Thermal Properties of Black Iron Pipe

These days, black iron pipe is made from a mild steel.
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Although black iron pipe has iron in its name, it's actually made of low-grade, mild steel. Mild steel is a soft steel that can be easily welded and cut with a torch. Dealers and industry professionals in America will simply refer to schedule 40 steel pipes when talking about black iron pipe. Mild steel is used because it can bend; it can be cut with a torch and is much easier to work with overall. Knowing what black iron is made of is important because the iron's thermal properties are different from those of mild steel.

Thermal Conductivity

Thermal conductivity is the ability of a material to conduct heat. The formula for finding the thermal conductivity is btu/(hr-ft^2-F). To solve this equation, subtract the hours of contact from the length in feet of the pipe squared, minus the temperature of the heat source in Fahrenheit. Multiply this by the btu, which is the British thermal units found by dividing the weight of the pipe by the temperature change. The thermal conductivity for black iron pipe ranges from 26K to 37.5K meaning that it is a good heat conductor. K stands for kelvin, the measurement of heat energy.


Density is the ratio of an object's mass to its volume. The more mass that object has, the denser it is. The density of black iron pipe is .284 pounds per inch meaning that it is not very dense. For example titanium is about half as dense as mild steel and aluminum is a third as dense at mild steel. This calculation is found by dividing the mass of the pipe by its volume.

Specific Heat Capacity

Specific heat capacity is the amount of heat per unit mass required to raise the temperature by one degree Celsius. The specific heat of black iron pipe is .122 British thermal units per pound per degree. The formula for finding the specific heat is (btu/lb/F).

Melting Point

The melting point of black iron is 2,570 degrees Fahrenheit.

Thermal Expansion

Thermal Expansion is when an object begins to expand as the temperature around it increases. As an object is heated, the molecules begin to move rapidly and expand outward. The coefficient of thermal expansion of black iron pipe is 6.7. To find the amount of thermal expansion, multiply the temperature increase by the thermal expansion coefficient. Multiply the product of the temperature increase and the coefficient of thermal expansion by the total length of the pipe.

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