JP3217003B2 - Surface treatment method for iron-based materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment method for an iron-based material capable of preventing the progress of corrosion in a structural material of a bridge or a cast iron pipe requiring corrosion resistance.

[0002]

2. Description of the Related Art In general, as a surface treatment method for preventing corrosion of a base material made of an iron-based material such as steel or cast iron, for example, a zinc spraying method and an aluminum spraying method are known. In these methods, a sprayed coating is formed by continuously spraying molten particles of a metal, such as zinc or aluminum, which is more susceptible to corrosion than the base material, onto the surface of the base material. In this type of method,
The thermal spray coating itself acts as a sacrificial corrosion layer that suppresses erosion by being corroded in place of the base material, thereby preventing corrosion of the base material.

[0003] In addition to the above-described method of forming a sacrificial corrosion layer, pure aluminum is sprayed on the surface of a base material, and then an annealing heat treatment is performed. A method for preventing corrosion of a base material is known. As this type of method, for example, JP-A-7-157
No. 857 proposes a coating method. In this publication, as shown in FIG. 2A, aluminum or aluminum alloy is sprayed on a cast iron
2 is formed, and a corrosion-resistant metal such as Ni or Cr is deposited on the deposited aluminum layer 12 by thermal spraying to form a corrosion-resistant metal surface layer 13, which is subjected to an annealing heat treatment, as shown in FIG. First, the Al—Fe alloy layer 12 a and the A
A method of coating the 1-corrosion resistant metal alloy layer 13a is disclosed. The thermal spray coating formed by these methods, such as the Al—Fe alloy layer 12a and the Al—corrosion resistant metal alloy layer 13a, is less likely to be corroded than the base material, and is not a sacrificial corrosion layer as described above. It acts as a corrosion-resistant alloy layer that has its own corrosion resistance and can prevent the progress of corrosion, thereby preventing corrosion of the base material.

[0004]

However, in the method of forming a sprayed coating as a sacrificial corrosion layer as described above, if the coating is left in a corrosive environment, the sprayed coating disappears as the corrosion progresses. There is a disadvantage that the anticorrosion effect is lost because the surface of the base material is exposed to a corrosive environment. In addition, the thermal spray coating of this type has low hardness,
For example, when assembling as a product or when embedding underground, there is a problem that the sprayed coating is immediately damaged and corrosion proceeds therefrom.

In the conventional method for forming a corrosion-resistant alloy layer disclosed in Japanese Patent Application Laid-Open No. Hei 7-157857, the aluminum layer 12 to be deposited and the corrosion-resistant metal surface layer 13 are alloyed, The ferrite annealing treatment must be performed so that Al in the metal 12 diffuses into the cast iron material 11 and the corrosion-resistant metal surface layer 12. Further, instead of the annealing treatment, a method of forming a corrosion-resistant alloy layer by performing a diffusion heat treatment such as calorizing is also known. However, similarly to the above-described method, a heat treatment for alloying to improve corrosion resistance is performed. The points you need remain the same. For this reason, there is a problem in that each heat treatment step is extra, and labor and cost are increased as compared with a method of simply forming a film by thermal spraying such as the above-mentioned zinc thermal spraying or aluminum thermal spraying.

Further, in this type of method, since the base material is more easily corroded than the corrosion-resistant alloy layer, once the corrosion-resistant alloy layer is damaged and the surface of the base material is exposed to a corrosive environment, a sacrificial corrosion layer is formed. As compared with the method, there is a drawback that the corrosion easily proceeds and the anticorrosion effect is significantly reduced. Therefore, in the method of forming a thermal spray coating as a corrosion-resistant alloy layer, the hardness of the coating becomes a serious problem. On the other hand, as mentioned above,
Zinc, aluminum and the like are used as a material for forming the film, but their corrosion resistance is limited. For this reason, rapid solidification alloys with anticorrosion effects have been studied with the aim of improving corrosion resistance.However, although they have excellent strength, rapid solidification alloys with anticorrosion effects have not yet been developed. At present, there is a problem that a film having sufficient corrosion resistance cannot be obtained in a severe corrosive environment.

