Do Metal Castings Need Heat Treating?
Metal casting is an incredibly versatile and flexible process that can be used for a huge range of applications as the huge product portfolio of MRT Castings shows.
Whilst most aluminum castings are used in the ‘as cast’ condition, there are certain applications that require higher mechanical properties, or different properties that the ‘as cast’ material can’t provide. Each individual industry and casting has different requirements for the final casting. These special characteristics can include the composition of the metal, such as its ductility, hardness and abrasion resistance.
The majority of these characteristics can be added to metal through heat treating the casting – a series of extreme heats and fluctuations (or lack off) that improve the metallurgical properties of the material to produce the desired effect. In the following there are just a few of the methods that MRT Castings uses, to provide the perfect casting, regardless of the application.
Quenching is arguably the most common heat treating method that people may think of when they envision metal working. It’s the act of quenching red hot metal into oil/water to rapidly cool it – changing the metallic structure. This process, make most metals much harder and abrasion resistant than before however, can also make it much more brittle.
Annealing is most likely a term that you would have come across when hearing about metal work. It’s the act of heating up the material to close to its melting point and then allowing it to cool naturally. This relaxes the structure of the metal and makes it less brittle. Annealing is usually done after quenching to retain hardness but release the internal stresses and stop it from being brittle.
Age hardening is a technique where heat is applied to the casting for a long time (as long as 20 hours). It’s a complicated process that, in simplistic terms, blocks the molecule’s ability to dislocate freely – resulting in much less ductile material and much higher yield strength.
Heat treating all metals, including aluminum, is a balancing act. Where one quality of the material improves, another property gets lessened. The ‘harder’ a material becomes the less ductile and malleable it is. The less softer and malleable it is, the less hard it becomes.
If you wand to know more about Heat Treatment read the related article: Reaching Optimum Properties: Heat and Surface Treatment in the Die Casting Industry
This article was first published by MRT Castings.
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