Study on Characteristics of Weld Defect and Its Prevention in Electron Beam Welding (Report II) : Some Metallurgical Features of Weld Porosities

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In this report, same as in the previous report, in our attempt to determine the causes of formation of A-porosity, R-porosity and AR-porosity that occur when performing electron-beam welding, we used SUS304 stainless steel and seven kinds of alloys, and we probed weld-metallurgically into the relativity between the porosities, materials and solidifying structure. A-porosity occurring to stainless steel and carbon steel was recognized mostly along the ripple line, cold shut or bonded part with segregation of manganese being noted on its internal surface. It is presumed that the nitrogen and oxygen contained in the alloys has no direct effect on the occurring of porosity. R-porosity, like A-porosity, was present in abundance along the ripple line with distinct segregation of high vapor pressure elements in the alloys being recognized on its internal surface like manganese in stainless steel and carbon steel and magnesium in 5083 alloy. AR-porosity observable in aluminum alloy saw its incidence mostly along the bonded part and on its internal surface was noted segregation of high vapor pressure element, as in the case of R-porosity.
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