Rolling Operation Research Articles

Characterization of hot rolled scales-root cause identification and remedial action

Hot rolled steel strips are produced by rolling of steel slabs of 210mm thickness at 1150–1200°C through roughing and finishing mills of a hot strip mill to a thickness of 1.6–6mm. During hot rolling, some adherent oxides, known as scales, is formed on the strip surface in the reheating furnace prior to hot rolling due to high temperature oxidation. But these scales should be removed away by the usual hydraulic descaling method during hot rolling operation. Primary scale that is not removed by de-scaler in hot strip mill and subsequently gets rolled into the surface is known as rolled in scale (RIS).This RIS creates serious surface quality problem in the finished product. So scales are removed by acid treatment, known as Pickling operation. Here HR steel strip is passed through the acid bath. But the efficiency of the picking process depends on the micro-structural characteristics of scale, e.g. presence of different phases in scale, interfacial morphology. Thus the microstructural characteristics have to be understood for efficient removal process.There are several methods of determining the nature of the oxide scales present on the hot rolled sheets. Amongst the conventional techniques, Scanning Electron Microscopy, EDS analysis, X-ray characterization and electron X-ray Diffraction techniques (XRD) are presently being used for scale characterization.In current study different types of rolled in scales have been characterized depending on the following parameters: appearance, prone grades, photographs of defect, metallographic characterization, present information, knowledge and experience at hot strip mill. Finally based on the analysis the root cause and remedial action of different types of scale have been identified.

Non-contact charge temperature measurement on industrial continuous furnaces and steel charge emissivity analysis

Continuous furnaces are commonly used for steel billet reheating before a rolling operation. It is necessary to perform a number of measurements to set-up and operate the optimization system of the furnaces correctly. A charge temperature measurement using infrared detectors can be one of the usable measurement techniques. This non-contact measurement method is based on the detection of infrared radiation emitted from a measured surface. The radiation intensity depends on the surface temperature and emissivity, which is one of the most important parameters for infrared measurements. Advantages of the non-contact temperature measurement, as well as some problems regarding the surface emissivity, are presented. The direct steel billet temperature measurement procedure using infra-red detectors, emissivity determination procedures, and example results are introduced. It is shown that steel emissivity can vary from approx. 0.17 to 0.8, depending on the surface state, scale formation, and wavelength interval. These problems are critical for the charge temperature measurement using the infra-red detectors, and are discussed in this paper.

Multi scale cellular automata and finite element based model for cold deformation and annealing of a ferritic–pearlitic microstructure

Numerical modelling of microstructure evolution during cold rolling and the subsequent annealing of a two phase ferritic–pearlitic sample under an α/γ phase transformation regime is the subject of the present work. The multi scale model based on the digital material representation taking into account exact representation of the microstructure morphology is used in the research to investigate inhomogeneous strain distribution during cold rolling. Obtained results are then incorporated into the discrete cellular automata model of static recrystallization. Data transfer between the finite element and cellular automata models is performed by means of the interpolation method based on the Smoothed Particle Hydrodynamic. Details about the developed cellular automata model of static recrystallization are presented within the paper. The complete multi scale model is finally validated against a series of experimental cold rolling and subsequent annealing operations. Various annealing conditions were used as case studies to prove robustness of the developed numerical approach.

Advances in predicting damage evolution and fracture occurrence in metal forming operations

The paper reports the latest trends in prediction of damage evolution and fracture during metal forming processes. Both uncoupled (e.g. the Oyane law) and coupled (e.g. Continuum Damage Mechanics-based laws) models are outlined and applications of the two approaches are presented. In particular, three application cases, which may be characterized by fracture events, are discussed: (i) a cold forging sequence, where a fracture criterion is utilized in combination with a damage accumulation law; (ii) a hot stamping operation conducted on high strength steel sheets, where the Continuum Damage Mechanics approach is used instead of the conventional one based on Forming Limit Curves; (iii) a hot rolling operation, where the Lemaitre law is modified to take into account the influence of the temperature and initial microstructure.

