In order to obtain the titanium pipe castings with good quality patch welding, the following points should be noted in the process of patch welding:
(1) The surface of the patch welding castings must be clean and dry, the castings are not allowed to be directly touched by hand before loading into the welding box.
(2) In the process of refill welding titanium tube to prevent tungsten electrode and refill weldments short-circuit, resulting in tungsten electrode fracture, resulting in tungsten inclusions in the welded joints.
(3) When the area and depth of the patch welding area are relatively large, should be divided into several times far layer welding, and wait until the previous layer of welding layer is completely cooled before the next layer of welding, Do not allow – welded into the next time to prevent casting deformation.
(4) If the filler weld is almost over, should gradually reduce the current, and reduce the melting zone. Therefore, it is recommended to use a pulsed current to prevent sharp arc breakage, resulting in cracks.
(5) After the end of refill welding should be allowed to cool castings in the box for a period of time before opening the box to remove the castings, in order to prevent the rapid cooling of the castings’ weld zone cracks or deformation; the length of the cooling time depends on the wall thickness of the castings, usually in the 15-30mm.
(6)Titanium tube castings after welding, should be timely annealing or hot isostatic pressure, and should not be shelved for too long, usually no more than 5 days.
(7) The number of patch welding should not exceed the provisions of the relevant technical documents.
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