Monday, 19 June 2023
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4–6 p.m.
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Registration
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6 p.m.
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Reception
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Tuesday, 20 June 2023
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7 a.m.
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Registration and Breakfast
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8 a.m.
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Introductions and Opening Remarks
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8:05 a.m.
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Liquid Metal Embrittlement or Solid Metals-Induced Embrittlement of AHSS in the Manufacturing Process
Ming Shi, General Motors
Due to the unique and complex microstructures of AHSS, third-generation AHSS are more susceptible to new types of embrittlement during manufacturing and services such as liquid metal embrittlement (LME) during welding, liquid metal embrittlement and solid metal-induced embrittlement (SMIE) during manufacturing and services and hydrogen embrittlement during services. In this paper, a case study on the LME or SMIE is presented on an MS1500 martensitic sheet steel. A tube made from the MS1500 shows the LME or SMIE when the low-melting-point metals are in direct contact with the sheet metal after the e-coating and painting processes. Countermeasures of preventing LME or SMIE is also proposed and validated in the applications.
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8:30 a.m.
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On Local Formability/Ductility of New Advanced High-Strength Steels: Temperature, Bake Hardening and Strain Rate Effects
Jun Hu, Cleveland-Cliffs Inc.
Multiple advanced high-strength steels have been developed in recent decades to meet the needs of various automotive applications. Nevertheless, in some cases, cracking issues under practical forming conditions still limit the applications of these new AHSSs, despite the relatively high tensile elongations measured by laboratory test conditions. Accordingly, and inspired by the concept of the Local-Global Formability Chart, this work will be conducted to investigate and compare the true fracture strain (TFS) of a few representative new AHSS sheet samples and the possible TFS evolution by some critical application-based effects, such as temperature, bake hardening, and strain rate. The objective of this work is to highlight the importance of the local formability/ductility and provide the corresponding references to the future AHSS development strategy.
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8:55 a.m.
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LME Cracking Mitigation in Zn-Coated Advanced High-Strength Steel During Resistance Spot Welding
Jianxu Hu, Honda Development & Manufacturing of America LLC
In some cases, cracking issues under practical forming conditions limit the applications of new AHSSs, despite the relatively high tensile elongations measured by laboratory test conditions. Accordingly, and inspired by the concept of the Local-Global Formability Chart, this work will be conducted to investigate and compare the true fracture strain (TFS) of a few representative new AHSS sheet samples and the possible TFS evolution by some critical application-based effects, such as temperature, bake hardening and strain rate. Explanations and discussions of the material mechanisms based on the test results will also be presented. The ultimate objective of this work is to highlight the importance of the local formability/ductility.
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9:20 a.m.
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Multi-Part Integration Concepts Using Press-Hardened Steel Laser Welded Blanks
Nachiket Gokhale, ArcelorMittal Tailored Blanks NV
The automotive industry is undergoing a radical transformation from internal combustion engine (ICE) toward battery-electric vehicles (BEV). OEMs worldwide are addressing the sustainability challenges by developing multiple powertrain configurations (ICE, Hybrid, BEV) coupled with modular platforms. This requires reimagining the body architectures and assembly process.
Laser-welded blank technology for press-hardened steels (PHS-LWB) is a proven solution to optimize vehicle weight, performance and cost. Also, it reduces the carbon footprint in all stages of vehicle life cycle assessment (LCA). AMTB in collaboration with ArcelorMittal R&D will showcase PHS-LWB design concepts called Multi-Part Integration (MPI) concepts. This presentation will demonstrate how MPI designs help OEMs reduce the overall carbon footprint, reduce assembly time and cost, amplifying the traditional benefits of PHS-LWBs.
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9:45 a.m.
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Break
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10:10 a.m.
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New Coating Development for Press Hardening Steels
Constantin Chiriac, Ford Motor Co.
This study presents the development of a new coating for PHS as an alternative to the traditional aluminized AlSi10Fe3 coating that is currently used in the hot stamping process. The new coating was applied on a 22MnB5 steel substrate in a coil form and then subjected to an industrial trial to produce a high-volume production structural part for a current program. The new coating demonstrated a good resilience at high temperatures by suppressing the scale formation during heating in the furnace, a good heat transfer during die quenching by meeting the required mechanical properties for part specification and acceptable window process for RSW and e-coating performance without shotblasting after the hot stamping process.
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10:35 a.m.
