JPH09155407A - Method for producing ferritic stainless steel sheet with excellent r value - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a ferritic stainless steel sheet excellent in r value with a single cold rolling process without any process annealing by specifying each pass draft in multipass rolling using small diameter roll in all the cold rolling processes. SOLUTION: When the ferritic stainless steel sheet is manufactured by the single cold rolling process, the sheet is multipass rolled using a small diameter roll having a work roll of 100mm or smaller diameter in all the cold rolling processes. This draft at each pass is controlled within 5-12%. In the suitable embodiment, cumulative draft quantity is 80% or less. The standard of the ferritic stainless steel sheet is 0.3-1.0mm as the thickness is order to be usually an end product as it is. Thereby, density of 100} texture is reduced and the ferritic stainless steel sheet excellent in r value is obtained. Further, the heat treatment and rolling processes following the process annealing is able to be omitted and accordingly the manufacturing cost is able to be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a ferritic stainless steel sheet having an excellent r value, and more particularly to a method for producing a ferritic stainless steel sheet that is performed in one cold rolling step without performing an annealing treatment in the middle. .

[0002]

2. Description of the Related Art Conventionally, in order to produce a thin steel sheet of a stainless steel sheet having a good r value for drawing applications, it has been common to use a small diameter roll and two cold rolling steps in which an intermediate annealing is performed on the way. there were.

However, due to recent demands for reduction in manufacturing cost, methods for performing cold rolling in a single cold rolling step while omitting intermediate annealing have been researched and developed, and some have already been developed. Suggestions have been made. An outline of such a conventional technique by a patent publication is as follows.

Japanese Examined Patent Publication No. 2-410 discloses a method for producing a ferritic stainless steel sheet having excellent surface properties and workability. First, a work roll having a diameter of 300 mm or more is used to roll 60% or more of the total reduction amount. Since then, it has been proposed to roll using a work roll with a remaining rolling amount of 100 mm or less in diameter, but this causes problems in the steel plate shape due to large changes in work roll preparation and rolling conditions. Not practical.

Japanese Patent Publication No. 2-14122 discloses a method for producing a ferritic stainless steel sheet having excellent workability, in which cold rolling is divided into a former stage and a latter stage in the same manner as described above, and the former cold rolling is performed with a diameter of 150 mm. It has been proposed to use a work roll of mm or more so that the cumulative amount of reduction in the preceding stage of cold rolling is 60% or more of the total reduction. However, even with this method, there are problems in work roll preparation and steel plate shape.

[0006] Japanese Patent Publication No. 2-15283 discloses a method for producing a ferritic stainless steel sheet having excellent ridging and r value by cold rolling to a final thickness of 150 to 300 mm.
The method of using the work roll is disclosed.

As described above, in the prior art, in order to omit the intermediate annealing, the cold rolling is divided into the former stage and the latter stage, work rolls having different diameters are used, or the cumulative reduction amount is reduced. As described above, the result does not always meet the original purpose of omitting the process.

In the prior art, it is considered inevitable to use a work roll having a relatively large diameter in order to improve the r value, and as a result, a large work roll is not required if an intermediate annealing step is not performed. There is a problem that workability deteriorates because it is necessary to combine a work roll with a small diameter and a work roll with a small diameter, and in particular, the total reduction amount is specified in the preceding stage.

[0009]

SUMMARY OF THE INVENTION Here, an object of the present invention is to solve the problems in the prior art as described above.
It is an object of the present invention to provide a method for producing a ferritic stainless steel sheet having an excellent r value that can complete cold rolling in one cold rolling step without performing annealing treatment in the middle.

Specifically, the object of the present invention is to have a diameter of 100 mm.
It is an object of the present invention to provide a method for producing a ferritic stainless steel sheet having an excellent r value even by using a work roll having a small diameter as described below, by a single cold rolling method.

More specifically, the present invention provides a method for producing a ferritic stainless steel sheet having an r value of 1.2 or more in one cold rolling step by a Sendzimir rolling machine using a work roll having a small diameter of 100 mm or less. Is.

[0012]

Means for Solving the Problems The present inventors have obtained the following findings as a result of various studies to achieve the above object.

That is, conventionally, a large-diameter roll of, for example, 150 mm or more is used as the work roll in the preceding stage.
This is to improve the rolling efficiency as well as improve the value, but because large rolls cannot provide a large reduction amount (the work hardening of ferritic stainless steel is not large), it is possible to cool only in the previous stage. Since it is impossible to reach the final plate thickness by rolling, cold rolling of the former stage is performed after the former stage, and in the latter stage, rolling with a small diameter roll is forced. However, as long as such a method is adopted,
It is unavoidable to change rolls or install another rolling line, which inevitably increases manufacturing costs.

Therefore, it is desirable from the standpoint of improving the overall rolling efficiency and reducing the manufacturing cost that the problems such as roll change can be avoided by rolling with small diameter rolls from the beginning to the end in all stages. did.

Therefore, as a result of further various studies on the influence of the relationship between the work roll diameter and the rolling reduction on the r value in that case, when the work roll diameter is 100 mm or less,
By performing each pass at a rolling reduction of 5 to 12%, the cumulative rolling reduction can be set to 80% or less, and a ferritic stainless steel sheet with excellent r value can be obtained. The present invention has been completed, knowing that improvement and reduction of manufacturing cost can be realized.

