The characteristics of the plastic mold heat treatment - - - - - - - Xiang in the plastic

( A) Carburizing steel plastic mold heat treatment characteristics of 1. With high hardness, high wear resistance and high toughness of plastic mould, should choose carburizing steel to make, and carburizing, quenching and low temperature tempering as the final heat treatment. 2. Requirements of the carburized layer, generally the thickness of the carburized layer of 0. 8 to 1. 5 mm, when pressing containing hard packing plastic mould carburizing layer thickness requirements of 1. 3 to 1. 5 mm, pressing soft plastic carburizing layer thickness of 0. 8 to 1. 2mm。 Carburizing layer of carbon content is 0. 7% ~ 1. 0% is preferred. If using carbon and nitrogen were permeability, wear resistance, corrosion resistance, oxidation resistance, prevent stickiness is better. 3. Carburizing temperature is in commonly 900 ~ 920 ℃, small complex cavity mould desirable carbonitriding in 840 ~ 860 ℃ temperature. Carburizing heat preservation time is 5 ~ 10 h, specific answer to choose according to the requirements of carbonitriding layer thickness. Carburizing process based on hierarchical carburizing process, namely high temperature stage ( 900～920℃) Give priority to with rapid infiltration of the carbon parts surface; Medium temperature stage ( 820～840℃) To increase the thickness of carburized layer is given priority to, so in the carburized layer to establish uniform and reasonable distribution of carbon concentration gradient, facilitate direct quenching. 4. After carburizing and quenching process according to different steel grade, after carburizing can be respectively used: reheated quenching; Classification of direct quenching after carburizing ( Such as alloy carburizing steel) ; Medium temperature direct quenching after carbonitriding ( If use industrial pure iron or mild steel cold extrusion forming of small precision mould) ; Air cooling quenching after carburizing ( Such as high alloy carburizing steel manufacturing large and medium-sized mold) 。 ( 2) Hardened steel plastic mold heat treatment 1. Shape more complex mould, after the heat treatment, rough machining and finish machining, to ensure minimum deformation during heat treatment, for precision mould, deformation should be less than 0. 05%. 2. Plastic model cavity surface is very strict, so to ensure that in the process of quench heating cavity surface oxidation, decarburization, erosion, overheating, etc. Should be in a protective atmosphere furnace or after strict DNA in the salt bath furnace heating, if using common box type resistance furnace heating, should be coated on the surface of the cavity protective agent, at the same time to control the heating rate, cooling should choose more moderate cooling medium, control of cooling speed, in order to avoid in the process of quenching deformation, cracking and scrap. General with hot bath quenching is beautiful, also can adopt the precooling quenching. 3. Should be timely tempering after quenching and tempering temperature is higher than that of mould temperature, tempering time should be sufficient, long myopic mould material and section size, but at least in more than 40 ~ 60 min. ( 3) Hard plastic die steel heat treatment 1. Pre hardened steel is hard supply, generally do not need to heat treatment, but sometimes I need to change forging, die blanks must be heat treatment after forging. 2. Forecasts in advance of hard steel usually adopts the spheroidizing annealing heat treatment, the purpose is to eliminate forging stress and obtain uniform spheroidal pearlite structure, reduce the hardness, improve plasticity and improve the machining performance of die blanks or cold extrusion forming performance. 3. Pre hardened steel, hard process simple, most use conditioning treatment, obtain tempered sorbite structure after quenched and tempered. High temperature tempering temperature range is very wide can meet all kinds of work that the mold hardness requirements. Because this kind of steel hardenability is good, the quenching oil cooling, air cooling, or can be used when nitrate quenching classification. Table 3 - 27 for part of the pre hardened steel, hard process, for your reference.