Comprehensive Analysis of ASTM A179 / A179M Standards
Date:2026-02-06
Standard Number: ASTM A179 / A179M
"A179" represents the Imperial unit version.
"A179M" represents the International System of Units (SI, Metric) version. The technical content is equivalent, only the units differ.
Chinese Name: Seamless Cold-Drawn Low-Carbon Steel Tubes for Heat Exchangers and Condensers
Core Applications: Specifically used in heat exchange equipment, such as shell-and-tube heat exchangers, condensers, evaporators, heating coils, etc., operating under pressure.
Key Processes: Seamless + Cold Drawing
1. Material and Chemical Composition
Steel Grade: Usually low-carbon steel, the most common grade is SAE 1010.
Example of Chemical Composition Requirements (Smelting Analysis):
Carbon: ≤ 0.18%
Manganese: 0.27 - 0.63%
Phosphorus: ≤ 0.035%
Sulfur: ≤ 0.035%
Silicon: ≥ 0.10% (Deoxidizer, usually in fully killed steel)
Key Points: Low carbon content ensures good weldability and machinability, while strength is achieved through cold working.
2. Manufacturing Process
Seamless: Manufactured by piercing, without longitudinal welds, exhibiting good uniformity and high pressure resistance, which is fundamental to the safety of heat exchanger tubes.
Cold Drawing: Steel tubes are drawn at room temperature using a die. This process brings two core advantages:
High Dimensional Accuracy: Small inner and outer diameter tolerances, uniform wall thickness, facilitating tube expansion and ensuring heat transfer efficiency.
High Surface Smoothness: Smooth inner wall, reducing flow resistance and scale adhesion.
Improved Mechanical Properties: Work hardening significantly improves yield strength and tensile strength.
3. Dimensions and Tolerances
Common Outer Diameter Range: 3/16 inch to 3 inches (4.76 mm to 76.2 mm), with 3/4 inch (19.05 mm) and 1 inch (25.4 mm) being the most common.
Common Wall Thickness: Usually expressed in BWG (Birmingham Wire Gauge) or inches, such as BWG 16, 18, 20, with thinner wall thicknesses (typically 0.035 inches to 0.165 inches, or 0.9 mm to 4.2 mm).
Strict Tolerance Requirements: Clearly defined tolerances for outer diameter, wall thickness, length, and straightness ensure ease of installation and expansion joints.
4. Mechanical Properties
Tensile Strength: ≥ 325 MPa (47,000 psi)
Yield Strength: ≥ 180 MPa (26,000 psi)
Elongation: For gauge lengths of 50 mm or 2 inches, longitudinal specimen elongation must be ≥ 35%, indicating good ductility.
5. Heat Treatment
Stress-relieving annealing is typically required after cold drawing to eliminate internal stresses generated during cold working. This improves:
Corrosion resistance (especially susceptibility to stress corrosion cracking).
Dimensional stability.
Maintaining a sufficient balance of strength and toughness.
The standard specifies that the annealing temperature should not exceed 1200°F (650°C).
6. Inspection and Testing
To ensure quality, the standard requires several tests:
Hydrostatic Test: Mandatory. Each steel pipe must be tested under the specified pressure without leakage. The pressure value is calculated based on the wall thickness and outer diameter to ensure pressure resistance.
Flanging Test: Checks the ductility of the steel pipe. The pipe end is enlarged by a certain proportion (e.g., 15% increase in outer diameter); no cracks should appear.
Flattening Test: The pipe section is flattened to a specified height to check its ability to withstand plastic deformation and assess internal and external surface defects.
Non-destructive Testing (Optional): Eddy current testing (EDY) or ultrasonic testing (UT) can be performed upon request to detect more subtle defects.
Dimensional and Surface Inspection: Dimensions are checked on each pipe, and internal and external surfaces are visually inspected. Defects harmful to use are not permitted.
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