JPH05331664A - Galvanized member and its manufacture - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance of a member in a severe service environment by incorporating ceramic particles into a zinc base metallic plated film to form the surface of the member. CONSTITUTION:At the time of applying galvanizing or galvannealing to a steel used for a large-sized structure, as a plating bath, the one contg. hot dip zinc or a hot dip zinc alloy and ceramic particles is used. Then, a galvanized or galvannealed film uniformly and dispersedly incorporated with ceramic fine particles is formed. For uniformly floating and dispersing the ceramic particles into the plating bath and uniformly incorporating them into the plated film, the ceramic particles in which the difference in the density with the zinc or zinc alloy is regulated to <=2 are preferably used. Moreover, it is effective to use the plating bath contg. 0.07 to 13wt.% ceramic particles and to regulate the content of the ceramic particles in the plated layer into 0.1 to 10wt.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot-dip Zn-plated member or hot-dip Zn alloy-plated member used for large-scale structures (road bridges, high-voltage power transmission towers) and the like, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, for building materials, bridge members and the like, members whose surfaces are simply dip plated with molten zinc or molten zinc alloy are generally used.

[0003]

By the way, in recent years, the environment for use has become severe due to acid rain and the like, and the demand for high corrosion resistance on members used has increased.

An object of the present invention is to provide a new hot-dip galvanized member having improved corrosion resistance and a method for producing the same.

[0005]

As a structure for achieving the above object, a hot dip galvanized member of the present invention has a structure in which a zinc plating film or a zinc alloy plating film forming a surface of the member is made of ceramics for improving corrosion resistance. The fine particles are uniformly dispersed and contained.

In order to uniformly suspend and disperse the ceramic particles in the hot-dip galvanizing bath or hot-dip zinc alloy plating bath so as to be uniformly contained in the plating film, the density difference from the hot-dip zinc or hot-dip zinc alloy plating is 2 or less. It is preferred to use ceramic particles (of approximately equal density).

Alternatively, it is also effective to use a zinc or zinc alloy plating layer containing 0.1 to 10% by weight of ceramic particles in the plating layer.

Further, when the steel material is subjected to hot-dip galvanizing or hot-dip galvanizing, a plating bath containing 0.07 wt% to 13 wt% of ceramic particles having a density difference of 2 or less with the hot-dip zinc or the hot-dip zinc alloy is used as a plating bath. By using, it becomes possible to manufacture a hot-dip galvanized member that can be expected to have improved corrosion resistance.

[0009]

[Function] To improve the corrosion resistance of building materials, bridge members, etc.,
It is important to disperse and contain the ceramic fine particles uniformly in the zinc plating film or zinc alloy plating film formed on the surface of the member. For that purpose, the ceramic particles should be uniform in the hot dip galvanizing bath or hot dip zinc alloy plating bath. It is an important point to suspend and disperse it.

By so-called immersion plating, in which the member is dipped in a crucible of molten zinc or molten zinc alloy in which the ceramic particles are uniformly suspended and dispersed, the ceramic particles are uniformly distributed on the surface of the member. A plating film dispersedly contained is formed, and the corrosion resistance is improved.

In order to prevent agglomeration of the ceramic particles in the molten zinc or molten zinc alloy bath due to the floating of the ceramic particles only and to disperse the particles uniformly in the bath, the density is almost equal to that of the molten zinc or molten zinc alloy. Use ceramic particles. Alternatively, the density of the molten metal is made smaller so that it is almost equal to that of the ceramic particles. For example, Zn is mixed with Al having a low density to make the Zn-Al alloy system bath have a density smaller than that of Zn to match the density of the ceramic. This 2
By using any one of the above methods, it becomes possible to uniformly suspend and disperse the ceramic particles in the molten Zn or the molten Zn alloy.

Molten Zn exhibits a density of 6.5 g / cm ³ at 447 ° C. On the other hand, SiO ₂ is 2.2 g / cm ₃ , Al ₂
O ₃ has a density of 4.0 g / cm ³ , and when these particles are put into a crucible of molten Zn, they are all floated on the bath surface. In this state, even if the member is dip plated, the particles are evenly distributed in the Zn plating film. It is impossible to disperse and contain.

However, if zirconia (ZrO ₂ ) particles are used, since the density is 6.1 g / cm ³ , the difference in density with molten zinc is small, and if they are put into a molten zinc crucible, they will be uniformly dispersed in suspension. The above condition can be easily obtained. Therefore, by subjecting the member to immersion plating, a zinc plating film in which ZrO ₂ particles are uniformly dispersed and contained is formed on the member surface.
A plating film having sufficient corrosion resistance can be obtained.

Further, in order to contain a certain amount or more of ceramic particles in the Zn plating film, it is necessary to contain an appropriate amount of ceramic particles in the plating bath.

