The Experts below are selected from a list of 426 Experts worldwide ranked by ideXlab platform

Mihaly Reger - One of the best experts on this subject based on the ideXlab platform.

  • Effect of Mushy Zone Permeability on the Formation of Centerline Segregation in Slab Casting
    Materials Science Forum, 2014
    Co-Authors: Mihaly Reger, Balázs Verő, Róbert Józsa, Zsolt Csepeli
    Abstract:

    A complex mathematical model characterizing the Centerline Segregation level in the mid region of continuously cast slabs was developed. The basic heat transfer and solidification model connected to the semi-empirical liquid feeding model (LMI - Liquid Motion Intensity model) gives the possibility to estimate the Centerline Segregation parameters of slab cast under industrial circumstances. Solid shell deformation changes the volume of the space available for the liquid inside the slab and hereby also changes the conditions of liquid supply.

  • Diffusion of Carbon in the Centerline Region of Continuous Cast Slabs
    Materials Science Forum, 2010
    Co-Authors: Mihaly Reger, Balázs Verő, Ibolya Kardos, Fábián Enikő-réka, György Kaptay
    Abstract:

    The paper deals with the stability of Centerline inhomogenity of continuously cast slabs and hot rolled products. The Centerline Segregation is a disadvantageous failure of slabs which can affect the quality properties of the final products. During hot rolling of the slabs the Centerline Segregation pattern will become thin and stretched and it can also be detected in the middle part of heavy plates and coils. It is a common experience that the Centerline Segregation of heavy plates can not be easily decreased by post heat treatment. The pattern of the Centerline Segregation was modeled physically by preparing a sandwich structure of steel plates with different levels of carbon and alloying elements. Homogenization experiments were performed and the samples were examined metallographically. Diffusional calculations proved the governing role of carbon activity which is influenced by the distribution of alloying elements.

  • centreline Segregation of cc slabs
    Materials Science Forum, 2010
    Co-Authors: Mihaly Reger, Heli Kytonen, Balazs Verő, Arpad Szelig
    Abstract:

    Industrial data set with 400 CC (continuous casting) steel slabs were analysed by a statistical method for revealing the real connections between the technological parameters, heat transfer model results and the precisely determined Centerline Segregation index. Because of the poor correlations a new model was developed in which the shrinkage and deformations of the shells of the slabs can also be taken into account. It has been proved that the stopping of liquid movement below about 30 % liquid ratio plays an important role in the Centerline Segregation formation. The conclusions of the calculations are in good accordance with the results of the metallographical analysis.

  • The Effect of Alloying Elements on the Stability of Centerline Segregation
    Defect and Diffusion Forum, 2010
    Co-Authors: Mihaly Reger, Balázs Verő, Ibolya Kardos, Péter Varga
    Abstract:

    The paper deals with the stability of Centerline inhomogenity of continuously cast slabs and hot rolled products. The Centerline Segregation is a disadvantageous failure of slabs which can affect the quality properties of the final products. During hot rolling of slabs the Centerline Segregation pattern will become thin and stretch and it can also be detected in the middle part of heavy plates and coils. It is a common experience that the Centerline Segregation of heavy plates can not be easily decreased by post heat treatment. The pattern of the Centerline Segregation was modeled physically by preparing a sandwich structure of steel plates with different levels of carbon and alloying elements. Homogenization experiments were performed and the samples were examined metallographically. Diffusional calculations proved the governing role of carbon activity which is influenced by the distribution of alloying elements.

  • The Effect of Heat Treatment on the Stability of Centerline Segregation
    Strojniski Vestnik-journal of Mechanical Engineering, 2010
    Co-Authors: Mihaly Reger, Balazs Vero, Imre Felde, Ibolya Kardos
    Abstract:

    The paper deals with the stability of Centerline inhomogenity of the continuously cast slabs. The pattern of the Centerline Segregation was modeled physically by preparing a sandwich structure of steel plates with different levels of carbon and alloying elements. The eligibility of sandwich structured samples for diffusional experiments, i.e. the permeability of the metal-metal boundaries in the samples from diffusional point of view was checked by the comparison of measured and theoretically calculated hardness value for plain carbon steels. Diffusional homogenization experiments were performed and the samples were examined metallographically. Great microstructural difference remains between the core and cover layers after a long time diffusional homogenization if there is a difference also in the manganese content in the thickness direction of the sandwich structured sample. Manganese has a double role in this process: it reduces the possibility of homogenization of carbon and exaggerates the effect of this slight difference in carbon content during austenite decomposition.

