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R D K Misra - One of the best experts on this subject based on the ideXlab platform.

  • Significance of Finish Cooling Temperature to Microstructure and Property Relationship of Low-Carbon V-N-Cr Microalloyed High-Strength Steel
    Journal of Materials Engineering and Performance, 2019
    Co-Authors: Yue Liu, Lin-xiu Du, Hong Yan Wu, Bin Zhang, R D K Misra
    Abstract:

    Herein, three final cooling temperatures were employed to achieve high strength and toughness communication in the V-N-Cr Microalloyed steels. This study shows that V-N-Cr Microalloyed steel primarily consisted of ferrite, granular bainite, acicular ferrite, and a small quantity of M/A phase at the final cooling temperature of 600 °C, while the polygonal ferrite, lamellar bainite, granular bainite, and a small fraction of acicular ferrite were obtained at 450 °C. The width of lamellar bainite was ~ 200-400 nm, and acicular ferrite was composed of fine non-parallel ferrite platelet structures with high dislocations densities. As the final cooling temperature decreased further, the microstructure included granular bainite and lath bainite at 350 °C. The nanoscale precipitates of V-N-Cr Microalloyed steel were divided into two types, large-scale precipitates near the grain boundary that precipitated at high temperatures and small precipitates of diameter 5-10 nm at low temperatures, which significantly contributed toward strength. The hot rolled low-carbon V-N-Cr microalloy steel exhibited optimal mechanical properties at the final rolling temperature of 830 °C, as well the final cooling temperature was 450 °C. The highest yield strength and tensile strength of V-N-Cr Microalloyed steel were 835 MPa and 989 MPa, respectively. The outstanding impact toughness of 161 J tested at − 60 °C was received. The transformation strengthening and precipitation hardening played a crucial role in affecting the thermo-mechanical properties.

  • microstructure and mechanical properties of tmcp heavy plate Microalloyed steel
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2014
    Co-Authors: Hui Xie, Xiuhua Gao, R D K Misra
    Abstract:

    Abstract A Microalloyed steel heavy plate was subjected to two-stage controlled rolling and two-stage continuous cooling to explore the microstructure and mechanical properties in the plate. The objective was to obtain superior mechanical properties in the plate by exploiting the advantage of Microalloyed precipitates in stimulating intragranular ferrite nucleation. Yield strength, tensile strength, and percentage of elongation of 550 MPa, 655 MPa, and 26.5% were obtained at quarter-thickness and 515 MPa, 645 MPa, and 29.5% at mid-thickness. The impact energy determined at −40 °C was ~93 J and 71 J for quarter-thickness and mid-thickness regions, respectively. The microstructure consisted of polygonal ferrite, acicular ferrite, and pearlite. Microalloyed precipitates provided effective nucleation sites for intragranular ferrite and ensured near-homogenous microstructure and mechanical properties in the heavy steel plate.

  • microstructural evolution and mechanical properties of high strength Microalloyed steels ultra fast cooling ufc versus accelerated cooling acc
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2013
    Co-Authors: Shuai Tang, Z Y Liu, G D Wang, R D K Misra
    Abstract:

    Abstract We describe here the microstructural evolution and mechanical properties of high strength Microalloyed steels processed using different cooling trajectory. Pilot-scale studies demonstrated that high strength of ∼700 MPa can be obtained in a Microalloyed steel using ultra fast cooling (UFC) positioned at the exit of hot rolling mill, while the yield strength obtained via the conventional thermo-mechanical controlled processing (TMCP) with accelerated cooling (ACC) is ∼100 MPa less. The underlying reason is that ultra fast cooling positioned immediately after hot rolling enhances strengthening associated with precipitation and grain refinement. Theoretical calculations and experiments indicated that grain refinement and precipitation in TMCP with in-front UFC led to strength increment of ∼49 and 54 MPa, respectively over the conventional TMCP with ACC process. Furthermore, the microstructural characterization indicated that the density of high angle grain boundaries was increased and the average size of precipitates was reduced from ∼34 nm to ∼10 nm, when the cooling pattern is changed from ACC to UFC. The theoretical estimate also indicated that when the cooling profile is changed from the conventional ACC to UFC+ACC, and to UFC, a higher degree of precipitation is responsible for increase in strength in UFC processed hot rolled Microalloyed steels.

