|
Alloy |
UNS Number |
SAE Number |
|
254SMO |
UNS S31254 |
GENERAL PROPERTIES
Alloy 254 SMO is a high end, molybdenum and nitrogen alloyed super austenitic stainless steel with low carbon content. It demonstrates outstanding resistance to pitting, crevice corrosion stress cracking, and corrosion fatigue uniform corrosion. Alloy 254 SMO is substantially stronger than the common austenitic grades, with strength nearly twice that of 300 series stainless steel. It is also characterized by high ductility and impact strength. With high levels of chromium, molybdenum, and nitrogen, Alloy 254 SMO is frequently used in high chloride environments, such as brackish water, seawater, pulp mill bleach plants, and other chloride process streams. In some applications it has even been found to be a more cost effective substitute for high nickel and titanium alloys.
RESISTANCE TO CORROSION
The high content of alloying elements gives Ultra 254 SMO exceptionally good resistance to uniform corrosion. It can withstand a wide range of acids due to the high alloying content of chromium and molybdenum. Resistance to pitting and crevice corrosion is determined mainly by the chromium, molybdenum, and nitrogen content. 254 SMO has high amounts of these elements and is suitable for demanding environments like chlorinated sea water. Resistance to stress corrosion cracking increases with increased content of nickel and molybdenum in particular. This means that Ultra 254 SMO has very good resistance to stress corrosion cracking.
PHYSICAL PROPERTIES
|
Melting Point |
Density |
Specific Gravity |
Modulus of Elasticity |
|
1320-1390 ℃ |
8.0 g/cm3 |
7.8 |
195 GPa |
MECHANICAL PROPERTIES
|
Alloy |
Tensile Strength |
Yield Strength |
% Elongation |
|
254SMO |
98,600 |
43,500 |
50 |
CHEMICAL PROPERTIES
|
Alloy |
C |
Si |
Mn |
P |
S |
Cr |
Ni |
Mo |
Cu |
N |
|
254SMO |
0.020 |
0.80 |
1.00 |
0.030 |
0.010 |
20 |
18 |
6.1 |
0.7 |
0.20 |
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.
HEAT TREATMENT
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.
Stainless steel grade 254 SMO does not respond to heat treatment. Hardening is possible only through cold reduction.
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