JPH07155809A - High gloss austenitic stainless steel sheet and method for producing the same - Google Patents

Abstract

(57) [Summary] [Purpose] For austenitic stainless steel sheets,
An object of the present invention is to provide a material and a method that make the unevenness of the original plate harmless and have stable gloss. [Structure] As a high-gloss stainless steel plate having an area ratio of dents of 0.7% or less and a method of manufacturing the same, Ra = 1 in the first pass in a range of a reduction ratio of 50% or more in a finish cold rolling step.
Roll with a rough roll of 1.0 to 1.6 μm, then Ra =
Finish cold rolling is performed by rolling at least one pass with a roll of 0.1 to 0.5 μm, and further rolling at least two passes of a final pass with a smooth roll of Ra = 0.01 to 0.06 μm, or a similar smooth roll. Is used to perform non-lubricated temper rolling at a rolling reduction of 0.3 to 3%. [Effect] It is possible to obtain a high-gloss stainless steel plate without being significantly affected by the previous history.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention has excellent surface gloss, especially J
Gs (4) which is the gloss index specified in IS Z8741
The present invention relates to an austenitic stainless steel sheet having a high gloss of 5 °) in the C direction of 800 or more and a method for producing the same.

[0002]

2. Description of the Related Art BA products, 2B products, polished products and the like are examples of austenitic stainless steel thin plate products defined by JIS standards. In these sheet products,
A surface property having high smoothness is strongly required.

In order to meet such demands, in finish cold rolling, rolling is performed by exchanging rolls from a roll having a rough surface to a fine roll in each pass or every 2 to 3 passes, and rolling. Has built in the surface texture of. However, in such conventional cold rolling, the optimum work roll roughness pattern for each pass was unclear, so the unevenness of the original plate during cold rolling was rendered harmless and the high gloss surface texture was stabilized. It was difficult to build it. As a result, the surface gloss of cold-rolled product sheets has a high rejection rate, and further improvement is required.

[0004]

The surface dents that deteriorate the glossiness of a plate in BA products and 2B products or increase the number of times of polishing when performing polishing treatment such as mirror polishing in the next step are It is considered that the cause is irregularities on the surface of the hot-rolled steel strip before cold rolling, grinds in flaw removal grinding, rolls in intermediate rolling such as tandem rolling, or oil pits during cold rolling.

The present invention has been made in view of the current state of the art.
Gloss index G standardized in JIS Z8741 by clarifying the condition of the surface depression that affects the glossiness of the product plate and the number of polishing
A high-gloss austenitic stainless steel sheet for obtaining the surface condition of a cold-rolled sheet for ensuring a surface gloss of s (45 °) C direction of 800 or more, and a method for producing the same. It is an object.

[0006]

In order to achieve the above object, the present invention provides a Gs specified in JIS Z8741.
(45 °) C direction is configured by defining the surface condition of the cold rolled plate for ensuring a surface gloss of 800 or more, the reduction ratio in finish cold rolling, and the surface roughness of the rolling roll. The summary is as follows.

(1) A high-gloss stainless steel sheet, characterized in that, in the surface after cold rolling, the surface recesses having a depth of 0.1 μm or more have an area ratio of 0.7% or less. (2) In the finish cold rolling step of the austenitic stainless steel sheet, cold rolling is performed under the condition that the total reduction ratio is 50% or more, and the rolling conditions in each pass of the cold rolling are:
(A) In the first pass, the surface roughness is Ra = 1.0 to
Rolling with a rolling ratio of 1.6 μm and a rolling reduction of 15 to 30%, and (b) in the intermediate pass from the second pass, with a rolling roll having a surface roughness Ra = 0.1 to 0.5 μm, Rolling with a rolling reduction of 10 to 20% per pass, and (c) in a finishing pass having at least two passes, the rolling reduction with a rolling roll having a surface roughness Ra = 0.01 to 0.06 μm. Is 8 to 20%, and a method for producing a high-gloss austenitic stainless steel sheet. (3) Following the method described in (2) above, Ra = 0.0
0.3 with no lubrication using 1-0.06μm smooth roll
A method for producing a high-gloss austenitic stainless steel sheet, which is characterized by performing temper rolling at a rolling reduction of 3%. (4) Bright annealing is performed subsequently to the method described in (2) above, and then a rolling rate of 0.3 to 3% without lubrication using a smooth roll having Ra = 0.01 to 0.06 μm. A method for producing a high-gloss austenitic stainless steel sheet, which comprises temper-rolling. (5) The surface roughness of the material for rolling in the finish cold rolling step is Ra = 0.1 to 1.0 μm, (2), (3), (4), (5). , (6) The method for producing a high-gloss austenitic stainless steel sheet according to any one of (6).

