What specific temperature range is associated with process annealing for low carbon steels?

Process annealing for low carbon steels is typically conducted in the temperature range of 550°C to 650°C. This heat treatment process is employed primarily to reduce the hardness and improve the ductility of the steel, allowing for better formability during subsequent processing.

Within this temperature range, the softening of the material occurs due to the recrystallization of the microstructure. This means that the previously cold-worked steel, which has been strengthened and hardened through deformation, can be restored to a more ductile state. The process effectively helps in relieving internal stresses and refining the grain structure, making the steel easier to work with in further manufacturing stages.

The other temperature ranges provided are either too low or too high for process annealing specific to low carbon steels. Lower temperatures (like those in the range of 300°C to 400°C) may not achieve the necessary effects of recrystallization effectively, while the higher ranges (like 700°C to 800°C) might result in excessive grain growth and potential damage to the material properties. Thus, 550°C to 650°C is the optimal range for this specific heat treatment process.