Ti—55M高温Ti合金焊缝塑性的改善

考察了Ti-55M高温Ti合金焊接接头力学性能,结果显示焊缝在明显的室脆性,探讨了Ti-55M焊缝室温塑性的各种影响因素,尝试使用调整焊缝化学成分的方法改善Ti-55M焊缝的塑性,选择ELI级Ti-5Al-2.5Sn焊丝、配合脉冲氩弧焊工艺和适当的焊后热处理制度、获得的焊缝塑性接近母材的塑性,接头的室温和高温强度以及高温持久等重要性能能够满足母材技术指标要求。     

Electrochemical behavior of YAG laser-welded NiTi shape memory alloy

Electrochemical behaviors of laser-welded Ti-50.6%Ni（mole fraction） shape memory alloy and the base metal in 0.9% NaCl solution were investigated by electrochemical techniques as corrosion potential measurement, linear and potentiodynamic polarization. The results indicate that the laser-welded NiTi alloy is less susceptible to pitting and crevice corrosion than the base metal, which is demonstrated by the increase in polarization resistance（Rp） and pitting potential（φpit） and decrease in corrosion current density（Jcorr） and mean difference between φpit and φprot values. It is confirmed by scanning electron microscope micrographs that pits could be observed on the surface of base metal but not on the surface of laser-welded alloy after potentiodynamic tests. An improvement of corrosion resistance of laser-welded NiTi alloy could be attributed to almost complete dissolution of inclusions upon laser welding.     

Repair welding of ductile cast iron by laser cladding process: microstructure and mechanical properties

Abstract

The aim of this research was to determine the feasibility of a newly developed process in the repair of cracked gas turbine casings made of ductile cast iron. This study investigated the microstructural characteristics, metallurgy and mechanical properties of the repair weldments produced using fibre laser cladding. Optical microscopy, scanning electron microscopy and element probe microanalysis were used to investigate the microstructure at the cladding weld interface. The mechanical properties of the cladded specimens were evaluated after laser cladding. Our results revealed that the weldability of ductile cast iron can be enhanced by performing laser surface pretreatment to sublimate graphite nodules. Microhardness at the interface of the laser cladded weldments depended largely on the range of the heat affected zone and the degree of phase complexity. Under tensile loading, failures were limited to the base metal region of the weldments. Test results demonstrate that the impact toughness of the interface between the fusion zone and the base metal can be enhanced through the application of post-cladding heat treatment.     

Main methods and technological features of welding dissimilar plastics

The interface formed between the metal and the porcelain of laser-welded Ni–Cr–Mo alloy was studied on a metallurgical basis. The characterization was carried out by using optical microscope, electron scan microscopy and X-ray dispersive spectroscopy techniques and mechanical three-point flexion tests, in the laser-welded region, with and without porcelain. The union of the porcelain with the alloy is possible only after the oxidation of the metallic surface and the subsequent application of a bonding agent known as opaque. The porcelain applied to the base metal and weld bead showed different behaviours – after the flexion test, the base metal showed cracks, while that in the weld bead broke away completely. It was noted that the region subjected to laser welding had lower adherence to the porcelain than the base metal region, due to microstructural refinement of the weld bead. These results can be shown by the X-ray dispersive spectroscopy carried out on the regions studied. The flexion tests demonstrated that the Ni–Cr–Mo alloy subject to laser welding had significant alterations in its mechanical properties after application of the porcelain.     

316L不锈钢薄板脉冲激光焊工艺参数及接头组织特征

研究了0．1 mm 316L不锈钢薄板脉冲激光焊工艺参数特征，分析了接头的组织和力学性能。结果表明：0．1mm 316L不锈钢薄板脉冲激光焊时适宜用小电流、大脉宽、高速度、高频率；焊缝中心为细小的等轴晶，边缘是细小的柱状晶；焊接接头的抗拉强度可达到母材的95％，伸长率可达到母材的85％。     

镀锌板激光焊接接头锌的分布及耐蚀性试验

研究了镀锌板激光焊接接头锌的分布及焊接接头耐蚀性能。定量及SEM分析表明,焊缝中表面只残留少量锌,在焊缝两侧的热影响区,锌层厚度呈梯度分布。激光焊缝窄,基材锌层阳极保护作用得以保存,激光焊接板仍具有较好耐蚀性。     

Microstructure and Oxidation Characteristics of Laser and GTAW Weldments in Austenitic Stainless Steels

The present investigation reports microstructure and high-temperature oxidation behavior of GTAW and laser weldments of 316L stainless steel. The microstructure and oxidation behavior of composite laser weldment are found to be influenced by the welding speed. In GTAW weldment, weld metal shows higher oxidation rate as compared to base metal of same weldment. Furthermore, the inoculation of Ce in GTAW weld influences the microstructure and oxidation characteristics. The scale morphologies, scale adherence, and spallation have been characterized by SEM and EDAX.     

