ASTM A423/A423M specifies minimum-wall-thickness seamless and electric-resistance-welded low-alloy steel tubes for pressure-containing parts such as economizers.
Referenced Edition: ASTM A423/A423M-19(2024)
Standard Title: Standard Specification for Seamless and Electric-Welded Low-Alloy Steel Tubes
The specification covers Grade 1, Grade 2, and Grade 3.
ASTM A423 is closely associated with economizer tubing, but its scope is not limited exclusively to economizers.
Each ASTM A423 grade has its own chemical-composition and mechanical-property requirements.
| Grade | Material Characteristics & Selection Considerations |
|---|---|
| Grade 1 | Copper-bearing low-alloy steel with controlled additions including copper, chromium, and nickel. Commonly associated with economizer and heat-recovery applications requiring this specified material. |
| Grade 2 | A distinct alloy chemistry that should not be treated as a simple strength variation of Grade 1. Selection should follow the equipment specification and exact Grade 2 requirements. |
| Grade 3 | A separate low-alloy composition within the specification. Chemistry, mechanical properties, and heat-treatment requirements must be verified against the ordered grade. |
The grade must be stated in the RFQ and purchase order.
ASTM A423 specifies separate chemical-composition limits for Grades 1, 2, and 3.
Controlled elements can include:
Because the grades use different alloy systems, one generic chemical-composition table should not be applied to all ASTM A423 tubing.
The exact grade should be confirmed before quotation and production.
ASTM A423 includes grade-specific mechanical requirements.
| Property | Requirement Basis |
|---|---|
| Tensile Strength | According to the specified grade and applicable tube condition |
| Yield Strength | According to the specified grade and applicable tube condition |
| Elongation | According to the specified grade and applicable requirements |
| Hardness | According to the specified grade and applicable tube condition |
The ordered grade should be identified before material selection or comparison with another boiler or economizer tube specification.
ASTM A423 is a minimum-wall-thickness tube specification.
For example:
OD 50.8 × 4.0 mm — Minimum Wall
This is a different manufacturing requirement from a tube ordered on an average-wall basis.
RFQs should clearly state:
Outside Diameter × Minimum Wall Thickness
| Manufacturing Route | Description |
|---|---|
| Seamless | Seamless low-alloy steel tubes covered by ASTM A423 |
| ERW | Electric-resistance-welded low-alloy steel tubes covered by ASTM A423 |
The required manufacturing route should be identified in the purchase order.
FYN’s primary product focus is ASTM A423 seamless low-alloy steel tubes. The standard’s manufacturing scope and FYN’s confirmed supply scope should be distinguished.
Heat-treatment requirements depend on the grade and manufacturing condition.
Cold-finished tubes receive the applicable heat treatment after final cold finishing.
The required heat-treatment route should be verified against:
Additional heat-treatment requirements should be stated at the RFQ stage.
ASTM A423 tubes are subject to applicable material, mechanical, and integrity verification.
| Inspection Area | Applicable Verification |
|---|---|
| Chemical Composition | Chemical analysis |
| Mechanical Properties | Tensile and hardness testing |
| Forming Performance | Flattening and flaring testing |
| Tube Integrity | Hydrostatic testing and applicable nondestructive electric testing |
| Dimensions | Dimensional inspection |
| Surface Condition | Surface inspection |
| Identification | Material identification |
Project-specific inspection requirements should be identified before production.
Economizers recover heat from boiler flue gas and transfer it to boiler feedwater before the water enters the boiler or steam-generating section.
Material selection must consider both water-side conditions and flue-gas-side conditions.
| Area | Relevant Information |
|---|---|
| Water Side | Feedwater temperature and water chemistry |
| Flue-Gas Side | Inlet and outlet temperatures, composition, and corrosion conditions |
| Fuel | Fuel type and sulfur content |
| Tube Operating Conditions | Expected tube-wall temperature and design pressure |
| Tube Configuration | Tube geometry, layout, and applicable fabrication requirements |
Specifying ASTM A423 alone does not establish that a particular grade is suitable for every economizer operating condition.
Potential operating factors include:
The correct grade should be selected together with the boiler or economizer design requirements.
