Thermal Expansion Coefficient of Carbon Steel
| Value | 0.0000117 1/K |
| Status | Measured: ± 5.00e-07 1/K (0.043 relative) |
| Source | ASM Handbook, Vol. 1 / ASME B31.1 Power Piping |
| Categories | Material PropertiesEngineering & Trade |
| part per million per kelvin | 11.7 ppm/K |
| part per million per Celsius degree | 11.7 ppm/°C |
| part per million per Fahrenheit degree | 6.5 ppm/°F |
| microinch per inch per Fahrenheit degree | 6.5 μin/(in·°F) |
| percent per Celsius degree | 0.00117 %/°C |
| percent per Fahrenheit degree | 0.00065 %/°F |
| per kelvin | 0.0000117 1/K |
| per Celsius degree | 0.0000117 1/°C |
| per Fahrenheit degree | 0.0000065 1/°F |
| per Rankine degree | 0.0000065 1/°R |
Learning zone
A 100 m steel pipe run heated 100 °C grows 117 mm — the length of a fist. That is the entire reason for expansion loops, guides, anchors and bellows in piping, and for expansion joints in bridges and rails. Restrain the same steel completely and you get thermal stress σ = E α ΔT, which for 100 °C is 200e9 × 1.17e-5 × 100 = 234 MPa: enough to yield A36 outright, with no external load at all. Note that this stress is independent of length and cross-section, which surprises people every time.
The coefficient itself is stable and unglamorous — carbon steel varies by only a few percent across grades — but the companion values are not. Austenitic stainless expands about 50 % more, aluminium twice as much, and PVC almost five times as much, so dissimilar-material assemblies are where expansion causes trouble: stainless pipe on carbon steel supports, aluminium cladding on steel framing, plastic pipe in a metal hanger system. Concrete is the fortunate exception, expanding at almost exactly the same rate as steel, which is what makes reinforced concrete possible at all.