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17-7PH
ISO M (stainless steel)Precipitation-hardening stainless steel (semi-austenitic). Number: UNS S17700 (Type 631). Standard: ASTM A693 (sheet/plate, Grade 631), AMS 5528 (sheet, strip and plate), AMS 5529 (cold-rolled sheet and strip), and others.
🌐JIS and international equivalents
“Close” means composition or properties are not exactly the same. Before substituting, check the values in each standard.
| System | Designation | Number | Relation | Confidence |
|---|---|---|---|---|
| UNS | 17-7PH | UNS S17700 (Type 631) | — | |
| JIS | SUS631 | JIS G 4303 (bar) and others | equivalent | Agrees in 2+ sources[7][8][9] |
| EN | X7CrNiAl17-7 | 1.4568 | close | Agrees in 2+ sources[7][8] |
| ISO | ISO 15510 number 4568-177-00-I | 4568-177-00-I | close | One source / reference[7] |
| GB | 07Cr17Ni7Alformer designation 0Cr17Ni7Al | S51700 (as listed in the Japan Stainless Steel Association table) | close | One source / reference[8][7] |
Differences between the equivalents (from the sources)
- JIS SUS631: In the Japan Stainless Steel Association comparison table SUS631 = S17700, and the Baosteel cross-reference also has S17700, 631 = SUS631. The JIS composition of Nippon Steel (C ≤0.09, Ni 6.50-7.75, Cr 16.00-18.00, Al 0.75-1.50, etc.) is the same figures as Cleveland-Cliffs and ATI. Sanyo's table gives Ni as 6.50-7.55, which disagrees. Mechanical properties differ greatly between JIS (TH1050 tensile strength >=1140) and the US acceptance value (>=1241)
- EN X7CrNiAl17-7: Corresponds to SUS631 in the Japan Stainless Steel Association comparison table (per EN 10088). The Baosteel cross-reference also gives 1.4568, but writes the symbol as X7CrNi17-7 (without Al)
- GB 07Cr17Ni7Al: The grade name comes from the Baosteel cross-reference (07Cr17Ni7Al = S17700, 631 = SUS631); the unified numerical code S51700 appears only in the Japan Stainless Steel Association table. The number has not been checked against Chinese sources
📄Related specifications (AMS, ASTM etc.)
Specifications called up on purchase orders and drawings. AMS are SAE aerospace material specifications, split by product form (bar, plate, forging), melting practice and heat treatment. Standard texts are paid, so only titles and scopes checked on the publishers’ public pages are shown.
| Spec | Scope | Confidence |
|---|---|---|
| AMS 5528 | Steel, Corrosion-Resistant, Sheet, Strip, and Plate 17Cr - 7.1Ni - 1.1Al Solution Heat Treated, Precipitation HardenableSheet, strip and plate. Supplied solution treated (Condition A); the user heat treats to TH1050 or RH950 | Agrees in 2+ sources[10][1] |
| AMS 5529 | Steel, Corrosion Resistant, Sheet and Strip, 17Cr - 7.1Ni - 1.1Al, Solution Heat Treated and Cold Rolled, Precipitation Hardenable, 0.0015 to 0.050 Inch (0.038 to 1.27 mm) Nominal ThicknessCold-rolled sheet and strip (Condition C). Aged to CH900 | Agrees in 2+ sources[11][2] |
| AMS 5568 | Steel, Corrosion- and Heat-Resistant, Welded Tubing 17Cr - 7.1Ni - 1.1Al Solution Heat Treated, Precipitation-HardenableWelded tube. Solution-treated condition | Agrees in 2+ sources[12][2] |
| AMS 5644 | Steel Bars and Forgings, Corrosion Heat Resistant, 17Cr - 7Ni - 1AlBar and forgings | One source / reference[13][2] |
| ASTM A693 | Standard Specification for Precipitation-Hardening Stainless and Heat-Resisting Steel Plate, Sheet, and StripPlate, sheet and strip (Grade 631, UNS S17700). Supplied solution treated | Agrees in 2+ sources[14][1] |
All ASTM standards on Kezuriba: ASTM standards quick reference.
