Hot Coils Research Articles

Effect of hot coil immersion cooling process on microstructure and properties of strip steel and oxide scales

ABSTRACT Coils obtained at the end of hot rolling of four different low carbon steels (DX54D, HX180YD, DX51D and HCT590X) were subjected to immersion in water for cooling (IC) as against the normal natural cooling (NC). IC produces significant improvements in the microstructure, scale formation, distribution of mechanical properties and surface quality. A model developed to simulate thermal history in the hot coil being cooled indicates that the 0.1°C/min core cooling rate in NC increased by over 7 times in IC, thereby decreasing the temper softening effects. Results of the tests performed exhibit a greater uniformity in the longitudinal properties and a 30–50% reduction in the band spread. The volume fraction of carbide on the DX54D steel is reduced by 20–30%, and the yield platform length is increased from 2.6 to 3.4%. The IC process was observed to significantly inhibit the formation of the banded structure in the HCT590X steel and the average yield strength of the coil increased by ∼30 MPa. The thickness of the oxide scale in all the steels decreased by 30–40% and the FeO content in the scale increased by 10–20%.

Multi-strategy modified sparrow search algorithm for hyperparameter optimization in arbitrage prediction models.

Deep learning models struggle to effectively capture data features and make accurate predictions because of the strong non-linear characteristics of arbitrage data. Therefore, to fully exploit the model performance, researchers have focused on network structure and hyperparameter selection using various swarm intelligence algorithms for optimization. Sparrow Search Algorithm (SSA), a classic heuristic method that simulates the sparrows' foraging and anti-predatory behavior, has demonstrated excellent performance in various optimization problems. Hence, in this study, the Multi-Strategy Modified Sparrow Search Algorithm (MSMSSA) is applied to the Long Short-Term Memory (LSTM) network to construct an arbitrage spread prediction model (MSMSSA-LSTM). In the modified algorithm, the good point set theory, the proportion-adaptive strategy, and the improved location update method are introduced to further enhance the spatial exploration capability of the sparrow. The proposed model was evaluated using the real spread data of rebar and hot coil futures in the Chinese futures market. The obtained results showed that the mean absolute percentage error, root mean square error, and mean absolute error of the proposed model had decreased by a maximum of 58.5%, 65.2%, and 67.6% compared to several classical models. The model has high accuracy in predicting arbitrage spreads, which can provide some reference for investors.

PREDICTION OF RESIDUAL STRESS AFTER HOT ROLLING AND COILING PROCESSES

Residual stresses are a subject of great industrial and academic interest. Detection and prediction methods can be experimental, analytical and numerical furthermore there is a substantial amount of developed techniques. In this context, this manuscript intends to propose an analytical methodology for predicting residual stresses in the thickness of hot-rolled steel sheets, followed or not by coiling/uncoiling, by developing the basic differential equation of deflections, aided by a numerical prediction of the temperature profile throughout the cooling process. Basically, the sources of residual stresses are considered to be the austenite/products phase transformation, the evolution of the temperature gradient and the deformation/relief caused by coiling and uncoiling. Prediction results were compared to experimental own results and that from a reference. There was a good coincidence of values when the profile raised was the one caused by the temperature gradient. Other sources found no support for the cases analyzed. New experimental results are needed for conclusions to mature.

Temperature modeling and analysis of transfer bar using hot coil box technology

Temperature modeling and analysis of transfer bar using hot coil box technology

Theoretical and numerical assessment of an enhanced Humidification-Dehumidification desalination system based on Indirect Evaporative cooling and Vapour Compression Refrigeration

