On a regular basis we have articles provided by furnace builder Aichelin about “CO2 Emissions & The Heat Treatment Industry”. In this 5^th article Aichelin speaks about the relative difference of CO2 emissions in Induction hardening as opposed to conventional heat treating in a large gear component.

The pursuit of enhanced durability and extended lifespan for technical components has led to an increased focus on the heat treatment of ferrous metals. However, the significant energy consumption associated with this process necessitates further optimization measures. The industry is facing mounting pressure to reduce CO2 emissions resulting from heat treatment processes. It is anticipated that legislators will impose stricter restrictions on maximum allowable emission levels in the future, potentially enforcing penalties and compensation payments to address this issue.

Modern heat treatment is essential to meet requirements for wear resistance, dimensional accuracy, and durability. In the case of steel, classical quenching and tempering, as well as thermochemical heat treatment processes like case hardening, are commonly used and should be referenced.

The introduction of thermal energy into the workpiece can be accomplished using various methods, differing in type of heat transfer and mechanism. Conventional heat treatment in a furnace relies on conduction, radiation, and convection. The necessary energy is typically supplied through the thermal conversion of fossil fuels, such as natural gas, or electric radiant heaters. Alternatively, electrical energy can be used for inductive heating of components.

Another distinction between these processes is the heat input into the components. In a furnace, components are exposed to a hot atmosphere, facilitating heat transfer into the material to achieve the desired temperature. By selecting the gas composition within the furnace atmosphere, the surface layer of the component can be influenced. Gas carburizing, for example, aims to increase the carbon concentration of the surface layer. This is typically achieved using endothermic gas or nitrogen/methanol gas mixtures as additional carbon sources. Differentiating between energy-related and process-related emissions is crucial in this context.

Inductive heat treatment operates by inducing a high-frequency alternating current in the boundary layer of the component through an inductor. This generates an alternating electromagnetic field in the immediate vicinity of the inductor. When an electrically conductive component is placed within this electromagnetic field, a directional voltage is induced, resulting in heat flow near the surface of the component. The heat is produced by the material’s resistance. Induction heat treatment does not include thermochemical heat treatment processes.

Inductive heat treatment offers significant advantages for surface hardening or partial hardening zones. In terms of CO2 emissions, the mass of heated steel is a crucial factor. With induction heating, the energy required for heating can be minimized, focusing only on austenitizing the hardened zones. Additionally, induction technology enables automated serial processing, which is particularly appealing to the automotive industry.

The choice of the heat treatment process should consider the specific requirements of the application, associated costs, and environmental considerations. Achieving a balance between production costs and CO2 emissions is crucial for sustainable and efficient heat treatment practices. Considering CO2 emissions per kilogram of component, gas-based furnace heating tends to have higher emissions due to fossil fuel usage. Inductive heat treatment offers the advantage of potentially lower emissions as it does not rely on fossil fuel combustion.

In recent months, due to rising energy costs and, in some cases, a lack of security of supply, the industrial heat treatment sector – particularly in Europe – has seen a trend towards electrically heated systems.

However, the reasons for this trend are complex and depend on numerous parameters. Plant operators are actively working on converting their existing conventionally fired kilns to electric operation. It is important to note that the composition of electricity and associated CO2 emissions from electricity production vary between European countries. When comparing the anticipated CO2 emissions resulting from natural gas combustion to those from using electricity as an energy source, higher regional CO2 emissions may occur. Therefore, it is essential to consider the availability and utilization of energy sources that are as carbon-neutral as possible.

The Aichelin Group is a leading supplier of thermal and thermochemical process equipment. With more than 150 years of know-how, we are able to advise you on large-scale process applications and to offer you and your company a tailor-made product solution – both in the field of induction heat treatment and with regard to classic thermal process plants.

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