M2 high-speed steel

Identity and purchase specification

For BÖHLER S600, the treatment section gives 1100–1210°C austenitizing and an 80-second hold after complete heating, maximum 150 seconds. The separate 180-second hold at 1210°C belongs to the CCT experiment. Follow the treatment guidance for the actual stock and retain the CCT hold as a test condition. BÖHLER S600 treatment and CCT data

M2 is a molybdenum-tungsten high-speed tool steel identified as UNS T11302. Carpenter's nominal analysis gives carbon 0.82%, chromium 4.25%, molybdenum 5%, tungsten 6.25% and vanadium 1.8%, with iron balance and other elements. Nominal producer chemistry is not a complete specification acceptance table. Carpenter M2 product page

ASTM's official scope identifies A600-92a(2024) as a high-speed tool-steel specification covering M2 among its molybdenum types. It covers specified annealed hot-rolled and cold-finished forms used primarily to fabricate tools. That material specification does not qualify a finished drill, cutter or die for a particular operation. ASTM A600 official scope

BÖHLER S600 identifies 1.3343 / HS6-5-2C, air-melted or air-melted-plus-ESR routes, and a long-product data restriction despite listing plate. Preserve that scope when using its data. BÖHLER S600

Specify exact grade or producer product, standard edition, stock form, dimensions, delivery condition, surface allowance and inspection documents. Preserve heat/lot identity through cutting and thermal processing. A label saying only “HSS” does not establish M2 chemistry, and an M2 certificate does not establish a tool's coating, edge geometry or final hardness.

Application and failure mechanism

Universal Stainless describes M2 primarily for cutting-tool applications and separately offers plate in a producer-defined dimensional range. Availability of a plate product does not make a long-product heat-treatment dataset a plate guarantee. Universal Stainless M2

For a cutter, identify the work material, cutting mode, interruptions, rigidity, cooling, edge geometry and acceptable wear criterion. Separate abrasive wear, adhesion, edge chipping, gross fracture and thermal softening. A harder tool may resist one mechanism while performing worse against another. Choose the tool system and process together; the grade name supplies neither a universal cutting speed nor a guaranteed service interval.

Supplied condition is not finished-tool hardness

S600 lists annealed delivery at ≤280 HB, tensile strength ≤950 MPa, and separately hardened-and-tempered bars, BHT, at ≥62 HRC. BÖHLER delivery conditions

Specify final hardness and test location, plus any decarburization, retained austenite, carbide distribution or core uniformity requirements.

Carpenter's technical bulletin labels its mechanical information typical/average and describes hot-hardness behavior using different prior tempering conditions. A room-temperature hardness reading and hardness measured while hot answer different questions. Carpenter M2 technical bulletin

Heat treatment: preserve timing and specimen basis

For S600, BÖHLER gives 1100–1210°C austenitizing, holding 80 seconds after complete heating, maximum 150 seconds, followed by the listed quench choices. Its tempering section recommends 550–570°C, at least two hours and three cycles with cooling to room temperature. The tempering chart identifies vacuum, 3 × 2 hours and a 25 mm square specimen. These are named-product reference conditions, not a cycle for arbitrary stock. BÖHLER thermal guidance and chart footer

The same sheet's CCT diagram lists a 180-second hold at 1210°C. Treat a diagram's experimental basis separately from the treatment section's stated maximum; do not merge them into a new shop instruction. BÖHLER CCT basis

Carpenter's historical M2 bulletin gives a different furnace-hardening range, 1177–1232°C, and warns of decarburization during thermal processing. It discusses multiple tempers with intermediate cooling. Those instructions belong to that product and source edition, not an averaged combination with S600. Carpenter heat-treatment guidance

Finishing, regrinding and repair

Plan rough machining, stress relief where needed, heat treatment and final grinding as a sequence. Establish allowable stock removal, final dimensions and edge/surface acceptance before processing. Inspect for distortion and surface damage at the stage where correction remains possible. A dimensionally correct tool can still have an unacceptable working surface.

Carpenter says its machining tables are guidance for initial setup and require adjustment for each job. Those stock-machining data should not be confused with speeds for using the finished M2 cutter on another material. Carpenter machinability scope

For regrinding, specify the recovered geometry, surface condition and any recoating requirement. Count accepted output after each regrind separately when estimating tool economics. For repair welding, EDM or a later coating heat cycle, obtain product-specific processing guidance and verify the affected tool rather than assuming that its original certificate still describes the local condition.

Bounded mass estimate

Carpenter lists density 0.294 lb/in³. For an ideal 0.5 in diameter, 6 in long solid blank, original arithmetic gives:

V = π × 0.5² / 4 × 6 = 1.1781 in³

m = 1.1781 × 0.294 ≈ 0.3464 lb.

This excludes tolerances, flute removal, holes and coatings. It supports an initial stock estimate, not a finished-tool mass or acceptance test. Carpenter physical properties

Source editions and related reference

BÖHLER's inspected sheet prints S600 EN_GB – 09.2026. Carpenter's bulletin prints Edition Date 11/01/1988 and ©2020; the copyright is not evidence of a new technical edition. ASTM identifies A600-92a(2024), with its record updated 14 March 2024. No separate technical revision date was verified for the producer webpages. Confirm current contractual requirements independently of this draft's review date.

Grades, tempers and conditions