Casting Plant Research Articles

Application of Modern Automation and Control Processes in Direct Chill Casting Production Equipment

It is well known that magnesium melts exhibit a strong exothermic reaction with oxygen and water and present an explosion hazard during processing. To ensure a safe working environment for operators in magnesium (Mg) direct chill foundries, it was therefore necessary to develop the whole processing chain, from melting, alloying, casting and heat treatment through to the extrusion of Mg profiles. The automation, simulation and process control was a key factor in this development. To fully automate the process, it was necessary to adapt an existing casting plant, to develop both a new launder system from the furnace to the die and new sensors (level control, visualization) and to create control software that is able to control the plant and continuously log various parameters of the casting process for maintenance via the Internet.

Metallurgical, operational and economic benefits of SMART®/ ASTC technology in continuous casting

The technological package SMART®/ASTC, developed by VAI and already applied in many continuous casting plants worldwide, combines automatic strand taper control (ASTC) with hydraulically adjustable SMART®segments. It allows to improve significantly the internal quality of both slabs and blooms. The principle and working mode of these equipments are described and their multiple benefits are presented.

Flow, Thermal and Microstructural Analysis during Cast Rolling of Steel in In‐line Strip Production Process

A mathematical model was developed to describe the in‐line hot rolling deformation and recrystallization behaviour of austenite after the solidification on a thin slab casting plant. The most significant features of the cast rolling process were taken into consideration: through‐thickness thermal gradients, inhomogeneous stress and strain, temperature discontinuity between the strip and the rolls. A HSLA (High Strength Low Alloy) steel has been chosen to perform the experiments of cast rolling. The characteristic constants ruling the microstructural evolution of that steel were computed and integrated into the computational module which manages the structural stress‐strain and strain rate computation. The developed approach is based on the Navier‐Stokes’ equations which were used to compute the speed field in the strip during the deformation. Then a model providing a proper constitutive equation was structured on the basis of the Yada's model based on evolution of the dislocation populations. The use of the Navier‐Stokes’ formalism allows to reach the resolution of the structural problem from the data measured easily during the industrial practice (i.e. speed of the rolled product at the entry and at the exit of a stand, the temperature of the rolled material). The validation of this computational approach was obtained by a comparison between the prior austenite grain size of the strip in different positions of the hot rolling process, as well as by a comparison between the computed deformation power and the measured one provided by the engines moving the rolls.

An LCA study of a primary aluminum supply chain

The production of aluminum billets—starting from the conversion of bauxite to alumina, the processing of alumina to aluminum, and the final cast product—is studied using a Life Cycle Assessment (LCA) approach. The aluminum supply chain consists of a refinery, a smelter, and a casting plant. In the LCA model, the environmental loads of four different case scenarios were investigated. The scenarios included various approaches employed for improving the environmental performance of the system for the production of 1 ton of aluminum metal. The final impact assessment results for the overall environmental loads of the supply chain showed cumulative decreases of 2.2% and 3.8% for Scenarios 2 and 3, respectively. In Scenario 2, scrap metal was reduced from the casting plant. For Scenario 3, the reduction of scrap metal from casting was accompanied by improvements of both energy efficiency and reject rates at the smelter. A significant cumulative decrease of 32.8% was obtained in Scenario 4, which was mainly due to the reduction of red mud from the refinery by about 50%.

レンズモデルによる鋳造作業者の造形動作の評価(バイオ・人間工学)

In this paper, evaluation of work procedures from the aspect of ergonomics is conducted for the purposes of skill acquisition and reduction of workload. For our research target of casting process in real casting plant, workload is analyzed through motion study and OWAS (Ovako Working Posture Analysis System), which is a standard index for workload analysis, and the result is then applied into a psychology model, called Lens model. From the above, difference in operation motion between skilled and un-skilled worker can be considered.

Model for the industrial prediction of carbonitride precipitation in HSLA steels cast by a thin slab casting plant

In HSLA steels (high strength low alloys), the most important strengthening mechanisms are grain refinement and precipitation hardening by second phases. Therefore, the control of precipitation and chemical composition of the second phases is essential. A model based on thermodynamics alone does not predict the precipitation phenomena that are observed in thin slabs. This paper introduces a kinetic model that makes it possible to take into account the influence of the thin slab casting process on the precipitation and composition of carbonitrides.

Implementation of a cold tundish at the CST continuous casting plant

Companhia Siderurgica de Tubarao (CST) has continually been carrying out process improvements in order to increase and maintain the slab production to 5 Mt/year. The technology that makes it possible to start the continuous casting using a tundish at cold temperature is one of the developments that will help CST to meet that goal. This paper describes the implementation of the cold tundish at CST, using the approach already adopted at other plants of the Arcelor Group. Through the implementation of the cold tundish process it was possible to reduce not only the time for setting-up the continuous casting machine, but also the gas consumption and the noise at the casting platform, thus improving the operators environment.

