In order to obtain titanium tube castings with good repair welding quality, the following points should be paid attention to in the process of repair welding:
(1) the surface of the rewelding casting must be cleaned and dried, and the casting shall not be directly touched by hand before loading into the welding box.
(2) during the process of welding the titanium tube, the tungsten electrode and the welding part shall be prevented from short circuit, which may lead to the fracture of the tungsten electrode and the inclusion of tungsten in the welding spot.
(3) when the area and depth of the welding area are large, the welding of the far layer shall be divided into several times, and the welding of the next layer shall not be carried out until the previous layer has been completely cooled down.
(4) at the end of repair welding, the current should be gradually reduced to narrow the melting zone.Therefore, it is recommended to use pulse current to prevent sharp arc break and crack.
(5) after the completion of repair welding, the casting should be allowed to cool in the box for a period of time before opening the box and taking out the casting, so as to prevent cracking or deformation in the welding area caused by sudden cooling;The cooling time depends on the wall thickness of the casting, usually between 15 and 30mm.
(6) after the repair welding of the titanium tube casting, it shall be timely annealed or hot isostatic pressure, and shall not be put aside for too long, usually no more than 5 days.
(7) the number of times of repair welding shall not exceed the provisions in the relevant technical documents.
Titanium pipe manufacturers are required to reweld titanium pipe environment should not have flowing air, other aspects of the same as in the welding box repair welding.However, special attention should be paid to:
(1) the area of repair welding shall not be too large, and the flow of nitrogen during repair welding shall be large, and the gas shall not be stopped in the middle;
(2) after repair welding, nitrogen shall be used to protect the area until it cools down;
(3) for some special castings, such as complex thin-walled castings, to prevent oxidation on the back of the welding zone, argon can be blown on the back until the casting cools down;
(4) the operator of repair welding is required to have a high technical level.