Uni- and bi-axial deformation behavior of laser welded advanced high strength steel sheets

Bead-on-plate butt joints of 2.5 mm hot rolled DP600/DP600 and 1.2 mm cold rolled TRIP700/TRIP700 steel sheets were performed using 6 kW CO₂ laser beam welding. The welding speed ranged from 1.5 to 3.0 and from 2.1 to 3.9 m/min in DP/DP and TRIP/TRIP steel weldments respectively. A top surface helium gas was used as a shielding gas at a flow rate of 20 l/min. Metallographic examinations and transverse tensile testing (DIN EN 895: 1995) were carried out to characterize the weldments. The formability of base metals and weldments were investigated by standard Erichsen test (DIN EN ISO 20482). It was found that the uniaxial plastic behavior of both DP600 and TRIP700 base metals was in agreement with Swift and modified Mecking–Kocks models respectively. In a perpendicular tensile test to the weld line, all specimens were fractured at the base metal however the strengths were somewhat higher than those of base metal. There was a significant reduction in formability caused by welding of both DP/DP and TRIP/TRIP steel weldments and the formability has been improved with the increase of the welding speed.     

AZ31镁合金激光焊件的力学性能和应力腐蚀行为

采用Nd-YAG激光对AZ31 HP镁合金进行激光自熔焊接。显微组织分析表明,使用或不使用填料（焊料）AZ61镁合金得到的激光焊接接头的平均晶粒尺寸大约为12μm,显微硬度和拉伸强度与母材相近。然而,慢应变速率拉伸表明,在ASTM D1384溶液中两种焊接接头的抗应力腐蚀性能比母材略差。可观察到应力腐蚀裂纹在焊缝金属萌生并向热影响区（HAZ）扩展。然而,在以AZ61镁合金为填料（焊料）获得的焊接接头中,观察到裂纹起源及扩展出现在热影响区（HAZ）。在慢应变速率拉伸试验中,由于试样表面暴露在腐蚀环境中,在氢氧化镁/氧化镁层形成局部损伤,从而导致应力腐蚀裂纹的生成。     

Characteristics of Nd： YAG laser welded 600 MPa grade TRIP steel

Microstructures and mechanical properties of Nd: YAG laser welded transformation induced plasticity (TRIP) steel with tensile strength of 645 MPa were studied. Due to high cooling speed of laser welding, the weld metal mainly consists of martensite different from the base metal, which is composed of ferrite matrix with bainite and a little retained austenite. Therefore, the weld metal has maximum hardness at welded joint. The yield strength and tensile strength of welded specimens tested perpendicular to weld line were almost equal to those of the base metal. But the yield strength and tensile strength of welded specimens tested parallel with weld line were a little higher than those of the base metal. The formability of laser welded TRIP steel was decreased compared with that of the base metal.     

Microstructural and aqueous corrosion aspects of laser-surface-melted type 304 SS plasma-coated mild steel

Plasma spray deposition of metals, ceramics, or plastics onto base metals to produce wear- and corrosion-resistant surfaces is a promising technique whereby base metal performance can be considerably im-proved. Because these coatings invariably contain pores, voids, and cracks, laser surface melting may be employed to improve their homogeneity. This study focuses on the corrosion performance of laser- sur-face- melted type 304 SS plasma- coated mild steel specimens. Mild steel strips were plasma coated with an approximately 100 to 200 μm thick layer of type 304 by transferred plasma jet. These specimens were sub-sequently laser irradiated using a 3 kW continuous- wave CO₂ gas laser. Eight different sets of specimens were selected based on different laser beam travel speeds. Scanning electron microscopic studies of the plasma- coated specimens revealed both pancake and flowery types of deposited particles. Optical micro-scopic studies followed by anodic polarization experiments were carried out on these specimens in IN H₂SO₄ medium. It was observed that specimens with laser beam interaction times ranging from 30 to 120 ms showed relatively better general corrosion performance than specimens with interaction times of from 15 to 24 ms.     

The influence of output current on the tensile strength of laser-welded titanium joints

The objective of this study was to examine the influences of the laser output current on the tensile strength of laser-welded titanium bar. Titanium bars of 3 mm in diameter were perpendicularly cut to 30 mm in length for the laser welding. Two bars were fixed to each other with a jig and welded vertically with the light of a laser beam. The tensile strengths of laser-welded titanium joints increased until the output reached 250 A, but decreased as the output current exceeded 250 A. The tensile strengths were significantly lower than that of non-welded parent metal.     

Improvement in the ductility of molybdenum alloys due to grain boundary segregation

An improvement in the tensile ductility from the traditional 3–20% in 6.35-mm-thick molybdenum weldments has been achieved through the addition of Zr, Al, C and B at the ppm level. Atom probe tomography has revealed segregation of Zr, B and C to and depletion of O at the grain boundaries in the base metal and the heat affected zone.     

