JPH071001A - Stainless steel sheet for mirror finished surface material and its manufacture - Google Patents

Abstract

PURPOSE:To clarify the number of surface recess which affects the mapping property of a product sheet and the number of times of mirror grinding, to determine the surface condition of a cold rolled sheet for ensuring highly smooth surface having the mapping property of >=90% and also to provide a manufacturing method for attaining the conditions at the time of manufacturing a stainless steel sheet for mirror finished surface material. CONSTITUTION:This base stock is a stainless steel strip whose number of surface recess of a depth of >=0.05mum is <=60 per the length of 10mm in the surface of the base stock before mirror grinding. As the cold rolling method for obtaining it, at least one pass of rolling is executed under the condition that draft is >=10% with use of the rolls having roll roughness Ra of >=0.4mum, rolling of pass after that is executed under the condition that draft per one pass is 10-30 % and rolling speed is in the range of 200-1000m/min with use of the rolls having roll roughness Ra of <=0.2mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stainless steel plate having high smoothness and excellent surface properties, and more particularly to a stainless steel plate for a mirror polishing material and a method for producing the same.

[0002]

2. Description of the Prior Art As a stainless steel thin plate product, JIS
There are BA products, 2B products, abrasive products, etc. which are specified in the standard. In these thin plate products, it is strongly demanded that the stainless steel plate for a mirror surface material has high smoothness and excellent surface properties.

In order to meet such demands, conventionally, in cold rolling, rolls are sequentially exchanged from a roll having a rough surface to a roll having a fine surface roughness in each pass or every two to three passes, and rolling is performed to obtain surface properties. Has built in. However, in such a conventional cold rolling, in order to secure a surface texture having high smoothness after cold rolling, a considerable number of passes are required, and a considerable number of rolls having different surface roughness are prepared. There must be.

On the other hand, as a method of improving the surface gloss, for example, as disclosed in Japanese Patent Application Laid-Open No. 2-175005, pre-rolling is performed by applying a lubricant to the extent that seizure can be prevented before cold rolling. In the subsequent finish cold rolling, there is a method of defining the upper limit of the surface roughness of the work roll of the final 1 to 3 passes to reduce the surface unevenness. However, although this method can reduce the surface roughness of the cold-rolled sheet to some extent, it is not sufficient to secure the surface texture having high smoothness, and further improvement is required.

[0005]

The causes of surface irregularities that increase the number of times of polishing in polished products of stainless steel sheets for mirror surface materials include the surface irregularities of the hot-rolled steel strip before cold rolling and the grinding marks caused by flaw removal grinding. It is thought that there are rolls formed by intermediate rolling such as tandem rolling and oil pits during cold rolling. Therefore, the inventors of the present invention effectively and efficiently reduce and eliminate the above-mentioned surface irregularities in the stainless steel strip having high smoothness and in the manufacturing process capable of obtaining the stainless steel strip having excellent surface properties and the steel strip. The examination was done.

The present invention clarifies surface irregularities that affect the image clarity of a product plate and a predetermined number of polishing times, and obtains surface conditions of a mirror polishing material for ensuring a highly smooth surface having an image clarity of 90% or more. At the same time, the purpose is to present the manufacturing conditions for obtaining the surface.

[0007]

[Means for Solving the Problems] In cold rolling, when using a roll which is extremely smooth as compared with the plate surface,
The irregularities on the surface may be significantly reduced and disappeared. However, in such a case, the correlation between the surface roughness due to Ra and Rmax and the image clarity is small. Therefore, the smoothness of the surface was evaluated by using the number of surface recesses instead of Ra and Rmax. Here, the number of surface dents is the number of surface dents having a depth of 0.05 μm or more due to the surface roughness present in the mirror-polishing material.

The present invention has been completed as a result of various studies on the number of peaks of surface roughness and manufacturing conditions of a material for mirror-polishing, and its gist is as follows. (1) On the surface of the material before mirror polishing, the number of surface recesses with a surface roughness of 0.05 μm or more is 60 per 10 mm length.
The number of stainless steel sheets for mirror surface materials is less than or equal to one. (2) In the cold rolling before the final annealing, rolling with a roll surface roughness Ra of 0.4 μm or more is performed with a rolling reduction of 10% or more, and the roll surface roughness is R in the second and subsequent passes.
a, the rolling ratio per pass is 10 to 30% and the rolling speed is 200 to 1000 by using a roll of 0.2 μm or less.
Rolling is performed in the range of m / min. (3) After the cold rolling described in (2), reducing atmosphere annealing is performed, and then temper rolling with an elongation of 0.2% or more is performed without lubrication.