If the amount of ceramic particles contained in the plating bath is small, the content of ceramic particles in the Zn plating film is small, and therefore the effect of improving corrosion resistance cannot be expected so much.

On the other hand, if the amount of the ceramic particles in the plating bath is too large, the ceramic particles will agglomerate, resulting in a non-uniform content even when they are contained in the Zn plating film. The corresponding improvement in corrosion resistance cannot be expected.

Therefore, it is necessary to include some suitable amount of ceramic particles in the plating bath. In the present invention, as an appropriate amount, 0.07 wt% to 13 wt% of ceramic particles are contained.

[0018]

EXAMPLES Some examples of the present invention will be described below. Using ZrO ₂ (zirconia) as the ceramic fine particles to be mixed in <Example 1> molten Zn bath. ZrO ₂ has a density of 6.1 g / cm ³ , which is a feature that it is very close to the density of molten Zn (450 ° C.) of 6.5 g / cm ³ . Therefore, particles do not rise even when placed in a molten Zn crucible and are uniformly dispersed in the molten Zn. Therefore, ZrO is uniformly dispersed in a Zn plating film formed on the surface of a plated component manufactured by immersion plating. ₂ fine particles can be contained.

A specific example of this embodiment is shown below. Metal Z
n is 7 kg ZrO ₂ fine particles (average particle size 0.3 μm) are placed in a 140 g alumina crucible and heated at 450 ° C. in an electric furnace.
It was heated and held in the molten state to bring it into a molten state.

The degreased and pickled steel sheet is immersed in this for 30
It was held for a second and then pulled up. A Zn plating film containing ZrO ₂ particles uniformly dispersed was formed on the surface of the steel sheet. The amount of ZrO ₂ contained in the film is 2% by weight.

A salt-spray test was conducted on the Zn-plated steel sheet containing the ZrO ₂ particles, and the time until the occurrence of red rust was compared with that of the hot-dip Zn-plated steel sheet. As shown in FIG. 1, it was confirmed that the Zn-plated steel sheet containing ZrO ₂ particles took a long time until the occurrence of red rust, and the corrosion resistance of the present invention was excellent.

Further, samples having different ZrO ₂ contents in the Zn plating film were prepared, and a salt spray test was carried out in the same manner as described above to evaluate the time until the occurrence of red rust. The results are shown in FIG. 2. The effect of improving the corrosion resistance is that the amount of ZrO ₂ is 0.1.
It became clearer than 10% by weight, and it was found that if it exceeds 10% by weight, the effect is saturated even if ZrO ₂ is further contained. Therefore, the proper range of ZrO ₂ content is 0.1 wt% to 1
It can be said to be up to 0% by weight.

Further, a molten Zn bath (density 6.5 g / c
TiO ₂ (titania: density 4.2 g / cm ³ ) having a density difference of 2.3 from m ³ ) was mixed in the molten Zn bath.
A considerable amount of TiO ₂ floats on the surface of the Zn bath, and Ti
O ₂ could not be evenly dispersed in the bath.

On the other hand, when zircon having a density difference of 1.9 from the molten Zn bath (density of 4.6 g / cm ³ ) was mixed in the molten Zn bath, a fairly good uniform dispersion state could be obtained. .. From this, the density difference between the molten Zn bath and the ceramic particles should be within 2.

Example 2 By adding a metal having a density lower than that of Zn to molten Zn, it is possible to obtain a molten bath of an alloy having a density lower than that of a molten Zn bath alone. In this example, by adding 55% by weight of Al (density: 2.6 g / cm ³ ) to Zn, the density as a Zn-Al alloy bath could be reduced to 4.0 g / cm ³ . It is also effective to add Si (density 2.3 g / cm ³ ) or the like in addition to Al, and a Zn-Al-Si ternary alloy bath may be used.

Since the density of the molten alloy bath can be set to 4.0 g / cm ³ , even if Al ₂ O ₃ (alumina) particles (density 3.9 g / cm ³ ) are mixed with the alloy, the density is almost the same. Since they are the same, they do not float on the bath surface, and Al ₂ O ₃
It was possible to uniformly suspend and disperse the particles in the molten alloy bath.

A concrete example is as follows. 1.8 kg of metal Zn, 2.2 kg of metal Al and Al ₂ O
200 g of ₃ (average particle size 0.2 μm) was put into an alumina crucible and heated and held at 450 ° C. in an electric furnace to be in a molten state.

Immerse the degreased and pickled steel plate in this bath,
After holding for 30 seconds, it was pulled up. Al _{2 on the} steel plate surface
A Zn-Al alloy plating film containing O ₃ particles uniformly dispersed was formed. Al ₂ O ₃ contained in the plating film
Is 5% by weight.

