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Born in the year of Mu Chun, he graduated from Xi'an Wei's Metal Thermal Processing Technology program in 1983. Since then, he has been directly involved in professional technical work. Currently, he serves as the director and engineer at the Heat Treatment Branch of Hefei Bearing General Factory. He has also authored several technical reports.
The production line equipment includes a nitrogen-based atmosphere casting chain furnace system. The original conveyor belt drive shaft and passive shaft used a flash chain transmission mechanism. However, this design led to issues such as misalignment during operation, making maintenance difficult and increasing the risk of damage to the mesh belt. To address this, we replaced the passive wheel sprocket with a light wheel, which improved the overall performance. Additionally, the motor was modified to reduce noise and prevent overheating. These changes significantly enhanced the efficiency of the 6-connected shaft transmission system, leading to better performance of the fan, compressor, air storage tank, filter, cold dryer, carbon molecular sieve, crude nitrogen storage tank, and methanol cracking equipment.
The original feeding mechanism had issues with gas removal, causing problems in the process. We addressed this by improving the system, ensuring more efficient gas handling. The lifting hopper chain had low strength and was prone to stretching, so we replaced the low-carbon steel chains with spring steel, effectively preventing chain jamming.
In the nitrogen generator, the original AC solenoid valve (model 4, 18, 220V) was prone to failure, affecting the nitrogen purity. We upgraded it to a DC solenoid valve (model 24V) and added a transformer, eliminating the previous point of failure.
To improve the quality of the nitrogen, activated carbon was added to the filter, allowing for better removal of hydrophobic water from compressed air and preventing molecular sieve poisoning. This enhancement overcame the limitation of the original filter, which only removed suspended particles.
Nitrogen purity and analysis are crucial for heat treatment processes. Testing results showed that the nitrogen purity reached 99.995%. When the dew point is high, the workpiece surface appears blue; when the dew point is at -40°C, the surface turns silvery white. Adjusting the dew point is key to controlling the color of the ferrule.
There are two ways to lower the dew point: reducing the moisture content in the gas and minimizing residual oxygen after the deoxygenation process. Methanol is used to catalytically crack at low temperatures, producing hydrogen that reacts with crude nitrogen to form water and remove oxygen. The quality of the gas supplied to the molecular sieve is mainly determined by moisture content, which affects both adsorption capacity and crude nitrogen quality. High humidity can cause the molecular sieve to become saturated prematurely, leading to a higher dew point. Therefore, minimizing moisture in the gas supply is essential.
Under normal conditions, the optimal pressure for the molecular sieve is between 0.6 and 0.8 MPa. Ensuring proper pressure in the furnace is critical for maintaining stable gas flow. Excessive pressure increases hydrogen consumption and reduces the effectiveness of the molecular sieve. Adjusting the pressure of the nitrogen tank helps manage the dew point and gas quality.
According to industry statistics, there are approximately 130 million low-noise deep groove ball bearings in China. However, domestic high-grade bearings still struggle to meet market demands due to limitations in technology and manufacturing. Compared to foreign standards, Chinese bearings often have issues with vibration and noise levels, affecting their performance and lifespan.
To address these challenges, some manufacturers have focused on improving design, tooling, cleanliness, ball processing, grease, and cage technology. These efforts have yielded positive results. Controlling bearing noise has become a key issue for the industry, as it directly impacts product competitiveness.
Luo Yang Bearing Research Institute and Luoyang Bearing Factory formed a joint team to study noise reduction in 60822 bearings. Their goal was to enhance vibration and noise control, ultimately improving product quality and user experience.
The hydrogen peroxide content is an important factor in achieving a silvery-white finish. Production practice shows that controlling hydrogen content around 13% is ideal under consistent methanol cracking conditions.
The amount of hydrogen per pass is determined by the quality of crude nitrogen and the oxygen removal rate. If the crude nitrogen has low oxygen content, less hydrogen is needed. Conversely, if the crude nitrogen quality is high, more hydrogen may be required to maintain the desired performance.
Controlling the molecular sieve’s pressure and crude nitrogen production helps regulate the dew point and hydrogen content. With a nitrogen purity of 99.995% and hydrogen content of 13%, the dew point should be maintained at -60°C to ensure high-quality products with a silvery-white surface. During periods of high humidity, adjusting the gas production pressure and increasing the supply pressure can help lower the dew point while meeting production needs.
Production data confirms that the equipment can achieve a gas volume of 25 m³/h, satisfying all requirements. Process parameters were continuously revised and tested, resulting in improved performance. For example, with an outer diameter of 150 mm, selecting the appropriate process has proven to be ideal.
The furnace gas supply volume is 172,131 m³, accounting for 2% of the total gas volume. The furnace mouth gas supply volume is 81 m³, representing 0.25% of the total. When heating 406, the tempering time is 3 hours, and the hardness of the parts ranges from 61 to 62, with the largest difference observed.
This report summarizes the process parameters, production practices, and improvements made. It highlights the importance of continuous testing and optimization to achieve the best results.