RAFM钢TIG焊和电子束焊疲劳性能实验和分析模拟

利用ANSYS 对低活化铁素体马氏体(RAFM)钢进行非熔化极气体保护焊(TIG 焊)与电子束焊的抗疲劳模拟分析，再利用SDS200 电液伺服疲劳试验机对TIG 焊和电子束焊的两种RAFM 钢试件进行实验。通过施加相同梯度负荷对TIG 焊和电子束焊试件进行焊缝的疲劳性能实验。与实验结果对比分析，结果显示电子束焊优于 TIG 焊，但在一定负载下可以用TIG 焊代替电子束焊。     

超导芯片铟焊质量试验研究

为考察超导芯片接地钎焊质量,参照电子元器件试验方法相关国家标准,模拟超导器件工作温度和真空环境制作了试验装置,对钎焊后的超导芯片样品进行了温度冲击试验、完整超导器件系列环境试验,并对试验数据和结果进行了分析。     

如何避免电器元件的虚焊

在电学实验中,焊接是保证电路发挥功能的重要工艺过程.焊接质量的好坏,直接影响线路及电子装置的工作性能.笔者在多年的教学实践中,发现除个别学生在调试时安装错误外,大部分的毛病是虚焊. 虚焊会使电路工作不正常,而且易于脱落,给电路的调试带来很大的不便.因此在进行焊接时尤应注意.如何防止焊接中的虚焊呢?我采用以下方法,取得一定成效.     

激光穿透焊的三维数值模拟

本文对激光穿透焊进行了三维数值模拟，除考虑焊接速度影响外，还研究了Ｍａｒａｎｇｏｎｉ对流对熔池流动与传热的影响。将三维数值模拟结果与相应的二维模拟结果进行了比较，结果表明，Ｍａｒａｎｇｏｎｉ对流对熔池的形成有很大的影响，因此不可忽略。本文还给出了估计激光穿透焊中蒸气孔尺寸与焊接热效率的方法。     

大功率盘形激光焊飞溅特征分析

焊接过程的在线监控是保证激光焊接质量的关键, 为此, 首先要找到焊接过程传感特征量变化规律以及与焊缝质量间的关系. 飞溅是大功率盘型激光焊接过程中的一个重要现象, 其特征与焊接质量、焊接过程稳定性以及能量利用率等有着密切的联系. 以大功率盘形激光焊接304不锈钢为试验对象, 研究焊接过程中的飞溅特征. 在紫外波段和可见光波段应用高速摄像机摄取焊接过程中产生飞溅的瞬态特征, 通过计算机图像处理技术分析飞溅的数量、面积、行程和质心高度特征参量. 以焊件熔宽作为衡量焊接质量与焊接过程稳定性的因素, 对飞溅特征量进行线性和高次拟合, 研究飞溅特征参量的波动规律, 并与焊件熔宽的变化对比, 探索焊接过程的飞溅特征参量变化规律. 试验结果表明, 根据飞溅特征量变化规律能够对大功率盘形激光焊接304不锈钢板焊接质量做出动态评估, 为实现焊接质量的在线监控提供了试验依据.     

焊后热处理对聚变堆用奥氏体不锈钢MAG焊焊缝金属冲击韧性的影响

对聚变堆用316LN奥氏体不锈钢熔化极活性气体保护电弧焊(MAG焊)接接头进行不同温度的热处理,并在液氮温度下进行夏比冲击试验。利用光学显微镜、扫描电镜、EDS分析等研究了热处理温度对接头微观组织、断口形貌及析出物的影响。结果表明,873K热处理可以显著提高焊缝金属冲击韧性,但随着热处理温度的上升,焊缝金属逐渐出现沿着晶界分布的析出物,韧性逐渐下降。断口均为延性断裂,但随着热处理温度的升高,韧窝变浅、数量变少。韧窝底部存在球状析出和不规则状析出,球状析出在焊接过程中产生,不因热处理温度而变化,不规则析出随着热处理温度的升高逐渐增多。焊材中的Mo含量过高导致焊缝金属中Mo在晶界大量偏聚,促进了σ相的析出,当σ相在晶界形成连续分布后,焊缝金属冲击韧性显著下降。     