[0009]

The reason for limiting the present invention will be described in detail below. As a surface condition of a material for mirror polishing for obtaining a stainless steel strip having a highly smooth surface with an image clarity of 90% or more, the inventors of the present invention have determined that the number of surface recesses having a depth of 0.05 μm or more in the same material. Was found to be 60 or less per 10 mm in length.

Since the material for mirror-polishing is mainly used as a building material, a plate thickness of 1.2 mm or more is often used, but if it exceeds 4.0 mm, handling becomes extremely difficult in construction. Therefore, the preferable plate thickness is 1.2 to 4.0 mm.

When a hot rolled annealed steel strip of SUS430 was cold-rolled from a plate thickness before cold rolling of 5.0 mm to a finish plate thickness of around 2.0 mm, the image clarity and depth of the mirror-polished material were 0. 05
FIG. 1 shows the result of investigation on the relationship between the number of surface recesses of μm or more. The number of surface recesses having a depth of 0.05 μm or more in the same material is measured in the C direction (direction orthogonal to the rolling direction) at a threshold value of 0.05 μm using a roughness meter. Here, since the minimum polishing amount in mirror polishing is about 0.05 μm, it was considered that the number of surface recesses having a depth of 0.05 μm or more affects the mirror polishing property.

As is apparent from FIG. 1, the depth is 0.05 μ
When the number of the surface recesses of m or more is 60 or less per 10 mm in length, it is possible to have a highly smooth surface having an image clarity on the material surface of 90% or more.

The inventors of the present invention have found that the number of surface recesses having a depth of 0.05 μm or more in the mirror polishing material is 6 per 10 mm in length.
As a cold rolling condition for the number of rolls to be 0 or less, a roll having a roll surface roughness Ra of 0.4 μm or more in the first pass is rolled at a reduction rate of 10% or more, and the roll surface roughness Ra is 0. Using a roll having a diameter of 2 μm or less, the rolling reduction per pass is 10 to 30%, and the rolling speed is 200 to 100.
It was found to be in the range of 0 m / min.

When a hot rolled annealed steel strip of SUS430 was cold-rolled from a plate thickness before cold rolling of 5.0 mm to a finish plate thickness of around 2.0 mm, a depth of 0.05 in the material for mirror polishing was obtained.
FIG. 2 shows the results of an examination of the relationship between the range in which the number of surface recesses of μm or more is 60 or less per 10 mm in length, the roll surface roughness of the preceding pass and the cumulative rolling reduction of the same pass.

As is apparent from FIG. 2, if the cumulative reduction ratio of the cold rolling by the roll having the roll surface roughness Ra of 0.4 μm or more is in the range of 10% or more, the surface of the mirror-polishing raw material is The number of surface recesses having a depth of 0.05 μm or more is 60 or less per 10 mm in length.

Roughness Ra0.
Fig. 3 shows the results of a 3-pass rolling experiment assuming a cold rolling condition of a middle- and lower-stage pass by using a cut plate cold rolling machine, using a cut plate sample which was rolled by a roll of 4 µm or more at a rolling reduction of 15% or more with a reduction ratio of 15% or more. Shown in. Here, the effect on the number of surface depressions was evaluated in three stages. "Conspicuous" indicates that the number of surface recesses is less than half that before rolling, "Slightly" indicates that the number of surface recesses has decreased compared to before rolling, and "None" indicates that there is no reduction effect. It was evaluated as if it was not done. As is clear from FIG. 3, the roll roughness Ra is 0.2 μm.
It can be seen that the effect of reducing the number of surface depressions of the material is remarkable when cold rolling is performed using a roll having the following.

When a hot rolled annealed steel strip of SUS430 was cold-rolled from a plate thickness before cold rolling of 5.0 mm to a finish plate thickness of around 2.0 mm, the number of surface recesses in the material for mirror polishing was long. FIG. 4 shows the results of an examination of the relationship between the rolling reduction and the rolling reduction per pass by a roll having a roll surface roughness Ra of 0.2 μm or less and a range of 60 or less per 10 mm.

As is apparent from FIG. 4, the reduction rate per pass by the roll having a roll surface roughness Ra of 0.2 μm or less and the rolling speed is 200 to 1%.
If rolling is performed in the range of 000 m / min, the number of surface recesses with a depth of 0.05 μm or more on the surface of the material for mirror polishing can be 60 or less per 10 mm length, and the image clarity is 90%.
It can have a highly smooth surface as described above.

When the rolling reduction per pass exceeds 30%, the finished plate thickness is 1.2 mm or more, which is heavy, which imposes a heavy burden on the facility from the viewpoint of the current facility specifications, making it practically difficult to roll. When the rolling speed exceeds 1000 m / min,
It is in the flash point region from the viewpoint of the current rolling oil specifications, and practically it is difficult to roll.

