Bar Rolling Research Articles

THE CONCEPT OF OPTIMAL BAR ROLL PASS DESIGN. REPORT 3. SPACE OF ROLL PASS DESIGN SCHEMES

Based on the system approach and on the experience accumulated at theoretical data, design and industrial development of bar rolling, the Chair “Metal Forming” of Ural Federal University develops the universal “Concept of optimum calibration”. The general ideology of roll pass design optimization is stated in article “The concept of optimal bar roll pass design. Report 1. Basic statements”. In the article “The concept of optimal bar roll pass design. Report 2. Calibers space” the structure, appointment and maintenance of the information block reflecting so-called “calibers space” are considered. According to the general concept of optimization, the following task that needs to be solved is the problem of creation of information block so-called “space of schemes of roll pass design” which will be used further as the first space of optimization. The concept “space of schemes of roll pass design of a bar-rolling mill” is considered as the space containing all possible virtual schemes of rolling of a concrete profile on the concrete rolling mill. For formation of the space of schemes of rail calibrations it is necessary to generate separate virtual schemes and to consistently fill this space with them. Thus, the space of calibrations schemes is formed of separate unique calibrations schemes. For formation of this space from separate calibers, it is offered to use the specialized algorithms which are “generators of schemes of roll pass design”. As an example, the structure of the generator prepared for creation of such space for rolling of railway rails is considered. It is revealed that all known rail calibrations can be presented in the form of essentially the same block structure which is used as the central element of the schemes generator of rail calibrations. Usage of described and similar generators in relation to rolling process of a concrete profile on the concrete rolling mill allows obtaining spaces of acceptable schemes of calibrations. Such spaces are necessary for the subsequent optimizing procedures for search of the best calibration scheme from all possible calibrations. The considered approach for creation of calibrations schemes space can be used during creation of computer-aided engineering systems and optimization of calibrations of rolling rolls.

Surface Pressure Treatment of Titanium Alloy Bars by Transverse Rolling

The results of the process experimental studies of titanium alloys transverse rolling bars are presented. The efficiency of using such a process for reducing the surface roughness is shown. The samples were tested after rolling on corrosion-resistance resistance, ultrasonic testing, and also the study of the metal microstructure was made. For the bars transverse rolling in industrial conditions, a tooling was developed and created, intended for installation on operating centerless lathes instead of tooling with a cutting tool. Production tests of new equipment has shown its good performance.

Roll Pass Design and Simulation on Continuous Rolling of Alloy Steel Round Bar

Reasonable design of roll pass schedule is the prerequisite for a successful shape rolling process. In this paper three dimensional elastoplastic finite element simulation with thermal mechanically coupled analysis is applied to study the roll pass design of the hot continuous rolling of Ф100mm alloy steel round bar from 200mm×200mm square cast bloom. Due to the larger plastic strain occurring at the corner of the workpiece, the method of bias meshing for the cross section is adopted to fine the elements of surface and corner area. The stress, strain, temperature distribution, rolling force and rolling moment of the hot continuous rolling are simulated to analyze the plastic deformation and the position and cause of possible rolling defects in order to confirm the roll pass design. The simulated results of cross section sizes of rolled steel at the exit of each pass are in good agreement with the measured values.

Decomposition Method for New Single-Machine Scheduling Problems From Steel Production Systems

Production scheduling is a crucial task in modern steel plants. The scheduling of a wire rod and bar rolling process is challenging in many steel plants, which has a direct impact on their production efficiency and profit. This article studies a new single-machine scheduling problem with sequence-dependent setup time, release time, and due time constraints originated from a wire rod and bar rolling process in steel plants. In this problem, jobs have been assigned to batches in advance. The objective is to schedule the batches and jobs on continuous time to minimize the number of late jobs. A mixed-integer program is created as a baseline model. A baseline method is used to solve this NP-hard problem by solving the baseline model. We further design a two-stage decomposition method after analyzing the characteristics of this problem. Both actual and simulated instances with varying sizes are solved by using the proposed methods. The results demonstrate that the baseline method can only solve some small-scale cases, while the decomposition method can solve all small-scale cases and some medium-scale cases. Finally, we reveal the impacts of different instances on the performance of the proposed decomposition method. Note to Practitioners —This article deals with a new single-machine scheduling problem arising from an industrial wire rod and bar rolling process. A baseline method is given to tackle this problem by solving an established mixed-integer program. Afterward, a two-stage decomposition method is proposed such that an industrial size problem can be solved. Computational results of both actual and simulated cases show that it is more efficient than the baseline method in solving the scheduling problem. It can get an optimal solution of the concerned problem with one-week-scale batches and jobs in short time, thereby proving the readiness to put it in industrial use.

