How to prevent the fracture and failure of Cylinder Head Bolts?

1. Select high-quality materials
Choose high-strength, high-temperature resistant alloy steel as the material of the cylinder head bolt to ensure that it can still maintain sufficient strength and toughness under high temperature and high pressure environment. Improve the hardness and strength of the bolt through reasonable heat treatment processes (such as quenching and tempering), and enhance its fatigue resistance, creep resistance and oxidation resistance.

2. Optimize design and process
During the design stage, fully consider the stress conditions and working environment of the bolt, and adopt reasonable structure and size design to reduce stress concentration and fatigue damage. Ensure the processing accuracy and surface quality of the bolt, avoid defects such as thread damage and folding cracks, and improve the fatigue life of the bolt.
Surface treatment: Perform appropriate surface treatment on the bolt (such as galvanizing, phosphating, etc.) to improve its corrosion resistance, wear resistance and fatigue resistance.
3. Reasonable installation and tightening
During the installation process, tighten the bolts strictly according to the specified torque value to ensure that the preload force is moderate and evenly distributed. Avoid excessive preload force causing overload and fracture of the bolt, or insufficient preload force causing loosening and failure of the bolt.
Regularly inspect and maintain the cylinder head bolts, and promptly detect and deal with problems such as bolt loosening, wear, and corrosion. Bolts with safety hazards should be replaced in time to avoid fracture accidents.
4. Avoid external environmental influences
In high temperature environments, measures should be taken to reduce the temperature of the engine cylinder head, such as strengthening the heat dissipation effect of the cooling system and using heat-insulating materials to reduce the thermal stress on the bolts.
In humid and highly corrosive environments, the anti-corrosion treatment of the cylinder head bolts should be strengthened, such as applying anti-corrosion grease and installing waterproof covers to extend the service life of the bolts.
5. Improve the performance of stress concentration areas
Increase the fillet size in stress concentration areas such as the transition area between the bolt head and the rod, and the transition area between the thread and the bare rod to reduce the degree of stress concentration and improve the fatigue strength of the bolts.
Optimize the design of the bolt structure, such as using stud connections, to disperse stress and improve the reliability of the connection.
6. Pay attention to hydrogen embrittlement
During the production and use of bolts, pay attention to avoid hydrogen generated during heat treatment, electroplating, pickling and other processes from penetrating into the metal. For materials such as high-strength steel that are prone to hydrogen embrittlement, they should be selected with caution and appropriate anti-hydrogen embrittlement measures should be taken.