on the surface of the steel plate at that portion, and a valley is formed. Also,
The place where the roll skin is transferred becomes a valley. 4 (b),
The state appears in (c).

FIG. 5 shows the contact state between the steel plate surface and the roll-polished eyes and the steel plate surface due to relative sliding when cold rolling is carried out by a roll whose abrasive grain direction used in the manufacturing method of the present invention is the roll axis direction. FIG. 6 is a diagram for explaining a change in
(A) is sectional drawing which shows the contact condition in the board width direction of a roll and a steel plate, (b), (c) is a figure which shows the board width direction of the steel plate surface after rolling, and the roughness curve of a rolling direction, respectively. Is.

During rolling, at the roll bite portion other than the neutral point, the roll-polished convex portions slide on the surface of the rolled material in the rolling direction, and smooth portions are formed in the slipped portions. Further, a part of the rolled material rises along the concave portions of the roll-polished mesh to form minute convex portions in the plate width direction. Further, the slippage at this time acts as a shearing force on the very surface layer of the steel sheet surface, so that the amount of plastic deformation of the very surface layer becomes large. If the amount of plastic deformation is large, the number of starting points for recrystallization during finish annealing becomes large and the crystal grains become small. When annealing is performed in an oxidizing atmosphere, it is necessary to remove the scale by pickling etc. before temper rolling.In that case, since the crystal grains on the steel sheet surface are small, the etch pits in the grain boundary grooves are shallow, The center line valley depth (Rv) is smaller than the line mountain height (Rp).

Even if the direction of the grind is slightly inclined from the circumferential direction to the axial direction, it is possible to form a smooth surface due to the slip of the grind, but the degree thereof is low. In addition, when the inclination is 30 ° or more, a sufficient smooth surface is generated, but there are many shear force components in the width direction, and a plate deviation occurs during rolling, making it difficult to stabilize rolling,
Further, the steel sheet is twisted, which impairs the sheet passing property in the next step, which is not preferable. Therefore, the direction of the grind is set to the roll axis direction in which the shearing force component in the width direction is not generated. It should be noted that the fact that the direction of the polishing mesh is the axial direction does not mean that all the polishing meshes are 90 ° with respect to the roll circumferential direction,
It may be slightly inclined with respect to the roll axial direction as long as the rolling stability is not impaired, and the roll axial direction is 0 °.
Then, it is preferably within + -10 °.

Next, the center line average roughness (Raθ) in the circumferential direction of the roll is set to 0.05 to 0.3 μm, which is 0.05.
If it is less than μm, the roll roughness is too small compared to the lubricating oil film thickness and the steel plate surface roughness, so the projections (top of roughness) of the roll polishing do not reach the steel plate surface sufficiently and slippage does not occur on the steel plate surface. This is because the smooth surface is not generated, the oil pit is generated, and the center line valley depth (Rv) is large with respect to the center line mountain height (Rp).

On the other hand, when Raθ exceeds 0.3 μm, during rolling, even the valleys of the roll-polished mesh are caught in the surface of the steel sheet, and the swelling generated in the front surface in the sliding direction is large, and the friction coefficient during rolling is high, and rolling occurs. Becomes unstable. Furthermore, abrasion powder is often generated, and new defects such as local seizure defects and indentation defects due to abrasion powder of rolled material occur. Further, the roughness after cold rolling is large, and the center line average roughness (Ra) does not become 0.15 μm or less even after temper rolling. Therefore,
The upper limit of Raθ is 0.3 μm.

Diameter of work roll and roll in contact with the work roll: Sliding on the surface of the steel sheet due to the roll polishing projections during rolling is the contact arc between the roll and the rolled material during rolling, that is, point A shown in FIG. The longer the length from point to point C, the more. When the oil film is extremely thin, this length increases as the rolling reduction increases and the work roll diameter increases. However, when the diameter of the work roll becomes large, the rolling oil is often drawn into the roll bite, the oil film becomes thick, and an oil pit is generated, resulting in a recess. Specifically, when the diameter of the work roll is 150 mm or more, a sufficient smoothing effect cannot be obtained, so the diameter of the work roll is set to less than 150 mm. More desirable is 100 mm or less.

