Stainless Steel 17-7 PH
AISI/SAE 17-7 PH · UNS S17700 · ASTM 631, A693 · EN 1.4568, X7CrNiAl17-7 · JIS SUS631
17-7 PH (UNS S17700) is a semi-austenitic, aluminium-bearing precipitation-hardening stainless steel supplied soft in Condition A, formed or cold rolled, then hardened by austenite conditioning (TH/RH routes) or by ageing cold-rolled strip (CH900).
Values for the Condition A condition
17-7 PH tempers and conditions
17-7 PH is supplied in 7 conditions, soft to hard. Condition A is the default FabDigit quotes; the values on this page are for it.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Condition ADefault solution annealed (1040 °C, air cooled) | As-supplied soft condition for forming, blanking, drawing and welding before hardening; not a service condition where strength is needed. | 276 | 896 | 35 | 175 HB | — |
Condition T | Intermediate transformed (martensitic) state on the way to TH1050; supplied only when the customer will do the final age. | 760 | 1,035 | 10 | 32 HRC | 2.2 % IACS |
Condition R-100 | Refrigerated intermediate state preceding the RH950 age; higher final strength route than TH but less dimensional stability. | 830 | 1,140 | 8 | 35 HRC | 2.2 % IACS |
Austenite conditioned (760 °C) + aged 565 °C / 90 min | Workhorse hardened temper for parts formed in Condition A: ~1275 MPa with the best ductility and dimensional stability of the hardened tempers. | 1,170 | 1,275 | 8 | 42 HRC | — |
Austenite conditioned (955 °C) + refrigerated (−73 °C) + aged 510 °C /… | Highest-strength heat-treated temper for bar, wire and thin sheet where ~1450 MPa is needed and some ductility loss is acceptable. | 1,310 | 1,450 | 6 | 46 HRC | — |
Condition C | Cold-rolled strip/wire temper used for springs and flat parts that will be aged to CH900 after forming. | 1,310 | 1,450 | 3 | 43 HRC | 2.2 % IACS |
Cold rolled (Condition C) + aged 480 °C / 1 h | Maximum-strength temper (~1700 MPa) for flat springs, diaphragms and retaining rings in thin gauges; almost no ductility left. | 1,620 | 1,725 | 2 | 49 HRC | — |
What is 17-7 PH?
17-7 PH (UNS S17700) is a semi-austenitic, aluminium-bearing precipitation-hardening stainless steel supplied soft in Condition A, formed or cold rolled, then hardened by austenite conditioning (TH/RH routes) or by ageing cold-rolled strip (CH900). It gives spring-temper strengths of 1200–1800 MPa with corrosion resistance close to 304 and useful strength retention to about 315 °C, which is why it dominates aerospace springs, diaphragms, clamps, retaining rings and thin-gauge fittings. Limits are low ductility and notch toughness after ageing, dimensional change during transformation heat treatment, poor weldability of the aged condition, and chloride pitting/SCC susceptibility well below that of austenitic 316. 17-7 PH has a density of 7.81 g/cm³ (0.282 lb/in³), heavier than 57% of stainless steel grades. It melts at 1,400°C (2,552 °F). 17-7 PH has a yield strength of 276 MPa (40 ksi) and a tensile strength of 896 MPa (130 ksi) — weaker than 76% of stainless steel grades. Elongation at break is 35% and the elastic modulus is 200 GPa (29 Msi).
What is 17-7 PH used for?
- Aerospace springs
- Belleville washers
- Retaining rings
- Diaphragms and bellows
- Hose and duct clamps
- Thin-gauge aircraft fittings
- Instrument flexures
Advantages
- Forms and bends easily — 70/100, better than 79% of stainless steel grades
Limitations
- Low strength — 276 MPa (40 ksi), worse than 76% of stainless steel grades
17-7 PH properties
Typical room-temperature values for 17-7 PH-Condition A; bars are the position among stainless steel grades.
Physical3
17-7 PH has a density of 7.81 g/cm³ (0.282 lb/in³), heavier than 57% of stainless steel grades. It melts at 1,400°C (2,552 °F).
Mechanical13
17-7 PH has a yield strength of 276 MPa (40 ksi) and a tensile strength of 896 MPa (130 ksi) — weaker than 76% of stainless steel grades. Elongation at break is 35% and the elastic modulus is 200 GPa (29 Msi).
Thermal5
It conducts heat at 16.4 W/m·K (9.48 BTU/hr·ft·°F), better than 69% of stainless steel grades. Thermal expansion is 11 µm/m·K (6.11 µin/in·°F).
Electrical3
17-7 PH conducts electricity at 2.2 % IACS, worse than 61% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (62/100), worse than 52% of stainless steel grades.
Sustainability4
Producing a kilogram of 17-7 PH takes about 60 MJ of energy and emits 5 kg of CO₂ — more than 70% of stainless steel grades. Typical recycled content is 35%.
Manufacturability7
17-7 PH's machinability is poor (32/100, worse than 62% of stainless steel grades); weldability good (55/100); formability very good (70/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the stainless steel family
Yield strength against density for every stainless steel grade FabDigit runs. 17-7 PH is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 17-7 PH
Is 17-7 PH easy to machine?
Machine in Condition A with rigid setups, positive rake carbide, heavy feeds and flood coolant (work-hardens badly); rough before ageing and finish after TH1050/RH950 where only light cuts and grinding are practical.
Can 17-7 PH be welded?
GTAW/resistance-weld in Condition A with matching or 17-7 PH filler and no preheat, then give the full conditioning + ageing cycle to restore strength; welding aged material leaves soft, low-ductility zones.
