JPH0673681B2 - Manufacturing method of high function surface roughness adjustment alloyed hot dip plated steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a method for producing an alloyed hot dip plated steel sheet having excellent formability and image clarity after coating.

<Prior Art> Thin steel sheets that require a finished appearance after painting, such as exterior panels of automobile bodies, electric appliances, and sheet metal furniture, are conventionally made of cold-rolled steel sheets. For compatibility, surface roughness is adjusted by temper rolling. However, the rate of using surface-treated steel sheets is rapidly increasing, especially from the viewpoint of rust prevention of steel sheets for automobiles, and compatibility between the post-painting image clarity and the press formability of the surface-treated steel sheet has become an issue. In the case of a surface-treated steel sheet with a relatively thin weight such as electroplating, the surface roughness of the cold-rolled steel sheet, which is the original plate, is maintained even after the surface treatment. It is almost possible with technology.

However, if further measures for rust prevention are required, it is necessary to carry out a surface treatment with a thick weight, such as hot-dip galvanized steel sheet subjected to alloying treatment.In that case, the surface roughness should be the same as that of the original plate. The problem is that they are completely different.
That is, the surface roughness of the galvannealed steel sheet largely changes from the surface roughness of the original plate in both the hot dip galvanizing step and the alloying step. It is known that the final surface roughness of the galvannealed steel sheet is roughened due to peculiar fine irregularities and adversely affects both the post-painting image clarity and the press formability.

Nowadays, the finish quality of painted surfaces of automobiles has recently attracted attention as an important quality control item because it can directly appeal to customers the high sense of automatic difference and high overall quality. As one of the indicators of finish quality of painting, there is sharpness, and in order to improve it, the painting technique has been mainly improved. On the other hand, the surface roughness of a thin steel sheet has generally been roughened by a dent weight due to the conventional press formability. However, with the improvement of coating technology, the relationship between the surface roughness of the thin steel plate that becomes the base material of the coating surface and the surface roughness after coating becomes clear, and the post-painting clarity is improved by controlling the steel plate surface roughness. It has become increasingly clear that it is possible.

Conventionally, the surface roughness of a cold-rolled steel sheet was controlled by temper rolling using a skin pass roll that was shot dull, but the main purpose is to improve press formability. In order to improve the image clarity after painting, it is necessary to reduce the surface roughness of the cold-rolled steel sheet.
It is also introduced in SAE (SAE Tech, Peper Se, No.800208) paper by LAN et al.

However, if this result is applied as it is, a problem remains from the viewpoint of formability. It is impossible to manage both the moldability and the sharpness by controlling the average roughness, as in conventional shotdal processing. JP-A-62-168602 and JP-A-62-224405 disclose a surface roughness control technique for achieving both post-painting image clarity and formability in a cold-rolled steel sheet. However, this applicable steel type was limited to the cold-rolled steel plate or the surface-treated steel plate, which has a light weight and is capable of accepting the surface roughness of the original plate as it is after the surface treatment.

That is, in the case of a surface treatment with a thick weight such as hot-dip galvanized steel sheet, or when the surface is roughened by further alloying treatment, conventionally, surface roughness control for sharpness or molding Roughness control to achieve compatibility with sex was considered impossible, and research for this was neglected.

<Problems to be Solved by the Invention> In the above-mentioned prior patents, all target steel types were limited to cold-rolled steel sheets and surface-treated steel sheets having a thin weight. It is a steel type whose surface roughness is basically determined by temper rolling, and the reason is that the target roughness control can be relatively easily performed in this process. On the other hand, the galvannealed steel sheet has fine irregularities on the surface,
Due to the presence of these irregularities, it was said that the effect of roughness control as in the case of cold-rolled steel sheets cannot be expected.

The present invention discloses a surface roughness management technique for improving both the post-painting image clarity and formability of an alloyed hot-dip plated steel sheet to the level of a cold-rolled steel sheet. It is an object of the present invention to provide a method for producing an alloyed hot-dip plated steel sheet which is both excellent.

