Heat treatment temperature for restoring mechanical properties of Q345R (R-HIC)
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Material: Q345R (R-HIC), thickness 95mm, supplied in normalized condition. In cylinder rolling (cold forming), when the deformation rate exceeds the requirements specified in standard JB 4732, heat treatment is required to restore the mechanical properties. What is the appropriate temperature for this? Some say 650 degrees, while others claim it can reach 920 degrees.
Check page 107 of NB/T47015-2011; the temperatures for post-weld heat treatment are specified there.
According to GB150, this should be subjected to re-normalizing treatment, and a heat treatment test plate is also required.
1. The heat treatment to restore material properties for carbon steel and low-alloy steel refers to recrystallization annealing. 2. Recrystallization annealing: The workpiece that has undergone cold plastic deformation is heated above its recrystallization temperature and held there for an appropriate period of time. Through recrystallization, the crystallographic defects generated during cold deformation are largely eliminated, and uniform equiaxed grains are formed anew; this type of annealing serves to remove the effects of strain strengthening and residual stresses. 3. The recrystallization annealing process involves heating the metal that has been cold-deformed to a temperature above its recrystallization point and holding it there for an appropriate period of time, after which it is cooled slowly to room temperature. The purpose of this is to transform the deformed grains back into uniform equiaxed grains, while simultaneously eliminating work hardening and residual internal stresses, thereby restoring the structure and properties of the steel to their state before cold deformation. 4. Recrystallization annealing: \"Low-temperature annealing, when used to eliminate the work hardening resulting from cold deformation (such as cold drawing, cold rolling, cold stamping, etc.), is called recrystallization annealing.\" The heating temperature for recrystallization annealing should be 150–250°C above the steel’s recrystallization temperature, that is, 650–750°C; after holding at this temperature, the material is cooled in air. During recrystallization annealing, uniform and fine equiaxed grains can be obtained through ‘recrystallization’, thereby reducing hardness and restoring plasticity. ”
What is the recrystallization temperature of Q345R? Where is it specified that the recrystallization annealing temperature should be 150-250 degrees higher than the recrystallization temperature?