Press-related requirements


    In the processing of high-strength steels the required press forces are often underestimated. This applies to the cutting forces (which can be precisely determined but can cause surprises with their severe impact shock) as well as to the required slide and blankholder forces in the drawing operation.  
    Because of the work-hardening of the sheet material the preference for restriking of radii and contours is to be avoided. On the other hand, the higher strength of the material, depending on the selected blank thickness, require about two or three times the press force as conventional deep drawing steel grades.  
    In addition, because of the extreme ratio of strength to material thickness a significantly greater blankholder force is required for deep drawing in order to avoid the formation of wrinkles (compare also stainless steel processing). The lower the capacity for deformation, the more difficult is the deep drawing process.  Martensite phase steels, for example, have elongation at failure ratios of just a few percent.  This permits only very simple forming and bending operations such as for side-impact elements. 
    It should also be noted that impact shock during processing of high-strength steels are considerably greater than calculated force requirements would lead you to expect. Due to the abrupt snap-through of the material, unlike softer steels no energy at all is absorbed by the workpiece itself. All the energy of the frame-stretched press system flows directly into the die, press, and foundation. This is important to consider in the design of the line.