Q1: Primary designation of steel is based on its

ANS:D - alloying elements content.

Alloying elements are additional elements added to steel in varying amounts to modify its properties according to specific requirements. These elements are added during the steelmaking process and can significantly alter the characteristics of the steel. Some common alloying elements and their effects include:

1. Chromium (Cr): Increases hardness, corrosion resistance, and wear resistance. Stainless steels contain significant amounts of chromium.
2. Nickel (Ni): Enhances toughness, ductility, and corrosion resistance, particularly at low temperatures. Nickel is often used in stainless steels and high-strength low-alloy (HSLA) steels.
3. Manganese (Mn): Improves hardenability, strength, and wear resistance. Manganese is commonly added to structural steels and wear-resistant steels.
4. Molybdenum (Mo): Enhances strength, hardness, and creep resistance at elevated temperatures. It is often used in high-temperature applications and in steels for tools and machinery.
5. Vanadium (V): Increases strength, toughness, and hardenability. Vanadium is commonly used in high-strength low-alloy (HSLA) steels and tool steels.
6. Tungsten (W): Improves wear resistance, hardness, and high-temperature strength. Tungsten is commonly used in tool steels and high-speed steels.
7. Cobalt (Co): Enhances strength, hardness, and magnetic properties. Cobalt is often used in specialty steels and magnetic materials.
8. Copper (Cu): Improves corrosion resistance and electrical conductivity. Copper is commonly added to certain types of stainless steels and corrosion-resistant alloys.

These alloying elements can be added individually or in combination to achieve specific properties desired for a particular application. The content and combination of alloying elements are carefully controlled during the steelmaking process to achieve the desired balance of properties in the final steel product.