452 is a specialty stainless designation used in the valve and elevated-temperature service segment of the market. It belongs to the same general family as well-documented chromium-molybdenum martensitic valve and turbine steels — grades like AISI 422 (X20CrMoWV12-1) and the older "Greek Ascoloy" (Type 418) — which combine a chromium-based martensitic matrix with molybdenum, and in some variants vanadium or tungsten, to hold strength and hardness at service temperatures well above what a standard 410/420-type stainless can tolerate. That family of alloys is used for exhaust and steam valve components, turbine blading and fasteners, and other parts that see both mechanical load and sustained heat.

One note on sourcing this page: unlike AISI 440A/440C or the Custom 455 designation, "452" is not a number that maps to a widely published primary standard (ASTM, SAE/AISI, DIN/EN, or UNS) that could be independently cross-checked against an authoritative source. Some third-party machining reference sites carry a "Stainless Steel 452" data sheet, but it lists an unusual assay (27% Cr with 1.5% C) with no verifiable equivalent-standard cross-references attached to it — a combination that doesn't correspond to any recognized martensitic or ferritic stainless standard and looks like a database placeholder rather than certified mill data. Rather than repeat that figure, this page describes the alloy family 452 belongs to and its expected machining behavior. If you are machining a specific heat of 452 to a customer print, confirm the certified chemistry and hardness against that print or mill certificate rather than a generic reference table.

No cross-reference to a Wnr., DIN/EN, or UNS number could be independently verified for this specific designation. If your print references a specific specification (an AMS, ASTM, or house specification number), use that document's chemistry and heat-treat condition rather than a generic 400-series stainless data sheet.

A certified composition table is not published here because it could not be verified against a primary standard (see note above). As a family, Cr-Mo(-V) martensitic valve and turbine steels typically run in the range of 11-13% chromium, 0.15-0.30% carbon, roughly 0.75-1.5% molybdenum, and small additions of vanadium and/or tungsten (where present) for elevated-temperature strength — figures given here for general orientation only, not as an assay for this designation.

Chromium-molybdenum martensitic valve and turbine steels machine similarly to other air-hardening martensitic stainless grades: moderate-to-severe work hardening if the tool rubs instead of shearing cleanly, low thermal conductivity that keeps heat concentrated at the cutting edge, and a matrix that is usually supplied and heat treated to a moderate hardness (commonly in the 25-35 HRC range for valve and turbine service) rather than machined dead soft. The molybdenum and vanadium/tungsten additions that give this family its elevated-temperature strength also raise abrasive wear on the tool compared to a plain 410/420 stainless, so expect tool life to fall between a standard martensitic stainless and a hot-work tool steel.

Sharp, positive-rake carbide with steady feed to stay ahead of the work-hardened layer, rigid workholding, and generous coolant for both lubrication and heat removal are the standard approach. Where the part will see final hardening after machining, remove as much stock as practical before heat treatment, since cutting forces and tool wear increase once the part reaches its service hardness.

Starting-point figures for the Cr-Mo martensitic valve/turbine steel family in a moderately hardened, pre-service condition. Confirm against actual hardness and heat-treat condition of the specific part.

Turning

Parting / Grooving

Milling