Mold Material Selection Needs To Meet The Performance Requirements

- Sep 03, 2018-

4. Machinability


Machinability (cuttability, machinability): Refers to the ease with which a metal material is machined and becomes a qualified workpiece. The machinability is usually measured by the surface roughness of the workpiece after machining, the allowable cutting speed and the degree of wear of the tool. It is related to many factors such as chemical composition, mechanical properties, thermal conductivity and degree of work hardening of metal materials. Hardness and toughness are generally used for the rough judgment of the machinability. Generally speaking, the higher the hardness of the metal material, the harder it is to cut, and the hardness is not high, but the toughness is large and the cutting is difficult. Generally, non-ferrous metals (non-ferrous metals) have better machinability than iron metal, and cast iron is better than steel.


5. Annealing processability


Annealing is a metal heat treatment process that involves slowly heating a metal to a temperature for a sufficient period of time and then cooling it at a suitable rate. The purpose is to reduce hardness, improve machinability, eliminate residual stress, stabilize size, reduce deformation and crack tendency, refine grains, adjust microstructure, and eliminate tissue defects. Accurately, annealing is a heat treatment process for materials, including metallic materials and non-metallic materials. Moreover, the annealing purpose of the new material is also different from the traditional metal annealing.


6. Hardenability


The ability of steel to obtain hardness after quenching is called hardenability of steel. The hardenability and hardenability of steel are two completely different concepts. The hardenability of steel refers to the ability of steel to achieve the highest hardness under ideal conditions, which depends mainly on the carbon content of martensite. Steel with good hardenability does not necessarily have high hardenability. For example, the hardenability of low carbon alloy steel is quite good, but its hardenability is not high, and the hardenability of high carbon tool steel is poor, but its hardenability is high.


7. Forgeability


The metal has thermoplastic properties and can be subjected to press working in a heated state (various temperatures are required for various metals), and is said to be malleable. Refers to the ability of metal materials to change shape without cracking during press working. It includes the ability to perform hammering, rolling, drawing, extrusion and the like in a hot or cold state. The forgeability is mainly related to the chemical composition of the metal material.


The ability of metal materials to withstand plastic deformation without cracking during forging, also known as process plasticity. The forgeability index is usually expressed by the amount of deformation of the metal material when the surface begins to crack under a certain plastic deformation mode. This deformation amount is called the critical deformation amount. The deformation modes of various forging processes are different, and the indicators indicating the forgeability are also different. The upset is expressed in terms of compression ratio, the extension is expressed as elongation or the reduction ratio, and the torsion is expressed in twist angle.


8. Quenching deformation cracking tendency


The conventional quenching volume change is small, the shape is warped, the distortion is slight, and the abnormal deformation tendency is low. Conventional quenching cracking has low sensitivity and is not sensitive to quenching temperature and workpiece shape.


9. Grindability


The relative loss of the grinding wheel is small, the amount of grinding without the limit of grinding is large, and it is not sensitive to the quality of the grinding wheel and the cooling condition, and it is not easy to cause abrasion and grinding crack.