Past GDIS™ Presentations

Currently Mubea uses micro-alloyed advanced high-strength steel (AHSS) to produce shape blanks and formed parts with variable gauges. Two new ideas will be presented to enhance the application of TRB®: 1st, Tailored Properties TRB® and 2nd, Work-Hardened TRB®.

For tailored properties the final TRB® blank will not only have different thicknesses along the part, the highest thickness plateau will also have higher mechanical properties. With this, Mubea can offer higher strength level than previously available, and a new degree of freedom will be achieved by having an additional parameter to vary with two different strength levels.

For the work-hardened solution the general idea is to skip the annealing step after flexible rolling. This opens multiple applications / routes, for parts with simple, limited drawn geometry; at first, this material option, thanks to the saving on the annealing operation, and to the adoption of a lower raw material grade to start from, constitutes a low-cost alternative when compared to regular TRB grades for cold forming. Second aspect, by using higher strength raw material, it’s possible to offer strength levels beyond the current highest material grade (HSLA CR500 grade current limit for TRB®).

AISI has recently completed a comprehensive study to highlight the advantages of steel bumper systems. This proposed presentation will compare the performance and technical cost of (2) efficient steel intensive solutions to a current contemporary aluminum design. In addition, a brief review of benchmarking data will be provided.

Ultra-high strength press hardened steels have quickly become important materials to consider in the vehicle light weighting process due to their superior strength and material down-gauge potential. In this research, the introduction of a hot stamped Usibor® 1500-AS to Ductibor® 1000-AS tailor welded part is considered in a demonstration structure, representative of a sport utility vehicle front end frame module.

The tailor welded hot stamped part is intended to replace the current 590 MPa tensile strength galvanneal coated sheet steel side frame main rails within the vehicle’s front end frame module. In a frontal crash situation the forward portion of the side frame member absorbs crash energy by crumpling along its length, reducing the deceleration felt by the occupant. The aft portion of the side frame member remains sturdy during the crash, protecting the occupant from intrusion of structural members. The proposed side frame main rails are hot stamped from a tailor welded blank (TWB), consisting of a Ductibor® 1000-AS crush tip (crash energy absorption) and a Usibor® 1500-AS high strength rear region (occupant compartment intrusion resistance).

The results of a numerical parametric study will be presented considering the side frame main rail to establish the mass reduction that can be achieved by replacing the 590 MPa strength baseline material with ultra-high strength hot stamped steels. Results from preliminary crash testing of the Ductibor® 1000-AS crush tip will also be presented.

The predominate material used in press hardening processes is AlSi-coated 22MnB5 material in the automotive industry to produce body structure components with tensile strength of approximately 1.5 GPa. The applications of the uncoated 22MnB5 material are very limited due to its surface oxidations during the hot stamping process.

Increasing the tensile strength and bendability of the press-hardened steel (PHS) material will enable lightweighting while maintaining crash protection. Considering the demand of new PHS for better oxidation resistance and further mass reduction, a new uncoated PHS, 20MnCr, is introduced in this paper. 20MnCr materials has slightly reduced carbon level, with chromium and silicon additions for oxidation resistance when compared to the conventional 22MnB5 material. This novel PHS material has an ultimate tensile strength of 1.7 GPa with bending angle above 55° at 1.4mm thickness. This steel is not pre-coated but possesses excellent oxidation resistance property at high temperature, thus eliminating the need for AlSi coating or shot blasting post processing of uncoated 22MnB5 to maintain surface quality.

Microstructural mechanisms used to enhance bendability and energy absorption are discussed for the novel steel. Performance evaluations such as: weldability, component level crush and intrusion testing and corrosion, are conducted on samples from industrial coils and its performances are compared with AlSi coated22MnB5 material.

Increasing automotive requirements for improved corrosion life on frames and chassis components have created a challenge for OEMs and suppliers to improve corrosion resistance of painted welds. This corrosion resistance is linked to the formation of surface silicates or “silicate islands” on the weld surface. These islands consist of multi-component oxides formed during the welding process via chemical reactions between the shielding gas and various deoxidizing elements in the base metal and welding consumable. The impact of these silicate islands on corrosion life stems from their non-conductive nature that interferes with the electrostatic painting process commonly utilized by the automotive industry.

