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Heat treatment characteristics of plastic mold

    （一）渗碳钢塑料模的热处理特点   

(1) heat treatment characteristics of plastic die for carburizing steel

    1.对于有高硬度、高耐磨性和高韧性要求的塑料模具，要选用渗碳钢来制造，并把渗碳、淬火和低温回火作为最终热处理。 

1. For plastic molds with high hardness, high wear resistance and high toughness, carburized steel should be selected to manufacture, and carburizing, quenching and low temperature tempering as the final heat treatment.  

   

   

    2.对渗碳层的要求，一般渗碳层的厚度为0.8～1.5mm，当压制含硬质填料的塑料时模具渗碳层厚度要求为1.3～1.5mm，压制软性塑料时渗碳层厚度为0.8～1.2mm。渗碳层的含碳量为0.7%～1.0%为佳。若采用碳、氮共渗，则耐磨性、耐腐蚀性、抗氧化、防粘性就更好。   

2. For the requirements of carburizing layer, the thickness of carburizing layer is generally 0.8-1.5mm, the thickness of carburizing layer is required to be 1.3-1.5mm when plastics containing hard fillers are pressed, and 0.8-1.2mm when soft plastics are pressed. The carbon content of carburized layer is 0.7% to 1%. If carbon and nitrogen are used, the wear resistance, corrosion resistance, oxidation resistance and viscosity resistance will be better.   

    3.渗碳温度一般在900～920℃，复杂型腔的小型模具可取840～860℃中温碳氮共渗。渗碳保温时间为5～10h，具体应根据对渗层厚度的要求来选择。渗碳工艺以采用分级渗碳工艺为宜，即高温阶段（900～920℃）以快速将碳渗入零件表层为主；中温阶段（820～840℃）以增加渗碳层厚度为主，这样在渗碳层内建立均匀合理的碳浓度梯度分布，便于直接淬火。   

3. The carburizing temperature is generally 900-920 C, and 840-860 6550 The carburizing and holding time is 5 ~ 10h, and it should be chosen according to the requirement of the thickness of the seeping layer. The carburizing process is suitable to adopt staged carburizing process, that is, the high temperature stage (900-920 C) is mainly to rapidly carburize into the surface layer of the parts; the middle temperature stage (820-840 C) is mainly to increase the thickness of the carburized layer, so that a uniform and reasonable carbon concentration gradient distribution is established in the carburized layer for direct quenching.   

    4.渗碳后的淬火工艺按钢种不同，渗碳后可分别采用：重新加热淬火；分级渗碳后直接淬火（如合金渗碳钢）；中温碳氮共渗后直接淬火（如用工业纯铁或低碳钢冷挤压成形的小型精密模具）；渗碳后空冷淬火（如高合金渗碳钢制造的大、中型模具）。 

4. The quenching process after carburizing can be adopted according to the different steel grades: reheating quenching; direct quenching after staged carburizing (such as alloy carburized steel); direct quenching after medium temperature carbonitriding (such as small precision die formed by cold extrusion of industrial pure iron or low carbon steel); air cooling quenching after carburizing (such as high alloy carburized steel). Large and medium moulds made of carbon steel.  

   

   

    （二）淬硬钢塑料模的热处理   

(two) heat treatment of hardened steel plastic mold

    1.形状比较复杂的模具，在粗加工以后即进行热处理，然后进行精加工，才能保证热处理时变形最小，对于精密模具，变形应小于0.05%。   

1. Complicated shape of the mold, after rough processing heat treatment, and then finishing, to ensure the minimum deformation of heat treatment, for precision mold, deformation should be less than 0.05%.   

    2.塑料模型腔表面要求十分严格，因此在淬火加热过程中要确保型腔表面不氧化、不脱碳、不侵蚀、不过热等。应在保护气氛炉中或在严格脱氧后的盐浴炉中加热，若采用普通箱式电阻炉加热，应在模腔面上涂保护剂，同时要控制加热速度，冷却时应选择比较缓和的冷却介质，控制冷却速度，以避免在淬火过程中产生变形、开裂而报废。一般以热浴淬火为佳，也可采用预冷淬火的方式。   

2. Plastic mold cavity surface requirements are very strict, so in the quenching and heating process to ensure that the cavity surface is not oxidized, not decarbonized, not corroded, but not heated. Should be heated in awww.yunchengbanjia.cn www.diandongmeny.cn www.qidianmoji.cnwww.linmoji.cnwww.dalianyanglao.cnwww.gaibanmuju.cn protective atmosphere furnace or in a strictly deoxidized salt bath furnace, if the use of ordinary box-type resistance furnace heating, should be coated on the surface of the mold cavity protectant, while controlling heating speed, cooling should choose a more moderate cooling medium, control cooling speed, to avoid deformation, cracking and scrap in the quenching process. . Generally, hot bath quenching is preferred, and pre cooling quenching can also be used.   

