JP3241495B2 - Manufacturing method of ferritic stainless steel sheet with excellent gloss - Google Patents

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 excellent gloss.

[0002]

2. Description of the Related Art A ferritic stainless steel sheet having a bright-finished pure finish is excellent in luster, and thus is used for many purposes, such as for interior / exterior use in buildings, a molding material for automobiles, and a reflector for stoves. Needless to say, good gloss is required for these applications, but it is said that the higher the gloss, the better, and the gloss of Cr plating (1500 or more) is considered to be ideal. However, in the case of a ferritic stainless steel sheet manufactured by cold rolling, irregularities on the surface of the rolling material caused by shot blasting and acid cleaning remain as fine defects even after cold rolling, and sufficient glossiness is not obtained. The current situation is that it cannot be obtained.

[0003] As a method for improving the gloss of a stainless steel sheet, there has been conventionally known a method in which bright pure conditions are defined or cold rolling conditions are defined. A method of defining the bright baking pure condition is disclosed in Japanese Patent Application Laid-Open No. 58-123830. This method is a method in which the partial pressures of H ₂ O and H ₂ are defined, and bright baking is performed in a specific temperature range. However, in this method, since a material having insufficient gloss finished by ordinary cold rolling is bright-purified, sufficient gloss is obtained to the extent that the gloss is not deteriorated after bright-purification. Absent.

Further, as a method for defining the cold rolling conditions, there are JP-A-63-49305 and JP-A-2-92402. In these methods, gloss is obtained by defining the surface roughness of the rolling roll or defining the rolling reduction in the final pass of the cold rolling. However, these only define the conditions of the final pass of the cold rolling, and the surface defects up to the last pass remain as oil pits even in the last pass, so that the glossiness of the present invention is 1100 or more. Cannot be obtained stably.

[0005] In the present specification, glossiness is defined as JIS Z-
It refers to gloss G _S (20 °) specified in 8741. An object of the present invention is to propose a manufacturing method capable of stably obtaining a ferritic stainless steel sheet having a gloss of 1100 or more.

[0006]

Means for Solving the Problems The present inventors investigated not only the production conditions but also the combination with the chemical composition of the steel to obtain a gloss of 1100 or more for bright-finished pure ferritic stainless steel. As a result of the study, the present invention has been completed. That is, the present invention relates to a method for producing a ferritic stainless steel sheet which is finished by brightening and purifying, wherein a steel having a total weight ratio of C and N of 0.10% or less is subjected to two or more passes of cold rolling to a predetermined thickness. When rolling at a final pass, the rolling is performed at a rolling reduction of 15% or more using a rolling roll with an average surface roughness of 0.030 μm or less in the final pass, and a rolling with an average surface roughness of 0.020 μm or less in the final pass. Using roles
A method for manufacturing ferritic stainless steel sheets with excellent gloss, characterized by using rolling rolls finished with a rolling reduction of 10% or more and having an average surface roughness of 0.010 μm or less in temper rolling after bright baking. is there.

[0007]

The present inventors first studied the effects of components on the glossiness of products finished by bright sintering and temper rolling using more than ten kinds of ferritic stainless steels having different components. As a result, as shown in FIG. 1, it was found that the glossiness of the product had a correlation particularly with the C + N amount. That is, the glossiness of the product increases as the amount of C + N decreases. This is considered for the following reason. It is believed that the gloss of the product depends on the degree of repair of the surface fine defects in each rolling pass. In particular, the repair of surface fine defects in the final pass is important because the rolling is close to the final product.

On the other hand, since the repair of fine defects is performed by elongating and crushing the defects by cold rolling, it is considered that the softer the rolled stainless steel, the easier the defects are to be repaired. According to the investigations of the present inventors, it has been confirmed that the hardening of the ferritic stainless steel becomes difficult as the amount of C + N decreases. Therefore, C +
It is considered that the reason why the glossiness of the product is improved as the N content is lower is that the material is hardly work-hardened and the fine defect can be easily repaired in the final pass.

Here, in the ferritic stainless steel sheet, Nb, which is a stabilizing element for C and N, and
There is an example where Ti is added. These elements combine and precipitate with a part of C or N, and have an effect of reducing the original solid solution effect of C and N. Therefore, when these elements are added, the work hardening is reduced, and the glossiness of the product is improved. However, in these steel types that are problematic in terms of corrosion resistance, C and N are reduced, and the total content is usually within the component range of the present invention. Alternatively, it is not necessary to specifically consider the addition of Ti.

However, even if the amount of C + N is limited to a total of 0.10% or less by weight as described above, the white circle of 16Cr in FIG.
As shown in the example of steel, it is difficult to stably obtain a gloss of 1100 or more under ordinary cold rolling conditions. Then, the present inventors next examined the effect of cold rolling conditions on the gloss of products using SUS430 having a C + N content of 0.10% by weight. As a result, it was found that the glossiness did not necessarily increase even if a low-roughness roll having an average surface roughness of 0.020 μm was used only in the last pass of the cold rolling. The present inventors have investigated the cause in detail, and as a result, when a rough roll is used in the last pass, even when using a low-roughness roll in the final pass, the rolling oil is found in deep depressions in the steel sheet surface. It has been found that this is because a lot of so-called oil pits remain in which the defects remain even after the sealing and rolling.

