JPS62137106A - Manufacture of high luster stainless steel strip - Google Patents

Abstract

PURPOSE:To obtain a steel strip having a higher degree of luster than that of a Sendzimir mill rolling material by changing an average roughness or/and an average inclination of roughness of the surface of a work roller, when rolling and manufacturing a stainless steel band by a cold tandem mill. CONSTITUTION:In the first, or the first and the second stands of a tandem mill, a stainless steel strip is rolled by using a work roller whose average roughness Ra of the surface is >=0.5mu. Also, in the last, or the last stand and the stand before the last stand by one, said steel strip is rolled by a work roller whose surface roughness is <=0.15mu, average roughness Ra, and in which an average inclination of roughness being a ratio of the roughness Ra and an average pitch Sm of the roughness is <=1X10<-3>. Also, in other intermediate stand than said stands, said steel strip is rolled by a work roller of the surface roughness in which an average roughness Ra is 0.15-0.5mu, and an average inclination (Ra/Sm) is <=6X10<-3>.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a stainless steel strip with high gloss by rolling a stainless steel strip in a cold tandem mill.

[Conventional technology]

Conventionally, in cold rolling of stainless steel strip, the diameter IQ
A Sendzimir rolling mill having a work roll with a small diameter of 0 mmφ or less was used. The reason for this is that
This is because, as disclosed in No. 3362, stainless steel has high deformation resistance and severe work hardening, so rolling with a pressure of 1 or more and high tension is required.

However, when strong reduction rolling is performed with this small-diameter work roll, the rolling pressure becomes large, so the rolling oil supplied between the work roll and the plate tends to run out of oil film, and the copper after rolling In order to improve the luster on the surface of the belt, mineral oil is supplied as is, resulting in rolls and '! Since the cooling capacity of the I4 zone is insufficient and the steel strip is exposed to high temperatures between the work roll and the steel strip during rolling, oil film breakage is more likely to occur. As a result, heat streaks occurred and remained as surface flaws on the steel 912, and the steel strip could not be made into a product.

Therefore, as a measure to prevent this heat streak, 250
The productivity of stainless steel strips on the Sendzimir rolling mill, which has small diameter work rolls and requires rolling at low speeds of less than mμm, was extremely low.

However, in recent years, tandem mills that roll ordinary steel are rolling stainless steel strips using work rolls with a larger diameter than those of Sendzimir mills.
JP-A-59-38334, JP-A-59-107030
No. 3, discloses a method of cold rolling using a large diameter work roll of 150 mmφ or more.

The first reason is that by increasing the diameter of the work roll, a large amount of rolling oil is drawn between the work roll and the plate, making it difficult for the work roll and plate to come into contact with each other, making it difficult for heat streaks to occur. This is because it can be rolled at a higher speed than the Sendzimir mill.

The second reason is that tandem mills use a rolling oil emulsion, most of which is water, so compared to the Sendzimir mill that uses rolling oil as it is, the cooling capacity is significantly improved and As a result of sufficient cooling, heat streaks are less likely to occur and high-speed rolling is possible.

The third reason is that in the case of the Sendzimir mill, the copper strip was rolled in reverse on one stand, which required a large amount of time to finish the steel strip to the specified thickness, but in the case of the tandem mill, many mills were used to roll the copper strip. Because it uses a stand, ■
This is because it is possible to finish the steel strip to a predetermined thickness only by changing the direction, and the rolling time can be greatly shortened.

When rolling stainless steel strips with this tandem mill, a larger diameter work roll is used compared to the Sendzimir mill.
In addition, as a result of using a rolling oil emulsion with a large cooling f running force, a large amount of rolling oil is drawn between the work roll and the plate, allowing high speed rolling without generating heat streaks.

However, as a large amount of this rolling oil is drawn in, it becomes difficult for the work rolls to come into contact with the plate, and as a result, the surface roughness of the steel strip after rolling is significantly greater than that in the Sendzimir mill. However, tandem mill rolled stainless steel strips have always had the problem of being significantly inferior in gloss compared to Sendzimir mill rolled materials.

Therefore, various methods were considered to solve this problem of reduced gloss. First, low-speed rolling was considered as a way to reduce the amount of rolling oil drawn in, but this resulted in a significant drop in productivity and was not adopted in practice. It's difficult.

Also, when considering the rolling oil aspect, it is possible to (1) reduce the amount of rolling oil supplied, and (2) improve the rolling oil. As a result, heat streaks occur frequently and the steel strip cannot be used as a product. Also.

