Materials and heat treatment, automotive high-strength bolts generally refer to products of grade 8.8 or above, which not only require high tensile strength and yield ratio, but also have high low-temperature impact performance. One of the difficulties in manufacturing is also high-strength bolts Conditioning treatment.
For the heat treatment quality of automotive high-strength bolts, the steel content should be controlled at the upper limit of carbon content, which can not only improve the strength and toughness of the steel, but also reduce the segregation tendency; the control of alloying elements at the upper limit can increase the hardenability of the steel and improve the toughness; Minimize the content of harmful residual elements to ensure the purity of steel.
During the quenching and tempering process, the changes in the internal organization and performance of the bolt cannot be monitored in real time, which is one of the difficulties in quality control.
The bolt head mark should be carefully checked before installing the furnace to ensure that the information of the bolts to be processed is accurate and not lost after heat treatment and identifiable, the quenching and heating process is strictly controlled, the carbon potential must be accurate, and the time for each batch of bolts to be quenched is recorded.