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Liu D.-L.,Jiangsu Suzhou Steel Group Co. | Tan L.,Jiangsu Suzhou Steel Group Co. | Yang H.-X.,Great Wall Motor Co. | Bao Y.-Z.,Control Iron and Steel Research Institute, China
Journal of Iron and Steel Research | Year: 2013

The beneficial effects of the elements Nb, V, Ti and N in microalloyed forging steels was reviewed. Among these elements, the vanadium is the most effective and commonly used strengthening element for nonquenched and tempered steels due to its high solubility in the steels. The effects of grain refinement and precipitation strengthening can be achieved in non-quenched and tempered steels through micro-alloying elements Nb, V and Ti inhibiting the recrystallization of deformed austenites and grain growth, and enchancing strain induction precipitation during hot processing. Although the Nb, V and Ti are all strengthening elements, their strengthening effect and strengthening mechanism vary with the C and N content of these steels. Therefore, it would be the most effective way to improve strength and toughness of the ferrite-pearlite non-quenched and tempered steels through making use of the microalloying characteristics of the elements Nb, V, Ti and N and meanwhile applying the proper forging process. Source


He Y.,Kunming University of Science and Technology | He Y.,Control Iron and Steel Research Institute, China | Zhan Z.,Kunming University of Science and Technology | Tan L.,Jiangsu Suzhou Steel Group Co. | And 3 more authors.
Jinshu Rechuli/Heat Treatment of Metals | Year: 2013

Effect of Nb on microstructure of microalloyed forged steel during hot work process was investigated by the Gleeble 3800 compression tester. The results show that Nb can increase the recrystallization temperature (Tnr) range of the microalloyed forged steel, and expand the austenitic unrecrystallized zone, inhibit austenitic recrystallization. The higher strain rate and the lower deformation temperature can easily lead to finer recrystallized grain size. Addition of Nb obviously refine grain size and pearlite colony size of the steel and decreases the pearlite lamellar spacing and the size of the lamellae. Source


Man T.,Kunming University of Science and Technology | Man T.,Control Iron and Steel Research Institute, China | Gao P.,Kunming University of Science and Technology | He Y.,Kunming University of Science and Technology | And 4 more authors.
Jinshu Rechuli/Heat Treatment of Metals | Year: 2014

Hot compression experiments were carried out to study the effect of forging process on microstructure of Nb-V non-quenched and tempered steel on Gleeble-3800 thermal simulation machine. The results show that compared with non-quenched and tempered steel with single V adding, after forging, the grain size of Nb-V alloyed non quenched and tempered steel is fine, and blocky ferrite content increases and uniformly distributes, the pearlite interlamellar spacing decreases and distributes randomly, that improves the toughness of the steel. Reducing the cooling speed is in favor of proeutectoid ferrite growth, promote net ferrite transform to blocky ferrite and more uniform distributed, which is beneficial to improve the toughness of the steel. Increasing forging deformation can make the microstructure fines. Source


Man T.-H.,Kunming University of Science and Technology | Man T.-H.,Control Iron and Steel Research Institute, China | Gao P.,Kunming University of Science and Technology | He Y.-G.,Kunming University of Science and Technology | And 4 more authors.
Advanced Materials Research | Year: 2014

The effect of forging process on microstructure and performance of V-Ti, V-Nb-Ti non-quenched and tempered microalloying steel was investigated in this study. By comparing thecharacteristics between V-Ti and V-Nb-Ti microalloyed non-quenched and tempered steels by the forging process,the machinsm of micro-alloy technology and forging process for dynamic recrystallization and microstructure refinement was investigated. It revealed that addition of Nb in micro-alloying steel can increase significantly non-recrystallization temperature during forging process, and enhance the V (C, N) precipitation strengthening effect of V-Ti microalloyed non-quenched and tempered steels. V-Nb-Ti microalloying technology and controlling forging temperature in non-recrystallization region, can refine grain size, promote proeutectoid ferrite emerging and pearlite morphology alienating. By controlling final forging temperature in non-recrystallization region, the strength and toughness of V-Nb-Ti micro-alloy non-quenched and tempered steels can be improved. © (2014) Trans Tech Publications, Switzerland. Source


Man T.-H.,Kunming University of Science and Technology | Man T.-H.,Control Iron and Steel Research Institute, China | Gao P.,Kunming University of Science and Technology | Zhang Z.-H.,Wuhan University of Science and Technology | And 3 more authors.
Kang T'ieh/Iron and Steel | Year: 2015

The study carried out thermal deformation experiment by Gleeble-3800 thermal simulation, and the austenite dynamic recrystallization process of non-quenched and tempered steel with different V contents in single pass compression with strain rate 0.1-10 s-1 and deformation 60% at 950-1 150℃ was studied. The calculated dynamic recrystallization activation energies of V1 steel increased by 79.617 kJ/mol than that of V2 steel, and the increase of vanadium content delays the austenite dynamic recrystallization. Based on the experimental results and combined with the actual production, the optimal parameters of thermal process were determined. ©, 2015, Chinese Society for Metals. All right reserved. Source

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