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Hu C.-L.,Shanghai JiaoTong University | Meng L.-F.,Shanghai JiaoTong University | Zhao Z.,Shanghai JiaoTong University | Gu B.,Jiangsu Sunway Precision Forging Co. | Cai B.,Jiangsu Sunway Precision Forging Co.
Transactions of Nonferrous Metals Society of China (English Edition) | Year: 2012

Aiming to analyze the serious earing defects in initial extrusion process of aluminum controller housing, simulation was carried out by DEFORM-3D and the results showed a good agreement with the experimental work. Based on the simulation results, it is easy to find that the non-uniform velocity of metal flow is the main cause leading to earing defects. Therefore, a novel process scheme which tried to avoid the defects by using a punch with a group of resistance ribs at the bottom was put forward. For further study, the orthogonal experiment method was adopted to optimize the novel process. The width of the rib d, the thickness of the rib t, the length of the longest rib L and the inclination angle α were selected as design variables, and the height difference Δh along the top edge of the controller housing after extrusion which could reflect the earing was determined as the optimized objective. Finally, the optimized scheme was obtained. Compared with the initial process, the height difference Δh was reduced to 3.32 mm from 14.09 mm and the earing defects have been obviously improved in the optimized scheme. © 2012 The Nonferrous Metals Society of China.


Zhang Y.,Shanghai JiaoTong University | Hu C.L.,Shanghai JiaoTong University | Zhao Z.,Shanghai JiaoTong University | Li A.P.,Tongji University | And 2 more authors.
Materials and Design | Year: 2013

The low cycle fatigue (LCF) behaviour of a Cr-Mo-V matrix-type high-speed steel (matrix-type HSS), which was used as cold forging tool material, was investigated. Fatigue tests were conducted under strain-controlled cyclic loading conditions with different axial strain amplitude levels at room temperature. The tests indicated that hysteresis loops formed when the total strain amplitude was 1.5%, 1.0% and 0.75%. At total strain amplitudes that were less than 0.7%, there was no cyclic plastic deformation or hysteresis loop observed. The material fatigue behaviour was analysed specifically at the above three strain levels to investigate the cyclic plastic deformation of the material because the low cycle fatigue behaviour was of principal interest in this study. At all selected total strain amplitudes, the cyclic stress responses showed cyclic softening, and reached a "quasi-stabilised" softening state before the material finally ruptured from fatigue. The cyclic strain-stress relationship and the strain-life relationship were obtained through the test results, and related material parameters were calculated. Fractographic and metallographic analyses were also conducted in this study. The metallographic structure of the steel before and after heat treatment was examined. Two types of carbide phases were found in the steel. The fatigue damage process through the crack initiation and propagation was explained by observing the features of the fractures. © 2012 Elsevier Ltd.


Hu C.L.,Shanghai JiaoTong University | Zhao Z.,Shanghai JiaoTong University | Gong A.J.,Jiangsu Sunway Precision Forging Co | Shi W.B.,Jiangsu Sunway Precision Forging Co
Journal of Materials Engineering and Performance | Year: 2014

The effect of warm deformation parameters and cooling rates on transformation of the microstructure of 40Cr steel was investigated using both single- and double-pass compression tests. The compression tests were performed at temperatures ranging from 800 to 700 °C followed by controlled cooling at rates from 0.1 to 5 °C/s. All of the final transformation microstructures were observed by optical microscopy, and they were mainly composed of ferritic and pearlitic microstructures. For further quantitative analysis, a program based on image processing technology was developed to automatically calculate the volume fractions of ferrite and pearlite. After qualitative and quantitative analysis of the final microstructures, the results showed the following. The ferrite volume fraction significantly increased with increasing strain for the same deformation temperature. The strain rate had almost no effect on the ferrite fraction at the lower cooling rates. The ferrite fraction markedly increased with increasing strain rate when the cooling rate was greater than 1 °C/s. The ferrite fractions after single- and double-pass compression were 27-49 and 24-43% for a total strain of 0.7. The cooling rate after deformation had a remarkable effect on the microstructure morphology, and the ferrite volume fraction significantly decreased with increasing cooling rate. © 2014, ASM International.


