254 SMO stainless steel tube

254 SMO stainless steel tube
The 254 SMO stainless steel tube is an austenitic stainless steel tube. Due to its high molybdenum content, it has extremely high pitting and crevice corrosion resistance. The 254 SMO stainless steel tube was developed and developed for use in halide-containing environments such as seawater. 254SMO is the 1978 patent steel number of Avesta, Sweden
 


The 254 SMO stainless steel tube has good resistance to uniform corrosion. Especially in halide-containing acids, the steel is superior to ordinary stainless steel. Its C contains <0.03%, so it is called pure austenitic stainless steel tube.
 

Manufacturing process
Since the 254S MO stainless steel tube is a high-alloy material, it is quite complicated in the manufacturing process. Generally, people can only rely on traditional techniques to manufacture such special stainless steel tubes, such asseamless, pouring, forging, calendering and the like.
 
 
Heat treatment
If additional heat treatment is needed due to further processing the following is recommended.
Solution annealing
1150–1200°C (2100–2190°F), quenching in water. Thin-walled tubes min. 1130°C (2060°F), quenching in air/water.
 
 

National standards:
UNS S31254, DIN/EN 1.4547, ASTM A280, ASME SA-240
Matching welding consumables:
ERNiCrMo-3 welding wire, ENiCrMo-3 welding rod
 
 

Chemical composition (nominal) %

Standards	Grade	C	Si	Mn	P	S	Cr	Ni	Mo	N	Cu
Outokumpu	254 SMO	≤0.020	≤0.80	≤1.00	≤0.030	≤0.010	19.5-20.5	17.5-18.5	6.0-6.5	0.18-0.22	0.5-1.0
ASTM A182	F44 S31254	≤0.020	≤0.80	≤1.00	≤0.030	≤0.010	19.5-20.5	17.5-18.5	6.0-6.5	0.18-0.22	0.5-1.0
DIN EN 10088-3-2005	X1CrNiMoN20-18-7 1.4547	≤0.020	≤0.70	≤1.00	≤0.030	≤0.010	19.5-20.5	17.5-18.5	6.0-7.0	0.18-0.25	0.5-1.0

 
 
 
Mechanical properties

Standards	Grade	Tensile strength	Yield strength	Elongation	Hardness
Outokumpu	254 SMO	≥650 MPa	≥300 MPa	≥ 35%	≤96 HRB

 
 
 
 
Features of 254SMO stainless steel tube
1. 254SMO stainless steel pipes also have high crevice corrosion resistance in seawater, and only a few types of stainless steel pipes have this property.
2. The corrosion resistance of 254SMO stainless steel tubes in acidic solutions and oxidizing halide solutions such as paper bleaching can be compared to nickel-based alloys and titanium alloys with the strongest corrosion resistance.
3. Since the 254SMO stainless steel tube has a high nitrogen content, its mechanical strength is higher than other types of austenitic stainless steel tubes. In addition, the 254SMO stainless steel tube also has high ductility and impact strength as well as good weldability.
4. The high molybdenum content of the 254SMO stainless steel tube allows it to have a higher oxidation rate during annealing, resulting in a rougher surface than the normal stainless steel tube after pickling. However, this has no adverse effect on the corrosion resistance of the steel.
 
 

Application areas of 254SMO stainless steel pipe:
1. Ocean: marine structures in the sea environment, seawater desalination, marine aquaculture, seawater heat exchange, etc.
2. Environmental protection field: flue gas desulfurization device for thermal power generation, wastewater treatment, etc.
3. Energy field: atomic power generation, comprehensive utilization of coal, and ocean wave power generation.
4. Petrochemical industry: refining, chemical and chemical equipment.
5. Food field: salt making, soy sauce brewing, etc.
6. High concentration chloride ion environment: paper industry, various bleaching devices