H46 is a martensitic, roughly 12% chromium stainless steel developed for structural strength at sustained elevated temperature, typically in the 900°F to 1200°F (482°C to 649°C) range. It's essentially a niobium (columbium) and vanadium microalloyed derivative of the 410-type martensitic stainless family — small additions of vanadium, niobium/tantalum, and nitrogen refine the carbide structure and improve temper resistance, letting the alloy hold strength at temperatures where a plain 410 would start to soften. Its low coefficient of thermal expansion relative to austenitic stainless grades is a key reason it gets specified in rotating and structural components that would otherwise grow or distort excessively when heated.

Because of that temperature capability, H46 is used almost exclusively in power generation and aerospace: steam and gas turbine blading, rotating hardware, and structural parts that need creep resistance competitive with lower grades of austenitic heat-resisting steel but without the higher thermal expansion that comes with an austenitic matrix. It is supplied and machined in an annealed or lightly tempered condition and then heat treated afterward to its final strength level, so most shops encounter it in a moderate-hardness state comparable to other quenched-and-tempered 12% chromium stainless grades.

H46 machines like a moderately alloyed martensitic stainless rather than like a free-cutting or austenitic grade. The 10-14% chromium and modest molybdenum content raise cutting forces and abrasive tool wear above what you'd see in a plain carbon or low-alloy steel, while the vanadium and niobium carbonitrides that give the alloy its temper resistance also act as small, hard, abrasive particles at the cutting edge. Because there's no sulfur or free-machining addition in this chemistry, chip breaking depends entirely on insert geometry and feed selection rather than on the material fracturing on its own.

Like other martensitic stainless grades, H46 has a real tendency to work-harden if the tool rubs instead of shearing cleanly — light, hesitant cuts or a dull edge will burnish the surface and make the next pass noticeably tougher to start. Keeping a steady, adequately loaded feed and a sharp, positive-rake edge is the most effective way to avoid that spiral. Chromium-stainless alloys also conduct heat less efficiently than plain steel, so cutting temperature concentrates closer to the tool tip; a coated carbide grade with good hot hardness holds up better across a full tool life than an uncoated one.

Rigidity matters as much as tool selection here. Any deflection or chatter accelerates edge wear on an alloy that's already carrying hard carbonitride particles, and because H46 is typically used in high-value aerospace or power-generation components, dimensional consistency and surface finish carry real cost consequences if tool wear is allowed to progress unchecked mid-cut.