When the work roll has a small diameter, the abrasion of the polishing eye increases relatively. Also, when the roll contacting the work roll such as the backup roll has a conventional polishing eye in the circumferential direction, the polishing eye has Since the direction is different from that of the work roll, the grind of the work roll is easily deformed and worn. Therefore, the lower limit of the diameter of the work roll is preferably 40 mm. In the present invention, all the rolls in contact with the work roll are rolls with the same polishing grain as the work roll in the axial direction. By doing so, deformation and wear are reduced, which is preferable. More preferably, the surface hardness of the work roll is set to Hv 800 or more by Cr plating or the like.

At least the final rolling pass of the cold rolling mill: The rolls used in the manufacturing method of the present invention can be used not only in all the passes of cold rolling but also in the final pass only, and the effect can be obtained. However, even if a normal roll is used in the final pass and the roll used in the present invention is used in the preceding pass, the effect of the roll eye is almost lost in the final pass. Therefore, in the final pass, it is necessary to use rolls whose rolls are in the roll axial direction. Use of rolls having roll eyes in the roll axial direction for a few passes including the final pass makes the effect of the roll eyes more reliable.

Although the rolling reduction in the rolling pass with the roll having the roll eyes in the roll axial direction is not particularly limited, since the diameter of the work roll is small, if the rolling reduction is small, the contact arc length with the steel sheet becomes short, Since the relative slip length between the steel plate and the roll is also small, it is preferably 10% or more.

Annealing / pickling and temper rolling: The conditions of annealing / pickling and temper rolling are not particularly limited because they may be standard methods adopted when manufacturing conventional BA products and 2B products.

For example, the annealing temperature is 750 to 850 ° C. for 30 to 40 seconds for ferritic stainless steel, and 1050 to 1200 ° C. for austenitic stainless steel.
For 30 to 50 seconds, the atmosphere may be a reducing atmosphere or an oxidizing atmosphere. However, when annealing is performed in an oxidizing atmosphere, it is necessary to pickle the scale on the surface with nitric acid, a nitric hydrofluoric acid mixture or the like as in the conventional case. The temper rolling may be unlubricated or lubricated. However, as in the conventional case, the rolling reduction is set to 0.6% or more for ferritic stainless steel to eliminate yield point elongation, and 0.4% or more for austenitic stainless steel to improve smoothness.

The production method of the present invention can be applied to a stainless steel sheet having any composition, so that the ingredients are not particularly limited.

[0043]

[Example] As a cold rolling mill, the diameter is 60 mm, 100 m
A 4Hi rolling mill capable of equipping work rolls with m, 145 mm, and 400 mm and a width of 400 mm was used. The SUS430 ferrite stainless steel plate and the SUS304 austenitic stainless steel plate having a plate thickness of 3.2 mm and a plate width of 300 mm shown in Table 1 were used as test materials.

[0044]

[Table 1]

Test numbers 1 to 6 and 14 to 18 in Tables 3 and 4
11 types of rolling rolls having the surface roughness and the grain size shown in Table 1 were prepared, and cold rolling was performed for 7 passes under the rolling conditions shown in Table 2.
In addition, except for Test Nos. 8 and 10, the roll diameter is up to 6 passes:
Roll with 100 mm, polishing eye: circumferential direction, surface roughness: Ra0.15 roll (No. 13 roll in Table 4), the last 1
Various rolls whose paths are shown in Tables 3 and 4 were used. Table 2 shows combinations of test materials and used rolls for each test number. The backup roll is also test number 2
Except for 0, the polishing direction and roughness were the same as those of the work roll.

