What is Oil Quenching and How is it Done?

30 June 2022

Various construction companies rely heavily on metal parts and products to make their projects successful. Metal architectural pieces, after all, are durable, versatile, and long-lasting.

But raw metal architectural pieces may not be robust enough in withstanding weather and other outdoor elements. And so, companies would only opt for architectural pieces that have been subjected to various heat treatment processes. One heat treatment process that can enhance the qualities of small and large architectural pieces is oil quenching.

An Overview of the Quenching Process

Heat treatment is comprised of various steps. And one of the most crucial steps in this process is quenching. Quenching is the rapid cooling of workpieces in water, air, or oil after subjecting them to high temperatures. As they cool down, the involved parts may attain certain properties needed by industries.

As mentioned, quenching can be done through water, air, or oil. While all these quenching mediums have their respective benefits and limitations, most industries prefer oil as their primary quenching medium as it provides more benefits to the parts compared to others. 

Three Main Stages of Oil Quenching 

Oil quenching is done in multiple stages. The first stage is the vapour stage, which is the formation of a vapour blanket around the submerged part. A vapour forms around the part since it is hotter than the quenchant, the quenching medium used in cooling the workpiece.

The second stage is the boiling stage, which is the boiling of the quenchant. During this stage, the submerged parts cool the fastest since the vapour blanket has already dissipated. Its dissipation allows the quenchant to contact the parts flawlessly, removing most of the heat through boiling.

Oil quenching ends in the convective stage. This stage allows convention and conduction to remove heat away from the parts. Convection is the movement of a liquid due to the tendency of hotter and less dense material to rise, while colder and denser material to sink. Conduction, alternatively, is the tendency of heat dissipating through a substance on which temperature differences exist in the liquid. Oil tends to be disturbed strongly during quenches, forcing this medium to flow upward through the workload.

Primary Advantages of Oil Quenching

What makes oil quenching advantageous for parts and products is it can transfer heat more quickly than other quenching mediums without causing cracks and distortion. Another great advantage of oil quenching is it can be modified freely. The temperature, viscosity, and other chemical properties of the quenching medium can be altered to provide varying outcomes to the heat-treated parts. Oil quenching can likewise accommodate different types of metals, making the process more versatile than others.

Oil quenching can utilise either fast oils or hot oils. Fast oils work best with parts out of low-carbon steel and low-hardenability alloys. Hot oils, alternatively, can process high-hardenability alloys effectively.  

The versatility and adjustability of oil quenching make it ideal for large architectural pieces. To know more about architectural blackening, you can contact us at Alpha Detroit Heat Treatment.

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