Welding Temperature Field Research Articles

Thermal, metallurgical and mechanical analysis of circumferentially multi-pass welded P92 steel pipes

A coupled thermo-metallo-mechanical model is proposed to analyse the temperature, stress and microstructure fields in multi-pass welding of P92 pipes. An axisymmetric model is adopted to increase the efficiency of the simulation. To preserve the temperature field from a three-dimensional (3D) analysis, a procedure is proposed to convert the 3D result into a two-dimensional (2D) form, which is compared to temperature fields created by other 2D heat transfer analyses. A metallurgical algorithm, which does not need the calibration with metallurgical experiments, is implemented in the finite element (FE) analysis to predict spatial distributions of product phases during multi-pass welding. Comparison between the predictions and the metallurgical graphs is made to verify the effectiveness of the metallurgical analysis after twenty thermal cycles. Hardness test is also employed to characterize the microstructure and to validate the metallurgical predictions. Five temperature fields, one created from the newly proposed approach and four from existent ones, are used as external loads to conduct the mechanical analysis. The volumetric change due to the phase transformation is considered as an extra volumetric strain, which is implemented by user subroutine. The stress distributions predicted using the five temperature fields are plotted together with the 3D stress result to examine the effectiveness of the developed procedure. The stress at the external surface of the pipe is measured by the X-ray diffraction technique, and is further compared to the stress predictions. The advantage of the model is demonstrated by comparing the computational time consumed in the mechanical analysis.

Numerical and Experimental Research on Distribution and Evolution of Coupling Residual Stresses Induced by Cutting-Welding Continuous Process

Thermal cutting and welding are usually applied on component sequentially in shipbuilding, and the coupling residual stresses will be induced during this continuous process, which make the residual stress distribution different to that induced by single process. This research took a typical continuous process as the object: first, the mild steel plate was cut in half by oxygen flame, and then welded together. Based on the regression equations of initial residual stress distribution induced by cutting, a simplified numerical model was presented to investigate the distribution and evolution of coupling residual stresses with stress measurement validation based on X-ray diffraction. The research concluded that the distribution of coupling residual stresses, induced by cutting-welding continuous process, is mainly affected by the process, which can generate a wider distribution of high stresses. The evolution of coupling stresses is determined by the distance to seam (Γ1~Γ3)and the period undergoing (T1~T3), and the influence of initial residual stresses on coupling stresses was also investigated. 1. Introduction Shipbuilding consists of a series of processes applied sequentially, and the components of hull have to experience more than one process during shipbuilding, so the residual stresses in hull should be considered as the result of coupling effects between different processes, and it was named as coupling residual stress in this research. A typical kind of coupling residual stress in shipbuilding is induced by thermal cutting-welding continuous process, for example: first, the steel plates are cut into designed shapes, and then welded together to form the subassembly. During this continuous process, the coupling effects will be generated between the stress field of thermal cutting and the temperature field of welding, and superimposed with welding stresses. As a result, the cutting-welding coupling residual stresses will be presented. compared to the residual stresses induced by single process, coupling residual stresses need experience the evolution effected by much more factors, and finally have a more complex distribution. However, the residual stresses due to single process have gained most of the attention of researchers so far, and there is a lack of the studies on coupling residual stresses during continuous process (McPherson 2007).

Numerical simulation and experimental research on temperature and stress fields in TIG welding for plate of RAFM steel

The Reduced Activation Martensitic/Ferritic steel (RAFM steel) is known as one of the most important materials for future fusion reactor blanket and the welding process is unavoidable for blanket structure, so it is extremely necessary to research his welding performance. Some simulations and experiments about welding processes of RAFM steel have been done in this paper. The multi-welding processes for medium thickness plate of RAFM steel were simulated in three-dimensional finite element models by ANSYS software. The temperature fields and stress fields from simulation were contrasted with that from experiments respectively, and the heat affected zones of welding were calculated and checked. Meanwhile, the metallic texture graphic analysis for welded zones was performed. The results from both are very similar, and the fused metal welding zones are very well without obvious defects by used 316L welding padding. The hardness on welding zone is much higher than the heat-affected zone, also base materials. All of them can provide beneficial reference for blanket design and processing of Chinese Fusion Test Reactor.

