Journal articles: 'Ferritic-Bainitic steels'

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Cabrini, Marina, Lorenzi Sergio, Pesenti Bucella Diego, and Pastore Tommaso Tommaso. "Hydrogen Embrittlement and Diffusion in High Strength Low Alloyed Steels with Different Microstructures." Insight - Material Science 2, no. 1 (2019): 8. http://dx.doi.org/10.18282/ims.v2i1.182.

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<p class="BodyText1">The paper deals with the effect of microstructure on the hydrogen diffusion in traditional ferritic-pearlitic HSLA steels and new high strength steels, with tempered martensite microstructures or banded ferritic-bainitic-martensitic microstructures. Diffusivity was correlated to the hydrogen embrittlement resistance of steels, evaluated by means of slow strain rate tests. </p>

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Abd El Rahman, Sherif Ali, Ahmed Shash, Mohamed K. El-Fawkhry, Ahmed Zaki Farahat, and Taha Mattar. "Designing, Processing and Isothermal Transformation of Al-Si Medium Carbon Ultrafine High Strength Bainitic Steel." Defect and Diffusion Forum 380 (November 2017): 1–11. http://dx.doi.org/10.4028/www.scientific.net/ddf.380.1.

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Medium-carbon, silicon-rich steels are commonly suggested to obtain a very fine bainitic microstructure at a low temperature slightly above Ms. Thereby, the resulted microstructure consists of slender bainitic-ferritic plates interwoven with retained austenite. The advanced strength and ductility package of this steel is much dependent on the fineness of bainitic ferrite, as well as the retained austenite phase. In this article, the aluminum to silicon ratio, and the isothermal transformation temperature have been adopted to obtain ultra-high strength high carbon steel. Optical and SEM investigation of the produced steels have been performed. XRD has been used to track the retained austenite development as a result of the change in the chemical composition of developed steels and heat treatment process. Mechanical properties in terms of hardness and microhardness of obtained phases and structure were investigated. Results show that the increment of aluminum to silicon ratio has a great effect in promoting the bainitic transformation, in tandem with improving the stability and the fineness of retained austenite. Such an advanced structure leads to enhancement in the whole mechanical properties of the high carbon steel.

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Kulecki, P., E. Lichańska, and M. Sułowski. "The Effect of Processing Parameters on Microstructure and Mechanical Properties of Sintered Structural Steels Based on Prealloyed Powders / Wpływ Parametrów Wytwarzania Na Strukturę I Własności Mechaniczne Spiekanych Stali Wykonanych Na Bazie Proszków Stopowych." Archives of Metallurgy and Materials 60, no. 4 (2015): 2543–48. http://dx.doi.org/10.1515/amm-2015-0411.

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The object of the study was to evaluate the effect of production parameters on the structure and mechanical properties of Cr and Cr-Mo PM steels. The measurements were performed on sintered steels made from commercial Höganäs pre-alloyed powders: Astaloy CrA, Astaloy CrL and Astaloy CrM mixed with carbon, added in the form of graphite powder grade C-UF.Following mixing in a Turbula mixer for 30 minutes, green compacts were single pressed at 660 MPa according to PNEN ISO 2740 standard. Sintering was carried out in a laboratory horizontal furnace at 1120°C and 1250°C for 60 minutes, in 5%H2-95%N2atmosphere. After sintering, the samples were tempered at 200°C for 60 minutes in air. The steels are characterized by ferritic - pearlitic, bainitic - ferritic and bainitic structures.Following mechanical testing, it can be assumed that steel based on Astaloy CrA pre-alloyed powder could be an alternative material for steels based on Astaloy CrL powder. These steels sintered at 1250°C with 0.6% C had tensile strengths about 650 MPa, offset yield strengths about 300 MPa, elongations about 8.50 %, TRSs about 1100 MPa, hardnesses 220 HV.

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Wirths, Vera, Rainer Wagener, Wolfgang Bleck, and Tobias Melz. "Bainitic Forging Steels for Cyclic Loading." Advanced Materials Research 922 (May 2014): 813–18. http://dx.doi.org/10.4028/www.scientific.net/amr.922.813.

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Light-weight design is one of the main drivers for material development in the automotive industry. For optimum weight reduction new materials and their fatigue behavior under real cyclic service loads have to be taken into account (Gassner test). Currently the casted components made from Austempered Ductile Iron (ADI) show better service fatigue life for variable load cases than some traditional forging steels because of it’s inherent retained austenite. The traditional forging steels are the precipitation hardening ferritic-pearlitic steels (PHFP steel) and the martensitic quenched and tempered (Q&T) steels. The next steel generation for forged components in the drive train might be bainitic steels with an optimized microstructure with respect to cyclic behavior. Depending on the chemical composition and the heat treatment it includes a ferritic primary phase and a secondary phase, which consists of either carbides, martensite, retained austenite or M/A constituents. By alloying of more than 1% Si the formation of cementite will be suppressed and a carbide free bainite (CFB) will be formed. The secondary phase of this CFB contains retained austenite, which has the possibility to close crack tips by local compression stresses due to the transformation to martensite. As a result of this CFB exhibits better cyclic properties than the commonly used forging steels. The materials and process design as well as results of the fatigue behavior will be presented.

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Vuorinen, E., V. Heino, N. Ojala, O. Haiko, and A. Hedayati. "Erosive-abrasive wear behavior of carbide-free bainitic and boron steels compared in simulated field conditions." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 232, no. 1 (2017): 3–13. http://dx.doi.org/10.1177/1350650117739125.

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The wear resistance of carbide-free bainitic microstructures have recently shown to be excellent in sliding, sliding-rolling, and erosive-abrasive wear. Boron steels are often an economically favorable alternative for similar applications. In this study, the erosive-abrasive wear performance of the carbide-free bainitic and boron steels with different heat treatments was studied in mining-related conditions. The aim was to compare these steels and to study the microstructural features affecting wear rates. The mining-related condition was simulated with an application oriented wear test method utilizing dry abrasive bed of 8–10 mm granite particles. Different wear mechanisms were found; in boron steels, micro-cutting and micro-ploughing were dominating mechanisms, while in the carbide-free bainitic steels, also impact craters with thin platelets were observed. Moreover, the carbide-free bainitic steels had better wear performance, which can be explained by the different microstructure. The carbide-free bainitic steels had fine ferritic-austenitic microstructure, whereas in boron steels microstructure was martensitic. The level of retained austenite was quite high in the carbide-free bainitic steels and that was one of the factors improving the wear performance of these steels. The hardness gradients with orientation of the deformation zone on the wear surfaces were one of the main affecting factors as well. Smoother work hardened hardness profiles were considered beneficial in these erosive-abrasive wear conditions.

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Eggbauer, Gernot, and Bruno Buchmayr. "Optimized Cooling Strategies for Bainitic Forging Steels." Key Engineering Materials 716 (October 2016): 472–80. http://dx.doi.org/10.4028/www.scientific.net/kem.716.472.

