Austenite decomposition during press hardening of a boron steel—Computer simulation and test

Åkerström, Paul; Oldenburg, Mats

doi:10.1016/j.jmatprotec.2006.02.013

Cited by 119 publications

(49 citation statements)

References 11 publications

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“…For example, in safety critical beams in automobiles, instead of utilising a fully martensite phase, regions of ductile phases, such as ferrite and pearlite, can be incorporated to enhance energy absorption or tune crash deceleration pulses; this concept is described in a patent by Thomas and Detwiler (2009) on optimizing structural performance by microstructural design, which can be realized by controlling thermal conditions during forming. As a result, comprehensive studies have been carried out on the phase transformation behaviour of boron steels during cooling, such as the experimental characterisation of cooling rate effects (Gárlipp et al, 2001), and modelling of austenite decomposition (Åkerström and Oldenburg, 2006). This knowledge could be applied to selective quenching in hot stamping.…”

Section: Introductionmentioning

confidence: 99%

Experimental characterisation of the effects of thermal conditions on austenite formation for hot stamping of boron steel

Lin

Balint

et al. 2016

Journal of Materials Processing Technology

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The formation of austenite in manganese-boron steels during selective heat treatment has great significance in the application of innovative hot stamping processes. Heat treatment tests were designed according to the thermal cycle of industrial heating and hot stamping processes and were conducted on a Gleeble 3800 thermomechanical testing system. Specimens were subjected to non-isothermal (heating rates: 1K/s-25K/s) and isothermal (soaking temperatures: 1023K-1173K) temperature profiles. A high-resolution dilatometer was employed to detect the dimensional change of the specimens associated with austenitization. The dilatometric measurement was quantitatively related to the volume fraction of austenite. By analysing the evolution curves of austenite fraction, the effects of heating rate and temperature on the progress of austenite formation under both non-isothermal and isothermal conditions were investigated and characterised, improving the current understanding of the mechanisms that control austenite formation in manganese-boron steels. Imperial College London Reviewer #1: General:This submission presents new and significant results on austenite formation during heating cycles for a commercial Mn-B steel (22MNB5). The data and insights presented will be valuable in the design of selective heating and quenching processes for hot stamping of this steel grade. However, the Discussion is deficient. The need to analyse the (same) dilatometer data several different ways is not obvious. See responses to the specific comments below -in particular, see the response to specific comment 5. Specific:1. p.6: Section 2 is a lengthy description of 'textbook material'. It should be deleted and replaced with a brief summary of the issues/knowledge gaps which were addressed in the present study. This revised summary should be included in Section 1. Section 2 has been reduced and incorporated into a revised Section 1 (p. 6-8). The information that remains is necessary for later discussion Thank you for these corretions. All have been updated according to the suggestions. The comments from Reviewer #3:In order to gain a better understanding of the kinetics of the austenite formation in boron steels, in this work the formation of austenite in a manganese-boron steel has been investigated by the authors through dilatometry and theoretical analysis. The authors have conducted heat treatment tests on a Gleeble 3800 thermomechanical testing system. Specimens were subjected to non-isothermal heating rates (1K/s, 5 K/s and 25K/s) and different isothermal soaking temperatures (1023K, 1073K,1123K and1173K) . A high resolution dilatometer was employed to detect the dimensional change of the specimens associated with austenitization and a method was proposed to quantitatively relate the dilatometric measurement to the volume fraction of austenite. The effects of heating rate and soaking temperature on the progress of austenite formation under both non-isothermal and isothermal conditions were investigated by analyzing the evolu...

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Section: Introductionmentioning

confidence: 99%

Experimental characterisation of the effects of thermal conditions on austenite formation for hot stamping of boron steel

Lin

Balint

et al. 2016

Journal of Materials Processing Technology

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“…This model was implemented in LS-Dyna, and the material properties of the boron-manganese steel at elevated temperatures could be extracted based on a previous study by Å kerström and Oldenburg [7]. The stamping tools corresponded to rigid bodies, and their initial and constant boundary temperature corresponded to 40 C. A constant heat transfer coefficient of 6000 Wm À2 K À1 was used for the uncoated tool-blank interface, which coefficient was extracted from the work on a validated austenite decomposition model presented in [8]. The heat capacity was assumed as the same for the X40CrMoV5-1 tool material (see [9]), and the thermal conductivity of the tools was provided by the steel supplier as shown in Table 2.…”

