JPH062102A - Method for controlling carburization - Google Patents

Abstract

PURPOSE:To easily form a carburizing layer having a prescribed thickness by applying a paste-like reduction plating composition on the surface of a metallic member to be carburized to form a plating film and then subjecting it to a gas carburizing treatment. CONSTITUTION:After applying the paste-like reduction plating composition consisting of metallic salt capable of reduction plating, such as copper sulfate, complexing agent, such as EDTA/2Na, reducing agent of formaldehyde, such as thickener of gelatine, and bulking agent, such as silica-series, etc., on the surface of the metallic member to be carburized, the plating reaction is executed, e.g. at 10-80 deg.C for 1-10min to form a Cu plating layer uniformly dispersing pin holes. Thereafter, the remaining plating composition is washed down, and by passing through the pin holes of the plating layer by the gas carburizing method using natural gas, methane, CO, etc., the prescribed thickness of the carburized layer is formed. Even if the shape of the metallic material to be treated is complicate, the prescribed thickness of the carburized layer can easily be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention applies a reduction plating composition in the form of a paste to a predetermined portion of a material to be carburized and then forms a plating film having a desired thickness by changing temperature or plating time as plating conditions. The present invention relates to a carburizing control method for obtaining a desired carburized layer depth in carburizing by performing gas carburizing after forming.

[0002]

2. Description of the Related Art Generally, as a carburizing method, a solid carburizing method using powder of charcoal, coke, bone ash, graphite, etc. as a carburizing material, and a carburized material in a molten salt containing potassium cyanide as a main component. For example, a liquid carbonitriding method in which a member such as a gear is placed and carburizing and nitriding are simultaneously performed with generated carbon monoxide and nitrogen, and performed in natural gas, carbon monoxide, methane, ethane, propane oil vapor or alcohol. A gas carburizing method is known.

In this gas carburizing method, it is possible to carry out carburizing control by inserting parts into a carburizing furnace and heating them with a heat pattern to control carburization to a predetermined depth.

However, in such carburizing control, the carburizing depth can be adjusted by adjusting the carburizing gas concentration, the temperature in the furnace, and the treatment time in the carburizing furnace, but a uniform carburizing layer is formed on the surface of the component. Therefore, it is impossible to form a carburized layer having a carburized depth partially different depending on the shape of the part.

As a method of partially changing the carburizing depth,
After the carburizing process, the carburized layer on the surface of the part is treated with a glider,
After that, the carburizing depth is partially corrected by performing a quenching process, but it takes time and labor, and there is a problem in mass productivity.

[0006] Further, although a liquid or paste carburizing preventive material is applied to a portion which is not desired to be carburized and then carburized, a carburizing preventive material in liquid or paste form is applied at a constant depth in a coating device. In addition, since it is difficult to apply the coating uniformly, it is not possible to control carburization by the coating thickness.

Further, even if the liquid coating is possible by changing the composition, it is necessary to change the composition every time the desired carburizing depth is reached, and it is difficult to control the carburizing by one method.

As a technique related to these problems, locally carburizing the bearing by thin plating of 10 to 200 μm or forming a coating layer such as mottled thermal spraying and then carburizing. Discloses a method (Japanese Patent Laid-Open No. 51-41647) in which the depth of the carburized layer is moderate (semi-carburized).

Further, in the metal thermochemical treatment by the salt bath method or the powder method (two metal diffusion infiltration method), the self-adhesive tape containing the metal powder made of natural or synthetic fiber is locally coated to locally apply it. JP-A-51-50240 discloses a method for preventing the diffusion of activated carbon.

Further, regarding a method of applying a carburizing agent to a desired position, a wax is preliminarily applied instead of a masking tape which is often used for painting, etc., to a portion which does not need to be coated with a carburizing agent, and then the anti-charging agent is applied. A simple and accurate method of applying a carbonizing agent by applying a carbonizing agent (JP-A-52-78721)
Is disclosed.

[0011]

[Problems to be Solved by the Invention] However, JP-A-51-4
In the method disclosed in 1647, the carburizing gas is completely cut off at a plating thickness of 10 to 200 μm, it becomes a complete carburizing instead of semi-carburizing, and in the case of mottled spraying, carburizing unevenness occurs, Both have practical problems.

[0012] Further, JP-A-51-50240 or JP-A-52-787.
The method disclosed in Japanese Patent No. 21 completely prevents carburization of carbon, and therefore has a problem that the carburization depth cannot be freely adjusted.

