Reason Analysis on Fracture of a High-Strength Bolt for Steel Grid Structure

A high-strength bolt for steel grid structure fractured early during use. Base on macroscopic inspection, chemical composition analysis, hardness testing, scanning electron microscope and spectrum analysis and so on, the fracture reasons of the bolt were analyzed. The results show that:the fracture of the bolt was mainly caused by the presence of metallurgical defects and inadequate heat treatment technology; under the action of the load, the stress concentration was produced in the center of the bolt with a large number of slag inclusions, then crack source appeared in the region of the stress concentration; meanwhile, the poor tempering heat treatment structure increased the brittleness of the bolt, and ultimately resulted in the rapid brittleness fracture of the bolt. Finally the corresponding preventive measures were put forward.