Can 17-7 PH be formed, bent or molded?
Form, draw and blank only in Condition A (behaves like a springy 300-series, allow generous springback); expect ~0.5–1 % growth in TH1050 and shrinkage in RH950, so fixture and allow for dimensional change.
Manufacturability
The process limits FabDigit applies to 17-7 PH. Every 17-7 PH part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Fair32 / 100 |
|---|---|
| ISO material group | M.3 |
| Cutting speed (rough / finish) | 120 / 140 m/min |
| Minimum wall | 0.8 mm |
| Minimum internal radius | 1.5 mm |
| Drill depth limit | 4× diameter |
| Best surface (machined / polished) | Ra 1.6 / — |
| Hardenable after machining | No |
Sheet metal
| Formability | Fair70 / 100 |
|---|---|
| Weldability | Better55 / 100 |
17-7 PH chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| C0.09 max per ASTM A693/AMS | ≤ 0.09 | 0.07 |
| Mn | ≤ 1 | 0.5 |
| Si | ≤ 1 | 0.4 |
| P | ≤ 0.04 | |
| S0.030 max (0.04 in some specs) | ≤ 0.03 | |
| Cr | 16 – 18 | 17 |
| Ni | 6.5 – 7.75 | 7.1 |
| AlNiAl precipitation hardener | 0.75 – 1.5 | 1.15 |
| Fe | balance |
What surface finishes work on 17-7 PH?
Descale after heat treatment (aluminium-rich oxide is tenacious — pickle or grit blast), then passivate per AMS 2700/ASTM A967; takes a good mechanical or electropolish finish and accepts electroless nickel or Cd/Zn-Ni plating with baking to avoid hydrogen embrittlement.
Surface treatments FabDigit runs on stainless steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Plating
Organic Coating
CVD Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Stainless Steel 17-7 PH in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- S17700
- AISI / SAE
- 17-7PH
- ASTM
- 631A693A693 Type 631
- AMS
- 5644
- EN / DIN / Werkstoff-Nr.
- 1.4568X7CrNiAl17-7
- GB (China)
- 0Cr17Ni7Al07Cr17Ni7Al05Cr17Ni7Al
- JIS
- SUS631
- Trade names
- Alloy 631
How much does 17-7 PH cost?
17-7 PH is a specialty-cost stainless steel ($$$$$), pricier than about 58% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
17-7 PH — frequently asked
What is 17-7 PH used for?
17-7 PH is typically used for aerospace springs, belleville washers, retaining rings, diaphragms and bellows, hose and duct clamps and thin-gauge aircraft fittings. In short: high-hardness aerospace PH.
What is the yield strength of 17-7 PH?
17-7 PH has a typical yield strength of 276 MPa (40 ksi) and a tensile strength of 896 MPa (130 ksi) — weaker than 76% of stainless steel grades. Strength varies by condition: see the 7 listed tempers.
Is 17-7 PH easy to machine?
Not especially — machinability is rated poor (32/100, worse than 62% of stainless steel grades). Machine in Condition A with rigid setups, positive rake carbide, heavy feeds and flood coolant (work-hardens badly); rough before ageing and finish after TH1050/RH950 where only light cuts and grinding are practical.
Can 17-7 PH be welded?
Yes — weldability is rated good (55/100). GTAW/resistance-weld in Condition A with matching or 17-7 PH filler and no preheat, then give the full conditioning + ageing cycle to restore strength; welding aged material leaves soft, low-ductility zones.
What surface finishes work on 17-7 PH?
Descale after heat treatment (aluminium-rich oxide is tenacious — pickle or grit blast), then passivate per AMS 2700/ASTM A967; takes a good mechanical or electropolish finish and accepts electroless nickel or Cd/Zn-Ni plating with baking to avoid hydrogen embrittlement.
Can 17-7 PH be formed, bent or molded?
Form, draw and blank only in Condition A (behaves like a springy 300-series, allow generous springback); expect ~0.5–1 % growth in TH1050 and shrinkage in RH950, so fixture and allow for dimensional change.
What is the difference between 17-7 PH Condition A and 17-7 PH-CH900?
Condition A is the default condition — as-supplied soft condition for forming, blanking, drawing and welding before hardening; not a service condition where strength is needed. CH900: maximum-strength temper (~1700 MPa) for flat springs, diaphragms and retaining rings in thin gauges; almost no ductility left. Yield strength is 276 MPa in Condition A versus 1,620 MPa in CH900.
How much does 17-7 PH cost?
17-7 PH is a specialty-cost stainless steel ($$$$$), pricier than about 58% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Can FabDigit make parts in 17-7 PH?
Yes — 17-7 PH is available for CNC machining and sheet metal; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM A693 — Precipitation-Hardening Stainless Steel Plate, Sheet and Strip — ASTM International (2016)
- AMS 5644 / AMS 5528 / AMS 5529 / AMS 5678 (17-7 PH bar, sheet, strip, wire) — SAE International (2020)
- EN 10088-2 / EN 10151 (1.4568, X7CrNiAl17-7) — CEN (2014)
- JIS G 4304 / G 4313 (SUS631) — JSA (2019)
- 17-7 PH Stainless Steel product data bulletin — AK Steel / Cleveland-Cliffs (2016)
- ASM Specialty Handbook: Stainless Steels — ASM International (1994)
- MMPDS-2023, Chapter 2 (precipitation-hardening stainless steels) — Battelle/FAA (2023)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.