تعيين مشخصات كلي خط نورد گرم ورق به منظور دستيابي به اهداف مكانيكي و متالورژيكي يك طبقه از محصولات

چكيده انگليسي :

Determination of the General Specification of a Hot Strip Rolling Product Line to Approach Mechanical and Metallurgical Goals in a Typical Type of Products Valiollah Bagherian v bagherian@me iut ac ir Date of Submission 2015 08 16 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Mohammad Reza Forouzan forouzan@cc iut ac irAbstract Improving the hot strip mill process is mandatory for the steel industry owing to the increasingly severespecifications being imposed by end users Within this objective the development of a metallurgical model that links theoperating variables in the mill with microstructure and mechanical properties of the final products becomes of greatimportance This model could provide useful information for process control and optimization reducing the need ofcostly on line experimentation In this thesis some previously published experimental and theoretical studies of hotrolling are reviewed The aim of this work is to present a metallurgical model that could describe the microstructuralevolution of C Mn steels during hot rolling During hot deformation the average dislocation density of the materialincreases several orders of magnitude Two metallurgical processes become active to reduce the dislocation excess recovery and recrystallization In austenite the later is the most important restoration process Depending ontemperature strain and strain rate the recrystallization could begin during deformation dynamic recrystallization or inthe interpass time static recrystallization In order to describe the microstructural evolution it is needed a descriptionof the recrystallization progress and the resulting austenite grain size after each reduction step in the rolling mill Inaddition further modifications of the grain size could take place if the recrystallization after deformation is complete andis followed by grain growth After hot deformation the austenite transforms to ferrite perlite and or bainite Thetransformation kinetic and final phase distribution depend strongly on the austenite microstructure grain size andaccumulated strain and on the cooling and coiling conditions Due to the important metallurgical differences betweenthe several phases that may appear it is needed an accurate description of the final microstructure in order to evaluatethe mechanical properties of the material The present work combines the use of models developed from hot torsion testdata and from the analysis of industrial mill logs Logged data were collected from the Mobarakeh Steel Complex MSC nine stand thirteen pass HSM For each strip the following data were used chemical composition strip width strip thicknesses before and after all passes work roll rotational speeds roll forces interpass times and temperatures mean values for each pass The previous parameters were then employed to calculate the true strains strain rates andMFSs according to the Sims formulation roll flattening redundant strain and forward slip between roll and stripand were organized using MATLAB software An MFS model was developed to predict the strip rolling behaviors ofplain C Mn It is based on an improved Misaka MFS equation and takes into account the quantities of the importantalloying elements the extent of recrystallization between passes strain accumulation and the possibility that DRX isinitiated during a given pass A metallurgical algorithm that comprises the prediction of the microstructural evolutionduring hot rolling austenitic range and the subsequent phase transformation was developed for C Mn steels Keywords Mean flow stress MFS Recovery Static recrystallization Dynamic recrystallization Grain size Hot torsion test Microstructural evolution during hot rolling

باقريان، ولي اله

تعيين مشخصات كلي خط نورد گرم ورق به منظور دستيابي به اهداف مكانيكي و متالورژيكي يك طبقه از محصولات

تنش جريان ميانگين , بازيابي , تبلور مجدد استاتيكي , تبلور مجدد ديناميكي , اندازه دانه , آزمون پيچش گرم , تحولات ريزساختار حين نورد گرم