Robert Vollmer

Investigation of Weld Seam Structures of Tailor Welded Blanks for Hot Stamping

Increasing safety requirements for hot stamped structural car body parts are demanding sufficient mechanical properties of integrated welding seams. Especially conventional tailor welded AlSi-coated 22MnB5 sheets are only fulfilling these requirements when ablated before laser welding and thermo-mechanically treated in a correct way. This paper shows a method that evaluates the hot stamping process of tailor welded blanks by press hardening different sheet thicknesses and thickness combinations in a testing tool. Furthermore, appropriate testing methods for the evaluation of mechanical properties of the welding seam are introduced. The results are ultimately compared with a special developed FEM analysis to predict failure cases in future.

Application of Laser Cladding in Forming Processes—Functionally Graded Coatings

Innovative tooling steels, optimized geometries and thin film coatings are effective methods for improving performance characteristics like abrasive tool wear. Laser cladding is an additional technology with potential to solve both, tool wear and heat transfer problems for deep drawing, cutting, hydroforming and hot forming processes. This technology combines a base material with a highly process orientated coating. The work deals with the application of a functionally graded coating for hot stamping tools. Laser cladding of aluminum bronze on a mild steel substrate is performed and the thermal performance of this configuration is tested.

Reducing tool wear by partial cladding of critical zones in hot form tool by laser metal deposition

This paper points out a production method to reduce tool wear in hot stamping applications. Usually tool wear can be observed at locally strongly stressed areas superimposed with gliding movement between blank and tool surface. The shown solution is based on a partial laser cladding of the tool surface with a wear resistant coating to increase the lifespan of tool inserts. Preliminary studies showed good results applying a material combination of tungsten carbide particles embedded in a metallic matrix. Different Nickel based alloys welded on hot work tool steel (1.2343) were tested mechanically in the interface zone. The material with the best bonding characteristic is chosen and reinforced with spherical tungsten carbide particles in a second laser welding step. Since the machining of tungsten carbides is very elaborate a special manufacturing strategy is developed to reduce the milling effort as much as possible. On special test specimens milling tests are carried out to proof the machinability. As out...