In this work, a theoretical study and a numerical performance analysis of a novel Humidification-Dehumidification (HDH) desalination system, that simultaneously exploits an Indirect Evaporative Cooling (Maisotsenko cycle, IEC) device and a Vapour Compression Refrigeration cycle (VCR), are proposed. The IEC device is here employed as a very efficient saltwater evaporator-air humidifier, by an optimized mass exchange process between saltwater and working airstream. Both thermal exchanges of the VCR cycle are used: the hot coil pre-heats the inlet air to enhance the effectiveness of the evaporation process, while the cold one provides the cooling capacity to condense freshwater. The numerical model is based on data of actual commercial devices and considers their effective operational mode. The parametric analysis and the yearly simulations in different climatic areas show very promising results (GOR and RWA factor equal to 3.4 and 5.0∙106 in the best operative condition, equal to 3.2 and 4.1∙106 in the best climate situation) that lead to consider this technology as very competitive among HDH desalinations systems.

Effects of spacing on flaming and smoldering firebrands in wildland–urban interface fires

Firebrand (ember) attack has been shown to be one of the key mechanisms of wildfire spread into wildland–urban interface communities. After the firebrands land on a substrate material, the ignition propensity of the material depends on not only the attributes (e.g. shape, size, and numbers) but also the distribution of the firebrands. To help characterize this process, this study aims to investigate the effects of gap spacing on the burning behaviors of a group of wooden samples. Experiments are conducted using nine wooden cubes, 19 mm on each side. These samples are arranged in a 3 × 3 square pattern on suspension wires and are ignited by hot coils from the bottom surface. The gap spacing (s) between the samples varies in each test (ranging from 0 to 30 mm). After ignition, the samples are left to burn to completion. The burning process is recorded using video cameras. Sample mass loss and temperatures are monitored during the flaming and smoldering processes. The results show that the flame height and the sample mass loss rate have non-monotonic dependencies on the gap spacing. When the gap spacing reduces, the flame height and the mass loss rate first increase due to enhanced heat input from the adjacent flames to each sample. When s ≤ 10 mm, flames from individual samples are observed to merge into a single large fire. As s further decreases, the air entrainment at the flame bottom decreases and the flame lift-off distance at the flame center increases, resulting in an increased flame height, decreased flame heat feedback to the solid samples, and a decreased mass loss rate. The decreased mass loss rate eventually leads to a decrease in the flame height as well. The gaseous flame height is correlated to the solid burning rate. The correlation generally follows previous empirical equations for continuous fire sources. For the smoldering combustion, compared to a single burning sample, the smoldering temperature and duration significantly increase due to the thermal interactions between adjacent burning samples. To help interpret the results of the burning experiments, thermogravimetric analysis is also performed in air and nitrogen, resulting in heating rates ranging from 10 to 100 K/min.

572 Burn injury from smoking electronic cigarettes while on supplemental oxygen

IntroductionBurn injuries from exploding electronic cigarettes have been well documented in the medical literature and lay press, as have injuries from smoking conventional cigarettes while on supplemental oxygen. However, there is a paucity of literature regarding injuries from smoking electronic cigarettes while on supplemental oxygen. Empirically, it might seem safe to use e-cigarettes while on oxygen, but it can result in explosion. The electronic cigarette coil can heat up to 350°C and serve as a source of ignition. The purpose of this study is to describe and characterize this relatively novel and uncommon mechanism of injury.MethodsThis study was a descriptive review of 2013-2016 National Burn Repository (NBR) Data. Injury description fields were queried for “oxygen”, “O2”, “electronic cigarettes”, and various abbreviations and misspellings. Demographics, burn size, length of stay, expected length of stay using 1.1 days per %TBSA, and LOS index were reported. In addition, a Google search for lay press articles using the terms “smoking,” “’oxygen,” and “electronic (or e) cigarettes was performed, and these cases were tabulated.ResultsOf approximately 60,000 NBR entries, only 8 records of injury while smoking e-cigs on oxygen were found. Patients were predominantly male (63%) with a mean age of 63±9 years old, burn size of 3.4%±4 TBSA and LOS of 5.8±7 days. Inpatient stay averaged 1.65 days per %TBSA, which was 150% of expected LOS for the cohort. Two patients sustained third degree burns of 0.5% and 11%TBSA. Three patients were intubated, and had a mean of 3.33 ventilator days. Most injuries occurred at home (88%), while one occurred in a hospital. All 8 patients had Medicare and none of them suffered mortality. A google search revealed three distinct lay press articles regarding this topic.ConclusionsAlthough an uncommon mechanism of injury, smoking electronic cigarettes on supplemental oxygen can result in injury and a significant hospital stay. Limitations in abstraction from the database and/or reporting might have resulted in an under capture of the true number of injuries. Circumstances resulting in this phenomenon warrant further investigation, as it is unclear if it occurs from malfunction or a hot coil alone. Patients who are prescribed home O2 should be warned about this potential danger.

