Welding Energy Input Research Articles

Microstructure and Mechanical Properties of IN690 Ni-Based Alloy/316LN Stainless-Steel Dissimilar Ring Joint Welded by Inertia Friction Welding.

Inertia friction welding (IFW) was used to join large-diameter hollow bars made of Inconel 690 and 316LN successfully. The interfacial characteristics, microstructure, mechanical properties and fracture mechanism of welded joints under different process parameters were investigated. The results indicated that a joining mechanism with mechanical interlocking and metallurgical bonding was found in IFW joints. There was a significant mechanical mixing zone at the welding interface. The elemental diffusion layer was found in the "wrinkles" of the mechanical mixing zone. A tiny quantity of C elements accumulated on the friction and secondary friction surfaces. The tensile strength and impact toughness of the joints increased with the total welding energy input. Increasing the friction pressure could make the grain in all parts of the joint uniformly refined, thus enhancing the mechanical properties of welded joints. The maximum tensile strength and impact toughness of the welded joint were 639 MPa and 146 J/cm2, reaching 94% and 68% of that for Inconel 690, respectively, when the flywheel was initially set at 760 rpm, 200 MPa for friction pressure, and 388 kg/m2 for rotary inertia. Due to the Kirkendall effect in the welded joint, superior metallurgical bonding was at the welding interface close to the Inconel 690 side compared to the 316LN side.

Microstructural investigations on laser welded Al-30wt.% B4C composite

In order to tailor the microstructures and mechanical properties of laser welded Al-B4C composite, it is necessary to elucidate the chemical reactions between B4C reinforcement and Al matrix during laser welding process. In this study, 3 mm thick Al-30wt.% B4C plates were laser welded using different parameters. Then the microstructure, reaction products, tensile properties and fracture surface of welded joint were studied. The results show that the reaction products of the weld zone can be controlled by varying the welding energy input, but the full penetration welded joint requires high energy input (120 KJ/m in this paper). For the full penetration welded joint, all B4C particles and part Al matrix react to form irregularly particle-like AlB2C2 and coarse needle-like Al4C3 phases, the joint efficiency is 67%. The failure mechanism of AlB12C2 is cleavage fracture, and the failure mechanism of Al4C3 is interfacial decohesion and pull out. The interfacial decohesion between Al4C3 and Al matrix results in crack initiation due to their weak bonding interface. The cracks propagate, connect and penetrate the brittle AlB12C2 phase and eventually lead to brittle fracture of the joint.

Experimental Investigation on Vibro-Acoustic Characteristics of Stiffened Plate Structures with Different Welding Parameters

Varied welding process parameters result in different welding energy inputs and welding residual stresses, significantly impacting the vibro-acoustic characteristics. This work investigated the influence of different welding energy inputs on the vibro-acoustic characteristics of the stiffened plate structure. Several experiments on the stiffened plate structure with different welding energy inputs were conducted regarding modal, underwater vibration, and acoustic radiation. The results revealed that welding energy input had the most significant impact on the first-order natural frequency, and the impact first becomes higher and subsequently decreases as welding energy input increases. The welding energy input had relatively little effect on the peak point distribution of vibration and acoustic radiation curves but could affect the peak point amplitude. With the increase in welding energy input, the overall vibration acceleration level and sound radiation level in each frequency band decreased and then increased. The best result was obtained when the welding energy input was 167 J/cm with a welding current of 200 A, a welding voltage of 25 V, and a welding speed of 3.02–3.06 mm/s. Based on construction technology, this research can provide some instructive insights for enhancing the acoustic stealth performance of ships and marine structures.

Low energy ultrasonic welding for Cu-Cu joining accelerated via Cu nanoparticles

Decreasing welding energy input with enhanced welding quality is difficult to achieve in ultrasonic welding. In this study, a nanoparticle-accelerated ultrasonic welding technique using a Cu nanoparticle (Cu NP) interlayer was proposed. Lap shear tests revealed that the addition of Cu NPs drastically increased the load carry capacity by 253 % for Cu-Cu joints welded with an ultrasonic energy as low as 200 J, reducing the energy input to half of that without Cu NPs. This low energy requirement was attributed to the increase in peak temperature. The clamping force drove Cu NPs to fill and sinter in the interfacial gaps, which also significantly reduced the welding energy required for intimate contact in the early stage of welding. Furthermore, severe plastic deformation, enhanced friction, and nanosized grains induced by the Cu NPs facilitated material flow, accelerated elemental diffusion, and grain refinement at the interface. The enhancement of dynamic recrystallization in the base metal caused by the Cu NPs was confirmed by the calculated Zener-Hollomon parameter and critical recrystallization strain.

