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Hydraulic piston rod stress relief annealing
Jan 31, 2019

In the process of surface quenching of the hydraulic piston rod, since it is tempered by the residual heat of the product itself, and the tempering temperature is gradually reduced, there is no complete tempering and heat preservation process, the tempering time is short, and the stress is eliminated. Incomplete, there is a large residual stress in some products. Moreover, in the subsequent grinding process, the residual internal stress of the grinding internal stress and the surface quenching may overlap.

 

As a result, once the stress exceeds the tensile strength of the hydraulic piston rod, stress cracks are generated on the surface of the product. If the stress does not exceed the tensile strength of the material and is present in the product as residual stress, the plating may be cracked due to redistribution of stress during subsequent chrome plating or use, causing cracks in the chrome plating layer.

 

Based on this tensile force, the anneal must be performed prior to chrome plating of the hydraulic piston rod to eliminate internal stresses caused by grinding and surface treatment. In general, the hydraulic piston rods have good mechanical properties after quenching and tempering, and are ready for subsequent surface treatment. The stress relief annealing is arranged before the electroplating after the grinding process to completely eliminate the residual stress inside the piston rod, improve the plating quality and the product qualification rate, and improve the service life of the piston rod.