Endless Rolling Research Articles

Optimization of Billet Tube Mold Designs for High-Speed Continuous Casting

Endless rolling urgently requires an increase in the casting speed of continuous casting. For the continuous casting process of a high-casting-speed billet, the heat flux of the mold would be much higher, requiring a stronger cooling performance and longer mold life to match the high-speed casting. Mold material, thickness, and slot structure have a great influence on the casting speed. To design a more efficient billet casting mold, a three-dimensional thermal-stress-coupled analysis model of a 150 mm × 150 mm mold was established in this research to analyze the thermal state of a mold with high casting speed; in addition, the material, thickness, and water slot structure, which pertain to the mold cooling performance, were also studied. The results show that the billet mold of Cu-Ag with a thinner thickness and right-corner water slot is better in terms of casting speed. Regarding the material, the Cu-Ag mold has a higher thermal conductivity efficiency; its hot surface temperature is 4.89 °C lower, its equivalent stress is 7 MPa lower, and its longitudinal deformation is 0.0023% lower compared with the deoxidized phosphorus copper mold. Regarding the thickness, the thinner mold has a 60.76 °C lower hot surface temperature, its equivalent stress is 340 MPa lower, and its longitudinal deformation is 0.0443% lower compared with the thicker mold. For the water slot structure, the mold with the right-angled water slot has a 2.895 °C lower hot surface temperature, its equivalent stress is 37 MPa lower, and its longitudinal deformation is 0.0039% lower compared with the mold with a rounded-corner water slot.

CLIMATE CHANGE IN THAR DESERT: A CASE STUDY OF CHURU TOWN, RAJASTHAN, INDIA

Human induced climate change is the largest most pervasive threat to the natural environment and societies the world has ever experienced. Arid ecosystem is more prone to such phenomenon. Deserts are most typically associated with soaring temperatures, permanently dry air, and endless rolling sand dunes. But in summer in “Thar” desert, it becomes so cold and freeze. The Thar desert climate refers to a specific type of climate that encompasses more than one weather type. But for last one decade its changing in a very different ways, i.e., Too hot in summer and too cold in winter. It is an alarming situation of climate change, where we can understand with this small example. In Churu district of north Rajasthan, where the sandy ground sizzles in the summers and the wind feels like a hot air boiler in the month of June. The temperatures in those months easily climb up to the high 400 Celsius. Just month, May 2020, the temperature rose to 500 Celsius – and was the highest in the world. Two years, when the mercury breached even the 510 Celsius marks in Churu in early June 2019 – more than halfway to the boiling point of water – for many it was a side bar. Six months later, by December-January in some years, Churu has seen just-below zero degrees Celsius temperatures. And in February 2020, the India Meteorological Department found the lowest minimum temperature in the plains of India to be in Churu, at 4.10 Celsius. In view of above the present study has been undertaken to deliberate the climate change impact in small desert town.

誘導加熱接合での酸化物残存に及ぼす接合条件の影響

In the No.3 hot rolling mill, Chiba Works of JFE Steel, the endless rolling process, in which roughly rolled bars are joined and rolled continuously in the finishing mill, has been put into operation for mild steels. On the other hand, this process is not applied to high-tensile-strength steels, because alloy elements contained in the high-tensile-strength steels, such as silicon and manganese, form oxide layers at the joining interface, disrupting the joining process. In laboratory joining tests, by heating until the joining surface melted, the oxides layer was discharged from the interface and steels that form oxide with a low melting temperature were successfully joined. FEM flow analysis revealed that the viscosity of oxide is the most important parameter for discharging. The low melting temperature of oxide leads to the low viscosity, resulting in the discharge of the oxide layer.

