Welding Mode Research Articles

Friction stir welding of fillet joints of aluminum alloys, schemes for fastening parts and determining welding modes

Experiments on welding of fillet joints of AMG6 aluminum plates by friction with stirring are carried out. Various schemes for fixing parts during welding are considered. An optimal scheme is determined that reduces the occurrence of defects. Studies are carried out to optimize the welding mode. Keywords: fillet joint, friction stir welding, friction welding. vnchrnkh@gmail.com

Образование сварных твердофазных соединений проволок при изготовлении пористых сетчатых материалов из стали 12Х18Н10Т

The experience of using turbine blade shells based on porous mesh materials in aerospace products and high-temperature gas turbines has shown that they are subject to destruction when under the influence of pressure fluctuations. So, first of all, fatigue failure occurs, in those permeable shells where there are no high-quality connections of structure-forming elements. It has been established that in diffusion welding and rolling welding, the strength of welded bonds increases with an increase in the process temperature, as well as in the vacuum depth and deformation time in diffusion welding. Research findings show that at strain rates of 10–2…1.0 s–1, the low quality of welded joints is explained by the high deformation resistance of microroughnesses on the contact surfaces of the wires and the low rate of diffusion mass transfer in the connection zone. The study establishes that under the conditions of diffusion and impact welding in vacuum, the formation of a solid-phase joint is possible on the entire surface of the macrocontact. At the same time, in percussion welding, the influence of the temperature value in the investigated interval on the quality of welded bonds is much lower than that for processes with lower loading rates. Practical recommendations are given for determining the optimal modes of wire mesh welding in the manufacture of porous mesh materials made of 12Kh18N10T steel.

Study of mode transition in three-dimensional laser beam oscillating welding of aluminum alloy

Although 2-d (two-dimensional) beam oscillation can reduce the porosity defects during laser welding of aluminum alloys, it distributes the heat input, resulting in a higher power required to form a capillary. Therefore, this research draws attention to an alternative approach, which is considered to be beneficial to laser absorption in oscillation laser beam welding, 3-d (three-dimensional) oscillation of the laser beam. (3-d oscillation means that the laser spot moves on the two-dimensional plane and the defocus change simultaneously, causing the heat input to change) An experiment was designed where the variation of oscillation frequency leads to significant changes in capillary behavior. The result shows that the increase of vertical oscillation can promote the formation of a capillary. When the oscillation frequency reaches some special values, the capillary appears and disappears periodically, such as the vertical oscillating frequency is 5 Hz, rotation oscillating frequency is 200 Hz. Meanwhile, welding pores are generally distributed at the position where the capillary begins to disappear. The reason for promoting capillary formation during 3-d laser beam oscillation, and the change of normalized temperature, which is meaningful for understanding the welding mode transition, is illustrated by a simplified model. Compared with traditional linear welding, the experimental results show that it is possible to obtain lower porosity seam during 3-d laser beam oscillation welding in low feed rate, and the mechanism of stabilizing the molten pool is discussed qualitatively.

Pressure forming of sheet panels with internal channels

A technological scheme and calculations of pressure welding modes and gas shaping of channels between two-layer sheet blanks are given. The creep-plastic state of an anisotropic deformable material is assumed. The equations of deformations, pressure during upset and gas forming as a function of time are obtained. Keywords: creep-plastic state of the material, deformations, power, time, pressure, exposure. vladimir-chudin@yandex.ru

Laser Spot Welding a Three-Layered Panel in Different Spatial Positions

The aim of the work is a comparative analysis of structural features and mechanical characteristics of spot welded joints of thin-sheet stainless steels 03Х11Н10М2T and 12Х18Н10Т, produced by laser welding in different welding positions. The change in the welding position from vertical to flat allowed extend the ranges of variation of welding modes from about ±5% to about ±10%, at which it is possible to produce a welded joint with satisfactory shape and mechanical characteristics. Higher strength is typical for welded joints obtained in a flat position. It also concerns the maximum value of the shear stress, which for the flat position is higher by approximately 10%, and the average value, which is higher by approximately 24%. In addition, the results of mechanical shear tests of these joints have a significantly lower dispersion.

