Round Billet Research Articles

Numerical Simulation of Solute Transport Behavior During the Grade Transition of Round Billet Continuous Casting

Grade transitions in continuous casting can significantly improve casting machine productivity and reduce production costs. Accurate prediction of the mixing zone length is essential. A two‐dimensional transient model for grade transition in continuous casting is developed by integrating fluid flow, thermosolute transfer, and solidification. The model predicts the mixing zone changes at various casting speeds. The results indicate that positive segregation of the old steel (Q355NE) occurred at the billet's center, while the maximum negative segregation appears in the billet shell region. The process involves pausing the solidification of the grade transition connectors and the billet shell before casting is resumed with the introduction of a new steel (42CrMo). The extent of the mixing zone is determined by the carbon concentration at the centerline and 1/2 R. Numerical simulations of the temperature field and solute distribution trends are closely aligned with experimental data, validating the accuracy of the solute transport model. Although excessively slow speeds may disrupt the straightening process, reducing the casting speed and decreasing the mixing zone size. This study result provides theoretical guidance for the grade transition in large section round billet continuous casting.

Numerical modelling of continuous casting of round billets with turbulence in the melt

The present work aims to solve the continuous casting benchmark problem in axisymmetry with turbulence in the melt by the meshless method. The physical model of the liquid-solid system that involves mass, momentum and energy conservation is formulated in the mixture continuum approximation. The melt is assumed Newtonian and incompressible. A k-epsilon Reynolds averaged Navier-Stokes turbulence model is implemented with Abe-Kondoh-Nagano closures. The mushy region is modelled as a Darcy porous media with the Kozeny-Carman permeability model. The solution of partial differential equations is implemented locally using collocation with radial basis functions and explicit time-stepping. The velocity pressure coupling is performed using the fractional step method. The validation of the model is assessed by comparing its outcomes with the results of the finite volume method. A sensitivity study of the varying casting speed and temperature on the velocity, temperature, and solid fraction fields is shown.

Production Efficiency of Ribbon-Type Sections by the Drawing Method in Doubled-Roll Roller Dies

Introduction. The process of drawing is used to produce a wide range of fashion sections of complex configuration, including thin-walled, ribbon-type, and periodical section profiles.Problem Statement. Because of the complexity of steel ribbon production with flattening machines and high capital intensity of flattening production, since the second half of last century, the manufacturers have been trying to use alternative methods of flattening, in particular drawing in monolithic and double-roll roller dies.Purpose. The purpose of this research is to establish regularities of the influence of different sizing systems and process parameters on the regularities of shape change and energy-force parameters of the drawing process in double-roll roller dies and to determine the most effective schemes for achieving the maximal metal expansion while producing ribbon-type sections.Material and Methods. The materials used are as follows: round billets of 5.9 mm in diameter, made of steel brand St.08А; the methods used are as follows: cool billet processing with varying crimping in the double-roll rol ler die with different gauge systems.Results. The regularities of metal shape change and energy-force parameters alternation of the ribbon-type sec tion drawing process in doubled double-roll roller dies by using different gauge systems have been established. Marginal conditions of the deformation in double-roll dies, which provide stable and smooth drawing process according to the criterion of deformed metal safety factor, have been studied experimentally. The most efficient gau ge system of doubled roller dies, which provides maximal metal expansion while producing ribbon-type sections have been determined experimentally.Conclusions. It has been proposed to use the metal drawing technology in doubled double-roll roller dies with “bullhead-accelerated gauge” system while producing ribbon-type sections with a width-to-thickness ratio of more than 2, for achieving the maximal metal expansion per transition. In addition, such a process is energy efficient as the force of pulling through the roller die decreases.

