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ASTM A789

ASTM A789

ASTM A789 is a standard for seamless and welded Ferritic/Austenitic stainless steel tubing for services requiring general corrosion resistance, with particular emphasis on resistance to stress corrosion cracking. These steel are susceptible to embitterment if used for prolonged periods at elevated temperatures. As a welded tube factory, MW supplies above standards in welded condition. Above standards are widely used for industrial pressure tubing and piping. And MW is certified with PED 2014/68/EU and AD2000, which is specialized certification for pressure tubing and piping. Bright Annealing: Hydrogen bright annealed in line to 1900 ℉(1040℃) minimum and rapidly water quenched is processed for all grades. Surface Condition: The tubes, after final heat treatment(Bright annealing), shall be chemically descaled or pickled free of scale. When bright annealing is used, pickling or chemical descaling is not necessary.

Available Grades and Chemical Requirements

Available Grades and Chemical Requirements

Grade

Composition, %

C

Mn

P

S

Si

Ni

Cr

Mo

N

max

max

max

max

Austenitic

304

0.08

2.0 max

0.045

0.03

1.00

8.0-11.0

18.0-20.0

304L

0.03

2.0 max

0.045

0.03

1.00

8.0-13.0

18.0-20.0

316L

0.03

2.0 max

0.045

0.03

1.00

10.0-14.0

16.0-18.0

2.0-3.0

310S

0.08

2.0 max

0.045

0.03

1.00

19.0-22.0

24.0-26.0

321

0.08

2.0 max

0.045

0.03

1.00

9.0-12.0

17.0-19.0

Austenitic-Ferritic

S31803

0.03

2.0 max

0.03

0.02

1.00

4.5-6.5

21.0-23.0

2.5-3.5

0.08-0.2

2205

0.03

2.0 max

0.03

0.02

1.00

4.5-6.5

22.0-23.0

3.0-3.5

0.14-2.0

2507

0.03

1.2 max

0.035

0.02

0.80

6.0-8.0

24.0-26.0

3.0-5.0

0.24-0.32

Mechanical Properties

Mechanical Properties

Grade
UNS
Designation
Tensile Requirements
Hardness Requirements
Tensile Strength, min
Yield Strength, min
Elongation in 2 in. or (50mm), min
Rockwell, max
Vickers max
ksi
Mpa
ksi
Mpa
%
304
S30400
75
515
30
205
35
B90
200
304L
S30403
70
485
25
170
35
B90
200
316L
S31603
70
485
25
170
35
B90
200
310S
S31008
75
515
30
205
35
B90
200
321
S32100
75
515
30
205
35
B90
200
S31803
90
620
65
450
25
30
290
2205
S32205
95
655
70
485
25
30
290
2507
S32750
116
800
80
550
15
32
300

Mechanical Test

Mechanical Test

Test
ASTM
MW
Flare
Not Required
Required
Flattening
Required
Required
Flange
Required
Required
Reverse Bend
Required
Required
Reverse Flatening
Required
Required
Tesion Test
Required
Required
Hardness
Required
Required
Eddy Current
Required
Required ᵃ
Hydrostatic
Required
Not Required
Air Underwater Test
Not Required
Required ᵇ
Note:
ᵃ : Hydrostatic or Nondestructive Electric Test: MW each tube is subjected to 100% online eddy Current Test.
ᵇ : Air Underwater Pressure Test: MW all Tubing is examined by the air underwater pressure test. Inspection is made of the entire external surface of the tube after holding the pressure for not less than 10 s after the surface of the water has become calm. If any tube shows leakage during the air underwater test, MW Metal reject it.

Tolerances for ASTM A789 tubes

Tolerances for ASTM A789 tubes

Outer Diameter in. [mm] Tolerance
Thickness Tolerance
Length Tolerance
Up to 1/2"
≤12.7mm
±0.13mm
±15%
+3.2mm/0mm
1/2"to 1 1/2"
≥12.7-38.1mm
±0.13mm
±10%
+3.2mm/0mm
1 1/2" to 3 1/2"
≥38.1-88.9mm
±0.25mm
±10%
+4.8mm/0mm, these tolerance apply to cut lengths up to and including 24ft(7.3m). For lengths greater than 24ft(7.3m), the above tolerance shall be increased by 1/8 in.(3mm) for each 10ft(3m) or fraction thereof over 24ft. Or 1/2 in (13mm), whichever is lesser.
3 1/2" to 5 1/2"
≥88.9-139.7mm
±0.38mm
±10%
5 1/2"to 8"
≥139.7-203.2mm
±0.76mm
±10%
*In accordance with Standard ASTM A789

