鋳鉄および球状黒鉛鋳鋼の溶接(第 1 報) : アーク溶接組織について

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The metallographic studies have been performed on the structure of weld heat-affected zone in cast irons. The typical heat-affected zone was obtained by the single-bead test, in which a single bead of about 10 to 12cm was put on a cast-iron plate of 200×75×20mm, by using various electrodes under the different conditions. Two layers, ledeburitic and martensitic, are observed in a heat-affected zone, the former varing in its thickness with the melting point of electrode. In martensitic layer, "white" martensite is mainly observed in the case of using cast-iron electrode, whereas in other cases using nickel and low-carbon steel electrodes by the same current, and in a case using cast-iron electrode by a higher current, it shows "dark" martensite. When the carrying speed of electrode is reduced, even in the case of cast iron electrode, primary cementite and troostite acommpanying it are observed in the matrix of dark martensite. The isothermal transformation diagrams were determined for two species of cast iron and a nodular graphite cast steel. In these diagrams, the boundary line between white and dark martensites was determined below Ms temperature. It is deduced that the two types of martensite are corresponding to fast and slow cooling below Ms temperature, the critical cooling velocity being about 1℃/sec. There is practically no difference in hardness between the martensitic layers of nickel electrode and of cast-iron electrode, if the welding conditions are the same. The amount of retained austenite was about 17 to 27%, though it reached about 40% in a few microscopic observations, also indicating no appreciable difference between the electrodes. The diffusion of nickel from deposit metal to the heat-affected zone by the weld thermal cycle is not likely to occur, since the diffusion coefficient of nickel in austenite is relatively low. The superior properties of nickel electrode may be attributed to the high ductility of weld metal, the martensitic heat-affected zone being not essentially different from those of other electrodes.
社団法人溶接学会の論文
1960-10-25

鋳鉄および球状黒鉛鋳鋼の溶接(第 1 報) : アーク溶接組織について

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