17-7PH, AISI 631, 1.4568, X7CrNiAl17-7 and UNS S17700 is a precipitation hardened semi-austenitic stainless steel from the group of age-hardened PH with the highest content of Chromium - 17% and Nickel - 7% in relation to PH of grades 15-5 and 17-4. It has excellent strength properties, high hardness and elasticity, good corrosion resistance and resistance to high temperatures and deformation. In terms of chemical composition, the corrosion resistance equals that of AISI 301 / 1.4310 steel, in terms of mechanical properties it is a much better choice for responsible parts and components exposed to fatigue. In the annealed state, the steel has an austenitic structure, after heat treatment of ageing it turns into martensite, increasing its strength properties along with obtaining magnetic properties., that is melted as AOD melt type. This alloy offers excellent fatigue strength and good corrosion resistance. main used on valve parts, tanks, springs, spring washers, food knives, diaphragms, low and high temperature parts, heat exchangers, special fittings and installations, machine constructions and components. Steel is intended for the aerospace, petroleum, chemical and petrochemical industries, energy, food and cryogenic industry in the form of strips, wires, sheets and bars.stainless steel grade 17-7 PH is suitable for use in fresh water and industrial atmospheres, and mild chemical and oxidizing environments. It is recommended that 17-7 PH should not be used in salt water or reducing environments.
AISI 631, AMS 5528, AMS 5529, AMS 5568, AMS 5678, ASTM A313 (631), ASTM A564 (631), ASTM A579 (631), ASTM A693 (631), ASTM A705 (631), DIN 1.4568, MIL S-25043, DIN 1.4568, AMS 5673, AMS 5824, ASME SA705, ASTM A579 (grade 62), MIL SPEC, MIL-W-46078, SAE J217, SAE J467, AMS 5644 (type 631),
Forming characteristics of stainless steel grade 17-7PH, 631, X7CrNiAl17-7, UNS S17700 are similar to stainless steel grade 301. For radical forming operations, intermediate annealing may be required.
| Grade | Chemical composition WT % | |||||||
|---|---|---|---|---|---|---|---|---|
| C | Mn | Si | P | S | Cr | Ni | Al | |
| 17-7PH | Max 0.09 | Max 1.0 | Max 0.5 | Max 0.025 | Max 0.025 | 16.00 - 17.25 | 6.50 - 7.75 | 0.75 - 1.25 |
| S17700: AMS 5529/5528, AMS 5644, AMS 5678 | Max 0.09 | Max 1.0 | Max 1.0 | Max 0.040 | Max 0.030 | 16.0 - 18.0 | 6.5 - 7.7 | 0.75 - 1.50 |
| X7CrNiAl17-7, 1.4568 | Max 0.09 | Max 1.0 | Max 0.7 | Max 0.040 | Max 0.015 | 16.0 - 18.0 | 6.5 - 8.3 | 0.7 - 1.5 |
| SUS 631 | Max 0.09 | Max 1.0 | Max 1.0 | Max 0.040 | Max 0.030 | 16.00 - 18.00 | 6.50 - 7.75 | 0.75 - 1.50 |
| Properties | Metric | Imperial |
|---|---|---|
| Thermal conductivity | 16.4 W/mK | 114 BTU in/hr.ft2.°F |
| Thermal expansion co-efficient (@0.000-100°C/32-212°F) | 11 µm/m°C | 6.11 µm/m°C |
For heat treating stainless steel grade 17-7PH, 631, X7CrNiAl17-7, three important steps need to be carried out - austenite conditioning, cooling to transform the austenite to martensite, and precipitation hardening to condition TH 1050 or RH 950.
Annealing of stainless steel grade 17-7PH, 631, X7CrNiAl17-7 is performed at 1066°C (1950°F) for 3 min for every 0.1 inch (2.5 mm) of thickness, and then air cooled.
Stainless steel grade 17-7PH, 631, X7CrNiAl17-7 is solution annealed at 1177°C (2150°F) for 4 h and air cooled. Same step is performed at 1079°C (1975°F) for 4h and air cooled, then at 843°C (1550°F) for 24h and air cooled, and at 760°C (1400°F) for 16h and air cooled. This completed the precipitation hardening process. For excellent results and performance, the material should be clean and free from scale and impurities.
Common arc and resistance methods can be used with stainless steel grade 17-7 PH. It is recommended that during fusion welding inert gas shielding should be performed to reduce the oxidation of aluminum during the process.
Machinability of stainless steel 17-7PH, AISI 631, 1.4568, X7CrNiAl17-7 and UNS S17700 is rated at 75 % of B1112. On machining, this alloy displays long gummy chips and requires chip breakers. It is recommended that slow speeds and constant feeds while machining will provide excellent results.
Steel grade
Special steel