Engineering Carbide-Free Bainitic Steels with High Silicon for Superior Strength and Toughness

NOVEMBER 2-4, 2025 NANJING, JIANGSU PROVINCE, CHINA THE 9th INTERNATIONAL CONFERENCE ON HIGH STRENGTH LOW ALLOY STEELS PROCEEDINGS HSLA Steels 2025 Organized by The Chinese Society for Metals (CSM) Co-organized by Nanjing Iron & Steel Co., Ltd. Supported by CBMM | Niobium Vanitec-CISRI Vanadium Technology Center The Vanadium International Technical Committee (VANITEC) CITIC Metal Co., Ltd. State Key Laboratory of Metallic Materials for Marine Equipment and Applications Committees Organized by The Chinese Society for Metals (CSM) Co-organized by Nanjing Iron & Steel Co., Ltd. Supported by CBMM | Niobium Vanitec-CISRI Vanadium Technology Center The Vanadium International Technical Committee (VANITEC) CITIC Metal Co., Ltd. State Key Laboratory of Metallic Materials for Marine Equipment and Applications Conference Structure Honorary Chairman Yuqing Weng, The Chinese Society for Metals Conference Chairman Xiaogang Zhang, The Chinese Society for Metals Conference Vice Chairmen Zhiling Tian, The Chinese Society for Metals Chengjia Shang, University of Science & Technology Beijing International Advisory Board Harry Bhadeshia, University of Cambridge, UK Wolfgang Bleck, RWTH Aachen University of Technology, Germany Julie Cairney, The University of Sydney, Australia Tadashi Furuhara, Tohoku University, Japan Junyan Fu, CITIC Metal Co., Ltd., China Robert (Bob) Glodowski, RJG Metallurgical LLC, USA Xinping Mao, University of Science & Technology Beijing, China Rafael Mesquita, CBMM | Niobium, Brazil John Speer, Colorado School of Mines, USA Fumitaka Tsukihashi, The University of Tokyo, Japan Guodong Wang, Northeast University, China Fucheng Zhang, North China University of Science and Technology, China International Scientific Committee Chairmen: Aimin Guo, CITIC Metal Co., Ltd., China Caifu Yang, Central Iron & Steel Research Institute Company Limited, China Members: Frank John Barbaro, University of Wollongong, Australia Shaohui Chen, Jiangsu Shagang Group, China David Crowther, Vanitec Ltd., UK Haiwen Luo, University of Science & Technology Beijing, China Mingxin Huang, The University of Hong Kong (HKU), HK, China Hardy Mohrbacher, NiobelCon bvba, Belgium Jitendra Patel, International Metallurgy Ltd., UK Elena Pereloma, University of Wollongong, Australia Mingliang Qiao, Nanjing Iron & Steel Co., Ltd., China Jose-Maria Rodriguez-Ibabe, CEIT, Spain Qingyun Sha, Ansteel Group, China Colin Scott, CanmetMATERIALS, Canada Dong-Woo Suh, POSTECH, Korea Jing Wang, Hunan Iron & Steel Group Co., Ltd., China Guosen Zhu, Shougang Group Co., Ltd., China Li Wang, China Baowu Group, China Kaiming Wu, Wuhan University of Science and Technology, China Wei Xu, Northeast University, China Jian Yang, Shanghai University, China Zhigang Yang, Tsinghua University, China Guo Yuan, Northeast University, China Hongliang Yi, Northeast University, China Caidong Zhang, HBIS Group Co., Ltd., China Secretary-General Xinjiang Wang, The Chinese Society for Metals Deputy Secretary-General Zhongzhu Liu, CITIC Metal Co., Ltd., China Xuehui Chen, Central Iron & Steel Research Institute Company Limited, China Preface This is a collection of papers presented at the 9th International Conference on High Strength Low Alloy Steels (HSLA Steels 2025). HSLA Steels 2025 is organized by The Chinese Society for Metals, co-organized by Nanjing Iron & Steel Co., Ltd. and supported by CBMM | Niobium, CITIC Metal Co., Ltd., Vanitec-CISRI Vanadium Technology Center, Vanitec Ltd. and State Key Laboratory of Metallic Materials for Marine Equipment and Applications. The HSLA Steels conference series has been successfully organized by The Chinese Society for Metals in Beijing (1985, 1990, 1995, 2011, 2022), Xi’an (2000), Sanya (2005) and Hangzhou (2015) since 1985 and grown into the leading platform for scientific and technological exchange in HSLA Steels. With an initial submission of more than 150 abstracts from 12 countries for HSLA Steels 2025, after peer review process there are 50 papers published in these proceedings, which cover the following fields: (1) Physical Metallurgy (2) Products for Automotive, Infrastructure and Maritime Industry (3) Performance, Safety and Application (4) Process Technologies for High Quality Products. We would like to express our sincere gratitude to