D2 steel got its start in the early part of the 20th century as part of a group of high-carbon, high-chromium cold-work tool steels. These steels were designed for industrial tooling like stamping dies, punches, and shear blades. In those environments, the goal was simple: build something that could keep cutting or shaping metal day after day without wearing out or changing shape. D2’s formula hit the sweet spot for this kind of work, offering high hardness, strong wear resistance, and good stability when heat-treated. It became widely recognized under designations like SKD11 in Japan, 1.2379 in Germany, Hitachi SLD, and Uddeholm Sverker 21.

D2 falls into a category sometimes called “semi-stainless.” With nearly 12 percent chromium, it’s just under the 13 percent mark generally used to define stainless steels. That means it resists corrosion better than simple carbon steels, but it isn’t immune to rust, especially in damp or acidic environments. For industrial use, this was more than enough. A bit of oil or cleaning kept the tooling in shape, and the trade-off for increased wear resistance was well worth it.

For decades, D2 was mainly found in factory settings. Its high wear resistance came from the large volume of carbides in the steel, and that quality made it perfect for applications where tools had to last a long time without sharpening. This same property, however, made it more difficult to machine, grind, and finish compared to simpler steels like O1 or 1095. That extra work was acceptable in tooling, but it was one reason it took longer for D2 to make its way into knife blades.

By the mid-to-late 20th century, knifemakers began to see the potential. D2 could hold an edge far longer than many steels traditionally used for knives, and it had enough toughness for heavy cutting tasks. Makers like Jimmy Lile and Bob Dozier became well known for using D2 in their knives, showing that it could excel in everything from hunting knives to everyday carry folders. The edge retention quickly became one of its most valued traits, especially for users who wanted to spend more time working and less time sharpening.

As steel technology advanced, D2 saw new variations. Powder metallurgy processes led to CPM-D2, developed by Crucible Industries, which uses powdered metal to create a finer, more uniform distribution of carbides. This improves toughness and often makes sharpening a bit easier without sacrificing the steel’s edge retention. Other innovations, like friction forging, have been used to produce D2 blades with very hard, wear-resistant edges and tougher spines, giving them a balance suited for hard use while minimizing breakage risk.

Today, D2 is found in a wide range of knives, from high-end customs to affordable production models. Its mix of long-lasting sharpness, reasonable corrosion resistance, and availability makes it a go-to choice for both manufacturers and knife enthusiasts. While newer steels with higher corrosion resistance and finer carbide structures compete for attention, D2’s track record speaks for itself. It’s a steel that started in heavy industry, proved itself in the hands of skilled knifemakers, and continues to earn its place in toolboxes, pockets, and on belts around the world.