Journal articles: 'Ferritic steel. Thermodynamics'

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Lu, Qi, Wei Xu, and Sybrand van der Zwaag. "A Material Genomic Design of Advanced High Performance, Non-Corroding Steels for Ambient and High Temperature Applications." Materials Science Forum 783-786 (May 2014): 1201–6. http://dx.doi.org/10.4028/www.scientific.net/msf.783-786.1201.

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This work presents an artificial intelligence based design of a series of novel advanced high performance steels for ambient and high temperature applications, following the principle of the materials genome initiative, using an integrated thermodynamics/kinetics based model in combination with a genetic algorithm optimization routine. Novel steel compositions and associated key heat treatment parameters are designed both for applications at the room temperature (ultra-high strength maraging stainless steel) and at high temperatures (ferritic, martensitic and austenitic creep resistant steels). The strength of existing high end alloys of aforementioned four types are calculated according to the corresponding design criteria. The model validation studies suggest that the newly designed alloys have great potential in outperforming existing grades.

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Xuguang, DONG, and FU Junwei. "Precipitation Thermodynamics of TiN in B439M Ferritic Stainless Steel during Solidification." Journal of Mechanical Engineering 56, no. 18 (2020): 73. http://dx.doi.org/10.3901/jme.2020.18.073.

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Chen, Xingrun, Guoguang Cheng, Yuyang Hou, and Jingyu Li. "Inclusions evolution during the LF refining process of 439 ultra-pure ferritic stainless steel." Metallurgical Research & Technology 116, no. 6 (2019): 619. http://dx.doi.org/10.1051/metal/2019048.

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The morphology, composition, size, and number of inclusions in 439 ultra-pure ferritic stainless steel samples were analyzed using an automatic scanning electron microscope combined with an energy-dispersive X-ray spectrometer. In addition, the appropriate contents of titanium, aluminum, and calcium were analyzed through the coupling of thermodynamics calculation and experimental results. CaO-Al2O3-MgO inclusions existed in the 439 steel before Ti additions in the ladle furnace (LF) refining process. After Ti addition in the LF refining process, the inclusions were transformed into CaO-Al2O3-MgO-TiOx inclusions. The evolution of these inclusions was consistent with thermodynamic calculation, which indicated that when the Al, Ca, and Ti contents were within a reasonable range, Ca treatment could significantly modify the aluminate and spinel to form CaO-Al2O3-MgO liquid inclusions. In addition, the compositions of inclusions after the addition of titanium were mostly located in the Al2O3-TiOx stable phase. The collision of the CaO-Al2O3-MgO liquid inclusions and Al2O3-TiOx inclusions resulted in the modification of the CaO-Al2O3-MgO-TiOx inclusions. The compositions of most inclusions were located in the liquid zone. The control range of the aluminum, calcium, and titanium contents was obtained: logAl% ≥ 1.481logTi% − 0.7166, Ca% ≥ 34.926(Al%)3 − 3.3056(Al%)2 + 0.1112(Al%) − 0.0003.

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Park, Joo Hyun, Sang-Beom Lee, and Henri R. Gaye. "Thermodynamics of the Formation of MgO-Al2O3-TiO x Inclusions in Ti-Stabilized 11Cr Ferritic Stainless Steel." Metallurgical and Materials Transactions B 39, no. 6 (November 11, 2008): 853–61. http://dx.doi.org/10.1007/s11663-008-9172-4.

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Kazakov, A. A., O. V. Fomina, A. I. Zhitinev, and P. V. Melnikov. "Basic physical and chemical concepts for controlling δ-ferrite content when welding with austenite-ferrite materials." Voprosy Materialovedeniya, no. 4(96) (January 8, 2019): 42–52. http://dx.doi.org/10.22349/1994-6716-2018-96-4-42-52.

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The paper shows the influence of steel chemical composition on δ-ferrite behavior throughout the entire range of temperature considering welding consumables. Materials for joints are manufactured of the 10Kh19N11M4F, currently used for welding high-strength low-alloy steels. This steel prospects for welding high-nitrogen corrosion-resistant steels saving their non-magnetism, including the zone of welded joint, were analyzed on the basis of these studies. Using thermodynamic modeling, critical parameters were found that determine the behavior of δ-ferrite during solidification and subsequent cooling of solid steel. The most important parameters are the depth of the σ-ferritic transformation and the maximum equilibrium temperature of austenitization, which were used to interpret the experimental data obtained during hot physical modeling of welding. The areas of promising compositions of materials for welding of low-alloyed high-strength and high-nitrogen corrosion-resistant steels without hot cracks and providing, if necessary, the non-magnetic seam were found and depicted on a fragment of an improved Scheffler – Speidel diagram.

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Klancnik, G., Steiner Petrovic, and J. Medved. "Thermodynamic calculation of phase equilibria in stainless steels." Journal of Mining and Metallurgy, Section B: Metallurgy 48, no. 3 (2012): 383–90. http://dx.doi.org/10.2298/jmmb121119048k.

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In this paper two examples of thermodynamic investigation of stainless steels using both, experimental and modeling approach are described. The ferritic-austenitic duplex stainless steel and austenitic stainless steel were investigated using thermal analysis. The complex melting behavior was evident for both alloy systems. Experimentally obtained data were compared with the results of the thermodynamic calculations using the CALPHAD method. The equilibrium thermal events were also described by the calculated heat capacity. In spite of the complexity of both selected real alloy systems a relative good agreement was obtained between the thermodynamic calculations and experimental results.

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Juuti, Timo, Timo Manninen, Sampo Uusikallio, Jukka Kömi, and David Porter. "New Ferritic Stainless Steel for Service Temperatures up to 1050 °C Utilizing Intermetallic Phase Transformation." Metals 9, no. 6 (June 7, 2019): 664. http://dx.doi.org/10.3390/met9060664.

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A large number of thermodynamic simulations has been used to design a new Nb-Ti dual stabilized ferritic stainless steel with excellent creep resistance at 1050 °C through an optimal volume fraction of Laves (η) phase stabilized by the alloying elements Nb, Si and Mo. By raising the dissolution temperature of the phase, which also corresponds to the onset of rapid grain growth, the steel will better maintain the mechanical properties at higher service temperature. Laves phase precipitates can also improve creep resistance through precipitation strengthening and grain boundary pinning depending on the dominant creep mechanism. Sag tests at high temperatures for the designed steel showed significantly better results compared to other ferritic stainless steels typically used in high temperature applications at present.

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Ivanisenko, Julia, Ian MacLaren, Xavier Sauvage, Ruslan Valiev, and Hans Jorg Fecht. "Phase Transformations in Pearlitic Steels Induced by Severe Plastic Deformation." Solid State Phenomena 114 (July 2006): 133–44. http://dx.doi.org/10.4028/www.scientific.net/ssp.114.133.

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The paper presents an overview of a number of unusual phase transformations which take place in pearlitic steels in conditions of the severe deformation, i.e. combination of high pressure and strong shear strain. Strain-induced cementite dissolution is a well-documented phenomenon, which occurs during cold plastic deformation of pearlitic steels. Recently new results which can shed additional light on the mechanisms of this process were obtained thanks to 3DAP and HRTEM investigations of pearlitic steel deformed by high pressure torsion (HPT). It was shown that the process of cementite decomposition starts by carbon depletion from the carbides, which indicates that the deviation of cementite’s chemical composition from the stoichiometric is the main reason for thermodynamic destabilisation of cementite during plastic deformation. Important results were obtained regarding the distribution of released carbon atoms in ferrite. It was experimentally confirmed that carbon segregates to the dislocations and grain boundaries of nanocrystalline ferrite. Another unusual phase transformation taking place in nanocrystalline pearlitic steel during room temperature HPT is a stress induced α→γ transformation, which never occurs during conventional deformation of coarse grained iron and carbon steels. It was concluded that this occurred due to a reverse martensitic transformation. The atomistic mechanism and the thermodynamics of the transformation, as well as issues related to the stability of the reverted austenite will be discussed.

