JPS5974252A - Zn alloy for hot dipping with high corrosion resistance - Google Patents

Abstract

PURPOSE:To obtain the titled Zn alloy capable of surely forming a layer with superior corrosion resistance and high adhesive strength on the surface of a steel material by hot dipping by restricting the composition of a Zn alloy contg. Ti, Mn and Al. CONSTITUTION:This Zn alloy for hot dipping with high corrosion resistance has a composition consisting of, by weight, 0.1-2.0% Ti, 0.1-3.0% Mn, 0.1-1.6% Al and the balance Zn with inevitable impurities. 0.01-0.4% Si may be added to the composition. When the surface of a steel material is hot dipped using the Zn alloy, a material having superior corrosion resistance and capable of being bent without stripping and cracking its Zn alloy layer can be obtd. Ti provides sufficient corrosion resistance to Zn even in a severe corrosion environment, and Mn increases the degree of solubilization of Ti in the Zn matrix to improve the corrosion resistance. Al inhibits the formation of a brittle Fe-Zn alloy layer, and Si improves the flowability of the hot dipping bath.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention is a method for hot-dip plating to obtain a material that has excellent corrosion resistance and does not peel or crack even when subjected to bending, by hot-dip plating the surface of a steel material. This invention relates to a highly corrosion-resistant Zn alloy for use.

Generally, a method of hot-dip plating Zn or a Zn alloy on the surface of a steel material is known as an inexpensive and simple method for improving the corrosion resistance of a steel material.

In addition, many Zn alloys for hot-dip plating have been proposed. It is true that these conventional hot-dip coatings of Zn alloys have provided steel materials with relatively good corrosion resistance, but they do not necessarily show sufficient corrosion resistance when placed in harsh usage environments. Furthermore, since a brittle Fe-Zn alloy layer is usually formed between the base material and the plating layer, when this is subjected to bending, it is unavoidable that the plating layer will peel or crack. .

Therefore, from the above-mentioned viewpoints, the present inventors developed a hot-dip coating that exhibits excellent corrosion resistance even under harsh usage conditions and that does not cause peeling or cracking in the plated layer even when subjected to bending. In order to obtain products reliably and easily, especially Z for hot-dip plating.
As a result of research on n alloys, it was found that when Mn is added to Zn, the Zn-Mn alloy formed by combining with Zn has good compatibility with T1, so the range of T1 content in Zn is expanded. In addition, Mn acts as a shuttle to disperse and precipitate T1 compounds uniformly, and also has the effect of refining the crystal grains of the alloy itself.Moreover, the T1 content increases due to the inclusion of Mn, In addition, Zn alloys with finer grains have significantly better corrosion resistance.
On the other hand, if M and optionally further include a Si mirror, the formation of an Fe-Zn alloy layer between the plating layer and the substrate can be significantly suppressed.
It has been found that there is no phenomenon of peeling of the plating layer or cracking of the plating layer caused by the Zn-based alloy layer.

Therefore, the present invention has been made based on the above knowledge, and a Zn alloy for hot-dip plating with Ti: 0.
1-2.0%, Mn: 0.1-3.0%,
Contains M: 0.1 to 1.64% and further contains S, i: 0.01 to 0.4% K as necessary, and the remainder is Zn and unavoidable impurities. By hot-dipping this Zn alloy, especially on the surface of steel materials, it is possible to use it stably over a long period of time in harsh corrosive environments and to perform bending without peeling or cracking of the plating layer. It is characterized by the following points.

Next, the reason why the composition range of the Zn alloy of the present invention is limited to the above-mentioned range will be explained.

0) T1 Does the Ti component have the effect of imparting excellent corrosion resistance that satisfies even in severe corrosive environments?
111 cannot secure the desired excellent corrosion resistance, and on the other hand, if the content exceeds 2.0%, the plating workability will be impaired, and therefore it will be difficult to maintain the plating workability in a good state. The temperature of the hot-dip plating bath must be raised considerably, and as a result, the material to be plated dissolves in the plating bath and significantly disturbs the bath composition. It was determined that In addition, 0.45
The content is preferably 1.20%.

(b) Mn As mentioned above, the Mn component increases the solid solubility of T1 in the Zn matrix, refines the crystal grains and partially dispersed precipitated Ti compounds, and improves the uniform distribution of the T1 compound throughout the whole. It has the effect of improving corrosion resistance, but if the content is less than 0.1 qb', the desired effect will not be obtained, while if the content exceeds 3.0 qb', the toughness of the alloy will be extremely reduced. The total content is 0.1 to 3.0 because the plating layer tends to deteriorate and cracks and peels.
The person in charge was appointed as the person in charge. Note that the content is preferably 0.4 to 1.8%.

