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Marion Merklein - One of the best experts on this subject based on the ideXlab platform.

  • Characterization of tribological conditions within direct Hot Stamping
    Journal of Materials Processing Technology, 2020
    Co-Authors: Patrik Schwingenschlögl, Marion Merklein
    Abstract:

    Abstract The aim of this study is to create a detailed process understanding regarding the tribological conditions within direct Hot Stamping. Hot Stamping has established as a common technology for manufacturing safety-relevant components in modern car bodies. However, due to the high forming temperatures within Hot Stamping applications, no suitable lubricants have been developed yet. As a consequence, high friction and severe wear occur during the forming. This affects the tool wear as well as the resulting part quality. For improving the robustness and the efficiency of industrial Hot Stamping processes, future measures to reduce the tribological loads have to be found. The key to the development of such measures is a detailed process understanding of the tribological conditions. Within this study, friction and wear are analyzed for different workpiece and tool temperatures, relative velocities and contact pressures. Based on the experimental results, detailed knowledge of the critical cause-effect relations between process parameters and tribological behavior is acquired. The friction behavior is analyzed via strip drawing experiments under Hot Stamping conditions. The amount of wear is determined via confocal microscopy measurements before and after the experiments. The results of this study help to improve the process understanding of the tribological conditions within the Hot Stamping process and to develop future measures for reducing tool wear.

  • Increasing the Adhesive Wear Resistance of Hot Stamping Tools by Modifying the Surfaces
    Key Engineering Materials, 2018
    Co-Authors: Franziska Neubauer, Tobias Reil, Konstantin Hofmann, Marion Merklein
    Abstract:

    Over the last few years lightweight construction became increasingly important in modern cars. Motivated by reducing greenhouse gas emission the car industry is currently working on different approaches to decrease the weight of structural body parts. In this regard, a reduced sheet thickness of these components and therefore a reduced overall weight can be achieved by using high-strength steels. Hot Stamping has been established as a suitable manufacturing process for these steel grades, in which a Hot austenitic blank is formed and quenched simultaneously. The high strength of the formed parts is realized by the phase transformation of an austenitic to a martensitic structure during Hot Stamping. Due to the alternating thermo-mechanical loads, which occur during forming and quenching, the Hot Stamping tools are highly stressed. In addition, when the blank slides over the surface of its counterpart, a substantial adhesive wear occurs, which is the predominant wear mechanism in Hot Stamping. The aim of this study is, to increase the wear resistance of the tools by modifying the surface. In this context, the chemical affinity between the interacting components need to be reduced in order to decrease the adhesive wear on the Hot Stamping tool, which is possible by alloying the base material. For this reason, the wear development is investigated for samples alloyed with different materials with a modified pin-on-disc test. This experimental setup enables a continuous contact of the tool with the blank and thermal alternating stress of the pin. The contact area is investigated with a laser-scanning microscope to qualify the tool surface before and after the experiments by measuring the tool topographies. The results of an unalloyed and alloyed tool will be compared with each other to evaluate the wear behavior. In order to quantify the amount of wear the wear volume will be calculated with an algorithm of the software WinSam. The experiments will be carried out under process like conditions to ensure transferability to the real Hot forming process.

  • Hot Stamping of ultra high strength steel parts
    Cirp Annals-manufacturing Technology, 2017
    Co-Authors: Kenichiro Mori, Tomoyoshi Maeno, Paolo Francesco Bariani, Stefania Bruschi, Marion Merklein, Alexander Brosius, Bernd-arno Behrens, Jun Yanagimoto
    Abstract:

    Abstract The demand for new processes to produce high strength parts, under appropriate cost and productivity, has grown with weight reduction and crash safety improvements in automobile design. The Hot Stamping processes of quenchable steel sheets potentially offer not only small forming load and high formability, but also high strength and no springback by die quenching. This paper aims to provide an overview of the state-of-the-art in such Hot Stamping processes, including quenchability, formability, heating and cooling approaches and lubrication. The paper also includes a description of the mechanism of formability and quenching, tailoring, analysis of Hot Stamping processes and applicability.

