Silicon and copper do not exceed what percentage in steel, and what are their primary properties?

• A. 0.60%; Silicon improves oxidation resistance and hardenability; Copper improves atmospheric corrosion resistance when present >0.15%
• B. 0.20%; Silicon reduces oxidation; Copper reduces corrosion resistance
• C. 1.0%; Silicon improves machinability; Copper increases magnetic properties
• D. 0.01%; Silicon deoxidizes; Copper reduces heat resistance

Answer: (A)

In steel, small amounts of alloying elements are limited to gain specific benefits without harming ductility or weldability. Silicon’s main role is as a deoxidizer, and it also helps with oxidation resistance and can modestly improve hardenability. Keeping silicon under about 0.60% provides these advantages without making the steel too brittle or hard to work with.

Copper’s primary purpose is to boost atmospheric corrosion resistance, which is why it’s used in weathering steels. The protective effect becomes noticeable once copper is present above roughly 0.15%; higher amounts can further improve outdoor durability but may affect cost and weldability.

So the best match is that silicon should not exceed about 0.60%, with its given benefits, and copper begins to provide improved atmospheric corrosion resistance when present above about 0.15%.