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Ke Yang - One of the best experts on this subject based on the ideXlab platform.
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Processing of Ultralow Carbon Pipeline Steels with Acicular Ferrite
Journal of Materials Science & Technology, 2009Co-Authors: Xiao Furen, Ming-chun Zhao, Yiyin Shan, Bo Liao, Ke YangAbstract:Acicular Ferrite microstructure was achieved for an-ultralow carbon pipeline,steel through the improved thermomechanical control process (TMCP), which was based on the transformation process of deformed austenite of steel. Compared with commercial pipeline steels, the experimental ultralow carbon pipeline steel possessed the satisfied strength and toughness behaviors under the current improved TMCP, although it contained only approximately 0.025% C, which should mainly be attributied to the microstructural characteristics of Acicular Ferrite.
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challenge of mechanical properties of an Acicular Ferrite pipeline steel
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006Co-Authors: Yiyin Shan, Bo Liao, Furen Xiao, Gui-ying Qiao, Chunling Zhang, Yong Zhong, Ke YangAbstract:In modern industry, the developing tendency and prospect for productions of the oil and gas pipeline steels is to further improve the strength and toughness by advanced manufacture process of the thermo-mechanical control process (TMCP) to refine microstructure. In this work, the hot deformation behavior as well as its effect on the phase transformation of the clean Acicular Ferrite pipeline steel with simple chemical composition has been investigated. According to the result, the optimum TMCP parameters were designed. Furthermore, the rolling test was carried out on the experimental rolling mill. The results show that, the high strength and excellent toughness of the clean Acicular Ferrite pipeline steel can be obtained by controlling the TMCP parameters of the production process appropriately. (c) 2006 Elsevier B.V. All rights reserved.
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Effects of Chemical Composition and Hot Deformation on Continuous Cooling Transformation Behavior of Acicular Ferrite Pipeline Steels
Multidiscipline Modeling in Materials and Structures, 2006Co-Authors: Furen Xiao, Yiyin Shan, Bo Liao, Gui-ying Qiao, Chunling Zhang, Yong Zhong, Ke YangAbstract:As an optimal microstructure of pipeline steels, Acicular Ferrite is widely found in steels used in oil and gas pipeline transportation because it possesses both high strength and good toughness. In this paper, the microstructure of Acicular Ferrite and its continuous cooling transformation (CCT) diagrams of six steels with different carbon and alloy additions have been studied by using dilatometry, optical metallography. And the effects of different hot deformation processes on the CCT diagrams and microstructures have also been studied. Furthermore, the effects of microalloyed elements and hot deformation on continuous cooling transformation have been discussed. The results show that lower carbon content and alloy additions such as Mn, Nb, Ti, Mo, Ni and/or Cu in steels will promote the formation of Acicular Ferrite. The hot deformation promotes the Acicular Ferrite transformation and refines the microstructures of final products.
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Acicular Ferrite formation during hot plate rolling for pipeline steels
Materials Science and Technology, 2003Co-Authors: Ming-chun Zhao, Y.-y. Shan, F.-r. Xiao, Ke YangAbstract:The transformation of supercooled austenite in a commercial pipeline steel was investigated by means of continuous cooling transformation (CCT) and hot simulation experiments. Based on the obtained results, an improved thermomechanical control process (TMCP) was proposed, which could produce a mixed microstructure dominated by Acicular Ferrite. Results indicated that an increase in the cooling rate could improve the percentage of Acicular Ferrite in the final microstructure under the present experimental conditions. Furthermore, the Acicular Ferrite dominated microstructure could be obtained by a two stage controlled rolling in the austenite recrystallisation region plus the non-recrystallisation region and controlled cooling at a cooling rate of 30 K s(-1).
