Intricate components. Parts that need high precision. Knives or other tools that will need upkeep. All these products benefit from a metal that offers high machinability.
That quality is what 416 stainless steel offers, making it one of the most popular stainless steel materials available.
A decent level of corrosion resistance and costs on the lower end don’t hurt, either. One thing 416 stainless doesn’t have a great deal of is hardness. Fortunately, Heat treating it to improve that hardness is a straightforward process. But it’s important to get it right. To help you get good results, refer to this introductory guide to heat treating 416 stainless steel, with recipes.
What Is 416 Stainless Steel?
416 stainless steel is magnetic, martensitic steel, meaning that it’s composed of at least 50% iron and between 11-17% chromium.
At 85% machinability, it’s the most machinable of stainless steels. But it’s also less corrosion resistant than other austenitic grades (with 18% chromium).
- High machinability due to sulfur content, which acts as a lubricant during machining.
- Corrosion resistance for mildly corrosive environments such as air, fresh water, and some chemicals
- Moderate strength with ability to harden up to Rockwell C35 via heat treating
- Heat resistance to avoid scaling in temperatures up to 1400°F
- Moderate hot workability for forging–not to exceed 2200°F
416 stainless steel is a good fit in applications that need robust mechanical properties in not-so-severe environments and atmospheric conditions. For example, it’s not suitable for marine environments or parts that require intense cold forming or fusion welding.
- Bolts, nuts, screws, and other fasteners
- Valves and fittings
- Motor shafts, gears, and pistons
- Firearm components
- Knives and other food tools
Heat Treatments for 416 Stainless
Heat treating 416 stainless steel is similar to other stainless steel heat treating processes. It involves several steps to achieve desired mechanical and physical properties. We recommend consulting with the manufacturer on the specific recipes for your application. But here's an overview of these processes to get you started:
The annealing process helps relieve stresses in the metal, further improving machinability and formability.
Heat to 1550-1650°F and hold for a half-hour per inch of thickness. Then cool in a furnace at no more than 50°F/hour down to 1100°F. Follow with air, water, or oil cooling.
The hardened condition of 416 stainless has maximum corrosion resistance and tensile strength.
Heat to 1875-1985°F. Quench larger sections in oil or smaller sections in air.
Hardening can make metal brittle. Tempering solves this problem, improving toughness, ductility, and impact resistance.
Heat to 400-1400°F (best at the low or high end of this range) for 1-4 hours. Air cool.
Key Considerations & Best Practices
Here are some important things to keep in mind to ensure you get the right results in heat treating.
- Avoid overheating. You could reduce corrosion resistance. Carefully control the temperature at each stage of the heat treatment process.
- Quench carefully. Being too quickly or too slow can cause cracking, distortion, or other defects. Choose your quenching medium based on manufacturer recommendations.
- Mind your tempering time. Over-tempering can cause the material to lose the hardness you just gave it. Under-tempering means your steel may still be brittle.
- Control quality. Keep a close eye on the temperature and times in your recipes. Test for desired hardness with a Rockwell hardness tester.
- Be safe. Wear proper safety equipment. Choose a heat source that offers safety features, such as Hot Shot Ovens’ for heat treating with Cool-Touch Technology.
Now you should have a good handle on what it takes to heat treat 416 stainless steel. Enjoy your adventures with this versatile material. If you have questions along the way, feel free to contact the Hot Shot team!