In response to this issue, Lincoln Electric has developed a new solid wire and welding waveform that combine to provide a complete solution for lower surface silicate formation. This new wire, SuperArc® XLS, utilizes a unique mixture of deoxidizing and surface tension modifying elements to minimize surface silicate formation. The new waveform was developed specifically for the unique chemistry of SuperArc® XLS to improve droplet transfer and deliver a high speed, low spatter, low silicate weld for high volume production.

The purpose of this study was to compare paint adhesion and corrosion resistance of welds made with SuperArc® XLS versus welds made with an industry standard GMAW wire. All lap welds were completed with the same weld settings and environmental conditions, after which they were processed using a matrix of three different pre-treatments and two different final coating methods. The 12 distinct combinations of wire/pre-treatment/coating were then subjected to 120 cycles of a cyclical corrosion testing protocol. Results from this testing showcase the improvement in corrosion resistance between SuperArc® XLS and an industry standard GMAW wire.

Laser heat treating (LHT) on automotive stamping and trim dies has resulted in overall cost reductions, shorter processing times, improved quality. These improved results have resulted in multiple advantages for OEMs that use LHT when compared with OEMs treating identical dies with conventional methods. This paper highlights the technical aspects of LHT, cost saving and latest advancements associated with this process.

speed and distance, as well as tool and sheet material, surface finish and coating. The wear over the die radius primarily consisted of a combination of ploughing and galling mechanisms. The ploughing mechanism was found to occur over the entire blank contact region, with two distinct zones observed within the overall contact region. Tool die galling-induced failure occurs more likely at the severe contact pressure/small sliding distance conditions, which take place during the initial portion of the stamping process, showing to be critically important to the overall tool wear response. Therefore, degrees of ploughing- and galling-induced failures seem relevant to the die contacting radius (i.e., die/sheet contacting angles) during the stamping operating transient stage. This work is to develop a table-top inclined sliding tribometer which can change contact angles of die material/metal sheet from 0 to 20 degrees, contact pressure from 0 to 2 GPa and the sliding stroke distance from 0 to 100 mm. The instrument can have an index stage movement so that the sliding wear track is generated on a fresh metal sheet surface in each sliding stroke. A data acquisition system can record contact load, friction force and sliding distance, from which coefficient of friction (COF) and sliding energy can be calculated. Severe wear and galling occur when the COF is significantly increased. The wear behavior of die materials and metal sheets can be observed afterward. Those information is important for better understanding wear behavior at different contact angles and quite valuable for simulation of metal forming.

This presentation will summarize work of the Auto/Steel Partnership (A/SP) project, repairability of advanced high strength steels (AHSS). This project is focused on the evaluation of various weld repair processes and to provide joint test data for use by OEMs. The materials tested were MS1500, MS1700 and press-hardened steel (PHS). The team evaluated the following joining processes; resistance spot welding (RSW), metal inert gas (MIG) welding, MIG brazing and mechanical fastening. Production and service adhesives were also considered. The team utilized coupon test assemblies fabricated from various grades of AHSS. A variety of repair process joints were destructively tested. The test parameters included shear tension and cross tension quasi-static, shear tension fatigue, and cross-sections.

The resulting data can be used by OEMs to update repair process strategies using these advanced high-strength steels.

In conventional high strength steels niobium’s role is very evident: it provides grain refinement and precipitation hardening, both being the main mechanisms for strengthening such low-carbon HSLA steels. Advanced high strength steels, on the contrary, utilize a hard second phase being dispersed in a softer matrix for achieving an attractive combination of high strength and good ductility. Microstructural design on that basis has resulted in dual phase steels, complex phase steels and various forms of TRIP aided steels including 3rd generation steels. Despite that niobium initially has not been regularly alloyed to advanced high strength steels, it is nowadays widely used for optimizing their properties. Essentially, niobium is also refining the microstructure of advanced high strength steels resulting in a better homogeneity of phases, which improves bendability as well as the hole expansion ratio. Besides, niobium boosts the strength especially of the ferritic and bainitic phase by precipitation hardening. In ultra-high strength AHSS, the niobium carbide precipitates can also act as hydrogen traps and thus counteract delayed cracking. The presentation will give an overview of the so-far identified metallurgical effects of niobium in AHSS and will demonstrate the beneficial implications for processing in the mill and properties at the end user.

