4 Common Types of Heat Treatment Process

15 March 2022

Heat treatment is a process that is loved by many industries as it can alter the physical and even the chemical properties of a material. Used primarily for compatible metals, the process of heat treatment can easily improve their wear resistance, durability, workability, strength, and magnetic properties.

There are three stages of heat treatment that workpieces undergo. The first stage is heating, which is done by exposing the workpieces to high temperatures to heat them uniformly. The heating rate of workpieces depends primarily on their heat conductivity, overall condition, and size. The next stage is soaking. This specific stage keeps the workpieces at an appropriate temperature until they acquire the needed internal properties. The soaking time depends on the workpieces’ chemical analysis and mass. The last stage is cooling, which reverts the workpieces’ temperature to room temperature.

To date, there are four types of heat treatment processes that maximise the mentioned stages.

  1. Annealing

Annealing is a type of heat treatment process that helps metals relieve stress, enhance ductility, and improve grain structures. It can also soften the metals. With annealing, metal workpieces can be processed and machined without developing internal stresses and brittle spots.

Generally, the annealing process is done by slowly heating the metals to between 400 and 1,000 Degrees Celsius (material dependent),soaking them, and cooling them by buying the workpieces in insulating material or turning off the furnace. The workpieces are often cooled gradually to below260 degrees Celsius. The time needed for soaking the workpieces depends on their type and mass.

  • Normalising

Normalising is a type of heat treatment that removes internal stresses from various metal fabrication processes like machining, forging, welding, and casting. This type of heat treatment is often done to workpieces, particularly ferrous metals, before they undergo any hardening.

The process of normalising can be similar to annealing, especially when it comes to heating. The only difference between the two is their cooling phase. Normalising cools the workpieces through the air, which introduces changes in their microstructure. Cooling the workpieces through air likewise makes normalising a little bit faster than the annealing process.

  • Hardening

Hardening is another type of heat treatment that aims to make workpieces harder and stronger. However, hardening can also make workpieces more brittle due to decreased ductility. To remove the brittleness of workpieces, they are recommended to undergo tempering.

Two stages of heat treatment are utilised in conducting the hardening process. These stages are heating and soaking. The third phase of hardening is different, as it rapidly cools the workpieces by plunging them into the brine, oil, wateror air cooling (usually nitrogen gas for cleanliness). Rapid cooling, which is known as quenching, is most applicable with steels.

  • Tempering

Tempering, ultimately, is a type of heat treatment that may be similar to annealing. The finished workpieces, however, would boast different properties since they are heated in much lower temperatures. Through tempering, workpieces become easier to machine or weld. They would likewise attain workable strength, flexibility, ductility, and hardness.

Before tempering is conducted, the workpieces must undergo hardening first. Afterwards, the workpieces can be tempered by heating them to a temperature below their hardening temperature, letting them soak at the set temperature, and cooling them.

To know more about these types of heat treatment, you can call us at Alpha Detroit Heat Treatment.

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