ASTM A815 S31803 Duplex Steel Buttwelded 90Deg Elbow Pipe Fitting
B16.9
ASTM A815 Standard for Malleable Ferritic, Ferritic Austenitic, and
Martensitic Stainless Steel Pipe fittings
S31803 belongs to duplex stainless steel. 22% chromium duplex
(austenitic/ferritic) steel (2205 type), with moderate to high
strength and good resistance to common corrosion/stress,
corrosion/cracking.
This duplex steel has the ability to withstand chloride
environments and sulfide stress corrosion, and its strength is
approximately twice that of standard austenitic stainless steel.
When higher mechanical strength/lighter weight is required, this
alloy can be successfully used as a substitute for 300 series
austenitic stainless steel. F51 is easy to use with many standard
arc welding equipment for welding, but it is not recommended for
oxygen and ethylene block welding because there may be
carbonization of the welding metal.
Duplex Steel ASTM A815 S31803 Chemical composition
| Grade | C | Mn | Si | P | S | Cr | Ni | Mo | Fe | Other |
| S31803 | ≤0.03 | ≤2 | ≤1 | ≤0.03 | ≤0.02 | 21~23 | 4.5~6.5 | 2.5~3.5 | margin | N 0.08~0.2 |
Duplex Steel ASTM A815 S31803 Minimum mechanical performance value
| Grade | Tensile strength (Rm N/mm2) | Yield strength (RP 0.2N/mm2) | Elongation rate (A5%) | Brinell hardness (HB) |
| S31803 | 620 | 450 | 25 | 290 |
What is duplex stainless steel?
First, let's get to know duplex stainless steel. Duplex Stainless
Steel (Duplex Stainless Steel, referred to as DSS), refers to
ferrite and austenite each accounted for about 50%, generally less
phase content also needs to reach at least 30% of stainless steel.
In the case of low C, the Cr content is 18% to 28%, and the Ni
content is 3% to 10%. Some steels also contain Mo, Cu, Nb, Ti, N
and other alloying elements. This kind of steel has the
characteristics of austenitic and ferritic stainless steel,
compared with ferritic, higher plasticity, toughness, no room
temperature brittleness, intergranular corrosion resistance and
welding performance are significantly improved, while also
maintaining the ferritic stainless steel 475℃ brittleness and high
thermal conductivity, with superplasticity and other
characteristics. Compared with austenitic stainless steel, it has
higher strength and higher resistance to intergranular corrosion
and chloride stress corrosion. Duplex stainless steel has excellent
pitting resistance and is also a nickel-free stainless steel.
The characteristics of duplex stainless steel include:
1. molybdenum containing duplex stainless steel has good resistance
to chloride stress corrosion under low stress, compared with
austenitic stainless steel, high strength and resistance to
intergranular corrosion and chloride stress corrosion has been
significantly improved.
2. duplex stainless steel has the characteristics of austenitic and
ferritic stainless steel, compared with ferrite, plasticity,
toughness is higher, with superplasticity and other
characteristics.
3. Duplex stainless steel is neither prone to welding hot cracks
like the welding heat affected zone of ferritic stainless steel,
nor more sensitive to welding hot cracks like austenitic stainless
steel.
4. duplex stainless steel and austenitic stainless steel corrosion
resistance is equivalent, some duplex stainless steel (such as
25%Cr, especially nitrogen containing high chromium duplex
stainless steel) corrosion resistance and crevice corrosion
performance exceeds 316L.
Duplex stainless steel with high strength, good impact toughness
and good overall and local resistance to stress corrosion. Its
yield strength is twice that of austenitic stainless steel, giving
this alloy a performance advantage over ordinary stainless steels
such as 304, 316. Because of the obvious advantages in performance,
the price of this duplex steel is generally higher than that of
ordinary austenitic stainless steel. Therefore, when customers
purchase products, they also need to choose according to the
specific pipeline design requirements.
