Heat treatment processes require a precisely controlled atmosphere for the process to be successful.
These metal processes are often used to manufacture critical parts in special alloys for industries such as aerospace, automotive, petrochemical ornuclear power. Poor control of the furnace atmosphere can affect alloy quality, with financial and safety consequences.
How to ensure efficient heat treatment in a controlled atmosphere?
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If the atmosphere in the heat treatment furnace is not controlled, the alloy may become contaminated. This can lead to loss of strength and ductility, as well as increased brittleness. The alloy's microstructure can also be affected, resulting in poor dimensional stability and reduced service life. In addition, uncontrolled atmospheres can cause corrosion and other forms of damage to the alloy.
In some cases, contamination can even cause the alloy to crack or break.
A controlled atmosphere is essential for efficient heat treatment. By preventing contamination, it ensures that the treated alloy retains its properties.
This is particularly important in theautomotive, chemical and nuclear energy industries, where the following conditions apply:
The absence of a controlled atmosphere can lead to chemical reactions on the surface of the metal assembly to be heat-treated, compromising its quality and performance and leading to rejected parts.
Such conditions result in financial losses, lost time and potentially dangerous repercussions for the customer who uses the part without detecting the weakness. In addition, a poorly controlled atmosphere can lead to a damaged furnace or, worse still, injured employees.
A controlled atmosphere heat treatment furnace provides an optimum environment for metal components during the heat treatment process.
By carefully controlling the composition and flow rate of the gas inside the furnace, precise temperature control is achieved. precise temperature control and minimal oxidation or decarburization.
The result is improved product quality and consistency, as well as increased production efficiency.
To ensure efficient heat treatment in a controlled atmosphere, it is important to carefully monitor and control the following parameters:
By carefully controlling these parameters, it is possible to achieve precise heat treatment in a controlled atmosphere, resulting inimproved productquality and consistency.
The inert gases most commonly used in heat treatment processes are argon (Ar), helium (He) and nitrogen (N₂).
The extent to which an atmosphere can be described as inert depends on factors such as the type of gas, its level of purity, the temperatures involved and the material being processed. Depending on the gas or gas mixture used, the process will be dedicated to different types of heat treatment: annealing, neutral quenching, tempering, nitriding, sintering or brazing.
Fuji Electric gasanalysers are used to control the atmosphere in all these processes, with fast and accurate measurement capabilities for ratios such as Ar/He, Ar/N₂, He/N₂, H₂/Ar or H₂/N₂.
The latter is required to control a hydrogen-rich atmosphere. This is implemented to reduce iron oxide to iron and decarburize steel. It also contributes effectively to heat transfer and can react with a presence of oxygen.
Fuji Electric's solution for controlling the H₂/N₂ is a compact industrial cabinet integrating:
Take the following example:
Since thermal conductivity varies from one component to another, any change in the concentration of the measured component results in a variation in the thermal conductivity of the sampled gas, which in turn affects the temperature of the platinum wire.
Theanalyser uses these temperature variations to determine the gas content.
The furnace gas is continuously extracted by a heated and filtered sampling probe. It is then routed via a heated sampling line to the wall-mounted compact cabinet.
This integrates the TCD thermal conductivityanalyser and the entire sampling system specially designed to ensure the safety of theanalyser and guarantee accurate, representative and reliable measurement of H₂ concentration.
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