JP2020163402A - Manufacturing method of ferritic stainless steel sheet, and ferritic stainless steel sheet - Google Patents

Abstract

To provide a ferritic stainless steel sheet capable of reducing flaw formation on a sheet surface, for example, at a transportation time, and excellent in flaw resistance; and to provide its manufacturing method.SOLUTION: In a manufacturing method of a ferritic stainless steel sheet, an intermediate material having a thickness of 3.0 mm or less is subjected to a cold rolling step for performing cold rolling with rolling reduction of 5 to 45% and forward slip of 1 to 8%, and after the cold rolling step, a shape correction step with elongation of 0.1 to 0.8% is performed, to thereby obtain the ferritic stainless steel sheet having a thickness of 0.5 mm or less. The ferritic stainless steel sheet is also provided.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a ferritic stainless steel sheet and a ferritic stainless steel sheet.

Ferritic stainless steel sheets typified by SUS430 and the like are used for various purposes because of their good workability and low cost. For example, Patent Document 1 describes a compound-based thin-film solar cell in which the average roughness Ra of the surface on which the insulating layer of the stainless steel substrate is formed is 85 nm or less. It is described that the stainless steel substrate described in Patent Document 1 is a ferritic stainless steel substrate, and it is described that the average roughness Ra is adjusted in order to obtain good element characteristics in the substrate material. There is.

Japanese Unexamined Patent Publication No. 2014-107510

In recent years, due to the miniaturization of electronic components and the like, ferritic stainless steel sheets are also required to have higher quality on the surface. On the other hand, when producing a ferritic stainless steel sheet, defects are formed on the surface of the sheet due to foreign matter accumulated on the wiper during line passing and minute irregularities on the roll surface. This defect causes various defects, and when used as a substrate for an electronic component such as a solar cell, it becomes a factor that deteriorates the performance of the electronic component due to a change in dimensional accuracy. Such surface defects can be removed by using a polishing machine such as a grinder, but it also causes a decrease in productivity due to an increase in man-hours and conversely a factor of forming new defects by polishing. Therefore, a ferrite-based stainless steel sheet having high flaw resistance and excellent surface properties and strength is desired. Patent Document 1 does not study the improvement of flaw resistance as described above.
Therefore, an object of the present invention is to provide a ferrite-based stainless steel sheet having excellent scratch resistance on the surface of the sheet and a method for producing the same.

One aspect of the present invention includes a cold rolling step of performing cold rolling of an intermediate material having a thickness of 3.0 mm or less with a reduction rate of 5 to 45% and an advanced rate of 1 to 8%, and the cold rolling. A method for producing a ferritic stainless steel sheet, which comprises a shape straightening step of performing shape correction with an elongation rate of 0.1 to 0.8% after the process to obtain a ferritic stainless steel sheet having a thickness of 0.5 mm or less. ..

Another aspect of the present invention is a ferritic stainless steel thin plate having a thickness of 0.5 mm or less, in which the load at the start of the test is 0.5 N and the load at the end of the test is 2.0 N in the scratch test. When the amount of change in the depth of the flaw is D [μm] and the amount of change in the width of the flaw is W [μm] when the load is 2.0N, based on the depth and width of the flaw when is 0.5N. , A ferritic stainless steel thin plate having a D × W value of 15 or less in the rolling direction and the direction perpendicular to rolling.

According to the present invention, it is possible to provide a ferrite-based stainless steel sheet having excellent scratch resistance on the surface of the sheet and a method for producing the same.

An embodiment of the present invention will be described below. In the present specification, the numerical range represented by using "~" means a range including the numerical values before and after "~" as the lower limit value and the upper limit value. Further, in the present specification, the term "process" is used not only as an independent process but also as a term as long as the intended purpose of the process is achieved even when it cannot be clearly distinguished from other processes. included.
First, an embodiment of the ferritic stainless steel sheet of the present invention will be described. The thin plate in the present invention also includes a steel strip wound in a coil shape and a rectangular thin plate produced by cutting the steel strip.

The composition of the ferrite-based stainless steel sheet of the present embodiment may be, for example, a ferritic stainless steel represented by JIS-G4305 or an improved alloy thereof as a typical component. Preferably, in mass%, it contains 0.12% or less of C, 0.75% or less of Si, 1.0% or less of Mn, 16.0 to 18.0% of Cr, and the balance is Fe and unavoidable. Use ferritic stainless steel composed of impurities.

