446 is a high-chromium ferritic stainless steel built around roughly 25% chromium with very low carbon and no significant nickel addition. Without nickel to stabilize an austenitic microstructure, 446 solidifies and remains ferritic (body-centered-cubic) at room temperature, which makes it magnetic and, like other ferritic grades, not hardenable by heat treatment — any strength gain has to come from cold working.

What sets 446 apart from more common ferritic grades like 430 is chromium content well above the 16-18% typical of that family. That extra chromium delivers outstanding resistance to scaling and oxidation at high temperatures along with solid general corrosion resistance, but it comes at some cost to toughness — very high-chromium ferritic alloys are more prone to brittleness and grain growth when held at elevated temperature for extended periods. Low carbon keeps the base alloy comparatively soft and ductile for its chromium level, which helps formability and weldability but also means it forms long, tough chips rather than breaking cleanly under a cutting tool.

446 is specified almost exclusively for high-temperature service rather than aqueous corrosion resistance — furnace components, heat-treating fixtures, combustion hardware, and other parts that need to resist scale in hot, oxidizing atmospheres. Shops running it should expect chip control, not abrasive tool wear, to be the main machining challenge.

446's machining behavior is shaped less by hardness and more by ductility and heat management. Being ferritic — non-heat-treatable and essentially free of austenite — it doesn't work-harden nearly as aggressively as 304 or 316 under the cutting edge, which is a real advantage over the 300-series grades. The trade-off is that its low carbon content leaves it soft and tough, so instead of fighting a hardened skin, the operator is fighting long, stringy chips that resist breaking and want to wrap around the tool and workpiece.

Because chip control, rather than abrasive wear, is the main obstacle, insert selection should prioritize a sharp cutting edge with a chipbreaker geometry designed to curl and fracture a ductile chip. A positive rake and light honing keep cutting forces low and encourage clean shear rather than tearing, which helps chip formation stay controlled. Feed rate plays an outsized role here — feeding too light lets the material deform and smear instead of shearing cleanly, which worsens both chip control and surface finish.

Thermal conductivity in ferritic stainless is somewhat better than in austenitic grades, so heat dissipates a little more readily into the chip, but it's still well below carbon steel, and coolant remains important for tool life and dimensional stability on thin sections. Because 446's low carbon and high toughness make it behave much like the far more common 304 and 316 grades under the tool, insert families developed for austenitic stainless generally perform well on 446, provided the chipbreaker geometry is tuned for a tough, ductile chip rather than an abrasive one.