The steel used to make springs needs to be tough, resilient material. While you might not be making a spring in your shop anytime soon (or maybe you are?), the same qualities that make for a good spring steel also happen to be great for making strong knife blades.

Interested in using one of these metals for knife making? You’ll need to get to know the processes for heat treating spring steel so that you can optimize the hardness and other key properties.

To get you started, let’s take a closer look at the heat treatment process for the three types of spring steel most popular with today’s hobbyist knife makers.

What Is Spring Steel?

The term “spring steel” refers to a low-alloy steel with high tensile strength, excellent elasticity, durability, and resilience.

Composition

Spring steels are typically characterized by high carbon content (up to 1%), which gives them their strength and resilience.

They also often contain alloying elements such as manganese, silicon, and chromium, which can improve toughness and hardenability.

Applications

As the name suggests, spring steels are used to make a wide range of spring components for machinery and automotive applications.

In addition, spring steels are ideal for:

• Knives and other cutting tools
• Jewelry—think bangles, rings, necklaces, etc.
• Decorative metalwork like wall hangings, sculptures, or garden ornaments
• Musical instruments, including strings for guitars, harps, pianos, and more

Popular Varieties of Spring Steel for Knives

Spring steels 1095, 5160, and 9260 are all good options for knife making and other applications where strength, durability, and toughness are important. The right choice will depend on the specifics of your application.

After heat treating 1095 steel is a simple carbon steel alloy known for its hardness, toughness, and ability to hold a sharp edge. With proper heat treating you can attain hardness up to Rockwell C 58. 5160 steel is a tough metal with lower edge retention. 9260 steel is known for its flexibility, tensile strength, and resistance to impact, thanks in part to its significant silicon content.

How to Heat Treat Your Spring Steel

No matter which you use, the right firing schedule for your spring steel heat treatment process will depend on your desired hardness, the thickness of your blade or part being treated, and other factors.

Below, we get into some general heat treating guidelines for each type.

Make sure you use a furnace with precise temperature control (like a USA-made Hot Shot knife heat treating oven, for example). And always consult a materials expert to determine parameters for the best results in your application.

1095 Steel Heat Treatments

Annealing

Soften your steel and relieve stresses to avoid warping during other heat treatments.

1. Insert your workpiece into your oven.
2. Heat to 1,500 °F to 1,600 °F. Allow the metal to equalize at target temperature.
3. Soak for 10 - 15 minutes.
4. Remove from the furnace when it gains a uniform cherry-red color. Air cool.

Some experts recommend multiple cycles, repeating at progressively lower temperatures (1,500 °F, 1,350 °F) after the metal has cooled to black.

Hardening

Achieve optimal hardness for your project (up to Rockwell C 66).

1. Insert your workpiece. Heat your furnace 1,450 to 1,525 °F.
2. Soak for up to 15 minutes.
3. Quench immediately in a preheated (to ~120 °F) fast quench oil such as Parks 50.

Tempering

Reduce brittleness.

1. Return your workpiece to the furnace. Heat to 300 to 650 °F. Lower temp gives you higher hardness but less toughness. Higher temp will result in lower hardness and maximum toughness.
2. Hold for 2 hours.
3. Allow the workpiece to cool in ambient air.
4. Repeat process 1x.

5160 Steel Heat Treatments

Normalizing

Refine the microstructure of your metal.

1. Heat your workpiece in the furnace to 1,600 °F.
2. Soak for 20 minutes.
3. Allow to air cool.

Annealing

1. Heat to 1,250 °F.
2. Soak for 2 hours.

Hardening

1. Heat to 1,525 – 1,560 °F.
2. Soak for 5 to 30 minutes – the thicker the part, the longer the soak.
3. Quench immediately in a fast speed oil.

Tempering

1. Heat to 350 - 450 °F.
2. Soak for 1 hour.
3. Air cool.
4. Repeat.

9260 Steel Heat Treatments

Normalizing

1. Heat your workpiece in the furnace to 1,650 °F.
2. Soak for ~30 minutes per inch of thickness.
3. Allow to air cool.

Annealing

1. Heat to 1,400 ºF.
2. Cool at 10 ºF/hour to 1225 ºF.
3. Soak for 10 hours.
4. Air cool.

Hardening

1. Heat to 1,525 - 1,580 ºF.
2. Soak ~30 minutes per inch of thickness.
3. Quench immediately in high-speed oil.

Tempering

1. Heat to 880 - 980 ºF.
2. Soak for 1 hour.
3. Air cool.

Tips, Key Considerations & Best Practices

These different types of spring steel each present different challenges, but here are a few pointers that apply across the board.

Protect your workpiece. Reduce scaling by covering your workpiece with foil or an anti-scale coating such as ATP-641. Alternatively, an argon gas kit can help.

Don’t skip your starter steps. High-carbon spring steels are prone to cracking during quenching. Normalizing and annealing steps help you avoid these frustrations.

Quench with care. Be quick, but don’t hurry. Take your time transferring your red-hot steel to the quench oil to avoid accidents. Wear protective gear and stay safe!

Consider cryo. Some experts recommend putting spring steel through an extremely low temperature treatment. It may help further improve hardness, wear resistance, and stability. But it’s an extra step, and most research shows only marginal benefits.

Check your hardness. Since hardness is one of the primary attributes of spring steel, make sure you’re getting what you’re looking for with a calibrated Rockwell hardness tester.

Now that you have some of the fundamentals down, it’s time to spring into action and create something tough with spring steel!