HEAT TREATMENT

Question 1

Identify a heat treatment for ferrous metals and describe the resulting grain structure

Answer 1

Normalising: produces a fine uniform grain structure, that strengthens the metal throught grain size strengthening

Question 2

Describe one heat treatment process of surface hardening steel (shaft, gears and railway lines)

Answer 2

Carburising: soaking the metal at red heat in a carbonaceous material or atmosphere which increases the carbon content of the case to be about (0.8%)
-used when the steel contains little carbon (less than 0.2%) so the core remains relatively soft and tought

Nitriding: involves changing the surface composition of the steel by diffusing nitrogen into it to produce hard nitride compounds into the surface layers

Flame and induction hardening: used to harden steels with a greater carbon content of 0.3% (0.4-0.6%)
Induction hardening is done by electric current for smaller components axles, shafts etc
Flame hardening is used for larger jobs such as gear teeth and machine beds

Question 3

Describe a non-heat treatment process of surface hardening steel

Answer 3

Working hardening the surface layers by abrading, working by hammering and sliding