Further, in order to solve the problem, the present inventors have already applied it to various carburizing treatment systems, and as a carburizing control method capable of adjusting the carburizing depth to a desired one, a carburizing agent is used as an aggregate or a hot carburizing agent. It was proposed to disperse it in a melt resin to form a sheet or a tape, and to apply this carburizing control agent to the carburization control surface of a work by subjecting it to hot melt treatment at appropriate times.

However, since the sheet- or tape-shaped carburizing control agent is a two-dimensional flat molded article, it becomes difficult to attach it when the workpiece has a three-dimensional processed surface.

For example, for a screw surface in which a concave curved surface and a convex curved surface are combined intricately, or for a surface having a deep conical concave shape, a sheet having a uniform thickness in the direction perpendicular to the surface is used. It is difficult to manufacture and it is also difficult to attach.

Further, even if it is possible to cope with this, when the number of kinds of workpieces is limited, the shape of the sticking portion of the sticking machine can be limited and used, but it is not suitable for a large number of small quantities.

For this multi-product productivity, it is possible to use the above-mentioned liquid anticorrosive agent and pasty anticorrosive agent by, for example, precision spray coating by diluting with a solvent.

However, in this case, the problem of sagging after coating,
The problem that the local application depends on the spray pattern, and the high-concentration compound of boron oxide required for carburization control has slurry characteristics, and the diameter of the boron oxide is large, the orifice of the spray is calibrated. Is large, and there is a problem due to abrasion of the orifice portion due to the hardness of boron oxide.

Therefore, in the present invention, the application is simple,
Another object of the present invention is to provide a carburization control method in which the carburization control film produced has a uniform thickness.

[0020]

In order to solve the above problems, in the present invention, a metal salt such as copper sulfate, EDTA is used.
· A reduction plating composition consisting of a complexing agent such as 2Na, a reducing agent such as formaldehyde, a thickener, and a filler is applied to predetermined portions of the material to be carburized, and then the plating conditions include temperature and plating time. It proposes a carburization control method in which the carburized material is subjected to gas carburizing treatment after forming a plating film having a desired thickness by changing the above.

Here, copper sulfate is particularly preferable as the metal salt, but the metal salt is not limited to this, and a metal salt capable of reduction plating such as nickel, chromium and silver can be used.

As the complexing agent, EDTA.2Na
In addition, sodium tartrate (potassium), sodium citrate, sodium succinate and the like can be mentioned.

Examples of the reducing agent include glutaraldehyde, dimethylaminoborane, boric acid, sulfuric acid and the like, in addition to formaldehyde.

Examples of the thickener include gelatin, sodium alginate, sodium acrylate, and commercially available water-soluble thixotropic agents.

Examples of the filler include silica-based fillers, kaolin, diatomaceous earth, alumina, oxides of titanium and the like, and nitrided boride.

[0026]

Since the reduction plating composition used in the present invention is made into a paste by adding a thickener, a filler, etc., it is partially applied to the shape of a part which is a carburized material by a conventional nozzle coating device. Plating is possible.

After the plating composition is applied to the surface of the material to be carburized, the plating reaction is performed at a temperature in the range of 10 to 80 ° C. for a plating time of 0.1 to 10 minutes.

The metal salt in the plating composition applied by this plating reaction is reduced by a reducing agent to form a plating film having a desired thickness on the surface of the carburized material. After the completion of the plating reaction, the plating composition is washed away, and the material to be carburized is subjected to a conventionally known gas carburizing treatment.

The plating reaction can be promoted or suppressed by adjusting the plating time or the temperature conditions such as heating or cooling. Therefore, by adjusting these plating conditions, the plating film formed after the reduction plating composition is applied can be formed. The desired thickness can be specified.

As the plating method, there are a reduction plating method, an electrolytic plating method, and a displacement plating method. The reduction plating method is advantageous in the following points.

That is, the pinholes are usually regarded as defects in the plating process, but in the carburizing process, the carburizing gas penetrates through the pinholes of the plating film, and the carburizing degree changes depending on the existence and generation rate of the uniform pinholes. Therefore, in carrying out carburization control, it is necessary to uniformly generate pinholes in the plating film and to control the generation rate thereof.

Another characteristic required of the plating film used for carburization control is that the plating film does not peel off during the high heat treatment during carburization. It is advantageous in the following points.