Underwater Robotic Welding of Lap Joints with Sandwiched Reactive Multilayers: Thermal, Mechanical and Material Analysis

ABSTRACTUnderwater welding using reactive materials pre-deposited at the junction surfaces as a self-contained, in-situ ignitable heat source mitigates external power and gas supply requirements. Consequently, lending itself to robotic implementation eliminating the cost along with health and safety hazards of human welder-divers. This project reports on lap joining of aluminum sheets with sandwiched commercial reactive Ni-Al multilayers that are perforated to allow for melt fusion under compression upon ignition, in saline and deionized water as well as air for comparison. Finite-element thermal simulations are employed to study the resulting welding temperature field and melt conditions. Infrared pyrometry and thermocouple measurements during welding were used to validate the computational simulations. The lap joints are subjected to standard shear testing, and comparable compliance, strength and toughness values of the welds are assessed for underwater and dry joints. Scanning electron (SEM) of the weld sections reveal rapidly melting and solidifying microstructures of the parent metal, with minimal melt flow and perfusion of nickel aluminide aggregates from the reacted multilayers, and no signs of cavitation.

Analytical Algorithm Expressions in Simulation of the Temperature Field in Electric Resistance Spot Welding

Analytical Algorithm Expressions in Simulation of the Temperature Field in Electric Resistance Spot Welding

Numerical Simulations on the Laser Spot Welding of Zirconium Alloy Endplate for Nuclear Fuel Bundle Assembly

In the nuclear industry, a critical welding process is joining of an end plate to a fuel rod to form a fuel bundle. Literature on zirconium welding in such a critical operation is limited. A CFD model is developed and performed for the three-dimensional non-linear thermo-fluid analysis incorporating buoyancy and Marnangoni stress and specifying temperature dependent properties to predict weld geometry and temperature field in and around the melt pool of laser spot during welding of a zirconium alloy E110 endplate with a fuel rod. Using this method, it is possible to estimate the weld pool dimensions for the specified laser power and laser-on-time. The temperature profiles will estimate the HAZ and microstructure. The adequacy of generic nature of the model is validated with existing experimental data.

FEM prediction of welding residual stresses in fibre laser-welded AA 2024-T3 and comparison with experimental measurement

Welding generates a considerable amount of residual stresses which affect the structural integrity of welded components. It is often assumed that the magnitude of residual stresses around the welded joint is as high as the yield stress of the material. In this investigation, such assumption was found to be overly conservative and failed to accurately represent the distribution of residual stresses in fibre laser-welded aluminium alloy 2024-T3 sheets. Welding simulation based on the finite element method was used to reliably determine the distribution and magnitude of transient residual stress fields and distortions in thin sheets welded using three different sets of welding parameters. The accuracy of the finite element models was checked by calibrating with experimentally measured weld pool geometries and temperature field prior to conducting parametric studies. X-ray and neutron diffraction measurements were performed on the surface and in the bulk of the welded components, respectively, and compared with numerical results. The influence of weld metal softening, welding parameters and restraints on residual stresses and distortion were investigated systematically by numerically simulating ideal conditions which eliminate the practical limitations of conducting experimental studies, for process optimization as well as evaluation of in-service structure integrity and failure modes of the welded sheets.

Influence of oscillation frequency and focal diameter on weld pool geometry and temperature field in laser beam welding of high strength steels

As weld pool geometry and thermomechanical strains are known to affect formation of solidification cracks, the influence of a superimposed beam oscillation on these characteristics is investigated for this paper. In this context the effects of the oscillation frequency and focal diameter on the weld pool and temperature field are determined by means of infrared thermography. As a result an increase of the weld pool size for larger focal diameters and a more even shape of the seam edges for higher frequencies can be identified.

Effect of Magnetic Field on the Weld Temperature Field and Flow Behavior of Molten Pool in Al/Steel CMT Welding Process

Effect of Magnetic Field on the Weld Temperature Field and Flow Behavior of Molten Pool in Al/Steel CMT Welding Process

Determination of residual stresses in fibre laser welded AA2024-T3 T-joints by numerical simulation and neutron diffraction

This paper presents an experimental and numerical study of residual stress states and deformation in fillet welded AA2024-T3 T-joints produced using a high-power fibre laser. Welded sheets with one and three stiffeners were prepared, respectively, to determine changes in microstructure, residual stress, distortion and micro-hardness. 3D sequentially coupled thermo-mechanical finite element models were developed to analyse welding temperature fields, and accurately simulate welding residual stresses and deformation. The simulated results were calibrated using the experimental database on weld pool geometry obtained from optical metallography and temperature fields measured using thermocouples. Residual stress measurements were made using neutron diffraction techniques and sheet distortions were measured using a coordinate measuring machine. The influence of various mechanical boundary conditions on angular and cambering sheet distortions was examined to optimise the restraint parameters. The application of element death and rebirth and dummy element techniques were studied and compared to incorporate the effect of filler metal deposition during welding. The level of residual microstrain was evaluated by diffraction peak width analysis, which indicated the maximal values in the weld metal. The effect of grain growth with respect to strength was of minor importance, whereas, considerable softening in the weld metal was observed.