Effect of Microstructure on High-Strength Low-Alloy Steel Welded Joint Toughness with Simulation of Heat-Affected Zone Coarse-Grained Area

A simulated coarse-grained heat affected zone microstructure formation mechanism is established in high strength low alloy steels using electron backscatter diffraction (EBSD). The governing effect of dispersion and ratios between different types of ferritic structural constituents on variation in impact strength is demonstrated. It is assumed from results of simulating a heat affected zone coarse-grained area that a reduction in welding energy input leads to a shift in ductile-brittle transition temperature towards a lower temperature.

Effect of welding energy on the corrosion and tribological properties of duplex stainless steel weld overlay deposited by GMAW/CMT process

Duplex stainless steels (DSS) show good mechanical properties, wear, corrosion resistance and fatigue strength. In order to decrease operational costs in paper and pulp industry, DSS is employed through weld overlay coatings on mild or low carbon steel components. In this work, the aim was to evaluate the DSS weld overlay properties obtained through deposition of ER 2209 duplex stainless steel alloy on a mild steel plate (ASTM A 516 Gr 60). The deposition was performed through GMAW/CMT welding process. The coatings were deposited using four heat inputs: 0.53, 1.01, 1.27 and 1.74 kJ/mm. Moreover, microstructural characterization by optical microscopy showed that heat input influences ferrite/austenite phase balance. Secondary austenite that precipitates due to the welding process in DSSs are Widmanstätten austenite (WA), grain boundary austenite (GBA), partially transformed austenite (PTA) and intragranular austenite (IGA). The amount of secondary austenite increases with welding energy input. The secondary austenite improves abrasive wear resistance while corrosion resistance is the lowest when welding energy is 1.74 kJ/mm.

Laser material interaction parameter: New tool for developing property diagrams for welds

Detailed processing-property correlation studies have been attempted on laser beam welded AA 5024 (Al-Mg-Sc) alloys. These alloys are mostly used for integrally stiffened panels for aerospace applications. Different combinations of laser power, weld speed, beam diameter, and beam shape were chosen, and an optimized yield stress and uniform elongation map has been obtained. A comparative assessment of weld quality was done for the solid-state laser and the CO2 laser with two heat transfer modes, i.e., deep penetration (keyhole) and partial penetration (conduction) modes used for various aforementioned parameters. The weld parameters are ranked thereafter according to their merits and demerits encountered in this work. It has been seen that flexibility in terms of power, speed, and energy of a solid-state laser is more compared to the CO2 laser. Fundamental laser material interaction parameters have been studied, and an optimization strategy was formulated based on specific point energy of beam material interaction. The weld pool geometry has also been studied and correlated with interaction parameters. Weld size, shape, geometry, and evidence of solidification cracking have been studied from weld cross section macrographs. Variations of weld yield strength and elongation with welding energy input have been investigated thoroughly. Based on the above examinations, exaction of the optimal processing window is achieved.

Effect of laser-MIG hybrid welding on microstructure and properties of seismic steel plate for buildings

Abstract Single pass multi-layer welding tests were carried out on 10Ni5CrMoV steel plate for construction, the effects of welding energy input and welding speed on the microstructures, hardness and impact energy at −40 °C of 10Ni5CrMoV steel welded joints were studied. The results showed that, with the decrease of welding energy input and the increase of welding speed, the structure in the weld zone gradually transforms from granular bainite to martensite and a small amount of upper bainite, and the grain size in the coarse and fine grain areas in the heat affected zone gradually decreases, and the content of granular bainite decreases. The optimum welding process for 10Ni5CrMoV steel is welding energy input with 7.5 KJ/cm and welding speed with 1.25 m/min, at this time, the weld structure is granular bainite, acicular ferrite, a small amount of upper bainite and a small amount of martensite; The dispersed Al2O3, TiN or TiC composite phase formed during welding process can be used as nucleation core of ferrite, helpful to form acicular ferrite in the weld zone, and the welded joint of 10Ni5CrMoV steel has the best impact toughness.

