JPS5838219B2 - Method for manufacturing cast steel parts with wear resistance on the surface layer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new method for manufacturing a cast steel member having internal toughness and wear resistance on the outer surface layer.

Conventionally, in the production of cast steel members as described above, carbide ceramics such as WC, SiC,
After mixing TiC, etc., or metal powder such as Ni, Cr, Ni-Cr, etc. with some kind of binder and a solvent such as water or alcohol and applying it to the surface of a sand mold, cast steel is poured into the same mold to form the ceramic or metal powder. Methods have been adopted to form a wear-resistant layer by transferring and integrating a powder layer to a casting, or to form a hardened layer by plating a cast steel product with Cr plating or surface treatment with a metal solvent, etc. Ta.

However, the former is the coating layer itself applied to the sand mold.
Because the bonding force between particles and the adhesion force to the sand mold are small, and because the coating layer contains a binder, the coating layer will deteriorate due to the decomposition of the binder due to the high heat during molten metal and the generation of gas that accompanies this decomposition. It was extremely difficult to form an even wear-resistant alloy layer because it collapsed and was further washed away by the molten metal.

In addition, the latter method using plating requires a thin hardened layer and a complicated pretreatment process for the material, resulting in high costs, and in the case of metal welding, there is a problem that the shapes of parts to which it can be applied are limited. It is.

The present invention has been made with the aim of solving the drawbacks of the conventional methods as described above, and is therefore characterized by the use of a wear-resistant material such as a self-fusing alloy at desired locations on the mold surface of the mold. The present invention is characterized in that after forming a hot melt coating made of an effective and solvent-compatible metal material, cast steel is poured into the same mold, thereby transferring and integrating the hot melt coating onto the cast steel product.

The present invention will be described in detail below. Fig. 1 is a mold diagram for explaining the present invention. In the present invention, as shown in the figure, it is possible to form a welding mold with a wear-resistant effect at desired locations 2, 2.2 on the mold surface. Cast steel, such as SC37, SC47, etc., is cast into a mold 1 in which a solvent coating 3, 3, 3 of the material is formed, and the solvent coating 3, 3.3 is transferred and fused to the cast steel product. This forms a wear-resistant layer.

In other words, in the present invention, a solvent film is transferred instead of the conventional transfer of a coating layer using a powder kneaded material, and therefore the coating layer does not collapse during casting or be washed away by molten metal as in the conventional method. Since the film thickness can be easily adjusted, the wear-resistant layer is not too thin as is the case with plating methods, and since the coating film shape is transferred to the mold rather than to the casting itself, for example, Even in the case of curved holes, it is possible to form a wear-resistant layer on the surface of the hole, and there are almost no restrictions on the shape of the hole.This method solves all of the disadvantages of conventional methods.

As for solvent metals, any material that can be used as a solvent and has a wear-resistant effect can be applied.For example, products with excellent wear-resistant layers using self-fluxing alloys that are generally commercially available as solvent materials for wear resistance are applicable. The case of using a self-fluxing alloy will be explained below along with its examples.

Figure 2 shows a part of the surface of a flan sand mold for casting steel coated with a self-fusing alloy having the composition shown in the table below to form a dissolution film with a thickness of about 0.3 nm, and then SC37 applied to the same mold. 1500℃
This is a micrograph of a cross section of a casting cast in the same cross section, and the hardness measured on the same cross section is HV447.2 at the depth of the tenon of the transfer layer of the melt coating, and HV5.30 further below. However, in the cast steel part, the HV was around 120.

As mentioned above, self-fusing alloys contain a considerable amount of B in addition to Ni and Cr.
It goes without saying that Ni and Cr are alloyed with Fe, and Cr further forms Cr carbide to provide wear resistance, but B is extremely important when transferring the surface coating. It works effectively.

In other words, the oxides that are concentrated at the boundary between the solvent coating and the cast material during casting inhibit the adhesion between the casting material and the solvent coating, but B has the function of preventing this. In addition, boron nitride and boron carbide, which are added to the diet, increase hardness and contribute to wear resistance.

The preferable thickness of the solvent coating is between 0.05 and 1 mm. If it is less than 0.05 mm, it is too thin and sufficient wear resistance effect cannot be obtained, and if it is more than 1 mm, it is practically useless and costly. I don't like it because it causes high temperatures.

The casting temperature is a major factor that affects the transfer of the solvent film.

In other words, if it is too high, the molten film will diffuse into the material to be transferred, and if it is too low, sufficient transfer will not be possible due to a decrease in the fluidity of the molten metal and an increase in the solidification rate.
Good results were obtained at 20'C, and in casting within this range, it is possible to transfer the solvent coating in good condition to castings with a thickness of 3 or more, and the thickness of the member to be transferred is 3-5
The preferred range is between 0 and 0.

Although the case of self-fusing alloys has been described above, it goes without saying that the present invention is not limited to the above-mentioned alloys, and can be applied to any metal material that has a wear-resistant effect and can be melted.

In addition to the above-mentioned furan sand mold, any mold that can be used for casting steel, such as a CO2 mold or a self-hardening sand mold, as well as a metal mold or a dry powder mold, can of course be used in the present invention.

The present invention is as described above, and by melting a metal material with a wear-resistant effect into a mold and transferring it to a casting to form a wear-resistant layer, it is possible to eliminate the conventional method. It is an extremely excellent method for manufacturing cast steel parts with wear-resistant surfaces, and can be used as-cast, such as in slurry pump casings, and has high durability. The present invention is extremely suitable for manufacturing parts that require wear resistance and low cost, and the industrial value of the present invention is significant.

[Brief explanation of the drawing]

FIG. 1 is a diagram of a mold for the present invention, and FIG. 2 is a micrograph of a cross-sectional microstructure of a casting according to a first embodiment of the present invention. 1...mold, 2... desired location on the mold surface, 3... melt coating.

Claims (1)

[Claims] 1. After applying a solvent coating made of a wear-resistant and solvent-resistant metal material such as a self-fusing alloy to a desired location on the mold surface of a mold, cast steel is poured into the same mold to apply the solvent coating to a cast steel product. A method for manufacturing a cast steel member having a wear-resistant surface layer, the method comprising: transferring and integrating a cast steel member with a surface layer having wear resistance.