Characteristic:
The high concentration of molybdenum,chromium and nitrogen made
254SMO has very good resistance to pitting and crevice corrosion
performance. Copper improved corrosion resistance in some of the
acid . In addition, due to its high content of nickel,chromium and
molybdenum, so that 254SMO have a good stress strength corrosion
cracking performance.
1.A lot of a wide range use of experience has shown that even iin
higher temperatures, 254SMO in the sea water is also highly
resistant to corrosion performance gap, only a few types of
stainless steel with this performance.
2.254SMO such as bleach paper required for the production of acidic
solution and the solution halide oxidative corrosion resistance and
corrosion resistance can be compared to the most resilient in the
base alloy of nickel and titanium alloys.
3.254SMO due to a high nitrogen content, so its mechanical strength
than other types of austenitic stainless steel is higher. In
addition, 254SMO also highly scalable and impact strength and good
weldability.
4.254SMO with high molybdenum content can make it higher rate of
oxidation in the annealing , which after the acid cleaning with
rough surface than normal stainless steel is more common than the
rough surface. However,has not adversely affected for the corrosion
resistance of this steel .
Metallurgical structure
254SMO is face-centered cubic lattice structure. In order to obtain
austenitic structure, 254SMO general annealing in the 1150-1200℃.In
some cases, the material maybe with the traces of metal middle
phase (χ phase and α-phase). However,their impact strength and
corrosion resistance are not adversely affected in normal
circumstances. When placed in the range of 600-1000℃, they may
phase in the grain boundary precipitation.
Corrosion resistance
254SMO with very low carbon content, which means that the danger by
the heating caused of carbide precipitation is very small. Even in
the 600-1000℃ after one hour sensitization still able to Strauss
through the intergranular corrosion test (Strauss Test ASTMA262
order E).However, because of the high-alloy steel content. In the
above-mentioned temperature range intermetallic phase with the
possibility of metal in the grain boundary precipitation. These
sediments do not make it occur intergranular corrosion in the
corrosive media applications, then,welding can be carried out
without intergranular corrosion.But in the heat of concentrated
nitric acid, these sediments may be caused intergranular corrosion
in heat-affected zone. If ordinary stainless steel in the solution
that containing chloride, bromide or iodide,it will show pitting,
crevice corrosion or stress corrosion cracking form by localized
corrosion. However, in some cases,the existence of halide will
speed up the uniform corrosion. Particularly in the non-oxidizing
acid. In pure sulfuric acid, 254SMO with a much greater corrosion
resistance than 316(common stainless steel),but with abated
corrosion resistance compared to 904L (NO8904) stainless steel in
high concentrations. In the sulfuric acid containing chloride ions
, 254SMO with the largest corrosion resistance ability.The 316 can
not be used for stainless steel in hydrochloric acid since it may
occur localized corrosion and uniform corrosion, but 254SMO can be
used in diluted hydrochloric acid in general temperatures,uder the
border region do not need to worry about corrosion occurred.
However, we must try to avoid the gap cracks. In the fluoride
silicate (H2SiF4) and hydrofluoric acid (HF), the corrosion
resistance of ordinary stainless steel is very limited, and 254SMO
can be used in a very wide temperature and concentration.
Applied field:254SMO is a mult-purpose material can be used in many industrial
applications:
1. Petroleum, petrochemical equipment, petro-chemical equipment,
such as the bellows.
2. Pulp and paper bleaching equipment, such as pulp cooking,
bleaching, washing filters used in the barrel and cylinder pressure
rollers, and so on.
3. Power plant flue gas desulphurization equipment, the use of the
main parts: the absorption tower, flue and stopping plate, internal
part,spray system.
4. At sea or sea water processing system, such as power plants
using sea water to cool the thin-walled Condenser, desalination of
sea water processing equipment,can be applied even though the water
may not flow in the device.
5. Desalination industries, such as salt or desalination equipment.
6. Heat exchanger, in particular in the working environment of
chloride ion.