On the other hand, in the reduction plating method, by removing the surfactant from the plating composition and defining the plating conditions, uniform pinholes are formed in the plating film and the generation rate thereof is controlled. It is possible.

In the reduction plating method, the adhesion of the plating film to the surface of the carburized material is good, and the plating film does not peel off during the high temperature treatment during carburization.

On the other hand, in the displacement plating method, the adhesion of the plated film to the material to be carburized is not sufficient, and the plated film may peel during carburization.

Further, it is difficult to form a plating film having a predetermined thickness even if the plating conditions such as temperature and plating time are adjusted.

Further, in the electrolytic plating method, since the carburized material is usually immersed in the plating bath, all the carburized material is plated, and masking is required to partially plate the material. Becomes difficult to work with.

Further, in the electrolytic plating method, a plating film having no pinhole is formed, and the carburizing gas is completely cut off by this.

[0039]

In summary, according to the present invention, since the paste-like reduction plating composition is used, even if the surface shape of the carburized material has a three-dimensional structure, the plating composition can be partially accurate. It can be applied well.

Since the thickness of the plating film formed on the surface of the carburized material is constant regardless of the coating thickness of the plating composition, the coating thickness of the plating composition may be somewhat rough. .

Further, in the present invention, since the above-mentioned plating composition is used and the reduction plating is performed by adjusting the temperature or the plating time, the plating film having a desired thickness having pinholes uniformly on the surface of the carburized material. Is formed, and this plating film enables desired carburization control.

[0042]

EXAMPLES Examples of the present invention will be shown below. Example 1 SCM-420 steel (50 mm x 50 mm x 5 mm) was used as a test panel, and on this surface, 2.5 g of copper sulfate and sodium hydroxide were used.
4.0g, EDTA / 2Na 6.5g, formaldehyde 8.
A plating composition consisting of 0 g, 10 g of gelatin, 3 g of silica-based filler, and 150 g of water was applied.
Min., 26 min., 34 min., And then rinse off the plating composition to a thickness of 0 to 1 μm on the surface of the test panel.
Plating films of ˜2 μm and 2-3 μm were formed. Then, carburization was controlled by the gas carburizing method.

Comparative Example 1 A test panel similar to that used in Example 1 was used, electrolytically plated, and the plated test panel was polished to a plating thickness of 3 μm, 5 μm, 7 μm, 9 After adjusting to μm, carburization was controlled by the gas carburizing method as in Example 1.

Comparative Example 2 The same test panel as in Example 1 was used, and this was used as copper sulfate.
Immerse in a plating solution consisting of 15 g / liter, sulfuric acid 0.75 g / liter, and ion-exchanged water 1 liter for 30 seconds, 60 seconds, and 120 seconds. μm
The plating film was formed, and then the carburization was controlled by the gas carburizing method. The results of Example 1 and Comparative Examples 1 and 2 are shown in Table 1 below.

[0045]

[Table 1]

Further, with respect to the test panel subjected to the carburization control treatment according to Example 1, the carburization depth (mm) and Vickers hardness (H
The relationship with V) was determined and the results are shown in FIG. Similarly, with respect to the test panel subjected to the carburization control treatment according to Comparative Example 1,
The relationship between carburizing depth and Vickers hardness was determined, and the result is shown in FIG.

Assuming that the Vickers hardness of 550 HV is the carburizing depth limit (effective hardening depth), from FIG. 1 in Example 1, the blank is 0.8 mm, and the plating treatment time is 4 minutes.
0.78 mm, 0.7 mm for 10 minutes of immersion, 0.66 mm for 26 minutes of immersion,
It is clear that it is 0.61 mm for 34 minutes of immersion.

On the other hand, with respect to the test panel subjected to the carburization control treatment in Comparative Example 1, the film thicknesses of 3 μm, 5 μm, 7 μm and 9 μm were not carburized.

[Brief description of drawings]

FIG. 1 shows a relationship curve between carburizing depth and Vickers hardness of a test panel carburized in Example 1.

FIG. 2 shows a relationship curve between carburizing depth and Vickers hardness of a test panel carburized in Comparative Example 1.

Claims (1)

[Claims] 1. A reduction plating composition comprising (a) a water-soluble metal salt, (b) a complexing agent, (c) a reducing agent, (d) a thickening agent, and (e) a filler is treated with a material to be carburized. , And then form a plating film with uniform pinholes of desired thickness by changing the temperature or plating time as plating conditions, and then subjecting the carburized material to gas carburization A carburizing control method characterized by: