Plates and bars of all CSA G40.21M grades can be satisfactorily formed on a press brake or other conventional cold bending equipment, but there’s a considerable difference in the formability of the different grades due to the strength level and chemical composition differences.
The following table summarizes the research results and is offered as a guide to the minimum bend radius that can be expected for different grades and thicknesses. These criteria apply strictly to longitudinal bends, as transverse bends may require up to twice the indicated radius. It’s assumed that the bend isn’t carried out on an edge that has been flame-hardened by gas cutting or on heavily burred or work hardened by shearing, unless there’s been some special edge preparation, such as grinding or chipping.
Suggested minimum bend radius: longitudinal bends
|Grade||< 6||6 to 12||12 to 25||25 to 40||40 to 50|
|350G||2 1/2t||3 1/2t||--||--||--|
|260W(A36)||1 1/2t||1 1/2t||2t||3t||--|
|350W||2 1/2 t||2 1/2t||4t||--||--|
|400W||3 1/2t||3 1/2t||6t|
|400WT||3 1/2t||3 1/2t||6t||--||--|
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1 Acknowledgement: Formability is taken from the Dominion Bridge Steel Handbook, CSA G40-21M-1978 Specifications Section, page 122.
Sizes are based on thickness in mm.
(t: times thickness of material = bending radius)
Hot forming is recommended for all thicknesses not showing a value in the above table. Since temperature can be a major cause of bend failure, in no case should bending be carried out at a metal temperature below 15C. Material of 350 MPa and higher yield strength will require greater bending and hold down force than lower strength steels, and provisions must be made for a greater than usual degree of springback.