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Welding Operation Precautions And Welding Inspection For Titanium And Titanium Alloys
Jun 29, 2018

Welding operation precautions

(1) When welding, the angle between the welding wire and the weldment should be kept as small as possible, and basically no horizontal toggle is required. When the swing is required, the frequency should be low, the amplitude should not be too fast, and the wire feeding should be stable. The filler wire should always be kept under argon protection during welding. After the arc extinguishing, the welding wire shall not be exposed to the atmosphere immediately and shall be taken out when the weld is removed from the protection. If the wire is contaminated or discolored by oxidation, the contaminated part should be removed.

(2) It is forbidden to induce arcs or test arcs on the surface of the weldment; the quality of arcing and arcing shall be ensured during welding; the arc pits shall be filled when the arc is closed, and the interlayer joints of multilayer welding shall be staggered with each other.

(3) Except for special requirements, each weld shall be welded one time after the other. If it is forced to be interrupted for any reason, it must be checked during re-welding and no weld cracks will be allowed.

(4) If tungsten welding occurs inadvertently during the welding operation, the welding operation shall be stopped. The tungsten point shall be removed with a polisher. The tungsten end shall be ground again. After the requirements are reached, the welding operation may be resumed. The requirements are the same as those for starting the welding operation.

(5) In order to reduce welding distortion, tack welding is performed between the joint groove before welding. The tack welding should be the same as the formal welding process. The length of the tack weld should be 10 to 15 mm, and the height should be 2 to 4 mm. More than 2/3 of the wall thickness. Welds in tack welds must not have cracks or other defects. Twelve welds at both ends should be ground to a gentle slope.

(6) If one of the following conditions occurs in the welding environment of the titanium tube, welding should be stopped when no protective measures are taken: wind speed 2m/s; relative humidity greater than 90%; rain and snow; temperature below 0°C.

(7) The weld repair process is the same as the original welding process. The number of repairs at the same site must not be more than twice. If secondary repairs are required, repairs should be made. After the approval of the welding responsibility engineer, it shall be noted in the construction record.

 Welding inspection

(1) The welder should clean up the surface of the welded bead and require a good appearance. The width is preferably 2mm over the edge of the groove, and the height of the fillet of the fillet weld meets the design requirements and the appearance is smoothly transitioned. The surface quality shall meet the following requirements: No undercuts, cracks, unmelted, pores, slag inclusions, splashes shall not be allowed; weld seam height: when the wall thickness is less than 5mm, it is 0-1.5mm; when the wall thickness is greater than 5mm When, for 1 ~ 2mm; c weld surface misalignment amount should not exceed 10% of the wall thickness, and not more than 1mm.

(2) The bottom bead shall be infiltrated. The test method shall be carried out according to "Nondestructive Testing of Pressure Vessels" (JB4730), and shall be qualified without cracks and any other surface defects.

(3) To inspect the color of each weld surface, the color change is the color change of the surface oxide film at different temperatures, and their mechanical properties are also different.

Note: The method of distinguishing between low temperature oxidation and high temperature oxidation should adopt pickling method. Pickling can remove purple, blue is low temperature oxidation, except for those who can not afford to high temperature oxidation.

Note: Immediately after pickling, rinse with clean water and dry.

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


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