Spheroidize annealing

You do soft annealing when you want a material to be easier to machine or form again. You heat the part to just below the transformation temperature and hold it there long enough. The carbon in the structure spheroidizes, the material becomes softer, and hardness decreases. This is especially important for higher-alloyed or hardened and tempered steels that would otherwise be too brittle or hard for further processing. After annealing, you let the part cool slowly to avoid building up new stresses.