MECHANICAL properties of many metallic materials can be manipulated by the process called “heat treatment”, a phenomenon practiced since antiquity. The practice now is an advanced science in any manufacturing of metallic components.
Steel and aluminium alloys are among the most popular heat-treatable materials that are widely used in the manufacture of automotive parts to achieve the desired properties.
Heat-treatment produces a great variety of micro structural changes or transformation within the metal matrices during heating and cooling in their solid states. The right transformation that occurs in the final micro structure will result in the component having the mechanical properties required to serve its function.
Steel is an alloy of iron and carbon with iron being the base metal. Heat-treatment procedures transform the iron-carbon compound in the steel matrices into a variety of steel micro structures. These transformations result in the variation of the properties of steel, such as; tensile strength, hardness, toughness, ductility etc.
Heat-treatment processes such as annealing, hardening, normalizing and tempering are familiar among metallurgists and engineers in manipulating the properties of steel at various levels of processes and finishing work in components manufacturing.
On a similar account aluminium alloy with silicon is the most popular lightweight material that is heat-treatable. The alloy, in the presence of a right quantity of silicon and magnesium, transforms into aluminium-silicon-magnesium compound in the micro structure of the alloy after heat-treatment. The procedures strengthen the alloy as well as improve its properties amongst which are; ductility, tensile strength, impact strength and fracture resistance.
The quality of tools (moulds and dies) for mass production of components as described in the previous article, demand right heat-treatment procedures to ensure longer operational lives.
This article does not intend to elaborate in depth on the scientific and metallurgical aspects of heat-treatment of metals, but suffice to demonstrate the importance of heat-treatment of in achieving the required properties of metals used in any engineering endeavour and in the manufacture of quality parts and components.
There are 20 local heat-treatment companies that provide heat-treatment services, such as; vacuum hardening, carburising, carbonitriding, nitriding, annealing and tempering, to the local automotive industries.
Heat-treatment facilities are best installed within the production line of a mass component manufacturing set-up. This is to ensure that operation flows are without interruptions. Sub-contracting heat-treatment work to another party may render inefficiency in the production line process sequence.
There seems to be sufficient metallurgical and practical knowledge on heat-treatment processes amongst the downstream steel industries due to their long term establishments.
However, knowledge on metallurgical aspects and heat-treatment procedures for aluminium alloys seems inadequate within the local aluminium parts manufacturers. Some of the producers heat-treat their manufactured parts without in-depth knowledge on the microstructural transform that occurs during the process.
Enhancing the heat-treatment knowledge and capabilities amongst the aluminium industrialist is crucial as the nation embarks on the manufacture of energy efficient vehicles.
Aluminium as a lightweight material is expected to be extensively used in these vehicles.