When it is necessary to anneal a piece of steel quickly, the process may be accomplished by heating it to a uniform red heat and then allowing it to cool in the air. A current of air should not be allowed to strike it until the red disappears. The instant the red disappears, the steel should be plunged in water and left until cool. Soapsuds or oil give better results than water. While water annealing is not to be advocated for general use, in an emergency it is extremely useful.
While annealing is intended primarily to soften steel, it has another use, which is to do away in a great measure with the tendency which steel has to spring when hardened. This tendency arises from the internal stresses which are caused by the various operations through which the steel passes in the steelmill or forgeshop.
When steel is to be annealed to remove stresses, the skin, i.e., the outer surface, is first cut away. The remaining piece must be large enough to be machined to size without straightening after annealing, as the operation of straightening steel when cold tends to set up strains that show themselves when the steel is hardened.