Killed steel is steel that has been completely deoxidized by the addition of an agent before casting so that there is practically no evolution of gas during solidification. They are characterized by a high degree of chemical homogeneity and freedom from gas porosity. The steel is said to be "killed" because it will quietly solidify in the mould, with no gas bubbling out. Common deoxidizing agents include aluminum. Aluminum reacts with the dissolved gas to form aluminum oxide. The aluminum oxide precipitates provide the additional benefit of pinning grain boundaries, thereby preventing grain growth during heat treatments. For steels of the same grade a killed steel will be harder than rimmed steel. A216-WCB and A105N used in valve manufacturing by both Newco and L&T are fully killed steel.
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Prepared By D. Romphf