Strip Coil Research Articles

Efficient Finite Element Simulation of Cold Rolled Strip Coiling Process Considering Additional Contact Deformation between Layers

Efficient Finite Element Simulation of Cold Rolled Strip Coiling Process Considering Additional Contact Deformation between Layers

Discontinuous dynamic recrystallization behavior and texture evolution of large-size pure titanium flat ingot via electron beam cold hearth melting during short process direct hot rolling

Large-size pure titanium ingots melted by single electron beam cold hearth melting (EBCHM)) could be rolled into large-width and heavy-weight titanium strip coils using short process without forging. It is crucial to study the large-span refinement mechanism from highly coarse grains, whose sizes are in the order of ∼cm, to micronmeter. In this study, the recrystallization mechanism and texture evolution of pure titanium with a size of 1570 × 200 × > 8000 mm was investigated by multi-pass simulated rolling and experimental rolling. The results indicated the hot deformation can result in marked reduction in grain size of the as-cast grain, from 3 to 5 cm to 17–23 μm. The discontinuous dynamic recrystallization (DDRX) mechanism of a pure titanium ingot during direct multi-pass hot deformation causes the reconstruction of as-cast microstructure and refinement of hot rolling microstructure. Furthermore, DDRX occurred, during hot deformation, and was accompanied with weakening of deformation texture. Raising the initial hot deformation temperature results in a modification of the texture type of the {0001} crystal plane. The strength of the texture experiences a decrease initially and then eventually an increase. This alteration in strength is inversely related to the degree of dynamic recrystallization. Based on the simulated rolling experiment, the results of experimental rolling also found the coarse as-cast grains was broken and reconstructed. It has strength (average yield strength: 334 MPa, ultimate tensile strength: 371 MPa), ductility (total elongation: 30 %). Such a combination of mechanical properties makes the hot rolling plate a potential choice for sheet practical application.

ANNEALING OF COLD-ROLLED STRIPS IN SHIELDING GAS ATMOSPHERE

The results of modeling the processes of annealing cold-worked coils of extra-thin steel strip of high quality
 in protective atmospheres of hydrogen and nitrogen in bell-type furnaces are presented. An algorithm for calculating
 the optimal value of the heating time is given, taking into account the thermophysical properties of both processed
 hard-worked coils of extra-thin steel strip and protective atmosphere gases. A technique for optimizing the modes
 of annealing of hard-worked coils of extra-thin steel strip in a bell-type furnace in a pure nitrogen environment relative
 to the basic mode in a pure hydrogen environment is presented.

Реалізація методів розрахунку в спеціалізованій комп’ютерній системі напружено-деформованого і температурного стану рулонів сталевих штаб

Реалізація методів розрахунку в спеціалізованій комп’ютерній системі напружено-деформованого і температурного стану рулонів сталевих штаб

Coil shape defects prediction algorithm for hot strip rolling based on Siamese semi-supervised DAE-CNN model

Purpose Coil shape quality is the external representation of strip product quality, and it is also a direct reflection of strip production process level. This paper aims to predict the coil shape results in advance based on the real-time data through the designed algorithm. Design/methodology/approach Aiming at the strip production scale and coil shape application requirements, this paper proposes a strip coil shape defects prediction algorithm based on Siamese semi-supervised denoising auto-encoder (DAE)-convolutional neural networks. The prediction algorithm first reconstructs the information eigenvectors using DAE, then combines the convolutional neural networks and skip connection to further process the eigenvectors and finally compares the eigenvectors with the full connect neural network and predicts the strip coil shape condition. Findings The performance of the model is further verified by using the coil shape data of a steel mill, and the results show that the overall prediction accuracy, recall rate and F-measure of the model are significantly better than other commonly used classification models, with each index exceeding 88%. In addition, the prediction results of the model for different steel grades strip coil shape are also very stable, and the model has strong generalization ability. Originality/value This research provides technical support for the adjustment and optimization of strip coil shape process based on the data-driven level, which helps to improve the production quality and intelligence level of hot strip continuous rolling.

