JPH0426745A - Colored alloy plating coating - Google Patents

Abstract

PURPOSE:To form a colored alloy plating coating free from the generation of peeling and cracks on a steel, in a coated film of a zinc alloy constituted of Mn, Fe and the balance Zn, by forming a surface layer of a eta phase and a lower part layer of a zeta phase. CONSTITUTION:At the time of forming a coated film constituted of a zinc alloy on a steel by using a zinc alloy plating bath contg. Mn or the like, the temp. of the zinc alloy coating bath is controlled to the range of about 430 to 480 deg.C. In this way, the colored plating film in which the surface layer is formed of a eta phase (contg., by weight, 0.3wt.% Mn, about 0.003% Fe and the balance Zn) and the lower part layer is formed of a zeta phase (fundamentally consisting of FeZn13 and contg. about 0.2wt.% Mn or the like) and free from the generation of peeling and cracks can be obtd.

Description

[Detailed Description of the Invention] Utilization of Ryu-shi 2 This invention relates to a coating that does not peel off from the steel material after plating and does not cause cracks in the coating when colored hot-dip galvanizing is applied to steel material. .

In the conventional colored hot-dip galvanizing with addition of Mn, etc.,
A desirable color development such as brown was obtained.

Goose” 1 branch strain, 1 leg strength.

However, in the case of Mn-added hot-dip galvanizing, for example, the film may peel off from the copper phase or cracks may occur in the film during the cooling process after plating, resulting in problems such as a high defect rate and the durability of the plating film. There was a problem that impact resistance was weak. Therefore, the inventors made the following invention as a result of intensive study.

The present invention is characterized in that: (1) the surface layer of the plating film made of a zinc alloy is an η phase, and the lower layer is a ζ phase;

(2) The colored plating coating according to claim 1, wherein the zinc alloy is composed of Mn, Fe, and zinc.

In the present invention, the surface layer of the plating film is required to be in the η phase, and each of the lower layers is required to be in the ζ phase.

The above phase is a phase that is formed as a plating layer when coloring and sizing iron products made of zinc alloy. The zinc used here is distilled zinc ingot (purity of 98.5% or higher), purest zinc ingot (purity of 99.995% or higher), and electrolytic zinc ingot (purity of 99.99%). above) etc.

Furthermore, an alloy to which Mn or the like is added as an additional element for coloring is used.

Here, the η phase is Mn0,3wt%, Fed,003wt%
The balance is zinc, and the ζ phase is based on F e Z n,
This contains 0.2 wt % of coloring additive elements such as Mn.

The inventors have discovered that a coating consisting of the layer described in item 1 does not cause cracks in the coating and is strong against external mechanical forces. Examples of methods for obtaining the above phase include the following methods.

That is, the zinc alloy plating bath temperature is 4.30 to 480°C.
By controlling the temperature within this range, peeling of the film from the steel material and generation of cracks can be prevented during the cooling process after plating and the heat treatment process to improve the film properties. If the bath temperature is lower than 430°C, plating cannot be performed well, and if the bath temperature is higher than 480°C, there is a high probability that the coating will peel off from the steel material and cracks will occur. Such a phenomenon is not observed in normal hot-dip galvanizing, but only occurs when Mn is contained. This occurs because Mn promotes alloying of iron and zinc.

That is, when Mn is contained, at a bath temperature exceeding 4.80° C., the normally existing ζ phase (FeZn,) disappears, and the iron-zinc alloy layer becomes almost the δ1 phase (FeZn,). As a result of intensive studies, the inventors found that this is the cause of peeling of the film from the steel material and the occurrence of cracks. It has been found that plating at 480° C. is a condition that can prevent peeling and cracking from the steel material.

Example 1 A zinc alloy bath containing 0.3% by weight of Mn was fixed at a temperature of 460°C, and a steel material was immersed for 3 minutes and then allowed to cool. Regarding this sample, the presence or absence of peeling of the coating from the steel material, cracks in the coating, and coating structure were investigated.

As a result, the surface phase was η phase, and the lower layer was ζ phase r. Therefore, no peeling of the coating from the steel material or occurrence of cracks in the coating was observed.

Example 2 A zinc alloy bath containing 0.2% by weight Mn was fixed at a temperature of 450°C, and the copper phase was immersed for 3 minutes, then heat treated at 500°C for 10 minutes to improve the properties of the plating film, and then allowed to cool. did. Regarding this sample, the presence or absence of peeling of the coating from the steel material, cracks in the coating, and coating structure were investigated. As a result, the surface phase was η phase, and the lower layer was ζ phase. Therefore, the coating did not peel off from the steel material and did not develop cracks.

Comparative Example 1 A zinc alloy bath containing 0.3% by weight of Mn was fixed at a temperature of 500° C., and the steel material was immersed for 3 minutes and then allowed to cool. Regarding this sample, the presence or absence of peeling of the coating from the steel material, cracks in the coating, and coating structure were investigated.

As a result, no ζ phase was observed, and the occurrence of cracks was observed.

By implementing the present invention, the following effects can be obtained.

(1) Hot-dip galvanizing can provide a preferable coating that does not cause peeling or cracking. (2) Hot-dip galvanizing with Mn or the like can easily provide a strong brown coating.

Claims (2)

[Claims] (1) A colored plating coating, characterized in that the surface layer of the plating film made of a zinc alloy is an η phase, and the lower layer is a ζ phase. (2) The colored plating coating according to claim 1, wherein the zinc alloy is composed of Mn, Fe, and the balance is zinc.