  • Modelling Kinetics of Phase Transformation for the Indirect Hot Stamping Process
    Key Engineering Materials, 2013
    Co-Authors: Paul Hippchen, Marion Merklein, Arnulf Lipp, Michael Fleischer, Hannes Grass, Craighero Philipp
    Abstract:

    To configure the indirect Hot Stamping process, a finite-element-based prediction of the parts geometry and mechanical properties is required. In case of indirect Hot Stamping, inhomogeneous cooling schedules cause different phase transformation points and products. The volume expansion caused by phase transformation of fcc into bcc leads to transformation induced stresses that are important for the calculation of overall stresses in press hardened components. To calculate theses stresses correctly, it is necessary to study the kinetics of phase transformation in consideration of the cooling path of an indirect Hot Stamping process. Dilatometer tests are employed to obtain the kinetics of phase transformation is determined in dilatometer tests. These results are used to identify the parameters for the phase transformation models implemented in the material model *MAT_244 [ that is implemented in the finite-element-code LS-DYNA [. In this context the material model parameters are identified by using evolutionary optimization strategies. Based on the identified parameters the predictive quality of the implemented phase transformation models will be studied in order to improve their prediction accuracy for the indirect Hot Stamping process.

  • determination of tribological conditions within Hot Stamping
    Production Engineering, 2008
    Co-Authors: M Geiger, Marion Merklein, J Lechler
    Abstract:

    Innovative Hot sheet metal forming technologies are gaining an increasing significance in the scope of application of more and more innovative high and ultra high strength steels in the automotive industry. With respect to a numerical process design beside the mechanical and the thermal material characteristics the friction coefficient represents an important input parameter for finite element (FE) simulation. Within the scope of this paper an evaluation method for the determination of the friction coefficient μ for the direct Hot Stamping process of boron-manganese steels will be presented. Therefore cup deep drawing tests at elevated temperatures following the time-temperature-characteristic of the Hot Stamping process are carried out. For the calculation of the friction coefficient the approach according to Siebel for the modeling of the maximum drawing force is used.

Jun Yanagimoto - One of the best experts on this subject based on the ideXlab platform.

  • Hot Stamping of ultra high strength steel parts
    Cirp Annals-manufacturing Technology, 2017
    Co-Authors: Kenichiro Mori, Tomoyoshi Maeno, Paolo Francesco Bariani, Stefania Bruschi, Marion Merklein, Alexander Brosius, Bernd-arno Behrens, Jun Yanagimoto
    Abstract:

    Abstract The demand for new processes to produce high strength parts, under appropriate cost and productivity, has grown with weight reduction and crash safety improvements in automobile design. The Hot Stamping processes of quenchable steel sheets potentially offer not only small forming load and high formability, but also high strength and no springback by die quenching. This paper aims to provide an overview of the state-of-the-art in such Hot Stamping processes, including quenchability, formability, heating and cooling approaches and lubrication. The paper also includes a description of the mechanism of formability and quenching, tailoring, analysis of Hot Stamping processes and applicability.

  • valuation method for effects of Hot Stamping process parameters on product properties using Hot forming simulator
    Journal of Materials Processing Technology, 2011
    Co-Authors: Katsuyoshi Ikeuchi, Jun Yanagimoto
    Abstract:

    Abstract Hot Stamping is one of the Hot forming processes for manufacturing products of lightweight construction such as lightweight vehicles. Knowledge on the characteristics of the Hot Stamping process is significant in designing and optimizing the process conditions, dies and tools; however, until now, the characteristics of this process, such as the relationships between a product property and die temperature and between a product property and cooling rate, and the springback amount, have not been clarified consistently or precisely. A new valuation method used to measure the effects of Hot Stamping conditions on product properties as a function of process parameters is proposed in this paper. This method utilizes a Hot forming simulator, which is a precision press with feedback temperature control and controlled cooling, and permits to know the various characteristics of the Hot Stamping process. Here, the basic construction of the proposed method is presented, and its application to the characterization of the Hot Stamping process of high-strength steel sheets, such as an evaluation of the changes in product properties upon varying the forming conditions and process parameters, is shown and discussed.

Amir Abdollahpoor - One of the best experts on this subject based on the ideXlab platform.

