double protective medium 双重保护介质
According to the different welding materials, if adopts the carbon dioxide gas or mixed gas to be the protective medium to carry out the welding.
根据焊接材料的不同，可采用二氧化碳气体或混合气体作为保护介质进行焊接。
Firstly, in this paper water absorption of concrete protective coatings hi different corrosive medium is studied.
本文首先研究了不同腐蚀介质下混凝土保护涂层的吸水行为。
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