Path bridging: A novel local search methodology for optimizing scheduling in highly constrained continuous galvanizing line operations

Local search for weighted sum coloring problem

The Continuous Galvanizing Line (CGL) has mechanisms in which electric drives are interconnected by the processed strip. The subject to investigation is the entrance zone, the mechanism for welding the ends of the rolls, the drive strip to ensure the continuity of the galvanizing process. During welding the speed of the input zone is zero and the process of selecting a strip from the input drive is in progress at the input of the technological zone. After the welding operation is completed, the value of strip speed exceeds the strip processing speed in the technological zone. To study processes in an interconnected electromechanical system, a mathematical description of the electric drives and the processed strip. The study of such interconnected electric drives should be carried out. The research results are presented in the form of oscillograms of the operation of electric drives when performing various technological operations.

Steel coils are welded end to end for processing in a continuous galvanizing line of a cold rolling mill. Failure of the welds in the line during processing results into mill stoppages causing huge production downtime. An automated ultrasonic-based non-destructive measurement system for assessing the weld integrity of 0.6–2-mm-thick steel sheets immediately after welding is described. The system was designed to detect any physical weld defects, viz., lack of fusion, expulsion, cracks, etc., which compromises the integrity of weld leading to its failure in the processing line. A high-frequency ultrasonic probe with an integrated water chamber was designed for enabling high-speed non-contact automated inline inspection of the weld considering the limited inspection time available in the mill (40 s). A prototype scanning system was made using the developed ultrasonic probe which was successfully able to detect the weld defects formed in actual plant samples.

An efficient local search framework for the minimum weighted vertex cover problem

The main process variables to produce galvanized dual phase (DP) steel sheets in continuous galvanizing lines are time and temperature of intercritical austenitizing (tIA and TIA), cooling rate (CR1) after intercritical austenitizing, holding time at the galvanizing temperature (tG) and finally the cooling rate (CR2) to room temperature. In this research work, the effects of CR1, tG and CR2 on the ultimate tensile strength (UTS), yield strength (YS), and elongation (EL) of cold rolled low carbon steel were investigated by applying an experimental central composite design and a multivariate regression model. A multi-objective optimization and the Pareto Front were used for the optimization of the continuous galvanizing heat treatments. Typical thermal cycles applied for the production of continuous galvanized AHSS-DP strips were simulated in a quenching dilatometer using miniature tensile specimens. The experimental results of UTS, YS and EL were used to fit the multivariate regression model for the prediction of these mechanical properties from the processing parameters (CR1, tG and CR2). In general, the results show that the proposed multivariate model correctly predicts the mechanical properties of UTS, YS and %EL for DP steels processed under continuous galvanizing conditions. Furthermore, it is demonstrated that the phase transformations that take place during the optimized tG (galvanizing time) play a dominant role in determining the values of the mechanical properties of the DP steel. The production of hot-dip galvanized DP steels with a minimum tensile strength of 1100 MPa is possible by applying the proposed methodology. The results provide important scientific and technological knowledge about the annealing/galvanizing thermal cycle effects on the microstructure and mechanical properties of DP steels.

Intelligent Quality Monitoring System as an Effective Tool for Quality Control in Continuous Galvanizing Line at Tata Steel

In a continuous galvanizing line (CGL), three so-called pot rolls are usually used to guide steel strips in a zinc pot. Generally zinc pot rolls are coated with WC–Co to protect the pot roll surface from severe corrosion by molten zinc. The degradation process of the WC–Co coating was evaluated through analyses of coated pot rolls used in a CGL zinc pot for 33 and 56 days. The rolls were coated by high velocity oxygen fuel spraying with WC–12% Co powders that were produced through sintering and crushing processes. On the surface of the WC–Co coated rolls, several types of deposits were observed including top dross (Fe2Al5 inter-metallic compound) that might induce dross defect on the surface of galvanized steel. The diffusion depth of zinc into the WC–Co coating used for 33 days was only 10 μm, but some areas were severely attacked along cracks within the coating layer because of a preferential reaction with aluminum. Through SEM study, we observed that not only zinc but also aluminum diffused into the WC–Co coating after being in the zinc pot for 56 days. In some cases, Al–Fe–Zn layers were observed on the surface of the spray coating. Those layers were analyzed to be Fe2Al5 as their chemical compositions are very similar to those of Fe2Al5 top dross. However, they are not the Fe2Al5 dross, but the reaction products between molten zinc and the coating layer according to their morphologies.

