JPH0732004A - Method for producing ferritic stainless steel sheet with excellent gloss - Google Patents

Abstract

PURPOSE:To stably obtain a ferrite base stainless steel sheet with excellent gloss. CONSTITUTION:When a ferrite base stainless steel sheet whose contents of C and N are less than 0.10% is rolled with cold rolling into a prescribed thickness, it is rolled with rolls of their average surface roughness less than 0.030mum and with the draft more than 15% before the final pass, further at the final pass, it is rolled with rolls of their average surface roughness less than 0.020mum and with the draft more than 10%, and after bright annealing, it is temper-rolled with rolls of their average surface roughness less than 0.010mum.

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 Prior Art A ferritic stainless steel sheet having a bright finish and a pure finish has excellent luster and is therefore used in many applications such as interior and exterior construction, molding materials for automobiles, and reflectors for stoves. Needless to say, good gloss is required for these applications, and it is said that the higher the gloss, the better, and the Cr-plated gloss (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 material for rolling generated by shot blasting or acid cleaning remain as fine defects even after cold rolling, and sufficient glossiness is obtained. The current situation is that they cannot get it.

As a method for improving the gloss of a stainless steel plate, a method of defining bright baking pure conditions or cold rolling conditions has been conventionally known. A method for defining the pure conditions for bright baking is disclosed in JP-A-58-123830. In this method, the partial pressures of H ₂ O and H ₂ are defined, and bright baking is performed within a specific temperature range. However, in this method, since the material of insufficient gloss, which is finished by ordinary cold rolling, is bright baked, the gloss is not deteriorated after the bright baking and sufficient gloss is obtained. Absent.

As a method for defining the cold rolling conditions, there are JP-A-63-49305 and JP-A-2-92402. These are methods for obtaining gloss by defining the surface roughness of the rolling roll or further defining the reduction ratio in the final pass of cold rolling. However, these only specify the conditions of the final pass of cold rolling, and the surface defects up to the final prepass remain as oil pits even in the final pass, so that the glossiness of the object of the present invention is 1100 or more. Can't get stable.

In this specification, the gloss level is JIS Z-
The gloss level 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 glossiness of 1100 or more.

[0006]

[Means for Solving the Problems] In order to obtain a gloss of 1100 or more for brightly baked pure ferritic stainless steel, the present inventors investigated not only the manufacturing conditions but also the combination with the chemical composition of the steel. As a result of examination, the present invention has been completed. That is, the present invention is a method for producing a ferritic stainless steel sheet, which is finished by performing bright annealing, in which the total weight ratio of C and N is 0.10% or less, and the steel is given a predetermined thickness by cold rolling for two or more passes. When rolling into the final pass, rolling with an average surface roughness of 0.030μm or less is used to roll at a reduction ratio of 15% or more in the final pass, and further, in the final pass, an average surface roughness of 0.020μm or less is rolled. Using a roll
A method for producing a ferritic stainless steel sheet with excellent gloss, characterized by using a rolling roll having an average surface roughness of 0.010 μm or less in temper rolling after finishing with bright reduction and 10% or more rolling reduction. is there.

[0007]

The present inventors first examined the effect of the components on the glossiness of products finished by bright baking and temper rolling using dozens of types of ferritic stainless steels having different components. As a result, as shown in FIG. 1, it was found that the glossiness of the product has a correlation with the amount of C + N. That is, the glossiness of the product increases as the C + N amount decreases. This is probably due to the following reasons. It is considered that the glossiness of the product depends on the degree of repair of fine defects on the surface in each rolling pass. Particularly, the repair of surface fine defects in the final pass is important because the rolling is close to that of the final product.

On the other hand, since fine defects are repaired by extending the defects by cold rolling, it is considered that the softer stainless steel to be rolled, the easier the defects are to be repaired. The investigations by the present inventors have confirmed that ferritic stainless steel becomes harder to work harden as the amount of C + N decreases. Therefore, C +
It is thought that the reason why the gloss of the product is improved as the N content is lower is that the material is hard to work and harden and the fine defects are easily repaired in the final pass.

Here, in the ferritic stainless steel sheet, in order to improve the corrosion resistance, Nb, which is a stabilizing element of C and N, and
You can see an example of adding Ti. These elements combine with a part of C or N to be precipitated and have the effect of reducing the original solid solution effect of C and N. Therefore, when these elements are added, work hardening is reduced and the glossiness of the product is improved. However, with regard to these steel types having corrosion resistance as a problem, C and N are reduced, and the total content is usually within the range of the components of the present invention. Alternatively, it is not necessary to consider the addition of Ti specially.

