Continuous cooling transformation (CCT) characteristics and prior-austenite grains of boron microalloyed steels with and without titanium were investigated to obtain the necessary information for heat treatment of these steels. Transformation characteristics were determined by using dilatometer tests, microscopic observation, and hardness measurements. In addition, the effects of titanium addition on the sizes of prior-austenite grains and precipitates were analysed. The results show that the changes in austenite grain size are not very distinct, and adding titanium only slightly refines the austenite grains. The CCT diagrams showed that the ranges of transformation products were shifted to the right side by the addition of titanium. The ferrite transformation starting temperatures were reduced on addition of titanium. Titanium addition induced decreased critical cooling rates for bainite transformations. The hardenability of boron microallyed steel is increased by adding titanium because more boron segregate to prior-austenite grain boundaries.
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References
1.
ChenJLiFLiuZYet al.Influence of deformation temperature on gamma-alpha phase transformation in Nb-Ti microalloyed steel during continuous cooling. ISIJ Int. 2013;53(6):1070–1075. doi: 10.2355/isijinternational.53.1070
2.
ZhaoJWJingZYKimJSet al.Effects of tungsten on continuous cooling transformation characteristics of microalloyed steels. Mater Design. 2013;49(17):252–258. doi: 10.1016/j.matdes.2013.01.056
WangCDingHTangZYet al.Effect of isothermal bainitic processing on microstructures and mechanical properties of novel Mo and Nb microalloyed TRIP steel. Ironmak Steelmak. 2015;42(1):9–16. doi: 10.1179/1743281214Y.0000000191
5.
CizekPWynneBPDaviesCHJet al.Effect of composition and austenite deformation on the transformation characteristics of low-carbon and ultralow-carbon microalloyed steels. Metall Mater Trans A. 2002;33(5):1331–1349. doi: 10.1007/s11661-002-0059-8
6.
TimoshenkovAWarczokPAlbuMet al.Influence of deformation on phase transformation and precipitation of steels for Oil country tubular goods. Steel Res Int. 2014;85(6):954–967. doi: 10.1002/srin.201300198
7.
LeePJRaudenskyMHorskyJ.Development of accelerated cooling for new plate mill. Ironmak Steelmak. 2013;40(8):598–604. doi: 10.1179/1743281212Y.0000000089
8.
JunHJKangJSSeoDHet al.Effects of deformation and boron on microstructure and continuous cooling transformation in low carbon HSLA steels. Mater Sci Eng A. 2006;422(1):157–162. doi: 10.1016/j.msea.2005.05.008
9.
WangXHeXL.Effect of boron addition on structure and properties of low carbon bainitic steels. ISIJ Int. 2002;42:38–46. doi: 10.2355/isijinternational.42.Suppl_S38
10.
WuBPLiLHWuJTet al.Effect of boron addition on the microstructure and stress-rupture properties of directionally solidified superalloys. Int J Miner Metall Mater. 2014;21(11):1120–1126. doi: 10.1007/s12613-014-1017-3
11.
PanTWangXYSuHet al.Effect of alloying element al on hardenability and mechanical properties of micro-b treated ultra-heavy plate steels. Acta Metall Sin. 2014;50(4):431–438.
12.
HwangBSuhDWKimSJ.Austenitizing temperature and hardenability of low-carbon boron steels. Scripta Mater. 2011;64(12):1118–1120. doi: 10.1016/j.scriptamat.2011.03.003
13.
TerzicACalcagnottoMGukSet al.Influence of boron on transformation behavior during continuous cooling of low alloyed steels. Mater Sci Eng A. 2013;584(9):32–40. doi: 10.1016/j.msea.2013.07.010
14.
MunDJShinEJChoiYWet al.Effects of cooling rate, austenitizing temperature and austenite deformation on the transformation behavior of high-strength boron steel. Mater Sci Eng A. 2012;545(21):214–224. doi: 10.1016/j.msea.2012.03.047
15.
BardelcikAWorswickMJWellsMA.The influence of martensite, bainite and ferrite on the as-quenched constitutive response of simultaneously quenched and deformed boron steel – experiments and model. Mater Design. 2014;55(6):509–525. doi: 10.1016/j.matdes.2013.10.014
16.
DasCRAlbertSKBhaduriAKet al.Effect of boron addition and initial heat-treatment temperature on microstructure and mechanical properties of modified 9Cr-1Mo steels under different heat-treatment conditions. Metall Mater Trans A. 2013;44(5):2171–2186. doi: 10.1007/s11661-012-1584-8
17.
MejíaIBedolla-JacuindeAMaldonadoCet al.Determination of the critical conditions for the initiation of dynamic recrystallization in boron microalloyed steels. Mater Sci Eng A. 2011;528(12):4133–4140. doi: 10.1016/j.msea.2011.01.102
18.
ChipresELMejíaIMaldonadoCet al.Hot ductility behavior of boron microalloyed steels. Mater Sci Eng A.2007;460(1):464–470. doi: 10.1016/j.msea.2007.01.098
19.
KimSIChoiSHLeeY.Influence of phosphorous and boron on dynamic recrystallization and microstructures of hot-rolled interstitial free steel. Mater Sci Eng A. 2005;406(1):125–133. doi: 10.1016/j.msea.2005.06.040
20.
KimSKangYLeeC.Variation in microstructures and mechanical properties in the coarse-grained heat-affected zone of low-alloy steel with boron content. Mater Sci Eng A. 2013;559:178–186. doi: 10.1016/j.msea.2012.08.072
21.
ZhaoJWLeeJHKimYW.Enhancing mechanical properties of a low-carbon microalloyed cast steel by controlled heat treatment. Mater Sci Eng A. 2013;559:427–435. doi: 10.1016/j.msea.2012.08.122
22.
ChoiYSKimSJParkIMet al.Boron distribution in a low-alloy steel. Met Mater Int. 1997;3(2):118–124. doi: 10.1007/BF03026135
23.
QuiSTXiaoLJLiuJQet al.Softening mechanism of boron-bearing low-carbon hot strips produced by TSCR route. Acta Metall Sin. 2006;42(11):1202–1206.
