55NCDV6 is a nickel-chromium-molybdenum-vanadium alloy tool steel from the AFNOR system, equivalent to Wnr. 1.2711 / DIN 54NiCrMoV6. It belongs to the same family of high-strength, high-toughness tool and mold steels as the better-known P20 group, but carries a heavier alloy load — nickel and chromium build hardenability and core toughness, molybdenum resists temper embrittlement in thick sections, and a small vanadium addition refines grain size and adds fine, wear-resistant carbides. The result is a steel that hardens deeply and evenly even in large blocks, which is exactly why it shows up in tooling that has to stay tough and dimensionally stable at heavy cross-sections.

55NCDV6 is supplied and machined in the annealed condition and then hardened and tempered afterward, typically reaching the mid-40s to mid-50s HRC in finished service, well above what a pre-hardened mold steel like P20 delivers as-supplied. That makes it a common choice for large injection and die-casting mold bases and cavity blocks, forging and trim dies, and other high-stress tooling where both deep hardenability and resistance to shock loading during service matter more than out-of-the-box hardness.

In its annealed delivery condition (roughly 229–255 HB), 55NCDV6 machines similarly to other nickel-chromium-molybdenum tool steels — moderate cutting forces, predictable chip formation, and reasonable tool life with a properly matched coated carbide grade. The vanadium addition is small but noticeable: its fine carbides add a bit more abrasive wear on the cutting edge than a plain Cr-Mo grade like 4140, so edge wear tends to be the limiting factor more than heat generation or built-up edge.

Because this steel is almost always roughed and finish-machined before hardening, shops typically remove the bulk of the stock in the annealed state and leave grinding stock for after heat treatment, since post-hardening the material climbs into tool-steel territory (45–55 HRC) where machining shifts to grinding rather than turning or milling. Rigid setups and sharp, wear-resistant tooling in the annealed stage help minimize the stock that has to be removed by grinding later.

Chip control is generally favorable in the annealed condition, with continuous-to-segmented chips that break well with standard chipbreaker geometries. A coated carbide grade with good abrasion resistance, combined with steady feed rates that avoid dwelling or rubbing, gets the most consistent results and the longest tool life on this alloy.