Hot Rolling Production Research Articles

Modeling of transient bottom jet impingement boiling

In manufacturing of hot rolled steel products, run-out table cooling plays a critical role to obtain the desired microstructure and mechanical properties. Therefore, it is important to control and simulate cooling on the run-out table. Specifically, the transition boiling regime is critical here as heat extraction increases with decreasing steel temperature. A new mechanistic heat flux model is proposed to map boiling curves in the impingement and parallel flow zones for bottom jet impingement cooling of a stationary steel plate with a planar nozzle. In particular, a transition boiling model originally developed for steady state conditions has been extended to the transient conditions of jet impingement boiling.

Methods of reducing-sizing block finishing passes form optimization aimed at accuracy improving of finished profile geometric dimensions

Accuracy of hot-rolled products dimensions is one of main indices of quality and along with strength and structure metal characteristics, determines quality and competiveness of the hot-rolled products. Increase of rolling accuracy enables to make the rolled products in “minus” area of tolerance and to save metal at the expense of a profile running metre mass decreasing. It is possible only at rolling in accurately calculated finishing passes, manufactured according to adjusted rolling accuracy and with outlets of optimal form. Analysis of calibration efficiency application accomplished, the calibration being of “oval–circle” version with application of three-radius construction of reducing-sizing block round passes of wire rod rolling mill at production of 5.5 mm diameter wire rod. A numeral model elaborated for production of 5.5 mm diameter wire rod at a wire-rod mill using a base sizing “oval–circle”. To study geometric dimensions of 5.5 mm diameter wire rod, manufactured at 150 mill with application of “oval– circle” base sizing, samples of 80K steel were collected. The selection was done out of the head and of the tail of a coil. Based on energy-power data and speed parameters of a real rolling process, a mathematic model of 5.5 mm diameter wire rod rolling with application “oval–circle” base sizing was constructed. Wire rod mill 150 finishing gages form optimization was accomplished aimed at an increase of geometric dimensions of final profile accuracy. Analysis of efficiency of multi-radius cutting of finishing stands rolling passes was done for production of 5.5 mm diameter wire rod.

Study of innovation technology possibilities of steel hot-rolled tempered strip production

Hot-rolled strip having normalized level of mechanical properties, produced with high accuracy as well as having decreased level of surface defects is considered often as an alternative to a cold-rolled product. An area of its utilization includes, in particular, production of automobile parts by cold stamping and blanking operations. Analysis of experience of mastering of hotrolled pickled strip technology instead of cold-rolled one as a marketable product revealed a series of problems related to provision of normalized level of surface roughness and obtained values of geometric parameters accuracy. Results of complex study represented, carried out by scientists of MGTU after G.I. Nosov together with PAO MMK within the period of mastering of new technology of hot-rolled pickled tempered strip production. Within the study a new technological flow-chart was elaborated for 3.1 mm thick steel hot-rolled pickled strip of steel 07ГБЮ production, excluding the stage of cold rolling. An operation of tempering was envisaged as a finished one, w enabled to increase resistance of hot-rolled pickled strip against cyclic loads. It was determined, that after tempering the coarseness uniformity increases along the whole surface and coil length of pickled strip. The carried out complex studies enabled to elaborate the technological effect, applied to hot-rolled products at the stage of finishing without cold rolling operation, that enables to have the level of properties in the hot-rolled pickled tempered strip, correspondent to existing world standards for such a product.

The Research and Application of Industrial Robot in Steel Deep Processing Field

The paper describes technical research results of four categories of robots in steel deep processing field, including integrated code reading and temperature measuring robot for hot rolling production line, code spraying robot, slag-dredging robot for galvanizing line and coiling machine sleeve mounting robot for color coating line and proposes the development trend of industrial machinery in the steel industry.