药芯焊丝TIG焊电弧特性的光谱分析

利用光谱诊断方法结合高速摄像研究所提出的药芯焊丝的填丝TIG焊接新工艺的电弧特性,借助高速摄像研究药芯焊丝TIG焊的熔滴过渡方式;通过对焊接电弧进行光谱采集点扫描,对采集的谱线进行元素标定,以药粉中活性元素K和Na作为追踪目标,统计得到电弧中药粉成分的分布范围;并利用Boltzmann图法计算TIG焊电弧的温度场分布,分析了熔滴过渡方式对电弧温度场分布的影响。研究结果表明,通过调整丝极间距,得到药芯焊丝TIG焊的三种典型的熔滴过渡方式：滴状过渡(2 mm)、渣柱过渡(5 mm)和搭桥过渡(7 mm)。药粉中的活性元素K和Na等集中分布在熔池上方的电弧空间,且其分布受丝极间距的影响,丝极间距越小其分布越靠近钨极,容易造成对钨极的污染。不填丝TIG焊的电弧温度分布呈钟罩形,等温线关于钨极轴线近似对称分布;与不填丝TIG焊相比,药芯焊丝TIG焊的电弧温度场受熔滴过渡的影响发生了不同程度的扭曲,滴状过渡的电弧温度场扭曲严重,焊接过程中飞溅较大;相比于滴状过渡,渣柱过渡和搭桥过渡的电弧温度场扭曲程度较小且焊接过程稳定,适合该TIG焊方法的使用。     

拼焊式SiC反射镜热变形分析

为了考核拼焊式SiC反射镜在一定温度波动范围内的面形稳定性,利用有限元方法模拟了在温度水平试验条件5℃温差下反射镜的热变形情况。利用曲面方程拟合方法处理镜面变形数据,计算出变形后的镜面面型误差RMS值为1.841nm,满足航天用反射镜对面形指标的要求,考核了该反射镜在一定环境温度范围内的面形稳定性。将模拟结果与相同条件下的环境试验结果相比较,二者误差为3%,具有较好的一致性。验证了该有限元模型以及性能参数的合理性,可为今后更大口径的拼焊式SiC反射镜的研制提供数值模拟基础和材料参数依据。     

爆炸焊界面附近熔化层厚度估算

 爆炸焊接界面附近温升是由爆炸绝热压缩和畸形变形能沉积两者造成的。通过计算绝热压缩温升和畸形变形能沉积产生的温升，给出熔化判据，估计出了爆炸焊接界面熔化层的厚度。     

进口松香型焊膏的成分分析

本文采用离心分离的方法沉淀出松香型焊膏的无机组分，并用发射光谱测定无机成分；优选了氯仿：95％乙醇：25氨水：水＝35：30：2：2（体积比）作为焊膏有机组分的薄层色谱展开剂，在薄层板上呈现清晰的4个斑点，以此展开剂作为柱色谱的流动相，成功地分离了各种有机组分，并采用红外、质谱等手段鉴定了所含组分的结构。     

Precipitation and fracture behaviour of Fe–Mn–Ni–Al alloys

The effects of Al addition on the precipitation and fracture behaviour of Fe–Mn–Ni alloys were investigated. With the increasing of Al concentration, the matrix and grain boundary precipitates changed from L1₀ θ-MnNi to B2 Ni₂MnAl phase, which is coherent and in cube-to-cube orientation relationship with the α′-matrix. Due to the suppression of the θ-MnNi precipitates at prior austenite grain boundaries (PAGBs), the fracture mode changed from intergranular to transgranular cleavage fracture. Further addition of Al resulted in the discontinuous growth of Ni₂MnAl precipitates in the alloy containing 4.2?wt.% Al and fracture occurred by void growth and coalescence, i.e. by ductile dimple rupture. The transition of the fracture behaviour of the Fe–Mn–Ni–Al alloys is discussed in relation to the conversion of the precipitates and their discontinuous precipitation behaviour at PAGBs.     

