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.
80CrV2 vs. Carbon Steel
80CrV2 is called “carbon steel with steroids” because it has Cr and V alloying that helps to achieve the maximal hardness and toughness. In theory, plain carbon steel can achieve the same, but in practise, alloying elements are needed.
Cr improves hardenability and enables reliable oil quenching, which prevents warping and cracking. Despite 0.8% carbon, due to Cr, some carbides remain undissolved during austenitization (steel is slightly hypereutectoid). Instead of lamellar pearlite, 80CrV2 has a tendency to form small carbide particles (divorced eutectoid transformation, DET). When hardened, these carbides at ferrite grain boundaries nucleate austenite grains more efficiently than pearlite, resulting in a smaller initial austenite grain size. V forms extremely small VC carbides that “nail” austenite grain boundaries in their place, so grain growth does not occur. For these reasons, 80CrV2 usually has a smaller grain size than carbon steel.
In hardened steel, if the austenite grain size is small enough, a brittle fracture along former austenite grain boundaries does not occurs, and maximum toughness can be achieved. Yes, small enough, not infinitely small, austenite grain size is needed for maximum toughness. Plain carbon steel does not always have it, while 80CrV2 nearly always has it.
Forging
When forging, heat the specimen to the 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. The high forging temperature dissolves all carbides and liberates alloying elements, including V, which is normally in VC carbides. Hardenability increases and forgings may get some bainite and martensite in structure when air-cooled. This microstructure is difficult to file, grind or drill, and untempered martensite may crack during prolonged waiting (delayed cracking). You can remove martensite and bainite by heating the forging from room temperature to non-magnetic and cooling in the air. It 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 forge hardening because the carbides dissolve too slowly, but it is suitable for furnace hardening, which takes longer. Forging refines the carbides, and thus, a forged material hardens easily in a 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 waiting may result in cracking of untempered martensite. The best combination of hardness and toughness can be attained when a blade is tempered at 160-180°C for 1-2 h. It produces a hardness of 62-63 HRC.