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Strategies for Testing and Preventing LME for Third-Generation AHSS
Katharina Steineder, voestalpine Stahl GmbH
Liquid metal embrittlement (LME) currently represents the greatest threat in the large-scale application of third-generation AHSS. Therefore, a reliable testing tool that produces significant benchmark values to characterize LME is necessary. This contribution presents two options with different focuses to describe and quantify the phenomena, a spot welding test and a hot tensile test. Furthermore, by alloying with boron, a possibility of improving the robustness of a susceptible steel against LME is presented. Based on hot tensile tests and high-end analysis of grain boundary chemistry a hypothesis on the underlying mechanism is proposed.
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11 a.m.
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An Overview of Recent Advances in Zinc-Based Coatings for AHSS
Ana Paula Domingos Cardoso, International Zinc Association
This paper overviews recent advances in Zn-based coatings applied by hot-dip galvanizing (HDG) and other deposition processes on AHSS. Zn coating deposition on AHSSs has been a challenge because of their sensitivity to the segregation of surface-selective oxidizing elements that can be detrimental to coating adhesion. H embrittlement of Zn-coated AHSS can also affect user properties, including the risk of delayed cracking. The recent efforts on Zn coating processing and characterization to avoid this risk are discussed. Other reviewed topics include ZnAlMg coatings providing improved corrosion resistance, PVD coatings that reduce H embrittlement risks, and processing of coatings on hot press-formed steels that have sufficient Zn content to provide sacrificial protection to the steel substrate.
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11:30 a.m.
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Lunch
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12:30 p.m.
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Development of a Lean Single-Phase Nano-Precipitate-Strengthened SP590 Sheet Steel With Outstanding Formability: A DP590 Alternative?
Amar De, Big River Steel
A very-low-carbon Ti-microalloyed chemistry was selected to produce family of cold-rolled and batch-annealed high-strength, high-formable sheet steels through a continuous strip processing mill. The objective of the current product development was to develop a single-phase ferrite matrix with strengthening mostly derived from nano-precipitates of TiC. Chemistry and hot rolling processing were designed to result in very fine-sized TiC precipitates distributed homogenously in ferrite after hot rolling and coiling. A low annealing temperature was chosen to attain full recovery as well as full recrystallization of ferrite grains. Mechanical property evaluation indicated minimum yield strength development of 500 MPa with outstanding global as well as local formability. The sheet steel so developed excels in formability properties that is exhibited by sheet steels of similar strength.
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12:55 p.m.
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Back to the Roots: Production Concepts for Advanced Automotive HSLA Steels
Hardy Mohrbacher, NiobelCon bvba
Due to the microstructural homogeneity of single-phase ferrite structures, high-strength, low-alloy (HSLA) steels have particularly good local formability and better facilitate bending and stretch-flanging operations in comparison to dual-phase steels. The current contribution will present a concept of extending the yield strength range of cold-rolled HSLA steels above 500 MPa. This methodology utilizes optimized precipitation of microalloy carbides either prior to or during the annealing process in which recrystallization of ferrite is suppressed prior to partial or full austenitizing. The resultant microstructure achieves greater strengths than those traditionally produced for automotive applications of cold-rolled HSLA steels. The implications of mass adoption of such enhanced cold-rolled HSLA steels as well as the locus of achievable property combinations will be discussed.
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1:20 p.m.
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Characterization of Local Deformation and Fracture Behavior in Ferrite + Martensite Dual-Phase Steels With Different Grain Sizes
Myeong-Heom Park, Kyoto University
Low-carbon dual-phase (DP) steels composed of ferrite and martensite have been widely used in automotive industry due to their good strength-ductility balance and large strain hardening ability. In the present study, local deformation behavior and microvoid evolution were characterized using digital image correlation (DIC) technique with careful scanning electron microscope (SEM) observation of tensile-deformed microstructures. The coarse-grained DP specimen (28.9 μm) exhibited a strong strain-localization in ferrite grains, and several large-sized micro-voids were observed in the necked region. In contrast, the fine-grained DP specimen (11.8 μm) showed relatively homogeneous deformation only having small-sized microvoids. Such differences in local deformation behavior might contribute significantly to the change of post-uniform elongation.
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1:45 p.m.
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Toward Improving Cross-Tension Spot Weld Strength of Quenched & Partitioned Steel Spot Welds
Mohan Subramanian, Cleveland-Cliffs Middletown Works
Mechanical properties of resistance spot welds in quenched and partitioned (Q&P) steels have been shown to be reduced under traditional spot welding conditions. These challenges have been noted in both zinc-coated and uncoated grades during quasi-static tensile tests. Reduced spot weld strength of Q&P steels is primarily attributed to the brittle microstructure observed in the fusion zones of these spot welds. To improve the fracture toughness of Q&P 1180 spot welds, four different post-weld process modification parameters were added to the spot weld schedule. Compared to the baseline spot welds made without any process modifications, spot welds made with these four post-weld process modifications exhibited 30–60% increase in the cross-tension spot weld strength. Microhardness tests, microstructural characterizations and elemental segregation analyses were performed on these spot welds to understand the underlying microstructural evolutions that resulted in an increase in the spot weld strength of Q&P steels. Results indicate reduction of phosphorus segregation at the edge of fusion zone has been the predominant strengthening mechanism that resulted in maximizing the strength/ductility of spot welds.