[0046]

[Table 2]

[0047]

[Table 3]

[0048]

[Table 4]

After cold rolling, the shape and surface roughness of the steel sheet were measured and shown in Tables 3 and 4. In addition, the shape was evaluated by the degree of twist, and the degree of no twist was ◯, the degree of mildness was Δ, and the degree of fairly large was x. Further, the surface roughness is shown in Tables 3 and 4 by measuring the center line average roughness, the center line peak height, and the center line valley depth in the rolling direction and the strip width direction.

Next, the rolled steel sheet is subsequently annealed and pickled under the conditions shown in Table 5, and the roll diameter is 800 mm,
A work roll having a surface roughness of 0.01 μm was temper-rolled at a rolling reduction of 0.8%.

[0051]

[Table 5]

The surface roughness of the steel sheet after temper rolling was measured. As in the measurement after cold rolling, the center line average roughness, the center line peak height, and the center line valley depth were measured in the rolling direction and the strip width direction, and the average values are shown in Tables 3 and 4.

Finally, # 800 cloth was used to polish to a target glossiness at a line speed of 50 m / min.
The evaluation was performed by the number of times of polishing until the target glossiness was obtained. Tables 3 and 4 show the evaluation results. It should be noted that, compared with the conventional examples of the test numbers 13 and 17, the number of times of polishing could be reduced by 2 times or more. ◯: The number of times of polishing could be reduced by 3 times or more: ◎; Those that were able to reduce were described as Δ in the comprehensive evaluation column of Table 2.

The steel sheets according to the method of the present invention all have a comprehensive evaluation of O and A, but the steel sheets cold-rolled under the conditions other than the method of the present invention are inferior in shape and surface quality after cold-rolling and temper-rolled. No significant improvement in the surface texture was observed even after carrying out, and no significant improvement in the number of times of polishing the rag was observed.

[0055]

The steel sheet produced by the method of the present invention is capable of reducing the number of times of polishing of the cloth for polishing the surface of the steel sheet and finishing it to the target surface texture, and the production efficiency of the high gloss material can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing the surface roughness of a steel plate, where (a) is Rv / Rp ≦
Condition of surface roughness in case of 1, (b) is conventional Rv / Rp ≧ 1
It is a figure which shows the state of surface roughness in the case of.

FIG. 2 is a diagram for explaining the direction of roll polishing eyes (roughness of roughness).

FIG. 3 is a cross-sectional view of a roll bite portion for explaining that there is slippage between a roll surface and a steel sheet surface in cold rolling.

FIG. 4 illustrates a contact state of a steel plate surface with a roll polishing eye and a change in the steel plate surface due to relative sliding when cold rolling is performed using a conventional roll whose polishing eye direction is a roll circumferential direction. FIG.

FIG. 5 shows the contact state of the steel plate surface with the roll polishing eyes and the steel plate surface due to relative sliding when cold rolling is performed with a roll whose rolls used in the production method of the present invention have a roll axis direction being the roll axis direction. It is a figure for explaining change.

[Explanation of symbols] 1 roll 2 steel plate 3 steel plate after rolling 4th roll

Claims (2)

[Claims] 1. A center line average roughness (R
a) is 0.15 μm or less, the ratio of center line peak height (Rp) to center line valley depth (Rv) (Rv / Rp) is 1.0 or less, and center line valley depth is 0.5 μm or less. A stainless steel plate with excellent abrasiveness, which is characterized by 2. A work roll used for at least a final rolling pass of a cold rolling mill and a roll in contact with the work roll, wherein the polishing marks on the roll surface are in the roll axial direction, and the center line average in the roll circumferential direction is averaged. Roughness (Raθ) is 0.
05-0.3 μm and the work roll diameter is 150
A method for producing a stainless steel sheet having excellent polishability, which comprises cold rolling a stainless steel sheet using a roll having a size of less than mm, annealing, pickling if necessary, and temper rolling.