15CrMoG High-Pressure Alloy Tube for Thermal Power Plants

When steam lines run hot and pressurized, plain carbon steel is no longer enough. 15CrMoG is a Chinese chromium-molybdenum alloy tube grade engineered for the superheaters and headers of thermal power plants, with an international cousin in ASTM A335 P11.

This article details the chemistry, properties and specification of 15CrMoG high-pressure alloy tube from Zhantong's alloy program.

Chemistry and Why Cr-Mo

15CrMoG contains roughly 1% chromium and 0.5% molybdenum, which raise high-temperature strength and oxidation resistance versus carbon steel. Molybdenum especially improves creep strength, while chromium forms a protective oxide scale.

The balanced chemistry keeps weldability reasonable when proper preheat and post-weld heat treatment are applied.

Manufacturing Route

Tubes are seamless, hot-rolled or cold-drawn, then normalized and tempered to stabilize the ferritic-pearlitic structure. Zhantong controls grain size, hardness and tensile properties per GB 5310.

For bent superheater sections, post-bend heat treatment restores uniformity at the stress concentration.

Property Comparison With P11

15CrMoG is the GB equivalent of ASTM A335 P11; both share similar Cr-Mo levels and creep behavior. Dual certification lets a single tube satisfy both Chinese and international plant codes.

Designers pick based on available documentation and the governing code of the project (GB 5310 or ASME SA-335).

High-Temperature Performance

Rated for service around 540–545 °C, 15CrMoG resists creep and scaling far better than carbon steel. It is a workhorse for subcritical and many supercritical boiler components.

Above its limit, higher-alloy grades (12Cr1MoVG, T91) are selected instead.

Where It Is Used

Applications include boiler superheaters, reheaters, headers and high-temperature steam pipes in power and cogeneration plants. It also appears in refinery and petrochemical high-heat lines.

For long seams and bends, qualified welding procedure with preheat avoids cold cracking.

Specification and Inspection

Specify by GB 5310 (or SA-335 P11), outer diameter, wall, heat treatment and end finish. Require ultrasonic and flattening tests plus heat-analysis mill reports.

Confirm design temperature so the wall schedule meets allowable stress with oxidation margin.