JP2002239604A - Method of manufacturing cold-rolled stainless steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a cold-rolled stainless steel sheet by which the generation of gloss irregularity which is generated on the surface is reduced than that by a conventional method even in the case that cold rolling is performed using a hot-rolled ferritic stainless steel for a base stock. SOLUTION: When manufacturing the cold-rolled stainless steel sheet by applying the cold rolling having a plurality of passes to the hot-rolled stainless steel sheet of a material to be rolled, before starting the cold rolling, the surface roughness of the hot-rolled stainless steel sheet is adjusted to <=2 times of the surface roughness of the work rolls which are used for the 1st pass. At that time, it is preferable to perform the adjustment with a grinder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a cold-rolled stainless steel sheet, and more particularly, to a method for reducing unevenness in gloss generated on the surface of a ferritic stainless steel such as SUS430, which is particularly likely to cause unevenness in gloss. The present invention relates to a technology for manufacturing a cold-rolled stainless steel sheet that can be suppressed.

[0002]

2. Description of the Related Art A cold-rolled stainless steel sheet (before cutting is a steel strip because it is manufactured continuously) is prepared by hot-rolling a material of a desired steel type in advance into a steel strip (called a hot-rolled steel strip). After being pickled, it is further rolled cold. The cold rolled stainless steel strip manufactured through such a process is required to have excellent surface gloss for its use.

For this reason, various methods of cold rolling stainless steel sheets for imparting surface gloss have been conventionally studied. For example, Japanese Patent Application Laid-Open No. 1-122603 discloses a hot-rolled stainless steel sheet subjected to intermediate annealing and pickling. 5% reduction in steel strip
Pre-treatment of non-lubricated rolling to reduce surface irregularities, and to continuously perform multiple passes (meaning that a pair of upper and lower rolls are passed a plurality of times, one pass is referred to as one pass) A technique for performing rolling is disclosed. In addition, in order to perform multiple passes of cold rolling on the material to be rolled, usually,
A so-called "tandem mill" in which a pair of upper and lower rolls constitute one set (referred to as one stand), a plurality of stands are arranged in series, and the material to be rolled is sequentially and continuously passed, or the material to be rolled is rolled a plurality of times in one stand. A reversible (reverse) type rolling mill in which the roll is reciprocated between rolls is used.
In the case of a reversible rolling mill, since a stainless steel has a large deformation resistance, a multi-high rolling mill having a small-diameter work roll such as a Sendzimir mill is often used. Further, in the cold rolling of stainless steel, the rolls are exchanged in the middle of each pass from the viewpoint of placing importance on the surface gloss of the product.

In the technology described in Japanese Patent Application Laid-Open No. 1-122603, in order to suppress a surface defect called an oil pit which occurs in a steel plate subjected to lubrication-free rolling, during cold rolling, the first stand is moved from the last stand to the last stand. In the stand one step before, or in each pass from the first pass to the pass immediately before the final pass, the surface roughness is set to the average roughness Ra.
Cold rolling using a work roll in the range of 0.4 to 0.7 μm, and using a work roll having a surface roughness of 0.25 μm or less in average roughness Ra at the final stand or the final pass. Is applied to improve the gloss of the steel strip surface.

[0005]

However, there are cases where sufficient gloss cannot be obtained even with the technique described in JP-A-1-122603. This is because band-like gloss unevenness occurs along the rolling direction, and this tendency is particularly remarkable in ferritic stainless steel such as SUS430.

In view of the above circumstances, the present invention provides a method of manufacturing a cold-rolled stainless steel sheet in which even when a hot-rolled ferritic stainless steel sheet is cold-rolled as a material, the occurrence of gloss unevenness on the surface can be suppressed more than before. It is intended to provide.

[0007]