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Mejía, Ignacio, Gladys Y. Díaz-Martínez, and Arnoldo Bedolla-Jacuinde. "Metallographic Characterization of a Ti-Containing Low-Density Fe-Mn-Al-C Steel in As-Cast Condition." MRS Proceedings 1812 (2016): 47–52. http://dx.doi.org/10.1557/opl.2016.17.

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ABSTRACTLow-density steels, with an excellent combination of outstanding mechanical properties, ultimate tensile strength and specific weight reduction, have been attracting great attention as a new group of materials in many industrial applications, particularly in the automotive industry. The aim of this work was to characterize the microstructure of a Ti-containing low-density Fe-Mn-Al-C steel in the as-cast condition. For this purpose, Ti-containing low-density steel was melted in an induction furnace using high purity raw materials and cast into a metal ingot mold. Chemical composition of the studied steel was Fe-32Mn-7.0Al-2.2C-0.5Ti (wt%). Samples were prepared by standard metallographic technique (grinding and polishing) and chemically etched with 2% nital solution, in order to reveal the dendritic microstructure. Microstructure observations were performed by scanning electron microscopy and the chemical nature of the present phases was determined by energy-dispersive X-ray. X-ray diffraction was performed at room temperature using a diffractometer with Cu Kα radiation. Phase equilibria by thermodynamic calculations for the studied steel were performed using JMatPro® software package. In general, results revealed a finer dendritic microstructure composed of ferritic matrix and austenite islands. The presence of ferrite and austenite in the steel was also confirmed by X-ray diffraction.

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Liu, Yan, Jian Ming Wang, Yang Liu, and Chun Lin He. "Effect of Magnesium Addition on the Cast Microstructure of a Kind of HSLA Steel." Applied Mechanics and Materials 395-396 (September 2013): 293–96. http://dx.doi.org/10.4028/www.scientific.net/amm.395-396.293.

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A new technology to obtain a fine-structured and high-toughness HAZ of HSLA steel for high heat input welding is developed using metallurgical thermodynamics, physical chemistry of metallurgy and material processing methods synthetically in this study. A kind of HSLA steel is designed in this experiment. The thermal stability second phase particles which would not be dissolved or aggregated at high temperature will be expected by means of adding magnesium into the steel in the form of Mg-Zr alloy. The effect of magnesium addition on the cast microstructure of HSLA steel was analysed. The results show that The cast microstructure is mainly consist of lamellar and acicular ferrite, a small amount of pearlite and bainite. Compared with the original steel, there are acicular ferrites presenting in the experimental steel after adding 3 wt% Mg and 5 wt% Mg, which are the microstructure that we hope to get. The acicular ferrite will have a positive impact on the mechanical properties of the subsequent rolled steel.

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Dai, Yu Mei, and Yong Qing Ma. "Study on Effects of Pretreatment on Carbide of a Medium-Alloy High Carbon Steel." Advanced Materials Research 194-196 (February 2011): 271–74. http://dx.doi.org/10.4028/www.scientific.net/amr.194-196.271.

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The effect of pre-treatment on carbide transformation and morphology of a medium-alloy high carbon steel (0.86C, 0.84Cr, 1.85W, 0.95Mo, 0.31V) with multi-elements was investigated in this paper. The results show that there are multiple types of carbides (M3C、M23C6、M7C3、M6C、MC) in the annealed steel. The morphology of carbide in the annealing microstructure largely relate to the process before annealing. Carbides with disperse spherical and short rod-like distribution exist in the ferritic matrix when the steels are annealed at 820−860°C. The spherical carbides in the ferritic matrix can be obtained by isothermal annealing at 680−720°C after heating at 800°C. The morphology of carbides with different pretreatment process relate to carbide transformation, which can be described by calculating based on phase equilibrium thermodynamic.

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e, Silva, L. Nakamura, and F. Rizzo. "Application of computational modeling to the kinetics of precipitation of aluminum nitride in steels." Journal of Mining and Metallurgy, Section B: Metallurgy 48, no. 3 (2012): 471–76. http://dx.doi.org/10.2298/jmmb120703058e.

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In previous works the possibilities and limitations of the application of calculations in the Al-Fe-N system to describe the precipitation of AlN in steel, both in the solid state and during the solidification were discussed and some difficulties related to the extension of these calculations to more complex steel systems, due to limitations in the thermodynamic data were also presented. Presently, the precipitation kinetics of AlN in ferrite (BCC) and austenite (FCC) is discussed. The correct description of the precipitation of AlN in both phases is relevant to: (a) the precipitation at higher temperatures, in the austenite field, that occurs in some steels, (b) the concurrent precipitation of this nitride with the annealing treatment, when the steel is mostly ferritic, used in the processing of some types of deep drawing steels (c) the precipitation of this nitride in some silicon alloyed electric steels at relatively high temperatures, when these steels can have significant fractions of BCC and FCC in their microstructure. The precise knowledge of the precipitation-dissolution behavior of AlN in special in these two latter classes of steels is of great importance to their correct processing. In this work, a computational tool for simulating multiparticle precipitation kinetics of diffusion-controlled processes in multi-component and multi-phase alloy systems is employed in an attempt to describe these precipitation processes. The results are compared with experimental data on precipitation. The assumptions necessary for the application of the multi-particle modeling tool are discussed, agreements and discrepancies are identified and some possible reasons for these are indicated. Furthermore, the impact of the use of different sources of data on steel processing development is discussed and the need for further studies highlighted.

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Lad’yanov, V. I., G. A. Dorofeev, E. V. Kuz’minykh, V. A. Karev, and A. N. Lubnin. "ALUMINOBAROTHERMIC SYNTHESIS OF HIGH-NITROGEN STEEL." Izvestiya. Ferrous Metallurgy 62, no. 2 (March 30, 2019): 154–62. http://dx.doi.org/10.17073/0368-0797-2019-2-154-162.

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High-nitrogen austenitic steels are promising materials, combining high strength, plasticity and corrosion resistance properties. However, to produce high-nitrogen steel by conventional metallurgical methods under high nitrogen pressure, powerful and complex metallurgical equipment is required. From energy-saving viewpoint, an alternative and simpler method for producing high-nitrogen steels can be aluminothermy (reduction of metal oxides by metallic aluminum) under nitrogen pressure. Thermodynamic modeling of aluminothermic reactions in a nitrogen atmosphere was carried out by the authors. Aluminothermy under nitrogen pressure was used to produce high-nitrogen nickel-free Cr – N and Cr – Mn – N stainless steels with a nitrogen content of about 1 %. Microstructure (X-ray diffraction, metallography and transmission electron microscopy techniques) and mechanical properties were examined. Thermodynamic analysis has shown that the aluminothermic reduction reactions do not go to the end. The most important parameter of the synthesis is the ratio of Al and oxygen in the charge, the correct choice of which provides a compromise between completeness of oxides reduction, content of aluminum and oxygen in steel (the degree of deoxidation), and its contamination with aluminum nitride. Cr – N steel ingots in the cast state had the structure of nitrogen perlite (ferrite-nitride mixture), and Cr – Mn – N steel – ferrite-austenite structure with attributes of austenite discontinuous decomposition with Cr2 N precipitations. Quenching resulted in complete austenization of both steels. The compliance of the austenite lattice parameter obtained from the diffractograms for quenched Cr – Mn – N steel with the parameter predicted from the known concentration dependence for Cr – Mn – N austenitic steels indicated that all alloying elements (including nitrogen) were dissolved in austenite during aging at quenching temperature and fixed in the solid solution by quenching. Study of the mechanical properties of quenched Cr – Mn – N steel has shown a combination of high strength and ductility. It is concluded that by the aluminothermic method a high-nitrogen steel can be obtained, which, by mechanical properties, is not inferior to industrial steel – analog manufacted by electroslag remelting under nitrogen pressure.

