Study And Application Of The Process Control Technology Of Thin Plate In 5-meter Heavy Plate Mill Of NISCO

With the rapid development of nuclear power,vessels,energy resources and engineering machinery,there has been an increasing demand for steel plates of 10mm-thickness and3000mm+ width,which raises the quality requirement for the plates and the relative technology.This research mainly aims to improve the quality of thick-heavy steel plates and ensure its mass production by formulating effective optimization methods for plate shape and thickness control,on the basis of an integrated overview of the relative field of study,and the control technology and optimization projects 5-meter heavy plate mill of NISCO.The research methods mainly involve field data analysis,programming development,machinery function adaption etc.The main research content is listed as follows:(1)A literature review of the status quo of medium-thick plates and relative equipment at home and abroad is conducted,and also an analysis of the market status and industry trend of wide-thin steel plates is performed.The content and technology direction of this research is selected by targeting at the status of 5-meter heavy plate mill of NISCO and control system.(2)The definition of plate shapes and the characteristics of indicators concerning cross sections are analyzed,including convexity degree,flatness and wedge.Also,an introduction to the plate-shape control technology in hydraulic bending rolling,CVC(Continuously Variable Crown),roll cooling and so on,are given.Attempts to improve wide-thin plate shape control capability targeting at real problems during production are done,by upgrading functionality in the aspects of bending control,CVC control,procedural cooling and thermal crown control,rectangularity control.(3)The theoretical foundation of this thesis is studied,mainly covering medium-thick mill thickness and thickness auto-control AGC(Automatic Gauge Control)technology,for a solution for thickness accuracy of wide-thin products.A better accuracy of wide-thin plate thickness control is achieved by field problem analysis,improvements in thickness control setting model in process control system,upgrading in core thickness model accuracy factors including temperature,flow stress,rolling force,and thus achieving,as well as parameter &control logic optimization of AGC system.(4)This research upgrades auxiliary process of wide-thin steel plates,such as pre-level model optimization and development of reverse leveling for a higher quality after hot leveling.Also,it is found that a higher qualified rate could be achieved by adopting heat treatment and then offline slow cooling before cold leveling,as well as the designing special slow coolingdevice.And a more consistent and stable production is ensured by the upgrading of slab design of wide-thin steel plates and production plan programming.(5)The main achievement of this research lies in that the research findings are successfully applied in wide-thin steel plate process control of 5-meter heavy plate mill of NISCO,that is,the general qualified rate is remarkably raised from 60% to 94% and the main criterion of products parallel international standards.