Performance and robustness assessment of H∞ active anti-roll bar control system by using a software environment

Abstract The active anti-roll bar system has been proven to be one of the most effective solutions to improve roll stability of heavy vehicles. In a previous work, the authors proposed an H∞ controller for this system. The Genetic Algorithms method was used to handle the vehicle roll stability and the energy consumption of the actuators via the Pareto optimality. This paper aims to assess the overall effectiveness of the proposed controller with nonlinear heavy vehicle models, which are already set up in the TruckSim® software. The controller is then evaluated in hard conditions to show the high performance and robust with the nonlinearity effects, such as the load distribution between the two axles, the side wind gusts and the abrupt steering. To conduct testing of the H∞ active anti-roll bar control system, we propose a co-simulation structure between TruckSim® and Simulink®: the nonlinear vehicle model is determined from TruckSim®, based on using the block S-function of Simulink. Meanwhile, the controller and the actuators are built directly in the Matlab/Simulink ® environment. The validation results are made through two different types of heavy vehicles: a tour bus and a truck, using a selection of different velocities and scenarios. The results show that by using the H∞ active anti-roll bar control system, in comparison to the passive anti roll bar system, roll stability is improved to minimise the risk of vehicle rollover.

Creep Features of Ti-600 Alloy at the Temperature of 650°C

Creep tests were carried out on one kind of near alpha titanium alloy named after Ti-600 alloy at the temperature of 650°C, and with the stresses of 150MPa, 200MPa, 250 MPa, 300 MPa and 350 MPa, respectively. The alloy ingot was conventionally forged and rolled to diameter 18mm bars. The creep samples were cut from the rolling bars and were solutioned at 1020°C for 1 h, air cooling, then aged at 650°C for 8 h, air cooling (STA). Steady state creep rate and the stress exponent n at different stresses were calculated for the alloy. Threshold stress σ0 was introduced to get the true stress exponent p. Creep deformation mechanism was also investigated. The results indicated that the steady state creep rate will increase with the rise of stress, and the creep time will also be shortened at the same time. At 650°C, the threshold stress is 83.8MPa. The value of n and p is 7.7 and 3.3 respectively for the alloy crept at lower stress region (150-200MPa); and which is 2.1 and 4.7 respectively for the alloy crept at relatively higher stress region (200-350MPa). Constitutive equations of steady state creep rate were also established for the alloy crept at 650°C. The creep deformation for the alloy is controlled by dislocation slipping at lower stress region, and which is mainly controlled by dislocation climbing and subordinately controlled by dislocation slipping at higher stress region.

Challenges of Nb Application in Thermomechanical Processes of Steels for Long Products

Nb is a classical microalloying element in the design of thermomechanical treatments in low carbon steels for flat products applications. However, its use in medium-high carbon grades, as occurs in hot rolling of bars, is less common. This is, in part, because of the diversity of characteristics required to those grades of steels and the less knowledge about the function of Nb in these cases. Consequently, less information is reported concerning thermo-mechanical processing of Nb microalloyed steels in long products applications. In this case, it is necessary to consider the singularities related to these processes, such as the short interpass times and the wide range of chemical compositions usually applied on these products. Short interpass times result in high strain rate values that can lead to metallurgical changes on the mechanisms occurring during the hot rolling must be considered. Moreover, the high Carbon contents applied in long products, usually between 0.20–0.40%, can influence the Nb solubility and precipitation in each stage of the process: prior to hot rolling on the reheating furnace, during the process and after hot rolling, depending on the cooling strategy adopted and on the post-rolling heat treatments that can be applied. This paper analyses different singularities associated with the use of Nb microalloying for long products. Several aspects, such as the partial or complete dissolution of the Nb prior to hot rolling, its role in the control of austenite microstructure and its incidence in the final microstructure and mechanical properties, will be considered.

