Dissertations / Theses on the topic 'Steel rolling mill'

The steel production is a highly capital and energy intensive industry that due to recent raw materials’ price increase and lowered demand, it has been squeezed and forced to look more deeply on how to add value to the customer at lower operative costs. The project was carried out on site at the ArcelorMittal’s millin Esch-Belval, Luxembourg which comprises an integrated melt shop, continuous casting plant and the rolling mill with the objectives of proposing optimization rules for the cold sector of the rolling mill and to analyze the impact of the future truckbay shipment area. The course of action followed was to draw a Value Stream Map (VSM) in order to understand the plants’ current status and serve as a roadmap to build a discrete event simulation model that after its validation, served as a support tool to analyze what-if scenarios. Similarly, a current status analysis of the  shipment/stock area was conducted collecting statistics about potential truckshipments and finally proposing a series of recommendations for its operation. The main proposed solutions to optimize the rolling mill’s cold sector were:(a) Integer programming model to globally optimize the scrap level when cutting the mother beams to customer size beams. (b) Updating pacemaker parameters and (c) Local process time improvements. Concerning the future truck loading, the simulation model was used as a support tool to dimension the transition area between the cranes’ and forklift operations resulting in a 6-9 bundles buffer capacity. Additionally, the current length-based storage policy was found to have competitive objectives so a turnover class-based storage policy is proposed with A, B, C classes which should provide an improved organization of the stock and travel distance of the cranes. The evaluation of the cranes’ performance remains an issue since there are currently no objective measures like, for instance, travelled distance. Optical measuring devices are suggested as one option to have a performance indicator that would help further investigate root cause problems in the shipping/stock area.

Includes bibliographical references (leaves [105]-110).
The microstructural evolution of AISI304 stainless steel in the Steckel mill rolling process is investigated. This study includes the analysis of mill logs, microstructural examination of the mill product, deformation simulations and post deformation heat treatments. The mill logs from industry contains information about various process variables such as temperature, roll speed, dimensions of the mill strip and forces applied to it during the hot mill rolling process. The strain, strain rates and stresses on the mill strip can be calculated from the mill logs. An understanding of the metallurgical changes during rolling process can be gained by analysing the mean flow stress trends that evolve during rolling. Microstructural examination of the strip in different regions allows us to evaluate the property variations in the strip. This was done with microhardness testing, conventional optical microscopy and electron backscatter diffraction. The middle section of the strip demonstrated full recrystallization whereas the head and tail sections demonstrated no signs of recrystallization. The property differences through thickness proved to be negligible. Laboratory simulation was done in uniaxial compression testing on a Cam Plastometer. It was found that the temperature has a profound influence on the flow stress and the microstructure. The strain rates experienced in hot rolling does not have a significant effect on the flow stress and no measurable effect on the hardness. Heat treatments were done on the deformed uniaxial compression samples. The results of these heat treatments were analysed by two different methods: to deform the sample again after the heat treatment and to compare the yield stress from the first and second deformation and to measure the changes in room temperature hardness with the heat treatment time. The latter led to the development of a time to 50% recrystallization equation that allows the prediction of a direct annealing time for complete softening at the conclusion of the hot rolling process.