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New steel grades for forged components are designed to meet the requirements of the automotive industry in order to obtain excellent strength and toughness behavior as well as a high endurance limit. Beside precipitation hardened ferritic-pearlitic steels, bainitic steels have gained more and more importance. Basic considerations on the alloy design (C-, Si-, Cr-; B-content) are done using JMatPro-Calculations and by some experimental trials. Using the thermomechanical testing system Gleeble 3800, various cooling strategies have been applied and the kinetics of the bainite formation has been measured at different holding temperatures and times. A detailed microstructural characterization has been done with relation to the mechanical properties. The isothermal tests are compared to continuous cooling situations. Finally, forging trials are performed to find out the most suitable and robust production schedule to be used in practice. The actual findings support the increasing use of bainitic steels for forged parts, especially regarding material saving, independence of cross section and good fatigue performance.

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Hodgson, Peter, Subrata Mukherjee, Hossein Beladi, Xiang Yuan Xiong, and Ilana B. Timokhina. "Atomic Scale Investigation of Solutes and Precipitates in High Strength Steels." Materials Science Forum 762 (July 2013): 14–21. http://dx.doi.org/10.4028/www.scientific.net/msf.762.14.

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Two steels, ferritic, high strength with interphase precipitation and nanobainitic, were used to show the advances in and application of atom probe. The coexistence of the nanoscale, interphase Nb-Mo-C clusters and stoichiometric MC nanoparticles was found in the high strength steel after thermomechanical processing. Moreover, the segregation of carbon at different heterogeneous sites such as grain boundary that reduces the solute element available for fine precipitation was observed. The APT study of the solutes redistribution between the retained austenite and bainitic ferrite in the nanobainitic steel revealed: (i) the presence of two types of the retained austenite with higher and lower carbon content and (ii) segregation of carbon at the local defects such as dislocations in the bainitic ferrite during the isothermal hold.

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Menzel, Max, Anastasia Höhne, Gerhard Gevelmann, Andreas Tomitz, Ulrich Prahl, and Wolfgang Bleck. "Application Specific Microstructure Development in Microalloyed Bainitic Hot Strip." Materials Science Forum 949 (March 2019): 76–84. http://dx.doi.org/10.4028/www.scientific.net/msf.949.76.

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During the hot rolling of bainitic steels, time and temperature must be controlled within narrow limits to avoid undesirable ferritic or martensitic phase fractions. In order to design a reliable process window for the production of bainitic steels, the effects of the different process parameters on the phase transformation and the final properties of a microalloyed and a non-microalloyed steel were investigated. Thermomechanical tests with the possibility of producing secondary samples were conducted to analyze the influence on the mechanical properties strength and toughness. Transmission electron microscopy (TEM) and electron probe micro analysis (EPMA) were used to investigate the origin of the differing properties. In particular, it has been found that thermomechanical rolling of the microalloyed steel leads to an improvement in strength. This is partly due to the transformation kinetics and partly to strain-induced precipitations. Further, the hardening behavior is affected by the secondary phase within the bainitic matrix configured through the cooling strategy. Coarse Martensite/Austenite (MA) structures reduce toughness, whereas finely dispersed MA islands increase the hardening potential. Furthermore, the results from the material experiments were used to develop a rate model in combination with a nucleation model to predict the kinetics of the phase transformation and the shape of the bainitic microstructure.

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di Schino, Andrea, and Claudio Guarnaschelli. "Microstructure and Cleavage Resistance of High Strength Steels." Materials Science Forum 638-642 (January 2010): 3188–93. http://dx.doi.org/10.4028/www.scientific.net/msf.638-642.3188.

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The relationship between microstructure and cleavage resistance in quenched and tempered high strength bainitic and martensitic steels is investigated by means of Charpy-V three-point bending tests, uniaxial tensile test on unnotched specimens and EBSD. Steels under investigation are low/medium carbon (C=0.10%-0.40%) steels with yield strength in the range YS=500-1000 MPa. Results show that the tensile strength and the cleavage resistance of Q&T steels appear to be controlled by different structural parameters and not, as in the case of polygonal ferritic steels, by the same structural unit. In particular, yield strength is controlled by the mean subgrain size, whereas the structural unit controlling the critical cleavage stress is the covariant (bainitic or martensitic) packet, whose size is slightly lower than the average unit crack path (UCP). The critical stage in the fracture process appears to be the propagation of a Griffith crack from one packet to another, and the resistance offered by high-angle boundaries is approximately the same as that of low-C steels with bainitic or polygonal ferrite microstructure.

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Nyyssönen, Tuomo, Olli Oja, Petri Jussila, Ari Saastamoinen, Mahesh Somani, and Pasi Peura. "Quenching and Partitioning of Multiphase Aluminum-Added Steels." Metals 9, no. 3 (2019): 373. http://dx.doi.org/10.3390/met9030373.

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The quenching and partitioning response following intercritical annealing was investigated for three lean TRIP-type high-Al steel compositions. Depending on the intercritical austenite fraction following annealing, the steels assumed either a ferrite/martensite/retained austenite microstructure or a multiphase structure with ferritic, bainitic and martensitic constituents along with retained austenite. The amount of retained austenite was found to correlate with the initial quench temperature and, depending on the intercritical annealing condition prior to initial quenching, with the uniform and ultimate elongations measured in tensile testing.

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Sun, Mingxue, Yang Xu, and Tiewei Xu. "Cu Precipitation Behaviors and Microscopic Mechanical Characteristics of a Novel Ultra-Low Carbon Steel." Materials 13, no. 16 (2020): 3571. http://dx.doi.org/10.3390/ma13163571.

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We studied the effect of Cu addition on the hardness of ultra-low carbon steels heat treated with different cooling rates using thermal simulation techniques. The microstructural evolution, Cu precipitation behaviors, variations of Vickers hardness and nano-hardness are comparatively studied for Cu-free and Cu-bearing steels. The microstructure transforms from ferritic structure to ferritic + bainitic structure as a function of cooling rate for the two steels. Interphase precipitation occurs in association with the formation of ferritic structure at slower cooling rates of 0.05 and 0.2 °C/s. Coarsening of Cu precipitates occurs at 0.05 °C/s, leading to lower precipitation strengthening. As the cooling rate increases to 0.2 °C/s, the interphase and dispersive precipitation strengthening effects are increased by 63.9 and 50.0 MPa, respectively. Cu precipitation is partially constrained at cooling rate of 5 °C/s, resulting in poor nano-hardness and Young’s Modulus. In comparison with Cu-free steel, the peak Vickers hardness, nano-hardness and Young’s Modulus are increased by 56 HV, 0.61 GPa and 55.5 GPa at a cooling rate of 0.2 °C/s, respectively. These values are apparently higher than those of Cu-free steel, indicating that Cu addition in steels can effectively strengthen the matrix.

