Study On Properties Of One Side Welding Joints And Protection Mechanism Of Back Weld Of Stainless Steel

China is the largest consumer of stainless steels in the world at present. It is predicted that stainless steels apparent consumption will reach 5 million tons in 2007, which is equal to the total amount of that of entire Europe. With the vigorous development and the drastically increasing consumption of stainless steels in our country, more and more stainless steels will have to be welded and high efficient welding will become an inevitable developmental trend. As a result, it is important to research the technology of high-efficient stainless steels welding. Study on welding joints properties of high efficiency welding material and protection mechanism of back weld of stainless steel was carried out systematically and comprehensively in this paper: (1) A metal cored wire GDMA308 for submerged arc welding was developed, which could be used for welding 0Cr18Ni9 stainless steel. Experimental results show that its detachability is excellent, and the weld has not the phenomenon of "black skins"; compared with solid wire H0Cr21Ni20, its welding speed can be increased in the same welding conditions, which is favorable for preventing the austenitic grains from coarsing. (2) One side welding based on stainless steels was performed by using the above self-made metal cored wire and ceramic backing. Experimental results show that welding current, welding voltage and welding speed are the main factors influencing back weld shaping in one side welding. Although little chemicals permeated into weld seam, they have no obvious effects on the properties of weld joints. Experiments on CO2 gas shielding GDQA308L flux cored wire one side welding using ceramic backing were also implemented. Its influence factors are not as complex as that of submerged arc welding. Back chipping may be avoided and working efficiency is improved by using ceramic backing in welding stainless steel medium plate. (3) Procedure qualification on TIG flux-cored wires such as GDQA308L-T-1 weld rod, GDQA308L-T-2 weld rod and GDQA316-T flux cored wire were carried out. The results show that the back weld is well protected and not oxidized. So backing gas can be exempted for the purpose of improving welding efficiency. (4) Welding stainless steels with no backing gas by using solid wire ER308L-Si, ER316L-Si and mixed gases (He+Ar+CO2) was put forward for the first time and the...