Machining 101: What Work Hardening Is and How to Avoid It

Work hardening is a process that often occurs during metal machining. If you’re a machinist, you’ve probably encountered either the process’s term or result in your work. Though “hardening” might seem like a good thing when working with metal, that is not always the case. Below, we review what work hardening is and how to avoid it in your machining projects.

What Is Work Hardening?

Work hardening is a process where metal becomes harder and stronger after being subjected to mechanical stress. It often occurs because of bending, shaping, cutting, and other machining processes. Stainless steel, high-temperature alloys, and titanium are particularly prone to work hardening.

Although this hardening increases the metal’s durability, it also makes the material more resistant to cutting, drilling, or further shaping. This is challenging for machinists because it makes working with metals more difficult and potentially lowers the quality of the results.

Common Causes of Work Hardening

Understanding why work hardening happens is the first step toward preventing it. The main causes include the following:

• Incorrect machining speeds and feeds: Using inappropriate cutting speeds or feed rates can increase friction and mechanical stress, which lead to work hardening.
• Dull or worn tools: Tools that aren’t sharp fail to cut efficiently, which generates more heat and pressure on the material, making it more likely to harden.
• Lack of proper cooling: Excessive heat buildup during machining accelerates work hardening.
• Interrupted cutting: Operations that involve starting and stopping can increase stress on the metal, leading to hardening.

How To Avoid Work Hardening

Now you know what work hardening is and what causes it. Below, find tips on how to avoid it in your machining projects.

Optimize Speeds and Feeds

Adjust your cutting speed and feed rate to minimize the mechanical stress on the metal.

Use the Right Tools

Use high-quality, sharp cutting tools, especially ones made specifically for the type of metal you’re machining. Carbide tools or inserts are often a good choice for metals prone to work hardening.

Apply Proper Cooling

By decreasing friction, minimizing tool wear, and preventing overheating, cutting fluids have a central role in machining that naturally lowers the risk of work hardening. Just make sure you’re using the right cutting fluids for your material and operation.

Avoid Interrupted Cuts

Try to employ continuous cutting operations whenever possible. Reducing start-and-stop motions decreases the chance of creating stress points on the material.

Work hardening can make machining operations challenging, but with the right tools, techniques, and awareness, you can avoid it. By optimizing your processes, you’ll extend your tool life, achieve better surface finishes, and reduce waste.