<div class="htmlview paragraph">A Hot Dip Simulator has been constructed at Inland Steel Research Laboratories to support product development and process optimization. The Hot Dip Simulator can reproduce the heat treating, galvanizing, and galvannealing processes that occur on a continuous galvanizing line. The equipment and computer control system provide a high degree of experimental control and flexibility. This allows simulation of the galvanizing and galvannealing processes at coating lines located at Inland's Indiana Harbor Works and at l/N Kote. The primary use of the Hot Dip Simulator has been to determine the effects of process variables on the galvannealing process and on galvannealed products.</div>

Numerical analysis of wiping jet flow in Continuous Galvanizing Line

Galvanizing facilities are highly energy intensive operation with electrical and fuel energy representing a significant share of their total energy usage. Furnaces are extensively used in galvanizing process. Production process expertise along with the energy conservation practices can play a significant role in proper usage of energy at galvanizing facilities. Therefore, benchmarking galvanizing energy consumption and understanding the specific energy consumption by various elements are critical. E-GEPDSS (Enhanced Galvanizing Energy Profiler Decision Support System) was built to identify this specific energy consumption by using heat balance analysis. The use of E-GEPDSS does not hinder the production process and the user may run the model for different set of operating conditions and observe the results. The results obtained from the analysis will help the user to make energy enhancing decisions.;This research involved the analysis of galvanizing operations focusing on the furnace side of energy consumption. The furnace heat balance was built and applied using the data collected from a host company during the plant visit. Sensitivity analysis were done to study the impact of changing process and product parameters on the total heat loss from the system.;From the energy analysis conducted for the furnace equipment at the host facility, it was found that the useful heat absorbed by the product is only 50% of the heat supplied to the furnace and rest of heat dissipates as losses. Heat losses from surfaces, walls, water cooling and stack are significant. Heat loss due to opening and phase change heat loss seem not to be significant. Emissivity, dimensions of the furnace, temperature of the zones, thermal conductivity of insulation materials and the strip temperature at the entry and exit of each zone have significant impact on the total heat loss. In the future, the model will be applied extensively to more galvanizing lines in order to help the galvanizers to have a better understanding about the energy consumption while producing their product.

A common measurement problem in industry is when a variable of interest has a spatial or two-dimensional distribution. Typical applications occur in the processing of rolled metal strip or in the production of paper. This paper deals with the estimation and control of zinc coating mass in a continuous galvanizing line. This problem has inherent spatial characteristics. The proposed algorithm estimates both cross-machine direction and machine direction components. The algorithm has been implemented in an industrial setting, and data from this installation is presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

本論文では, 適応ファジィモデリングを提案し, 本手法の鉄鋼プロセスにおける連続溶融亜鉛メッキライン(CGL)の付着量制御への適用について述べる.CGLでは, 大きなむだ時間が存在するため, メッキ鋼板の亜鉛付着量を精度良く制御するためには, フィードフォワード制御が必要である.このフィードフォワード制御を精度良く行うためには, 制御モデルが非線形特性を十分記述できることと, 長期に亙っての制御精度を保証・維持するための適応機能, の2つが不可欠である.本論文では, これらの2つを満たしたファジィモデリングの適用について紹介する.また, 適用例を用いて我々の手法が有効であることを示す.

An Overview on the Texture Evolution of Cold Rolled IF Steels and Zn Coating During Galvanizing and Galvannealing

Pre-quenching induced lath structures and enhanced TRIP effect to optimize the strength-ductility of ultrahigh-strength hot-galvanized steel

The Traveling Salesman Problem (TSP) is one of the most widely discussed problems in combinatorial optimization. It has many practical applications in fields of distribution and logistics management, scheduling problems etc. Since these problems are hard, in addition to exact algorithms, research has focused on heuristic techniques to solve TSPs. Computational time is a major concern while solving large TSPs. This problem intensifies further if the graph becomes asymmetric (ATSP). Metaheuristics like tabu search are widely used to find a reasonably good tour fast. Given the practical relevance of ATSPs the lack of literature on it is surprising. The primary objective of our work is to implement tabu search for large ATSPs to obtain good tours in reasonable time. To do that, we make the underlying graph sparse by developing an elite tour based preprocessing scheme. Tabu search is implemented on this reduced graph which results in a reduction of computational time. We also create diversified initial tours suitable for multi-start tabu search in this process. We present our computational experiences both on randomly generated instances and benchmark instances.