| 摘要 |
PURPOSE:To enable penetration wleding of steel pipes of thick-walled materials easily in all butt positions, by using a high S filler wire contg. S in a specific range in automatic TIG welding. CONSTITUTION:Steel pipes of >=3mm. wall thickness are automatically TIG- welded in all butt positions by using a filler wire regulated to 0.015-0.030% S, and the content of S in weld metal is controlled to 0.012-0.025%, whereby the permissible range of the current value at which a penetration bead of a projecting shape is formed, and the selection of welding conditions is made extremely easy. The use of the high S wire results in the decreased temp. at which the solidification of molten steel is completed, the difficulty in the flow of the molten steel in a molten pool on account of an increased viscosity of the molten steel prior to solidifying, and the possibility of formation of the penetration bead having a projecting shape in a wide current range. If the content of S is <0.012%, the effect of forming penetration is not accomplished, and if said content is excessive, the formation of a fish eye, the decrease in notch toughness, etc. arise; therefore 0.025% is an upper limit. |
