The Study On Recrystallization Behavior And Microstructure Evolution Of RE (Rare Earth) D36Ship Plate Steel During Hot Deformation

In recent years, the demanding of ship plate continues to increases, has good market prospects,it is expected to become the first shipbuilding country until2015in world, ship steel plays animportant role in the national economy production. Rare earth can purify the steel liquid, changethe sizes of inclusions, micro-alloyed, improve the microtructure as-casted. Baotou is the mostabundant reserves of rare earth country, has the advantage be richly endowed by nature in the REapplication.In view of the situation of Baogang plate steel, the high temperature softening behavior ofD36steel was studied by rare earth. According to the chemical composition of D36steelelements, different amounts of rare earth was added and got three furnace smelted steels, withthe amount of60ppm and the amount of100ppm of the mixed rare earth, the evolution of themicrostructure, recrystallization and phase changing mechanism during hot rolling were researched,the optimize project was draw up.Using Gleeble-1500D hot simulation machine, making the single, dual-pass compressionexperiments, D36rare-earth steel dynamic recrystallization rule in70%distortion at single-pass andstatic recrystallization rule at dual-pass has been researched. The results showed that: effect of REon dynamic recrystallization critical strain was more obvious, the critical strain of RE content to100ppm and RE content to60ppm samples were higher than the without RE samples, rare-earthexperimental steel must overcome the larger critical so dynamic recrystallization coulded beoccurred; RE influenced on double-pass static recrystallization softening rate at high-temperaturedeformation more obviously than low temperature deformation, and compared without RE samples,experimental steel passes softening rate was accelerated by adding100ppm RE. Based on single,dual-pass experimental results and cumulative strain calculation, and two multi-pass experimentprojects have been framed. The Experiment results showed that: in the multi-pass deformationprocess, the experimental steel occured to strain cumulative effect, to a certain extent, the experimental steel softening phenomenon was more obvious and pass static recrystallization wasinhibitted; RE obvious refined organization, the first experimental project strain cumulative effectwas the best and the most thin grain size could reach to7.95μm.The content of pearlite was decreased, the content of ferrite and inhibit the formation of pearlitephase was increased. As adding rare earth precipitates size was slightly increased, and mainlydistributed in intracrystalline.