Thermal Conductivity: Carbon Steel Pipe vs. Other Steel Pipes

Among numerous performance indicators, thermal conductivity is a key comparative parameter for the carbon steel pipe, alloy steel pipe, and stainless steel pipe in applications such as heat exchange, media transportation, and energy systems. In the energy, oil and gas, industrial pipeline, and building structure sectors, carbon steel pipes have consistently been the mainstream choice for global engineering projects. Compared to stainless steel and alloy steel pipes, carbon steel pipes not only have advantages in cost and supply stability, but their thermal conductivity is also a crucial technical indicator that is often overlooked in engineering selection.

What is Thermal Conductivity?

Thermal conductivity, denoted by the symbol λ, is an indicator that measures a material's ability to conduct heat. It is defined as the amount of heat passing through a material per unit thickness, unit area, and unit temperature difference.

1. SI Units of Thermal Conductivity

The SI unit for thermal conductivity is watts per meter per Kelvin (W/m·K).

The higher the thermal conductivity, the stronger the heat transfer capacity of the material;

The lower the thermal conductivity, the better the heat insulation and heat preservation capacity of the material.

2. Formulas for Thermal Conductivity of Different Metals

The formula for thermal conductivity is:

Q=-k · A · (dT/dx)

Where:

Q is the heat transferred,

k is the thermal conductivity,

A is the cross-sectional area for heat transfer,

(dT/dx) is the temperature gradient.

Thermal Conductivity of Different Steels

Common Steel Thermal Conductivity Ranges (Room Temperature Conditions)

Note:

Actual thermal conductivity is affected by chemical composition, heat treatment state, microstructure, and temperature changes. The above data are commonly used reference ranges in engineering.

Thermal Conductivity: Carbon Steel Pipe vs. Other Steel Pipe

1. Thermal Conductivity of Carbon Steel Pipe

Carbon steel contains only trace amounts of elements besides carbon and iron. This type of steel is the most widely used, accounting for approximately 90% of total steel production. Carbon steel pipes have the highest thermal conductivity, averaging 45 watts per Kelvin per meter.

For steels with a carbon content exceeding 0.1% (the specific value depends on the steel thickness), their strength can be improved through heat treatment. The most common heat treatment processes used by manufacturers include annealing, quenching, and tempering.

The Effect of Heat Treatment on the Thermal Conductivity of Carbon Steel

For carbon steel pipes with a carbon content ≥0.1%, common heat treatment processes include:

Annealing: Improves microstructure uniformity;

Normalizing: Enhances overall mechanical properties;

Quenching & Tempering: Improves strength and toughness.

2. Thermal Conductivity of Alloy Steel and Tool Steel Pipes

Alloy steels contain added elements such as nickel, copper, chromium, and/or aluminum. The addition of these metals significantly affects the steel's strength and other important properties, such as ductility, corrosion resistance, and machinability.

Tool steels, another major type of metal, are ideal for manufacturing cutting and drilling equipment due to the presence of tungsten, molybdenum, cobalt, and vanadium. The addition of these elements significantly improves heat resistance and durability.

3. Thermal Conductivity of Stainless Steel Pipes

Stainless steel has a thermal conductivity as low as 15 W/(mK), which allows it to better maintain the stability of ambient temperatures compared to other types of steel.

Due to its stability at high temperatures, stainless steel is commonly used in food processing, ovens, and conveyor belts—applications frequently exposed to high temperatures.

FAQ

1. Why does carbon steel have higher thermal conductivity than stainless steel?

The main reasons include:

Carbon steel has a low alloy element content and a simple crystal structure;

it has high free electron migration efficiency and low heat transfer resistance;

the high chromium and nickel content in stainless steel significantly reduces its thermal conductivity.

2. How to choose the right carbon steel pipe for thermal applications?

It is recommended to focus on:

The operating pressure and temperature range of the carbon steel pipe; the type of medium (steam, hot water, oil, gas);

the corresponding international standards (ASTM / EN / API).

Whether insulation or anti-corrosion coating is required.

3. How does temperature affect the thermal conductivity of carbon steel pipe?

Yes. 

As temperature increases, the thermal conductivity of carbon steel generally decreases slowly.

However, under most industrial conditions (≤400°C), carbon steel pipes still maintain: Stable thermal conductivity; predictable heat transfer behavior.

Conclusion

Carbon steel pipes have significantly better thermal conductivity than alloy steel and stainless steel pipes. They also offer lower raw material and processing costs, adhere to comprehensive international standards, have stable delivery times, and are suitable for over 80% of industrial conveying systems.