Influence Of Heat Input Research Articles

Influence of heat input in electron beam process on microstructure and properties of duplex stainless steel welded interface

The influence of heat input in electron beam (EB) process on microstructure, mechanical properties, and pitting corrosion resistance of duplex stainless steel (DSS) welded interface was investigated. The rapid cooling in EB welding resulted in insufficient austenite formation. The austenite mainly consisted of grain boundary austenite and intragranular austenite, and there was abundant Cr2N precipitation in the ferrite. The Ni, Mo, and Si segregation indicated that the dendritic solidification was primarily ferrite in the weld. The weld exhibited higher hardness, lower toughness, and poorer pitting corrosion resistance than the base metal. The impact fractures of the welds were dominated by the transgranular cleavage failure of the ferrite. The ferrite was selectively attacked because of its lower pitting resistance equivalent number than that of austenite. The Cr2N precipitation accelerated the pitting corrosion. In summary, the optimised heat input slightly increased the austenite content, reduced the segregation degree and ferrite texture intensity, decreased the hardness, and improved the toughness and pitting corrosion resistance. However, the effects were limited. Furthermore, optimising the heat input could not suppress the Cr2N precipitation. Taking into full consideration the microstructure and properties, a heat input of 0.46 kJ/mm is recommended for the EB welding of DSS.

Influences of heat input, welding sequence and external restraint on twisting distortion in an asymmetrical curved stiffened panel

Welding distortion not only degrades the fabrication accuracy of ship hull blocks but also decreases the productivity due to correction works. The accurate prediction of welding-induced distortion will help control the dimension accuracy. In this study, a computational approach based on inherent strain theory and interface element method was employed to efficiently and precisely estimate welding-induced deformation for large welded structures generated during assembly process. In the proposed approach, the local shrinkage due to heat input were considered by inherent strain components. On the other hand, the gap as well misalignment between the two parts to be joined, and the change of stiffness during assembly process were taken into account by interface elements. Meanwhile, the geometrical nonlinearity was included in the developed computational approach. In the current study, the features of welding deformation in an asymmetrical curved stiffened panel were numerically investigated by mean of the new computational approach. In addition, the influences of heat input, welding sequence and external restraint on the twisting distortion of the curved stiffened panel were further studied.

The influence of heat input on microstructure and mechanical properties for dissimilar welding of galvanized steel to 6061 aluminum alloy in a zero-gap lap joint configuration

The microstructure of dissimilar joint between galvanized steel and 6061 aluminum alloy was studied by experiments and numerical simulation. Three types of experiments including full factor experiments to establish processing window, four chosen parameters to analyze macro profile of weld joints, and two parameters closing to upper and lower limits of processing window were carried out in this study. Besides two common intermetallic compounds (lamellar IMC and acicular IMC) which were reported before, other two new intermetallic compounds (IMC), namely stellate IMC and skeleton IMC were found at the joint under high linear energy density (LED). The chemical compositions and possible phase types of different IMCs observed were determined according to energy dispersive spectroscopy (EDS) results. The temperature histories during welding were simulated based on a finite volume model to further investigate the influence of LED on diffusion process which was thought to be the decisive factor for IMC growing. The growth orientation and phase morphology were determined by temperature histories, local iron atom fraction and constitutional supercooling. The increasing linear energy affected both macro morphology and microstructure of weld joints. It could be concluded that the increasing linear energy was harmful for mechanical properties because it increased thickness of lamellar IMC and brought some new brittle phases which led to some microcracks.

Experimental Study of Welded Joints of Aluminium Alloy AW6082

This paper considers mechanical properties of the welded joints of aluminium alloy AW6082 under varying metal inert gas welding conditions, determined by tensile and microhardness tests. The test joints were produced at different welding current and welding speed. Cross sections of the welding zones have been analysed. The influence of heat input on the tensile strength properties and hardness of the base metal, heat affected and fusion zones were studied. The behaviour of double-V butt weld joints was investigated by tensile tests. Static tensile test and metallographic examination results showed minimum strength in the heat affected zone (HAZ). It was found that the lowest hardness values were obtained in the fusion zone and near the fusion line where rupture occurred.

