JPH03118902A - Manufacture of cold rolled steel sheet for super deep drawing - Google Patents

Abstract

PURPOSE:To improve the press formability of the cold rolled steel sheet for super deep drawing by executing the machining in the specified roughness on the surface of a work roll by a laser dulling machine and executing the machining in the specified roughness on the steel sheet surface by this work roll. CONSTITUTION:The aggregation of a small crater like recessed part and a ring like rise part of the outer edge thereof is executed on the surface of a rolling work roll by a laser dulling machine. The ratio Sm/d of the mean center distance Sm among the recessed parts thereof to the diameter D of the ring like rise part outer edge is taken 1.0-1.7 and the center line mean roughness Ra of the surface is 3mum. The machining that the center line mean roughness Ra becomes the roughness >=1.5mum is executed on the surface of the steel sheet by this work roll. Thus, the quality trouble of the sheet face can be eliminated.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method of manufacturing a cold rolled steel plate for ultra-deep drawing using a rolling work roll whose surface has been specially processed using a laser dull processing machine. It is.

<Prior Art> Generally, as a method for imparting formability to a steel plate, a method of transferring dull marks onto the surface of the steel plate using a rolling work roll subjected to shot dulling is generally used.

According to this method, for relatively light drawing applications such as steel plates for automobiles, the steel plate surface roughness is Ra 1.5μ.
However, for ultra-deep drawing applications such as past tabs, in addition to improving the material quality, the steel plate surface roughness is finished to be as rough as possible < Ra 1.5 μm or more, and the oil pooling effect is actively improved. It is necessary to convert it to 111.

Conventionally, as a method of converting this oil pool effect to 1111,
A method of obtaining a high roughness of the plate surface by roughening the shot grains and roughening the surface roughness of the roll is known.

<Problem to be solved by the invention> However, in order to obtain a plate surface with high roughness, Sijinoto grains are
The above conventional method of granulating and rolling processing results in large irregularities on the roll surface due to mixed shot grains, which significantly impairs the quality of the board surface such as dullness, and also causes uneven oil pooling due to irregular irregularities. , mold galling during pressing,
There is a problem in that it tends to lead to defects such as wrinkles.

An object of the present invention is to provide a method for manufacturing a cold-rolled steel sheet for ultra-deep drawing that solves these problems.

The present applicant has disclosed in Japanese Patent Application Laid-Open No. 151205/1983,
Although it has been shown that machining a roll with a regular surface roughness using a laser dulling machine is effective for this purpose, the present invention further improves this.

<Means for Solving the Problems> The present invention provides a rolling work roll that is formed of a set of fine crater-shaped recesses and a ring-shaped raised part on the front side at the outer edge of the recess and that are adjacent to each other. The ratio 5Lll/D of the average center-to-center distance Sea between the recesses and the diameter of the outer edge of the ring-shaped raised portion is within the range of 1.0 to 1.7, and the centerline average roughness Ra of the surface is 34 or more. Processing is performed using a laser dull processing machine, and the work roll gives the surface of the steel plate a center line average roughness Ra of 1.
This is a method for producing a cold-rolled steel sheet for ultra-deep drawing, which is characterized by not performing processing to obtain a roughness of 5- or more.

Effects> Since the present invention uses laser beam irradiation instead of dulling using shot grains, rolls due to mixed shot grains, dull balding on the board surface, etc. do not occur at all, and the board surface is Since the irregularities can be controlled arbitrarily, the top position of the oil pool can be controlled arbitrarily, which has a large effect on improving formability, especially during ultra-deep drawing.

In order to improve formability, the roll surface should be made up of a collection of minute crater-shaped recesses and ring-shaped raised parts on the outer edge of the recesses, and the average center distance between adjacent recesses should be 1iiIS11. It is necessary that the ratio SL1/D to the diameter of the outer edge of the ring-shaped raised portion be 1.7 or less. However, if SIl/D is less than 1.0, the rings overlap and accurate pitch control cannot be performed, so it is assumed that Ss/D≧1.0.

In addition, in ultra-deep drawing applications, since the flow of the material is large, wrinkle defects will occur during pressing unless Ra is made rougher than usual. To avoid this wrinkle defect, Ra≧1.
A level of 5μ is typically required.

For this reason, the center line average roughness Ra of the roll surface is 3 μm.
It is necessary to perform the above processing.

In addition, p p I (Peaks Per Inch
: The larger the number of peaks per inch), the more advantageous. This is because the larger PP■, the greater the oil pooling effect and the lower the sliding resistance.

<Example> Examples of the present invention will be described below.

A large bathtub shown in FIG. 1 was pressed using a cold-rolled steel sheet manufactured by the method of the present invention and a cold-rolled steel sheet subjected to a conventional shot dulling process. Conventionally, large bathtubs have had the problem of easily forming wrinkles on the backrest when pressed.

Table 1 shows the materials of the test materials.

Table 1 shows the surface shape of the work roll used in the method of the present invention. A-/L/surface S11/D is 1.5, Ra
is 31M, and Ra=3pm on the plate surface of the sample material in Table 1.
Processed. On the other hand, the plate surfaces of the test materials shown in Table 1 were processed to Ra=3 um by conventional shigitdal processing.

Table 2 shows the results of pressing the large bus shown in FIG. 1 using cold-rolled steel sheets processed in these two ways.

Table 2 As can be seen from Table 2, the steel sheets manufactured according to the present invention have a wider formable range, that is, a BHF range, and less wrinkles and cracks than steel sheets subjected to conventional sirot dull processing.

<Effects of the Invention> As explained in Figure 1 (2) to 2, the present invention eliminates problems with the quality of the board surface, and also makes it possible to provide regular irregularities on the board surface, thereby reducing oil pools. The amount and position can be controlled arbitrarily, and in particular, it becomes possible to significantly improve the press formability of cold-rolled steel sheets for ultra-deep drawing.

[Brief explanation of drawings]

Figure 1 shows a large bathtub, Figure 1 (1) is a plan view,
FIG. 1(2) is a front view, and FIG. 1(3) is a side view. FIG. 2 is an enlarged view showing one example of the surface shape of the work roll used in the present invention, FIG. 2 (1) is a plan view, and FIG. 2 (2) is a cross-sectional view. .

Claims (1)

[Claims] The surface of a rolling work roll is composed of a set of minute crater-shaped recesses and a ring-shaped raised part on the front side at the outer edge of the recessed part, and the average center distance Sm between adjacent recessed parts and the ring-shaped raised part This work roll has been processed using a laser dull processing machine so that the ratio Sm/D to the diameter D of the outer edge is within the range of 1.0 to 1.7, and the center line average roughness Ra of the surface is 3 μm or more. A method for producing a cold-rolled steel sheet for ultra-deep drawing, characterized in that the surface of the steel sheet is processed to have a center line average roughness Ra of 1.5 μm or more.