聚变堆用CLF-1 钢与316L 钢TIG 焊接接头组织与性能初步研究

对用W19123L 为焊丝的聚变堆用低活化CLF-1 钢与316L 钢的钨极氩弧焊(TIG)焊接接头金相组织及性能进行了初步研究。结果表明：焊接接头成型良好、无缺陷;金相组织表明焊接接头由CLF-1 侧(母材区、热影响区、熔合区)、过渡层、焊缝区、316L 侧(母材区、热影响区、熔合区)组成;室温拉伸试验结果优于母材的最低要求值;弯曲试验后的焊接接头内外表面完好,无裂纹产生,变形均匀;焊接接头冲击值成凹型分布,焊缝区冲击值最低,焊缝两侧热影响区冲击值次之,母材冲击值最高,316L 侧冲击值略高于CLF-1 侧,均满足焊接接头设计值;焊接接头上表面1.6mm 硬度波动较大,略高于1/2T 和下表面1.6mm 处,焊接接头1/2T 和下表面1.6mm 硬度分布较均匀,从CLF-1 侧到316L 侧有下降趋势。整体焊接性能基本稳定,满足异种钢焊接性能匹配要求。     

Comparison of microstructure and mechanical properties of ultra-narrow gap laser and gas-metal-arc welded S960 high strength steel

The microstructural characteristics and mechanical properties, including micro-hardness, tensile properties, three-point bending properties and Charpy impact toughness at different test temperatures of 8 mm thick S960 high strength steel plates were investigated following their joining by multi-pass ultra-narrow gap laser welding (NGLW) and gas metal arc welding (GMAW) techniques. It was found that the microstructure in the fusion zone (FZ) for the ultra-NGLW joint was predominantly martensite mixed with some tempered martensite, while the FZ for the GMAW joint was mainly consisted of ferrite with some martensite. The strength of the ultra-NGLW specimens was comparable to that of the base material (BM), with all welded specimens failed in the BM in the tensile tests. The tensile strength of the GMAW specimens was reduced approximately by 100 MPa when compared with the base material by a broad and soft heat affected zone (HAZ) with failure located in the soft HAZ. Both the ultra-NGLW and GMAW specimens performed well in three-point bending tests. The GMAW joints exhibited better impact toughness than the ultra-NGLW joints.     

Experimental investigation and metallographic characterization of fiber laser beam welding of Ti-6Al-4V alloy using response surface method

In the present study, experimental investigations of fiber-laser-beam-welding of 5 mm thick Ti-6Al-4V alloy are carried out based on statistical design of experiments. The relationship between the process parameters such as welding power, welding speed, and defocused position of the laser beam with the output responses such as width of the fusion zone, size of the heat affected zone, and fusion zone area are established in terms of regression models. Also, the most significant process parameters and their optimum ranges are identified and their percentage contributions on output responses are calculated. It is observed that welding power and speed plays the major role for full penetration welding. Also, welding power shows direct effect whereas welding speed shows the inverse effect on the output responses. The bead geometry is influenced by the defocused position of the laser beam due to the change in power density on the workpiece surface. However, overall fusion zone area is unaffected. Mechanical characterization of the welded samples such as microstructural analysis, hardness, and tensile tests are conducted. It is noticed that the hardness value of the FZ is higher than the HAZ and BM zone due to the difference in cooling rate during welding which promotes the formation of α′ martensitic phase in the FZ. Also, an average hardness value in the FZ is compared for two different defocusing positions (i.e. 1 and 2 mm). It is found that hardness value is higher for 1 mm defocused position than 2 mm due the decrement in grain size below a critical range at 2 mm defocused position. The ultimate tensile strength and % elongation of the welded samples are degraded as compared to BM which can be further improved by post heat treatment.     

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.     

Using Taguchi method to optimize welding pool of dissimilar laser-welded components

In the present work, CO₂ continuous laser welding process was successfully applied and optimized for joining a dissimilar AISI 316 stainless-steel and AISI 1009 low carbon steel plates. Laser power, welding speed and defocusing distance combinations were carefully selected with the objective of producing welded joint with complete penetration, minimum fusion zone size and acceptable welding profile. Fusion zone area and shape of dissimilar austenitic stainless-steel with ferritic low carbon steel were evaluated as a function of the selected laser welding parameters. Taguchi approach was used as statistical design of experiment (DOE) technique for optimizing the selected welding parameters in terms of minimizing the fusion zone. Mathematical models were developed to describe the influence of the selected parameters on the fusion zone area and shape, to predict its value within the limits of the variables being studied. The result indicates that the developed models can predict the responses satisfactorily.     

