Funnel Mold Research Articles

Study on Mushy Zone Coefficient in Solidification Heat Transfer Mathematical Model of Thin Slab with High Casting Speed

When the casting speed of the thin slab continuous caster is increased, the ratios of the solid and liquid phases in the solidification front of the molten steel in the mold change, which affects the thickness of the solidified shell. In order to accurately calculate the thickness of the solidified shell and determine the value range of the mushy zone coefficient suitable for the mathematical model of solidification heat transfer at high casting speed, this paper established the solidification heat transfer mathematical model in thin slab funnel mold, and the influence of different mushy zone coefficients on the accuracy of solidification heat transfer mathematical model was analyzed and compared with the actual solidified shell thickness. The results showed that, when the casting speed was increased to 4~6 m/min and the coefficient of the mush zone coefficient was 3 × 108~9 × 108 kg/(m3⋅s), the thickness of solidified shell calculated by the solidification heat transfer model was in good agreement with that measured in practice. The research in this paper provides an important reference for the establishment of the solidification heat transfer mathematical model at high casting speed in the future.

Effect of the Intensity of Single-Ruler Electromagnetic Braking on the Flow Pattern in a Thin-Slab Funnel Mold

Effect of the Intensity of Single-Ruler Electromagnetic Braking on the Flow Pattern in a Thin-Slab Funnel Mold

Modelling Study of EMBr Effect on Interface Fluctuation and Melt Flow in a Thin Slab Mould

Electromagnetic brakes (EMBrs) are regularly used in continuous casting to control interface fluctuations in a mould. In the research, to appraise the damping effect of EMBr technique, namely EMBr-ruler technique, the influence of magnetic field intensity on behaviours of melt flow and interface fluctuation in a Compact Strip Production (CSP) thin slab funnel mould are numerically simulated. The numerical results illustrate that the existence of the EMBr-ruler technique is conducive to inhibiting the impact of the ascending circulation on the interface in the CSP funnel mould. With the gradual enhancement of magnetic intensity, the service efficiency of the EMBr-ruler on the fluctuation of two-phase steel/slag interface is enhanced. For instance, by applying a magnetic induction intensity of 0.5 T, the maximum fluctuation height of two-phase steel/slag interface is decreased to 6.4 mm. This can well prevent surface defects, such as slag entrapment.

Analysis of Uneven Wear Mechanism of Narrow-Face Copper Wall of Funnel Mold

In thin-slab continuous casting, due to the influence of the special shape of the funnel mold, cracks at the corner of the slab shell are more likely to occur than those in conventional slab shells, and a serious wear phenomenon also appears on the narrow face of the copper wall of the mold. Aimed at the corner cracks of thin slabs and the wear phenomenon of the copper wall, a new 3D stress analysis model in a funnel mold has been developed to simulate the stress-–train behavior of the slab shell under high-speed continuous casting. The results show that at the position 600 mm below the meniscus, the gap begins to appear at the corner of the slab; the maximum value of the first principal stress appears at the corner. The shell is squeezed by the copper wall during the downward movement in the funnel mold, and the slab shell in the funnel area moves towards the narrow face. The displacement causes the deformation of the slab shell to extend to the corners, the deformed shell is pressed against the corner of the copper wall. A new type of copper wall was designed for production, and it was found that the cracks at the corner of the slab shell were greatly reduced.

