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Wu M.,Jiangsu University of Science and Technology | Lu X.,Jiangsu University of Science and Technology | Cen Y.,HuDong ZhongHua Ship Building Company Ltd | Wang H.,HuDong ZhongHua Ship Building Company Ltd
Hanjie Xuebao/Transactions of the China Welding Institution | Year: 2012

With the three-dimensional finite element and experimental method, the residual stress in the AH36 steel plate of 6 mm in thickness under different welding conditions was studied in this paper. The results showed that the peak stress, which was the largest with the combined welding method, was related with the welding heat input under the same cooling condition. The longitudinal stress distribution varies with cooling conditions for the same welding process. Compared with the conventional welding, the welding residual stress distribution, especially in the peak residual tensile stress, was improved by water cooling. An experiment with the same parameters was carried out to verify the finite element simulation results. The experimental results are consistent with the numerical results, which indicates that the welding stress evolution under different welding conditions can be simulated with the three-dimensional finite element simulation technology, and provide the basis of the control of welding residual stress. Source


Hu Y.,Wuhan Naval University of Engineering | Sun W.,HuDong ZhongHua Ship Building Company Ltd | Kong X.,Wuhan Naval University of Engineering | Su X.,Wuhan Naval University of Engineering
Cailiao Kexue yu Gongyi/Material Science and Technology | Year: 2015

In order to improve the corrosion resistance of AH36 hull structural steel in seawater, calcium-treatment of molted steel was introduced into its steelmaking procedure. The effect of calcium-treatment on inclusions and resistance against pitting corrosion of AH36 steel was studied by scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), and other test methods such as indoor interval immersion tests, AC impedance tests, and potentiodynamic polarization tests combined with SEM analysis after polarization tests were also included. The results show that the content of CaS in the modified inclusions after calcium-treatment influences the resistance against pitting corrosion significantly. The resistance against pitting corrosion of AH36 steel enhance significantly after calcium-treatment while Al2O3 and aluminosilicate inclusions are transformed into CaO-Al2O3 spherical complex inclusions without CaS or containing few CaS. The pitting susceptibility of calcium-treated steel will be enhanced with the increase of the content of CaS in the modified spherical complex inclusions, because the corrosion of substrate around the modified inclusions containing more CaS can be induced more easily. When calcium-treatment of the AH36 steel containing higher level of S is not carried out sufficiently, CaS inclusions or complex inclusions mainly composed of CaS may be formed, which results in a deterioration in the resistance against pitting corrosion. ©, 2015, Harbin Institute of Technology. All right reserved. Source


Lu X.,University of Science and Technology of China | Wu M.,University of Science and Technology of China | Cen Y.,HuDong ZhongHua Ship Building Company Ltd | Wang H.,HuDong ZhongHua Ship Building Company Ltd | Shen S.,HuDong ZhongHua Ship Building Company Ltd
Hanjie Xuebao/Transactions of the China Welding Institution | Year: 2012

Using the three-dimensional finite element method, the residual deformation of joints obtained with the AH36 steel plate with thickness of 6 mm under different welding conditions was studied in this paper. The numerical simulation results showed that the longitudinal distortion and the angular distortion changed dramatically. As to different welding methods, the deformation was small when the unique CO 2 gas arc welding was used, while large deformation was found when the CO 2 arc and SAW were combined together. The residual deformation was controlled effectively by water cooling, especially for angular deformation with the unique CO 2 gas arc welding. To verify the finite element simulation results, an experiment using the same parameters was done. With some error, the experimental results were consistent with the numerical results, indicating that the welding deformation in different welding conditions can be simulated with the three-dimensional finite element method. Source


Lu X.,Jiangsu University of Science and Technology | Cen Y.,HuDong ZhongHua Ship Building Company Ltd | Wang H.,HuDong ZhongHua Ship Building Company Ltd | Wu M.,Jiangsu University of Science and Technology
Hanjie Xuebao/Transactions of the China Welding Institution | Year: 2013

The weldability experiments of DH40 ship building steel were carried out by using the flux-cored wire CO2 gas shielded multi-pass welding technology. The microstructure and mechanical properties of the joint were studied systematically and the impact toughness was discussed, especially the reason why the impact toughness at HAZ of 5 mm from fusion line of weld root decreased greatly. The results showed that the tensile strength of joints is higher than that of the base metal of 575 MPa. All the samples used in the bending test are qualified and meet the plasticity requirement. The brittleness band is easily formed at HAZ, 5 mm from the fusion line at the weld root. The effect of microstructure heredity results in the coarse crystal grain, which is the secondary reason for the impact ductility decreasing, and the basic reason is the formation of a large amount of granular bainite. Source

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