Hu C.,Shanghai JiaoTong University | Zhao Z.,Shanghai JiaoTong University | Zhang Y.,Shanghai JiaoTong University | Xu X.,Jiangsu Sunway Precision Forging Co.
Applied Mechanics and Materials | Year: 2011

40Cr steel is categorized as quenched-tempered steels and is widely used in gears, bolts, couplings, spindles, etc. To study the plastic deformation behaviour of the steel after quenching and tempering, compression and double-pass compression tests have been carried out. The quenched samples are tempered at the temperature of 540°C, 580°C, 600°C and 630°C, and the microstructures, compression load, hardness after compression and load of double-pass compression are investigated. The compression peak load is higher when the tempering temperature is lower. The hardness average and its increase amplitude decrease with the tempering temperature. An interesting phenomenon of the double-pass compression load can be well explained by the microstructures. © (2011) Trans Tech Publications.


Hu C.,Shanghai JiaoTong University | Zhao Z.,Shanghai JiaoTong University | Gong A.,Jiangsu Sunway Precision Forging Co. | Shi W.,Jiangsu Sunway Precision Forging Co.
Materials and Manufacturing Processes | Year: 2015

Deformation behavior was investigated in detail from cold extrusion and upsetting tests on medium carbon steel. A new "cold forging after quenching and tempering" (CFAQT) process was proposed. Compared with conventional processes, including annealing before cold forging, plus quenching and tempering after forging, the CFAQT process could shorten the process chain and avoid subsequent heat treatment distortion with clear energy-saving and cost-reduction benefits. The CFAQT process was applied successfully in the mass production of a lock set for industrial automobile wheels and in laboratory spline extrusions. Copyright © Taylor & Francis Group, LLC.


Li S.-L.,Shanghai JiaoTong University | Hu C.-L.,Shanghai JiaoTong University | Zhao Z.,Shanghai JiaoTong University | Gong A.-J.,Jiangsu Sunway Precision Forging Co Ltd | Shi W.-B.,Jiangsu Sunway Precision Forging Co Ltd
Cailiao Rechuli Xuebao/Transactions of Materials and Heat Treatment | Year: 2014

Hot deformation behavior and continuous cooling transformation of 40Cr steel after deforming were investigated by a single-pass compression test on a thermo-mechanical simulator at different temperatures, strain and cooling rates. The content of the ferrite in the steel at defferent experimental parameters was obtained by metallographic observation using binaryzation and the median filter processing technology. The results show that the austenite accelerates to decompose with the increasing the volume fraction of ferrite, and the content of the ferrite increase by increasing the deformation amount. The effect of deformation degree on the phase transformation of 40Cr steel is significant and is irrespective of cooling rate. The decrease of deformation temperature promotes the transformation of austenite into perlite, and is more sensitive to cooling rate.


Ying Z.,Shanghai JiaoTong University | Hu C.-L.,Shanghai JiaoTong University | Zhen Z.,Shanghai JiaoTong University | Xu X.-L.,Jiangsu Sunway Precision Forging Co. | And 2 more authors.
IET Conference Publications | Year: 2010

The failure mechanism of YXR3, a kind of matrix-type high speed steel (HSS), which is widely used in cold forging tooling, was studied in this paper. Through metallographic analysis of YXR3 in different conditions, such as before and after heat treatment and mechanical tests, the metallurgical structures and changes of the steel were analyzed. The failure analysis was conducted to specimens of uniaxial tension, low cycle fatigue, and impact tests by observing the macroscopic and microscopic fractographs and fracture morphology features of YXR3 steel in different loading conditions. The morphology and distribution of all phases in YXR3 steel were clearly found in the SEM micrographs by EBSD (Electron Back-Scattering Diffraction), and the major cracking modes and crack origins were investigated by observing the microcracks, which would be beneficial for finding out the fracture mechanism of YXR3 steel from microscopic perspective. The results of this study could help the tool designer to improve the tool design and manufacture which can avoid the abnormal appearance of tool fracture during cold forging.


Li H.,Hefei University of Technology | Chen W.,Hefei University of Technology | Zhou R.,Hefei University of Technology | Shi W.,Jiangsu Sunway Precision Forging Co. | Wu Y.,Hefei University of Technology
Zhongguo Jixie Gongcheng/China Mechanical Engineering | Year: 2014

Based on the geometric features of back gear with double boss, a new two-step warm forging process before finishing was put forward to reduce the number of cold forging process. Empty corners in the bottom of profile of all teeth were found when using the above process. In order to solve the problem, a rigid plastic FE model was built to simulate the warm forging process. The velocity, stress and strain field were investigated, and the metal flow rules were discussed with the experimental results. Then a qualified gear was achieved through expanding the radial wave shape by means of an indentation established in die. The measured results show that the new process can satisfy a high level precision of forging. The work presented herein may be used as basic data for the design of the precision forging processes. ©, 2014, China Mechanical Engineering Magazine Office. All right reserved.

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