
XIYE ua kom zoo dua cov thev naus laus zis hluav taws xob arc, thiab tau txais qhov sib npaug zoo tshaj plaws los ntawm cov khoom siv raw, cov khoom seem preheating, kev txuag hluav taws xob, kev tiv thaiv ib puag ncig, kev tswj hwm txheej txheem, kev tswj hwm tsis siv neeg, lub voj voog smelting, peev xwm, thiab lwm yam.
Cov khoom siv no yog ib puag ncig, muaj txiaj ntsig zoo, ua haujlwm tau zoo, siv tau ntau yam nqi los tsim cov hlau tshwj xeeb.