17-4PH properties
A martensitic precipitation-hardening stainless with about 17 % chromium, 4 % each of nickel and copper, and niobium. It's machined soft, then hardened by a single low-temperature ageing cycle that barely distorts the part.
- TypeMartensitic precipitation-hardening stainless. Magnetic in every condition
- StandardsJIS G4303 SUS630 · ASTM A564 UNS S17400 · EN 1.4542 · GB 05Cr17Ni4Cu4Nb
- Density7.75 g/cm³
- Condition ASolution annealed, as supplied. Roughly 30–33 HRC, and this is the condition we machine in
- H900Aged at 482 °C. Typically 40–44 HRC and around 1310 MPa tensile. The strongest of the common conditions
- H1025Aged at 552 °C. Typically 35–38 HRC, with better toughness than H900
- H1075Aged at 579 °C. Typically 32–36 HRC and around 1000 MPa tensile. Toughest of the three
- CorrosionBetter than 410 and 420 martensitic stainless, below 304 and well below 316L. Not a marine grade
- AgeingH900, H1025 or H1075 as the drawing names. Every batch checked on our Mitutoyo QMH 14BX before it ships
- CertificateMill test certificate to EN 10204 3.1 on request
H900 and H1075 are different materials in practice. They start from the same bar and end up ten points of hardness and 300 MPa apart. A drawing that says "17-4PH" with no condition is incomplete, and we ask for the condition before quoting.
17-4PH compared with related grades
| Grade | JIS (Japan) | US (ASTM / AISI / UNS) | GB/T (China) | EN / DIN (Europe) | Cross-reference |
|---|---|---|---|---|---|
| 17-4PH the grade itself | SUS630 (JIS G4303) | 17-4PH · UNS S17400 · ASTM A564 630 | 05Cr17Ni4Cu4Nb | X5CrNiCuNb16-4 · EN 1.4542 | Standard equivalent |
| 15-5PH tougher, more ductile | SUS XM-12 | 15-5PH · UNS S15500 · ASTM A564 XM-12 | 05Cr15Ni5Cu4Nb | X5CrNiCuNb16-4 variant · EN 1.4545 | Check the MTC |
| SUS 420J2 hardenable, cheaper, less corrosion resistant | SUS420J2 | 420 · UNS S42000 | 30Cr13 | X30Cr13 · EN 1.4028 | Standard equivalent |
| SUS 316L corrosion, no hardness | SUS316L | 316L · UNS S31603 | 022Cr17Ni12Mo2 | X2CrNiMo17-12-2 · EN 1.4404 | Standard equivalent |
Designations taken from JIS G4303, ASTM A564, GB/T 20878 and EN 10088-3. 15-5PH is listed because US drawings often name it where the part is loaded across the grain. It's a separate alloy with lower delta-ferrite content (it's not a condition of 17-4PH). Last reviewed 13 September 2026.
Specify the grade and aging condition
H900 for maximum strength
Valve components, shafts, pump parts and fixtures where the part is loaded and space is tight. Roughly 40–44 HRC and about 1310 MPa tensile. The cost is lower toughness and lower resistance to stress-corrosion cracking.
H1075 for toughness
Around 32–36 HRC with much better impact behaviour and better stress-corrosion resistance. When the drawing is silent and the part sees shock loading, this is usually the condition the designer actually wanted.
Condition A is how the bar is supplied
Bar arrives solution annealed at roughly 30–33 HRC. Parts are sometimes left in it, but the material is not at its intended properties and it's more prone to stress-corrosion cracking than the aged conditions. If that's what you intend, write it on the drawing.
Not a marine or chloride grade
17-4PH resists corrosion better than 410 or 420, and considerably worse than 316L. In seawater or chlorides it pits. If the part has to be both hard and chloride-resistant, settle the material before the drawing is released.
Ageing changes the size
The part shrinks slightly during ageing, by a few ten-thousandths per unit length for H900 and less at the higher temperatures. For tight-tolerance features we machine in Condition A, age, then grind or finish-turn to size. The extra operation is already in the quotation.
Cheaper alternatives
If you need hardness and the part only sees mild corrosion, hardened SUS 420 is cheaper and easier to source in Vietnam. If you need corrosion resistance and no hardness, 316L is cheaper again. 17-4PH makes sense when you really need both.
Machining process
We machine in Condition A, the parts are aged to the drawing condition, then we finish the features that have to hold size. Get that order wrong and the part is scrap.