The effect of laser impingement angle on the optimization of melt pool geometry to improve process stability during high-speed laser welding of thin-gauge automotive steels

Automated laser welding is a popular fusion joining method used for numerous applications involving the joining of similar and dissimilar materials of varying thicknesses. Laser welding offers several advantages over other fusion joining methods such as: high reliability and consistency in the quality of the welds, high production rates, ease of process optimization, higher power density and lower heat input, significantly reduced heat affected zone due to the ability to effectively deliver energy to a highly localized area, and most importantly, improved joint efficiency. However, without proper optimization, the laser welded joints can have significant external and internal defects such as porosity, humping, concavity, and undercut which are widely known to adversely affect the mechanical performance of the joint. The laser welding process is most commonly optimized by adjusting the laser power and the welding speed, but this usually increases the processing time which can be costly in an industrial setting. This work explores the optimization of high-speed laser welding of thin-gauge automotive steels by changing the laser impingement angle during open-keyhole mode welding. The numerical simulations and the experimental results presented in this study clearly show that by optimizing the laser impingement angle, the melt pool geometry can be effectively controlled which eliminates surface defects such as weld concavity and undercut when welding thin-gauge steels at high-speeds without the need for expensive consumables and tighter setups needed for wire-feeding capabilities. The findings presented in this paper hold a major relevance to industries that employ fiber laser systems in welding and additive manufacturing applications which can benefit from improved process efficiencies while minimizing defects.

Features of manufacturing and clinical application of porous titanium implants for treatment of injuries and diseases of the spine

When treating injuries and diseases of the spine, it becomes necessary to replace the vertebral body or intervertebral disc with an implant. Such an implant should ensure the performance of the supporting function of the spine and facilitate the formation of a bone block (fusion). For this purpose, the most effective can be considered porous titanium that meets the requirements for biocompatibility, strength characteristics and rigidity. The possibility of obtaining such implants by diffusion welding of a specially twisted wire made of VT1-0 alloy and subsequent thermal hydrogen treatment, including thermal diffusion saturation of the implant blank with hydrogen and its subsequent removal during vacuum annealing, is considered. It is shown, that thermal hydrogen treatment makes it possible to transform the mechanical contacts of the wire after diffusion welding of the work piece into physicochemical ones. This makes it possible to increase the strength characteristics of the implant with a high volumetric porosity (up to 60–70 %) and bring its rigidity closer to the rigidity of the vertebrae. Optimization of the modes of diffusion welding and thermal hydrogen treatment was carried out to obtain a high complex of strength and plastic characteristics of implants. Clinical studies of the use of porous implants obtained by the proposed technology have shown their high efficiency in the treatment of injuries and diseases in the cervical, thoracic and lumbar spine. 247 clinical cases of the use of "cellular" porous implants (54 patients with injuries and 193 with degenerative-dystrophic diseases of the spine) were considered. In 214 cases, an improvement in the condition of patients was noted (86.6 %). Deterioration was observed in 4 patients (1.6 %), which was associated with contusion and edema of the spinal cord after the injury. It was found that in a relatively short period (up to 5–6 weeks), through the growth of bone tissue occurs through the implant. In this case, the formation of osteophytes on the lateral surface of the implant is not observed, which reduces the likelihood of injury.

Influence of welding modes on decarburization in the heat-affected zone of r91 steel in welded joints of dissimilar steels after high-temperature tempering

The Paton Welding Journal, 2022, №03. International Scientific-Technical and Production Journal «The Paton Welding Journal» «The Paton Welding Journal» has been published monthly since 2000 in English, ISSN 0957-798X. «The Paton Welding Journal» is a cover-to-cover English translation of the «Avtomaticheskaya Svarka» (Automatic Welding) journal. The «Avtomaticheskaya Svarka» journal has been published monthly since 1948 in Russian, ISSN 005-111X.