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2:10 p.m.
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Comprehensive Analysis on Quenching and Partitioning on a 30MnV6 Microalloyed Steel
Marco Belfi, Politecnico di Milano
Characterization of the effect of different quenching and partitioning treatments on retained austenite (RA) stabilization on the final microstructure and on tensile properties was performed on a 30MnV6 microalloyed steel. The amount of RA and its location into the final microstructure were evaluated through x-ray diffraction (XRD) and electron backscatter diffraction (EBSD). Moreover, different initial microstructural conditions were employed to investigate the effect of a starting mixed austenite-ferrite microstructure on the effectiveness of the treatment, in order to tailor the material final tensile properties according to its actual utilization.
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2:35 p.m.
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Deformation-Induced Martensitic Transformation at Tensile and Compressive Deformations of High-Carbon Bainitic Steel
Rintaro Ueji, National Institute for Materials Science
Deformation-induced martensitic transformation (DIMT) during tensile or compressive deformation of the high-carbon bainitic steel was studied. The microstructure before the deformation was bainite with the retained austenite whose volume fraction was 35%. The tensile deformation is accompanied by more significant work hardening than compression. This was due to the suppression of DIMT at the compressive deformation, confirmed by both measurements of the electron backscatter diffraction (EBSD) and the in-situ neutron diffraction at J-PARC. It was also found that the increasing lattice strain at austenite by tensile deformation retarded with the DIMT, while this retardation was not found at the compression. These results indicate the significant dependence of the DIMT on the polarity of deformation in the high-carbon bainitic steel.
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3 p.m.
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Break
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3:25 p.m.
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The Influence of Testing Parameters on Hole Expansion in 980 MPa Steel
Su Liu, ArcelorMittal Global R&D – East Chicago
The impact of cutting clearance on hole expansion ratio was studied in a galvanized third-generation advanced high-strength steel containing retained austenite with an ultimate tensile strength greater than 980 MPa. Varying cutting clearances from 6 to 28% for the punched hole were made on a 1.6-mm sheet followed immediately by hole expansion testing. An optimal cutting clearance delivering the highest hole expansion was identified at 22% cutting clearance, much greater than the standard 10–12% cutting clearance. Furthermore, the influence of time after punching was studied as well by testing at 24 and 48 hours after hole punching. The role of the microstructure was further examined at select cutting clearances and to be discussed.
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3:45 p.m.
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Evaluation of Aging and Zn-Coating Effects on Sheared Edge Formability in Sheet Steels
Aiden Carley-Clopton, Colorado School of Mines
Sheared edge ductility is a critical factor to consider for formed advanced high-strength steel parts. Previous studies have found that hole expansion ratio (HER) decreases with room temperature aging for a variety of steel grades. The current study examines this phenomenon in five grades of sheet steel with varying strength levels and microstructures. Additionally, the effect of hot-dip Zn coatings was evaluated using a DP800 steel annealed at different dewpoints and then hot-dip galvanized or left in the bare condition.
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4:10 p.m.
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A Study of Hole Expansion Ratio on 780-MPa-Grade Advanced High-Strength Steels
Sukjin Lee, Hyundai Steel
Current demands for weight reduction to improve fuel efficiency and to reduce emission without sacrificing passengers’ safety in automotive chassis parts have increased application needs of AHSS such as dual-phase steels (DP), ferrite-bainite steels (FB) and complex-phase steels (CP). However, these steels often encounter edge cracking phenomena occurring in sheet flanges during press-forming procedures, although such problems do not arise for mild steels. Limiting criteria below which steel sheets should not be failed during stretch flanging operations are generally expressed as HER evaluated from hole expansion tests. In this study, recent progresses on HER were discussed in relation with aspects of fundamental deformation and punch geometries and were correlated with basic tensile properties and steel microstructures.
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4:35 p.m.
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Effects on Microstructure on hole Expansion Ratio of AHSS
Fusheng Sun, Cleveland-Cliffs Inc.
Different microstructures of AHSS show various mechanical property, HER and damage mechanisms. In this research, effects of microstructures on HER were studied on multi-phase (MP), and CP AHSS, such as MP780, MP980, and CP980. In contrast to global formability depending on uniform elongation, HER of AHSS is most governed by its local crack growth resistance, not significantly by strength and elongation. The microstructures of AHSS have significant impact on the HER. The detailed effects of rolling bandings and microstructure, such as microtextures, bainite, martensite, and grain sizes on the HER are discussed in this paper.