Experimental and computational study of the equivalent thermal conductivity coefficient when heating a strip coil

Heating of layered metal cages in bell furnaces, for example, stops from strip coils, due to the presence of gas gaps between the layers in them, leads to an increase in the temperature drop in the radial direction with a simultaneous temperature drop along the height of the charge. An accurate calculation of the heating time of the charges of strip coils requires knowledge of the temperature field in them, and, consequently, the radial equivalent coefficient of thermal conductivity and the end coefficient of thermal conductivity, on which the consumption of electricity, fuel and the performance of the furnace will depend. The formula and method for calculating the equivalent coefficient of thermal conductivity in the radial and end directions of ta strip coil are proposed, based on the numerical solution of the differential equation of thermal conductivity using an explicit difference scheme, a constant coefficient of thermal conductivity and boundary conditions of the first kind, suggesting the useof its experimental values as the tem perature of the roll surface at various points in time. The values of the thermal conductivity coefficients calculated according to the proposed formula and methodology were confirmed by experimental laboratory heating of a 0,3 mm thick steel strip coil made of electrical steel E3412; height, inner and outer diameters of the coil, respectively: 52,0; 51,882; 79,667 mm; with the number of tape layers per side equal to 46; with a filling coefficient of 0,86 and the degree of contact of layers – 2,9%. The strip coil was heated both together with the furnace to a temperature of 920 °C, and when it was loaded into a preheated furnace to a temperature of 620 °C, followed by heating to 920 °C and holding. When forming the charges, two heating options were carried out: radial and end heating.

A source for the continuous generation of pure and quantifiable HONO mixtures

Abstract. A continuous source for the generation of pure HONO mixtures was developed and characterized, which is based on the Henry's law solubility of HONO in acidic aqueous solutions. With the help of a peristaltic pump, diluted nitrite and sulfuric acid solutions are mixed in a temperature-controlled stripping coil, which is operated with pure nitrogen or synthetic air at gas flow rates of 0.5–2 L min−1. Caused by the acidic conditions of the aqueous phase (pH ≈ 2.5), nitrite is almost completely converted into HONO, which partitions to the gas phase limited by its known solubility in water. The source shows a fast time response of ∼ 2 min (0 %–90 %) at higher concentrations and an excellent long-term stability (2σ noise < 1 %). The HONO emission of the source perfectly correlates with the nitrite concentration from the sub-ppb range up to 500 ppb. The rate of NOx formation increases quadratically with the HONO concentration from non-detectable values at atmospheric relevant HONO concentrations reaching a NOx content of 1.6 % at 500 ppb. A general equation based on Henry's law is developed, whereby the HONO concentration of the source can be calculated using measured experimental parameters, i.e. nitrite concentration, liquid flow rates, gas flow rate, pH of the solution, and temperature of the stripping coil. In the equation, the known Henry's law constant of HONO in sulfuric acid solutions is used. For the calculation of the effective Henry's law constant, the acid dissociation equilibrium of HONO / nitrite is used as a variable to adjust the theoretical HONO concentration to the measured values. From the average of all experimental data the equilibrium of HONO / nitrite is described well by pKa=1021.53/T-0.449. The pKa of 3.0 ± 0.1 (1σ) at 25 ∘C is in good agreement with the range of 2.8–3.28 published in former studies. A standard deviation between all measured and theoretical HONO concentrations of only ±3.8 % was observed, and a conservative upper-limit accuracy of the HONO concentration of better 10 % is estimated. Thus, for the first time, a stable HONO source is developed which can be used for the absolute calibration of HONO instruments.

MathConnex mathematical package for calculating the equivalent thermal conductivity of a strip coil

When heating complex metal loads (layered, fibrous, granular), the gas gaps in them increase the temperature difference across the charge section and lead to an increase in the duration of its heating. Optimizing the time of complex loads heating, which helps to reduce fuel consumption and improve the heated metal quality, requires knowledge of temperature fields in them, which, in turn, depend on the equivalent thermal conductivity of the complex load. For their calculations mathematical modeling can be used, which requires a highly qualified researcher. Carrying out of laboratory and experimental researches takes a lot of time and demands big material expenses, thus the received results are applicable only to a concrete charge. A number of authors give formulas for calculating the equivalent thermal conductivity of the strip coil. However, the practical use of such formulas is difficult due to the presence of difficult to determine parameters: the degree of the strip layers contact, thermal conductivity of different layers of strip and gas gaps between them, heat transfer coefficients by radiation in the gaps between layers. In this case, different formulas for calculating the equivalent thermal conductivity give signifi cantly different results. In the present work, for 20 steel strip coils with height, inner and outer diameters, respectively, 1; 0.4–0.966 m; with a strip thickness of 0.001; 0.003; 0.006 m, the number of layers per side 17; 25 and 50, for the coefficients of strip coil filling 0.70; 0.75; 0.80; 0.85; 0.90; 0.95; 0.97; 0.99, 0.999, the degrees of the strip layers contact 2.8–3.0% and different heated media (air, nitrogen, hydrogen), the reduced thermal conductivity coefficients were calculated according to various formulas using the MathConnex mathematical package (part of MathCadPro). On the basis of the conducted researches the formula for calculation of equivalent thermal conductivity of strip coils is chosen. The results of the calculation are in good agreement with the literature data, it can be used to calculate temperature fields and thermophysical parameters in layered metal loads, as well as to calculate their heating time and furnace performance.

