Coarse-grain annealing

Grain coarsening annealing is done to coarsen the steel structure. You heat the part to a proper temperature and then let it cool slowly in the furnace. This gives you a coarse grain, which improves machinability and reduces the risk of cracking during welding. But be careful: if you cool the part too quickly or don't hit the right temperature, the grain will be fine. And fine grain is more troublesome for welding, you don't want that. The whole process must run smoothly and controlled, then it'll be fine.