ASTM A778 Stainless Steel Pipe
ASTM A778 Stainless Steel Pipe
Introduction
ASTM A778 is the standard specification for welded, unannealed austenitic stainless steel pipe intended for low to moderate temperatures and general corrosive service. Unlike ASTM A312, which includes both seamless and welded pipes and requires heat treatment, ASTM A778 covers only welded pipes and does not require annealing. This specification is often used for applications where the stringent requirements of ASTM A312 are not necessary, offering a suitable alternative at a potentially lower cost.
ASTM A778 Specifications
Scope
ASTM A778 covers welded, unannealed austenitic stainless steel pipes in various grades, including TP304, TP304L, TP316, TP316L, and others. These pipes are intended for general corrosive service and low to moderate temperature applications.
Chemical Composition
The chemical composition of ASTM A778 stainless steel pipes varies depending on the grade. The following table summarizes the typical chemical composition for some common grades:
This specification covers welded unannealed tubular products 3 in. (75 mm) through 48 inch. (1200 mm) in outside diameter and in nominal wall thicknesses of 0.062 in. (1.5 mm) through 0.500 in. (12.5 mm) produced to this specification. Tubular products having other diameters, or wall thickness, or both may be furnished provided it complies with all other requirements of this specification.
|
Chemical Composition(%) |
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|
Grade |
C |
Si |
Mn |
P |
S |
Cr |
Ni |
Mo |
N |
Cu |
|
|
201 |
≤0.15 |
≤0.75 |
5.5~7.5 |
≤0.060 |
≤0.03 |
16.00~18.00 |
3.5~5.5 |
– |
– |
0.08 |
1.5 |
|
202 |
≤0.15 |
≤1.00 |
7.5~10.00 |
≤0.060 |
≤0.03 |
17.00~19.00 |
4.0~6.0 |
– |
≤0.25 |
||
|
301 |
≤0.15 |
≤1.00 |
≤2.00 |
≤0.045 |
≤0.03 |
16.00~18.00 |
6.00~8.00 |
– |
|||
|
302 |
≤0.15 |
≤1.00 |
≤2.00 |
≤0.035 |
≤0.03 |
17.00~19.00 |
8.00~10.00 |
– |
|||
|
304 |
≤0.07 |
≤1.00 |
≤2.00 |
≤0.045 |
≤0.03 |
18.00~20.00 |
8.00~10.50 |
– |
|||
|
304L |
≤0.030 |
≤1.00 |
≤2.00 |
≤0.045 |
≤0.03 |
18.00~20.00 |
9.00~13.00 |
– |
|||
|
310S |
≤0.08 |
≤1.00 |
≤2.00 |
≤0.045 |
≤0.03 |
24.00~26.00 |
19.00~22.00 |
– |
|||
|
316 |
≤0.08 |
≤1.00 |
≤2.00 |
≤0.045 |
≤0.03 |
16.00~18.00 |
10.00~14.00 |
2.00~3.00 |
|||
|
316L |
≤0.03 |
≤1.00 |
≤2.00 |
≤0.045 |
≤0.03 |
16.00~18.00 |
12.00~15.00 |
2.00~3.00 |
|||
|
321 |
≤0.08 |
≤1.00 |
≤2.00 |
≤0.045 |
≤0.03 |
17.00~19.00 |
9.00~13.00 |
– |
|||
|
430 |
≤0.12 |
≤0.75 |
≤1.00 |
≤0.040 |
≤0.03 |
16.00~18.00 |
– |
||||
|
2205 |
≤0.03 |
≤1.00 |
≤2.00 |
≤0.030 |
≤0.015 |
22.00~23.00 |
4.5~6.5 |
2.5~3.5 |
|||
|
2507 |
≤0.03 |
≤0.08 |
≤1.20 |
≤0.035 |
≤0.015 |
24.00~26.00 |
6.00~8.00 |
3.0~5.0 |
|||
|
904L |
≤0.02 |
≤1.00 |
≤2.00 |
≤0.045 |
≤0.035 |
19.00~23.00 |
23.00~28.00 |
4.0~5.0 |
1.0~2.0 |
||
|
INCONEL 028 |
≤0.03 |
≤1.00 |
≤2.50 |
≤0.030 |
≤0.030 |
≤28.0 |
≤34.0 |
≤4.0 |
≤1.4 |
||
|
MONEL 400 |
≤0.30 |
≤0.5 |
≤2.00 |
– |
≤0.024 |
– |
≥63.0 |
– |
≤34.0 |
||
|
INCONEL 800 |
≤0.10 |
≤1.00 |
≤1.50 |
– |
≤0.015 |
≤23.0 |
≤35 |
4.0~5.0 |
– |
≤0.75 |
Ti≤0.6 Al≤0.6 |
Mechanical Properties
The mechanical properties of ASTM A778 stainless steel pipes are suitable for general service applications. The typical mechanical properties include:
- Tensile Strength: Minimum 515 MPa (75 ksi)
- Yield Strength: Minimum 205 MPa (30 ksi)
- Elongation: Minimum 35% in 2 inches
Schedule
ASTM A778 pipes are available in various schedules, indicating the wall thickness. Common schedules include:
- Schedule 5S
- Schedule 10S
- Schedule 40S
- Schedule 80S
The choice of schedule depends on the specific application requirements, including operating pressure and temperature.