Paramagnetic resonance in La2NiMnO6 probed by impedance and lock-in detection techniques

We studied the frequency-dependent (f = 1 GHz to 5 GHz) microwave absorption in the double perovskite La2NiMnO6 at room temperature using two cavity-less methods: An indirect impedance method that uses a radio frequency impedance analyzer and a folded copper strip coil for the frequency range f = 1–2.2 GHz and a lock-in based broadband setup using a coplanar waveguide for microwave excitation in the frequency range f = 2–5 GHz. The high-frequency resistance of the strip coil exhibits a sharp peak and the reactance curve crosses zero at a critical value of dc magnetic field as a consequence of the paramagnetic resonance in the sample. The resonance fields (Hr) obtained from both the techniques increase linearly with frequency. Line shape analysis and analytical fitting were performed to characterize the material in terms of its initial susceptibility and damping parameters. From the fit, we obtain a large spectroscopic g-factor, equal to 2.1284, which supports the presence of Ni2+ cation with strong spin-orbit coupling.

Magnetoimpedance of Epitaxial Y3Fe5O12 (001) Thin Film in Low-Frequency Regime

The atomically flat interface of the Y3Fe5O12 (YIG) thin film and the Gd3Ga5O12 (GGG) substrate plays a vital role in obtaining the magnetization dynamics of YIG below and above the anisotropy field. Here, magnetoimpedance (MI) is used to investigate the magnetization dynamics in fully epitaxial 45 nm YIG thin films grown on the GGG (001) substrates using a copper strip coil in the MHz-GHz frequency region. The resistance (R) and reactance (X), which are components of impedance (Z), allow us to probe the absorptive and dispersive components of the dynamic permeability, whereas a conventional spectrometer only measures the field derivative of the power absorbed. The distinct excitation modes arising from the resonance in the uniform and dragged magnetization states of YIG are respectively observed above and below the anisotropy field. The magnetodynamics clearly shows the visible dichotomy between two resonant fields below and above the anisotropy field and its motion as a function of the direction of the applied magnetic field. A low value of a damping factor of ∼4.7 - 6.1 × 10-4 is estimated for uniform excitation mode with an anisotropy field of 65 ± 2 Oe. Investigation of below and above anisotropy field-dependent magnetodynamics in the low-frequency mode can be useful in designing the YIG-based resonators, oscillators, filters, and magnonic devices.

Substantiation for the Implementation of Controlled Coil Cooling Technology after Hot Rolling of Strip Steel

The analysis of technology for the production of hot-rolled strip steel in coils has shown that the technological instructions for this metallurgical processing stage finishes at the stage of winding a finished hot strip into a coil. The development and implementation for technology to control the cooling of hot-rolled strip coils in accordance with the grade-and-size assortment, as well as with customer’s requirements, are necessary.

A General Modeling Methodology for the Quasistatic Behavior of Spiral Torsion Springs

Abstract Due to their robustness, compactness, simplicity, and the possibility of nonlinear torque curves, spiral springs are being increasingly contemplated for industrial application. Recent manufacturing technologies and materials allow for the creation of spiral springs of various shapes and geometries able to provide the required torque curves. Modeling the behavior of this kind of springs is highly complex due to the strong nonlinearities arisen from large deflections and the possibility of coiling of strip length around the spring barrel or arbor. For this reason, up to our knowledge, existing models only provide design features such as deflection and torque curve for the simplest strip geometries, and fewer models supply, only if no strip coiling occurs, reactions at the strip-barrel and strip-arbor clampings. In addition, to our knowledge, just semi-empirical models for strip-barrel, -arbor and -strip contact forces or friction torques were available. In this work, we introduce a novel general, an analytical quasistatic model for the calculation of all the above spring characteristics for any length-dependent strip material and initial geometry and strip cross-sectional shape and for any barrel and arbor radii. The strip deflection curvatures are calculated minimizing the sum of elastic and gravitational potential energies under geometrical constraints associated with eventual strip coiling. Once the curvatures are calculated, the spring internal, contact, and reaction forces can be straightforwardly calculated by solving the elastica differential equations. Friction is taken into account by evaluating the contact conditions at the strip coiled sections.