Development of a computer program for calculating the geometric parameters of the deformation zone and mill tuning parameters in the process of producing hot-rolled seamless tubes

Determining the optimal tuning parameters for a piercing mill is a labor-intensive process. There are various calculation methods available for determining the tuning parameters of a piercing mill but implementing these methods can be time-consuming. Therefore, the developed computer program for calculating the geometric parameters of the deformation zone during the piercing of round billets and the tuning parameters of the piercing mill represents an innovative tool for calculating the tuning parameters of the piercing mill. The program allows for the establishment of optimal parameter values required to achieve the desired quality and accuracy of the steel piercing process. The main functions of the program include the analysis and processing of input data, such as the billet diameter, steel grade, roll calibration, and piercing mill tools. Based on this data, the program utilizes a developed mathematical model to calcu-late the optimal tuning parameters of the piercing mill, considering the required process characteristics and the desired level of product quality. One of the key features of the program is its high accuracy and universality. It takes into con-sideration multiple factors that affect the piercing process and enables reliable production forecasting. The program has a user-friendly interface, making it convenient for both specialists and shop floor personnel in the field of hot-rolled seamless tube production. The developed computer program is a valuable tool for manufacturers and research centers involved in steel piercing. It helps improve production efficiency, enhance product quality, and reduce time and costs associated with piercing mill setup. The program represents a significant contribution to the development and improve-ment of piercing technology in industrial settings

Effect of magnetic alternate stirring on solidification structure of the round billet

ABSTRACT In this study, a permanent magnet stirrer was constructed for the implementation of experiments on different magnetic field stirring modes. Through experiments, it can be observed that when the fixed speed of 200 rpm and the alternate stirring mode of magnetic field was adopted, the loose area in the core of ingots was reduced from about 72 mm2 to 21 mm2, which significantly improved the density and element uniformity of the ingot. A Φ220 mm SAE1527 round billet was selected as industrial trial steel. When the stirring current and frequency was 350 A and 3 HZ, the electromagnetic stirring of the mold was adjusted from continuous stirring to alternate stirring mode. The solidification structure of the billet has been improved to a certain extent. Furthermore, the number of spot segregation larger than 0.5mm2 was reduced from 43 to 26, thereby improving the uniformity of internal elements in the billet.

Numerical Simulation of the Effect of Solidified Shell Conductivity and Billet Sizes on the Magnetic Field with Final Electromagnetic Stirring in Continuous Casting.

Coupled with the results of a 2D heat transfer model, a 3D electromagnetic stirring round billet model is developed, which is considered for the difference in the conductivity of solidified shell and molten steel. The electromagnetic field distribution features of the billet and the effect of round billet sizes on the electromagnetic field are investigated. It is found that as the solidified shell conductivity of the Φ600 mm round billet increases from 7.14 × 105 S·m-1 to 1.0 × 106 S·m-1, the magnetic induction intensity decreases and the maximum value of electromagnetic force drops from 7976.26 N·m-3 to 5745.32 N·m-3. The magnetic induction intensity on the center axis of the stirrer rarely changes in the range of Φ100-Φ200 mm. With the increase in the round billet from Φ300 mm to Φ600 mm, the magnetic induction intensity and the electromagnetic force on the center axis of the stirrer decrease slowly and then significantly. In the range of 2-8 Hz, as the current strength reaches its maximum, the electromagnetic force can be increased by increasing the current frequency for round billets of Φ100-Φ500 mm, while there is an optimal current frequency for round billets larger than Φ600 mm.

Application of shaped tube as preform to eliminate the forming defects of ribbed tube in multi-pass drawing

Thin-walled ribbed tube with small-diameter is a newly designed structure, which is used in nuclear fuel cladding. Due to the high precision requirements of nuclear industry applications, the integral forming and precision forming of ribbed tube are the focus of research. However, the forming defects — rib grooves often fail to achieve the precision forming of ribbed tube. Therefore, the two-pass drawing process is designed to realize the integral forming of ribbed tube and the forming mechanism of ribbed tube is analyzed. Further, the effect of round tube as billet on the forming accuracy of ribbed tube is studied. The results show that the rib groove defects are caused by local large deformation and excessive metal flow, which can not be completely eliminated only by changing the billet size of round tube. Based on this, three kinds of shaped tubes as preforms instead of round billet are proposed for eliminating the rib groove defects to realize the precision forming of ribbed tube. The effects of different preform schemes on the forming accuracy, drawing force and stress distribution of ribbed tube are compared and discussed. By selecting the optimal preform scheme and applying it to multi-pass drawing, the completely defect-free ribbed tube is obtained. At the same time, after adopting the appropriate billet size, the rib filling fullness of the tube is further improved and closer to the target size. Moreover, the microstructure of ribbed tube after multi-pass drawing are observed. The martensite and deformation twins appeared due to work hardening and the grain size refinement degree of different positions are different due to different deformation degree.