Numerical investigation on the effects of different heating systems and coil tube arrangements on the free convection heat transfer in a confined space filled with high viscosity fluid

Laminar free convection heat transfer in a confined space filled with high viscosity fluid is numerically investigated for different heating systems and coil tube arrangements at Rayleigh (Ra) numbers in the range of 103 ≤ Ra ≤ 107. In the heating system where the hot coil tubes are immersed in the high viscosity fluid, the effects of the horizontal and vertical distances between the coil tubes and the positions of the coil tubes along the vertical axis on the heat transfer characteristics are studied. The heating system where the coil tubes are placed outside the confined space is also considered. Two-dimensional unsteady conservation equations of the continuity, momentum and energy are discretized and solved by using the finite volume method. The results show that the average Nusselt numbers on all coil tubes except the lower coil tube at Ra = 107 increase as the horizontal and vertical distances between the coil tubes increase. It is found that the horizontally aligned coil tube arrangement is more effective in terms of overall Nusselt number on the coil tube than the vertically aligned coil tube arrangement. The heating system where the coil tubes are outside the confined space at Ra = 107 provides an improvement of 3.25% in average Nusselt values compared to the heating system with horizontally aligned coil tube arrangement. The horizontal distance between the coil tubes, the positions of the coil tubes along the vertical axis and different arrangements of coil tubes have considerable effects on the total Nusselt number. However, the effect of the vertical distance between the coil tubes on the total Nusselt number is negligible at high Ra numbers, 105 ≤ Ra ≤ 107. The numerical method and solution procedure are validated by comparing the results with the available data in the literature.

Effect of impurities on the microstructure and mechanical properties of a low carbon steel

ABSTRACT Impurity elements of Cu, Ni, Sn and Cr have been added to a model low-carbon strip steel to mimic the levels that could arise due to increased scrap recycling during steel production. The microstructure and tensile properties of the base composition and impurity added compositions after thermomechanical processing, consisting of hot rolling and simulated coil cooling, have been investigated. The addition of impurities results in a lower bainite fraction, a smaller effective grain size and the precipitation of Cu-rich particles. Meanwhile, higher strength and lower ductility are found in the steel with impurities.

Evaluation of Fire Resistance for a Recycled 0.15 mass% Carbon Steel

Abstract A recycled steel with 0.2 % offset stress higher than 295 MPa was verified as a candidate for fire-resistant use, based on an academic standard in Japan. The chemical compositions were 0.15 mass% carbon-0.02 mass% silicon-0.5% mass% manganese and unavoidable alloy elements. The amount of elements inevitably contained in recycling was kept within the regulation, and then the dispersion of tensile properties among hot coils was controlled to be sufficiently small. The recycled steel satisfied the requirements by the academic standard in terms of tensile properties at elevated temperatures. No significant evolution was observed in the ferrite-based microstructure within the temperature and time range tested. The plastic deformation is apparently a strain-controlled one up to 400°C and a strain rate-controlled one at 600°C and 700°C. At 500°C, it is in the middle of the two. In the adopted test method, a constant strain rate was realized over the entire strain range except for the beginning stage of deformation. A peak strain rate occurs at about 0.2 % strain, which brings about the uncertainty in determination of 0.2 % offset stress at elevated temperatures. However, the constant strain rate requirement is satisfied in the determination of 1 % offset stress that the academic standard specifies.

