JP2002080952A - Home building material excellent in corrosion resistance, and home building member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a home building material and a home building member having more excellent corrosion resistance in comparison with the conventional hot dip metal coated steel sheet and a precoated steel sheet, and corrosion resistance equat to or higher than that of the galvanized steel sheet produced with a post-plating method and bearable to use for a long term. SOLUTION: The material home building and member can be obtained by applying hot dip Zn-Al-Mg base alloy coating composed of 1-4 wt.% Mg, 4-22 wt.% Al and the balance Zn with inevitable impurities. In the hot dip Zn-Al-Mg base alloy coating, further, 0.002-0.1 wt.% Ti and 0.0005-0.045 wt.% B can be contained and further, if necessary, at least one kind of easily oxidizing elements selected among the rare earth elements, Y, Zr or Si can be contained at 0.005-2.0 wt.%. As the use, this material is suitable to a structural material, such as column, beam, sleeper, and a secondary member such as roof panel, an exterior, an interior, a building metal material, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a housing material and a housing member coated with a hot-dip Zn-Al-Mg-based alloy having excellent corrosion resistance, and more specifically, to a column, a beam, a daiki and the like. And secondary members such as roof panels, exterior materials, interior materials, and housing members such as architectural hardware.

[0002]

2. Description of the Related Art Conventionally, structures such as pillars, beams, and pulleys,
For housing materials and housing members used for secondary members such as roof panels, exterior materials, interior materials, construction hardware, etc., common steel and high-strength steel are made of hot-dip Zn or hot-dip Zn-5 by continuous hot-dip plating equipment. Coated steel sheet with weight percent Al plating,
Painted hot-dip galvanized steel sheets obtained by applying a coating to galvanized steel sheets, and coated steel sheets obtained by directly coating various steel sheets are used and formed into various members.

On the other hand, ordinary steel sheets, high-strength steel sheets and the like are formed into a predetermined shape and then immersed in a hot-dip plating bath (hereinafter, referred to as a hot-dip plating bath).
Many housing members are manufactured (referred to as "post-plating method"). The post-plating method is excellent in terms of corrosion resistance because it can increase the amount of plating applied, but is easily immersed in a high-temperature plating bath after forming, and is easily affected by thermal distortion. Therefore, there is a problem that the appearance is degraded even when the coating is applied, and the adhesion of the coating film is degraded. In addition, in order to apply plating after molding processing,
The productivity is inferior to forming a plated steel sheet manufactured by a continuous plating process with high productivity into a housing member.

[0004]

DISCLOSURE OF THE INVENTION The present invention has excellent corrosion resistance as compared with conventional hot-dip coated steel sheets and painted steel sheets, has corrosion resistance equal to or higher than that of galvanized steel materials manufactured by a post-plating method, and withstands long-term use. It is intended to provide a housing material and a housing member that can be used.

A hot rolled steel sheet with a scale or a structural material manufactured by processing a painted material after pickling and descaling is subjected to zinc plating on the base when the scale or the coating film deteriorates with time. As it is not protected by zinc, the underlying iron starts to corrode immediately. Also, the molten Z
Steel frames manufactured by processing n-plated steel sheets or hot-dip Zn-5 mass% Al-plated steel sheets have poor corrosion resistance because there is no plating on the end faces or welds produced by the processing. And applying a Zn-rich paint.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to provide:
4% by weight, Al: 4 to 22% by weight, the balance can be achieved by a hot-dip zinc-based alloy-plated housing material and housing member composed of Zn and inevitable impurities. The hot-dip zinc-based alloy plating can further contain 0.002 to 0.1% by weight of Ti and 0.0005 to 0.045% by weight of B, and if necessary, rare earth elements, Y, Zr or At least one oxidizable element selected from Si can be contained in an amount of 0.005 to 2.0% by weight.

[0007] Housing members of the present invention include structures such as pillars, beams and pulleys, secondary members such as roof panels, exterior materials, interior materials, and building hardware.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below. The housing material (member) of the present invention is preferably manufactured by a continuous hot-dip plating process from the viewpoint of productivity, but can also be manufactured by a conventional post-plating method.

The housing material and housing member of the present invention include:
Mg: 1 to 4% by weight, Al: 4 to 22% by weight, balance Zn
In addition, hot-dip Zn-Al-Mg based plating made of unavoidable impurities is applied.