Investigation and Optimization of Load Distribution for Tandem Cold Steel Strip Rolling Process

In order to improve the cold rolled steel strip flatness, the load distribution of the tandem cold rolling process is subject to investigation and optimization. The strip deformation resistance model is corrected by an artificial neural network that is trained with the actual measured data of 4500 strip coils. Based on the model, a flatness prediction model of strip steel is established in a five-stand tandem cold rolling mill, and the precision of the flatness prediction model is verified by rolling experiment data. To analyze the effect of load distribution on flatness, the flatness of stand 4 is calculated to be 7.4 IU, 10.6 IU, and 16.8 IU under three typical load distribution modes. A genetic algorithm based on the excellent flatness is proposed to optimize the load distribution further. In the genetic algorithm, the classification of flatness of stand 4 calculated by the developed flatness prediction model is taken as the fitness function, with the optimal reduction of 28.6%, 34.6%, 27.3%, and 18.6% proposed for stands 1, 2, 3, and 4, respectively. The optimal solution is applied to a 1740 mm tandem cold rolling mill, which reduce the flatness classification from 10.8 IU to 3.2 IU for a 1-mm thick steel strip.

Microwave magnetoabsorption in R0.6Sr0.4MnO3 (R = Pr and Nd)

We report microwave (MW) magnetoabsorption (ΔP) at room temperature in R0.6Sr0.4MnO3 (R = Pr and Nd) samples. ΔP as a function of dc magnetic field (− 2.5 kOe ≤ Hdc ≤ 2.5 kOe) was measured for a broad frequency range ( f = 0.1–4 GHz) of an MW magnetic field using a vector network analyzer and a copper strip coil which encloses one of the above samples. As the external dc magnetic field decreased from the maximum value, ΔP initially increases and shows a maximum for a critical field and then decreases as the field approaches zero. The critical field value increases with increasing frequency of the MW signal. Line shape analysis of the obtained spectra suggests that the observed features in ΔP are caused by ferromagnetic resonance in R = Pr and electron paramagnetic resonance in R = Nd samples, which were later confirmed using a coplanar waveguide-based broadband magnetic resonance spectrometer.

Detection of L-band electron paramagnetic resonance in the DPPH molecule using impedance measurements.

Detection of electron paramagnetic resonance (EPR) using a microwave cavity resonating at a fixed frequency (between 9 and 10 GHz) remains the most popular method to date. Here, we report a cavity-less technique which makes use of only an impedance analyzer and a copper strip coil to detect L-band EPR (f = 1–3 GHz) in the standard EPR marker 2,2-diphenyl-1-picrylhydrazyl (DPPH). Our method relies on measuring the magnetoimpedance (MI) response of DPPH through a copper strip coil that encloses DPPH. In contrast to commercial EPR which measures only the field derivative of power absorption, our method enables us to deduce both absorption and dispersion. Changes in resistance (R) and reactance (X) of the copper strip while sweeping an external dc magnetic field, were measured for different frequencies (f = 0.9 to 2.5 GHz) of radio frequency current in the coil. R exhibits a sharp peak at a critical value of the dc magnetic field, which is identified as the resonance field and X shows a dispersion at the same frequency. The data were analyzed to obtain line width and resonance field parameters. The resonance field increased linearly with frequency and the obtained Landé g factor of 1.999 ± 0.0197 is close to the accepted value of 2.0036, measured in the X-band. The simplicity of this technique can be exploited to study paramagnetic centers in catalysis and other materials.

Investigation on the control of multiphase flow behavior in a continuous casting tundish during ladle change

The transient multiphase flow behavior in a single-strand tundish during ladle change was studied using physical modeling. The water and silicon oil were employed to simulate the liquid steel and slag. The effect of the turbulence inhibitor on the slag entrainment and the steel exposure during ladle change were evaluated and discussed. The effect of the slag carry-over on the water-oil-air flow was also analyzed. For the original tundish, the top oil phase in the impact zone was continuously dragged into the tundish bath and opened during ladle change, forming an emulsification phenomenon. By decreasing the liquid velocities in the upper part of the impact zone, the turbulence inhibitor decreased considerably the amount of entrained slag and the steel exposure during ladle change, thereby eliminating the emulsification phenomenon. Furthermore, the use of the TI-2 effectively lowered the effect of the slag carry-over on the steel cleanliness by controlling the movement of slag droplets. The results from industrial trials indicated that the application of the TI-2 reduced considerably the number of linear inclusions caused by ladle change in hot-rolled strip coils.

