Alloy 254

Introduction

Stainless steel grade 254 SMO™ is a very high end austenitic stainless steel. It is designed with a combination of impact toughness resistance to chloride stress corrosion cracking, pitting and crevice corrosion with strength that is twice that of the stainless steel 300 series. For certain applications, grade 254 SMO™ has been reported to be a cost-effective substitute for high nickel and titanium alloys. It is known to possess excellent workability as well. The following sections will discuss in detail about stainless steel grade 254 SMO™.

Equivalent Grades Of Alloy 254

Zeon Grade Alloy Name UNS EN / DIN / W Nr. Trademarks
Zeon254 Alloy 254 UNS S31254 1.4547 SMO254

Chemical Composition Of Alloy 254

Element Content (%)
Iron, Fe 55.69
Chromium, Cr 20
Nickel, Ni 18
Molybdenum, Mo 6.1
Nitrogen, N 0.20
Carbon, C 0.010

Physical Properties Of Alloy 254

Properties Metric Imperial
Density 8 g/cm3 0.289 lb/in3

Mechanical Properties Of Alloy 254

Properties Metric Imperial
Tensile strength 680 MPa 98600 psi
Yield strength 300 MPa 43500 psi
Modulus of elasticity 195 GPa 28300 ksi
Shear modulus 75 GPa 10900 ksi
Poisson’s ratio 0.30 0.30
Elongation at break 50 % 50 %
Hardness, Brinell 210 210

Thermal Properties Of Alloy 254

Properties Metric Imperial
Thermal expansion co-efficient (@20-100°C/68-212°F) 16.5 µm/m°C 9.17 µin/in°F
Thermal conductivity 14 W/mK 97.2 BTU in/hr.ft².°F
Corrosion Resistance Properties of Alloy 254
The high chromium content and particularly the molybdenum content gives 254 SMO excellent resistance to pitting and crevice corrosion. Tests in natural seawater at 60°C (140°F) have shown that SMO254 can be exposed for prolonged periods, without suffering crevice corrosion.

Processing Alloy 254

Machinability Stainless steel grade 254 SMO™ is quite tough to machine due to the extremely high work hardening rate and lack of sulfur content; however using sharp tools, overpowered machine tools, positive feeds, good amount of lubrication, and slow speeds tend to provide good machining results.
Welding: Welding of stainless steel grade 254 SMO™ requires filler material without which it results in poor strength properties. Filler metals such as AWS A5.14 ERNiCrMo-3, and alloy 625 are recommended. Electrodes used in the process, have to match with AWS A5.11 ENiCrMo-12.
Annealing Annealing of this material should be performed at 1149-1204°C (2100-2200°F), which should be followed by a water quench.
Hot Working Forging, upsetting and other operations relating to this material can be performed at 982 - 1149°C (1800 - 2100°F). It is recommended that temperatures do not exceed this range as it would result in scaling and reduction in the workability of the material. To re-attain maximum corrosion resistant properties, it is advisable to perform post-process annealing.
Cold Working Cold working can be carried out using all the traditional methods; however the process would be tough due to its high work hardening rate. The result will provide the material with increased strength and toughness.
Hardening Stainless steel grade 254 SMO™ does not respond to heat treatment. Hardening is possible only through cold reduction.

Applications Of Alloy 254
Saltwater handling Tall oil distillation columns Flue gas desulfurization scrubbers Components used in petroleum production Food processing equipment
Process equipment in chemical industry Bleaching equipment in the pulp and paper industry Flue-gas cleaning Desalination Heat exchangers