Constitutive behavior models for steels are typically semi-empirical, however recently neural network is also being used. Existing neural network models are highly complex with a large network structure i.e. the number of neurons and layers. Furthermore, the network structure is different for different grades of steel. In the present study a simple neural network structure, 3:4:1, is developed which models flow behavior better than other models available in literature. Using this neural network structure constitutive behavior of 8 steels: 4 carbon steels, V and V-Ti microalloyed steels, an austenitic stainless steel and a high speed steel could be modeled with reasonable accuracy. The stress-strain behavior for the vanadium microalloyed steel was obtained from hot compression tests carried out at 850-1150 C and 0.1-60 s-1. It is found that a better estimate of the constants in the semi-empirical model developed for this steel could be obtained by simultaneous nonlinear regression. A model that can predict the effect of chemical composition on the constitutive behavior would be industrially useful for e.g., in optimizing rolling schedules for new grades of steel. In the present study, a neural network model, 5:6:1, is developed which predicts the flow behavior for a range of carbon steels. It is found that the effect of manganese is best accounted for by taking Ceq=C+Mn/6 as one of the inputs of the network. Predictions from this model show that the effect of carbon on flow stress is nonlinear. The hot strip mill at Jindal Vijaynagar Steel Ltd., Toranagallu, Karnataka, India, was simulated for calculating the rolling loads, finish rolling temperature (FRT) and microstructure evolution. DEFORM-2d a commercial finite element package was used to simulate deformation and heat transfer in the rolling mill. The simulation was carried out for 18 strips of 2-4 mm thickness with compositions in the range and 0.025-0.139 %C. The rolling loads and FRT could be calculated within 15 % and 15 C respectively. Analysis based on the variation in the roll diameter, roll gap and the effect of roll flattening and temperature of the roll showed that an error of 6 % is inherent in the prediction of loads. Simulation results indicated that strain induced transformation to ferrite occurred in the finishing mill. The microstructure after rolling was validated against experimental data for ferrite microstructure and mechanical properties. The mechanical properties of steels with predominantly ferrite microstructures depend on the prior austenite grain size, strain retained before transformation and cooling rate on the run-out table. A parametric study based on experimental data available in literature showed that a variation in cooling rate by a factor of two on the run-out table gives rise to only a 20 MPa variation in the mechanical properties.

Estudaram-se os efeitos da fração volumétrica de carboneto eutético e da dureza da matriz sobre a resistência à fadiga térmica de ferros fundidos brancos multicomponentes. Utilizaram-se ligas do sistema Fe-4Cr-V-2Mo-2W-2C, V variando entre 5 e 8% e Fe-4Cr-8V-Mo-2W-2C, Mo variando entre 2 e 5%. Corpos-de-prova com a geometria de discos com seção variável foram temperados e revenidos para obtenção de dois valores de microdureza da matriz: 450 HV e 650 HV. Conduziram-se ensaios de fadiga térmica por 100 e 500 ciclos. Cada ciclo envolveu aquecimento por indução da superfície até a temperatura de 600°C em 10 segundos e subseqüente resfriamento em água por 45 segundos (equalização das temperaturas do núcleo e da superfície). Os corpos-de-prova foram caracterizados antes e após os ensaios de fadiga térmica. Antes dos ensaios, caracterizaram-se os carbonetos eutéticos (tipos, morfologia, fração volumétrica, tamanho, forma e distribuição dos carbonetos) e a microdureza da matriz. Após os ensaios, caracterizaram-se as trincas de fadiga térmica macroscópicas e microscópicas (número e profundidade) e a microdureza da matriz. A nucleação de trincas de fadiga térmica ocorre predominantemente na superfície do corpo-de-prova, induzidas por concentradores de tensão mecânicos e metalúrgicos. As trincas nucleiam na matriz (a rugosidade age como concentrador de tensão mecânico) e em carbonetos (interface carboneto/matriz ou no próprio carboneto). A taxa de nucleação sofre influência da fração volumétrica de carboneto eutético (seu aumento promove aumento da taxa de nucleação) e da dureza da matriz (seu aumento promove diminuição da taxa de nucleação). A propagação de trincas ocorre predominantemente pela interface carboneto/matriz ou através do carboneto. A taxa de propagação sofre influência da distribuição de carboneto eutético. Quanto maior a relação “continuidade de carbonetos/distância livre média entre carbonetos”, maior a taxa de propagação de trincas. A taxa de propagação de trinca diminui com o aumento do tempo de ensaio, independentemente da fração volumétrica de carboneto eutético e da dureza da matriz. O regime de propagação durante os primeiros 100 ciclos é caracterizado pela propagação instável da trinca controlada pela tenacidade à fratura do material; de 100 a 500 ciclos, a propagação é controlada pela magnitude da tensão. O tamanho do corpo-de-prova também influenciou os resultados dos ensaios: o aumento do tamanho promove aumento das taxas de nucleação e propagação. Este resultado é atribuído ao aumento do gradiente térmico ao longo do corpo-de-prova com o aumento do seu diâmetro.
The effects of the volume fraction of eutectic carbides and of the matrix hardness on the thermal fatigue resistance of multicomponent white cast iron were investigated. Alloys Fe-4Cr-V-2Mo-2W-2C, V ranging from 5 to 8 wt% and Fe-4Cr-8V-Mo-2W-2C, Mo ranging from 2 to 5 wt % were used. Disc shaped samples were quench and tempered for obtaining two matrix microhardness levels: 450 HV and 650 HV. Thermal fatigue tests were carried out for 100 and 500 cycles. Each cycle involved high frequency induction heating of the surface to 600°C and subsequent cooling in water during 45 seconds (equalization of the bulk and surface temperature). The test specimens were characterized before and after the thermal fatigue tests. Before the tests, eutectic carbide (type, morphology, volume fraction, syze, shape and distribution of carbides) and matrix microhardness were characterized. After the tests, the macroscopic and microscopic thermal fatigue cracks (number and depth) and matrix microhardness were characterized. The nucleation of the thermal fatigue cracks takes place mostly at the specimen surface, induced by mechanical and metallurgical stress risers. The crack nucleates at the matrix (roughness as mechanical stress risers as well as at carbides (at the carbide/matrix interface or at the carbide itself). The nucleation rate is influenced by the volume fraction of eutectic carbide (the higher the volume fraction, the higher the nucleation rate) and by the matrix microhardness (the higher the microhardness, the lower the nucleation rate). The crack propagation mostly takes place at the carbide/matrix interface or through the carbide. The propagation rate is affected by the carbide distribution. The higher the “carbide continuity/carbide free path” ratio, the higher the propagation rate. The propagation rate decreases with increasing test time, regardless the eutectic carbide volume fraction and the matrix microhardness. The propagation behaviour during the first 100 cycles is characterized by instable crack propagation controlled by the fracture toughness of the material; from 100 to 500 cycles, the propagation is controlled by the stress magnitude. The syze of the test specimen also influenced the tests results: the larger the specimen syze, the higher the nucleation and propagation rates. This is attributed to the effect of increasing thermal gradient across the specimen with increasing specimen diameter.

