SUS631/1.4568/UNS S17700/17-7PH Stainless Steel

One of the most frequently used in the the aerospace industry and when meticulous, elaborate parts are needed, 17-7PH Stainless Steel is a common choice.

A stable, chromium-nickel-aluminum steel, 17-7PH Stainless Steel is a precipitation hardening steel with a high strength and moderately resistant to corrosion. In terms of corrosion resistance, 17-7 PH is comparable to 304 stainless steel and a better choice when compared to the 400 series of stainless steel.

17-7PH Stainless Steel is further strengthened by a low temperature precipitation hardening treatment (also termed aging). The industry standard is to age Condition R material at 950°F for one hour, resulting in an end condition of RH 950. Condition T material is aged at 1050°F for 90 minutes, resulting in an end condition of TH 1050. Typical room temperature mechanical properties are listed in Table 2. Very high strength properties are obtained. TH 1050 provides more ductility at a reduced strength level.

Grade 17-7PH Stainless Steel is mostly found in washers and springs.

It is used in applications which require high strength and corrosion resistance

It is also used in intricate parts due its low distortion on heat treatment.

Grade 17-7PH Stainless Steel can be welded using arc and resistance welding techniques. Inert gas shielding is preferred during fusion welding in order to reduce oxidation of aluminum. It is not necessary to perform pre-heating and post-weld annealing processes.

Grade 17-7PH Stainless Steel is annealed at 1066°C (1950°F) for 3 min for 0.1 in. (2.5 mm) of thickness followed by air cooling.

Aging of grade 17-7PH Stainless Steel can be done at 1177°C (2150°F) for 4 h followed by cooling. This process is followed by heating at 1078°C (1975°F) for 4 h and cooling. It is again heated at 844°C (1550°F) for 24 h and cooled, and heated at 760°C (1400°F) for 16 h followed by cooling to complete precipitation hardening process.

Grade 17-7PH Stainless Steel can be easily cold worked using common methods in the condition A.

Solution treated material is heavily cold worked which results in condition C material.

Condition C material is heated at 482°C (900°F) for 1 h in condition CH900 followed by cooling. Solution treated material is heated at 955°C (1750°F) for 10 min after fabrication in condition A1750 followed by rapidly cooling at room temperature.

 

Within 1 h of treating to condition A1750, it is cooled at -73°C (-100°F) for 8 h in condition R100. It is then heated at 510°C (950°F) for 90 min in condition RH 950 followed by cooling. After fabrication, it is heated at 760°C (1400°F) for 90 min in condition T.

 

Within 60 min of cooling, it is then cooled at 13°C (55°F) for 30 min. From condition T, it is heated at 565°C (1050°F) for 90 min in condition TH1050 followed by cooling.