| 摘要 |
PURPOSE:To eliminate the air bubble in the working part on the inside circumferential surface in the welding groove of steel pipes through a water-cooled welding method quickly and to prevent the decrease in heat transfer rate, by requlating the length on one side in said working part and finishing the part within a prescribed distance from the bead end on the inside surface to a specular surface. CONSTITUTION:A welding groove wherein the length L1 in the working part (DC working part) 3 on the inside circumferential surface of the pipe in a welding groove is made >=200mm. and the range 8 of a distance L2 from the toe of weld is finished to a specular surface is formed in the case of adapting a water- cooled welding method in butt welding of steel pipes 1. Flowing water 2 is passed in the pipes 1 in this state and the water-cooled welding in the part 3 is executed. As a result, the generation and stagnation of the bubble near the toe of weld heated to a high temp. in the stage of welding are suppressed and the decrease in the heat transfer rate on the inside surface of the pipe owing to the generation of the air bubble is prevented. The temp. difference in the thickness direction is assured; therefore, the residual stress in the inside surface of the pipe is made compressive over the entire circumference of the pipe. |
