3) particle size distribution refers to the relative content of particles of different sizes, also known as particle size composition. Powder size composition of a wide range, the product density is high, good performance, especially for the strength of the product edge is particularly advantageous.

4) technical features:

(1) loose packing density loose packing density also known as loose packing ratio, refers to the unit volume of free loose packing powder quality. It is determined by particle size, particle shape, particle size composition and intergranular pore size. The size of slack loading ratio affects the performance of pressing and sintering, and is a very important parameter for die design. For example, the loose packing density of reduced iron powder is generally 2.3-3.0g/cm3. If reduced iron powder with loose packing density of 2.3g/cm3 is used to press the blank with density of 6.9g/cm3, the compression ratio (the ratio of filling height of powder to the blank height) is 6.9:2.3=3:1.

(2) fluidity it refers to the time required for the free fall of 50g powder in the powder flowmeter to the end of the flow. The shorter the time, the better the fluidity. The powder with good fluidity is conducive to the rapid and continuous powder loading and the uniform powder loading of complex parts.

(3) the compressibility of the pressing powder includes compressibility and formability. Compressibility determines the strength and density of the blank,

It is usually expressed by the compression ratio of the powder body before and after pressing. The compressibility of powder is mainly determined by its hardness, plastic deformation ability and work hardenability. The powder after annealing has good compressibility. In order to ensure the quality of the blank, make it have a certain strength, and facilitate the transportation in the production process, the powder must have good formability. Formability is related to the physical properties of the powder, and is also affected by particle size, particle shape and particle size composition. In order to improve formability, a small amount of lubricant such as zinc stearate, paraffin wax, rubber, etc. is often added to the powder. Usually the bending strength or compressive strength of the blank is used as the index of formability test.