New type plastic mold steel
Normal 45 steel or 40Cr steel is often used to manufacture plastic molds.Plastic molds with high hardness requirements are made of steel such as CrWMn or Crl2MoV.For the plastic mould with higher working temperature, the hot die steel with high toughness can be selected.A series of new die steels are developed recently in order to meet the higher requirements of dimensional accuracy and surface quality for plastic cavities.
1) carburized plastic mold steel
Carburizing type plastic die steel is mainly used for cold extrusion molding cavity complex plastic mould, this kind of low carbon steel, often add element Cr, at the same time adding suitable amount of Ni, Mo and v, role is to improve the hardenability and carburizing ability, to facilitate the cold extrusion forming, this kind of steel in the annealed state must have a high plasticity and low deformation resistance, annealing hardness 1 00 HBS or less.Carburizing and quenching and tempering were carried out after cold extrusion forming, and the surface hardness was up to 58– –62HRC.This kind of steel has special steel abroad, such as Sweden 8416, the United States P2 and P4.12CrNi3A and 12Cr2Ni4A steel and 20Cr2Ni4A steel are commonly used in China, with good abrasion resistance, no collapse and surface peeling, and longer die life.The elements cr, Ni, Mo and V in steel increase the hardness and wear resistance of the carburized layer and the strength and toughness of the core.
2) pre-hardened plastic mold steel
The carbon content of this kind of steel is 0.3-o. 55%, and the common alloying elements are Cr, Ni, Mn, v, etc.In order to improve its machinability, s, ca and other elements were added.Through the development, introduction and development of several typical plastic mold steel y55crnimn-movs (SMI) is developed in China including S series free-cutting plastic mold steel, its characteristics are pre-hard state delivery hardness of 35_40 HRC, has good cutting processing, processing without heat treatment, can be used directly.Ni solid solution was added to strengthen and increase toughness, and Mn and S were added to form free-cutting phase MnS.Add Cr, Mo, V, increase the hardenability of steel 8Cr2S steel is free cutting precision mold steel.
3) aging hardening plastic mold steel
MASI is a kind of typical maraging steel.After solid solution treatment at 8150C, the hardness was 28-32hrc, and mechanical processing was carried out. After aging at 4800C, intermetallic compounds such as Ni3Mo and Ni3Ti were folded out, and the hardness reached 48-52hrc.Steel has high strength and toughness, small size change in aging and good welding and patching performance, but steel is expensive and not very popular in China.
4) corrosion-resistant plastic mold steel
Polyvinyl chloride (Pvc) and ABS plus flame retardant resin as raw materials of plastic products, in the process of forming the decomposition of corrosive gases, will corrode the mold.Therefore, the plastic mold steel is required to have good corrosion resistance.There are two kinds of corrosion resistant plastic mold steels: martensite stainless steel and precipitation hardening stainless steel.Foreign companies such as Sweden ASSAB STVAX (4Crl3) and ASSAB 8407.
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