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Mujanović, Emir, Bojan Zajec, Tadeja Kosec, et al. "Activation and Repassivation of Stainless Steels in Artificial Brines as a Function of pH." Materials 12, no. 23 (2019): 3811. http://dx.doi.org/10.3390/ma12233811.

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When planning oil wells with stainless steel components, two possible reasons for depassivation have to be considered—chemical depassivation caused by acidizing jobs and mechanical depassivation caused by various tools and hard particles. The study explores conditions causing chemical activation of investigated steels and circumstances under which repassivation occurs after activation. The main focus of the study is to determine, how quickly various steels can repassivate under different conditions and to find pH values where repassivation will occur after depassivation. The investigated steels were ferritic (martensitic or bainitic) in the cases of 13Cr, 13Cr6Ni2Mo, and 17Cr4Ni2Mo, austenitic in the case of 17Cr12Ni2Mo, and duplex (austenitic and ferritic) in the case of 22Cr5Ni3Mo. Potentiodynamic experiments were employed to obtain electrochemical properties of investigated steels, followed by immersion tests to find ultimate conditions, where the steels still retain their passivity. After obtaining this information, scratch tests were performed to study the repassivation kinetics. It was found that repassivation times are similar for nearly all investigated steels independent of their chemical composition and microstructure.

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G. Caballero, Pujante, Sourmail, et al. "Advanced Heat Treatments and Complex Ferritic Structures for Bearing Steels." Metals 9, no. 11 (2019): 1137. http://dx.doi.org/10.3390/met9111137.

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Nanostructured bainitic steels exhibit an optimum strength/toughness combination as a consequence of their extremely fine structure. They have also demonstrated potential for wear-resistance applications. The aim of this work was to develop bearing steels by the multi-scale control of complex ferritic structures, designed using atomic transformation theory and processed by novel heat treatments. Based on the results, the new ball bearings outperformed conventional grades, approaching more expensive material options.

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Salinas, Alvaro, Alfredo Artigas, Juan Perez-Ipiña, et al. "Effects of Heat Treatment on Morphology, Texture, and Mechanical Properties of a MnSiAl Multiphase Steel with TRIP Behavior." Metals 8, no. 12 (2018): 1021. http://dx.doi.org/10.3390/met8121021.

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The effect that the microstructure exerts on the Transformation-Induced Plasticity (TRIP) phenomenon and on the mechanical properties in a multiphase steel was studied. Samples of an initially cold-rolled ferrite–pearlite steel underwent different intercritical annealing treatments at 750 °C until equal fractions of austenite/ferrite were reached; the intercritical treatment was followed by isothermal bainitic treatments before cooling the samples to room temperature. Samples in the first treatment were heated directly to the intercritical temperature, whereas other samples were heated to either 900 °C or 1100 °C to obtain a fully homogenized, single-phase austenitic microstructure before performing the intercritical treatment. The high-temperature homogenization of austenite resulted in a decrease in its stability, so a considerable austenite fraction transformed into martensite by cooling to room temperature after the bainitic heat treatment. Most of the retained austenite transformed during the tensile tests, and, consequently, the previously homogenized steels showed the highest Ultimate Tensile Strength (UTS). In turn, the steel with a ferritic–pearlitic initial microstructure exhibited higher ductility than the other steels and texture components that favor forming processes.

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Zikeev, V. N., G. A. Filippov, I. P. Shabalov, O. V. Livanova, and D. M. Solov’ev. "Changes in the fracture strength parameters of ferritic–bainitic and bainitic pipe steels during operation." Russian Metallurgy (Metally) 2016, no. 10 (2016): 977–80. http://dx.doi.org/10.1134/s0036029516100244.

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Iza-Mendia, Amaia, and Isabel Gutiérrez. "Microstructure-Mechanical Properties Relationships for Complex Microstructures in High Strength Steels." Materials Science Forum 783-786 (May 2014): 783–88. http://dx.doi.org/10.4028/www.scientific.net/msf.783-786.783.

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Due to the increased complexity of steel microstructures, when considering the application of available Hall-Petch type equations for yield strength prediction, a number of difficulties raises. For example, the correlation between grain size measurements by EBSD technique and optical microscopy (OP) in complex microstructures is required in order to integrate data to the traditional equations developed for OP results and ferrite-pearlite microstructures. Besides, the introduction of some additional terms to the equations to account for precipitation, C in solution and forest dislocation contributions presents some difficulties that need to be overcome to improve prediction accuracy. Different microstructures (ferrite-pearlite, bainite, quenched and Q&T) have been produced by thermal and thermomechanical treatments, followed by microstructural characterisation and mechanical testing. A Hall-Petch coefficient dependent on the boundary misorientation distribution is proposed. This approach allows dealing in a similar way ferritic, bainitic and martensitic microstructures. The Hall-Petch coefficient, thus defined, corresponds to the previously proposed by Pickering for ferrite, while bainitic microstructures give a smaller value. Additionally, the equation used to express the fracture appearance transition temperature of ferritic-pearlitic microstructure has been generalized from the developments made in the calculation of the yield stress.

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Nastich, S. Yu. "Ferritic-bainitic structure and ductile fracture resistance of high-strength pipe steels." Russian Metallurgy (Metally) 2013, no. 10 (2013): 765–71. http://dx.doi.org/10.1134/s0036029513100108.

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Chen, Shangping, Radhakanta Rana, and Chris Lahaije. "Study of TRIP-Aided Bainitic Ferritic Steels Produced by Hot Press Forming." Metallurgical and Materials Transactions A 45, no. 4 (2014): 2209–18. http://dx.doi.org/10.1007/s11661-013-2163-3.

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Venturini, Roberto, Paolo Daniele Avancini, Nicola Barbier, and Alessandro Rizzi. "Arvedi ESP Technology - The Hot Rolling of HS and AHS Thin Gauge Steel Strips." Materials Science Forum 854 (May 2016): 42–47. http://dx.doi.org/10.4028/www.scientific.net/msf.854.42.

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After 5 years from start-up, Arvedi ESP Technology has achieved outstanding performances in terms of production, products and quality. The technology has proved particularly suitable for the production of thin gauge strips (< 2 mm). This paper presents the experiences in the production of high strength and advanced high strength steels, such as micro-alloyed S550MC, dual phase DP600 and ferritic bainitic HR60 in thin gauge strips on the ESP line of Acciaieria Arvedi S.p.A. in Cremona. Some aspects of the industrial production process for these steel grades are highlighted on the basis of casting and rolling parameters and microstructural and mechanical investigation.

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Koh, S. U., J. S. Kim, B. Y. Yang, and K. Y. Kim. "Effect of Line Pipe Steel Microstructure on Susceptibility to Sulfide Stress Cracking." Corrosion 60, no. 3 (2004): 244–53. http://dx.doi.org/10.5006/1.3287728.

