The Background: Accurate Atmosphere Control Is Critical in Gas Carburizing
Carburizing is a widely used thermochemical surface treatment method that adds carbon to the surface of low-carbon steels, enhancing hardness and wear resistance while preserving core toughness. Among different carburizing methods, including solid, liquid, and gas-based processes, gas carburizing has become the mainstream solution in modern heat treatment due to its advantages in atmosphere uniformity, better process control, and compatibility with complex part geometries.
- Carrier Gas (mainly CO, N2, H2, with small amounts of CO2, H2O, CH4) establishes the chemical environment necessary for carbon diffusion. Carbon monoxide (CO) serves as the main carbon carrier, dissociating at high temperatures to release atomic carbon onto the steel surface. Nitrogen (N2) plays a key role in diluting flammable gases and stabilizing the atmosphere.
- Enriching Gas, typically low concentrations of hydrocarbons such as methane (CH4) or propane (C3H8), is injected in precisely controlled quantities to increase carbon concentration and adjust the chemical balance as required during the process.
To control the depth and uniformity of carbon diffusion, modern gas carburizing operations rely on a key parameter known as carbon potential (CP), an index that reflects the carbon activity in the furnace atmosphere. Rather than being a static parameter, CP must be continuously adjusted throughout the process to match the desired case depth and avoid defects such as soot formation or over-carburization.
The Challenge: Complex Gas Reactions and Monitoring Limitations in Carburizing Furnaces
- 2CO C (on steel surface) +CO2
- CH4+H2O CO+3H2
- CH4 C (on steel surface) + 2H2
Changes in CO2, CH4, or CO concentrations can shift reaction equilibria, altering the carbon potential and leading to variations in case depth, surface quality, or soot formation.
Industrial systems usually utilize oxygen probes to monitor CP indirectly. These probes provide real-time measurements of oxygen partial pressure, which, when combined with assumed values for CO and other gases, allow the carbon potential to be estimated using a process factor or CO factor. However, such estimates are only accurate under stable equilibrium conditions that do not always reflect actual furnace dynamics. As a result, oxygen probe–based control systems may respond inaccurately, especially if unreacted CH4 accumulates or if CO concentrations fluctuate, increasing the risk of under- or over- carburization.
The Solution: Gasboard-9031EX for Real-Time Multi-Gas Monitoring in Carburizing Furnace
Acknowledging the industrial demands of real-time and accurate monitoring of reactive gas compositions within the furnace to achieve precise carbon potential control, Cubic Instruments, a leading manufacturer of gas sensors and gas analyzers, has specifically developed Gasboard-9031EX online gas monitoring system to meet the demands of high-precision gas monitoring and analysis applications.
Utilizing Cubic’s proprietary non-dispersive infrared (NDIR) gas sensing technology, Gasboard-9031EX delivers high-resolution measurements of CO, CO2, and CH4 concentrations simultaneously, assisting accurate carbon potential calculation and rapid adaptation to dynamic process changes, and avoid the delays and estimation errors in traditional indirect methods.
Designed for demanding heat treatment environments, Gasboard-9031EX integrates a robust stainless steel sampling probe with automatic heating and dual-stage filtration to ensure stable operation in variable furnace conditions. An intelligent purge function prevents probe blockage, ensuring measurement continuity. The PLC-controlled operation automates the entire cycle of gas sampling, backflushing, and drainage, enabling unattended monitoring.
In addition, Gasboard-9031EX supports seamless data integration with control systems via multiple interfaces. The connectivity enables real-time remote monitoring and closed-loop atmosphere regulation, enhancing both operational efficiency and process transparency.
With an explosion-proof rating of Ex d IIC T4 Gb and minimal maintenance requirements, Gasboard-9031EX meets both safety and performance standards for critical furnace applications.
Key Benefits for Carburizing Operations:
- Highly accurate and responsive control of CO, CO2, and CH4 to support stable carbon potential
- Enhanced process consistency, surface quality, and repeatability
- Reduced enrichment gas waste and energy consumption caused by estimation errors
- Lower maintenance burden and 24/7 autonomous operation
- Reliable deployment in hazardous industrial environments
Why Choose Cubic Instruments
With over two decades of experience in gas sensing technologies, Cubic Instruments has built a strong foundation in developing application-specific gas analysis solutions for industrial process control, including heat treatment furnace atmosphere control, metallurgical processes, CDQ systems, syngas production, hydrogen production, and petrochemical refining.
Gasboard-9031EX exemplifies Cubic’s commitment to innovation, precision, and reliability. By combining proven technology with deep application expertise and comprehensive support services, Cubic Instruments helps operators achieve quality objectives while reducing operational costs and process complexity.
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