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硼钢碳氮共渗工艺控制不当时,容易在共渗层中出现表层和过渡区两类非马氏体黑色组织,它们的出现是渗层相应部位上淬透性不足的表现。这两类黑色组织产生的原因不同,因而工艺因素的影响也不尽相同。前者主要是由于合金元素的内氧化以及碳、氮化合物形成所引起的;后者是由于硼在渗层中发生了再分布以及硼的存在状态发生明显变化所引起的。 综合考虑避免硼钢碳氮共渗层的两类黑色组织,较合理的工艺是:采用较高的共渗温度,后期通氨,共渗期油量高些、氨量低些,渗后尽快冷却。
When boron steel carbonitriding process is improperly controlled, it is easy to appear two types of non-martensite black tissues in surface and transition zone in the co-permeation layer, and their appearance is the manifestation of insufficient hardenability on the corresponding part of the layer. The causes of these two types of black tissue are different, so the impact of process factors is also different. The former is mainly caused by the internal oxidation of alloying elements and the formation of carbon and nitrogen compounds. The latter is caused by the redistribution of boron in the diffusion layer and the obvious change of the existence of boron. Considering the two types of black structure to avoid carbon steel nitrided layer of boron steel, a more reasonable process is: the use of higher co-permeation temperature, the latter part of ammonia, co-infiltration of higher oil content, lower ammonia, seepage as soon as possible cool down.