<Means for Solving the Problems> That is, according to the present invention, after the steel sheet is hot dip plated and alloyed, the steel sheet surface roughness is 1.0 by the average roughness Ra by polishing.
After adjusting to less than 0.1 μm and more than 0.1 μm, the skin pass roll whose surface roughness is adjusted according to the purpose has an elongation of 0.
When manufacturing a high-performance surface-roughness-adjusted alloyed hot dip plated steel sheet by subjecting it to a temper rolling of 2% or more and a sheet thickness (mm)% or less,
For the purpose of imparting formability to the alloyed hot-dipped steel sheet, the skin pass roll has a surface roughness of Ra.
, 1.0 μm or more and 3.0 μm or less, and the protrusions protruding from the roll polishing surface by 1 μm or more are distributed so that the closest spacing is 10 μm or more and 100 μm or less. For the purpose of imparting a sharpness after painting to a hot-dip plated steel sheet, the skin pass roll has a surface roughness Ra of 1.0 μm or more and 3.0 μm or less, and a convex portion protruding from the roll-polished surface by 1 μm or more. Contact interval 100 μm or more 300 μm
It is intended to provide a method for producing a highly functional surface-roughness-adjusted alloyed hot-dipped steel sheet characterized by using a sharpness-oriented type surface roughness-adjusting roll distributed as follows.

Further, for the front and back surfaces of the steel sheet, the formability-oriented roll and the sharpness-oriented roll may be used separately.

It is preferable that the intervals of the surface roughness convex portions of the surface roughness adjusting skin pass roll used for these are not separated from the average value by 20% or more.

The present invention will be described in more detail below.

The steel type to which the present invention is applied is a thick-coated surface-treated steel sheet with a change in surface roughness, and as an example, zinc, lead, tin, etc. are suitable for hot dip coating. Further, even in the case of a hot-rolled steel sheet whose surface is not controlled from the beginning, the method of the present invention has the same effect.

As for the surface roughness of the galvannealed steel sheet, the surface is roughened as a whole as shown in FIG. 2 due to the fine irregularities formed in the alloying step after plating as described above. Under this condition, the image clarity and the moldability are improved by adjusting the surface roughness within a range that can be realized in the subsequent steps. For this purpose, it was found that the conventional management of average roughness or PPI (the number of peaks per 1 inch) is not sufficient, and it is necessary to further limit the surface roughness structure.

Therefore, in the present invention, by controlling the surface roughness using another parameter, it is attempted to achieve both the formability of the alloyed hot-dip galvanized steel sheet and the post-painting image clarity, and the manufacturing method thereof. Established

That is, in order to properly adjust the roughened surface of the galvannealed steel sheet as shown in FIG. 2 as in the present application, first, the surface roughening is performed so that the roughened surface of the galvannealed steel sheet is smoothed to some extent by polishing. After adjusting the degree, it is effective to carry out temper rolling with a skin pass roll whose surface roughness is adjusted according to the purpose such as formability or image clarity. Although the surface roughness is finally controlled by temper rolling, it is preferable to use a laser-dulled roll as the roll. The plit roll is laser-dulled to form an uneven pattern to be applied to the hot dip plated steel sheet. This dulling roll is pressed against the plated steel sheet at a reduction rate that gives a desired transfer rate.
Thereby, the transfer rate can be set within a desired range. That is, a hot dip plated steel sheet having excellent formability and / or sharpness can be obtained.

More specifically, first, the alloyed hot-dip galvanized is polished to obtain a steel plate surface roughness with an average roughness Ra of 1.0 μm or less, 0.1
Adjust to μm or more. The reason for adjusting to this range is to make the base material necessary for transferring the target roughness in the subsequent adjustment rolling. Then, the polishing may be performed using a means such as a belt type grinder.

Next, temper rolling is performed by a skin pass roll whose surface roughness is adjusted according to the purpose. This temper rolling is performed at 0.2% or more and a sheet thickness (mm)% or less. If it is out of this range, the transfer of the roughness pattern is insufficient, or the material is deteriorated, which is not preferable.

Adjusting the surface roughness according to the purpose means, for example, imparting formability and / or post-painting image clarity to the hot dip plated steel sheet.

In order to make the surface roughness with an emphasis on moldability, a skin pass roll with a surface roughness Ra of 1.0 μm or more,
It is preferable to use a surface roughness adjusting roll in which protrusions protruding 3.0 μm or less and 1 μm or more from the polished surface of the roll are distributed so that the closest spacing is 10 μm or more and 100 μm or less.

