JP2683419B2 - Cold rolling method for stainless steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention, when cold-rolling a stainless steel strip, makes it possible to reliably obtain a stainless steel strip having a target luster. Regarding the method.

[Conventional technology]

For stainless steel products, hot-rolled material is annealed, or descaling is performed by shot blasting and pickling without annealing, cold rolling, and then bright annealing or annealing pickling (annealing is performed in a combustion gas atmosphere). It is manufactured by temper rolling. The product that has undergone the bright annealing process has a high gloss and is called a BA product. The product manufactured by the annealing pickling process is called 2B product, and its gloss is inferior to that of BA product.

However, even for 2B products, the gloss level required by the user must be ensured, and the variation in gloss must be reduced.

As described above, the stainless steel is subjected to shot blasting after hot rolling to cause cracks in the oxide scale layer on the surface, and then the scale is removed by pickling. At this time,
As a result of shot blasting, irregularities are produced on the surface of the stainless steel strip, and when the irregularities remain even after the subsequent cold rolling, the gloss is significantly deteriorated.

Therefore, some proposals have been made regarding a method for producing a stainless steel sheet having excellent gloss.

For example, in JP-A-60-61104 and JP-A-62-137106, the hot-rolled material having a large surface roughness is smoothed by cold rolling by defining the surface roughness of the work roll.

Further, JP-A-61-49705 aims at smoothing a hot rolled material by positively generating a heat streak during cold rolling, that is, by rolling in a state close to dry friction.

[Problems to be solved by the invention]

In order to prevent the roughness of the hot-rolled material from being shot-blasted, the tension-leveler or the like has recently been used to perform bending and then shot-blasting. This is because the oxide scale layer can be cracked by bending, so that the projection energy of shot grains in shot blasting can be reduced, and therefore, no large unevenness is generated on the surface.

On the other hand, in cold rolling, it was mainstream to roll stainless steel with a roll diameter of 100 mm or less in a reverse type or tandem arrangement to roll stainless steel, but recently, a medium diameter roll with a larger roll diameter ( Diameter 100-300
mm), rolling with a tandem rolling mill having large diameter rolls (diameter 300 to 650 mm), or rolling with a combination of large diameter, medium diameter and small diameter rolls in tandem has been attempted. It is well known that the larger the roll diameter, the worse the gloss.

Furthermore, on the other hand, even with the same 2B product, there are several levels of gloss level required by the user, and it is necessary to suppress variations in gloss between products.

That is, the surface roughness of the hot-rolled sheet varies depending on the descaling process and there are some cold rolling methods, so it is very difficult to reliably obtain the gloss required by the user. It was also difficult by the techniques described in JP-A-60-61104, JP-A-61-49705, JP-A-62-137106 and the like.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a cold rolling method for a stainless steel strip capable of reliably obtaining a target gloss.

[Means for solving the problem]

The present invention measures the surface roughness of a hot rolled stainless steel sheet after pickling, determines the roll diameter of the rolling mill according to the value of the roughness and the gloss grade required after cold rolling, and determines this diameter. It is a method of cold rolling stainless steel, characterized in that cold rolling is carried out using the work roll of the present invention.

[Action]

FIG. 1 shows the relationship between the surface roughness of hot-rolled sheet and the gloss after temper rolling for each cold-rolled work roll diameter. This graph shows a reduction rate of 75%
The rolling conditions are as follows: hot-rolled sheet thickness: 4.0 mm, cold-rolled sheet finished sheet thickness: 1.0 mm, rolling speed: 300 mpm, and finish 2B.

The surface roughness of the hot-rolled sheet depends on the mechanical descaling conditions before pickling as described above. When using hard shot blasting, Rmax is 30 to 35 μm, and when bending is sufficiently effective, shot blasting can be extremely light. At this time, Rmax
Is 15 to 20 μm.

FIG. 1 shows the glossiness after temper rolling (skin pass) when these hot rolled sheets were cold rolled under the above conditions. Here, the gloss after temper rolling (hereinafter simply referred to as gloss) is 800 or more as a top grade, 600 or more as a normal grade, and 500 or more as a low level grade.

From FIG. 1, for example, when the required gloss grade is a normal grade and the surface roughness of the hot rolled sheet is Rmax = 30 μm, the roll diameter is determined to be 90φ.

Figure 1 shows the case where the rolling reduction is 75%, and the curve changes suddenly when the rolling reduction is different. FIG. 2 shows an example of the relationship between the surface roughness of the hot-rolled sheet and the gloss after temper rolling under the following conditions.

Rolling conditions: Hot rolled sheet thickness: 4.0mm Cold rolled sheet finish sheet thickness: 0.8mm Reduction ratio: 80% Rolling speed: 300mpm Finish: 2B [Example] SUS430 hot coil rolled to 4.0mm thickness by hot rolling Annealing and pickling were performed. After that, the surface roughness was measured and found to be Rmax = 30 μm. This coil has a thickness of 1.0 mm after cold rolling. Since it is used for general purposes, the gloss level is aimed at normal grade.

From these conditions, the required roll diameter is 200 mmφ from Fig. 1.
It can be read as follows. As a rolling mill with a roll diameter of 200 mmφ or less, there is a 20-high reverse rolling mill with a roll diameter of 90 mmφ, so cold rolling from 4.0 mm thickness to 1.0 mm thickness is performed, and then annealing / pickling and temper rolling are performed. After applying (2B finish), a normal grade of gloss was obtained as originally intended.

〔The invention's effect〕

INDUSTRIAL APPLICABILITY According to the present invention, it becomes possible to stably manufacture a stainless steel sheet having a desired gloss regardless of the roughness of the hot rolled sheet.

[Brief description of the drawings]

Fig. 1 is a graph showing the relationship between the surface roughness of hot-rolled sheet and the gloss after temper rolling when cold-rolled from 4.0 mm to 4.0 mm. Fig. 2 shows the hot-rolled sheet thickness of 4.0 mm. 3 is a graph showing the relationship between the surface roughness of hot-rolled sheet when cold rolled to 0.8 mm and the gloss after temper rolling.

Claims (1)

(57) [Claims] 1. A surface roughness of a hot-rolled stainless steel sheet after pickling is measured, and a roll diameter of a rolling mill is determined according to the roughness value and a gloss grade required after cold rolling. A method for cold rolling stainless steel, characterized in that cold rolling is performed using a work roll having the same.