Hot Rolling Line Research Articles

A Comparative Study of the Oxidation Behavior of Hot-Rolled Steel established from Medium and Thin Slabs oxidized in 20% H2O-N2 at 600-900°C

This study focuses on the oxidation behavior of oxide scale on hot-rolled steel from a Thailand steel industry. Hot-rolled steel established from the medium and thin slabs was studied. The oxidation behavior was conducted in a horizontal furnace with 20%H2O-N2 to simulate steel oxidation during the hot rolling line. The scale was formed at a temperature range of 600-900°C for 30, 60, and 90 min. The scale morphology can be seen via Scanning Electron Microscope (SEM-EDS). The oxide phase was investigated via X-Ray Diffraction (XRD). The results show that iron oxides such as hematite (Fe2O3) and magnetite (Fe3O4) were produced on the studied steel. The oxidation behavior of the studied steel was followed by a parabolic law. The mass gain increased with increasing temperatures. The steel established from a medium slab exhibited a lower oxidation rate than the steel established from a thin slab. The reason for this could be the high amount of oxide containing silicon at the steel-scale interface, which promoted the oxidation resistance of the steel established from the medium slab. The influence of different slab types and its alloying elements was studied to comprehend the oxidation behavior. As a result, the alloying element in the hot-rolled steel was controlled in the design process.

Researches regarding power quality at the hot rolling mills’ power supply

The study described in the paper was carried out through measurements taken at a feed station in a hot rolling line. The aforementioned measures are appropriate for the purpose of analyzing power quality. The measurements were taken using a three-phase power quality analyzer. Measurements were taken for voltage and current values, as well as for active, reactive, and apparent powers. The analysis of the measurements taken indicates that the power quality is affected by the nonlinearity of the load. As a consequence, the level of reactive power becomes higher, leading to a reduced power factor.

Leveraging Knowledge Graph Reasoning in a Multihop Question Answering System for Hot Rolling Line Fault Diagnosis

Leveraging Knowledge Graph Reasoning in a Multihop Question Answering System for Hot Rolling Line Fault Diagnosis

Strip Thickness and Profile–Flatness Prediction in Tandem Hot Rolling Process Using Mechanism Model‐Guided Machine Learning

This study is focused on the multivariable, nonlinear, strong‐coupling, and time‐varying characteristics of the quality control process of hot strip rolling. Using the rolling process data from a continuously variable crown (CVC) mill of a 1580 mm hot tandem rolling line, a new prediction model of the strip thickness, profile, and flatness in hot rolling based on rolling mechanism model‐guided machine learning (ML) is developed. The weighted processing (WP) method is used to fuse the rolling mechanism and process data, to improve the relationship between the strong correlation features and the model. Combined with nondominated sorting genetic algorithm III (NSGA‐III), multiple parameters of multioutput support vector regression (M‐SVR) are optimized. The results show that the root mean square error (RMSE), mean square correlation coefficient (R 2), and mean absolute error (MAE) of the strip thickness, crown, and flatness are 2.0159, 1.3191, and 0.9355; 0.9854, 0.9895, and 0.9873; and 16.601, 1.126, and 0.604, respectively. Moreover, the established method of data fusion rolling mechanism shows strong capability to improve the model prediction accuracy, increasing it by 60%. Thus, it can offer theoretical guidance for realizing accurate control of the quality of strips and improving the quality of hot‐rolled products.

Improvement of Elevated Temperature Wear Resistance of Side Guides Using Microstructural Engineering (Case Study: Hot Rolling Line of Mobarakeh Steel Complex)

Improvement of Elevated Temperature Wear Resistance of Side Guides Using Microstructural Engineering (Case Study: Hot Rolling Line of Mobarakeh Steel Complex)

Study and Modeling of Slab Deformation Processes in the Roughing Stands of Severstal’s Mill-2000 Hot-Rolling Line

Study and Modeling of Slab Deformation Processes in the Roughing Stands of Severstal’s Mill-2000 Hot-Rolling Line

A new dust removal technology used in hot rolling mills: Atomized spray with higher dedusting efficiency

