JPS5934441B2 - Temper rolling method for cold rolled steel sheets - Google Patents

Description

[Detailed description of the invention] The present invention relates to a temper rolling method for cold rolled steel sheets.

Cold-rolled steel sheets are produced by removing scale from hot-rolled steel sheets by pickling, cold-rolling them to a specified thickness, recrystallizing and annealing them, and then temper-rolling them. Manufactured.

Cold-rolled steel sheets are used in a wide range of applications, including automobiles and light electrical products, due to their beautiful surface and good workability.

The surface finish of cold-rolled steel sheets is generally dull due to the adhesion of paint and advantages in processing.

The surface finish is adjusted by adjusting the surface condition (roughness, number of ridges) of the temper roll in consideration of the roughness specified by the user and the intended use.

Normally, the roll surface is 1.0 to 3.0 μRa, 200
PPI or lower is used, but the steel plate rolled by these rolls has a dull profile or is uneven, resulting in poor finish appearance after painting, and during press processing, the lubricating oil film runs out, reducing workability. .

The inventors of the present invention have conducted many experiments with the aim of solving these problems, and have found that if the surface profile is defined within a certain range, the appearance of the painted finish and press workability can be improved. .

The gist of this is that the relationship between roll surface roughness (μRa) and number of protrusions (PPI) for hardened steel sheets is
This is a temper rolling method for cold-rolled steel sheets using dull rolls adjusted to 290-30X (μRa)≧1.30 μRa)≧290-30X (μRa).

The reason for limiting the numerical values of the present invention as described above will be explained in detail below.

In order to improve the paint finish appearance or press workability of cold rolled steel sheets, the surface of the temper roll is improved by processing methods such as electric discharge dulling and shot blasting to improve the surface roughness (μR).
In the relationship between a) and the number of peaks (PPI), PPI (cutoff level 1.20 to 1.30μRa) > 290 = 30X (
Finish to a dull surface of μRa).

This relational expression was obtained from experiments in the present invention, and the unit of roll surface roughness Ra is the center line average roughness, and the unit of peak number is PPI.
(Peaks per 1 nch) is the number of peaks per inch of length.

Furthermore, the cutoff level refers to the surface roughness of the roll (μR
Determine a) by setting the top of each mountain to a certain height standard (
Ra).

In the present invention, the cutoff level of 1.20 to 1.30μ is determined by accurately counting the peaks using a surface roughness meter.
Furthermore, the height of the ridges on the transferred steel plate is made uniform, which improves the appearance after painting and the lubrication performance during press working, thereby improving press workability.

However, if the cutoff level is less than 1.20μ, the number of ridges that are effective for improving press workability will be reduced, and
If the thickness exceeds 30μ, the number of effective ridges will decrease, and there is also the problem that the steel plate cannot withstand the frictional force during press processing, resulting in breakage and surface flaws on the surface after press forming.The figure shows a temper rolling roll. Surface roughness (Ra) and number of peaks (PPI)
) shows the correlation between

Temper rolling rolls become PP when Ra increases due to the processing method.
I tends to become smaller.

Furthermore, profiles with low PPI have uneven peak heights, resulting in uneven and diffuse reflection of light on the painted surface, resulting in poor appearance.Also, during press working, the amount of lubricating oil held on the steel plate surface is small, and the steel plate surface Since the press die and the press die contact each other unevenly, the contact pressure at the crest increases, resulting in poor workability.

For this reason, the aforementioned surface profile, namely PP
I (1,20-1.30μRa)≧290ri←30×(
μRa), it is possible to stably improve the painted finish appearance and press workability.

Such dull rolls according to the invention are made by electrical discharge dulling or by shot blasting using specially selected grids.

Next, examples of the present invention will be described.

The sintered sheet manufactured through the normal cold rolled steel sheet manufacturing process is rolled using various dull rolls in a temper rolling mill.
The paint finish appearance and press workability were investigated.

The appearance was determined by visual inspection, and the workability was determined by the coefficient of friction (μ) on the surface of the steel plate during cylindrical pressing.

The above results are shown in the table below.

As is clear from this table, Samples 1 to 3 according to the present invention are superior to conventional materials 4 to 6 in terms of appearance and pressability.

[Brief explanation of drawings]

Figure 1 shows the Ra and PPI of the temper roll in the present invention.
FIG. 3 is a diagram showing the influence of the relationship on the appearance of the painted finish.

Claims (1)

[Claims] 1 Roll surface roughness (μ
Ra) and number of peaks (PPI) are PPI (cutoff level 1.20-1.30 μRa)>290-30×(μ
A method for temper rolling a cold-rolled steel sheet, characterized by temper rolling with dull rolls adjusted to Ra).