Which of the following has the least value of ultimate tensile strength (UTS) ?

ANS:B - High carbon steel

High carbon steel is a type of steel that contains a higher percentage of carbon compared to other types of steel. While there is no precise cutoff for what constitutes "high carbon" steel, it generally refers to steel with a carbon content ranging from about 0.6% to 1.5% by weight. Here are some key characteristics and properties of high carbon steel:

1. Increased Hardness: The higher carbon content in high carbon steel contributes to its increased hardness and wear resistance compared to low or medium carbon steels. This makes high carbon steel suitable for applications where hardness and abrasion resistance are important, such as cutting tools, knives, springs, and machinery parts.
2. Improved Strength: High carbon steel typically exhibits higher tensile and yield strengths compared to low or medium carbon steels. This increased strength is attributed to the carbon atoms strengthening the steel matrix through solid solution strengthening and forming hard and brittle compounds like cementite (Fe3C) during heat treatment.
3. Lower Ductility: One drawback of high carbon steel is its lower ductility compared to low or medium carbon steels. The presence of more carbon atoms results in a less malleable and more brittle material. As a result, high carbon steel is more prone to fracture under high stress or impact loading, especially in applications where deformation and toughness are critical.
4. Greater Susceptibility to Heat Treatment: High carbon steel responds well to heat treatment processes such as quenching and tempering, allowing for precise control over its mechanical properties. Through heat treatment, high carbon steel can achieve a balance of hardness, strength, and toughness suitable for specific applications.
5. Potential for Enhanced Corrosion Resistance: In some cases, high carbon steel may exhibit improved corrosion resistance compared to low or medium carbon steels due to the formation of protective surface layers during heat treatment or through the addition of alloying elements.

Overall, high carbon steel offers a combination of high hardness, strength, and wear resistance, making it suitable for a wide range of industrial and commercial applications where these properties are required. However, its lower ductility and greater susceptibility to brittleness must be considered in the design and use of components made from high carbon steel.