  • effect of cooling rate on the microstructure and mechanical properties of nb Microalloyed steels
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007
    Co-Authors: S Shanmugam, R D K Misra, T Mannering, D Panda, N K Ramisetti, S Jansto
    Abstract:

    Abstract We describe here the effect of cooling rate on the microstructure and mechanical properties of Nb-Microalloyed steels that were processed as structural beams at three different cooling rates. Nb-Microalloyed steels exhibited increase in yield strength with increase in cooling rate during processing. However, the increase in the yield strength was not accompanied by loss in toughness. The microstructure at conventional cooling rate, primarily consisted of polygonal ferrite-pearlite microconstituents, while at intermediate cooling rate besides polygonal ferrite and pearlite contained significant fraction of degenerated pearlite and lath-type ferrite. At higher cooling rate, predominantly, lath-type (acicular) or bainitic ferrite was obtained. The precipitation characteristics were similar at the three cooling rates investigated with precipitation occurring at grain boundaries, on dislocations, and in the ferrite matrix. The fine scale (∼8–12 nm) precipitates in the ferrite matrix were MC type of niobium carbides. The microstructural studies suggest that the increase in toughness of Nb-Microalloyed steels with increase in cooling rate is related to the change in the microstructure from predominantly ferrite-pearlite to predominantly bainitic ferrite.

  • impact toughness and microstructure relationship in niobium and vanadium Microalloyed steels processed with varied cooling rates to similar yield strength
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006
    Co-Authors: S Shanmugam, R D K Misra, T Mannering, D Panda, S Jansto
    Abstract:

    Abstract We describe here the relationship between microstructure and impact toughness behavior as a function of cooling rate for industrially processed Nb- and V-Microalloyed steels of almost similar yield strength (∼60 ksi). Both Nb- and V-Microalloyed steels exhibited increase in toughness with increase in cooling rates during processing. However, Nb-Microalloyed steels were characterized by relatively higher toughness than the V-Microalloyed steels under identical processing conditions. The microstructure of Nb- and V-Microalloyed steels processed at conventional cooling rate, primarily consisted of polygonal ferrite–pearlite microconstituents, while Nb-Microalloyed steels besides polygonal ferrite and pearlite contained significant fraction of degenerated pearlite. The microstructure of Nb- and V-Microalloyed steels processed at relatively higher cooling rate contained degenerated pearlite and lath-type (acicular) ferrite in addition to the primary ferrite–pearlite constituents. The fraction of degenerated pearlite was higher in Nb-Microalloyed steels than in the V-Microalloyed steels. In both Nb- and V-Microalloyed steels the precipitation characteristics were similar with precipitation occurring at grain boundaries, dislocations, and in the ferrite matrix. Fine-scale (∼5–10 nm) precipitation was observed in the ferrite matrix of both the steels. The selected area diffraction (SAD) pattern analysis revealed that these fine precipitates were MC type of niobium and vanadium carbides in the respective steels and followed Baker–Nutting orientation relationship with the ferrite matrix. The microstructural studies suggest that the increase in toughness of Nb-Microalloyed steels is attributed to higher fraction of degenerated pearlite in the steel.

S Jansto - One of the best experts on this subject based on the ideXlab platform.

  • effect of cooling rate on the microstructure and mechanical properties of nb Microalloyed steels
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007
    Co-Authors: S Shanmugam, R D K Misra, T Mannering, D Panda, N K Ramisetti, S Jansto
    Abstract:

    Abstract We describe here the effect of cooling rate on the microstructure and mechanical properties of Nb-Microalloyed steels that were processed as structural beams at three different cooling rates. Nb-Microalloyed steels exhibited increase in yield strength with increase in cooling rate during processing. However, the increase in the yield strength was not accompanied by loss in toughness. The microstructure at conventional cooling rate, primarily consisted of polygonal ferrite-pearlite microconstituents, while at intermediate cooling rate besides polygonal ferrite and pearlite contained significant fraction of degenerated pearlite and lath-type ferrite. At higher cooling rate, predominantly, lath-type (acicular) or bainitic ferrite was obtained. The precipitation characteristics were similar at the three cooling rates investigated with precipitation occurring at grain boundaries, on dislocations, and in the ferrite matrix. The fine scale (∼8–12 nm) precipitates in the ferrite matrix were MC type of niobium carbides. The microstructural studies suggest that the increase in toughness of Nb-Microalloyed steels with increase in cooling rate is related to the change in the microstructure from predominantly ferrite-pearlite to predominantly bainitic ferrite.

