The Difference Between the Four Types of Steel Heat Treating

Heat is an extraordinary thing. In fact, when you know how to control heat, you can change and manipulate materials to your whim—even steel, one of the hardest materials known to man.

But how you go about steel heat treatment in Gastonia, NC depends largely upon what your goal is. Read on for more information about the four different types of steel heat treating—hardening, tempering, annealing, and normalizing—and the differences between them.


The goal of hardening is just what the name suggests: it’s meant to make the steel harder, or stronger. This is accomplished by first putting the steel through a slow heating process, then soaking it until it has reached a certain temperature. Finally, you submerge the steel into some sort of liquid—usually oil or water—to cool it down quickly and finish the hardening process.

Unlike other types of heat treating in Gastonia, NC, hardening can run the risk of making your steel more brittle if you don’t do it properly. This risk can be mitigated by tempering the steel after hardening it—keep reading for more info on that process!


As mentioned above, steel that’s been hardened can often turn out a little on the brittle side—and sometimes it can even get too hard. Fortunately, tempering can help ease the stress you’ve put on the steel during the hardening treatment.

Here’s how tempering works. First, you heat the steel to a specific temperature that is cooler than the temperature it was hardened at. Then you keep the steel there for a set length of time, and finally cool the steel in open air.


Annealing is essentially the opposite of hardening: instead of trying to make the steel stronger and more rigid, you’re trying to make it softer and more pliable.

When annealing steel, you start the same way other types of steel heat treatments begin. Slowly bring the metal to a specific temperature. After soaking it at this temperature for a while, you allow it to organically cool by turning the furnace off and leaving the metal in until it cools down. How long you allow it to cool depends on the type of metal you’re using, and what the metal is ultimately intended to be used for.


Normalizing is very similar to annealing—in fact, its goals and processes are virtually the same. With both steel heat treatments, the aim is to remove stress from the metal and make it less hard.

But here’s where normalizing differs from annealing: normalized steel retains more strength than annealed steel. Furthermore, normalized steel cools in open air after being removed from the furnace, unlike annealed steel, which will stay in the furnace while cooling.

Know your goals

Still feeling confused about which type of steel heat treatment is best? Well, it all really depends on your goals—and keep in mind that more than one type of treatment can be used on the same piece of steel.

Whatever type of heat treating you need, the team at J.F. Heat Treating Inc. is here to get the job done for you. Our team is experienced in all four types of steel heat treatment in Gastonia, NC—hardening, tempering, annealing and normalizing—and we take care to ensure consistent, high-quality results. Reach out to learn more.

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