Silicon in steel has what primary effect regarding oxidation resistance and hardenability?

Silicon in steel has what primary effect regarding oxidation resistance and hardenability?

• A. 0.60%; Silicon improves oxidation resistance and hardenability
• B. 0.10%; Silicon reduces oxidation
• C. 1.5%; Silicon increases weldability
• D. 0.05%; Silicon improves magnetic characteristics

Answer: (B)

Silicon in steel mainly boosts oxidation resistance at high temperatures and increases hardenability when used in moderate amounts. It does this in two ways. First, silicon promotes the formation of a protective oxide layer on the surface (silicon oxide) during high-temperature exposure, which slows down the rate of oxidation compared with silicon-free steel. Second, silicon affects the transformation behavior of austenite during cooling: it slows carbon diffusion and shifts the transformation, making it easier for martensite to form in thicker sections, which enhances hardenability. In practice, roughly around 0.6% silicon is a common level that yields noticeable improvements in both oxidation resistance and hardenability, without introducing excessive brittleness or welding difficulties.

Silicon in steel mainly boosts oxidation resistance at high temperatures and increases hardenability when used in moderate amounts. It does this in two ways. First, silicon promotes the formation of a protective oxide layer on the surface (silicon oxide) during high-temperature exposure, which slows down the rate of oxidation compared with silicon-free steel. Second, silicon affects the transformation behavior of austenite during cooling: it slows carbon diffusion and shifts the transformation, making it easier for martensite to form in thicker sections, which enhances hardenability. In practice, roughly around 0.6% silicon is a common level that yields noticeable improvements in both oxidation resistance and hardenability, without introducing excessive brittleness or welding difficulties.