28. Cov teeb meem dab tsi uas yuav tshwm sim thaum muaj cov kav dej kauv ntau lawm? Yuav ua li cas lawv thiaj tshwm sim? Yuav ua li cas lawv thiaj zam? 28.1. Ua rau ntawm pore qhov tsis xws.

Thaum lub sij hawm vuam txheej txheem ntawm kauv hlau kav, yog tias muaj cov roj voids tam sim no nyob rau hauv weld nws tus kheej, qhov tsis haum no tau xa mus ua qhov tsis taus. Qhov laj thawj tseem ceeb rau qhov tshwm sim ntawm qhov chaw tsis zoo yog qhov tsis zoo ntawm weld nto, uas tuaj yeem muaj noo noo lossis xeb. Thaum lub sij hawm vuam txheej txheem, cuam tshuam los ntawm qhov kub ntawm hluav taws xob vuam, cov impurities xws li noo noo pib mus rau yaj. Raws li kev evaporation ntawm ya raws lossis xeb yog ua kom qeeb, voids tau tsim nyob rau hauv cov hlau molten, thiab cov vows tsim cov roj ntsha tsis xws luag thaum lub sij hawm vuam. Qhov teeb meem no tshwj xeeb tshaj plaws thaum zawj walding, qhov twg tsis tiav kev ntxuav ntawm cov zawj muaj kev cuam tshuam nrog cov roj ntsha tsis xws luag. Lub xub ntiag ntawm cov roj tsis xws luag muaj qhov tsis zoo ntawm Weld, raws li nws txo qhov kev sib koom ua ke, ua kom muaj kev phom sij ntawm kev sib tsoo hauv Weld.