ASME SA213 TP304H Stainless Steel Seamless Heat Exchanger Tube Bright Annealed

ASME SA213 TP304H Stainless Steel Seamless Heat Exchanger Tube Bright Annealed

ASME SA213 is a standard issued by the American Society of Mechanical Engineers, specifically for seamless ferritic and austenitic alloy steel tubing used in boilers, superheaters, and heat exchangers. It specifies the material's chemical composition, mechanical properties, heat treatment requirements, and testing methods, serving as the fundamental basis for ensuring the safe and reliable operation of the tubing under high-temperature and high-pressure environments.

The "H" in TP304H indicates High Carbon, with a carbon content range (0.04-0.10%) higher than that of ordinary 304 (≤0.08%). The "H" type is specifically designed for high-temperature applications; the higher carbon content allows for the formation of more stable carbides at high temperatures, thus providing higher high-temperature strength (creep resistance).

Chemical composition - Stainless steel 304/304L/304H

Bright annealing is a heat treatment process performed in a protective atmosphere. Its core objectives are:

• Eliminating work hardening: After cold drawing or cold rolling, the internal grains of the tube deform, generating stress, increasing hardness, and decreasing plasticity. Annealing allows for recrystallization, restoring plasticity and toughness.
• Achieving optimal corrosion resistance: By dissolving carbides into the austenitic matrix, it prevents the precipitation of chromium carbides at grain boundaries, thus maintaining its inherent corrosion resistance.
• Maintaining a bright surface: This is the most crucial difference. Traditional annealing is performed in air, resulting in severe black oxide scale, requiring subsequent pickling. Bright annealing, however, is performed in a reducing or inert atmosphere such as hydrogen, nitrogen, or a hydrogen-nitrogen mixture, completely avoiding surface oxidation. After exiting the furnace, the tube surface retains its original metallic color, remaining bright and free of oxidation.

Mechanical difference

ASME SA213 TP304H Stainless Steel Seamless Heat Exchanger Tube Application

• Power plant boiler superheaters
• Ethylene cracking furnace tubes
• Chemical heat exchangers
• High-tech/clean systems