In order to effectively remove the oxide scale dusts in the hot rolling strip steel, this study focuses on the principle of atomized spray and use it to develop a new dust removal technology used in the hot rolling mills. Through establishing a mathematic model of particle collision, 4 critical factors most affecting the dedusting efficiency are analysed: the diameter of nozzles, the diameter of water droplets, the diameter of dust particles, and the spray pressure. For further discovering the principles of the movements and concentration changes of the dust particles, a numerical model is established based on the gap space between the hot rolling mills. 2 scenarios of running the atomized dedusting or not are simulated to compute the dedusting efficiency so that the dedusting effect of the atomized spray can be confirmed for the hot rolling. The case study on the 1580 mm hot rolling line in WISCO plant demonstrates a successful dedusting efficiency of 93.50% on the R2 rough rolling mill. The spray pressure of 0.5 MPa and the nozzle diameter of 1.4 mm are appropriate to generating the proper water droplets with the diameter of 71.1 μm in order to capture the dust particles with the mean diameter of 27 μm. The study on the principles and simulations of the atomized spray facilitates more efficient dust removal for cleaner hot rolling mills.

Strip Crown Prediction in Hot Rolling Process Using Random Forest

This paper established a model based on an ensemble method to predict strip crown using 230,000 coils of data obtained from a hot rolling line. Before modeling, a specific method was proposed to reduce noise and remove outliers, and a new dataset of 5657 samples was generated. Parameter tuning considering mean squared error (MSE) was carried out to establish three machine learning models including support vector machine (SVC), regression tree (RT), and random forest (RF). Determination coefficient (R2), mean absolute error (MAE) and root mean squared error (RMSE) were used as indicators to evaluate the prediction of models. Results showed that the RF had the best performance with the highest R2 of 0.707, as well as the lowest RMSE of 5.66 μm. Moreover, an additional method that repeated the three models 100 times was developed, and box plots were used to visualize the distribution of R2, MAE and RMSE. RF can correct for decision trees to reduce overfitting to their training set, improving the generalization, and in this paper, the trained RF which had stable performance is considered as the most recommended model. After that, for RF, rankings of rolling process variable were validated to make a comparison with the existing physical understanding.

Analysis on the effect of sound insulation reconstruction in operation room of steel rolling production line in a steel plant

Objective: To investigate the effect of sound insulation improvement on the noise exposure of workers in the operation room of hot rolling line for wide and heavy plate. Methods: From September 2019 to September 2017, based on the occupational health Survey, the data of 25 fixed operation rooms and workers in operation rooms of a steel rolling production line were collected retrospectively, the noise exposure levels before and after the improvement of sound insulation were statistically analyzed. Results: The noise exposure value of the workers, the qualified rate of 0 Grade 8 hours equivalent noise (L(EX, 8 h)) ≤85 dB (A) and the qualified rate of the design limit value of the operation room were all higher than those before the modification, the difference was statistically significant (P<0.01) , after the renovation, the Class II and above noise hazards were eliminated, the equivalent continuous a sound level (L(Aeq, 8 h)) >75 dB (A) of the workers in the operation room was 8h, and the noise level in the operation room still did not meet the Ergonomics limit standard. Conclusion: The improvement of sound insulation can effectively improve the working environment of noise workplace operating room and reduce the workers'noise exposure level.

Research on Production Technology of Asymmetrically Hot Rolled Stainless Steel Clad Plate

The hot rolled single sided stainless steel clad plate of 316L stainless steel and Q345C steel was carried out in a hot rolling line by the technology of “electron beam vacuum welding and hot rolling”. High quality single sided stainless steel clad plates were produced by asymmetrical compound billet and asymmetrically rolling. The productions of stainless steel clad plate have reached the requirements of GB / T 8165-2008. The interface shear strength is greater than 320 MPa. The yield strength is greater than370 MPa. The tensile strength is greater than 520 MPa. The elongation is greater than 30%, A good metallurgical bonding between stainless steel and carbon steel was achieved. The bonding rate reached 100%. The composite interface is straight and perfect. The pilot production in the study has laid down the certain basis for the production of the single-side dissimilar-material composite board.

Fault Location of Strip Steel Surface Quality Defects on Hot-Rolling Production Line Based on Information Fusion of Historical Cases and Process Data

Surface quality is the most important index to improve the overall quality of strip steel. In order to implement the fault location on the hot-rolling line with surface defects of strip steel, a fault tracing model based on information fusion of historical production cases and process data is proposed. For historical cases, the model determines the defect cause labels through text similarity calculation, and fuzzy semantic inference is used to obtain the probability distribution of defect causes on this basis; for the process data, the model uses L1 regularization method for feature selection, and XGBoost integration method is used to train the correlation model between process data and defects to determine the contribution of each feature in the data source. Finally, based on the D-S evidence theory, different rules are set to merge the two judgments to determine the probability of each source of failure on the hot-rolling production line. The model is applied to the real production environment of iron and steel enterprises, and it is verified that the proposed method can effectively assist experts in decision-making, which greatly improves the efficiency of tracing the source of faults on the hot-rolling production line.

