Choosing the appropriate bolt strength grade is crucial for ensuring connection safety and preventing loosening or breakage. Appropriate selection based on application requirements can effectively avoid connection failures caused by overload, fatigue, corrosion, and other factors.
Determine the Load Type and Match the Strength Grade Different working loads determine the stress forms that the bolts must withstand, directly affecting the selection of the strength grade:
Static Load Scenarios (e.g., ordinary brackets, equipment housings)
Stable loads, no vibration or impact.
4.8 or 5.8 grade carbon steel bolts can be used, offering low cost and meeting basic strength requirements.
Dynamic Load/Impact Load Scenarios (e.g., engine brackets, construction machinery)
Repeated stress and vibration exist, easily leading to fatigue fracture.
10.9 or 12.9 grade high-strength alloy steel bolts should be selected, combined with thread rolling technology to improve fatigue resistance.
Alternating Stress Environments (e.g., bridges, wind turbine towers)
Long-term cyclic tension and compression result in high fatigue risk.
We recommend using bolts of grade 8.8 or higher, and give priority to the RAHT process (heat treatment followed by thread rolling) to improve fatigue life.
