Carburizing process improves the performance of electric variable speed drive axles

Carburizing process improves the performance of electric variable speed drive axles

Introduction
With the continuous development of the electric vehicle market, the performance of electric variable speed drive axles as one of its core components directly affects important indicators such as the vehicle’s cruising range, power output and service life. As a common heat treatment process, carburizing process has been increasingly widely used in the field of electric variable speed drive axle manufacturing in recent years. This article will explore in depth the many aspects of carburizing process to improve the performance of electric variable speed drive axles.

1. Introduction to carburizing process
Definition: Carburizing is a chemical heat treatment process that infiltrates carbon atoms into the surface of steel parts. By infiltrating active carbon atoms into the surface of the workpiece at high temperature, followed by quenching and low-temperature tempering, the chemical composition and organizational structure of the workpiece surface are changed to improve its mechanical properties such as hardness, wear resistance and fatigue strength, while the core still maintains its original toughness.
Process method: Common carburizing processes include solid carburizing, gas carburizing and liquid carburizing. Among them, gas carburizing is widely used in the production of electric variable speed drive axle parts due to its advantages such as fast carburizing speed, uniform carburizing quality and easy control.

2. Key components and performance requirements of electric variable speed drive axles
Key components: Electric variable speed drive axles are mainly composed of motors, transmissions, differentials and axle housings. Among them, gears in transmissions and differentials and drive shafts are more urgently in need of carburizing technology.
Performance requirements: These key components are subjected to high contact stress, bending stress and impact load during operation, so they need to have high hardness and wear resistance to resist surface wear and fatigue pitting. At the same time, they also need to have sufficient strength and toughness to withstand impact loads to prevent premature failure of parts.

3. Specific performance of carburizing technology on improving the performance of electric variable speed drive axles
(I) Improving hardness and wear resistance
Principle: After carburizing, a high-carbon carburized layer is formed on the surface of the key parts of the electric variable speed drive axle. After quenching and low-temperature tempering, the surface hardness can be significantly improved, generally reaching HRC58-64, and the wear resistance is also greatly improved, thereby effectively reducing the wear of parts during operation and extending the service life.
Case: After a certain electric vehicle manufacturer adopted carburizing technology on the gear parts of its electric variable speed drive axle, the wear of the gears was reduced by about 60% compared with that before carburizing, and the service life was extended by more than double.
(II) Enhanced fatigue resistance
Principle: The carburized layer has a certain residual compressive stress, which can balance the tensile stress generated by the parts during operation, thereby reducing the generation and expansion of surface microcracks and improving the contact fatigue strength and bending fatigue strength of the parts. At the same time, the fine structure of the transition layer between the carburized layer and the base metal further improves the fatigue resistance of the parts.
Data support: Studies have shown that the contact fatigue strength of the electric variable speed drive axle gears treated by carburizing can be increased by 30%-50% and the bending fatigue strength can be increased by 20%-30% under the same working conditions.
(III) Optimize the comprehensive mechanical properties of parts
Principle: The carburizing process can improve the surface hardness and wear resistance of the parts while ensuring that the core of the parts has good toughness and strength, so that the parts can better resist deformation and fracture when subjected to impact loads. In addition, by reasonably controlling the carburizing process parameters, the depth and organizational structure of the carburized layer can be optimized to achieve the best match between the surface and core performance of the parts.
Actual effect: For the transmission shaft parts in the electric variable speed drive axle, the surface hardness and wear resistance are high after carburizing, and they can withstand the friction and wear generated during frequent starting and stopping and acceleration; while the core has good toughness and is not easy to break when subjected to impact loads, ensuring the safety and reliability of the car’s driving.
(IV) Improving the meshing performance of parts
Principle: In the electric variable speed drive axle, the meshing performance of the gear directly affects the efficiency and stability of power transmission. The carburizing process can improve the hardness and precision of the gear tooth surface, reduce the deformation and wear of the tooth surface, thereby improving the meshing performance of the gear, reducing noise and vibration, and improving the efficiency and stability of power transmission.
Experimental comparison: A research institute conducted a meshing performance test on the gears before and after carburizing. The results showed that the noise of the gears after carburizing was reduced by about 5dB during the meshing process, the vibration amplitude was reduced by about 30%, and the power transmission efficiency was increased by about 8%.

4. Factors and control affecting the effect of carburizing process
Carburizing temperature and time: Carburizing temperature is generally between 900℃-930℃. Too high temperature will lead to coarse grains and increased brittleness of carburized layer. Too low temperature will reduce carburizing speed and affect production efficiency. Carburizing time needs to be reasonably controlled according to the size and performance requirements of the parts to ensure sufficient carburized layer depth.
Carbon potential control: Carbon potential is one of the important process parameters in the carburizing process, which determines the carbon content and organizational structure of the carburized layer. Too high carbon potential will lead to too high carbon content in the carburized layer, which is prone to problems such as network carbides and grain boundary oxidation. Too low carbon potential will lead to insufficient carbon content in the carburized layer, and the hardness and wear resistance will be reduced.
Quenching and tempering process: The quenching and tempering process after carburizing has a vital influence on the final performance of the parts. The selection of quenching temperature and medium needs to be optimized according to the material and performance requirements of the parts to obtain a good match between hardness and toughness. Control of tempering temperature and time can further eliminate quenching stress and stabilize the organization and performance.
Raw material quality: The chemical composition, purity and organizational structure of the raw materials have an important influence on the carburizing process effect and the final performance of the parts. It is necessary to select high-quality carburizing steel and strictly control the quality of raw materials to ensure the smooth progress of the carburizing process and the stable and reliable performance of the parts.
Pretreatment of parts: Before carburizing, the parts need to be pretreated, such as machining, forging, normalizing, etc., to eliminate the stress inside the parts, improve the organizational structure and surface quality, and create good conditions for the carburizing process.

5. Application status and development trend of carburizing process in the manufacture of electric variable speed drive axles
Application status: At present, carburizing process has become one of the key technologies in the manufacture of electric variable speed drive axles, and is widely used in the production of key parts such as gears and drive shafts. Many automobile manufacturers and parts suppliers are constantly increasing the research and development and application of carburizing technology to improve the quality and performance of products and meet market demand.
Development trend: With the continuous development of electric vehicle technology and the intensification of market competition, the performance requirements for electric variable speed drive axles will become higher and higher. The carburizing process will also continue to develop in the direction of intelligence, environmental protection and high efficiency. For example, the use of advanced carburizing equipment and control systems can achieve precise control and automated production of the carburizing process; research and development of new carburizing materials and process methods can improve carburizing efficiency and quality, reduce production costs and environmental pollution, etc.

6. Conclusion

As an effective surface strengthening technology, the carburizing process is of great significance in the manufacture of electric variable speed drive axles. It can significantly improve the hardness, wear resistance, fatigue resistance and comprehensive mechanical properties of key parts, improve the meshing performance of parts, thereby extending the service life of parts and improving the performance and reliability of the entire electric variable speed drive axle. However, in practical applications, it is necessary to strictly control the carburizing process parameters, optimize the process flow, and comprehensively consider factors such as raw material quality and pretreatment to give full play to the advantages of the carburizing process and meet the needs of the continuous development of electric vehicles. In the future, with the continuous innovation and progress of technology, the carburizing process will surely play a more important role in the field of electric variable speed drive axles and provide strong support for the development of the electric vehicle industry.