Explain torque calculation, wrench calibration and on-site testing methods for high-strength bolts, analyze risks caused by torque deviation, and provide safety fastening and re-inspection standards.

Explain torque calculation, wrench calibration and on-site testing methods for high-strength bolts, analyze risks caused by torque deviation, and provide safety fastening and re-inspection standards.

Compare the performance differences between black oxide and galvanizing treatment for grade 8.8, 10.9 and 12.9 high-strength bolts, providing selection standards for different working conditions.