The process properties and interface behavior of CO_2 laser brazing with automatic wire feed for galvanized steel sheets were investigated, in which the brazing filler metal was CuSi3 and no flux was used. As to the a...The process properties and interface behavior of CO_2 laser brazing with automatic wire feed for galvanized steel sheets were investigated, in which the brazing filler metal was CuSi3 and no flux was used. As to the appearance quality of the brazing seams, the roles of the processing parameters, such as brazing speed, wire feeding rate, inclination and feeding direction of the wire, laser power, spot diameter and heating position, were assessed. The further investigation indicates that the behavior of the active elements Si, Mn and Zn are significantly influenced by energy input. At the interface, the microstructure of the base metal was composed of columnar crystals and the acicular α solid solution was found on the filler metal side.展开更多
This study provides a detailed failure analysis of galvanized steel wires(3 mm in diameter) for a 35 k V transmission and distribution line, which was carried out by combining the conventional material analysis method...This study provides a detailed failure analysis of galvanized steel wires(3 mm in diameter) for a 35 k V transmission and distribution line, which was carried out by combining the conventional material analysis methods with the finite element method(FEM). It is found that the failed material had good plasticity(5% in elongation),and under the soft torsion loading condition(0.75 in stress state soft coefficient), the ductile fracture should occur on the material. Additionally, the theoretical number of torsions calculated by the FEM was 26.2 times, while the actual number of torsions achieved by the test was only 2.2 times and the local fracture surface exhibited brittle fracture characteristics. The results showed that the local torsion brittle fracture of the material with good plasticity was caused by triaxial stress in the torsion condition, which led to the formation of cavity in the pulling stress area in the material’s center, and the finite element calculation results indicated that the stress state soft coefficient at the cavity was distributed between 0.31 and 0.38, and the stress concentration at the cavity was more than twice the normal value. Besides, the Widmanstatten structure formed as the improper hot working process is the corresponding structural reason.展开更多
拉吊索在侵蚀环境作用下易受氯离子、氧气、水等物质的腐蚀作用,严重影响了缆索系统的耐久性。本文通过开展镀锌平行钢丝外加电流阴极保护(Impressed Current Cathodic Protection,ICCP)试验,研究外加电流对桥梁索体钢丝的阴极保护效果...拉吊索在侵蚀环境作用下易受氯离子、氧气、水等物质的腐蚀作用,严重影响了缆索系统的耐久性。本文通过开展镀锌平行钢丝外加电流阴极保护(Impressed Current Cathodic Protection,ICCP)试验,研究外加电流对桥梁索体钢丝的阴极保护效果,根据钢丝在侵蚀过程中的微观损伤演化以及腐蚀速率、抗拉强度、延伸率、瞬断电位、开路电位、极化曲线、疲劳性能等力学性能指标的变化规律,从而确定ICCP电压的施加范围。结果表明:随着保护电压的负向偏移,ICCP的保护效果更佳,当保护电压位于-1.3 V时对延缓钢丝腐蚀的效果最好,腐蚀速率最低,抗拉强度、延伸率和疲劳寿命的损失率最低,且延性得到显著提升。展开更多
文摘The process properties and interface behavior of CO_2 laser brazing with automatic wire feed for galvanized steel sheets were investigated, in which the brazing filler metal was CuSi3 and no flux was used. As to the appearance quality of the brazing seams, the roles of the processing parameters, such as brazing speed, wire feeding rate, inclination and feeding direction of the wire, laser power, spot diameter and heating position, were assessed. The further investigation indicates that the behavior of the active elements Si, Mn and Zn are significantly influenced by energy input. At the interface, the microstructure of the base metal was composed of columnar crystals and the acicular α solid solution was found on the filler metal side.
文摘This study provides a detailed failure analysis of galvanized steel wires(3 mm in diameter) for a 35 k V transmission and distribution line, which was carried out by combining the conventional material analysis methods with the finite element method(FEM). It is found that the failed material had good plasticity(5% in elongation),and under the soft torsion loading condition(0.75 in stress state soft coefficient), the ductile fracture should occur on the material. Additionally, the theoretical number of torsions calculated by the FEM was 26.2 times, while the actual number of torsions achieved by the test was only 2.2 times and the local fracture surface exhibited brittle fracture characteristics. The results showed that the local torsion brittle fracture of the material with good plasticity was caused by triaxial stress in the torsion condition, which led to the formation of cavity in the pulling stress area in the material’s center, and the finite element calculation results indicated that the stress state soft coefficient at the cavity was distributed between 0.31 and 0.38, and the stress concentration at the cavity was more than twice the normal value. Besides, the Widmanstatten structure formed as the improper hot working process is the corresponding structural reason.
文摘拉吊索在侵蚀环境作用下易受氯离子、氧气、水等物质的腐蚀作用,严重影响了缆索系统的耐久性。本文通过开展镀锌平行钢丝外加电流阴极保护(Impressed Current Cathodic Protection,ICCP)试验,研究外加电流对桥梁索体钢丝的阴极保护效果,根据钢丝在侵蚀过程中的微观损伤演化以及腐蚀速率、抗拉强度、延伸率、瞬断电位、开路电位、极化曲线、疲劳性能等力学性能指标的变化规律,从而确定ICCP电压的施加范围。结果表明:随着保护电压的负向偏移,ICCP的保护效果更佳,当保护电压位于-1.3 V时对延缓钢丝腐蚀的效果最好,腐蚀速率最低,抗拉强度、延伸率和疲劳寿命的损失率最低,且延性得到显著提升。
