Cast iron guide rails are quenched and heat treated using a medium frequency induction heating machine. What should I do if distortion defects occur?

When cast iron guide rails are quenched and heat treated with a medium frequency induction heating machine, the guide rails may produce distortion defects due to various factors, thus affecting their service life. Therefore, it is very important to analyze the causes of defects and find solutions.

(1) Distortion rules of medium frequency induction quenching of workbench guide rails. Test and production results show that the distortion law of induction quenching of gray cast iron guide rail surface is that the heating surface is relatively concave, and the degree of distortion is related to the stiffness of the workbench. When the guide rail surface is quenched and heated using a medium-frequency diathermy furnace, the distortion stress caused by thermal expansion is released from the high-temperature plastic state, followed by cooling and quenching, and the guide rail structure undergoes martensitic phase transformation. Due to the different crystal structure, the volume increases by about 4%. , due to the restraint of the rigid matrix, which limits the elongation of the hardened layer, the excess elongation can only force the guide rail surface to be concave to achieve stress balance.

(2) Pre-bending process before guide rail quenching. Since the guide rail has a concave amount after quenching, after testing, a pre-bending process is performed before quenching. Through pre-bending, a compressive stress is artificially applied to the surface of the guide rail, so that the processed guide rail removes the pre-tension force and returns to its free state. A convex shape is formed, and the compressive stress becomes tensile stress. After quenching, the concave distortion of the guide rail causes the compressive stress and tensile stress on the surface of the guide rail to cancel each other out, and the guide rail tends to be straight. In this way, not only the grinding amount is uniform during finishing, but also the depth of the hardened layer is consistent, and the guide rail distortion is small, thus ensuring the accuracy of the workbench.

This article briefly introduces the causes and solutions of distortion defects in cast iron guide rails. I hope it will be helpful to your work.