1.Tube can be judged by the echo.
Click on each tube and listen for the echo at the nozzle. If the echo is high, then? Sharper, already annealed. Because the internal crystal structure of the annealed part is more uniform and dense, higher pitch echoes can be generated without annealing. Due to a large number of organizational defects, it can absorb part of the sound energy, so the tone at the nozzle is very low and dull. If possible, it can be detected by sonar.
2. Use a digital multimeter with higher accuracy to measure the resistance per unit length (e.g. 2 meters). The resistance of stainless steel should be measurable. The resistance of annealed steel is less than that of unannealed steel. Dry before test, no liquid. These methods can distinguish annealed and non-annealed stainless steel welded pipes.