the International Advisory Board and Scientific Committee for their valuable suggestions and support. We are very grateful to Mr. Xin Zhao and Ms. Fang Liu from CSM, Dr. Zhongzhu Liu, Dr. Guodong Zhang and Dr. Yongqing Zhang from CITIC Metal, Dr. Tao Pan, Dr. Xuehui Chen from CISRI, Dr. Zhenjia Xie from USTB, Dr. Linheng Chen, Dr. Yi Fan and Ms. Xiaohui Wu from Nanjing Iron & Steel Co., Ltd. for their contributions to the conference planning and management. We also thank Metallurgical Industry Press for preparing the proceedings. Finally, we acknowledge the financial support from Nanjing Iron & Steel Co., Ltd., CBMM | Niobium, CITIC Metal Co., Ltd., Vanitec-CISRI Vanadium Technology Center and Vanitec Ltd. to the publication. Prof. Zhiling Tian Prof. Chengjia Shang Executive Chairmen of HSLA Steels 2025 Beijing, October, 2025 ·III· Contents Contents Plenary Lecture 003 Niobium-Driven Innovations in Advanced Steels Rafael Mesquita, Jose Bacalhau, Caio Pisano, Roney Lino, Wenjun Wang 010 Vanadium in Modern Steels: A Versatile Microalloying Element for Enhanced Strength, Toughness, and Wear Resistance Yu Li, David N. Crowther Physical Metallurgy for Innovation 019 Dual-Phase Steel Strengthened by Interphase-Precipitated TiC Nanocarbides Jer-Ren Yang 025 Modelling Microstructure Evolution in Line Pipe Steels M. Militzer, W. J. Poole, M.Y. Tseng, J. Swan, S. Roy, R. Birch, S. Patel, M. Gaudet 026 Reduced Operational Costs and Lower Embodied Carbon for Commodity Grade Steels Using Ultra Low Niobium (ULNb) Alloying Solution Dr Jitendra Patel Eng.D, MBA, C.Eng., FIMMM 032 Microstructural Understanding in Low-Carbon Bainitic Steels D. de Castro, F. G. Caballero, D. San Martín, C. Capdevila 035 Microstructure Characterization of SM570 Steel Plate and Exploration of Its Mechanical Property Improvement by Adding Appropriate Amounts of Alloying Elements Changching Ho, Shinghoa Wang, Jerren Yang, Pohan Chiu, Tzuching Tsao 038 Strengthening Scenarios in Heavy-Gaged Plate Steel Using Niobium, Molybdenum, Nickel and Boron Alloying Hardy Mohrbacher 043 Impact of Nb and V on Nanoprecipitate Formation in Novel Advanced Ferritic-Martensitic Steels Javier Vivas, David San-Martín, David De-Castro, Eberhard Altstadt, Martin Houska, Esteban Urones-Garrote, Francisca G. Caballero, Marta Serrano, Rebeca Hernández, Carlos Capdevila 046 Effect of Cooling Temperature on Strength and Microstructure of Hot Rolled S760 Steel for Industrial Applications D. Sidorenko, M.Y. Rekha, B. Lin, B. Ehrhardt, E. Poliak 049 Effective Improvement in Mechanical Properties of Medium Mn Steel by Warm Rolling Yan Zhang, Yu Yan ·IV· Contents 051 Study on the Influence of Residual Elements on HC420LA Yuqiao Zhao, Pengfei Gao, Xin Xu, Xuming Liu, Shengrui Su, Bingquan Ai, Junsheng Wang 055 Effect of Electrochemical Hydrogen Charging on Precipitation in 6061 Aluminum Alloy Myeongjin Lee, Junyoung Chae, Siwhan Lee, Heungnam Han 058 Achieving High Strength and High Ductility of Dual-Phase Steel via Alternating Lamellar Microstructure Gang Niu, Chao Ding, Mengjie Wamg, Aicheng Liu, Huibin Wu 062 Devlopment of GPa Grade Galvanized Multi-phase Steel Bearing Nb Bingquan Ai, Xuming Liu, Pengfei Gao, Zhiyu Geng, Jingjing Wang 066 Elucidation of the Mechanism Governing Electrochemically-Induced Martensitic Transformation Junyoung Chae, Guihyung Lee, Hyukjae Lee, Yeonggeun Cho, Dameul Jeong, Young-Kyun Kwon, In-Ho Jung, Sung-Joon Kim, Heung Nam Han 069 Metallurgical Functionalities of Microalloys during Annealing of Cold Rolled Automotive Steel Hardy Mohrbacher and Caio Pisano 074 Effect of Thermomechanical Processing Parameters on the Microstructure of High Strength Low Alloyed Steel Gholam Ali Baqeri, Chris Killmore, Elena Pereloma 075 Study on Improving Vanadium Precipitation Rate for Vanadium Microalloyed Power Angle Steel Fu Han, Junhua Qiu, Hui Wen, Wei Deng 081 Research on the Continuous Cooling Phase Transformation Behavior of Medium Manganese Steel Yu Du , Tao Liu , Yuwei Zhou , Xiuhua Gao , Hongyan Wu , Linxiu Du 084 The Performance and Microstructure of 11MnNiMoDR Steel Plate for Low-temperature Pressure Vessels Lianyun Xi, Zhanglong Xie, Jie Yin, Junzhou Ji, Zhengyang Wu 090 Effect of Ni on the Transformation Behavior of Undercooled Austenite in Si-Mn-Cr-B System High-Strength Spring Steel Hongwei Zheng, Wei Deng, Ye Jiang, Yang Wang 094 Microstructure and Performance