结构钢焊条冷焊铸铁半熔化区白口层优化试验研究

本文应用回归正交优化原理,试验研究了结构钢焊条冷焊铸铁半熔化区无白口组织时,最佳匹配的规范参数,为减少和消除白口组织探讨了新途径.     

LSND法焊接镍合金薄板结构有限元分析

翘曲变形是薄板结构焊接时难以避免的问题，它严重影响产品的质量，近年来在试验研究的基础上发展了一种低应力无变形焊接工艺（LSND），本文根据有限元分析结果对这一工艺作进一步探讨。     

铸铁缺陷的大线能量补焊

铸铁缺陷补焊中产生白口组织是修补铸铁件缺陷的技术难题之一。作者认为调整成分;加大线能量,创连石墨化有利条件;再辅之适当工艺措施,可能得到解决。由试验得到证明;肯定了大线能量在铸铁缺陷补焊中的有效作用。     

周期性热源下焊接温度场的边界元计算

采用边界单元法对周期性焊接热源作用下的三维焊接温度场在傅立叶变换空间域进行了求解，在计算中利用局部影响原理，大大减小了快速傅氏变换的计算工作量，使得本文算法的工程应用成为可能。     

爆炸焊接中复板倾斜放置条件下形成射流的质量和速度

首次考虑基板、抛掷角对射流形成的影响，利用一维准定常流体力学理论，推导了倾斜放置条件下复板、基板碰撞时形成的射流质量、运动方向和运动速度的表达式。     

弧焊过程电信号分析系统的研究

弧焊过程电信号分析系统是研制高质量焊接电源设备的一种重要测试技术手段，本文基于Windows环境、调整数据采集卡PCL1800和工控机通用平台，采用VisualC＋＋0开发出高速侈功能弧焊电信号测试分析软件，该系统能精确测定焊接过程的弧焊电压和焊接电流波形，并提出焊接过程动特性的特征信息，从而为高性能焊机的研制和焊接工艺参数的优化提供了一个强有力的工具。     

吸烟焊枪在药芯焊丝CO2气保焊中的作用

采用吸烟焊枪进行药芯焊丝CO₂气保焊,通过记录烟尘扩散形态和焊接电流电压变化,采用高速摄像分析熔滴过渡过程,以及对比焊缝表面成形和采用X射线探伤揭示焊缝缺陷,并与未吸烟时对比,研究了不同吸烟功率和焊枪倾角下吸烟焊枪的吸烟行为及其对焊接过程和焊接质量的影响. 结果表明:焊接烟尘被有效吸入吸烟焊枪,其烟尘扩散形态整体呈锥形,并随吸烟功率的增加,其气流挺度增加,吸尘效果增强. 熔滴过渡仍表现为大滴排斥过渡,吸烟只是使熔滴过渡频率稍有增加. 采用不同功率以及焊枪倾角,均能得到表面成形良好和无缺陷的焊缝.     

12Cr1MoV/TP347H异种钢焊接接头时效过程中界面组织演变

The interfacial microstructure evolution of 12Cr1MoV/TP347H dissimilar steel welded joints with a nickel-based filler metal during aging was studied in detail to elucidate the mechanism of premature failures of this kind of joints. The results showed that not only a band of granular Cr₂₃C₆ carbides were formed along the fusion boundary in the ferritic steel during aging, but also a large number of granular or plate-like Cr₂₃C₆ carbides, which have a cube–cube orientation relationship with the matrix, were also precipitated on the weld metal side of the fusion boundary, making this zone be etched more easily than the other zone and become a dark etched band. Stacking faults were found in some Cr₂₃C₆ carbides. In the as-welded state, deformation twins were observed in the weld metal with a fully austenitic structure. The peak microhardness was shifted from the ferritic steel side to the weld metal side of the fusion boundary after aging and the peak value increased significantly. Based on the experimental results, a mechanism of premature failures of the joints was proposed.     

Isothermal oxidation behavior and mechanism of a nickel-based superalloy at 1000℃

The oxidation behavior of a nickel-based superalloy at 1000°C in air was investigated through X-ray diffraction, scanning electron microscopy, andenergy-dispersive spectroscopy analysis. A series of oxides, including external oxide scales (Cr2O3, (TiO2 + MnCr2O4)) and internal oxides (Al2O3,TiN), were formed on the surface or sub-surface of the substrate at 1000°C in experimental still air. The oxidation re-sistance of the alloy was dependent on the stability of the surface oxide layer. The continuity and density of the protective Cr2O3 scale were affected by minor alloying elements such as Ti and Mn. The outermost oxide scale was composed of TiO2 rutile and MnCr2O4 spinel, and the growth of TiO2particles was controlled by the outer diffusion of Ti ions through the pre-existing oxide layer. Severe internal oxidation oc-curred beneath the external oxide scale, consuming Al and Ti of the strength phaseγ′ (Ni3(Al,Ti)) and thereby severely deteriorating the sur-face mechanical properties. The depth of the internal oxidation region was approximately 35μm after exposure to experimental air at 1000°C for 80 h.