Means for Solving the Problems In order to achieve the above object, the inventor of the present invention, in the process of manufacturing a stainless steel cold-rolled steel sheet by using a stainless steel hot-rolled steel sheet after annealing and pickling, as a material to be rolled, firstly The cause of the uneven gloss produced on the surface of the cold-rolled steel sheet was investigated. As a result, in the initial pass of the cold rolling, abrasion powder and the like are unevenly adhered to the surface of the work roll, and unevenness of surface roughness called coating unevenness is formed. It has been found that gloss is uneven when transferred to the surface of a material. That is, when the material to be cold-rolled is a hot-rolled stainless steel sheet after annealing and pickling, the surface roughness of the steel sheet is usually the arithmetic average roughness Ra (hereinafter, referred to as JIS B 0601). The average roughness (Ra) is about 2.0 μm. On the other hand, the surface roughness of the work roll used in the cold rolling is 0.2 to 0. 0 in terms of the average roughness Ra in the case of the work roll used from the first pass to one pass before the final pass.
7 μm, 0.1 for work roll used for final pass
It is about μm. Therefore, in the first pass, since the surface roughness of the material to be rolled is larger than the surface roughness of the work roll, a film such as abrasion powder uniformly formed on the surface of the work roll during rolling (coating). ) Was stripped off by the material to be rolled, resulting in the above-mentioned coating unevenness, which was found to be the cause of the band-like gloss unevenness occurring on the surface of the material to be rolled. Therefore, the inventor has conducted intensive research on the prevention of the occurrence of the band-shaped gloss unevenness, and made the countermeasure according to the present invention.

That is, the present invention provides a method of manufacturing a stainless steel cold-rolled steel sheet by successively performing cold rolling on a stainless steel hot-rolled steel sheet as a material to be rolled in a plurality of passes. A method for manufacturing a cold-rolled stainless steel sheet, characterized in that the surface roughness of the steel sheet is adjusted to twice or less the surface roughness of the work roll used in the first pass.

In this case, the adjustment is preferably performed by grinding with a grinder, and the surface roughness of the work roll used in the first pass is set to an average roughness Ra of 0.2 to 0.3 μm.
m is preferable. Further, the present invention is effective when the material to be rolled is a ferritic stainless steel.

[0010]

Embodiments of the present invention will be described below.

The present invention is applied to a case where a hot-rolled stainless steel sheet is annealed and pickled, and then cold-rolled in a plurality of passes to form a cold-rolled steel sheet. Then, in the present invention, before subjecting the hot-rolled steel sheet to cold rolling, the surface roughness is adjusted to twice or less the surface roughness of the work roll used in the first pass of cold rolling. According to the investigation by the inventor, if the surface roughness of the hot-rolled steel sheet to be rolled is not more than twice the surface roughness of the work roll, the coating (wear) of the work roll surface during the first pass rolling is performed. This is because it became clear that the coating can be maintained uniformly without peeling off the powder film, and the occurrence of gloss unevenness can be suppressed.

In the present invention, the surface roughness of the hot-rolled steel sheet may be adjusted by any means. However, actually, in consideration of workability, grinding with a grinder is preferable. It is also possible to preliminarily perform cold rolling and grinding using a work roll whose surface roughness has been adjusted. However, this method is less preferred. Normally, a hot-rolled steel sheet subjected to cold rolling has a large average surface roughness of about 2.0 μm after annealing and pickling, causing coating unevenness on a work roll used at the time of the preliminary rolling and causing gloss unevenness. It is because it causes.

The work roll used as a reference for the surface roughness of the hot-rolled steel sheet in the first pass is a stainless steel sheet not only in a tandem mill in which a plurality of stands are arranged in series but also in a single reversible system. This is because the steel sheet may be reciprocated (passed) a plurality of times in a mill and cold-rolled. When a tandem mill is used, the average surface roughness of the work roll used for the first stand may be used as a reference, but in the present invention, the work roll used for the first pass is used so as to be applicable to any rolling mill. It is. In actual operation, work rolls are usually replaced and re-ground every time a certain number of hot-rolled steel strip coils are processed. Adjusted to roughness. When the operation is performed, the surface roughness slightly changes, but since the amount of the change is known from experience, the frequency of replacing the work roll used in the first pass is not so high. Therefore, in the present invention, the surface roughness of the hot-rolled steel sheet, which is the material to be rolled, is determined in consideration of the predetermined surface roughness of the work roll used in the first pass and the fluctuation of the surface roughness during operation. Just do it. The surface roughness referred to in the present invention means an arithmetic average roughness Ra defined in JIS B0601.

Further, in the present invention, the surface roughness of the work roll used from the first pass to one pass before the final pass has an average roughness Ra in the range of 0.2 to 0.3 μm. Is preferred. If the average roughness Ra exceeds 0.3 μm, the surface gloss cannot be imparted to the stainless steel sheet,
If it is less than μm, the surface roughness of the hot-rolled steel sheet before cold rolling is set to 0.
This is because it is necessary to make the thickness less than 4 μm, so that the load for adjusting the surface roughness of the hot-rolled steel sheet increases. In addition, in the present invention, the surface roughness of the work roll used in the final pass is:
It is preferable to use one having an Ra of 0.15 μm or less from the viewpoint of obtaining surface gloss.

