JPH0480306A - Manufacture of double layered sintered parts - Google Patents

Abstract

PURPOSE:To make bonding strength firmly and to obtain the above double layered sintered parts having large strength by executing thermal-spraying at high velocity with metal powder on surface of base material while heating at high temp., forming build-up layer and successively, sintering. CONSTITUTION:The base material 2 is manufactured with suitable machining by using a carbon steel, etc., as the raw material. In shape of the base material 2, a through-hole 2a for inserting a cam shaft at center part is formed and outer peripheral surface 2b as one of the surface is formed as the similar shape as the desired cam shape. The thermal spraying is executed to surface to be hardened in the base material 2, i.e., to the outer peripheral surface 2b to be the cam surface in this practical example, with plasma thermal spraying method, while heating the powder 3 of high speed steel, etc., at high temp. to the arrow mark A direction to form the build-up layer 4. After heating the assembling type cam 1 formed the build-up layer 4 to the temp. being suitable to the raw material of build-up layer 4 in a heating furnace, this is slowly cooled, and by diffusing the high speed steel in the build-up layer 4 into carbon steel of the base material 2, the bonding between the base material 2 and the buildup layer 4 is made to firm, and also after improving the density of build-up layer 4, finishing machining is executed to complete the assembling type cam 1.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing two-layer sintered parts, and particularly to a two-layer sintered part that has strong bonding strength regardless of the shape of the part and has a high-density build-up layer. The present invention relates to a method for producing a two-layer sintered part, which allows the production of a sintered part.

BACKGROUND OF THE INVENTION Conventional methods for manufacturing two-layer sintered parts include: After pasting a sheet material made by mixing metal powder and resin into a sheet shape on the necessary parts of a base material manufactured by an appropriate method, A method of manufacturing by heating in a sintering furnace is known. However, this conventional method has the drawback that the attached sheet material may shift during sintering, making it impossible to obtain a part with the desired shape. Further, since the sheet material contains a large amount of resin, it has the disadvantage that it shrinks significantly due to sintering and changes its shape. In addition, because the resin content is burned and disappears, the density of the part where the sheet material is attached is low (sufficient mechanical strength cannot be obtained, and the applications of parts manufactured by this manufacturing method do not require strength. It has the disadvantage that it is limited to certain locations.Furthermore, it requires a long sintering time to completely incinerate the resin, resulting in high production costs and low production efficiency.

As another method, a method of creating two layers by press molding has been proposed, but this method has the disadvantage that it can only be applied to parts with a shape that can be press molded, and its applications are limited. Ta.

Purpose The present invention has been made to eliminate the drawbacks of the prior art described above, and its purpose is to thermally spray metal powder onto the surface of a base material at high speed while heating it to a high temperature. By forming a build-up layer, a high-density build-up layer is formed, and this method ensures the mechanical strength of the build-up layer and minimizes shrinkage of the build-up layer due to sintering. The goal is to improve the reliability of manufactured parts and greatly expand their applications.

Another purpose is to make it possible to manufacture parts of all shapes as two-layer sintered parts, which was impossible with conventional methods, by forming the build-up layer by thermal spraying, and to
The objective is to reduce the manufacturing cost of layer sintered parts.

Another purpose is to form a build-up layer with strong bonding strength to the base material by fixing the metal powder to the base material by thermal spraying, and to further strengthen the bonding strength by sintering, resulting in extremely high strength. The objective is to obtain a two-layer sintered part.

Structure: In short, the method of the present invention involves spraying heated metal powder at high speed onto the surface of a base material manufactured by processing a metal material to form a high-density build-up layer, and then spraying the metal powder in a predetermined manner in a heating furnace. The method is characterized in that the base material and the built-up layer are sintered and joined by heating to a certain temperature.

The present invention will be explained below based on embodiments shown in the drawings. To explain the manufacturing method of the two-layer sintered part 1 according to the present invention by taking the manufacturing of an assembled cam as an example, in FIG. 1, a base material 2 is manufactured from carbon steel by appropriate machining. The shape of the base material 2 is such that a through hole 2a for inserting a camshaft (not shown) is formed in the center, and an outer circumferential surface 2b, which is an example of the surface, is formed in a shape that approximates the desired cam shape. .

Referring to FIG. 2, a hardened surface of the base material 2, the outer circumferential surface 2b which becomes the cam surface in this embodiment, is coated with powder 3 of high speed steel by, for example, plasma spraying while being heated to a high temperature. The overlay layer 4 is formed by thermal spraying in the direction of arrow A.

