What ASTM A179 Seamless Heat Exchanger Tube Is
ASTM A179/A179M carries the title "Standard Specification for Seamless Cold-Drawn Low-Carbon Steel Heat-Exchanger and Condenser Tubes". It applies to seamless cold-drawn low-carbon steel tube made with a specified minimum wall for heat exchangers, condensers and similar heat transfer equipment. The seamless route means the hollow is pierced and cold drawn rather than welded, so there is no seam to act as a preferential corrosion path and wall concentricity is easier to hold over long lengths.
Two properties drive the choice of this grade: a smooth bore that stays clean in service, and low hardness that lets the tube be rolled and expanded into a tubesheet without splitting.
Dimensional Range and Wall Tolerance
Tube is normally supplied with outside diameters from 1/8 in to 3 in (3.2 mm to 76.2 mm) and minimum walls of 0.015 in (0.4 mm) and above. Outside this window the mechanical requirements are not applied, although supplementary sizes can be negotiated.
| Outside diameter | Wall tolerance | Over (+) | Under (-) |
|---|---|---|---|
| 1 1/2 in (38.1 mm) and under | % of specified wall | 20 | 0 |
| Over 1 1/2 in (38.1 mm) | % of specified wall | 22 | 0 |
Because only plus variation is allowed, the wall never falls below the ordered minimum, which protects the design pressure rating of the exchanger.
Chemistry and Mechanical Properties
| Element | C | Mn | P | S |
|---|---|---|---|---|
| Range, % | 0.06-0.18 | 0.27-0.63 | 0.035 max | 0.035 max |
| Tensile strength | Yield strength | Elongation | Hardness |
|---|---|---|---|
| 325 MPa min | 180 MPa min | 35% min | 72 HRB max |
Carbon is held in a narrow band, and phosphorus and sulfur are capped at 0.035% each. That combination produces a ductile, weldable tube with predictable forming behaviour and good toughness at low ambient temperatures.
Manufacturing Route and Heat Treatment
Steel is melted to the specified chemistry and cast into rounds or billets.
The billet is pierced and progressively cold drawn over a mandrel to reach wall and diameter.
The final cold-drawing pass sets dimensional accuracy and the surface finish of the bore.
Tube is heat treated at 1200 °F (650 °C) or higher to relieve cold work.
Tube is straightened, cut to length, tested, marked and packed.
Cold drawing is what delivers the high dimensional accuracy and smooth surface; the heat treatment that follows is what restores the softness needed for fabrication, keeping hardness under the 72 HRB ceiling.
Test and Inspection Regime
Hydrostatic test of each tube, which the purchaser may replace with a non-destructive electric test.
Flattening test on samples taken from two tubes per lot, to confirm ductility.
Flaring test, or a bending test when specified in place of flaring.
Hardness verification against the 72 HRB maximum.
Dimensional and visual examination, plus marking of grade and size on the bundle.
These checks are what allow the tube to be released for pressure equipment service with traceability from heat number to finished length.
Applications, Ordering and Fabrication
Typical duty includes shell-and-tube heat exchangers, surface condensers, feedwater heaters, air coolers and other low-pressure or atmospheric heat transfer circuits where thin wall and clean surface matter more than strength.
When ordering, state the specification and grade, the outside diameter and minimum wall, the length or U-bend requirement, end finish, and the testing you require. Tubesheet holes should be reamed and cleaned before expansion, and the roller schedule should be followed so that wall reduction stays within design limits. Straight lengths and U-bent bundles are both available, with plain, bevelled or weld-prepared ends.
Frequently Asked Questions
Q: Why is A179 tube cold drawn rather than hot finished?
A: Cold drawing gives tighter dimensional tolerance, a smoother bore and a cleaner surface, which reduces fouling and improves heat transfer in the exchanger.
Q: What is the minimum wall thickness available?
A: Minimum walls start at 0.015 in (0.4 mm). Tubes thinner than that, or with an outside diameter below 1/8 in (3.2 mm), are outside the mechanical property requirements of the specification.
Q: How is the tube protected before shipment?
A: Tubes are cleaned, straight or U-bent as ordered, marked with grade and size, and bundled and protected so that the bore and ends reach the fabricator undamaged.
Q: Can A179 tube be welded?
A: Yes. With carbon at 0.18% maximum and no deliberate alloying, the grade has good weldability, and standard procedures for low-carbon steel apply.
Q: What service temperature is appropriate?
A: The grade is intended for heat exchangers and condensers handling low-pressure or atmospheric duty. For sustained high-temperature, high-pressure boiler service, a boiler tube grade such as ASTM A192 should be selected instead.
Q: Which tests are mandatory on every order?
A: Hardness, dimensional and visual examination apply to all tube, together with either a hydrostatic or an agreed non-destructive electric test, and the flattening test on samples from each lot.