The action and mechanism relating to the disappearance of surface irregularities in cold rolling are not always clear, but are presumed as follows. By increasing the rolling speed and rolling under high pressure using rolls that have smoothness compared to the plate surface, the rolling oil temperature decreases because the plate temperature rises, and the lubricating film between the plate and roll becomes extremely thin. Depending on the place, a phenomenon of lubrication failure occurs. At the location where the lubrication is broken, the unevenness is transferred to the roll surface and becomes a smooth surface.

In order to cause such surface smoothing uniformly, it is effective to use a roll having a relatively rough roll surface at the initial stage of rolling to make the surface texture before cold rolling constant. Since this effect is insufficient at a rolling reduction of less than 10%, the rolling reduction by a roll having a roll surface roughness Ra of 0.4 μm or more is set to 10% or more. The rolling at this time may be divided into two or more passes, but at least one pass is required. In the latter pass, the roll roughness of the final finishing pass should be 0.05μ in order to further promote the surface smoothing.
It is preferable to use m or less.

On the other hand, it is preferable to perform the final annealing by reducing atmosphere annealing because the highly smooth surface obtained by the cold rolling plate can be maintained as it is. Further, it is preferable to perform temper rolling by non-lubricating rolling because the high smoothness of the product sheet is further improved. If the elongation is less than 0.2%, the image clarity is not sufficiently improved. Therefore, the elongation of the non-lubricated temper rolling is set to 0.2% or more.

[0023]

EXAMPLES Table 1 shows examples of the present invention and comparative examples. As the steel type, SUS430 and SUS304 are used, and the cold rolling conditions, the surface conditions of the cold rolled sheet, the conditions of final annealing and temper rolling are shown. The number of surface recesses is measured in the C direction (direction perpendicular to the rolling direction) at a threshold value of 0.05 μm using a roughness meter. Image clarity is JIS H 868
It is measured based on 6. The specular polishability was evaluated by actual evaluation using a line of a manufacturer of polished products. When the number of polishing is used as a polishing index, ○ indicates less than before,
The mark Δ indicates the same level as the conventional one, and the mark X indicates a case where the number increased compared to the conventional one.

In the present invention example, the image clarity of the same material is 90% or more as compared with the comparative example and the conventional example, the specular polishability evaluation in the polishing step is good, and it is understood that it has high smoothness. . Further, it can be seen that the cold rolling speed of the present invention example is significantly improved as compared with the conventional example.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

[0028]

As is apparent from the above, according to the present invention, it is possible to obtain a stainless steel strip excellent in surface properties having a high smoothness with a mirror polishing material having an image clarity of 90% or more. Further, the cold rolling method according to the present invention can perform rolling work with extremely high efficiency as compared with the conventional method.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the image clarity of a mirror-polishing material and the number of surface recesses having a depth of 0.05 μm or more in the same material using a SUS430 steel strip.

FIG. 2 is a range in which the number of surface recesses having a depth of 0.05 μm or more is 60 or less per 10 mm length on the surface of the material for mirror-polishing using a SUS430 steel strip, and the roll surface roughness of the preceding pass. The figure which shows the relationship of the total reduction ratio of the same pass.

[FIG. 3] Roughness Ra ≧ 0.4 of hot rolled annealed SUS430 steel sheet
Using a cut plate sample rolled with a roll of μm with a rolling reduction of 15% or more, the effect of reducing the number of surface recesses and medium
The figure which shows the relationship of roll roughness of a latter stage pass.

FIG. 4 is a range in which the number of surface recesses having a depth of 0.05 μm or more is 60 or less per 10 mm length and the roll surface roughness Ra is 0 on the surface of the mirror-polishing raw material using the SUS430 steel strip. The figure which shows the relationship of the rolling reduction and the rolling speed per 1 pass of the cold rolling by the roll which has .2 micrometer or less.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiro Yangi 3434 Shimada, Hikari City, Yamaguchi Prefecture Shin Nippon Steel Co., Ltd.

Claims (3)

[Claims] 1. The number of surface recesses having a depth of 0.05 μm or more on the surface of the material before mirror polishing is 60 per 10 mm in length.
A stainless steel plate for a mirror surface material, characterized in that the number is less than or equal to one. 2. In the cold rolling before the final annealing, at least one pass is rolled, and a roll having a roll surface roughness Ra of 0.4 μm or more is used and a subsequent pass is rolled under the condition of a rolling reduction of 10% or more. A mirror surface characterized by rolling using a roll having a surface roughness Ra of 0.2 μm or less at a rolling reduction of 10 to 30% per pass and a rolling speed of 200 to 1000 m / min. For manufacturing stainless steel sheets for lumber. 3. A stainless steel for mirror surface material, which is characterized in that after cold rolling according to claim 2, annealing in a reducing atmosphere is performed, followed by temper rolling with an elongation of 0.2% or more without lubrication. Steel plate manufacturing method.