1. Ua kom raug thiab meej cov paib raws li cov duab kos duab kos duab;weld los yog txhim kho kev txhawb nqa kab, kab, txhawb nqa steel ncej, thiab lwm yam, thiab cov welds yuav tsum muaj dej-pov thawj thiab corrosive raws li qhov yuav tsum tau ua ntawm cov duab kos.2. Cov khoom siv uas xav tau ...
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