Font Size: a A A

Multi-Parameter Coupled Numerical Simulation Of Strip Hot Rolling

Posted on:2007-04-16Degree:DoctorType:Dissertation
Country:ChinaCandidate:G M ZhangFull Text:PDF
GTID:1101360182983104Subject:Mechanical design and theory
Abstract/Summary:PDF Full Text Request
Hot rolled steel strip is an important steel product, and it is widely used in manyfields. The past nearly half century has seen the rapid progress of strip production. Ascritical evaluation standards of quality, strip crown and flatness are traditionally theprimary concerns in the production and research of strip hot rolling. In recent years, moreand more attentions have been paid to the microstructure and property of rolled strip,especially for newly developed steel grades such as HSLA (High Strength Low Alloy)steels, dual-phase steels, and IF (Interstitial-free) steels, many of which are rolled tocorrect and homogeneous property specifications. It is therefore increasingly important tocontrol and improve the microstructure and property of rolled strip.To meet the society demands and the competitive market, steel companies have tomake continuous improvement to the precisions of shape, dimensions and properties ofstrip product, meanwhile shorten the lead time and reduce the development and productioncost. Advanced development tools are needed to enable them design and analyze the steelproduct and rolling process in an efficient and productive manner, moving away fromrelying upon the accumulated experience of expensive and time consuming trial and errorapproach. With the development of computer technology, numerical simulation has gainedwidespread application in strip rolling industry. Mathematical models of strip hot rollingbased on the fundamental principles of continuum mechanics, heat transfer, and physicalmetallurgy can provide more scientific and effective tools for the design and control ofrolling process to obtain steel products with desired shape, dimensions, and mechanicalproperties.Various phenomena such as mechanical, thermal and metallurgical changes occurduring the hot rolling of steel strip, and there exists complex interplay between them.Accurate modeling of strip hot rolling therefore requires a rigorous treatment of thecoupling relation, which, however, is not enough considered in earlier studies. Based onsystemic investigation of the progress in theoretical research of strip hot rolling, involvingdeformation, heat transfer and metallurgical aspects, and taking the multi-physical processcoupled and three dimensional nature of strip hot rolling problem into consideration, amulti-parameter coupled three-dimensional computer simulation system of strip hotrolling is developed in present work.The simulation system consists of three elemental models: deformation model, heattransfer model and microstructural evolution model. The rigid-plastic FEM(finite elementmethod ) is a powerful tool for analyzing metal forming process, and it is employed toanalyze the plastic deformation of workpiece in this study. Besides, by using influentialfunction method to calculate roll deflection and elastic FEM to calculate flattening in rollgap, a three-dimensional computer model for analysis of rolling deformation has beendeveloped and verified though example simulations. Temperature is an important processvariable during strip hot rolling, and the temperature distribution through strip acrosssection at any moment from heating furnace to coiler is obtained with aquasi-three-dimensional mathematical model, developed by using two dimensional FEM.For the convenience of being coupled with FE models for themomechanical analysis, amicrostructural evolution model based on incremental formulation proposed byYanagimoto et al is employed to analyze the microstructure changes during strip hotrolling. At last, iterative procedures are introduced in the calculation flowchart ofsimulation system to account for the strongly interdependence between metal flow,temperature, and metallurgical phenomena.To examine the correctness and reliability of the system developed, simulations ofplate hot rolling at laboratory scale were performed and the simulated results werevalidated by experimental measurements from Rolling Lab of Yanshan University. Furthermore, simulation of continuous rolling process in FTSR (Flexible Thin Slab Rolling), anadvanced production technology for hot rolled strip, was also conducted with thesimulation system and the simulated results were compared with industrial logs andmeasurements. It shows that the simulation system is capable of analyzing the standdeformation under load, tracking the metal flow, temperature variation and themicrostructural evolution of rolled strip during hot rolling, and predicting the rolling loads,strip dimensions and microstructure. It can be used to design and optimize strip rollingprocess, as well as rolling mill, and to improve the precisions of dimensions andmicrostructure.
Keywords/Search Tags:Strip hot rolling, Microstructural evolution, Multi-parameter, Numerical simulation, Rigid-plastic finite element method, Computer simulation system
PDF Full Text Request
Related items