A study on effect of heat input on mode of welding, microstructure and mechanical strength in pulsed laser welding of Zr-2.5 wt.%Nb alloy

In the present study, Zr-2.5 wt.%Nb alloy plates of thickness 4 mm have been welded using pulsed Nd:YAG laser system at different process parameters and characterized in terms of microstructural evolution, hardness, residual stress, and mechanical properties. It has been observed that heat input plays an important role on mode of welding. The full penetration up to a thickness of 4 mm of the alloy has been achieved at a minimum laser heat input of 800 J mm−1 without any crack and porosity formation. For avoiding the porosity formation in the weld zones, a transition mode between conduction and keyhole has been used by optimizing laser process parameters. The microstructural analysis revealed that the fusion (FZ) is consists of predominant lath type α′ martensitic phase with small amount of randomly distributed acicular type of α′ martensite phase. However, the heat affected zone (HAZ) have lath type α′ martensitic phase together with αZr phase. Further, in the FZ and HAZ regions, the presence of retained βZr phase is higher as compared to the base metal (BM). The change in microstructure and phase field of different weld zones has been explained by evaluating the time-temperature profiles and cooling rates using COMSOL multi-physics simulation. In addition, the FZ and HAZ zones have been found to have tensile residual stress of the order of 280 MPa and 145 MPa as compared to the BM (-70 MPa). The microhardness in the FZ region has been observed to be higher (240–260 HV0.1) as compared to the BM (∼185 HV0.1) due to the formation of martensitic phase. The tensile room temperature testing showed that the mechanical strength of as welded sample is significantly higher than the base metal with lower ductility. The fractography of the fractured surfaces confirmed ductile nature of failure in the as welded samples.

Improving the quality and efficiency of friction stir welding of aluminum alloy plates

Friction stir welding (FSW) is best suited for welding large-sized aluminum alloy parts. Finding optimal welding conditions and methods for minimizing defects arising during welding is an urgent task, the solution of which is necessary for the commissioning of FSW technology into the industry. The introduction of this method for welding rocket fuel tanks will increase the productivity of manufacturing products and their strength. The aim of this study is to improve the quality of friction stir welding of 7,6 mm thick Al-Mg6% aluminum alloys, as well as to increase productivity. The aim is achieved by finding optimal welding conditions and modernizing the welding method for simultaneous stripping by milling. The optimal welding modes found as a result of the study allow ensuring the strength of the welded joint, reaching 98% of the strength of the base material. The modernized welding method allows milling (deburring) to be carried out simultaneously with welding, which can significantly reduce the manufacturing time of the product, for which deburring is a necessary operation. As a result of the study, the welding modes were also revealed, leading to the appearance of hidden defects, which can reduce the strength of the welded joint by 2 times. A conditional diagram showing the appearance of defects in various combinations of modes has been compiled.

Role of ultra-fine intermetallic particles and martensite in strengthening of AISI 321/Cu/Ti laser welded joint

The study of the influence of phase transformations on residual stresses in heterophase materials is very important for predicting the service life of machines and constructions. Welded joints made of dissimilar materials are of particular interest. The chemical and phase compositions, microstructure, microhardness, strength, and fracture surface characterization of dissimilar AISI 321/Cu/Ti laser joints have been studied. Distinctive features of the laser welding conditions are the displacement of the focal spot to the steel/Cu interface and the deepening of the focus by 3 mm. The chosen mode of laser welding made it possible to obtain the following chemical composition of the melting zone (MZ): 55.3 wt% Cu, 32.2 wt% Fe, 8.5 wt% Cr, 4.0 wt% Ni, and 1.0 wt% Ti. After crystallization in MZ, two supersaturated solid solutions are formed: one based on copper and the other based on iron. During post-welding cooling, (Fe,Cr)2Ti intermetallic particles sized 10 nm homogeneously precipitate in the Cu-based solid solution, and 10-nm TiCu4 particles precipitate in the Fe-based solid solution. Fe-based regions become additionally hardened (to 540 HV 0.025) due to the formation of martensite crystals in the austenite matrix. Alloying of titanium with copper causes βTi stabilization at the interface Ti/MZ. During contact melting of titanium, Ti2Cu intermetallic particles of three types emerged: from 2 to 5 μm eutectic, from 0.1 to 0.5 μm eutectoid, and those homogeneously precipitated in βTi during cooling, sized 10 nm. After quickly cooling, the compressive residual stresses formed in the welded joint. When specimens with welded joints were tensile tested, they fractured in the MZ according to a mixed type. Ductile fracture occurred in Cu- and Fe-based microconstituents by the MZ zone; brittle fracture occurred in the zone with (βTi + Ti2Cu) structure near Ti. The ultimate tensile strength of the resulting welded joints is 470–515 MPa, and this significantly exceeds the available data.