- SequenceRough and semi-finish in Condition A · age to the drawing condition · grind or finish-turn critical features
- MillingDoosan, Haas, Hision and FANUC RoboDrill machining centres, 3, 4 and 5-axis
- TurningMori Seiki and Okuma lathes to Ø 310 × 800 mm, at ±0.005 mm typical
- GrindingOkamoto and Chevalier surface and NC grinding after ageing, to 500 × 200 × 250 mm, ±0.005 mm typical
- Wire EDMSodick wire cut for hardened features and sharp internal corners, to ±0.003 mm
- ToolingRigid setups and sharp carbide. In Condition A it cuts more like a tough alloy steel than like 304
- HardnessEvery aged batch verified on our Mitutoyo QMH 14BX micro hardness tester before packing
- InspectionMitutoyo CRYSTA-APEX V CMM in a climate-controlled lab, reported in inch and millimetre
These are figures we hold day to day and not a blanket specification. On an aged part they apply to the features finished after ageing. If a tolerance has to come through the ageing cycle with no finishing afterwards, mark it on the drawing and send it with the RFQ. General tolerance follows ISO 2768 fine or medium class as your print calls it.
Compatible finishing processes
- AgeingH900, H1025 and H1075 to the drawing condition, hardness checked on our Mitutoyo QMH 14BX before shipping
- PassivationPassivation to the ASTM A967 class your drawing names
- BlastingGlass or ceramic bead blast, on media never used on carbon steel
- PlatingElectroless nickel or thin dense chrome where wear resistance is required beyond the base hardness
- MarkingLaser marking. We prefer it to stamping, which can start a crack in an aged part
- Not forAnodising, and not for zinc plating without a hydrogen embrittlement bake specified on the drawing
Put the condition on the drawing, in the title block. "17-4PH H900" is a material specification. "17-4PH" is half of one. We check the hardness of every aged batch on our own tester before it ships and report the reading, but we can only check it against a number you have given us. Full finishing and heat treatment list →
Ordered in, with the ageing planned
- StockNot routinely held in Vietnam. Bar is ordered in per job in Condition A
- Lead timeProcurement plus one ageing cycle on top of our standard 14 days after PO. Confirmed at quote
- ConditionTell us H900, H1025, H1075 or Condition A at RFQ stage. It changes the process route as well as the price
- SizesRound bar is the easiest form to get; plate and large sections take longer. Send the raw size you need
- QuoteWithin 24 business hours of a complete RFQ
- CertificateEN 10204 3.1 mill certificate on request, plus our own hardness reading on the aged batch
Both the bar and the ageing cycle are planned per job, so the real lead time comes with the quotation. If the programme has a date attached, send the date with the RFQ. We don't substitute 15-5PH, 420 or any other grade for 17-4PH without your written approval.
Common questions
Is SUS630 the same as 17-4PH?
Yes. SUS630 to JIS G4303, UNS S17400 to ASTM A564 and EN 1.4542 are the same precipitation-hardening stainless, and they cross-reference cleanly.
What is the difference between H900 and H1075?
The ageing temperature, and with it the material you end up with. H900 is roughly 40–44 HRC and about 1310 MPa tensile. H1075 is roughly 32–36 HRC and about 1000 MPa, with much better toughness. You cannot swap one for the other.
My drawing just says 17-4PH. What will you do?
Ask you before quoting. The condition changes the process route as well as the price, and no finishing step turns one condition into another.
Does the part change size when it's aged?
Yes, slightly and predictably. It shrinks a few ten-thousandths per unit length, most at H900. We machine in Condition A, age, then finish the features that have to hold size.
Can you supply the parts aged?
Yes, to H900, H1025 or H1075 as the drawing names. Every hardened batch is checked on our Mitutoyo QMH 14BX before it ships.
Is 17-4PH suitable for seawater?
Not really. It resists corrosion better than 410 or 420 martensitic stainless and considerably worse than 316L, and it pits in chlorides. If the part must be hard and chloride-resistant, put the service environment in the RFQ.
Can you machine 15-5PH instead?
We can quote it if your drawing calls for it. We don't supply 15-5PH against a 17-4PH drawing, or the reverse, without your written approval. They're two separate alloys, and the names are not interchangeable.
Related information
316L stainless steel
When the requirement is corrosion rather than hardness, and why chlorides change the answer.
SKD11 / D2 tool steel
Hardened tool steel at 58–62 HRC, wire cut and ground after hardening.
Finishing and heat treatment
Every heat treatment condition we specify, and the hardness check we run before parts leave.