Relationship Product

Typical Chemical Composition %

Typical Mechanical Properties

ASTM A554 Wall Thickness/Outside Dimention Tolerances

Wall Thickness Tolerances
± 10% of specified wall thickness

APPLICATIONS

Boiler
Boiler
ASTM A789 stainless steel tubes are duplex stainless steel tubes, which means they have a two-phase microstructure consisting of grains of both austenitic and ferritic stainless steel. This duplex structure gives these tubes enhanced strength and resistance to stress corrosion cracking compared to regular austenitic or ferritic grades. In the context of boiler applications, ASTM A789 stainless steel tubes are used for their: High Thermal Conductivity: Effective heat transfer is a critical aspect of boiler performance, and the thermal conductivity of duplex stainless steel is higher than that of austenitic grades, aiding in efficient heat exchange. Corrosion Resistance: Boilers are environments where corrosion resistance is crucial due to constant exposure to water and high temperatures. The chromium and molybdenum content in ASTM A789 tubes provide excellent resistance to pitting and crevice corrosion. Strength: The duplex structure provides high strength, allowing for thinner wall tubes that can withstand high pressure. This is especially important in high-pressure boiler applications. Durability: The enhanced strength and corrosion resistance contribute to the long service life of boilers, reducing maintenance and replacement costs. Temperature Resistance: These tubes can withstand high temperatures without losing their mechanical properties, making them suitable for the thermal stresses encountered in boilers. In summary, the use of ASTM A789 stainless steel tubes in boilers allows for the construction of highly efficient, durable, and reliable systems that perform well under corrosive and high-pressure conditions, withstanding the harsh operational realities of modern boiler systems.
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Superheater
Superheater
ASTM A789 stainless steel tubes, known for their duplex structure, combine the advantages of both austenitic and ferritic stainless steel. Their application in superheaters is attributed to several key properties: High Temperature Resistance: Superheaters operate at high temperatures to increase the steam temperature beyond its saturation point. ASTM A789 tubes can withstand these elevated temperatures while maintaining structural integrity. Corrosion Resistance: These tubes offer excellent resistance to various forms of corrosion, which is crucial in superheaters where steam can lead to oxidation and corrosion issues. Strength at High Temperatures: The duplex stainless steel maintains its mechanical strength even at the high temperatures found in superheaters, enabling the use of tubes with thinner walls that can still withstand the pressure, contributing to better heat transfer efficiency. Thermal Expansion: The coefficient of thermal expansion for duplex stainless steel is lower than that of austenitic grades, which means that ASTM A789 tubes are less prone to thermal stress during rapid temperature changes that are typical in superheaters. Good Fatigue Resistance: The superheating process can cause thermal fatigue due to cyclic heating and cooling. ASTM A789 stainless steel tubes have good fatigue resistance, enhancing the durability of superheaters. In superheaters, ASTM A789 tubes are therefore highly valued for their ability to contribute to the efficiency and longevity of the system, ensuring that the superheated steam is delivered at consistent pressures and temperatures without significant heat loss, material degradation, or failure.
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Heat-exchanger
Heat-exchanger
ASTM A789 stainless steel tubes are ideal for heat exchangers due to their duplex structure, offering combined benefits of austenitic and ferritic steels. They provide: Corrosion Resistance: Exceptional protection against corrosive substances, including chlorides, preventing pitting and crevice corrosion. Strength and Durability: High tensile and yield strength allow for the use of thinner-walled tubes that can withstand high pressure, enhancing heat exchanger longevity. Thermal Efficiency: Better thermal conductivity than austenitic steels for efficient heat transfer. High-Temperature Capability: Maintains integrity at high temperatures critical for heat exchanger performance. Reduced Thermal Expansion: Lower expansion rate minimizes stress from temperature changes. Cost-Effectiveness: Stronger material permits thinner walls, cutting down on costs and yielding lighter, easier-to-install heat exchangers. ASTM A789 tubes are thus a top choice for heat exchangers, delivering durability, efficient operation, and cost savings across various industrial applications.
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Condenser
Condenser
The ASTM A789 specification covers seamless and welded ferritic/austenitic stainless steel tubing for general service. This type of stainless steel tube, with its high resistance to corrosion and excellent mechanical properties, is well-suited for use in condensers in the following ways: Heat Transfer Efficiency: ASTM A789 tubes are typically made from duplex stainless steel, which combines the advantageous properties of both austenitic and ferritic stainless steels. The duplex structure facilitates efficient heat transfer, which is crucial for the condensation process. Corrosion Resistance: Condensers often deal with aggressive media and varying temperatures. The chemical composition of ASTM A789 stainless steel tubes provides superior resistance to pitting, crevice corrosion, and stress corrosion cracking, making them ideal for such harsh environments. Strength and Durability: These tubes have high mechanical strength, which allows for thinner wall construction without compromising durability. This can lead to cost savings and also improve heat transfer properties. Pressure Resistance: ASTM A789 tubes can withstand high pressures, which is essential for the reliable operation of condensers, especially in industrial and power generation applications. In condensers, the ASTM A789 tubes are often used in systems where reliability and maintenance of performance under corrosive conditions are vital. They enable efficient condensation of vapors into liquid form while maintaining system integrity over extended operational periods.
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Distillation Column
Distillation Column
ASTM A789 stainless steel tubing is often employed in distillation columns for its advantageous properties in chemically aggressive and high-temperature environments. Here's a brief overview of its application in such settings: Corrosion Resistance: The duplex stainless steel composition of ASTM A789 tubes offers excellent resistance to corrosion, which is crucial for distillation processes that can involve corrosive substances and by-products. High-Temperature Performance: The tubing can withstand the elevated temperatures typical of distillation processes, maintaining structural integrity and performance without degradation over time. Mechanical Strength: The high strength-to-weight ratio of duplex stainless steel allows for the design of thinner-walled tubes that support the structure of distillation columns while facilitating efficient heat exchange. Longevity and Durability: ASTM A789 stainless steel tubes provide a reliable solution for distillation applications, reducing the need for frequent replacements due to their durability and extended lifespan in harsh operating conditions. By using ASTM A789 stainless steel tubing in distillation columns, industries ensure a balance between cost-efficiency and high performance, with reduced risk of process contamination due to corrosion or equipment failure.
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