Fig.1. The hot pipe bending process using local induction heating: (a) Pipe bending; (b) Position of neutral axis and weld joint.

Samples for mechanical tests were cut at different positions in X90 bend, as shown in Fig.2. Tensile specimens were machined into flat of 50 mm gauge length according to ASTM E8M specification. The tensile tests were performed at room temperature using a low loading speed of 3 mm/min on SHT 4605 testing machine. CVN impact tests were performed on standard samples with 55 mm × 10 mm × 10 mm according to ASTM standard E23. The V notch parallel to the normal direction, three parallel specimens were taken at -10 ℃, and the average value of the absorbed energy was obtained as the result of the impact test. The impact toughness was tested on a 500J instrumented pendulum impact tester. Considering the temperature of specimens increase in the process of transfer, and the specimens were cooled to below the test temperature 5 ℃.