The present inventors have paid attention to this point, and have investigated the effects of roll roughness and rolling reduction in each pass. As a result, it was found that in order to improve the gloss of the final product, it is necessary to set the average surface roughness of the roll in the pre-final pass to 0.030 μm or less, and to set the rolling reduction to 15% or more. Further, it was also found that in the final pass, the average surface roughness of the roll needs to be 0.020 μm or less and the rolling reduction 10% or more in order to sufficiently repair fine defects on the surface. In the case where the above conditions are applied in the pre-last pass and the final pass, the influence of the roll roughness of the last-before-last pass on the gloss of the product is extremely small.

From the above, the C and N contents are expressed as the sum of the weight ratios.
By using a ferritic stainless steel of 0.10% or less as a material and defining the cold rolling conditions of the final pre-pass and the final pass as described above, a much higher gloss than conventional can be obtained.
Bright sintered and refined ferritic stainless steel products are usually subjected to temper rolling after refining. At this time, the surface roughness of the rolling roll to be used needs to be finer than the surface roughness of the steel plate after bright firing. According to the study of the present inventors, in order to obtain a gloss of 1100 or more of the final product, at least the average surface roughness of the roll used in the temper rolling needs to be 0.010 μm or less.

According to the present invention, as described above, the cold rolling conditions of the final pre-pass and the final pass are defined as described above using ferritic stainless steel having a total C and N content of 0.10% or less by weight. Further, it is an epoch-making method for producing a ferritic stainless steel sheet, in which a glossiness of 1100 can be stably obtained for the first time by further defining the conditions of the temper rolling after bright firing.

In the present invention, the conditions for bright sintering are as follows:
The condition conventionally used, that is, the condition in which the ferrite stainless steel sheet is maintained at an appropriate temperature and for an appropriate time in an inert or reducing gas atmosphere according to the composition of the ferritic stainless steel sheet may be used. In this case, from the viewpoint of surface quality, care must be taken so that a temper color does not occur due to the formation of a thick oxide film during bright baking.

[0015]

EXAMPLES Table 1 shows the chemical composition of the test materials, cold rolling conditions, and experimental results. Here, the cold rolling condition A is a condition in the present invention, and a steel strip having a thickness of 4.0 mm is rolled in six passes by a rolling roll having an average surface roughness of 0.2 μm, and the seventh pass is reduced to 0.082 μm, 8 Pass 0.030μm, Pass 9
Rolled by rolling rolls with an average surface roughness of 0.013μm, 0.6m
The thickness is to be m, and it is to be finished with a rolling roll having an average surface roughness of 0.008 μm in the temper rolling after bright sintering. The cold rolling condition B is a condition which has been conventionally performed, and a steel strip having a thickness of 4.0 mm is rolled for 7 passes by a rolling roll having an average surface roughness of 0.2 μm, and the eighth pass is reduced to 0.10 μm. Rolling the 9th pass with a rolling roll having an average surface roughness of 0.030 μm
It has a thickness of 0.6 mm and is finished with a rolling roll having an average surface roughness of 0.008 μm in the temper rolling after bright firing.

[0016] Both the embodiment and the comparative example have a thickness of 4.0 mm and a weight of 5 mm.
Using hot-rolled material of ton or more, cold rolling, bright blasting, and lubrication-free temper rolling were performed. The glossiness after temper rolling was measured at ten portions of the steel strip, and the average value was represented.
Table 2 shows the experimental results when the cold rolling conditions were changed according to the sheet thickness using the steels shown in the third row of Table 1. The working row 12 in Table 2 is the cold rolling condition A, and the comparative example 14 is B.

From these Examples and Comparative Examples, it is possible to obtain the glossiness for the first time by adjusting the C + N content of the ferritic stainless steel to 0.10% or less by weight and optimizing the cold rolling condition and the temper rolling condition. It turns out that it is possible to achieve 1100 or more.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

According to the present invention, the total amount of C and N of the ferritic stainless steel is limited, the rolling conditions of the final pre-pass and the final pass in the cold rolling are specified, and the refining after bright firing is performed. By defining the rolling conditions, it has become possible to stably obtain a glossiness of 1100 or more, which could not be achieved by simply defining the cold rolling conditions and bright sintering pure conditions conventionally performed. .

[Brief description of the drawings]

FIG. 1 is a graph showing the correlation between the glossiness after temper rolling and the amount of C + N when 16Cr steel is manufactured under cold rolling conditions A and B.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-127903 (JP, A) JP-A-6-182402 (JP, A) JP-A-3-42151 (JP, A) JP-A-2- 310319 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B21B 1/22-3/02 B21B 27/00

Claims (1)

(57) [Claims] 1. A method for producing a ferritic stainless steel sheet which is finished by brightening and purifying, wherein a steel having a total weight ratio of 0.10% or less of C and N is subjected to cold rolling of two or more passes to a predetermined thickness. When rolling to the final pass, using a rolling roll having an average surface roughness of 0.030 μm or less in the last pass.
% With a rolling reduction of at least 10% using a rolling roll with an average surface roughness of 0.020μm or less in the final pass. A method for producing a ferritic stainless steel sheet having excellent gloss, characterized by using a rolling roll having a roughness of 0.010 μm or less.