    3.淬火后应及时回火，回火温度要高于模具的工作温度，回火时间应充分，长短视模具材料和断面尺寸而定，但至少要在40～60min以上。    

3. Tempering should be timely after quenching, tempering temperature should be higher than the working temperature of the mold, tempering time should be sufficient, depending on the mold material and section size, but at least 40-60 minutes above.    

    （三）预硬钢塑料模的热处理   

(three) heat treatment of pre hardened steel plastic mold

    1.预硬钢是以预硬态供货的，一般不需热处理，但有时需进行改锻，改锻后的模坯必须进行热处理。  

1. The pre-hardened steel is supplied as pre-hardened steel. Generally, no heat treatment is needed, but sometimes it needs to be forged. The forged blank must be heat treated.  

  

  

    2.预硬钢的预先热处理通常采用球化退火，目的是消除锻造应力，获得均匀的球状珠光体组织，降低硬度，提高塑性，改善模坯的切削加工性能或冷挤压成形性能。   

2. Spheroidizing annealing is usually used in the pre-heat treatment of pre-hardened steel. The purpose is to eliminate forging stress, obtain uniform spherical pearlite structure, reduce hardness, improve plasticity, and improve the cutting performance or cold extrusion formability of die blank.   

    3.预硬钢的预硬处理工艺简单，多数采用调质处理，调质后获得回火索氏体组织。高温回火的温度范围很宽能够满足模具的各种工作硬度要求。由于这类钢淬透性良好，淬火时可采用油冷、空冷或硝盐分级淬火。 

3. The Pre-hardening process of the pre-hardened steel is simple. Most of the pre-hardened steel is tempered and tempered to obtain the tempered sorbite structure. The temperature range of high tempering is very wide, which can meet various working hardness requirements of dies. Because of the good hardenability of these steels, oil cooling, air cooling or nitrate grading quenching can be used for quenching.  

    （四）时效硬化钢塑料模的热处理   

(four) heat treatment of age hardening steel plastic mold

    1.时效硬化钢的热处理工艺分两步基本工序。首先进行固溶处理，即把钢加热到高温，使各种合金元素溶入奥氏体中，完成奥氏体后淬火获得马氏体组织。第二步进行时效处理，利用时效强化达到最后要求的力学性能。  

1. the heat treatment process of age hardening steel is divided into two steps. Firstly, the steel is heated to high temperature, so that all kinds of alloying elements are dissolved in austenite, and the martensite structure is obtained after austenite quenching. The second step is aging treatment, and the ultimate mechanical properties are achieved by aging.  

  

  

    2.固溶处理加热一般在盐浴炉、箱式炉中进行，加热时间分别可取：1min/mm、2～2.5min/mm，淬火采用油冷，淬透性好的钢种也可空冷。如果锻造模坯时能准确控制终锻温度，锻造后可直接进行固溶淬火。   

2. Solution treatment heating is usually carried out in salt bath furnace and box furnace. The heating time is 1 min/mm and 2-2.5 min/mm respectively. The quenching is oil-cooled, and the steel with good hardenability can also be air-cooled. If forging die blank can accurately control the final forging temperature, after forging, direct solution quenching can be carried out directly.   

    3.时效处理最好在真空炉中进行，若在箱式炉中进行，为防模腔表面氧化，炉内须通入保护气氛，或者用氧化铝粉、石墨粉、铸铁屑，在装箱保护条件下进行时效。装箱保护加热要适当延长保温时间，否则难以达到时效效果。

3. Aging treatment is best carried out in a vacuum furnace. If it is carried out in a box furnace, a protective atmosphere should be introduced into the furnace to prevent oxidation of the die cavity surface, or alumina powder, graphite powder and cast iron chips should be used to aging under the protective condition of packing. It is necessary to prolong the holding time of heating protection, otherwise it will be difficult to achieve the aging effect.