Development and Application of Asynchronous Roll Shifting Strategy of Double Attenuation Work Roll in Hot Rolling

In view of the problems of the violent crown fluctuation and unstable shape control in the endless rolling production line, the field measurement results show that the abnormal crown fluctuation is related to the shifting limit position of the work roll after the uneven wear occurs. For this reason, the asynchronous roll shifting strategy is developed, which has double attenuation of roll shifting amplitude and roll shifting step. By coupling the roll wear contour model, the roll thermal contour model and the rolls-strip integrated model, the strip crown calculation model of the whole rolling unit is established, and the causes of abnormal crown fluctuation are revealed theoretically. In addition, the simulation analysis of the important parameters of asynchronous roll shifting strategy of double attenuation working roll is made by using this model. The number of strips in a roll shifting cycle is found to be too large or too small, which is not benefited by the control of the strip crown stability due to the influence of roll wear and roll thermal crown. A rolling unit has many shifting cycles. When the roll shifting amplitude at the end of a rolling unit is smaller, which can make the amplitude difference between adjacent roll shifting cycles greater, it is easier to avoid the uneven edge wear area and to control the strip crown stability. The industrial test shows that the maximum crown fluctuation in a rolling unit decreases by 21.05%, and the maximum crown fluctuation of adjacent strips decreases by 28.57%, which significantly improves the stability of crown control.

New economically effective steel strips production technologies (based on materials of international conferences)

Production of steel rolled products by using traditional metallurgical technologies are rather material- and energyintensive and its concentration at gigantic steel plants resulted in the increased expenses for transportation of raw materials and finished products. To solve the problems, a practice of comparatively small metallurgical plants (mini-mills) construction is becoming widespread in the world steel industry. The mini-mills include modern electric arc furnaces, ladle steel treatment facilities and steel continuous casters combined with continuous rolling mills. The review complied from materials of international conferences, taken place in 2015–2019. In the review achievements in equipment and technology of metal products at mini-mills development considered, as well as analysis of modern economical methods of steel coils presented. It was shown, that the methods of strips endless rolling, widely used already at industrial scale in several countries, enable producing rather thin hot-rolled strips from liquid steel. Universal casting-rolling aggregates (CRA) developed, by which high quality strips of rather wide assortment can be produced. For a mass production of rather thin (down to 0.8 mm) hot-rolled strips, which can in many applications substitute more expensive coldrolled ones, compact aggregates of endless casting-rolling are recommended, which provide the yield of up to 98%. Concepts of the CRA elaborated for production of steel strips of wide assortment, from ultrathin strips to thick (25 mm) ones. The concepts include application of thermomechanical treatment to increase the mechanical properties of the rolled products from various steels, including low-alloyed ones.

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.

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.

Correction to: Investigation of the cause of the chatter and physical behavior of a work roll in compact endless rolling

The original version of this article contained a mistake. Dong Kyu Lee has been corrected to Dong Gyu Lee. This error is regrettable.

Investigation of the cause of the chatter and physical behavior of a work roll in compact endless rolling

Mechanical devices that contain many rotating elements such as rolling mills inevitably generate vibrations. Vibrations not only cause unnecessary loads but also affect the quality of the manufactured product. Therefore, it is important to identify the causes of vibration in such mechanical devices and control them appropriately. In this study, the various causes of vibration in a rolling process were investigated, and the vibration types present in a compact endless-rolling mill (CEM) process were analyzed and compared. Three typical causes of vibration were analyzed. Based on these results, the cause of the vibrations that occur during changes in the processing conditions in a CEM can be inferred. More specifically, numerical analysis was conducted to study the physical behavior of work rolls (WRs) according to changes in the rolling process conditions. Using these analysis results, a mechanism to produce vibrations similar to those occurring in a CEM was proposed. The results of tracking the center position of a work roll showed that the direct effects of contact pressure on vibration were minimal, and changes in the lubrication type for the physical interaction between a WR and the contact strip were identified as a cause of vibration.

Finite Element and Experimental Analyses on the Formability of Steel Sheets Produced by Compact Endless Cast and Rolling

Although the compact endless cast and rolling mill (CEM) is a promising candidate as a next-generation energy-saving steel process, due to its short history, the formability of the steel sheet produced by the CEM process are not known yet. Herein, drawability and stretchability of low-carbon steel sheets produced by the CEM process are investigated and compared with those of conventional hot-rolled low-carbon steel sheets, to estimate its applicability to industrial parts. Finite element analyses using the Gurson-Tvergaard-Needleman damage model were conducted and compared with the experimental results. Homogeneous microstructure and relatively strong textures of {111}||ND γ-fibers and 〈110〉||RD α-fibers were developed in the CEM-processed steel in comparison with the conventional hot-rolled specimen. The drawn cup of the CEM specimen showed weak earing phenomena, while having higher limiting drawing ratios (2.0 and 1.95 in the experimental and numerical simulation, respectively). Furthermore, a difference in limit dome height between the two specimens is negligible. Therefore, it is confirmed that CEM-processed steels have comparable properties of strength and formability, provide an effective manufacturing process, and exhibit good potential as a next-generation energy-saving process.

