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许多承受动载荷的机器零件,要求表面有高的耐磨性,高的接触疲劳强度,高的弯曲或扭转疲劳强度,要求心部保持一定的塑性和韧性。为达到这些要求,长期以来人们习惯采用化学热处理,其中以低碳钢渗碳为主要手段。渗碳固然是较成熟的工艺,但是它存在许多缺点,主要有:(1)渗碳工艺时间长,效率低;(2)消耗大量合金钢(如20Cr、18Cr-Mnti、20CrM_0、22CrMnMo 等);(3)渗碳质量不稳定,不易控制,尤其用井式渗碳炉易产生脱碳现象,使渗碳件的疲劳强度大大降低(据有关资料介绍,如脱碳层为0.05mm 时,疲劳强度降低30～35％);
Many of the machine parts that are subjected to dynamic loads require high wear resistance on the surface, high contact fatigue strength, high bending or torsional fatigue strength, and require the heart to maintain a certain degree of plasticity and toughness. To meet these requirements, people have long been accustomed to using chemical heat treatment, in which low-carbon steel carburizing as the main means. Carburization is a more mature technology, but it has many shortcomings, mainly including: (1) carburizing process takes a long time and low efficiency; (2) consume a large amount of alloy steel (such as 20Cr, 18Cr-Mnti, 20CrM_0, 22CrMnMo, etc.) ; (3) instability of carburizing quality, not easy to control, especially with Pit type carburizing furnace easy to produce decarburization, so that the fatigue strength of carburized parts greatly reduced (according to relevant information, such as decarbonization layer is 0.05mm, Fatigue strength reduced by 30 ~ 35%);