JP3239545B2 - Aluminizing treatment method for metal surface - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for aluminizing a metal substrate surface by a melt immersion method.

[0002]

2. Description of the Related Art Aluminizing treatment of a metal surface has been widely used for the purpose of improving heat resistance. FIG. 7 shows the outline of the aluminizing treatment on the metal surface by the conventional melt immersion method. As shown in FIG. 7A, a metal work 3 as a material to be processed is immersed in a molten metal 2 based on aluminum placed in a processing tank 1, and the work 3 pulled up from the processing tank 1 is
As shown in FIG. 7B, the heater 4 is heated to diffuse aluminum adhering to the surface of the work 3 into the base metal to form a thin film of an intermetallic compound on the work surface.

The present applicant has previously filed a patent application for an invention relating to aluminizing on a metal surface (Japanese Patent Laid-Open No.
0461). In this method, a nickel-based steel work is immersed in a molten aluminum containing boron and hafnium, and Ni-Al (B,
A thin film of an Hf) -based intermetallic compound is formed.

[0004]

In the conventional aluminizing treatment by the melt dipping method generally used, the film formed on the metal surface is hard, brittle, and lacks toughness.
For example, when applied to parts with a cooling / heating cycle such as an engine pre-chamber or an exhaust manifold, the reliability of the product becomes extremely poor. In addition, the method disclosed in the above-mentioned publication has a problem that the material cost is high because a nickel-based alloy is used as a base material, and nickel is eluted on the surface during the heat diffusion treatment, so that it is difficult to obtain the surface accuracy of the product.

[0005] The present invention solves the above-mentioned problems, and provides a method for aluminizing a metal surface from an iron-based alloy as a base material and capable of forming a film having a tough surface and good surface accuracy. The purpose is to do so.

[0006]

SUMMARY OF THE INVENTION The present invention is characterized in that an iron-based alloy work is immersed in a manganese-containing molten aluminum and then subjected to a heat diffusion treatment to form a film of an intermetallic compound on the work surface. Aluminizing treatment method for the metal surface.

[0007]

[Action] It has been confirmed from the test results that the addition of manganese (Mn) to the molten metal improves the toughness of the film formed on the treated product. The reason is unknown,
The coating is made of a binary alloy made of Al-Ni, Al-Cr, Ai-Fe and the like and a ternary alloy containing these alloys. When a treatment using a molten metal to which Mn is added is performed, one of these alloy systems is formed. It is presumed that segregation at the boundary with the iron-based alloy metal as the base material contributes to improvement of the toughness of the film.

[0008]

EXAMPLES In the aluminizing treatment of a metal surface by the melt immersion method, the characteristics of the film formed on the surface are considered to be influenced by the following factors. Type of base material (processed product) Type of component added to aluminum-based molten metal Amount of component added to aluminum-based molten metal Temperature of aluminum-based molten metal Base metal (processed product) molten metal Immersion time in the diffusion heat treatment temperature Diffusion heat treatment time Therefore, for each of the above factors, select the ones that are considered appropriate, apply aluminization treatment using a test piece to each, and attach A tensile test was performed to evaluate the properties of the surface film.

Regarding the type of base material (workpiece),
Austenitic iron-base heat-resistant alloy (MIC-LC) and martensitic high chromium heat-resistant steel (SUH616) were used.
m), a plate-shaped test piece was prepared and subjected to an aluminizing treatment. MIC-LC is a material used for a high-load hot plug of a diesel engine. The composition of the MIC-LC is represented by the following percentage by weight. C: 0.05-0.2, Si: 0-1.0, Mn: 0
1.0, P: 0 to 0.03, S: 0 to 0.03, Cr:
30.0-33.0, Ni: 24.0-28.0, C
o: 2.0 to 4.0, Nb: 0.2 to 0.5, N: 0.
15 to 0.3, balance Fe SUH616 is a material used for a low-load hot plug of a diesel engine.
Is as follows. C: 0.2 to 0.25, Si: 0 to 1.0, Mn: 0.
5 to 1.0, P: 0 to 0.04, S: 0 to 0.03, C
r: 11.0 to 13.0, Ni: 0.5 to 1.0, W:
0.75-1.25, Mo: 0.75-1.25, V:
0.2-0.3, balance Fe

Regarding the types of components to be added to the aluminum-based molten metal, those with no addition (normal aluminization treatment) and those with 0.8% by weight of boron (B) added , Manganese (Mn).
The treatment was carried out using three kinds of molten metals with the addition of 5% by weight. Since the temperature of the molten metal cannot be changed significantly, two levels of standard 690 ° C. and 710 ° C. were used. The immersion time of the base material (processed product) in the molten metal is 1 minute and 5 minutes.
It was set to two-minute level. The temperature and time of the diffusion heat treatment are 1000 ° C., 6
It was fixed to the 1/0 level.