Application of neural networks for predicting hot-rolled strip crown

In this paper, a prediction model for hot-rolled strip crown based on an artificial neural network (ANN) is presented. Considering the mean squared error (MSE) and correlation coefficient (R), production data of 10,133 coils collected from a hot rolling plant are used to establish models. A feed-forward neural network with one hidden layer, a non-dominated sorting genetic algorithm II (NSGA II) optimized ANN, and a deep neural network (DNN) are applied to evaluate the prediction performance. Parameter settings of the ANN and NSGA II including learning rate, hidden neurons, activation function and population size, and crossover probability, are investigated to acquire the optimal model. The structure of the DNN, including how many layers and units the network should contain, is also studied. Prediction performance comparisons of the ANN, NSGA II-ANN, and DNN are presented. Among the ANN, NSGA II-ANN and DNN, the results show that the DNN has the highest prediction accuracy. Root mean squared error (RMSE) of the proposed DNN is 2. 06μm, and 97.04% of the prediction data have an absolute error of less than 5μm. Through model response surfaces, effects of four key operating parameters are investigated. The results indicate that the proposed DNN with strong learning ability and generalization performance can be well applied to hot rolling production.

Transient liquid phase bonding of carbon steel components using Ni-based foils – A comprehensive joint characterization

The transient liquid phase bonding (TLPB) process is one of the selected joining technologies to replace threaded connections in solid expandable tubulars. In particular, for expandable hot-rolled seamless carbon steel tubular products using Ni-based amorphous metallic foils as filler material.In this work, a comprehensive mechanical properties and microstructural characterization was carried out in TLP-bonded bars for this base metal/filler material combination. Both the joint and the heat affected zone exhibited a strength which compares well with the base metal, and a ductility in accordance with that which is typically specified for steel arc-welded joints. A coalesced lath-like bainitic microstructure was found at the joint. In addition, and by means of orientation imaging, a parent austenite grain - which is shared by the joint and an adjacent ferrite grain from the base metal - was found, which demonstrates the epitaxial nature of the TLPB solidification process.Also, a cell-block-like structure at ferrite grains next to the joint was detected, due to the plastic deformation developed in tensile-tested samples at room temperature.

Texture Evolution during Hot Deformation of Al-Cu-Li-Mg-Zn-Zr-Sc Alloy

The Gleeble-3800 unit was used to simulate physically the upsetting of cast and hot rolled semi-finished products from aluminum-lithium alloy V-1461 over the temperature range of 400-460°C and the strain rates of 1-60 s-1. Following texture analysis of upset samples showed the most typical preferred crystallographic orientations and its formation features depending on the temperature-strain rate schedules. The formation of recrystallization type orientations at a strain rate of 60 s-1 is a distinctive feature of the cast samples’ behavior during deformation. In general, the established regularities of texture formation allow to produce a hot-rolled semi-finished products from V-1461 alloy with a given structure’s crystallography in compliance with requirements for blank’s forming and product’s operation.

Hot rolling strips at the casting and rolling unit during coil-to-coil and endless rolling modes

The study of hot rolled steel production technology with an assessment of the impact of the main technological processes and operations on the quality of the finished product, the possibility of expanding the range of steel grades and production efficiency is an important condition for improving the technical level and development of rolling production. Combining the processes of casting billets and hot rolling was a very relevant and economically profitable solution, which in turn was the prerequisite for the creation of casting and rolling units. Production of hot rolled products at the casting and rolling units in compared with the traditional multistep technology, reduces the production cycle and, despite the low production volumes, can compete with the hot rolling mills in the cost of products due to the specific equipment layout and resource-saving and energy-saving technologies.For studying the thermal state of the metal in line of the casting and rolling unit a modular mathematical model was developed. The spatiotemporal temperature distribution of the metal was described with use non-stationary heat conduction equation with boundary conditions of the second and third kinds depending on the type of heat exchange. The algorithm for calculating the production of hot rolled products is based on a combination of modules, each of which describes a specific boundary condition and carries information about the object or objects, as well about the working and additional tools used in the simulation. The model uses the results obtained during laboratory research under plane strain compression on the installation of the Gleeble 3800. Simulation of the rolling process is performed in «Deform 3D». The developed model can be used to study the thermal state of the metal in the hot rolling production of high-quality steel grade.

