Page 17 - MetalForming Magazine February 2023 - Metal Forming for the Automotive Industry

Cutting Edge
reports that it has stamped DP780 steel with 65 percent of its rated press-ton- nage capacity, but when the part was modified to TM1320 steel, the press was not able to stamp the piece—doing so required 107-percent press capacity.
In addition, a European press maker recently stated that its sales of transfer presses rated more than 2500 metric tons recently have been skyrocketing. These presses, whether flywheel or ser- vomechanical, have high energy con- sumption. However, the overall energy required to run the line may still be significantly lower than for a hot stamping line when considering the energy consumption of the furnace.
Advantages of Hot Stamping, or Disadvantages of Cold Stamping
New cold-stamped steel grades require significant capital investment for the mill, along with a complicated
Comparison of springback of a channel formed from three different steel grades. Note: The part is not optimized for reduced springback.
thermomechanical processing route to achieve high strength and elonga- tion. Hot-stamped steel, on the other hand, per ton can cost considerably less than 3rd Gen AHSS, especially if uncoated.
When strength level increases, many believe that springback can become very hard to control, but most tool makers now rely on sheet metal-form- ing simulation for springback predic- tions that include the required kine-
matic hardening models. Even with the Yoshida-Uemori model (see earlier Cut- ting Edge articles for details), one OEM reports that only 55 percent of a sim- ulated part fell within ±1-mm deviation with the real part. For 1180-MPa and higher-strength steels, many tool mak- ers also consider the elastic deflections of the tools. When running a coupled simulation including elastic deforma- tion of the tools, the match rate (the area within 1-mm deviation) increased from 55 percent to 93 percent.
Part productivity between hot and cold stamping depends on the part dimensions and thickness. In an ideal case, hot stamping lines may run at speeds to 24 parts/min.—in the range of some cold stamping lines. In realistic conditions, most often cold stamping will be more productive. Lastly, die wear, galling and die-cracking prob- lems may increase during cold stamp- ing as steel strength rises. MF
FOLLOW
TECHNOLOGY • NEWS • INFORMATION • EVENTS •
@MetalForming @PrecisionMetalforming @MetalForming Association(PMA) Magazine
14 MetalForming/February 2023
www.metalformingmagazine.com