ASTM A423 Grade 1 Tubes – Low-Alloy (Cor-Ten Type) Tubes for Economizers & Air Preheaters
ASC LLP, Mumbai, supplies ASTM A423 Grade 1 tubes (ASME SA423 Gr 1), seamless and electric-resistance welded, for economizers, air preheaters and other pressure parts where corrosion resistance matters. In addition, every lot comes with an EN 10204 3.1 certificate. See also our corten steel tubes.
What is ASTM A423 Grade 1?
ASTM A423 covers minimum-wall-thickness, seamless and electric-resistance-welded low-alloy steel tubes for pressure-containing parts, such as economizers, and other applications where corrosion resistance is important. It is a tube specification, so tubes are ordered by outside diameter and minimum wall, not by pipe size and schedule.
Grade 1 has a copper-chromium-nickel-phosphorus chemistry similar to Cor-Ten A, which is why it is often called a “corten” tube. However, the purpose is different from structural weathering steel: A423 Grade 1 is used inside boilers and flue-gas equipment, where its alloying improves resistance to acid dew-point corrosion. For outdoor structural or architectural pipe, see ASTM A847 corten pipes instead.
A423 Grade 1 Tubes – Quick Facts
- Specification: ASTM A423 / A423M, ASME SA423, Grade 1
- Product: seamless or ERW tubes, ordered to minimum wall
- Size range: ½” to 5″ OD (12.7 – 127 mm), while walls run from 0.9 to 12.7 mm
- Strength: 415 MPa tensile and 255 MPa yield min
- Heat treatment: normalised, or as needed to meet the specification
- Main uses: economizers, air preheaters (APH) and flue-gas heat recovery
Key Properties of A423 Grade 1 Tubes
- Corrosion resistance: copper, chromium, nickel and phosphorus improve resistance in flue-gas and acid dew-point conditions compared with plain carbon steel tubes.
- Pressure service: because it is made to a pressure-tube specification, each tube is tested and certified.
- Moderate strength: 415 MPa tensile, which is similar to common carbon steel boiler tubes.
- Fabrication: can be expanded, bent and welded with suitable procedures; in addition, ERW tubes are economical for long straight runs.
Heat-Exchanger & APH Service vs Structural Weathering Use
A423 Grade 1 and structural weathering pipes share a similar alloy idea, but they serve different jobs. Therefore, the right specification depends on the application:
- Economizers, air preheaters and flue-gas coolers: specify ASTM A423 Grade 1 tubes, ordered by OD × minimum wall.
- Outdoor structures, handrails and architectural pipe: specify ASTM A847 or corten welded / seamless pipe, ordered by NPS and schedule.
- General heat-exchanger tubes without special corrosion needs: carbon steel A179 or A214 tubes are usually sufficient.
ASTM A423 Grade 1 Tube Sizes
| Item | Range |
| Outside diameter | ½” to 5″ (12.7 – 127 mm) |
| Minimum wall thickness | 0.035″ to 0.500″ (0.9 – 12.7 mm) |
| Common APH / economizer sizes | for example 38.1, 44.5, 50.8 and 63.5 mm OD, typically |
| Length | Straight lengths or cut to length; U-bends on request |
A423 tubes are ordered by OD and minimum wall thickness. Consequently, pipe schedules such as SCH 40 do not apply to this specification.
A423 Grade 1 Mechanical Properties
| Property | A423 Grades 1 & 2 |
| Tensile strength, min | 415 MPa (60 ksi) |
| Yield strength, min | 255 MPa (37 ksi) |
| Elongation in 50 mm, min | 25% (reduced for thin-wall longitudinal strip tests) |
These are specification minimums; for example, the 25% elongation applies to full-section tests. In addition, tubes are tested for flattening, flaring and flange performance, as the specification requires.
A423 Grade 1 Tube Specifications
| Item | Details |
| Specification | ASTM A423 / A423M, ASME SA423, Grade 1 |
| Manufacture | Seamless or electric-resistance welded (ERW) |
| Heat treatment | Normalised, or other treatment needed to meet the specification |
| Mechanical tests | Tension, flattening, flaring and flange tests |
| Ends | Plain; alternatively, bevelled on request |
| Certificate | EN 10204 3.1; in addition, 3.2 / third-party inspection on request |
How to Order A423 Grade 1 Tubes
- Specification and grade: ASTM A423 (or ASME SA423) Grade 1.
- Manufacture: either seamless or ERW.
- Size: OD × minimum wall thickness; also length and quantity.
- Extras: U-bending, end finishing, NDE or third-party inspection, if required.
Heat Treatment of A423 Tubes
A423 requires all tubes to be normalised, or given whatever heat treatment is needed to meet the specification. As a result, the delivered tubes have a uniform structure suitable for expanding into tube sheets and for bending.