(c) As mentioned above, the AA M component suppresses the formation of a brittle Fe-Zn alloy layer between the surface of the substrate and the plating layer during hot-dip plating, and thereby suppresses the formation of the Fe-Zn alloy layer during bending. Zn
Prevents peeling and cracking of the plating layer caused by the alloy layer,
It also has the effect of mitigating the hardening of the plating layer due to Mn content, but if the Mn content is less than 0.1%, the desired effect cannot be obtained, while if the Mn content exceeds 1.6elI, the corrosion resistance will be reduced. Therefore, the content was determined to be between 0.1 and 1.6. In addition, 0.3 to 0.8
It is desirable to include a person in charge.

(a) SI The SI component not only improves the fluidity of the plating bath to form a smooth and glossy plating layer, but also further suppresses the formation of the Fe-Zn alloy layer and dramatically improves corrosion resistance. Since it has a certain effect, it is included as necessary especially when these properties are required. However, if the content is less than o, ois, the desired effect of improving the above effect cannot be obtained; on the other hand, if the content is less than o.
If the content exceeds 4%'i, the plating properties will be impaired, so the content was set at 0.01 to 0.4. Note that the content is preferably 0.03 to 0.20%.

Next, the Zn alloy of the present invention will be explained using examples and comparing with comparative examples.

The present invention Zn having the component composition shown in Table 1 for each example
Alloys 1-25. Comparative Zn alloys 1 to 4. and pure Zn hot-dip plating baths, and then the plating bath temperature was set to 46
A steel plate having a thickness of 0.4 and pretreated with ZnC42-NH4Ct-based flux was immersed for 5 seconds in the hot-dip plating bath maintained at a predetermined temperature within the temperature range of 0 to 560°C, and the surface of the steel plate was coated. By forming a plating layer with a thickness of 210 μm on one side, the Zn alloy plated steel sheet 1 of the present invention
25. Comparative Zn alloy plated steel sheets 1 to 4. and conventional Zn
Each plated steel plate was manufactured. In addition, comparison Zn alloy 1
~4 is.

In both cases, the content of one of the constituent components (first
Marked with * on the front? (as shown in the figure) have a composition outside the scope of this invention.

Next, the resulting Zn alloy plated steel sheet 1 of the present invention
~25. Comparative Zn alloy plated steel sheets 1 to 4. and conventional Z
In addition to observing the presence or absence of an Fe-Zn alloy layer, the n-plated steel sheet was subjected to a salt spray test based on J Engineering S-Z2371 and a bending test based on K J I S-Z224BVC. In addition, in the bending test, the state of the plating layer on the bent surface was observed, and there was no peeling or cracking in the plating layer (marked O if there was no negative sign).
Cases in which peeling and cracking were clearly observed in the plating layer were evaluated with an X mark. These measurement results are also shown in Table 1.

From the results shown in Table 1, according to the Zn alloys 1 to 25 of the present invention, the Zn alloy plated steel sheets 1 to 25 of the present invention were
All of them show excellent corrosion resistance and have a plating layer with good adhesion that does not peel or crack even when subjected to bending. Comparative Zn alloy plated steel sheets 1 to 4 each hot-dip plated with Comparative Zn alloys 1 to 4 having compositions outside the scope of the present invention were tested in at least one of the formation of a corrosion-resistant 9 alloy layer and the bending evaluation. It shows inferior results in points. Furthermore, even in conventional Zn-plated steel sheets that have been melt coated with pure Zn, a Fe--Zn alloy layer is formed, and the corrosion resistance and adhesion of the plating layer are extremely poor. Furthermore, as seen in Zn alloy plated steel sheets 1 to 6 of the present invention, it is clear that the higher the T1 content in the presence of predetermined amounts of Mn and At, the better the corrosion resistance becomes.

Furthermore, it was confirmed that when the Zn alloy of the present invention was hot-dipped and further subjected to chromate treatment, the corrosion resistance was further improved.

As mentioned above, according to the highly corrosion-resistant Zn stand for hot-dip plating of the present invention, excellent corrosion resistance can be ensured even under severe usage conditions, especially by hot-dip coating the surface of the steel material. , and has extremely good adhesion to the surface of steel materials, with almost no formation of a brittle Fe-Zn alloy layer, resulting in industrially useful effects such as no peeling or cracking of the plating layer during one bending process. It is possible.

Applicant Sadaharu Nagahori Applicant Masanori Oshima Agent Tomi 1) Kazuo

Claims (2)

[Claims] (1) Ti': 0.1-2.0%, Mn:
0.1-3.0%', At! 2. A highly corrosion-resistant Zn alloy for hot-dip plating, characterized in that it has a composition C or more (weight range) containing 0.1 to 1.6% of Zn and the remainder consisting of Zn and unavoidable impurities. (2) Ti: 0.1-2.0%, Mn: 0
．． 1-3.0%, Ml: 0.1-1.6%, Si:
A highly corrosion-resistant Zn alloy for hot-dip plating, characterized in that it contains 0.01 to 0.4% Zn, and the remainder consists of Zn and unavoidable impurities (the above weight range).