(2) Improvements in rolling oil have been investigated, and improvements in gloss are being made by improving additives such as base oil and oiliness agents, but there are problems in preventing heat streak and improving gloss17. There is a need to balance the two, but this is not yet sufficient and is a topic for future research.

Further, a method of rolling by changing the roughness of the work roll is disclosed only in the case of a Senshimia mill. For example, Japanese Patent Publication No. 57-13362 and Japanese Patent Publication No. 57-41801. In the Sendzimir mill, which uses small-diameter work rolls and is forced to operate at low speeds, these methods are effective in maintaining the gloss of the surface of the copper strip after rolling, or in preventing surface defects that occur during rolling. Even if it is effective, in tandem mills that use large-diameter work rolls and roll at high speed, there are cases where it is not effective at all in improving gloss. For example, as shown in the conventional example in Table 3 (2) of the embodiment,
The roughness of the work roll is Ra0.2-1 in the bath before finishing.
．． Even if the roughness is 0 μm, the roughness of the work roll of the 1st stand will be explained later when rolling with a work roll having the same roughness from the first stand and rolling with a work roll with a smaller roughness only in the final stand. RaO, 5 μm or more.

Furthermore, even after these tandem mill rolled steel strips are subjected to a final annealing pickling process and a skin pass rolling process, the surface gloss of the stainless steel strip remains unchanged, compared to the conventional Sendzimir mill rolled steel strip. It was significantly inferior.

The surface gloss of the steel strip after Sendzimir mill rolling is determined by JIS
According to Z8741 gloss measurement method 5 (GS20°) 3
00 or more.

Therefore, as a result of intensive research, the present inventors aimed for a gloss level of 300 or higher, and found that when manufacturing a stainless steel strip by rolling it using a cold tandem mill, the first stand, or the first stand and the second stand Rolled with work rolls having a surface roughness of average roughness Ra0.5 gm or more, and rolled with work rolls whose roll surface roughness was gradually decreased as the stands reached the later stages, and the final stand had an average roughness of Ra0.
．． We developed a new rolling technology using work rolls with a surface roughness of 15 gm or less, and were able to achieve this goal.

However, 2. In addition, it was desired to improve the gloss to a higher grade (gloss of 450 h or higher) of the Sendzimir mill rolled material.

[Problem that the invention seeks to solve]

The present invention solves the above-mentioned problems when rolling a stainless steel strip at high speed in a tandem mill, and improves the surface gloss of the rolled stainless steel strip to a higher grade (gloss level of 450 or higher) than that of Sendzimir mill rolled material. The present invention provides a rolling method that significantly improves gloss.

[Means for solving problems]

The present invention aims to solve the problems of the prior art described above, and employs the following technical means.

When manufacturing a stainless steel strip by rolling it using a cold tandem mill, (1) At the first stand, or the first stand and the second stand, a work roll having a surface roughness of average roughness Ra of 0.5 gm or more is used. ■ The final stand, or the final stand and the final one.
On the stand in front of the stand, the average roughness Ra0.15 lm or less,
and rolling with a work roll having a surface roughness in which the average roughness slope Ra/Sm, which is the ratio of the average roughness Ra to the average roughness pitch Sm, is 1 x 10-3 or less, (3) Other than the above. average roughness Ra021 on the intermediate stand of
range from 5 to 0.5 μm, and the average slope of roughness Ra/
This is a method for manufacturing a crystalline stainless steel strip, which is rolled with a work roll having a surface roughness of S m of 6XIO-3 or less.

[Effect]

Hereinafter, the operation of the present invention will be explained in detail.

After hot rolling, the surface roughness of the cold-rolled stainless steel base material was intermediately annealed and pickled. As a result of mechanical descaling during this pickling, the average roughness Ra became significantly rougher, with an average roughness of 3 to 5 gm. The surface is extremely uneven. When this base material is conventionally rolled in a tandem mill using work rolls with a surface roughness Ra of 0.2 gm to 0.3 μm, there will be residual residue from the base material on the surface of the stainless steel strip after rolling. There are many large dents, which are the primary cause of the reduction in gloss.