Kinematics analysis and optimization of the fast shearing-extrusion joining mechanism for solid-state metal

Dynamical Joining of the solid-state metal is the key technology to realize endless hot rolling. The heating and laser welding method both require long joining time. Based on super deformation method, a 7-bar and 2-slider mechanism was developed in Japan, and the joining time is less than 0.5 s, however the length of each bar are not reported and this mechanism is complex. A relatively simple 6-bar and 1-slider mechanism is put forward, which can realize the shearing and extrusion motion of the top and bottom blades with a speed approximately equal to the speed of the metal plates. In order to study the kinematics property of the double blades, based on complex vector method, the multi-rigid-body model is built, and the displacement and speed functions of the double blades, the joining time and joining thickness are deduced, the kinematics analysis shows that the initial parameters can’t satisfy the joining process. Hence, optimization of this mechanism is employed using genetic algorithm(GA) and the optimization parameters of this mechanism are obtained, the kinematics analysis show that the joining time is less than 0.1 s, the joining thickness is more than 80% of the thickness of the solid-state metal, and the horizontal speeds of the blades are improved. A new mechanism is provided for the joining of the solid-state metal and a foundation is laid for the design of the device.

Study of the Solid-State Joining Process for Endless Hot Rolling

In this study, the joint strength and microstructure of carbon steels welded by an super-deformation joining process in air were investigated. The two block of model steels are overlapped and heated. The steels are welded with 1000% deformation at approximately 1000°C.The joint strengths are evaluated by uniaxial tension testing. The joint microstructures and fractured surfaces are investigated with OM and SEM. The results revealed that the mechanical properties of joint are close to the matrix’s, the grains adjacent to the interface are merged into one grain, which indicates that both blocks are soundly joined,fracture surface was covered with dimple indicating ductile fracture occurred. Joint fracture behavior is initiated by the brittle fracture of scale inclusions and growth around the internal oxides. Surface scale is the most important factor of sound joining.

Discussion of Monitor and Control Strategies to Enhance Butt Joint Quality for Endless Bar Rolling System

Endless bar rolling technology with its intrinsic nature may be used to maximize the production efficiency and reduce production costs. While how to improve the butt joint quality of endless bar rolling system is of research worth with high application value. Hence, a novel control strategy based on the online feedback of process parameters is proposed to enhance the butt joint quality of endless bar rolling system. Firstly, with consideration of the features and state of the art for endless bar rolling system, influence factors over the butt joint quality of endless bar rolling system were analyzed. Secondly, to meet the requirements of high butt joint quality, the quality control strategy of flash butt welding was designed and online feedback from image measurement technology and eddy current array technology were introduced. Finally, the control strategy designed was verified by simulations. The results verify that the process parameters can be adjusted and optimized online via application of these nondestructive testing technologies for the welding quality, consequently, the numbers of shutdown the system is reduced and productivity is improved.

