Thermal conductivity of metals - Understanding heat transfer in materials

Metals are not only valued for their strength and reliability; they are also excellent at conducting heat. Heat moves quickly through metal, which is why it is an ideal material for saucepans, radiators, and large-scale industrial machinery. Metal’s capacity to conduct heat is a major factor  in why they are so widely used across different industries. Understanding how different metals handle heat transfer can guide you towards the best material choice for any project.

This guide explains how heat moves through different metals, what affects their conductivity, and how this property is applied in engineering and industry. We will focus on the most popular and affordable metals; steel, aluminium, brass, and copper to help guide you in choosing the right one for your project.

Introduction to thermal conductivity in metals

Thermal conductivity measures how efficiently heat travels through a material when a temperature difference exists. In metals, this process is especially effective because of their structure: positively charged ions in a 'sea' of free-moving electrons.

So, why are metals good conductors of heat? The answer lies in these free electrons. As heat is applied to one part of the metal, electrons quickly transfer energy to cooler areas, making metals excellent at spreading heat evenly. This explains why metals are so widely used in the manufacture of cooking utensils, cooling systems,  and heat exchangers.

Factors affecting thermal conductivity in metals

While most metals conduct heat effectively, their performance varies based on several key factors:

• Atomic Structure: Materials with fewer atomic collisions during heat transfer typically conduct heat better. Copper and silver rate highly as they have tightly packed atoms and highly mobile electrons.

• Purity: Impurities create ‘roadblocks’ for electron flow which reduces overall conductivity. Pure metals consistently outperform alloys in thermal transfer efficiency.

• Temperature: A rise in temperature increases atomic vibrations, which can interfere with efficient heat transfer in certain metals.

• Alloying: Adding elements to base metals ( stainless steel or brass for example) changes electron behaviour, often reducing thermal conductivity.

• Crystalline Structure and Grain Boundaries: Metals with fewer grain boundaries allow smoother electron and phonon (heat carrying vibrations) movement, boosting conductivity.

Understanding these factors enables engineers to select the appropriate metal for the job, whether it is dissipating heat from electronic components or withstanding high temperatures within industrial furnaces.

Comparing thermal conductivity of common metals

Not all metals conduct heat in the same way; some transfer it quickly, while others are much slower. The table below highlights commonly used metals and their typical thermal conductivity values, measured in Watts per metre-Kelvin (W/m·K):

Metal’s Approx. Thermal Conductivity (W/m·K)

• Silver 429

• Copper 401

• Aluminium 237

• Brass 109

• Mild steel 50

• Stainless steel 16

• Gold 318

• Iron 80

Silver is the champion for conducting heat, though many manufacturers rarely use it due to the expense. Copper is a more practical choice, which is why it is commonly used in many industries. Aluminium deserves a mention too, especially where weight is a consideration. You'll commonly find it in laptop cooling systems, car radiators, and LED fixtures because it moves heat effectively without adding bulk.

You can learn more about these materials and their uses on our website:

• Aluminium

• Mild steel

• Stainless steel

• Brass

• Copper

Aluminium and its thermal properties

With a thermal conductivity of around 237 W/m·K, aluminium offers impressive heat transfer while keeping weight to a minimum. As it is resistant to corrosion and relatively inexpensive, it has become the go-to material for products such as automotive parts, HVAC systems, and electronic housings.

When considering the conductivity of aluminium, it offers an excellent balance of strength, weight, and thermal performance; ideal for both structural and heat-sensitive applications.

Thermal conductivity of steel and stainless steel

Mild steel possesses   thermal conductivity classed as ‘moderate’, approximately 50 W/m·K. While not the strongest conductor, it delivers reliable strength and affordability for structural applications.

The thermal conductivity of stainless steel is typically around 16 W/m·K. The presence of alloying elements like chromium and nickel makes it highly corrosion-resistant, but this also reduces its ability to conduct heat effectively.

Despite this, stainless steel remains essential in environments where hygiene and durability are more important than heat transfer, such as in commercial kitchens and medical equipment.

High thermal conductivity materials in metal engineering

Silver, copper, and aluminium have  the highest thermal conductivity. . These materials are widely used in heat exchangers, thermal management systems, and precision engineering applications.

• Copper is widely used in the manufacture of electronic, HVAC systems and motors,  due to its excellent thermal and electrical conductivity.

• Silver, although expensive, is used in specialised high-efficiency electronics and aerospace technologies.

• Aluminium is ideal for lightweight cooling applications in laptops, vehicles, and LED lighting.

When selecting high thermal conductivity materials, engineers weigh factors such as weight, corrosion resistance, and cost to find the best fit.

Applications of thermal conductivity in metal industries

Understanding the thermal conductivity of metals is key in various sectors:

• Construction: Thermal properties influence insulation design, roofing systems, and cladding applications.

• Automotive and Aerospace: Lightweight metals like aluminium help manage engine heat while reducing overall vehicle weight.

• Electronics: Copper and gold excel at conducting both heat and electricity efficiently in circuit boards and connectors.

• Food processing and catering: Stainless steel is preferred for its durability and hygiene, even if it sacrifices some conductivity.

The conductivity of gold, although not the highest, is still impressive, and when combined with its corrosion resistance, it is used in high-end electronics and precision components.