Mg content in the plating layer: 1 to 4% by weight Mg contained in the plating layer causes a Zn-based corrosion product containing Mg to be formed on the outermost layer of the plating layer, and together with Al in the plating layer, the general atmosphere. This has the effect of reducing the corrosion rate of the plating layer under the environment. This effect is due to the fact that Zn-based corrosion products containing Mg are stably present on the plating layer for a long period of time, and the formation of zinc oxide that deteriorates corrosion resistance is suppressed.

Furthermore, a part of the Zn-based corrosion products containing Mg flows into the cut end face generated by cutting or the like and the non-plated portion caused by welding, and has a remarkable effect of suppressing corrosion of iron on the end face. . Further, by adding Mg, the plating layer becomes hard, so that it is hard to be damaged and the occurrence of scratches that can be a starting point of rust is suppressed. This is because the intermetallic compound Zn ₂ Mg is uniformly and finely dispersed in the plating layer, and this Zn ₂ Mg is a component of the ternary eutectic solidification structure of Zn / Al / Zn ₂ Mg.

Al content in the plating layer: 4 to 22% by weight Zn and Mg in the plating layer form Zn-based corrosion products containing Mg, whereas Al in the plating layer has extremely strong adhesion. It forms Zn-Al-based corrosion products and contributes to improvement of corrosion resistance. In addition, when Al is contained in the plating layer, Zn / Al / Zn ₂ Mg ternary eutectic appears in the solidification structure of the plating layer. Since this ternary eutectic structure is finer than the Zn / Zn ₂ Mg bi-eutectic structure, the ternary eutectic structure is more preferable from the viewpoint of corrosion resistance and plating layer hardness. However, even if Al is added in excess of 22% by weight, the above effect is saturated, and the melting point of the plating metal increases with an increase in the Al content, so that it is necessary to maintain the plating bath at a high temperature. become worse.

[0013] Suppose Zn- containing no Al in the plating layer.
In the case of the Mg-based alloy, when the Mg-containing Zn-based corrosion product flows out, the corrosion of the plating layer rapidly progresses because there is no Zn-Al-based corrosion product having strong adhesion to the base.

[0014] The hot-dip Zn-Al-Mg based alloy plating of the present invention may further contain at least one of Ti and B or an easily oxidizable element selected from rare earth elements, Y, Zr and Si, if necessary. Can be.

[0015] Ti content in the plating layer: 0.002 to
0.1 wt%, B content in the plating layer: 0.0005 to 0.045 wt% Z which impairs the surface appearance by adding Ti and B in combination.
Z that suppresses generation of n ₁₁ Mg ₂ phase and crystallizes in the plating layer
The n-Mg based intermetallic compound can be substantially only Zn ₂ Mg.

Specifically, when Ti is contained in an amount of 0.002% by weight or more, generation of a Zn ₁₁ Mg ₂ phase can be effectively suppressed. A Ti—Al-based precipitate grows on the surface of the plating layer, and irregularities are formed on the plating layer, thereby impairing the appearance. Also,
When B is contained in an amount of 0.0005% by weight or more, Zn
The formation of ₁₁ Mg ₂ phase can be suppressed,
If it exceeds 045% by weight, Ti-B-based, Al
-B-based precipitates grow, and irregularities (thumps) are formed on the plating layer, thereby impairing the appearance.

The oxidizable element (rare earth element,
Y, Zr, Si): at least one of 0.005 to 2.
0 wt% Al and Mg contents of the present invention are relatively high in the molten Zn-A
The 1-Mg-based plated steel sheet (member) has an effect of suppressing the phenomenon of “deterioration of the surface gloss of the plating layer” which is unique to the present steel sheet. "Degradation of surface gloss of plating layer" is a phenomenon in which a plating surface having a beautiful metallic luster changes to a gray color as time passes immediately after production, and is not preferable in terms of surface appearance. Such a discoloration phenomenon is caused by adding at least one of rare earth elements, Y, Zr, and Si to 0.005.
It can be suppressed by adding more than weight%. However, the effect is saturated even if it is added in excess of 2.0% by weight, so it is preferable to add 0.005 to 2.0% by weight.

Further, the higher the Al content of the plating layer, the more locally the Fe-Al intermetallic compound is formed at the interface between the plating layer and the steel substrate. Although there is a concern that the layer may be peeled off, this problem can be avoided by including a small amount of Si in the plating layer.