碩士
國立高雄第一科技大學
電腦與通訊工程系
90
The purpose of this thesis is to design and implement a sixteen stands steel bar rolling mill control system. Steel bar rolling mill is one kind of several profile steel mill plant. The main focus of this thesis is on the "condition of continuous rolling”. And the control technologies of the minimum tension control in roughing /intermedium mill section stands, the loop control in finishing mill section stands, the crop /cobble shear control and the pouring reel control are used to achieve the condition. Also those block diagrams of control programs are listed and discussed.

Spindle failure during fast steel rolling is one of the major equipment failures encountered at Onesteel Whyalla Steelworks (WS). Spindle failure whilst infrequent has been occurring over a long period of time and is a significant cost impost in terms of replacement parts, repair and lost production. Previous attempts at mechanical analysis and spindle redesign have not rectified the problem. This thesis presents an in-depth investigation of the problem and uses a completely new approach, modeling and control, to obtain a solution to the problem.

碩士
國立中山大學
高階經營碩士班
99
Abstract Modernized steel plant belongs to high technique and capital-intensive industry. However, the independent ability of domestic industry in supplying steel plant equipment is so limited. Hence, almost all the equipment of steel plant are provided by foreign supplier. How to assure the big investment of project could be successful eventually, the selection of qualified equipment supplier becomes critical. The evaluation of equipment supplier is so difficult due to too many factors to be considered. Today, the evaluation by personal subjective thinking can’t be applied to the assessment of both technique and non-quantifiable factors. Therefore, it is necessary to develop a wide, comprehensive and practical approach for the evaluation of equipment supplier. This research adopt AHP(Analytic Hierarchy Process) to construct multiattribute decision-making mode. Then, by using the decision-making process to evaluate the equipment supplier. So that such a decision-making behavior is more objective and integrity, and the sequence of priority of equipment supplier can be referred by decision making level. This decision making model is to be applied to the actual case-China Steel Corporation NGO (Non-Grain Oriented) electric steel project which is currently proceeded on. This research will evaluate and distinguish the priority of potential equipment supplier. The top three will be selected for final run of the bidding. Trust the above-mentioned method for selection of equipment supplier is quite in order. It not only helps to reduce the risk but it also increases both efficiencies and quality of decision making. Through study, we acknowledged that equipment technology management is the most important item. Per priority and weight in whole evaluation factors, the top five are selected. Finally, the top three equipment suppliers in NGO project are selected as well.