of Ti Deoxidized Low Carbon Steel Zhu Yan, Chao Wang, Guo Yuan 096 Effect of Microalloying System and Hot Rolling Parameters on the Strength of Low Carbon Steels Dagman A.I., Koldaev A.V., Naumenko V.V., Arutyunyan N.A., Matrossov M.Yu. 097 Microstructure and Mechanical Properties of Cu-bearing Medium Mn Steel Via Intercritical Quenching and Tempering Process Yunzi Yan, YunBo Xu, Jiayu Li, Hao Hu 102 Analysis of Surface Crack of High Strength Austenitic Stainless Steel Continuous Casting Billet Kunyu Wang, Yu Zhang, Xiangyu Zhang, Dong Pan ·V· Contents Performance, Safety and Application 109 Development of a Prototype Steel for a New Type of Ultra-high Strength Austenitic Non-magnetic Stainless Steel Dong Pan, Yu Zhang, Xiangyu Zhang, Kunyu Wang 112 Low Temperature Mechanical Properties of 460MPa Polar Ship Steel and Its Welded Joints Wang Chaoyi, Yan Lin, LI Wenbing, Zhang Ning 119 Microstructure and Mechanical Properties of 1000MPa Low-carbon Bainite-martensitic Steel Welded Joints Xingjian Ma, Zhenyu Fei, Jingjie Wang, Yi Fan, Wei Li 121 Influence of Cr Content on Corrosion Resistance of Supercritical CO2 Pipeline Steel Ba Li, Qilin Ma, Shujun Jia, Bing Wang, Qingyou Liu, Chengjia Shang 123 Mechanism of Cementite Morphology in Enhancing Plasticity of EH 40 Hull-Structural Steel Zhongran Shi, Qiang Wang, Zuoning Chen, Qing Yu, Zhongwen Wu, Zhen Wang Process Technologies for High Quality 133 Effects of Heat Treatment Processing on Microstructure and Properties of 410S+Q345R Clad Plate Shan Jiang, Zhouyu Zeng, FeilongWang 136 Predicting Austenite Yield Strength in Steels by using Artificial Intelligence Isaac Toda-Caraballo, Carlos Garcia-Mateo 139 Multi-scale Simulation and Machine Learning-Based Toughness Prediction of HSLA Weld CGHAZ Zhixing Wang 142 Effect of Intercritical Annealing on Tensile Properties of Cr Alloying Medium-Mn Steel Shengrui Su, Pengfei Gao, JingjingWang, Bingquan Ai, Yuqiao zhao 146 Physics-Informed Machine Learning for Predicting Strength and Flow Behavior of Steels Shasha Zhang, Changqing Shu, Guojin Xiang, Zhengjun Yao 150 Influence of Nb, V and Ti Microalloying on Microstructure and Mechanical Properties of Hot Stamping Steel Zhang Xiangyu, Qin Zhe, Zhang Yu, Pan Dong Wang Kunyu, Li Zhihui 156 Research on Key Technologies for Optimizing Processes and Enhancing Production Capacity of Thin Plates Heat Treatment An Jiale Process Technologies for High Quality 2025 Products for the Automotive, Energy, Infrastructure and Maritime Industry, etc. 2025 ·200· Products for the Automotive, Energy, Infrastructure and Maritime Industry, etc. Engineering Carbide-Free Bainitic Steels with High Silicon for Superior Strength and Toughness Radhakanta Rana1, Lucia Morales-Rivas2, Jose A. Jimenez2, Carlos Garcia-Mateo2 (1. Tata Steel, Wenckebachstraat 1, 1970 CA, IJmuiden, the Netherlands 2. MATERALIA-Steel Research Group, Department of Physical Metallurgy, National Center for Metallurgical Research(CENIM-CSIC), Avenida Gregorio del Amo, 8, Madrid, 28040, Spain) Abstract: This research presents the development and comprehensive evaluation of high-silicon (1.5–2.5wt.%) carbide-free bainitic (CFB) steels engineered for industrial hot rolling, targeting coiling temperatures of 310℃ and 350℃. Designed to meet the automotive industry’s demand for materials with both ultrahigh strength and enhanced toughness, these novel steels utilize elevated silicon content to suppress cementite formation and optimize bainitic microstructures with retained austenite. Four distinct steel compositions, produced via vacuum induction melting, were hot rolled to final thicknesses of 3mm and 12 mm under industrially relevant cooling regimes. Microstructure characterization by SEM and XRD revealed bainitic ferrite fractions of 60–95%, with variable amounts of retained austenite (2–17%), fresh martensite (3–20%), and tempered martensite (0–13%), depending on coiling temperature. Lower coiling at 310℃ promoted finer microstructures with higher hardness and carbon-enriched austenite. Mechanical testing demonstrated ultimate tensile strengths of 1409–1644 MPa and total elongations up to 19.3%. The steels exhibited excellent low-temperature impact toughness, exceeding 27 J at –40℃, and superior notch resistance and crack initiation delay in Kahn tear tests, especially for samples coiled at 310℃. The research successfully identifies processing