The plated steel sheet (member) may be subjected to a chromate or non-chromium chemical conversion treatment to improve corrosion resistance and coating adhesion. Several μm
If a certain amount of organic resin coating is applied after the chemical conversion treatment, the corrosion resistance and the scratch resistance are further improved, and when a lubricating component is contained in the resin, molding into various members becomes easy. In addition, by coating the coated steel sheet (member) depending on the usage environment,
Corrosion resistance can be enhanced and a beautiful appearance can be obtained.

The hot-dip galvanized steel sheet (member) having the plating composition of the present invention has the feature that the plating layer is harder than the conventional hot-dip galvanized steel sheet (member). This is because the intermetallic compound Zn ₂ Mg is dispersed in the plating layer, and since the plating layer is hard, when processing the plated steel sheet into various housing members of the present invention, or during transportation,
Since it has a feature that it is hard to be damaged by flying objects and contact objects during construction, it is also possible to suppress the generation of scratches that are the starting point of rust.

[Example 1] A square steel pipe having a thickness of 2.3 mm and a cross section of 100 mm square (welding: high frequency welding, coating weight of plating: 8) with a plating composition changed under the following conditions:
0g / m ² , chemical conversion treatment: general chromate treatment) according to JIS
A salt spray test of Z2371 was performed to evaluate corrosion resistance. (The corrosion resistance was evaluated on the outer surface of the square steel pipe.) Weld beads were not repaired. Al content in plating layer: 3.0, 6.3, 20.0% by weight Mg content in plating layer: 0, 0.5, 0.8, 1.2, 2.0, 3.0,
4.3% by weight Si content in the plating layer: 0.01% by weight of Si is added only for those having an Al content of 20.0% by weight to suppress the development of the Fe-Al alloy layer.

In order to evaluate the red rust resistance in the vicinity of the weld bead portion and in the vicinity of the end face, attention is paid to the effect of Mg, and an index B (evaluation of the bead portion) and an index T
(Evaluation of end face part) was used. When the Al content is the same,
The index B was (red rust generation time in the vicinity of the bead portion at an Mg content of X% by weight) / (red rust generation time in the vicinity of the bead portion at a Mg content of 0% by weight). When the Al content was the same, the index T was (red rust generation time near the end face at a Mg content of X wt%) / (red rust generation time near the end face at a Mg content of 0 wt%). Table 1 shows the evaluation result (index B) of the bead portion and the evaluation result (index T) of the end face portion.
Show.

[0023]

[Table 1]

As can be seen from Table 1, when the Al content is within the range of the present invention, and when the Mg content is about 1% by weight or more, the indices B and T are significantly increased. It is clear that the rust resistance of the plating layer near the end face is improved. However, the effect is saturated even if Mg is added in excess of 4% by weight, so the preferred range of Mg is 1 to 4% by weight. Further, when the Al content is less than 4% by weight, no remarkable improvement in red rust resistance is observed even when Mg exceeds 1% by weight.

[Example 2] A round steel pipe having a thickness of 1.2 mm and an outer diameter of 22 mm (welding: high frequency welding, coating weight: 125 g / m2) was prepared by changing the plating composition under the same conditions as in Example 1.
² , Chemical conversion treatment: General chromate treatment) according to JIS Z23
Seventy-one salt spray tests were performed to evaluate corrosion resistance. (Evaluation position of corrosion resistance is the outer surface of the round steel pipe.) After welding, bead cutting was performed to repair Zn-5 wt% Al with an average thickness of 8 μm by thermal spraying. In order to evaluate the red rust resistance of the weld bead repair sprayed portion, an index B (evaluation of the bead repair sprayed portion) defined by the following calculation was used, paying attention to the effect of Mg. Al
When the contents are the same, the index B is (Mg content X weight%
At the time of red rust generation at the bead repair sprayed part) / (red rust generation time at the bead repair sprayed part at Mg content of 0% by weight). Table 2 shows the obtained results.

[0026]

[Table 2]

As can be seen from Table 2, when the Al content is within the range of the present invention and the Mg content is about 1% by weight or more, the index B is significantly increased. It is clear that the red rust resistance is improved. However,
Even if Mg is added in excess of 4% by weight, the effect is saturated. When the Al content is less than 4% by weight, even if Mg exceeds 1% by weight, no remarkable improvement in red rust resistance is observed.

