11 Energy-Saving Measures for Heat Treatment Processes

Heat treatment, an indispensable part of manufacturing, has always been a focus of attention due to its energy consumption. With the deepening of green manufacturing and sustainable development, minimizing energy consumption while ensuring product quality has become a research hotspot in the industry. The following 11 major energy-saving measures for heat treatment processes cover multiple aspects, including process optimization, equipment upgrades, and waste heat utilization, providing practical, feasible paths for energy conservation and emission reduction in the heat treatment industry.

I. High-Temperature Rapid Carburizing, Shortening Process Cycles
Traditional carburizing processes are usually carried out at around 930℃, while increasing the carburizing temperature to 1050℃ can significantly reduce the process cycle by 40%. For example, using a low-pressure carburizing process in a vacuum furnace at 1050℃ not only results in rapid carburizing but also low raw material gas consumption and low emissions. Acetylene low-pressure carburizing technology further achieves high-temperature carburizing, further shortening the process cycle and achieving energy-saving goals.

II. Low-Temperature Nitrogen-Carburizing, Replacing Traditional Nitrogenating
Traditional gas nitriding processes are high-temperature, long-time processes that typically require 30-70 hours. The carbonitriding process can reduce the processing temperature from 850-930℃ to 550-580℃ and shorten the processing time to 2-3 hours. This process not only significantly reduces energy consumption but also reduces workpiece deformation and improves production efficiency.

III. Carbonitriding Replaces Thin-Layer Carburizing, Reducing Temperature and Time

For workpieces with a carburizing layer depth of less than 1mm, carbonitriding can replace thin-layer carburizing, reducing the processing temperature from 930℃ to 850℃ and shortening the time by 30%. Due to the lower quenching temperature and shorter time, the deformation of the workpiece after quenching is also smaller, making it a highly efficient, energy-saving process choice.

IV. Zero-Holding Quenching, Eliminating Holding Time

In traditional heat treatment processes, holding time usually accounts for 1/2 or 1/3 of the total heating time. However, for thin parts such as carbon steel and low-alloy structural steel, a zero-holding quenching process can be used. That is, after heating the workpiece to the austenitizing temperature, it is quenched directly without holding. Practice has proven that this process eliminates the time required for workpiece heat treatment and austenite homogenization, reducing energy consumption by 20%-30% without affecting the workpiece’s final performance.

V. Induction Heating Replaces Overall Heating, Achieving Localized Energy Savings
Surface heating methods, such as induction and laser heating, can replace traditional overall heating methods. For example, replacing overall heating quenching with induction heating can save 33%-50% of energy, and replacing carburizing quenching can save up to 90%. This localized heating method heats only specific parts of the workpiece, resulting in significant energy savings, reduced workpiece deformation, and improved product quality.

VI. Sub-Cryogenic Quenching, Lowering Heating Temperature
Sub-critical quenching technology achieves a balance between energy consumption and material properties by lowering the austenitizing temperature. For example, reducing the mold heating temperature from 1050℃ to 950℃ can reduce energy consumption per unit product by approximately 15%, while material deformation can also be reduced by approximately 30%. This process achieves significant energy savings while ensuring material performance.

VII. Post-Forging Residual Heat Quenching: Energy Saving Through Waste Heat
Forgings retain a high temperature after forging. Utilizing this residual heat for quenching eliminates the need for reheating, significantly reducing energy consumption. For example, using residual heat to normalize or quench 20CrMnTi steel after forging not only shortens the time and increases productivity but also improves the steel‘s strength and toughness.

VIII. Integrated Quenching-Tempering Process: Reducing Heating Steps
Combining the quenching and tempering processes reduces the number of heating and cooling steps, significantly lowering energy consumption. For example, using an integrated quenching-tempering process for some shaft parts can reduce unit product energy consumption by approximately 10%. This streamlined process not only saves energy but also improves production efficiency.

IX. Recovering Quenching Tank Waste Heat for Preheating Air or Water

During quenching, the quenching medium absorbs a large amount of heat. This heat can be recovered through a heat exchanger and used to preheat combustion air or cleaning water. For example, recovering the heat from quenching oil to preheat combustion air to 200°C can reduce fuel consumption per unit product by approximately 15%.

X. Recovering Furnace Heat for Preheating Workpieces or Heating:

During operation, heat treatment furnaces emit a significant amount of heat. This heat can be recovered using heat pipes or heat pumps to preheat workpieces or heat the plant. For example, recovering the heat from an electric resistance furnace to preheat workpieces to 150°C can reduce electricity consumption per unit product by approximately 10%.

XI. Recovering Waste Heat from Flue Gas to Generate Steam or Preheat Combustion Air:

For combustion-type heat treatment furnaces, the flue gas contains a large amount of waste heat. Recovering this heat through waste heat boilers or air preheaters can generate steam or preheat combustion air. For example, utilizing waste heat boilers to recover flue gas heat from natural gas furnaces can produce steam worth up to 800,000 yuan annually, demonstrating significant economic benefits.

In summary, these 11 major energy-saving measures in heat treatment processes, from different perspectives, provide comprehensive solutions for energy conservation and emission reduction in the heat treatment industry. The implementation of these measures not only reduces production costs and enhances enterprises’ market competitiveness but also contributes to environmental protection, achieving a win-win situation for both economic and social benefits. With continuous technological advancements and innovation, it is believed that more efficient, energy-saving technologies will be applied in the heat treatment field in the future, driving the industry towards greener, more sustainable development.