Chapter 11 - Mirco-structure and Metallography | Heat-Treatment of Metals

Question 1

Heat-Treatment 1

Answer 1

altering the physical and sometimes chemical properties of a material.

Question 2

Heat-Treatment 2

Answer 2

Use: Metallurgical

Question 3

Heat-Treatment 3

Answer 3

Uses heating or chilling to extreme temperatures to achieve a desired result such as hardening or softening

Question 4

Heat Treatment 4

Answer 4

only applies to processes where the heating and cooling are done to alter properties intentionally

Question 5

Changing of Yield Point of a material:

Answer 5

1) Quenching: Cooled quickly, using water, oil or salt.
2) Low Temper
3) High temper
4) Normalized: Cooled with room temp
5) Full Anneal: Controlled cooling rate (slowest rate by oven or isolator) makes metal as soft as possible

Question 6

Annealing 1

Answer 6

Primary use: soften steel

• prepares metal for cold forming/machining
• allows recrystallisation

Question 7

Annealing - Process

Answer 7

Low carbon steels may harden through cold working

heated to around 100°C below lower critical temp, soaked, cooled in air

Question 8

Spheroidising

Answer 8

• High Carbon steels may be annealed just below the lower crit. temp
• improves machinability

Question 9

Normalising

Answer 9

• internal stresses caused by rolling or forging are removed.
• Steels are heated above upper crit. temp, soaked, cooled in air
• cooling rate faster than annealing => smaller grain structure

Question 10

Stress Relieving

Answer 10

A component is reheated & held at temp for a period of time then cooled slowly.

Question 11

Quenching

Answer 11

Dipping metal in water whilst red hot = v hard and brittle metal

Question 12

What does Quenching prevent?

Answer 12

The structure from changing back to BCC from FCC

Question 13

Tempering

Answer 13

• Almost always done after quenching due to lack of toughness and ductility
  (at expense of some strength)
  Heated to 220-300°C