Also, if you want to make the surface roughness that emphasizes the clarity after painting, use a skin pass roll with a surface roughness Ra of 1.
It is preferable to use a surface roughness adjusting roll in which the convex portions projecting from 0 μm or more to 3.0 μm or less and 1 μm or more from the roll-polished surface have a closest spacing of 100 μm or more to 300 μm or less.

In the above-mentioned various parameters of moldability and image clarity after coating, if the surface roughness Ra is less than 1.0 μm, the formability becomes insufficient, and if it exceeds 3.0 μm, the level of image clarity decreases, especially when coating. The remaining surface recesses afterwards pose a problem, which is not preferable. Further, when the closest distance between the convex portions is less than 10 μm, the concave portions become rough, resulting in poor moldability and poor image clarity. If it exceeds 300 μm, galling tends to occur, and the moldability also deteriorates. The closest distance between the convex parts can be appropriately selected according to the application or the user's request by obtaining the moldability or image clarity.
The value of μm is not critical and is merely an example.

The front and back surfaces of the alloyed hot-dip plated steel sheet may have the same surface roughness, but for example, the front surface uses the above-mentioned skin pass roll of the formability-oriented type, and the back surface uses the above-described skin pass roll of the sharpness-oriented type. It can also be used to provide different surface roughness.

Transfer of the concavo-convex pattern provided on the skin pass to the steel plate may be performed by appropriately selecting the reduction of the skin pal or the number of times.

The uneven pattern on the roll is preferably given by a laser as described above in terms of regularity and certainty.

As described above, when the laser pass processed skin pass roll is used, a predetermined regularity can be obtained. The regularity of the unevenness is advantageous in terms of the image clarity and the uniformity of the slidability. In order to obtain this effectiveness, it is preferable to set the interval to a roughness within 20%.

FIGS. 3 and 4 show the surface profile of the alloyed hot-dip galvanized steel sheet according to the present invention obtained as described above, and FIG. 2 shows the surface profile of the untreated conventional galvannealed steel sheet. The surface of the conventional type shown in FIG. 2 is randomly roughened by the crystal growth by the alloying treatment, whereas the flat type and the concave and convex portions are desired in the present invention shown in FIGS. 3 and 4. It can be seen that it is formed at the ratio of. The flat portions and the uneven portions are preferably arranged regularly as shown in FIGS. 3 and 4. It should be noted that Moho in Fig. 3 has SRa (average roughness measured by a three-dimensional roughness measuring instrument) of 1.0 μm and SRmax
(Maximum roughness obtained with a three-dimensional roughness measuring instrument) is 11.3 μm,
The SRa of FIG. 4 is 0.9 μm and the SRmax is 9 μm, and the SRa of FIG. 2 is 1.3 μm and the SRmax is 14 μm.

<Examples> Next, the present invention will be specifically described based on Examples.

(Example 1) A cold-rolled steel plate having a thickness of 0.7 mm was used as a base plate (average roughness 0.86 μ).
m), 45/45 (g / m ² ) basis weight hot-dip galvanized on both sides under a single condition, and subjected to alloying treatment at 540 ° C x 3 sec, alloying as illustrated in Fig. 2 A galvanized steel sheet was obtained. This corresponds to Comparative Steel 1 shown in Table 1.

After the hot-dip galvanized steel sheets thus obtained were polished, laser dull-processed dull rolls were used to obtain various dull-worked steel plates as shown in Table 1. Table 1 shows the surface characteristics and the following test results of these. The test results are shown in FIG.

Comparative Steel 1 has a large friction coefficient due to the rough surface formed during the alloying process, and therefore has poor formability.

Comparative Steel 2 had a surface roughness after polishing that was too large and could not be sufficiently controlled in the subsequent skin pass.
Poor moldability and sharpness.

Comparative Steel 3 has a small elongation rate due to the skin pass roll, does not have a sufficient target element transfer rate, and has poor formability and sharpness.

Comparative Steel 4 has an excessively large gap between the skin pass roll and the convex portion, and thus the gap between the concave portions transferred to the surface of the steel sheet also becomes large, and further, the effect of oil decreases, so that the formability is poor.

On the other hand, it is understood that the steel of the present invention has excellent formability and sharpness.

The measurement and test of each property were performed as follows.

(1) Surface Roughness A roughness parameter was obtained by measuring a three-dimensional roughness profile and analyzing the raw data.

