How to maintain preload and anti-loosening performance in high-temperature environments?
Publish Time: 2026-02-19
1. Challenges to Bolt Performance in High-Temperature EnvironmentsHigh-temperature resistant bolts face severe challenges in high-temperature applications. As temperature rises, the mechanical properties of metallic materials change significantly, primarily manifested in a decrease in yield strength and tensile strength. When the temperature exceeds the material's critical value, the bolt is prone to creep, i.e., continuous plastic deformation under constant stress. This creep leads to a gradual decrease in preload, potentially causing connection failure. Furthermore, high temperatures can cause differences in the coefficients of thermal expansion between the bolt and the connected components, generating additional thermal stress and further affecting connection reliability.2. Material Selection is Fundamental to Maintaining PreloadThe choice of material for high-temperature resistant bolts is crucial. Commonly used high-temperature resistant materials include austenitic stainless steel, nickel-based alloys, and titanium alloys. These materials possess excellent high-temperature strength and creep resistance, effectively resisting stress relaxation at high temperatures. The heat treatment process is equally important; processes such as solution treatment and aging treatment can optimize the material's microstructure and improve its stability at high temperatures. 3. Key Technologies for Preload ControlApplying the correct preload is crucial for ensuring the reliability of high-temperature connections. Insufficient preload can lead to loosening, while excessive preload may cause premature bolt failure. In high-temperature environments, it is generally recommended to use an initial preload slightly higher than that at room temperature to compensate for preload loss caused by high temperatures. Torque control, angle control, and hydraulic tensioning are commonly used preload control methods. Among them, hydraulic tensioning offers more precise preload control and is particularly suitable for critical high-temperature connections. During installation, a calibrated torque wrench should be used, and the tightening sequence and torque value should be strictly followed.4. Innovative Applications of Anti-Loosening Structure DesignAnti-loosening performance is another key indicator for high-temperature resistant bolts. Traditional anti-loosening methods, such as spring washers and lock nuts, are prone to failure at high temperatures. Modern anti-loosening technologies employ various innovative designs: wedge-shaped lock nuts utilize a wedge-shaped bevel to generate additional locking force; self-locking threads achieve anti-loosening through special angles designed in the thread profile; and metal deformation locking utilizes localized deformation of the nut to generate continuous clamping force. For extreme high-temperature environments, mechanical anti-loosening methods such as welding and cotter pin locking can be used to ensure absolute reliability of the connection.5. Surface Treatment and Coating ProtectionSurface treatment significantly improves the performance of high-temperature resistant bolts. High-temperature anti-oxidation coatings such as aluminide coatings and MCrAlY coatings effectively prevent oxidation and corrosion on the bolt surface, extending service life. Solid lubricating coatings such as molybdenum disulfide and graphite can reduce the thread friction coefficient, making preload control more precise and reducing the risk of seizing at high temperatures. Traditional surface treatments such as phosphating and galvanizing are prone to failure at high temperatures; appropriate surface treatment processes should be selected based on the actual operating temperature.Maintaining preload and anti-loosening performance of high-temperature resistant bolts in high-temperature environments is a systematic project that requires comprehensive consideration of multiple aspects, including material selection, design optimization, installation control, surface protection, and maintenance management. Only by fully mastering the technical points of high-temperature bolts can the safe and reliable connection of high-temperature equipment be ensured, providing a solid guarantee for industrial production.