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5:30 p.m.
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Reception
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Wednesday, 21 June 2023
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7 a.m.
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Breakfast
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8 a.m.
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Introduction and Opening Remarks
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8:05 a.m.
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Effect of Steel Subsurface Structure on the Liquid Metal Embrittlement Behavior of Third-Generation Advanced High-Strength Steels
Anirban Chakraborty, ArcelorMittal Global R&D – East Chicago
To obtain excellent reactive wetting behavior during galvanizing operation, steels are annealed at atmosphere having a high partial pressure of oxygen (pO2). This annealing atmosphere produces excellent wettable surface and promotes steel subsurface structure containing decarburized layer along with network of internal oxides. It is well known that Zn-coated 3G-AHSS is susceptible to LME during the assembly welding and limiting its application in the automotive industry. The present study is focused on the effect of steel subsurface structure on LME behavior of 3G-AHSS. For this purpose, industrially produced full hard steel samples were annealed in an atmosphere which produced reactively wettable surface followed by galvanized.
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8:30 a.m.
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The Effect of a Si Reduction and Substitution on the LME Sensitivity of Third-Generation AHSS
Matthias Wallner, voestalpine Stahl GmbH
Based on laboratory melts containing 0.2% C, 3% Mn and different ratios of Si:Al, the LME sensitivity of AHSS was investigated; thereby the focus of the research lay on the effect of a substitution of Si by Al. Hot tensile tests were performed to simulate the fast heating, temperature and stress occurring during welding. From these tests, the ductility loss due to LME was measured. Furthermore, spot welding with prolonged welding time was also performed whereby the crack lengths were measured. To get a better knowledge of the influence of Si and Al on the Zn-Fe phase formation in equilibrium state, Thermo-Calc© calculations have been performed.
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8:55 a.m.
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Influence of Paint Baking on Microstructure and Mechanical Behavior of Resistance Spot Welds
David Marshall, Colorado School of Mines
The automotive paint-baking cycle has been reported to improve mechanical properties of Gen3 welds while DP welds are unaffected. To understand these different behaviors, Gen3 and DP welds were heat treated to simulate the subcritical, intercritical and upper critical heat-affected zone (HAZ) microstructures. Specimens were tested in unbaked and baked conditions. Simulated HAZ microstructures were compared to weld microstructures. Mössbauer effect spectroscopy was used to quantify fractions and carbon contents of carbide and retained austenite pre- and post-baking. The results suggest that a difference in tempering response of the intercritical HAZ microstructure in DP and Gen3 spot welds may explain the sensitivity of Gen3 welds and the insensitivity of DP welds to baking.
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9:20 a.m.
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Development of a High-Mn-Containing PHS for LME Resistance
Joseph McDermid, McMaster University
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9:45 a.m.
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Hydrogen Embrittlement of Ultrahigh-Strength Steels for Automotive Application: Risk Assessment and Mitigation
Dominique Cornette, ArcelorMittal Global R&D Gent
It is well known that delayed failure is due to a combination of critical diffusible hydrogen contained in the material and an applied or residual mechanical stress for a given metallurgy. This presentation gives an overview of the different mechanical tests and medium generally used for the introduction of hydrogen. As local diffusible hydrogen is difficult to quantify, stress corrosion cracking (SCC) tests are generally preferred instead of trying to position critical level of diffusible hydrogen versus hydrogen coming from the environment. Cyclic corrosion tests have been defined for corrosion status equivalency with natural exposure.
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10:10 a.m.
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Break
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10:35 a.m.
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Evolution of Phase Transformations and Mechanical Properties During Hot Stamping Operations
Garret Angus, Cleveland-Cliffs Research & Innovation
The understanding of how the steel alloys perform during hot stamping is critical to both steelmaker as well as the producer of the hot-pressed component. Microstructure evolution, mechanical properties and the overall physical quality of the hot-stamped component are sensitive to the thermal history. Significant data for time-temperature transformation relationships exists; however, generally the data has been generated using linear cooling rates. In practice, cooling profiles achieved during the process are more complex than the near linear profiles. This research aims to better understand the phase transformation of hot-stamped steels by designing thermal profiles based on a mix of transfer times and-die to-part contact pressure.
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11 a.m.
