Which statement best describes killed steels' quality?

• A. Lowest quality.
• B. Moderate quality.
• C. Unknown quality.
• D. Highest quality.

Answer: (D)

Killed steel is fully deoxidized during production, usually by adding elements like silicon or aluminum to remove oxygen. This deoxidation prevents re-oxidation as the metal solidifies, so the steel forms with minimal gas porosity and a uniform microstructure. That evenness provides more reliable mechanical properties and better weldability, which is why killed steel is considered the highest quality among common steels. Other steels that aren’t fully deoxidized can trap gas or have uneven composition, leading to porosity and variability that lower quality.