We talked about the annealing technology of stainless steel earlier. Would it be helpful to you? Today we will learn about several annealing processes for stainless steel welded pipes. Please take a look:

The commonly used annealing processes include:

① Complete annealing. Used to refine the coarse overheated structure of medium and low carbon steel with poor mechanical properties after casting, forging, and welding. Heat the workpiece to a temperature above which all ferrite is transformed into austenite at 30-50 ℃, hold it for a period of time, and then slowly cool down with the furnace. During the cooling process, austenite undergoes another transformation, which can refine the microstructure of the steel.

② Spheroidizing annealing. It is used to reduce the high hardness of Tool steel and bearing steel after forging. Heat the workpiece to a temperature 20 to 40 ℃ above the temperature at which austenite begins to form in the steel. After insulation, slowly cool it down. During the cooling process, the layered cementite in the pearlite becomes spherical, thereby reducing the hardness.

③ Isothermal annealing. Used to reduce the high hardness of certain alloy structural steels with high nickel and chromium content for cutting processing. Generally, the austenite is cooled to a relatively unstable temperature at a faster rate, and the temperature is kept for an appropriate period of time. The austenite transforms into troostite or sorbite, and the hardness can be reduced.

④ Recrystallization annealing. Used to eliminate the hardening phenomenon (increase in hardness and decrease in plasticity) of metal wires and sheets during cold drawing and cold rolling processes. The heating temperature is generally 50-150 ℃ below the temperature at which the steel begins to form austenite. Only in this way can the work hardening effect be eliminated and the metal soften.

⑤ Graphitization annealing. Used to transform cast iron containing a large amount of cementite into malleable cast iron with good plasticity. The process operation involves heating the casting to around 950 ℃, holding it for a certain period of time, and then cooling it appropriately to decompose the cementite into flocculent graphite.

⑥ Diffusion annealing. Used to homogenize the chemical composition of alloy castings and improve their performance. The method is to heat the casting to the highest possible temperature without melting, keep it warm for a long time, and wait for the diffusion of various elements in the alloy to become evenly distributed before slowly cooling.

⑦ Stress relieving annealing. Used to eliminate internal stress in steel castings and welded components. For steel products that begin to form austenite after heating at a temperature below 100-200 ℃, internal stress can be eliminated by cooling in air after insulation.