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Optimization of Heat Treatment of PHS1500 Steel With Galvannealed (GA) Coating During Hot Stamping
Henrique Lacerda Eleuterio, USIMINAS
In this study, modified galvannealed (GA) boron steel samples were heat treated and hot stamped on a laboratory scale. The influence of austenitizing heat treatment on the stability of GA coating and steel was assessed by modifying process parameters. The excellent surface quality of the coating and hot-stamped parts free of cracks resulting from LME were obtained by increasing the heating rate and soaking temperature. Microstructural evolution of GA coating and structural integrity of steel during the hot stamping process were investigated. It was possible to quantify the coating evolution during hot forming, to understand the effect of these heating rates on the product properties and to establish an optimized heat treatment for hot stamping of this steel.
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11:25 a.m.
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Design of Hot-Stamped High-Strength Steels Through Process Optimization to Enhance Their Hydrogen Embrittlement Resistance
Markus Uhlirsch, SWERIM AB
The use of hot-stamped advanced high-strength sheet steels (HS-AHSS) with strengths over 1,800 MPa in automotive applications is limited. This is mainly due to the risk for hydrogen embrittlement (HE). To mitigate this risk, these steels can be designed to contain vanadium carbides (VC), which are able to immutably trap hydrogen. Design of HS-AHSS with VC requires optimization of the conventional manufacturing and processing route of these steels. This work aimed to optimize the VC as a function of coil annealing temperature using Gleeble® simulations. The results helped to understand the influence of coiling temperature on the VC type and their capability for hydrogen trapping.
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11:50 a.m.
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Effect of Rapid Heating on Microstructure and Mechanical Properties of Advanced High-Strength Steels
Eliseo Hernandez, Cleveland-Cliffs Middletown Works
The rapid heating of steels has come under the spotlight over the last two decades. The promising developments of rapidly heated steels stem from the short times involved during the thermal treatment path by applying heating rates of three orders of magnitude and the formation of grain-refined multi-phase microstructures after quenching. However, the requirements for combinations of strength, ductility and formability intended for several crash resistance components cannot be obtained just via rapid heating followed by direct cooling to room temperature. Hence, this work studies the effectiveness of rapid heating combined with quenching and partitioning and “austempering” treatments for developing advanced high-strength steels.
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12:15 p.m.
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Lunch
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1:15 p.m.
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Critical Assessment of Equations Describing the Relations Between Lattice Parameters and Carbon Content for Both Unstrained Austenite and Compressed Austenite
Stefan van Bohemen, Tata Steel Europe Ltd.
Literature shows various expressions for the relationship between the austenite lattice parameter and carbon content. Two groups of relationships can be identified, namely for unstrained austenite and compressed retained austenite in quenched steels. The carbon dependence of the lattice parameter in unstrained austenite was investigated through experiments at high temperature by Onink et al. These high-temperature data are re-analyzed using a more accurate formulation for the thermal expansion of austenite. The obtained equation for unstrained austenite is compared to the widely used equation for compressed austenite in a martensite matrix, which represents the most extreme case of compression.
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1:40 p.m.
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Numerical Investigations of Interface-Controlled Phase Transformations During Intercritical Annealing of DP Steels
Clélia Couchet, Universite de Lorraine
Austenite formation kinetics during intercritical annealing of various steels have been simulated. The interface conditions were studied in multi-constituent systems. A regime transition from no partitioning local equilibrium to partitioning local equilibrium occurs at the beginning of the holding stage. Austenite formation kinetics are found to be highly sensitive to substitutional partitioning during the holding stage. For instance, silicon partitioning in ferrite strongly slows the austenite formation kinetics. The simulated austenite fraction is close to the fraction determined by in-situ high-energy x-ray diffraction experiments. Based on these simulations and Wycliffe’s work, a simplified phase transformation model has been developed that reproduces the local composition profiles and global transformation kinetics with high fidelity.
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2:05 p.m.
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A Study of the Carbon Distribution in Bainitic Ferrite
Colin Scott, CanmetMATERIALS
The carbon distribution in bainitic ferrite (BF) of two carbide-free bainite alloys isothermally transformed at three different temperatures was studied using a unique combination of in-situ high-energy x-ray diffraction (HEXRD), atom probe tomography (APT) and electron energy loss spectroscopy. Results from all three techniques are consistent and unambiguously confirm the presence of significant excess carbon levels in BF, even in these low nominal carbon (0.22 wt.%) steels. The carbon concentration in BF decreases as the transformation temperature increases, but remains significant up to 430°C. Further, statistical analysis indicates that the excess carbon content does not follow a normal distribution.
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2:30 p.m.
