JPS61205129A - Electric plated steel plate having gloss after coating - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Application Field) This invention relates to an electroplated steel sheet that becomes glossy when painted (Prior Art) In recent years, outer panels for automobiles and outer panels for home appliances have been developed. Electrolytic galvanized steel sheets and the like are often used as steel sheets. This type of coated steel sheet is usually processed through a series of processes including pickling, rolling, ECL, annealing, and temper rolling.
Electroplating is performed using a cold-rolled steel sheet with a = o, a ~ 1.2 μr IL) as a base plate, and because it has excellent paint adhesion, it has excellent corrosion resistance after painting.

(Problems to be Solved by the Invention) However, since the surface finish of the original plate is dull as described above, the gloss level is very poor even after coating after plating.

Therefore, in the case of galvanized steel sheets, it is possible to create a glossy surface by using bright finish rolls in a temper rolling mill after plating, but if the pressure is adjusted dry, roll defects may occur due to zinc powder. In addition, in the case of wet pressure adjustment, white rust occurs on the galvanized surface, which complicates the manufacturing process.
This results in i.

The present invention has been made to solve the above problems, and aims to provide an electroplated steel sheet that can be manufactured using conventional processes and has a glossy surface after coating in the final use.

(Means for Solving the Problems) Therefore, the electroplated steel sheet of the present invention is a steel sheet in which the surface finish of a cold-rolled steel sheet as a base is prite, and electroplating is applied thereon. It will have excellent gloss. That is, the smaller the surface roughness of the cold-rolled steel sheet, the better the gloss after coating of the electroplated steel sheet using this as a base sheet. However, as the surface roughness is reduced, the rolling load must be increased during rolling of the original sheet, and in such a case, the number of surface defects (corrugation marks) on the product increases. The inventors of the present invention investigated how to set the surface roughness of the original plate to obtain a steel plate without product surface defects and with good gloss after painting. It has been found that if the surface defects are smaller, the degree of surface defects will exceed the allowable range that can be produced as a product, and if the Ra is larger than 0245 μm, the gloss of the final coated product will be extremely poor. Ta. Regardless of the plating method used, the results are the same in the case of single or alloy plating with Zn, Ni, Fe, Mn, Co, Cr, etc., or composite plating with multiple layers of single plating and/or alloy plating. It was the same. Therefore, in the present invention, the surface roughness Ra is 0.15 μm or more.
Alone, alloy and/or on cold rolled steel sheet in the range of 45μm or less
Nu's basic special care is to apply these composite electroplating methods.

It goes without saying that, depending on the required quality characteristics, the present invention also includes one in which only one side is finished with the above-mentioned prite finish and the other side is finished with a standard dull finish.

(Example) The present invention will be described in detail below based on the accompanying drawings. In this example, pickling, rolling, and ECL.

Annealed cold rolled steel plate (thickness 0.5m, width 1219cm)
, elongation rate l. The coil (1) of No. 3) was temper-rolled using the first EE rolling mill stand (2) and the second rolling mill stand (3), and then wound up using the recoiler (4). At this time, the first rolling mill stand (2) applied a rolling load of 500 tons and rolled the steel plate to give the surface of the steel plate a Usdal shape (Ra=1.0 μrIL). Further, in the second rolling mill stand (3), rolling was carried out while changing the rolling load between 100 and 900 tons, and the surface of the steel plate was bright-finished (finished with #120 grindstone) to perform surface adjustment.

Using such a cold-rolled steel sheet as a plated original plate, 10t/- on one side
Single zinc electroplating (with normal plating thickness) was performed to obtain a product. Furthermore, this electroplated steel sheet was painted to obtain a final product. FIG. 2 is a graph showing the degree of corrugation marks on the surface of the product produced in this example and the glossiness of the final product obtained by painting after plating. Among these, the quality of the product surface is divided into 6 grades from A top to B bottom, and evaluated.
Items above medium B can be shipped as products. The glossiness of the final product was also evaluated for six floors from ■ to ■, and those rated ■ or higher were considered to be usable as outer panels for home appliances. In the X-axis direction, the surface roughness (Ra) of the cold-rolled steel sheet, which is the original sheet before plating, and the magnitude of the rolling load of the second rolling mill stand (3), which is involved in this surface roughness, are taken. . As is clear from this figure, the smaller the surface roughness of the cold-rolled steel sheet, the better the gloss of the final product. On the other hand, in order to reduce the surface roughness of the cold-rolled steel sheet, it is necessary to increase the rolling load of the second rolling mill stand (3), but corrugation marks on the product surface become noticeable accordingly. According to these results, if the surface roughness Ra of the cold-rolled steel sheet is in the range of 0.15 to 0.45 μm, the product surface quality will be medium B or higher, and the gloss of the final product will also be higher than ■. be able to.

(Effects of the Invention) As explained above, the electroplated steel sheet of the present invention can be manufactured by a normal manufacturing process, has no surface defects, and has no surface defects.
It has excellent properties as a steel sheet for automobiles and home appliances, such as being glossy after painting.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing a part of the manufacturing process of a steel plate according to an embodiment of the present invention, and FIG. 2 is a graph diagram showing trial driving results in this embodiment. In the figure, (1) is the coil, (2) is the first rolling mill stand,
(3) shows the second rolling mill stand, and (4) shows the recoiler.

Claims (1)

[Claims] A post-painting method characterized by electroplating alone, an alloy, and/or a combination thereof on a cold-rolled steel sheet having a surface roughness Ra of 0.15 μm or more and 0.45 μm or less. Electroplated steel sheet with luster.