Knowledge of the thermal conductivity of various grades of stainless steel helps to determine the right material for the proper application. Thermal conductivity is the ability a material has to conduct heat and is usually given in watts per meter-kelvin (W/m·K). Stainless steels are classified into different types according to their microstructure; each has varied thermal properties.
Austenitic Stainless Steels
Common Grades: 304, 316
Thermal Conductivity: Approximately 16.2 W/m·K at 20°C
Characteristics: These steels have lower thermal conductivity compared to other types of stainless steel, mainly due to the higher content of nickel. They are well known for high corrosion resistance and are largely applied in processes where both corrosion resistance and formability are necessary.
Ferritic Stainless Steels
Common Grades: 430, 409
Thermal Conductivity: About 23.9 – 25.0 W/m·K
Characteristics: Ferritic steels have higher thermal conductivity compared to austenitic grades. They have applications in automotive exhaust and appliances due to their good thermal conductivity and moderate corrosion resistance. They are magnetic.
Martensitic Stainless Steels
Common Grades: 410, 420
Thermal Conductivity: About 24.9 W/m·K
Characteristics: The martensitic steels exhibit high values of strength and hardness. It possesses good thermal conductivity, which is comparable to the ferritic steels. All these features combine to form the principal applications for cutlery, surgical instruments, and turbine blades.
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Common Grades: 2205, 2507
Thermal Conductivity: Approximately 19.0 W/m·K
Characteristics: Duplex steels are a combination of some of the characteristics of austenitic and ferritic stainless steels. They have moderate thermal conductivity, high strength, and excellent resistance to stress corrosion cracking. They find wide applications in chemical processing, oil, and gas industries, and in marine environments.
Comparison with Other Metals: Note that stainless steels generally have lower thermal conductivity than other metals, for example, aluminum or copper. For example, the value for aluminum is around 205 W/m·K, and for copper, it is around 385 W/m·K; hence, these materials would be more applicable in situations where good heat dissipation is needed.
Practical Implications: Most commonly used stainless steels have lower thermal conductivity than many metals, including aluminum or copper, and thus are less effective at conducting heat. This, however, becomes an advantage when retention of heat is important, as in the case of cookware or a thermal barrier in insulation. In applications where heat must be given off quickly, then materials with higher thermal conductivity would be more suitable.
Knowledge of the thermal conductivity of various grades of stainless steel helps make appropriate decisions about material selection, ensuring optimum performance in a very wide range of applications.