Flatness Analysis and Control of Strips with Different Thickness in 2250 mm Hot Tandem Rolling

Aiming at the flatness difference between thick strip and thin strip under the same flatness control strategy on a 2250 mm hot tandem rolling line, a flatness calculation model is firstly established in this paper. With the unknown variable–transversal flow of metal solved by finite element methods, the flatness calculation model is used to analyze and compare the flatness and longitudinal residual stress evolution during thick strip and thin strip rolling. The result shows that under the premise of the constant exit relative crown in the downstream stands, the distribution of metal transversal flow due to larger reduction ratio in F2 and F3 stand causes the flatness of thin strip differing much from that of thick strip. In order to improve the flatness quality, a crown setup method is proposed. Based on the relationship among the distribution of metal transversal flow, entry relative crown, and the change of relative crown obtained from the finite element model, the exit crown of thin strip at each stand is optimized by genetic algorithm with a restriction of achieving the target crown at exit of F7 stand and a goal of good flatness quality during rolling.

Effect of Slab Centerline Segregation on DWTT Properties of 22mm Thick X80M Hot Rolled Steel Strip

The replacement of 22mm thick X80M hot rolled strip for the traditional heavy plate production technology has remarkable advantages in improving the yield, reducing the cost of manufacturing and improving the outer diameter adjustment of pipeline. Low temperature anti Drop Weight Tear Test (for short DWTT) performs one of the key research problems of 2250mm hot rolling line production of this specification. Aiming at the problem of the substandard performance of rolled DWTT development process, the slab fracture morphology of different proportion and slab thickness direction component segregation degree of system were analyzed through the electron microscope. The results showed that the thickness of steel strip was serious segregation and is the main factor affecting the performance of DWTT. By optimizing the caster arc alignment and secondary cooling water, then improving the central segregation effect, the performance of DWTT can be effectively improved, and a stable development and production of 22mm thickness X80M pipeline steel hot rolledstrip can be achieved.

Microstructural Evolution and Dynamic Partitioning Behavior in Quenched and Partitioned Steels

Direct quenching and dynamic partitioning (DQ&amp;P) process is a promising approach and there continues to be lack of understanding concerning cooling condition in the hot strip rolling line. Here, the authors have simulated DQ&amp;P process in low carbon Si–Mn steel using a thermal simulator. The effect of quenching temperature, relaxation process, and cooling rate on microstructure and hardness is studied. The results suggest that retained austenite is less sensitive to quenching temperature and the volume fraction of retained austenite including film‐like and blocky shape is ≈7–11%. The relaxation process leads to ferrite transformation and recovery of defects, resulting in increase in retained austenite, and reduced hardness. It is interesting that the quenching temperature and hardness do not show an inverse relation. It is important that the isothermal transformation at high quenching temperature below Ms promotes retained austenite. Moreover, the low coiling cooling rate less than 0.1 °C s−1 from quenching temperature to room temperature is adequate for carbon partitioning. In the view of thermodynamics and kinetics, an appropriate processing window of coiling temperature between 200 and 320 °C plus low cooling rate less than 0.1 °C s−1 is proposed for hot rolled DQ&amp;P steels.

Non-Metallic Inclusions and Hot-Working Behaviour of Advanced High-Strength Medium-Mn Steels

AbstractThe work addresses the production of medium-Mn steels with an increased Al content. The special attention is focused on the identification of non-metallic inclusions and their modification using rare earth elements. The conditions of the thermomechanical treatment using the metallurgical Gleeble simulator and the semi-industrial hot rolling line were designed for steels containing 3 and 5% Mn. Hot-working conditions and controlled cooling strategies with the isothermal holding of steel at 400°C were selected. The effect of Mn content on the hot-working behaviour and microstructure of steel was addressed. The force-energetic parameters of hot rolling were determined. The identification of structural constituents was performed using light microscopy and scanning electron microscopy methods. The addition of rare earth elements led to the total modification of non-metallic inclusions, i.e., they replaced Mn and Al forming complex oxysulphides. The Mn content in a range between 3 and 5% does not affect the inclusion type and the hot-working behaviour. In contrast, it was found that Mn has a significant effect on a microstructure.