Review of Reheat Crack in Welded Joint of Low Alloy Heat-Resistant Steels

The current research status of reheat crack in welded joint of low alloy heat-resistant steels are outlined. Some new phenomena discovered in engineering in recent years are summarized, and related problems that remain to be studied are also presented. Reheat crack in welded joint is occurred frequently during postweld heat treatment (PWHT) or in service at elevated temperature. Mainly four mechanisms leading to reheat crack, respectively, impurity segregation grain boundary weakening, precipitation hardening, creep rupture and no-precipitation zone weakening have been generally accepted now. Several essential factors consist of parent material chemical composition, microstructure and thickness of welded joint, filler material, preheat and postheat procedures, welding energy input, PWHT parameter, and stress and strain and so on. Theoretical calculation methods, criterion of RoA (Reduction of Area) and several experimental methods are put forward to evaluate reheat crack susceptibility. Based on new issues emerged in engineering, problems of concerning reheat crack are necessary to be researched, which include at least mechanism and influence factors of new multi-element composite strengthening heat-resistant steels, the mitigation measures for increasing wall thickness weldment, the root cause analysis and prevention methods of conventional low alloy heat-resistant steels for long term service.

Parametric study in similar ultrasonic spot welding of A5052-H32 alloy sheets

Ultrasonic spot welding (USW) is a solid-state joining process highly applicable to lightweight alloy materials with high diffusivity rates in the melt state. To improve the understanding of the USW process and to enhance the weld strength in similar Al alloy welding, this work focused on a parametric study using some process parameters such as vibration amplitude and welding time. Experiments were conducted using lateral-drive USW machine operating in time control mode. Weld quality of USWed joint was analyzed based on the weld strength obtained by lap-shear tests and the fracture pattern subsequently characterized. Mixed fracture pattern of shear and pull-out exhibited a higher lap-shear failure load, while solely shear and pull-out was a distinct fracture pattern in lower lap-shear failure load. Shorter welding time was needed for higher vibration amplitude to generate enough temperature and to prevent over welding. Joint microstructures revealed that longer welding time produced over welding which gave short but intensified weld interface waviness, resulting to a shorter fracture path. The horn and anvil tip surface patterns influenced on the variation in temperature rise measured at the weld part and the extent of part marking/sticking. The temperature rise measured on the weld surface was useful to determine over welding condition. Weldability map of USWed Al alloy sheets could be constructed from the results of weld strength and fracture type, and an effective welding energy input was determined from welding process parameters combination.

Study on the Weldability of ZG30Cr06A Needling Material

ZG30Cr06A as a newly developed material is made into needling of mining machinery’s hydraulic support. Its tensile strength is up to 800MPa. In the paper, the weldability of ZG30Cr06A was thoroughly studied. The sensitivity to cold crack of ZG30Cr06A was tested by means of maximum hardness of HAZ and Y-slit type cracking test. And the variation of microstructure and properties of weld joints under different welding energy conditions was studied. The results show that ZG30Cr06A steel has a certain cold crack and hot crack tendency and a little reheat crack sensitivity in welding. Embrittlement and softening often appear in the HAZ. When the workspaces of 30mm were welded at room temperature, the maximum hardness of HAZ was up to 389HV. And the joints have a tendency to quenched hardening and bigger sensitive to cold crack. The welded joints would not produce cold crack when the preheat temperature is up to 120°C in welding. Because there is more influence of welding energy input on the microstructure and properties of joint, so in order to avoid the appearance of embrittlement and softening in HAZ and ensure weld quality, the welding energy input of ZG30Cr06A steel whose thickness is 30mm should be controlled less than 40 kJ/cm during the welding.