A Zn—Al alloy-plated steel sheet containing Al ₂ O ₃ particles was subjected to a salt spray test to obtain Zn-A.
The time until the occurrence of red rust was compared with the steel sheet only coated with 1-alloy. As shown in FIG. 3, Zn-containing Al ₂ O ₃ particles was used.
It was confirmed that the time required for the red rust to develop on the Al alloy-plated steel sheet was long and the corrosion resistance of the present invention was excellent.

Example 3 ZrO ₂ (zirconia) was used as fine ceramic particles to be mixed in the molten Zn bath. 7 g, 140 g, 300 g, 900 of ZrO ₂ fine particles (average particle size 0.3 μm) per 7 kg of metallic Zn
g and 1500 g were placed in an alumina crucible and heated and held at 450 ° C. in an electric furnace to be in a molten state. Metal Z
When the amount of ZrO ₂ particles was 900 g or more with respect to n 7 kg, the particles were aggregated in the bath and were not uniformly dispersed.

The degreased and pickled steel sheet is dipped in this for 3
It was held for 0 seconds and then pulled up. ZrO ₂ amount ZrO ₂ particles amounts 5g contained in Zn plating film on the steel sheet
When 0.1% by weight, 140 g is 2% by weight, 300
When g, 3.5% by weight, when 900g, 10% by weight, 1
It is 20% by weight at 500 g.

The Zn-plated steel sheet containing the ZrO ₂ particles was subjected to a salt spray test to compare the time until the occurrence of red rust with the steel sheet with only the hot-dip Zn coating.

As shown in FIG. 4, the effect of improving the corrosion resistance is Zr.
The amount of O ₂ became clearer than 0.1 wt%, and when it exceeded 10 wt%, it was found that the effect was saturated even if ZrO ₂ was further contained as in FIG.

As described above, ZrO is added to Zn of 7 kg.
_When 2900 g or more is added, the particles are not evenly dispersed in the bath, and it can be said that the addition of more than this is not effective. Therefore, it can be said that the appropriate range of the ZrO ₂ content in the Zn film is from 0.1 wt% to 10 wt%.

The proper lower limit of the ZrO ₂ content in the bath is 5 g of ZrO ₂ (0.0% by weight) with respect to 7 kg of Zn.
7 wt%) and the upper limit is 900 g per 7 kg of Zn
(Weight ratio is 13 wt%).

Although some embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made within the scope of the technical idea of the present invention. It goes without saying that all of them belong to the technical scope of the present invention.

[0037]

As described above, the hot dip galvanized member of the present invention is prepared by adding ceramic particles to the Zn or Zn alloy plating layer produced by immersion plating in a hot dip Zn bath or hot dip Zn alloy bath. By reducing the density difference between the metal bath and ceramic particles,
Eliminates the rise of ceramic particles in the molten metal bath,
Zn produced by immersion plating after being uniformly dispersed in the bath
Alternatively, fine particles of ceramics are uniformly contained in the Zn alloy plating layer, and the plating layer is formed on the surface of the member, thereby significantly improving the corrosion resistance of the member.

Further, as an appropriate amount of the ceramic particles required to be contained in the plating bath, the ceramic particles in the plating bath having a density difference from molten zinc of 2 or less are set to 0.07 wt% to 13 wt%. It is possible to manufacture a member that can prevent aggregation of particles and can be expected to have improved corrosion resistance.

[Brief description of drawings]

FIG. 1 is a comparison diagram of red rust generation time in a salt spray test in the case of the first embodiment of the present invention.

FIG. 2 shows ZrO ₂ in a Zn plating film in the example.
It is a comparison figure of the red rust generation time in a salt spray test in the case of the sample which changed the content.

FIG. 3 is a comparison diagram of red rust generation time in a salt spray test in the case of the second embodiment of the present invention.

FIG. 4 is a comparison diagram of red rust generation time in a salt spray test in the case of the third embodiment of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kunihiko Nakagawa 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima City Mitsubishi Heavy Industries Hiroshima Works

Claims (4)

[Claims] 1. A hot dip plated member having a zinc or zinc alloy plated layer containing ceramic particles formed on the surface of the member. 2. A zinc or zinc alloy plating layer containing ceramic particles, which has a density difference of 2 or less from that of molten zinc or a molten zinc alloy.
The hot dip plated member described. 3. The hot dip plated member according to claim 1, which has a zinc or zinc alloy plating layer containing 0.1 to 10% by weight of ceramic particles in the plating layer. 4. When performing hot dip zinc or hot dip zinc alloy plating on steel material, 0.07 wt% to 13 wt% of ceramic particles characterized by having a density difference of 2 or less with hot dip zinc or hot dip zinc alloy as a plating bath. % Of the plating bath is used.