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An In-Situ Study of Neighborhood Effects on Mechanical Stability of Retained Austenite and Mechanical Behaviors of Deformation-Induced Martensite in a Multi-Phase TRIP Steel
Jiyun Kang, Massachusetts Institute of Technology
This work will explore the effects of the microstructural neighborhood on the mechanical stability of retained austenite and the mechanical behaviors of mechanically induced martensite using ferrite-containing QP steel as a model alloy. High-resolution in-situ SEM/EBSD characterization and in-situ synchrotron XRD tensile tests are performed to quantitatively evaluate the local and global deformation of this alloy. Comprehensive screening of potentially competing microstructural parameters, including composition, orientation and orientation relationships, is presented. The results demonstrate a strong influence of micromechanical neighborhood effects, suggesting the important role of ferrite in controlling the transformation.
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2:55 p.m.
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Laser Ultrasonics-Based Microstructure Design of Advanced Steels
Matthias Militzer, University of British Columbia
Microstructure engineering is a critical aspect for thermomechanically controlled processing of advanced high-strength steels. In-situ laser ultrasonics for metallurgy (LUMet) is a powerful tool to monitor austenite grain growth, recrystallization and austenite decomposition during thermomechanical laboratory simulations to expedite the development of microstructure process models. This approach will be illustrated for low-carbon steels with complex ferrite-bainite and/or ferrite-martensite microstructures. A particular emphasis will be on the continuous recording of austenite conditioning and subsequent decomposition to design robust runout table cooling strategies for obtaining target fractions of transformation products in hot-rolled products.
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3:20 p.m.
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Break
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3:45 p.m.
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Key Technologies Meeting UHSS and Third-Generation AHSS CAL/CGL Processing Challenges
David Barbier, Fives KEODS
The continuous development of UHSS and the emergence of third-generation AHSS are giving perspectives for massive lightweighting of body-in-white structural applications and remain a key differentiator for future electrical mobility efficiency improvement. Their manufacturing imposes, however, additional constraints compared to conventional alloys due to their high alloying content and complex metallurgical cycles, including high soaking temperatures and cooling rates during annealing step or hot dip coatability issues. Moreover, these constrains challenge continuous annealing line and continuous galvanizing line operations in terms of heat treatment flexibility in a context of increasingly complex product mix. Such metallurgical and operational challenges can now be overcome thanks to newly developed technologies whose advantages and features will be further presented.
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4:10 p.m.
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Effect of Chemical Composition on the Microstructure and Properties of As-Cast AHSS Slabs
Bryan Webler, Carnegie Mellon University
The chemical composition of AHSS grades is carefully designed to achieve specific microstructures and properties in the fully processed condition. The level of alloy additions can lead to challenges in upstream processing. This work focuses on as-cast AHSS slabs, which can exhibit cracking at temperatures below about 400°C. Previous work has shown grades with elevated levels of Mn and Si exhibit a ductile-to-brittle transformation in this temperature range. This work will examine as-cast steels with 0.2 wt.% C, 3 wt.% Mn and varying levels of Si, Al, and Si+Al. The differences in microstructural features and mechanical behavior will be discussed.
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4:35 p.m.
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ANDRITZ Metals, HXT® Knife Technology for Shearing Advanced High-Strength Steel
Brian Shaw, ANDRITZ Metals USA Inc.
As AHSS grades have evolved in recent years, equipment limitations for processing AHSS grades have been uncovered. ANDRITZ Metals initially addressed the limitations of shearing AHSS by developing the HXT technology for ASKO rotary knife applications that include sidetrimmers on pickle lines and coil finishing lines, and coil slitting operations. The latest advancements in AHSS are now demanding that this HXT technology be adapted for the fracture mechanics of straight shear knives and scrap chopper knives. Successful in-service trials have shown that straight shear knives with HXT edge technology applied to them are now able to significantly exceed the knife performance of standard knives when shearing AHSS.
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5:00 p.m.
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Advantages of Horizontal Single-Belt Casting in the Casting of Advanced High-Strength Steels (AHSS)
Mihaiela M. Isac, McGill University
Horizontal single-belt casting (HSBC) is an emerging near-net-shape-casting process for producing thin slabs of steel directly from the molten state, prior to reduction. Due to the nature of this process, it possesses significant advantages compared to conventional continuous casting methods for producing AHSS alloys. For such steels, where the strong work-hardening effects of these Hatfield-like steels preclude the use of conventional hot rolling mills, the HSBC process would only require a five- to tenfold reduction in gauge, versus an impossible three-hundredfold reduction requirement for traditional rolling mills, without a series of interspersed annealing steps. In the present work, the cast and final microstructures of selected twinning-induced plasticity and transformation-induced plasticity steels produced via HSBC was accomplished using a pilot-scale HSBC system.
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5:25 p.m.
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Effect of Specimen Preparation Method on Edge Quality, Tensile Properties and Fracture Mechanism of an Advanced Dual-Phase Steel Grade
Almila Gulfem Ozgultekin, Borcelik Celik Sanayi Ve Ticaret A.S.