  • Understanding wear conditions during Hot Stamping
    Advanced High Strength Steel and Press Hardening, 2016
    Co-Authors: Michael P. Pereira, Amir Abdollahpoor, Bernard Rolfe, Peng Zhang, C. Wang
    Abstract:

    Wear and galling are significant issues during production Hot Stamping processes. This paper uses thermo-mechanical finite element analysis to study the contact pressure, sliding distance and temperature conditions that occur at the wearing interface during Hot Stamping. Several Hot Stamping processes are studied, representing the numerous methods that are used in industry to form a typical hat-shaped channel component. These process include crash forming (without blankholder), Stamping with a blank holder with an applied blank holder pressure, and Stamping with a clearance blank holder (i.e. with spacer blocks). This paper identifies the distinct contact pressure and temperature conditions that occur for each of these forming methods. The regions of the most severe contact conditions are notably different for each of the forming methods. The work from this paper will form the basis for the development of suitable temperature dependent wear models and low cost wear tests for industrial Hot Stamping applications.

  • Experimental investigation of tailored Hot Stamping parts
    Advanced High Strength Steel and Press Hardening, 2016
    Co-Authors: Amir Abdollahpoor, Bernard Rolfe, Michael P. Pereira, Z. J. Wang, Yi Sheng Zhang
    Abstract:

    It is known that tailored Hot stamped parts, which have locally graded properties, can improve car crashworthiness. In this experimental study, a heated tool was used to decrease the temperature difference between the Hot blank and the tool which led to lower cooling rates and softer properties. First, a flat heated tool was used to investigate the effects of process parameters on metallurgical and mechanical properties. Based on the range of parameters examined, press force and quenching time did not have a significant effect on the post-formed mechanical properties. In the next step, a hatshaped channel tool with heating system was used to produce tailored Hot Stamping parts. The results show considerable differences between hardness values of the top and side faces in the soft section, while the hardness was almost uniform in the hard section. These experimental results generally compare well with the results of previous numerical parametric studies performed by the authors, which identified less robustness of the tailored Hot Stamping process compared to conventional Hot Stamping.

  • Advances in tailored Hot Stamping – innovations in material and local patchwork topology
    Advanced High Strength Steel and Press Hardening, 2016
    Co-Authors: Bernard Rolfe, Amir Abdollahpoor, Michael P. Pereira, Hui Kong, Erik J. Pavlina, Daniel Fabijanic, K. H. Hu
    Abstract:

    Hot Stamping is now commonplace in the automotive industry. The continuing need by automotive manufacturers to reduce weight while increasing crashworthiness has driven the industry to seek new Hot Stamping solutions. Tailored Hot Stamping can be thought to produce a part that has patchwork of hard and soft regions. In this context, patchwork means that there is a relational organization (topology) to the network of hard and soft regions. The next generation of tailored Hot Stamping will therefore combine new steel grades together into a single part, and secondly will be able to locally tailor material properties to meet detailed engineering targets. The key to meeting engineering demands will be how the patchwork material properties are organized on the part. This paper will briefly outline our latest research in tailoring parts.

  • Sensitivity of the final properties of tailored Hot Stamping components to the process and material parameters
    Journal of Materials Processing Technology, 2016
    Co-Authors: Amir Abdollahpoor, Xiangjun Chen, Namin Xiao, Bernard F. Rolfe
    Abstract:

    The final mechanical properties of Hot stamped components are affected by many process and material parameters due to the multidisciplinary nature of this thermal-mechanical-metallurgical process. The phase transformation, which depends on the temperature field and history, determines the final microstructure and consequently the final mechanical properties. Tailored Hot Stamping parts - where the cooling rates are locally chosen to achieve structures with graded properties - has been increasingly adopted in the automotive industry. In this case, the robustness of final part properties is more critical than in the conventional Hot Stamping parts, where the part is fully quenched. In this study, a wide range of input parameters in a generalized Hot Stamping model have been investigated, examining the effect on the temperature history and resulting final material properties. A generic thermo-mechanical finite element model of Hot Stamping was created and a modified phase transformation model, based on Scheil's additive principle, has been applied. The comparison between modeling and experiments shows that the modified phase transformation model coupled with the incubation time provides higher accuracy on the simulation of transformation kinetics history. The robustness of four conditions relevant to tailored Hot Stamping was investigated: heated tooling (with low and high tool conductance), air cooling, and conventional Hot Stamping. The results show the high robustness of the conventional Hot Stamping compared to tailored Hot Stamping, with respect to the stamped component's final material properties (i.e. phase fraction and hardness). Furthermore, tailored Hot Stamping showed higher robustness when low conductivity tools are used relative to high conductivity tools.

