BENDING OF HIGH STRENGTH STEEL (II)

In the last article, we talk about what should do and what should be taken into consideration before the bending of high strength steel. In this article, we will mainly focus on the punch and die.

(1)The punch and should be made of low-alloy high-strength structural steel. It is assembled, easy to be processed, and installed.

(2)The high-strength plate has a larger rebound after bending, and so the angle of the die should be small.

(3)The die edge radius should be at least half the plate thickness. Alternatively, the die width should be increased in order to minimize pressure on the die edge radius, and consequently reduce the risk of die marks.

(4)The suitable punch radius, along with the die width, is the most important parameter. When bending high strength steel, the final inner radius often becomes somewhat smaller than the radius of the punch. The R of the punch should be larger. According to the parameters provided by the steel supplier, R ≥ 4s (s is the plate thickness).

(5) The radius tip of the punch should be applied with extra hardening to obtain higher hardness in case of causing compressive deformation during bending.

(6) The hardness of both radius of the die should be harder just like the punch radius to improve the wear resistance of the lower die. If possible, we can use two rollers on both radius, usually GCr15. Hardness can be HRC55-60. And it is easy to be replaced after a long time. The two rollers can rotate with the bending of the workpiece. There is no sliding friction between the pieces, only rolling friction, which can protect the workpiece surface. The face is not scratched.

(7) Usually bending capacity should be above 300t/m according to the plate thickness.