Diffusion Annealing for Segregation Reduction

Diffusion annealing is done to fix casting segregation. During casting, alloying elements settle unevenly, and you anneal it out by leaving the part in the furnace long and hot. This allows atoms to migrate and the chemistry to equalize. This is important before welding, because if you leave the segregation in, you'll get trouble with cracks or an unclean structure when welding. The furnace should have a uniform temperature, and you must give the part enough time – it takes hours. And remember: after annealing, let it cool slowly, don't open the furnace and pull the part out quickly.