JPH06182402A - Highly brilliant stainless steel sheet and its production - Google Patents

Abstract

PURPOSE:To provide a material by which the gloss is improved and a production method for the material in a stainless steel sheet. CONSTITUTION:As for a highly gloss stainless steel sheet having the area ratio of a recessed part to be<=10% after cold rolling and a production method for the sheet, in a finishing cold rolling process, the draft allotment of 20-40% is obtained by using a rough roll having Ra of 0.4-1.6mum in a first pass and the draft allotment of 20-40% is obtained by using a flat roll having Ra of 0.01-0.06mum in a second pass. The draft allotment of 10-30% is obtained by using a flat roll having Ra of 0.01-0.06mum in a third pass and the sheet is cold rolled by using a flat roll having Ra of 0.010.06mum in the residual pass. As necessary, non lubricant refining rolling is carried out by using a flat roll having Ra of 0.01-0.06mum to obtain the draft of 0.3-3%.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention has excellent surface gloss, especially JI.
Gs (45, which is the gloss index specified in S Z8741)
°) The present invention relates to a stainless steel plate having a high gloss of 800 or more in the C direction and a method for manufacturing the same.

[0002]

2. Description of the Related Art As steel thin plate products, there are BA products, 2B products and polished products which are specified in JIS standards. It is strongly demanded that these thin plate products have 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 property 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. Further, in this case, the smoothness of the surface in cold rolling is evaluated by the average roughness Ra and the maximum roughness R.
A correlation between the surface roughness of the cold-rolled sheet and the glossiness of the product sheet was confirmed even when the surface roughness such as max was used.

On the other hand, as a method for improving the glossiness of the surface, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2-175005, pre-rolling is carried out by applying a lubricant to prevent seizure before cold rolling. In the subsequent finish cold rolling, there is a method of defining the upper limit of the surface roughness of the final work roll of 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 insufficient to secure the surface texture having high smoothness, and further improvement is required.

[0005]

The surface dents that deteriorate the glossiness of the plate in BA products and 2B products and increase the number of times of polishing in polished products are the unevenness of the hot-rolled steel strip and the scratch removal before cold rolling. The cause is considered to be a grinding grain by grinding, a roll grain formed by intermediate rolling such as tandem rolling, an oil pit during cold rolling, and the like. Therefore,
The present inventors have made it possible to effectively and efficiently reduce and eliminate the above-mentioned dents in the surface of a stainless steel strip having high smoothness and an excellent surface property and a manufacturing process capable of obtaining the same. Study was carried out.

For this reason, the present invention clarifies surface dents which affect the glossiness of the product plate and the number of polishing, and JIS Z8
Gloss index Gs (45 °) specified in 741 is 8 in the C direction
The purpose is to obtain the surface condition of the cold rolled plate for ensuring a surface gloss of 00 or more and to present the manufacturing condition for obtaining the same surface condition.

[0007]

The present invention, for the above-mentioned purpose, is provided with Gs (45) specified in JIS Z8741.
°) It is composed of the surface condition of the cold-rolled sheet for ensuring a surface gloss of 800 or more in the C direction, the reduction ratio of finish cold rolling, the reduction amount of each rolling, and the surface roughness of the rolling roll. The main points are as follows.

(1) A high-gloss stainless steel plate in which the surface depressions having a depth of 0.1 μm or more are 1.0% or less in area ratio on the surface of the cold rolled plate. (2) In the finish cold rolling process of the stainless steel plate, 1
For the rolling of the pass, cold rolling with a reduction distribution of 20 to 40% is performed using a rough roll of Ra = 0.4 to 1.6 µm, and then the rolling of the second pass is performed to Ra = 0.01 to 0. Cold rolling with a reduction distribution of 20 to 40% using a smooth roll of 06 μm,
Subsequently, the rolling of the third pass is Ra = 0.01 to 0.06μ.
cold rolling with a reduction distribution of 10 to 30% using a smoothing roll of m, followed by rolling of the remaining passes Ra = 0.01 to
Cold roll the remaining draft using 0.06 μm smooth rolls. However, the reduction distribution is such that the total reduction amount in the finish cold rolling step is 100% (%) (3) (2) followed by Ra = 0.01-
0.3 to 3 without lubrication using 0.06 μm smooth roll
Temper rolling is performed at a reduction rate of%. (4) Bright annealing is performed subsequently to the method described in (2), and then smoothing is performed with a smoothing roll of Ra = 0.01 to 0.06 μm at a rolling reduction of 0.3 to 3% without lubrication. Perform quality rolling.

