金屬中山熱(re)處理(li)工藝(yi)大體可分為整(zheng)體中山熱(re)處理(li)、表(biao)面(mian)中山熱(re)處理(li)和化學中山熱(re)處理(li)三大類：

3、化學(xue)中(zhong)(zhong)山(shan)熱(re)處理(li)是(shi)(shi)通過改變(bian)工(gong)件表(biao)層(ceng)(ceng)化學(xue)成分、組織和性能(neng)的金屬中(zhong)(zhong)山(shan)熱(re)處理(li)工(gong)藝。化學(xue)中(zhong)(zhong)山(shan)熱(re)處理(li)與表(biao)面(mian)中(zhong)(zhong)山(shan)熱(re)處理(li)不(bu)同之處是(shi)(shi)后者改變(bian)了(le)工(gong)件表(biao)層(ceng)(ceng)的化學(xue)成分。化學(xue)中(zhong)(zhong)山(shan)熱(re)處理(li)是(shi)(shi)將工(gong)件放在含(han)碳、氮或其他(ta)(ta)合金元素的介質(氣體(ti)、液體(ti)、固體(ti))中(zhong)(zhong)加(jia)熱(re)，保溫較長時(shi)間(jian)，從而使工(gong)件表(biao)層(ceng)(ceng)滲(shen)入(ru)碳、氮、硼和鉻(ge)等(deng)元素。滲(shen)入(ru)元素后，有(you)時(shi)還要(yao)進行其他(ta)(ta)中(zhong)(zhong)山(shan)熱(re)處理(li)工(gong)藝如淬(cui)火(huo)及回火(huo)。化學(xue)中(zhong)(zhong)山(shan)熱(re)處理(li)的主要(yao)方法有(you)滲(shen)碳、滲(shen)氮、滲(shen)金屬。