A286 is an austenitic precipitation hardened (PH) stainless steel. It has excellent creep strength and can be used at higher temperatures (up to 700°C) than the 12% CrMoV martensitic stainless steels.
Approximate Composition – 15% Cr, 25.0% Ni, 1.3% Mo, 0.30% V, 0.05% C, 2.0% Ti, 0.15% Al (Exact composition ranges vary between EN and ASTM standards).
This grade combines the following characteristics:
- Moderate strength – 900 MPa UTS, 600 MPa 0.2% PS at room temperature
- Excellent high temperature strength – 460 MPa 0.2% PS at 550°C, 380 MPa at 650°C
- Excellent creep strength – 415 MPa rupture stress at 550°C at 100000 hours, 132 MPa at 650°C
- Good toughness due to austenitic structure, even at cryogenic temperatures
- Good corrosion resistance
- Very low magnetic permeability
- Weldable with care.
A286 is a metallurgically complex stainless steel. Its main purpose is to provide high temperature creep strength. Creep is time dependent deformation at elevated temperatures. It does this using a precipitation hardening mechanism involving a compound of nickel, titanium and aluminium. This compound is formed in tiny particles by solution annealing at 980°C followed by an ageing treatment at about 720°C. It is these particles which impart the very high strength to this grade. Although not primarily designed for use at low temperatures, the combination of high strength, good toughness and non-magnetic properties make it a candidate for cryogenic applications.
Applications which illustrate these features include:
Pressure equipment, high temperature bolting, steam turbines, nuclear reactors, gas turbines, rocket engines, jet engines, exhaust systems, cryogenics.