How should we deal with the fracture failure defects caused by quenching the drive axle half shaft using a medium frequency induction heating machine?

The half shaft is an important part of the wheel loader drive axle, and its material is 35CrMO steel. The half shaft has to withstand huge friction during work. Therefore, we often use a medium frequency induction heating machine to quench the half shaft to improve its hardness, wear resistance and service life. The technical requirements for the drive shaft stipulate that the depth of the medium-frequency induction heating quenching hardened layer on the 145mm diameter platform is 3-7mm. During production, it was found that several drive axle half-shafts broke and failed at the 120mm diameter bearing stop, causing certain economic losses. Today, let’s take a look at the half-shaft breakage defect and how we should deal with it.

In order to prevent the half shaft from breaking and failing after quenching, the medium-frequency induction heating and cooling should cover the entire area from the 120mm diameter bearing stop to the 140mm diameter platform, and the quenching hardened layer should be continuously transitioned. To this end, the following process improvement measures have been taken:

(1) Improve the sensor design to make it meet the requirements.

(2) Tempering should be carried out immediately after quenching heat treatment using medium frequency induction heating equipment to eliminate internal stress after quenching. The tempering temperature is ≤250℃ to prevent the first type of temper brittleness.

(3) Reduce the power of the medium frequency induction heating machine to prevent overheating of the 120mm part when heating is extended.

(4) Use special-shaped inductor magnets to heat the workpiece once, and adjust the number and arrangement of the magnets so that the flange fillets, rods and platform parts are heated at the same time, with a moderate heating speed to prevent local overheating defects.

As an important part of the automobile, the quality of heat treatment of half shafts is crucial. However, during the production process, affected by the workpiece's own factors, environmental factors and heat treatment processes, the half shaft may produce some quenching defects. Therefore, it is very important to master its preventive measures. After adopting the above-mentioned process improvement measures in production, the quality of the half-shaft after medium-frequency induction heating quenching was excellent and fully met the technical requirements. No quality defects such as quenching cracks were found. The production quality of the workpiece was stable, and good technical and economic benefits were achieved.