What Are the Common Materials for Boiler Tubes?

What are boiler tubes?

Boiler tubes are made from carbon steel or alloy steel and can withstand high pressures and temperatures. Boiler tubes are seamless and come in two types: medium pressure and high pressure, depending on the intended use. Boiler tubes are important to many industries, especially steam boilers, power plants, and factories.

Boiler tubes are made with great care to ensure they are strong and reliable. Let's take a closer look at how they are made. Material selection Seamless boiler tubes are a key factor in ensuring safe and efficient operation of boilers. Given the demanding operating conditions inside a boiler, the material must meet stringent performance requirements. Therefore, seamless boiler tubes are usually made from high-quality carbon steel, alloy steel, or stainless steel. The service life of seamless boiler tubes depends on various factors such as material type, operating environment, and maintenance, but they typically last more than 10 years.

Commonly used materials for high-pressure boiler tubes

At present, steel high-pressure boilers have been widely used in petrochemical, machinery, metallurgy, energy, light industry, national defense, environmental protection, ocean, space, life and other industrial sectors and scientific research fields. The specifications are Ф10~1064mm and above. Many enterprises have the production capacity of high-pressure boiler tubes. The steel types they use are also very high, including high-quality carbon steel 20G, manganese steel SA-106C, SA-210C, copper steel 15Mo3, SA-209T1a, chrome-molybdenum steel SA-213T2, 15CrMoG, SA-213T22, chrome-molybdenum-vanadium steel 12Cr1MoVG, 12Cr2MoWVTiB (steel 102), SA-213T91, chrome-nickel steel SA-213TP304H, SA-213TP347H and other materials.

Commonly used high-quality carbon steel (10, 20), alloy steel (12crmo, 15crmo), heat-resistant steel (12cr2mo, 15cr5mo), stainless steel (1cr18ni9, 1cr18ni9ti) are used for manufacturing. In addition to the chemical composition and various mechanical properties of steel pipes, water pressure, flattening, expansion and other tests, as well as surface quality and non-destructive testing must be guaranteed.

Materials: 20G, 20MnG, 25MnG, 15MoG, 20MoG, 12CrMoG, 15CrMoG, 12Cr2MoG, 12CrMoVG, 12Cr3MoVSiTiB, 1Cr18Ni9, 1Cr18Ni11Nb

Boiler tube material requirements:

The materials used for boiler tubes must be carefully selected to meet the following requirements:

(1) High temperature resistance and high strength
High-pressure boiler tubes are often in high temperature and high pressure conditions during use. Under the action of high-temperature flue gas and water vapor, the pipes will oxidize and corrode. The steel pipes are required to have high lasting strength, high oxidation resistance, corrosion resistance and good structural stability. The working conditions of high-pressure boiler tubes are very harsh. They must work safely for 10 to 20 years or even longer under high pressure, high temperature and high-speed air flow, water flow and coal gas erosion and corrosion.

(2) Thermal conductivity
Boiler tubes, especially high-pressure boiler tubes, are pipes for transporting high-temperature and high-pressure steam or hot water, and play an important role. In the design and use of high-temperature boiler tubes, thermal conductivity is a very critical indicator.

Heat conduction is the process of heat transfer from a high-temperature object to a low-temperature object. In high-temperature boiler pipes, heat conduction is mainly conducted through the tube wall. The thermal conductivity of the tube wall is related to the thermal conductivity, wall thickness, tube diameter, temperature gradient, etc. of the material.

Materials Commonly Used for Boiler Tubes

The selection of materials for boiler tubes depends largely on the operating conditions inside the boiler, including temperature, pressure, and the potential for corrosion. Here are the most commonly used materials for manufacturing high-pressure and medium-pressure boiler tubes:

1. Carbon Steel

Carbon steel is one of the most widely used materials for medium-pressure boiler tubes. It provides excellent mechanical strength and is relatively cost-effective. The most common types of carbon steel used for boiler tubes are:
20G: Often used for low and medium-pressure boilers, 20G is a high-quality carbon steel with a good balance of strength and thermal conductivity.
20MnG and 25MnG: These grades offer increased tensile strength and are suitable for applications involving slightly higher pressures.

2. Alloy Steel

Alloy steel is essential for high-pressure and high-temperature applications. Alloying elements such as chromium, molybdenum, and vanadium are added to improve heat resistance, strength, and corrosion resistance. Commonly used alloy steels include:
12Cr1MoVG: A chromium-molybdenum-vanadium steel that offers excellent high-temperature performance, often used in superheaters and reheaters of high-pressure boilers.
15CrMoG: This material is known for its resistance to oxidation and corrosion, making it suitable for high-pressure applications where both thermal stability and resistance to erosion are important.
12Cr2MoG: Another chromium-molybdenum alloy, providing enhanced resistance to high-temperature oxidation and pressure.

3. Heat-Resistant Steel

For applications requiring exceptional heat resistance, heat-resistant steel is used in high-temperature boilers. These steels are designed to maintain strength and resist oxidation under extreme conditions:
12Cr2Mo: Known for its excellent heat resistance, this steel is typically used in medium-pressure to high-pressure boilers where temperatures can reach up to 450°C.
15Cr5Mo: This material offers improved high-temperature strength and is often used in environments with severe temperature fluctuations.