The surface roughness of the roll was obtained by taking a replica and measuring its three-dimensional roughness.

(2) Convex portion spacing The roughness analysis of (1) was performed by image processing to determine the convex portion spacing.

(3) Two lines were drawn at intervals of 100 mm before the skin pass, the line interval was measured again after the skin pass, and the elongation rate before and after that was obtained.

(4) Formability Formability is closely related to the coefficient of friction between the sample and the mold material.
Therefore, the coefficient of friction was calculated from the pull-out resistance when the sample was pulled through by applying a pressing load of 100 kg by sandwiching the sample from both sides with a mold material (SKD-11, 2 cm width).

(5) Vividness after coating 3 coats on the sample (Electrode: Elekron 9400 manufactured by Kansai Paint
20μ, middle coat TP-26 sealer, top coat Amylak TH
After applying -13202 (black) to 50 μm), the DOI value was measured.

The DOI value is measured with a Hunter DORIGON meter, and the amount of specular reflection light when irradiated with light from the direction of 30 ° of the sample normal is Rs,
When the amount of light reflected at an angle of ± 0.3 ° from regular reflection is R _0.3 , DOI = (Rs−R _0.3 ) / Rs × 100. This evaluation method is a human visual judgment,
It shows a good correlation with the conventional evaluation methods such as the PGD method, which checks whether the test pattern can be identified on the sample.

<Effects of the Invention> According to the method of the present invention, an alloyed hot-dip plated steel sheet having a large surface roughness is first preliminarily adjusted to a surface roughness by polishing, and then the formability and / or the sharpness requirement are satisfied. Since long rolling is performed with a skin pass roll having a surface roughness with a degree of adjustment according to the above, an alloyed hot-dip plated steel sheet having excellent formability and sharpness according to the purpose of use and user requirements can be obtained. The same effect can be obtained in the case of a double-layer plated steel sheet in which the surface of the alloyed hot-dip plated steel sheet is further plated.

[Brief description of drawings]

FIG. 1 is a graph showing the results of Example 1. FIG. 2 is a conventional hot-dip galvanized steel sheet, and FIGS. 3 and 4 are measurement examples of the three-dimensional roughness profile of the present invention. The magnification is 100 times in each of the vertical and horizontal directions (x, Y axes) and 500 times in the roughness (vertical Z axis) direction.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideo Abe 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Co., Ltd. Technical Research Division (56) References JP-A-60-86257 (JP, A) JP-A-61 -147906 (JP, A)

Claims (3)

[Claims] 1. A skin pass in which the surface roughness of a steel sheet is adjusted to 1.0 μm or less and 0.1 μm or more in terms of average roughness Ra by hot-dip galvanizing and alloying the steel sheet and then adjusting the surface roughness according to the purpose. When producing an alloyed hot dip plated steel sheet by temper rolling with an elongation of 0.2% or more and a sheet thickness (mm)% or less by a roll, for the purpose of imparting formability to the alloyed hot dip plated steel sheet As the skin pass roll, the surface roughness Ra
1.0 μm or more and 3.0 μm or less, 1 μm from the roll polishing surface
For the purpose of imparting post-painting sharpness to the alloyed hot-dip plated steel sheet using a surface roughness adjusting roll in which the protrusions protruding above are distributed so that the closest spacing is 10 μm or more and 100 μm or less, As the skin pass roll, the surface roughness Ra is 1.0 μm or more and 3.0 μm or less, and the protrusions protruding from the roll polishing surface by 1 μm or more are the closest spacing 100 μm or more and 300 μm
A method for producing a highly functionalized surface-roughness-adjusted alloyed hot-dip plated steel sheet, which comprises using surface-roughness adjustment rolls distributed so as to have a thickness of m or less. 2. The front and back surfaces of a steel sheet according to claim 1, wherein
A method for producing a high-performance surface-roughness-adjusted alloyed hot-dipped steel sheet that achieves both excellent post-painting image clarity and excellent formability by using different types of surface roughness adjustment rolls. 3. The highly functional surface roughness adjusting alloy according to claim 1 or 2, wherein the intervals of the surface roughness convex portions of the surface roughness adjusting skin pass roll are not more than 20% apart from their average value. Manufacturing method of chemical-dip galvanized steel sheet.