Ensure efficient heat treatment in a controlled atmosphere

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 or nuclear power. Poor control of the furnace atmosphere can affect the quality of the alloys and have financial and safety consequences.

How to ensure efficient heat treatment in a controlled atmosphere?

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 the automotive, chemical and nuclear energy industries, where the following conditions apply:

• high temperatures
• aggressive chemicals
• extreme pressures

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.

• Furnace atmosphere: The atmosphere in the kiln must be constantly monitored and controlled to maintain the desired gas composition.
• Temperature : The temperature inside the kiln must be closely monitored and controlled to ensure consistent product quality.
• Humidity : The humidity inside the furnace should be carefully monitored and controlled to avoid oxidation or decarburisation of the metal components.
• Pressure: The pressure inside the furnace should be carefully monitored and controlled to avoid excessive gas flow into the furnace.

By carefully controlling these parameters, it is possible to achieve precise heat treatment in a controlled atmosphere, resulting in improved product quality and consistency.

Gas analysers: reliable process control for furnaces, metallurgy, semiconductor industry and gas seals

Fuji Electric gas analysers are used to control the atmosphere in all these processes, with capabilities to measure fast and precisely 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 effectively aids in heat transfer and can react with any oxygen present.

The Fuji Electric solution for controlling the H₂/N₂ is a compact industrial cabinet incorporating:

• the thermal conductivity detection analyser (TCD) called ZAF,
• and a gas sampling system specifically adapted and designed for the furnace's operating conditions.

Consider the following example:

• Temperature > 1000 °C
• H₂ > 50 %
• High levels of humidity during low hydrogen phases
• A significant amount of solid particles

Because the thermal conductivity is different among gas components, when there is a change in the concentration of the component under measurement, the thermal conductivity of the sample gas will change to affect the temperature of the platinum wire.
The analyser uses the temperature change to determine the gas concentration.

Heat Treatment Furnace control gas analyser system design

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 theTCD thermal conductivity analyser and the entire sampling system specially designed to ensure analyser safety and guarantee accurate, representative and reliable measurement of H₂ concentration.

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