1.Ua los ntawm Q235 txias dov hlau 2.Txhua yam tsis siv neeg txiav 3. Phau ntawv khoov 4. Kev tuav vuam 5. Tshuaj pickling 6.phosphorization 7.Semi-Cov khoom tiav kev sim ua ke 8. hmoov txheej 9.Professional Ntim