How to tell whether stainless steel industrial pipes are annealed or not？

Annealing is a heat treatment process for stainless steel industrial welded pipes. Its purpose is to eliminate residual stress, stabilize dimensions, and reduce deformation and crack tendencies. Since it is difficult to tell whether a stainless steel welded pipe has been annealed with the naked eye, some methods can be used to help identify it.

1. Use echo to determine whether the pipeline has been annealed. You can tap the welded pipe with slightly greater force and listen to the echo at the nozzle with your ears. If the echo is high and sharp, it means it has been annealed. This is because the internal crystallization of annealed parts is relatively uniform and dense, and the structure without annealing will have more defects and absorb most of the sound wave energy, so the echo at the nozzle is relatively small. If possible, use sonar to detect it.

2. Use a digital multimeter with good accuracy to measure the resistance value of each pipe per unit length (such as 6 meters). The resistance of stainless steel is relatively high, and the resistance value after annealing is smaller than that without annealing. There should be no liquid left on it before testing.

It should be noted that not all stainless steel industrial welded pipes produced by manufacturers will be annealed. Because the additional steps will incur costs, annealing is performed as needed, but manufacturers must also avoid using unannealed stainless steel industrial pipes for fraud.