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Comparison on strength and toughness behaviors of microalloyed pipeline steels with Acicular Ferrite and ultrafine Ferrite
Materials Letters, 2002Co-Authors: Ming-chun Zhao, Ke Yang, Yiyin ShanAbstract:A laboratory smelted microalloyed pipeline steel was conducted by two different thermomechanical control process (TMCP) on a pilot rolling mill to produce two currently interesting microstructures, i.e., Acicular Ferrite and ultrafine Ferrite. Strength and toughness behaviors of these two microstructures were investigated. Compared with commercial pipeline steels, the experimental steel with Acicular Ferrite and/or ultrafine Ferrite possessed the satisfied strength and toughness behaviors, although this steel contained only about 0.025% carbon. Furthermore, Acicular Ferrite was better candidate microstructure for pipeline steels than ultrafine Ferrite. (C) 2002 Elsevier Science B.V All rights reserved.
H. K. D. H. Bhadeshia - One of the best experts on this subject based on the ideXlab platform.
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chapter 7 Acicular Ferrite
Steels: Microstructure and Properties (Fourth edition), 2017Co-Authors: H. K. D. H. BhadeshiaAbstract:Non-metallic inclusions are anathema when it comes to the design of strong steels because they become the initiation sites for fracture. Huge efforts have been made devoted to making clean steels – the oxygen concentration of a hard bearing steel is routinely less than 10 ppm. However, there are other structural steels that have to be welded where the localised heat input generates microstructures in the heat-affected zone that are undesirable. The alloys that are used to deposit the weld must have good properties in the as-cast state. In both of these circumstances, specific non-metallic inclusions are a positive boon in that they provide substrates for the intragranular nucleation of bainite. As a consequence, highly organised sheaves of bainite are altered into a more chaotic arrangement that frequently deflects propagating cracks and hence enhances the toughness. This is the so-called Acicular Ferrite that is the subject of this chapter.
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7 Acicular Ferrite
Steels (Third Edition)#R##N#Microstructure and Properties, 2006Co-Authors: H. K. D. H. BhadeshiaAbstract:Publisher Summary This chapter deals with the mechanism by which Acicular Ferrite forms and the role of inclusions in stimulating its formation. Bainite and Acicular Ferrite have essentially the same transformation mechanism, but their microstructures differ in detail because the former nucleates at grain surfaces and hence it grows in the form of sheaves of parallel platelets. Acicular Ferrite, on the other hand, nucleates intragranularly on non-metallic inclusions, which are in effect point nucleation sites. The platelets of Acicular Ferrite therefore radiate from the individual inclusions, thus generating a microstructure, which is much more disorganized with adjacent platelets pointing in different directions. There are many kinds of non-metallic inclusions, which are effective in stimulating intragranular nucleation, but some titanium compounds are found to be particularly potent. The exact mechanism of nucleation remains to be resolved. Acicular Ferrite grows without diffusion, but the excess carbon is not retained in the supersaturated Ferrite. It is partitioned into the residual austenite shortly after growth. The transformation is accompanied by shear, and rather smaller dilatational displacements, which together with the reproducible orientation relationship, the plate shape and lack of chemical composition change fit a displacive mechanism of transformation.
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Effect of plastic deformation on the formation of Acicular Ferrite
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2003Co-Authors: C.h. Lee, H. K. D. H. Bhadeshia, Hu-chul LeeAbstract:Abstract The effect of plastic deformation on the transformation of austenite to Acicular Ferrite in a Fe–Mn–Si–C alloy steel containing non-metallic inclusions was investigated. The transformation to Acicular Ferrite is retarded and the final fraction of Acicular Ferrite is reduced in plastically deformed austenite, which is a characteristic of a displacive transformation mechanism. The increase in the chemical driving force for transformation due to large undercooling below the Bs temperature overcomes the efficacy of dislocations in preventing the growth of Acicular Ferrite.