In the present embodiment, for example, cold rolling is performed on an intermediate material having the above-mentioned composition. As this intermediate material, a hot-rolled material or a strip-shaped material obtained by pre-cooling the hot-rolled material can be used. When an oxide layer is formed on the surface of the intermediate material, the oxide layer may be removed, for example, mechanically or chemically. Further, the edge may be trimmed so that defects such as cracks do not occur from the edge of the cold-rolled material during cold rolling. Such processing can be performed to obtain an intermediate material. The thickness of this intermediate material is adjusted to 3.0 mm or less in order to efficiently produce a ferritic stainless steel sheet of 0.5 mm or less in the end. The preferred thickness of the intermediate material is 2.0 mm or less, and the more preferable thickness of the intermediate material is 1.0 mm or less.

Subsequently, in the present embodiment, the intermediate material is cold-rolled (cold-rolling step) in order to obtain a desired plate thickness and surface texture. The rolling reduction during this cold rolling step is adjusted to 5 to 45%. Thereby, the thickness of the thin plate and the advanced rate described later can be controlled to desired values. If the reduction rate is less than 5%, it is possible that the desired shape cannot be obtained because the desired elongation difference at each width direction position cannot be adjusted. On the other hand, if the reduction rate exceeds 45%, there is a possibility that a desired shape cannot be obtained because the elongation difference between the respective width direction positions is too large. The upper limit of the preferable reduction rate is 40%, and the lower limit of the preferable reduction rate is 8%. Although this cold rolling may be carried out in a plurality of passes, it is preferable to roll in one pass in order to obtain desired characteristics while suppressing surface defects.

In the cold rolling step of the present embodiment, it is preferable to adjust the advanced ratio to 1% to 8%. This advanced rate is an index showing the speed difference of the rolled material between the inlet side and the outlet side of the cold rolling roll. The larger the advanced rate, the more plastic flow occurs on the surface of the thin sheet, and the center of the cross section of the thin sheet and the thin plate. There is a tendency for a stress difference from the surface portion to easily occur. By adjusting this advanced rate to the above-mentioned range and performing cold rolling, it is possible to suppress the generation of cracks from fine flaws. Further, it is possible to reduce the tensile stress applied to the thin plate, and it tends to be easy to apply a large compressive stress to the surface of the thin plate in the shape correction step described later. .. The lower limit of the preferred advanced rate is 2%, and the upper limit of the preferred advanced rate is 7.5%. In order to keep this advanced rate within the above-mentioned numerical range, the parameters of rolling rate, rolling speed, rolling roll diameter and roll roughness may be adjusted.

In order to optimally exhibit the rolling form of the present embodiment, the thickness after cold rolling shall be 0.5 mm or less. It is preferably 0.2 mm or less, and more preferably 0.1 mm or less. Although the lower limit is not particularly limited, it can be set to 0.01 mm because the shape tends to change if the material is too thin.

In the manufacturing method of the present embodiment, shape correction is performed on a thin plate that has been cold-rolled (shape correction step). As a result, it is possible to correct the wave shape such as ear waves and medium elongation remaining on the thin plate to improve the flatness, and to apply compressive residual stress to the thin plate to improve the flaw resistance. As the device used for this shape straightening, a conventionally used shape straightening device such as a roller leveler or a tension leveler can be used (in the present embodiment, the tension leveler is used). Here, the shape correction sets the elongation rate to 0.1 to 0.8% in order to apply an appropriate compressive residual stress to the thin plate. If the elongation rate is out of the above numerical range, it may not be possible to apply an appropriate compressive residual stress to the thin plate, and the flatness of the thin plate is also lowered, which is not preferable. The lower limit of the preferable elongation rate is 0.2%, and the upper limit of the preferable elongation rate is 0.75%. The lower limit of the more preferable elongation rate is 0.3%, and the upper limit of the more preferable elongation rate is 0.7%. The ferritic stainless steel sheet obtained by the manufacturing method of the present embodiment described above can be wound into a coil by a winder to form a thin sheet coil, which can be supplied to the next step.

