Copper powder has certain advantages in improving the thermal conductivity of powder metallurgy products

Copper powder has certain advantages in improving the thermal conductivity of powder metallurgy products

Powder metallurgy materials have unique chemical composition, physical and mechanical properties that cannot be obtained by traditional melting and casting processes. For example, the porosity of the materials can be controlled, the material structure is uniform, and there is no macro segregation (after solidification of the alloy, there is no non-uniform chemical composition on different parts of its section due to the macro flow of liquid alloy), which can be molded at one time. For powder metallurgy parts, the main factor that determines the mechanical properties is the density of sintered parts. Any factor that is conducive to improving the density of sintered parts can improve the mechanical properties of the final product. The higher the density of sintered parts, the higher the mechanical properties. However, as long as the density of sintered parts cannot reach the theoretical density of corresponding dense materials, the mechanical properties of sintered parts are lower than that of corresponding dense materials. For example, for steel, it should be noted that the strength of carbon steel (iron based sintered material made of iron and carbon) and sintered steel added with alloy elements increases with the increase of alloy element content, but the toughness and impact energy value decrease. Therefore, the toughness and impact energy of iron based powder metallurgy structural parts decrease with the decrease of material density and increase of material content.

In the production of powder metallurgy structural parts, re pressing and secondary sintering are often used to improve the material density of parts. Re pressing is similar to finishing, and high pressure is only used to increase the overall density of parts. The influence of cold work hardening can be eliminated by secondary sintering. Secondary sintering refers to sintering again after re pressing. Therefore, the strength and toughness of structural parts materials can be improved due to the high density of materials after re pressing and secondary sintering.

Key words: powder metallurgy PM powder metallurgy copper based iron based structural parts conductive melting casting process