Methods for forming of profile pipes from round billet

Shaped tubes production tendencies and the methods of their manufacturing are considered. An analysis of rollforming methods from a round billet is carried out. Approaches to the various rollforming design methods from a round billet are outlined. An angle modification method is proposed as the most probable in the production of shaped tubes from a round billet.

Research on cross wedge rolling forming technology of railway axles

This paper introduces a new forming method of railway axles: the square bloom is forged into a round axle billet by fast forging machine, then the round billet is rolled into the rough axle by the cross-wedge rolling machine. In order to prove the feasibility of this method, we have done an experimental trial of the technology on making scale-down Chinese railway freight axles with the scale ratio 1:1.4. The test result shows that the new method can double the productivity compared with the single forging method, save about 9% materials and improve shape accuracy of rough axle. Microstructure and mechanical properties of the axles formed by the new method have been tested and the test results show that the yield strength is greater than 345Mpa, the tensile strength is greater than 610Mpa, and the grain size reaches grade 8, which meets the standard requirements; The transverse and longitudinal impact toughness is greater than 21J, and the cross-sectional hardness distribution is uniform; The fatigue toughness test shows that the KQ value of the journal and shaft body in the deformation area of cross wedge rolling is slightly larger than that of the wheel seat, which indicates that the CWR process has no negative effect on fracture toughness of axles.

Simulation of the Kinematic Condition of Radial Shear Rolling and Estimation of Its Influence on a Titanium Billet Microstructure.

The finite element method (FEM) computer simulation of the three-high radial shear rolling of Ti-6Al-4V alloy round billets was conducted using QForm software. The simulation was performed for the MISIS-100T rolling mill's three passes according to the following rolling route: 76 mm (the initial billet diameter) →65 mm→55 mm→48 mm (the final billet diameter). The change in the total velocity values for the points on the radius of the 48 mm diameter billet was estimated while passing the rolls' draft. The relative increase in the accumulated strain was estimated for the same points. Then, experimental shear rolling was performed. Grain sizes of the α- and β-phases were estimated in the cross section of the final billet at the stationary stage of rolling. The grain size distribution histograms for different phases were plotted. An area was found in the billet's cross section in which the trend of change in the total velocity of the points changed. This area represented a neutral layer between the slowing peripheral segments of the billet and the accelerating central segments of the billet. Inside this neutral layer, the limits of the cylindrical surface radius value were estimated. Experimental radial shear rolling was performed to compare the experimental rolling results (the billet microstructure investigation) with the computer simulation results. The computer simulation obtained two estimations of the radius limits: 8-16 mm (based on the analysis of the total velocity change) and 12-16 mm (based on the accumulated strain's relative increment change). The experimental rolling obtained two more estimations of the radius limits: 8.4-19.5 mm and 11.3-19.7 mm-based on the results of the microstructure investigation. It was confirmed that varying the kinematic and deformation parameters of radial shear rolling allows regulation of the thickness of the peripheral fine-grain layer and the diameter of the central coarse-grain layer of the rolled billets.

Study on the effect of mould alternate stirring on the internal quality of the round billet

ABSTRACT In this paper, the effects of mold alternate stirring and single-direction continuous stirring on the internal quality of the billet were compared. When the mold alternate electromagnetic stirring was adopted, with the increase of stirring current form 260A to 350A, the central shrinkage cavity of the billet was disappeared, and the proportion of central equiaxed crystal zone increased gradually from 18.67% to 25.00%. The number of spot segregation larger than 1.0 mm2 in the billet was reduced from 18 to 10, and the maximum positive segregation of carbon and manganese decreased from 1.059 and 1.020 to 1.029 and 1.012, and the maximum negative segregation increased from 0.959 and 0.989 to 0.972 and 0.991, which improved the uniformity of elements distribution of the round billet. Through the above analysis, it can be seen that the mold alternate stirring mode with suitable parameters can improve the internal quality of the billet.