Technical Details, Dimensions, and Tolerances
Dimensions
The dimensions of ASTM A778 pipes are specified by their outside diameter (OD) and wall thickness. The standard sizes range from 1/8 inch to 24 inches in outside diameter. Common dimensions include:
- Outside Diameter (OD): 1/8 inch to 24 inches
- Wall Thickness: Specified according to the schedule, ranging from 0.035 inches (Schedule 5S) to 0.500 inches (Schedule 80S).
Tolerances
ASTM A778 specifies precise tolerances to ensure the pipes meet quality and performance standards. These tolerances include:
- Outside Diameter (OD): ±0.1% of the specified OD
- Wall Thickness: ±10% of the specified wall thickness
- Length: Pipes are typically supplied in random lengths of 5-7 meters, with a tolerance of ±50 mm.
Wall Thickness & Tolerance
The wall thickness of ASTM A778 pipes is critical for their performance in general service applications. Tolerances on wall thickness are essential to ensure consistent performance. The standard tolerances include:
- Wall Thickness Tolerance: ±10% of the specified wall thickness.
- Minimum Wall Thickness: The minimum wall thickness must not be less than 87.5% of the specified nominal wall thickness.
Materials and Manufacture
Materials
ASTM A778 pipes are made from austenitic stainless steels, which are known for their excellent corrosion resistance, good strength, and good weldability. Common grades include TP304, TP304L, TP316, and TP316L, each offering specific advantages for different applications.
Manufacture
The manufacturing process for ASTM A778 pipes involves several steps to ensure quality and performance:
- Welded Pipe Production: Welded pipes are produced by forming and welding strips of stainless steel. The weld seam is typically subjected to heat treatment to ensure homogeneity and strength.
- Cold Working: Cold working processes such as cold drawing or cold pilgering may be used to achieve the desired dimensions and surface finish.
Tests
To ensure the quality and performance of ASTM A778 pipes, several tests are conducted:
Hydrostatic Test
A hydrostatic test is performed to verify the pipes’ ability to withstand internal pressure. The pipes are filled with water and pressurized to a specified level, typically 1.5 times the design pressure, to check for leaks and structural integrity.
Nondestructive Testing (NDT)
Nondestructive testing methods are used to detect internal and surface defects without damaging the pipes. Common NDT methods include:
- Ultrasonic Testing: High-frequency sound waves are used to detect internal flaws.
- Eddy Current Testing: Electromagnetic induction is used to detect surface defects.
- Radiographic Testing: X-rays or gamma rays are used to inspect the internal structure.
Mechanical Tests
Mechanical tests are conducted to verify the pipes’ mechanical properties, including:
- Tensile Test: Measures tensile strength, yield strength, and elongation.
- Hardness Test: Verifies hardness levels to ensure compliance with specified limits.
- Flattening Test: Checks the pipe’s ability to withstand deformation without cracking.
Heat Treatment
Unlike ASTM A312, ASTM A778 does not require annealing. However, certain applications may benefit from optional heat treatments:
Solution Annealing
Solution annealing involves heating the pipes to a temperature above the critical temperature (usually around 1040-1120°C) and then rapidly cooling them in water or air. This process dissolves precipitated carbides and restores the material’s corrosion resistance and ductility.
Stress Relieving
Stress relieving involves heating the pipes to a temperature lower than the critical temperature (usually around 400-500°C) and then cooling them slowly. This process relieves internal stresses caused by manufacturing processes such as cold working.
Conclusion
ASTM A778 stainless steel pipes offer a reliable and cost-effective solution for general corrosive service and low to moderate temperature applications. These pipes are produced to meet specific chemical composition and mechanical property requirements, ensuring performance and durability. The specification provides flexibility in manufacturing and testing, allowing for a balance between cost and performance. Through rigorous manufacturing processes, precise dimensions and tolerances, and comprehensive testing, ASTM A778 pipes deliver dependable performance in a variety of applications.
ASTM A312 Stainless Steel Pipe Specification Standard Specification for Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes ASTM A312 pipe is common use stainless pipe for industries. It covers diameters from 1/8” to 30” and thickness from SCH 10S to SCH 80S. General use material grades are TP304/304L, TP316/316L.
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