Metal powder to suppress the main shall be guaranteed density and density distribution of the two indicators, depending on the mold pressing process and its parameters and structure of the rational design and selection.
In general, the performance of metal powder parts are its relative density (ie, the actual density of powder in the powder material with the ratio of the theoretical density) is closely related to the relative density is larger, the higher the performance. And specific parts of the suppression of the powder, manganese powder in addition to powder raw materials, components, particle shape and size, its density depends only on the degree of suppression of deformation: the suppression of the stress state, deformation temperature, deformation, strain rate and friction conditions.
In the actual production process, to ensure that pieces of steel to suppress the densification of the main measures is the use of large deformation (high pressure), low strain rate and the use of active friction, therefore, in mass production, boron powder the need to design or use a special hydraulic machine at the same time to take advantage of positive development and improvement of methods to suppress the friction and the corresponding mold structure.
It should be noted, also can be used to suppress other ways to ensure powder densification, such as cold isostatic pressing (CIP) or special compaction, but requires expensive equipment investment. Therefore, suppression of pieces of steel, in order to press tonnage, not too large (generally guaranteed to suppress parts of the relative density ρ '= 0.75 ~ 0.8 can be), often using high density of the subsequent processing, such as the suppression of parts of the impregnated , liquid phase sintering, melting skeleton doped, sintered billet thermoplastic processing (forging, hot extrusion, HIP, etc.).
There is a high density for the powder compaction of the new dedicated "static - dynamic" press, nickel powder can replace the expensive CIP or HIP equipment. The principle is the complete suppression of the static, then the powder to suppress the impact of the limited pulse (the pulse cylinder complete), after this manner, can suppress parts of high-speed steel powder relative density from 0.72 to 0.85 to 0.80 ~ 0.93, densification effect is very obvious.
If the pieces of metal powder densification process can be used to suppress external measures to ensure uniform density then depends mainly on the suppression of the density distribution is uniform billet, metal powder supplier that suppress the process and the corresponding mold design is reasonable. Uneven green density of pressed powder substance is suppressed when the external force, non-uniform deformation of the flow of powder particles. Specific suppression of steel, are: (1) powder and die wall, punch and mandrel surface friction exists between the role of outside; (2) along the direction of the workpiece cross-section suppression shape or size changes, such as: band , outer flange, the surface is not parallel to the surface or surfaces, etc. In other words, suppression of the density distribution of the pieces of the measures according to their shape and size to decide. Source:http://www.mhcmp.com