氧化铁皮对CO_2半自动单面焊气孔倾向的影响

INFLUENCE OF IRON OXIDE SKIN ON GAS POROSITY IN ONE-SIDE SEMIAUTOMATIC CO_2 WELDING WITH CERAMIC BACKIG STRIP

本文就坡口上的氧化铁皮对ＣＯ_２半自动陶质衬垫单面焊气孔倾向的影响进行了试验研究，利用Ｘ射线检测、ＯＭ、ＳＥＭ、ＥＤＸ和ＸＲＤ等方法对焊道进行了宏观及徽观分析。结果表明，氧化铁皮主要由Ｆｅ_３Ｏ_４、Ｆｅ_２Ｏ_３和ＦｅＯ组成，并参与反应生成ＣＯ气体；打底层焊缝中形成大量夹杂物易于气泡的形核；陶质衬垫的保温作用使打底层焊道上部先于底部结晶，气泡不易逸出而形成气孔。本文还探讨了防止气孔产生的措施。

The experimental investigation of the influence of iron oxide skins on the groove surface on formating porosity was carried out in one-side semiautomatic CO_2 welding. The macro and micro structure of the one-side weld bead was analyzed by means of OM, SEM, EDX and XRD. The main results obtained are summarized as follows. The iron oxide skins are composed of Fe_3O_4, Fe_2O_3 and FeO, which react with carbon and form CO gas in the weld bead. There are a large number of slay inclusions in the one-side weld bead and gas bubbles heterogeneously nucleate easily. The upper bead of the one-side weld bead first solidities because of the insulation work of ceramic backing strip, at the bottom of the one-side weld bead the gas bubbles do not escape easily and then formate porosity. At the end, some preventative measures of formating porosity are discussed.