parameters and alloy designs for CFB steels that achieve an exceptional synergy of strength, ductility, and toughness—attributes highly desirable for next-generation automotive structural components. Key words: hot rolled, bainite, austenite stability, microstructure, mechanical properties 1 Introduction The automotive industry demands stronger and more ductile hot-rolled (HR) steels for increased safety and to meet stricter emission standards. Contemporary HR steels, such as high-strength low alloy (HSLA) and complex phase (CP) steels, are limited in ultimate tensile strength (UTS) to approximately 1000 MPa, restricting their application in automotive structural components due to inadequate formability at higher strengths. In response, research has focused on third-generation advanced high-strength steels (3G-AHSS), particularly carbide-free bainitic (CFB) steels, which combine ultrahigh strength with enhanced ductility by suppressing carbide formation and stabilizing retained austenite via alloying with silicon. This study investigates high-silicon (1.5–2.5wt%) CFB steels produced via hot rolling and varying coiling temperatures to optimize microstructure and mechanical performance for demanding automotive and structural applications. ·201· Engineering Carbide-Free Bainitic Steels with High Silicon for Superior Strength and Toughness 2 Experiment Methods and Materials Four high-silicon CFB steel compositions (F1–F4), Table 1, were designed and cast via vacuum induction melting into 25kg ingots, subsequently hot rolled to strips of 3 mm and 12 mm thickness. After hot rolling, samples were coiled at either 310℃ or 350 ℃, simulating industrial coil cooling conditions. Microstructures were examined using scanning electron microscopy (SEM) and X-ray diffraction (XRD), with quantitative phase analysis performed by Rietveld refinement. The volume fractions of bainitic ferrite, retained austenite, and martensite were determined alongside measurements of carbon content, dislocation density, and bainitic plate thickness. Mechanical properties were assessed by tensile testing (ASTM E8), Charpy V-notch impact testing (ASTM-A370), Kahn tear tests (ASTM B871-01), and Vickers hardness testing. Table 1 Chemical composition of the steels in wt.% Steel C Si Mn Cr Mo F1 0.25 1.83 2.03 1.44 0.22 F2 0.30 1.52 1.26 1.67 0.24 F3 0.30 2.48 1.51 1.43 0.23 F4 0.30 2.54 1.77 1.22 0.24 2.1 Typical Experimental Results The main results of the study demonstrate that the high-silicon carbide-free bainitic steels developed through precise alloy design and controlled processing exhibit a unique combination of ultrafine microstructures and exceptional mechanical performance. Across all compositions and coiling conditions, the steels achieved microstructures dominated by bainitic ferrite (60–95% by volume, with plate thicknesses ranging from 53– 94nm), complemented by varying fractions of retained austenite (2–17%), fresh martensite (3–20%), and tempered martensite (0–13%), see Figure 1. The selected coiling temperature was found to play a critical role in tailoring these phase fractions and refining the microstructure. Specifically, lower coiling temperatures (310 ℃) promoted finer bainitic plates, higher carbon contents in austenite and ferrite, and greater mechanical stability of the retained austenite phase, as reflected by lower Md temperatures. Consequently, these changes enhanced the tensile strength and crack resistance of the material. All investigated steels attained ultrahigh ultimate tensile strengths, ranging from 1409 to 1644 MPa, and showed good total elongation values between 9% and 19.3%, Figure 1, far surpassing those of conventional cold-formable steels. The optimum combination of strength and ductility was achieved with F3 steel coiled at 310℃, which exhibited a yield strength of approximately 1206 MPa, a UTS of 1563 MPa, and a total elongation of 19.3%. Notably, the overall trend indicated that higher fractions of thin-film retained austenite, coupled with increased stability, directly contributed to improved ductility and strain hardening, as shown by the correlation between elongation and the f V  /Md parameter, where f V  represents th e volume fraction of thin films of austenite. Impact toughness testing further revealed the resilience of these steels, Figure 2. Charpy V-notch impact energies consistently surpassed the