Microstructure evolution and mechanical property of pulsed laser welded Ni-based superalloy

For evaluating the microstructure evolution and mechanical property of Ni-based Hastelloy C-276 weld joint by the pulsed laser welding, the influence of pulsed laser welding on the microstructure and mechanical property of the weld joint is investigated by the analysis of the microstructure morphology, microhardness, phase structure and tensile property. The results indicate that, in the fusion zone three sections are divided on the basis of the patterns of grain structures. In the weld joint, the element segregation is found, but the trend of brittle phase׳s formation is weakened. The weld microhardness presents just a little higher than that of base metal, and there is no obvious the softened heat affected zone. Meanwhile in the weld joint, the phase structure is still the face-center cubic with the tiny shift of peak positions and widened Full Width at Half-Maximum. The yield strength of weld joint is the same as that of base metal, and the tensile strength is nearly 90% of that of base metal. The decreased tensile strength is mainly attributed to the dislocation piling-up.     

焊后热处理对核聚变用316LN焊接接头的影响

采用了TIG对核聚变用316LN奥氏体不锈钢进行焊接,并对焊接接头进行了焊后热处理,利用光学显微镜、扫描电镜分析手段研究了焊后热处理对焊接接头微观组织和力学性能的变化。试验结果表明,焊缝中为奥氏体组织,并未发现第二相析出物存在。焊后热处理对接头的拉伸性能影响不大,均断裂在母材位置,但显著提高了接头的延伸率。接头低温冲击试验也展现了良好的抗低温冲击性能。断口分析发现,接头呈韧性断裂。     

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采用了TIG对核聚变用316LN奥氏体不锈钢进行焊接,并对焊接接头进行了焊后热处理,利用光学显微镜、扫描电镜分析手段研究了焊后热处理对焊接接头微观组织和力学性能的变化.试验结果表明,焊缝中为奥氏体组织,并未发现第二相析出物存在.焊后热处理对接头的拉伸性能影响不大,均断裂在母材位置,但显著提高了接头的延伸率.接头低温冲击试验也展现了良好的抗低温冲击性能.断口分析发现,接头呈韧性断裂.     

ITER PF֧�Žṹ���Ӽ���

The manufacturing process and welding technology of PF coil support are introduced, and the taken technical measures to control the deformation stress of welding, to improve low temperature impact toughness and to control the weld ferrite content are explained. The machine accuracy and the quality were improved through post weld stress relief and anti deformation measures.     

ITER PF支撑结构焊接技术

介绍了ITER PF 支撑结构制造工艺及焊接技术方案,阐述了对控制焊接变形应力、提高低温冲击韧性、控制焊缝铁素体含量等采取的技术措施。焊后应力消除方案以及防变形措施使得加工精度和成品质量得到了提高。     

Effects of relative positioning of energy sources on weld integrity for hybrid laser arc welding

This study is concerned with the effects of laser and arc arrangement on weld integrity for the hybrid laser arc welding processes. Experiments were conducted for a high-strength steel using a 4 kW Nd: YAG laser and a metal active gas (MAG) welding facility under two configurations of arc–laser hybrid welding (ALHW) and laser–arc hybrid welding (LAHW). Metallographic analysis and mechanical testing were performed to evaluate the weld integrity in terms of weld bead geometry, microstructure and mechanical properties. The morphology of the weld bead cross-section was studied and the typical macrostructure of the weld beads appeared to be cone-shaped and cocktail cup-shaped under ALHW and LAHW configurations, respectively. The weld integrity attributes of microstructure, phase constituents and microhardness were analyzed for different weld regions. The tensile and impact tests were performed and fracture surface morphology was analyzed by scanning electron microscope. The study showed that ALHW produced joints with a better weld shape and a more uniform microstructure of lath martensite, while LAHW weld had a heterogeneous structure of lath martensite and austenite.     