However, even if the total amount of C + N is limited to 0.10% or less in total, the white circle 16Cr in FIG.
As shown in the example of steel, it is difficult to stably obtain a glossiness of 1100 or more under normal cold rolling conditions. Therefore, 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 even if a roll having a low roughness of 0.020 μm in average surface roughness is used only in the final pass of cold rolling, the glossiness does not necessarily increase. The present inventors, as a result of investigating the details of this cause, when a rough roll is used in the final pre-pass, even if a roll with a low roughness is used in the final pass, rolling oil is contained in the deep recesses of the steel sheet surface. It was found that this is because many so-called oil pits, which are contained and have defects remaining after rolling, are generated.

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

From the above, the amounts of C and N in the total weight ratio are
By using 0.10% or less of ferritic stainless steel as a raw material and defining the cold rolling conditions for the final pre-pass and the final pass as described above, much higher gloss than before can be obtained.
The brightly ferritic stainless steel product is usually temper-rolled after calcination. At this time, the surface roughness of the rolling roll to be used needs to be finer than the surface roughness of the steel sheet after bright baking. According to the investigation by the present inventor, in order to obtain the glossiness of 1100 or more in 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.

As described above, the present invention defines the cold rolling conditions for the final pre-pass and the final pass as described above, using a ferritic stainless steel as a raw material in which the total amount of C and N is 0.10% or less. Further, it is an epoch-making method for producing a ferritic stainless steel sheet in which the glossiness of 1100 can be stably obtained for the first time by defining the condition of the temper rolling after the bright baking.

The conditions for bright baking in the present invention are as follows:
The condition that has been conventionally used, that is, the condition that the temperature is maintained for a proper time at an appropriate temperature according to the composition of the ferritic stainless steel sheet in an inert or reducing gas atmosphere. In this case, from the viewpoint of surface quality, it is necessary to take care not to cause temper color due to the formation of a thick oxide film during bright baking.

[0015]

EXAMPLES Table 1 shows the chemical composition, cold rolling conditions and experimental results of the test materials. Here, the cold rolling condition A is a condition in the present invention, in which a steel strip having a plate thickness of 4.0 mm is rolled for 6 passes by a rolling roll having an average surface roughness of 0.2 μm, and the seventh pass is 0.082 μm, 0.030 μm for pass, 9 for pass
0.6m by rolling with a rolling roll having an average surface roughness of 0.013μm
The thickness is m and is finished by a rolling roll having an average surface roughness of 0.008 μm in the temper rolling after bright baking. The cold rolling condition B is a condition that has been conventionally used. A steel strip having a plate 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 0.10 μm. Roll the 9th pass with a rolling roll with an average surface roughness of 0.030μm
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 temper rolling after bright baking.

In both the embodiment and the comparative example, the plate thickness is 4.0 mm and the weight is 5
Cold rolling, bright baking, and non-lubricating temper rolling were performed using hot rolled materials of ton or more. The glossiness after temper rolling was measured at 10 parts of the steel strip, and represented by the average value.
Table 2 shows the experimental results when the steel shown in Example 3 of Table 1 was used and the cold rolling conditions were changed according to the plate thickness. 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, the glossiness can be measured 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 ferritic stainless steel is limited, the rolling conditions of the pre-final pass and the final pass in cold rolling are specified, and the tempering after bright annealing is performed. By specifying the rolling conditions, it has become possible to stably obtain a glossiness of 1100 or higher, which could not be achieved only by specifying the cold rolling conditions and bright baking pure conditions that were conventionally performed. .

[Brief description of drawings]

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

Claims (1)

[Claims] 1. A method for producing a ferritic stainless steel sheet, which is finished by bright annealing, wherein the total weight ratio of C and N is 0.10% or less steel is cold-rolled for two or more passes to a predetermined thickness. 15) using a rolling roll with an average surface roughness of 0.030 μm or less in the last pass.
Rolling with a rolling reduction of 10% or more, and using a rolling roll with an average surface roughness of 0.020 μm or less in the final pass, finishing with a rolling reduction of 10% or more, and the average surface by temper rolling after bright baking. A method for producing a ferritic stainless steel sheet having excellent gloss, which comprises using a rolling roll having a roughness of 0.010 μm or less.