  • impact toughness and microstructure relationship in niobium and vanadium Microalloyed steels processed with varied cooling rates to similar yield strength
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006
    Co-Authors: S Shanmugam, R D K Misra, T Mannering, D Panda, S Jansto
    Abstract:

    Abstract We describe here the relationship between microstructure and impact toughness behavior as a function of cooling rate for industrially processed Nb- and V-Microalloyed steels of almost similar yield strength (∼60 ksi). Both Nb- and V-Microalloyed steels exhibited increase in toughness with increase in cooling rates during processing. However, Nb-Microalloyed steels were characterized by relatively higher toughness than the V-Microalloyed steels under identical processing conditions. The microstructure of Nb- and V-Microalloyed steels processed at conventional cooling rate, primarily consisted of polygonal ferrite–pearlite microconstituents, while Nb-Microalloyed steels besides polygonal ferrite and pearlite contained significant fraction of degenerated pearlite. The microstructure of Nb- and V-Microalloyed steels processed at relatively higher cooling rate contained degenerated pearlite and lath-type (acicular) ferrite in addition to the primary ferrite–pearlite constituents. The fraction of degenerated pearlite was higher in Nb-Microalloyed steels than in the V-Microalloyed steels. In both Nb- and V-Microalloyed steels the precipitation characteristics were similar with precipitation occurring at grain boundaries, dislocations, and in the ferrite matrix. Fine-scale (∼5–10 nm) precipitation was observed in the ferrite matrix of both the steels. The selected area diffraction (SAD) pattern analysis revealed that these fine precipitates were MC type of niobium and vanadium carbides in the respective steels and followed Baker–Nutting orientation relationship with the ferrite matrix. The microstructural studies suggest that the increase in toughness of Nb-Microalloyed steels is attributed to higher fraction of degenerated pearlite in the steel.

Ke Yang - One of the best experts on this subject based on the ideXlab platform.

  • Effect of applied stress and microstructure on sulfide stress cracking resistance of pipeline steels subject to hydrogen sulfide
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007
    Co-Authors: Ming-chun Zhao, Ming Liu, Andrej Atrens, Yiyin Shan, Ke Yang
    Abstract:

    Effects of applied stress and microstructure on sulfide stress cracking resistance of pipeline steels subject to hydrogen sulfide were investigated by the single-edge notched tensile method using a Microalloyed steel and a non-Microalloyed steel. The failure time increased with the decreasing applied stress, and finally the threshold stress intensity factor was calculated for acicular ferrite (AF) and ferrite-pearlite (FP) in these two steels. The strength was not the dominant factor for the SSC, and aged Microalloyed AF had the best SSC resistance in coincidence with the highest strength. The SSC resistance in sort ascending was non-Microalloyed AF, non-Microalloyed FP, Microalloyed FP, Microalloyed AF and aged Microalloyed AF. The SSC was explained from hydrogen penetration and microstructural characteristic. The localized hydrogen concentration was enhanced by applied stress. The higher the applied stress, the more easily the SSC occurred. Carbonitrides and pinned dislocations contributed in better SSC resistance.

  • acicular ferritic microstructure of a low carbon mn mo nb Microalloyed pipeline steel
    Materials Characterization, 2005
    Co-Authors: Yiyin Shan, Furen Xiao, Bo Liao, Deliang Ren, Ke Yang
    Abstract:

    Abstract The transformations during continuous cooling and isothermal processes, the effects of hot deformation and the morphology of the final microstructure of a low-carbon Mn–Mo–Nb Microalloyed pipeline steel designed for acicular ferrite microstructure were investigated. The results show that there are three independent “C” curves for isothermal phase transformation, i.e., TTT diagram, of low-carbon Microalloyed steel, namely, polygonal ferrite–pearlite transformation “C” curve, the massive ferrite transformation “C” curve and the bainitic transformation “C” curve, respectively. Hot deformation accelerates acicular ferrite transformation and refines the steel's matrix. The microstructure of acicular ferrite for pipeline steels was discussed.

S Shanmugam - One of the best experts on this subject based on the ideXlab platform.

  • effect of cooling rate on the microstructure and mechanical properties of nb Microalloyed steels
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007
    Co-Authors: S Shanmugam, R D K Misra, T Mannering, D Panda, N K Ramisetti, S Jansto
    Abstract:

    Abstract We describe here the effect of cooling rate on the microstructure and mechanical properties of Nb-Microalloyed steels that were processed as structural beams at three different cooling rates. Nb-Microalloyed steels exhibited increase in yield strength with increase in cooling rate during processing. However, the increase in the yield strength was not accompanied by loss in toughness. The microstructure at conventional cooling rate, primarily consisted of polygonal ferrite-pearlite microconstituents, while at intermediate cooling rate besides polygonal ferrite and pearlite contained significant fraction of degenerated pearlite and lath-type ferrite. At higher cooling rate, predominantly, lath-type (acicular) or bainitic ferrite was obtained. The precipitation characteristics were similar at the three cooling rates investigated with precipitation occurring at grain boundaries, on dislocations, and in the ferrite matrix. The fine scale (∼8–12 nm) precipitates in the ferrite matrix were MC type of niobium carbides. The microstructural studies suggest that the increase in toughness of Nb-Microalloyed steels with increase in cooling rate is related to the change in the microstructure from predominantly ferrite-pearlite to predominantly bainitic ferrite.