Dynamical Reliability of Four-high Rolling Mill under Stochastic Strip Characteristics Excitation

It has great significance to research the dynamical reliability probability of rolling mill rolls system for improving its stochastic dynamical reliability and products quality rolled. The fifth-octave vertical vibration stochastic dynamical model of rolls system was established, and the pseudo-excitation method was used to obtain the power spectral density and the variance variation characteristics with the rolling speed and time under stationary rolling force stochastic excitation, and the stochastic dynamical reliability of rolls system was analyzed by using the first-passage failure criterion. The results show that rolls system reliability has strong relationship with stochastic excitation intensity and thickness tolerance of rolled strip and damping of the roll gap, among them, the stochastic excitation intensity and thickness tolerance of rolled strip have greater influence on the dynamical reliability of rolls system than other parameters, and rolls system stochastic dynamical reliability can be improved by mainly controlling the rolled plate/strip accuracy and roll gap damping, thus improving the quality of rolled strip in rolling operation.

Effect of high pressure rolling on weld-induced residual stresses

The formation of large residual stresses continues to be a problematic side effect of all common welding processes. In this work, localised high pressure rolling of gas metal arc welds to relieve these residual stresses has been investigated using strain gauging and neutron diffraction. Rolling was found to remove undesirable tensile stresses and even induce large compressive ones, though only when applied after rather than during welding. Strain measurements taken during combined welding and rolling operations show that this is because material at the weld line continues to yield as it cools. This erases any beneficial effect on the stress distribution of rolling at high temperature. A method of rolling using an oscillating force is also presented and found to be just as effective as the equivalent static force process.

Large-Area Nanotemplate Process and Its Application to Roll Imprint

This study developed a stitching process for unit element nanotemplates based on step and repeat imprinting for use in enlarged soft mold fabrication. This mold was subsequently used for the custom-developed roll-to-plate UV nanoimprint process. The distinctive features of roll UV imprinting include the following: (1) the UV source is embedded within a roll mold made of quartz so that it can illuminate a resist coated on either a transparent or an opaque substrate, (2) the press-contact between the resist and soft mold wrapped around the quartz mold was designed to synchronize the rolling operation with the linear motion of the substrate, which helped minimize the residue thickness, and (3) a compressed pneumatic force was applied along the contact line of the roll imprint, which helped attenuate any possible level mismatch on the stitched mold surface.

Deep rolling of austenitic steel AISI 304 at different temperatures – near surface microstructures and fatigue

AbstractIn metastable austenitic stainless steelsthe formation of high dislocation densities, compressive residual stress states, strain-induced martensite and nanocrystalline regions are the most important consequences of mechanical surface treatments leading to retarded fatigue crack initiation as well as propagation. These properties can be altered in a characteristic way applying different deep rolling temperatures. The main objective of this paper is to clarify the role of the different near surface microstructures introduced by deep rolling operations on the fatigue behaviour of steel AISI 304 especially in the low cycle fatigue region. For this purpose special experimental techniques were applied allowing deep rolling operations in the temperature range between −192 °C and +700 °C. Results clearly show that the amount of strain induced martensite by deep rolling in near surface layers is less important than the stability of the microstructures under fatigue loading.

Effects of construction-related factors on chip seal performance

Chip seal is an economical type of asphalt pavement that is widely used in countries such as Turkey, Australia, South Africa and New Zealand. However, unlike hot mix asphalt pavements, the performance of this type of pavement can be affected by many different parameters. Although these parameters have been identified in the literature, the extent to which each of these parameters affects the performance of chip seal has not yet been determined. The leading parameters affecting chip seal performance are those related to construction, including the adhesion capability of the aggregate used in construction, natural dust amount of the aggregate, ambient temperature during construction, bitumen temperature in the bitumen distributor tanks, time between bitumen spraying and aggregate spreading, time between aggregate spreading and rolling, time between construction stages, surface temperature during construction, aggregate and bitumen designs, in situ plate test values and per cent embedment of the aggregates. To determine the effect of these construction parameters on pavement performance, they were observed and measured on five test roads. The chip-sealed test roads were monitored for 1year with nondestructive tests and observations to determine which construction-related parameters affect the performance of the pavement. The study results indicated that macrotexture loss is the most important deterioration factor in chip-sealed pavements; initial texture depth is also important with respect to the long-term performance of chip-sealed pavements. Rolling operations is another important factor for the performance of chip seal. If rolling operations are performed at high ambient temperatures, the per cent embedment of the aggregate will increase, causing the chip seal to deteriorate more rapidly. Consequently, the ambient temperature during the construction of chip seal is important; thus, chip seal should not be constructed at ambient temperatures lower than 30°C or higher than 43.5°C.

