JPS58221248A - Zn-al-cr alloy for hot dipping - Google Patents

Abstract

PURPOSE:To enhance the corrosion resistance, adhesive strength and work efficiency of the resulting titled alloy by adding a very small amount of Mg to a Zn-Al-Cr alloy having a specified composition. CONSTITUTION:This Zn-Al-Cr alloy for hot dipping is obtd. by adding a very small amount of Mg to a Zn-Al-Cr alloy. The relation between Al and Cr (wt%) in the Zn-Al-Cr alloy satisfies an equation Al=(3.5-5.0)+Cr.X (where X is 4-15, Al<=8.0, and 0.05<=Cr<=0.6).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pyrolead alloy for hot-dip plating, and more particularly to a Zn-At-Or-based hot-dip plating alloy having excellent corrosion resistance and adhesion.

In recent years, the use of galvanized steel products has been expanding rapidly, and in particular, there is a demand for hot-dip galvanized alloys with even improved corrosion resistance in order to reduce the thickness of structural steel materials due to their weight reduction. There is. A method of increasing the corrosion resistance of galvanized products is to increase the amount of zinc plating, and to use Ti and Zr, which are said to be effective in improving corrosion resistance.
A method of adding elements such as XSi and Or is generally adopted. However, alloy plating has defects that cause variations in corrosion resistance and adhesion due to poor stability of the alloy composition in the plating bath. Zn-47-Or
0.4% hl, 0.6 as mass-based hot-dip plating alloy
t4Mt.

Although an alloy containing Q, 4% Or and the remainder Zn has been disclosed, the effect of improving corrosion resistance in this alloy is insufficient.

The present invention provides Zn-At-
The purpose of the present invention is to provide an 0r-based hot-dip plating alloy.

As a result of intensive research to achieve the above object, the present inventors found that A.
The present invention was completed by discovering that excellent corrosion resistance is exhibited when the composition of t and Or is within the range shown by a certain relational expression.

The present invention provides a Zn-At-Or alloy containing At and O.
The composition expressed in weight% with r is At = (3,5~5.0)-1-Or-X
-・・・・=(1) (In the formula, This is a Zn-At-Or hot-dip plating alloy characterized by containing Mf.

In the present invention, the composition of At and Or is determined by the relational expression (1
), when X is in the range of 4 to 15, excellent corrosion resistance is exhibited in the salt spray test, as shown in FIG. X
If the value is less than 4, the corrosion resistance tends to gradually decrease, and if it exceeds 15, oxidation rapidly progresses, which is not preferable. When the amount of At added exceeds 8.0%, the viscosity of the plating bath increases,
Moreover, since the solidification temperature range becomes large, thermal separation tends to occur due to long-term holding, which is not preferable. Also, Or
If the amount added exceeds 0.6 inch, the plating bath temperature will increase, which is not preferable. Furthermore, Mf is added in an amount normally added to Zn--At alloys to prevent intergranular corrosion.

The present invention focuses on At and Or in Zn-At-Or alloys.
By limiting the compositional relationship between the two, it is possible to provide an alloy for hot-dip plating that has improved corrosion resistance, adhesion, and even workability, and is of extremely great industrial significance.

The present invention will be explained in more detail below using examples. However, the present invention is not limited to the following examples.

Example: A cold-rolled steel plate with a thickness of 0.3 cm was degreased with a 6T aqueous solution of caustic soda, pickled with 6T hydrochloric acid, further washed with water, and then treated with 10% NH,
OA-Zn0t2 (However, NH, +01-/Zn
0t2=3/l) immersed in an aqueous solution. The steel plate'
After drying in an electric furnace, a Zn-At-Or system plating bath having the At and Or compositions shown in Table 1 was further coated with MP 0.04.
% was added for 10 seconds and then pulled out to obtain a plated steel plate. The corrosion rate (f/n?h) of the plated steel plate in the salt spray test and the number of times until the plating film peeled off in the repeated bending test are shown in Table 1 together with comparative examples.

The salt spray test was conducted in accordance with JIS Z-2371, and after 72 hours of salt water spraying, the product was immersed in a 5% ammonium acetate aqueous solution at ℃ for 1/2 second to remove rust, and the weight was measured to calculate the corrosion rate. did. Further, the bending angle in the repeated bending test was (5) degrees.

Comparative Example A steel plate treated in the same manner as in the Example was immersed in a plating bath having the composition shown in Table 1 in the same manner as in the Example to obtain a plated steel plate. The obtained plated steel sheet was subjected to a salt spray test and a repeated bending test in the same manner as in the examples.

The results are shown in Table 1 along with Examples.

[Brief explanation of the drawing]

Figure 1 shows the relationship between X and corrosion rate (
In the curve diagram showing the relationship between f/ihr), (1) is Or = Q, and l wt% (2) is Or
= Q, 3 wt% (3) shows the case where Or = Q, 5 wt%. Patent applicant: Nisso Metal Co., Ltd. Representative: Haru Ito Twice
Yoshimi Yokoyama 7-

Claims (1)

[Claims] 1. In the Zn-At-Or alloy, At and Or
The composition expressed in weight % is At=(3,5~5.0) + Or −X (wherein,
X represents any number from 4 to ]5. ) A Zn-At-Or alloy for hot-dip plating, which has the following relationships: At≦8.0 0.05≦Or≦0.6 and contains a trace amount of M2.