The Experts below are selected from a list of 174 Experts worldwide ranked by ideXlab platform

J Vojvodič Tuma - One of the best experts on this subject based on the ideXlab platform.

  • Properties and fracture of structural steels with yield stress of 373–737 MPa in ambient to Nil Ductility Temperature range
    Journal of Materials Processing Technology, 2002
    Co-Authors: J Vojvodič Tuma
    Abstract:

    Abstract By lowering the testing Temperature down to below the Nil Ductility Temperature (NDT −20°C) the yield stress, tensile strength and the uniform elongation are increased, while the reduction of area is slightly decreased and the Charpy notch toughness strongly decreased. After strain ageing, the tensile properties are increased, the uniform elongation strongly decreased and the reduction of area slightly decreased. The effect of low Temperature on the tensile properties is similar for as-delivered and strain-aged steels. The tensile fracture of as-delivered and strain-aged steels at the NDT −20°C is ductile, while the Charpy-V notch toughness (CVN) fracture is brittle at a significantly higher Temperature. The fracture of CVN specimens in the transition Temperature range is basically similar to the fracture of notched tensile specimens tested with loading rates in the range 0.1–1500 m/s at the NDT. The mechanism of CVN fracture is discussed.

  • Low-Temperature tensile properties, notch and fracture toughness of steels for use in nuclear power plant
    Nuclear Engineering and Design, 2001
    Co-Authors: J Vojvodič Tuma
    Abstract:

    Abstract The tensile and toughness properties of eight steels with yield stresses of 265–1003 MPa in plates of thickness 20–60 mm and a microstructure of polygonal ferrite and pearlite, quenched-and-tempered ferrite and pearlite, and tempered martensite were determined in the interval from ambient Temperature to the Nil-Ductility Temperature (NDT)−20 °C. It was found that the yield stress and tensile strength were increased after strain ageing and testing at the NDT±20 °C. Uniform elongation was greatly diminished after strain ageing and it was slightly increased at the NDT±20 °C. The reduction of area was only slightly decreased after strain ageing, even at testing Temperatures down to NDT−20 °C. The greatest notch toughness was found for the steel with a microstructure consisting of quenched-and-tempered ferrite and pearlite. A new equation is derived which relates notch and fracture toughness in the Temperature range NDT±20 °C and is valid for the lower shelf-notch toughness region.

Vojvodic J Tuma - One of the best experts on this subject based on the ideXlab platform.

  • properties and fracture of structural steels with yield stress of 373 737 mpa in ambient to Nil Ductility Temperature range
    Journal of Materials Processing Technology, 2002
    Co-Authors: Vojvodic J Tuma
    Abstract:

    Abstract By lowering the testing Temperature down to below the Nil Ductility Temperature (NDT −20°C) the yield stress, tensile strength and the uniform elongation are increased, while the reduction of area is slightly decreased and the Charpy notch toughness strongly decreased. After strain ageing, the tensile properties are increased, the uniform elongation strongly decreased and the reduction of area slightly decreased. The effect of low Temperature on the tensile properties is similar for as-delivered and strain-aged steels. The tensile fracture of as-delivered and strain-aged steels at the NDT −20°C is ductile, while the Charpy-V notch toughness (CVN) fracture is brittle at a significantly higher Temperature. The fracture of CVN specimens in the transition Temperature range is basically similar to the fracture of notched tensile specimens tested with loading rates in the range 0.1–1500 m/s at the NDT. The mechanism of CVN fracture is discussed.

O. V. Sych - One of the best experts on this subject based on the ideXlab platform.

  • Scientific and Technological Bases for Developing Cold-Resistant Steel with a Guaranteed Yield Strength of 315–750 MPa for Arctic Conditions. Part 1: Alloying Principles and Requirements for Sheet Product Structure
    Inorganic Materials: Applied Research, 2019
    Co-Authors: O. V. Sych
    Abstract:

    Abstract—The results obtained upon choosing rational alloying and microalloying for cold-resistant steels with a guaranteed yield strength of 315–750 MPa on the basis of established interrelations between phase transformations, structure, mechanical properties, serviceability parameters, and the content of main alloying elements are presented. Quantitative requirements for various structural parameters and their maximum permissible difference throughout sheet product thickness up to 100 mm have been developed, depending on the strength category and manufacturing technology (thermomechanical treatment with accelerated cooling, quenching from separate furnace heating or rolling heating with high Temperature tempering) to provide guaranteed characteristics of strength, cold resistance (impact energy KV at a testing Temperature from –60 to –80°С, critical ductile-to-brittle transition Temperature Тkb, and Nil Ductility Temperature NDT), and crack resistance according to the criterion of critical crack tip opening displacement (CTOD).