Constructional Features and Energetic Parameters Influence on Structure Formation and Sealed Welded Joints Properties in the Production of Capsules for Hot Isostatic Pressing

The features of the formation of the structure of welded joints for various welding modes and energy parameters of welding capsules for hot isostatic pressing are given. Mechanical properties are investigated for each of the modes.

Influence of Friction Stir Welding Modes of Copper and Aluminum Alloys

The article discusses the influence of the parameters of friction stir welding modes on the formation of the outer surface of the weld and the thickness of the intermetallic layer for the thickness of the welded samples of 3 mm. Changing the rotation speed from 600 rpm to 1000 rpm of the welding tool allows you to control the amount of energy input to transfer the welded material into a superplastic state. The welding speed was varied from 20 mm/min to 80 mm/min. The most optimal mode was for an aluminum and copper alloy with a thickness of 3 mm, a rotation speed of 900 rpm, a welding speed of 25 mm/min, an angle of inclination of 30 at which the mechanical properties of the welded seam approached the most plastic material (aluminum). The article considered thermal cycles measured near the pin from the side of the aluminum and copper alloy. The maximum temperature was 900 K on a copper alloy. The parameters of welding modes also affect the formation of intermetallic layers. If the thickness of the intermetallic layer does not exceed 4-5 μm, then increased values of the mechanical strength of the welded dissimilar joint are observed.

Welding Mode Justification for a T-Joint

The paper proposes a method for calculating the mode of single-pass arc welding depending on the geometric parameters of the T-fillet weld. The authors reveal the dependence of the residual welding stress level on the welding mode, taking into account the stress concentration due to uneven heating and transverse weld shrinkage. Resulting from the comparison of three modes of single-pass arc welding (manual, mechanized, and automatic), the optimal modes that ensure the maximum lifetime of welded structures are determined.

Investigation of the Nature of Damage to Welded Flexible Compensating Elements Made of Austenitic Stainless Steels

Welded flexible compensating elements made of austenitic stainless steels, such as metal hoses and bellows expansion joints, operate in a complex stress state; therefore, almost all corrosion damage of these products occurs in a stressed state. In addition, in welded joints, defects are possible associated with elastic-plastic deformations and stresses arising in the manufacturing process. Paper considers the defects of welded joints of multilayer bellows expansion joints made of stainless steels AISI 304 and AISI 316 types. The influence of the parameters of the argon tungsten electrode welding mode, with or without filler wire, on the mechanical characteristics of welded joints was studied. Mechanical tests of samples of welded joints were carried out on a tensile testing machine. The optimal range of variation of the parameters of the welding mode has been established, in which the plastic characteristics of the welded joints have maximum values. A metallographic study of the microstructure of welded joints of metal hoses and bellows expansion joints was carried out. The influence of the content of nonmetallic inclusions in the material of products on the conditions of melting and crystallization of the weld pool, contributing to the appearance of pores and hot cracks in the metal of the weld and the heat affected zone, has been established. To reduce the influence of the content of non-metallic inclusions in the weld metal and the heat-affected zone on the conditions of melting and crystallization of the weld pool, it is recommended to carry out preliminary heat treatment of the austenitic steel strip.

Studying Phase and Structural Transformation Upon Formation of Weld Joint of Rail Steel. Report 3. Using Thermal Kinetic and Isothermal Diagrams of Austenite Decomposition while Selecting Optimum Modes of Electric Welding

Studying Phase and Structural Transformation Upon Formation of Weld Joint of Rail Steel. Report 3. Using Thermal Kinetic and Isothermal Diagrams of Austenite Decomposition while Selecting Optimum Modes of Electric Welding

Влияние предварительной химической обработки на качество твердофазных сварных соединений проволок при изготовлении пористых сетчатых материалов

Porous mesh materials with an organized structure, stable and reproducible properties are used in the manufacture of filter elements, thermal protection systems, rocket and turbojet engines, and other products with a given set of properties. The interlayer strength of such materials is significantly affected both by the modes of plastic deformation and welding and by the technology of preliminary chemical cleaning of the wire mesh surface. Etching work-pieces in a mixture of inorganic acids and organophosphorus complexones reduces the thickness of oxide films and additionally activates the contact surfaces in the welded joint. The study introduces the etchant solutions for treating VT1-0 titanium and corrosion-resistant 12Kh18N10T steel wires. The solutions increase the strength of the welded joints made by vacuum rolling welding and diffusion welding, compared with similar processes without pretreatment. The study also specifies the modes of technological processes of chemical etching and diffusion welding of 12Kh18N10T steel meshes, which provide maximum interlayer strength.