  • Robustness of the Tailored Hot Stamping Process
    Advanced Materials Research, 2014
    Co-Authors: Bernard Rolfe, Amir Abdollahpoor, Xiangjun Chen, Michael P. Pereira, Namin Xiao Xiao
    Abstract:

    The final mechanical properties of Hot stamped components are affected by many process and material parameters due to the multidisciplinary nature of this thermal-mechanical-metallurgical process. The phase transformation, which depends on the temperature field and history, determines the final microstructure and consequently the final mechanical properties. Tailored Hot Stamping parts – where the cooling rates are locally chosen to achieve structures with graded properties – has been increasingly adopted in the automotive industry. Robustness of the final part properties is more critical than in the conventional Hot Stamping. In this paper, the robustness of a tailored Hot Stamping set-up is investigated. The results show that tailored Hot Stamping is very sensitive to tooling temperature, followed by latent heat radiation emissivity, and convection film coefficient. Traditional Hot Stamping has higher robustness compared to tailored Hot Stamping, with respect to the stamped component’s final material properties (i.e. phase fraction, hardness).

Yi Sheng Zhang - One of the best experts on this subject based on the ideXlab platform.

  • Modeling of Hot Stamping process procedure based on finite state machine (FSM)
    The International Journal of Advanced Manufacturing Technology, 2017
    Co-Authors: Liang Wang, Qiang Wang, Yi Sheng Zhang
    Abstract:

    Hot Stamping technology of high strength steel creates new possibilities for vehicle manufacturers in promoting safety and fuel efficiency. The proportion of Hot Stamping parts in vehicles increases each year, and there are already hundreds of different types of Hot Stamping lines throughout the world. However, few studies regarding modeling of Hot Stamping process procedure have been reported, nor have there been studies regarding cooperative scheduling of manufacturing units (including heating units, transferring units, and forming units), or the relationship between productivity and energy consumption. With the shortening of the vehicle life cycle, auto parts manufacturing must be flexible for multiple types and small batches to meet the challenges of the market. In this paper, a model of the Hot Stamping process procedure based on finite state machine is established, then the model is adapted for the procedure control of a Hot Stamping line, consisting of multi-chamber furnaces, linear conveying robots, and a mechanical servo press. The cooperative scheduling of various manufacturing units, especially the method which matches multiple heating chambers with a single forming die, is focused on. Finally, a Hot Stamping line with multi-chamber furnaces is designed and implemented, and the analysis of its production sequence, energy consumption, and delivery cycles is performed. The results show that with the new modeling method of Hot Stamping process based on finite state machine, the new developed Hot Stamping line is capable of multiple production objectives and flexible configuration in accordance with production and delivery periods. This active configuration aids in extending equipment life and reduce energy consumption. The modeling method expands production models for Hot Stamping, from the mass production model to multiple types and small batches production model.

  • Experimental investigation of tailored Hot Stamping parts
    Advanced High Strength Steel and Press Hardening, 2016
    Co-Authors: Amir Abdollahpoor, Bernard Rolfe, Michael P. Pereira, Z. J. Wang, Yi Sheng Zhang
    Abstract:

    It is known that tailored Hot stamped parts, which have locally graded properties, can improve car crashworthiness. In this experimental study, a heated tool was used to decrease the temperature difference between the Hot blank and the tool which led to lower cooling rates and softer properties. First, a flat heated tool was used to investigate the effects of process parameters on metallurgical and mechanical properties. Based on the range of parameters examined, press force and quenching time did not have a significant effect on the post-formed mechanical properties. In the next step, a hatshaped channel tool with heating system was used to produce tailored Hot Stamping parts. The results show considerable differences between hardness values of the top and side faces in the soft section, while the hardness was almost uniform in the hard section. These experimental results generally compare well with the results of previous numerical parametric studies performed by the authors, which identified less robustness of the tailored Hot Stamping process compared to conventional Hot Stamping.

