welding titanium tubing

The production technology of welding titanium tubing with low strength and low alloy is relatively mature. In terms of high pressure resistance and structural stress resistance, thick-walled titanium seamless pipes are generally used. However, due to the low yield of titanium seamless pipes, long production cycle and other factors, vigorously developing it has become a trend in the titanium pipe industry. Compared with titanium seamless pipe, titanium welded pipe has more and more obvious comprehensive advantages.

The production standard of titanium welded tube is ASTM B338/ASTM B862. The domestic thin-wall welding titanium tubing adopts single-gun or multi-gun Tig/PAW self-fusion welding. After welding, the online heat treatment process is adopted. By optimizing the welding and annealing processes, the microstructures of the base metal and weld heat affected zone are basically similar, and the welding stress is eliminated. The welded structure is uniform, so as to obtain ASTM B862 titanium welded tube with good quality.

Quality Tests Requirements

1. Assessment of pipe weld quality shall be performed by either the flattening test or the guided bend test. Test specimens shall be selected randomly from each lot of pipe manufactured. Test plates of the same material may be attached to the pipe and welded as prolongations of the pipe longitudinal seam.
1.1 Guided Bend Test-For Grades 1, 2, 2H, 7, 7H, 11,13, 14, 16, 16H, 17, 26H, and 33 a longitudinal or transverse guided bend test of the weld shall be performed in accordance with the method outlined in the ASME Boiler and Pressure Vessel Code, Section VIII, Paragraph UNF-95. The ductility of the weld shall be considered acceptable when there is no evidence of cracks after bending in the weld or between the weld and the tube metal. Test specimens shall be randomly selected from the pipe manufactured in accordance with requirements.
1.2 For Grades 3, 5, 9, 12, 15, 18, 19, 20, 21, 23, 24, 25, 34, 35, 37, and 38 the requirements for the guided bend test
shall be negotiated between the manufacturer and the purchaser.

2. Flattening Test-tig welding titanium tubing in the final condition shall be capable of withstanding, without cracking, flattening
under a load applied gradually at room temperature until the distance between the load platens is H inches. The weld shall be positioned at either 90° or 270° to the direction of the applied load. H is calculated as follows:

H = Minimum flattened height, in. (mm),
t = nominal wall thickness, in. (mm) and,
D = nominal pipe diameter, in. (mm) (not pipe size), and
For Grades 1, 2, 2H, 3, 7, 7H, 11, 13, 14, 16, 16H, and 26H.
e = 0.04 through 1 in. pipe size, and
e = 0.06 over 1 in. pipe size.
For grades not shown above, the requirements for the flattening test shall be negotiated between the manufacturer and purchaser.
2.1 All calculations are rounded to two decimal places. Examination for cracking shall be by the unaided eye.
2.2 When low D–to–t ratio tubular products are tested, because the strain imposed due to geometry is unreasonably
high on the inside surface at the six and twelve o'clock locations, cracks at these locations shall not be cause for
rejection if the D–to–t ratio is less than ten (10).

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