Papers by Author: Li Yong Ni

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Authors: Li Yong Ni, Suo Qing Yu, L. Li, S.Y. Zhu, Hua Gui Huang
Abstract: High transversal properties requirements of heavy axial forgings, traditionally, often are met through the selection of high-performance materials, the improvement of metallurgical quality and repeated forging. But the production costs and power consumption are both high. A new slant forging method is adopted, by controlling the metal flow direction in forgings, to achieve the increase of transversal mechanical properties. Finite element method was applied to study the influence of forging process parameters on flow lines in axial forgings, providing theoretical guidance for the eventual realization of the forging method.
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Authors: Shi Cheng Xiao, L.P. Zhang, Li Yong Ni, Wen Hua Yang, H.L. Liu
Abstract: Research was conducted for stretching with horizontal V-shaped anvils (HVA) and common flat anvils (FA). The forgoing research gave the simulation results of single blowing during stretching, and did not pay attention to the influence of the deformation, resulting from the previous blowing, upon the next blowing. ANSYS software is adopted to simulate the through-continuous blowing of HVA and FA forging methods. The transversal stress distribution along the horizontal central axis on the crosssection of the stretched forging is analyzed. The simulation results show that during the stretching with flat anvils, when the ratio of the flat anvil width to the billet height is 1.0 and the ratio of the billet width to the billet height is 0.5, the transversal stress is tensile all the time, and increases as the stretching goes. On the contrary, during the HVA stretching, the stress is compressive and its absolute value increases gradually. The results show that the HVA stretching method is prior to the FA stretching method in the controlling of transversal stress. Conducted physical experiment verified the results.
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Authors: Li Yong Ni, Peng Chao Kang, Suo Qing Yu, Zhu Bai Liu
Abstract: Considering the difficulty for the dynamic recrystallization to happen in Steel 26Cr2Ni4MoV, which was used to manufacture low-pressure steam turbine rotors generally, after-forging static recrystallization was studied with the thermo-torsion method. In order to investigate the influence of multi-step cumulative deformation on after-forging static recrystallization of Steel 26Cr2Ni4MoV, the thermo-torsion method was adopted to conduct a constant-temperature four-step torsion test at 900°C. The time gap between each step in the test agreed with that in real production. Results show that the influence of multi-step cumulative deformation on after-forging static recrystallization is almost the same with that of single-step deformation. It means that the nucleation and the growth of after-forging static recrystallization are related mainly to the last deformation and temperature-keeping time. Grain size can be controlled through the last deformation and temperature-keeping time. The findings supply the theoretical foundation for the said-steel controlled forging processes.
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Authors: Guo Hui Liu, Zheng Zhuang, Peng Liu, Li Yong Ni, Shi Yong Zhu, Jia Jia Chen, Hou Chao Lin, Long Hua Liu
Abstract: Forgings quality depends on the blooming processes and the deforming processes. The blooming processes are composed of upsetting and stretching, both of which influence the forgings quality very much. However, it is ignored. Methods are put forth to improve the forgings quality. It is surely of much significance.
1067
Authors: Li Yong Ni, Peng Chao Kang, Zhi Yi Huo, Zhu Bai Liu
Abstract: It is difficult for the dynamic recrystallization to happen in Steel 26Cr2Ni4MoV, used to manufacture low-pressure steam turbine rotors generally. Static recrystallization was important in the fine crystals generation. Considering this, thermo-torsion method was adopted to investigate the spontaneous austenite recrystallization of steel 26Cr2Ni4MoV. Results show that even minute strain can promote the nucleation and growth of spontaneous austenite recrystallization dramatically, and the increase of temperature can also do so. The discovery can contribute to the realization of controlled forging.
116
Authors: Suo Qing Yu, L.P. Zhao, A.B. Wang, H.C. Lin, J.J. Chen, G.D. Yao, Li Yong Ni
Abstract: Physical simulation was conducted on the process of upsetting cylinder between flat platens by using colorful plasticine. The results of the physical simulation are basically consistent with rigid-plastic finite element analysis, which supports the rigid-plastic mechanical model for the cylindrical billets whose height-diameter ratio are greater than 1. Further physical simulation is conducted on cylinders upsetting between platen and supporting ring. The experimental method provides a reference for physical simulation of large deformation.
1129
Authors: Li Yong Ni, Yong Jun Zhang, Suo Qing Yu, Zhu Bai Liu
Abstract: Heavy axial forgings made by conventional methods have obvious fibrous tissue in the axial direction, leading to the anisotropy of mechanical properties. The forging method with horizontal V-shaped anvils (HVA) is introduced to control fibrous tissue flow direction, to improve the anisotropy of mechanical properties of axial forgings. The forging method is superior to the common flat anvils (FA) forging method in inner stress states, metal tissue, overall properties and geometrical shapes of forgings. Qualitative physical simulation and pilot production for the HVA forging method are conducted, verifying the fact that the HVA forging method is an effective process to control the mechanical properties of axial forgings. The HVA forging method may reduce the anisotropy of the mechanical properties of axial forgings and increase their uniformity by 5~50%.
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Authors: F. Liu, S.X. Lin, A.B. Wang, Li Yong Ni
Abstract: The simulation of shaper kinematics and dynamics rules is conducted with MATLAB. The rules of ram displacement, speed, acceleration and links forces rules are obtained and shown in figures. The research results can be used for the design optimization of shaper contractures. Redundant programming is not necessary any more, since MATLAB is applied into the simulation. The study method is of instructive significance for the kinematics and dynamics analyses of similar mechanism.
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Authors: Li Yong Ni, Peng Chao Kang, Zhu Bai Liu, Wen Hua Yang
Abstract: In order to investigate the nucleation and growth of after-forging static recrystallization of low-pressure rotor steel 26Cr2Ni4MoV, the thermo-torsion experiment was conducted at 900°C,1000°C and 1100°C, respectively. The outer deformation of the used specimens was 0.21. The specimens were kept under a certain temperature for different periods. Results show that the recrystallization grain grew slowly at 900°C and the grain size became even after 30 minutes. The sizes of most grains were almost constant and only several grains grew bigger after 60 minutes. When the specimens were kept at 1000°C and 1100°C for one minute, static recrystallization was completed and the grain size was even. The said research could provide theoretical base for the controlled forging and after-forging heat treatment.
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