17-4 PH stainless steel
Selecting UNS S17400 by product form and heat-treated condition, with bounded properties, corrosion considerations and fabrication controls.
Tags: materials, stainless-steel, precipitation-hardening
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Identity and purchasing basis
ATI typically supplies 17-4 PH plate, sheet and strip solution annealed, at 38 HRC maximum. Its H900 flat-product figures are 1,310 MPa minimum tensile and 1,172 MPa minimum yield. If machining precedes aging, record delivery and final conditions separately and verify each against its applicable requirement. ATI delivery and H900 tables
17-4 PH, also identified as Type 630 and UNS S17400, is a martensitic precipitation-hardening stainless steel. Carpenter markets its product as Custom 630 and separately offers a modified Project 70+ version for improved machinability. Preserve producer and product identity rather than treating a shared generic designation as proof of identical processing or certification. Carpenter Custom 630 product identity
ATI's product page lists chromium 15.0–17.5%, nickel 3.0–5.0%, copper 3.0–5.0% and carbon 0.07% maximum, among other controlled elements. This selected composition is a producer reference, not the complete acceptance requirement for every form or specification. ATI 17-4 chemistry
Product standards and delivery condition
ASTM A693-24 covers precipitation-hardening stainless steel plate, sheet and strip. Its scope explains that suitable low-temperature treatments develop mechanical properties. It is a flat-product specification, not universal acceptance evidence for bar, a casting or an additively manufactured component. ASTM A693-24 scope
ATI states that its flat products are typically supplied solution annealed, with 38 HRC maximum hardness, while the displayed strength entries are for H900. Read the condition attached to the property rather than assigning an aged value to incoming stock. ATI delivery-condition note
Keep incoming and final condition in separate fields when machining precedes aging. Retain heat or lot traceability through cutting, and record subsequent welding, heating or deformation. A mill certificate describes its stated delivered product; it does not establish the finished component's complete process history.
Bounded mechanical-property examples
ATI publishes the following H900 flat-product entries for its plate, sheet and strip offerings, alongside ASTM A693, ASME SA-693 and AMS 5604. Confirm dimension, sampling and test requirements in the governing purchase specification before using the website summary for acceptance. ATI H900 product tables
| Quantity | Published H900 entry |
|---|---|
| Tensile strength, minimum | 1,310 MPa |
| Yield strength, minimum | 1,172 MPa |
| Elongation, minimum | 5% |
| Hardness | 40–47 HRC |
These are not solution-annealed values or universal design allowables. They do not establish fatigue life, fracture toughness, allowable pressure or the strength of a particular notch, weld or fastener connection.
Carpenter separately reports typical room-temperature Custom 630 results: H900, 1,262 MPa 0.2% yield strength and 1,365 MPa tensile strength; H1150, 869 MPa and 993 MPa, respectively. These typical entries illustrate condition dependence and must not be merged with ATI's minimum-value table into a new specification. Carpenter typical mechanical properties
For a comparison, identify whether each number is typical, a specification minimum or a delivered test result. Match temperature, direction, section, condition and specimen basis. Obtain missing details before assuming that values from two producers describe equivalent acceptance or design inputs.
Aging and dimensional change
Carpenter describes H900 aging of solution-treated stock at 900°F (482°C) for one hour, followed by air cooling. Its H1150 route uses 1150°F (621°C) for four hours, followed by air cooling; H1150M is a separate multistep condition. Its solution-treatment guidance warns against using Condition A without age hardening because of stress-corrosion-cracking susceptibility. Carpenter heat-treatment section
These descriptions identify source conditions rather than supply a qualified furnace procedure. Establish the required cycle, starting state, load arrangement, cooling and acceptance for the actual part. Do not infer an H condition from a hardness reading alone or shorten its designation on a drawing.
Carpenter gives approximately 0.0004–0.0006 length/length contraction from Condition A to H900. For an unconstrained nominal 100 mm feature, that corresponds to 0.04–0.06 mm, by direct multiplication. This is a preliminary allowance calculation, not a dimensional guarantee for a complex part. Carpenter hardening deformation
Set machining allowance and final inspection around representative processing trials. Include fits, sealing faces, straightness and datum relationships; a bulk length estimate cannot predict every local distortion or tolerance change.
Corrosion and service qualification
Carpenter links improved stress-corrosion-cracking resistance to hardening at 1025°F (552°C) and above. Its qualitative corrosion chart nevertheless rates seawater and sour oil/gas as restricted and recommends testing. Hardness or the word “stainless” cannot establish suitability for an unspecified exposure. Carpenter corrosion guidance
Document fluid chemistry, concentration, contaminants, temperature, aeration, deposits, crevices and sustained stress. Include cleaning chemicals, shutdown conditions and excursions. Obtain evidence relevant to the final condition and joint; a corrosion result for an open coupon cannot settle every assembled interface.
For code-governed or sour service, determine the actual current material, condition, hardness and construction requirements. A historical producer reference or an application list does not qualify an individual finished part. Assess strength, toughness, corrosion and life together rather than treating the highest tensile number as the preferred condition.
Fabrication and release record
Plan machining, forming, joining and thermal operations around the specified starting and final states. Qualify tooling and parameters on the actual stock and geometry. Keep generic alloy guidance separate from the approved workshop procedure and inspection plan.
For a welded assembly, define base-material condition, joint preparation, filler, heat input, thermal treatment and acceptance. Confirm the properties required in weld and heat-affected regions. For another manufacturing route, including additive manufacture, obtain route-specific evidence rather than transferring wrought flat-product values.
At release, retain the certificate, ordered specification, drawing, final condition, processing records and inspection results together. Resolve substitutions against that complete record. Establish relevant fatigue, leak, dimensional or corrosion acceptance for the actual component and its service.
Source applicability
ASTM's publisher identifies A693-24. ATI's live product page and Carpenter's inspected Custom 630 sheet do not provide a clear technical revision date used here. Obtain current controlled documentation for contractual decisions; website copyright or upload dates do not establish technical editions. Review date: 2026-11-01, America/Los_Angeles.