Stainless steel tubing coil is a type of stainless steel pipe that can range from tens to hundreds of meters in single length. Depending on the application, stainless steel tubing coil can include stainless steel industrial pipes, ultra-long coils, U-shaped pipes, pressure pipes, heat exchange pipes, fluid pipes, spiral coils, etc. But do you know why stainless steel tubing coil needs to undergo annealing treatment? Today, JWB will introduce the reasons for annealing stainless steel tubing coil for your reference.
Reduce hardness and improve machinability. The hardness of stainless steel welded pipes is relatively high, approximately ≤201HBW; ≤92HRB; ≤210HV. Only in a softened state can the stainless steel welded pipes be successfully coiled to form the stainless steel tubing coil we see.
Eliminate residual stress, stabilize dimensions, and reduce the tendency for deformation and cracking.
Refine the grains, adjust the structure, and eliminate structural defects.
In production, the annealing process is widely used. According to the purpose of the annealing required by the workpiece, there are various annealing process specifications. Common ones include full annealing and stress relief annealing. Among them, the stainless steel tubing coil continuous bright annealing furnace is used frequently.
It mainly consists of an unwinding rack, a heating furnace body, a water-jacketed cooling box, a winding mechanism, etc. The bright annealing furnace for stainless steel tubing coil uses four-zone temperature control heating with silicon carbide rods or spiral resistance wires as heating elements. The heating temperature can reach up to 1150℃. The furnace core tube uses high temperature-resistant stainless steel 310S pipe, arranged in a single layer along the length direction of the heating furnace, and the annealed pipe passes through the furnace core tube for heating.
The furnace body has a split structure, which is convenient for maintenance. It has good sealing, low heat loss, and good insulation. To quickly cool the annealed stainless steel tubing coil, the annealing furnace is equipped with a water cooling box, which has stainless steel tubes inside as cooling pipes. By cooling the annealed pipes, a supersaturated stainless steel solid solution can be obtained, meeting the process requirements for hardness and brightness.
In addition, a dedicated winding unit is set at the rear of the water cooling box, allowing the annealed pipes to be wound into coils, with a hydrogen protection input device to prevent oxidation of the inner hole of the pipe during winding. Hydrogen is introduced into the inner hole of the pipe during the winding process to ensure that the inner and outer brightness of the annealed tubing is maintained.