The present invention has been made in view of the above-mentioned problems, and provides an excellent anticorrosion effect without heat treatment by adding Mg and Zn and forming an intermetallic compound having good corrosion resistance. It is another object of the present invention to provide a method for preventing corrosion by forming a high hardness alloy film that is difficult to peel off.

[0008]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have studied in detail the factors that affect the anti-corrosion effect of the rapidly solidified alloy material, and found that it is contained in the rapidly solidified aluminum alloy. The present inventors have newly found that an intermetallic compound composed of a transition metal and Al greatly affects the improvement of corrosion resistance, and have accomplished the present invention. That is, in the surface treatment method of the present invention, 6 to 35 wt.
%, One or two of Mg and Zn in total of 0.3 to 0.3%
3.2% by weight, a rapidly solidified alloy material containing a total of 6 to 35% by weight of one or two or more kinds of transition metals composed of Fe, Mn, and Cr, and the balance substantially consisting of Al, is sprayed or overlaid. It is characterized in that the corrosion resistance of the iron-based material is improved.

It is generally considered that transition metals, such as Fe and Cr, adversely affect corrosion resistance and strength when they enter aluminum. However, by rapidly cooling and solidifying the aluminum alloy to which the transition metal is added, the transition metal is supersaturated in aluminum and the dense intermetallic compound is uniformly distributed in the matrix of the aluminum alloy. Therefore,
As described above, in the rapidly solidified alloy material composed of an aluminum alloy containing 6 to 35 wt% of a transition metal, an intermetallic compound composed of a transition metal and Al is formed in a matrix. Since the intermetallic compound itself is considered to have good corrosion resistance, the rapidly solidified alloy material formed by uniformly dispersing the intermetallic compound exhibits an excellent anticorrosion effect. Also, Si
Is contained in the matrix, Si is solid-dissolved in the matrix to obtain a high-hardness structure, and as a result, the hardness is improved while maintaining the excellent anticorrosion effect as described above. I have.

Using such a rapidly solidified alloy material, an Al alloy film is formed on the surface of the iron-based material by thermal spraying or overlaying. In the structure of the Al alloy film, since the intermetallic compound having good corrosion resistance due to the rapidly solidified alloy material is uniformly and uniformly dispersed, the corrosion resistance of the Al alloy film is improved, and the Al alloy film is corroded by the base metal. It is possible to prevent the progress of corrosion as a hard corrosion resistant alloy layer. Therefore, when this Al alloy film is formed, it already has an excellent anti-corrosion effect, so that it is not necessary to perform heat treatment such as diffusion or annealing.
Furthermore, since the hardness of the rapidly solidified alloy material is improved as described above, the Al alloy film is hardly damaged. That is, the Al alloy film functions as a corrosion-resistant alloy layer having both high hardness and high corrosion resistance.

Further, Mg, Z is used for the rapidly solidified alloy material.
Since n is contained, when the above-mentioned Al alloy film is kept at, for example, room temperature to cause age hardening, high hardness and fine precipitates are formed in the matrix and the hardness is improved. Therefore, high hardness is maintained even when the Si content is suppressed. Therefore, the Al alloy film has excellent toughness, the peeling of the film is suppressed, and the corrosion of the base material can be prevented. The rapidly solidified alloy material as described above may be in the form of a powder or a wire, and can be used as a raw material for the thermal spraying method or the overlay method.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a thermal spray coating method according to an embodiment of the present invention will be described. The thermal spray coating method of the present embodiment uses a powdery rapidly solidified alloy material (hereinafter, corrosion-resistant Al alloy powder) made of an aluminum alloy as a thermal spray raw material,
As shown in FIG. 1, a corrosion-resistant Al alloy film 2 is formed on the surface of a base material 1 made of cast iron by a thermal spraying method, and the base material 1 is left at room temperature for a long time. The corrosion-resistant Al alloy powder is obtained by adding an Al raw material obtained by adding one or two or more of Si, Mg and Zn and one or two or more of transition metals Fe, Mn and Cr to pure aluminum at a melting point of 50%.
Melting is performed at a high heating temperature of about 200 ° C. to obtain a molten Al alloy, which is manufactured by a rotating water flow method.
According to the rotary water flow method, as disclosed in Japanese Patent Application Laid-Open No. 17605/1992, a cooling liquid layer is formed on the inner peripheral surface of the cooling cylinder while swirling and flowing down. Is obtained by supplying a jet of the liquid, dividing the jet by a swirling cooling liquid layer, and rapidly solidifying in the cooling liquid layer to obtain metal powder. According to this method, an extremely high cooling rate can be obtained, so that amorphous metal powder can be easily obtained.