Section: Simulation Of the Press Hardening Experimentsmentioning

confidence: 99%

Development of a Tribological Test Programme Based on Press Hardening Simulations

et al. 2017

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Press hardening is widely utilized to form ultrahigh-strength steels characterized by a high strength-toweight ratio for automotive components. Press hardening processes include heating boron-manganese steels to austenite phase, forming the steels at a high temperature, and cooling the formed blanks until the martensite phase is reached. However, press hardening processes lead to severe contact conditions between the blank and the tools including contact pressure, relative sliding, and high temperatures, which result in tool wear and increased maintenance cost. The contact conditions that occur in the stamping tool are difficult to study on site. Additionally, simplified tests, such as pin on disc and ball on disc, are insufficient to reproduce press hardening conditions in laboratory environments. The aim of this study includes developing a tribological test with press hardening conditions in which tool steel pins continuously slide on fresh and hot boron-manganese steel strips. The test programme mimics press hardening conditions with respect to sliding distance, sliding velocity, contact pressure, and surface temperature that were studied based on finite element (FE) simulations of a press hardening experiment. Furthermore, a FE simulation of the tribological test is established and it provides contact temperature in the pin tip with a high accuracy. A tribological test is used to study friction and mass loss with variational pressures and velocities that represented typically variational contact conditions in the press hardening. The tribological test is also used to obtain correlations between the tribological behaviours and process parameters in press hardening including pressure and sliding velocity.

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“…Several papers in the literature have investigated and reported the significant effect of the deformation on the final phase distribution during hot stamping [12][13][14][15]. The majority of early numerical models that have been developed for final phase distribution prediction during hot stamping have had limited success because of their inability to account for the effect of deformation [9,[16][17][18][19]. The predicted phase volume fractions by such models for a hot stamped part have been off by 30-40% in the regions with deformation.…”

Section: Introductionmentioning

confidence: 99%

“…Also, all the phase distribution prediction models that have been developed so far for tailored hot stamping process have used metallography and microhardness measurements for phase quantification during model development and validation [9,[16][17][18][19][20]. The final microstructure produced in boron steel after tailored hot stamping is a complex mixture of martensite, bainite and ferrite phases depending on the thermal and mechanical processing conditions [1,[6][7][8][9]20].…”

Section: Introductionmentioning

confidence: 99%

Artificial Neural Network (ANN) based microstructural prediction model for 22MnB5 boron steel during tailored hot stamping

Chokshi

Dashwood

Hughes

2017

Computers & Structures

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Abstract:Because of demand for lower emissions and better crashworthiness, the use of hot stamped 22MnB5 boron steel has greatly increased in manufacturing of automobile components. However, for many applications it is required that only certain regions in hot stamped parts are fully hardened whereas other regions need be more ductile. The innovative process of tailored hot stamping does this by controlling the localized microstructures through tailored cooling rates by dividing the tooling into heated and cooled zones. A barrier to optimal application of this technique is the lack of reliable phase distribution prediction model for the process.We present a novel Artificial Neural Network (ANN) based phase distribution prediction model for tailored hot stamping. The model was developed and validated using data generated from extensive thermo-mechanical physical simulation experiments and instrumented nanoindentation based phase quantification method. Advanced statistical techniques were used for preventing overfitting, for making the optimal use of available experimental data and for quantification of prediction uncertainty. The final predictions made by the ANN model during its independent validation have shown good agreement with the experimentally generated data and have a RMS prediction error of just 7.7%, which is a significant improvement over the existing models.

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Austenite decomposition during press hardening of a boron steel—Computer simulation and test

Cited by 119 publications

References 11 publications

Experimental characterisation of the effects of thermal conditions on austenite formation for hot stamping of boron steel

Experimental characterisation of the effects of thermal conditions on austenite formation for hot stamping of boron steel

Development of a Tribological Test Programme Based on Press Hardening Simulations

Artificial Neural Network (ANN) based microstructural prediction model for 22MnB5 boron steel during tailored hot stamping

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