电子枪零件钽钼激光焊接显微结构和性能分析

采用脉冲固体激光器电子枪零件钼和钽进行激光焊接工艺试验,利用金相显微镜、扫描电镜、万能材料试验机、电子显微硬度分析仪、X 射线衍射仪、振动台、电子枪真空除气系统等研究了电子枪金属零件焊缝焊接表面成形、接头区域的组织形貌、界面元素分布、断口形貌、显微硬度与接头力学性能、焊接接头物相、电子枪随机振动及工作状态下电性能和热性能。 结果表明,优化焊接参数后焊接的电子枪经受了在微波管中连续高温工作的考验。 振动试验和电子枪性能试验检验了电子枪组件的焊接牢固程度和焊接质量,验证了激光焊接工艺在小批量微波管研制、生产和应用过程中的可靠性。     

2A97-T3铝锂合金激光焊接接头微观组织与织构的EBSD研究

从2A97-T3铝锂合金激光焊接头的上水平面、横截面、纵截面和下水平面进行取样,对接头的微观组织和织构进行了分析。利用电子背散射衍射（EBSD）技术的多种表征方法,如OIM、PF、IPF、取向角分布、ODF、晶粒形貌图,并结合激光焊过程的数值模拟,研究了激光焊作用下接头微观组织的演变机理。结果表明,由于薄板冷轧工艺和激光焊加工的非平衡特性,导致接头不同截面的晶粒形态、取向和微观织构存在明显差异。这种组织的不均匀性是接头性能各向异性的根本来源。因此,有必要对接头的不同截面进行分析,进而对微观组织和织构获得全面性和空间性的认识。激光诱导下,热影响区发生了动态再结晶和亚结构晶粒的形成和长大,焊缝区则产生了微观组织的重熔现象,该过程会导致母材原有织构特征在热影响区减弱、在焊缝区消失。     

Properties of titanium alloy AT2 and weldments of the alloy

Conclusions Alloy AT2 and weldments of the alloy have high strength and ductility at temperatures from 500 to –253°. The deformability of the weld seam is approximately the same as that of the alloy. The corrosion resistance in hydrochloric and phosphoric acids is the same for the weld seam and the base metal. Alloy AT2 and weldments of the alloy are more resistant to hydrochloric and phosphoric acids than alloy VT1.E. O. Paton Institute of Electric Welding of the Academy of Sciences, Ukrainian SSR. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 1, pp. 66–68, January, 1976.     

Structure and properties of steel 12Kh18N10T after prolonged operation at −183°C

Conclusion Static and dynamic tests showed that prolonged operation (operating stress around 40% of the yield strength at room temperature) at –183° leads to no essential changes in the ductility or toughness of the base metal or weldments.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 32–34, May, 1976.     

Tensile properties and fracture toughness of 18Ni (250 grade) maraging steel weldments

Abstract

Gas tungsten arc welding was performed on 18Ni (250 grade) maraging steel sheet using two different filler wires: one of the same composition as the base material and the other containing more cobalt and aluminium and less molybdenum and titanium. Weld specimens were then aged under four different sets of conditions. After metallographic characterisation, mechanical properties including hardness, tensile strength and ductility, and fracture toughness were evaluated. Results showed that use of the matching filler material led to lower strength but higher ductility than in the other case; this was attributed to the presence of reverted austenite in the former (caused by segregation, especially of molybdenum) at the fusion zone substructure boundaries. In both types of weld metal, a re-solution treatment followed by aging at 480°C resulted in optimum tensile properties. Fracture toughness of the aged weldments was in general close to that of the parent material aged at 480°C; some deterioration occurred only when welds with pronounced segregation were made at high temperature.     

铝合金5A02不等厚板的CO2激光填粉拼焊

在填加粉末的条件下,采用CO2激光器焊接铝合金5A02不等厚板,研究焊接参数对焊缝成形的影响;利用金相显微镜、扫描电镜、拉伸试验机分别研究了激光拼焊板焊接接头的力学性能、断口形貌及微观组织特点.结果表明,填加粉末可使5A02不等厚薄板的激光焊接过程的稳定性显著提高,在比较宽的参数范围内,可以得到成形良好的焊缝;拼焊板的横向拉伸试样均断裂于薄板热影响区,拉伸性能与母材中变形能力较好的板料所占比例有关,该比例越大则拼焊板具有较大的延伸率,变形能力越强;拼焊板的焊缝组织极为细小,在熔合线附近开始向焊缝中心生长的是树枝状晶,在焊缝中心是等轴晶.     

基于Pro/E二次开发的焊缝缺陷空间位置可视化

详述了基于Pro/E和VC开发向导的复杂结构激光焊件缺陷可视化的开发步骤,开发了复杂结构激光焊件缺陷三维可视化应用程序,实现了复杂结构激光焊件内部缺陷的可视化,并可实现焊件的结构尺寸的自适应调整和内部缺陷尺寸和空间位置的自适应调整,为射线检测二维成像三维可视化提供了新思路.