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Acicular Ferrite morphologies in a medium-carbon microalloyed steel
Metallurgical and Materials Transactions A, 2001Co-Authors: I Madariaga, I. Gutiérrez, H. K. D. H. BhadeshiaAbstract:The influence of time and isothermal transformation temperature on the morphology of Acicular Ferrite in a medium-carbon microalloyed steel has been studied using optical and transmission electron microscopy (TEM). This study has been carried out with the analysis of the microstructures obtained with one- and two-stage isothermal treatments at 400 °C and 450 °C, following austenitization at 1250 °C. The heat treatments were interrupted at different times to observe the evolution of the microstructure at each temperature. The results show that a decrease in the isothermal transformation temperature gives rise to the development of sheaves of parallel Ferrite plates, similar to bainitic sheaves, but intragranularly nucleated. These replace the face-to-edge nucleation that dominates the transformation at higher temperatures. The TEM observations reveal that the plates correspond to upper Acicular Ferrite and the sheaves to lower Acicular Ferrite. In this last case, cementite precipitates are present at the Ferrite unit interiors and between the different platelets.
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solid state nucleation of Acicular Ferrite on minerals added to molten steel
Acta Materialia, 1997Co-Authors: J M Gregg, H. K. D. H. BhadeshiaAbstract:A technique has been developed for making samples of steel with controlled additions of powdered mineral phases. Alloys made using this technique have been studied from the point of view of the Acicular Ferrite microstructure, which forms when Ferrite plates nucleate heterogeneously on non-metallic inclusions. It is observed that titanium oxide particles are most efficient in nucleating Acicular Ferrite. It is suspected that nucleation is enhanced around these particles because of their chemical interaction with surrounding steel, causing localized depletion in either carbon or manganese. Such local depletion zones thermodynamically stabilize the Ferrite phase over the parent austenite, thus causing nucleation.
Ming-chun Zhao - One of the best experts on this subject based on the ideXlab platform.
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Processing of Ultralow Carbon Pipeline Steels with Acicular Ferrite
Journal of Materials Science & Technology, 2009Co-Authors: Xiao Furen, Ming-chun Zhao, Yiyin Shan, Bo Liao, Ke YangAbstract:Acicular Ferrite microstructure was achieved for an-ultralow carbon pipeline,steel through the improved thermomechanical control process (TMCP), which was based on the transformation process of deformed austenite of steel. Compared with commercial pipeline steels, the experimental ultralow carbon pipeline steel possessed the satisfied strength and toughness behaviors under the current improved TMCP, although it contained only approximately 0.025% C, which should mainly be attributied to the microstructural characteristics of Acicular Ferrite.
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Acicular Ferrite formation during hot plate rolling for pipeline steels
Materials Science and Technology, 2003Co-Authors: Ming-chun Zhao, Y.-y. Shan, F.-r. Xiao, Ke YangAbstract:The transformation of supercooled austenite in a commercial pipeline steel was investigated by means of continuous cooling transformation (CCT) and hot simulation experiments. Based on the obtained results, an improved thermomechanical control process (TMCP) was proposed, which could produce a mixed microstructure dominated by Acicular Ferrite. Results indicated that an increase in the cooling rate could improve the percentage of Acicular Ferrite in the final microstructure under the present experimental conditions. Furthermore, the Acicular Ferrite dominated microstructure could be obtained by a two stage controlled rolling in the austenite recrystallisation region plus the non-recrystallisation region and controlled cooling at a cooling rate of 30 K s(-1).
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Comparison on strength and toughness behaviors of microalloyed pipeline steels with Acicular Ferrite and ultrafine Ferrite
Materials Letters, 2002Co-Authors: Ming-chun Zhao, Ke Yang, Yiyin ShanAbstract:A laboratory smelted microalloyed pipeline steel was conducted by two different thermomechanical control process (TMCP) on a pilot rolling mill to produce two currently interesting microstructures, i.e., Acicular Ferrite and ultrafine Ferrite. Strength and toughness behaviors of these two microstructures were investigated. Compared with commercial pipeline steels, the experimental steel with Acicular Ferrite and/or ultrafine Ferrite possessed the satisfied strength and toughness behaviors, although this steel contained only about 0.025% carbon. Furthermore, Acicular Ferrite was better candidate microstructure for pipeline steels than ultrafine Ferrite. (C) 2002 Elsevier Science B.V All rights reserved.
