How to Heat Treat 440 Stainless

440 stainless is a common, modern knife steel.

The 440 series of stainless steels are a good choice for knife-making because they have reasonable resistance to stains and corrosion while retaining the hardness and toughness of carbon steels. The 440A, 440B and 440C steels are too difficult to form in their hardened state, so you will need to anneal the blank before you can form the blade. Fortunately, you do not have to quench 440 stainless when you heat treat it; it reaches full hardness of 55 to 57 on the Rockwell C scale with simple air cooling.

Things You'll Need

• Heat treating oven
• Tongs

Instructions

1. Place the blank, the unfinished piece that will become your knife blade, in the heat treating oven and heat slowly to between 1,550 and 1,650 degrees Fahrenheit to anneal it. This process removes any prior heat treatment and makes the metal soft enough to grind or otherwise shape. Do not heat faster than 400 degrees per hour. Hold the final temperature for one hour, then gradually reduce the temperature to 1,000 degrees Fahrenheit. Do not cool faster than 50 degrees per hour. Remove the blank from the oven and allow it to air cool in a draft-free area at normal room temperature. At this point, you may machine or grind the blank to its finished shape.

2. Harden the blade. Place it into the oven and heat slowly to between 1,400 and 1,450 degrees Fahrenheit. Do not allow the temperature to increase more than 400 degrees per hour. Hold the blade at 1,400 to 1,450 degrees for one hour and then heat the blade as quickly as possible to between 1,850 and 1,950 degrees Fahrenheit. Hold this temperature for 30 minutes.

3. Remove the blade from the oven and allow it to completely cool in still, room-temperature air.

4. As soon as the blade is cool, place it in the oven and heat it to 300 degrees Fahrenheit. Hold it at that temperature for one hour.

5. Remove the blade from the oven and allow it to cool completely in still, room temperature air.

Tips & Warnings

• Always use tongs, heat-resistant gloves and eye protection when working with hot metal.

References

• Latrobe Specialty Steel Company: LSS (tm) 440C Stainless Knife Steel (pdf)