Cov kev cai yooj yim rau kev ua liaj ua teb cov khoom siv ua liaj ua teb yog: cov hniav saum npoo yuav tsum muaj qhov hardness txaus thiab hnav tsis kam, thiab cov hniav yuav tsum muaj zog txaus los tiv thaiv ntau yam kev ua tsis tiav ntawm cov hniav. Ib txhij, nws yuav tsum muaj cov khoom txias thiab kub ua haujlwm kom tau raws li ntau yam kev xav tau ntawm cov iav. Qhov kev ua tau zoo ntawm cov iav yog nyob ntawm cov khoom siv kho tshuab, lub cev, thiab tshuaj lom neeg uas cov khoom yuav tsum muaj raws li kev ua haujlwm tau teev tseg; qhov no yog thawj zaug los xyuas kom meej thaum xaiv cov ntaub ntawv.
Cov khoom siv ua haujlwm. Kev tsim khoom txhua qhov yuav tsum tau ua qee cov kauj ruam ua; Yog li ntawd, qhov yooj yim uas cov khoom raug ua tiav rau hauv qhov chaw ncaj qha cuam tshuam rau qhov zoo ntawm cov khoom, kev ua haujlwm ntau lawm, thiab cov nqi ua haujlwm. Cov khoom siv iav feem ntau muaj xws li tempered steel, quenched steel, thiab hardened steel. Cam khwb cia hlau muaj zog me ntsis qis dua forged steel thiab feem ntau yog siv rau cov iav loj.
