Uranus B6 is Aperam/Industeel's proprietary name for what is otherwise known worldwide as 904L — a fully austenitic, high-alloy stainless steel built around roughly 25% nickel, 20% chromium, 4.5% molybdenum, and 1.5% copper. Unlike duplex grades, Uranus B6 has no ferrite phase at all: it is 100% austenite, and every one of those alloying elements is there to push corrosion resistance and toughness well past what standard 300-series stainless can offer. The heavy nickel and copper additions in particular give it strong resistance to reducing acids such as dilute sulfuric acid, a combination 316L struggles with.

With a PREN (Cr + 3.3×Mo) in the mid-30s, Uranus B6 sits above 316L and comfortably below the true 6-Mo superaustenitic grades, making it a workhorse alloy for sulfuric acid handling, flue-gas desulfurization equipment, pulp and paper bleaching lines, and seawater-adjacent process equipment where 316L pits or crevice-corrodes too quickly but a 6-Mo or duplex grade would be overkill on cost. Because it's fully austenitic with no ferrite to shorten the chip or share cutting loads, it behaves like a much more aggressive version of 316L at the tool edge — high work hardening, high ductility, and a strong tendency to gall and build up on cutting edges if speeds or geometry aren't matched to it.

Uranus B6 machines like a more demanding cousin of 316L rather than anything resembling a duplex grade. With no ferrite phase to interrupt the microstructure, the entire cross-section work-hardens under the cutting edge the way austenitic stainless always does — but the higher nickel, copper, and molybdenum content raises cutting forces and heat generation noticeably above standard 300-series levels. Chips tend to be long, tough, and gummy, and built-up edge is a constant risk if the tool isn't kept sharp and moving at an appropriate speed.

Because there's no ferrite to help fracture the chip the way there is in a duplex grade, chip control depends almost entirely on insert geometry and consistent feed. A sharp, positive-rake edge that shears the material cleanly outperforms a heavier, negative geometry here — the priority is minimizing the dwell time under the edge that drives work hardening, not surviving mechanical shock the way it is on duplex or superduplex grades. Coolant is essential both for heat removal and for helping evacuate the stringy chip, and rigid, low-deflection setups pay off heavily in tool life since any regeneration of the cut re-hardens material the edge has to pass through again.