For all kinds of steel products—knives, hand tools, automotive parts, etc.—tempering is an essential step after hardening via heat treating.
Tempering happens at a lower temperature than other heat treatments. So you might be wondering whether you can use your home kitchen oven for tempering instead of investing in an actual heat treat oven. Let’s dig into this issue and see whether it makes sense for you.
Why Tempering Matters
Hardening steel puts a lot of stress on the metal. It may come out being too brittle for many applications.
Nobody wants a knife with a cutting edge that chips or shatters. Tempering helps fix the post-hardening brittleness and increase toughness. It makes your steel products more durable.
Basics of Steel Tempering
Tempering steel follows steps similar to other steel heat treating: Heat the part up to a certain temperature. Hold it there for a specified time. Then, allow it to cool.
Notes on Target Tempering Temperature
In the case of tempering, you heat the steel to a lower temperature than hardening, annealing, etc. The target tempering temp can range from 300 °F up to 950 °F.
You can achieve that low end easily with your kitchen oven. What about the middle to high end of the critical temperature range in the same oven? Not so much.
So what temperature do you need? The right target and soak time depend on your type of steel as well as your desired properties. Tempering reduces the hardness of steel. So, if you want to keep your steel as hard as possible, use the low end of the temp range. Be sure to verify the final hardness with a hardness tester.
Want max toughness and don’t mind sacrificing a bit of hardness? Crank up the temperature.
Tempering Recipes for Different Types of Steel
Let’s take a look at a few sample processes for tempering steel. By the way, please note that the following are broad guidelines. You should consult a materials expert or your steel supplier on your optimal tempering specs.
- Heat to one of the following ranges:
- For the highest hardness (such as for cutting tools), use 300-350°F (149-177°C) for a hardness of Rockwell C 62 - 64.
- To split the difference between hardness and toughness, go with 500 - 550°F for Rockwell C 58 - 60.
- Hold for two hours, with an additional hour for every inch of thickness over 2 inches.
- Remove from the oven and air cool.
It’s possible to go higher with toughness for D2 steel by raising the temperature to 950 °F and doing a double temper (one at the highest temperature, then another at a lower temp).
But you can’t pull this off since you can’t get a conventional oven hot enough.
- Heat to 300 to 650 °F. The lower tempering temp gives you higher hardness but less toughness. The higher temp will result in lower hardness and maximum toughness.
- Hold for 2 hours.
- Allow the workpiece to cool in ambient air.
- Repeat the process once to lock in the advantages.
O1 Tool Steel
- For most applications, heat to 400 - 450 °F. For knives and other cutting tools, heat to the lower end of the temperature range—300 - 375 ºF.
- Hold for 2 hours (plus 1 hour per inch of thickness beyond 2 inches).
- Remove from the oven and allow it to air cool to room temperature.
Interested in recipes specifically for stainless steel? Check out our guide to tempering stainless steel in a conventional oven.
Key Considerations of Kitchen Oven Steel Tempering
OK, so we’ve established that you can accommodate some—but not all—of your steel tempering needs in your home oven.
The other key challenge is precision.
Kitchen oven thermometers are often unreliable. And if you do any cooking or baking in your oven, you may have discovered that it doesn’t heat things consistently. A convection fan can help, but not only somewhat.
A Look at Your Other Tempering Options
You could also try rigging a toaster oven. The small size and close proximity to the heating element make it possible to reach the lower end of tempering ranges more quickly.
Cover it with insulation to help contain the heat. Put a reliable thermometer in there. But as you can probably guess, achieving the correct temperature without a heat treat oven isn’t easy with this option.
If you really want to do steel tempering at home, there’s one more option: get a dedicated oven for tempering.
Hot Shot Ovens for heat treating, for example, are built to maintain critical temps for long periods. Our heat treat ovens can get a lot hotter than your kitchen oven. But they’re insulated with Cool-Touch technology to protect you and your home.
Our Verdict on Tempering Steel in Your Home Oven
Doing your own steel tempering is a worthy pursuit. Heat treat ovens often have long lead times. And sending out the work adds cost to every project.
You can save money and take pride in tempering the project yourself.
But here’s the thing. Experts advise tempering promptly after hardening. And you simply can’t do hardening in your kitchen oven.
So, while there’s an up-front investment with a dedicated home heat treat oven, it pays off in more reliable results. And the more steel heat treating you do with it, the faster your return on investment.
Ready to give it a try? Contact our experts for help getting started.