Heat treatment of welded joints in Sakhalin-2 transmission gas pipeline

The conditions of automatic and manual argon-shielded arc welding of VZh171 creep-resisting alloys are determined. The results of the investigations on the technological and mechanical properties and also of the structure of the welded joints are presented.     

Effect of friction welding parameters and heat treatment on the quality of welded joints in creep-resisting deformable nickel alloys

Methods of friction welding creep-resisting deformable nickel alloys and heat treatment are investigated. Welding conditions are selected. The results of mechanical tests and the determination of short- and long-term strength and impact bending resistance are presented, and the data obtained in metallographic and fractographic studies of the welded joints are described.     

Diffusion welding of components made of creep-resisting alloys (part 1)

The efficiency of diffusion welding components made of nickel creep-resisting alloys is confirmed. It is proposed that to increase the mechanical properties and decrease the extent of plastic deformation of components and also prevent the softening of the welded nickel creep-resisting alloys welding should be carried out using nickel interlayers.     

黄铜H62搅拌摩擦焊接头的微观组织及性能

针对H62黄铜进行搅拌摩擦焊实验研究,初步分析工艺参数对接头的组织及力学性能的影响。结果表明:当焊接速度与搅拌头旋转速度的比值保持在0.09~0.15之间,压入深度在0.1~0.2 mm之间时,可得到组织致密、无孔洞的搅拌摩擦焊接头;用搅拌摩擦焊得到的黄铜接头的力学性能比母材低,但比熔化焊得到的接头性能要高,其平均抗拉强度可达到母材的88%。     

Diffusion welding of components made of creep-resisting alloys: diffusion welding of titanium-based creep-resisting alloys (Part 2)

The efficiency of using diffusion welding for joining components of nickel creep-resisting alloys is confirmed. It is proposed that the mechanical properties can be improved, the extent of plastic deformation of components reduced, and softening of the welded nickel creep-resisting alloys prevented using nickel-based interlayers.     

Arc welding with the effect of directional gas‐jet flows on the molten pool

The experimental results show that postweld heat treatment in specific conditions of oil transmission pipelines welded by high-frequency welding results in the structural state of the welded joints and, correspondingly, the strength and corrosion properties of the welded joints similar to that of the parent metal. Requirements and reference specimens of the structure of the welded joints, ensuring high corrosion resistance of the welded pipes, were developed.     

Reconditioning rotor components of gas turbine engines produced from titanium alloys by welding using modified submicrocrystalline filler materials

Experimental results show that the application of standard methods of reconditioning components of titanium alloys reduces the mechanical properties of welded joints by up to 30%. The main reasons for this are structural changes and weld defects. The modified (La, Y and B) filler materials were developed from titanium alloys with a submicrocrystalline structure. These materials produce the equiaxed and ductile structures in welded joints in titanium alloys so that the mechanical properties of the welded joints equal 0.9 of the properties of the parent metal. Consequently, the range of repairs of rotors of gas turbine engines can be greatly widened.     

Effect of the surface roughness of friction stir welded joints on the fatigue characteristics of welded joints in V-1461 and V-1469 aluminium–lithium alloys

Investigations were carried out into the effect of friction stir welding conditions of V-1461 and V-1469 aluminium–lithium alloys on surface roughness and mechanical properties of welded joints. The general parameter of the welding conditions was the heat input coefficient determined by the ratio of the speed of rotation of the tool to the welding speed. The optimum range of friction stir welding conditions of sheets of the investigated alloys was determined. In this stage, the surface finish of the welded joint after welding is much better (required for increasing the fatigue characteristics and high-quality deposition of protective coatings), there are no defects and the strength of the welded joint is equal to 0.75–0.85 of the strength of the parent material. The production of the welded joints with reduced surface roughness (R_z ≤ 40 μm) greatly increases the fatigue characteristics of the welded joints (low-cycle fatigue strength equals more than 300,000 cycles without fracture).     

钛合金搅拌摩擦焊接最新研究进展

钛合金具有密度低、比强度高,耐蚀性好,加工性能优异等优点,主要应用于航空航天、交通运输和石油化工等领域。当钛合金作为结构材料应用在不同领域时,传统的熔融焊接方法会产生较大残余应力,组织粗化,变形大,裂纹和孔隙等缺陷;而采用搅拌摩擦焊接技术可以避免传统熔融焊接方法产生的缺陷,从而大幅度提高钛合金焊接接头质量。目前,钛合金的搅拌摩擦焊接技术已成为国内外研究热点。主要介绍搅拌摩擦焊接的原理、工艺特点,国内外关于钛合金FSW焊接接头的宏观形貌、微观组织(晶粒大小、织构)和力学性能等方面的最新研究进展,最后展望了钛合金FSW未来的研究方向。     

Friction welding of pipes of a zirconium alloy with 2.5% niobium

Investigations were carried out into the ductility properties of a number of titanium alloys in heating from 750 to 1050°C and ATs5K5 and AMts aluminium alloys. The extreme temperature ranges with increased ductility are determined. The conditions of diffusion welding of T-joints in alloys are determined to produce joints without visible defects with the simultaneous formation of a smooth transition (fillet) in the fin–web section. Examples of a number of welded joints are discussed.     

Friction stir welding of thick plates of Al–Mg–Sc alloy

A technology is developed for single-pass friction stir welding (FSW) of 11- and 35-mm-thick plates of Al–Mg–Sc alloys. The microstructural and mechanical heterogeneity of the welded joints is investigated. The welded joints obtained under the optimum welding conditions are free from macrodefects. The strength of the welded joint equals 98% of the strength of the parent metal, which is higher than the strength of fusion-welded joints. It is concluded that the FSW of thick plates of Al–Mg–Sc alloy can be used efficiently in practice.     