[0015]

EXAMPLE A cold rolled stainless steel plate (steel type: SUS430) was manufactured using a 12-stage reversible multi-high rolling mill. At that time, in order to confirm the effect of the present invention, the hot rolled steel sheet as the material to be rolled was rolled while changing the surface roughness in various ways, and the occurrence of gloss unevenness of the rolled cold rolled steel sheet was investigated. The size of the hot-rolled steel sheet used is 0.8 to 8.0 mm in thickness and 800 in width.
１1600 mm. The surfaces of these hot-rolled steel sheets were ground using a grinder after annealing and pickling, and the surface roughness was adjusted in the range of 0.06 to 1.80 μm in average roughness Ra. However, only those with Ra of 1.80 μm remain as they were after annealing and pickling, and are not ground by a grinder. Cold rolling is performed by rolling of 3 to 7 passes,
A work roll having an average surface roughness (Ra) adjusted to 0.20 μm is used from the first pass to the last previous pass, and an average surface roughness (Ra) is 0.10 μm for the final pass.
The work roll adjusted to m was used. The work roll is made of die steel and has a roll diameter of 80 to 1 mm.
The one having a diameter of 20 mm was used.

Then, the obtained cold-rolled steel sheet was again subjected to annealing and pickling, and the occurrence of gloss unevenness of the cold-rolled steel sheet was examined by visual observation. Regarding the presence / absence of gloss unevenness, those in which strip-shaped unevenness could be recognized in the rolling longitudinal direction were regarded as having gloss unevenness.

The occurrence rate of gloss unevenness is calculated by calculating the average roughness Ra (μm) of the surface of the hot-rolled steel sheet and the average roughness Ra (μm) of the surface of the work roll used from the first pass to one time before the final mass. It arrange | positioned by the ratio (base plate roughness / roll roughness), and is shown in FIG. Here, the gloss unevenness occurrence rate is determined by cold-rolling 30 coils of a hot-rolled steel strip having the same average surface roughness, examining the number of coils having gloss unevenness generated at that time, and calculating the following equation. I asked. Gloss unevenness occurrence rate (%) = (number of gloss unevenness generating coils / 30) × 100 From FIG. 1, when the base plate roughness / roll roughness is set to 2 or less according to the present invention, the gloss unevenness of the stainless cold-rolled steel sheet as a product is determined. It is clear that the incidence can be kept low. Further, according to the conventional method of cold-rolling a hot-rolled steel sheet as it is after annealing and pickling, the ratio of base plate roughness / roll roughness is 1.80 μm / 0.20 μm = 9, and the occurrence rate of gloss unevenness Is as large as 15%. On the other hand, in the cold-rolled steel sheet according to the present invention, the occurrence rate of gloss unevenness is suppressed to 3% or less.

In the above embodiment, the stainless steel type is ferritic SUS430, but the present invention can be applied to other ferritic steel types or austenitic steel types without any problem.

[0019]

As described above, according to the present invention, when manufacturing a cold-rolled stainless steel sheet, it is possible to prevent gloss unevenness and to reduce the gloss unevenness occurrence rate.

[Brief description of the drawings]

FIG. 1 shows the ratio of the surface roughness Ra (μm) of a hot-rolled steel sheet to the surface roughness Ra (μm) of a work roll used from the first pass of cold rolling to one time before a final mass (base plate) It is a figure which shows the relationship between (roughness / roll roughness) and the incidence rate of a cold rolled steel plate.

Claims (3)

[Claims] When producing a cold rolled stainless steel sheet by successively performing cold rolling on a stainless steel hot rolled steel sheet as a material to be rolled in a plurality of passes, the surface roughness of the hot rolled stainless steel sheet before cold rolling is started. A method for producing a cold-rolled stainless steel sheet, wherein the surface roughness is adjusted to twice or less the surface roughness of a work roll used in the first pass. 2. The method according to claim 1, wherein the adjustment is performed by grinding with a grinder. 3. The method for producing a cold-rolled stainless steel sheet according to claim 1, wherein the work roll used in the first pass has an average surface roughness (Ra) of 0.2 to 0.3 μm. .