Special attention should be paid to:
(1) The repair welding area should not be too large, the flow rate of nitrogen should be larger during the repair welding process, and the gas should not be stopped in the middle;
(2) After the repair welding is completed, nitrogen protection should be continued until the area cools down;
(3) For some special castings, such as complex thin-walled castings, in order to prevent the backside of the repair welding area from oxidizing, argon gas can be blown onto the backside until the casting cools;
(4) Repair welding operators are required to have a high technical level.
In order to obtain titanium tube castings with good repair welding quality, the following points should be noted during the repair welding process:
(1) The surface of the casting for repair welding must be clean and dry. The casting is not allowed to be touched directly by hand before being put into the welding box.
(2) During the repair welding process of titanium tubes, be careful not to short-circuit the tungsten electrode and the repair welding parts, which may cause the tungsten electrode to break and cause tungsten inclusions in the solder joints.
(3) When the area and depth of the repair welding area are relatively large, welding should be carried out in multiple remote layers, and the next layer of welding must be completely cooled before welding of the next layer can be carried out. It is absolutely not allowed to be welded in one go. To prevent casting deformation.
(4) At the end of the 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 interruption and cracks.
(5) After the repair welding is completed, the casting should be allowed to cool in the box for a period of time before unpacking the casting to prevent cracks or deformation in the welding area of the casting due to rapid cooling; the length of cooling time depends on the wall thickness of the casting, usually 15-30mm .
(6) After repair welding of titanium tube castings, they should be annealed or hot isostatically pressed in time and should not be left alone for too long, usually no more than 5 days.