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Abstract The purpose of this experiment was to evaluate the effect of microstructure on sulfide stress cracking (SSC) properties of line pipe steel. Different kinds of microstructures, with chemical compositions identical to one steel heat, were produced by various thermomechanically controlled processes (TMCP). Coarse ferrite-pearlite, fine ferrite-pearlite, ferrite-acicular ferrite, and ferrite-bainite microstructures were investigated with respect to corrosion properties, hydrogen diffusion, and SSC behavior. SSC was evaluated using a constant elongation rate test (CERT) in a NACE TM0177 solution (5% sodium chloride [NaCl] + 0.5% acetic acid [CH3COOH], saturated with hydrogen sulfide [H2S]). The corrosion properties of steels were evaluated by potentiodynamic and linear polarization methods. Hydrogen diffusion through steel matrix was measured by an electrochemical method using a Devanathan-Stachurski cell. The effect of microstructure on cracking behavior also was investigated with respect to crack nucleation and propagation processes. Test results showed that ferrite-acicular ferrite microstructure had the highest resistance to SSC, whereas ferrite-bainitic and coarse ferritie-pearlitic microstructures had the lowest resistance. The high susceptibility to SSC inferritie-bainitic and coarse ferritic-pearlitic microstructures resulted from crack nucleation on hard phases such as grain boundary cementite in coarse ferritie-pearlitic microstructures and martensite/retained austenite (M/A) island in bainitic phases. Hard phase cementite at grain boundaries or M/A constituent in bainitic phases acted as crack nucleation sites and could be cracked easily under external stress; consequently, the susceptibility of steel to SSC increased. Metallurgical parameters including matrix structure and defects such as grain boundary carbides and inter-lath M/A constituents were more critical parameters for controlling SSC than the hydrogen diffusion rate.

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Bachniak, Daniel, Roman Kuziak, Danuta Szeliga, and Maciej Pietrzyk. "Mean field model of phase transformations in steels during cooling, which predicts evolution of carbon concentration in the austenite." Metallurgical Research & Technology 118, no. 4 (2021): 411. http://dx.doi.org/10.1051/metal/2021046.

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The objectives of the paper were twofold. The first was exploring possibility of fast and reliable modelling of phase transformations during cooling of steels, accounting for the evolution of the carbon concentration in the austenite. Existing discrete models require long computing times and their application to optimization of industrial processes is limited. Therefore, a model based on the modified JMAK equation was proposed. Control of the carbon concentration in the austenite during ferritic and bainitic transformations allowed to predict incomplete austenite transformation and occurrence of the retained austenite. Moreover, prediction of the onset of pearlitic transformation after the bainitic was possible. The model was validated by comparison the predictions with the results of physical simulations. Numerical simulations for various industrial processes were performed. Problem of the difference in the incubation time between isothermal and constant cooling rate tests was raised.

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Ruiz, M. A. Doñu, J. A. Ortega Herrara, N. López Perrusquia, V. J. Cortés Suárez, and L. D. Rosado Cruz. "Effect of the Aging Treatment in Micro-Alloyed Steel." MRS Proceedings 1481 (2012): 55–61. http://dx.doi.org/10.1557/opl.2012.1632.

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ABSTRACTThis work study the effect on aging thermal treatment on micro-alloyed steels API X70 pipe, microstructure and mechanical properties such a yield strength (Y), hardness (Hv) and Young´s modulus (E) are presented in this work. Thermal treatment consists of two phases: i) The solution treatment introducing samples in a electric induction furnace at 1100 °C for 30 min under argon atmosphere and water quenching, ii) aging process for five temperature in the range between 204 to 650 °C for 30 min of time exposition and water quenching, respectively. The microstructural characterization was examined by optical microscopy and matrix samples aging showed microstructures like acicular ferritic, polygonal ferritic and bainitic-ferritic, and the secondary phases were examined by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) obtained by SEM evidencing the presence of precipitates composed of vanadium (V), niobium (Nb) and titanium (Ti). The mechanical properties were evaluated by depth sensitive indentation test at the samples aging, the results showed increase of the (Hv) and (E)to the conditions of low temperature aging.

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Bouquerel, Jérémie, Kim Verbeken, Bruno C. De Cooman, Yvan Houbaert, Patricia Verleysen, and Joost Van Slycken. "Physically Based Model for Static and Dynamic Behaviour of TRIP Steel." Advanced Materials Research 15-17 (February 2006): 744–49. http://dx.doi.org/10.4028/www.scientific.net/amr.15-17.744.

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Low alloy multiphase TRansformation Induced Plasticity (TRIP) steels offer an excellent combination of a large uniform elongation and a high strength. This results from the composite behaviour of the different phases that are present in these steels: polygonal ferrite, bainitic ferrite and a martensite/austenite constituent. In order to obtain a clear understanding of the behaviour of the different constituents within the multiphase steel, they were prepared separately. The stress-strain relationship of the different single phase and multiphase steels were simulated with physically based micromechanical models. The model used to describe the stress-strain curves of the separate phases is based on the Mecking-Kocks and Seeger-Kocks theories and uses physical properties such as the microstructural properties and the chemical composition of the different phases. Strain-induced transformation kinetics, based on a generalized form of the Olson-Cohen law, were used to include the influence of the transformation of the metastable austenite. Static stress-strain properties of multiphase steels were modelled by the successive application of a Gladman type mixture law for two-phase steels. The model yields detailed information of stress and strain partitioning between the different phases during a static tensile test. A model for the dynamic stress-strain properties of ferritic steels is also proposed.

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Tlatlik, Johannes, and Dieter Siegele. "Investigation and Modeling of Local Crack Arrest in Ferritic-Bainitic Steels Under Dynamic Loading." Procedia Structural Integrity 13 (2018): 243–48. http://dx.doi.org/10.1016/j.prostr.2018.12.041.

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Graux, Alexis, Sophie Cazottes, David De Castro, et al. "Design and Development of Complex Phase Steels with Improved Combination of Strength and Stretch-Flangeability." Metals 10, no. 6 (2020): 824. http://dx.doi.org/10.3390/met10060824.

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This study presents the design and development of a hot-rolled bainitic steel, presenting a good combination of strength and stretch-flangeability, for automotive applications. Ti, Nb, and Mo were added in the steel composition in order to control austenite grain sizes, enhance precipitation hardening, and promote the formation of bainite. This study focuses on the effect of process parameters on final microstructures and mechanical properties. These parameters are the finishing rolling temperature, which conditions the austenite microstructure before its decomposition, and the coiling temperature, which conditions the nature and morphology of the ferritic phases transformed. A preliminary study allowed to determine the austenite grain growth behavior during reheating, the recrystallization kinetics, and the continuous cooling transformation curves of the studied steel. Then, a first set of parameters was tested at a semi-industrial scale, which confirmed that the best elongation properties were obtained for homogeneous bainitic lath/granular microstructures, that can be produced by choosing a coiling temperature of 500 ∘ C . When choosing those parameters for the final industrial trial, the microstructure obtained consisted of a homogeneous lath/granular bainite mixture that presented a Ultimate Tensile Strength of 830 MPa and a Hole Expansion Ratio exceeding 70%.

