Information on the Heat Treatment of Cast Irons

15 September 2021

To date, a wide array of alloys can be utilised to create reliable parts and components. One of the alloys that are being maximised by many industries is cast iron.

Cast iron is an alloy of iron that is comprised of more than 2% carbon as well as varying amounts of manganese, silicon, sulphur, and phosphorus. The presence of these elements allows this specific alloy to possess great fluidity, low melting point, exemplary pouring characteristics, excellent machinability, and resistance to wear and deformation.

Most cast iron parts and components are used by the automotive, construction, and electronics industries. The formation of these products is possible through different heat treatment techniques. To know more about them, here is some information on various heat treatment techniques of cast irons.

Stress Relieving

Stress relieving is a heat treatment technique that subjects the cast iron to a constant temperature below its critical temperature before exposing it to controlled cooling. As the temperature gets higher, the mechanical properties of the cast iron typically change. Once the desired mechanical properties are achieved, the cast iron is then cooled. For most castings, a furnace cooling to 260°C can be done. Cooling to 95°C, alternatively, is a must for those that possess intricate shapes. This specific technique is applied to cast iron to effectively minimise residual stresses and dimensional changes.

Annealing

Another heat treatment technique that can be applied to cast iron is annealing. It is a heat treatment technique that changes the microstructure of the cast iron, therefore changing its electrical or mechanical characteristics. When applied to cast iron alloy, annealing can easily reduce its hardness, increase its ductility, and eliminate internal stresses on its structure. Annealing is typically done by heating the cast iron for a specific amount of time before letting it cool slowly to room temperature. Various types of cast iron can go through different heating and cooling cycles to achieve distinct purposes.

Quenching and Tempering

Both quenching and tempering are typically applied on cast irons to improve their ductility and relieve internal stresses. But to yield great results, various parameters should be selected and controlled. Selecting and controlling the parameters such as the temperature can then prevent the cast irons from distorting, warping, burning, or quench cracking. Before performing these techniques, the heating of the cast irons must be done gradually to avoid inducing thermal stresses. The parts that were soaked must then be quenched. Tempering is subsequently done at a temperature range of 120 to 595°C.

When processing specific types of cast iron, different heat treatment techniques can be done. For example, high-alloy white iron castings can be processed through stress relief heat treatment and tempering. Grey cast irons and ductile cast irons, alternatively, can benefit from stress relief heat treatment and annealing at varying temperatures.

To know more about heat treatment techniques of cast irons, you can contact us at Alpha Detroit Heat Treatment. We provide a wide range of services for all your heat treatment needs.

Source:

Herring, D. H. (2020, March 19). Heat Treatment of Cast Irons. 2018–12-12 | Industrial Heating. https://www.industrialheating.com/articles/94644-heat-treatment-of-cast-irons

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