Printable PDF: 17-7PH Stainless Steel Alloy Data Sheet
17-7 PH is a precipitation-hardening stainless steel that provides high strength and hardness, excellent fatigue properties, good corrosion resistance, good formability, and minimum distortion upon heat treatment. The alloy provides valuable property combinations particularly well suited for aerospace applications. This special alloy also provides benefits for other applications requiring high strength and good corrosion resistance, as well as excellent properties for flat springs at temperatures up to 600°F (316°C).
|Cr:||16.0 – 18.0|
|Ni:||6.5 – 7.75|
Standard Heat Treatments
This material requires three essential steps in heat treating:
1) Austenite conditioning.
2) Cooling to transform the austenite to martensite.
3) Precipitation hardening to Condition TH 1050 or RH 950.
To obtain the highest mechanical properties from the alloy, Condition A material is transformed to martensite at the mill by cold reduction to Condition C. Hardening to Condition CH 900 is accomplished with a single, low-temperature heat treatment.
AMS 5528, AMS 5529, MIL-S-25043, ASTM A693 (Listed as Grade 631-UNS S17700)
Typical Mechanical Properties – Typical Room Temperature Mechanical Properties
Typical mechanical properties are based on AK source on ASTM A693
Tensile Strength (UTS)* ksi (MPa): 130 ksi (896 MPa)
0.2% YS* ksi (MPa): 40 ksi (276 MPa)
Elongation% in 2” (50.8 mm): 35%
Hardness Rockwell: 85 HRBW
Condition: TH 1050
Tensile Strength (UTS)* ksi (MPa): 200 ksi (1379 MPa)
0.2% YS* ksi (MPa): 185 ksi (1276 MPa)
Elongation% in 2” (50.8 mm): 9%
Hardness Rockwell: 43 HRCW
Condition: RH 950
Tensile Strength (UTS)* ksi (MPa): 235 ksi (1620 MPa)
0.2% YS* ksi (MPa): 220 ksi (1517 MPa)
Elongation% in 2” (50.8 mm): 6%
Hardness Rockwell: 48 HRCW
Tensile Strength (UTS)* ksi (MPa): 220 ksi (1517 MPa)
0.2% YS* ksi (MPa): 190 ksi (1310 MPa)
Elongation% in 2” (50.8 mm): 5%
Hardness Rockwell: 43 HRCW
Condition: CH 900
Tensile Strength (UTS)* ksi (MPa): 265 ksi (1827 MPa)
0.2% YS* ksi (MPa): 260 ksi (1793 MPa)
Elongation% in 2” (50.8 mm): 2%
Hardness Rockwell: 49 HRCW
Density – lbs/in³ (g/cm³)
Condition A: 0.282 (7.81)
Condition TH 1050: 0.276 (7.65)
Condition RH 950: 0.276 (7.65)
Modulus of Elasticity (E) – ksi (Gpa)
Condition A: –
Condition TH 1050: 29.0 x 10³ (200)
Condition RH 950: 29.0 x 10³ (200)
Electrical Resistivity – microhm-cm
Condition A: 80
Condition TH 1050: 82
Condition RH 950: 83
Magnetic Permeability – @ 50 oersteds
Condition A: 1.4 – 3.6
Condition TH 1050: 120 – 167
Condition RH 950: 113 – 130
Magnetic Permeability – @ 200 oersteds (Maximum)
Condition A: 1.4 – 3.2 (1.4 – 3.6)
Condition TH 1050: 46 – 55 (134 – 208)
Condition RH 950: 44 – 52 (119 – 135)
Thermal Conductivity – BTU/hr/ft.²/in/hr/°F (W/m•K)
300°F (149°C): –
500°F (260°C): –
900°F (482°C): –
Condition TH 1050:
300°F (149°C): 117 (16.87)
500°F (260°C): 128 (18.46)
900°F (482°C): 146 (21.05)
Condition RH 950:
300°F (149°C): 117 (est) (16.87)
500°F (260°C): 128 (est) (18.46)
900°F (482°C): 146 (est) (21.05)
Coefficient of Expansion
70 – 200°F (21 – 193°C): 8.5 x 10-6 (15.3)
70 – 400°F (21 – 204°C): 9.0 x 10-6 (16.2)
70 – 800°F (21 – 427°C): 9.6 x 10-6 (16.0)
Condition TH 1050:
70 – 200°F (21 – 193°C): 5.6 x 10-6 (10.1)
70 – 400°F (21 – 204°C): 6.1 x 10-6 (11.0)
70 – 800°F (21 – 427°C): 6.6 x 10-6 (11.9)
Condition RH 950:
70 – 200°F (21 – 193°C): 5.7 x 10-6 (10.3)
70 – 400°F (21 – 204°C): 6.6 x 10-6 (11.9)
70 – 800°F (21 – 427°C): 6.9 x 10-6 (12.4)
Corrosion resistance in Conditions TH 1050 and RH 950 is generally superior to that of the standard hardenable chromium types of stainless steels such as Types 410, 420 and 431, but is not quite as good as chromium-nickel Type 304. Corrosion resistance in Condition CH 900 approaches that of Type 304 in most environments.
In Condition A, the alloy can be formed comparably to Type 301. It work-hardens rapidly and may require intermediate annealing in deep drawing or in forming intricate parts. Springback is similar to that of Type 301. This alloy is extremely hard and strong in Condition C. Therefore, fabrication techniques for such materials must be used.
