Hence, other forms of deoxidation are preferred over aluminum-killed steel. It has been recognized from the early days of continuous-casting operation that casting difficulties and poor surface conditions are often experienced with aluminum-killed steels. Steels that are required for large castings are not killed with aluminum, because the suppression of carbon monoxide gas causes piping defects inclusions of alumina also causes defective castings. There are many steel-processing operations where aluminum killing of steel is undesirable. For killing, these steels usually have a substantial amount of aluminum added in the ladle, in the mold, or both.ĭeoxidation of steel by aluminum suppresses the formation of carbon monoxide during solidification, which controls formation of blowholes. The steel requiring deep drawing and certain extra-deep-drawing steels with low-carbon up to maximum 0.12% is of this grade. Alloy steels, forging steels, and steels for carburizing are this type of steel. Killed steels are generally used when a homogeneous structure is required in the finished steels. To minimize piping, almost all killed steels are cast in hot-topped big-end up molds. In some applications, calcium silicide or other special strong deoxidizers are also used. Aluminum together with ferroalloys of manganese and silicon is used for deoxidation. Killed steel is deoxidized to such an extent that there is no gas evolution during solidification. Ramesh Singh, in Applied Welding Engineering (Third Edition), 2020 Killed steel
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