✈Main aerospace uses (as stated in the sources)
- Cleveland-Cliffs says it has a combination of properties particularly suited to aerospace applications, and also lists flat springs, Belleville washers, eyelets and strain gauges (up to 600°F)[1]
- ATI says it has been used in aerospace and in many spring applications requiring high strength. Vacuum arc remelted and electroslag remelted material is also available for applications under cyclic stress[2]
- MIL-HDBK-5J: used where high strength and corrosion and oxidation resistance up to 600°F are needed; the heat-treatment temperature cycle is compatible with brazing of honeycomb panels[6]
⚗Chemical composition (mass %)
Ranges differ between specifications, so each one has its own column (dark figures agree in several sources, light figures come from one source).
| Element | Spec ① | Spec ② |
|---|---|---|
| C | ≤ 0.09[1][2] | — |
| Si | — | ≤ 1[1][2] |
| Mn | — | ≤ 1[1][2] |
| P | — | ≤ 0.04[1][2] |
| S | — | ≤ 0.03[1][2] |
| Cr | — | 16 – 18[1][2] |
| Ni | — | 6.50 – 7.75[1][2] |
| Al | — | 0.75 – 1.50[1][2] |
- Spec ① Composition from Cleveland-Cliffs and ATI (applicable specifications AMS 5528, 5529, ASTM A693 Grade 631, etc. are listed together; which standard the values come from is not stated)
- Spec ② Cleveland-Cliffs, ATI
⚖Density
7.81 g/cm³
Value for the solution-treated condition (Condition A). Cleveland-Cliffs 0.282 lb/in³ (7.81), ATI 7810 kg/m³ and Sanyo's SUS631 7.81 agree. Density decreases after heat treatment: TH1050 is ATI 7.67, Cleveland-Cliffs 7.65, MIL-HDBK-5J 0.276 lb/in³ (≈7.64); RH950 is ATI 7.64, Cleveland-Cliffs 7.65
Calculate weight in 17-7PH →💪Mechanical properties
“Reference” values are not specified minimums from the standard but figures published by makers and others.
| Condition | Tensile MPa | Yield MPa | Elong. % | Hardness | Type of value |
|---|---|---|---|---|---|
| Condition A (solution treated at 1950±25°F/1066°C) | ≤ 1034 (150 ksi) | ≤ 379 (55 ksi) | ≥ 20 | HRB 92 max | Acceptance value in the material specification (Cleveland-Cliffs Table 2 "Properties acceptable for material specification"; no standard named) One source / reference[1] |
| Solution treated S (JIS SUS631, 1000-1100°C, rapid cooling) | 1030 (Sanyo's table writes ">=1030") | 380 (Sanyo's table writes ">=380") | ≥ 20 | HBW 229 max | JIS specified value (from Sanyo Special Steel catalog) One source / reference[5] |
| TH1050 (1400°F x 90 min, cool to 60°F or below and hold 30 min, then 1050°F x 90 min air cool) | ≥ 1241 (180 ksi) | ≥ 1034 (150 ksi) | ≥ 6 (plate 0.188-1.000 in, AMS 5528) / sheet >=6, >=5, etc. depending on thickness (Cleveland-Cliffs) | HRC 38 min (Cleveland-Cliffs) | Agrees between the Cleveland-Cliffs Table 2 acceptance value and the S-basis value for AMS 5528 plate (MIL-HDBK-5J Table 2.6.10.0(b)) Agrees in 2+ sources[1][6] |
| TH1050 (JIS SUS631) | ≥ 1140 | ≥ 960 | ≥ 5 | HBW 363 min | JIS specified value (from Sanyo Special Steel catalog) One source / reference[5] |
| TH1050 (typical value, sheet and strip) | 1345 | 1205 | 8 | HRC 42 | Typical value (ATI datasheet) One source / reference[2] |
| RH950 (1750°F x 10 min air cool, -100°F x 8 h, 950°F x 60 min air cool) | ≥ 1448 (210 ksi) | ≥ 1310 (190 ksi) | ≥ 5, >=4, >=3 depending on thickness | HRC 44 min | Acceptance value in the material specification (Cleveland-Cliffs Table 2; no standard named) One source / reference[1] |