Subsequently, the ferrite-based stainless steel sheet of the present embodiment will be described. In the ferritic stainless steel sheet of the present embodiment, the load at the start of the test is 0.5N and the load at the end of the test is 2.0N in the scratch test, and the depth and width of the flaw when the load is 0.5N are used as a reference. The amount of change in the depth of the flaw when the load is 2.0 N (the depth of the flaw when the load is 2.0 N-the depth of the flaw when the load is 2.0 N) is D [μm], and the amount of change in the width of the flaw. When (width of flaw at 2.0 N-width of flaw at 0.5 N) is W [μm], the value of D × W in the rolling direction is 15 or less, and D × W in the direction perpendicular to rolling. The value is 15 or less. The ferrite-based stainless steel sheet of the present embodiment having the above characteristics is less likely to be scratched by foreign matter accumulated on the wiper during line passing and minute irregularities on the roll surface, and has good surface properties without adding a polishing process. Have. This contributes to the improvement of etching performance in applications used for etching such as metal masks, and in electronic component substrate applications, it is possible to further improve the adhesion with the insulating layer. There is a tendency to improve the effect of enhancing the bondability with the member. Here, as the scratch tester, a nanoindenter generally used in a scratch test may be used. In this embodiment, a diamond indenter having a tip angle of 120 ° is used for a sample size of 25 mm × 25 mm, and the ruled distance is 5 mm, the ruled speed is 5 mm / min, the load speed is 3 N / min, and the load is from 0.5 N to 2.0 N. The sample was scratched while increasing, and the depth and width of the scratch were observed with a laser microscope. Even if D × W is within the above numerical range, if the depth of the flaw or the width of the flaw is extremely large, the surface state may not exhibit various good characteristics such as improved adhesion. Therefore, the rolling direction. The preferred flaw depth in the above can be set to 1 μm or less, the preferred flaw width can be set to 20 μm or less, the preferred flaw depth in the direction perpendicular to rolling can be set to 0.5 μm or less, and the preferred flaw width can be set to 10 μm or less.

First, a strip-shaped intermediate material having the composition shown in Table 1 and having a thickness of 0.3 mm was prepared, and after preliminary cold rolling was performed on the above-mentioned intermediate material, the rolling reduction ratio was 13% and the advanced ratio was 4%. Cold rolling was carried out in one pass under the conditions to prepare a Fe—Ni alloy thin plate having a thickness of 0.08 mm. After that, the sample No. which is an example of the present invention. In No. 1, shape correction with an elongation rate of 0.7% was performed, and sample No. 1 as a comparative example. No shape correction was performed on No. 2.

A 25 mm × 25 mm test piece was taken from the ferrite-based stainless steel sheet of the examples of the present invention and the comparative example after cold rolling and shape correction, and a scratch test was performed. The test equipment uses Nanotech's Revest-RST, and a load speed of 3 N / min, a ruled distance of 5 mm, and a ruled speed of 5 mm / min using a diamond indenter of Rockwell_120 °, and the load is from 0.5 N to 2.0 N. The test was conducted while varying linearly. A laser microscope (OLYMPUS_OLS-4000) was used for observing the flaws after the test. As a result of the test, based on the depth and width of the flaw when the load is 0.5N, the amount of change in the depth of the flaw when the load is 2.0N is D [μm], and the amount of change in the width of the flaw is W [ In the example of the present invention, D × W in the rolling direction was 11.5 and D × W in the direction perpendicular to the rolling was 8.0. On the other hand, in the comparative example, D × W in the rolling direction was 16.9, and D × W in the direction perpendicular to rolling was 13.9. From this, it was confirmed that the thin plate of the example of the present invention has high flaw resistance and is suitable for applications requiring high surface texture.

Claims (2)

A cold rolling process in which cold rolling is performed on an intermediate material having a thickness of 3.0 mm or less with a reduction rate of 5 to 45% and an advanced rate of 1 to 8%.
After the cold rolling step, a shape straightening step of performing shape straightening with an elongation rate of 0.1 to 0.8% is provided.
Obtain a ferritic stainless steel sheet with a thickness of 0.5 mm or less.
Manufacturing method of ferritic stainless steel sheet. A ferritic stainless steel sheet with a thickness of 0.5 mm or less.
In the scratch test, the load at the start of the test is 0.5N and the load at the end of the test is 2.0N.
Based on the depth and width of the flaw when the load is 0.5N, the amount of change in the depth of the flaw when the load is 2.0N is D [μm], and the amount of change in the width of the flaw is W [μm]. When
A ferritic stainless steel sheet having a D × W value of 15 or less in the rolling direction and the direction perpendicular to rolling.