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Large Aluminum Steel Rolls in the factory

Gas Density Sensor

For accurate, inexpensive, in-situ gas measurement in variety of metals heat treatment applications

Ask the Expert

Liang He - Metals Processing R&D Engineer
Liang He

Metals Processing R&D Engineer, North America

Why is control necessary for a protective atmosphere?

The simplest nonreactive atmosphere for thermal processing of a metal or material is a pure inert gas or vacuum, yet neither offers protection against trace impurities such as oxygen, water, and carbon dioxide, which are almost invariably present in the heat treating furnace atmosphere. 
The problem of trace impurities is exacerbated as the temperature increases. Depending on the process and material, even small variations in the temperature or impurity level can shift a reducing or neutral atmosphere to an oxidizing one, with a negative impact on the quality of the treated parts. 
To counteract the temperature effect, reactive species (H2 and CxHy) can be added to scavenge impurities and maintain the required potential for the material being processed. Control systems have gained increasing acceptance to regulate the amount of reactive species added. However, ensuring proper control is not simply a matter of installing elaborate equipment; it also requires accurate knowledge of which variables must be controlled and how close the control must be in any given case.


Hot Zone Nitrogen-Hydrogen Atmosphere Monitoring with Gas Density Sensor

In the sintering furnace, continuous measurement and control of furnace atmosphere is increasingly important to improve quality control, reduce costs, and comply with regulatory requirements. To continuously measure dew point and hydrogen concentration together gives the furnace operator the ability to know more accurately the furnace atmosphere composition and flow pattern. Air Products has developed a novel gas density sensor and successfully implemented it for hydrogen concentration measurement of hot zone nitrogen-hydrogen atmosphere.