Papers by Keyword: Hot Stamping

Abstract: Hot stamping of manganese–boron steels is widely used in automotive manufacturing to produce ultra-high-strength components with tensile strengths exceeding 1500 MPa . Conventional industrial heating relies on gas-fired roller hearth furnaces, which require 5 – 10 min to reach austenitization and exhibit low energy efficiency . Resistance heating offers a compact and energy-efficient alternative, enabling heating rates above 100 K/s and full austenitization within seconds. However, rapid heating of uncoated steels leads to severe oxidation, and established coating systems such as AlSi are not designed for diffusion-controlled bonding within such short times . This study demonstrates that resistance heating in an XHV-adequate atmosphere – consisting of nitrogen and monosilane – suppresses oxidation while simultaneously enabling adhesion of a pre-laminated aluminum foil to the steel substrate. For coating preparation, 22MnB5 sheets were roughened by corundum blasting, cleaned, and laminated with an aluminum foil using a flat-die pressing tool. The pre-coated blanks were heated in a self-developed resistance-heating chamber, in which the oxygen concentration was reduced to an XHV-adequate level. Several heating profiles were investigated to determine suitable process windows for coating formation. The results show that resistance heating achieves austenitization within a few seconds, reducing heating times by more than an order of magnitude compared to furnace heating. The XHV-adequate atmosphere reliably prevents scale formation, enabling completely oxidation-free surfaces during rapid heating. Under these conditions, the laminated aluminum foil bonds uniformly to the substrate, forming a continuous coating layer. Metallographic cross-sections and SEM analyses confirm the formation of Al–Fe intermetallic phases at the interface, demonstrating robust metallurgical bonding suitable for subsequent hot stamping operations. Overall, the combination of resistance rapid heating and an XHV-adequate atmosphere provides a highly energy-efficient process route for hot stamping while offering an opportunity to integrate aluminum-based protective coatings directly into the heating step. This approach addresses the limitations of current furnace-based heating and coating technologies and opens a promising pathway toward more flexible, sustainable, and functionally integrated hot-stamping process chains.

Abstract: In this study, a hot stamping process, which delivers ready-to-use parts for the production of aircraft components is applied as an alternative manufacturing method to, for instance, machined parts. The research has been focused on examining the formability of an aluminium alloy at high temperatures. An extensive experimental campaign has been conducted to establish the optimal hot stamping process parameters. As a final stage of the development, a demonstrator corresponding to a wing rib with AA2198 aluminium-lithium alloy has been successfully produced. After the corresponding heat treatment, material properties have been restored.

Abstract: The restoration parts made metallic materials by the method hot die forging is considered. Technological processes for restoring parts by hot stamping have a number advantages: shaping occurs in dies a simple design, existing forging and pressing equipment is used with the use standard automation and mechanization tools. In the process restoration parts by hot plastic deformation, it is possible to restore the shape and dimensions the worn surface, as well as to obtain the required microstructure the metal the restored part, which makes it possible to increase its service life due to subsequent thermo mechanical processing. A study was made the reasons for the loss performance the ball pins the torque rod, designs dies were developed for the restoration worn solid parts by the method hot forging. Parts are restored by creating targeted metal flows into the wear area using hot plastic deformation. It has been established that the hardness the metal in the middle part the restored part "Ball pin" increased by 30 ... 32% in relation to serial parts. When heated to the temperature forging and deformation the metal, the internal damage the metal accumulated inside the part is restored. This allows you to increase the durability the restored parts by 26…30%.

Abstract: 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 safety-relevant areas of the passenger cell, such as the A-pillar, B-pillar, tunnel and sill. For hot-stamping processes, it is necessary to austenitize the blanks. Heating the sheet metal up to 930 °C in a furnace is very energy-intensive. In large-scale industrial applications, the sheets are generally heated in gas-fired roller hearth furnaces up to 60 m long. Apart from the poor energy balance and the high CO₂ emissions of such furnaces, they are associated with high investment and maintenance costs, large space requirements and a long heating time. Rapid heating by means of the Joule effect and direct current instead of alternating current offer an energy-efficient and environmentally friendly alternative for sheet metal heating. Therefore, this technology can make a major contribution to environmental protection and resource saving. Within the scope of this work, parts were rapid-heated and subsequently hot-stamped by means of a novel heating system based on direct current with energy savings of up to 80 %. Using electricity guarantees a good CO₂ balance. In addition, resistance heating with a new type of DC-heating system and an adapted process chain is compared with conventional furnace heating. In thermographic images and microstructural examinations of the hot-stamped parts, it can be demonstrated that this direct-current technique is well suited for achieving homogeneous hardness and strength in the whole sheet metal. Thus, this new heating system can enhance the efficiency of the hot-stamping technology.