Mechanical Properties Prediction for Hot Rolled Alloy Steel Using Convolutional Neural Network

A convolutional neural network (CNN)-based method for predicting the mechanical properties of hot rolled steel using chemical composition and process parameters is proposed. The novel contribution of this research is to introduce the prediction method of CNN into the steel properties prediction field by converting the production data into two-dimensional data images. Compared with the traditional artificial neural network method, the CNN adopts the idea of local connection and weight sharing, which reduces the complexity of the network model, and uses convolution and pooling operations to extract local features for better prediction precision. The experiments in this paper show that the proposed CNN model with the optimal structure provides higher prediction accuracy and higher robustness when compared with other prediction model reported in the literature. Finally, the metallurgical phenomena in the steel rolling processes are verified by sensitivity analysis using the proposed CNN model. The results are consistent with the metallurgical properties of the steel materials used in the experiments. Therefore, the proposed CNN model has a guiding significance in predicting the mechanical properties of hot rolled steel products in practical applications.

Achievements of Endless Strip Production in Rizhao Steel

The equipment and technology characteristics of endless strip production line in Rizhao steel were analyzed and the achievements of endless strip production in Rizhao steel were illustrated with detailed productive data in 2017. The achievements of endless continuous casting process was introduced from the aspects of the mold level deviation, the casting speed and the tundish temperature. The achievements of endless continuous rolling process was described from the rolling length, the mechanical properties and the microstructure at different position along the width. The achievements of endless continuous casting and rolling process was discussed from the product qualification rate, the yield rate, the thin strip ratio, the accident rate and the energy consumption. The productive practice of endless strip production (ESP) shows that the longest number of continuous casting furnace reached to 15 heats (4500 tons), the longest rolling length in single casting period was 182 km, the qualified rate of products was up to 99.73%, the yield rate was up to 97.51% and the thin strip ratio had a maximum value of 40.57%. At the same time, its accident rate was below 2.02% and its energy consumption was less than 27.26 kgce·ton-1. These achievements indicated that the ESP line in Rizhao steel had the advantages of low cost, good performance and green manufacturing, so the endless rolling technology will be rapidly promoted and the hot rolled thin products by ESP will further expand the market.

Advanced Technology of Combined Thin Slab Continuous Casting and Steel Strip Hot Rolling

On the basis of proceedings of an international symposium on casting and rolling complexes the latest solutions for hot-rolled strip production by a combined process of continuous thin slab casting and rolling are reviewed. Advanced developments in the field of equipment and technologies are presented. The main tendencies and future tasks on this subject are noted.

Development of heat treatment modes for a two-phase titanium alloy to form regulated structure and properties complex

The article shows the possibility of creating structure of the same type and, accordingly, a close level of properties in hot-rolled semi-finished products of the VST2K alloy with different chemical composition by means of heat treatment.

Effect of Hot Rolling Production Parameters on 12% Chromium Steel Structure and Properties

The effect of heating temperature and deformation during hot rolling on the microstructure and mechanical properties of steel grade 07Kh12NMFB (0.07C–12Cr–Ni–Mo–V–Nb) are studied. It is established that a change in the plastic deformation regime, without having a significant effect on strength properties, leads to significant changes in steel impact strength. No effect of hot rolling production parameters on steel microstructure after the final heat treatment is detected. Based on research results a heating temperature up to 1150 °C for rolling steel grade 07Kh12NMFB and deformation of not less than 25% are recommended.

Digital Control of Electrically Welded Pipe Manufacturing Technology in a Tesa 20–102 Mill

In order to manufacture hot-reduced pipe from welded pipe billets in a continuous stretch-reducing mill (SRM) 20–102 coiled hot-rolled product is used of normal precision with respect to thickness, specified in GOST 19903. The actual value of longitudinal difference in thickness for the main mass of coiled rolled product comprises 70% of the proportion of pipe tolerance with respect to thickness, which makes it difficult to satisfy the specifications of GOST 10704 and GOST 3262 for pipe wall thickness, and also increases the metal consumption factor for a ton of finished product. Due to development of a rapid algorithm and a calculation program for reduction production regimes, rational calibration of rolls, pipe stretching between mills and stands in a 22-stand SRM, a control system for hot-reduced pipe manufacturing technology is created and introduced. As a result of this the longitudinal difference in pipe wall thickness compared with the longitudinal difference in strip wall thickness is reduced by an order of magnitude. This makes it possible to manufacture pipe in the minus range of permissible values for deviation of wall thickness, to reduce the metal consumption factor, to increase the output of finished product, to reduce specific energy expended in pipe rolling in the SRM, and to assimilate manufacture of a thin-walled range of pipes.