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Orlov, Victor, Leonid Levkov, Vladimir Dub, Alan Balikoev, and Dmitry Shurygin. "New approach to development and manufacturing technologies of duplex steel." E3S Web of Conferences 121 (2019): 04010. http://dx.doi.org/10.1051/e3sconf/201912104010.

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We conducted a brief review of current production and application of duplex and super duplex steels for manufacture of equipment exposed to the hazard of sulphide stress-corrosion cracking, sea water and other corrosive environment. The super duplex steel with enhanced corrosion-mechanical characteristics in comparison with the known steels of austenitic-ferritic class was developed. Based on the concepts of formation of a special structure of two-phase austenitic-ferritic steels in the process of crystallization, the possibilities of compositional, technological, thermal and special impact techniques are considered and advanced ways of controlling physical, chemical, structural homogeneity and properties of super duplex steels are developed. Electroslag remelting with the application of low-frequency alternating current provides effective control over the length of the two-phase area, the size of the primary dendrites of the austenitic and ferritic phases, the average distance between their axes, the parameters of the crystallizing cell, the development of liquation phenomena and the size of the growing non-metallic phases. Within framework of the proposed approach, the thermodynamic and kinetic conditions for the formation and growth of hardening phases are assessed, a new composition and a complex technology for the manufacture of corrosion-resistant super duplex steels for gas and oil production equipment has been developed. Thermodynamically stable, having sizes of 30-300 nm, niobium nitrides and carbonitrides are located inside the grains of the ferritic phase. At the same time, the sigma phase and chromium carbide precipitates at the intergrain boundaries are not observed. The results of the determination of mechanical and corrosion properties in accordance with the NACE TM 0177 standard (method A), tests of corrosion witness-samples in field conditions demonstrate the advantages and prospects of using new super duplex steel for the manufacture of oil and gas production equipment operating in an environment with high H2S content and CO2 under significant mechanical loads, without the risk of brittle fracture.

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Falat, L., V. Homolová, J. Kepic, M. Svoboda, and A. Výrostková. "Microstructure and properties degradation of P/T 91, 92 steels weldments in creep conditions." Journal of Mining and Metallurgy, Section B: Metallurgy 48, no. 3 (2012): 461–69. http://dx.doi.org/10.2298/jmmb120701057f.

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The studies were performed on dissimilar ferritic/austenitic weldments between 9Cr tempered martensitic steels of the grades either P/T 91 or 92 and unstabilised AISI316H austenitic steel. The welded joints were fabricated using the fusion welding by tungsten inert gas (TIG) method with Ni-based filler metal. Microstructural analyses were performed using light and electron microscopy. Microstructural gradient in heat-affected zone (HAZ) of 9Cr steels remained preserved during creep exposure. All weldments fractured by the type IV failure within their intercritical HAZ (ICHAZ) regions. The most remarkable microstructural change during creep was the precipitation of intermetallic Laves phase. Experimentally determined phases of the samples after creep exposure are in good agreement with equilibrium thermodynamic calculations.

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Juuti, Timo J., Timo Manninen, and David Porter. "Influence of Cooling Rate on Free Interstitial Concentration in Type 430 Ferritic Stainless Steel." Key Engineering Materials 611-612 (May 2014): 111–16. http://dx.doi.org/10.4028/www.scientific.net/kem.611-612.111.

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In ferritic steels, the amount of free C and N should be as low as possible to avoid the formation of Cottrell atmospheres and their associated discontinuous yielding and Lüders bands during forming. During the post-annealing cooling of ferritic stainless steel, carbides and nitrides of the type MX and M23C6precipitate. The volume fraction of the precipitates is determined by chemical composition, microstructure and the cooling path. In some cases, precipitation might not be sufficient to remove all free interstitials from the matrix, in which case, the process parameters or composition of the steel should be reconsidered. Here, thermodynamic and kinetic calculations using Thermo-calc and TC Prisma software have been made to investigate the precipitation of C and N as a function of total interstitial content and cooling rate. According to the calculations, decreasing the cooling rate would result in a more efficient precipitation and hence, less free C and N in the matrix, but the amount is not sufficient to remove the upper yield point. Furthermore, changing the C and N content of the steel was found to have insignificant influence. However, the free C and N could possible be bound through a more complex cooling.

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Redjaïmia, Abdelkrim, and Antonio Manuel Mateo Garcia. "On the M23C6-Carbide in 2205 Duplex Stainless Steel: An Unexpected (M23C6/Austenite)—Eutectoid in the δ-Ferritic Matrix." Metals 11, no. 9 (August 25, 2021): 1340. http://dx.doi.org/10.3390/met11091340.

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This study is focused on isothermal and anisothermal precipitation of M23C6 carbides from the fully ferritic structure of the (γ + δ) austenitic-ferritic duplex stainless steel X2CrNiMo2253, (2205). During isothermal heat treatments, small particles of K-M23C6 carbide precipitates at the δ/δ grain-boundaries. Their formation precedes γ and σ-phases, by acting as highly potential nucleation sites, confirming the undertaken TEM investigations. Furthermore, anisothermal heat treatment leads to the formation of very fine islands dispersed throughout the fully δ-ferritic matrix. TEM characterization of these islands reveals a particular eutectoid, reminiscent of the well-known (γ-σ)—eutectoid, usually encountered in this kind of steel. TEM and electron microdiffraction techniques were used to determine the crystal structure of the eutectoid constituents: γ-Austenite and K-M23C6 carbides. Based on this characterization, orientation relationships between the two latter phases and the ferritic matrix were derived: cube-on-cube, on one hand, between K-M23C6 and γ-Austenite and Kurdjumov-Sachs, on the other hand, between γ-Austenite and the δ-ferritic matrix. Based on these rational orientation relationships and using group theory (symmetry analysis), the morphology and the only one variant number of K-M23C6 in γ-Austenite have been elucidated and explained. Thermodynamic calculations, based on the commercial software ThermoCalq® (Thermo-Calc Software, Stockholm, Sweden), were carried out to explain the K-M23C6 precipitation and its effect on the other decomposition products of the ferritic matrix, namely γ-Austenite and σ-Sigma phase. For this purpose, the mole fraction evolution of K-M23C6 and σ-phase and the mass percent of all components entering in their composition, have been drawn. A geometrical model, based on the corrugated compact layers instead of lattice planes with the conservation of the site density at the interface plane, has been proposed to explain the transition δ-ferrite ⇒ {γ-Austenite ⇔ K-M23C6}.

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Cerra Florez, Mauro Andres, Gemma Fargas Ribas, Jorge Luiz Cardoso, Antonio Manuel Mateo García, Joan Josep Roa Rovira, Moises Bastos-Neto, Hamilton Ferreira Gomes de Abreu, and Marcelo José Gomes da Silva. "Oxidation Behavior of Maraging 300 Alloy Exposed to Nitrogen/Water Vapor Atmosphere at 500 °C." Metals 11, no. 7 (June 24, 2021): 1021. http://dx.doi.org/10.3390/met11071021.