Effect of heat input on microstructure and properties of hybrid fiber laser-arc weld joints of the 800 MPa hot-rolled Nb-Ti-Mo microalloyed steels

Hybrid fiber laser-arc welding (HLAW) process was applied to a novel hot-rolled Nb-Ti-Mo microalloyed steels of 8 mm thickness. The steel is primarily used to manufacture automotive and construction machinery components, etc. To elucidate the effect of heat input on geometry, microstructure and mechanical properties, different heat inputs (3.90, 5.20 and 7.75 kJ/cm) were used by changing the welding speeds. With increased heat input, the depth/width of penetration was decreased, and the geometry of fusion zone (FZ) changed to “wine cup-like” shape. In regard to the microstructural constituents, the martensite content was decreased, but granular bainite (GB) content was increased. The main microstructural difference was in the FZ cross-section at 7.75 kJ/cm because of the effect of thermal source on the top and bottom. The microstructure of the top part consisted of GB, grain boundary ferrite, and acicular ferrite, while the bottom part was primarily lath martensite. The hardness distribution was similar for different heat inputs. Hardness in FZ, coarse-grained HAZ and mixed-grained HAZ was higher than the base metal (BM), but for the fine-grained HAZ was similar or marginally less than the base metal (BM). Tensile strain was concentrated in the BM such that the fracture occurred in this region. In summary, the geometry, microstructure, and mechanical properties of weld joints were superior at heat input of 5.20 kJ/cm.     

Effects of B segregation on Mo-rich phase precipitation in S31254 super-austenitic stainless steels: Experimental and first-principles study

Precipitation in super-austenitic stainless steels will significantly affect their corrosion resistance and hot workability. The effects of Cr and Mo on precipitation behaviors were mainly achieved by affecting the driving force for precipitation, especially Mo has a more substantial promotion effect on the formation of the σ phase than Cr. In the present study, B addition to the S31254 super-austenitic stainless steels shows an excellent ability to inhibit precipitation. The effect of B on the precipitation behaviors was investigated by microstructure characterization and theoretical calculations. The experimental observation shows that the small addition of B inhibits the formation of the σ phase along grain boundaries and changes from continuous to intermittent distribution. Moreover, the inhibitory effect increased obviously with the increase of B content. The influence of B addition was theoretically analyzed from the atomic level, and the calculation results demonstrate that B can inhibit the formation of σ phase precipitates by suppressing Mo migration to grain boundaries. It is found that B and Mo are inclined to segregate at Σ 5 and Σ 9 grain boundaries, with B showing the most severe grain boundary segregation tendency. While B distribution at the grain boundary before precipitation begins, the segregation of Mo and Cr will be restrained. Additionally, B's occupation will induce a high potential barrier, making it difficult for Mo to diffuse towards grain boundaries.     

等离子弧焊接熔池演变过程的模拟和验证

本文建立了描述等离子弧焊接熔池相变传热与流动的三维数理模型,考虑表面张力、电磁力和浮升力的作用,并针对等离子弧焊接特点,改进组合式体积热源模型,上部采用双椭球热源,下部采用圆锥体热源。重点分析了焊接熔池形状和温度场的演变过程,熔合线的模拟形状与实验焊缝吻合,较好地呈现了焊缝的凸起和熔池宽度,验证了数学模型和热源模型的正确性。本文还进一步开展了焊接功率和焊接速度的影响分析。研究结果表明,流动对焊缝形状的影响不容忽略,而表面张力在三个流动驱动力中占主导地位;焊接功率越大,焊接速度越小,越有利于焊件焊透,数值模拟得到优化的焊接功率和速度有益于实际焊接生产质量及效率。