In the above-described powder production method, in the present embodiment, the cooling rate is set to about 10 ⁴ ° C / sec or more. By performing such rapid solidification, a corrosion-resistant Al alloy powder in which the transition metal is supersaturated in the matrix is obtained. Further, an intermetallic compound is dispersedly formed on the matrix, and its size is as fine as about several μm. In this production method, since the rapid solidification conditions such as the cooling rate are easily adjusted, a desired intermetallic compound can be formed. The corrosion-resistant Al alloy powder obtained by the above-described manufacturing method is composed of 6 to 35 wt% of Si, 0.3 to 3.2 wt% of one or two of Mg and Zn, and one or a transition metal of Fe, Mn, and Cr. This is a rapidly solidified alloy powder containing 6 to 35% by weight in total of two or more kinds and the balance substantially consisting of Al. Further, in the matrix of the corrosion-resistant Al alloy powder, a transition metal is dissolved in a supersaturated solid solution, and an intermetallic compound composed of a transition metal and Al (hereinafter, a transition metal-Al intermetallic compound) is formed. .

Since the transition metal is supersaturated in the matrix, the solid solution of the matrix is strengthened. Further, the transition metal-Al intermetallic compound is dense. Such an intermetallic compound is considered to have good corrosion resistance, and since it is formed uniformly distributed in the matrix, the corrosion-resistant Al alloy powder exhibits an excellent anticorrosion effect. That is,
Since a total of 6 to 35 wt% of one or more transition metals composed of Fe, Mn, and Cr is contained,
It has an effect of forming an Al intermetallic compound to give an anticorrosion effect. However, if it is less than 6 wt%, the transition metal-Al
When the amount of the intermetallic compound is small and this effect is insufficient, on the other hand, when it exceeds 35 wt%, the amount of the transition metal-Al intermetallic compound becomes excessive, the material becomes brittle, and coarse crystal grains precipitate to prevent corrosion. Fades. In addition, the content of the transition metal is preferably 8 to 30 wt%.

Further, since Si is contained in the corrosion-resistant Al alloy powder, Si is dissolved in the matrix and a structure having high hardness is obtained. Since the transition metal-Al intermetallic compound having good corrosion resistance as described above is formed in such a matrix, the corrosion-resistant Al alloy powder maintains an excellent anticorrosion effect. That is, Si has an effect of improving the hardness without lowering the corrosion resistance, but if it is less than 6 wt%, these effects are insufficient, while if it exceeds 35 wt%, the material becomes brittle. The content of Si is preferably 8 to 30% by weight.

Using the above-mentioned corrosion-resistant Al alloy powder as a thermal spraying material, a corrosion-resistant Al alloy film 2 is formed on the surface of a base material 1 which is a material to be sprayed by a flame spraying method. In the flame spraying method, a corrosion-resistant Al alloy powder is supplied and melted in a flame of acetylene and oxygen as fuel gas, and the melted powder particles are sprayed on the surface of the base material 1 with compressed air to form a sprayed coating. Is formed. The rapidly solidified alloy material is used in the powder state as a thermal spraying material, but is not limited to this. For example, a corrosion-resistant Al alloy powder is formed into a rod or wire by hot plastic working such as hot extrusion or hot forging. It can also be used as a body. Of course, it is also possible to use a rapidly solidified alloy material in the form of a rod or wire directly from the Al melt by an appropriate rapid solidification method.

