After the heat treatment of steel castings should be used. Because the internal cast member cast in the presence of pores, cracks, shrinkage and shrinkage, coarse grains, tissue heterogeneity and residual stress within the casting defects, the strength of steel castings, especially ductility and toughness greatly reduced. For the grain refinement, uniform organization and eliminate stress, steel castings must be normalized or annealed. Steel after normalizing treatment, higher mechanical properties after annealing, the cost is low, so more often. However, due to normalizing annealing process can cause relatively large internal stress, apply only to the carbon content of less than 0.35% of steel castings. Because of low carbon steel casting plastic good, easy to crack when cooled. To reduce stress, steel castings, after normalizing, tempering should be carried out. For the carbon content of ≥0.35%, complex structure and is easy to produce cracks in steel castings, can be annealed. It should not be hardening steel castings, or vulnerable to cracking.

2. Steel casting smelting
Steel smelting commonly used open-hearth electric arc furnace and induction furnace. Open hearth furnace is characterized by large capacity, you can use scrap as raw material, can accurately control the composition of the steel and smelting high energy and low alloy steel casting, used for melting high quality requirements of liquid steel with large steel castings. Three-phase electric arc furnace furnace shutdown and easy to operate, can guarantee the quality and composition of liquid steel, to charge less stringent requirements, easy to heat up, it can refine high quality steel, high alloy steel and special steel, which is the production of molded common equipment castings. In addition, the use of frequency or medium frequency induction furnace, capable of melting steel and a variety of advanced low carbon content steel. Induction furnace melting fast burning of alloying elements is small, low energy consumption, and high quality liquid steel that fewer impurities, inclusions less suitable for small steel workshop use.

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