ASTM A178 / ASME SA178 Grade A Carbon Steel Welded Boiler Tube Heat Exchanger Tube

This specification ASTM A178/ASME SA178 covers minimum-wall-thickness, electric-resistance-welded tubes made of carbon steel and carbon-manganese steel intended for use as boiler tubes, boiler flues, superheater flues, and safe ends. The welding process of the tube is mainly manufactured using resistance welding (ERW) technology, which is suitable for high temperature and high pressure environments.

ASTM A178 GR. A carbon steel welded boiler tubes and heat exhcanger tubes are usually delivered in a cold worked state and require stress relief annealing (if required by the application scenario). Welding seams require 100% eddy current or ultrasonic testing to ensure no defects, and require individual water pressure testing. The pressure is calculated based on the wall thickness and diameter to ensure sealing.

ASTM A178/ ASME SA178 Carbon Steel Welded Tubes Chemical Composition

ASTM A178 Gr.A Carbon Steel Welded Boiler and Heat Exchanger Tube Mechanical Properties

The low carbon content of ASTM A178/ASME SA178 Gr. A carbon steel welded boiler tube and heat exchanger tube can improve welding performance and reduce the risk of embrittlement in the heat affected zone. At the same time, it has moderate strength and excellent plasticity, suitable for cold bending and expansion processing.

ASTM A178 GR.A carbon steel tube has high production efficiency and high material utilization rate due to the ERW process, so the overall cost will be significantly lower than the same specification seamless pipe, which is also the biggest advantage of ASTM A178 GR.A carbon steel tube. At the same time, since ASTM A178 GR.A is made by strip steel rolling and welding, the wall thickness tolerance is usually better than hot-rolled seamless tube. In occasions such as economizers that require a large number of thin-walled pipes, the economic advantage is huge. The low carbon content of ASTM A178 GR.A ensures its good cold processing and field welding performance.

During the use of ASTM A178 GR.A, it should be noted that despite strict heat treatment and NDT requirements, the weld is still different from the seamless parent material in structure, which is a potential weak link. When it is used in harsh conditions such as high temperature, high pressure, corrosion, fatigue, and stress concentration, it needs to be carefully considered. At the same time, the maximum operating temperature of ASTM A178 GR.A is usually limited to below 400°C (750°F), and the performance degradation of the weld area under long-term high temperature may be faster than that of the parent material. When used in situations where expansion tubes are required, special attention should be paid to the expansion process control to avoid overstress or cracking in the weld area.

ASTM A178/ASME SA178 Gr.A Carbon Steel Welded Boiler Tube and Heat Exchanger Tube Core Application Areas

(1) Boiler system

ASTM A178 Gr. A carbon steel welded tube is a commonly used material for medium and low pressure boiler tubes, especially suitable for water/steam environments with temperatures ≤ 450 ℃. Specific applications include:

• Water Walls: Located on the heating surface of the boiler furnace, they need to directly absorb radiant heat. The welding performance and plasticity of Gr. A carbon steel welded tubes can meet the processing requirements of dense tube rows.
• Economizers: Economizers use flue gas waste heat to preheat boiler feedwater, with a working temperature mainly in the low temperature range (usually<300 ℃). Gr. A carbon steel welded tubes have advantages in corrosion resistance and economy in this low temperature range.
• Steam Drum Connection Tube: In low-pressure steam cycle systems, pipelines need to withstand periodic thermal stress, which poses a risk of high fatigue and cracking. Gr.A carbon steel welded tubes have good ductility and can reduce the risk of fatigue cracking.

(2) Heat exchange equipment

• Condensers: ASTM A178 carbon steel welded tube can be used for steam condensation in power plants or ships, and Gr. A tubes perform well in freshwater or low salinity cooling water environments.
• Petrochemical heat exchanger: ASTM A178 GR. A carbon steel welded tube is suitable for heat exchange in non corrosive media such as oil and gas, such as preheaters in refineries and natural gas coolers.
• Waste heat recovery system: ASTM A178 GR. A carbon steel welded tube industrial waste heat boiler recovers low-temperature waste gas waste heat (such as steel plants, cement plants), and Gr. A has significant cost-effectiveness advantages.