  • impact toughness and microstructure relationship in niobium and vanadium Microalloyed steels processed with varied cooling rates to similar yield strength
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006
    Co-Authors: S Shanmugam, R D K Misra, T Mannering, D Panda, S Jansto
    Abstract:

    Abstract We describe here the relationship between microstructure and impact toughness behavior as a function of cooling rate for industrially processed Nb- and V-Microalloyed steels of almost similar yield strength (∼60 ksi). Both Nb- and V-Microalloyed steels exhibited increase in toughness with increase in cooling rates during processing. However, Nb-Microalloyed steels were characterized by relatively higher toughness than the V-Microalloyed steels under identical processing conditions. The microstructure of Nb- and V-Microalloyed steels processed at conventional cooling rate, primarily consisted of polygonal ferrite–pearlite microconstituents, while Nb-Microalloyed steels besides polygonal ferrite and pearlite contained significant fraction of degenerated pearlite. The microstructure of Nb- and V-Microalloyed steels processed at relatively higher cooling rate contained degenerated pearlite and lath-type (acicular) ferrite in addition to the primary ferrite–pearlite constituents. The fraction of degenerated pearlite was higher in Nb-Microalloyed steels than in the V-Microalloyed steels. In both Nb- and V-Microalloyed steels the precipitation characteristics were similar with precipitation occurring at grain boundaries, dislocations, and in the ferrite matrix. Fine-scale (∼5–10 nm) precipitation was observed in the ferrite matrix of both the steels. The selected area diffraction (SAD) pattern analysis revealed that these fine precipitates were MC type of niobium and vanadium carbides in the respective steels and followed Baker–Nutting orientation relationship with the ferrite matrix. The microstructural studies suggest that the increase in toughness of Nb-Microalloyed steels is attributed to higher fraction of degenerated pearlite in the steel.

S. Gunduz - One of the best experts on this subject based on the ideXlab platform.

  • The Effect of Vanadium and Titanium on Mechanical Properties of Microalloyed PM Steel
    Powder Metallurgy and Metal Ceramics, 2016
    Co-Authors: S. Gunduz, Hayriye Karabulut, Mehmet Akif Erden, Muhsin Turkmen
    Abstract:

    The effect of Ti and V additives on the microstructure and mechanical properties of Microalloyed powder metallurgy (PM) steels is investigated. The microstructure of Microalloyed PM steels is characterised with the help of optic microscope, SEM and EDS. The results showed that the addition of Ti and V elements has a beneficial effect on the improved mechanical properties. Ti–V Microalloyed PM steels can be used to take advantage of improved grain refining propensity of titanium, whilst allowing vanadium to be used as dispersion strengtheners and to enhance the hardenability and transformation characteristics.

  • Microstructural characterization and mechanical properties of Microalloyed powder metallurgy steels
    Materials Science and Engineering: A, 2014
    Co-Authors: Mehmet Akif Erden, S. Gunduz, Mustafa Türkmen, Hasan Karabulut
    Abstract:

    Abstract The effects of Ti additions on the microstructures and mechanical properties of Microalloyed powder metallurgy (PM) steels were investigated. The microstructure of the Microalloyed PM steels was characterized with the help of optic microscope, SEM and EDS. Experimental results showed that Ti Microalloyed steels can be produced by PM technology. The addition of Ti increases the strength in the sintered conditions. In addition, Ti limits grain growth during austenitization prior to cooling. By limiting austenite grain growth, the precipitates result in significant improvement in strength.

  • influence of cooling rate and tempering on precipitation and hardness of vanadium Microalloyed steel
    Materials & Design, 2005
    Co-Authors: S. Gunduz, R C Cochrane
    Abstract:

    Abstract In the present work precipitate distributions in a C–Mn–Al–V–N Microalloyed steel and hardness were examined for as-received, heat-treated and heat-treated & tempered samples. Examination of as-received and heat-treated samples from the vanadium Microalloyed steels using transmission electron microscopy revealed quite different precipitate distributions. The type and sizes of the precipitate particles and also hardness of the steel samples were markedly affected as the austenitisation time and cooling rates were changed. Tempering steel samples after air cooling produced fine matrix precipitates which are closely spaced, obstruct moving dislocations and hence make the steel harder.