At the beginning of the 2000s, I introduced 80CrV2 to Finland’s leading knife blade producer, Laurin Metalli. Its adoption was a success. We believe that our decision had a significant impact on its explosive growth in popularity. I have a special affinity for this steel grade. I use it in my own blades and I want as many bladesmith as possible to succeed with it. Here are some of my forging and heat treatment instructions for blade smiths.
80CrV2 vs. Carbon Steel
80CrV2 is called “carbon steel with steroids” because the addition of Cr and V alloying elements helps achieve the maximum hardness and toughness. In theory, plain carbon steel can achieve the same results, but in practice, alloying elements are needed to improve hardenability and control grain size. A good hardenability enables reliable oil quenching, which prevents warping and cracking typical for water quenching. A small grain size is essential for a good toughness. If the austenite grain size remains below a critical value, a hardened steel does not fracture in a brittle manner along former austenite grain boundaries, and the steel achieves maximum toughness. Plain carbon steel does not always have a small enough austenite grain size, while 80CrV2 nearly always has it. 80CrV2 attains a smaller grain size than carbon steel because Cr decreases the austenite initial grain size while V prevents grain growth.
Forging
When forging, heat the specimen to light yellow heat (1200°C) and hammer as long as a red heat is visible (600°C). Slightly exceeding these limits does not necessarily cause any harm (burn or crack). A tricky feature of 80CrV2 is that forgings may harden when cooled. The high forging temperature dissolves all carbides, liberating Cr and V. This increases hardenability, and forgings may get some bainite and martensite despite slow air cooling. This structure is difficult to file, grind, or drill, and untempered martensite may crack during waiting (delayed cracking).
You can remove martensite and bainite by heating the forging from room temperature to non-magnetic, but not higher, and cooling in the air. At low austenitization temperatures, some Cr-containing cementite and all VC carbides remain undissolved, and air cooling produces a soft structure and small grain size, which is a good starting condition for hardening.
Hardening
80CrV2 steel plates are usually sold in a soft annealed condition. Industrial soft annealing takes several hours, so the carbides have plenty of time to grow to relatively large sizes. The soft annealed state is not suitable for fast hardening in blacksmith forge because the carbides dissolve too slowly, but it is suitable for furnace hardening, which takes longer. High forging temperature dissolves large carbides and they reborn small, so the forged steel can easily be hardened in forge.
Like high carbon steels, 80CrV2 hardens when quenched from the non-magnetic temperature. However, due to Cr alloying, 80CrV2 needs a bit higher hardening temperature to attain the maximum hardness. So, after the disappearance of magnetism, continue heating until you notice a change in the heat colour. The target temperature is about 840°C.
Quench in oil because water results in cracking. Hot canola oil (about 70°C) works well. As-quenched hardness is 65-66 HRC.
Tempering
Temper instantly when a blade is cooled down to room temperature because too long waiting may result in cracking of untempered martensite. The best combination of hardness and toughness can be attained when a blade is tempered at 170-180°C for 1-2 h. It produces a hardness of 62-63 HRC.