industrial threshold of 27J at –40 ℃, with absorbed energies at room temperature ranging from 43 to 75 J, Figure 2. The toughness showed little sensitivity to coiling temperature or sample orientation, and fractographic analysis confirmed the predominance of ductile fracture features even at the lowest test temperatures of –100 ℃. Complementary Kahn tear tests confirmed high notch resistance, particularly in steels processed at the lower coiling temperature—again coinciding with higher retained austenite stability. ·202· Products for the Automotive, Energy, Infrastructure and Maritime Industry, etc. Overall, the study establishes that through careful regulation of composition and processing, high-silicon carbide-free bainitic steels can be engineered to surpass the strength, ductility, and toughness limitations of current industrial steels, opening opportunities for their use in advanced structural and automotive applications. Figure 1 For F3 steel, representative SEM images of the microstructures, where some examples of bainitic ferrite (αb), tempered martensite (α′ T), blocky (γb) and thin films ( γf ) of retained austenite as well as martensite-austenite (MA) constituents, are identified. Also included the typical engineering stress-strain curves at the two coiling temperatures (CT) of 350℃ and 310℃. Figure 2 Charpy impact toughness tested in longitudinal and transversals directions for both the coiling conditions (CT) of all the steels. Industry specifications of 27J energy at -40℃ indicated by doted lines. The typical experimentalerror in the measurements was in the range of 3-5J. 3 Conclusions Through alloy design and controlled processing, these high-silicon CFB steels offer a remarkable combination of ultrahigh strength, ductility, and toughness, outperforming many commercially available ultrahigh strength steels and demonstrating their suitability for demanding structural applications. ·203· Engineering Carbide-Free Bainitic Steels with High Silicon for Superior Strength and Toughness Acknowledgement The authors gratefully acknowledge the support of the European Research Fund for Coal and Steel under the Contract RFCS-02-2022-RPJ No 101112425. References [1] R. Rana, E. Cordova-Tapia, L. Morales-Rivas, J.A. Jimenez and C. Garcia-Mateo, Mechanical behaviour and microstructural characteristics of high-silicon ultra-strong bainitic steels for hot rolling practice, Mater. Sci. Eng. A 931 (2025), pp. 148236.R. [2] R. Rana, E. Cordova-Tapia, J.A. Jimenez, L. Morales-Rivas and C. Garcia-Mateo, Design of carbide free bainitic steels for hot rolling practices, Philos. Mag. Lett. 104 (2024), . [3] R. Rana and S.B. Singh, eds., Automotive Steels. Design, Metallurgy, Processing and Applications, Elsevier, 2017. [4] R. Rana, S. Chen, A. Haldar and S. Das, Mechanical Properties of a Bainitic Steel Producible by Hot Rolling, Arch. Metall. Mater. 62 (2017), pp. 2331-2338. [5] R. Rana, E. Cordova-Tapia, L. Morales Rivas and C. Garcia-Mateo, Design and Properties of Hot Rolled Tough Carbide Free Bainitic Steels, Mater. Sci. Forum 1105 (2023), pp. 219-224. [6] S.P. Chen, R. Rana, B. Xiao and A. Haldar, The Effects of Hot Deformation of Austenite on the Bainite Transformation in a Fe-C-Mn-Si-Cr Steel, Mater. Sci. Forum 941 (2018), pp. 486-491. [7] S. Chen, R. Rana and C. Lahaije, Study of TRIP-Aided Bainitic Ferritic Steels Produced by Hot Press Forming, Metall. Mater. Trans. A 45 (2014), pp. 2209-2218. ·219· Subject Index low carbon steel ·································· 094 low cycle ·········································· 032 low temperature properties ······················ 112 lower emission ···································· 026 low-temperature pressure vessels ·············· 084 low-temperature toughness ····················· 204 lüders strain ······································· 038 M M/A-constituent ·································· 172 machine learning model ························· 181 machine learning ··························· 136, 139 magnetic permeability ··························· 109 martensite ········································· 150 mechanical characterization ···················· 043 mechanical properties ································ ····················· 035, 051, 109, 136, 150, 200 mechanical property ······················· 075, 084 medium manganese steel ························ 081 