304 Stainless Steel Thermal Conductivity
Use approximately 15 W/m·K at 20°C for typical annealed 304 stainless steel. Official producer data give about 16.2 W/m·K at 100°C and 21.4 W/m·K at 500°C—so temperature and source must accompany every value.
Outokumpu typical room-temperature value; NIST cryogenic fit gives about 15.1 at 293 K.
Typical 304/304L value published by Cleveland-Cliffs.
Conductivity rises with temperature across this service range.
“304 conductivity” without a reference temperature is incomplete.
What is the thermal conductivity of 304 stainless steel?
At room temperature, annealed 304 stainless steel has a typical thermal conductivity near 15 W/(m·K), equivalent to about 8.7 Btu/(h·ft·°F).
This is not one immutable constant. The National Institute of Standards and Technology (NIST) cryogenic fit for UNS S30400 calculates approximately 15.1 W/(m·K) at 293 K. Outokumpu lists 15 W/(m·K) at room temperature for Core 304/4301. Cleveland-Cliffs publishes 16.2 W/(m·K) at 100°C and 21.4 W/(m·K) at 500°C for 304/304L.
That source comparison corrects a common online error: many summaries repeat 16.2 W/(m·K) as a 20°C value even though a major producer's table associates it with 100°C. The difference may look small, but a 7–8% conductivity shift passes directly into a one-dimensional Fourier conduction result when everything else is held constant.
For early calculations, use 15 W/(m·K) at 20°C, then replace it with data matched to the actual mean metal temperature, product form, condition and project quality requirements. For cryogenic work, use the NIST temperature-dependent curve rather than extending a room-temperature number downward.
304 stainless steel thermal conductivity values and chart
Conductivity rises substantially from cryogenic temperature to 500°C. The low-temperature values below come from the NIST UNS S30400 curve fit; the elevated-temperature anchors come from Cleveland-Cliffs producer data.
| Temperature | Kelvin | Thermal conductivity | Imperial equivalent | Data basis |
|---|---|---|---|---|
| −196°C | 77 K | 7.92 W/(m·K) | 4.58 Btu/(h·ft·°F) | NIST polynomial fit |
| −173°C | 100 K | 9.22 W/(m·K) | 5.33 Btu/(h·ft·°F) | NIST polynomial fit |
| −100°C | 173 K | 11.87 W/(m·K) | 6.86 Btu/(h·ft·°F) | NIST polynomial fit |
| 0°C | 273 K | 14.59 W/(m·K) | 8.43 Btu/(h·ft·°F) | NIST polynomial fit |
| 20°C | 293 K | 15.12 W/(m·K) | 8.74 Btu/(h·ft·°F) | NIST fit; Outokumpu typical value 15 |
| 100°C | 373 K | 16.2 W/(m·K) | 9.36 Btu/(h·ft·°F) | Cleveland-Cliffs typical value |
| 200°C | 473 K | ≈17.5 W/(m·K) | ≈10.1 Btu/(h·ft·°F) | Linear planning interpolation |
| 300°C | 573 K | ≈18.8 W/(m·K) | ≈10.9 Btu/(h·ft·°F) | Linear planning interpolation |
| 400°C | 673 K | ≈20.1 W/(m·K) | ≈11.6 Btu/(h·ft·°F) | Linear planning interpolation |
| 500°C | 773 K | 21.4 W/(m·K) | 12.36 Btu/(h·ft·°F) | Cleveland-Cliffs typical value |
The chart joins published reference points and clearly labeled planning interpolations; it is not a material certification curve. NIST's cryogenic correlation is valid over its stated low-temperature range, while producer values provide the elevated-temperature anchors.
Calculate conduction through a 304 stainless steel wall
Enter hot-side and cold-side temperatures, wall thickness and area. The tool estimates conductivity at the mean wall temperature, then applies one-dimensional Fourier conduction.
Define the wall
At a mean wall temperature of 87.5°C, the model uses about 16.0 W/(m·K).
How does 304 compare with copper, aluminum and other steels?
At room temperature, 304 transfers heat far less readily than copper, aluminum or plain carbon steel. Ferritic stainless grades also tend to conduct better than austenitic 304.
| Material | Typical conductivity near room temperature | Relative to 304 | Design interpretation |
|---|---|---|---|
| 304 stainless steel | ≈15 W/(m·K) | 1.0× | Corrosion-resistant austenitic baseline; slow lateral heat spreading. |
| Ferritic stainless, EN 1.4016 / Type 430 | ≈25 W/(m·K) | ≈1.7× | Better conduction, but grade choice must also satisfy corrosion and fabrication requirements. |
| Non-alloy steel | ≈55 W/(m·K) | ≈3.7× | Transfers heat faster but does not provide 304's general corrosion resistance. |
| Aluminum | ≈235 W/(m·K) | ≈15.7× | Excellent heat spreading; often used as a core in clad cookware. |
| Copper | ≈400 W/(m·K) | ≈26.7× | Very high conductivity, with different cost, strength, joining and corrosion tradeoffs. |
These figures are comparative typical values, not substitution approvals. Conductivity is only one selection criterion. Corrosion environment, cleanability, strength, thermal expansion, weldability, magnetic response, code status, cost and product availability can reverse a choice that looks obvious from heat flow alone.