The Insurance Institute for Highway Safety (IIHS) has been conducting side impact crash tests since 2003. To understand how the side crashworthiness program can be enhanced, an ongoing research effort is focused on understanding the correlation between IIHS ratings and the driver death rate. In addition, the performance of good-rated late-model vehicles has been assessed in higher severity side crash tests. The objective of this study is to summarize the ongoing work and potential next steps toward developing a new crash test procedure or updating ratings criteria to further advance side crashworthiness. Analysis of real-world crashes indicates that tightening the rating criteria can potentially advance vehicle designs. Additionally, adopting a higher severity crash test may address additional real-world injury-causing crashes. Modifications to the IIHS MDB are needed for the 60 km/h test to be more representative of deformation and injury patterns caused by light truck vehicles (LTVs). This presentation will cover concluded research.

Vehicle lightweighting efforts to improve fuel economy require adequate material characterization and simulation tools to improve efficiency without compromising safety. With crash-induced deformation leading to complex stress states on the structural components, we focus the present investigation in the differences in fracture behavior of thin sheets under plane strain states of tension and bending. A numerical analysis is presented to compare the stress-strain response of VDA bending and in-plane notched tensile tests within the localized zone of deformation. The analysis suggests the significant stress state differences in bending and tension are mainly driven by the effects through the sheet’s thickness. These results offer an insight in the fundamental mechanisms contributing to the differences in fracture strain in bending and tension tests. As only one input value is possible for each triaxility level, the consequences of an apparent increase in ductility in bending (with respect to the in-plane tension) in the material characterization are discussed. The effects on the ability to reliably predict fracture in automotive crash and other large structures, commonly modelled using shell elements, are also mentioned.

Keywords: Ductile fracture modeling, material model, crash, shell mechanics, plane strain

Nearly all vehicles produced have front subframes, also referred to as engine cradles in front engine vehicles, which are considered a part of the vehicle suspension. Significant effort has been invested into reducing the mass of engine cradle assemblies. Many aluminum and aluminum/steel hybrid engine cradles are currently in production and carbon fiber prototypes have even been developed. Mass optimized steel engine cradles, on the other hand, receive less attention. Advanced high-strength steels (AHSS) are rarely used since engine cradles are primarily stiffness driven assemblies, and lightweighting manufacturing technologies, such as tailored blanks, are rarely employed. This presentation will take a closer look at mass reduction methods for optimized steel engine cradle designs and propose new lightweight steel designs with corresponding mass and cost estimates.

Use of press hardened parts in Body-In-White (BIW) structures has evolved in recent years to encompass wide range of part complexity, size and mechanical properties. In addition, the number of components per vehicle has also increased pushing demand for more capital investments. Suppliers of press hardened parts need to accommodate these changes while staying competitive. Advanced design of heat treatment furnace has to offer a unique furnace design that provides flexibility to handle future part sizes minimizes down time to increase line utilization and offers a unique solution to produce tailor tempered parts for crash performance.
This paper presents advanced innovative design of continuous roller furnace. These types of furnaces are generally used in hot forming lines. Design is focused on optimal heating layout, modern drives of rollers, new design and other items respecting the optimal technological and technical aspects. Also the technological functions like the dew point temperature regulation, oxygen rate regulation. All results are based on the theoretical background of heat and mass transfer, con-firmed by numerical Finite Element Method (FEM) analysis. Based on the long-time experiences with manufacturing and development of the machinery for the automotive industry, new roller furnaces were designed using modern methods including the FEM analyses for numerical simulations of heating processes and heating power distribution. The numerical solution of many mathematical problems involves the combination of external and internal conditions and different technological processes.

This presentation will summarize work of the Auto/Steel Partnership (A/SP) projects, Gas Metal Arc Welding (GMAW) of Advanced High Strength Steel (AHSS). This project is focused on the development and validation of 3rd Gen GMAW process for AHSS for use by the automakers. The Project Team identified (3) different AHSS grades for evaluation. Two GI coated materials were welded using gas metal arc welding techniques and the welds produced were tested using X-ray and quasi-static lap shear tensile tests. The other non-coated steels were welded using different fillers to evaluate differences in filler strength materials. Micro-hardness and metallurgical examinations were conducted to evaluate the welds. Lap tensile shear coupons for coated and uncoated steels were tested to determine tensile shear strength, fracture locations, and other weld metallurgical properties.
In general for 3rd Gen AHSS, coated steel is susceptible to Liquid Metal Embrittlement (LME). Based on observation, there is no concern under current welding procedures.

