| 1 | Mechanical and Metallurgical Characterization of HSLA X70Welded Pipeline Steel Subjected to Successive Repairs显示文摘The aim of this work is to study the influence of successive weld repairs on the microstructure and the mechanical behavior of the heat-affected zone(HAZ) of an HSLA X70 steel. Detailed microstructural examination combined to grain size measurement showed that beyond the second weld repair, the microstructure of the HAZ undergoes significant change in the grain morphology and grain growth. The results of the X-ray diffraction analyzed using MAUD software indicated an increase in the crystallite size and a decrease in the dislocation density according to the number of weld repair operations. Consequently, a loss of mechanical properties, namely the yield strength and the toughness with the number of weld repairs, was recorded. Beyond the second weld repair operation, the properties of the welded joint do not fulfill the standards applied in piping industry. | Bouzid Maamache Mabrouk Bouabdallah Abdelhalim Brahimi Youcef Yahmi Billel Cheniti Brahim Mehdi | 2016 | Acta Metallurgica Sinica(English Letters)2016，29，6： | 2 |
| 2 | Work Hardening Behavior of 1020 Steel During Cold-Beating Simulation显示文摘The present research of cold-beating formation mainly focused on roller design and manufacture, kinematics, constitutive relation, metal flow law, thermo-mechanical coupling, surface micro-topography and microstructure evolution. However, the research on surface quality and performance of workpieces in the process of cold-beating is rare. Cold-beating simulation experiment of 1020 steel is conducted at room temperature and strain rates ranging from 2000 to 4000 s^(-1) base on the law of plastic forming. According to the experimental data, the model of strain hardening of 1020 steel is established,Scanning Electron Microscopy(SEM) is conducted, the mechanism of the work hardening of 1020 steel is clarified by analyzing microstructure variation of 1020 steel. It is found that the strain rate hardening effect of 1020 steel is stronger than the softening effect induced by increasing temperatures, the process of simulation cold-beating cause the grain shape of 1020 steel significant change and microstructure elongate significantly to form a fibrous tissue parallel to the direction of deformation, the higher strain rate, the more obvious grain refinement and the more hardening effect. Additionally, the change law of the work hardening rate is investigated, the relationship between dislocation density and strain, the relationship between work hardening rate and dislocation density is obtained.Results show that the change trend of the work hardening rate of 1020 steel is divided into two stages, the work hardening rate decreases dramatically in the first stage and slowly decreases in the second stage, finally tending toward zero. Dislocation density increases with increasing strain and strain rate, work hardening rate decreases with increasing dislocation density. The research results provide the basis for solving the problem of improving the surface quality and performance of workpieces under cold-beating formation of 1020 steel. | Fengkui CUI Yuanfei LING Jinxue XUE Jia LIU Yuhui LIU Yan LI | 2017 | Chinese Journal of Mechanical Engineering2017，30，2： | 2 |
您所在的机构暂未开通此部分的功能，请联系管理员