Photo AI
3.1 Name ONE property of steel that is tested by conducting a bending test on steel - NSC Mechanical Technology Automotive - Question 3 - 2018 - Paper 1
Question 3
3.1 Name ONE property of steel that is tested by conducting a bending test on steel. 3.2 Give TWO reasons for conducting EACH of the following heat-treatment proces... show full transcript
Worked Solution & Example Answer:3.1 Name ONE property of steel that is tested by conducting a bending test on steel - NSC Mechanical Technology Automotive - Question 3 - 2018 - Paper 1
Step 1
Name ONE property of steel that is tested by conducting a bending test on steel.
Answer
One property of steel that is tested by conducting a bending test is its ductility. Ductility refers to the ability of steel to deform under tensile stress, which is crucial in determining how much bending or shaping can occur without fracture.
Step 2
Give TWO reasons for conducting EACH of the following heat-treatment processes on steel: 3.2.1 Annealing
Answer
-
To relieve internal stresses: Annealing helps in reducing residual stresses in the steel that may have developed during previous processing, leading to improved dimensional stability.
-
To soften the steel: The process makes the steel more workable by reducing hardness, which allows for easier machining and forming.
Step 3
3.2.2 Case hardening
Answer
-
To produce a wear-resistant surface: This process creates a hard exterior layer to protect against wear and abrasion, which is essential for components subjected to friction.
-
To ensure the core remains tough: By hardening the outer layer while retaining a tough core, case hardening provides a combination of hardness for wear resistance and ductility to absorb impacts.
Step 4
Explain why the tempering of steel is done after the hardening process.
Answer
Tempering is performed after hardening to alleviate brittleness caused during the hardening process. It helps in relieving internal stresses and simultaneously increases the toughness of steel, making it less prone to cracking under stress.
Step 5
State the THREE factors that must be considered during all heat-treatment processes.
Answer
-
Heating temperature: The temperature to which the steel is heated is critical, as it influences phase changes and the resulting properties.
-
Soaking time: This refers to the duration allowed for the steel to maintain the required temperature before quenching, impacting the uniformity of the heat treatment.
-
Cooling rate: The rate at which the steel is cooled after heat treatment affects the hardness and microstructure of the steel.
Step 6
Explain the hardening process of steel.
Answer
The hardening process involves heating the steel to a temperature between 30°C to 50°C above its critical temperature, referred to as Austenitizing. Steel is held at this elevated temperature to transform its structure into austenite, allowing for uniform distribution of carbon. Subsequently, the steel is rapidly cooled by quenching in either water, brine, or oil. This rapid cooling traps carbon within the iron structure, transforming it into martensite, a very hard but brittle form of steel.