Plastic products are widely used in industry and daily life, the plastic mold has to precision, large scale and multi cavity in the direction of development, performance requirements of plastic mold steel is more and more high, some developed countries independent plastic mold steel series.
The cutting performance for large, complex and precise extrusion and injection mould, usually pre hardened to 28-35HRC, then cutting and grinding to the required size and accuracy, directly put into use, so as to avoid the deformation of heat treatment, oxidation and decarburization of defects. Join the cutting elements S, Co and rare earth, used to improve the performance of cutting hardened steel.
The surface of the mirror processing performance of laser disc and plastic lens plastic products such as roughness is high, mainly by the mold cavity roughness to ensure that the general mold cavity roughness than the plastic products of high level. The mirror processing performance of die steel is related to the purity, microstructure and hardness of steel and the machining technique of mirror surface. High hardness, fine microstructure and less non-metallic inclusion are beneficial to improve the polishing performance of mirror surface.
The design of etching performance, some plastic products require clear and plump surface patterns, as well as leather industry, large skin pattern, embossed version, all require die steel has good pattern lithography performance,
Corrosion resistance, chlorine and fluorine resin, and the addition of anti - combustion agent in ABS resin, will release corrosive gas during the molding process. For this kind of plastic mold, corrosion resistant plastic mould steel or surface chrome plated or nickel phosphorus amorphous surface coating shall be adopted.
In addition to the above special performance requirements, plastic mould steels are also required to have good wear resistance and repair welding properties.
2. types and characteristics of new plastic mould steels
The hardened, Quenched and tempered types belonging to this kind of steel are P20, 718 (Sweden) and H13 steel. 718 steel can be regarded as an improved type of P20 steel, and H13 steel is a typical hot work die steel. The carbon content of these steels is 0.30%-0.50%, which belongs to Cr-Mo series quenched and tempered steel.
The hard, easy to cut shape belongs to this type of steel, such as 5NiSCa, SM1 and 8Cr2S. Compared with the hardened and tempered steel, the carbon content increased, and a certain amount of easy cutting element S or S-Ca was added to improve the cutting performance. The single S steel has good cutting performance in low and medium speed cutting conditions. Because the MnS in the steel will elongate in the direction of deformation after thermal deformation, the anisotropy of the steel increases, and the lateral plasticity and toughness of the steel decrease remarkably.
Aging hardening belongs to this kind of steel, such as 25CrNi3MoA1\PMS\SM2 and 06CrNi6MoVTiA1 steel. Among them, PMS steel has excellent mirror polishing performance. This kind of steel belongs to low carbon and low nickel age hardening type. After high temperature solution treatment of austenitic low carbon martensite, its hardness is about 50HRC, in order to machining, after high temperature tempering, well tempered sorbite, the hardness decreased to 24HRC, processing the mold cavity, at 500-540 DEG C during the ageing treatment, the precipitation of NiA1 alloy phase, the deformation the matrix hardness rose to 40HRC. the aging treatment is very small, can be controlled below 5/10000, this kind of steel is suitable for the production of high precision plastic mold, but also in the softening treatment to low thickness, cold extrusion molding method for manufacturing complex mold cavity.
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