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Reis, Luís G., Bin Li, and Manuel de Freitas. "Comparative Study of the Additional Hardening Effects of Three Structural Steels." Materials Science Forum 514-516 (May 2006): 534–38. http://dx.doi.org/10.4028/www.scientific.net/msf.514-516.534.

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For a safe and reliable design of components, it is needed to study the effects of multiaxial loading and particularly the non-proportional loadings on the fatigue damage. The objective of this paper is to evaluate and compare the additional hardening effects of proportional and non-proportional loading paths. Low-cycle fatigue behaviour of three structural steels: CK45 (ferritic-perlitic microstructure) normalized steel, 42CrMo4 (bainitic microstructure) quenched and tempered steel and stainless steel (austenitic microstructure) X10CrNiS 18 9 are studied under different proportional and non-proportional loading paths and different levels. A series of tests of biaxial low-cycle fatigue composed of tension/compression with static or cyclic torsion were carried out on a biaxial servo-hydraulic testing machine Instron 8088. The experiments showed that the three materials studied have very different additional hardening behaviour, under multiaxial cyclic loading paths. The local cyclic stress/strain states are influenced by the multiaxial loading paths due to interactions between the normal stress and shear stress during cyclic plastic deformation. The microstructure is an important key and has a great influence on the additional hardening. The additional hardening effect is dependent of the loading path and also the intensity of the loading.

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Altamirano, G., I. Mejía, A. Hernández-Expósito, and J. M. Cabrera. "Effect of boron on the continuous cooling transformation kinetics in a low carbon advanced ultra-high strength steel (A-UHSS)." MRS Proceedings 1485 (2012): 83–88. http://dx.doi.org/10.1557/opl.2013.253.

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ABSTRACTThe aim of the present research work is to investigate the influence of B addition on the phase transformation kinetics under continuous cooling conditions. In order to perform this study, the behavior of two low carbon advanced ultra-high strength steels (A-UHSS) is analyzed during dilatometry tests over the cooling rate range of 0.1-200°C/s. The start and finish points of the austenite transformation are identified from the dilatation curves and then the continuous cooling transformation (CCT) diagrams are constructed. These diagrams are verified by microstructural characterization and Vickers micro-hardness. In general, results revealed that for slower cooling rates (0.1-0.5 °C/s) the present phases are mainly ferritic-pearlitic (F+P) structures. By contrast, a mixture of bainitic-martensitic structures predominates at higher cooling rates (50-200°C/s). On the other hand, CCT diagrams show that B addition delays the decomposition kinetics of austenite to ferrite, thereby promoting the formation of bainitic-martensitic structures. In the case of B microalloyed steel, the CCT curve is displaced to the right, increasing the hardenability. These results are associated with the ability of B atoms to segregate towards austenitic grain boundaries, which reduce the preferential sites for nucleation and development of F+P structures.

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Pietrowski, S. "Wearing Quality of Austenitic, Duplex Cast Steel, Gray and Spheroidal Graphite Iron." Archives of Foundry Engineering 12, no. 2 (2012): 235–44. http://dx.doi.org/10.2478/v10266-012-0067-0.

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Wearing Quality of Austenitic, Duplex Cast Steel, Gray and Spheroidal Graphite Iron The current work presents the research results of abrasion wear and adhesive wear at rubbing and liquid friction of new austenitic, austenitic-ferritic ("duplex") cast steel and gray cast iron EN-GJL-250, spheroidal graphite iron EN-GJS-600-3, pearlitic with ledeburitic carbides and spheroidal graphite iron with ledeburitic carbides with a microstructure of the metal matrix: pearlitic, upper bainite, mixture of upper and lower bainite, martensitic with austenite, pearlitic-martensitic-bainitic-ausferritic obtained in the raw state. The wearing quality test was carried out on a specially designed and made bench. Resistance to abrasion wear was tested using sand paper P40. Resistance to adhesive wear was tested in interaction with steel C55 normalized, hardened and sulfonitrided. The liquid friction was obtained using CASTROL oil. It was stated that austenitic cast steel and "duplex" are characterized by a similar value of abrasion wear and adhesive wear at rubbing friction. The smallest decrease in mass was shown by the cast steel in interaction with the sulfonitrided steel C55. Austenitic cast steel and "duplex" in different combinations of friction pairs have a higher wear quality than gray cast iron EN-GJL-250 and spheroidal graphite iron EN-GJS-600-3. Austenitic cast steel and "duplex" are characterized by a lower wearing quality than the spheroidal graphite iron with bainitic-martensitic microstructure. In the adhesive wear test using CASTROL oil the tested cast steels and cast irons showed a small mass decrease within the range of 1÷2 mg.

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RoŻniata, E., and R. Dziurka. "The Phase Transformations in Hypoeutectoid Steels Mn-Cr-Ni." Archives of Metallurgy and Materials 60, no. 1 (2015): 497–502. http://dx.doi.org/10.1515/amm-2015-0080.

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Abstract The results of a microstructure and hardness investigations of the hypoeutectoid steels Mn-Cr-Ni, imitating by its chemical composition toughening steels, are presented in the paper. The analysis of the kinetics of phase transformations of undercooled austenite of steels containing different amounts of alloying elements in their chemical composition, constitutes the aim of investigations. Metallographic examinations were carried out on a Axiovert 200 MAT light microscope. Sections were etched with a 3% HNO3 solution in C2H5OH. Dilatometric tests were performed using L78 R.I.T.A dilatometer. Using dilatometer the changes of elongation (Δl) of the samples with dimensions Ø 3×10 mm as a function of temperature (T) were registered. Obtained heating curves were used to precisely determine the critical temperatures (critical points) for the tested steels, while the differentiation of obtained cooling curves allowed to precisely define the temperatures of the beginning and the end of particular transition to draw CCT diagrams. Four CCT diagrams worked out for the tested hypoeutectoid steels (for quenching of steel) are - in the majority of steels - separated by the undercooled austenitic range and are of the letter „C” shape. However, for steels with Mn and Ni the separation of diffusive transformations from the bainitic transformation by the stable austenitic range is not observed. Hardenability of four investigated hypoeutectoid steels is similar, but still not high. To obtain martensite in the microstructure of these steels, it is necessary to apply the cooling rate higher than 25°C/s. The exception constitutes the Mn - Ni steel, in which only cooling with the rate higher than 50°C/s allows to achieve the martensitic microstructure and to avoid diffusive transformations (pearlitic and ferritic).

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Kyriakopoulou, Helen, Panagiotis Karmiris-Obratański, Athanasios Tazedakis, et al. "Investigation of Hydrogen Embrittlement Susceptibility and Fracture Toughness Drop after in situ Hydrogen Cathodic Charging for an X65 Pipeline Steel." Micromachines 11, no. 4 (2020): 430. http://dx.doi.org/10.3390/mi11040430.

