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Normalising
Suggested answers
Activity 1
- How does normalising differ from the annealing process?
It differs from annealing in that the metal is heated to a higher termperature and then removed from the furnace for air-cooling.
- List some of the causes of internal stress, which normalising is designed to remove.
The purpose of normalising is to remove internal stresses induced by heat treatment, welding, casting, forging, forming or machining.
- How and why would you normalise low-carbon steels?
Usually, low-carbon steels do not require normalising; however, if these steels are normalised, no harmful effects result.
- What major property does normalised steel have and what type of loading will it best withstand?
Normalised steel is much tougher than any other structural steel and will withstand impact loadings?
Activity 2
- List some of the advantages of the fluidised bed furnace heating process.
They deliver:- fast, uniform heating
- process flexibility with quick changeover
- low operating and capital costs
- How are these furnaces controlled, heated and what is their temperature range.
The furnaces are computer controlled, heated by gas or electricity and reach a maximum temperature of 2200°F.
- List some of the heat treatment operations, which this type of furnace can perform.
Some of the operations include:- hardening
- tempering
- Nitriding
- carburising
Activity 3
Explain the meaning of the terms:
- normalising
- non-destructive testing
- notched bar test.
Normalising: A heat treatment process that has the object of relieving internal stresses, refining the grain size and improving the mechanical properties. The steel is heated to 800–900°C according to analysis, held at temperature to allow a full soak and cooled in still air.
Notched bar test: A test to determine the resistance of a material to a suddenly applied stress, i.e. shock. A notched test piece is employed in an Izod or Charpy machine and the results are recorded in joules.
Non-destructive testing: Those forms of testing that do not result in permanent damage or deformation to the part being tested. Typical examples are magnetic crack detection, ultrasonic inspection, x-ray inspection and gamma radiography.
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