Effects of mold electromagnetic stirring on heat transfer, species transfer and solidification characteristics of continuous casting round billet

In this study, the temperature distribution, species transfer, and solidification behavior in round billet continuous casting with mold electromagnetic stirring (M-EMS) was numerically investigated. The joule heat induced by the M-EMS and the liquid fraction profiles in the mushy zone were observed, whereby it was found that increasing current intensity caused further increase in electromagnetic force, which reduced the impact depth of liquid steel while accelerating the dissipation of superheat. The high liquid fraction in the mushy zone at the exit of the secondary cooling zone were 68.1% (case 1) and 77.1% (case 6). The central carbon contents of the round billets were 0.337 wt% (case 1) and 0.335 wt% (case 6). Moreover, the proportion of solidification microstructure and secondary dendrite arm spacing of the round billet samples were compared, which revealed that increasing the current intensity, casting speed, and cooling intensity, were all conducive to improving the uniformity of carbon distribution and compactness of the solidification structure.

Effects of Pulsed Magneto-Oscillation on the Homogeneity of Low Carbon Alloy Steel Continuous Casting Round Billet

Pulsed Magneto-Oscillation (PMO) is a newly developed and effective homogenization technique, and has been successfully applied in rectangular continuous casting, but its processing parameters and effective stability in round billet continuous casting have not been investigated. In this paper, the effects of PMO on the solidification structure and the macrosegregation of Φ 178 mm continuous casting round billets for low carbon alloy steel were studied by industrial experiments. The results show that PMO can stably increase the equiaxed grain area, and reduce the macrosegregation of billets. Moreover, it has strong adaptability to steel grade and continuous casting process parameters. Compared with the billets without PMO treatment, for 93.8% of billets (15 billets) solidified with PMO, the equiaxed grain area ratio increased by an average of 5.8%, while for 87.5% of billets (14 billets), the carbon segregation index range decreased by an average of 0.06, though different steel grades, superheat and casting speed were used in the experiment. It is believed that convection caused by Lorentz force can accelerate the heat dissipation of steel liquid, and reduce the temperature of a liquid at the solidification front, while the magnetic oscillation effect is conducive to dendrite fragmentation. Both effects lead to refinement of the solidification structure and reduction of macrosegregation.

Evolution of Non-Metallic Inclusions in 27SiMn Steel

To study the evolution of non-metallic inclusions in 27SiMn steel, the 27SiMn steel produced using the LD-LF-CCM process was sampled in various stages in a steel factory. The evolutionary behavior of inclusion in various processes was systematically analyzed by scanning electron microscopy (SEM-EDS), and the total oxygen content and nitrogen content in 27SiMn steel were measured at various production steps. On the basis of the calcium treatment for 27SiMn steel, the equilibrium reactions for Ca-Al were calculated according to the thermodynamic equilibrium model. The results showed that the types of inclusions at the start of LF stations are mainly Al2O3-FeO and MnS-Al2O3. Before calcium treatment, the inclusions are mostly calcium aluminate and CaO-MgO-Al2O3. Compared with the process after soft blowing, the number density of inclusions in tundish increased by 77.88%, possibly due to secondary oxidation. From the soft blowing process to the continuous casting round billet, the inclusions translate into spherical CaO-MgO-Al2O3-SiO2, and a large number of CaS were observed. One part of the CaS precipitated separately, the other part was semi-wrapped with the composite inclusions. At the same time, calcium treatment increases the number density, mean diameter, and the area fraction of inclusions. The mass fraction of T.O. (total oxygen content) increased significantly after soft blowing, and the N content increased greatly from station to tundish. The change trend of N content in steel was basically consistent with that of T.O. content. It was necessary to prevent the secondary oxidation of molten steel during calcium treatment and the casting process. When the liquidus temperature of liquid steel is 1873 K, w[Al] = 0.022%, and w[Ca] in steel is controlled between 1.085 × 10−6 and 4.986 × 10−6, the Al2O3 inclusion degeneration effect is good.

Modeling of the Nonuniform Microstructure and Microsegregation Formation of the Shell in Round Billet Continuous Casting

To explore the influence of nonuniform heat transfer on the grain structure and microsegregation of carbon in shells inside the mold, a multiscale model considering heat conduction and dendritic growth is constructed for the round billet continuous casting. Adopting measured heat flux as the boundary conditions, heat conduction in the mold is solved by the finite difference scheme, and dendritic growth is modeled by the cellular automaton model. The temperature distribution of the round billet under measured heat flux is calculated, and the grain structure and the microsegregation of carbon in four selected regions are simulated. Herein, it is shown in the results that the different local heat fluxes lead to dissimilar variations in the surface temperature and grain structure of the shell. A close relationship exists between the carbon microsegregation and local heat flux; the carbon microsegregation decreases with heat flux. The high heat flux accelerates columnar dendritic growth and fines the columnar dendritic array so that the secondary arms are less developed and the microsegregation is improved.

