Products Description
ASTM A178 Boiler Tubes & A178 Superheater Tubes
Electric Resistance Welded Tubes for High-Temperature Applications
Welcome to our comprehensive guide on ASTM A178 boiler tubes and A178 superheater tubes. As core components in thermal energy transfer systems, these electric resistance welded (ERW) tubes are engineered for reliability in demanding high-temperature, high-pressure environments found in power plants, industrial boilers, and heat exchangers.
The ASTM A178 specification covers minimum-wall thickness, electric-resistance-welded carbon steel tubes for use in boilers, superheaters, and heat exchangers. These tubes are designed to withstand high temperatures and pressures while maintaining structural integrity.
Material Composition
ASTM A178 tubes are manufactured from carbon steel with controlled chemical composition to ensure optimal performance in high-temperature environments.
Manufacturing Process
Electric Resistance Welding (ERW) creates a homogenous bond without filler metals, resulting in excellent dimensional accuracy and weld quality.
Heat Treatment
All A178 tubes undergo post-weld heat treatment at temperatures ≥1650°F (900°C) to relieve stresses and enhance mechanical properties.
Product Specifications
Parameters
- Standard: ASTM A178
- Manufacturing Process: Electric Resistance Welding (ERW)
- Material: Carbon Steel
- Grades: Gr. A, Gr. C
- Available Outside Diameter: 12.7–127 mm
- Available Minimum Wall Thickness: 0.9–9.1 mm
Primary Applications
Chemical Composition Comparison
| Chemical Composition (%) | ||||
|---|---|---|---|---|
| Grade | C | Mn | P | S |
| Gr. A | 0.06-0.18 | 0.27-0.63 | ≤0.035 | ≤0.035 |
| Gr. C | ≤0.35 | ≤0.80 | ≤0.035 | ≤0.035 |
Mechanical Properties
| Mechanical Properties | |||
|---|---|---|---|
| Grade | Tensile Strength ksi [MPa] |
Yield Strength ksi [MPa] |
Elongation In 2 in. or 50mm |
| Gr. A | ≥47 [325] | ≥26 [180] | ≥35% |
| Gr. C | ≥60 [415] | ≥37 [255] | ≥30% |
Grade A vs. Grade C: Critical Differences
The fundamental difference between ASTM A178 Grade A and Grade C lies in their carbon content, which directly impacts their mechanical properties and suitable applications.
| Grade | Plasticity | Strength | Advantages |
|---|---|---|---|
| Gr. A | ✓ | Low carbon content provides excellent ductility, easier welding and processing, with relatively lower high-temperature strength. | |
| Gr. C | ✓ | Higher carbon content delivers greater strength and creep resistance, maintaining shape and strength in long-term high-temperature environments. Requires stricter welding controls. |
Selection for Optimal Performance
ASTM A178 Grade A
- Best for: Medium temperature and pressure applications
- Advantage: Cost-effective solution with excellent formability
- Typical Use: Boiler tubes in industrial settings with moderate operating conditions
ASTM A178 Grade C
- Best for: High-temperature, high-pressure environments requiring long-term stability
- Advantage: Superior strength and creep resistance
- Typical Use: Superheater tubes, high-pressure boiler sections, critical heat exchangers
Electric Resistance Welding (ERW) Advantages
ERW technology uses high-frequency electrical resistance to heat the steel, followed by pressure application to achieve complete material fusion without filler metals.
ERW Benefits:
- High Production Efficiency: Continuous manufacturing process reduces costs
- Excellent Dimensional Accuracy: Consistent wall thickness and diameter
- Superior Weld Quality: Homogenous bond with minimal defects
- No Filler Metal: Clean weld seam without contamination risk
Quality Assurance & Testing Requirements
ASTM A178 mandates rigorous testing to ensure tube integrity and performance under demanding conditions:
| Test | Grade A | Grade C |
|---|---|---|
| Flattening Test | Specimens from 2pcs per lot + additional safe-end material samples | Specimens from 2pcs per lot |
| Flange Test | Specimens from 2pcs per lot + additional safe-end material samples | Specimens from 2pcs per lot |
| Tension Test | - | Specimens from 2pcs per lot |
| Reverse Flattening Test | One test on each 450m of finished tubing | |
| Hydrostatic/Nondestructive Test | Either hydrostatic or nondestructive electric test on each tube | |
| Product Analysis | ✓ | ✓ |
| Crush Test | ✓ | - |
| Ultrasonic Test | ✓ | ✓ |
ASTM A178 Grade A/C Welded Boiler Tube - Precision engineered for high-temperature applications
Frequently Asked Questions
1. Is the weld seam a weak point that could potentially crack?
No, when manufactured according to ASTM A178 specifications, the ERW weld is not a weak point. Every tube undergoes non-destructive testing or hydrostatic testing before shipment to ensure the weld is completely defect-free. The post-weld heat treatment further enhances the weld integrity by relieving internal stresses.
2. How consistent is the product quality between different production batches?
We maintain exceptional consistency through strict adherence to both ASTM A178 standards and ISO 9001 Quality Management System requirements. Each batch is accompanied by a complete Material Test Certificate (MTC) providing full traceability, including chemical analysis and mechanical test results. Our statistical process control ensures minimal variation between production runs.
3. What is the maximum service temperature for A178 tubes?
ASTM A178 Grade A tubes are typically suitable for service temperatures up to approximately 800°F (427°C), while Grade C tubes can withstand higher temperatures up to 850°F (454°C) due to their higher carbon content and improved creep resistance. Actual maximum temperatures depend on specific operating pressures and conditions.
4. Can A178 tubes be bent or formed after manufacturing?
Yes, both Grade A and Grade C tubes can be cold-formed, with Grade A offering superior formability due to its lower carbon content. For tight radius bends or significant deformation, proper bending equipment and techniques should be employed to avoid compromising the tube integrity. Post-bending inspection is recommended for critical applications.
ASTM A178 boiler tubes
ASTM A178 boiler tubes and superheater tubes represent the industry standard for reliable performance in high-temperature heat transfer applications. The choice between Grade A and Grade C depends on your specific temperature, pressure, and mechanical requirements. With proper selection, installation, and maintenance, these ERW tubes provide decades of dependable service in demanding industrial environments.
For technical specifications, pricing, or application engineering support, contact our team of experts today.