It is a steel grade in ASME SA-209 standard, a small-diameter carbon-molybdenum steel pipe for boilers and superheaters, and a pearlescent heat-resistant steel. China transplanted it into GB53 10 in 1995 and named it 20MoG. Its chemical composition is simple, but it contains molybdenum, so its thermal strength is better than that of carbon steel while maintaining the same technological properties as that of carbon steel. However, the steel is easy to graphitize after long-term operation at high temperature, so its service temperature should be controlled below 5 10℃ to prevent overheating, and the addition of Al should be limited during smelting to control and delay its graphitization process. The steel pipe is mainly used for water cooling wall, superheater and reheater, and the wall temperature is below 5 10℃. Its chemical components are C0. 15-0.25, Si0. 10-0.50, Mn0.30-0.80, S≤0.025, P≤0.025 and mo 0.44-0.65；; . Normalized intensity level σs≥220, σ b ≥ 415mpa; Plasticity δ≥30.

Small diameter steel pipes are seldom used in our factory. Low-temperature superheater (29 tons) is used in Iranian furnace (referring to single furnace).