The shaft components of machine tools, particularly the main spindle, are typically equipped with thrust ball bearings and operate at high speeds, often generating significant heat. If this heat is not properly managed, it can lead to overheating of the angular contact ball bearings, causing a rise in temperature within the corresponding parts of the machine tool. This thermal expansion may result in deformation, affecting the precision and machining accuracy of the machine. In severe cases, it can even cause misalignment between the spindle and tailstock, potentially leading to bearing damage or failure.
The rated fatigue life of a bearing refers to the number of revolutions that 90% of a group of identical bearings can endure under the same operating conditions before experiencing rolling fatigue failure. When the rotational speed is constant, this life is often expressed in terms of operational time.
When analyzing the life of a thrust ball bearing, it's important to consider more than just fatigue life. Factors such as lubrication performance, noise levels, wear, and other operational constraints must also be taken into account. For example, the grease life of a lubricated bearing depends on the type of lubricant used and environmental conditions. Since these factors vary across different applications, the acceptable limits for each bearing may differ, making it essential to establish realistic usage thresholds beforehand.
Therefore, simply examining the damage to an angular contact ball bearing may not reveal the true cause of the failure. However, by understanding the operating conditions, the surrounding structure, and the events leading up to the incident, combined with a detailed analysis of the bearing’s condition, it becomes possible to identify the root cause and prevent similar issues from recurring.
The decision to replace a bearing is based on several factors, including the extent of damage, mechanical integrity, importance of the component, operating environment, and the next scheduled maintenance. If any of the inner ring, outer ring, rolling elements, or cage show cracks, gaps, or structural damage, the bearing should no longer be used and must be replaced immediately.
Wear failure is one of the most common types of bearing failure. It can generally be categorized into two main types: abrasive wear and adhesive wear, depending on the nature of the contact and the materials involved.
1. **Oil Film Resistance Diagnosis Technology**: This method uses consistent evaluation criteria across different working conditions but is less effective for detecting surface peeling, indentation, or cracks. It is suitable for machines where the rotating shaft is accessible.
2. **Vibration Diagnosis Technology**: Widely used and capable of online monitoring, this technique offers fast and reliable results due to its mature theoretical foundation. It is especially effective for fault detection in angular contact ball bearings in rotating machinery.
3. **Iron Spectrum Diagnosis Technology**: This non-invasive method allows early detection of fatigue failures and provides insights into wear mechanisms. It is ideal for oil-lubricated bearings but less effective for those using grease.
4. **Temperature Diagnosis Technology**: Simple and effective for identifying overheating, this method is commonly used for routine inspections of bearings in various machines.
5. **Optical Fiber Monitoring and Diagnosis Technology**: Offers high sensitivity and accurate signal extraction from the bearing surface, allowing direct monitoring of quality, wear, load, and lubrication conditions. It is best suited for machines where sensors can be mounted in the housing.
6. **Acoustic Emission Diagnostic Technology**: Enables quick and easy fault detection, and supports online monitoring. Though a newer technology, it is still being widely adopted in the field.
When handling oil-free bearings, always ensure your hands are clean and dry before touching them. Apply high-quality mineral oil to protect against corrosion. During rainy seasons or humid weather, extra care should be taken to prevent rust. Under ideal operating conditions—such as when the rolling surfaces are well-separated by a lubricating film and contamination is minimized—angular contact ball bearings can last longer than standard calculations suggest. However, they should never be subjected to direct impacts, hammering, or pressure through the rolling elements, as this can cause irreversible damage.
As the angular contact ball bearing rotates, the raceway surfaces of the inner and outer rings come into contact with the rolling elements. The running track should appear smooth and even. Any irregularities or signs of abnormal wear should be carefully noted during inspection.
In certain metallurgical processes, precise control over chemical composition is critical. For example, when adding aluminum-manganese titanium warming agents to scrap steel, the endpoint carbon content must be carefully adjusted. The tapping temperature is set at 1700°C with a carbon content of 0.34% and phosphorus content below 0.007%. During the tapping process, high-chromium alloys, Si-Mn alloys, and carbon powder are introduced to adjust the composition, while slag blocking operations help remove impurities. Bottom argon stirring is used to reduce oxygen content in the molten steel. In the LF refining stage, a low-alkalinity CaO-Al₂O₃ slag system is employed to achieve a desulfurization rate of 50%-70%, reducing Al-type inclusions. By controlling the interface tension between inclusions and deoxidation products, low-melting compounds can form, effectively removing Al₂O₃ inclusions and Class D inclusions containing CaO. After composition and temperature adjustments, weak argon stirring is applied to ensure homogeneity. When the temperature exceeds the casting temperature by 20–30°C, further inclusion flotation occurs, ensuring a cleaner final product.
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