Reheat Furnace Thermodynamic, Kinetic and Combustion Considerations for TMCP Processing

The reheat furnace process step has a profound effect on the TMCP performance, final hot rolled steel quality and mechanical property consistency during the production of hot rolled steels. The uniformity of heating applied across the entire width and length of the slab or billet is critical in the achievement of customer properties regardless of the chemistry. The resultant ferrite grain size in the final hot rolled product is significantly governed by the initial prior austenite grain size. Numerous reheat furnace process metallurgy and combustion parameters in actual operation affect mill productivity, microstructure, austenite grain size, scrap rate and diverts. This reheating step in the steelmaking process often receives low priority in the evaluation of product quality and mechanical property performance, especially the toughness through the plate thickness. Heat transfer conditions of radiation, convection and conduction affect furnace heating efficiency. In laboratory studies, the furnace heating step is typically quite uniform resulting in a homogeneous and fine prior austenite grain size. During production, it is much more difficult to control the uniformity of heating and heat transfer consistency along the entire length and through the thickness of the work piece. The furnace conditions are correlated to product quality via furnace process variables such as the air to gas ratio, furnace burner condition, furnace pressure, energy efficiency, adiabatic flame temperature (AFT) and furnace refractory condition. Operational practice recommendations are presented to minimize inhomogeneous heating which results in inferior product quality, hot rolling model anomalies and toughness variations in the through-thickness-direction.

Manufacturing technologies of steel seamless tubes for production of hard-to-recover hydrocarbons

The review contains main directions in the development of modern steelmaking, hot rolling technologies and heat treatment aimed to follow increased requirements to seamless tubes for production of oil and gas under severe conditions. New targets of PJSC “Gazprom” in development of new resources have determined new technical requirements to pipes for low temperature application, resistant to hydrogen sulfide and carbon dioxide corrosion. Basic metal science approaches are given to develop new chemical compositions of high quality steels containing minimum of sulfur, phosphorous and solute gases. Corresponding heat treatment routes are determined for formation of martensitic microstructure in full wall section during quenching with subsequent high tempering for required combination of high strength and ductility. It was shown that optimal combination of high strength and toughness at 60 °C below zero can be achieved by alloying of chromium-molybdenum steel containing about 0.25 wt. % of carbon with strong carbon forming elements such as vanadium and niobium. Sustainability of these steels to stress sulfide cracking was achieved through grain refinement with microalloying by molybdenum in concentrations corresponding to strength grades that gives high hardenability and retards tempering of martensite. New compositions of corrosion resistant martensitic 13 % chromium steel were carried out that was resulted in required resistance to carbon dioxide environments with improved low temperature toughness and high strength. The authors present results of reconstruction of steel making and hot rolling production lines at JSC “Volzhskii Pipe Plant” providing the required quality of new products from continuously cast steel billets to finished tubes.

Identification of the “rolled-in scale” type sheet surface defect

Rolled-in scale” defect is put down to one of main surface defects of sheet rolled products. It deteriorates salable condition of cold-rolled sheet, adhesion of surface coatings to metal base during galvanizing, chrome plating, applying of polymer materials, stipulates increased corrosion of metal rolled products etc. External view of “rolled-in scale” defect is very similar to the whole number of sheet surface failures, as scratch, rolled impurities, slag inclusions, rolled undersurface gas bubble etc. Exact identification of the abovementioned defect is important for elaboration of measures for its elimination and is possible only by application of metallographic methods. Results of metallographic study of cold-rolled sheet defect, identified as “rolled-in scale” presented. Technology of hot-rolled sheet production usually is the reason for this defect, when formed on the billet surface furnace and/or air scale is partially rolled into the rolled product surface. Such a defect on the cold-rolled sheet surface, inherited from the hot-rolled sheet surface is considered as a rejected feature. Studies by optical and raster electron microscopes using X-ray spectral microscopy analysis results in determining real reason of the presumable “rolled-in scale” defect. In this case the rolling-in of residuals of slag surface layer and slag-making mixtures into the hot-rolled sheet surface is the reason. The residuals are inherited from metallurgical stage, mainly continuous casting, as well as pickling process and cold-rolled sheet alkaline cleaning.

