JPS6148568B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a stainless steel material for painting, and particularly to a highly productive method for producing a stainless steel material for painting, which has excellent paint adhesion, manual processing, and sheet metal workability. Painted stainless steel plates can eliminate the cold luster characteristic of stainless steel and have anti-glare properties.
It can be used outdoors, it can prevent rust and dirt during processing or construction, it will not rust like corrugated iron even if the paint film is damaged during snow removal in northern countries, and it is laminated with tiles, PVC steel plates, and acrylic resin films. Because it is lighter than steel plates and has excellent earthquake countermeasures, demand for it as a building material, especially for roofs, is rapidly increasing. Although coated stainless steel sheets have such excellent properties, they also have the following problems. (a) Stainless steel has high corrosion resistance, so it is difficult to ensure adhesion with paint through chemical treatment like galvanized steel. (b) Stainless steel is harder than galvanized iron, and is hand-processed.
Sheet metal processing is difficult. In order to solve these problems, stainless steel materials for painting have conventionally been manufactured by the following process, as disclosed in, for example, Japanese Patent Application Laid-Open No. 52-22517. Ordinary stainless steel thick plate material → Intermediate rolling process →
Intermediate annealing pickling process→finish rolling process→finish annealing pickling process→skin pass process In these conventional manufacturing processes for stainless steel for painting, the final annealing pickling process and skin pass process are different from normal stainless steel manufacturing. It has the characteristics shown in Table 1.

[Table] The conventional method having the characteristics described above has the following problems. (A) The line speed for finish annealing and pickling (hereinafter referred to as finish AP) is reduced to approximately 1/2 in order to soften and coarsen the surface roughness by over-annealing and over-pickling compared to ordinary stainless steel. Finished as it is
AP productivity is very poor. (B) Normally, in the case of stainless steel, a skin pass is performed mainly to correct the shape and obtain gloss, while for painted stainless steel, the shape correction is performed using a tension leveler installed on the painting line, and the gloss is applied by painting. It is unnecessary and the skin pass process should originally be omitted, but in order to ensure paint adhesion, a dull skin pass is performed and cannot be omitted. (C) Normally, the rolling reduction rate by skin pass is at most about 1% due to the characteristics of skin pass rolls, and even if the surface roughness of the dull skin pass material is increased, it is only 0.5 to 1.5μ at most. Roughness does not provide sufficient paint adhesion. (D) Even if it is softened by oversintering during finishing AP, it will inevitably become hard due to the rolling reduction in the subsequent skin pass. (E) The surface after the Dalkin pass has an acute angle, as shown in the surface roughness chart of stainless steel material for painting by the conventional method in Figure 1, and the flow of paint during painting is poor, resulting in poor paint adhesion. . An object of the present invention is to solve the problems of the above-mentioned prior art and to provide a highly productive method for manufacturing a stainless steel material for painting which has excellent paint adhesion and sheet metal workability. The gist of the present invention is as follows. That is, a stainless steel material for painting comprising the steps of annealing and pickling, intermediate rolling, and finish cold rolling the stainless steel material through intermediate annealing and pickling, and a step of final annealing and pickling the finish rolled material. In the manufacturing method, the material that has undergone the intermediate annealing and pickling step is finish cold rolled at a rolling reduction rate of 2 to 25% using rolls with a roll surface average roughness Ra of 2 to 20μ, and This is a method for manufacturing a stainless steel material for painting, which includes a step of final annealing and pickling a material that has been subjected to an inter-rolling step under the same conditions as a normal stainless steel material, and omits a skin pass step. Next, the manufacturing conditions of the present invention will be explained in detail. The rolls used in finish cold rolling are limited to a roll surface average roughness of Ra2 to 20μ. This is because if the average roughness of the roll surface is Ra less than 2μ, even if the cold rolling reduction is 2% or more and sufficient transfer is made to the stainless steel sheet surface, the surface roughness of the stainless steel sheet surface will be insufficient and paint adhesion will be poor. , Ra is 20μ
If the roughness is exceeded, the surface roughness of the coated stainless steel material that has been manufactured will become noticeable and the product quality will be impaired. Next, the finish cold rolling reduction ratio was limited to 2 to 25% based on the results of the following basic experiment. i.e.
SUS304 stainless steel material, finished roll surface roughness
Finish rolling was performed using rolls with Ra = 4.5μ at various reduction rates to a finish plate thickness of 0.3 mm, and the final sintering temperature was 1100.
°C, furnace life 54 under the same conditions as regular stainless steel
Finish sintering was performed in seconds, and the surface roughness and hardness were investigated, and the results are shown in Figure 2. As is clear from Figure 2, as the finishing reduction rate increases, the surface roughness of the stainless steel material increases and the hardness increases;
If the reduction rate is less than 25%, the transfer rate to the stainless steel plate surface of the finishing roll is poor, rough surface roughness cannot be obtained, and paint adhesion is insufficient.
Since the Hv hardness is 145 or more, which is hard and has poor sheet metal workability, the reduction ratio in finish rolling was limited to a range of 2 to 25%. Next, the finishing AP was set to the same conditions as normal stainless steel. In the conventional method, the finishing AP was set to be higher than usual, that is, the line speed was reduced to about 1/2, thereby softening and coarsening the surface roughness. However, in the method of the present invention, softening and coarsening of the surface roughness are achieved by controlling the finishing reduction rate, so there is no need to control the finishing AP at all, and from the standpoint of productivity and energy saving, it is usually The same conditions as stainless steel were used. Next, the reason for omitting the skin pass process will be explained. FIG. 3 shows the relationship between the rolling reduction rate of the skin pass and the increase in hardness of the steel plate.Although there is a difference depending on the rolling reduction rate, the steel plate becomes harder due to the skin pass. In the case of ordinary stainless steel, a skin pass is mainly performed to correct the shape and obtain gloss, while in the case of painted stainless steel, the shape correction is performed using a tension leveler installed on the painting line, and the gloss is achieved by applying a skin pass to the surface of the painted stainless steel. However, in the conventional method, the surface roughness was determined by a dull skin pass, so it was not necessary and could not be omitted. However, in the present invention, since the surface roughness is ensured during finish rolling, the dull skin pass is not necessary, and the omission of this has brought about significant effects such as prevention of hardness increase, improvement of productivity, and energy saving. Although the present invention was explained using the example of SUS304,
SUS430 can also be manufactured in exactly the same way. Example A 0.3 mm stainless steel material for painting made of SUS304 was manufactured under the manufacturing conditions of the present invention shown in Table 2 by performing finishing cold rolling, finishing AP, and omitting the skin pass. For comparison, the same results were obtained using the conventional method.
SUS304 0.3mm stainless steel material for painting is the first
The final cold rolling, final AP, and skin pass processes were performed under the conditions shown in the table. These stainless steel materials for painting were painted under the following conditions. Top coat: Silicone polyester resin Primer: Urethane-modified epoxy resin film Mixture: 25μ The characteristics of these painted stainless steel materials and coated stainless steel plates were investigated, and some of the results are also shown in Table 2. Figure 4 shows a surface roughness chart of the stainless steel material for painting manufactured by the method of the present invention.
It can be seen that the irregularities are more rounded than the chart diagram of the conventional method shown in FIG. This is because according to the method of the present invention, after the surface roughness is controlled during finish rolling, the surface roughness is further pickled, so the unevenness becomes rounded, and the paint flows easily during painting, resulting in better paint adhesion than the conventional method. There is. The surface conditions of stainless steel materials for painting are shown in Figure 5 using the conventional method and Figure 6 using the method of the present invention.
As shown in the figure, it can be seen that the surface condition of the method of the present invention is rougher than that of the conventional method.

