关于熔化极气体保护焊熔滴自由过渡的分类与名称问题
ABOUT THE CLASSIFICATION AND THE CHINESE DESIGNATION OF THE METAL TRANSFER MODES OF FREE FLIGHT IN MIG WELDING
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摘要: 本文研究了国产7021马氏体时效钢(18Ni)焊接接头在3.5% NaCl水溶液中的应力腐蚀行为。结果表明,在峰值温度为1280℃左右的热影响区中焊接热循环并不影响断裂韧性,但严重降低对应力腐蚀的抗力,使该区成为焊接接头的薄弱环节。其原因可能与焊接,过程钛、钼等合金元素在晶界的偏聚和晶粒长大有关。焊后经820℃×1h固溶处理,临界应力腐蚀强度因子KISCC得到一定提高,双重固溶处理可进一步改善,而三次900℃×20min水冷处理效果最显著,晶粒明显细化,应力腐蚀裂纹由沿晶破坏转变为穿晶塑性破坏。但上述固溶处理对焊缝的作用与热影响区不同。一次或二次固溶有使焊缝KISCC降低的趋势,只有多次固溶可保持较好的水平并能与热影响区性能相匹配。Abstract: In order to clarify the confusion in the classification and designation of the metal transfer modes of free flight in MIG welding in our country,some views were presented in this paper.The rationality and basis of the recommended classification and designation were based on the thermal and mechanical effect of the are appearance.In addition,the transition conditions and the relationshape between the critical transition current and the are appearance in the MIG welding were also discussed.
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