铁素体-贝氏体复相组织低碳钢的力学特性_图文

1、11,21331.1100042.1100043.201900,./(I(II.,I.,TG1421005-3093(200705-0517-06 Mechanical behaviors of a low carbon steel with a duplexmicrostructure of bainite and ferriteLI Long1DING Hua1,2WEN Jinglin2SONG Hongmei3ZHANG Pijun31.School of Materials and Metallurgy,Northeastern University,Shenyang1100042.

2、The State Key Lab.of Rolling and Automation of Northeastern University,Shenyang1100043.Baosteel Technology Center,Baoshan Iron&Steel Group Co.,Shanghai201900*Supported by National Natural Science Foundation of China No.50271015.Manuscript received September10,2006;in revised form April23,2007.*T

3、o whom correspondence should be addressed,Tel:(02483687746,Email:hding ABSTRACT Controlled rolling followed by accelerated cooling process was carried out to investigate the microstructure and mechanical properties of a low carbon steel with a duplex microstructure of bainite and ferrite.The duplex

4、microstructure may be classied as the grain boundary allotriomorphic ferrite/bainite(I typeand equiaxed ferrite and bainite(II type.The stressstrain curves were obtained by tensile testand mechanical behaviors of the tested steels were analyzed.Optical microscopy and transmission electron microscopy

5、 were used to characterized the duplex microstructures consisting of ferrite and bainite.The results show that the bainitic ferrite possesses lathshaped and there are a lot of carbides in I type matrix.The yield strength exceeds400MPa and work-hardening exponent is greater than0.35for the tested ste

6、el with I type structure.KEY WORDS metallic materials,low carbon steel,ferrite,bainite,work-hardening,ow stress curve,14;,5.,*No.50271015.2006910;2007423.:,6.,1,7,.P B Pickering Mo-B8,.9,10./,9,11.Mo Cr Mn,.51821/,.1(,%:C0.10,Si 0.23,Mn 1.06,S 0.006,P 0.009,N 0.0016.50kg ,50mm ×100mm ×120m

7、m.,612mm.Gleeble1500A r3680(5/s,ThermocalcA e3842.8.450mmTMCP (ThermoMechanical Controlled Process.1200,2h.1.(Finish rolling temperature,FRT850(A e3800(A e3A r3.,50.,3540/s.(Coiling temperature,CT500,.,INSTRON4206,5mm/min,.3.LEICA Q550IW .LEICA Q550IW.0.2mm,EM400T.22.11,/9(I,1a,(II,1b.A r3Thermocalc

8、 A e3,800A r3A e3,850A e3.(1,1Table 1Inter-pass reduction distribution in hot rolling processRolling passParameter 12345Outlet thickness/mm 35221410 6.5Rolling temperature/11001000<950900,880850,800Reduction/%0.360.460.450.340.43 1Fig.1Optical microstructures of tested steel with dierent nish rol

9、ling temperature (a850(sample1,(b800(sample 25:51921(TEMFig.2TEM micrographs of sample 1(aferrite laths,(bcarbides.(1a,850.,;,.,(GBA,(BF(2a.,Fe 3C(2b.800,24,13,.2.22,I s 420MPa,s /bII.I,(20%,.,1.II,80%,1.II,.,.dd=0(1(1,.,1dd1.1dd./4.,3HSLA/(DP12.HSLADP3.3,2Table 2Mechanical properties of controlled

10、rolling and accelerated cooling plate steelWork-hardening MicrostructureSample FRT/CT/s /MPa b /MPa s /b 5/%exponent n ln K type 1800500520347.8470.70.7434.50.354±0.0016.925±0.002II520 21DP12of controlled rolling and accelerated cooling plate steelAl Ps/MPab/MPa5/% 23.231ddFig.3Relationshi

11、p between1ddandof dierentsteel412Fig.4Stress versus strain curves of the tested steel with I and II type microstructure/,1ddHSLA DP.,1dd.4,I II1dd,.(=Kn(2 ,K;n.n u=u.n u,n u.,n n=d ln/d lnp:n.n0.1650.225,n0.110.12,DP n0.180.20,0.2612,/n0.38( 2,n3;/0.3714(HSLAn(0.36 .II,(;,.,12.,.2.34,I(1 ,II(2.12.I,

12、(2,;II,I,.5(2.5,I II ,.,5:5215Fig.5Comparison with measured and calculated re-sults ofow stress of the tested steels(aItype(sample1,(bII type(sample2,longi-tudinal,(cII type(sample2,transverse.,.,(2.3,.A e3,/;A e3A r3,./,0.35.Journal of Materials Processing Technology,136, 100(2003(,20(3,240(20065W

13、ANG Guodong,LIU Xianghua,LI Weijuan,DU Linxiu, ZHANG Hongmei,Industrial rolling trials of super-SS400 steel,Iron and Steel,36(5,39(2001(,Super-SS400,36(5,39(20016YANG Ping,CHANG Shouhai,CUI Fenge,SUN Zuqing, Orientational characteristics of ferrite during strain en-hanced transformation in a Q235plain carbon steel,Chi-nese Journal of Materials Research,16(3,251(2002(,Q235,16(3,251(20028F ANG Hongsheng,ZHENG Yankang,HUANG Jinfeng, BO Xiangzheng,Prospect of bainitic steels,Metal Heat Treatment,(7,11(19