Edge cracking prevention in 2507 super duplex stainless steel by twin-roll strip casting and its microstructure and properties

In the present work, the microstructure, mechanical properties and corrosion resistance of 2507 super duplex stainless steel (SDSS) fabricated by conventional hot-rolling and strip casting were investigated, respectively. Large deformation in the course of conventional hot-rolling destroyed the coherency of ferrite/austenite interphase and leaded to a deviation from the ideal K-S orientation relationship, which accelerated the precipitation of sigma phase at the phase interface in 2507 SDSS. These brittle particles provided numerous potential void nucleation sites and promoted the propagation of cracks along the ferrite/austenite interface, resulting in severe cracking during conventional hot-rolling. High-quality thin strip without edge cracking was manufactured by strip casting and the edge cutting-off of hot-rolled products was avoided, leading to a significant reduction in cost compared to the conventional process. Meanwhile, the mechanical properties and corrosion resistance of 2507 SDSS fabricated by this new technology reached the same standard of conventional productions. High Temperature-Short Time (HTST) heat treatment was applied in the preparation of the final product, which significantly improved the strength of 2507 SDSS.

The study of the thermal state of the metal in the production of the hot rolled strips in «Deform 3D»

The mathematical model of the thermal state of the sheet metal has been developed, taking into account radiation heat exchange and convection between the metal surface and the environment, the impact of descaling, heat transfer at the contact of metal with rollers, and also the heating of the metal due to plastic deformation. The model uses the results of mechanical tests obtained on the installation of the Gleeble 3800 under plane strain compression. Simulation of the rolling process is performed in the software complex «Deform 3D». The results of mathematical modeling adequately reflect the study of the thermal state of the metal produced in a sheet rolling shop. The model can be used to study the thermal state of the metal in the hot rolling production of high-quality steel grade.

The Integration of Process and Product Metallurgy in Niobium Bearing Steels

A review of the technological integration of both the process and physical metallurgical advancements of value-added niobium (Nb) microalloyed thermo-mechanical controlled process (TMCP) steels have evolved into the development of higher quality steels for more demanding end user requirements. The connection of process and physical metallurgy is evolving through the integration of research that is aimed at improving product quality. However, often the connection of the process metallurgical parameters is not reported, especially with industrial data. The importance of this innovative metallurgical connection is validated by the market demand for reduced fuel consumption, improved quality, and CO2 emissions in both the automotive and construction sectors. This situation has further increased the demand for new higher quality Nb-bearing steel grades. This integrative process/physical metallurgical (IP/PM) approach applies to both low and high strength steel grades in numerous applications. Often, the transition from laboratory melted and TMCP to the production scale is challenging. The methodology, process control, and key production steps that are required during the melting, ladle metallurgy, continuous casting, thermal, and hot rolling production conditions often vary significantly from the laboratory conditions. Understanding the reasons and corrective action for these variations is a critical product development success factor. These process metallurgy parameters for the industrial melting, casting, reheating, and hot rolling of Nb grades are connected and correlated to the resultant microstructures, physical metallurgy, and mechanical properties. These advanced high strength steels are microalloyed with Nb, V, Ti and/or other elements, which affect the austenite-ferrite transformation. Niobium enables the achievement of substantial grain refinement when the plate or sheet is rolled with the proper reheat, hot reduction, and thermal schedule. A recently developed key metallurgical transition is in progress applying this integrative approach with the use of MicroNiobium. A reduction of Mn and C levels with the complementary refinement of the microstructural grain size through MicroNiobium additions improves the robustness of the steel to better accommodate some process metallurgy variations. Applications are evolving in lower strength steels with Nb to achieve complementary grain refinement.