Q1: Out of the following materials, the one which generally exhibits an yield point is

ANS:D - hot rolled mild steel

Hot rolled mild steel refers to steel that has been heated above its recrystallization temperature and then passed through rollers to achieve the desired shape and dimensions. Here's a breakdown of the process and characteristics:

1. Heating: The steel is heated above its recrystallization temperature, which is typically around 1100°C for mild steel. Heating makes the steel more malleable and easier to shape.
2. Rolling: Once heated, the steel is passed through a series of rollers to reduce its thickness and shape it into the desired form, such as sheets, plates, or structural shapes like beams or channels.
3. Cooling: After rolling, the steel is allowed to cool naturally. This cooling process is slower than in the case of cold rolling, and it allows the steel to normalize, which means it retains some of the internal stresses and grain structure from the rolling process.

• Less precise dimensions: Hot rolling is not as precise as cold rolling, so the resulting products may have slightly less uniform dimensions.
• Surface finish: The surface finish of hot rolled steel is rougher compared to cold rolled steel, with a characteristic scale layer formed during the cooling process.
• Grain structure: The grain structure of hot rolled steel tends to be larger and less uniform compared to cold rolled steel.
• Lower hardness: Hot rolled steel generally has lower hardness compared to cold rolled steel, making it easier to machine and form.