  • Scientific and Technological Bases for Developing Cold-Resistant Steel with a Guaranteed Yield Strength of 315–750 MPa for Arctic Conditions: Part 2. Manufacturing Technology, Structure, Properties, and Serviceability of Sheet Products
    Inorganic Materials: Applied Research, 2019
    Co-Authors: O. V. Sych
    Abstract:

    Abstract—The paper presents results of the industrial implementation of hot plastic deformation and thermal treatment schemes for the production of rolled sheet products based on cold-resistant steel with yield strength not lower that 315–750 MPa for the Arctic. On the basis of the studies performed, a set of scientific and technological techniques has been developed for various technological processes (thermomechanical treatment followed by accelerated cooling, quenching from the rolling heating, and separate furnace heating with high-Temperature tempering). The developed complex method provides the formation of a structure having an acceptable heterogeneity and anisotropy level corresponding to different morphological and crystallographic parameters throughout the entire thickness of rolled products up to 100 mm based on low-alloy steels with a yield strength not lower than 315–460 MPa and up to 60 mm based on economically alloyed steels with a yield strength not lower than 500–750 MPa. The structure of sheet products is presented that provides guaranteed characteristics of strength, cold resistance (impact energy KV at a testing Temperature ranging from –60 to –80°C, critical ductile-to-brittle transition Temperature Tkb, and Nil Ductility Temperature NDT), and crack resistance according to a CTOD criterion in a low-Temperature range to meet the requirements of the RMRS “Rules for the Classification and Construction of Ships” for steel with the Arc40 index.

  • Scientific and Technological Bases for Developing Cold-Resistant Steel with a Guaranteed Yield Strength of 315–750 MPa for Arctic Conditions. Part 1: Alloying Principles and Requirements for Sheet Product Structure
    Inorganic Materials: Applied Research, 2019
    Co-Authors: O. V. Sych
    Abstract:

    —The results obtained upon choosing rational alloying and microalloying for cold-resistant steels with a guaranteed yield strength of 315–750 MPa on the basis of established interrelations between phase transformations, structure, mechanical properties, serviceability parameters, and the content of main alloying elements are presented. Quantitative requirements for various structural parameters and their maximum permissible difference throughout sheet product thickness up to 100 mm have been developed, depending on the strength category and manufacturing technology (thermomechanical treatment with accelerated cooling, quenching from separate furnace heating or rolling heating with high Temperature tempering) to provide guaranteed characteristics of strength, cold resistance (impact energy K V at a testing Temperature from –60 to –80°С, critical ductile-to-brittle transition Temperature Т _kb, and Nil Ductility Temperature NDT), and crack resistance according to the criterion of critical crack tip opening displacement (CTOD).

  • Scientific and Technological Bases for Developing Cold-Resistant Steel with a Guaranteed Yield Strength of 315–750 MPa for Arctic Conditions: Part 2. Manufacturing Technology, Structure, Properties, and Serviceability of Sheet Products
    Inorganic Materials: Applied Research, 2019
    Co-Authors: O. V. Sych
    Abstract:

    —The paper presents results of the industrial implementation of hot plastic deformation and thermal treatment schemes for the production of rolled sheet products based on cold-resistant steel with yield strength not lower that 315–750 MPa for the Arctic. On the basis of the studies performed, a set of scientific and technological techniques has been developed for various technological processes (thermomechanical treatment followed by accelerated cooling, quenching from the rolling heating, and separate furnace heating with high-Temperature tempering). The developed complex method provides the formation of a structure having an acceptable heterogeneity and anisotropy level corresponding to different morphological and crystallographic parameters throughout the entire thickness of rolled products up to 100 mm based on low-alloy steels with a yield strength not lower than 315–460 MPa and up to 60 mm based on economically alloyed steels with a yield strength not lower than 500–750 MPa. The structure of sheet products is presented that provides guaranteed characteristics of strength, cold resistance (impact energy K V at a testing Temperature ranging from –60 to –80°C, critical ductile-to-brittle transition Temperature T _kb, and Nil Ductility Temperature NDT), and crack resistance according to a CTOD criterion in a low-Temperature range to meet the requirements of the RMRS “Rules for the Classification and Construction of Ships” for steel with the Arc40 index.

Hanqian Zhang - One of the best experts on this subject based on the ideXlab platform.

  • Thickness Dependence of Toughness in Ultra-Heavy Low-Alloyed Steel Plate after Quenching and Tempering
    Metals, 2018
    Co-Authors: Huibin Liu, Hanqian Zhang
    Abstract:

    Due to the limitations of manufacturing techniques, inhomogeneous microstructures and properties along the thickness direction have been a big challenge for heavy and ultra-heavy plates of quenched and tempered low-alloyed steel. In this study, variation in microstructures and mechanical properties were investigated from the surface to the center of a 130 mm-thick ultra-heavy steel plate. Emphasis was made on toughness performance including impact toughness and crack resisting ability. It was found that the ultimate tensile strength at the plate surface, quarter and center thickness at room Temperature are 715, 643 and 618 MPa, respectively. Meanwhile, the ductile-brittle transition Temperature defined by fracture appearance for these three plate positions are −100, −30 and −15 °C, respectively. Moreover, the crack resisting ability represented by the Nil-Ductility Temperature are −40, −25 and −10 °C for these three positions respectively. Investigation by field emission scanning electron microscopy (FE-SEM) and electron backscatter diffraction (EBSD) revealed that the plate surface features finer matrix grain and carbide precipitation, as well as greater frequency of high angle misorientation. These microstructural features contribute to enhancing deformability, retarding cleavage initiation and hindering crack propagation, leading to the pronounced increase in the energy for fracture propagation and the overall impact energy as compared to the other two plate positions.

