Duplex stainless steel 2205 (00Cr22Ni5Mo3N, S31803) chemical composition%
Grade C
≤ Mn
≤ P
≤ S
≤ Si
≤ Ni Cr Mo N
2205 0.030 2.0 0.03 0.02 1.0 4.5-6.5 2.5-3.5 0.08-0.2 21-23

Duplex stainless steel 2205 (00Cr22Ni5Mo3N, S31803) mechanical properties
Grade Temperature / state yield strength σb
       ≥ (ksi)
  Tensile strength σ0.2
           ≥ (ksi) Elongation δ
Gauge 2in or 50mm (or 4D), ≥,%
Plate 2205 70ºC / annealing 7510535
Plate 2205 200ºC / anneal 5090
Board 400ºC / anneal 2205 4580
2205 board 600ºC / anneal 4079
 
   2205 duplex stainless steel uses: used in oil refining, fertilizer, paper, petroleum, chemical resistance, high temperature concentrated nitric acid and other marine heat exchangers and cold shower unit and devices.

The main representative of duplex stainless steel grades
     DSS can generally be divided into four categories:
         Low alloy type - representative grades are UNS S32304 (23Cr-4Ni-0.1N)
                       PREN value of 24 ~ 25
        Alloy type - representative grades are UNS S31803 (22Cr-5Ni-3Mo-0.15N),
                       PREN value of 32 to 33
         High alloy type - standard grades are UNS S32550 (25Cr-6Ni-3Mo-2Cu-0.2N),
                       PREN value of 38 ~ 39
         Super duplex stainless steel type - standard grades have UNS S32750 (25Cr-7Ni-3.7Mo-0.3N),
                       PREN value> 40
     (※ PREN pitting index PREN = Cr% + 3.3 × Mo% + 16 × N%)
   Low alloy type UNS S32304 molybdenum-free, in terms of stress corrosion can replace AISI304 or 316 to use.
   Corrosion resistance of the alloy type UNS S31803 is between AISI 316L and 6% Mo + N austenitic stainless steel.
   High alloy type, typically containing 25% Cr, also contains molybdenum and nitrogen, and some also contain copper and tungsten, corrosion resistance of these steels is higher than 22% Cr
Duplex stainless steel.
   Super duplex stainless steel type, with high molybdenum and nitrogen, and some also contain tungsten and copper, suitable for harsh media conditions, with good
General corrosion and mechanical properties, can be compared with the super austenitic stainless steel beauty.
                     The main chemical composition of representative grades
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Duplex stainless steel chemical composition,%
Grade Type UNS C Cr Ni Mo Cu N
Low alloy type S32304 ≤0.03 23 4 0.05 / 0.20
Alloy type S31803 ≤0.03 22 5 3 0.08 / 0.20
Alloy type S32205 ≤0.03 22 5 3 0.14 / 0.20
High alloy type S32550 0.04 25 6 3 2 0.10 / 0.25
Super DSS S32750 ≤ 0.03 25 7 4 0.24 / 0.32

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   As can be seen from the table: S 32205 is derived from the steel S31803 in ASTM A 240 / 240M-99a in the standard
1999 was satisfied that the subject matter, it's Cr, Mo and N elements interval than the narrow, easy to reach equilibrium phase (ie two similar half and half)
Improve the strength of steel, corrosion resistance and weldability, and more for the high performance requirements and the need for welding materials such as oil and gas pipelines
And so on.
4 duplex stainless developments
    It is noteworthy that the low manganese duplex stainless steel alloy development. Past decade related to countries such as the United States, South Africa and other research to manganese
Generation nickel duplex stainless steel development, but in addition to casting, the development of new steel grades and more have metastable austenitic, martensitic after by cold deformation
Changes to improve the strength, it is difficult to make use of the welding member, it is difficult to adapt certain environments, such as corrosive environment may result in stresses, and
Use very limited in recent years in Sweden developed low low manganese nickel duplex stainless steel is more mature, well-targeted, in order to replace the use of nickel-
304 wide, and may even replace a considerable price and 304, currently in use are not widely 2304 duplex stainless steel, with the actual promotion of
Value, it is noteworthy.
   Sweden Avesta Polarit AB developed LDX 2101 duplex stainless steel (21.5% Cr, 5% Mn, 1.5% Ni, 0.22% N)
, Due to increased nitrogen in steel, to obtain a stable austenite phase balance and stability are better organized, analysis of intermetallic phases
That is not sensitive to the precipitation of the most sensitive temperature 650 ℃, 10h after heat shock value was reduced to 50J, its organizational stability compared with 2205 steel
Okay. The high-strength steel, corrosion and 304 equivalent, can be welded, the life cycle cost compared to austenitic stainless steel is low.
   LDX 2101 steel industry has conducted trial, after AOD / CLU continuous casting furnace refining, production of long products and plate cast embryo embryo, but the current
Has not been widely promoted, given that it has good overall performance, a wide range of potential uses, especially as a useful structure
Future, for example, instead of 2205 is used as a bridge structure, the system can also be used in reinforced concrete, to solve the chlorine from
Environmental pollution problems in the sub-corrosion materials, in addition, can be replaced by 304 and 316 steel containers, towers, hot water tanks and heating
And so on.
   From the point of view of the world consumption of stainless steel, duplex stainless steel represents a very small share, its price is higher, the price ratio
Look: If 304,304L is 1, 316L of 1.3, compared with 1.6 and 2205, indicating that in order to increase the market share of duplex stainless steel,
There should be more affordable, with the most common 304 (304L) steel compete with new steel grades or valuable, of course, in this respect also
There are a lot of work to do.
     It is worth mentioned as well as the development of super duplex stainless steel containing manganese, developed in Germany, containing 25% Cr, 6% Mn, 6% Ni, 3% M
o, 2% W, and ~ 0.5% N, and Cu as well as high alloy steel, of the steel by solid solution strengthening, σ0.2 reach 550MPa, containing more than 0.15%
Similar steels N's was nearly 70MPa, the critical pitting temperature (CPT) reached 70 ℃, good corrosion resistance, wear in Austria also opened
Made a BO A920 (26% Cr, 7% Ni, 3% Mn, 4% Mo, 0.35% N) super duplex stainless steel, PREN value of 45, σ0.2 of ~ 6
00MPa, AK is 100 ~ 200J, suitable for small-size high-speed operation of the system components. These two steels is still in the laboratory stage
Both of these steels are improved by adding manganese solubility of nitrogen, due to the high alloy content, organizational stability is relatively low, easily precipitate
Brittle phase. [Wujiu 2003.09.12]