[0009]

According to the present inventors, as a surface property condition of a cold-rolled plate of a stainless steel plate having a high-gloss surface having a glossiness of 800 or more specified by JIS Z8741, the depth of the surface of the cold-rolled plate is It was found that the surface depressions of 0.1 μm or more are 1.0% or less in area ratio.

The high-gloss stainless steel sheet and the method for producing the same according to the present invention are applied to a stainless steel sheet which has undergone a specific process, such as rolling roll roughness, rolling reduction amount, reduction distribution, and number of reductions in a finish cold rolling step. In addition to performing the conditions in the optimum range, in addition to tempering rolling without lubrication,
The feature is that the material is annealed in a reducing atmosphere and then applied.

The reason for limiting the present invention will be described below. First, the area ratio of surface depressions in the high-gloss stainless steel sheet of the present invention will be described. The factor that affects the gloss of the stainless steel sheet is that the average roughness of the surface, that is, the smoothness is the largest, but even a steel sheet having an extremely small 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 cause is due to fine recesses remaining on the surface, and as the type of recesses, grain boundary etching defects remaining before the finish cold rolling step or For those that have been surface ground before the finish cold rolling process, residual defects such as grinding residuals before the finish cold rolling process, and other coarse defects of rolling rolls and oil generated during rolling It was found that there are things such as pits that occur during finish cold rolling. Then, as a result of diligently studying the cold rolling conditions for preventing the occurrence of dents, by setting the area ratio of the dents on the surface of the cold rolled plate having a depth of 0.1 μm or more to 1.0% or less, It has become possible to manufacture high-gloss stainless steel sheets with Gs 800 or higher.

As for the measurement of the dents, if the depth of the dents is less than 0.1 μm, the dents cannot be clearly distinguished by using an optical microscope. Therefore, the depth of 0.1 μm or more is observed with a 200 × optical microscope. The area ratio of the depression is measured. As shown in FIG. 1, when the area ratio exceeds 1.0%, the gloss starts to deteriorate, and when it exceeds 1.0 μm, Gs <800. Therefore, the stainless steel sheet of the present invention has a depth of 0.1 μm or more. The area ratio of the dents is preferably 0.7% or less.
It should be 0% or less.

The inventors of the present invention have established a finish cold rolling technique and a temper rolling technique capable of preventing the dents from remaining and occurring, and the basic concept thereof is shown in a schematic diagram in FIG. The history (oil pits, cracks, grain boundary etching defects, grinding residue) before the finish cold rolling step is erased by rolling the first pass of the rough roll. Then, the eyes of rolling by the rough roll of the first pass are crushed by the smooth roll rolling of the second pass. At this time, the coarse roll has almost crushed eyes, but many oil pits remain along the roll eyes. Furthermore, rolling with a smooth roll in the third pass makes it possible to extremely reduce the oil between the material and the roll. Then, the oil pits generated in 3 are eliminated, and a smooth rolled surface equivalent to the surface of the smooth roll is obtained. Finally, it is rolled with a smooth roll to a desired reduction amount.

When finish cold rolling is carried out on the basis of the above-mentioned technical idea, the surface of the rough roll in the first pass cannot be erased if the roughness is too low, while the roughness is large. If the rolling is excessive, it becomes difficult to sufficiently crush the rough rolls. Therefore, the roughness of the rough roll is Ra =
It must be in the range 0.4-1.6 μm. Also,
Similarly with respect to the reduction amount, if the reduction amount is small, the previous history cannot be sufficiently erased, and if it is too large, it will be difficult to sufficiently crush the rough rolls by smooth rolling,
The reduction amount of the rough roll rolling is 20 to 4 of the total reduction amount.
It should be 0% (Fig. 3). And when cold-rolled under the above conditions, the material subjected to pickling descaling after hot-rolling, the material subjected to annealing pickling after hot-rolling, and the material that has been cold-rolled to the above-mentioned material and further It is possible to erase the history of the material surface that has been subjected to annealing pickling. In addition, it has the same effect on the material that has been polished or ground before the finish cold rolling.

The surface of the smoothing roll of the second pass is 3
The same as the surface of the smooth roll of the pass is required,
Since the roll of the 3rd pass matches the final smoothness of the stainless steel plate surface, the smaller the surface roughness of the smooth roll is, the better the smoothness of the stainless steel plate surface is. Rolls are difficult to manufacture and control and are expensive in cost. In the present invention,
In order to obtain the desired gloss, the surface roughness Ra of 0.01 μm or more is sufficient, while the upper limit must be Ra of 0.06 μm or less to obtain a high-gloss stainless steel plate.