Therefore, in order to eliminate these large dents during rolling, we rolled the work rolls with various surface roughnesses, and as a result, as shown in Figure 1, the surface roughness Ra of the first stand was 0.5 μm.
When rolling using the above work rolls, the dents on the surface of the copper strip after rolling will change from the conventional average roughness Ra of 0.2 lm to 0.
．． It was found that the thickness was significantly reduced compared to 3 μm. In Figure i1, the horizontal axis shows the average roughness of the work roll of the first stand, and the vertical axis shows the concave surface a ratio of the surface of the copper strip after rolling. However, in some cases, it may not be possible to completely eliminate these dents, so we considered using work rolls with a large surface roughness for rolling from the second stand onwards.As shown in Figure 2, we found that rolling It has become clear that dents can be completely eliminated by rolling using work rolls with Ra of 0.5 μm or more from the second stand onwards. Second
In the figure, the horizontal axis shows the average roughness of the work roll on the second stand.
The vertical axis shows the area ratio of dents on the surface of the copper strip after rolling.

However, even after the third stand, the surface roughness Ra was 0.5 μm.
When rolling with a work roll having a roughness higher than that, the roll roughness is transferred to the copper strip, which is the second cause of reduction in gloss, and as shown in Figure 3 (a), the copper strip after rolling is The surface glossiness does not improve. In FIG. 3, the horizontal axis shows the stand number, and the vertical axis shows the average roughness of the work roll of each stand and the glossiness of the surface of the copper strip on the outlet side of each stand.

Therefore, work rolls with an average roughness Ra of 0.5 gm or more are placed on the first stand, or on the first and second stands.
I decided to use it on a stand.

Next, the copper strip after rolling on the first stand or the first stand and the second stand was rolled with rolls having a large roughness, so the surface roughness was large, and the gloss was extremely low as it was.

Therefore, it is necessary to reduce the surface roughness of the copper strip in the second stand or intermediate stands after the third stand. We have carefully considered the impact on As a result, when the average roughness Ra is 0°5 pLm or more, the roughness of the surface of the copper strip after rolling is large. Rolling does not improve gloss. In addition, the average roughness Ra is 0.1
In the case of rolls of 5 p-m or less, between the smooth roll surface and the highly rough copper strip surface transferred from the previous stand,
As a result of the rolling oil being trapped, the surface roughness of the copper strip can hardly be reduced in the intermediate stand, and the glossiness of the steel strip after rolling cannot be improved, as shown in FIG. 3(b).

Therefore, in the intermediate stand, the average roughness Ra is 0-1.
By rolling with work rolls in the range of 5 m to 0.5 m, the large roughness transferred to the copper strip in the previous stand can be reduced, and an example is shown in Fig. 3(c). As shown, the glossiness of the copper strip surface after rolling can be improved.

At this time, as long as the average roughness Ra is within the range of 0.15 to 0.5 gm, even if the average roughness Ra of the subsequent stage is somewhat rough, the glossiness will not deteriorate and this will deviate from the technical idea of the present invention. It's not a thing.

By the way, as mentioned above, the average roughness Ra of the surface roughness of the steel strip after Sendzimir mill rolling is 0.15 ILm or less, and the gloss at this time is 300 according to JIS Z8741 gloss measurement method 5 (GS20'). That's all.

Therefore, in order to make the gloss of the stainless steel strip after tandem mill rolling equal to or higher than that after Sendzimir mill rolling, in addition to rolling using work rolls with the above-mentioned surface roughness on each stand, In the final stand, it is necessary to use a work roll with a smaller surface roughness to roll a stainless steel strip having a roughness equal to or less than that of the copper strip after Sendzimir mill rolling.

Therefore, we investigated various surface roughnesses of the work rolls on the final stand, the final stand, and the stand immediately before, and as shown in Figure 4, the average roughness Ra was 0.
．． If it is 15 μm or less, the average roughness Ra of the surface roughness of the copper strip after tandem mill rolling is (L15 μm 15p), and the gloss level is also significantly better than that of the stainless steel strip after Sendzimir mill rolling. This became clear.In Figure 4, the horizontal axis shows the surface roughness of the work roll, and the vertical axis shows the glossiness of the surface of the copper strip.

The present inventors further investigated various means for improving the gloss with the aim of achieving a higher grade (gloss of 450 or higher) of the Sendzimir mill rolled material. First, in the intermediate stand, in order to improve the gloss, it is good to make the surface of the copper strip smooth, but if the average roughness Ra of the work roll is too small, the gloss will not improve as mentioned above. After intensive research on the roughness of work rolls with smooth surfaces and Ra ranging from 0.15 gm to 0.5 JLm, we found that the models shown in Figures 5 (a) and (b) were created depending on the roll polishing method. As shown, even if the average roughness Ra is approximately the same, the smoothness of the roll surface may differ, and the average pitch Sm ( The average slope of roughness Ra /
New findings were obtained that S m affects the final gloss of steel strip.