Influence of submerged entry nozzle on funnel mold surface velocity

Abstract In this article, physical and numerical simulation of the flow field in flexible thin slab caster funnel mold at high casting speed is carried out with a five-hole submerged entry nozzle (FHSEN), and characteristics of the flow field on funnel mold liquid level under different casting speeds (4, 5, and 6 m·min−1) and different submerged depths (130, 160, and 190 mm) are studied by comparing with the new submerged entry nozzle (NSEN) designed. Physical simulation is based on the funnel mold prototype. Numerical simulation is carried out based on FLUENT software, and industrial experiments of two kinds of submerged entry nozzle are also carried out. The results show that in the case of both physical and numerical simulation, the maximum surface velocity of the FHSEN funnel mold is 0.58 m·s−1, and the funnel mold liquid level is prone to slag entrapment. The NSEN funnel mold’ maximum surface velocity is 0.37 m·s−1. Compared with the FHSEN, the NSEN funnel mold’ maximum surface velocity decreases by 0.21 m·s−1, and funnel mold surface velocity decreases significantly. Finally, the accuracy of simulation results is verified by industrial tests, and it is also show that NSEN can greatly reduce funnel mold surface velocity and probability of slag entrapment.

Effect of EMBr on Flow in Slab Continuous Casting Mold and Industrial Experiment of Nail Dipping Measurement

In this study, a funnel mold (FM) model of a multi-mode electromagnetic braking (EMBr) device was developed, and the magnetic flux density at different currents was obtained by MAXWELL software. By using the magnetohydrodynamics (MHD) module of FLUENT software, the volume of fluid binomial flow turbulence model and the EMBr mathematical model of the steel/slag flow field were coupled, and the characteristics of the molten steel flow and the liquid-level fluctuation in the 1520 mm × 90 mm FM with the casting speed of 6 m/min were calculated under the effect of the electromagnetic field. The FM liquid-level characteristic information under production conditions was obtained in a nail board industrial experiment and compared with the magnetic-fluid coupling model. The results show that the EMBr can significantly change the flow behavior of molten steel. When the magnetic pole current is not less than 800-600 A, the maximum liquid-level fluctuation height decreases from 18 mm without EMBr to less than 5 mm, and the liquid-level cannot easily entrap slag. Considering the EMBr effect and production cost, the reasonable magnetic pole current should be 800-600 A. The reliability of numerical simulation was also verified by the industrial test results of the nail board.

Heat transfer behaviour of funnel mould copper plates with high casting speed during different water supply processes

ABSTRACT In the process of high casting speed, the study of funnel mould (FM) cooling process is particularly important. Based on the copper plate temperature measured by thermocouple, a mathematical model of the inverse heat transfer problem of the thin slab/copper plate was developed to calculate the boundary heat flux, then a positive mathematical model of thin slab/copper plate/cooling water coupled heat transfer has been developed, and the influence of the cooling water flows from top to bottom in the water channels on the heat transfer behaviour of the FM copper plate was analysed. The results show that when the cooling water flows from top to bottom in the water channels was adopted, the peak temperature of the copper plate hot face decreased 117°C, the maximum temperature of the cooling water decreased 24°C. Cooling water velocity and temperature have little influence on heat transfer of copper plate.

Heat transfer behavior in ultrahigh-speed continuous casting mold

AbstractThe growth rate of the shell thickness in the funnel mold for ultrahigh-speed continuous casting of steel has a significant effect on the shell surface quality. By using the node temperature inheritance algorithm, a three-dimensional transient thermal conductivity model of the liquid steel solidification inside the mold was established, and the effects of casting temperature and speed on the heat transfer behavior of the thin slab were investigated. The results show that with an increase in the casting speed from 4.0 to 6.0 m·min−1, the maximum thickness of the shell at mold exit was reduced from 26 to 12.8 mm, and the maximum temperature of the slab surface at mold exit increased from 1,210 to 1,305°C. However, the increase of casting temperature from 1,550 to 1,560°C had little effect on the surface temperature and thickness of the slab shell.

