a b s t r a c tIn this study, the high temperature wear behavior of hot forming tool steel grades is investigated by successive sliding of a pre-alloyed Usibor1500P s strip heated at high temperature. Experimental tests are performed at high temperature on an instrumented Deep-Drawing Process Simulator (DDPS). This laboratory pilot is employed to rank different steel grades used as tool materials in the hot-stamping process. The wear damage of the tool (die radius) is characterized by profilometry and SEM observations, and three quantitative criteria are determined from 2D profile measurements to assess adhesive and abrasive wear. Under examined conditions at high temperature, a predominant transfer mechanism is observed, while abrasive wear appears as minor damage. When the surface hardness of the tool material is not great enough, the sub-surface of the die radius can exhibit a plastic shear deformation of about 10 mm in depth. This leads to emission of wear debris coming from the cumulated cyclic plastic deformation of the sub-surface. In contrast, for high surface hardness, the adhesive wear rapidly reaches an asymptotic state.

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Hot stamping and quenching of boron steel is a novel technology to produce structural automotive parts with an excellent crash performance. It offers the opportunity to produce thinner parts with complex shapes and higher mechanical properties. In order to increase the simulation expertise of the hot stamping process,, an experimental device has been designed and developed to accurately measure the thermal contact resistance (TCR) under representative process conditions. This parameter characterizes the heat transfer intensity between the tools made in Z160 steel and Usibor 1500P blank (a precoated carbon/manganese steel) at the contact interface. In this paper, we present an approach to determine experimentally the evolution of the TCR under different contact pressure (2 to 30 MPa).

A methodology is developed in this article to assess the wear damage occurring on a die radius in a deep-drawing process. Profilometric and topographic measurements were performed with a whitelight-source confocal microscope on the rubbed part of the die radius, using a repeatable procedure. Four new quantitative damage criteria were defined from 2D profiles, to quantify and determine the degree of regularity of both adhesive and abrasive damage. This method allows different tool steels to be classified in terms of their adhesive and abrasive wear behavior, with fairly good repeatability and reliability.

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In the present paper, an experimental device designed and developed to estimate the thermal contact resistance (R C ) at the blank/tool interface is presented along with the simulation chain used to validate the experimental results. The designed stamping tool is composed of a die and a punch made in Z160CDV12 steel and presenting an omega shape. Sample and tools are thermally instrumented with thermocouples type K sheathed with silky glass, forming heat flux-meters in the most interesting locations in the tools. Hot stamping tests are carried out under different contact pressure values covering the range from 5 to 30 MPa. Tested blank material is a C-Mn steel, named Usibor 1500P. Temperatures measurement in the tool and the blank allow the estimation of Rc evolution for every contact pressure. Experiments were carried out in the same conditions of the industrial process. The recorded blank temperature shows systematically a slope change around 400°C; it is linked to the microstructure transformation from austenite to martensite. This metallurgical transformation is also observed on the R C evolution curve. Linked to the microstructure transformation, this singularity tends to vanish with increasing pressure. That is due to the increasing of the cooling velocity with the stamping pressure increasing. Results have been established as correlation of type: R C = R C (P) to be used for numerical simulation through Pam-Stamp and Abaqus. Experimental and numerical parameters have been compared and the small temperature difference shows the good quality of results.