Cautions for Cold Forming

1) Cutting Plan

When steel plates are cold-formed, thorough consideration must be given starting with the cutting plan.

 

A．Directional Difference in Properties of Steel Sheets

When a steel plate is bent during forming, the extent of cracking can differ greatly according to the bending direction （refer below Fig.）

 

 

Fig. 1    :   Relationship between end face cracking and shear plane orientation & clearance

Materials tested: SS400

6.0mmt Bend radius: 6.0mm

Bending angle: 180°

 

In particular, cracks tend to occur easily along inclusions that have been elongated at a right angle to the hot rolling direction （refer below Fig. ）, so bendability and flange creation can be extremely poor in such direction.

 

Bending at right angle to the rolling direction （Mark C）

Therefore, as part of the cutting plan, consideration should be made so that, as much as possible, the direction of severe bending, tensile, or ironing becomes the same as the rolling direction （refer below Fig.）.

 

Bending parallel to the hot rolling direction （Mark L）

 

B．Orientation of Shear Plane

 

When steel plates are formed with their cross section as sheared, a great difference arises whether they are formed with their shear plane inside or outside of the bending. Specifically, there can be minor cracks in "a broken-out section" which covers an area of about half the sheared-end face, and furthermore burrs will be present.

For this reason, if a plate is bent with a broken-out plane outside （Fig. 20）, end face cracks are likely to occur. It is necessary to prevent cracking in consideration of bending so that a broken-out plane may be present inside. above Fig. 1 also indicates that the clearance degree in shearing affects the formation of work-hardened layers and thus influences

the end face workability.

 

Source: www.nssmc.com