Recycling of steel plant mill scale via iron ore sintering plant

During the processing of steel in steel mills, iron oxides will form on the surface of the metal. These oxides, known as mill scale, occur during continuous casting, reheating and hot rolling operations. Mill scale is a valuable metallurgical raw material since it contains 65–70% iron. JSW Steel Ltd is a 7 Mtpa integrated steel plant and generates 270 t of mill scale per day. Most of the materials of steel plant wastes are recycled through sinter making in most of the countries. Because of its physical, chemical and mineralogical properties, it can be used as a raw material in a process like sintering. The mill scale contains high amounts of Fe and low amounts of silica and alumina. Thus, recycling it through the sintering process helps in the saving of raw materials like iron ore and limestone. This paper presents preliminary findings of a study that investigates the potential for recycling steel mill scale in the sintering process. Experiments were conducted using the mill scale in sinter making from 0 to 70 kg/t of sinter. The total Fe and FeO contents of the sinter increased with the increase in mill scale addition. The sinter productivity decreased with the increase in mill scale addition due to a decrease in sinter bed permeability. The sinter strength and sinter mean size initially increased and reaches a maximum at mill scale addition of 40–50 kg/t of sinter and afterwards declines with the increase in mill scale addition. Sinter reduction degradation index and reducibility decreased with the increase in mill scale addition due to the increase in FeO content. Except sinter productivity, other desired sinter properties can be obtained with the use of 40–50 kg mill scale per tonne of sinter.

Roller Type and Operating Speed Effects on Rye Termination Rates, Soil Moisture, and Yield of Sweet Corn in a No-till System

A field experiment was conducted in Cullman, AL, to evaluate the effects of three different rollers/crimpers on the termination of a rye (Secale cereale L) winter cover crop, soil moisture, and yield of sweet corn (Zea mays saccharata L.) in a no-till system. The following roller types were tested: a straight bar roller, a smooth roller with crimper, and a two-stage roller. These rollers were tested at operating speeds of 3.2 km·h−1 and 6.4 km·h−1. The three rollers/crimpers were compared with a smooth drum roller (no crimping bars) plus glyphosate applied at rate 1.0 kg·ha−1 used as a control. Rye termination dates were selected to be 3 weeks before the recommended sweet corn planting date, which is in the beginning of May for this region. Data indicate that at 3 weeks after rolling for all seasons (2006–2008), 100% rye termination was reached with the smooth drum roller and glyphosate. Two weeks after rolling, average rye termination rates by rollers/crimpers alone were 54.6%, 30.0%, and 50.4% in 2006, 2007, and 2008, respectively. Three weeks after rolling, rye termination rates increased only by ≈10% compared with 2 weeks after rolling. These termination levels were below the recommended rate of 90% termination necessary for planting a cash crop into the cover residue. Lower rye termination was probably caused by rolling the rye in an early growth stage (flowering stage). The rollers’ operating speed did not influence rye termination rates. Similarly, roller type did not affect soil moisture during the first and second week after rolling. Applying glyphosate with rolling did not increase yield of sweet corn in any of the three growing seasons, and in 2006, sweet corn yield was lower compared with the roller alone treatments. These results are important to vegetable organic systems, in which use of herbicides is not allowed. No significant difference in sweet corn yield was found between operating speeds of 3.2 km·h−1 vs. 6.4 km·h−1 and between the assigned treatments in all growing seasons. However, significant differences in sweet corn yield were detected between the years, most likely as a result of different weather patterns. The lowest sweet corn yield of 3513 kg·ha−1 was reported in 2007 as a result of severe drought in spring and summer of 2007. The highest yield of 15,613 kg·ha−1 was recorded in 2006. In 2008, the yield was 10,158 kg·ha−1. Although the different roller designs were not as effective in ending the rye cover crop compared with the glyphosate treatment, sweet corn yields were unaffected. Multiple rolling operations over the same area could be useful if greater rye termination levels are required without the use of a herbicide, but this recommendation should be tested experimentally in more detail.

