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Dai W.,Northeastern University China | Wang X.,Northeastern University China | Zhao L.,China First Heavy Industries | Yu J.,Northeastern University China
Materials Transactions | Year: 2011

A significant number of nanotwins was fabricated in a cold-rolled Cu-Zn alloy after an electric current pulse (ECP) treatment in this study. Results showed that the formation of nanotwins was related not only to the α to β phase transformation, but also to the effect of the enhanced directional nucleation along the current direction during the heating caused by the ECP treatment. A theoretical analysis revealed that the nucleation rate of the higher conductivity phase (β phase) was significantly accelerated by the application of an electric current, which provided more nucleation places for the α phase during the subsequent rapid cooling process. Especially, during the cooling process, nanotwins with {111} twin planes in the α phase would be formed due to the stronger internal stress induced by the rapid cooling rate after the ECP treatment. © 2011 The Japan Institute of Metals.

He J.,Shanghai JiaoTong University | Gao F.,Shanghai JiaoTong University | Bai Y.,Shanghai JiaoTong University | Wu S.,China First Heavy Industries
Chinese Journal of Mechanical Engineering (English Edition) | Year: 2013

The large capacity servo press is traditionally realized by means of redundant actuation, however there exist the over-constraint problem and interference among actuators, which increases the control difficulty and the product cost. A new type of press mechanism with parallel topology is presented to develop the mechanical servo press with high stamping capacity. The dynamic model considering gravity counterbalance is proposed based on the virtual work principle, and then the effect of counterbalance cylinder on the dynamic performance of the servo press is studied. It is found that the motor torque required to operate the press is a lot less than the others when the ratio of the counterbalance force to the gravity of ram is in the vicinity of 1.0. The stamping force of the real press prototype can reach up to 25 MN on the position of 13 mm away from the bottom dead center. The typical deep-drawing process with 1 200 mm stroke at 8 strokes per minute is proposed by means of five order polynomial. On this process condition, the driving torques are calculated based on the above dynamic model and the torque measuring test is also carried out on the prototype. It is shown that the curve trend of calculation torque is consistent to the measured result and that the average error is less than 15%. The parallel mechanism is introduced into the development of large capacity servo press to avoid the over-constraint and interference of traditional redundant actuation, and its dynamic characteristics with gravity counterbalance are presented. © Chinese Mechanical Engineering Society and Springer-Verlag Berlin Heidelberg 2013.

Rong J.H.,Yanshan University | Hong X.,Yanshan University | Xiang G.Y.,Yanshan University | Shui J.J.,China First Heavy Industries
Applied Mechanics and Materials | Year: 2014

In order to effectively improve the calculation accuracy of finishing rolling force model for hot rolling wide and heavy stainless steel clad sheets, based on the E.Orowan unit pressure equilibrium differential equations and R.B.Sims unit pressure formulas, this paper divides hot-rolled composite deformation area into I, II two zones according to rolling stock jamming experiment, and then derives the finishing rolling force calculation formulas. Finally, by ANSYS/LS-DYNA thermal-mechanical coupling simulation and experiment, the results show that compared with measured values, the relative error of simulated values is about 20%, the relative error of calculated values is less than 10%. Therefore, the rolling force model can accurately predict the size of rolling force and effectively improve the calculation accuracy of rolling force. © (2014) Trans Tech Publications, Switzerland.

Qu M.-G.,Yanshan University | Sun S.-H.,Yanshan University | Bai X.-H.,China First Heavy Industries | Shi Z.-P.,Yanshan University | And 2 more authors.
Journal of Iron and Steel Research International | Year: 2014

The hot deformation behavior of as-cast AISI M2 high-speed steel containing mischmetal (RE) has been investigated on a Gleeble-3500 simulator in the temperature range of 1000-1150 °C and strain rate range of 0. 01 - 10 s-1 at true strain of 1.0. The mechanical behavior has been characterized using stress-strain curve analysis, kinetic analysis, processing maps, etc. Metallographic investigation was performed to evaluate the mechanism of flow instability. The results show that the deformation activation energy decreases with increasing deformation temperature; the efficiency of power dissipation increases with decreasing strain rate and increasing temperature; flow instability is observed at low-to-medium temperature and higher strain rate region when the strain is smaller, but extends to lower strain rate and high temperature regions with the increment of strain, in which it is manifested as flow localization near the grain boundary. Hot deformation equations and processing maps are obtained. The optimal processing window is suggested and the deformation mechanism is dynamic recrystallization (DRX). © 2014 Central Iron and Steel Research Institute.

Xie Y.,China First Heavy Industries
Hanjie Xuebao/Transactions of the China Welding Institution | Year: 2015

The weldability of A517Q rack steel was investigated systematically by means of oblique Y-groove cracking tests, maximum hardness tests on the heat affected zone (HAZ) and the mechanical property tests of welded joint. The results showed that under the restraint condition, the cold crack susceptibility of A517Q weld was increased with the thickness of tested plates increasing from 30 mm to 60 mm. Raising preheating temperature contributed to the reduction of cold crack tendency of steel and the hard level of HAZ. The welded joint of 177.8 mm thick A517Q rack steel plate exhibited high strength and toughness, meeting the requirements of usage. The microstructure of HAZ mainly consisted of lath-like martensite and lath-like bainite. The hardness of HAZ apparently exceeded weld metal zone and the parent metal, presenting a high harden tendency and a certain risk of cold cracking. ©, 2015, Harbin Institute of Technology. All right reserved.

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