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Aging heat treatments in maraging steels are fundamental to achieve the excellent mechanical properties required in several industries, i.e., nuclear, automotive, etc. In this research, samples of maraging 300 alloy were aged using a novel procedure that combines different steps with two atmospheres (nitrogen and water vapor) for several hours. The oxidized surface layer was chemical, microstructural and micromechanically characterized. Due to the thermodynamic and kinetic conditions, these gases reacted and change the surface chemistry of this steel producing a thin iron-based oxide layer of a homogeneous thickness of around 500 nm. Within the aforementioned information, porosity and other microstructural defects showed a non-homogeneous oxide, mainly constituted by magnetite, nickel ferrite, cobalt ferrite, and a small amount of hematite in the more external parts of the oxide layer. In this sense, from a chemical point of view, the heat treatment under specific atmosphere allows to induce a thin magnetic layer in a mixture of iron, nickel, and cobalt spinel ferrites. On the other hand, the oxide layer presents an adhesive force 99 mN value that shows the capability for being used for tribological applications under sliding contact tests.

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Tanaka, K., M. Hara, Yasu Yogo, Kou Nakanishi, and Carlos Capdevila. "Phase Transformation Modeling of Medium-Carbon Forging Steel." Materials Science Forum 539-543 (March 2007): 2443–48. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.2443.

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The kinetics of phase transformations in medium-carbon forging steels (MCFS) have been modeled based on CALPHAD multicomponent thermodynamics and the classical nucleation-growth theory. New treatments include the time dependency of parabolic growth rate of proeutectoid ferrite (α) , which account for the soft impingement effect by carbon enrichment in austenite (γ). And a potential transition of γ/α interface equilibrium has also been considered depending on temperatures and velocity of the moving interface. To make a realistic prediction of the onset of pearlite (P) transformation, a normal distribution of γ grain size has been assumed and successive α→P transformation kinetics in each grain size have been summated. The developed program coupled with thermodynamic solver, 'ThermoCalc', calculated the isothermal kinetics of MCFS and has been found to predict well the effect of minor difference of chemical composition / holding temperatures.

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Xu, Longyun, Jian Yang, Joohyun Park, and Hideki Ono. "Mechanism of Improving Heat-Affected Zone Toughness of Steel Plate with Mg Deoxidation after High-Heat-Input Welding." Metals 10, no. 2 (January 21, 2020): 162. http://dx.doi.org/10.3390/met10020162.

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In the present study, the mechanism of improving HAZ toughness of steel plate with Mg deoxidation after the simulated welding with the heat input of 400 kJ/cm was investigated through in situ observation, characterization with SEM-EDS and TEM-EDS, and thermodynamic calculation. It was found that intragranular acicular ferrite (IAF) and polygonal ferrite (PF) contributed to the improvements of HAZ toughness in steels with Mg deoxidation. With the increase of Mg content in steel, the oxide in micron size inclusion was firstly changed to MgO-Ti2O3, then to MgO with the further increase of Mg content in steel. The formation of nanoscale TiN particles was promoted more obviously with the higher Mg content in the steel. The growth rates of austenite grains at the high-temperature stage (1400~1250 °C) during the HAZ thermal cycle of steels with conventional Al deoxidation and Mg deoxidation containing 0.0027 and 0.0099 wt% Mg were 10.55, 0.89, 0.01 μm/s, respectively. It was indicated that nanoscale TiN particles formed in steel with Mg deoxidation were effective to inhibit the growth of austenite grain. The excellent HAZ toughness of steel plates after welding with a heat input of 400 kJ/cm could be obtained by control of the Mg content in steel to selectively promote the formation of IAF or retard the growth of austenite grain.

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Offerman, S. Eric, Henrik Strandlund, Niels H. van Dijk, Jilt Sietsma, Erik M. Lauridsen, L. Margulies, Henning Friis Poulsen, John Ågren, and Sybrand van der Zwaag. "Ferrite Formation during Slow Continuous Cooling in Steel." Materials Science Forum 550 (July 2007): 357–62. http://dx.doi.org/10.4028/www.scientific.net/msf.550.357.

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Ferrite formation during austenite decomposition in carbon-manganese steel is studied during slow continuous cooling by three-dimensional x-ray diffraction microscopy at a synchrotron source. The ferrite fraction and nucleation rate are measured simultaneously and independently in real time in the bulk of the specimen. Thermodynamic calculations involving both ortho- and paraequilibrium have been performed to determine the driving force for nucleation. From the experiments and thermodynamic calculations the activation energies are estimated for nucleation and the transfer of iron atoms across the interface of the cluster during ferrite nucleation in steel.

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N'Dah, Eugene, F. J. Bolívar, L. Sánchez, M. P. Hierro, Sofia Tsipas, and F. J. Pérez. "Al-Mn CVD-FBR Protective for Steam Corrosion Applications." Materials Science Forum 595-598 (September 2008): 351–58. http://dx.doi.org/10.4028/www.scientific.net/msf.595-598.351.

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Ferritic steels are usually used in boiler or supercritical steam turbines which operate at temperatures between 600-650°C under pressure. Protective coatings are often applied in order to increase their oxidation resistance and protect them against degradation. In this study new Al-Mn protective coatings were deposited by CVD-FBR on P92 ferritic steel. The initial process parameters were optimized by thermodynamic calculations using Thermo-Calc software. Then, those parameters were used in the experimental procedure to obtain Al-Mn coatings at low temperature and atmospheric pressure. Co-deposition was achieved at moderate temperatures in order to maintain the substrates` mechanical properties. The coatings` microstructure and phase constitution was characterized. Fe-Al intermetallic coatings containing Cr and Mn were obtained. The phase constitution is discussed with reference to the Fe-Al-Mn ternary phase diagram. The effect of diffusion heat treatment on the phase transformations as well as the steam oxidation resistance of these coatings at 650°C and 800°C was investigated.

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Harwarth, Michael, Adam Brauer, Qiuliang Huang, Mehdi Pourabdoli, and Javad Mola. "Influence of Carbon on the Microstructure Evolution and Hardness of Fe–13Cr–xC (x = 0–0.7 wt.%) Stainless Steel." Materials 14, no. 17 (September 4, 2021): 5063. http://dx.doi.org/10.3390/ma14175063.

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The influence of carbon on the phase transformation behavior of stainless steels with the base chemical composition Fe–13Cr (wt.%), and carbon concentrations in the range of 0–0.7 wt.%, was studied at temperatures between −196 °C and liquidus temperature. Based on differential scanning calorimetry (DSC) measurements, the solidification mode changed from ferritic to ferritic–austenitic as the carbon concentration increased. The DSC results were in fair agreement with the thermodynamic equilibrium calculation results. In contrast to alloys containing nearly 0% C and 0.1% C, alloys containing 0.2–0.7% C exhibited a fully austenitic phase stability range without delta ferrite at high temperatures. Quenching to room temperature (RT) after heat treatment in the austenite range resulted in the partial transformation to martensite. Due to the decrease in the martensite start temperature, the fraction of retained austenite increased with the carbon concentration. The austenite fraction was reduced by cooling to −196 °C. The variation in hardness with carbon concentration for as-quenched steels with martensitic–austenitic microstructures indicated a maximum at intermediate carbon concentrations. Given the steady increase in the tetragonality of martensite at higher carbon concentrations, as confirmed by X-ray diffraction measurements, the variation in hardness with carbon concentration is governed by the amount and stability of austenite.

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24

Aktaş Çelik, Gülşah, Maria-Ioanna T. Tzini, Şeyda Polat, Şaban Hakan Atapek, and Gregory N. Haidemenopoulos. "Matrix design of a novel ductile cast iron modified by W and Al: A comparison between thermodynamic modeling and experimental data." Metallurgical and Materials Engineering 26, no. 1 (April 16, 2020): 15–29. http://dx.doi.org/10.30544/449.