No
A steel hot rolling mill subjects steel slabs to high temperatures and pressures in order to form steel coils. We describe the scheduling problem for a steel hot rolling mill. We detail the operation of a commercial decision support system which provides semi-automatic schedules, comparing its operation with existing, manual planning procedures. This commercial system is currently in use in several steel mills worldwide. The system features a very detailed multiobjective model of the steel hot rolling process. This model is solved using a variety of bespoke local and Tabu search heuristics. We describe both this model and the heuristics used to solve it. The production environment is highly unstable with frequent, unforeseen events interrupting planned production. We describe how the scheduling system's models, algorithms and interfaces have been developed to handle this instability. We consider particularly the impact on existing planning and production systems and the qualitative improvements which result from the system's implementation.

碩士
國立高雄應用科技大學
金融系金融資訊碩士在職專班
106
In the face of globalization international economic situation and regional integration trend, Taiwan’s SME’s only to strengthen business management and to enhance industrial competitiveness in order to meet complicated and volatile economic environment. Besides continue to innovate,it is at any time on the enterprise medical examination-enterprise diagnosis, early detection of potential problems and weaknesses and tow improve, in order to ensure the sustainable development of enterprises. The case study of W Company,diagnosis process from the inside out, step by step. First of all, the external analysis of the steel pipe fitting industry belonging to the case company, from the industry upstream and downstream, the development of the process and the current situation, industry characteristics and import and export ractices,industry revenue and profit status analysis, the industry development in Taiwan and SWOT analysis and five force analysis.Second,the case of company to diagnose and analyse the breakeven profit of the profit basis, and on production,marketing,human resources,research and development, finance, administration, information management for diagnosis, the use of scholars travel Chu-yi You’s Finance/Management/Strategy analysis(FMSA), and comprehensively summarizes the financial urgency indicators of the case company, improves the management feasibility index and the policy feasibility index,and after the cross-analysis, the case study of company development problem, and then put forwardthe propose solutions, as a reference to provide business to enhance business performance.

碩士
國立中正大學
企業管理所
97
The steel industry is the foundation of all industries, it is the basic industry of the national construction and the national defense industry, and it has also being called the mother of industries. Due to the consideration of economic development and security reason of the national defence, the governments of most countries often taking high tariff, quota to limit or classifying as the specific project of importing etc., in order to protect the development of the national steel industry. The production facilities, equipments, raw materials and energy consumptions are all more costly than the general industries. Thus, the steel industries are highly capital and skill intensive. The steel industry in Taiwan has been through and strived for half a century. Nowadays, the complete foundation of the steel industry in Taiwan has been established and proceeds to grow up. However, the breakout of the global financial crisis last year causes the sudden stagnation for the demand of the steel-made products, and brings the severe crisis ever for the steel industry. In addition, the drastic fluctuation of the international petroleum price also causes the production costs to go up as well as the prices of a variety of energy and raw materials. Under the severe environment today, the profits in the steel industries have being shrinked. That forces the managers in this industry to take steps to deal with this situation. In addition to making great efforts to develop the new products, to increase the profit margins, and to maintain basic and smooth operations of produciton lines and the prerequisite in the scale of economy, managers can’t help but make more cost-effective decisions. Among these decision problems, the optimal productin planning problem and product mix problem are two of the most crucial problems to the steel industry. Thus, the objective of this research is to develop the mathematical programming models to cope with these two decision problems. By considering the hot-rolled line of wire rods and reforming bars material for real industry production, we take various kinds of limiting conditions under the realistic environment into the mathematical programming models, and obtain the best production planning and the optimal product mix for the case steel firm so that the corporate''s minimum total production costs and the best profit-making level can be achieved.