Q1: Carbon percentage in high speed steel tool material is 0.6 to 1.0. The hardness of carbon tool steels is increased, when it is alloyed with

ANS:A - vanadium & chromium

1. Vanadium:
   • Increases Hardness and Wear Resistance: When added to steel, vanadium forms very hard carbides, such as vanadium carbide (VC). These carbides are dispersed throughout the steel matrix, effectively increasing its hardness and wear resistance.
   • Improves Strength and Toughness: Vanadium can also contribute to the overall strength and toughness of steel. It refines the grain structure of the steel, which enhances its mechanical properties, such as tensile strength and impact resistance.
   • Enhances Hardenability: Vanadium promotes uniform and thorough hardening of steel during heat treatment, known as hardenability. This property allows the steel to achieve high hardness levels throughout its cross-section, even in thicker sections.
2. Chromium:
   • Improves Corrosion Resistance: Chromium is known for its ability to form a protective oxide layer on the surface of steel, known as chromium oxide (Cr2O3). This oxide layer acts as a barrier, protecting the underlying steel from corrosion and oxidation, hence enhancing its corrosion resistance.
   • Increases Hardenability: Chromium is also effective at increasing the hardenability of steel, similar to vanadium. It promotes the formation of chromium carbides (such as chromium carbide, Cr23C6) during heat treatment, which enhances the steel's ability to be hardened uniformly.
   • Enhances Strength and Toughness: Chromium contributes to the overall strength and toughness of steel. It can help refine the grain structure, which improves mechanical properties such as tensile strength and impact resistance.
   • Alloying Element in Stainless Steels: In addition to its role in carbon and alloy steels, chromium is a primary alloying element in stainless steels. In stainless steel, chromium content typically ranges from 10% to 30%, and it is responsible for providing the steel with its characteristic resistance to corrosion and staining.

In summary, vanadium and chromium are both important alloying elements in steel, each offering unique benefits such as increased hardness, wear resistance, strength, toughness, and corrosion resistance. Their addition to steel formulations allows manufacturers to tailor the properties of steel to meet specific application requirements, ranging from cutting tools and high-strength components to corrosion-resistant structures.