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In high-temperature applications of ferrous materials, as in the case of exhaust manifolds, high thermal and mechanical stability are required. Stainless steels and Ni-resist alloys having austenitic matrices are good candidates to meet these requirements at elevated temperatures; however, they are expensive materials and present difficulties in casting. Ferritic ductile cast irons, like the commercial SiMo alloy, are comparatively cheaper materials with better castability but they cannot be used above approximately 800 °C. Thus, to meet the requirements with low-cost materials having improved high-temperature properties, new alloys must be developed by ferrite forming elements having the potential to increase equilibrium temperature. In this study, initially, a novel ductile cast iron matrix was designed using 1 W and 0-4 Al wt.-% and their phases stable at room temperature, transformation temperatures, solidification sequences and thermal expansivity values were determined using thermodynamic calculations with Thermo-Calc software. Computational studies revealed that (i) designed alloy matrices had graphite and M6C type carbides embedded in a ferritic matrix at room temperature as expected, (ii) A1 temperature increased as aluminum content increased. The obtained values were all above that of commercial SiMo alloy, (iii) the detrimental effect of increased aluminum addition on graphite content, and thermal expansivity was observed. Secondly, microstructural and thermal characterizations of cast alloys were performed for validation – the obtained data were in good agreement with the thermodynamic calculations.

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25

Huo, Yong-Tao, Yan-Lin He, Na-Qiong Zhu, Min-Long Ding, Ren-Dong Liu, and Yu Zhang. "Deformation Mechanism Investigation on Low Density 18Mn Steels under Different Solid Solution Treatments." Metals 11, no. 9 (September 21, 2021): 1497. http://dx.doi.org/10.3390/met11091497.

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To meet the demand of the 10% weight reduction goal for automotive steel, the microstructure and mechanical properties of Fe-18Mn-Al-C steel with different carbon and aluminum contents were investigated under different solid solution treatments, and the deformation mechanisms of the experimental steels were elucidated. Aided by thermodynamic calculation, transmission electron microscopy (TEM) and in situ scanning electron microscope (SEM) analysis, it was shown that for the 18Mn-1.5Al experimental steel with about 20 mJ/m2 stacking fault energy (SFE), the twinning-induced plasticity (TWIP) effect always dominated in this steel after different solid solution treatments under tensile deformation. With the 7 wt% aluminum addition, the SFE of austenite was affected by temperature and the range of SFE was between 60 and 65 mJ/m2. The existence of δ-ferrite obviously inhibited the TWIP effect. With the increase in the solution treatment temperature, δ-ferrite gradually transformed into the austenite, and the n-value remained low and stable in a large strain range, which were caused by the local hardening during the tensile deformation. Due to the difference in the deformability of the austenite and δ-ferrite structure as well as the inconsistent extension of the slip band, the micro-cracks were easily initiated in the 18Mn-7Al experimental steel; then, it exhibited lower plasticity.

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26

Vakili-Tahami, F., D. R. Hayhurst, and M. T. Wong. "High-temperature creep rupture of low alloy ferritic steel butt-welded pipes subjected to combined internal pressure and end loadings." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 363, no. 1836 (September 28, 2005): 2629–61. http://dx.doi.org/10.1098/rsta.2005.1583.

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Constitutive equations are reviewed and presented for low alloy ferritic steels which undergo creep deformation and damage at high temperatures; and, a thermodynamic framework is provided for the deformation rate potentials used in the equations. Finite element continuum damage mechanics studies have been carried out using these constitutive equations on butt-welded low alloy ferritic steel pipes subjected to combined internal pressure and axial loads at 590 and 620 °C. Two dominant modes of failure have been identified: firstly, fusion boundary failure at high stresses; and, secondly, Type IV failure at low stresses. The stress level at which the switch in failure mechanism takes place has been found to be associated with the relative creep resistance and lifetimes, over a wide range of uniaxial stresses, for parent, heat affected zone, Type IV and weld materials. The equi-biaxial stress loading condition (mean diameter stress equal to the axial stress) has been confirmed to be the worst loading condition. For this condition, simple design formulae are proposed for both 590 and 620 °C.

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27

Liu, Xiao, and Jing Long Liang. "Thermodynamic Analysis and Observation of Inclusions in Ferritic Stainless Steel with Rare Earth." Advanced Materials Research 662 (February 2013): 441–44. http://dx.doi.org/10.4028/www.scientific.net/amr.662.441.

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The effect of RE on modifying inclusions of 430 ferrite stainless steel was studied by metallographic examination, SEM and electron spectroscopy. Thermodynamic calculation was used to analyze the formation of RE inclusions in 430 ferrite stainless steel. The result shows that sulfide and other irregular inclusions are modified to round or oval-shaped RE2O2S and RES.

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28

Weber, Sebastian, Mauro Martin, and Werner Theisen. "Development of Lean Alloyed Austenitic Stainless Steels with Reduced Tendency to Hydrogen Environment Embrittlement." Materials Science Forum 706-709 (January 2012): 1041–46. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.1041.

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Hydrogen gas is believed to play a more important role for energy supply in future instationary and mobile applications. In most cases, metallic materials are embrittled when hydrogen atoms are dissolved interstitially into their lattice. Concerning steels, in particular the ductility of ferritic grades is degraded in the presence of hydrogen. In contrast, austenitic steels usually show a lower tendency to hydrogen embrittlement. However, the so-called “metastable” austenitic steels are prone to hydrogen environmental embrittlement (HEE), too. Here, AISI 304 type austenitic steel was tensile tested in air at ambient pressure and in a 400 bar hydrogen gas atmosphere at room temperature. The screening of different alloys in the compositional range of the AISI 304 standard was performed with the ambition to optimize alloying for hydrogen applications. The results of the mechanical tests reveal the influence of the alloying elements Cr, Ni, Mn and Si on HEE. Besides nickel, a positive influence of silicon and chromium was found. Experimental results are supported by thermodynamic equilibrium calculations concerning austenite stability and stacking fault energy. All in all, the results of this work are useful for alloy design for hydrogen applications. A concept for a lean alloyed austenitic stainless steel is finally presented.

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29

Dheeradhada, Voramon S., Hongbo Cao, and Matthew J. Alinger. "Oxidation of ferritic stainless steel interconnects: Thermodynamic and kinetic assessment." Journal of Power Sources 196, no. 4 (February 2011): 1975–82. http://dx.doi.org/10.1016/j.jpowsour.2010.09.099.

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30

Oliveira, V. B., K. D. Zilnyk, and H. R. Z. Sandim. "Thermodynamic Simulation of Reduced Activation Ferritic–Martensitic Eurofer-97 Steel." Journal of Phase Equilibria and Diffusion 38, no. 3 (March 15, 2017): 208–16. http://dx.doi.org/10.1007/s11669-017-0530-2.

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31

Latreche, Hadj, Guido Tegeder, Gerhard Wolf, Patrick J. Masset, Till Weber, and Michael Schütze. "New Approaches to Improve High Temperature Corrosion Resistance in Chlorine-Based Atmospheres." Materials Science Forum 595-598 (September 2008): 307–21. http://dx.doi.org/10.4028/www.scientific.net/msf.595-598.307.