Abstract: High-strength aluminum alloys provide great potential for weight reduction in vehicle and aircraft production. Nevertheless, forming of these materials is limited at room temperature. Thermally supported forming operations such as hot forming and quenching (HFQ^®) allow forming of components without failure and reduced springback. Currently, the adhesive wear and high friction limit the use of HFQ^®-operations for high-strength aluminum alloys. Out of this reason, the present paper describes the tribological performance of new developed dry lubricants at elevated temperatures for the alloy AA7075. For this purpose, strip drawing tests were carried out in a modified open tribological system at temperatures between 20 °C and 400 °C. Additionally, the melting behavior of these lubricants, as well as the variation of the lubricant thickness, were investigated. The results show a reduction of the coefficient of friction at elevated temperatures.

Abstract: In the automotive industry, the development of electrically powered vehicles has become a major forward-looking topic. For improving the range and thus the efficiency of electric cars, lightweight construction has gained even more importance. In this regard, hot stamping has been established as a suitable and resource efficient process to manufacture high-strength and lightweight body-in-white components. This method combines hot forming and quenching of boron-manganese steel 22MnB5 in a single process step. As a result, complex structures with thin sheet thicknesses and high ultimate tensile strength up to 1500 MPa are generated. However, the use of lubricants is not possible at elevated temperatures, which subsequently leads to high thermo-mechanical tool stresses. As a side effect, high friction and severe wear occur during the forming process, which affect the resulting part quality and maximum tool life. Therefore, the aim of this study is to improve the tribological performance of hot stamping tools by using a laser implantation process. This technique is based on manufacturing highly wear resistant, separated and elevated structures in micrometer range by embedding hard ceramic particles into the tool material via pulsed laser radiation. As a result, highly stressed areas on the tool surface can be modified locally, which in turn influence the tribological and thermal behavior during the forming process. In this regard, laser implanted and conventionally tool surfaces were investigated under hot stamping conditions. A modified pin-on-disk test was used to analyze the friction coefficient and occuring wear mechanisms. Furthermore, quenching tests as well as hardness measurements were carried out to gain in-depth knowledge about the cooling behavior of the modified tool surfaces and its impact to the resulting mechanical part properties.

Abstract: Inspired by steel forming strategies, this study focuses on the effect of differential cooling on mechanical properties and precipitation kinetics during hot stamping of high strength AA7075 alloy. For this aim, different forming strategies were performed using segmented and differentially heated forming tools to provide locally tailored microstructures. Upon processing, uniaxial tensile tests and hardness measurements were used to characterize the mechanical properties after the aging treatment. Microstructure investigations were conducted to examine the strengthening mechanisms using the electron channeling contrast imaging (ECCI) technique in a scanning electron microscope (SEM). Based on the obtained results, it can be deduced that the tool temperatures play a key role in influencing the mechanical properties. Lower tool temperatures result in higher material strength and higher tool temperatures in lower mechanical properties. By changing the cooling rate with the use of differently heated forming tools, the mechanical properties can be controlled. Microstructure investigations revealed the formation of very fine and homogeneously distributed particles at cooled zones, which were associated with elevated mechanical properties due to the suppression of second phase particle formation during cooling. In contrast, coarse particles were observed at lower cooling rates, explaining the lower material strength found in these zones.

Abstract: Hot stamping, also known as press hardening in the context of sheet steel, has steadily gained relevance in the automotive industry, starting off as a specialist application and turning into a staple technique in the production of safety cage products in little more than a decade. However, despite the weight reduction offered by martensitic steels, further improvement could be obtained by substituting these components by high-performance aluminium. In this regard, the very same process of hot stamping could be employed to attain the required combination of shape complexity and mechanical properties at a reasonable cost for mass-market application, if the limitations imposed by cycle time and process window could be overcome. In this work, the feasibility of hot stamping of 6000-series aluminium alloy sheet is studied, first in dilatometry experiments and later in semi-industrial conditions in a pilot facility. A cycle time shortening strategy is employed, and compared to the conventional thermal cycle in terms of implementation and obtained results. In addition to basic characterization, aluminium thus processed is studied in terms of fracture toughness, in order to obtain data relevant to crashworthiness that can be readily compared with alternative materials.

Abstract: A new high temperature testing system was developed to evaluate high temperature deformation behavior in hot stamping process with high accuracy using a hybrid heating system consist of direct resistance heating and high-frequency induction heating. The uniform temperature distribution was achieved in the sheet steel tensile test specimen. The typical hot stamping thermal history was successfully simulated with the combination of the hybrid heating system and the gas cooling system. The strain distribution in high temperature deformation was confirmed to be uniform in the parallel portion of the specimen and the developed testing system may contribute to improving the accuracy in hot stamping CAE analysis.

Abstract: In this study, the effect of forming temperature, blank holder force, die entrance radius, die corner radius and blank local thickening on the springback of square cups were studied, by conducting finite element simulations of the hot stamping of 2024 aluminum alloy sheet blanks. Within the range of process parameters investigated in this study, increasing the forming temperature, blank holder force and die corner radius or decreasing the die entrance radius all lead to lower values of springback in hot stamped square cups after unloading. Compared to uniform blank, local-thickened sheet blank can significantly reduce the springback in hot stamped square cup. When the side length of the square-ring-shaped convex rib of the thickened blank is equal to the punch width and the convex rib faces downward, significant reductions in the springback, of at least 55.9%, can be achieved.