- Grade / Alloy
- 15-7 Mo
- EN / W.Nr.
- —
- AISI / SAE
- 632
- UNS
- S15700
- Family
- Precipitation hardening
Chemical composition
Chemical composition
Composition limitsComposition ranges for 15-7 Mo sheet within ASTM A693 / AMS 5520 scope.
| Element | Content (% by mass) |
|---|---|
| CrChromium | 14–16 |
| NiNickel | 6.5–7.75 |
| MoMolybdenum | 2–3 |
| AlAluminium | 0.75–1.5 |
| CCarbon | ≤ 0.09 |
| MnManganese | ≤ 1 |
| SiSilicon | ≤ 1 |
| PPhosphorus | ≤ 0.04 |
| SSulfur | ≤ 0.03 |
| FeIron | Balance |
Values describe the grade, not the analysis of a specific batch. The applicable product specification and material certificate determine acceptance. A dash does not mean zero.
What is 15-7 Mo?
15-7 Mo, also known as UNS S15700 and AISI 632, is a semi-austenitic PH stainless steel. In practical terms, it combines high strength, hardness and spring behaviour in thin-section parts. Springs and flexible components need more than the ability to carry a load once: they must also retain their function during movement. These characteristics help explain the applications of 15-7 Mo. Sheet and strip are particularly characteristic product forms for the grade.
15-7 Mo — heat-treatment conditions
For 15-7 Mo, TH1050, RH950 and CH900 also identify different starting routes. TH and RH conditions begin with solution-annealed material; CH900 begins with cold-rolled material. This explains the different spring and sheet properties found under the same grade name.
This overview covers sheet and strip conditions. RH950 subzero preparation and the Condition C starting state for CH900 are part of the condition, independently of the final ageing temperature.
Temperatures are nominal. Holding time starts after the material reaches the specified temperature. The table explains the conditions; furnace tolerances, section size and acceptance requirements follow the applicable product specification.
| Condition | Temperature (°C) | Time at temperature | Cooling |
|---|---|---|---|
| Condition A | Solution-annealed starting condition | Per product specification | Per product specification |
| Condition C | Cold-rolled starting condition | Not a heat treatment | — |
| T | 760; intermediate condition before TH1050 | 90 min | To 16 °C or below within 1 h; hold 30 min |
| R100 | 954; followed by −73 °C | 10 min; then 8 h at −73 °C | Return to room temperature before RH950 |
| TH1050 | 566 after Condition T | 90 min | Air |
| RH950 | 510 after Condition R100 | 1 h | Air |
| CH900 | 482 after Condition C | 1 h | Air |
15-7 Mo — mechanical properties by condition
Typical room-temperature values for sheet and strip. Condition A HRB and aged HRC use different hardness scales. CH900 depends on cold reduction and is not assigned a single general mechanical value.
MPa and N/mm² are equivalent units. Typical values are neither batch test results nor guaranteed acceptance limits; stated minima and maxima apply only within the product scope described.
| Condition | Tensile Rm (MPa) | Yield Rp0.2 (MPa) | Elongation (%) | Hardness |
|---|---|---|---|---|
| Condition A | 860 | 380 | 30 | 88 HRB |
| TH1050 | 1450 | 1380 | 6 | 43 HRC |
| RH950 | 1690 | 1515 | 6 | 48 HRC |
An approximate material-family conversion, not a test result for this grade.
What molybdenum contributes
15-7 Mo is closely related to 17-7 PH. Mo in its name stands for molybdenum. An addition of approximately 2–3 percent molybdenum contributes to its properties, including those relevant where high strength and behaviour at elevated temperature matter. This relationship does not make 15-7 Mo and 17-7 PH identical. Their compositions differ and, although their applications can overlap, each has its own material definition.
Springs and aerospace components
High-strength springs, flexible elements and various thin-section aerospace parts are recognised applications of 15-7 Mo. A thin metal component acting as a spring can carry a defined force within a compact space. Rather than relying on a thick section, the part makes use of the strength and elastic behaviour of its material. This is why 15-7 Mo is associated with flat products valued for their mechanical properties, rather than simply with general-purpose stainless sheet.
It is different from 15-5 PH
Similar numbers can cause confusion between 15-7 Mo and 15-5 PH. In fact, 15-5 PH has a different composition and structure and is identified as UNS S15500. The role of 15-7 Mo in thin sheet, strip and spring applications differs from the familiar use of 15-5 PH in shafts, connections and load-bearing components. High strength is a shared theme across the PH family, but the family is broad. The meaningful distinction is the combination of properties and applications, rather than simply the numbers in the names.
Typical application areas
Springs, flexible components and aerospace parts.
Product and cutting options
Relevant product forms for this material are listed below. Availability varies with grade and dimensions.