Thermomechanically Rolled Medium-Mn Steels Containing Retained Austenite/ Walcowane Termomechanicznie Stale Średniomanganowe Zawierające Austenit Szczątkowy

Abstract Chemical composition of four medium-Mn steels containing a various Mn content (3 and 5%) have been proposed in the present work. The two steels are base steels whereas the other two contain Nb microaddition. Thermomechanical rolling tests of 3.3 mm sheets have been carried out using a semi-industrial hot strip rolling line. Detailed investigations of the identification of structural constituents using light microscopy and scanning electron microscopy techniques have been performed. X-ray method has been applied to determine an amount of retained austenite and its C content. Significant microstructural parameters were revealed using an EBSD technique. It was found that the Mn addition affects strongly a microstructure type, stability of retained austenite and mechanical properties determined with a static tensile test. The steels containing 3% Mn are characterized by a good combination of strength and ductility whereas the tensile strength up to 1300 MPa is possible to obtain for the higher Mn content steels.

Numerical Simulation on Correcting Camber and Wedge of Steel Slabs in Hot Rolling Mill

In the hot rolling process, the steel slab may experience a temperature gradient along its transverse direction which may cause camber and wedge after rolling. Camber and wedge phenomenon will affect the quality of the steel plate. To eliminate camber and wedge phenomenon, a pair of side guides is placed before and behind the hot rolling mill. The position mode and the force mode are the control modes for side guides to correct the slab shape and to guide the slab to follow rolling direction. Finite element analysis using ABAQUS was applied to simulate hot rolling process to find the correction mechanism of rolling equipment. The centerline of slab was traced and the shape of slab was predicted. The difference of rolling load between work side and drive side of roller was determined. Furthermore, the load, stress and velocity distribution on the slab at roll bite were analyzed. By using numerical model, hot rolling parameters including side guide control strategy can be predicted, which can provide the hot rolling line as a guideline to improve the quality of the steel slab.

Three-dimensional Finite Element Analysis for Flying Shearing of X100 Hot-rolled Steel Plate

Increasing demands for transporting oil and natural gas promote the developing and production of high-grade pipeline steel. The hot rolling is a vital process to produce the steel plate of pipe fabrication. In a hot rolling line, a flying shear is used to shear the leading and trailing edges of a rough rolled plate. In the present research, three-dimensional FE model of flying shear was built on ABAQUS/Explicit, considering the motions of blades. The feeding rollers and shear blades are considered as rigid material, and the steel plate adopts elastic-plastic material model. Ductile damage criterion for X100 steel was built to simulate the material damage and fracture during the shear processing. By the simulation, the plastic deformation, the damage initiation and evolution, the fracture of steel plate can be obtained, which are coincided to production practise. The stroke-force curves of blades were generated from the FE simulation. The shearing force varying with the blade stroke was analyzed. FE simulation shows that the calculated force from FE model is much lower than that from empirical equation.

Effects of Process Parameters on Mechanical Adhesion of Thermal Oxide Scales on Hot-Rolled Low Carbon Steels

The present work investigated the effects of process parameters in a hot-rolling line, finishing and coiling temperatures, on mechanical adhesion of scale on low carbon steel substrate using a tensile test. Modification of our previous model to quantify mechanical adhesion energy was proposed for a system consisting of a cracked scale on a metallic substrate by introducing a distribution function of stress in scale. When a linear distribution was assumed, the quantified mechanical adhesion energy lay in the range of 40–890 J m−2. Higher finishing temperature had a prominent role on increasing final scale thickness and weakening scale adhesion. For scale with similar thickness, the mechanical adhesion energy was lowered for the sample subjected to higher temperature gradient between finishing and coiling temperatures. This was considered to be from the increased water vapour in atmosphere due to the higher amount of water used to cool down the steel strip. The mechanical adhesion test was further conducted to attest this assumption. It was found that humidified atmosphere during oxidation weakened the scale adhesion to low carbon steel substrate measured at room temperature.

Transducer Fault Detection of Hot Rolling Screwdown System Based on Sequential Probability Ratio Method

To solve the fault detection problems of position transducers operating continuously under complex conditions of hot rolling line, and improve the reliability of the control system, a fault detection method based on Kalman filter and sequential probability ratio was presented. Through building the control model of the system, processing the output data of transducers with Kalman filter, and processing the residuals with sequential probability ratio and improved methods, the judgment criterion of transducer fault detection and the method of data reconstruction were given. The simulation results show that, the method can quickly detect position transducer faults, give the reasonable estimated state value, and improve the reliability of the system.