4. Stainless Steel

Stainless steel is selected for its superior corrosion resistance, especially in environments prone to moisture or chemical exposure. It is commonly used for high-pressure applications and in situations requiring high resistance to corrosive media. Common grades of stainless steel for boiler tubes include:
1Cr18Ni9: Austenitic stainless steel with good corrosion resistance and strength at elevated temperatures, suitable for high-temperature steam environments.

1Cr18Ni9Ti: This variant includes titanium, improving the material's resistance to heat and corrosion, often used in environments with aggressive chemical exposure.

Boiler Tube Materials Standards & Specifications

Material Type	Standards	Common Sizes	Types
Carbon Steel	ASTM/ASME A/SA 106, ASTM A179, ASTM A192, ASTM/ASME A/SA 210, ASTM A333 Gr 1, 6, 7 to Gr 9	OD: 6mm to 1240mm, Thickness: 1mm to 50mm	Straight boiler pipe, U boiler steel pipe for tube exchanger bundle
Alloy Steel	ASTM/ASME A/SA 213 T1, T2, T5, T9, T11, T12, T22, T91, T92; ASTM A335 P1, P2, P5, P9, P11, P12, P22, P91, P92	OD: 6mm to 1240mm, Thickness: 1mm to 50mm	Straight boiler pipe, U boiler steel pipe for tube exchanger bundle
Stainless Steel	ASTM A268, ASTM A213, TP304/L, TP316/L, 310S, 309S, 317, 317L, 321, 321H, Duplex Stainless Steel	OD: 6mm to 1240mm, Thickness: 1mm to 50mm	Straight boiler pipe, U boiler steel pipe for tube exchanger bundle

Attribute	Carbon Steel Boiler Tubes	Stainless Steel Boiler Tubes	Alloy Steel Boiler Tubes
Chemical Composition	Iron and carbon, low carbon content (<0.35%)	At least 10.5% chromium, often with nickel, molybdenum	Iron, carbon, and various alloying elements (e.g., manganese, silicon, chromium, nickel)
Mechanical Properties	Lower strength and hardness	Good formability; moderate strength	Higher strength, toughness, and wear resistance
Corrosion Resistance	Low; may need coatings or linings	High due to chromium oxide layer	Good to excellent, depending on alloying elements
Applications	General-purpose, low to moderate temperature and pressure	Corrosive environments, food processing, chemical industry	High-temperature and high-pressure applications, such as in power stations
Cost and Economy	Lower initial cost; may require more maintenance	Higher initial cost; potentially lower lifecycle cost	Varies; can be more expensive due to alloy content
Environmental Impact and Sustainability	Regular maintenance may be needed	Recyclable; low maintenance	Varies; some alloys are highly recyclable
Lifespan	Shorter lifespan if not properly protected against corrosion	Longer lifespan due to self-healing properties and corrosion resistance	Long lifespan, especially in harsh environments; depends on alloy composition

Boiler tube components and materials used:

Boiler Component	Function Description	Typical Material Used
Water Wall Tubes	Main heat-receiving surface around the furnace.	Carbon Steel
Convection Tubes	Further heating of fluid in the convection area of the boiler.	Carbon Steel or Alloy Steel
Downcomer Tubes	Transport water from the steam drum to the downcomer.	Carbon Steel
Header (Collector)	Collects and distributes boiler water; not typically exposed to radiant heat.	Carbon Steel or Stainless Steel
Superheater Tubes	Heat saturated steam into superheated steam, improving steam quality.	Alloy Steel
Economizer Tubes	Use residual heat from exhaust gases to raise feedwater temperature.	Carbon Steel or Alloy Steel

Applications of Different Boiler Tube Materials

Classification of high-pressure boiler tube uses: used for heating surface tubes of low and medium pressure boilers (working pressure is generally not more than 5.88Mpa, working temperature is below 450℃); used for heating surface tubes, economizers, superheaters, reheaters, petrochemical industry tubes, etc. of high-pressure boilers (working pressure is generally above 9.8Mpa, working temperature is between 450℃ and 650℃).

According to the composition materials, it can be divided into 20G high-pressure boiler tube, 12Cr1MoVG high-pressure boiler tube, Gangyan 102 high-pressure boiler tube, 15CrMoG high-pressure boiler tube, 5310 high-pressure boiler tube, 3087 low and medium-pressure boiler tube, 40Cr high-pressure boiler tube, 1Cr5Mo high-pressure boiler tube, 42CrMo high-pressure boiler tube. For low pressure with low pressure, 20G is generally used. 20G, which is a kind of material in Q245R steel, belongs to boiler plate. g is the first letter of "pot" in boiler plate: g. Implementation standard: GB713-1997 (internal and external standards implement this standard) Scope of application: steel plates with a thickness of 6mm-150mm.

Because the steel plate is delivered with positive tolerance, the boiler plate also has a thickness additional value table. When calculating the weight of the steel plate theoretically, it is necessary to add the corresponding value in the table on the basis of the thickness. According to the requirements, the steel plate can be delivered after heat treatment: controlled rolling, normalizing, etc. The flaw detection standard is implemented as follows: JB/T4730.3-2005, divided into three levels.