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Chlorine gas is widely encountered in chemical industries, as well as in waste incinerators and plastic/polymer decomposition mills. The presence of chlorine may significantly reduce the life-time of the components. Under chlorine-based atmospheres, the process of scale formation may be considerably affected and the presence of chlorine usually impedes the formation of a long term protective dense oxide scale. Based on thermodynamic calculations and previous investigations, NiAl and NiAlMo APS-coatings were produced to be used as protection for conventional steels against chlorine corrosion. Indeed, thermodynamic diagrams showed that molybdenum should have a positive behaviour in “reducing”-chloridizing atmospheres, whereas aluminium has a positive behaviour in “oxidizing”-chloridizing atmospheres. Coatings of approximatively 300 μm thickness were thermally sprayed on Armco Iron and on a commercial ferritic 18 Cr steel. This work presents the corrosion behaviour of NiAl and NiAlMo APS-coatings under chlorine-based atmospheres at 800°C. In addition, metallographic characterisation as well as EPMA investigations of the coating cross sections were carried out before and after the corrosion tests.

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32

Ma, Yong Qing, Xiao Jing Zhang, and Yu Fen Liang. "Alloy Design and Application for Avoiding Carbide Network of CrWMn Steel by Phase Equilibrium Thermodynamic Method." Advanced Materials Research 690-693 (May 2013): 91–96. http://dx.doi.org/10.4028/www.scientific.net/amr.690-693.91.

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By the equilibrium phases of the steels with temperature, the causation of being carbide network of CrWMn steel frequently in the manufacture was analyzed, and an alloy design for avoiding carbide network of CrWMn steel was researched. The analyse and research show that in austenite area the boundary precipitation of M3C and M6C carbides during cooling process after forging or hot rolling is preferential origin of carbide network, and in later ferrite area the precipitation and congregation of the carbides should lead on network aggravation. When CrWMn steel adding 0.3~0.4Mo as supplement, in austenite area M3C carbide disappears and M23C6 carbide increases, and it is conceivable of lightenning congregation to austenite boundary as the transformation of M23C6 and M6C reciprocally, and the distribution of diversified carbides should become fine too. The practice results show that the carbide network of CrWMnMo0.35 steel is avoided under normal forging or hot rolling conditions, and the hardness after quenching at 850°C and tempering at 200°C is HRC62~63, which is agreement with alloy design forecast. The experiment and application show that the performance of CrWMnMo0.35 steel is better than that of customary CrWMn steel for machinery knives.

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33

Michelic, S. K., and C. Bernhard. "Experimental Study on the Behavior of TiN and Ti2O3 Inclusions in Contact with CaO‐Al2O3‐SiO2‐MgO Slags." Scanning 2017 (2017): 1–14. http://dx.doi.org/10.1155/2017/2326750.

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TiN and Ti2O3 are the predominant inclusion types in Ti-alloyed ferritic chromium stainless steels. In order to ensure the required steel cleanness level, an effective removal of such inclusions in the slag during secondary metallurgy is essential. This inclusion removal predominantly takes place via dissolution of the inclusion in the slag. The dissolution behavior of TiN and Ti2O3 in CaO-SiO2-Al2O3-MgO slags as well as their agglomeration behavior in the liquid steel is investigated using High Temperature Laser Scanning Confocal Microscopy and Tammann Furnace experiments. Thermodynamic calculations are performed using FactSage 7.0. The behavior of TiN is observed to be completely different to that of oxides. Ti2O3 dissolves quickly in slags, and its dissolution behavior is comparable to that of other already well examined oxides. In contrast, TiN shows a very intense gas reaction which is attributed to the release of nitrogen during contact with slag. Slags with higher SiO2 content show a significantly higher ability for the dissolution of TiN as compared to Al2O3-rich slags. The gas reaction is found to also significantly influence the final steel cleanness. Despite the easy absorption of TiN in the slag, the formed nitrogen supports the formation of pinholes in the steel.

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34

Levkov, Leonid, Dmitry Shurygin, Vladimir Dub, Konstantin Kosyrev, and Alan Balikoev. "New generation of super duplex steels for equipment gas and oil production." E3S Web of Conferences 121 (2019): 04007. http://dx.doi.org/10.1051/e3sconf/201912104007.

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Oil&gas producing industry today is increased production volumes from old deposits on land, offshore and deep-water. The materials used to create modern equipment that meets these trends should be distinguished by increased productivity in conditions of corrosion and high pressure, to ensure trouble-free operation. In such conditions, taking into account the necessary provision of acceptable cost indicators, there is no alternative to duplex steels. Their crystal structure simultaneously allows using the advantages of ferritic and austenitic phases. The report presents the results of using a compositional and technological methods for structure management, the rationale alloying with copper (3.0-3.3%). Application of ESR in the manufacture of steel billets of super duplex steel has demonstrated the ability to simultaneously achieve physical, chemical and structural homogeneity, ensuring high corrosion&mechanical characteristics. The thermodynamic and kinetic conditions for the formation of optimal phase steel composition are determined. Grounded heat treatment regimes, prevent the formation of sigma and psi-phase and contribute to the formation of stable intermetallides (30-300 nm). Based on the test results of “Gazprom-VNIIGAZ” LLC the new steel is recommended for the manufacture of valve bodies and in-vessel internals used in the fields, that containing H2S and CO2 up to 25% in the fluid.

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35

Wang, Yanlin, Meng Zhou, Xiaolu Pang, Xiaohua Chen, Zidong Wang, Alex Volinsky, and Hao Tang. "Thermodynamic Analysis of Ti3O5Nanoparticles Formed in Melt and Their Effects on Ferritic Steel Microstructure." Materials 11, no. 8 (August 2, 2018): 1343. http://dx.doi.org/10.3390/ma11081343.

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Based on the Wagner’s formalism combined with mass conservation, a thermodynamic analysis method has been developed previously. This method enables the calculation of the equilibrium matrix composition, precipitate composition and precipitate total molar fraction for TixOy(s) in molten metal, which can be determined at any appropriate temperature. In this present study, the Ti3O5 phase precipitation and the quantitative relationship between the addition of Ti, O and Ti3O5 in the molten steel were studied using the thermodynamic model. Using the combined multipoint dispersion supply method, electromagnetic stirring and well-dispersed 5-nm Ti3O5 nanoparticles were fabricated in the ferrite matrix of the as-cast high-strength steel with 0.05 wt % Ti—0.002 wt % O. The as-cast microstructure was improved by the homogeneously dispersed Ti3O5 nanoparticles through heterogeneous nucleation and grain refinement.

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36

Lee, Sang Hwan, and Kyung Jong Lee. "The Effects of Si on the Nucleation Kinetics of Ferrite in Dual Phase Steels." Advanced Materials Research 26-28 (October 2007): 1307–10. http://dx.doi.org/10.4028/www.scientific.net/amr.26-28.1307.

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It is generally accepted that Si promotes kinetics of polygonal ferrite due to thermodynamic factors such as Ae3 and maximum amount of ferrite formed. However, in this study, it was found that the difference between the measured rates of ferrite formation in C-Mn steel and Si added steel was much larger than that expected considering only thermodynamic factors. The classical nucleation theory with pillbox model was adopted to figure out what is the most controlling factor in formation of ferrite. The volume free energy change was calculated by use of the dilute solution model. The diffusivity of carbon (DC) was formulated as functions of C, Mn and Si by using experimental data. It was found that the volume free energy change was still predominant but the kinetic factors such as interfacial energy and the diffusivity of carbon by addition of Si were not negligible at lower undercooling. However, with increasing undercooling, the diffusivity of C was the most effective on the ferrite kinetics, though the ambiguity of treating interfacial energy was not yet clear.

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37

Chen, Zhuo, Min Li, Xufeng Wang, Shengping He, and Qian Wang. "Mechanism of Floater Formation in the Mold during Continuous Casting of Ti-Stabilized Austenitic Stainless Steels." Metals 9, no. 6 (May 31, 2019): 635. http://dx.doi.org/10.3390/met9060635.