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microstructural characteristic and toughening of an ultralow carbon Acicular Ferrite pipeline steel
Acta Metallurgica Sinica, 2002Co-Authors: Ming-chun Zhao, Yiyin Shan, Furen Xiao, Ke YangAbstract:The microstructural characteristic and its effect oil toughening of an ultralow carbon Acicular Ferrite pipeline steel were investigated by means of mechanical testing and microstructural analysis. Experimental results showed that the Acicular Ferrite dominated microstructure can be obtained for the ultralow carbon pipeline steel through the clean melting and the optimized thermo-mechanical processing. It was also found that there exists a layer of thin martensite film at the grain boundary of Ferrite. All these microstructural characteristics play important roles in enhancement of toughening for the ultralow carbon Acicular Ferrite pipeline steel.
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Investigation on the H2S-resistant behaviors of Acicular Ferrite and ultrafine Ferrite
Materials Letters, 2002Co-Authors: Ming-chun Zhao, Furen Xiao, Yi-ying Shan, Ke YangAbstract:Hydrogen-induced cracking (HIC) and sulfide stress cracking (SSC) of both Acicular Ferrite and ultrafine Ferrite in H2S environments were evaluated. The results show that the two microstructures have the optimum HIC resistance as well as the good mechanical properties. Moreover, Acicular Ferrite has the better SSC resistance than ultrafine Ferrite. (C) 2002 Elsevier Science B.V. All rights reserved.
Yiyin Shan - One of the best experts on this subject based on the ideXlab platform.
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Processing of Ultralow Carbon Pipeline Steels with Acicular Ferrite
Journal of Materials Science & Technology, 2009Co-Authors: Xiao Furen, Ming-chun Zhao, Yiyin Shan, Bo Liao, Ke YangAbstract:Acicular Ferrite microstructure was achieved for an-ultralow carbon pipeline,steel through the improved thermomechanical control process (TMCP), which was based on the transformation process of deformed austenite of steel. Compared with commercial pipeline steels, the experimental ultralow carbon pipeline steel possessed the satisfied strength and toughness behaviors under the current improved TMCP, although it contained only approximately 0.025% C, which should mainly be attributied to the microstructural characteristics of Acicular Ferrite.
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challenge of mechanical properties of an Acicular Ferrite pipeline steel
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006Co-Authors: Yiyin Shan, Bo Liao, Furen Xiao, Gui-ying Qiao, Chunling Zhang, Yong Zhong, Ke YangAbstract:In modern industry, the developing tendency and prospect for productions of the oil and gas pipeline steels is to further improve the strength and toughness by advanced manufacture process of the thermo-mechanical control process (TMCP) to refine microstructure. In this work, the hot deformation behavior as well as its effect on the phase transformation of the clean Acicular Ferrite pipeline steel with simple chemical composition has been investigated. According to the result, the optimum TMCP parameters were designed. Furthermore, the rolling test was carried out on the experimental rolling mill. The results show that, the high strength and excellent toughness of the clean Acicular Ferrite pipeline steel can be obtained by controlling the TMCP parameters of the production process appropriately. (c) 2006 Elsevier B.V. All rights reserved.
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Effects of Chemical Composition and Hot Deformation on Continuous Cooling Transformation Behavior of Acicular Ferrite Pipeline Steels
Multidiscipline Modeling in Materials and Structures, 2006Co-Authors: Furen Xiao, Yiyin Shan, Bo Liao, Gui-ying Qiao, Chunling Zhang, Yong Zhong, Ke YangAbstract:As an optimal microstructure of pipeline steels, Acicular Ferrite is widely found in steels used in oil and gas pipeline transportation because it possesses both high strength and good toughness. In this paper, the microstructure of Acicular Ferrite and its continuous cooling transformation (CCT) diagrams of six steels with different carbon and alloy additions have been studied by using dilatometry, optical metallography. And the effects of different hot deformation processes on the CCT diagrams and microstructures have also been studied. Furthermore, the effects of microalloyed elements and hot deformation on continuous cooling transformation have been discussed. The results show that lower carbon content and alloy additions such as Mn, Nb, Ti, Mo, Ni and/or Cu in steels will promote the formation of Acicular Ferrite. The hot deformation promotes the Acicular Ferrite transformation and refines the microstructures of final products.