Characterisation of quasi‐stationary temperature fields in laser welding by infrared thermography

AbstractIn this work, high‐speed thermography is shown to effectively capture quasi‐stationary temperature fields during the laser welding of steel plates. This capability is demonstrated for two cases, with one involving the addition of a ferritic‐bainitic filler wire, and the other involving the addition of a low‐transformation‐temperature (LTT) filler wire. The same welding parameters are used in each case, but the temperature fields differ, with the spacing between isotherms being greater in the case where the low‐transformation‐temperature filler material is added. This observation is consistent with the differences in the extent of the heat‐affected zone in each sample, and the shape of the weld pool ripples on the weld bead surfaces. The characterization of temperature fields in this way can greatly assist in the development of novel methods for reducing residual stresses, such as the application of low‐transformation‐temperature filler materials through partial‐metallurgical injection (PMI). This technique reduces or eliminates tensile residual stresses by controlling the temperature fields so that phase transformations take place at the optimum times, and success can only be guaranteed through precise knowledge of the temperature fields in the vicinity of the welding heat source in real time.

The influence of energy distribution factor during laser-MIG hybrid welding of Invar alloy

In this study, a three-dimensional (3D) finite element model was established to predict the shape of the molten zone and the temperature fields of multi-layer laser–MIG hybrid welding for Fe36Ni Invar alloy. The multi-layer laser–MIG hybrid welding experiments of 19.05-mm-thick Invar plates were conducted to obtain the well-welded joints. The molten zone shapes were compared to the simulated results to figure out the relation between the energy distribution factor and the welding temperature field. A combined heat source model was proposed to describe the interaction between laser heat source and arc heat source. Besides, the empirical formula of energy distribution factor was given. The metallography detection results showed that the increasing ratio of laser power in hybrid welding could increase the weld penetration depth and the increasing ratio of arc power in hybrid welding could increase the weld width. In addition, it was also found that the laser heat source in hybrid welding heat source contributed equiaxed grains, and weld centerlines had rotation, due to different ratios of energy distribution during the multi-layer laser–MIG hybrid welding.

Numerical analysis on temperature field in single-wire flux-aided backing-submerged arc welding

Single-wire flux-aided backing-submerged arc welding (FAB-SAW) technology has been widely used to weld thick steel plate due to its easy assembly and high heat input. The microstructure and property of welded joint are closely related to the thermal field of FAB-SAW process. In this research, the feature of thermal field for single-wire FAB-SAW was investigated. Based on the heat transfer mechanism, a three-dimensional transient model for thermal field was developed based on the influence of steel thickness, groove angle and ceramic backing. The temperature profile in single-wire FAB-SAW of D36 steel under different welding conditions was simulated by ANSYS. The characteristic of thermal field was analyzed and the influences of groove angle on temperature field for different plate thicknesses were discussed. The calculated geometries and dimensions of weld cross-section under different conditions show a good agreement with the experimental results. This newly built model can describe the thermal field accurately, which would be helpful to understanding the thermophysical mechanism of FAB-SAW and optimizing the welding process.

The Simulation of Temperature Field in Induction Welding of Composite Aluminum Alloy Thin-Walled Tube

Welding temperature is the main factor that influences the welding quality in the high frequency induction welding of composite aluminum alloy thin-walled tubes. The finite element analysis software ANSYS was used to simulate the temperature field. One complete penetration of thin-walled tube and boundary conditions of convection and radiation as well as latent heat phase change were taken into account. Then a linear heat source is used to load and calculate the temperature distribution and to draw thermal cycle curves of welding process. Research results of the temperature filed also provided the corresponding basis for further analysis of welding stress and strain.

Numerical Simulations of temperature for the in-service welding of gas pipeline

Finite element (FE) method is employed to simulate the temperature field of the in-service welding on a single bead-on-pipeline. The methane gas was introduced as a cooling media to investigate the temperature field of the heat affected zone (HAZ) based on the validation of the numerical models. The heat transfer coefficient is significantly influenced by the pressure and flow rate of the gas and wall thickness of pipeline, which leads to the magnitude of cooling time, horizontal and vertical sizes of HAZ and peak temperature at inner wall were reduced. While, the t8/1 increases first and then decreases with the variable wall thickness and it get the maximum value about 208.42s at wall thickness of 8mm. It indicates that the effect of the gas and wall thickness on the temperature field of in-service welding need to be concerned.

