Lub ntsiab tseem ceeb ntawm kev hloov pauv ntawm cov hlau thaum lub sij hawm cua sov yog kev hloov ntawm cov theem tsis austenitic mus rau austenitic theem, uas yog, cov txheej txheem ntawm austenitizing. Tag nrho cov txheej txheem muaj feem xyuam rau cov pa roj carbon diffusion. Ntawm cov ntsiab lus alloy, tsis yog carbide tsim cov ntsiab lus txo qhov ua kom lub zog ntawm cov pa roj carbon hauv austenite thiab nce tus nqi ntawm austenite tsim; Txawm li cas los xij, muaj zog carbide tsim cov ntsiab lus muaj zog cuam tshuam cov pa roj carbon diffusion hauv cov hlau thiab ua kom qeeb ntawm cov txheej txheem austenitizing.
Theem transformation thaum lub sij hawm steel txias yog hais txog lub decomposition ntawm undercooled austenite, xws li pearlite transformation (eutectoid decomposition), bainite transformation thiab martensite transformation. Txhawm rau coj tsuas yog cov txiaj ntsig ntawm cov ntsiab lus alloy ntawm isothermal transformation nkhaus ntawm undercooled austenite ua piv txwv, feem ntau cov ntsiab lus alloy, tshwj tsis yog cobalt thiab txhuas, ua lub luag haujlwm hauv kev ua kom qeeb ntawm isothermal decomposition ntawm austenite, tab sis txhua lub ntsiab lus plays lub luag haujlwm sib txawv. Kev cuam tshuam ntawm non carbide tsim cov ntsiab lus (xws li silicon, phosphorus, npib tsib xee, tooj liab) thiab me me ntawm carbide tsim cov ntsiab lus (xws li vanadium, titanium, molybdenum, tungsten) ntawm kev hloov pauv ntawm austenite rau pearlite thiab bainite tsis txawv, yog li qhov kev hloov pauv hloov mus rau sab xis.
Yog tias cov ntsiab lus ntawm carbide tsim cov ntsiab lus (xws li vanadium, titanium, chromium, molybdenum, tungsten) loj, kev hloov pauv ntawm austenite rau pearlite yuav qeeb qeeb, tab sis kev hloov pauv ntawm austenite mus rau bainite yuav tsis qeeb qeeb. Yog li ntawd, lub isothermal transformation curves ntawm ob qhov kev hloov pauv no yuav raug cais tawm ntawm "lub qhov ntswg" thiab tsim ob C-puab.