Thermal Stability of Retained Austenite in Advanced TRIP Steel with Bainitic Ferrite Matrix for Automotive Industries

Multiphase steels consisting of retained austenite and martensite/bainite microstructures such as TRIP, low-temperature-bainite, and Q&P steels are attractive candidates for the new-generation of AHSS. These steels exhibit a remarkable combination of strength and toughness which is essential to meet the objective of weight reduction of engineering-components, while maintaining the compromise of tough-safety requirements. Such good mechanical properties are due to the enhanced work hardening rate caused by austenite-to-martensite transformation during deformation and the strengthening contribution of martensite/bainite. The retained austenite can thermally decompose into more thermodynamically stable phases as a consequence of temperature changes, which is referred to as the thermal stability of retained austenite. TRIP-aided steel is an effective candidate for automotive parts because of safety and weight reduction requirements. The strength–ductility balance of high strength steel sheets can be remarkably improved by using transformation induced plasticity behavior of retained austenite. In manufacturing hot rolled TRIP-aided sheet steels, austenite transforms into bainite during the coiling process. Because black hot coils cool slowly after the coiling process, they are exposed at about 350–450°C for a few hours or days. Therefore, the metastable residual austenite can be decomposed into other phases. This decomposition of residual austenite can produce serious deteriorate of mechanical properties in hot rolled TRIP-aided sheet steels. The present work identified the decomposition behavior and study the thermal stability of retained austenite in the TRIP-aided steel with bainitic/ferrite matrix depending on coiling temperatures and holding times by means of DSC and XRD analysis.

On the performance of air conditioner with cold coil for cooling in the condenser

The improvement on living standard of the human makes inefficient energy consumption, like use of air conditioners. Application of utilization cold pipe using condensate water instead of air-cooled condenser is proposed in this paper as an efficient way to solve the problem. Experimental results show that the air conditioning system of the utilization of cold pipes using condensate water-cooled air condenser has a significant effect on the performance improvement of the vapor compression cycle and the rate of improvement is based as ambient air temperature decreases across to hot coil condenser. Power consumption can be decreased up to 6.4 % and total performance can be improved around 7.3% of the system.

Prediction of properties over the length of the coil during thermo-mechanical processing using DNN

ABSTRACT Certain mechanical properties of steel, such as elongation percentage, yield strength and ultimate tensile strength, form the basis for classification of steel coils into various categories. Methods to improve the prediction of such properties, using multiple chemical and physical process parameters, have remained an integral area of research in steel plants. In this paper, an important parameter, that is, the run-out table cooling profile of a hot strip mill coil, is considered along with the customary process parameters. This additional parameter allows a deep neural network-based model to predict the mechanical properties of steel for multiple segments along the entire length of the coil instead of the established single-segment property prediction process with very high R 2 value.

Thermomechanical Controlled Rolling of Hot Coils of Steel Grade S355MC at the Wide-Strip Rolling Mill 1700

Тhere has been developed technology, and pilot batch of hot rolling coils (6×1500 mm, steel grade S355MC) has been produced using thermo-mechanical controlled process (TMCP) for the wide-strip rolling mill 1700. The integrated technology for TMCP coil production (steel grade S355MC) has been firstly developed for the rolling mill 1700 in accordance with EN 10149-2. Air cooling for coils to 450°C after coiling has been firstly used in the developed technology, which provides for decrease in air scale and improvement of surface quality for the customers. It is possible to manufacture rolled products up to 6×1500 mm (steel grade S355MC) in accordance with EN 10149-2 using the existing equipment without exceeding the existing process constraints during its operation and without upgrading. It is possible to further master the rolled products, which are manufactured according to the TMCP technology.

