a) Good thermostability
The mould components are complicated in shapes and it is difficult to processing after quenching. That's why our first choice is the mould with good thermo stability. bucket mould can easily become small after heat treatment as for the expansion coefficient is relatively small, the rate of dimensional change will be reduced due to the temperature difference. If the bucket mould has a stable structure and dimension, then require no longer processing which can guarantee the mould dimensional accuracy and surface roughness requirements.
b) Sufficient surface hardness and wear resistance
Plastic bucket mould hardness is usually within 50-60HRC. The mould surface shall be sufficient in hardness after heat treatment so that the mould can have sufficient rigidity. The mould has to withstand greater compressive stress and friction as for the plastic mold filling and flow in the injection production, it requires the mould must have high shape and dimension stability, so the mould life can be ensured. However, the mould wear resistance depends on the steel chemical composition and heat treatment hardness; therefore to improve the mould hardness is conducive to improve the wear resistance.
c) Good polishing properties
The high quality bucket requires the bucket mould cavity surface roughness must be small. For example, the surface roughness of the injection mould cavity should be less Ra0.1~0.25, the optical surface should be Ra<0.1nm, the cavity shall be polished, thereby reducing the surface roughness value. Therefore the bucket mold steel should reach to these requirements: less material impurities, fine homogeneous organization, no fiber directionality, no pitting or defects in polishing.