Question 4
(a) State one reason each why the following heat treatment processes is carried out on metals.
(i) normalizing;
(ii) annealing;
(iii) case hardening;
(iv) tempering.
(b) State one function each of the following:
(i) flux;
(ii) electrode.
(c) State one safety precaution to be observed when welding with oxyacetylene gas.
(d) What is the filler metal for brazing?
Observation
Most of the candidates did not know the filler metal for brazing. They wrote borax which is the flux for brazing and not the filler metal. The correct responses are as given below.
- Stating one reason each why the following heat treatment processes is carried out on metals
- Normalizing - To refine the grain structure after working on metals.
- Annealing - It is to refine the structure of metals.
OR
- It is to soften metals.
- Case Hardening - It is to increase the outer surface hardness of low carbon steels.
(iv) Tempering - It is to relieve internal stresses in metals.
OR
- It is to re-align grain structure of metals.
- Stating one function each of the following
- flux - It is to clean and protect work surfaces.
- electrode – It serves as the filler material in arc welding.
(c) Stating one safety precaution to be observed when welding with oxy-acetylene gas
- Wear protective clothing.
- All oxy-acetylene welding cylinders should be kept upright.
(d) The filler metal for brazing.
- Spelter