Ferromanganese is used as a deoxidizer and alloy additive in steelmaking. It is a large amount of iron alloy. The manganese ore used to smelt ferromanganese generally requires 30-40% manganese in ferromanganese, the ratio of manganese to iron is greater than 7, and the ratio of phosphorus to manganese is less than 0.003.
Before smelting, the manganese carbonate ore is first roasted, and the fine ore is sintered into agglomerates. Ores with high iron and phosphorus content can only be used in combination, or manganese-rich slag with low iron and phosphorus content can be obtained through selective reduction. Coke is used as a reducing agent during smelting, and lean coal or anthracite is also used in some factories. The auxiliary raw material is mainly lime, and silicon dioxide is generally added when smelting manganese-silicon alloy.
Steel castings should be used after heat treatment. Due to the presence of casting defects such as pores, cracks, shrinkage cavities and shrinkage cavities, coarse grains, uneven structure and residual internal stress in steel castings in the as-cast state, the strength, especially the plasticity and toughness of steel castings are seriously affected. . decrease very much.
In order to refine grains, uniform structure and eliminate internal stress, steel castings must be normalized or annealed. Normalized steel has higher mechanical properties and lower cost than annealed steel, so it is widely used. However, since normalizing produces greater internal stress than annealing, it is only suitable for steel castings with a carbon content of less than 0.35%. Due to the good plasticity of low carbon steel castings, it is not easy to crack when cooling. In order to reduce internal stress, steel castings should be tempered at high temperature after normalizing. For steel castings with carbon content ≥ 0.35%, complex structure and cracks, only annealing treatment can be performed. Steel castings should not be quenched, otherwise they will crack easily.