Corrosion resistance A obtained by such a thermal spraying method
As shown in FIG. 1, the alloy film 2 is formed on the surface of the base material 1 with a uniform film thickness, and the transition metal-Al intermetallic compound resulting from the corrosion-resistant Al alloy powder is uniformly dispersed in the structure. ing. As described above, since the transition metal-Al intermetallic compound is considered to have good corrosion resistance, the corrosion resistance of the corrosion-resistant Al alloy film 2 is improved. For this reason,
The corrosion-resistant Al alloy film 2 becomes an alloy that is less susceptible to corrosion than cast iron, and thus acts as a corrosion-resistant alloy layer that is less susceptible to corrosion than the base material 1. Therefore, even if left in a corrosive environment, corrosion hardly proceeds and the film does not disappear, so that an excellent anticorrosion effect is maintained. Further, when a film is formed on the surface of the base material 1, since the corrosion resistance has already been improved, there is no need for a step for improving the corrosion resistance after the film is formed. That is, corrosion of the base material 1 can be prevented without performing heat treatment such as diffusion or annealing. As a result, the coating process is simplified, and the manufacturing cost is reduced.

Further, the hardness of the corrosion-resistant Al alloy powder is improved while maintaining an excellent corrosion protection effect due to the inclusion of Si. Therefore, the corrosion-resistant Al alloy film 2 is formed of a corrosion-resistant alloy layer having both high corrosion resistance and high hardness. Act as Therefore, a film that is hardly damaged and has improved corrosion resistance is formed, and corrosion of the base material 1 can be prevented. The base material 1 on which the corrosion-resistant Al alloy film 2 is formed is held at room temperature for a long time, for example, 72 hours. On the other hand, when the Si content is increased to a certain amount or more, the material becomes brittle, and there is a tendency that peeling occurs easily during thermal spraying.
In order to suppress this, one or two of Mg and Zn are contained in a total amount of 0.3 to 3.2 wt%. As described above, when Mg and Zn are contained, age hardening occurs at room temperature, and high hardness and fine precipitates are formed in the structure of the corrosion-resistant Al alloy film 2. Since the hardness of the corrosion-resistant Al alloy film 2 is ensured by these precipitates, the Si content can be suppressed, and the embrittlement of the material is suppressed, whereby the occurrence of peeling can be prevented. That is, Mg and Zn have an effect of improving hardness and contribute to prevention of deterioration of toughness. However, if the content is less than 0.3 wt%, such an effect is insufficient, and sufficient hardness is not secured. On the other hand, if the content exceeds 3.2 wt%, the amount of the precipitate becomes excessive, and the material becomes brittle,
Deterioration of strength occurs. In addition, the preferable content of Mg and Zn is one or two kinds in total of 0.5 to 3.0 wt%.

As a method for forming the corrosion-resistant Al alloy film 2, a build-up method can be adopted instead of the thermal spraying method. When this overlaying method or thermal spraying method is used, the corrosion resistance of the intermetallic compound in the corrosion-resistant Al alloy powder is almost constant.
1 is dispersed and formed on the alloy film 2. In particular, according to the thermal spraying method, it is easy to uniformly distribute the intermetallic compound having good corrosion resistance over a wide range of the surface of the base material 1 without bias, and the uniformity of the anticorrosion effect on the surface of the base material 1 is impaired. Nothing. Next, a corrosion-resistant Al alloy powder is manufactured by the above-mentioned rotating water flow method, and a cast iron material having an Al sprayed film formed on the surface is obtained by the flame spraying method using the alloy powder. It was left for a time to allow natural age hardening. At that time, after the thermal spraying and after the natural aging, the hardness of the Al sprayed coating was measured by a Vickers hardness tester. Then, a salt spray test was performed using this cast iron material, and the corrosion resistance of the Al sprayed coating was confirmed. Here, the chemical composition of the corrosion-resistant Al alloy powder is as shown in Table 1, and the thickness of the Al sprayed coating is 150 μm. or,
The cast iron material was a 150 × 50 × 5 mm plate material, and was preheated at 250 ° C. before thermal spraying. As a comparative example, the same test was performed on a cast iron material having a film made of pure aluminum manufactured under the same conditions.