Since it is necessary to crush the roll of the first pass in the rolling of the second pass, an amount of reduction equivalent to that is required, and thus the smooth rolling of the second pass requires a reduction distribution of the total reduction amount 20. % And above. At this time, if a too high reduction amount is applied, stable control becomes difficult with the current equipment, so the upper limit of the reduction amount was set to 40% of the total reduction amount.

Since the third pass rolling serves to eliminate the oil pits generated in the second pass rolling, the reduction amount must be 10% or more of the total reduction amount. On the other hand, even if a large amount of reduction is taken, the effect will be saturated and a large reduction load will be required, and excessive force will be applied to the equipment, which tends to cause uneven reduction in the plate width direction. 30% or less is good (Figs. 4 and 5).

The rolling of (1) is performed in order to roll to a predetermined rolling amount, but since it is necessary to maintain the surface smoothness built up to the 3rd pass of (3), the roughness of the roll is equivalent to Ra = It should be 0.01 to 0.06 μm. Under the above rolling conditions, smoothness is maintained regardless of the number of rollings.

When temper rolling is performed on the material produced as described above, it is necessary to use a roll equivalent to the smooth roll used in the finish cold rolling step. Further, in temper rolling, the shape and material are different. Since the rolling reduction is 0.3 to 3%, a rolling method without lubrication is necessary to prevent rolling oil from entering between the stainless steel plate and the roll during rolling. Furthermore, when bright annealing that does not generate oxide scale is performed before temper rolling, transfer of the smooth roll surface to the rolled steel sheet in temper rolling occurs more stably, resulting in a stainless steel sheet surface with higher gloss. .

[0020]

EXAMPLES Table 1 shows examples of the present invention and comparative examples. SUS304 and SUS430 are used as steel types, and the conditions before finish cold rolling, finish cold rolling, temper rolling and reducing atmosphere annealing are shown. Among the cold rolling processes before the finish cold rolling, * marks indicate rolling with a tandem mill using large diameter rolls, and other cold rolling refers to rolling with a Sendzimir mill using small diameter rolls. The present invention example has a recess area ratio of 0.7% or less, and is a stainless steel plate having a gloss higher than those of the comparative example and the conventional example. Comparative Example N
o. The same lubricating oil as that used in the finish cold rolling was used as the lubricating oil 28. 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. Gloss is J
It is measured based on IS Z8741.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Table 3]

[0024]

[Table 4]

[0025]

As is apparent from the above, according to the present invention, it is possible to manufacture a high-gloss stainless steel plate. In particular, the use of this technique makes it possible to adapt the previous history of the material 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 to greatly improve the efficiency 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 are removed by the method of the present invention.

FIG. 3 is a diagram showing optimum roll roughness in the first pass of the finish cold rolling step, and distribution of reduction with respect to total reduction amount.

FIG. 4 is a diagram showing optimum roll roughness in the second pass of the finish cold rolling process and distribution of reduction with respect to total reduction amount.

FIG. 5 is a diagram showing the optimum roll roughness in the third pass of the finish cold rolling step, and the distribution of reduction with respect to the total amount of reduction.

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

Claims (4)

[Claims] 1. The depth of the cold-rolled sheet is 0.
A high-gloss stainless steel plate having a surface recess of 1 μm or more in an area ratio of 1.0% or less. 2. In the finish cold rolling step of a stainless steel sheet, the first pass rolling is cold rolled at a rolling distribution of 20 to 40% by using a rough roll having Ra = 0.4 to 1.6 μm, Then, rolling of the second pass is performed by Ra = 0.01 to 0.06μ.
cold rolling with a reduction distribution of 20 to 40% using a smoothing roll of m, followed by rolling in the third pass Ra = 0.01 to 0.06μ.
cold rolling with a reduction distribution of 10 to 30% using a smoothing roll of m, followed by rolling of the remaining passes Ra = 0.01 to 0.06μ.
A method for producing a high-gloss stainless steel sheet, which comprises cold rolling the remaining reduction distribution using a smooth roll of m. However, the reduction distribution is 100% of the total reduction amount in the finish cold rolling process.
Allocation (%) 3. Following the method of claim 2, Ra =
A method for producing a high-gloss stainless steel sheet, which comprises 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 stainless steel sheet, which comprises temper rolling at.