3.1 Name ONE property of steel that is tested by conducting a bending test - NSC Mechanical Technology Welding and Metalwork - Question 3 - 2018 - Paper 1

1. To relieve internal stresses: Annealing allows the steel to relax its internal stresses, which can occur during previous manufacturing or processing stages.

2. To soften the steel: The process reduces hardness and increases workability, making it easier to shape in subsequent operations.

1. To produce a wear-resistant surface: Case hardening enhances the surface hardness of the steel, increasing its durability against wear and tear.

2. It must be tough enough internally: The core of the steel must maintain toughness to withstand the applied loads while the surface resists wear.

Tempering is done after hardening to reduce the brittleness caused by the hardening process. It helps relieve the internal stresses and increases the toughness of the steel, balancing strength and ductility.

1. Heating temperature/Carbon content: Correct temperature and carbon content must be maintained for effective heat treatment.

2. Soaking time: The duration at which steel is held at the required temperature must be controlled for uniform heat distribution.

3. Cooling rate/Quenching rate: The speed of cooling affects the final properties of the steel.

The hardening process of steel involves heating the material to a temperature between 30°C - 50°C above its critical temperature (A_c) and then rapidly cooling it, usually through quenching in water or oil. This rapid cooling transforms the steel's microstructure, forming a harder structure known as martensite, which significantly increases the hardness and strength of the steel.