Конструкция плиты для сборных дорожных покрытий

Experience in the operation of prefabricated concrete pavements with intensive traffic of heavy vehicles has shown that despite a high strength of the concrete slabs themselves it is necessary to arrange strong foundations. While laying concrete on the ground residual deformations are accumulating in it due to pressures which are initiated by elastically bending plates when vehicles are passing that leads to formation of voids under the plate and cracks in the plate itself. In order to increase rigidity of the plate (reduction of its settlement during the passage of vehicles) the author has proposed to arrange plates with two longitudinal ribs, and the plates themselves are to be laid on loose soil mixed with cement. The ribs are proposed to be placed on roll bars, i. e. symmetrically with respect to a longitudinal axis of the plate at a distance from each other which is equal to the distance between wheels of the calculated vehicle on one axis. In order to determine dependence of plate rigidity on a shape and a size of a cross section in longitudinal ribs calculations have been made while using a PC “Lira” and a finite element method. A finite element model of the plate has included 19152 nodes and 18943 finite elements. An elastic foundation has been modeled by vertical elastic links which are in every bottom node. The plate has been loaded with a load which is equivalent to the load from a calculated vehicle wheel at four points: a wheel in the middle of the plate; a wheel on the corner of the plate; two wheels at the same time on the line which is perpendicular to the longitudinal axis of the plate and located at the beginning (or end) of the plate; two wheels at the same time on the line which is perpendicular to the longitudinal axis of the plate and passing through its center. The following forms of a longitudinal rib having the same crosssectional area have been studied at the beginning: triangular, oval (semicircle) and rectangular. In the context of plate rigidity increase the most optimal form has been a triangular shape. Height differences in such a plate are the least in case of load action. So, for example, in comparison with a typical plate (plate without longitudinal ribs), presence of longitudinal ribs of triangular cross – section increases plate rigidity by an average of 50 % depending on the location of the calculated wheel on the plate (39–64 %). After determining an optimal shape of cross section for longitudinal ribs the dependence has been found for plate rigidity and it depends on a height of longitudinal triangular ribs. While having a constant volume of the plate and a constant a size of the rib base (32 cm) (approximate width of a calculated vehicle wheel) a rib height and a plate thickness have been changed. The calculations have made it possible to determine dependence of the plate rigidity on a height of a longitudinal rib. It has been determined that as for the given volume and dimensions of the plate the optimal rib height is 25 cm.

Mechanical anisotropy and local ductility in transverse tensile deformation in hot rolled steels: The role of MnS inclusions

The mechanical anisotropy and effects of MnS inclusions configuration on the local ductility in hot rolled bars with 0.03% sulphur were experimentally investigated and statistically regression analyzed. Results show that the elongation and reduction of area decline significantly as the angle between the gauge length and the transverse direction decreases, while the tensile strength and yield strength vary little. The reduction of area in transverse tensile tests of various rolled bars ranges widely from 6.5% to 38.1% and the differences in engineering stress–strain curve profile are mainly reflected in the local deformation stage. MnS inclusions configuration in the surface adjacent to fracture were classified into three types according to the morphology and three-dimensional distribution. When the type of MnS transitions from C to A to B, the reduction of area decreases obviously and area of ribbon-like fractures where most local deformation performs declines as well. Multiple linear regression of the parameters of MnS inclusions shows that the reduction of area is more sensitive to the length of single MnS inclusion or aggregation of tiny MnS inclusions and the local density of MnS inclusions. Voids in matrix tends to nucleate between the parallel MnS inclusions and along the line connecting two MnS inclusions with rounded or blunt tips and then grow and link up to form cracks. Besides, cracks can also be directly induced by the sharp tips of tiny MnS inclusions. In conclusion, the aggregated tiny MnS inclusions of type B should be avoided and the evenly distributed spindle-shaped MnS inclusions of type C are expected in steels requiring favorable transverse mechanical properties.