This presentation will summarize work of the Auto/Steel Partnership (A/SP) projects, gas metal arc welding (GMAW) of advanced high-strength steel (AHSS). This project is focused on the development and validation of 3rd Gen GMAW process for AHSS for use by the automakers. The project team identified (3) different AHSS grades for evaluation. Two GI coated materials were welded using GMAW techniques and the welds produced were tested using X-ray and quasi-static lap shear tensile tests. The other non-coated steels were welded using different fillers to evaluate differences in filler strength materials. Micro-hardness and metallurgical examinations were conducted to evaluate the welds. Lap tensile shear coupons for coated and uncoated steels were tested to determine tensile shear strength, fracture locations, and other weld metallurgical properties.

In general for 3rd Gen AHSS, coated steel is susceptible to liquid metal embrittlement (LME). Based on observation, there is no concern under current welding procedures.

This presentation describes a new method called generalized stress parameter (GSP) to predict fatigue life of gas metal arc weld joints (GMAW). GSP is based on the structural stress and the stress intensity factor and is based on a modified version of the Maddox equation. The structural stress accounts for the effect of global weldment geometry and the stress intensity factor captures the local effect of the weld angle and weld toe radius. Stress versus fatigue life (S-N) curve is developed using GSP and fatigue test results of various specimen configurations, material grades and thickness combinations. The developed S-N curve along with the GSP approach is used to predict the GMAW’s fatigue life of an actual OEM’s production control arm link subjected to variable amplitude loading. Laboratory tests of the above component subject to the same variable loading history are conducted. Comparison of the analysis results based on GSP and the test results revealed excellent correlation.

One of the driving principals of automotive engineering today is improving fuel efficiency thereby reducing carbon emissions. Many strategies have been implemented concurrently by the automotive OEMS such as improved aerodynamics and adopting alternative powertrains but the most widely implemented practice involves reducing vehicle mass. More than ever, innovative designs and light-weight materials are playing a significant role in enabling the engineering teams to design competitive vehicles that do not compromise performance. While offering various degrees of mass saving compared with traditional materials, rarely do these innovations integrate seamlessly into longstanding manufacturing and design practices. There are often headwinds associated with implementing new technologies. Examples of headwinds include complex manufacturing and assembly processes, additional equipment, new fastening schemes or unproven CAE modeling techniques.

MSC Smart Steel® is a new multilayer steel laminate engineered as a direct substitute for vehicle body parts stamped from low carbon steel. While offering up to a 35% mass save compared with same thickness standard steel, MSC Smart Steel® is produced as a coil, stamped in typical dies, spot welded with existing equipment and processed through standard electro-coat and paint systems – essentially minimal disruption to existing manufacturing systems. This is the first ever spot weldable low-density composite laminate to be used in a body application.

Following a five-year collaborative effort between Material Sciences Corporation and a strategic customer, MSC Smart Steel® is now validated for vehicle implementation and is going into production on multiple 2019 global platforms.

In support of a scientific foundation for the predictive design of composition and processing of quench and partition (Q&P) martensite/austenite TRIP steels, theory of coupled diffusional/displacive transformation is experimentally calibrated to control austenite carbon content and its associated mechanical stability. The calibrations are based on highly accurate experimental measurements using electron microscopy, high- energy x-ray diffraction and 3D atom probe tomography to quantify the amount and carbon content of retained austenite as a function of Q&P treatment. Varying the initial quench temperature to vary the initial retained austenite amount, it is demonstrated that carbon partitioning is affected by the direction of motion of the interface, favoring greater C partitioning for BCC->FCC motion. The variation in partition temperature is shown to have the maximum effect the austenite carbon content and its stability. The influence of processing parameters and alloy composition on the final Q&P microstructural characteristics are predicted via the developed mechanistic models and validated with a new series of experimental alloys. The effect of change in the microstructural features (phase composition, phase stability) on the mechanical properties would be discussed.