Generally, the environment for titanium pipe repair welding by manufacturers cannot have flowing air, and other aspects are the same as those in the welding box. However, special attention should be paid to:
(1) The area of repair welding should not be too large. The flow of nitrogen during repair welding should be larger, and the gas cannot be stopped in the middle;
(2) After repair welding, continue to apply nitrogen for protection until the area is cooled;
(3) For some special castings, such as complex thin-wall castings, in order to prevent the oxidation of the back of the repair welding area, argon can be blown on the back until the castings are cooled;
(4) Repair welding operators are required to have a high technical level.
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In order to obtain titanium pipe castings with good repair welding quality, the following points should be paid attention to in the repair welding process:
(1) The surface of the castings for repair welding must be cleaned and dried, and the castings are not allowed to be directly touched by hands before being put into the welding box.
(2) During the repair welding of titanium tubes, the short circuit between the tungsten electrode and the repair weldment shall be strictly prevented, resulting in the fracture of the tungsten electrode and the tungsten inclusion in the welding joint.
(3) When the area and depth of the repair welding area are relatively large, it should be welded in several far layers, and the welding of the next layer can be carried out only after the previous layer is completely cooled. It is absolutely not allowed to weld at one time to prevent the deformation of the casting.
(4) At the end of repair welding, the current should be gradually reduced to reduce the melting zone. Therefore, it is recommended to use pulse current to prevent sharp arc breaking and cracks.
(5) After repair welding, the castings should be allowed to cool in the box for a period of time before unpacking and taking out the castings to prevent cracks or deformation in the welding area of the castings caused by rapid cooling; The length of cooling time depends on the wall thickness of the casting, usually 15-30mm.
(6) Titanium pipe castings should be annealed or hot isostatic pressing in time after repair welding, and should not be left for too long, usually not more than 5 days.
(7) The number of repair welding shall not exceed the provisions of relevant technical documents.