Increasing demands of the automotive industry on safety performance and lightweighting in the last decades have led to the widespread application of advanced high-strength steels (AHSS) in the manufacturing of body-in-white components. Amongst many AHSS families, dual-phase (DP) grades constitute a desirable class for material replacement purposes of part manufacturers due to their high strength-ductility combination, better formability assets, and adaptability to the structural design of critical components. Nevertheless, successful steps toward the implementation of these new-generation materials require dedicated mechanical testing and the identification and integration of appropriate specimen preparation methodologies beforehand. In this study, the links between the specimen preparation approach, sample edge effects, and mechanical performance were investigated.
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6–9 p.m.
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Reception/Dinner
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Thursday, 22 June 2023
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7 a.m.
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Breakfast
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8 a.m.
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Introductions and Opening Remarks
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8:05 a.m.
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Influence of Alloy Composition and Thermomechanical Schedule on Microstructure and Tensile Properties of Dual-Phase Steels
Hany Khalifa, EZZ Group
Dual-phase steel offers a combination of distinguishing tensile properties as it possesses low yield strength and a high tensile strength. Thermomechanical-controlled processing (TMCP) in hot strip mill (HSM) is an economical and mass production industrial technique for manufacturing direct hot-rolled DP steel. The current work applied well-analyzed parameters of TMCP to develop tailored microstructure and tensile properties of direct hot-rolled DP steels in accordance with the capacity and layout of HSM. Physical simulation technique is utilized to simulate the TMCP. Coloration of the parameters of TMCP with the microstructure and tensile properties of DP steels is investigated in the current work.
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8:30 a.m.
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Effect of Mn-Enriched Cementite on Austenite Formation During Intercritical Annealing
Josh Mueller, Los Alamos National Laboratory
Cementite dissolution kinetics are expected to alter the manganese (Mn) concentration distribution within austenite that forms during intercritical annealing (IA) of medium‑Mn steels. The cementite effects have been previously documented through in-situ high‑energy x‑ray diffraction measurements of austenite fractions during intercritical annealing, with complementary DICTRATM simulation results that predicted slow dissolution of cementite while austenite growth occurred by means of a Mn‑diffusion-controlled transformation. The present work expands this discussion by presenting a combination of scanning electron microscopy, energy-dispersive x-ray spectroscopy, and Thermo-Calc® assessments of a Fe‑0.2C‑4.5Mn steel.
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8:55 a.m.
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The Effect of Serration Behavior on Strain Hardening and Deformation in 22Mn-0.6 Steel
Sukyoung Hwang, Kyoto University
High-Mn austenitic steels are well known for their high strain-hardening ability and outstanding mechanical properties, which is attributed to the twinning-induced plasticity (TWIP) effect. On the other hand, carbon-containing high-Mn austenitic steels show serration behavior on their stress strain curves. Despite the significant progress in understanding the TWIP effect in high-Mn austenitic steels, the role of the serration behavior on mechanical properties, especially strain hardening, has not yet been clarified. The present study aims to clarify the mesoscopic nature of serration behavior accompanying heterogeneous deformation characterized as the propagation of strain localized bands called Portevin–Le Chatelier (PLC) bands in high-Mn austenitic steel.
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9:20 a.m.
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Strain Rate and Temperature Dependence of Dynamic Recrystallization in a Lightweight FeMnAl Steel With Nickel Additions
Rogerio Antao Cardoso, Missouri University of Science and Technology
High-manganese austenitic steels with aluminum and nickel additions can achieve strength-to-weight ratios that are higher than titanium alloys while retaining excellent ductility. This study reports on the dependence of the flow stress and grain size on the dynamic recrystallization of a Ni-containing austenitic-based Fe-Mn-Al-C steel. Steels underwent solution heat treatment at 1,200°C for 2 hours followed by hot rolling process. Cast material with larger grains went through the same heat treatment, followed by water quenching. Single-hit compression tests on cylindrical specimens were performed under the strain rates of 0.01, 0.1 and 1 s-1 at 900, 1,000, 1,100 and 1,200°C, respectively, using a quenching/deformation dilatometer.
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9:45 a.m.
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Weldability Investigation on Lightweight Steels
Giacomo Villa, Politecnico Di Milano
A novel class of AHSS for the automotive sector is under development. Such steels are featured by high Mn and Al content, low density and high mechanical properties. Due to the very high content of alloying elements and their nature, it is possible to forecast criticalities in such process, like extremely high Ceq content, abnormal grain growth and k-carbides excessive precipitation. Such carbides are exploited for their strengthening effect in case of coherent carbide intragranular precipitation, but they have detrimental effect in case of intergranular precipitation. An austenitic lightweight steel alloy has been tested with different welding techniques and different material starting conditions. Microstructure and mechanical properties of the joints have been investigated.