The effect of internal contact pressure on thermal contact conductance during coil cooling

Coil cooling process is an important step in production of certain steel grades. Phase transformations for dual phase steels and precipitations for precipitation hardened steels occur mainly during the coil cooling. Generally, a coil goes through a coil conveyance chain before arriving at the final cooling storage at a steel plant. This conveyance chain contains various thermal contacts with different types of conveyors. Ambient temperatures and weather conditions may also change considerably. Those variables are relatively easy to measure and define in a simulation model whereas internal stresses and contact pressure inside the coil are very challenging to measure in industrial scale process. Thermal conductance between adjacent strip revolutions is dependent of contact pressure. In addition, thermal conductance is influenced by the combined thermal conductivity of steel and oxide layer of contact interfaces as well as thickness profile. In this paper the internal contact pressure between strip revolutions due to strip coiling and gravity are solved and considered when defining thermal conductance. Heat transfer is computed using FE-model, and GAPCON subroutine in Abaqus is utilized to calculate thermal contact conductance, taking into consideration the contact pressure between the strip revolutions. Also, the whole coil conveyance chain commencing from downcoiler mandrel to coil field cooling is implemented.

Broadband magnetoresistance in ferromagnetic and paramagnetic samples of La0.7Ca0.3−xSrxMnO3

We have studied the room-temperature magnetoimpedance of paramagnetic (x = 0.06) and ferromagnetic (x = 0.1) samples in La0.7Ca0.3−xSrxMnO3 series using a radio-frequency impedance analyzer and also microwave power absorption using a network analyzer. In both measurements, samples were enclosed tightly inside a copper strip coil and impedance or reflection coefficient of this copper strip coil was measured as a function of applied magnetic field for different frequencies of current (f = 0.1–2.5 GHz). The direction of the applied magnetic field was perpendicular to the alternating magnetic field produced by the coil. In the ferromagnetic sample (x = 0.1), magnetoresistance shows a peak around zero field for lower frequencies but a peak appears at H > 0 at higher frequencies. The position of the peak shifts towards higher fields with increasing frequency. A similar trend is also found for the paramagnetic sample (x = 0.06) but the peak occurs at a higher field compared to the ferromagnetic sample for the same frequency. Microwave power absorption also shows features similar to magnetoresistance. Line shape analysis of the data was performed by fitting the data to a Lorentzian function. It is concluded that the observed features are imprints of ferromagnetic resonance in x = 0.1 and paramagnetic resonance in x = 0.06 samples.

Calculating Strip Coil Heating Temperature in the Warm-Rolling Process for Difficult-to-Deform Metals

Calculating Strip Coil Heating Temperature in the Warm-Rolling Process for Difficult-to-Deform Metals

Investigating the Properties of Coil Tail in Ti–Nb–Mo Microalloyed Hot‐Rolled Strip

In the present study, the thermo‐mechanical controlled processing (TMCP) technology was applied to produce Ti–Nb–Mo microalloyed hot‐rolled steels. The strength at the tail of a strip coil is often found to be non‐uniform. The microstructural and the mechanical properties of the specimens in the outermost circle as well as in the third circle and the fifth circle from the outermost circle were analyzed in detail. The optical microscopy (OM) and the electron backscatter diffraction (EBSD) techniques are employed for the characterization of ferrite grains and grain boundaries. The precipitates were revealed by high‐resolution transmission electron microscopy (HR‐TEM) and energy dispersive spectroscopy (EDS). It is found that the precipitation strengthening induced by nano‐scale (Ti, Nb, Mo)C particles was the dominant factor for the disparity in properties in different positions of the coil tail. The volume fraction of nano‐scale (Ti, Nb, Mo)C particles increases from 0.220% in the outermost circle to 0.343% in the fifth circle. In addition, the lattice planes of (110)α and (100)(Ti, Nb, Mo)C followed a Baker‐Nutting orientation relationship. Nano‐scale (Ti, Nb, Mo)C particles mainly precipitated in ferrite grains during coiling and subsequent cooling. Furthermore, different cooling rates along the strip had inconspicuous influences on the grain size and lengths of ferrite grain boundaries.