17-7 PH

Type 17-7 PH is a Chromium-Nickel-Aluminum, austenitic stainless steel. It is the most formable of all PH grades and has the highest strength and hardness. It is less magnetic than other PH grades and offers minimal distortion upon heat treatment. This material maintains its valuable properties at temperatures up to 800° F (427° C).

Popular in aerospace

The alloy has excellent fatigue properties, good corrosion resistance and is easily formed. Due to the alloys good mechanical and physical properties, 17-7PH is particularly popular in the aerospace sector. The alloy can be used in the manufacture of flat springs up to 315°C (600°F).

Suitability

17-7PH offers high strength and hardness with minimum distortion under heat treatment. With good formability and excellent fatigue properties, the alloy provides good corrosion resistance. The attractive combination and strength and hardness results in use in such market sectors as aerospace and defence.

Chemical composition of stainless steel 17-7PH

*Not exclusively to the element mentioned, but that one predominates other elements that are used in smaller quantities.

Select AMS Number of 17-7 PH

Fabrication and working Instructions

Stainless Steel 17-7PH hardens rapidly during heat treatment and requires intermediate annealing in deep drawing or in forming intricate parts. In some conditions, like Condition C, for example, this steel can be very hard and strong, which means that advanced fabrication techniques for such materials should be used.

As for machining, special care must be applied to the speed at which the parts are machined. 17-7PH Stainless Steel can display long gummy chips during machining, and therefore slower speeds are recommended, accompanied by constant feeds.

17-7PH Stainless Steel can be welded by all conventional fusion and resistance techniques. However, if optimum mechanical properties are wanted, special care is recommended to find the best heat-treated conditions that should be done during the welding. The following heat treatments of the welded part are also essential for excellent mechanical properties. More precisely, austenite conditioning and precipitation hardening are mandatory after the welding is finished to obtain high strength.

Overall, 17-7PH is not as weldable as 17-4PH Stainless Steel. The reason for this is the high concentration of Aluminum, which deteriorates penetration of the weld, thus creating a bond that is not as strong. Weld slug formation can also be worsened during arc welding, which is another area that requires special care.

Depending on the condition, different heat treatments of 17-7PH are recommended:

• Condition A – mill Annealed at 1950 ± 25° F (1066 ± 14° C).
• Condition A1750 – mill Annealed at 1950 ± 25° F (1066 ± 14° C), then heat to 1750 ± 15° F (954 ± 8° C) for 10 minutes and air cool to room temperature.
• Condition T – mill Annealed at 1950 ± 25° F (1066 ± 14° C), then heat to 1400 ± 25° F (760 ± 14° C) and hold for 90 minutes. Finally, cool to 60° F (16° C) within 1 hour and hold for 30 minutes.
• Condition TH 1050 – mill Annealed at 1950 ± 25° F (1066 ± 14° C), then heat to 1400 ± 25° F (760 ± 14° C) and hold for 90 minutes. Next, cool to 60° F (16° C) within 1 hour and hold for 30 minutes. Finally, heat to 1050 ± 10° F (566 ± 5.5° C) and hold for 90 minutes, then air cool to room temperature.
• Condition R 100 – mill Annealed at 1950 ± 25° F (1066 ± 14° C), then heat to 1750 ± 15° F (954 ± 8° C) for 10 minutes and air cool to room temperature. Within 1 hour, start cooling to -100 ± 10° F (73 ± 5.5° C) and hold for 8 hours before air warming to room temperature.
• Condition RH 950 – the same as Condition R 100 only with added precipitation hardening at 950 ± 10° F (510 ± 5.5° C) for 60 minutes and then air cooling to room temperature.

Typical applications

Commercial applications for this engineering material include:

• Tooling in the Aerospace Industry
• CNC components
• Mould & gauge making
• General tooling
• Bulkheads
• Retaining rings
• Springs

Standard specifications

• AMS: 5528, 5529, 5568, 5644, 5678
• ASTM: A313, A564, A579, A693, A705
• UNS: S17700

Other industry standards we comply with

• W.NR 1.4541
• PWA-LCS
• GE Aircraft Engine (GT193)
• GE Aviation S-SPEC-35 AeDMS S-400
• RR SABRe Edition 2
• DFARS Compliant

Features

• Provides valuable property combinations particularly well suited for aerospace applications
• Provides benefits for other applications requiring high strength and good corrosion resistance
• High strength and hardness
• Excellent fatigue properties