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Hot stamping is a well-established and frequently used manufacturing process in automotive body construction. The number of components manufactured in this way is continuously increasing. Hot stamping is used to produce components with a completely martensitic structure, resulting in high strength and hardness. These components are mainly used in s...
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Context 1
... stamping takes place at a temperature above 720 °C, which according to Nürnberger et al. [12] should result in a fully martensitic microstructure. Table 1 shows the heating duration for the different heating processes and the measured energy consumption. Resistance heating was carried out with three different heating rates. ...Context 2
... this time, the uncoated sheet strongly reacts with the oxygen in the ambient air and highly oxidizes, as shown in the figure. Table 1 and Fig. 5b to d show that with increasing heating time of resistanceheated sheets, the scale formation and the energy consumption rise as well. However, the increasing energy consumption can be explained by the heat loss through thermal radiation and convection to the environment due to a longer lasting process and lower surrounding air temperature of about 25 °C compared to the furnace. ...Similar publications
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Citations
... Direct resistance heating involves passing an electrical current through the material to be formed, heating it through joule effect. In most cases, copper or aluminum electrodes linked to a generator are placed against the sheet to allow current flow [3,4]. This process is already promising, with studies showing it allows heating steel sheets over 800 • C in about 2 s with good temperature uniformity [5]. ...
... It is a crucial point in this process to allow uniform ductility over the entire sheet. Along the width, it mainly depends on the current density uniformity, which changes with the contact uniformity of the electrodes 2 of 7 and sheet [4]. Furthermore, the process demonstrates an efficiency between 75% and 95% when it is used to heat a steel sheet in a hot stamping process [6]. ...
... Eng. Proc. 2023, 43, x FOR PEER REVIEW 2 of density uniformity, which changes with the contact uniformity of the electrodes and shee [4]. Furthermore, the process demonstrates an efficiency between 75% and 95% when it i used to heat a steel sheet in a hot stamping process [6]. ...
... Principle of resistance heating of a rectangular sheet metal[26] ...
The manganese-boron alloy 22MnB5 is particularly used for structural and safety-relevant parts in the automotive industry. Parts made from this alloy are usually produced using the hot forming process. Here, the sheet is heated to over 950 °C using an industrial roller hearth furnace. The heated sheet is then simultaneously formed and quenched in a cooled tool with a temperature gradient of more than 27 K/s. This leads to the formation of a martensitic microstructure with a hardness value of over 450 HV10 and an elongation at break of less than 6%. The small strain potential of such components makes them difficult to form after hot-stamping. Due to the high temperature gradients of resistance heating, a sheet can be heat-treated locally without a large temperature transition zone. This can be used to locally soften already hot-stamped components for subsequent operations such as bending. Within the scope of this paper, resistance heating is used to soften a hot-stamped 22MnB5+AlSi sheet stripe of 3 mm width. The sheet could consequently be bent over an angle of 90° without cracking the substrate.
