The working condition of plastic mould is different with cold-punching mould,normally under working on 150-200℃,not only bearing pressure,but also sustain high temperature.Nowadays,according to the differences of plastic mold using condition and tooling method,the followings are the basic performance requests to plastic mould steel.
- excellent machinability
Most plastic molds,except EDM tooling,it need cutting machining and benchwork.To extend machining knives’ lifetime,enhance machinability,decrease suface roughness, plastic mold steel hardness should be proper.
- Good heat stability
Usually plastic mold spare parts are complex,it’s difficult to machining after quenching treatment.So we need try best to use good heat stability mould steel.After mold steel heat treatment, Because of low expansion,little deformation and very small dimension change,it ensure mould dimension precision and surface roughness.
- Good polishing property
High quality plastic molded parts request good polish on the mould cavity.So selected mould steel need less impurity,even minuteness. And it shouldn’t have hard spot defects.
- Enough surface hardness and wear resistance
Normally plastic mould steel hardness is less than 50-60HRC,after heat treatment,it has enough surface hardness,to ensure mold has enough rigidity. When plastic injection molding,because plastic material filling and flowing bear higher stress and friction,requesting mold keep good shape precision and dimension precision,to guarantee mould long lifetime. Mould wear resistance depends on steel chemical composition and heat treatment hardness. So increasing mold hardness is good for enhancing its wear resistance.
- 50# steel have certain strength and wear resistance
50# steel mostly used for mould base after hardening and tempering treatment. But because its big deformation,it only suitable for making small size and simple plastic parts.