[0008]

The high-gloss austenitic stainless steel sheet and the method for producing the same according to the present invention are applied to the final cold rolling step of rolling the cold rolling, rolling roll roughness, and rolling reduction of the stainless steel sheet that has undergone primary cold rolling in a tandem mill or a cluster mill. It is characterized in that the conditions of the rate and the number of times of rolling are carried out within a limited optimum range, and in addition, temper rolling without lubrication is carried out as cold rolling or after annealing in a reducing atmosphere.

The reasons for limitation of the present invention will be described below. First, the limitation of the area ratio of surface depressions in the high-gloss austenitic stainless steel sheet of the present invention will be described. The average roughness of the surface as a factor affecting the gloss of the stainless steel plate,
That is, although it has the highest smoothness, even a steel sheet having a very low average roughness has no gloss and the surface is whitish and cloudy. The present inventors have made a detailed analysis of the surface properties and found that this is due to the fine dents remaining on the surface. The types of dents include grain boundary etching residue before final cold rolling, and those with surface grinding before final cold rolling that leave unrolled defects such as grinding marks and other coarse defects. It has been found that there is something left over in the final cold rolling such as the residuals of the rolling rolls and the oil pits generated during rolling.

Then, as a result of diligent studies on the relationship between these depressions and surface gloss, a high-gloss austenitic stainless steel sheet was obtained by limiting the area ratio of the depressions on the surface having a depth of 0.1 μm or more to 0.7% or less. It turns out that it can manufacture stably. Regarding the degree of depression, if the depth is less than 0.1 μm, the depression cannot be clearly distinguished by using an optical microscope.
The area ratio is measured by observing with an optical microscope with a magnification of 00. FIG. 1 shows the measurement results of many samples, and it can be seen from this that when the area ratio exceeds 0.7%, the gloss is significantly deteriorated. Therefore, in the stainless steel sheet of the present invention, the area ratio of the recesses having a depth of 0.1 μm or more is 0.7%.
Below.

The inventors of the present invention have studied the finishing cold rolling technique capable of preventing the dents from remaining and generating, and found the conditions. The basic idea is schematically shown in FIG. That is, the dents (oil pit,
Cracks, grain boundary etching defects, and grinding residue) are scraped off by the first pass rolling of a high roughness roll. Subsequently, the eyes of the high-roughness roll rolling of the first pass are crushed by rolling with the medium-roughness roll of the intermediate pass. Furthermore, the plate surface is smoothed by a low roughness roll used for at least the final two passes.

When the finish cold rolling is performed based on the above technique, if the roughness of the surface of the rough roll in the first pass is too low, the previous history cannot be erased. On the other hand, if the roughness is too high, it becomes difficult to effectively crush the rough rolls by rolling in an intermediate pass. Therefore, the roughness of the rough roll is preferably Ra = 1.0 to 1.6 μm. is there. FIGS. 3, 4 and 5 show the relationship between the roll roughness (Ra) of the first pass, the glossiness of the product plate, the recessed area ratio, and the reduction distribution ratio, and the Ra range is preferable. Further, it is clarified that the reduction ratio of 15 to 30% is desirable. As for the rolling roll roughness of the same, as shown in FIGS. 6, 7 and 8, Ra =
The range of 0.1 to 0.5 μm is preferable. As shown in FIG. 9, the roll roughness used for the finishing pass of
The range of 0.01 to 0.06 μm is preferable. Further, as shown in FIGS. 10 and 11, also regarding the reduction ratio of the finish cold rolling, when the reduction ratio is small, the previous history cannot be sufficiently erased, and it is preferable to set it to 50% or more. . For the number of passes in ,,,
One or more passes are sufficient, and even if the number of passes is increased, almost the same effect was seen. In one case, as shown in FIG. 12, which shows the results of examining the influence of the number of rolling passes using a low roughness roll and the product glossiness, fine irregularities on the plate surface were smoothed by repeating two or more passes. The surface gloss can be improved. The reduction rate is 8 to 20.
% Is desirable. From the above, the high-roughness work roll was set only in the first pass, the medium-roughness work roll was set in one or more passes in the middle pass, and the low-roughness work roll was set in the last two passes or more.

The total reduction ratio in finish cold rolling is preferably 50% or more. When rolled under these conditions, cold rolling is performed on a material that has been cold-rolled on a material that has been hot-rolled and then pickled and descaled, or on a material that has been annealed and pickled after hot-rolling. It is possible to erase the history of the material that has been subjected to the annealing and the material that has been subjected to the annealing pickling. In addition, it has the same effect on the material that has been polished or ground before the final cold rolling.

When temper rolling is performed on the cold-rolled sheet produced as described above, it is necessary to use a smooth roll equivalent to the smooth roll used in the final finishing pass of finish cold rolling. In terms of shape and material, the rolling reduction is 0.3 to 3%. Therefore, it is desirable to perform rolling without lubrication in order to prevent rolling oil from entering between the stainless steel plate and the roll during rolling.

Further, when the bright annealing is performed before the temper rolling, the smooth roll surface in the temper rolling is more stably transferred to the rolled steel sheet, so that the surface has a higher gloss.