Lead as Test Rolling Material for Hot Complex Rolling of Steel

The low deforming force of Lead (Pb) and the proximity of its stress-strain response make it readily preferred as test material for laboratory modelling of complex hot steel rolling. Structural steel recrystallises from a temperature of approximately 500 °C. For Pb, this process starts within the range of-3 °C to 0 °C. The room temperature rolling of Pb delivers reasonable information of hot rolling of steel. This is however dependent on various parameters which include; deformation rate, degree of deformation, alloying elements and previous heat treatments. This work studies the deformation behaviour of Pb 99.94 Cu by carrying out rolling operations at different deformation rates and deformation degrees. Tension and compression tests were used to determine the ultimate tensile and compression strength, the yield strength and the Young´s Modulus, respectively. Flow curves were subsequently determined and compared to that of selected structural steels. The microstructures were analysed and were correlated with the deformation parameters taking cognisance of the role of recrystallisation during the rolling process.

Semantic data integration and monitoring in the railway domain

Information integration is a key for further growth of efficiency in management decisions for the railway domain. In the context of the EU project InteGRail (funded in the 6th framework programme) an integration approach leveraged by ontologies known from the semantic web and logic-based reasoning mechanisms has been successfully demonstrated. To this effect existing heterogeneous monitoring data acquired across the European railways (in the context of rolling stock, infrastructure, operations and traffic management) is logically integrated according to a formal information model. Based on distributed reasoning mechanism decentralised data and inferred knowledge does not have to be aggregated in a central repository but can be transparently accessed by applications independently from where it is acquired. We explain how the proposed techniques facilitate integration, analysis and interpretation of distributed observation data in the railway domain. In addition, the implementation of the presented approach...

Particle swarm optimisation-based support vector machine for intelligent fault diagnosis

In this paper, we present an application of support vector machines (SVMs) and particle swarm optimisation (PSO) to fault diagnosis. SVMs have been successfully employed to solve regression problem of nonlinearity and small sample. However, the practicability of SVM is affected due to the difficulty of selecting appropriate SVM parameters. PSO is a new optimisation method, which is motivated by social behaviour of organisms such as bird flocking and fish schooling. The method not only has strong global search capability but also is very easy to implement. Thus, the proposed PSO-SVM model is applied to diagnosis operation of rolling bearing failure in this paper, in which PSO is used to determine free parameters of SVM. The experimental results also indicate that the SVM method can achieve greater accuracy than grey model, artificial neural network under the condition of availability of small training data.

Effect of Niobium/Molybdenum Microalloying on SS316LN Steel

In recent years SS316LN microalloyed stainless steel is preferred for use as jacket material for Nb3Sn superconductor strands/wires. In the present investigation, microalloyed SS316LN is prepared in a vacuum induction melting furnace; Niobium and Molybdenum in their ferroalloy stage are considered as alloying element. This microalloyed steels are cast in water cooled copper mould. The tensile strength and elongation are measured and the fracture surface is studied under scanning electron microscope. It is observed that, there is a reduction of tensile strength and decrease in hardness of the steels prepared with addition of either/both the alloying elements; however there is an increase in ductility, which is helpful for cold rolling operation. From the micrographs it is observed that nitride precipitates are formed along the grain boundary, but formation of chromium carbide precipitates is reduced.

