Ti和Mn含量對(duì)CSP工藝Ti微合金鋼析出特征與強(qiáng)化機(jī)理的影響

1、 1112111,1000812,510730(EBSD(HRTEMTi Mn CSP Ti.:Ti Mn,Ti Mn,10nm TiC,M3C(Fe3C .,.CSP,Ti,TG113A04121961(201112154109 EFFECTS OF Ti AND Mn CONTENTS ON THE PRECIPI-TATE CHARACTERISTICS AND STRENGTHENINGMECHANISM IN Ti MICROALLOYED STEELSPRODUCED BY CSPWANG Changjun1,YONG Qilong1,SUN Xinjun1,MAO Xinping

2、2,LI Zhaodong1,YONG Xi11Institute of Structural Materials,Central Iron and Steel Research Institute,Beijing1000812Guangzhou Zhujiang Steel Limited Liability Company,Guangzhou510730Supported by National Basic Research Program of China(No.2010CB630805Manuscript received20110620,in revised form20110831

3、ABSTRACT As an advanced manufacturing technology to produce hot rolled strips,compact strip production(CSPprocess was developed at the end of last century and has been widely applied due to its high eciency and low cost.Compared with the traditional technology,the advantages of CSP technology benete

4、d from the renement of austenitic grains and precipitation strengthening in the steels.This is because cooling rate is higher during the solidication of slab and the direct charging slab temperature is also higher in the CSP process,resulting in much higher solute contents in the solid solution befo

5、re hot rolling than expected by the experiences from traditional steel production.So far, the Ti microalloyed steels produced by CSP process already have good performance and have drawn much attention on Ti precipitate behaviors and strengthening mechanism.However,the inuence of alloying element Mn

6、on the Ti microalloyed steels produced by CSP,especially the synergistic eect of Mn and Ti,was rarely reported.Therefore,in this work the microstructure and precipitate characteristics of two Ti microalloyed steels with dierent Ti and Mn contents produced by CSP process were studied by electron back

7、scatter diraction(EBSDtechnology and high resolution transmission*2010CB630805:20110620,:20110831:,1984,154247 electron microscope(HRTEM.The results show that the steel with higher Ti and Mn contents has a higher frequency of smallangle grain boundary.Furthermore,the weight fraction of TiC precipita

8、tes with particle size smaller than10nm increases signicantly,from7.6%in the lower Ti and Mn steel to 26.1%in the higher Ti and Mn steel.However,the amount of Fe3C precipitates decreases markedly. In addition,the strengthening mechanism analysis of the two tested steels show that grain renement stre

9、ngthening and dislocation strengthening make great contribution to the yield strength,while the precipitation strengthening is the primary reason which causes the dierence in the strength between two tested steels.KEY WORDS compact strip production(CSP,Ti microalloyed steel,strengthening mechanism,

10、mechanical properties(CSP80.,CSP,13.,.Nb V,Ti,Ti,Ti,TiC Ti,.,O,S N,TiO2,Ti.CSP Ti,Ti410,Ti1117.MnTi,Mn Ti,.CSP2Ti Mn Ti,TiMn,2Ti.12Ti,1.,21Ti,MnN.N CSP Ti,TiN,.150t(LF,5060mm,(11001150,(880900,580620.2,1.21,.,2%LeicaMEF4M(OM,;(EBSD;JEOL2100F(HRTEM(,X(XRD.22.1112.212Table1Chemical composition and lon

11、gitudinal mechanical properties of two tested steelsSteel Chemical compostion,atomic fraction,%Mechanical properties12:TiMnCSPTi1543 12Fig.1Optical micrographs of tested steels No.1(aand No.2(b(PFpolygonal ferrite,QPFquasipolygonal ferrite,GBgranular bainite, m. 2.2EBSD2EBSD12.,2(15,1,2.XR

12、D124.461071.01108mm 2.2.3131TEM EDS.EDS,Ti 4C 2S 2(90120nmTi(CN(1020nm.4a1TEM.,100nm.4be4a1HRTEM EDS 2SADEDS .EDS,Ti 4C 2S 2fccTi(CN.,1,212EBSDFig.2EBSD orientation maps of No.1(aand No.2(bsteels,and frequency distributions of ferrite grain boundary misorientation (c10nm (5,EDS TiC.HRTEM ,1,Ti 4C 2S

13、 2Ti(CN,Ti 4C 2S 2Ti(CN.62(10nmTEM ,(EDS.EDS,154447 31Ti4C2S2Ti(CNEDS Fig.3TEM image showing the composite precipitate of Ti4C2S2formed on Ti(CN(a,and EDS(band(c corresponding to regions1and2in Fig.3a 41Ti4C2S2Ti(CN1HRTEM EDS2SAED EDS Fig.4TEM image showing a string precipitates of Ti4C2S2and Ti(CN(

14、a,HRTEM image(band EDS(c corresponding to region1in Fig.4a,SAED(dand EDS(ecorresponding to region2in Fig.4a12:TiMnCSPTi1545TiC .2FeCrCu,Cu ,Fe,CrCu.,1(5,210nmTiC(6a.,2HRTEM, 5110nmTiCFig.5TEM image showing TiC precipitates smaller than10nm in No.1steel1Ti(CNTi 4C 2S 2,.7Fe 3C 12(.Fe 3C 2,2Fe 3C1.,1,

15、210nmTiC ,M 3C(Fe 3C,.2.42,12Ti(CN0.077%0.129%,Fe 3C0.287%0.093%,HRTEM.8X.,2,5nm,15.9%23.3%. 6210nmTiC(EDSFig.6TEM image showing TiC precipitates smaller than 10nm in No.2steel (a,and EDS obtained by scanningthe circle in Fig.6a(b 712Fe 3CFig.7TEM images showing the dierences of Fe 3C precipitates b

16、etween No.1steel (aand No.2steel (b1548 4 47 Ti Mn CSP ( Ti , , : (1 Mn HRTEM 1 , , Ti Mn 2 Ti , , Fig.10 Eect of Mn contents on the solubility products (a and molar free energy (b of TiC precipitation in austenite 10 Mn TiC Mn TiC , , TiC . TiC , C , Mn 2 M3 C (Fe3 C . 2 , (3 , 2 . (2 . , 10 nm TiC

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