Ua ntej vuam lub raj tuaj yeem yog cov pa hluav taws xob-acetylene huab cua sov, nyob rau hauv uas kub cua sov thiab induction kub dua kev tswj hwm.
Lub raj yog preheated, nws lub luag haujlwm yog kom ntseeg tau tias qhov kev tawm tswv yim weld, dua li rho tawm hauv cov hlau ib puag ncig, yog li kom tsis txhob muaj kev tsis txaus ntseeg. Preheating, lub teb chaw vuam thiab cov hlau ib puag ncig yog rhuab rau 40 lub sijhawm 150 degree, tuaj yeem tiv thaiv cov vuam hlau rau cov hlau ib puag ncig.
Txij li thaum preheating txo qhov sib txawv ntawm weld thiab cov hlau hluav taws xob ib puag ncig ntawm weld hlau kuj tseem raug txo qis, txo cov nyiam weld cracking thiab deformation. Ib qho ntxiv, preheating pab tshem tawm cov roj, tshwj xeeb yog nyob hauv weld nchuav hydrogen. Nyob rau hauv cov txheej txheem vuam, raws li kev vuam txoj kev siv, vuam pas nrig thiab cov raj khoom siv raj, thiab lwm yam. Preheat qhov kub yuav ntsuas tau siv tus pas ntsuas kub siab, portable pyrometer lossis thermocouple.
