Proper welding conditions, welding defects, joint micrography and hardness are investigated, in order to apply electron beam welding for nuclear and thermal power plant components made by carbon steel and Cr-Mo low alloy steel. Materials used are SGV49, SB49 and SM41A as carbon steel, and SCMV3A
(I 1/4Cr-1/2Mo steel) as Cr-Mo steel. The results are summarized as follows;
(1) Electron beam welding is applicable for these steels up to 100 mm thickness. Proper welding condition range in heat input per unit thickness lies between about 8 and 25 kJ/cm2.
(2) In order to prevent hot cracking, (P+S) content should be below 0.03% in steel whose C content is up to 0.35%.
(3) Porosity defect due to oxygen in steel did not occur in these commercial steels.
(4) Soundness of macro- and micrographies, and hardness of welded joint are confirmed.