Application of discrete event simulation for robust system design of a melt facility

This paper presents a methodology to identify robust operating regions through the selection of controllable factory variables, using discrete event simulation. A casting plant melt facility was used as an industrial test bed to develop these techniques. A robust system design was determined by response surface analysis of key production parameters. Furthermore, robust operating policies that maximise throughput, while minimizing work-in-progress and thus energy consumption were identified.

Algorithme D’optimisation Par Colonie De Fourmis Avec Matrices De Visibilité Multiples Pour La Résolution D’un Problème D’ordonnancement industriel

This paper presents an augmented Ant Colony Optimization (ACO) algorithm which we use to solve a single-machine scheduling problem found in an aluminium casting plant. The orders in this scheduling problem have sequence dependent setup times and three distinct objectives must be minimized. We show how the use of multiple visibility matrices contributes to the improvement of solution quality for this multi-objective problem.

Neural Fuzzy Mold Level Control for Continuous Steel Casting

Mold level control has been a major control task for continuous casting plants. The system involves nonlinearities such as stick-slip friction in the sliding gate, time-delay, friction force variations between molten steel and the inner wall of mold, and nozzle logging/unclogging. These complex problems should be solved to control mold level for steel cast. In this paper, we propose a neural fuzzy mold level control technique for solving these complex problems and give experiment studies to show the mold level control in continuous casting process.

APPLICATIONS OF OPTIMIZATION AND INVERSE MODELING TO ALLOY WHEEL CASTING

Although many major foundries use software, such as ProCAST TM and MagmaSOFT TM , to simulate filling and solidification of castings for process design, a number of the required input parameters (such as material properties and boundary conditions) are not well known. This has motivated the need for an optimization tool that uses an inverse modeling approach to determine these parameters, given appropriate experimental measurements. This article describes optimization strategies that have been used to tune computational models to plant conditions. These models are then used in a second phase of optimization that improves the operation of the casting plant thereby playing a major role in reducing costs and improving productivity and quality of cast products.

Quantitative assessment of segregates in continuously cast slabs by electron probe microanalysis

Due to the limited solubility of individual elements in the crystal lattice of steel, an enrichment of the residual melt and furthermore a formation of micro and macro segregates will appear during solidification of the steel melt. Depending on the chemical composition of the steel, the operation parameters of the casting plant and the slab dimension, the segregates will be formed with different intensities. The knowledge of the segregation effects is imperative for further processing of slabs and the subsequent products.The electron probe micro analyser (EPMA) makes feasible an objective assessment of the segregates due to solidification over the entire slab thickness. This is carried out by concentration mapping (CM), which is a method for the quantitative determination of element distributions over certain areas on the sample. In this paper some results taken from an investigation on steel grade 13 CrMo 4–5 are presented, and some casting technological measures derived from these results are proposed.

Tribological behavior of coatings for continuous casting of steel

There are a large number of steel making processes in which great demands are made on the surface behavior of several components that come into direct contact with steel under various conditions. Continuous casting is mainly a heat-extraction process. The mold must rapidly transfer heat from the steel to the cooling water. In continuous casting, steel solidification starts when it comes in contact with the mold liner's interior surface. The key job of every mold consists in cooling the molten steel in a controlled way. The mold is a major element in the overall economics of a continuous casting plant which explains the number of innovative approaches to increase the working life (length of time during which the mold shows acceptable dimensional stability to meet the quality standards) or to satisfy the new demands to be met by the mold liners. Coating the mold inner is a firmly established practice, in particular with electrolytic surface modification treatments, to cope with the various operating needs including low wettability, high hardness, good wear resistance and low cost. Several pin-on-disk tests were carried out to determine the friction and wear behavior of different coatings. The friction partner for all coatings was a K30 (WC–Co 9%) chip, the sliding speed was 10 cm/s at a temperature of 250°C and a load of 5 N. The sliding time was 200 h (720 000 revolutions for a radius of friction 16 mm). Additional tests for shorter times allowed verification of the morphological evolution of the wear track. All coatings were also evaluated using a scratch test. This test introduces stresses at the interface between the coating and the substrate as the sample is displaced at constant speed. The critical load ( L c) recorded from the scratch test translates the complex intrinsic properties of a specific coating into a very reproducible figure of great practical significance. This paper presents a tribological characterization of conventional electrolytic coatings, bare copper alloys and some new surface solutions for continuous steel casting molds.

A new steelmaking concept at Saldanha

For Saldanha steel’s meltshop, which is fed by mainly liquid hot metal and DRI, a tailor made steel plant design was required.SMS-Demag’s CONARC-system was selected, because it perfectly meets the requirements resulting from this raw material condition.Charging of liquid hot metal, dephosphorization, decarburization, and melting of DRI, is smoothly carried out in the new furnace concept, which combines BOF and EAF operation.Downstream of the meltshop a thin slab casting and rolling plant is installed, which is able to produce thin gauges of 1 mm with extraordinary high surface quality.

