Leaf springs are heat treated using a 60kw high-frequency induction heating power supply. How do we inspect their quality?

Automobile leaf springs are elastic elements whose function is to withstand the effects of the cabin and the load (static load). It can transmit vertical loads, mitigate and suppress the impact caused by uneven road surfaces, and limit the vibration of the body and wheels. In order to meet the needs of work, many manufacturers use 60kw high-frequency induction heating power supply to perform induction heat treatment on leaf springs. When performing specific process operations, a quality inspection process is usually performed to see whether the heat treatment results meet the requirements. Today, the editor will tell you about the specific content of this craft.

The stress conditions of leaf springs are relatively complex, usually with the combined effects of bending stress, compressive stress and shear stress. Therefore, the entire section must be quenched and tempered to obtain a tempered troostite structure, which has a high yield ratio and excellent The fatigue strength, etc., can meet the working requirements of the spring. Otherwise, if ferrite, pearlite or bainite structure appears after quenching, the mechanical properties of the spring after tempering will be seriously deteriorated. The microstructure after quenching and tempering treatment is generally divided into 8 grades according to the shape, quantity and distribution of tempered trotenite and ferrite after tempering. The following table is the grading standard of the metallographic structure of automobile leaf springs after heat treatment, 1- Level 4 is a qualified organization.

Tests show that if the quenched and tempered leaf spring contains bainite and ferrite, the tensile strength and impact toughness will be significantly reduced, especially the impact on the bending fatigue life will be more significant, see the table below.

As can be seen from the above table, strictly controlling the metallographic structure of leaf springs after heat treatment and selecting reasonable heat treatment heating and cooling process parameters are the prerequisites for ensuring the quality of leaf springs, and are also effective measures to increase their service life.