ASTM A423 Grade 1 Chemical Composition
| Element | Grade 1 (%) | Grade 2 (%) |
| Carbon (C), max | 0.15 | also 0.15 |
| Manganese (Mn) | 0.55 max | 0.50 – 1.00 |
| Phosphorus (P) | 0.06 – 0.16 | 0.04 max |
| Sulphur (S), max | 0.060 | 0.05 |
| Silicon (Si) | 0.10 min | – |
| Copper (Cu) | 0.20 – 0.60 | 0.30 – 1.00 |
| Chromium (Cr) | 0.24 – 1.31 | – |
| Nickel (Ni) | 0.20 – 0.70 | 0.40 – 1.10 |
| Molybdenum (Mo) | – | 0.10 min |
Grade 1 relies on copper, chromium, nickel and phosphorus, whereas Grade 2 uses copper, nickel and molybdenum with low phosphorus. Both grades have the same tensile requirements.
Grade 1 vs Grade 2
In practice, Grade 1 is the Cor-Ten A-type chemistry and is the grade most often ordered for air preheaters and economizers. Grade 2, by contrast, has low phosphorus and added molybdenum; it is specified when the designer calls for that chemistry. The grade should therefore follow the equipment specification.
Applications of ASTM A423 Grade 1 Tubes
| Equipment | Typical A423 Grade 1 use |
| Air preheaters (APH) | Tubular APH elements, especially at the cold end where acid condenses |
| Economizers | Tubes in flue-gas heat recovery sections, as well as feed-water preheating |
| Flue-gas coolers | Heat recovery downstream of boilers and furnaces |
| Heat exchangers | Tubes, especially where corrosion resistance is important |
Why Buy A423 Grade 1 Tubes from ASC LLP?
- Traceable material: EN 10204 3.1 certificates with chemistry and test results.
- Correct product advice: help choosing A423 tubes, A847 pipe or carbon steel tubes, because the service decides the specification.
- Cut lengths and bends: moreover, tubes can be supplied to length or U-bent.
- Export packing: finally, tubes are bundled, end-capped and packed for shipment.
Related tubes: SA179 seamless tubes, A214 heat-exchanger tubes and boiler tubes. For structural weathering products, see corten seamless pipes, corten welded pipe and our corten steel range.
Frequently Asked Questions – ASTM A423 Grade 1 Tubes
What is ASTM A423 Grade 1?
In short, it is a specification for seamless and ERW low-alloy steel tubes for pressure parts such as economizers, where corrosion resistance is important.
Is ASTM A423 a pipe or a tube specification?
It is a tube specification. Tubes are ordered by outside diameter and minimum wall, from ½” to 5″ OD, not by pipe schedule.
Is A423 Grade 1 the same as corten steel?
Its chemistry is similar to Cor-Ten A. However, A423 Grade 1 is a pressure tube for boilers and flue-gas equipment, not a structural weathering pipe.
What are the mechanical properties of A423 Grade 1?
It requires 415 MPa (60 ksi) tensile and 255 MPa (37 ksi) yield minimum, with 25% elongation.
What is the chemical composition of A423 Grade 1?
C 0.15% max, Mn 0.55% max, P 0.06–0.16%, Si 0.10% min, Cu 0.20–0.60%, Cr 0.24–1.31% and Ni 0.20–0.70%.
Where are A423 Grade 1 tubes used?
Mainly in air preheaters, economizers and flue-gas coolers, especially where acid dew-point corrosion occurs.
What should be used for structural corten pipe?
ASTM A847 or corten welded / seamless pipe, ordered by NPS and schedule, rather than A423 tubes.
Global Supply
ASC LLP supplies ASTM A423 Grade 1 tubes from Mumbai to customers in India, the Middle East, Europe, Africa, the Americas and South-East Asia. To get a prompt quotation, simply send OD, minimum wall, length, seamless or ERW, and quantity.
Countries We Export To
UNITED STATES, EUROPE, UK, UAE, SAUDI ARABIA, OMAN, KUWAIT, JORDAN, QATAR, INDONESIA, MALAYSIA, BRAZIL, SPAIN, ITALY, FRANCE, GERMANY, BAHRAIN, SRI LANKA, AZERBAIJAN, AUSTRALIA, AUSTRIA, PHILIPPINES, TURKEY, RUSSIA, IRAN, IRAQ, CANADA, KOREA, JAPAN, YEMEN, FINLAND, ZIMBABWE, HUNGARY, PORTUGAL, VIETNAM, MOROCCO, THAILAND, SOUTH AFRICA, MEXICO, SINGAPORE, GREECE, KUWAIT, POLAND, NEW ZEALAND, SWEDEN, SWITZERLAND, BELGIUM, BHUTAN, BANGLADESH, TAIWAN, ROMANIA, CAMBODIA, KAZAKHSTAN, AFGHANISTAN.
