The Different Types of Tempering

Heat treating is used in a variety of different industries to change a metal piece’s properties. There are a variety of different methods used, all of which give us different results. One of the most common methods is known as tempering, in which a workpiece is heated to a high temperature (but below its melting point), held at that temperature for a necessary period and then cooled at a slow rate.

This heat-treating process increases a metal’s toughness by lessening brittleness and reducing internal stresses, all while decreasing harness. But it’s important to note that there are several types of tempering out there. Continue reading to learn the differences between them:

  • Differential tempering: Also known as graded tempering or selective tempering, this process has been around for centuries. Because the process only tempers part of the metal, blacksmiths used differential tempering for swords, knives or other weapons that required a hard edge but some malleability in the rest of the tool.
  • Austempering: This process is often used for ferrous metals. During this process, the metal is heated to anywhere from 1,400 to 1,600 degrees before being quenched in oil or a nitrite-nitrate solution. It’s then cooled slowly at room temperature.
  • Martempering: Martempering is similar to austempering, but the quenching is performed at a much lower temperature to form a martensite. After the metal is heated, it’s quenched in a solution of salt and oil before being cooled.
  • Black tempering: As the name suggests, black tempering results in a black iron. It’s performed in the presence of inert gases where the temperatures are at least 1,740 degrees. The metal must be kept at this temperature for at least 20 hours, so it’s a time-consuming process.
  • White tempering: Speaking of time consuming, white tempering takes even longer. The metal must be held at 1,800 degrees for 60 hours. After that, the piece is removed and cooled at a rate of 50 degrees per hour. White tempering gives us malleable cast iron or porous cast iron.

Bring your pieces to J.F. Heat Treating Inc.

For the best heat treating, look no further than J.F. Heat Treating Inc. Here are a few reasons to choose us:

  • Wide array of services: There’s no reason to bring your metal to one company for hardening and another for tempering—we offer an array of metallurgical services. From aging to normalizing, we’re your go-to team for all of your metallurgy needs.
  • The best equipment: We don’t make do with outdated equipment. We only use the industry’s latest and greatest equipment to ensure our clients get the best results.
  • Decades of experience: Having the best equipment doesn’t mean much if you don’t know how to use it. J.F. Heat Treating Inc. has been in business for over 40 years, so you can trust that our specialists know what they’re doing and will deliver high-quality results.

The choice is clear the next time you need steel tempering, come to J.F. Heat Treating Inc. Contact us today to learn more about all of our services.

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