medium manganese steels ······················· 196 medium-Mn steel ································· 142 microalloying ························· 003, 069, 150 microhardness ···································· 055 microstructural characterization ················ 043 microstructural evolution ························ 097 microstructure effects ···························· 194 microstructure ········································ ········· 032, 062, 074, 133, 150, 186, 200, 207 nanoprecipitation ································· 043 N Nb-Ti microalloying ····························· 204 Ni ··················································· 090 niobium ······································ 003, 026 nitrided steels ····································· 010 non-magnetic steel ······························· 109 P pearlitic steels ···································· 010 physics-informed machine learning ··········· 146 pipeline steel ······································ 194 pipeline steels (X80) ····························· 010 polar ship steel ···································· 112 polygonal ferrite ·································· 172 porous plugs ······································ 162 power angle steel ································· 075 precipitated phase ································ 102 precipitation rate ································· 075 precipitation strengthening ················ 010, 075 precipitation··············· 038, 046, 055, 069, 074 process optimization ····························· 156 properties ······························ 062, 133, 186 punching ·········································· 181 purging plug ······································ 162 Q Q500qENH steel ································· 186 R recovery ··········································· 069 recrystallization ·································· 069 ·220· Subject Index refining ············································ 162 residual elements ································· 051 retained austenite ································ 081 retransformation ·································· 069 run-out table cooling ···························· 046 S SHCCT diagram ································· 119 Si-Mn-Cr-B ······································· 090 SM570 steel ······································ 035 spheroidization ··································· 123 spray height ······································· 159 SSRT ·············································· 194 steel for large diameter pipes ··················· 172 steel ················································ 026 steels ··············································· 146 strength ············································ 146 strength-ductility synergy ······················· 058 supercritical CO2 pipeline steel ················ 121 surface defect ····································· 159 sustainability ······································ 003 T tempering temperature ·························· 123 tempering ········································· 038 tensile properties ································· 097 tensile strength ··································· 051 thermal simulation ······························· 139 thermo-mechanical processing ················· 074 Ti-Oxide ·········································· 094 TMCP ··············································112 transformation behavior of undercooled austenite ·················································· 090 transformation kinetics ·························· 066 transformation ···································· 038 transmission electron microscope ············· 035 transmission electron microscopy ············· 019 U ULNb ·············································· 026 Ultra grade R6 steel ····························· 189 Ultrafine compound carbides ··················· 189 uniform elongation ······························ 172 V V microalloyed ··································· 075 vanadium microalloying ························ 010 W wear resistance ··································· 010 weld toughness ··································· 010 weldability ········································ 003 welding thermal cycle ····························119 Y Yield ratio controllable chain ·················· 189 yield strength ······························· 136, 142