Why is 304 stainless steel a relatively poor heat conductor?
Metals move heat through both mobile electrons and lattice vibrations. Pure copper is exceptionally effective because electrons travel with comparatively little scattering. Type 304 is a heavily alloyed iron–chromium–nickel solid solution, so the atomic lattice is much less uniform.
Chromium and nickel atoms differ from iron in size, mass and electronic character. Their random distribution, along with smaller contributions from manganese, silicon, carbon, nitrogen and defects, scatters heat-carrying electrons and phonons. Electrical resistivity rises and thermal conductivity falls. Cleveland-Cliffs lists 304/304L electrical resistivity around 72 μΩ·cm at 20°C, consistent with its modest heat conduction compared with pure copper.
The face-centered cubic austenitic structure is also part of the system. It gives 304 useful ductility, toughness and cryogenic performance, but the overall alloyed austenitic matrix does not transport heat like a pure metal. Ferritic stainless steels often have higher room-temperature conductivity because their chemistry and body-centered cubic structure differ.
How to use 304 conductivity in Fourier's law
For ideal one-dimensional conduction through a flat wall of uniform thickness, the heat-transfer rate is proportional to conductivity, area and temperature difference and inversely proportional to thickness.
Q = heat-transfer rate (W), k = thermal conductivity [W/(m·K)], A = area (m²), ΔT = temperature difference (K), and L = wall thickness (m).
Worked 304 plate example
Consider a 304 vessel wall with a hot-side temperature of 150°C, cold-side temperature of 25°C, area of 0.5 m² and thickness of 5 mm. The mean wall temperature is approximately 87.5°C, so a planning conductivity near 16.0 W/(m·K) is reasonable.
- ΔT = 150 − 25 = 125 K
- L = 5 mm = 0.005 m
- Q ≈ 16.0 × 0.5 × 125 / 0.005
- Q ≈ 200,000 W, or 200 kW
- Heat flux q″ = Q/A ≈ 400 kW/m²
Why the real rate is usually lower
The wall-only result assumes its surfaces are already held exactly at 150°C and 25°C. A real exchanger must move heat from a hot fluid to the wall, through the wall, then from the wall to the cold fluid. It may also have fouling and contact resistances.
The complete resistance may be written conceptually as:
The film coefficients hi and ho can dominate when the stainless wall is thin. Never treat the ideal wall calculation as exchanger duty without the rest of the resistance network.
Why wall thickness often matters more than a small k-value difference
Conduction resistance is L/(kA). Halving a uniform wall's thickness halves its conduction resistance, while changing conductivity from 15.0 to 16.2 W/(m·K) reduces that resistance by only about 7.4%.
| 304 wall thickness | Wall resistance per 1 m² at k = 15 W/(m·K) | Ideal heat flux at ΔT = 100 K | Interpretation |
|---|---|---|---|
| 0.5 mm | 0.0000333 m²·K/W | 3,000 kW/m² | Very low wall resistance; fluid films likely dominate. |
| 1.0 mm | 0.0000667 m²·K/W | 1,500 kW/m² | Common thin-sheet scale; check strength, forming and corrosion allowance. |
| 2.0 mm | 0.000133 m²·K/W | 750 kW/m² | Twice the conduction resistance of a 1 mm wall. |
| 5.0 mm | 0.000333 m²·K/W | 300 kW/m² | Wall resistance becomes more significant. |
| 10.0 mm | 0.000667 m²·K/W | 150 kW/m² | Thick structural wall may strongly limit pure conduction. |
When is low 304 thermal conductivity helpful—or harmful?
Type 304 is rarely chosen because it has the best heat conductivity. It is selected because corrosion resistance, fabrication, hygiene, toughness, availability and cost form a useful package. Thermal design then compensates for its conductivity.
Low conductivity can help
- Cryogenic inner vessels and supports: reduced solid conduction can help limit heat leak, although geometry, welds, insulation and radiation remain essential.
- Thermal barriers and handles: lower heat spreading can reduce transfer toward touch points compared with copper or aluminum.
- Hot process containment: heat may remain more localized, depending on insulation and fluid conditions.
Low conductivity can hurt
- Heat exchangers: more area, thinner walls or stronger convection may be required.
- Cookware: pure stainless spreads burner heat poorly, so quality pans often use aluminum or copper cores.
- Electronics and tooling: hotspots decay slowly unless a higher-conductivity insert or active cooling path is added.
Does surface finish change 304's thermal conductivity?
