The powder in powder metallurgy can be understood as a general term of performance

The powder in powder metallurgy can be understood as a general term of performance

Powder in powder metallurgy is actually the general term of all properties of powder, so what other properties does it specifically include? In fact, the powder also includes: the geometric characteristics of the powder; Chemical properties of the powder; Mechanical properties of powder; Physical and surface properties of powders however, the properties of powders are often related to the properties of powder metallurgy products. Let's look at the most basic geometric properties of the following powders:

(1) The particle size affects the processing and molding of the powder, the shrinkage in the sintering process and the final performance of the product. The properties of some powder metallurgy products are almost directly related to the particle size. For example, the filtration accuracy of the filter material can be determined empirically by dividing the average particle size of the original powder particles by 10. The properties of cemented carbide products are closely related to the grains of wc phase. In order to obtain cemented carbide with finer grain size, only wc raw materials with finer grain size can be used. Used in production practice

The particle size of the powder ranges from hundreds of nanometers to hundreds of microns. The smaller the particle size is, the greater the activity is, and the easier the surface is to oxidize and absorb water. When it is as small as hundreds of nanometers, the storage and transportation of the powder is not easy. When it is small to a certain extent, the quantum effect starts to play a role, and its physical properties will change greatly. For example, the ferromagnetic powder will become a superparamagnetic powder, and the melting point will also decrease with the decrease of the particle size.

(2) The particle shape of the powder depends on the preparation method of the powder, such as the powder prepared by electrolysis, and the particles are dendritic; The iron powder particles prepared by reduction method are spongy; In addition, some powders are egg shaped, disk shaped, needle shaped, onion shaped, etc. The shape of powder particles will affect the fluidity and bulk density of the powder. Due to the mechanical engagement between particles, the density of irregular powder is also very large, especially the density of dendritic powder is the largest. However, for porous materials, spherical powders are the best

The mechanical properties of powder are the technological properties of powder and the important technological parameters in powder metallurgy forming process. The bulk density of powder is the basis of weighing by volume method during compaction. The fluidity of the powder determines the filling speed of the powder to the mold and the production capacity of the press. The compressibility of the powder determines the difficulty of the pressing process and the applied pressure. The formability of the powder determines the strength of the billet.

The above is about the process of geometric and mechanical properties of powder metallurgy. It can be seen that the properties of powder are closely related to the properties of powder metallurgy products.