A low-alloy designation does not imply universal resistance to all economizer corrosion conditions.
| Parameter | ASTM A423 | ASTM A192 |
|---|---|---|
| Material | Low-Alloy Steel | Carbon Steel |
| Grades | Grade 1 / Grade 2 / Grade 3 | No grade designation |
| Manufacturing Route | Seamless / ERW | Seamless |
| Application Scope | Minimum-wall tubing for pressure-containing parts such as economizers | Boiler tubing for high-pressure service |
The correct material should follow the boiler or economizer design specification. ASTM A423 should not be treated as an automatic upgrade from ASTM A192.
| Standard | Material & Product Scope |
|---|---|
| ASTM A423 | Low-alloy steel tubing for pressure-containing parts such as economizers |
| ASTM A178 | Electric-resistance-welded carbon steel and carbon-manganese steel boiler and superheater tubes |
The specifications differ in material system and manufacturing requirements.
Material substitution requires engineering review and should not be based only on matching dimensions.
| Parameter | FYN Capability |
|---|---|
| Product Focus | Seamless Low-Alloy Steel Tube |
| Grades | Grade 1 / Grade 2 / Grade 3, subject to production confirmation |
| Manufacturing Process | Cold Drawn / Cold Rolled |
| Outside Diameter | 6–114 mm |
| Wall Thickness | 0.8–25 mm, subject to ASTM A423 requirements |
| Length | Up to 40 m |
| Inspection Options | Hydrostatic / UT / ET, as specified |
| Documentation | MTC / Inspection Documentation / Third-Party Inspection, as required |
FYN’s manufacturing capability is separate from the dimensional and technical requirements of ASTM A423.
Available combinations of grade, outside diameter, minimum wall thickness, and length are subject to technical review.
For economizer heat-transfer surfaces where ASTM A423 low-alloy steel tubing is specified by the boiler or equipment design.
For straight or fabricated tube assemblies used to recover sensible heat from boiler flue gas.
For applicable pressure-containing heat-transfer components in industrial waste-heat recovery systems.
For boiler heat-recovery sections where the specified grade meets operating and corrosion requirements.
For maintenance and retubing projects where the original equipment specification identifies ASTM A423.
For replacement projects, verify:
Available documentation can include:
Documentation requirements should be specified at the RFQ stage.
Typical packing options include:
Fabricated economizer tube elements require packing appropriate to their geometry and transportation method.
| Item | Details |
|---|---|
| Grade Availability | Subject to production confirmation |
| Minimum Order Quantity | According to grade, dimensions, and production requirements |
| Lead Time | According to grade, dimensions, quantity, fabrication, and inspection requirements |
| Packing | According to tube geometry and transportation requirements |
| Item | Information to Provide |
|---|---|
| Standard | ASTM A423/A423M and required edition, if specified |
| Grade | Grade 1 / Grade 2 / Grade 3 |
| Manufacturing Route | Seamless / ERW |
| Dimensions | Outside Diameter × Minimum Wall Thickness × Length |
| Quantity | Required order quantity |
| Product Configuration | Straight Tube / Fabricated Economizer Element |
| Geometry | Tube layout, drawing, and bend radius, where applicable |
| Design Conditions | Design pressure and design temperature |
| Water-Side Conditions | Water temperature and relevant water chemistry |
| Flue-Gas Conditions | Inlet / outlet temperatures and relevant gas conditions |
| Fuel | Fuel type |
| Corrosion Allowance | Required allowance, where applicable |
| Heat Treatment | Required treatment or delivery condition |
| Testing | Hydrostatic / NDT requirements |
| Documentation | Required inspection documents |
| Third-Party Inspection | Required scope, if applicable |
| Delivery | Destination |
For economizer replacement projects, send the existing MTC, tube drawing, economizer drawing, or tube-failure information for technical review.
Please send your requirements in the following format:
ASTM A423/A423M + Grade + Seamless / ERW + OD × Minimum Wall Thickness × Length + Quantity
For economizer projects, also include:
Design Pressure + Water Temperature + Flue-Gas Inlet / Outlet Temperature + Fuel Type + Tube Drawing
For replacement projects, provide the existing MTC, economizer drawing, or failed-tube information for material and dimensional review.