Therefore, the gist of the present invention is to provide a method for producing a ferritic stainless steel sheet in which the hot rolled sheet has a final thickness in one cold rolling step without intermediate annealing. The work roll diameter
A method for producing a ferritic stainless steel sheet having an excellent r value, which is characterized by controlling the rolling reduction in each pass within 5 to 12% when performing multi-pass rolling with a small-diameter roll of 100 mm or less. is there.

According to a preferred embodiment of the present invention, the cumulative reduction amount is
80% or less. In the present invention, the plate thickness of the ferritic stainless steel plate is not particularly limited, but usually the final product as it is, the thickness is about 0.3 ~ 1.0 mm,
Generally called a thin steel plate.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, in the conventional method, the stainless steel sheet, particularly the ferritic stainless steel sheet, is required to have high gloss and high surface quality.
Cold rolling is often performed by a small diameter work roll rolling mill typified by a Sendzimir rolling mill. On the other hand, however, the r-value of the small-diameter roll rolling is lower than that of the large-diameter roll rolling. Therefore, it is possible to improve the r-value by performing cold rolling in two or more cold rolling steps with intermediate annealing. I am trying. Generally, the r value depends on the texture, and it is known that when the amount of {111} texture is large, the r value is improved, while the {100} texture lowers the r value.

Therefore, the relationship between the r value and the rolling conditions during cold rolling of a ferritic stainless steel sheet was arranged, and the {100} structure tends to increase as the rolling reduction of one pass increases. The more rolled it is, the higher the density of the {100} structure and the thickness of the central layer is {100
The structure tends to become a structure. On the other hand, in rolling with a large-diameter roll, the formation of a {100} structure by rolling does not reach the center layer of the plate thickness within about 25% of the plate thickness. Therefore, if intermediate annealing is not performed, it is rather possible to leave the {111} structure in the center by cold rolling with large-diameter roll rolling.
It is effective in improving the value.

Therefore, in the present invention, when performing multi-pass rolling with a small-diameter roll having a diameter of 100 mm or less, the rolling reduction of each pass is conventionally 15 to 30% depending on the capability of the rolling mill. By performing light reduction rolling with reduction to 5 to 12%, it is possible to reduce the conventional thickness of the central layer to {100} to 25% of the thickness.
By reducing the density of the {100} structure, ferritic stainless steel with an excellent r value can be manufactured. In a preferred embodiment of the present invention, the effect of improving the r value is particularly exhibited at a cumulative rolling reduction of 80% or less.

If the amount of reduction in each pass is less than 5%, the number of passes will be large, and the required amount of accumulated reduction can be secured by a normal multi-stage cold rolling mill currently used, for example, a Sendzimir rolling mill. Can not do it. On the other hand, 12%
If it exceeds, the generation depth of the {100} structure may be more than 25% deeper than the surface layer, so deterioration of the r value cannot be avoided. Preferably, the amount of reduction in each pass is 8-12.
%.

[0022]

Next, the function and effect of the present invention will be described in more detail with reference to its examples. In this example, a Sendzimir rolling machine was used as the rolling machine for cold rolling, and the dimensions of the hot rolled sheet and the final product to be used as the raw materials were as follows. The unit of dimensions is mm.

SUS 430 3.2 × 1000 × C (hot rolled sheet) 〃 〃 2B 0.6 × 1000 × C (final product dimension) That is, in the present invention example, 3.2 mm hot rolled sheet is pickled and then subjected to intermediate annealing. Without further treatment, cold rolling was performed continuously in 13 passes to a thickness of 0.60 mm by a Sendzimir rolling mill using a work roll having a diameter of 63 mm.

As a comparative example, the same as the example of the present invention, but with a reduction ratio of 20% or more in each pass and a thickness of 0.60 in 7 passes.
Cold-rolled to mm. On the other hand, as a conventional example, the same Sendzimir rolling machine used in the above-mentioned example of the present invention was used to perform intermediate annealing (830 ° C. × 10 seconds) in the fourth pass to obtain a total of 8
Cold rolling was performed to 0.60 mm in the pass. The rolling conditions for each example are summarized in Table 1.

The results of measuring the r value of each cold-rolled material thus obtained are summarized below. As described above, according to the present invention, an r value of about the same as 2R can be obtained by one cold rolling in the cold rolling step. By setting the rolling reduction of each pass to 5 to 12%, the number of passes will be increased than usual, but it will be possible to carry out two to one rolling, and it will be possible to omit the heat treatment and rolling steps after the intermediate annealing. However, the effect of reducing the manufacturing cost from the practical point of view is great.
When the rolling reduction of each pass is 21% or more, r value = 1.0 and r value is not improved.

[0026]

[Table 1]

[0027]

The r value (average) is used as an evaluation of the workability of a ferritic stainless steel sheet, but in order to improve the r value (average), conventionally, two cold rolling steps with intermediate annealing are performed. Although the process was carried out, in the present invention, it was possible only by cold rolling in one cold rolling process, and even if a Sendiji rolling machine is used as an effect of the concrete manufacturing process. It is possible to efficiently manufacture a ferritic stainless steel sheet by cold rolling without the need for intermediate annealing, and it can be seen that its practical effect is great.

Claims (2)

[Claims] 1. A method for producing a ferritic stainless steel sheet in which a hot-rolled sheet has a final thickness in one cold rolling step without intermediate annealing, in which work roll diameter is changed in all stages of the cold rolling step. A method for producing a ferritic stainless steel sheet having an excellent r value, which comprises controlling the rolling reduction in each pass within 5 to 12% when performing multi-pass rolling with a small-diameter roll of 100 mm or less. 2. The method according to claim 1, wherein the cumulative rolling reduction is 80% or less.