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During the continuous casting (CC) of Ti-bearing steel, a steel lump can solidify in the mold (i.e., floater steel) more easily than in the Ti-free steels. This causes severe surface defects or even a breakout. We have examined the mechanisms of floater formation during the CC of 321 stainless steel by analyzing the inclusions in the floater steel and in the 321 steel that was sampled from the mold. Additionally, we calculated the disregistry between the metallic phases and common inclusions. The mineralogy and morphology of the inclusions were examined while using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Thermodynamic calculations on the TixOy inclusions at different oxygen potentials were performed while using FactSage 7.2. Using this approach, we determined that ferrite nucleates grow on TiN and MgO inclusions following solidification, which then form micro-aggregates as a result of dynamic collisions and alliances. Analysis of the mold slag from the metallurgy stage indicated that altering the basicity and properties of the mold flux systematically might minimize the reaction between the slag and steel, which would achieve a coordinated control over lubrication and heat transfer.

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38

Yu, Peng, Lin Zhang, Lin Xiu Du, and Jun Hu. "Mesoscopic Simulation of the Ferrite Nucleation on Austenitic Grain Boundary for Nanograined Steel." Materials Science Forum 817 (April 2015): 731–35. http://dx.doi.org/10.4028/www.scientific.net/msf.817.731.

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We use the cellular automaton (CA) modeling to investigate the ferrite nucleation on the austenite grains. On the basis of the thermodynamics and kinetics of phase transformation from austenite to ferrite, the CA modeling demonstrates that the size of nucleated ferrite grains is increased with increasing of cooling rates, and nucleation process is finished instantly at a given cooling rate. The initial austenite grain size plays an important role in the obtained ferrite nucleation number, and the potential nucleation cells are increased.

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39

Chen, Peng, Jian Fu, Jingkuan Yang, and Xiaowu Li. "A critical role of aluminium on austenite formation in high aluminium added steels." Metallurgical Research & Technology 117, no. 5 (2020): 502. http://dx.doi.org/10.1051/metal/2020047.

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Novel alloys with high aluminium addition have been developed recently for the new concepts of δ-TRIP, δ-QP and some other high-aluminium low-density steels. The aluminium addition dramatically affects the thermodynamics and kinetics of the formation of austenite. In the present study, the effect of aluminium on the initial microstructure of ferrite and pearlite has been investigated. The equilibrium prediction of phase fraction by thermodynamics calculations is in accordance with the measured austenite fraction during isothermal at intercritical temperature range; both results strongly demonstrate a significant influence of aluminium addition on intercritical region. The isothermal transformation of high aluminium steel during intercritical annealing was delayed, which has an instruction for process design of the industrial continuous annealing and galvanization. The austenite formation during heating in intercritical region was also obviously affected by aluminium addition. The transformation kinetics simulation conducted by DICTRA simulation, as well as the experimental results of dilatometry, indicate a delayed austenite transformation during heating process.

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Hsu, T. Y. "A Unified Technology Combining Plastic Forming and Heat Treatment of Steels." Materials Science Forum 475-479 (January 2005): 31–36. http://dx.doi.org/10.4028/www.scientific.net/msf.475-479.31.

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In order to diminish the industrial pollution to maintain the sustainable development and to reduce the cost of the steel production, a unified technology combining plastic forming and heat treatment for some steel parts production is suggested. This article mainly concerns part theoretical foundation of such technology, i.e. the thermodynamic and kinetic models of the ferrite and pearlite transformations under external stress. Simulation of the ferrite fraction after continuous cooling under stress in a low-alloyed steel is presented. The effects of stresses on bainitic and martensitic transformations are also briefly introduced. The unified technology seems favorable to be realized in manufacturing practice.

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Ohtani, Hiroshi, N. Hanaya, and Mitsuhiro Hasebe. "Thermodynamic Analysis of Steels by Incorporating First-Principles Calculations into the CALPHAD Approach." Materials Science Forum 539-543 (March 2007): 2413–18. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.2413.

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A thermodynamic analysis of the Fe−M−P (M = Nb, Ti) ternary system has been performed by combining first-principles calculations with the CALPHAD approach. Because of the lack of experimental information available, thermodynamic properties of orthorhombic anti-PbCl2-type FeMP were evaluated using the Full Potential Linearized Augmented Plane Wave method, and the estimated values were introduced into a CALPHAD-type thermodynamic analysis. Applying this procedure, the phase diagrams of the Fe−M−P ternary phase diagrams whose contents are uncertain so far were calculated with a high degree of probability. Phase diagrams for high-purity ferritic stainless steels obtained following the same procedure are also presented.

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42

Shi, Xiaofang, and Lizhong Chang. "Equiaxed Solidification of 430 Ferritic Stainless Steel Nucleating on Core-Containing Ti." High Temperature Materials and Processes 37, no. 9-10 (October 25, 2018): 951–59. http://dx.doi.org/10.1515/htmp-2017-0173.

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AbstractThe solidification structure of ferritic stainless steel can be refined by controlling the contents of Ti, O, and N in the liquid steel through the thermodynamic analysis and high-temperature experiment. It is found by the scanning electron microscopy technology, in which the composite core of Ti nitride-enwrapping Ti oxide can be formed in the solidification front, which promotes the nucleation of δ iron and refines the solidification structure. Meanwhile, the structure analysis of the composite core by the transmission electron microscope technology proves that the Ti oxide that exists in the centre of the composite core is Ti2O3 and the Ti nitride that exists in the outer layer of the composite core is TiN.

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43

Hamelin, Cory J., Ondrej Muránsky, Philip Bendeich, Ken Short, and Lyndon Edwards. "Predicting Solid-State Phase Transformations during Welding of Ferritic Steels." Materials Science Forum 706-709 (January 2012): 1403–8. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.1403.

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The current work presents the numerical analysis of solid-state transformation kinetics relating to conventional welding of ferritic steels, with the aim of predicting the constituent phases in both the fusion zone and the heat affected zone (HAZ) of the weldment. The analysis begins with predictions of isothermal transformation kinetics using thermodynamic principles, such that the chemical composition of the parent metal is the sole user-defined input. The data is then converted to anisothermal transformation kinetics using the Scheil-Avrami additive rule, including the effects of peak temperature and austenite grain growth. Subroutines developed for the Abaqus finite element package use the semi-empirical approach described to predict phase transformations in SA508 Gr.3 Cl.1 steel. To study the effect of the cooling rates and the ability of the current model to predict the final microstructure, two weld samples were subjected to autogenous beam TIG welds under a fast (TG5-F, 5.00 mm/s) and slow (TG5-S, 1.25 mm/s) torch speed. Model validation is carried out by direct comparison with microstructural observations and hardness measurements (via nanoindentation) of the fusion and heat affected zones in both welds. Excellent agreement between the measured and predicted hardness has been found for both weld samples. Additionally, it is shown that the correct identification of the partial austenisation region is a crucial input parameter.

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Cai, Xiao Hui, Zhen Yu Liu, and Guo Dong Wang. "Cooling Process for Precipitation Strengthening of Vanadium in Ferrite." Materials Science Forum 706-709 (January 2012): 2078–83. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.2078.