Prediction of residual stresses in electron beam welded Ti-6Al-4V plates

A thermo-metallurgical procedure based on the SYSWELD code was developed to predict welding temperature field, microstructure and residual stress in butt-welded Ti-6Al-4V plate taking into account phase transformation. The formation of martensite was confirmed by the CCT diagram and microstructure in the weld joint, which significantly affects the magnitude of residual stress. The hole drilling procedure was utilized to measure the values of residual stress at the top surface of the specimen, which are in well agreement with the numerical results. Both simulated and test results show that the magnitude and distribution of residual stress on the surface of the plate present a large gradient feature from the weld joint to the base metal. Moreover, the distribution law of residual stresses in the plate thickness was further analyzed for better understanding of its generation and evolution.

Analytic temperature field solution of dual laser welding heat sources and application in static recrystallization

The explicit temperature function of dual laser welding was presented, and the effect of welding pass distance and heat source distance on the thermal history was analyzed. There was excellent correlation between analytically solved and finite element method (FEM)-predicted dual laser welding temperature field. The analytical temperature function is applied to study the static recrystallization kinetics upon dual laser welding of nanobainite steel. By calculation, the optimal welding process parameters can be obtained when the static recrystallization fraction takes the maximum value. The corresponding temperature is above the martensite transus temperature and is appropriate to produce sufficient plastic strain in the austenite grains.

Analysis of Thermo-Elastic Fracture Problem during Aluminium Alloy MIG Welding Using the Extended Finite Element Method

The thermo-elastic fracture problem and equations are established for aluminium alloy Metal Inert Gas (MIG) welding, which include a moving heat source and a thermoelasticity equation with the initial and boundary conditions for a plate structure with a crack. The extended finite element method (XFEM) is implemented to solve the thermo-elastic fracture problem of a plate structure with a crack under the effect of a moving heat source. The combination of the experimental measurement and simulation of the welding temperature field is done to verify the model and solution method. The numerical cases of the thermomechanical parameters and stress intensity factors (SIFs) of the plate structure in the welding heating and cooling processes are investigated. The research results provide reference data and an approach for the analysis of the thermomechanical characteristics of the welding process.

Transient Thermal Modeling in Laser Welding of Metallic/Nonmetallic Joints Using <i>SolidWorks</i><sup>®</sup> Software

The purpose of this research is to develop a SolidWorks? model for transient temperature field of laser welding of PMMA/SS 304 materials for application in fabrication of the ultrasonic back-plate, with a view of optimizing the experimental conditions. The study is carried out on these materials because of the increasing application of both metals and non-metals. The work focuses specifically on these materials because they have been experimentally studied previously and as such, this study can be accepted as an assessment into feasibility of using SolidWorks? model to study the temperature field of the laser welding processes of metals and non-metals. The results of the SolidWorks? transient thermal model show that there is a concentration of high temperatures at the point of contact. It also shows that temperature decreases as we move in (between laser and the top face) to the thickness of the part. Additionally the maximum temperature occurs at the last point of the welding; this may be due to the accumulation of the temperature before arriving at the end. These findings are comparable to the previous simulated and experimental results on temperature field during laser welding of PMMA/SS 304 materials. However, SolidWorks? is shown to present a challenge in modeling a moving source of laser power.

Simulation on Temperature Field of Friction Stir Welding of 2A14 Aluminum Alloy Based on Equivalent Film Method

Backing plate has an important influence on the temperature field of workpiece during the friction stir welding process. In order to predict the temperature field of workpiece accurately, a thermal-fluid coupled friction stir welding calculation model including workpiece and backing plate was developed. In the model, an equivalent film method was proposed to simplify the contact heat transfer between workpiece and backing plate to a heat conduction problem. The computational fluid dynamic software FLUENT was ultilized to simulate the friction stir welding process of 2A14 aluminum alloy. As a result, the steady-state temperature field during the friction stir welding process was predicted and analyzed. The welding process test was carried out to verify the simulation results of temperature field. The compared results show that the simulated temperature and the measured values of all measuring points are in good agreement. Using the simulation method proposed in this paper, the calculation accuracy of temperature field during the friction stir welding process could be relatively high and the maximum error is 4.61%. In addition, there is a good corresponding relationship between the temperature distribution and the various regions of weld cross section.