The results of these tests are shown in Table 1. From the table, it can be seen that by adding Mg and Zn, the hardness of the Al sprayed coating at the time of thermal spraying is suppressed, and peeling of the coating is prevented. Actually, even when the Al sprayed film was observed, no peeling was observed in the film. Then, the film hardness was improved by natural age hardening, and a film having higher hardness and less occurrence of peeling than the comparative example was obtained.

[0021]

[Table 1]

The present invention is not limited to the above-described embodiment, and an appropriate powder producing means such as water or gas atomizing method can be applied instead of the rotary water flow method as the powder producing method. The thermal spraying method is not limited to flame thermal spraying, but may be, for example, a plasma thermal spraying method, and may use electricity as a heat source. or,
By forming the thermal spray coating only on the portions requiring corrosion resistance, the processing operation is simplified and the productivity is improved. The surface treatment method of the present invention is suitable for structural materials such as bridges made of iron-based materials, columns of buildings, roof materials, wall materials, landscape structures, and the like. In particular, when used as a method for coating a cast iron tube, it is possible to provide a cast iron tube having a low production cost and an excellent anticorrosion effect.

[0023]

As described above, according to the surface treatment method of the present invention, 6 to 35 wt% of Si, M
g or Zn of one or two kinds in total of 0.3 to 3.2 w
t, and a rapidly solidified alloy material containing a total of 6 to 35 wt% of one or more transition metals composed of Fe, Mn, and Cr, and the balance substantially consisting of Al. Since the corrosion resistance of the iron-based material is improved, an intermetallic compound having good corrosion resistance is formed in the matrix, and an excellent anticorrosion effect can be obtained. In addition, since Si is contained, the hardness can be improved while maintaining the excellent anticorrosion effect.

Since the rapidly solidified alloy material is sprayed or overlaid to improve the corrosion resistance of the iron-based material without performing a heat treatment, heat treatment steps such as annealing and diffusion can be omitted. As a result, the surface treatment operation is simplified, the operation efficiency can be improved, and the manufacturing cost can be reduced. At this time, the formed alloy film is less likely to be damaged, and can function as a corrosion-resistant alloy layer having both excellent corrosion resistance and high hardness. Further, since it contains Mg and Zn, high hardness and fine precipitates are formed by age hardening, and it is possible to improve toughness while maintaining high hardness. Therefore, it is possible to form a high-hardness alloy film that is difficult to peel off, and to prevent corrosion of the base material.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a corrosion-resistant Al alloy film formed on a base material according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a corrosion-resistant metal alloy layer formed on a conventional cast iron material.

[Explanation of symbols]

 1 Base material 2 Corrosion-resistant Al alloy film (corrosion-resistant alloy layer)

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Mutsuo Uchida 2-26-2 Ohama-cho, Amagasaki-shi, Hyogo Co., Ltd. Inside Kubota Works, Ltd. (72) Inventor Hiroaki Shimizu 2-26-26, Ohama-cho, Amagasaki-shi, Hyogo Kubota Corporation Inside the Mukogawa Works (56) References Special Table Hei 5-504172 (JP, A) Special Table Hei 5-502911 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 4/08 C22C 21/00 C23F 15/00

Claims (2)

(57) [Claims] 1. A method according to claim 1, wherein 6 to 35 wt.
%, One or two of Mg and Zn in a total amount of 0.3 to 3.2.
wt%, a rapidly solidified alloy material containing a total of 6 to 35 wt% of one or two or more transition metals of Fe, Mn, and Cr, and the balance substantially consisting of Al, is sprayed or built up. A surface treatment method for an iron-based material, characterized by improving the corrosion resistance of the iron-based material. 2. The method according to claim 1, wherein the rapidly solidified alloy material is in the form of a powder or a wire.