Tensile and impact behaviour of thermo mechanically treated and micro-alloyed medium carbon steel bar

In the present study, a comparison between thermo mechanically treated (TMT) and direct air cooled micro-alloyed hot rolled (MAHR) steel bar has been made in terms of microstructure, texture and mechanical properties. Tensile and Charpy impact tests were performed as a part of the mechanical investigation. Tensile strength and impact toughness values of TMT bar were higher than those of MAHR bar. It was also noticed that TMT bar exhibited better resistance to both ductile and brittle fracture at high and low temperatures compared to MAHR steel. This can be corroborated owing to the presence of fine tempered martensite at the periphery, a mixed microstructure of granular bainite, ferrite, and degenerated pearlite as an intermediate layer and a mixture of ferrite and pearlite at the core of the TMT bar. On the other hand, a coarse ferrite-pearlite phase mixture was present throughout the cross section for MAHR steel and sounded responsible for lower strength and impact toughness properties. Additionally, fractions of higher angle grain boundaries (HAGBs) in the core and smaller martensite packet around the rim section were also contributed beneficially to resist the cleavage crack propagation in TMT rebar. The higher intensity of gamma fiber of MAHR rebar has contributed lowest ductile-brittle transition temperature. Numerous cleavage cracks which were initiated from inclusions or carbide particles were also found responsible for crack propagation during both ductile and brittle types of fracture.

Effect of process isothermy on a stress-strain state during rolling of bars from titanium alloy

Effect of process isothermy on a stress-strain state during rolling of bars from titanium alloy

Residual mechanical behavior of (SD 500) hot rolled TMT reinforcing steel bars after elevated temperatures

This paper intends to present an experimental investigation carried out to study the influence of elevated temperatures on residual mechanical properties of super ductile (SD 500) hot rolled deformed TMT bars in comparison with conventional hot rolled and ordinary TMT steel bars. The study also presents a detailed analysis of effect of heating on residual ductility characteristics of SD 500 rebars after exposure to various temperatures using various prevalent methods in the available literature. The experimental study involved heated residual tensile tests carried out on rebar specimens after being exposed to elevated temperatures and subsequently cooling down to ambient conditions covering a wide range of available sizes (8 mm, 10 mm, 12 mm, 16 mm and 20 mm). A detailed description of the test results, observations and discussion on results obtained from the testing, including comparisons with the available information in the existing relevant literature have been presented with particular emphasis on the influence of high temperature on ductility of super ductile (SD 500) hot rolled TMT bars. The results so obtained suggest better performance of SD TMT over ordinary TMT and conventional hot rolled rebars in terms of key aspects of mechanical behavior after exposure to elevated temperatures. The outcomes of this study have direct implications on procedures used for predicting the ultimate behavior of structural elements during and following exposure to elevated temperatures.

Research on Three-Roll Screw Rolling Process for Ti6Al4V Titanium Alloy Bar

Abstract The effects of both the microstructure and the original grain size on three-roll screw rolling process of Ti6Al4V titanium alloy bar were studied in the present work. The microstructure of Ti6Al4V titanium bar had a great influence on the mechanical properties of the rolling bar. When the original size was large, the grains were apparently refined but the microstructure was uneven. But for semi-finished titanium bar composed of fine equiaxed grains, the grains after rolling were fine and uniform. During the rolling process, the Ti6Al4V titanium alloy microstructure changed from equiaxed structure to the basket-weave one. After annealing at 800℃ for 1.5 hours and then cooling in air, the average tensile strength decreased from 984 MPa to 964 MPa; while after annealing at 950℃ for 1.5 hours and then cooling by water, and aging at 540℃ for 6 hours then cooling by air, the average tensile strength increased from 979 MPa to 1107 MPa.

Effect of Heat Treatment on Tribological Characteristics of CuAl<sub>10</sub>Ni<sub>5</sub>Fe<sub>4</sub> Nickel Aluminum Bronze

Al bronze are the choice of material for relatively high wear applications besides appreciable mechanical and corrosion properties. In present work, the effect of different heat treatment processes on tribological characteristics of Ni-Al bronze (CuAl10Ni5Fe4, UNS C63000) has been studied. The hot rolled bar of 30 mm diameter was subjected to annealing, quenching and aging processes separately, consequently their effect on microstructure was studied and co-related with tribological characteristics. The formation and nucleation of various phases due to the thermal treatments were observed using optical microscopy. The wear behavior was studied using ball on disk arrangement with 100Cr6 ball and Ni-Al Bronze samples as disk. The characteristics and mechanism of wear track was studied using scanning electron microscope. It was observed that the water quenched sample followed by aging at 300°C exhibited best tribological characteristics.