  • Research on equipments and production line of Hot Stamping
    Proceedings of the 5th International Conference on Advanced Design and Manufacturing Engineering, 2015
    Co-Authors: Liang Wang, Yi Sheng Zhang
    Abstract:

    transportation; Abstract. Hot Stamping is a reliable way for the production of high performance auto parts with light weight. Hot Stamping process requires pre-blanking steel sheet to be transported and processed at elevated temperature, and the performance of Hot Stamping products is closely related to temperature. This paper presents 2 types of Hot Stamping lines independently developed, 2000kN test line and 6000kN production line. The 2000kN test line is composed of a chamber furnace for heating blanks, a 2000kN electric servo mechanical press for forming heated blanks and a joint robot for transporting. The production line has multi-chamber furnaces, high-speed multi-axis Cartesian robots and electric servo mechanical press. Hot Stamping process is carried out by heating equipments, transporting equipments and forming equipments cooperatively. Mechanical link servo press (MLSP) carries out Hot Stamping process by fast downward, slowly mold closing and holding pressure at bottom. Robots cooperatively transport Hot blanks as fast as possible for the sake of reducing exposure at air and temperature drop. Multi-chamber furnaces dispatch chambers into or out of production cycle to implement flexible production. The production line carries out continuous and efficient production at a steady beat.

  • conduction heating of boron alloyed steel in application for Hot Stamping
    International Journal of Precision Engineering and Manufacturing, 2015
    Co-Authors: Weikang Liang, Minglin Zhou, Yi Sheng Zhang
    Abstract:

    In traditional Hot Stamping process, heating of the sheet by radiation heating occupies most of cycle time, which limits the application of Hot Stamping in automotive industry. Thus a faster heating method has great significance on the Hot Stamping. The conduction heating overcomes shortage of the radiation heating because of higher heating rate and greater energy efficiency. It attracts increasing attention in the application of heating blanks in Hot Stamping. In the present study, a movable conduction heating device on die was designed in terms of the Joule’s Law. Heating experiments of boron alloyed steel were performed using the developed device. Heating rate and uniform temperature region were investigated in the non-heat preservation condition (NHPC) and the heat preservation condition (HPC). The results revealed that in the HPC, the heating rate was improved by 13.1 °C/s. In addition, the length of the uniform temperature region was lengthened by 15 mm. It was demonstrated that the HPC was preferred. Furthermore, it was indicated that the mechanical properties of the blanks in uniform temperature region of the conduction heating were also superior to that of the radiation heating.

  • A New Hot Stamping Process with Quenching and Partitioning Treatment
    Advanced Materials Research, 2015
    Co-Authors: Xiang Yun Yu, Kai Wang, Jian Li, Yi Sheng Zhang
    Abstract:

    A new Hot Stamping process with quenching and partitioning treatment is proposed in the paper. Compared to direct Hot Stamping process, the microstructures with some retained austenite not only including martensite are formed according to the constrained carbon equilibrium (CCE) model. During the new Hot Stamping process, tools with high temperature are used to control the quenching temperature (QT) between Ms and Mf, and the partitioning treatment of the part is also implemented in the tools by prolonging holding times. In this paper, different holding times (partitioning times) controlled by servo press, are used to research the influence of partitioning time on mechanical properties.

Paolo Francesco Bariani - One of the best experts on this subject based on the ideXlab platform.

  • Hot Stamping of ultra high strength steel parts
    Cirp Annals-manufacturing Technology, 2017
    Co-Authors: Kenichiro Mori, Tomoyoshi Maeno, Paolo Francesco Bariani, Stefania Bruschi, Marion Merklein, Alexander Brosius, Bernd-arno Behrens, Jun Yanagimoto
    Abstract:

    Abstract The demand for new processes to produce high strength parts, under appropriate cost and productivity, has grown with weight reduction and crash safety improvements in automobile design. The Hot Stamping processes of quenchable steel sheets potentially offer not only small forming load and high formability, but also high strength and no springback by die quenching. This paper aims to provide an overview of the state-of-the-art in such Hot Stamping processes, including quenchability, formability, heating and cooling approaches and lubrication. The paper also includes a description of the mechanism of formability and quenching, tailoring, analysis of Hot Stamping processes and applicability.

  • tribological performances of zn based coating in direct Hot Stamping
    Tribology International, 2014
    Co-Authors: Andrea Ghiotti, Stefania Bruschi, Francesco Sgarabotto, Paolo Francesco Bariani
    Abstract:

    Abstract In Hot Stamping of High Strength Steels, the severe tribological conditions make the metal sheet coating one of the most critical choices for the technical and economical success of the process. This paper presents the approach and the results in evaluating a Zinc-based coating applied to boron steel sheets in Hot Stamping operations. Thermal and physical-simulation experiments were carried out to evaluate the chemical interactions between the coating and the metal sheet and the tribological performances during the process. The coating proved to overcome most of the drawbacks of the currently utilized Al–Si coating.