Example 3 A square steel pipe having a section thickness of 2.3 mm and a 100 mm square (welding: high-frequency welding, coating weight: 8) with a plating composition changed under the following conditions:
0g / m ² , chemical conversion treatment: general chromate treatment) according to JIS
A salt spray test of Z2371 was performed to evaluate corrosion resistance. (Evaluation position of corrosion resistance is the outer surface of square steel pipe.) After welding, bead cutting was performed and Z with an average thickness of 7 μm was used.
An n-5 wt% Al thermal spray repair was performed. In order to evaluate the red rust resistance of the weld bead repair sprayed portion, an index B (evaluation of the bead repair sprayed portion) defined by the following calculation was used, paying attention to the effect of Mg. When the Al content is the same, the index B
Is (red rust generation time of the bead repair sprayed portion at an Mg content of X wt%) / (red rust occurrence time of the bead repair sprayed portion at a Mg content of 0 wt%). Al content in plating layer: 6.1% by weight Mg content in plating layer: 0, 0.6, 1.2, 2.2,
3.1, 4.5% by weight Ti content in plating layer: 0.03% by weight B content in plating layer: 0.006% by weight Table 3 shows the results obtained by examining the red rust resistance of the bead repaired and sprayed portion. .

[0029]

[Table 3]

As can be seen from Table 3, when Al, Ti, and B fall within the range of the present invention, the effect of improving red rust resistance is as excellent as the results of the other Examples containing no Ti and B. I understand.

Example 4 Square steel pipes having various plating layer compositions with a thickness of 2.3 mm and a cross section of 100 mm square (welding: high frequency welding, coating weight: 80 g / m ² , chemical conversion: general chromate treatment) ) Non-welded part (flat part)
Was subjected to a salt spray test according to JIS Z2371 to evaluate corrosion resistance. The corrosion resistance was evaluated based on the 5% red rust generation time of the flat portion. Table 4 shows the results.

[0032]

[Table 4]

When Al and Mg are within the range of the present invention, the corrosion resistance at the non-welded portion (flat portion) is determined by a comparative example (conventional M
It can be seen that this is very superior to that of the plating composition without g.

[0034]

As described above, the housing materials and housing members having the plating composition of the present invention have better corrosion resistance than conventional hot-dip coated steel sheets (members), so that the coating amount can be reduced. It is also possible to omit the coating process on the plated steel sheet. Since the plating layer is hard and hard to be damaged, the progress of corrosion due to the generation of the scratch can also be suppressed. Further, since it becomes possible to substitute a housing member manufactured by a conventional post-plating method, productivity can be improved and manufacturing costs can be reduced.

Claims (7)

[Claims] 1. A housing material having excellent corrosion resistance, which is coated with a hot-dip zinc alloy containing Mg: 1 to 4% by weight, Al: 4 to 22% by weight, the balance being Zn and unavoidable impurities. 2. The method according to claim 1, wherein the hot-dip galvanized alloy plating further comprises Ti:
0.002 to 0.1% by weight, B: 0.0005 to 0.0
The housing material having excellent corrosion resistance according to claim 1, which contains 45% by weight. 3. The hot-dip zinc alloy plating further contains 0.005 to 2.0% by weight of at least one oxidizable element selected from rare earth elements, Y, Zr and Si. Residential materials with excellent corrosion resistance described in 1. 4. A housing member excellent in corrosion resistance and coated with a hot-dip zinc alloy containing Mg: 1 to 4% by weight, Al: 4 to 22% by weight, the balance being Zn and unavoidable impurities. 5. The method according to claim 1, wherein the hot-dip zinc-based alloy plating further comprises Ti:
0.002 to 0.1% by weight, B: 0.0005 to 0.0
The housing member having excellent corrosion resistance according to claim 4, which contains 45% by weight. 6. The hot-dip zinc alloy plating further contains 0.005 to 2.0% by weight of at least one oxidizable element selected from rare earth elements, Y, Zr or Si. A housing member having excellent corrosion resistance as described in 1 above. 7. The housing member comprises a structural material, a secondary member, an exterior material,
The housing member having excellent corrosion resistance according to claim 4, which is an interior material or a building hardware.