Effect of different positions of final electromagnetic stirring for ϕ800mm vertical round billet on fluid flow and heat transfer

Effect of different positions of final electromagnetic stirring for ϕ800mm vertical round billet on fluid flow and heat transfer

Improvement of the secondary cooling mode for continuous casting of round billets at Ural Steel JSC

Formation of hot cracks on continuously cast round billets is the frequent problem in metallurgical production. The article presents the results of a study of the macrostructure, surface quality and technology of continuous casting of round billets with a diameter of 455 mm, produced at the bloom caster of Ural Steel JSC. The main defects of such billets are identified as surface cracks of “combined” type, namely, transverse cracks (the share among the billets with defects is 9.1%), cracks of the mesh form (the share among the billets with defects is 8.3%). The main reasons for the unsatisfactory quality of the ingot are determined: increased overheating of metal in the tundish, which can be partially compensated by reduction of the casting speed, and intensive cooling of billet surface in the first segments of secondary cooling, which increase thermal stresses in metal with consequent heating of surface layers. It was decided that the most effective way to minimize billet defects is to improve the secondary cooling technology in compliance with the regulated casting temperature and speed procedure. Thermal calculations of billet solidification are conducted. It was revealed that overcooling of billet surface occurs in the first segments of secondary cooling under the existing secondary cooling modes and temperature and speed modes of casting, which leads to additional thermal and phase stresses. In the third segment of the secondary cooling zone, heating of the billet surface is observed due to the heat of the central part. Rational flow rates of cooling agent for the secondary cooling segments of the bloom continuous casting machine are proposed. They include expansion of the active section of secondary cooling with a reduction of cooling agent consumption in the first segments will reduce the thermal cycling processes in the hardened crust and minimize the likelihood of cracking. The work was conducted under financial support of the RF Ministry of Science and High Education (project No. FZRU-2020-0011).

Non-uniform shrinkage analysis of round billet using element-free Galerkin method

Non-uniform shrinkage analysis of round billet using element-free Galerkin method

Theoretical study of the process of balls rolling with a diameter of 40 mm on a ball rolling mill

The following calibration scheme for rolling round steel is used for producing thermally hardened grinding balls with a diameter of 40 mm at JSC SSGPO for 320 variety rolling mill: a round billet with a diameter of 40 mm is produced from the initial billet of 120 × 120 mm. In the last developed scheme the square billet 150x150 mm is used as an initial billet for whole mill where the round steel with diameter of 40 mm is obtained from the above mentioned billet and then this round steel is used for production of balls with a diameter of 40 mm. Computer simulation of the ball rolling process in the Simufact Forming program was performed. The results of strain state distribution showed that the maximum processing level in the surface layers of balls is observed, while the stress state distribution showed that in the surface layers prevail high compressive stresses up to −400 MPa. Such stress-strain state leads to formation of gradient structure in the ball cross-section, where the surface layers will have more high mechanical properties. That is the most optimal result for details worked in condition of high values of friction.

The simulation of mould metallurgical behaviour under electromagnetic stirring for vertical large bloom

ABSTRACT According to the mould electromagnetic stirring of vertical round billet continuous casting, a three-dimensional mathematical model of electromagnetic field was established to study the distribution of magnetic field in the mould. On the centre cross section of agitator, the distribution of magnetic flux density is small in the centre and large in the edge, in the centre longitudinal section, the maximum value of magnetic flux density at the lower edge of the mould. The influence of electromagnetic parameters on the flow field and temperature field in mould was studied. When the section of round billet is 800 mm, the current intensity is 380 A and the current frequency is 3 Hz, and the proportion of equiaxial crystal is up to 43.6%. The central shrinkage hole, central crack and central porosity are all less than grade 1, and there is no white band, the stirring intensity of M-EMS is relatively ideal.