Parts made of cast steel are steel castings. It is similar to cast iron in properties, but better than cast iron in strength.
All steel castings shall be used after heat treatment. The strength, especially plasticity and toughness of steel castings are greatly reduced because of the casting defects such as porosity, crack, shrinkage cavity and porosity, coarse grain, uneven structure and residual internal stress. In order to refine the grain, uniform structure and eliminate the internal stress, the steel castings must be normalized or annealed. The mechanical properties of normalized steel are higher than that of annealed steel, and the cost is lower, so it is widely used. However, due to the large internal stress caused by normalizing treatment, it is only suitable for carbon content less than 0.35% Steel casting of. Because of the good plasticity of low carbon steel casting, it is not easy to crack when cooling.
In order to reduce the internal stress, the steel castings should be tempered at high temperature after normalizing. For carbon content ≥ 0.35% The steel castings with complex structure and easy to crack can only be annealed. The steel castings should not be quenched, otherwise they are easy to crack.