Do you know the Type of Surface Defects of Fastener Nuts?

 Fastener nuts are common parts of connectors. For the use of fastener nuts, common surface defects are: cracks, shear bursts, bursts, cracks, wrinkles, dents, cuts, and damage. The following is a detailed explanation of some problems of fastener nut surface defects by Track Bolt China Exporter.

Bridge Bolt

Bridge Bolt

1. Cracks

A crack is a clear (crystalline) fracture along the metal grain boundary or across the grain, and may contain inclusions of foreign elements. Cracks are often caused by excessive stress during metal forging or other forming processes or heat treatment. Cracks may also exist in the raw materials. When the workpiece is heated again, the cracks are usually discolored due to the sharpness of the scale.

(1) Quenching crack

Causes of quenching cracks: During the heat treatment process, quenching cracks may occur due to excessive thermal stress and strain. Quenching cracks are usually irregular, with irregular directions appearing on the surface of the nut.

Note: Quenching cracks of any depth, any length or any part are not allowed to exist.

(2) Forging cracks and slag inclusion cracks

Causes of forging cracks and slag inclusion cracks: Forging cracks may occur during the cutting or forging process and are located on the top or bottom surface of the nut, or where the top surface (bottom surface) meets the opposite plane. Slag inclusion cracks are caused by non-metallic slag inclusions inherent in the raw material.

Note:

The cracks located on the bearing surface or bottom surface and top surface of the nut shall meet the following requirements respectively:

a) There should not be more than two satin cracks running through the bearing surface, and its depth should not exceed 0.05D.

b) The crack extending into the screw hole should not exceed the complete thread of the first buckle.

c) The depth of the crack on the complete thread of the first buckle should not exceed 0.5H1.

D-thread nominal diameter; H1-thread actual tooth height; H1=0.541P; P-thread pitch.

(3) Cracks in the locking part of the all-metal effective torque lock nut

Cause: The cracks in the locking part of the all-metal effective torque lock nut may be generated in the process of beveling or forging or closing (flattening) and appear on the external or internal surface.

Note:

Due to the cracks generated by the forging and located in the locking part, it should be able to meet the mechanical and working performance requirements of the nut, and should also meet:

a. There should be no more than two cracks running through the top circumference, and its depth should not exceed 0.05D.

b. The crack extending into the screw hole should not exceed the complete thread of the first buckle.

c. The depth of the crack on the complete thread of the first buckle should not exceed 0.5H1.

Cracks due to closing (flattening) and located in the locked part should not be allowed.

D-thread nominal diameter; H1-thread actual tooth height; H1=0.541P; P-thread pitch.

Our company also has Bridge Bolt for sale, please contact us.


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