Duplex stainless steel pipe cold working process

The cold working process of duplex stainless steel pipes mainly includes a series of specific steps and precautions to ensure the quality and performance of the steel pipes.

First, since the yield strength of duplex stainless steel is twice that of austenitic stainless steel, a smaller deformation amount needs to be used during cold working than the latter. During cold rolling, appropriate vehicle speed and feed amount must be selected to minimize longitudinal wall thickness unevenness and roll folding. Similarly, the section shrinkage rate of steel pipes during cold drawing should not be too large.

Secondly, the intermediate softening and finished heat treatment of steel pipes is a key step. This is usually done using a continuous roller hearth furnace with a water curtain cooling device at the outlet. What needs special attention here is that it is forbidden to use electric contact heating, because this method is not easy to control the temperature, and the temperature rise rate is too fast, which can easily lead to over-temperature, thereby causing the number of ferrite phases to exceed the standard. Especially when rolling thin-walled tubes, if not properly controlled, uneven bamboo-like wall thickness may occur.

In addition, solution treatment of the finished pipe is also crucial. This step not only eliminates the residual stress from cold working of the finished pipe, but also ensures the appropriate two-phase ratio and the surface quality of the finished pipe.

Finally, in order to ensure the cold processing quality of duplex stainless steel pipes, some details need to be paid attention to, such as selecting appropriate lubricants and maintaining the cleanliness and accuracy of the equipment.