| 摘要 |
PURPOSE:To make efficiency high and hardness constant by remelting the inside surface of a steel pipe by using the plasma jets generated under prescribed conditions while moving either of the steel pipe and a plasma jet torch. CONSTITUTION:Plasma jets 6 are generated under the conditions of Ar contg. 5-20% H2 as a shielding gas, pure Ar as a plasma gas, 1-2l/min flow rate of the plasma gas, and 100-400A electric current. Under the injection of the jets 6, a torch 2 is moved in the axial direction of a steel pipe 1 which is not in rotation. The torch 2 is stopped, and the pipe 1 is rotated by as much as the width 7 melted by the plasma gas. After the rotation of the pipe 1 is stopped, the torch 2 is moved in the direction opposite from the above-mentioned direction. The torch 2 is stopped, then the pipe 1 is rotated in the same direction and at the same angle as mentioned above, and the above-mentioned operations are repeated. The opposed parts of the inside surface of the pipe 1 facing the torch 2 are remelted successively. |