Surface finish does not materially change the intrinsic bulk conductivity of a thick, homogeneous 304 wall, but it can change the heat transferred at the boundary.
Convection
Roughness, fouling, deposits and flow geometry can alter the fluid boundary layer and effective convection coefficient. Their impact belongs in the surface-film term, not in k for the bulk metal.
Radiation
Polished, oxidized, coated and roughened surfaces can have very different emissivity. At elevated temperature, radiative exchange may change substantially even though the alloy's internal conductivity is unchanged.
Contact resistance
Two nominally touching stainless surfaces meet only at microscopic asperities. Flatness, clamping pressure, oxidation and interface materials control contact conductance.
For a heat exchanger, keep separate values for bulk wall conductivity, hot-side convection, cold-side convection, fouling, radiation and contact interfaces. Combining them all into an “adjusted conductivity” can hide which physical mechanism needs improvement.
How does low conductivity affect welding 304 stainless steel?
Compared with carbon steel or aluminum, heat introduced into 304 spreads away from the weld less quickly. Combined with relatively high thermal expansion, this can concentrate temperature gradients and increase distortion risk.
Heat stays near the interaction zone
Lower conductivity can support efficient local melting, but excessive energy density or slow travel may enlarge the molten pool, oxidation and heat-affected region. Laser power, focus, travel speed and wobble must be qualified together.
Expansion and restraint matter
Austenitic stainless expands more than many carbon steels. Thin sheet, long seams and asymmetric fixtures can warp even when the weld looks visually sound. Joint sequence, clamping and heat input require control.
Repeated paths can compound temperature
Closely spaced welds, starts and stops, corners or high duty cycles may not cool as quickly as expected. Monitor part temperature when repeatability or appearance is critical.
304 and 304L are thermally similar
Lower carbon in 304L primarily improves resistance to sensitization after welding. Its thermal conductivity is close enough that the same planning values are commonly used, but the exact grade still matters for the welding procedure.
Thermal conductivity alone does not define a laser-welding setting. Thickness, fit-up, joint type, reflectivity, surface condition, shielding, filler wire, required penetration and inspection acceptance all belong in the process window.
How should engineers choose a conductivity value?
Seven mistakes that produce misleading heat-transfer results
Using 16.2 at 20°C without checking the table
A major 304/304L producer lists 16.2 at 100°C. Room-temperature references near 15 are also authoritative.
Ignoring mean wall temperature
For a wide temperature span, room-temperature k can understate elevated-temperature conduction.
Mixing conductivity units
W/(m·K), Btu/(h·ft·°F) and Btu·in/(h·ft²·°F) are not interchangeable.
Treating wall-only Q as exchanger duty
Convection films and fouling often dominate the complete resistance network.
Using one k for cryogenic design
At 77 K the conductivity is roughly half the room-temperature value. Use the NIST correlation within its documented range.
Changing grade on k alone
A higher-conductivity alloy may fail corrosion, hygiene, fabrication or code requirements.
Confusing finish with bulk k
Finish affects radiation, convection, fouling and contact behavior more directly than intrinsic conductivity.
304 stainless steel thermal conductivity FAQ
What is the thermal conductivity of 304 stainless steel at 20°C?
Is 16.2 W/m·K the room-temperature conductivity of 304?
Does 304 conductivity increase with temperature?
What is 304 thermal conductivity at liquid-nitrogen temperature?
How do I convert W/m·K to Btu/hr·ft·°F?
Is 304 a good heat conductor?
Is 304L thermal conductivity different from 304?
Does cold work change 304 thermal conductivity?
Does polishing 304 improve heat transfer?
Why does wall thickness matter so much?
What value should I use in FEA?
Does ASTM A240 provide one guaranteed 304 conductivity value?
Sources and data basis
- NIST Cryogenic Material Properties: 304 Stainless (UNS S30400) — polynomial coefficients for thermal conductivity from cryogenic to room temperature and stated curve-fit error.
- NIST Reference Tables — room-temperature comparison values for 304 stainless, aluminum and copper.
- Cleveland-Cliffs 304/304L Stainless Steel Product Data — density, resistivity, thermal conductivity at 100°C and 500°C, expansion and other typical properties.
- Outokumpu Core 304/4301 and its Core range datasheet — typical room-temperature conductivity, density, heat capacity and expansion data.
- Outokumpu Steel Grades, Properties and Global Standards — comparative typical properties for stainless and non-alloy steels.
- NIST SP 811, Appendix B.8 — conversion factor between Btu/(h·ft·°F) and W/(m·K).
- NIST publication: Thermal Conductivity and Electrical Resistivity of AISI Type 304 Stainless Steel — primary historical measurement reference.
Published physical properties are typical reference values, not acceptance guarantees for every production heat. Exact results depend on chemistry, condition, temperature, test method and product form. Engineering interpolation and calculator outputs on this page are identified as planning estimates.
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