Prediction of longitudinal facial crack in steel thin slabs funnel mold using different machine learning algorithms

PurposeLongitudinal facial cracks (LFC) are one of the major defects occurring in the continuous-casting stage of thin slab caster using funnel molds. Longitudinal cracks occur mainly owing to non-uniform cooling, varying thermal conductivity along mold length and use of high superheat during casting, improper casting powder characteristics. These defects are difficult to capture and are visible only in the final stages of a process or even at the customer end. Besides, there is a seasonality associated with this defect where defect intensity increases during the winter season. To address the issue, a model-based on data analytics is developed.Design/methodology/approachAround six-month data of steel manufacturing process is taken and around 60 data collection point is analyzed. The model uses different classification machine learning algorithms such as logistic regression, decision tree, ensemble methods of a decision tree, support vector machine and Naïve Bays (for different cut off level) to investigate data.FindingsProposed research framework shows that most of models give good results between cut off level 0.6–0.8 and random forest, gradient boosting for decision trees and support vector machine model performs better compared to other model.Practical implicationsBased on predictions of model steel manufacturing companies can identify the optimal operating range where this defect can be reduced.Originality/valueAn analytical approach to identify LFC defects provides objective models for reduction of LFC defects. By reducing LFC defects, quality of steel can be improved.

Heat transfer behaviour of funnel mould copper plates during thin slab continuous casting and channel structure optimization

ABSTRACT The heat transfer in funnel mold during thin slab continuous casting is rather complex and sensitive that the flow and temperature of cooling water as well as the roughness of channel walls may have significant influences on it. Herein, a 3-D heat transfer model of funnel copper plates coupling with the flow of cooling water in the channels was developed with the consideration of the fluid-solid interaction. The results show that the interfacial heat flux between the copper plate and cooling water decreases significantly with the increase of distance from channel root, and the temperature distribution of mold lower part is more uneven than that of the upper part. According to the magnitude and distribution of mold temperature, structure of mold copper plates like fillet radius and depth of concave channel, length of circular channels in wide face and roughness of channel wall were optimized.

Behavior and Removal of Inclusions by Means of the Use of Mathematical and Physical Simulations as Well as the Measured Vibrations with an Accelerometer in a Funnel Mold in Thin Slab Continuous Casting

Due to the inherent difficulty in making direct observations of the behavior of the dynamic flow of liquid steel and the inclusions in the continuous casting of the steel, mathematical and physical modeling, having great popularity and acceptance, has been an invaluable aid to the understanding of the fluid flow phenomena. Up to date, there is little information available in the literature regarding the behavior of the inclusions, especially inside the funnel type mold.It has been found that the accelerometer is a transducer capable of relating the vibration with the behavior of the inclusions in the continuous casting mold. It was indicated that higher levels of vibration in the thin slab mold is greater than the removal of inclusions therein.As a starting point of the results a mathematical modeling, previously carried on the work group, were used,1) where an analysis of the fluid flow process of the continuous casting thin slab was carried out. Two nozzle designs, two depths of 22 and 34 cm, and three casting speed of 4, 5 and 6 m/min were simulated. In all cases, just 100 particles were simulated within the flowing liquid metal, because once the mathematical calculations or the processing time increases as the quantity of particles grow. These have previously been treated with a liquid, sensitive to the black light, and then under this type of light the inclusions are luminescent. All cases were also solved in the simulation software Fluent® where a slag layer, in which all the inclusions that reach it are trapped, is generated at the meniscus of liquid metal.The area near the nozzle has a greater concentration of particles, which is due to low speed or flow pattern change in said zone. These inclusions are floating in this area eventually become stripped and trapped in the slag layer.

The Overview on Sticking Breakout Behavior for Thin Slab Continuous Casting

Breakout is the most detrimental event associated with the continuous casting process, with the overview of the sticking breakout behavior, a lot of valuable things had been acquired. For the mechanism of the sticking breakout forming, the key for the breakout prevention is decreasing the probability of the hot spot; the content of the carbon or alloy element, the wear and tear of the mould corner, the mould flux, the fluctuation of the casting speed and the fluctuation of the meniscus are easy to cause the sticking; and with high casting speed and the funnel mould, the thin slab continuous casting is more easier to lead to sticking breakout than the normal strand.