Controlled Cooling of Strip Coils on the Conveyer of a Hot-Rolling Mill

Research shows that the controlled cooling of strip coils should not begin in storage but rather during coil transportation to the store or to the next technological operation. That increases the effectiveness of coil cooling, thanks to the greater heat content of the metal or the greater cooling rates. On the basis of the research, proposals are made for controlled cooling of strip coils in existing lines for the transportation of hot coils to stores, with slow-cooling (thermostat) sections and accelerated-cooling sections. Controlled cooling of strip coils is also possible in newly constructed and reconstructed lines that transport coils of hot-rolled strip to the next technological operation, without intermediate storage.

Round Shape Rib Forming by Roll Forming Process

Roll forming process, due to increased product performance, higher quality, and lower cost with other advantages, has been made suitable process to form any shapes in the sheets. In this paper stress, strain and thickness distribution in the steel galvanized hot coil commercial (SGHC) sheet with Round shape ribs formed by roll forming process was investigated by a Finite Element code, ABAQUS software. The stress and strain distributions are considered during forming. Since in round shape ribs the flow of material is easier than quadrilateral one, the Stress distribution was more uniformand thinning strain was concentrated in the ribs with maximum value of 14.5% while this value in quadrilateral shape rib forming is 15.5%. The results show that this method is applicable in reducing the thickness strain.

A New Engineering Technique in Roller Design to Prevent Thinning of Sheet in Roll Forming Process

These days sheet metal forming is a widely used in different industrial fields with large production volumes. Formability of metal sheets is limited by localized necking and plastic instability. In sheet metal forming processes like drawing and stamping the main challenge is thinning of the metal sheet in some regions. To reduce thinning of the sheet product, roll forming has been suggested instead of stamping process. Thinning strain can cause necking, tearing or wrinkling which are failure of the metal sheet. In this study a new engineering technique is proposed in order to prevent thinning of the steel galvanized hot coil commercial (SGHC) in roll forming process. An explicit finite element code, ABAQUS software, was used to simulate the roll forming process. The results show that the proposed technique has an important effect on thinning of the sheet and can reduce it significantly. Investigation on the second and third and fourth rollers show the effect of modified roller dimension as on reducing the thickness. These reductions in second, third and fourth rollers are from 4 percent to 0.5 percent, 2.8 to 1.4 percent and from 1.4 to 0.7 percent respectively. The reasons of the new techniques effect were also discussed.

Improvement of the Efficiency of Hot Strip Rolling with Controlled Coil Cooling

Controlled coil cooling (CCC) improves the consumer properties of the entire range of products of continuous hot wide-strip rolling without costly thermal treatment. The CCC process also contributes to the improvement of the efficiency of hot strip rolling by reducing the loan payments due to the reduction of the overall production cycle and recovery of the great quantity of heat accumulated in all hot coils.

Nanostructured Strengthening of Springs and Spring Steels

The paper considers the problem of nanostructured strengthening of spring steels and springs, the idea of steel nanostructured strengthening determined not only by grain sizes but also by subgrain sizes is justified. Design schemes of thermal strain nanoscale substructure patterning in spring material produced by hot and cold coiling were implemented. Patterning of nanoscale substructure was experimentally proved. Strength analyses of spring steels and springs showed the dominant effect of nanoscale substructure on spring limited life increasing not less than 10 times at cyclic fatigue tests. Spring compression at cyclic loading decreases 10 times.

Recent Development of Thin Slab Casting and Rolling Technology in a Challenging Market

Thin Slab Casting and Rolling Technology, in particular CSP® technology (Compact Strip Production), is well established for hot coil production. From its introduction in 1989, CSP® technology has been continuously developed further. Today, on a CSP® plant, nearly the full range of high-quality steel grades can be produced with tightest geometrical and metallurgical tolerances under optimum economic conditions.