[Table] Also, from Table 2, the stainless steel material for painting manufactured by the method of the present invention is soft and has a large surface roughness.
It is clear that the coated stainless steel sheet obtained therefrom also has excellent paint adhesion. As is clear from the above examples, the method of the present invention has a roll surface average roughness of Ra of 2 to 20 during finish rolling.
Cold rolling is performed using μ rolls at a reduction rate of 2 to 25%, and finishing AP is performed under normal conditions and the skin pass process is omitted, resulting in a soft surface with a rough surface roughness and excellent paint adhesion. Although we were able to obtain a stainless steel material for painting, it also has the following effects in terms of manufacturing. (b) Since there is no need to perform finishing AP excessively as in the conventional method, the finishing AP line speed is approximately doubled,
Production efficiency is approximately doubled, and it is effective in saving energy. (b) The skin pass process is omitted, which helps lower unit consumption.

[Brief explanation of the drawing]

Figure 1 is a chart of the surface roughness of stainless steel material for painting manufactured using the conventional method, and Figure 2 is
Diagram showing the relationship between the finish rolling reduction rate, hardness, and surface roughness of SUS304, a material with a finish plate thickness of 0.3 mm, Part 3
The figure is a diagram showing the relationship between the reduction rate during skin pass and the amount of increase in hardness of the steel plate, Figure 4 is a chart of the surface roughness of the stainless steel material for painting manufactured by the method of the present invention, and Figures 5 and 6 These are micrographs showing the surface conditions of stainless steel materials for painting, in which FIG. 5 shows the material manufactured by the conventional method, and FIG. 6 shows the material manufactured by the method of the present invention.

Claims (1)

[Claims] 1. Stainless steel for painting, which comprises the steps of annealing and pickling, intermediate rolling, and finish cold rolling a stainless steel material through intermediate annealing and pickling, and finishing annealing and pickling the finish rolled material. The method for producing a material includes a step of final cold rolling the material that has undergone the intermediate annealing and pickling step at a rolling reduction rate of 2 to 25% using rolls with a roll surface average roughness Ra of 2 to 20 μ; A method for producing a stainless steel material for painting, comprising a step of finish annealing and pickling a material that has undergone a cold rolling process under the same conditions as a normal stainless steel material, and omitting a skin pass step.