.1 Molded parts refer to mold parts of molded products in direct contact with plastics, such as cavity, core, slider, insert, inclined top, side pull, etc.
.2 The material of molding parts is directly related to the quality and life of the mold, and determines the appearance and internal quality of the plastic products formed. It must be very careful. Generally, it must be selected according to the requirements and characteristics of the products and molds on the basis of the contract provisions and customer requirements.
.3 The selection principle of forming parts materials is: According to the types of plastic molding, products shape, size precision, appearance quality of products and use requirement, production batch size, etc., both material cutting, polishing, welding, corrosion, deformation, wear-resisting performance, at the same time considering economy and mould manufacturing conditions and processing method, to choose different types of steel.
.4 for the molding of transparent plastic products of the mold, the cavity and core need to choose high mirror polishing performance of high-grade imported steel, such as 718 (P20+Ni class), NAK80 (P21 class), S136 (420 class), H13 class steel, among which 718, NAK80 is pre-hard state, do not need to heat treatment; S136 and H13 steel are annealed, the hardness is generally HB160-200, after rough machining, vacuum quenching and tempering treatment, S136 hardness is generally HRC40-50, H13 steel hardness is generally HRC45-55 (can be determined according to the specific brand).
A) The cavity should choose high-grade imported steel with high mirror polishing performance, such as 718 (P20+Ni class), NAK80 (P21 class), etc., which are pre-hard and do not need heat treatment.
B) The core can be imported P20 or P20+Ni steel, such as 618, 738, 2738, 638, 318, etc., which are pre-hard; For small production of molds, domestic plastic mold steel or S50C, S55C and other imported high quality carbon steel can also be selected.
A) Medium imported P20 or P20+Ni steel is used for small and precision mold cavities and cores. B) Large and medium-sized moulds, the plastic moulds have no special requirements for steel, and the cavity can be used for middle-low grade imported P20 or P20+Ni steel; Core can choose low grade imported P20 steel or imported high quality carbon steel S50C, S55C, etc., can also choose domestic plastic mold steel. C) For etching cavity, when etching pear ground grain should try to avoid choosing P20+Ni class 2738 (738) brand.
A) For large and medium-sized molds, the cavity can choose low-grade imported P20 or P20+Ni steel, also can choose imported high-quality carbon steel S55C, S50C or domestic P20 or P20+Ni plastic mold steel; The core can be imported or domestic high quality carbon steel.
B) for small molds, if the output is high and the structure is complex, the cavity can be used for low-grade imported P20 or P20+Ni steel, or domestic P20 or P20+Ni plastic mold steel; The core can be made of plastic mould steel.
C) For small molds with simple structure and low output, domestic plastic mold steel or high quality carbon steel can be used for cavity and core.
8 For the molding of fluorine, chlorine and other corrosive plastics and all kinds of plastic moulds with flame retardants, if the product requirements are high, imported corrosion resistant steel can be used, and domestic corrosion resistant steel can be used for general requirements.
9 For the molding of plastic moulds with strong friction and impact on steel, such as those used for injection of nylon + glass fiber material, imported or domestic H13 steel should be selected with the advantages of high wear resistance, high heat tensile strength and high toughness.
.10 Molded inserts are generally made of the same material as the embedded parts. The insert material should be beryllium bronze or aluminum alloy for the parts that are difficult to cool or require high cooling effect.
A) Transparent parts should be selected high-grade imported steel with good polishing, such as 718, NAK80, etc..
B) Non-transparent parts, in general, middle-grade imported steel with high hardness and strength should be selected, such as 618, 738, 2738, 638, 318, etc., with nitriding treatment on the surface, the depth of nitriding layer is 0.15-0.2mm, and the hardness is HV700-900.
C) If the mold requirements are low, low-grade imported steel or domestic steel can also be selected, and the hardness of nitriding treatment is generally HV600-800.
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