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

  • Numerical Simulation on Solute Macro-Segregation in Thick Slab by Continuous Casting Process
    Hot Working Technology, 2010
    Co-Authors: Zhang Jiong-ming
    Abstract:

    This paper firstly simulated the fields of temperature,flow and solute transport with the business software CALCOSOFT under the real cooling condition of the 250 mm thick slab by continuous casting process.In order to verify the results simulated,composition analyzing was conducted using the samples along the transversal direction of the slabs.The result of macro Segregation simulated was extremely similar to that detected in the slabs.The flow induced by natural convection was strong at first stage of solidification and it could bring the surplus solute at the interface to the central part of the liquid,but due to the large amount of liquid the concentration of solute was diluted;however near the end of the solidification,due to the block effect of mushy region,the velocity of natural convection was too low to bring the solute to the center and thus Centerline Segregation was diminished remarkably.

  • Study on the effect of dynamic soft reduction on the Centerline Segregation of continuously casting pipeline steel slab
    2009
    Co-Authors: Zhang Jiong-ming
    Abstract:

    This paper introduces the effect of different position of dynamic soft reduction on the inner quality of continuously casting slab.By etching the testing sample of the slab and checking and examining the dendrites over the cross section of the slab sample as well as analyzing the chemical compositions of the sample along the gauge direction it's found out that the effect of dynamic soft reduction on the improvement in the central line Segregation of the slab is extremely prominent.Results of the dendrite examination show that the central line Segregation grades of all five testing samples of the slab for X70 pipeline steel are below B0.5 and both the internal crack grade and crack grade over the triangular zone are less than 0.5.Although the positions of the dynamic soft reduction for the five testing slabs are different,yet the internal quality of all the slabs are excellent and they are all in conformity with the inner control standards.In the meanwhile by calculating the Segregation ratio of the elements along the gauge direction according to the analysis of the chemical compositions of the sample it's found that the more desirable position of the dynamic soft reduction for the pipe line slab should be fs=0.5~0.8.

V. C. Srivastava - One of the best experts on this subject based on the ideXlab platform.

  • Development of Stretch Flangeable Grade Steels by Inclusion Engineering Approach
    Journal of Materials Engineering and Performance, 2018
    Co-Authors: G. K. Mandal, K. Ashok, P. Biswas, R. B. Sarkar, R. Sundara Bharathy, V. C. Srivastava
    Abstract:

    The demand for good stretch flangeability in high-strength automotive steels has necessitated due attention on steel cleanliness and processes. The presence of elongated MnS stringers and Centerline Segregation of nonmetallic inclusions adversely affects the transverse mechanical property. In the present investigation, stretch flangeability of industrially produced steel, with and without Ca treatment, has been compared with Ti-added steel, produced at 40 kg scale without Ca treatment. The study brings out the influence of Centerline Segregation and modification of nonmetallic inclusions on HER performance. The microstructural analysis of industrial steel revealed that the method of hole formation (punching/drilling) determines crack initiation mechanism. The inclusions, along with the second phase present in the Centerline, drive the crack propagation. An addition of Ti in liquid steel promotes formation of Al-Ti-O-based oxide, prior to MnS precipitation, during solidification and acts as nucleation site for MnS inclusion. This obviates the elongated stringer-type MnS inclusions. The Centerline Segregation-free Ti-modified steel, prepared at the laboratory scale, showed consistent HER property compared with industrial steel. It is also concluded that calcium treatment can be circumvented by modifying the sulfide stringer with the addition of Ti in the steel for further improvement in HER property.

Miaoyong Zhu - One of the best experts on this subject based on the ideXlab platform.