The Thermal Distortion of a Funnel Mold

This article investigates the thermal distortion of a funnel mold for continuous casting of thin slabs and explores the implications on taper and solidification of the steel shell. The three-dimensional mold temperatures are calculated using shell-mold heat flux and cooling water profiles that were calibrated with plant measurements. The thermal stresses and distorted shape of the mold are calculated with a detailed finite-element model of a symmetric fourth of the entire mold and waterbox assembly, and they are validated with plant thermocouple data and measurements of the wear of the narrow-face copper mold plates. The narrow-face mold distorts into the typical parabolic arc, and the wide face distorts into a “W” shape owing to the large variation in bolt stiffnesses. The thermal expansion of the wide face works against the applied narrow-face taper and funnel effects, so the effect of thermal distortion must be considered to accurately predict the ideal mold taper.

Design of Cavity Shape for a New Thin Slab Continuous Casting Mold

Because strain rate has an main influence on critical strain of shell in the mold, the increase or sudden change of strain rate makes critical strain decrease, the strain rate of shell must be controlled. Considering the shrinkage characteristic of solidified shell in the thin slab continuous casting mold, a new thin slab continuous casting funnel mold is developed. In the new mold, funnel curve curvature varies continuously, the curvature variation is small and constant, and the shell strain rate does not suddenly change. The funnel curve reaches G2 continuity. The expressions of horizontal and vertical curve in funnel area are given. Considering solidified shell shrinkage and deformation, the self-developed computation code is used to construct the funnel curved surface. The stress distribution of wide face shell is solved by a thermo-mechanical coupled model. Compared with import technology, the result indicates that the stress of wide face shell in mold decreases 20%, especially the stress decreases 35% at the area of cracking susceptibility. The possibility of cracking is reduced effectively and the quality of thin slab is improved in the new mold.

Development of a micro diamond grinding tool by compound process

This study presents a novel micro-diamond tool which is 100 μm in diameter and that allows precise and micro-grinding during miniature die machining. A novel integrated process technology is proposed that combines “micro-EDM” with “precision composite electroforming” for fabricating micro-diamond tools. First, the metal substrate is cut down to 50 μm in diameter using WEDG, then, the micro-diamonds with 0–2 μm grain is “plated” on the surface of the substrate by composite electroforming, thereby becoming a multilayer micro-grinding tool. The thickness of the electroformed layer is controlled to within 25 μm. The nickel and diamond form the bonder and cutter, respectively. To generate good convection for the electroforming solution, a partition designed with an array of drilled holes is recommended and verified. Besides effectively decreasing the impact energy of the circulatory electroforming solution, the dispersion of the diamond grains and displacement of the nickel ions are noticeably improved. Experimental results indicate that good circularity of the diamond tool can be obtained by arranging the nickel spherules array on the anode. To allow the diamond grains to converge toward the cathode, so as to increase the opportunity of reposing on the substrate, a miniature funnel mold is designed. Then the distribution of the diamond grains on the substrate surface is improved. A micro-ZrO 2 ceramic ferrule is grinded to verify the proposed approach. The surface roughness of R a = 0.085 μm is obtained. It is demonstrated that the micro-diamond grinding tool with various outer diameters is successfully developed in this study. The suggested approach, which depends on machining applications, can be applied during the final machining. Applications include dental drilling tools, precision optic dies, molds and tools, and biomedical instruments.