Texture and mechanical properties of API X100 steel manufactured under various thermomechanical cycles

Abstract The role of various finishing rolling operations on the texture and mechanical properties has been studied for API (American Petroleum Institute) X100 steel. It has been found that both the finish rolling start and end temperatures influence the final texture and thus, the mechanical properties and the anisotropy of these properties. High temperature finish rolling produces a very weak texture. This texture is a result of dynamic recrystallization, and associated with large grain size and inferior mechanical properties. A slightly delayed start of accelerated cooling led to the formation of large fraction of polygonal ferrite and increased the ductility at the expense of strength. Near-isothermal rolling in the range of 790–810 °C produced the highest texture intensities of both the desired {3 3 2}〈1 1 3〉 and the undesired {1 1 3}〈1 1 0〉 components. The latter texture components as well as the {1 0 0}〈1 1 0〉 component, mitigated the positive effect of the {3 3 2}〈1 1 3〉 component. On the other hand, a relatively higher finish rolling start temperature (840 °C) and a low finish rolling end temperature (700 °C) suppressed the strength of the {1 1 3}〈1 1 0〉 and {1 0 0}〈1 1 0〉 components, while the {3 3 2}〈1 1 3〉 component apparently was sufficient for the reduction of the anisotropy of mechanical properties. Partial deformation of the quasi-polygonal ferrites also appeared to have contributed to increasing the strength of the investigated steel.

Role of stacking fault energy on the deformation characteristics of copper alloys processed by plane strain compression

Abstract Samples of Cu–Al and Cu–Zn alloys with different compositions were subjected to large strains under plane strain compression (PSC), a process that simulates the rolling operation. Four compositions in the Cu–Al system, namely 1, 2, 4.7 and 7 wt.% Al and three compositions in the Cu–Zn system of 10, 20 and 30 wt.% Zn, were investigated. Adding Al or Zn to Cu effectively lowers the stacking fault energy (SFE) of the alloy and changes the deformation mechanism from dislocation slipping to dislocation slipping and deformation twinning. True stress–true strain responses in PSC were documented and the strain hardening rates were calculated and correlated to the evolved microstructure. The onset of twinning in low SFE alloys was not directly related to the low value of SFE, but rather to build up of a critical dislocation density during strain hardening in the early stage of deformation ( ɛ

Quasi Sliding Mode Control of Differential Linear Repetitive Processes With Unknown Input Disturbance

Linear repetitive processes are a distinct class of 2-D systems, which have extensive applications in the practical industry, such as long-wall coal cutting and metal rolling operations. In this paper, the observer-based sliding mode control (SMC) problem is investigated for differential linear repetitive processes with unknown input disturbance. The main advantage of the proposed scheme is that it eliminates the need for the state variables and pass profile variables to be fully accessible for its control. This is possible through the use of a sliding mode controller, which performs its control by employing state estimates obtained from the sliding mode observer. A sufficient condition for the existence of desired observer is established in terms of a linear matrix inequality, and an SMC law is synthesized to guarantee the stability along the pass of the overall closed-loop process. It is shown that the proposed control scheme ensures the reachability of the sliding surfaces in both the state estimate space and the estimation error space. An illustrative example is given to demonstrate the effectiveness of the proposed designed scheme.

Integrated approach to maintaining the temperature regime on continuous hot-strip mills

The hereditary nature of structural and textural changes that take place in metal during its continuous hot rolling makes it necessary to adopt an integrated approach to control of the main parameter of the rolling operation – the temperature of the metal as it is being rolled. It is shown that a systems approach needs to be taken to maintaining the prescribed temperature regime on all sections of the mill line, from the heating of the metal prior to rolling to cooling of the finished product as it is dispatched to the next production line.

Studies of the rolling of ribbed bars using the deform software package

The software package DEFORM-3D is used to construct a mathematical model of the rolling of ribbed bars that makes it possible to determine the change in the shape of the bar, the stress state of the metal in the deformation zone, and the energy-force parameters of the rolling operation. The model accounts for the strain-hardening of the metal during cold deformation and the periodic nature of this process. Experiments confirm that the model adequately describes the actual deformation process. The results obtained from the model can be used to design new production equipment and tools for the given method of metal-shaping and to assess the feasibility of using existing rolling mills to form ribs on different types of flat-rolled semifinished products.