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10:10 a.m.
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Break
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10:35 a.m.
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Medium-Manganese FeMnAlSiC Advanced High-Strength Steels
Alan Druschitz, Virginia Tech
FeMnAlSiC steels with chemistries in the range of 7.5–8.8 wt.% Mn, 1.0–2.0 wt.% Al, 1.5–2.0 wt.% Si, 0.30–0.75 wt.% C can be heat treated to produce nearly single-phase (austenite) or multi-phase (austenite plus ferrite) microstructures. The austenite plus ferrite microstructures have significantly higher hardness and higher yield strength compared to the nearly single-phase austenite microstructures. The chemistries of these steels were designed to produce TWIP and/or TRIP by adjusting the stacking fault energy of the austenite. In this study, four heats of FeMnAlSiC steels were investigated.
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11 a.m.
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TBD
Mathias Lamari, Universite de Lorraine
This presentation discusses a mean field micromechanical framework aimed at describing the tensile behavior of medium-Mn steels with austenite-ferrite-martensite microstructures. It is based on the description of the local behavior of each constituting phases and of the possible strain-induced martensitic transformation of retained austenite. The work hardening of both austenite and ferrite are modeled thanks to a size-sensitive model adapted from Mecking-Kocks-Estrin scheme including a kinematic hardening contribution. The parameters of the model have been calibrated on phase stresses determined along in-situ high-energy x-ray diffraction experiments coupled with DIC.
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11:25 a.m.
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Texture and Anisotropy Study on a Lightweight Steel
Giacomo Villa, Politecnico Di Milano
High-Mn and high-Al steel alloys are a class a steel on which there is wide and ongoing research. The main reasons are their light weight and high mechanical properties. This class of steels is featured by the precipitation of peculiar type of carbides, which can have a beneficial effect on the mechanical properties if they precipitate intragranularly in the austenite matrix. To exploit such strengthening effect, different thermal treatments have been studied and performed on an austenitic lightweight steel alloy. The evolution of the anisotropy and the texture in different condition have been studied considering different thermomechanical conditions.
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11:50 p.m.
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Lunch
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1 p.m.
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Microscopic Strain Path and Plastic Strain Heterogeneity in Multi-Phase Steels
Hyunseok Oh, University of Wisconsin – Madison
Deformation-induced microstructural strain localization is an important process affecting various mechanical properties of multi-phase steels. Micro-digital image correlation, an in-situ deformation experiment performed inside scanning electron microscopy, has been actively carried out to experimentally measure local strain and find a relationship with surrounding microstructure in steels. However, due to the complexity of the strain localization patterns, most studies investigate this phenomenon qualitatively. This presentation will introduce statistical methodologies for analyzing strain localization patterns, which can provide two new pieces of information: microscopic strain path and plastic strain heterogeneity. The new proposals help more deeply investigate the deformation micromechanisms of multi-phase steels, such as DP980 steel and martensitic stainless steel with reverted austenite.
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1:25 p.m.
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Application of Quenching and Partitioning Treatment and its Effect on Initiation Fracture Toughness in AISI 4140 Steel
Marco Belfi, Politecnico di Milano
Feasibility of quenching and partitioning on 4140 steel was investigated through the design and application of multiple single-step treatments. The treated material was characterized both regarding the microstructure (SEM) and the mechanical properties through tensile tests. XRD and EBSD analyses were conducted to evaluate the presence and the amount of retained austenite obtained. The designed treatments were reported to effectively introduce a fraction of retained austenite in the final microstructure, increasing the tensile properties with respect to a conventional quenching and tempering treatment, but maintaining good values for the elongation at break. In addition, fracture mechanics tests were performed in order to investigate the effect of presence and amount of RA on the toughness of the material.
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1:50 p.m.
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Study the Low-Cycle-Fatigue Behavior of Low-Carbon Multi-Phase Steel Developed Through Quenching and Partitioning Method
SK MD Arif, National Institute of Technology Durgapur
In this present investigation, low-carbon microalloyed steel was developed through Q&P treatment comprising austenitizing at 900°C for 30 minutes followed by quenching and partitioning at 300°C for 10 minutes. The treatment was applied to obtained multi-phase microstructure consisting of martensite, tempered martensite and retained austenite. Optical microscopy and scanning electron microscopy were applied, showing a microstructure consisting of a martensitic-bainitic matrix with finely distributed RA islands and some carbide. Experimental measurements show that the maximum volume fraction of RA can reach 0.10–0.20 depending on chemical composition.
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2:15 p.m.
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Conference Wrap-Up and Adjourn
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