Formation of the substructure and crystallography of welded joints in tungsten single crystals

The authors describe the experimental results for the structure, crystallography and properties of welded joints produced by electron beam welding with the speed of 5 to 95 m/h in single crystal tungsten plates with the orientation {100} 〈100〉 and {100} 〈110〉. The results show that welding can be used to produce welded joints in which the density of the dislocations in the weld metal and the misorientation angle at the sub-boundaries do not exceed the values permissible for the single crystals. The dependence of the mechanical properties of the metal of the welded joints on the welding conditions and the resultant structure and crystallography of the welded joints is determined.     

Properties and structure of friction stir welded joints in 1424 and V-1461 (Al–Li) alloys*

The effect of the friction stir welding (FSW) conditions on the structure of welded joint and mechanical properties of 1424 and V-1461 alloys is investigated. FSW is accompanied by the formation of a recrystallized fine-grain microstructure in the welded joint. It is shown that the increase of the heat input to the welded sheets does not increase the average grain size in the weld zone (the average grain size is 1.5–2.2 μm). The tensile strength of the welded joints depends on the welding conditions for both alloys. Special features of the microstructure formed in the zone of the welded joint are discussed and the effect of the microstructure on the mechanical properties of the welded joints and evolution under the effect of heat treatment after FSW are determined.     

Pressure welding of dissimilar creep-resisting alloys and simulation of the effect of the geometrical parameters of the specimen on the localisation of plastic deformation in the pressure welding zone

Computer modelling is used to investigate the possibilities of increasing the quality of welded joints in pressure welding of dissimilar creep-resisting materials in the presence of a relief on one of the welded surfaces. It is shown that the quality of welded joints depends on the geometrical parameters of the welded specimen.     

Special features of the formation of the structure of rotational friction welded joints in VZh175 creep-resisting wrought nickel alloy

ABSTRACT

The finite element method is used to construct the model for the determination of the temperature fields and strains in the welded joint zones. The effect of the welding conditions in the structure and mechanical properties of the welded joints is investigated. The mechanism of formation of the welded joint in the rotational friction welding of VZh175 nickel alloy is described.     

Fatigue Performance of Gas Tungsten Arc, Electron Beam, and Laser Beam Welded Ti-6Al-4V Alloy Joints

Titanium alloys have been successfully applied for aerospace, ship, and chemical industries because they possess many good characteristics such as high strength to weight ratio, superior corrosion resistance, and excellent high temperature resistance. Though these alloys show reasonable weldability characteristics, the joint properties are greatly influenced by the welding processes. The evaluation and prediction of fatigue life are very important for the welded joints to avoid catastrophic failure particularly in titanium alloys. This article compares the fatigue performance of Ti-6Al-4V alloy fabricated by gas tungsten arc welding, laser beam welding, and electron beam welding processes. The resultant fatigue properties of the welded joints are correlated with the tensile properties and microstructural characteristics. Of the three processes considered the joint welded by laser beam welding exhibits higher fatigue limit when compared with the other two processes due to the presence of fine lamellar microstructure in the weld metal region.     

TA15钛合金焊接接头性能与断裂行为研究

对TA15钛合金氩弧焊和电子束焊焊接接头的性能与微观组织进行了分析研究,并结合断口观察,对其断裂行为进行了研究.结果表明,两种焊接接头强度均与母材相当,而塑性明显降低.焊接接头热影响区组织均呈现从粗大等轴组织到魏氏组织的过渡变化特征.疲劳断裂位置一般位于靠近熔合线的焊缝区域,主要原因是此区域存在组织突变和熔合线气孔.焊接气孔对接头疲劳性能影响较大.两种焊接接头疲劳断口特征存在明显区别.     

大厚度钛合金结构电子束焊接制造基础研究

通过对大厚度电子束焊焊缝几何特征和接头组织和力学性能不均匀性的研究,提出焊缝几何特征表征参量和不均匀性表征因子;通过对接头损伤、断裂和疲劳的实验和理论研究,提出大厚度钛合金电子束焊接接头的失效机理;通过对焊接应力变形的理论和数值模拟研究,提出大厚度钛合金电子束焊接接头残余应力形成的机理;在上述研究的基础上,设计大厚度钛合金电子束焊接结构完整性评价体系.从而有望建立大厚度钛合金电子束焊接接头性能定量调控理论与工艺方法和有自主知识产权的大厚度钛合金电子束焊接结构强度、断裂和疲劳完整性评价的方法和指南.     

Laser welding of high-strength aluminium–lithium alloys with a filler wire

The possibilities of using laser welding with a filler wire for joining sheet materials made of V-1469 and V-1461 high-strength aluminium–lithium alloys are investigated. The optimum conditions of placing the filler wire in relation to the laser beam in the weld pool are determined. The optimum welding parameters resulting in the high-quality formation of the welded joint with equal sagging and excess metal and the absence of porosity and cracks are also determined. The mechanical properties of welded joints are outlined and the microstructure of the welded joint is investigated. The corrosion resistance of the produced welded joints is studied.     

Microstructure and properties of joints produced by laser welding with burning through

The mechanism of formation of the welded joint in laser welding with burning through of dissimilar and identical materials is investigated. The welded joints are examined by metallographic methods and mechanical tests, and the special features and the properties of the metal of the welded joint, and the weld zone and the parent metal of the welded components are described.