Avaliação do efeito da energia de soldagem sobre as tensões residuais resultantes em juntas soldadas com multipasse

A energia de soldagem pode ser ajustada tanto por meio do controle da potência (tensão e corrente de soldagem) quanto por meio da velocidade de soldagem. Tais formas de ajustes modificam os efeitos da energia de soldagem sobre a junta, o que pode influenciar de forma distinta as tensões residuais resultantes na mesma. Desta forma, o objetivo deste trabalho é avaliar o efeito da energia de soldagem, considerando seu ajuste através da alteração individual e independente da corrente e da velocidade de soldagem, sobre as tensões residuais resultantes em juntas soldadas com multipasse. Foram empregadas amostras de aço estrutural chanfradas em meio-v e soldadas utilizando eletrodo revestido. Aplicaram-se três energias de soldagem obtidas por meio de três níveis distintos de corrente e de velocidade de soldagem. As amostras foram levadas a um difratômetro de raios-x portátil onde foram levantados os perfis de tensões residuais na superfície das mesmas. Uma verificação importante foi que diferentes parâmetros de soldagem que resultam em aportes térmicos "iguais", geram níveis diferentes de tensões residuais, ou seja, a energia de soldagem não pode ser considerada de forma isolada em análises de níveis de tensões residuais resultantes da soldagem multipasse.

Numerical simulation of variable polarity vertical-up plasma arc welding process

Three-dimensional transient governing equations were developed based on conservation laws of energy, momentum and mass. These equations described physical phenomena of convection in weld pool and heat transfer in workpiece during variable polarity vertical-up plasma arc welding process. Boundary conditions for the developed governing equations were given. Welding energy input for variable polarity vertical-up plasma arc welding process was quantitatively expressed. Free surface deformation of the keyhole molten pool was coupled into calculation. Effect of wire filling on the geometry of molten pool and weld reinforcement was considered in the simulation. Correlations of temperature and thermophysical properties for aluminum alloy 2219 were quantitatively established. A control volume based finite difference method was used to solve the discrete governing equations. Moreover, dynamic evolutions of geometrical profile, dimension and fluid flow for the molten pool and keyhole were simulated through the developed computational routines, which achieved transient solution of fluid flow field coupling with thermophysical properties, temperature field and weld pool free surface deformation. Besides, the effect of the workpiece thickness on the moments of keyhole formation and stable keyhole establishment was analyzed, and thermal cycles for the main welding stage were calculated. In addition, experiments via variable polarity vertical-up plasma arc welding technique were conducted, and the established models were experimentally verified through weld cross-section profiles.

Development of an algorithm for tungsten inert gas welding of an austenitic stainless steel sheet

This paper examines the development of an algorithm for manual and robotic tungsten inert gas (TIG) welding of austenitic stainless steel sheet with a thickness of 0.9–2.0 mm. Generally, an algorithm is a means of describing an optimum course of a technological process and includes mathematical models for computation of individual quantities. In the present case the algorithm optimizes the course of TIG welding and welding parameters. It includes mathematical models for the computation of optimum welding current intensity, welding speed, energy input, arc length, gas flowrate and diameter of the non-consumable tungsten electrode as a function of sheet thickness. A general algorithm for manual and robotic welding of a butt-welded joint with a plain butt weld and a complete algorithm for four welded joints on a sheet with a thickness of 0.9–2.0 mm are stated. Conclusions are drawn and guidelines for future work are given.

Fracture Properties of Multipass Submerged Arc Weld of HSLA Steel Produced by Using Flux Cored Filler Wire.

Multi pass submerged arc welding of 25 mm thick structural steel plates has been carried out at different energy input using flux cored filler wire and basic agglomerated flux resulting the weld deposit having chemical composition confirming that of a high strength low alloy (HSLA) steel. Microstructure and hardness of different microstructural regions of the multipass weld has been studied. Tensile properties of the weld deposit has been found out by carrying out tensile test of the weld joint being fractured from the weld. Fracture toughness (KQ) and fatigue crack growth properties of the weld are studied and correlated with the welding energy input, microstructure and ultimate tensile strength of the weld. The increase in energy input has been found to reduce the hardness, ultimate tensile strength and yield strength, but to enhance the ductility and KQ of the weld primarily due to its influence on microstructure of the weld deposit. However, the increase in energy input has been found to reduce the da/dN at higher ΔK but, it has been found to enhance the same at lower ΔK. The KQ and da/dN of the weld are found to be well correlated with its tensile strength, where an increase in tensile strength reduces the KQ but enhances the da/dN at ΔK higher than 30 MPa √m.