| RH950 (JIS SUS631) | ≥ 1230 | ≥ 1030 | ≥ 4 | HBW 388 min | JIS specified value (from Sanyo Special Steel catalog) One source / reference[5] |
| RH950 (typical value, sheet and strip) | 1550 | 1380 | 7 | HRC 47 | Typical value (ATI datasheet) One source / reference[2] |
| Condition C (cold rolled at the mill) | ≥ 1379 (200 ksi) | ≥ 1207 (175 ksi) | ≥ 1 (Cleveland-Cliffs) | HRC 41 min (Cleveland-Cliffs) | AMS 5529 specified value (as stated by ATI) agrees with the Cleveland-Cliffs Table 2 acceptance value (ATI converts to 1380/1205 MPa) Agrees in 2+ sources[2][1] |
| CH900 (Condition C, 900°F x 60 min air cool) | ≥ 1655 (240 ksi) | ≥ 1586 (230 ksi) | ≥ 1 (Cleveland-Cliffs) | HRC 46 min (Cleveland-Cliffs) | AMS 5529 specified value (as stated by ATI) agrees with the Cleveland-Cliffs Table 2 acceptance value (ATI converts yield strength to 1585 MPa) Agrees in 2+ sources[2][1] |
1 MPa ≈ 145 psi (0.145 ksi). Hardness conversion · unit converter
🔧Machinability notes (as stated in the sources)
- In Sumitomo Electric's recommended conditions for turning stainless steel (M), SUS631 falls under the precipitation-hardening group, with cutting speeds of 90-115-140 m/min for finishing, 70-90-130 continuous, 50-80-120 light interrupted, and 40-70-100 m/min interrupted (lower limit-recommended-upper limit)[3]
- Heat treatment from Condition A to TH1050 or RH950 causes an expansion of about 0.004 in/in (about 0.0045 growth on transformation and about 0.0005 shrinkage on aging); from Condition C to CH900 it shrinks about 0.0005 in/in (Cleveland-Cliffs). MIL-HDBK-5J gives the net growth from A to TH1050 as 0.0045 in/in[1][6]
- Condition A (austenite) is easy to cold form. Because pickling the scale on TH1050 risks intergranular attack, vapor blasting is recommended (MIL-HDBK-5J)[6]
📚Sources
Primary sources (public documents from makers, industry associations and standards bodies), numbered where each value is cited. Many are in Japanese.
- clevelandcliffs.com https://www.clevelandcliffs.com/_assets/_eb15314af477616a40b17eafbaeabe27/clevelandcliffs/…
- atimaterials.com https://www.atimaterials.com/Products/Documents/datasheets/stainless-specialty-steel/preci…
- sumitool.com https://www.sumitool.com/downloads/cutting-tools/general-catalog/assets/pdf/a.pdf
- sandvik.coromant.com https://www.sandvik.coromant.com/en-us/knowledge/materials/workpiece-materials
- sanyo-steel.co.jp https://www.sanyo-steel.co.jp/english/product/special_steel/images/pdf/stainless_201712.pd…
- everyspec.com https://everyspec.com/MIL-HDBK/MIL-HDBK-0001-0099/MIL_HDBK_5J_139/
- jssa.gr.jp https://www.jssa.gr.jp/contents/products/standards/comparisons/
- esales.baosteel.com http://esales.baosteel.com/bsi/ologin/pdf/cpscxz/cpscxz1601.pdf
- nipponsteel.com https://www.nipponsteel.com/product/catalog_download/__icsFiles/afieldfile/2025/10/06/S011…
- saemobilus.sae.org https://saemobilus.sae.org/standards/ams5528g-steel-corrosion-resistant-sheet-strip-plate-…
- sae.org https://www.sae.org/standards/content/ams5529a/
- saemobilus.sae.org https://saemobilus.sae.org/standards/ams5568j-steel-corrosion-heat-resistant-welded-tubing…
- sae.org https://www.sae.org/standards/content/ams5644e/
- store.astm.org https://store.astm.org/standards/a693
Other materials
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