Mathematical modelling of controlled cooling and properties of hot rolled steel

Numerical model of controlled cooling in the production of steel hot rolled bars was developed. The numerical model and algorithm are completed to solve problems in controlled cooling of hot rolled bars in cooling beds. The controlled cooling is performed by special placement of hot rolled bars on cooling beds. By numerical model of controlled cooling is possible to predict a transient temperature field, microstructure evolution and hardness of round steel bars during their cooling in cooling beds. The numerical model of transient temperature field is based on control volume method. The hardness and microstructure distribution in steel bars has predicted by using equations of austenite decomposition kinetic. The algorithm for prediction is based the real chemical composition. Numerical model and computer program were experimentally verified by experimental work in a real industrial production of low-alloyed steel bars. The verification of developed numerical model was performed by comparison of simulated with experimentally evaluated results hardness and cooling curve.

THE CONCEPT OF OPTIMAL BAR ROLL DESIGN. REPORT 2. CALIBERS SPACE

Based on the system approach and on the experience accumulated at theoretical data, design and industrial development of bar rolling, the Chair “Metal Forming” of Ural Federal University develops the universal “Concept of optimum calibration”. The general ideology of roll pass design optimization is stated in article “The concept of optimal bar roll pass design. Report 1. Basic statements”. In the article “The concept of optimal bar roll pass design. Report 2. Calibers space” the structure, appointment and maintenance of the information block reflecting so-called “calibers space” are considered. According to the general concept of optimization, the following task that needs to be solved is the problem of creation of information block so-called “space of schemes of roll pass design” which will be used further as the first space of optimization. The concept “space of schemes of roll pass design of a bar-rolling mill” is considered as the space containing all possible virtual schemes of rolling of a concrete profile on the concrete rolling mill. For formation of the space of schemes of rail calibrations it is necessary to generate separate virtual schemes and to consistently fill this space with them. Thus, the space of calibrations schemes is formed of separate unique calibrations schemes. For formation of this space from separate calibers, it is offered to use the specialized algorithms which are “generators of schemes of roll pass design”. As an example, the structure of the generator prepared for creation of such space for rolling of railway rails is considered. It is revealed that all known rail calibrations can be presented in the form of essentially the same block structure which is used as the central element of the schemes generator of rail calibrations. Usage of described and similar generators in relation to rolling process of a concrete profile on the concrete rolling mill allows obtaining spaces of acceptable schemes of calibrations. Such spaces are necessary for the subsequent optimizing procedures for search of the best calibration scheme from all possible calibrations. The considered approach for creation of calibrations schemes space can be used during creation of computer-aided engineering systems and optimization of calibrations of rolling rolls.

Fabrication Technology and Material Characterization of Hot Rolled Cylindrical Fe-6.5 wt. % Si Bars

Cylindrical Fe-6.5 wt. % Si bars of 7.5 mm diameter were successfully fabricated from an as-cast ingot through three rolling stages, with 10 total passes: rough rolling at 850–900 °C and 8–10 m/min; medium rolling at 800–850 °C and 10–15 m/min; finish rolling at 800–850 °C and 12–18 m/min. The evolution of the microstructure, texture, and ordered structure were studied, and the mechanical properties were investigated. Results indicated that the grains were refined by the hot bar rolling. Area fractions of the {100}<011> and {011}<100> oriented grains decreased to 0 during hot bar rolling, whereas the {100}<001>, {011}<211>, and {112}<110> components increased. Furthermore, the γ fiber with {111}<110> component was dominant. After the hot bar rolling, the DO3 ordered phase was suppressed, and the B2 ordered domains were refined. Ductility of the as-rolled bar was better than that of the rotary-swaged bar, due to the absence of the DO3 ordered phase, and refinement of the grains in the rolled bar. Moreover, discontinuous dynamic recrystallization (DDRX) occurred at a high deformation rate during the rough rolling, and continuous dynamic recrystallization (CDRX) appeared at a low strain rate during the finish rolling. Hence, hot bar rolling technology is an excellent process for the fabrication of Fe-6.5 wt. % Si bars.