Next, with reference to FIG. 3, the assembled cam 1 with the built-up layer 4 formed thereon is heated in a heating furnace (not shown) to a temperature suitable for the material of the built-up layer 4, for example, 1260°C. The high-speed steel of the build-up layer 4 is diffused into the carbon steel of the base metal 2 by slow cooling, thereby strengthening the bond between the base metal 2 and the build-up layer 4 and improving the density of the build-up layer 4. After this, the assembled cam 1 is completed by appropriately performing heat treatment such as hardening treatment or finishing processing to improve shape accuracy.

Function The present invention is constructed as described above, and its function will be explained below. In Figures 1 to 3, base material 1
The material may be any metal, and is determined by comprehensively considering the performance required of the base material 1, such as mechanical strength, weldability with the parts to be assembled, ease of manufacture, cost, etc.
It can be manufactured by a machining method suitable for the material, such as cutting, powder metallurgy, or forging.

A thermal spraying method using a plasma jet is suitable for forming the build-up layer 4 on the base material 2, and gas plasma spraying is usually used.

Gas plasma spraying uses an anode nozzle with a small hole in the bottom of one side of a closed cylindrical container made of copper, and a cathode made of tungsten placed concentrically within the cylindrical container.
An arc is generated by applying a DC voltage between the anode and cathode while flowing arc gas through the anode nozzle, and a high-temperature plasma jet is ejected from a small hole. When the thermal spraying material powder 3 is supplied into the plasma jet, the thermal spraying material is heated to approximately 10,000°C to 20,000°C.
It melts in the plasma jet at temperatures as high as ℃, collides with the base material 2 at high speed, and is cooled in a very short time (on the order of milliseconds), changing from a molten state to a solid, resulting in a high temperature of the base material 2. There is no deformation caused by heat. This action is performed one after another to form a built-up layer 4 of the thermal sprayed material 3.

According to plasma spraying, the spraying material can be selected from a very wide range of materials with high melting points such as metals, oxides, carbides, and ceramics, and the material most suitable for the characteristics required for the part can be used.

In addition, since the collision speed with the base material 2 is extremely high, the bond with the base material 2 is strong, and the build-up layer 4 is dense with strong bonding force.Furthermore, the coating speed is fast, so the cost is low. A thick build-up layer 4 can be formed easily and efficiently.

After forming the overlay layer 4 on the surface 2b of the base material 2 as described above, the overlay layer 4 is diffused into the base material 2 by heating and sintering at a temperature suitable for the material of the overlay layer 4. The bonding force is further improved, and the bonding force between the particles of the build-up layer 40 is also improved, making it possible to manufacture a two-layer sintered part having an extremely high-density surface layer and strong bonding strength.

In this embodiment, the thermal spraying is explained as a gas plasma thermal spraying method, but the thermal spraying is not limited to the gas plasma thermal spraying method, and may be, for example, a water plasma thermal spraying method.

Effects As described above, the present invention forms a build-up layer by thermally spraying metal powder at high speed while heating it to a high temperature on the surface of the base material, so it has the effect of being able to form a high-density build-up layer. As a result, the mechanical strength of the built-up layer is ensured, and the shrinkage of the built-up layer due to sintering is minimized, thereby improving the reliability of parts manufactured by this method and greatly expanding its applications. There is an effect that can be done.

In addition, since the build-up layer is formed by thermal spraying, parts of all shapes can be manufactured as two-layer sintered parts, which was not possible with conventional methods, and the manufacturing cost of the two-layer sintered parts can be reduced. effective.

Furthermore, since the metal powder is fixed to the base material by thermal spraying, it is possible to form a built-up layer with strong bonding strength to the base material, and the bonding strength is further strengthened by sintering, resulting in an extremely strong two-layer layer. There is an effect that sintered parts can be obtained.

[Brief explanation of drawings]

The drawings relate to embodiments of the present invention, and FIG. 1 is a perspective view of the base material;
FIG. 2 is a perspective view showing the state of thermal spraying of metal powder, and FIG. 3 is a perspective view of a two-layer sintered part as a completed product. 1 is a two-layer sintered part, 2 is a base material, 2b is a surface, 3 is a metal powder, and 4 is an overlay layer.

Claims (1)

[Claims] A high-density build-up layer is formed by thermally spraying heated metal powder at high speed on the surface of a base material manufactured by processing a metal material, and then heated to a predetermined temperature in a heating furnace to form a high-density build-up layer. A method for manufacturing a two-layer sintered part, characterized by sintering and joining a material and the overlay layer.