Papers by Keyword: Accelerated Cooling

Abstract: The paper describes some aspects of a scientific and research project dedicated to mechanical property prediction in plates for pipe production rolled at PJSC MMK 5000 Mill. The prediction is based on billet thermal state modelling by thermo-mechanical control process (TMCP) of rolling and subsequent cooling. The central focus of the modelling is the calculation of billet layer-by-layer cooling trajectory. The paper presents some results of model verification by test rolling.

Abstract: Microstructure consisting of ferrite and bainite in low C-Mn steels with different manganese contents (0.75-1.49 mass %) can be formed by accelerated cooling. Microstructure observation reveals that the transformation products of 0.75%Mn and 1.06%Mn steel mainly consist of equiaxed ferrite and pearlite when hot finish deformation was processed at the temperature of 800°C, while the transformed products mainly contained irregular ferrite and upper bainite when finish rolling temperature (FRT) increases to 850°C or 900°C. However, a large amount bainite can also be attained in 1.49%Mn steel when FRT decreased to 800°C. The strength increases by about 100MPa with the increase of manganese content from 0.75% to 1.49%. The 1.06%Mn steel exhibits a superior strength-elongation combination by deforming at FRT of 850°C and then accelerated cooling at the cooling rate of about 40°C/s to coiling temperature in the range of 490~510°C.

Abstract: The research presented in the paper was carried out for the experimental steels with modified chemical composition allocated to pipelines for 760÷1180 °C range, strain rate s^–1 s^–1 and different distributions of particular reductions between passes were presented. Physical modeling of the rolling process was carried out upon using the GLEEBLE 3800 simulator. The research was based on the findings of the paper [1].

Abstract: The research presented in the current paper was carried out for the experimental steel designed for plate which meets the requirements for grade X100 according to API5L. Physical modeling of the rolling process was carried out using the GLEEBLE 3800 simulator. The tested steel is fine-grained constructional steel for making tubes for gas pipelines with the working pressure higher than 15 MPa. The fine-grained structure guarantees excellent plastic properties as well as high impact toughness. After rolling the steel should obtain the minimal yield point of 690 MPa and tensile strength over 760 MPa.

Abstract: The paper presents results of the numerical modelling of the plates accelerated cooling process after the rolling process. Research were carried out for one of the plate rolling mill technological conditions. Presented in the paper research were done for a few variants for X70 steel grade. As a result of the carried out research temperature distribution on the cross section of the cooled plates for the analyzed variants of the accelerated cooling process were obtain.

Abstract: Modern steel plate manufacture relies on the manipulation of recrystallisation and grain growth in order to obtain maximised and precise mechanical properties from low-alloyed feedstock. The models that describe this metallurgical process nowadays inform the design of the plant itself. They are also capable of application to the on-line control of rolling, as well as to several of the ancillary mill operations.

Abstract: In this work result of the theoretical analyses, witch the main purpose was modelling of the microstructure change during round bars rolling was presented. To determination of the austenite diameter during numerical modelling of the rolling process it is necessary to assign mathematical models of the microstructure change, relationship making the value of yield stress dependent on deformation parameters, temperature and strain range. Theoretical analysis was made in computer program Forge2008®, based on the finite-element method. An analysis was made for two cases: traditional - without accelerated cooling during rolling process and normalizing with one section of the accelerated cooling during rolling process for the ø26 mm round bars. Modification of the ø26 mm round bars rolling technology with accelerated cooling, affect the reduction of average austenite diameter, which cause improving impact resistance of the final product. Results of the theoretical analysis were verified in industrial conditions, in one of polish steelwork.

Abstract: In the present study, monotonic and cyclical torsional deformations of an X-70 microalloyed steel were conducted at austenite temperatures below the recrystallisation-stop temperature (T_5%). The austenite deformation is followed by accelerated continuous cooling to allow the investigation of the strain reversal effect on the subsequent phase transformation mechanisms. The transformation behaviours were studied by a dilatometry method, and the microstructures of the transformed products have been analysed using electron back scatter diffraction (EBSD). The results of this study shows that although subjected to the same total cumulative strain and the same cooling rate, strain path reversal by cyclical torsion produces lower temperature transformation products involving mainly a displacive mechanism, comparing to simple strain path deformation which leads to higher temperature transformation by a reconstructive mechanism.

Abstract: The paper presents the results of the numerical modelling and industrial research of the cooling ability of the device for the round plain bars accelerated cooling process. Research were carried out for one of the bar rolling mill technological conditions in a few variants. The paper purpose was determination of the cooling ability of device for accelerated cooling process to checking possibility of the using this device in the rolling line, during normalizing rolling process. Investigation results elaborated in the paper made the basis for determination of the heat exchange coefficients between cooled band and water. In the next stage of this paper numerical modeling of the normalizing rolling process with accelerated cooling of band in the final stage of the rolling process was carried out. In this investigation heat exchange coefficients between band and cooling medium (water), which were determinated with allowance of cooling possibilities of investigated device for band accelerated cooling were used. From the obtained results it was found that in the analysed bar rolling mill it is possible to decrease the band average temperature to about 900 °C, which is required during the normalizing rolling process.

Abstract: Recent trends in the production of high strength steel plate call for increasingly sophisticated thermo-mechanical treatment schedules, including the use of high rate accelerated cooling after finish rolling in order to achieve the desired microstructure and mechanical properties. Achieving the necessary cooling process control accuracy in such cases requires a sound understanding and description of the interactions between external heat transfer processes and changes in internal energy due to phenomena such as solid-state phase transformations. The thermal physical properties of the evolving microstructures of complex phase and martensitic steels vary greatly, and are strongly dependent on temperature and constituent phases. As a result, critical parameters such as thermal diffusivity cannot be accurately estimated without appropriate linkage to both phase transformation kinetics and temperature. In the present study, a numerical simulation has been developed to investigate the unsteady heat transfer and phase transformation behaviour of a moving steel plate during accelerated cooling. The simulation includes semi-empirical microstructure evolution sub-models, fitted to measured CCT data using non-linear regression. These are coupled to thermal-physical properties sub-models and thermal conduction calculations. A comprehensive suite of thermal boundary condition models which account for direct water cooling, forced convection film boiling, air cooling, radiation and heat transfer between plate and transport rollers are also included. The required equations for the plate temperature and microstructure evolution are solved numerically using a cell centred finite volume method, and the model has been validated by comparing simulated cooling stop temperatures with measurements obtained on the plate cooling section of an industrial plate mill. The predicted cooling stop temperatures of steel plates for different thicknesses, velocities and water flow rates are in good agreement with plant operational data.