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we offer astm a789 uns s31803 s32750 s32760 duplex stainless steel tubing in wide range of sizes, both welded and seamless stainless steel tubing, duplex steel maintains high strength and excellent corrosion resistance so it can be applied in harsh environment.
material characteristics
astm a789 specification covers seamless tube and welded tube of duplex and super duplex (uns s32205, uns s31803, uns s32760, uns s32750)stainless steel. these duplex steel tube are more prone to precipitation of sigma phase, nitrides and carbides than corresponding austenitic steels, causing embrittlement and reduced corrosion resistance. the formation of intermetallic phases such as sigma phase occurs in the temperature range 600-1000°c and decomposition of ferrite occurs in the range 350-500°c (475°c embrittlement). the high tensile strength of duplex steel tube also implies high fatigue strength. due to their high chromium content, duplex steels offer excellent corrosion resistance in many media.
manufacture & heat treatment
the astm a789/a789m uns 31803 tubes shall be made by the seamless or welded process with no filler metal added. it shall be quenched in cool air or water rapidly to a temperature of 1800°f[980°c]-1900°f[1040°c]. for seamless tubes, as an alternative to final heat treatment in a continuous furnace or batch-type furnace, while the tube temperature is not lower than the specified minimum solution treatment temperature, tubes may be immediately quenched in water or rapidly cooled by other means.
chemical composition requirements
chemical composition for astm a789 uns s31803 tubing, % | |
c | ≤0.030 |
mn | ≤2.00 |
p | ≤0.030 |
s | ≤0.020 |
si | ≤1.00 |
ni | 4.5-6.5 |
cr | 21.0-23.0 |
mo | 2.5-3.5 |
n | 0.08-0.20 |
mechanical properties
tensile strength,min. | yield strength,min. | elongation,min. | hardness brinell, max |
mpa | mpa | % | hb |
620 | 450 | 25 | 290 |
tests and inspection
a tensile test should be performed on samples with no more than 50 roots for astm a789 uns s31803 tubing. for more than 50 tubes, a tensile test should be carried out on samples of two tubes. flaring test(for seamless tubes) and flange test(for welded tubes) shall be performed on one end of each finished tube. the minimum expansion of the inner diameter is 10%. when required by the purchaser, the hydrostatic test shall be in accordance with specification a1016/a1016m, but the hydrostatic test pressure shall be calculated by 64000(441.2) instead of 32000(220.6).
