ASTM A789 DSS Tubing & ASTM A790 DSS Pipes

Duplex stainless steel tubing and pipes, either seamless or welded, are intended for services requiring general corrosion resistance, with particular emphasis on resistance to stress corrosion cracking. There are several prevalent duplex grades that can be readily sourced from most pipe mills: UNS S31803, UNS S32205, UNS S32750 and UNS S32760. Both S31803 and S32205 are designated as alloy 2205, while S32750 are designated as alloy 2507.

Duplex stainless steel tubing or tube, either seamless or welded, shall be manufactured in according with ASTM A789 (ASME SA-789), which is a hollow product of round or any other cross section having a continuous periphery. The tubing is produced to the actual outside diameter and minimum or average wall thickness specified by the purchaser. The wall thickness of tubing is normally given in decimal parts of an inch rather than as a fraction. When gauge numbers are given without reference to a system, Birmingham Wire Gauge (BWG) is implied.

Gauge No.	B.W.G. inch
0000	0.454
000	0.425
00	0.380
0	0.340
1	0.300
2	0.284
3	0.259
4	0.238
5	0.220
6	0.203
7	0.180
8	0.165
9	0.148
10	0.134
11	0.120
12	0.109
13	0.095
14	0.083
15	0.072
16	0.065
17	0.058
18	0.049
19	0.042
20	0.035
21	0.032
22	0.028
23	0.025
24	0.022
25	0.020
26	0.018
27	0.016
28	0.014
29	0.013
30	0.012
31	0.010
32	0.009
33	0.008
34	0.007
35	0.005
36	0.004

*The wall thickness indicated by Birmingham Wire Gauge numbers, 1 inch = 25.4 mm.

Duplex stainless steel pipe, either seamless or straight-seam welded, shall be manufactured in accordance with ASTM A790 (ASME SA-790), which is a tube with a round cross section conforming to the dimensional requirements for nominal pipe size & schedule number as tabulated in ASME B36.10M and ASME B36.19M. For custom-designed special DSS pipe have diameter not listed in the above mentioned standards, the nominal diameter corresponds to the outside diameter and the actual wall thickness shall be specified.

Chemical Composition Requirements

EL.	S31803	S32205	S32750	S32760
C	≤0.030	≤0.030	≤0.030	≤0.030
Mn	≤2.00	≤2.00	≤1.20	≤1.00
P	≤0.030	≤0.030	≤0.035	≤0.030
S	≤0.020	≤0.020	≤0.020	≤0.010
Si	≤1.00	≤1.00	≤0.80	≤1.00
Ni	4.5-6.5	4.5-6.5	6.0-8.0	6.0-8.0
Cr	21.0-23.0	22.0-23.0	24.0-26.0	24.0-26.0
Mo	2.5-3.5	3.0-3.5	3.0-5.0	3.0-4.0
N	0.08-0.20	0.14-0.20	0.24-0.32	0.20-0.30
Cu	-	-	≤0.50	0.50-1.00
W	-	-	-	0.50-1.00

*Product analyses for duplex grades S31803, S32205, S32750 and S32760 of both ASTM A789 and ASTM A790 shall conform to chemical requirements listed in the table. Unit: weight percentage.

Mechanical Properties

Test	S31803	S32205	S32750	S32760
Su	620 [80]	655 [95]	800 [116]	750 [109]
Sy	450 [65]	485 [70]	550 [80]	550 [80]
El.	25	25	15	25
HBW	290	290	300	310
HRC	30	30	32	32
HV	390	290	300	310

*Tensile and hardness requirements for ASTM A789 & ASTM A790 Grade S31803, S32205, S32750 and S32760.
*S_u: tensile strength, min. MPa [ksi]; *S_y: yield strength, min. MPa [ksi]; El.: elongation in 2″, min. %.
*Hardness, maximum: Brinell (HBW), Rockwell (HRC), Vickers (HV).

Manufacture & Heat Treatment

According to ASTM A789 or ASTM A790, the seamless duplex stainless steel tubing or pipe shall be made by a seamless hot-rolled or cold-drawn process. The welded duplex stainless steel tubing or pipe shall be made by an automatic welding process, with no addition of filler metal in the welding operation. All DSS tubes made to ASTM A789 and all DSS pipes made to ASTM A790 shall be furnished with the solution annealing treatment followed by a water quench. The solution annealing temperature ranges for S31803, S32205, S32750, and S32760 are 1870-2010°F [1020-1100°C], 1870-2010°F [1020-1100°C], 1880-2060°F [1025-1125°C], 1960-2085°F [1070-1140°F], respectively.

Applications

The ASTM A789 DSS tubing and ASTM A790 DSS pipe can be used for heat exhangers in refineries, chemical industries, process industries, and other industries using water as a coolant. They can be used for the connection of chemical tanks, chemical reactor vessels, flue gas filters, acetic and phosphoric acid handling systems, oil & gas flow lines, pulp and paper piping systems, food and brewery process piping, etc. Pipes and tubes made from super duplex grades S32750 and S32760 can be used for seawater desalination systems, oil and gas separators, salt evaporation piping, and geothermal well heat exchanging systems.