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The present research focuses on the investigation of an in situ hydrogen charging effect during Crack Tip Opening Displacement testing (CTOD) on the fracture toughness properties of X65 pipeline steel. This grade of steel belongs to the broader category of High Strength Low Alloy Steels (HSLA), and its microstructure consists of equiaxed ferritic and bainitic grains with a low volume fraction of degenerated pearlite islands. The studied X65 steel specimens were extracted from pipes with 19.15 mm wall thickness. The fracture toughness parameters were determined after imposing the fatigue pre-cracked specimens on air, on a specific electrolytic cell under a slow strain rate bending loading (according to ASTM G147-98, BS7448, and ISO12135 standards). Concerning the results of this study, in the first phase the hydrogen cations’ penetration depth, the diffusion coefficient of molecular and atomic hydrogen, and the surficial density of blisters were determined. Next, the characteristic parameters related to fracture toughness (such as J, KQ, CTODel, CTODpl) were calculated by the aid of the Force-Crack Mouth Open Displacement curves and the relevant analytical equations.

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Kurkin, A. S. "Study of isothermal decomposition of austenite using methods of mathematical modeling." Industrial laboratory. Diagnostics of materials 87, no. 6 (2021): 25–32. http://dx.doi.org/10.26896/1028-6861-2021-87-6-25-32.

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The capabilities of the numerical simulation of technological processes are limited by the accuracy and efficiency of determining the properties of materials which continuously change with repeated heating and cooling. The parameters of structural transformations are the principal factors affecting the properties of alloyed steels. We present a method for determining the parameters of formulas describing C-shaped curves of experimental diagrams of isothermal decomposition of austenite. The proposed approach makes it possible to reconstruct the entire C-shaped curve using a relatively small fragment near the «nose» (by three points). Joint processing of a series of curves provided determination of the parameters of ferritic, pearlitic and bainitic transformation kinetics. However, it is important to take into account the features of the diffusion decomposition of austenite. For example, ferrite and pearlite are formed in overlapping temperature ranges and have similar mechanical properties, but their combining into a single ferrite-pearlite structure complicates the construction of a mathematical model of transformation. The bainitic transformation has a transient character from diffusion to diffusionless one. As for the transformation temperature range, the limiting degree is a function of temperature (as in the case of martensitic transformation). It was shown that for ferrite-pearlite transformation the best results are obtained by the Kolmogorov – Avrami equation, and for the bainitic one — by the Austin – Rickett equation modified with allowance for an incomplete transformation.

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Araujo Barros, Renato, Antonio Jorge Abdalla, Humberto Lopes Rodrigues, and Marcelo dos Santos Pereira. "Characterization of a AISI/SAE 4340 Steel in Different Microstructural Conditions." Materials Science Forum 775-776 (January 2014): 136–40. http://dx.doi.org/10.4028/www.scientific.net/msf.775-776.136.

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The 4340 are classified as ultra-high strength steels used by the aviation industry and aerospace applications such as aircraft landing gear and several structural applications, usually in quenched and tempered condition. In this situation occurs reduction of toughness, which encourages the study of multiphasic and bainític structures, in order to maintain strength without loss of toughness. In this study, ferritic-pearlitic structure was compared to bainitic and martensitic structure, identified by the reagents Nital, LePera and Sodium Metabisulfite. Sliding wear tests of the type pin-on-disk were realized and the results related to the microstructure of these materials and also to their hardnesses. It is noted that these different microstructures had very similar behavior, concluding that all three tested pairs can be used according to the request level.

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Hausmann, K., D. Krizan, K. Spiradek-Hahn, A. Pichler, and E. Werner. "The influence of Nb on transformation behavior and mechanical properties of TRIP-assisted bainitic–ferritic sheet steels." Materials Science and Engineering: A 588 (December 2013): 142–50. http://dx.doi.org/10.1016/j.msea.2013.08.023.

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Araki, Toru, Masato Enomoto, and Koji Shibata. "Microstructural Aspects of Bainitic and Bainite-like Ferritic Structures of Continuously Cooled Low Carbon (<0.1%) HSLA Steels." Materials Transactions, JIM 32, no. 8 (1991): 729–36. http://dx.doi.org/10.2320/matertrans1989.32.729.

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Hui, Weijun, Yongjian Zhang, Xiaoli Zhao, Na Xiao, and Fangzhong Hu. "High cycle fatigue behavior of V-microalloyed medium carbon steels: A comparison between bainitic and ferritic-pearlitic microstructures." International Journal of Fatigue 91 (October 2016): 232–41. http://dx.doi.org/10.1016/j.ijfatigue.2016.06.013.

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Laitinen, Risto O., David A. Porter, L. Pentti Karjalainen, Pasi Leiviskä, and Jukka Kömi. "Physical Simulation for Evaluating Heat-Affected Zone Toughness of High and Ultra-High Strength Steels." Materials Science Forum 762 (July 2013): 711–16. http://dx.doi.org/10.4028/www.scientific.net/msf.762.711.

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Physical simulation of the most critical sub-zones of the heat-affected zone is a useful tool for the evaluation of the toughness of welded joints in high-strength and ultra-high-strength steels. In two high-strength offshore steels with the yield strength of 500 MPa, the coarse grained, intercritical and intercritically reheated coarse grained zones were simulated using the cooling times from 800 to 500 °C (t8/5) 5 s and 30 s. Impact and CTOD tests as well as microstructural investigations were carried out in order to evaluate the weldability of the steels without the need for expensive welding tests. The test results showed that the intercritically reheated coarse grained zone with the longer cooling time t8/5=30 s was the most critical sub-zone in the HAZ due to the M-A constituents and coarse ferritic-bainitic microstructure. In 6 mm thick ultra-high-strength steel Optim 960 QC, the coarse grained and intercritically reheated coarse grained zones were simulated using the cooling times t8/5 of 5, 10, 15 and 20s and the intercritical zone using the cooling times t8/5 of 5 and 10 s in order to select the suitable heat input for welding. The impact test results from the simulated zones fulfilled the impact energy requirement of 14 J (5x10 mm specimen) at -40 °C for the cooling times, t8/5, from 5 to 15 s, which correspond to the heat input range 0.4-0.7 kJ/mm (for a 6 mm thickness).

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Jirková, Hana, Jiří Vrtáček, Michal Peković, Tomáš Janda, and Ludmila Kučerová. "Influence of Chromium and Niobium on the Press-Hardening Process of Multiphase Low-Alloy TRIP Steels." Materials Science Forum 1016 (January 2021): 636–41. http://dx.doi.org/10.4028/www.scientific.net/msf.1016.636.

