Explore the industrial details of 20G high-pressure boiler steel pipes

1. Product introduction of 20G high-pressure boiler steel pipe
Boiler steel pipes are used under high temperatures and high-pressure conditions, so compared with general-purpose steel pipes such as structural pipes, their service conditions are harsh. If there is a problem with any steel pipe in the high-pressure boiler steel pipe, the equipment will be damaged, and the boiler explosion may even cause casualties. Therefore, there are clear and strict regulations in international codes and standards such as GB5310-95, ASTMA335, ASTMA106, and DIN17175. 20G high-pressure boiler steel pipe is a high-pressure boiler steel pipe commonly produced by the company. Currently, 20G steel accounts for 77% and is the most commonly used steel for boiler steel pipes.

Maximum operating temperature: Mainly used to manufacture heating surface tubes for high-pressure and higher-parameter boilers, such as low-temperature superheaters, reheaters, economizers, and water-cooled wall tubes. The maximum wall temperature for long-term use should be ≤480°C. When used in headers and steam pipes, the maximum wall temperature should be ≤430°C. Within this temperature range, the strength of this steel can meet the requirements of superheaters and steam pipes. It also has good oxidation resistance, plastic toughness, welding performance, etc. as well as good mechanical properties and corrosion resistance. When the wall temperature exceeds 500°C, the heating surface pipe must be made of alloy steel pipes, and different alloy steel pipes are selected according to the wall temperature. When the wall temperature exceeds 600°C, the United States, Japan, and other countries all use austenitic steel pipes, while European countries use high-chromium martensitic steel pipes. In my country, bainite heat-resistant steel is often used when the wall temperature is 600~620°C. In recent years, some austenitic steel pipes have also begun to be used in large-capacity and high-parameter boilers.

Implementation standard: GB/T 5310-2017 Seamless steel pipe for high-pressure boilers

2. Chemical composition of 20G high-pressure boiler steel pipe (%)
When 20G (high-quality carbon structural steel) supplied according to the requirements of GB5310 is used as heating surface pipe fittings, its maximum wall temperature for long-term use is ≤450°C. When used as headers and steam pipes, the long-term use temperature should be ≤425°C.

C：20G 0.17~0.23
Si: 0.17~0.37
Mn: 0.35~0.65
P：≤0.025
S：≤0.015

3. Mechanical properties of 20G high-pressure boiler steel pipe
Tensile strength (MPa): 20G 410~550
Yield strength (MPa): ≥245
Elongation (%): ≥24

4. Heat treatment system for 20G high-pressure boiler steel pipes
Heat treatment type
Normalizing: normalizing temperature 880℃~940℃
Note: National standard GB5310-95 stipulates that normalizing can be replaced when the final rolling temperature of hot-rolled pipes is not less than 900°C.