The precipitation hardening class of stainless steels is generally considered to be weldable by the common fusion and resistance techniques. Special consideration is required to achieve optimum mechanical properties by considering the best heat-treated conditions in which to weld and which heat treatments should follow welding. This particular alloy is generally considered to have poorer weldability compared to the most common alloy of this stainless class, 17-4PH Stainless Steel. A major difference is the high Al content of this alloy, which degrades penetration and enhances weld slag formation during arc welding. Also, the austenite conditioning and precipitation hardening heat treatments are both required after welding to achieve high strength levels. When a weld filler is needed, W 17-7 PH is most often specified.
Additional Information on 17-7 Stainless Steel
17-7 is a precipitation-hardening stainless steel that provides property combinations particularly well suited for use in aerospace applications. It performs well in applications that require high strength and corrosion resistance. Its properties include:
- Excellent strength and hardness
- Excellent fatigue properties
- Good corrosion resistance
- Good formability
- Minimum distortion when heat treated.
17-7 also provides outstanding value for other applications, such as flat springs, that require high strength, corrosion resistance and properties that hold at temperatures up to 600°F (316°C).
Standard Heat Treatment for 17 7 Stainless Steel
ESM-Hampshire is the one of industry’s foremost stainless steel re-roll mills, delivering high-quality products at competitive prices. We process stainless steel and Nickel-based alloys for a wide range of industries that include automotive, medical, petrochemical, aerospace, and consumer products.
Our standard heat treatment of these alloys requires three essential steps: austenitic conditioning, transformation of austenite to martensite, and age hardening.
Each step in the process ensures that you get the best possible product, as 17-7PH stainless steel has a unique combination of high strength, high toughness, and fatigue resistance attributed to its microstructure, which makes it a dual-phase-precipitation hardened stainless steel.
Austenitic conditioning – heats the steel to a temperature that changes crystal structure from ferrite to austenite. This allows for the absorption of carbon from the iron-carbides in carbon steel.
Transformation of Austenite to Martensite takes place by the rapid cooling (quenching) of the austenite at such a high rate that cubic austenite transforms to martensitic, a highly strained form that is supersaturated with carbon.
Precipitation Hardening, also known as age hardening or particle hardening, is a heat treatment technique used to increase the yield strength of 17-7PH stainless steel.
Obtaining the highest mechanical properties from the alloy means transforming Condition A martensite at our mill using cold reduction, to Condition C. Hardening to Condition CH 900 is done with a single, low-temperature heat treatment.
Note that stainless steel 17-7PH, when heat treated at cryogenic temperatures, modifies the chemical composition, giving the material higher hardness value. A higher value of Nickel in certain zones stabilizes the austenite. As a result, it does not transform to martensitic during aging at treatment TH 1050 and RH 950.
Different chemical composition and different heat treatment allow the production of material with good mechanical properties, as well as adequate microstructural constituents. This modified chemical composition of steel 17-7PH produces hardness in modified condition RH 950 higher than in TH 1050.
Applications of 17-7 Stainless Steel
Classified as a semi-austenitic stainless steel, 17-7 is used extensively in making parts used by the aerospace industry. It is also used in a variety of springs and washers, power boilers, and heat exchangers.
Currently, the 17-7 material is most often used in sheet and strip form when producing springs, clips, and bellows. It is finding new applications in the medical industry due to its high alloy content that provides high, spring-like strength, good ductility, and excellent corrosion, all important attributes for items manufactured for the medical industry.
Vacuum heat treatment technology is allowing the use of 17-7 steel alloy in new medical device design that is based on 17-7’s established set of mechanical properties with the additional benefit of producing bright, non-discolored medical devices. Using this technique does not require removing parts from the furnace for a separate cooling step. This reduces heat treatment costs and provides shiny, cost-effective medical instruments. Though not classified as a standard PH condition, this approach is gaining traction due to the medical industry’s interest.
Why Choose ESM?
ESM is customer driven and proud of our ability to roll precision strip to tighter tolerances, with both short lead times and smaller minimum amounts than our competition. We value your business and will work hard to get it and keep it, not only by producing quality products but by allowing you to receive material quickly.
Our state of the art conversion mill in Hampshire, Illinois is one of the leading producers of light gauge stainless steel strip, that is produced to precision thickness and widths based on our customer’s specifications. Our facilities for slitting, shearing, blanking, and edging, offer 17-7 PH stainless steel in coils or cut lengths in thicknesses .001 and heavier in accordance with your specifications.
Regardless of your industry, ESM can provide you with premier stainless steel and Nickel-based alloys that will serve your needs. Fill out a contact form for more information.
**The information and data in this product data sheet are accurate to the best of our knowledge and belief, but are intended for general information only. Applications suggested for the materials are described only to help readers make their own evaluations and decisions, and are neither guarantees nor to be construed as express or implied warranties of suitability for these or other applications. Data was obtained from our melt sources with data referring to mechanical properties and chemical analyses are the result of tests performed on specimens obtained from specific locations with prescribed sampling procedures; any warranty thereof is limited to the values obtained at such locations and by such procedures. There is no warranty with respect to values of the materials at other locations. Further information should be sought from the melt sources.