Definition - What does Semi-killed Steel mean?
Semi-killed steel refers to a type of metal alloy compound of iron and carbon that has been partially deoxidized with minimal gas release during solidification.
Semi-killed steel presents a high degree of homogeneity on the molecular level. It also has minimal degrees of gas porosity, making it ideal for heat treatment. Generally, more gas is evolved in semi-killed steel than in killed steel.
Corrosionpedia explains Semi-killed Steel
Semi-killed steel is mostly deoxidized with the carbon monoxide gaseous evacuation distributed throughout the ingot.
Semi-killed steel is an intermediate type of steel between killed and rimmed steels. It may also possess variable degrees of uniformity in composition. Similar types of steel include capped steel. Steel plates for ASTM-A36 must be killed or semi-killed.