Gabatarwar yanayin zafi

Ana ƙididdige yawan zafin jiki bisa ga canjin canjin ƙarfe. The quenching dumama zafin jiki na hypoeutectoid karfe ne kullum AC3 (30-50), da hypereutectoid karfe ne AC1 (30-50). Dalilin wannan ƙaddara shi ne cewa ga ƙarfe na hypoeutectoid, idan zafin zafin jiki ya kasance ƙasa da Ac3, yanayin zafi yana kunshe da austenite da ferrite, kuma ferrite yana riƙe da shi bayan quenching da sanyaya, don haka taurin ɓangaren bayan quenching bai kasance ba. uniform, kuma ƙarfi da Taurin suna raguwa. Manufar 30-50 mafi girma fiye da ma’anar Ac3 shine don tabbatar da cewa babban aikin aikin ya kai zafin jiki sama da maki AC3 a cikin ƙayyadadden lokacin dumama, ana iya narkar da ferrite gaba ɗaya a cikin austenite, abun da ke ciki na austenite yana da inganci, kuma austenite hatsi ba. lokacin farin ciki. Domin hypereutectoid karfe, lokacin da quenching dumama zafin jiki ne tsakanin AC1 da AC3, da dumama jihar ne lafiya austenite hatsi da undissolved carbides, da kuma cryptocrystalline martensite da uniformly rarraba spherical carbon ana samu bayan quenching. Wannan tsarin ba wai kawai yana da ƙarfi mai ƙarfi, babban ƙarfi, juriya mai ƙarfi ba, amma har ma yana da ƙarfi mai kyau. Idan quenching dumama zafin jiki ya yi yawa, carbides za su narke, austenite hatsi za su yi girma, kuma flaky martensite (twin martensite) za a samu bayan quenching, da microcracks, brittleness da quenching fatattaka hali suma za su karu. Saboda rushewar carbides, abun cikin carbon a austenite yana ƙaruwa, adadin da aka riƙe austenite bayan quenching yana ƙaruwa, da taurin da juriya na ƙarfe yana raguwa. Manufar 30-50 mafi girma fiye da Ac1 yayi kama da na hypoeutectoid karfe, wanda shine don tabbatar da cewa yawan zafin jiki na duk sassa a cikin aikin aiki ya fi na Ac1.