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Comparison on strength and toughness behaviors of microalloyed pipeline steels with Acicular Ferrite and ultrafine Ferrite
Materials Letters, 2002Co-Authors: Ming-chun Zhao, Ke Yang, Yiyin ShanAbstract:A laboratory smelted microalloyed pipeline steel was conducted by two different thermomechanical control process (TMCP) on a pilot rolling mill to produce two currently interesting microstructures, i.e., Acicular Ferrite and ultrafine Ferrite. Strength and toughness behaviors of these two microstructures were investigated. Compared with commercial pipeline steels, the experimental steel with Acicular Ferrite and/or ultrafine Ferrite possessed the satisfied strength and toughness behaviors, although this steel contained only about 0.025% carbon. Furthermore, Acicular Ferrite was better candidate microstructure for pipeline steels than ultrafine Ferrite. (C) 2002 Elsevier Science B.V All rights reserved.
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microstructural characteristic and toughening of an ultralow carbon Acicular Ferrite pipeline steel
Acta Metallurgica Sinica, 2002Co-Authors: Ming-chun Zhao, Yiyin Shan, Furen Xiao, Ke YangAbstract:The microstructural characteristic and its effect oil toughening of an ultralow carbon Acicular Ferrite pipeline steel were investigated by means of mechanical testing and microstructural analysis. Experimental results showed that the Acicular Ferrite dominated microstructure can be obtained for the ultralow carbon pipeline steel through the clean melting and the optimized thermo-mechanical processing. It was also found that there exists a layer of thin martensite film at the grain boundary of Ferrite. All these microstructural characteristics play important roles in enhancement of toughening for the ultralow carbon Acicular Ferrite pipeline steel.
Carlos Capdevila - One of the best experts on this subject based on the ideXlab platform.
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Effect of V and N Precipitation on Acicular Ferrite Formation in Sulfur-Lean Vanadium Steels
Metallurgical and Materials Transactions A, 2009Co-Authors: Carlos Capdevila, Carlos Garcia-mateo, J Chao, F G CaballeroAbstract:This article deals with the mechanical properties achieved in two S-lean laboratory-cast V steels with two different N content levels, as compared with commercial Acicular Ferrite steel. The designed heat treatments ensure an almost homogeneous microstructure consisting of Acicular Ferrite for N-rich and commercial steels and consisting of bainite for the N-lean steel. The results presented in this work demonstrate that, in the absence of sulfide inclusions, Acicular Ferrite is nucleated on V(C,N) precipitates. The mechanical tests indicate that N-rich Acicular Ferrite steel achieves the same toughness values as N-lean bainitic steel but with a substantial improvement in strength properties. The S-lean steels present better toughness properties than commercial Acicular Ferrite steel, which is consistent with the detrimental effect of inclusions on toughness.
