The Experts below are selected from a list of 300 Experts worldwide ranked by ideXlab platform

Roumen Petrov - One of the best experts on this subject based on the ideXlab platform.

  • exploring the microstructure and tensile properties of cold rolled low and medium carbon Steels after ultrafast heating and quenching
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2019
    Co-Authors: F Castro M Cerda, Bernd Schulz, Diego J Celentano, A Monsalve, I Sabirov, Roumen Petrov
    Abstract:

    Abstract The aim of the present study is to evaluate the impact of heating rate on the microstructure and tensile properties of cold-rolled low and medium carbon Steels. For this purpose, cold-rolled low and medium carbon Steels were subjected to short peak-annealing experiments at 900 and 1100 °C under three heating rates (10, 450 and 1500 °C/s). The microstructure reveals a mixture of phases and microconstituents (ferrite, bainite, and as-quenched martensite) which are related to the carbon heterogeneities in austenite. The microstructural characterization suggests that the grain refinement achieved after ultrafast heating has a minor effect on the yield and ultimate tensile strength, compared to the relative microstructural distribution. It is suggested that the interplay of various strengthening mechanisms in samples subjected to ultrafast heating rates are responsible for the observed increase in strength and ductility.

Birger Karlsson - One of the best experts on this subject based on the ideXlab platform.

  • Influence of short heat pulses on properties of martensite in medium carbon Steels
    Materials Science and Engineering: A, 2013
    Co-Authors: Krste Cvetkovski, Johan Ahlström, Birger Karlsson
    Abstract:

    The process of tempering a martensitic medium carbon steel was investigated with the aim to study resulting material properties. The experimental results were used to model residual stresses caused by local heating, with the finite element method. Tempering was followed for times from 0.1 s up to 1 h by using laser heating and conventional salt bath furnace treatments within the temperature interval 500–700 °C. In addition, the thermal expansion was evaluated using dilatometry. Experiments showed that the initial stages of martensite decomposition, associated with loss of crystal tetragonality, proceed almost instantly. An initial large decrease of hardness within the first tenth of a second of the tempering process was measured, followed by only limited further softening with increased tempering time. Thus for the current material the tempering time had limited influence on hardness, governed primarily by the peak temperature during the heating process. Finite element modelling of rapid local heating and cooling showed that the tempering behaviour and associated dilatation effects yield a peak temperature dependent residual stress field with a broad tensile stress distribution for the case of un-tempered martensite. However, for tempered martensite the residual stress field depends primarily on the heating rate and peak temperature and shows large gradients with tensile stresses in the surface and compressive below. Thereby, for both cases, residual stresses were obtained but with completely different residual stress gradients.

Chong Soo Lee - One of the best experts on this subject based on the ideXlab platform.

  • enhancing tensile properties of ultrafine grained medium carbon steel utilizing fine carbides
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2011
    Co-Authors: Taekyung Lee, Duk-lak Lee, Chan Hee Park, Chong Soo Lee
    Abstract:

    The aim of the present study is to evaluate the influence of nano-sized carbides upon tensile behavior in UFG Medium-Carbon Steels and to develop a material with improved tensile properties. UFG Medium-Carbon Steels with fine carbides were successfully fabricated by multi-pass caliber rolling at 773 K. Alloying chromium and molybdenum resulted in thinner pearlitic lamellae, which were transformed into finer particles after severe plastic deformation. The UFG steel containing the alloying elements exhibited superior tensile properties, which was attributed to the enhanced strain hardening rate by the imbedded finer particles. Subsequent annealing induced growth of grains and particles, which also recovered elongation at the expense of strength. All UFG Steels investigated here showed a yield-point phenomenon due to the decreased hardening rate and lack of mobile dislocations and their sources. The deteriorating effect of particle growth overwhelmed the improving effect of grain growth after annealing of the UFG Medium-Carbon steel, leading to a reduced strain hardening rate. This resulted in a positive correlation between a grain size and Luders elongation in the investigated UFG Steels.

Krste Cvetkovski - One of the best experts on this subject based on the ideXlab platform.

  • Influence of short heat pulses on properties of martensite in medium carbon Steels
    Materials Science and Engineering: A, 2013
    Co-Authors: Krste Cvetkovski, Johan Ahlström, Birger Karlsson
    Abstract:

    The process of tempering a martensitic medium carbon steel was investigated with the aim to study resulting material properties. The experimental results were used to model residual stresses caused by local heating, with the finite element method. Tempering was followed for times from 0.1 s up to 1 h by using laser heating and conventional salt bath furnace treatments within the temperature interval 500–700 °C. In addition, the thermal expansion was evaluated using dilatometry. Experiments showed that the initial stages of martensite decomposition, associated with loss of crystal tetragonality, proceed almost instantly. An initial large decrease of hardness within the first tenth of a second of the tempering process was measured, followed by only limited further softening with increased tempering time. Thus for the current material the tempering time had limited influence on hardness, governed primarily by the peak temperature during the heating process. Finite element modelling of rapid local heating and cooling showed that the tempering behaviour and associated dilatation effects yield a peak temperature dependent residual stress field with a broad tensile stress distribution for the case of un-tempered martensite. However, for tempered martensite the residual stress field depends primarily on the heating rate and peak temperature and shows large gradients with tensile stresses in the surface and compressive below. Thereby, for both cases, residual stresses were obtained but with completely different residual stress gradients.

Y. Unigovsky - One of the best experts on this subject based on the ideXlab platform.

  • Regression analysis of the mechanical properties—Composition dependencies for cast low- and Medium-Carbon Steels
    Journal of Materials Engineering and Performance, 2000
    Co-Authors: Y. Unigovsky
    Abstract:

    One of the principal problems in the production of steel castings is the increase in their mechanical characteristics. To ensure their prediction within the frames of the developed mathematical models, it is rather important to derive the dependencies of “composition-property” type. However, the available data either take into account the influence of one of the components only or are contradictory. In the present paper, on the basis of correlation analysis of the dependencies of tensile properties and impact strength of carbon Steels (0.15 to 0.30% C) produced, using basic and acid processes on the contents of five principal components of (C, Si, Mn, S, and P), we have obtained functional relations of the second order, allowing prediction of mechanical properties of steel at constant parameters of heat treatment as early as at the stage of casting and refining. It is established that at certain combinations of components, we observe trends in the “composition-property” dependencies differing from current notions.