JPH07204701A - Manufacture of ferritic stainless steel plate having low roping - Google Patents

Abstract

PURPOSE:To provide a manufacturing method for a ferritic stainless steel plate by which the height of roving is effectively reduced. CONSTITUTION:The ferritic stainless steel plate is refining rolled using a roll whose surface hardness is >=1000 to <=2000 Vickers hardness under a condition in which the draft of >=0.8% to <=2.0%. Thus, the height of roping is reduced in the ferritic stainless steel plate without requiring a new facility and an excessive process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temper rolling method for reducing the roping height of a ferritic stainless steel sheet.

[0002]

2. Description of the Related Art Ferritic stainless steel sheets are used in a wide range of fields because they have excellent surface gloss and color tone and are lower in price than austenitic stainless steel sheets. However, when a ferritic stainless steel sheet is cold-rolled, a "wrinkle" pattern parallel to the rolling direction, which is called roping or living, appears on the surface of the steel sheet, and aesthetics and commercial value are significantly impaired. The roping that occurs on ferritic stainless steel sheets is a "wrinkle" on the surface.
-Shaped unevenness, the size of which varies considerably depending on the previous history, but the width is 30 μm to 100 μm and the height is 0.1 μm
To about 0.8 μm. This roping occurs during cold rolling and becomes more noticeable in the final annealing.

As a countermeasure against this, improvements have been conventionally made by devising each process such as solidification, hot rolling, annealing after hot rolling, cold rolling, etc., but it is not yet satisfactory.
As conventional techniques, destruction of columnar crystals by hot rolling, promotion of recrystallization during hot rolling, prevention of coarse grains due to precipitation of γ phase,
It promotes recrystallization during annealing. Further, in a cold rolling process in which roping occurs, rolling using a hard roll has been performed to improve plastic working by crushing the generated roping.

[0004]

As a conventional technique for reducing roping, γ phase precipitation by adjusting the steel composition (for example, Japanese Patent Laid-Open No. 146456/1982) and electromagnetic stirring during casting (for example, Japanese Laid-Open Patent Publication No. Hei 4 (1999) -44156). 236717), two-division hot rolling method (for example, Japanese Patent Laid-Open No. 4-160117).
And long-time annealing (for example, JP-A-55-97430)
and so on. However, when introducing electromagnetic stirring / twice-division hot rolling into actual equipment manufacturing, it is necessary to use huge and complicated equipment, resulting in enormous equipment cost, and precipitation of γ phase and fine grain formation of coarse grains by simple recrystallization. However, since the annealing time becomes very long and the productivity is remarkably reduced, it is not desirable in industrial production, and the roping height cannot be effectively reduced.

On the other hand, an improved technique for reducing the roping height generated on the surface of the austenitic stainless steel sheet by using a hard roll in the cold rolling step is disclosed in Japanese Patent Application Laid-Open No. 2-240218. .
However, this method is originally applied to the cold rolling process in which roping occurs, and since the roping generation and crushing are competitively performed, the final roping height is sufficiently reduced to about 0.1 to 0.2 μm. It has not been effective yet. Further, since the ferritic stainless steel is harder to work harden than the austenitic stainless steel, the method disclosed in JP-A-2-240218 has a further effect of smoothing the surface irregularities (roping) in the ferritic stainless steel. Will be inferior.

Therefore, the main object of the present invention is to effectively reduce the roping height without using complicated equipment as compared with the conventional temper rolling process and without lowering the productivity. Another object of the present invention is to provide a method of temper rolling a ferritic stainless steel sheet.

[0007]

[Means for Solving the Problems] That is, the present invention uses a ferritic stainless steel sheet having a roll surface hardness of 1,000 to 2,000 in terms of Vickers hardness to obtain a rolling reduction of 0.8% to 2%. It is to perform temper rolling under the condition of 0.0% or less.

[0008]

In the temper rolling method for a ferritic stainless steel sheet according to the present invention, a hard rolling roll is used in the temper rolling step of a stainless steel sheet which has undergone a normal process, and the rolling reduction is carried out under the condition of a specific range. Is characterized by.

