| 摘要 |
PURPOSE: To prevent the generation of the scale by covering the metal surface with the reducing gas by applying the organic acid ester to the surface of the part to be heated at high temperature of the metal to be welded, and achieving the welding in this condition. CONSTITUTION: The organic acid ester such as lactic acid ester 3 is applied to the prescribed range of the metal to be welded, e.g. to a joint 2 side of the inner surface of a copper tube 1, and to the surface to which the joint 2 is welded. The copper tube 1 is assembled with the joint 2 in this condition to achieve the brazing using the brazing filler metal 4 of phosphor copper. Alternatively, welding is achieved by the arc welding, etc. When the metal surface is heated in the welding, the applied organic acid ester is also heated and evaporated, and further decomposed into the highly reducing gas such as methane, ethylene and hydrogen under the high temperature. The organic acid ester itself has the reducing effect under the high temperature. This reducing gas covers the metal surface to be welded, and reduces oxygen in the air to prevent the metal surface from being oxidized. |
