Plastic mold steel
Molds for the production of general-purpose plastic workpieces
Plastic mold Steel, used for the production of general plastic (such as polyethylene, polypropylene) workpiece mold.
Plastic mold steel introduction
In the plastic parts forming mold, the quality requirements such as the type of plastic to be pressed, the batch of production, the complexity of the workpiece, the dimensional accuracy and the surface roughness are the main factors that determine the choice of steel for plastic molds.
Plastics are roughly divided into two categories: thermosetting plastics and thermoplastics, and each category is divided into different varieties. Due to the different varieties of pressed plastics and the different requirements for the size, shape, accuracy and surface roughness of plastic products, there are different requirements for the wear resistance, corrosion resistance, heat resistance, pressure resistance, magnetic properties, micro-deformation and mirror polishing properties of plastic mold steel.
General purpose plastic mold steel
Steel for general-purpose plastic molds is used to produce molds for general-purpose plastic (such as polyethylene, polypropylene) workpieces. When the production batch is small, the dimensional accuracy and surface roughness have no special requirements and the mold section is not large, the carbon structural steel SM50, SM55 steel or low carbon steel 10, 20 steel can be used to manufacture, the former using tempering or normalizing treatment, the latter using carburizing and quenching tempering treatment. Due to its low deformation resistance and good plasticity, low carbon steel is mainly used in the manufacture of molds by pressing the mold cavity by cold extrusion forming. When the production batch is large, the mold size is large or the shape is complex, and the precision requirement is high, the alloy die steel with high hardenability is used, such as 3Cr2Mo (P20), 3Cr2NiMnMo, 4Cr5MoSiV1, 5CrNiMnMoVSCa, 8Cr2MnSiWMoVS: Alloy carburized steel, such as 20Cr, 20Cr2Ni4, 12CrNi3A, 20CrMnMo and other manufacturing. The former adopts quenching and high temperature tempering treatment; The latter is processed by carburizing and quenching tempering. But the alloy carburized steel is used when the mold is manufactured by the production process of cold extrusion pressing the mold cavity。
teel for wear resistant plastic molds
In order to produce molds for strengthening engineering plastic products (such as thermoplastic engineering plastic products with fiber reinforcement) or thermosetting plastic extrusion forming, die steel with good wear resistance is used. When the production volume is large, 4Cr5MoSiV1, Cr12MoV, Cr12Mo1V1 and other steel grades are used after quenching and tempering. In order to improve wear resistance, surface treatment can be performed.
Carburized plastic die steel
Alloy carburized steel can be used to manufacture the mold cavity by cold extrusion reverse printing. This kind of steel has good plasticity in the annealing state and is easy to extrude. In order to improve the wear resistance of the cavity, it is necessary to carburize after cold extrusion, and then quenching and low temperature tempering. The mold surface has high hardness and wear resistance, and the heart has good toughness, and the mold interchangeability is good. Commonly used steel numbers, such as the American ASTMA681 standard steel number P2~P6; ISO standard 5CrMo4, 7CrMoNi; China's commonly used 20Cr, 12CrNi2, 12CrNi3, 20CrMnTi, 20Cr2Ni4 and so on.
Corrosion-resistant steel for plastic molds
The production of polyvinyl chloride, fluorinated plastics or flame-retardant plastic molds with added flame retardants, due to the mold contact with corrosive media during the pressing process, plastic mold steel with good corrosion resistance should be selected, of which representative ones such as 4Cr13, 9Cr18, Cr17Mo, Cr14Mo, etc., are used after quenching。
High mirror plastic die steel
Pressing plastic products with low precision and surface roughness values, such as optical instrument parts, household appliance parts, etc., has low roughness values for the surface of the forming mold cavity. Need to adopt high purity and density of die steel (such as 3 cr2mo, 3 cr2nimnmo, 4 cr5mosiv1, Cr12Mo1V1, 25 crni3moal, etc.) or maraging steel [such as 18 ni (250), 18 ni (300)] and the low nickel maraging steel (06 ni6crmov TiAl), etc.
Non-magnetic plastic mold steel
The mold used for pressing magnetic plastics is generally made of non-magnetic die steel, such as 18-8 stainless steel, whose cavity is used after nitriding, or Mn13 wear-resistant austenitic steel, or non-magnetic die steel such as 7Mn15Cr2Al3V2WMo.
Pre-hardened free cutting plastic die steel
Many plastic die steel is often processed under the pre-hardened state (HRC30~45), due to high hardness, poor machinability, in order to facilitate cutting, extend tool life, reduce processing costs, the development of some special free cutting plastic mold, such as 8Cr2MnWMoVS, 5CrNiMnMoVSCa, 3Cr2MoS, 4Cr5MoSiV1, etc.
Commonly used brand
P20(1.2311,3Cr2Mo,P20M),718(3Cr2NiMo,718H,P20+Ni.,1.2738),2Cr13,3Cr13,4Cr13,H13,1.2344.1.2343.1.2312.1.2316,NAK80.DC53,S136,S136H,8402.8407.