NSC Mechanical Technology Welding and Metalwork Basic calculations: 9.1 What is residual stress?

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Question

9.1 What is residual stress?

Residual stresses are stresses that exist in a metal $A$ after cooling.

9.2 Describe the effect of hot working on steel:

In hot working, deformation and recrystallization occur simultaneously so that the rate of softening is greater than work hardening.
Hot-working should be finished at a temperature just above the recrystallization temperature.
To obtain a fine grain structure.
If the finishing temperature is too high, grain growth will occur while the metal is cooling above the recrystallization temperature and inferior properties will develop.

9.3 Study FIGURE 9.3 below and answer the questions that follow.

9.3.1 Identify the diagram in FIGURE 9.3.

9.3.2 Label A–E indicated on the diagram.

A. Temperature / Degrees Celsius
B. Austenite
C. Austenite and Cementite
D. Ferrite and Pearlite
E. Carbon content

9.4 State TWO results when metal is cooled rapidly.

The metal sets up internal and external stresses.
Causes cracks on the surface of the metal.
Causes deformation.
Hardness increases.
Marten site forms.

9.5 Name FOUR quenching media used for the heat treatment of steel.

Water
Brine
Oil
Air
Metal / Molten salts
Sand
Ash

9.1 What is residual stress? Residual stresses are stresses that exist in a metal $A$ after cooling - NSC Mechanical Technology Welding and Metalwork - Question 9 - 2020 - Paper 1

Worked Solution & Example Answer:9.1 What is residual stress? Residual stresses are stresses that exist in a metal $A$ after cooling - NSC Mechanical Technology Welding and Metalwork - Question 9 - 2020 - Paper 1

What is residual stress?

Describe the effect of hot working on steel:

Identify the diagram in FIGURE 9.3.

Label A–E indicated on the diagram.

State TWO results when metal is cooled rapidly.

Name FOUR quenching media used for the heat treatment of steel.

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