Explicit coupled thermo‐mechanical finite element model of steel solidification

AbstractThe explicit finite element method is applied in this work to simulate the coupled and highly non‐linear thermo‐mechanical phenomena that occur during steel solidification in continuous casting processes. Variable mass scaling is used to efficiently model these processes in their natural time scale using a Lagrangian formulation. An efficient and robust local–global viscoplastic integration scheme (Int. J. Numer. Meth. Engng 2006; 66:1955–1989) to solve the highly temperature‐ and rate‐dependent elastic–viscoplastic constitutive equations of solidifying steel has been implemented into the commercial software ABAQUS/Explicit (ABAQUS User Manuals v6.7. Simulia Inc., 2007) using a VUMAT subroutine. The model is first verified with a known semi‐analytical solution from Weiner and Boley (J. Mech. Phys. Solids 1963; 11:145–154). It is then applied to simulate temperature and stress development in solidifying shell sections in continuous casting molds using realistic temperature‐dependent properties and including the effects of ferrostatic pressure, narrow face taper, and mechanical contact. Example simulations include a fully coupled thermo‐mechanical analysis of a billet‐casting and thin‐slab casting in a funnel mold. Explicit temperature and stress results are compared with the results of an implicit formulation and computing times are benchmarked for different problem sizes and different numbers of processor cores. The explicit formulation exhibits significant advantages for this class of contact‐solidification problems, especially with large domains on the latest parallel computing platforms. Copyright © 2008 John Wiley & Sons, Ltd.

Fabrication of a miniature diamond grinding tool using a hybrid process of micro-EDM and co-deposition

A novel miniature diamond grinding tool usable for the precise micro-grinding of miniature parts is presented. A hybrid process that combines ‘micro-EDM’ with ‘precision co-deposition’ is proposed. The metal substrate is micro-EDMed to a 50 µm diameter and micro diamonds with 0–2 µm grains are ‘electroformed’ on the substrate surface, producing a miniature multilayered grinding tool. Nickel and diamond act as binders and cutters, respectively. A partition plate with an array of drilled holes is designed to ensure good convection in the electroforming solution. The dispersion of diamond grains and displacement of nickel ions are noticeably improved. A miniature funnel mould enables the diamond grains to converge towards the cathode to increase their deposition probability on the substrate, thereby improving their distribution on the substrate surface. A micro ZrO2 ceramic ferrule is finely ground by the developed grinding tool and then yields a surface roughness of Ra = 0.085 µm. The proposed approach is applied during the final machining process.

Analysis of flow field and temperature distribution in compact strip production casting process

A three-dimensional finite difference model has been formulated, using the commercial code CFX4, to describe the fluid flow and heat transfer in the funnel mould and secondary cooling segment of the compact strip production (CSP) casting process. Through simulation and computation with the established simulation model, influences of the factors such as casting speed, casting superheat, immersion depth of submerged entrance nozzle, amount of cooling water in the secondary cooling segment on flow field and temperature field in the funnel mould and secondary cooling segment of CSP technology were analysed.

Numerical Simulation of Coupled Molten Steel Flow and Temperature Fields in Compact Strip Production Casting

Based on the casting manufacture practice of steel slabs by CSP technology, the flow and the temperature fields of the funnel mould and the secondary cooling segment were simulated using the commercial code, CFX4. Compared with other physical investigations, the correlative data of the present simulation results are in good agreement with them. Therefore, a more comprehensive survey for metallurgy characteristic of the flow and the temperature fields in CSP continuous casting process can be achieved.

Flow Control in the Thin Slab Mould at the Corus Direct Sheet Plant

Thin slab casting forms the most important development in continuous casting of the past two decades. Within a short period of time the technology developed into a serious alternative for conventional slab casting, both with respect to productivity and product quality. Corus implemented the technology in its Direct Sheet Plant (DSP) enabling the production of thin-gauged coils. The development of thin slab casting technology has not come to an end yet. Further increase in productivity can be expected still respecting high quality standards. The control of the mould fluid flow is one of the key technologies for thin slab casting. Here not only the (complex) design of the submerged entry nozzle is important. A strong interaction exists with the shaping of the funnel mould and the layout of the electromagnetic brake (EMBR). Modern physical and numerical modelling techniques enable a detailed design study of all aspects of the process. This resulted in a new design of the EMBR for the DSP thin slab caster, based on a multi-pole approach. One pole is controlling the symmetry of the flow, where another two poles control the speed of the liquid steel in the meniscus area. By using this technology the operational window can be enlarged significantly without deterioration of the situation in the mould.