Oil Quenching

Oil Quenching

When it comes to steel heat treatment, it is clear that heat treated metal parts perform better. They resist wear and maintain their form while under pressure. An oven heats metal components to extreme temperatures and then submerged in a liquid bath for rapid cooling. Water was the traditional quenching medium.  However, oil quenching produces superior quality.

The Advantages of Oil Quenching

Oil quenching metals

Oil does not boil as quickly as water. This allows the parts to absorb more initial heat and cool for longer periods of time. It is a superior quenching heat treatment, and including certain additives in the oils customize results.

The process begins with heat. Metal parts are placed in an oven. Temperatures can reach as high as 2000 degrees. Once the desired heat has been achieved, the parts are transferred to a submersion tank. The metal is coated in the oils and undergoes three phases of cooling:

  • Vapor Blanket Phase – High heat vaporizes oil forming an insulating cloud around the metal.
  • Nucleate Boiling – Vapors dissipate, and heat energy transfers to the oil from the metal.
  • Convection – The oil is heated to its boiling point and heat energy quickly dissipates.
Oil quenching a fixture plug

Ideally, the vapor phase will be as short as possible. The vapors created by the searing hot metals act as an insulator that resists cooling. The prolonged period of nucleate boiling is the key advantage of quenching steel in oil over traditional hardening methods. The longer the parts remain in the second phase of the cooling process, the better the result.

Oil has a much higher boiling point than water. The metals do not reach the convection phase until the oil reaches 450 degrees or more. Metal treated in this way cool rapidly and evenly. This reduces the risks of cracking, distortions, and uneven soft spots.

The Different Types of Oil

Process of oil quenching metal

Different types of oil used in quenching can yield different results, and the type of oil used depends in part upon the type of metal being heat treated. Some oils control distortion and reduce the risk of cracking of a highly hardenable alloy by ensuring that there is not much variation between the surface temperature and the core temperature during a quench. These oils are called hot oils because they are kept at much higher temperatures.

Fast oils are used typically used on low-hardenability alloys and low-carbon steel and are so called because they have specific properties that cool items more quickly by altering the length of the different stages of the cooling process.

The Process of Heat Treating Oil Quenching

The process of quenching heat treated metal consists of three stages. The shortest stage is the boiling stage, which comes after the vapor stage and before the convection stage. In the initial vapor blanket stage, the hot metal is submerged into the quenching oil. The temperature difference between the hot metal and the cool liquid causes the oil to vaporize. Cooling of the metal is impeded by the vapors that surround the metal, like a blanket, and prevent heat transfer. The oil is boiled in the second stage, causing the vapor blanket to dissipate and allowing heat energy to transfer from the metal to the oil. Once the oil reaches its boiling point, heat energy dissipates during the convection stage.

Different Types of Oil Quenching

Additional Advantages

Oil is preferable to the traditional quenching medium of water because it reduces the risks of distortions or cracking by cooling metals more evenly and more quickly.

Our Industry Leading Expertise

At Specialty Steel Treating, we’ve been in the business of heat treating metals for 60 years. We’ve improved metals for manufacturing in the aerospace, automotive, and industrial equipment applications. Our quality control systems are industry leading.

We begin by assessing the profile of your metal components. Different alloys require specific solutions. The initial temperature and the reactions with the oils produce varying results. We monitor and control the precise amount of heat your metal parts receive.

The oils are also important. Additives change the boiling point and phases of oil quenching. Oils can also leave behind residues that interact with your metals. We optimize our procedures to achieve the best results for every project.

Obtain a Quote for Quench Treatments

Hardening metal parts is an exact process. Your critical components deserve our expertise and superior results. To find out how we can help, contact SST. Describe your project request in the quote form.

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“Before I retired, I was the coordinator for our plant’s aerospace, and precision heat treated product, and SST. I couldn’t have asked for better quality, and service. I recommend them 100 percent.”
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