インサート型電子ビーム溶接の特性とその実用化に関する研究(第 2 報) : 溶接部の冶金学的, 機械的特性

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Metallurgical and mechanical properties have been investigated concerning a dissimilar joint, 21/4Cr-1 Mo steel (ASTMF22) to austenitic stainless steel (AISI316), and a carbon steel (SM41A) joint produced by "Insert-type" electron beam welding technique. The conclusions can be summarized as follows : 1) In the restraint cracking test of a dissimilar joint using a Lehigh restraint cracking test specimen, crater cracking is observed at every crater irrespective of insert metal width and its material, that is, 25Cr-12Ni austenitic stainless steel and Inconel 600 but not any other cracking. 2) Microstructure of weld metal of a dissimilar joint is martensitic and austenitic respectively with introduction of 0.4mm-wide 25Cr-12Ni austenitc stainless steel insert metal and Inconel 600 insert metal. Carburized and decarbruized bands are respecitvely observed in weld metal and HAZ adjacent to 21/4 Cr-1 Mo steel base metal due to post-weld heat treatment with introduction of 25Cr-12Ni austenitic stainless steel insert metal. This decarburized and coarse grain zone tends gradually to increase with an increase of insert metal width. This trouble hardly occurs with introduction of Inconel 600 insert metal. Weld metal of carbon steel joint forms ferritic and pearlitic structure after post-weld heat treatment. 3) Hardness of weld metal zone of a dissimilar joint shows high value, that is, Hv 450 and Hv 320 approximately in as-welded condition and even in heat-treated condition respectively with introduction of 0.4mm-wide 25Cr-12Ni austenitic stainless steel. When 0.8mm and 1.2mm-wide 25Cr-12Ni austenitic stainless steel and Inconel 600 insert metal are introduced, hardness of weld metal zone is around Hv 200. Weld metal zone of carbon steel joint is softened up to Hv210 approximately by post-weld heat treatment. 4) By means of XMA area analysis along weld center and XMA line scanning across the welds at transverse cross-section, it has been proved that weld metal of a dissimilar joint fluctuates a little in Cr and Mn content with introduction of 25Cr-12Ni austentic stainless steel and in Ni, Cr and Fe content with introduction of Inconel 600 insert metal respectively. However, it may be safely said that fluctuation of concentration distribution of elements is not so remarkable as expected. Fluctuation of element of carbon steel joint is hardly recognized in weld metal zone in any case. Estimation formula is herein proposed on element distribution in weld metal zone produced by "Insert-type" electron beam welding technique. 5) Tensile, bending and impact properties of the welds are satisfactory in any case. 6) It might be condisered that there is hardly any appreciable difference in creep rupture strength resulting from insert metal width and its material at 550℃ and 600℃. It should also be added that creep rupture strength at 550℃ nearly approaches that of 21/4Cr-1 Mo steel joint derived from ASTM Data irrespective of insert metal width and its material. In addition, there is hardly any effect of decarburized and coarse grain zone on creep rupture properties and feature of fracture if rupture time is shorter than 2000h at 550℃ and 1000h at 600℃ respectively.
社団法人溶接学会の論文
1974-10-05

インサート型電子ビーム溶接の特性とその実用化に関する研究(第 2 報) : 溶接部の冶金学的, 機械的特性

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