The intermetallic compound film is formed on the work surface by the aluminizing treatment, and the film thickness greatly affects the performance such as the oxidation resistance of the film. In addition, a large change in the external dimensions of a product is an obstacle to production. The change in the outer size of the test piece before and after the aluminizing treatment was measured with a micrometer, and the change in the outer size was evaluated as being substantially equal to the film thickness. FIG. 1 shows the average thickness of the coating for MIC-LC, and FIG. 2 shows the average thickness of the coating for SUH616. As a whole, the higher the temperature of the molten metal and the longer the immersion time, the larger the film thickness tends to be. Also, when B is added, the film thickness increases.

As a method for evaluating the toughness of the film, a tensile test was used to evaluate the toughness. Tensile tester: 100KN Autograph Test method: A strain gauge is attached to one side of the test piece, and while performing a tensile test at room temperature, the coating surface on the opposite side of the surface where the strain gauge is attached is observed using a magnifying glass, and the coating is applied. When the surface cracks, read the stress and strain with a strain gauge. The test is performed until the test piece breaks, and the tensile strength and elongation at that time are read. The test piece of SUH616 was broken before the surface of the film was cracked, probably because of poor ductility, and could not be evaluated.
The test was performed only on the test piece C. Therefore, the following test results are all about MIC-LC test pieces.

FIG. 3 shows the test results of the tensile strength. From FIG. 3, in the treated product using the molten metal to which B was added, the tensile strength of the material was significantly reduced (indicated by sample number 0 in the figure), but the treated product using the molten metal to which Mn was added was: It can be seen that many of the materials are close to the tensile strength of the material.

FIG. 4 shows the stress at the time when the surface film is cracked. From FIG. 4, in the treated product using the molten metal to which B is added, a slight decrease in stress is seen.
The treated product using the Mn-added molten metal generally shows a high stress value, but the sample No. 11 (710 ° C., 1 minute) shows a particularly high stress value.

FIG. 5 shows the elongation test results. From FIG.
The sample No. 11 (Mn, 710 ° C., 1 minute) has the same degree of elongation as the tensile strength of the material (shown as sample number 0 in the figure), but the sample No. 12 (Mn, 710 ° C., 5 minutes) ), The elongation is about half, and in the other treatments, it is only 4-6%.

FIG. 6 shows the values read by a strain gauge at the time when cracks are formed on the film surface. From FIG. 6, the strain value of the 11th sample (Mn, 710 ° C., 1 minute) is the highest, and
A treated product using a molten metal to which n is added generally shows a high strain value. This indicates that it is effective to use a molten metal containing Mn to improve the toughness of the film.

From the above test results, it has been confirmed that the addition of Mn to the molten metal improves the toughness of the film formed on the treated product. Although the reason is unknown, the coating is made of a binary alloy composed of Al-Ni, Al-Cr, Ai-Fe and the like and a ternary alloy containing these alloys. It is presumed that one of these alloys segregates at the boundary with the base material (material to be treated) and contributes to the improvement of the toughness of the film.

[0018]

According to the present invention, an inexpensive iron-based alloy is used as a base material,
Since a film having toughness and good surface accuracy can be formed on the surface, the applicable range of the aluminizing treatment on the metal surface can be expanded, and the reliability of the treated product can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing an average film thickness of a sample using MIC-LC as a material.

FIG. 2 is a diagram showing an average film thickness of a sample using SUH616 as a material.

FIG. 3 is a diagram showing test results of tensile strength.

FIG. 4 is a diagram showing stress at the time when a crack is formed in a film.

FIG. 5 is a view showing a test result of elongation.

FIG. 6 is a view showing a strain value when a crack is formed in a film.

FIG. 7 is a diagram showing an outline of an aluminizing process.

FIG. 8 is a view showing a test piece.

[Explanation of symbols]

 1 treatment tank 2 molten metal 3 work 4 heater

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C23C 2/12 C23C 10/18

Claims (1)

(57) [Claims] An aluminizing treatment of a metal surface, characterized in that an iron-based alloy work is immersed in a manganese-containing molten aluminum and then subjected to a heat diffusion treatment to form an intermetallic compound film on the work surface. Method.