Annealing is a heat treatment process for stainless steel welded pipes. Its purpose is to eliminate residual stress, stabilize dimensions, and reduce the tendency of deformation and cracking.
What is annealing of 2205 stainless steel pipe?
With the pipe produced by cold working, carbide precipitation, lattice defects, and inconsistent structure and composition will cause the corrosion resistance of stainless steel to decline. At this time, annealing treatment (or solution treatment) is required.
Why is 2205 stainless steel pipe annealed?
Reduce the hardness of steel and improve the plasticity to facilitate cutting and cold deformation processing
Refine grains, homogenize steel structure and composition, improve steel properties or prepare for subsequent heat treatment
Eliminate residual internal stress in steel to prevent deformation and cracking.
2205 stainless steel tube annealing process
In production, the annealing process is widely used. According to the different purposes of annealing required by the workpiece, there are various annealing process specifications, commonly used are stress relief annealing, complete annealing and spheroidizing annealing.
Stress relief annealing. The common equipment for stress relief annealing of stainless steel tubes is a continuous bright annealing furnace for stainless steel tubes, which is a muffle type bright annealing furnace. The protective gas source adopts an ammonia decomposition furnace and is equipped with a gas purification device. Hangao Tech (SEKO Machinery) has carried out structural transformation of the muffle furnace, eliminating the method of mesh belt conveying and replacing it with continuous single-tube roller conveying on the line. The equipment has the characteristics of advanced control, remarkable energy saving, convenient maintenance, etc. The heating area of the whole line adopts PID automatic multi-zone temperature control. Stainless steel pipes heat-treated through our heat preservation stainless steel pipe bright annealing furnace reduce deformation and ensure the ellipticity of the pipes.
The stainless steel strips are evenly arranged on the feeding rack, sent to the annealing furnace through the conveyor belt, heated to 1050-1080 ℃ under the protection of a controllable atmosphere, and then kept for a short period of time, all the carbides can be dissolved in the annealing furnace. In the austenite structure, and then rapidly cooled to below 350 °C, a supersaturated solid solution, that is, a uniform unidirectional austenite structure, can be obtained.
Fully annealed. It is used to refine the coarse superheated structure with poor mechanical properties after casting, forging and welding of medium and low carbon steel. Heat the workpiece to a temperature of 30-50°C above the temperature at which all ferrite transforms into austenite, hold for a period of time, and then slowly cool with the furnace. During the cooling process, the austenite transforms again, which can make the steel structure thinner. .
Spheroidizing Annealing. It is used to reduce the high hardness of tool steel and bearing steel after forging. The workpiece is heated to 20-40°C above the temperature at which the steel begins to form austenite, and then slowly cooled after heat preservation. During the cooling process, the lamellar cementite in the pearlite becomes spherical, thereby reducing the hardness.
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