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Effect of V and N Precipitation on Acicular Ferrite Formation in Sulfur-Lean Vanadium Steels
Metallurgical and Materials Transactions A, 2009Co-Authors: Carlos Capdevila, Carlos Garcia-mateo, J Chao, F G CaballeroAbstract:This article deals with the mechanical properties achieved in two S-lean laboratory-cast V steels with two different N content levels, as compared with commercial Acicular Ferrite steel. The designed heat treatments ensure an almost homogeneous microstructure consisting of Acicular Ferrite for N-rich and commercial steels and consisting of bainite for the N-lean steel. The results presented in this work demonstrate that, in the absence of sul.de inclusions, Acicular Ferrite is nucleated on V(C,N) precipitates. The mechanical tests indicate that N-rich Acicular Ferrite steel achieves the same toughness values as N-lean bainitic steel but with a substantial improvement in strength properties. The S-lean steels present better toughness properties than commercial Acicular Ferrite steel, which is consistent with the detrimental e.ect of inclusions on toughness. © The Minerals, Metals & Materials Society and ASM International 2009.Peer Reviewe
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Influence of V Precipitates on Acicular Ferrite Transformation Part 2: Transformation Kinetics
ISIJ International, 2008Co-Authors: Carlos García, F G Caballero, Carlos Capdevila, J Cornide, Carlos Garcia De AndresAbstract:4 pages, 6 figures, 1 table.-- This is Part II of paper "Influence of V Precipitates on Acicular Ferrite Transformation", Part I available at: http://hdl.handle.net/10261/17759Vanadium Award 2009-Council of the Institute of Materials, Minerals and Mining-UK for the most outstanding paper in the metallurgy and technology of vanadium and its alloys. Sponsored and selected by the Vanadium International Technical Committee (Vanitec).A combination of thermodynamic models as well as some physical metallurgical principles has been used to analyse the influence that V(C, N) precipitates have on the transformation kinetics of Acicular Ferrite by isothermal decomposition of austenite. Those precipitates were found absolutely necessary for the nucleation of Acicular Ferrite as reported in Part 1 of this work, now in Part 2, through the proper design of a heat treatment route we have studied the effect that those precipitates have on the kinetics of Acicular Ferrite transformation.The authors would like to acknowledge the Commission of the European Communities for the financial support in the frame of the RFCS Programme for 2004 (RFS-PR-03136). Also to the Spanish MCYT through the project\ud MAT2005-24485-E.Peer reviewe
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Influence of V Precipitates on Acicular Ferrite Transformation Part 1 : The Role of Nitrogen
ISIJ International, 2008Co-Authors: Carlos Garcia-mateo, F G Caballero, Carlos Capdevila, Carlos Garcia De AndresAbstract:This paper (part 1 of a two part study) deals with the influence of N in its combination with V, as V(C, N) precipitates, on the decomposition of austenite into Acicular Ferrite. Likewise, the intragranular nucleation potency of V(C, N) precipitates is analyzed through the continuous cooling transformation diagrams (CCT) of two C–Mn–V steels with different contents of N under two different austenitising temperatures, i.e. different austenite grain sizes. The results clearly show that for austenite to decompose into Acicular Ferrite is necessary, first to have a representative fraction of V(C, N) precipitates within austenite, and second to decorate the austenite grain boundaries with proeutectoid Ferrite so bainite can not form. Part 2 of the study concerns with the influence that those precipitates have on the kinetics of Acicular Ferrite formation during austenite isothermal decomposition.
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Influence of Deformation and Molybdenum Content on Acicular Ferrite Formation in Medium Carbon Steels
ISIJ International, 2006Co-Authors: Carlos Capdevila, Carlos Garcia-mateo, F G Caballero, J. P. Ferrer, Víctor López, Carlos Garcia De AndresAbstract:The present work deals with the influence of deformation and molybdenum content on the subsequent austenite-to-Acicular Ferrite transformation during continuous cooling in medium carbon microalloyed steels. The results obtained demonstrate that higher deformation temperature induces a finer austenite grain size as a result of austenite recrystallisation processes during cooling down to austenite decomposition temperature. The higher the molybdenum content and severity of deformation are, the finer austenite grain is. Likewise, it was concluded that molybdenum suppress pearlitic microstructure, and clearly delay proeutectoid Ferrite field to longer times. By contrast, Acicular Ferrite transformation is enhanced in molybdenum rich steel, which not only affect the volume fraction but also the morphology of Acicular Ferrite. © 2006 ISIJ.Peer Reviewe
