High-pressure boiler steel pipes are a type of boiler steel pipe, belonging to the seamless steel pipe category. The manufacturing method is the same as that of seamless steel pipes, but there are strict requirements on the steel grades used. High-pressure boiler steel pipes are frequently used under high temperature and high pressure conditions. Under the action of high-temperature flue gas and steam, they will undergo oxidation and corrosion.
Basic Information on High-Pressure Boiler Steel Pipes
Specifications: 6mm-1240mm × 1mm-200mm
Manufacturing Processes: Precision drawing, bright finishing, hot rolling, cold drawing, hot expansion
Applications: Used as heating surface steel pipes in low and medium pressure boilers (working pressure generally not exceeding 5.88MPa, working temperature below 450℃); used as heating surface tubes, economizers, superheaters, reheaters, and petrochemical industry pipes in high-pressure boilers (working pressure generally above 9.8MPa, working temperature between 450℃ and 650℃). 

Manufacturing and Uses of High-Pressure Boiler Steel Pipes
(1) Manufacturing Methods of High-Pressure Boiler Steel Pipes:
① For general boiler steel pipes used at temperatures below 450℃, domestically produced pipes are mainly made from No. 10 and No. 20 carbon structural steel hot-rolled or cold-drawn pipes.
② High-pressure boiler steel pipes are frequently used under high temperature and high pressure conditions. Under the influence of high-temperature flue gas and steam, the boiler steel pipes will undergo oxidation and corrosion. High creep strength, high resistance to oxidation and corrosion, and good structural stability are required.
(2) Uses of High-Pressure Boiler Steel Pipes:
① General boiler steel pipes are mainly used to manufacture water-cooled wall tubes, boiling water tubes, superheated steam tubes, superheated steam tubes for locomotive boilers, large and small smoke tubes, and arch brick tubes, etc.
② High-pressure boiler steel pipes are mainly used to manufacture superheater tubes, reheater tubes, steam pipes, and main steam pipes for high-pressure and ultra-high-pressure boilers, etc.

What are the Heat Treatment Processes for High-Pressure Boiler Steel Pipes? 
Heat treatment is a method of changing the physical properties of high-pressure boiler steel pipes by using heating and cooling. Heat treatment can improve the microstructure of high-pressure boiler steel tubes, enabling them to meet desired physical requirements. Toughness, hardness, and wear resistance are some of the properties acquired through heat treatment. To obtain these properties, operations such as hardening, tempering, annealing, and surface hardening are required during heat treatment.
Temperature requirements for heat treatment of high-pressure boiler steel tubes:
1. Normalizing: Normalizing temperature 880℃-940℃ (20G, 20MNG, 25MNG); Normalizing temperature 890℃-950℃ (15MOG, 20MOG)
2. Normalizing plus tempering: Normalizing temperature: 900℃-960℃; Tempering temperature: 680℃-730℃ (15CRMOG, 12CR1MOVG)
3. Details related to the heat treatment of high-pressure boiler steel tubes:
Hardening: Hardening involves uniformly heating the high-pressure boiler steel tube to a suitable temperature, then rapidly immersing it in water or oil for quenching, or cooling it in air or a freezing zone to achieve the required hardness.
Tempering: Tempering can make hardened high-pressure boiler steel tubes brittle. The stress caused by rapid quenching can also cause the tube to fracture even with a light impact. Tempering is used to eliminate brittleness. Tempering involves reheating the high-pressure boiler steel pipe to a suitable temperature or color, followed by rapid cooling. While tempering slightly reduces the hardness of the high-pressure boiler steel pipe, it increases its toughness and reduces its brittleness.
Annealing: Annealing is a method to eliminate internal stresses and harden the steel in high-pressure boiler steel pipes. The annealing method involves heating the steel to above its critical temperature, then placing it in dry ash, lime, asbestos, or sealing it in a furnace to allow it to cool slowly.
Hardness: Hardness is a material's ability to resist the penetration of foreign objects. A common method for testing the hardness of high-pressure boiler steel pipes is to file the edge of the workpiece with a file, and the depth of the scratch indicates its hardness. This method is called the file test, but it is not very scientific. Using a hardness tester is extremely accurate and is the commonly used method for modern hardness testing. A commonly used test method is the Rockwell hardness test. The Rockwell hardness tester uses the depth to which a diamond penetrates the metal to determine the hardness of the high-pressure boiler steel pipe; the greater the penetration depth, the lower the hardness. The depth to which a diamond penetrates metal can be indicated by a pointer, and this number is called the Rockwell hardness number.
Forging: Forging is a method of shaping metal by hammering. When high-pressure boiler steel pipes are heated to forging temperature, forging, bending, drawing, and forming operations can be performed. Most high-pressure boiler steel pipes are easy to forge when heated to a bright cherry red color.
Brittleness: Brittleness refers to the property of high-pressure boiler steel pipes to easily break. Cast iron is highly brittle and can even break when dropped. Brittleness is closely related to hardness; high-hardness 20# precision steel pipes are usually also highly brittle.
Ductility: Ductility is the property of a metal to deform under external force without shattering. Ductile high-pressure boiler steel pipes can be drawn into thin wires.
Elasticity: Elasticity is the property of high-pressure boiler steel pipes to deform under external force and return to their original shape after the force is removed. Spring steel is a highly elastic material.
Hardness: Hardness is a measure of a metal's resistance to penetration or cutting by foreign objects. A common method to increase the hardness of high-pressure boiler steel pipes is quenching.
Earning Power: Earning power is another way of expressing the ductility or softness of a metal. It is a property of a metal that prevents it from cracking when deformed by hammering or rolling.
Toughness: Toughness is the ability of high-pressure boiler steel pipes to withstand vibration or impact. Toughness is the opposite of brittleness.