Further, as described above, one of the features of the present invention is that the first pass of the present invention eliminates the dents in the previous history of the material for rolling, and that the high gloss finish is obtained by the subsequent rolling of the second and subsequent passes. It is to adjust the surface. Therefore, the surface roughness of the material for rolling is Ra ≦ 1.0 with respect to the roughness of the rough roll Ra = 1.0 to 1.6 μm.
μm is desirable.

[0017]

EXAMPLES Examples of the present invention, comparative examples and conventional examples are shown in Table 1, Table 2, Table 3 and Table 4. SUS304 was used as the steel type, and the process before finish cold rolling and the conditions of finish cold rolling, temper rolling and reducing atmosphere annealing were changed. The finish cold rolling was performed by a Sendzimir mill using a small diameter roll. In the present invention example, the area ratio of the recess is 0.7% or less,
The variation of the surface gloss of the product shown in FIG. 13 can be suppressed as shown in FIG. 14 under the conventional finish cold rolling condition,
It has a high gloss stainless steel plate compared to the conventional example.
In addition, the area ratio of the recesses is obtained by enlarging the surface by 200 times and measuring the area of the recesses by image processing. The gloss is JIS
It is measured based on Z8741.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

[0021]

[Table 4]

[0022]

As is apparent from the above, according to the present invention, it is possible to stably manufacture a high-gloss stainless steel plate. In particular, when the technique is used, the previous history of the material can be applied with almost no problem, so that it is possible to consolidate the manufacturing process of the stainless steel plate intricately complicated for each steel type, and it is expected that the efficiency is greatly improved in industrial production.

[Brief description of drawings]

FIG. 1 is a diagram showing an influence of an area ratio of depressions on glossiness.

FIG. 2 is a diagram showing a mechanism by which surface defects of an original plate are removed by the method of the present invention.

FIG. 3 is a diagram showing the influence of the roll roughness of the first pass on the glossiness.

FIG. 4 is a diagram showing the influence of the roll roughness of the first pass on the area ratio of depressions.

FIG. 5 is a diagram showing the optimum roll roughness in the first pass and the reduction distribution with respect to the total reduction amount.

FIG. 6 is a diagram showing an influence of roll roughness of a mid-pass on glossiness.

FIG. 7 is a diagram showing the influence of roll roughness of a mid-pass on the area ratio of depressions.

FIG. 8 is a diagram showing optimum roll roughness of a mid-pass and reduction distribution with respect to total reduction amount.

FIG. 9 is a diagram showing the optimum roll roughness in the final pass of the finish cold rolling step, and the distribution of reduction with respect to the total amount of reduction.

FIG. 10 shows the effect of the finish cold rolling reduction rate on the glossiness.

FIG. 11 shows the influence of the finish cold rolling reduction rate on the area ratio of dents.

FIG. 12 is a diagram showing the effect of the number of passes of the low roughness roll in the latter stage of the pass on the glossiness.

FIG. 13 is a diagram showing variations in product evaluation in the conventional technique.

FIG. 14 is a diagram showing variations in product evaluation according to the present invention.

Front page continuation (72) Inventor Kozaburo Takaoka 3434 Shimada, Hikari City, Yamaguchi Prefecture Nippon Steel Works, Ltd.

Claims (5)

[Claims] 1. The surface after cold rolling has a depth of 0.
A high-gloss austenitic stainless steel sheet having a surface depression of 1 μm or more in an area ratio of 0.7% or less. 2. In the finish cold rolling process for producing an austenitic stainless steel sheet, cold rolling is performed under the condition that the total reduction ratio is 50% or more, and the rolling condition in each pass of the cold rolling is the first In the pass, the surface roughness is Ra
= 15 to 30% by a rolling roll of 1.0 to 1.6 μm
In the intermediate pass from the second pass, the rolling reduction is 10 to 20% per pass by the rolling roll having a surface roughness Ra = 0.1 to 0.5 μm. In a finishing pass having at least two passes or more, a high gloss, which is characterized in that rolling is performed by a rolling roll having a surface roughness Ra = 0.01 to 0.06 μm and a reduction rate per pass is 8 to 20%. Manufacturing method of austenitic stainless steel sheet. 3. Subsequent to the method of claim 2, Ra =
A method for producing a high-gloss austenitic stainless steel sheet, characterized by performing temper rolling with a rolling ratio of 0.3 to 3% without lubrication using a smooth roll of 0.01 to 0.06 μm. 4. The method according to claim 2 is followed by bright annealing, and subsequently using a smooth roll having Ra = 0.01 to 0.06 μm, a rolling ratio of 0.3 to 3% without lubrication. A method for producing a high-gloss austenitic stainless steel sheet, which comprises temper-rolling. 5. The high-gloss austenitic stainless steel according to claim 2, wherein the surface roughness of the material for rolling in the finish cold rolling step is Ra ≦ 1.0 μm. Steel plate manufacturing method.