Laser Beam Welded Aluminum-Titanium Dissimilar Sheet Metals: Neural Network Based Strength and Hardness Prediction Model

Abstract ‘Laser Beam Welding (LBW) is a welding technique used to join pieces of metal or thermoplastics with the aid of laser’. The beam offers a concerted heat source, which enabled higher, deeper welds and narrower welding rates. The procedure is commonly exploited in higher volume appliances using mechanization. It is dependent on penetration or keyhole mode welding. This paper intends to design a novel prediction model on LBW using the Optimized Neural Network (NN) framework. The input to the optimized NN is the welding properties like ‘Laser power, welding speed, offset, shielding gas, flow/pressure, focal distance and frequency (where power, speed and offset gets varied)’ that directly predict the hardness and tensile strength of welds since the NN is already trained with the provided data. In order to make the prediction model more accurate, this paper aims to train the NN using a new improved Trial Integer-based Whale Optimization Algorithm (TI-WOA) via updating the weight. Finally, the betterment of the suggested scheme is validated with respect to error analysis. Accordingly, from the analysis, it is observed that the proposed methods are 50%, 13.33%, 6.67% and 4% better than ANN-BP, RBF, ANN-GA and NN-WOA models, respectively, at 70th learning percentage.

Optimization of the pulsed arc welding parameters for wire arc additive manufacturing in austenitic steel applications

Industrial development continues to present challenges for manufacturers. One of them is additive manufacturing (AM) with metallic materials. One promising solution is wire arc additive manufacturing (WAAM). Currently, WAAM is a more promising tool for developers, firstly due to the simplicity of its realization and secondly for its cost-effectiveness. Building materials are represented by welding wires, so the deposition rate is favorable. A pulse power source is commonly used in this scheme of realization. Much less attention has been paid to the optimization of the power source working regime, i.e., welding mode. Indeed, the power determines the whole process of WAAM. Therefore, in the present work, an attempt has been made to perform a scientifically based design for the optimal welding mode. The austenitic welding wire was chosen to eliminate phase-transition effects in the solid state of the deposited metal. As a result of the investigation, the advantages of the designed welding mode for WAAM application are made clear. It was shown that the predominant effect on penetration depth possesses pulse current and its input is 49%, while other parameters, i.e., pause current, pulse on time, and frequency, have a less valuable impact. The Taguchi optimization algorithm allowed the development of a specific welding mode for providing better formation of the welds, more grain fined microstructure, and thus improved properties of the modeled wall. Successful efforts have been made to optimize welding modes for WAAM applications. This study is important for manufacturers as well as engineers and scientists.

Laser welding-brazing of NiTi/304 stainless steel wires with beam defocus and large offset

The brittleness of dissimilar NiTi-stainless steel (SS) welds caused by intermetallic compounds (IMCs) network limits their application in medical field. Inserting interlayer and special assembly are high-cost but still hard to eradicate the formation of IMCs. This work realized NiTi-SS wire joints with a high strength using laser welding-brazing mode through beam defocus and large offset. The effect of laser beam offset on joint appearance, microstructure, tensile strength and fractography was investigated. In welded-brazed joints, a fusion zone (FZ) of only one base metal formed while multilayered reaction microstructure at the brazed interface was observed. Without beam offset, a typical FZ was dominated by Ni3Ti+Fe2Ti IMCs network. The tensile strength was improved from 176.6 MPa of conventional welding mode without offset to 329.5 MPa of welding-brazing mode with 0.4-mm offset to SS side. The joint welded with large offset fractured at the brazed interface with a mixed ductile-brittle fracture; while brittle fracture inside the IMCs network of FZ was observed in the joint welded without beam offset. The enhancement of joint strength was attributed to the eradication of IMCs network in the FZ and a reaction layer with less Ti–Fe brittle IMCs. This welding-brazing mode can be applied to suppress the overall brittleness of NiTi-SS joints without using any interlayer.