不锈钢焊接件不等强度激光冲击与应力腐蚀试验研究

针对不锈钢焊接接头应力及组织分布不均匀,容易导致应力腐蚀开裂的问题,采用不等强度激光冲击波对316奥氏体不锈钢焊接接头进行处理。通过应力腐蚀试验、残余应力测试及微观组织分析,研究了激光冲击强化对焊接接头应力腐蚀抗性的影响及其作用机理。试验结果表明:激光冲击强化将焊接件的应力腐蚀断裂时间提高了33.48%。激光冲击波的作用,在焊接接头部位引入了高数值的残余压应力,一方面消除了热影响导致的残余拉应力,同时抵消了拉伸工作载荷的作用,降低局部应力梯度,从而延缓表面钝化膜的破裂;另一方面,激光冲击使焊接接头不同区域之间的微观组织均匀和细化,提高了微裂纹萌生的条件,降低了金属发生阳极溶解的可能性。两种因素的共同作用,使得不锈钢焊接接头的抗应力腐蚀性能显著增强。     

Interface microstructure and mechanical properties of laser welding copper–steel dissimilar joint

Relatively the high reflectivity of copper to CO₂ laser led to the difficulty in joining copper to steel using laser welding. In this paper, a new method was proposed to complete the copper–steel laser butt welding. The scarf joint geometry was used, i.e., the sides of the copper and steel were in obtuse and acute angles, respectively. During the welding process, the laser beam was fixed on the steel side and the dilution ratio of copper to steel was controlled by properly selecting the deviation of the laser beam. The offset of laser beam depended on the scarf angle between the copper and steel, the thickness of plate and the processing parameters used in the laser welding. The microstructure near the interface between Cu plate and the intermixing zone was investigated. Experimental results showed that for the welded joint with high dilution ratio of copper, there was a transition zone with numerous filler particles near the interface. However, if the dilution ratio of copper is low, the transition zone is only generated near the upper side of the interface. At the lower side of the interface, the turbulent bursting behavior in the welding pool led to the penetration of liquid metal into Cu. The welded joint with lower dilution ratio of copper in the fusion zone exhibited higher tensile strength. On the bases of the microstructural evaluation at the interface of the welded joint, a physical model was proposed to describe the formation mechanism of the dissimilar joint with low dilution ratio of copper.     

RAFMs 中厚板TIG 焊下的温度场和应力场研究

应用ANSYS 软件对低活化马氏体/铁素体钢(RAFMs)中厚板多道焊接过程进行三维有限元模拟,将得到的温度场和应力场分别与实验对比,对焊缝区和热影响区宽度进行预测,并通过焊接实验进行验证,同时对焊后的试件进行了金相分析和硬度测试。结果表明：温度场和应力场模拟结果和实测结果基本一致,焊缝区以及热影响区宽度的模拟结果和实测结果基本吻合;采用316L 焊丝填充的焊缝,焊缝与母材熔合较好,焊缝没有明显缺陷;硬度检测呈现：焊缝的硬度大大高于热影响区和母材。     

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应用ANSYS软件对低活化马氏体/铁素体钢(RAFMs)中厚板多道焊接过程进行三维有限元模拟,将得到的温度场和应力场分别与实验对比,对焊缝区和热影响区宽度进行预测,并通过焊接实验进行验证,同时对焊后的试件进行了金相分析和硬度测试。结果表明：温度场和应力场模拟结果和实测结果基本一致,焊缝区以及热影响区宽度的模拟结果和实测结果基本吻合;采用316L焊丝填充的焊缝,焊缝与母材熔合较好,焊缝没有明显缺陷;硬度检测呈现：焊缝的硬度大大高于热影响区和母材。     

低活化马氏体钢热等静压焊接接头性能初步研究

研究了低活化马氏体钢(CLF-1)热等静压(HIP)焊接接头的性能,经980℃/1h/空冷+740℃/2h/空冷的性能热处理后,接头组织保持着CLF-1钢母材回火马氏体组织;常温拉伸性能与母材相当,断口为韧窝状且有第二相粒子产生,为塑性断裂且断于焊缝;常温冲击功最高为母材的26.2%。初步分析认为焊接表面制备状态、表面污染物、表面清洗状态、表面氧化膜都会影响基体原子充分扩散,导致界面扩散层不均匀,焊缝裂纹敏感性增强,冲击功低,且不稳定。