The reasons for limitation of the present invention will be described below. As described above, the roping is a “wrinkle” -shaped unevenness of the stainless steel plate and has a height of 0.1 to 0.8 μm.
Usually, a stainless steel sheet is subjected to hot rolling-annealing, followed by cold rolling-bright annealing (or atmospheric annealing-pickling) and temper rolling to obtain a product, but roping occurs in the cold rolling step. Therefore, in order to obtain a steel sheet having a low roping height as a product, the crushing means is most effective in temper rolling. However, in order to crush a roping having a width of 30 to 100 μm and a height of 0.1 to 0.8 μm, a roll harder than the conventionally used roll surface hardness must be used. When rolled with the conventionally used high speed steel roll, it is 0.2-0.3μ compared to before rolling.
Although the m is reduced, roping with a height of about 0.1 to 0.2 μm remains.

FIG. 1 shows the relationship between the hardness of the roll surface in temper rolling and the roping height of the ferritic stainless steel sheet after rolling. As can be seen from this figure, when the surface hardness of the roll is increased, the effect of reducing the roping height becomes remarkable.
That is, it is clear that the hardness of the roll surface should be 1000 or more in terms of Vickers hardness in order to significantly reduce the roping height. Therefore, the hardness of the roll surface of the present invention is set to Vickers hardness of 1000 or more.

As a roll having a high surface hardness, a hard chrome plated roll, tungsten carbide (WC)
A roll, a SiAlON roll or the like may be used. Rolls with a hardness higher than that require advanced technology, and the manufacturing cost increases significantly. Further, as is clear from FIG. 1, even if temper rolling is performed with a roll having a Vickers hardness of more than 2000, the effect of reducing the roping height is small.
From the above, the surface hardness of the roll of the present invention is set to 1000 or more and 2000 or less in Vickers hardness.

The method of the present invention reduces the roping height in temper rolling after annealing, but it is also effective in rolling cold-rolled material if it is a ferritic stainless steel sheet. Further, the temper rolling of the present invention was examined by using a 2Hi rolling mill with one upper and one lower stage.
Further, the effect is exactly the same even if it is carried out by a multi-stage cluster mill rolling mill, and it is not particularly limited to a specific rolling mill type.

When the rolling reduction of the temper rolling is too low, there is no effect of reducing the roping height, and when it is too high, the effect is saturated. As shown in FIG. 2, the rolling reduction is 0.
If it is less than 8%, there is no effect, and if it exceeds 2.0%, the effect is saturated. Therefore, the rolling reduction of the present invention is 0.8% or more and 2.0% or less. From the above, FIG. 3 shows the temper rolling conditions effective for reducing the roping of the present invention.

[0014]

EXAMPLES Table 1 shows examples of the present invention, comparative examples and conventional examples. Using a SUS430 ferritic stainless steel slab, hot rolling, annealing and pickling were performed, and then the reduction rate was 50.
% Cold rolling, followed by bright annealing at 860 ° C. for 1 minute retention in a nitrogen-hydrogen mixed atmosphere. In addition, instead of bright annealing, some of the steel sheets were subjected to annealing / pickling in the atmosphere (annealing: 860 ° C., holding for 1 minute, pickling; salt treatment + nitric acid electrolytic pickling). Temper rolling was performed using these materials. The conditions for temper rolling are as shown in Table 1. The temper rolling was performed by a 2Hi roll rolling machine with one upper and one upper stage, and a work roll having a diameter of 100 mmφ was used.

The roping height is JIS B 0601.
According to the above, a chart of the sectional curve of the steel plate surface was taken using a stylus type roughness meter, and the height of the unevenness was read. The invention examples (No. 1 to No. 11) have a roping height of 0.1.
μm or less, comparative example, conventional example (No. 12 to 17)
A stainless steel plate with a low roping height is obtained compared to.

[0016]

[Table 1]

[0017]

As is apparent from the above, according to the method of the present invention, it is possible to manufacture a ferritic stainless steel sheet having a low roping height. In particular, if this technology is used, no new equipment is required, so equipment cost is not necessary, and further, there is almost no restriction on the previous history of the material and no extra process is required, so it is suitable for temper rolling of stainless steel. It is an effective means.

[Brief description of drawings]

FIG. 1 is a diagram showing the influence of the surface hardness of a rolling roll on the roping height of the surface of a tempered rolled plate.

FIG. 2 is a diagram showing the effect of a reduction rate on the roping height on the surface of a tempered rolled plate.

FIG. 3 is a diagram showing a temper rolling condition range effective for reducing roping.

Claims (1)

[Claims] 1. A ferritic stainless steel sheet having a Vickers hardness of 1,000 or more and 2,000 or less is used as a roll surface hardness, and the rolling reduction is 0.8% to 2.0%.
A method for producing a ferritic stainless steel sheet having a low roping height, characterized by performing temper rolling under the following conditions.