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Press-hardening is an intensively developing forming technology which is mainly used for the production of car body parts. Because it is a hot forming technology, small forming forces can be utilized and, due to the lower spring-back effect, more accurate products are achieved. In car bodies, materials with high energy absorption and a sufficient hardening coefficient are mainly used in impacted parts. One of these materials is TRIP multiphase steels with different chemical composition. In these steels, it is possible to achieve an ultimate strength up to 1000 MPa with the ductility of 20-30%. In order to achieve the desired properties, it is necessary to select a suitable heat treatment that allows to achieve a multiphase structure. Phase transformations and mechanical properties are influenced by the use of suitable alloying elements. Three low-alloy, multiphase TRIP steels with different chemical compositions with a carbon content of 0.2% were chosen for the experimental program. The first steel was alloyed only with manganese and silicon, in the second niobium was added, and in the third the influence of chromium on increase of hardenability and strength was investigated. Press-hardening was performed in a heated forming tool. To describe the effect of the cooling rate, the forming was carried out in a tool at room temperature and after preheating to 425°C. The influence of holding time in the tool at 425°C to support the formation of bainite and retained austenite stabilization was also investigated. Mixed ferritic-bainitic-martensitic structures with some retained austenite content were obtained.

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Stadler, Manfred, Martin Gruber, Ronald Schnitzer, and Christina Hofer. "Microstructural characterization of a double pulse resistance spot welded 1200 MPa TBF steel." Welding in the World 64, no. 2 (2019): 335–43. http://dx.doi.org/10.1007/s40194-019-00835-9.

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AbstractIn the automotive industry resistance, spot welding is the dominant technology in sheet metal joining of advanced high strength steels (AHSS). In order to improve the mechanical performance of AHSS welds, in-process tempering via a second pulse is a possible approach. In this work, two different double pulse welding schemes were applied to a 1200 MPa transformation-induced plasticity (TRIP)-aided bainitic ferrite (TBF) steel. The different microstructures in the welds were characterized via light optical and scanning electron microscopy. Additionally, hardness mappings with several hundred indents were performed. It is shown that the second pulse, following a low first pulse which is high enough to produce a weld nugget that fulfills the quality criterion of a minimum spot weld diameter of 4*√t, leads to partial reaustenitization and consequently to a ferritic/martensitic microstructure after final quenching. Hardness mappings revealed that this inner FZ is harder than the surrounding FZ consisting of tempered martensite. In contrast, if the highest current without splashing is chosen for the first pulse, the same second pulse does not reaustenitize the FZ but only temper the martensite.

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Petrunenkov, A. A. "Low-alloy ferritic-austenitic-bainitic steels obtained by a method of incomplete isothermal hardening from the (gamma+alpha)-area." Metal Science and Heat Treatment 33, no. 9 (1991): 647–50. http://dx.doi.org/10.1007/bf00811723.

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Larzabal, Gorka, Nerea Isasti, Jose Rodriguez-Ibabe, and Pello Uranga. "Evaluating Strengthening and Impact Toughness Mechanisms for Ferritic and Bainitic Microstructures in Nb, Nb-Mo and Ti-Mo Microalloyed Steels." Metals 7, no. 2 (2017): 65. http://dx.doi.org/10.3390/met7020065.

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41

Liang, Xiao Jun, Ming Jian Hua, C. Isaac Garcia, and Anthony J. DeArdo. "The Thermomechanical Controlled Processing of High-Strength Steel Plate: A New View of Toughness Based on Modern Metallography." Materials Science Forum 762 (July 2013): 38–46. http://dx.doi.org/10.4028/www.scientific.net/msf.762.38.

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Modern thermomechanical controlled processing (TMCP) of advanced steels is now an important processing route in the production of engineering structures and products that are of value to society. The principles of TMCP are now practiced in the hot mill, cold mill and press forming shops around the world. Successful TMCP means that the proper metallurgical microstructure has been obtained in the required areas of the steel. The ideal microstructure is often defined by the correct phase balance and dimensions either of the parent austenite or final ferritic phase. Technological and economic demands have led to ever increasing levels of strength, especially for applications such as large diameter linepipe. The operative yield strengths in 18mm hot rolled plate have increased from X52(ferrite pearlite) in 1970 to X80(ferrite-bainite) today. The next frontier is the X100-X120 strength range, where bainitic or martensitic microstructures are required. It is clear that achieving a high-strength bainitic microstructure in heavy plate requires a high Carbon Equivalent value (C. E. II or Pcm), a rapid cooling rate, and a low water-end temperature. The requirement of high toughness and good weldability also means a low carbon content. This paper will describe the results of a research program where a steel of C. E. 0.56 and Pcm 0.23 was reheated, rough rolled for grain refinement, finish rolled for austenite pancaking, and direct quenched to below the Bs temperature. It was found that the strength and especially the toughness of the fully processed plates could not be explained using conventional metallographic techniques in conjunction with known structure-property relationships. However, the application of modern metallographic techniques based on FEG-SEM incorporating OIM led to microstructural characterization that more fully explained the observed mechanical properties. Of particular importance were the amount of MA micro-constituent, the crystallographic packet size of the bainite, and the high angle boundary character, especially the CSL boundaries, found in the microstructure. In the future, improved modeling of microstructural evolution and attendant mechanical properties will incorporate these important features.

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42

Balart, M. J., C. L. Davis, and M. Strangwood. "Fracture behaviour in medium-carbon Ti–V–N and V–N microalloyed ferritic-pearlitic and bainitic forging steels with enhanced machinability." Materials Science and Engineering: A 328, no. 1-2 (2002): 48–57. http://dx.doi.org/10.1016/s0921-5093(01)01679-3.

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Arribas, Maribel, Radhakanta Rana, Chris Lahaije, Xabier Gómez, Iñigo Aranguren, and Iñaki Pérez. "Design and Properties of 1000 MPa Strength Level Hot-Formed Steels Possessing Dual-Phase and Complex-Phase Microstructures." Materials Science Forum 941 (December 2018): 352–57. http://dx.doi.org/10.4028/www.scientific.net/msf.941.352.

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In cold forming for automotive lightweight design, advanced high strength steels (AHSS) lead to limited formability, high springback and press forces, low stretch flangeability, multiple operations for complex geometries and large scrap rates. Two sets of AHSS, namely ferritic-martensitic dual-phase (DP) steel and martensitic-bainitic complex-phase (CP) steel with some amounts of retained austenite (RA), were designed for the hot-forming route, which eliminates the above drawbacks and guarantees higher performance in the body-in-white (BIW). Design of four DP and four CP alloys was accomplished using JMatPro6.0 thermodynamic software and available literature. The alloys were manufactured in the laboratory in cold-rolled gauge of ~1.5 mm and subjected to hot-forming cycles including hot deformation (up to 20% strain), using a dilatometer and a Gleeble 3800 machine. The thermal cycles of the DP alloys included an intercritical reheating whereas in-situ austempering or slow continuous cooling followed by supercritical reheating was used for the CP alloys. The results showed that yield strength (YS) of 605MPa & 695MPa, ultimate tensile strength (UTS) of 1097MPa & 1242MPa with a total elongation (TE) of 12.6% & 14.1% can be achieved in the best performing DP alloys with a martensite content of 65% & 60 vol.%. The best CP alloys with austempering achieved YS of 673MPa & 699MPa, UTS of 983MPa & 1026MPa and TE of 9.2% & 13.6% with RA of 4%-12 vol.%. The continuously-cooled alloys achieved even better properties. Higher bendability at 1.0 mm gauge in the critical direction was achieved in the CP alloys (90o&107o) than in the DP alloys (73o&76o).

