Mechanical Properties of
Duplex stainless steel
Table 3.
Typical mechanical properties of two duplex stainless steel alloys
|
Grade |
2205 |
UR52N+ |
|
Tensile Strength
(MPa) |
620 |
770 |
|
Proof Stress 0.2%
(MPa) |
450 |
550 |
|
Elongation A5
(%) |
25 |
25 |
Physical Properties of
Duplex stainless steel
Table 4.
Typical physical properties of two duplex stainless steel alloys
|
Property |
2205 |
UR52N+ |
|
Density
(g.cm3) |
7.805 |
7.810 |
|
Modulus of Elasticity
(GPa) |
200 |
205 |
|
Electrical Resistivity
(Ω.m) |
0.085x10-6 |
0.085x10-6 |
|
Thermal Conductivity
(W/m.K) |
19 at
100°C |
17 at
100°C |
|
Thermal Expansion
(m/m.K) |
13.7x10-6 to
100°C |
13.5x10-6 to
200°C |
Corrosion Resistance of
Duplex stainless steel
Duplex
stainless steel are extremely corrosion resistant. They have
high resistance to intergranular corrosion. Even in chloride and sulphide
environments, Duplex
stainless steel exhibit very high resistance to stress corrosion
cracking.
The super duplex grades are even more resistant to
corrosion.
Heat Resistance of
Duplex stainless steel
The high chromium content of Duplex
stainless steel
that p rotects against
corrosion, causes embrittlement at temperatures over about 300°C.
At low temperatures duplex stainless steels have better
ductility than the ferritic and martensitic grades. Duplex grades can readily be
used down to at least -50°C.
Fabrication of
Duplex stainless steel
Fabrication of all stainless
steel should be done only with
tools dedicated to stainless steel materials. Tooling and work surfaces must be
thoroughly cleaned before use. These precautions are necessary to avoid cross
contamination of stainless steel
by easily corroded metals that may discolour the surface of the
fabricated product.
Heat Treatment of
Duplex stainless steel
Duplex
stainless steel cannot be hardened by heat treatment. They can
however be work hardened.
Solution treatment or annealing can be done by rapid cooling
after heating to around 1100°C.
Machinability
Although machinable, the high strengths of Duplex
stainless steel makes
machining difficult. As an example, machining of 2205 is around 20% slower than
for 304.
Machining can be enhanced by using the following rules:
·
Cutting edges must be kept sharp. Dull edges cause excess work
hardening.
·
Cuts should be light but deep enough to prevent work hardening by
riding on the surface of the material.
·
Chip breakers should be employed to assist in ensuring swarf
remains clear of the work
·
Low thermal conductivity of austenitic alloys results in heat
concentrating at the cutting edges. This means coolants and lubricants are
necessary and must be used in large quantities.
Welding of
Duplex stainless steel
Duplex
stainless steel have
good weldability. All standard welding processes can be used. They are not quite
as easily welded as the austenitic grades but low thermal expansion in duplex
grades reduces distortion and residual stresses after welding. The recommended
filler material for 2205 stainless steel is 2209.
Applications of
Duplex stainless steel
Duplex
stainless steel
are typically used in:
·
Chemical processing, transport and storage
·
Oil and gas exploration and offshore rigs
·
Oil and gas refining
·
Marine environments
·
Pollution control equipment
·
Pulp & paper manufacturing
·
Chemical process plant
Supplied Forms
Aalco typically supplies 2205 duplex stainless steel in the
following forms:
·
Fittings & Flanges
·
Pipe
·
Plate
·
Sheet
·
Tube
·
Bar
|