JPH0515901A - Production of zinc-iron alloy hot dip coated steel sheet having excellent press formability and brightness - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a method for producing a hot-dip zinc-iron alloy plated steel sheet excellent in press formability and image clarity. [Constitution] The hot-dip galvanized iron-plated steel sheet is subjected to the first temper rolling, so that the surface waviness of the coated steel sheet WCa: 0.7 to 0.5
μm, surface roughness Ra: 0.5 to 1.0 μm, and then the second temper rolling keeps WCa: less than 0.5 μm and surface roughness Ra: 0.5 to 1.0 μm. [Effect] By doing so, the press moldability and the sharpness can be surely improved. Further, it is possible to obtain the effect that it can be ensured industrially.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a hot-dip zinc-iron alloy plated steel sheet excellent in press formability and image clarity.

[0002]

2. Description of the Related Art Conventionally, in order to improve the press formability of a galvanized steel sheet, the surface roughness pattern of the plated steel sheet is specified and the press formability is improved, as in JP-A-63-33591. Is disclosed. Further, as disclosed in JP-A-2-274853, it is disclosed that the press formability and the sharpness are improved by specifying the surface roughness parameters Ra and WCa of the plated steel sheet. In the production of hot dip galvanized iron-plated steel sheet, however, the shape is bad, and temper rolling is performed to correct the shape, so the target product surface roughness and waviness are obtained. It is difficult to give. Therefore, it is accompanied by drawbacks such as difficulty in surely improving press moldability and image clarity.

[0003]

The present invention is intended to solve these problems by subjecting a hot-dip galvanized steel sheet to a heat-alloying treatment and then applying a specific temper rolling condition. The gist is that after hot-alloying the hot-dip galvanized steel sheet, the first temper rolling causes surface waviness WCa of the coated steel sheet to be 0.7 to 0.5 μm and surface roughness Ra to be 0.5 to 1. The surface waviness WCa is less than 0.5 μm and the surface roughness Ra is 0.5 to 1.0 μm by the second temper rolling, and the press moldability and the sharpness are improved. There is a method for producing an excellent hot dip zinc-iron alloy plated steel sheet.

As described above, after the hot-dip galvanized steel sheet is heat-alloyed, the first temper rolling is followed by the second temper rolling, whereby the surface waviness WCa of the plated steel sheet is less than 0.5 μm.
By adjusting the surface roughness Ra to 0.5 to 1.0 μm, press moldability and image clarity are improved. To surely adjust such surface waviness and surface roughness,
Surface waviness WCa: 1.0 μm or less 0.7 μm or more, surface roughness Ra: 1.0-1.5 μm original plate (steel plate) is subjected to hot dip galvanizing (adhesion amount: 20 to 80 g / m ² ), and then the plate The surface roughness Ra is excellent in press formability by alloying the iron amount in the plating layer to 7 to 12% by heating at a temperature of 500 to 800 ° C. for several seconds to several tens of seconds and temper rolling as described above.
The surface waviness WCa, which is excellent in sharpness, is adjusted.

Next, as described above, the reason why the surface roughness Ra and the surface waviness WCa excellent in press formability and image clarity can be adjusted by the first temper rolling and the second temper rolling is as follows. The surface roughness of the alloy-plated steel sheet is roughened due to the unevenness of the alloy layer formed in the alloying step after plating, and the steel strip surface in this state is smoothed under rolling by the first temper rolling. , WCa: 0.7 to 0.5 μm, Ra: 0.5
Is reduced to .about.1.0 μm. Then, by the second temper rolling, the surface is smoothed again under reduction and unevenness is provided to keep Ra within the above range while WC
a: Reduce to less than 0.5 μm. By doing so, it is possible to finely adjust the roughness in order to suitably secure the press moldability and the sharpness. Only in the first temper rolling, operation under high pressure is required for reasons such as shape correction and securing a reduction ratio, surface waviness becomes WCa: 0.5 μm or more, and surface roughness Ra: less than 0.5 μm. If it exceeds 0.0 μm, sharpness and press moldability are significantly deteriorated, and it becomes difficult to perform fine roughness fine adjustment.

[0006]

EXAMPLES Next, examples of the method of the present invention will be described.

[0007]

[Table 1A]

[0008]

[Table 1B]

Note 1: In a continuous hot-dip galvanizing line, after hot-dip galvanizing, alloying treatment was performed in an alloying furnace in the line, and after cooling, it was treated by a temper rolling mill with two stands. Note 2: The amount of iron in the plating layer is 8-11%. Note 3: Press moldability was evaluated by visual judgment using "1R" bead in U bead test. Note 4: Image clarity was evaluated by visual judgment using a sharpness measuring device.

[0010]

EFFECTS OF THE INVENTION According to the present invention, excellent effects such as being industrially stable, having excellent press formability and image clarity, and being capable of adjusting the surface waviness and surface roughness of a plated steel sheet. Is obtained.

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C23C 2/40

Claims (1)

Claims: 1. A hot-dip galvanized steel sheet is heat-alloyed and then subjected to a first temper rolling to cause surface waviness WC of the plated steel sheet.
a: 0.7 to 0.5 μm, surface roughness Ra: 0.5 to 1.
The surface waviness W is set to 0 μm by the second temper rolling.
Ca: less than 0.5 μm, surface roughness Ra: 0.5 to 1.0 μ
A method for producing a hot-dip zinc-iron alloy plated steel sheet having excellent press formability and image clarity, which is characterized by holding at m.