Details of high-pressure boiler seamless steel pipes commonly used in industrial projects

High-pressure boiler steel pipe is a type of boiler steel pipe, (working pressure is generally not more than 5.88Mpa, working temperature is below 450℃) heating surface steel pipe; used for high-pressure boilers (working pressure is generally above 9.8Mpa, working temperature is between 450℃ and 650℃) belongs to the category of seamless steel pipes. The manufacturing method is the same as that of seamless pipes, but there are strict requirements on the type of steel used to manufacture steel pipes. High-pressure boiler steel pipes are often in high-temperature and high-pressure conditions during use. Under the action of high-temperature flue gas and water vapor, the steel pipe will oxidize and corrode. The steel pipe is required to have high lasting strength, high anti-oxidation and corrosion performance, and good organizational stability. High-pressure boiler steel pipes are mainly used to manufacture superheater tubes, reheater tubes, gas guide tubes, main steam pipes, etc. of high-pressure and ultra-high-pressure boilers.

The general production standards for high-pressure boiler steel pipes are national standard GB/5310, American standard ASME SA213, ASME SA335, etc. Commonly used materials include national standard materials: 20G, 15CrMoG, 12Cr1MoVG, and American standard materials: P11, P22, P91, P92, T11, T22, T91, T92, etc.

Due to long-term operation under high temperatures and high-pressure conditions, boiler steel pipes will creep, plasticity and toughness will decrease, the original structure will change, and corrosion will occur. Steel pipes used for boilers should have:

(1) Sufficient endurance strength;

(2) Sufficient plastic deformation capacity;

(3) Minimum aging tendency and hot brittleness;

(4) High oxidation resistance, coal ash resistance, resistance to natural gas corrosion at high temperature, steam and stress corrosion;

(5) Good structural stability and good process performance. The steel types of high-pressure boiler steel pipes include carbon steel and pearlite, ferrite, and austenite stainless heat-resistant steel.

To improve the thermal efficiency of thermal power generating units and reduce fuel consumption, countries around the world are mainly developing large-capacity, high-parameter (high temperature, high pressure) thermal power generating units (above 1000MW). The steam pressure is increased to 31.5-34.3MPa, and the superheated steam temperature reaches 595-650℃, developing towards ultra-high pressure critical pressure, which puts higher requirements on high-pressure boiler steel pipes. Appearance quality: Cracks, folds, rolling folds, scars, delamination, and hairline are not allowed on the inner and outer surfaces of the steel pipe. These defects should be completely removed. The cleaning depth shall not exceed the negative deviation of the nominal wall thickness, and the actual wall thickness at the cleaning location shall not be less than the minimum value allowed by the wall thickness.