gas backing meaning in English

气体垫

Icy water from a nearby river then cools the gas back to liquid form , to start the cycle again
附近冰冷的河水可用来将这些气体重新液化，从而循环利用。
The pqr shall include the composition and flow rate of the shielding and inert gas backing , when used
焊接工艺评定记录单上应包括封底焊时所用的惰性保护气体组成成分和流率。
5 all single - sided groove joints in nickel alloys , stainless steel and ferritic alloys containing more than two ( 2 ) percent chromium shall be welded using a gas tungsten - arc root pass with an inert gas back purge
铬含量超过2 %的镍合金、不锈钢和铁素体合金的单面坡口焊道用钨极气体保护焊，其根部焊道用惰性气体反吹。