Lot Sizing and Scheduling in an Automated Casting Plant

The studied casting plant has only a furnace and several molding machines in order to produce a known demand of different types of items which can be made of different alloys. There are two important and linked decision levels: for each programming period, which alloy should be produced in the furnace, and the quantity of items to be produced in each molding machine. Two cases are distinguished: a single alloy can produce all items, and different alloys are needed in order to produce the items. Assuming that the furnace is the production bottleneck, efficient problem-based solution methods are proposed.

Gain Scheduled PI-Control of Strip Casting Plant

The controller design for a double roller laboratory plant for continuous casting of thin steel strip is described. A nonlinear state-space model which represents the dynamics of the solidification and forming process has been developed. Based on this model the control concept using the force as the controlled variable has been derived. Variations in static and dynamic behaviour depending on the actual operating point are compensated by gain scheduling PI-controller parameters.

Characterization of Airborne Dust from Two Nonferrous Foundries by Physico-chemical Methods and Multivariate Statistical Analyses.

Airborne particulate matter was sampled at a copper smelter and at an aluminum casting plant. Size, shape, quantity, and microlocalization of chemical species in the particulates were measured using closed cassettes, cascade impactors, scanning electron microscopy, X-ray diffraction, infrared and atomic absorption spectrophotometries, secondary ion mass spectrometry, and photoelectron spectroscopy. Cluster and principal components analyses were used in interpreting results. Aerosol chemistry varies as a function of size, and composition becomes more complex as the aerosol size drops into the respirable fraction and lower. Surface chemical properties are evidenced where, generally, volatile species are enriched. A few site-specific elements and characteristics were identified. The formation of particulates may often be related to process and practices, yet the actual distribution of species in the air remains an intricate matter.

Zebra Mussels as Biomonitors for Organic Contaminants in the Lower Great Lakes

Abstract Zebra mussels were collected from 24 sites in Lake Erie, Lake Ontario and the St. Lawrence River between 1990 and 1992. Composite samples of whole mussels (15 sites) or soft tissues (9 sites) were analyzed for residues of organochlo-rine pesticides and PCBs to evaluate zebra mussels as biomonitors for organic contaminants. Mussels from most sites contained measurable quantities of most of the analytes. Mean concentrations were (in ng/g, whole mussel dry weight basis) 154 ΣPCB, 8.4 ΣDDT, 3.5 Σchlordane, 3.4 Σaldrin, 1.4 ΣBHC, 1.0 Σendosulfan, 0.80 mirex and 0.40 Σchlorobenzene. Concentrations varied greatly between sites, i.e., from 22 to 497 ng/g for ΣPCB and from 0.08 to 11.6 ng/g for ΣBHC, an indication that mussels are sensitive to different levels of contamination. Levels of ΣPCB and Σendosulfan were highest in mussels from the St. Lawrence River, whereas mirex was highest in those from Lake Ontario. Overall, mussels from Lake Erie were the least contaminated. These observations agree well with the spatial contaminant trends shown by other biomoni-toring programs. PCB congener class profiles in zebra mussels are also typical for nearby industrial sources, e.g., mussels below an aluminum casting plant contained 55% di-, tri- and tetrachlorobiphenyls versus 31% in those upstream. We propose the use of zebra mussels as biomonitors of organic contamination in the Great Lakes.

Flow Control of Molten Steel by Electromagnetic Brake in the Continuous Casting Mold.

In order to solve problems involved with the curved type continuous caster and high speed casting by controlling the steel flow in the mold, the Electromagnetic Mold Brake Ruler (EMBR) using a static magnetic field was installed and tested at No. 2 continuous casting plant at kwangyang Works, POSCO. The meniscus profile and surface velocity were measured to optimize EMBR operation and slab qualities were inspected under various operating conditions of the equipment, especially using two different types of core. The plant trials showed different results for each core type. High position of core which was a simple linear type located near the Submerged Entry Nozzle (SEN) outlets had a detrimental effect on the surface and internal qualities of slab. But low position of core which has a magnetic insulator at the core center and is located below the SEN reduced the sub-surface defects and non-metallic inclusions in the slab, especially at high throughput casting conditions.

Manufacturing integration

The integration requirements for manufacturing applications are determined by increasing productivity, flexibility and quality demands. Driven by the industrial needs for manufacturing integration such as co-operation of application systems, consistency of the information model and continuity of communication through all management and control levels, the VOICE project has mainly addressed the application of CIMOSA to distinct industrial scenarios which commonly require information integration in a heterogeneous infrastructure environment: troubleshooting aid and maintenance in assembly line; order planning and tool management in “big part” manufacturing and in an aluminum melting and casting plant. During the project, an integrating infrastructure composed of a set of distributed services, supporting the execution of the modelled manufacturing processes, has been developed and prototypes of services have been implemented and tested in the different VOICE industrial pilots.