When the workpiece is induction hardened using an ultrasonic induction heating power supply, how to select its hardness?

Workpieces such as crankshafts are subject to huge friction during work, and therefore require high hardness, wear resistance and service life. For this reason, we often use ultrasonic induction heating power to quench the crankshaft. However, during the quenching process, how hard must the workpiece be to meet the work requirements? Today, the editor will tell you how to choose the hardness of parts during induction hardening?

The hardness of induction hardening is essentially an index that reflects the ability of a local area on the surface of a metal material to resist plastic deformation. Under certain material and heat treatment specifications, it has a corresponding relationship with the tensile, bending and other performance indicators of the material.

The hardness range of induction hardened parts is determined according to the performance of the parts, generally including the following:

1) For parts that bear impact loads, or when parts such as gears and splines are hardened and toughness is required, the hardness should be appropriately reduced. For example, the flywheel ring gear uses 48-56HRC or 40-48HRC, etc.

2) Used for friction parts, such as crankshaft journals and cam surfaces. The higher the hardness, the better the wear resistance. 55-62HRC is commonly used for crankshaft journals, 56-63HRC is commonly used for camshafts, etc.

3) Used in parts subjected to crushing, torsion and shearing, the hardness should be high, such as the surface of forging hammers, automobile axles, leaf spring pins, etc. Commonly used are 56-63HRC, 50-55HRC, etc.

For gray cast iron, ductile iron and malleable iron parts, due to the presence of graphite, the hardness measured with a Rockwell hardness tester is the average hardness of martensite and graphite. The hardness range of ductile iron can reach 45-55HRC, and the hardness of gray cast iron can reach above 38HRC or above 40HRC.

For different workpieces, their quenching hardness is different, and the same part is used in different occasions, and its hardness is also different. If the hardness is too deep, the residual stress on the surface of the part will be reduced, which will increase the deformation of the part. The hardness is too shallow, which affects the use of the workpiece. Therefore, we should be particularly careful about the quenching hardness of the workpiece.