Arvedi ESP first thin slab endless casting and rolling results

The Italian steel producer Acciaieria Arvedi SpA operates a minimill for flat rolled products with a single casting line (maximum width, 1300 mm) in Cremona, Italy, with an annual output of 1·3 million tonnes per year of flat products using inline strip production (ISP) technology, patented by Arvedi. Following this positive experience with its continuous thin slab casting and rolling process, improved in several stages over the years and resulting in a stable production unit of high quality hot rolled strip, it was decided to invest in a new line adopting endless strip production (ESP) technology, also patented by Arvedi, a direct evolution of ISP. Owing to its highly compact layout with a total length of ∼180 m, lower investment costs are incurred for an Arvedi ESP line compared with conventional thin slab casting and direct rolling plants. Production costs are also noticeably lower than those of other thin slab plants and also of the ISP plant already operating in Cremona. Productivity of the ESP plant, based on a single casting line, will be ∼2 million tonnes per year for the first phase and a possible increase in mass flow from the caster may take capacity up to 3 million tonnes per year. Total energy and water consumption of the Arvedi ESP process is very low compared with that of a conventional casting and rolling process: depending on the final product, energy consumption will be 50–70% lower. Owing to endless rolling operations, the production of strip with uniform and repeatable mechanical properties will be possible along the entire strip width and length and with the line's ability to produce ultrathin hot rolled strip gauges of 0·8 mm (and lower), a subsequent cold rolling process will no longer be necessary for many strip applications. The Arvedi ESP plant is the first example of fully continuous production from liquid steel to hot rolled coil on the downcoiler in 4·5 min, and the Cremona plant is the reference plant (master plant) for sales of future ESP lines. The aim of this presentation is to provide data relative to the new plant and the first production results of the endless casting and rolling line. A contract was signed in 2006 with Siemens VAI as principal process and plant supplier of the new plant, and construction was completed in Cremona in autumn 2008. Start-up was completed in the first half of 2009.

強変形せん断接合法の熱間エンドレス圧延への適用

The endless hot rolling concept was introduced to meet the demand for diverse hot-rolled steel sheet products produced by a process that is cost-effective compared with the conventional batch-type process. Endless rolling involves joining the head and tail ends of two bars after rough rolling. A new solid-state joining technology was proposed to instantaneously obtain a joint with high integrity using relatively simple equipment. In this report, we present the mechanism of super deformation joining (hereinafter referred to as “SDJ”) and discuss results of our evaluation of the characteristics of joints to rolling. Super deformation by shearing creates new uncontaminated joint surfaces, and a large upsetting force at the completion of joining promotes metal bonding. SDJ was applied to the joining machine of POSCO POHANG #2HOT, and the use of endless hot rolling in commercial production was started in Jan. 2007. #2HOT is now producing approximately a hundred thousand tons of coils every month by endless hot rolling owing to the stabilization of operation.

強変形せん断接合法の熱間バー接合への適用性評価

The endless hot rolling concept was introduced to meet demand for diverse hot-rolled steel sheet products produced by a cost-effective process compared with the conventional batch-type process. Endless rolling involves joining the head and tail ends of two bars following their rough rolling. By applying solid-state joining utilizing the high temperature of the joined materials for endless hot rolling, a new joining technology was proposed to instantaneously obtain a sound and uniform joint as the base metal using a relatively simple equipment. This report presents type I super deformation joining that obtains a sound joint by incompletely shearing the overlapped materials. In laboratory tests, in the presence of a scale of 14 ∼ 24 μm thickness on the overlapping surface, the joint strength of the center of the joint area was approximately the same as that of the base metal, although reduction of area was smaller than that in the base metal. Obtaining a good joint shape with a small step around the joint area and evaluating the joint properties of wider plates remain as problems to be overcome.

The Arvedi Endless Strip Production line (ESP): from liquid steel to hot-rolled coil in seven minutes

The Arvedi Endless Strip Production plant to be started in Cremona, Italy, is presented. The design and plant configuration of this facility will allow fully-continuous casting and, for the first time in the world, endless rolling of highquality strip in a wide range of steel grades.

強変形せん断接合技術の開発とその実機適用

強変形せん断接合技術の開発とその実機適用

Latest equipment and technology highlights in endless cold rolling mills

In order to improve the productivity and quality results of tandem - cold rolling mills and coupled pickling - tandem lines, VOEST-ALPINE Industrieanlagenbau (VAI) offers a complete range of innovative solutions, which concern as well mechanical equipments as operation and control systems. This paper describes some of these innovations and illustrates them by project examples where these solutions were implemented.

Endless rolling technology for No. 3 hot strip mill at Chiba Works of Kawasaki Steel

Fully continuous finishing rolling, so-called “endless hot strip rolling”, has started in operation for the first time in the world. This unique technology realizes finishing rolling under an uninterrupted tension between rolling stands. As a result, product quality, productivity, and stability of rolling were improved. In addition, ultra-thin strip, like 1.0 mm thickness, has been produced without trouble.