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经验表明,要提高钢件的耐磨寿命、渗碳或碳氮共渗层中要有数量较多、尺寸较小、颗粒较圆、分布较匀的碳化物。用常规工艺难以获得这种形态的碳化物。本文提出的预处理法,即先在高碳势气氛中830℃预渗碳1～2小时,然后再常规渗碳或碳氮共渗,可以满足这个要求。预处理的温度低,奥氏体晶粒细,其饱和溶碳量也小,在高碳势气氛中易于形成分散细小的碳化物颗粒。在以后的常规渗碳或碳氮共渗中,即以这些预存的颗粒为核心,形成粒状的碳化物。
Experience shows that to improve the wear life of steel, carburizing or carbonitriding layer to have a larger number, smaller size, round particles, the distribution of more uniform carbide. Carbides of this form are difficult to obtain with conventional processes. Pretreatment method proposed in this paper, that is, in the high-carbon potential of 830 ℃ pre-carburizing 1 to 2 hours, and then conventional carburizing or carbonitriding, to meet this requirement. The pretreatment temperature is low, the austenite grains are fine, and the amount of saturated dissolved carbon is also small, and fine carbide particles are easily formed in a high carbon potential atmosphere. In the subsequent conventional carburizing or carbonitriding, that is, these pre-stored particles as the core, the formation of granular carbides.