Precautions For Titanium And Titanium Alloy Welding Operations And Welding Inspection

Welding operation precautions

(1) The angle between the wire and the weldment should be as small as possible when welding, and basically no horizontal elbow bar is required. When oscillation is required, the frequency should be low, the amplitude should not be too fast, and the wire feed should be smooth. During welding, the filler wire should always be under argon protection. After extinguishing the arc, the wire should not be exposed to the atmosphere immediately, but should be removed when the weld is out of protection. If the wire is contaminated or oxidized and discolored, the contaminated part should be removed.

(2) It is prohibited to start the arc or test the arc on the surface of the weldment; the quality of arc starting and arc initiation should be ensured during welding; the arc pit should be filled up when closing the arc, and the intermediate ends of the multi-layer weldment should be staggered.

(3) In addition to special requirements, each weld should be welded once. If interrupted forcibly for any reason, re-welding must be checked, and weld cracks are not allowed.

(4) If tungsten welding occurs inadvertently during the welding operation, the welding operation shall be stopped. The tungsten tip shall be removed using a polishing machine. The tungsten end shall be ground again. The welding operation shall be resumed only after the requirements are met. The requirements are the same as those for starting the welding operation.

(5) In order to minimize welding distortion, spot weld between the joint bevels before welding. Spot welding shall be the same as the formal welding process. The length of the spot weld shall be 10 to 15 mm and the height shall be 2 to 4 mm. More than 2/3 of the wall thickness. welds in the locating weld shall be free from cracks or other defects. The twelve welds at both ends shall be ground to a gentle slope.

(6) When one of the following conditions occurs in the titanium pipe welding environment, welding should be stopped without taking protective measures: wind speed 2m/s; relative humidity greater than 90%; rain and snow; temperature below 0°C.

(7) The welding repair process is the same as the original welding process. The number of repairs at the same location shall not exceed two. If a second repair is required, it shall be made. After approval by the engineer responsible for welding, it shall be recorded in the construction record.

Welding inspection

(1) The welder shall clean the surface of the weld and require a good appearance. The width should be 2mm beyond the edge of the bevel, and the height of the fillet weld of the fillet weld should meet the design requirements, and the appearance should be smooth transition. Surface quality should meet the following requirements: no biting, cracks, unfused, porosity, slag, spatter; weld height: 0-1.5mm when the wall thickness is less than 5mm; when the wall thickness is greater than 5mm, 1-2mm; c The amount of misalignment of the weld surface should not be more than 10% of the wall thickness, and not more than 1mm.

(2) The bottom weld channel shall be penetrated. The test method shall be carried out in accordance with "Non-destructive testing of pressure vessels" (JB4730), and it shall be qualified without cracks and other surface defects.

(3) Check the surface color of each weld, the color change is the color change of the surface oxide film at different temperatures, and its mechanical properties are different.

Note: The method of distinguishing between low-temperature oxidation and high-temperature oxidation should be acid washing method. Pickling can remove purple, blue is low temperature oxidation, except those who can not afford high temperature oxidation.

Note: Rinse with water and dry immediately after pickling.

(4) RT test 100% RT test for all welds. The test method is performed according to JB4730-2005.