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Gorynin, I. V., V. V. Rybin, I. P. Kursevich, A. N. Lapin, E. V. Nesterova, and E. Yu Klepikov. "Effect of heat treatment and irradiation temperature on mechanical properties and structure of reduced-activation Cr–W–V steels of bainitic, martensitic, and martensitic–ferritic classes." Journal of Nuclear Materials 283-287 (December 2000): 465–69. http://dx.doi.org/10.1016/s0022-3115(00)00210-5.

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45

Domovcová, Lucia, Pavol Beraxa, Milan Mojžiš, Michal Weiss, Martin Fujda, and Ľudovít Parilák. "Microstructure and Mechanical Properties of Steel Grade 14MoV6-3." Materials Science Forum 782 (April 2014): 137–40. http://dx.doi.org/10.4028/www.scientific.net/msf.782.137.

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Steel grade 14MoV6-3 is a low-carbon microalloyed steel with addition of chromium and molybdenum. This medium-strength steel exhibits a ferritic-bainitic microstructure after the heat treatment. This grade is designed mainly for power industry applications, withstanding operating temperatures up to 580 °C; in Železiarne Podbrezová, this particular grade is used for production of hot rolled seamless boiler tubes. In this paper we present the basic chemical concept of 14MoV6-3 steel along with its mechanical properties after the heat treatment. Further, analysis of the final microstructure, carbide phases and precipitation of vanadium is being presented as well. For this purpose, the yield stress theory has been proposed along with predictive nomograms for selected ferritic-bainitic phases. According to the results of DTA analyses, necessary conditions for heat treatment after rolling have been proposed. Finally, CCT diagrams for required ferritic-bainitic structure are presented as well.

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46

Golański, Grzegorz. "Mechanical Properties of G17CrMoV5 – 10 Cast Steel after Regenerative Heat Treatment." Solid State Phenomena 147-149 (January 2009): 732–37. http://dx.doi.org/10.4028/www.scientific.net/ssp.147-149.732.

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The paper presents results of research on the influence of regenerative heat treatment on structure and properties of G17CrMoV5 – 10 cast steel. Investigated material was taken out from a turbine frame serviced for over 250 000 hours (total service time) at the temperature of 535 oC. The cast steel after service revealed degraded bainitic-ferritic structure and was characterized by mechanical properties ranging below norm requirements. It has been proved that high tempering temperature in the case of cast steel with bainitic structure ensures optimum combination of mechanical properties and impact energy. It has also been shown that ferrite has a negative influence on impact energy of the cast steel with bainitic-ferritic structure.

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47

Babenko, Anatoly A., Leonid A. Smirnov, and Alena G. Upolovnikova. "The Effect of Boron, Manganese and Sulfur on the Microstructure and Mechanical Properties of Pipe Steel 17G1SU." Solid State Phenomena 316 (April 2021): 408–12. http://dx.doi.org/10.4028/www.scientific.net/ssp.316.408.

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The paper presents the results of the effect of boron, manganese and sulfur on the microstructure and mechanical properties of pipe steel 17G1SU. It was shown that the microstructure of boron-free steel sample containing 1.4% Mn and 0.01% S consists mainly of ferrite and a small amount of perlite. Samples microalloyed by boron are represented by a dispersed ferritic-bainitic structure. A decrease in ferrite grain size from 8.7 μm, in a comparative sample without boron containing 1.4% Mn and 0.010% S to 5.8 μm in a sample of steel containing 0.006% B, 1.6% Mn and 0.011% S, shows increasing the dispersity of the ferritic-bainitic structure. A decrease in the manganese content to 1.4, sulfur to 0.004% and an increase in boron concentration to 0.0011%, despite an increase in grain size to 6.8 μm, retain a fine-grained structure. The effect of boron, manganese, and sulfur content on the microhardness of the structural phases of the studied pipe steel samples is noted. The smallest microhardness of ferrite and perlite is observed in the base sample without boron, reaching 180 and 214 HV10, respectively. The microalloying of pipe steel containing 1.6% Mn, 0.011% S with boron is accompanied by an increase in the microhardness of the bainitic phase to 314 HV10, which increases to 400 HV10 with an increase in boron concentration to 0.011%, and a decrease in the content of manganese and sulfur to 1.4 and 0.003%. In this case, the microhardness of the ferrite phase, reaching an increase to 260 HV10, is practically independent of the content of boron, manganese, and sulfur. The mechanical properties of the experimental metal rolling with a thickness of 10 mm provide the production of rolled steel of strength class X80, without heat treatment, regardless of the content of boron, manganese, and sulfur, as a result of the formation of a finely dispersed ferrite-bainitic structure.

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Skołek, E., S. Marciniak, and W. A. Świątnicki. "Thermal Stability of Nanocrystalline Structure In X37CrMoV5-l Steel." Archives of Metallurgy and Materials 60, no. 1 (2015): 511–16. http://dx.doi.org/10.1515/amm-2015-0082.

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AbstractThe aim of the study was to investigate the thermal stability of the nanostructure produced in X37CrMoV5-1 tool steel by austempering heat treatment consisted of austenitization and isothermal quenching at the range of the bainitic transformation. The nanostructure was composed of bainitic ferrite plates of nanometric thickness separated by thin layers of retained austenite. It was revealed, that the annealing at the temperature higher than temperature of austempering led to formation of cementite precipitations. At the initial stage of annealing cementite precipitations occurred in the interfaces between ferritic bainite and austenite. With increasing temperature of annealing, the volume fraction and size of cementite precipitations also increased. Simultaneously fine spherical Fe7C3carbides appeared. At the highest annealing temperature the large, spherical Fe7C3carbides as well as cementite precipitates inside the ferrite grains were observed. Moreover the volume fraction of bainitic ferrite and of freshly formed martensite increased in steel as a result of retained austenite transformation during cooling down to room temperature.

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Safa, Mohamed, Rashad Ramadan, and Samir Ibrahim. "Processing and Evaluation of Ferritic-Bainitic Multi-phase Steel." Journal of Petroleum and Mining Engineering 19, no. 1 (2017): 71–80. http://dx.doi.org/10.21608/jpme.2017.39126.

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Chatzidouros, E. V., V. J. Papazoglou, and D. I. Pantelis. "Hydrogen effect on a low carbon ferritic-bainitic pipeline steel." International Journal of Hydrogen Energy 39, no. 32 (2014): 18498–505. http://dx.doi.org/10.1016/j.ijhydene.2014.09.029.

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Journal articles on the topic 'Ferritic-Bainitic steels'

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