That is, as a result of rolling stainless steel strips with work rolls with different average roughness slopes Ra/S m, the seventh
As shown in the example in the figure, Ra/S m is 6XIO-
It has been found that the glossiness can be further improved when it is 3 or less. In Figure 7, the horizontal axis shows the stand number.

The vertical axis shows the average roughness of the work roll and the gloss level of the copper strip surface on the exit side of each stand.

Therefore, in the intermediate stand, the average roughness Ra is O,1
Rolling was carried out using work rolls having a surface roughness in the range of 5 μm to 0.5 JLm and an average roughness slope Ra/S m of 6×10−” or less.

To further improve gloss, use the final stand or
By variously changing the roll grinding method of the work rolls used in the last stand and the previous stand, the average roughness slope Ra/Sm described above was changed while keeping the average roughness Ra below 0.15 lm. It was rolled. As a result, as shown in FIG. 8, it was found that when Ra/S m was 1×10 −3 or less, the gloss was significantly improved to a gloss of 450 or more. In FIG. 8, the horizontal axis shows the average slope of the roughness of the work roll, and the vertical axis shows the glossiness of the surface of the copper strip after rolling.

As a result of the above, the present invention has established a technology to obtain a copper strip with a higher grade of gloss than Sendzimir mill rolled material, which was thought to be completely impossible with conventional tandem mill rolling, when stainless steel (i7) is rolled with a tandem mill. It was done.

〔Example〕

Based on the rolling schedule shown in Table 1, using the hot rolled, intermediate annealed and pickled stainless steel base material shown in Table 2,
Stainless steel strips were rolled in a cold tandem mill according to the method of the present invention and the conventional method. The surface roughness, average slope of roughness, and results after rolling of these work rolls are shown in Tables 3 (1) and (2). For reference, the results after Sendzimir mill rolling are also appended.

From Table f51 Table 2 Table 3 Tables (1) and (2), the stainless steel strip rolled by the method of the present invention has no residual dents in the base material at all compared to the case of conventional tandem mill rolling. It is also seen that the glossiness is significantly improved, and it is possible to produce a stainless steel strip with a high fragility and a glossiness that is equivalent to or better than that obtained by Sendzimir mill rolling.

〔Effect of the invention〕

The steel strip produced by finishing annealing, pickling, and skin pass rolling the copper strip rolled by the method of the present invention has a gloss level that is equal to or higher than that of conventional Sendzimir mill products or higher grade Sendzimir mill products. It is highly effective in producing high-gloss stainless steel strips.

[Brief explanation of drawings]

Figure 1 is a graph of the average roughness of the work roll of the first stand and the area ratio of depressions on the surface of the copper strip after rolling. Figure 3 is a graph of the average roughness of the work rolls of each stand and the concavity area ratio of the surface of the copper strip after rolling. Figure 4 is a graph of the work roll average roughness of the final stand, or the final stand and the stand before it, and the glossiness of the surface of the copper strip after rolling. Figure 5 is a graph of the same average roughness. Figure 6 is a conceptual diagram showing the average pitch of roughness, Figure 7 is a graph of the average slope of roughness and gloss of the copper strip surface on the exit side of each stand, Figure 8 is a graph showing the average pitch of roughness. It is a graph of the average slope of the work roll roughness of the final stand, or the final stand and the stand immediately before the final stand, and the glossiness of the surface of the copper strip after rolling. Ra: average roughness of roll Sm: average pitch of roughness

Claims (1)

[Claims] 1. When manufacturing a stainless steel strip by rolling it using a cold tandem mill, (1) a surface with an average roughness Ra of 0.5 μm or more on the first stand, or the first stand and the second stand; (2) At the final stand, or at the final stand and the stand one step before the final, the average roughness Ra is 0.15 μm or less, and the average roughness Ra and the average roughness pitch Sm are Rolled with a work roll having a surface roughness with an average roughness slope Ra/Sm of 1 x 10^-^3 or less, and (3) an intermediate stand other than the above, with an average roughness Ra of 0.1.
range of 5 to 0.5 μm, and average slope of roughness Ra/S
A method for producing a high-gloss stainless steel strip, which comprises rolling with a work roll having a surface roughness of m = 6 x 10^-^3 or less.