Effect of Reheating and Deformation Processes on DWTT Performance for Heavy Gauge Pipeline Steel

DWTT (Drop weigh tear test) is an effective way to evaluate the fracture propagation for pipeline steel. The effects of slab reheating temperature, soaking time, single pass reduction ratio during recrystallization zone rolling and transfer bar ratio during non-recrystallization zone rolling on DWTT performance were studied for heavy gauge pipeline steel. And the grain refinement and toughening mechanism were discussed. It was found that the grain in the core of the plate can be refined by reducing the reheating temperature, increasing the single pass reduction ratio during recrystallization zone rolling and setting suitable transfer bar ratio during non-recrystallization zone rolling, which promote the DWTT property improvement for heavy gauge pipeline steel. The 30.9mm heavy gauge pipeline steel plate was industrial produced and the X70 UOE welded pipe with dimension in Φ1219×30.9mm was manufactured. The DWTT 85%FATT (fracture appearance transition temperature) of pipe body is as low as -20°C.

THE INFLUENCE OF MICROSTRUCTURAL FACTORS AND HEAT TREATMENT ON THE CORROSION RESISTANCE OF REINFORCING STEEL CLASS A 600

Currently, hot rolled bar reinforcement class A600 of low-alloy steels in the delivery condition has a high tendency to this very specific kind of destruction as stress corrosion cracking under tension (SCC). However, there are cases of collapse of pre-stressed concrete structures, in most cases initiated corrosion cracking under stress, put the problem this type of fracture is particularly acute. In stress corrosion cracking cracks occur, the occurrence of which depends not only on the structural state of the material, the type and level of stress, but also on the degree of aggressiveness of the environment in which the operation occurs. In this regard, it is very important to establish how the corrosion resistance of class A600 reinforcing steel varies depending on the change in the chemical composition, microstructure, the level of applied and residual micro-stresses, and various modes of heat treatment. The purpose of this paper is to study the effect of the above factors on the resistance of low-alloyed reinforcing steel class A600 stress corrosion cracking It is shown that the sensitivity of the reinforcement to stress corrosion cracking is largely determined by the chemical composition (mainly carbon content), the type of microstructure and the level of residual micro-stresses. The influence of heat treatment regimes on the corrosion resistance of A600-grade reinforcing steel in nitrates solutions is investigated. It is shown that the use of additional heat treatment (normalization and improvement) increases the corrosion resistance of steel. High corrosion resistance steel reinforcement has only a carbon content at the lower limit of the vintage composition, which is provided by the structure of homogeneous bainite with mechanical properties at the level of strength class A600. With higher mechanical properties, the steel reinforcement has lower corrosion resistance.

THE USE OF ENERGY EFFICIENT TECHNOLOGIES IN THE FRAMEWORK OF IMPLEMENTATION OF INVESTMENT PROJECT «ORGANIZATION OF PRODUCTION OF ROLLED BAR IRON WITH THE CONSTRUCTION OF SMALL-SECTION WIRE ROLLING MILL» OJSC «BSW – MANAGEMENT COMPANY OF HOLDING «BMC»

This article reveals the main energy efficient solutions and innovations implemented in the framework of the investment project «Organization of production of rolled bar iron with the construction of small-section wire rolling mill» in the open joint stock company «Belarusian metallurgical works (BSW) – Management Company of Holding «Belarusian Metallurgical Company (BMC)». This project was included in the list of the most important projects for the creation of new enterprises and industries that are crucial for the innovative development of the Republic of Belarus. Supplier of technology and equipment for the project were made by the company Danieli & C. Officcine Meccaniche SpA (Italy). The modern and unique equipment used in this investment project allows to use more than 90% of fuel and energy resources (by using the heat recuperator of flue gases, heat recovery boiler, recuperative burners, etc.). Implementation of the project allowed to carry out the maximum processing of production and to receive new production with higher added value.