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The precipitation of vanadium takes place mainly in ferrite by interphase precipitation or nucleation on dislocation line, which makes sense for the industry production due to the precipitation strengthening. The objective is to analysize the cooling process of V-steels to exert the precipitation strengthening of vanadium. The steels with 0.09%C-0.055%N/0.0107%N/0.0168%N/0.0193%N-0.08%V/0.085V steel are the researched steel grades. Using solid solubility products model and thermodynamic equation, the full solid solution temperature, nucleation rate curve and PTT curve of precipitation process are calculated. The effect of nitrogen on the precipitation behaviour of V(C,N) in γ and the precipitation of V(C,N) in α are simulated. Based on the calculation results the trial process is determined. The laboratorial trials are carried out with ultra fast cooling. The precipitate particles are observed by TEM. The solid solution amount increases monotonously and the size of precipitate particle decreases with the nitrogen content. The solid solution temperature of 0.055%N, 0.0107%N, 0.0168%N and 0.0193%N are 977.0°C, 1028.0°C, 1062.3 and 1078.9°C respectively. The laboratorial trial results shows that the tensile strength is improved about 100 MPa due to the precipitation strengthening. The relationship between the coiling temperature and the strength is parabolic curve downward and the relationship between the coiling temperature and the elongation is parabolic curve upward. This calculation can determine both the proper nitrogen content and the optimal cooling process. The trial results proves this method is feasible and efficiency.

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Yu, Y. C., S. H. Zhang, and S. B. Wang. "Effects of Cerium on the Inclusions and Pitting Corrosion Behavior of 434 Ferritic Stainless Steel." High Temperature Materials and Processes 37, no. 9-10 (October 25, 2018): 807–14. http://dx.doi.org/10.1515/htmp-2017-0094.

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AbstractThe effects of Ce addition on the inclusions and the pitting corrosion behavior of ferritic stainless steel were investigated. The results showed that Ce2O3·SiO2 and Ce2O2S inclusions were mainly found in 434 ferritic stainless steel containing 0.011% or 0.023 wt% Ce, which is the most appropriate addition of Ce that could contribute to produce the dispersive and fine rare earth inclusions. According to the thermodynamic analysis, Ce inclusions could be produced by rare earth elements combining with oxygen, sulfur, or preexisting SiO2. While the kinetic analysis and mechanism for formation of inclusions suggested that the area ratio of the pure SiO2 inclusion decreased with Ce increasing, and the difference of [Ce] concentration between the original inclusion interface and the SiO2 solid unreacted nuclear interface is the main reason to cause the different process of inclusion modification. Meanwhile, when the content of Ce was 0.011% or 0.023%, the resistance to pitting corrosion increased with the interface areas between the inclusions and the steel matrix decreasing. However, the excessive Ce addition resulted in the increase of size and quantity of inclusions, which would reduce the resistance to pitting corrosion.

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Yu, Zhi Chen, Zhen Li Mi, Qing Wu Cai, Jin Guo, and Na Gong. "Effect of Final Rapid Cooling Temperature on Ultra-Fine Carbides of Ti-Mo Ferrite Matrix Microalloyed Steel." Materials Science Forum 926 (July 2018): 3–10. http://dx.doi.org/10.4028/www.scientific.net/msf.926.3.

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The size and distribution of nanoscale precipitate particles in Ti-Mo ferrite matrix microalloyed steel under three different final rapid cooling temperatures were studied by scanning electron microscopy(SEM), transmission electron microscope(TEM) and microhardness test. The results show that the interphase precipitation could be weakened by the excessive final rapid cooling temperature. A higher supersaturated solid solubility and high-density dislocation in ferrite matrix can be obtained under a relatively lower final rapid cooling temperature, which makes it easier to precipitate in ferrite. The related thermodynamic analysis indicated that the precipitation behavior was influenced by the final rapid cooling temperature during austenite/ferrite region. It is not conducive to get a large amount of small size precipitates in Ti-Mo ferrite matrix microalloyed steel when the final rapid cooling temperature is too high or low.

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47

Zhao, Fan, Ning Bo Zhou, Guang Lei Liu, Zhi Lin Wang, and Ya Zheng Liu. "Hot Ductility of 20Cr13 Steel at High Temperature." Materials Science Forum 898 (June 2017): 778–82. http://dx.doi.org/10.4028/www.scientific.net/msf.898.778.

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Hot ductility of 20Cr13 steel at high temperature was investigated through tensile test. The main phases of the steel in temperature range of 600-1400 °C were calculated with thermodynamic software. The fracture morphologies and microstructure were observed by scanning electron microscopy. The steel showed good hot ductility in temperature range of 1000-1200 °C, and the area reduction was 82 % or more. In temperature range of 800-950 °C, the M23C6 precipitated at the grain boundary of austenite, and it fractured in the tensile process. Thus the micro-crack or micro-hole formed at the grain boundary of austenite, and the area reduction was 52-68 %. The ferrite precipitated at 800 or 1250 °C, and the micro-voids formed at interface of ferrite and austenite because of the discordant deformation of two phases, which was harmful to hot ductility. Moreover, quasi-cleavage fracture happened at 800 °C because of the ferrite cleavage, which further decreased hot ductility of the steel.

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Kuang, Shuang, Yong Lin Kang, Hao Yu, and Ren Dong Liu. "Simulation of Intercritical Austenization of a C-Mn Cold Rolled Dual Phase Steel." Materials Science Forum 575-578 (April 2008): 1062–69. http://dx.doi.org/10.4028/www.scientific.net/msf.575-578.1062.

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Formation of austenite strongly influences the microstructures and mechanical properties of dual phase steels. In present work, austenization process during intercritical annealing was studied in a Fe-C-Mn steel using Gleeble-1500 thermal simulator and quantitative microscopy. The experimental results show that austenite formation is separated into three different stages: (i) growth of high carbon austenite into pearlite rapidly until pearlite dissolution is completed; (ii) slower growth of austenite into ferrite; (iii) very slow equilibration between ferrite and austenite. The thermodynamic and kinetic analyses show that growth of austenite into ferrite is controlled by carbon diffusion in austenite in the primary stage and manganese diffusion in ferrite in the subsequent stage because diffusion coefficient of Mn in ferrite is several orders of magnitude smaller than that of C in austenite. The slow final equilibration between ferrite and austenite is obtained by manganese diffusion through the austenite. Based on the analysis, one dimensional diffusion model of intercritical austenization was developed and solved using finite volume method on the assumption that solute flux was local balance at interface, and the kinetics calculated was compared with experimental results. Simulated results indicate that growth of austenite reaches paraequilibrium in about one second, but remains thousands of seconds to reach final equilibrium. Simulated concentration profiles show that manganese atoms transferred from ferrite congregate in austenite near phase interface, which is consistent with the experimental phenomenon.

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Cha, Woo-Yeol, Dong-Sik Kim, Yong-Deuk Lee, and Jong-Jin Pak. "A Thermodynamic Study on the Inclusion Formation in Ferritic Stainless Steel Melt." ISIJ International 44, no. 7 (2004): 1134–39. http://dx.doi.org/10.2355/isijinternational.44.1134.

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50

Wang, Hong Po, Bo Peng, Li Feng Sun, Cheng Jun Liu, and Mao Fa Jiang. "Microstructure and Precipitates of High-Pure Ferritic Stainless Steels Stabilized by Niobium and Titanium." Materials Science Forum 749 (March 2013): 7–12. http://dx.doi.org/10.4028/www.scientific.net/msf.749.7.

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As stabilization elements added into ferritic stainless steels, various kinds of precipitates of niobium and titanium will form and have great effect on their microstructure, which has great effect on the mechanical and corrosion properties of the final products. Combined with thermodynamic calculation by FactSage software, microstructure and precipitates of ferritic stainless steels containing different niobium and titanium were investigated by optical microscope, scanning electron microscope, transmission electron microscope and energy dispersive spectrometer. The results show that titanium mainly exists in form of TiN but niobium exists mainly in form of NbC. Moreover, a certain amount of NbN particles precipitate when there is not enough titanium to react with nitrogen. TiN particles with size of 2μm~8μm promote the recrystallization but Nb-rich precipitates with size of less than 500nm suppress the recrystallization in the process of annealing.

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Journal articles on the topic 'Ferritic steel. Thermodynamics'

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