  • Modeling the Effect of Combined Electromagnetic Stirring Modes on MacroSegregation in Continuous Casting Blooms
    Metallurgical and Materials Transactions B, 2020
    Co-Authors: Rui Guan, Miaoyong Zhu
    Abstract:

    MacroSegregation is one of the most frequently observed defects in continuous casting blooms, which causes nonconformity in ultrasonic flaw detection of rolled products. To investigate the influence of combined EMS modes (M-EMS + F-EMS) on macroSegregation, a 3D multiphase solidification model based on the volume-averaged Eulerian approach was established to simulate the electromagnetic field, fluid flow, microstructural evolution, and solute transport of heavy-rail steel blooms subjected to different EMS processes. In this model, a hybrid model of the mushy zone and a back-diffusion model were introduced into the momentum and solute conservation equations to realize the calculation of microstructural evolution and solute transport with electromagnetic stirring. The predicted magnetic induction intensity, macrostructure, and macroSegregation were verified with Tesla meter measurements, etched macrostructure analysis, and infrared carbon-sulfur analysis. The calculation results showed that M-EMS had little effect on the improvement of the positive Centerline Segregation, whereas F-EMS effectively reduced the positive Centerline Segregation. Moreover, a combination of these EMS modes could further reduce the positive Centerline Segregation in continuous casting blooms. The change in solute concentration caused by M-EMS could be inherited by the position of F-EMS, which could enhance the metallurgical effects of F-EMS. These results were also verified through an industrial application.

  • Numerical simulation of slab Centerline Segregation with mechanical reduction during continuous casting process
    International Journal of Heat and Mass Transfer, 2018
    Co-Authors: Jiang Dongbin, Weiling Wang, Sen Luo, Miaoyong Zhu
    Abstract:

    Abstract The mechanical reduction is an effective way to improve the strand center Segregation during the continuous casting process, while the effect of reduction parameters on solute transport phenomenon has rarely been addressed. In the present work, a two-phase solidification model coupling the thermal shrinkage and mechanical reduction was established to investigate fluid flow and solute distribution in the continuous casting slab. In the model, an integrated method was used to define solid deformation, which was dependent on the solidification behavior in the center. The results show that the solidified shell contracting outward by thermal shrinkage will be compressed to slab center with mechanical reduction and the enriched liquid steel transporting downwards is suppressed, resulting in the center Segregation improvement. The reduction zone should cover the solidification range in the slab center, where the liquid fraction is between 0.95 and 0.01. The mechanical reduction applied in the earlier stage strongly influences the solidification end, while that in the later stage obviously affects center Segregation evolution. Moreover, it is found that the solid phase still contracts intensively to slab surface, even the liquid phase has already solidified. Therefore, the mechanical reduction should also be applied in the subsequent cooling stage to avoid the center porosity formation. Besides the reduction amount and position, the slab stretching in the reduction zone is also another important factor influencing the improvement of center Segregation.

  • Dynamic Soft Reduction for Continuously Cast Rail Bloom
    Journal of Iron and Steel Research International, 2007
    Co-Authors: Yong Chen, Su-bo Yang, Miaoyong Zhu
    Abstract:

    Abstract Center porosity and Centerline Segregation in continuously cast bloom can be minimized by the well-known method of dynamic soft reduction. Metallurgical results of soft reduction previously employed in continuous bloom casting for heavy rail steel in Panzhihua Iron and Steel Group were not fully achieved because of the improper soft reduction process. Therefore, experiments for optimizing the process parameters of soft reduction for bloom were carried out. The results show that the proportion of the center porosity, which is less than 1. 0, increases from 28. 41% to 99. 81%, while the proportion of the Centerline Segregation class increases from 40. 91% to 100%, and the proportion of the central cavity increases from 92. 05% to 100%, whereas the center carbon Segregation index decreases from 1. 17 to 1. 05. The internal quality and the mechanical performance of the rails produced from continuously cast blooms meet the requirement of high-speed tracks of 350 km/h.

Jingna Sun - One of the best experts on this subject based on the ideXlab platform.

  • Centerline Segregation mechanism of twin roll cast a3003 strip
    Journal of Alloys and Compounds, 2015
    Co-Authors: Huagui Huang, Jingna Sun
    Abstract:

    Abstract The Centerline Segregation mechanism of twin-roll cast A3003 strip was analyzed from the perspective of macro and micro, and a mathematical model considering flow field, solute field and temperature field has been developed. The distribution of Fe and Mn elements in A3003 alloy molten pool was obtained by the model. The simulated results agreed well with the measured data. The dendrites grew rapidly along 〈0 0 1〉 direction in the form of columnar crystal. Meanwhile, the solute elements were concentrated near the Centerline gradually, and the concentration of solutes would reach the maximum in the Kiss point zone. For A3003 strip, the content of Fe in the Kiss point zone was much higher than the rest, which is the primary cause for Centerline Segregation. The location of Kiss point is the main factor for Centerline Segregation, and the Segregation tends to decrease with the location rising.