  • Thickness Dependence of Toughness in Ultra-Heavy Low-Alloyed Steel Plate after Quenching and Tempering
    MDPI AG, 2018
    Co-Authors: Huibin Liu, Hanqian Zhang
    Abstract:

    Due to the limitations of manufacturing techniques, inhomogeneous microstructures and properties along the thickness direction have been a big challenge for heavy and ultra-heavy plates of quenched and tempered low-alloyed steel. In this study, variation in microstructures and mechanical properties were investigated from the surface to the center of a 130 mm-thick ultra-heavy steel plate. Emphasis was made on toughness performance including impact toughness and crack resisting ability. It was found that the ultimate tensile strength at the plate surface, quarter and center thickness at room Temperature are 715, 643 and 618 MPa, respectively. Meanwhile, the ductile-brittle transition Temperature defined by fracture appearance for these three plate positions are −100, −30 and −15 °C, respectively. Moreover, the crack resisting ability represented by the Nil-Ductility Temperature are −40, −25 and −10 °C for these three positions respectively. Investigation by field emission scanning electron microscopy (FE-SEM) and electron backscatter diffraction (EBSD) revealed that the plate surface features finer matrix grain and carbide precipitation, as well as greater frequency of high angle misorientation. These microstructural features contribute to enhancing deformability, retarding cleavage initiation and hindering crack propagation, leading to the pronounced increase in the energy for fracture propagation and the overall impact energy as compared to the other two plate positions

W. A. Baeslack - One of the best experts on this subject based on the ideXlab platform.

  • The effect of specimen strength and thickness on cracking susceptibility during the Sigmajig weldability test
    Welding Journal, 1996
    Co-Authors: J. C. Lippold, S. S. Shademan, W. A. Baeslack
    Abstract:

    The effects of yield strength and specimen thickness on the threshold stress for solidification cracking using the Sigmajig weldability test have been determined for A-286 stainless steel. An increase in test specimen yield strength results in a decrease in the threshold stress for cracking. This decrease is attributed in part to a decrease in the width of the plastically deformed weld zone as the yield strength increases, which enhances strain localization in this region and promotes solidification cracking. Over a range of yield strengths, an increase in specimen thickness generally results in higher threshold stress for cracking, which are attributed to an increased inherent restraint. The relationship between weld pool shape, the solidification grain and the fracture stress during transverse loading has been investigated by performing hot-Ductility tests of weld fusion zone specimens. The hot-Ductility behavior of specimens produced from welds exhibiting elliptical and teardrop-shaped weld pools is comparable. However, specimens produced from welds that exhibit a teardrop-shaped weld pool fracture along the fusion zone centerline above the Nil-Ductility Temperature, whereas specimens produced from welds that exhibit an elliptical-shaped weld pool fracture in the partially melted zone. A correlation was observed between the fracture stress measured by hot-Ductility testing andmore » threshold stresses measured using the Sigmajig test.« less

  • The effect of specimen strength and thickness on cracking susceptibility during the Sigmajig weldability test : Increasing strength and thickness reduce the threshold stress for solidification cracking in A-286 stainless steel
    Welding Journal, 1996
    Co-Authors: J. C. Lippold, S. S. Shademan, W. A. Baeslack
    Abstract:

    The effects of yield strength and specimen thickness on the threshold stress for solidification cracking using the Sigmajig weldability test have been determined for A-286 stainless steel. An increase in test specimen yield strength results in a decrease in the threshold stress for cracking. This decrease is attributed in part to a decrease in the width of the plastically deformed weld zone as the yield strength increases, which enhances strain localization in this region and promotes solidification cracking. Over a range of yield strengths, an increase in specimen thickness generally results in higher threshold stresses for cracking, which are attributed to an increased inherent restraint. The relationship between weld pool shape, the solidification grain structure and the fracture stress during transverse loading (as experienced during Sigmajig testing) has been investigated by performing hot-Ductility tests of weld fusion zone specimens. The hot-Ductility behavior of specimens produced from welds exhibiting elliptical and teardrop-shaped weld pools is comparable. However, specimens produced from welds that exhibit a teardrop-shaped weld pool fracture along the fusion zone centerline above the Nil-Ductility Temperature, whereas specimens produced from welds that exhibit an elliptical-shaped weld pool fracture in the partially melted zone. A correlation was observed between the fracture stress measured by hot-Ductility testing and threshold stresses measured using the Sigmajig test.