Which deoxidized process yields the softest steel with about 0.15% carbon?

• A. Capped steel
• B. Killed steel
• C. Rimmed steel
• D. Semi-killed steel

Answer: (C)

This question hinges on how the way steel is deoxidized during production affects its ductility and softness at a mild carbon level around 0.15%. When deoxidation is lighter, as in rimmed steel, oxygen is only partially removed and gas forms as the melt solidifies. Those gas pockets and the incomplete deoxidation push impurities toward the outer region, while the interior remains relatively soft and easy to deform. The result is a steel that is notably ductile and formable, with low strength for its carbon content, making it feel the softest among common deoxidized steels at about 0.15% carbon. In contrast, fully deoxidized (killed) steels are uniform and stronger, semi-killed steels sit between in strength and ductility, and capped steels improve surface finish but don’t achieve the same level of softness as rimmed steel. So for a gentle, highly formable mild steel around 0.15% carbon, rimmed steel is the best fit.