Does D2 Steel Need to Be Hardened for Your Factory’s Needs?

If you’re using D2 tool steel in your factory, you might be wondering if hardening is a necessary step. Let’s get directly to the answer.

The Short Answer: Yes, D2 Steel Needs Hardening

D2 steel must be hardened for nearly all tooling applications in a factory setting. It’s designed to be used in its hardened state to achieve its well-known exceptional wear resistance and high compressive strength. Using D2 steel without hardening means it won’t deliver the performance expected for demanding jobs.

Why Hardening is Essential for D2

D2 is a high-carbon, high-chromium tool steel. These elements are vital for its performance, but only when the steel is properly heat-treated.

Unlocking D2’s Key Properties

Hardening fundamentally changes D2’s microstructure, giving it:

• Excellent Abrasion Resistance: Essential for tools that cut, stamp, or form.
• High Hardness: Allows it to maintain a sharp edge and resist deformation.
• Good Toughness (when properly tempered): Enables it to withstand operational stresses.

What Happens if D2 Isn’t Hardened?

Without hardening, D2 steel remains in a softer, annealed state. While this state is good for machining, it lacks the hardness and strength for typical cold-work applications such as:

• Blanking dies
• Cold-forming punches
• Shearing blades
• Cold extrusion tooling

Unhardened D2 in these roles would wear quickly, deform, or fail, leading to factory downtime and increased costs.

Understanding the D2 Steel Hardening Process

D2 steel hardening is a controlled thermal process, not just a single step. Here’s a brief overview:

The Critical Role of Double Tempering: For D2 steel, double tempering is strongly recommended and often considered mandatory. D2 can retain austenite after the initial quench, which is unstable and can cause dimensional changes or cracking later. The first temper conditions the initial martensite and helps transform retained austenite; the second temper treats this newly transformed martensite.

For typical working hardness (58-60 HRC), D2 is often tempered between 482-516°C (900-960°F), utilizing “secondary hardening.” Lower temperatures (around 205°C or 400°F) can be used if maximum toughness is prioritized over some wear resistance.

We have another article on P20 heat treatment. Please click on the D2 tool steel heat treatment guide.

The Bottom Line: Hardened D2 for Optimal Performance

Yes, D2 steel absolutely needs to be properly hardened and then tempered to deliver the performance your factory requires for tooling. The process of austenitizing, air quenching, and multiple tempering cycles develops D2’s valued combination of high hardness, excellent wear resistance, and sufficient toughness. Using D2 in its unhardened state for tooling will lead to poor performance and premature failure.