BENDING OF HIGH STRENGTH STEEL (I)

High-strength plates currently mainly include WELDOX high-strength structural steel plates and HARDOX wear-resistant steel plates. Compared with ordinary plates, high-strength plates have the advantages of high strength, high hardness, and light weight, etc., and are getting more and more popular in industries with higher material performance requirements such as automobiles, large ships, pressure vessels, engineering machinery, and aerospace.

Bending high strength steel sheets and plates rarely proves to be difficult. However, there are certain issues that must be considered, which are dealt with in this article.

This series articles deal with free bending and shearing of HARDOX? wear plate and WELDOX? structural steel plate. In these steel grades, we have combined high strength with high purity, and we maintain close tolerances on thickness, which makes the steels eminently well suited for cold bending.

What should do before bending high strength steel?

1). Checking the quality of steel.

Surface damage can worsen bendability as it can be the cause of fractures. For heavy plates, defects on the plate such as scratches and rust can often be removed with careful grinding. Grinding scratches shall preferably be placed perpendicular to the bend line instead of parallel. Thermal cut and sheared edges also will damage the bending and tools. It should be deburred and rounded with a grinder.

2). Checking the rolling direction of the plate.

If possible, orient the rolling direction perpendicular to the bend line. The plate can often be bent tighter this way, than with the bend line parallel to the rolling direction.

3). Checking the toolings.

The toolings should be in good condition. And the tip of punch and both radius of the die should be harder than the steel. And also the punch and die should be set up in the right line.

What should be taken into consideration when bending high strength steel?

1). Pay attention to safety and follow the local safety directions. Only qualified people may be by or in the vicinity of the machine. When high strength steel is being bent, nobody should stand in front of the press brake.

2). Check that the punch together with the workpiece does not bottom out in the die.

3). Consider springback. Avoid rebending to correct the profile angle. The exposure of a material to previous forming processes reduces its bendability to a great extent.

4). Bending force, springback and, in general, minimum recommended punch radius increase with the strength of the steel.

In the next chapters, we will discuss more about the bending of high strength steel in aspects, like springback and tools.