An investigation on capability of hybrid Nd:YAG laser-TIG welding technology for AA2198 Al-Li alloy

This paper surveys the capability of the hybrid laser-arc welding in comparison with lone laser welding for AA2198 aluminum alloy experimentally. In the present research, a continuous Nd:YAG laser with a maximum power of 2000W and a 350A electric arc were used as two combined welding heat sources. In addition to the lone laser welding experiments, two strategies were examined for hybrid welding; the first one was low laser power (100W) accompanied by high arc energy, and the second one was high laser power (2000W) with low arc energy. Welding speed and arc current varied in the experiments. The influence of heat input on weld pool geometry was surveyed. The macrosection, microhardness profile and microstructure of the welded joints were studied and compared. The results indicated that in lone laser welding, conduction mode occurred and keyhole was not formed even in low welding speeds and thus the penetration depth was so low. It was also found that the second approach (high laser power accompanied with low arc energy) is superior to the first one (low laser power accompanied with high arc energy) in hybrid laser-arc welding of Al2198, since lower heat input was needed for full penetration weld and as a result a smaller HAZ was created.

High temperature abrasion resistance of differently welded structural steels

Structural steels provide a broad spectrum of heat, creep and wear resistance at different microstructures and hardness levels. Two different steel grades were chosen for investigation and simulated repair welds with different parameters were performed, aiming on the influence of heat input during welding and the resulting microstructure on the high temperature abrasion resistance. The impact on the wear resistance and its temperature dependence was evaluated within a high temperature three-body abrasion test and a hot hardness test rig. Results indicate a strong dependence of present microstructural phases and hardness on the wear resistance entailed by different welding parameters. Optimised parameters and low energy input during welding leads to stable hot hardness progress and wear conditions for the investigated materials.

Influence of heat input and radius to pipe thickness ratio on the residual stresses in circumferential arc welded pipes of API X46 steels

The present work aims to study residual stresses caused by circumferentially welding of two similar API X46 steel pipes by means of finite element modeling. Considering the metallurgical phase transformations and through thermal-mechanical uncoupled analysis, the 3D modeling was carried out by SYSWELD software. Materialistic thermal and mechanical properties of all phases were defined in terms of temperature as well as phase transformation properties. Residual stress was measured through hole-drilling method. The obtained results were used to verify the finite element model. By means of full factorial experiment designing method, effects of heat input and radius to pipe thickness ratio on maximum values of hoop and axial residual stresses were investigated. The effect of each factor was studied in 3 levels and by 9 experiments. Results of statistical analysis revealed that increase in heat input and radius-thickness ratio would lead to higher values of maximum hoop and axial residual stresses. However, interactions of high level of heat input and a low level of radius-thickness ratio increased inter-pass temperature and consequently caused a sudden raise in maximum values of residual stresses.

Experiment and multiphysic simulation of dough baking by convection, infrared radiation and direct conduction

To reduce energy consumption, the optimization of oven operating conditions requires a thorough understanding of the influence of heat input on the baking kinetics.The objective of this study is to simulate the hydrothermal behaviour and the deformation of bread dough during the baking stage. The complete baking process is simulated in a 2-dimensional model including conductive transfer with hearth, steam injection and convective and radiative heat transfer. In this article, the simulations are realized with the use of experimental boundary conditions (infrared flux, air temperature and vapour pressure, hearth and wall temperature).The numerical evolutions of different variables are compared to measured data: temperature (product and hearth), mass loss, local moisture content, total volume and gas pressure in the dough. A sensitivity analysis is performed to understand the impact of carbon dioxide generation and heat transfer on the process. Finally, the simulated energy required during baking is evaluated, observing direct conduction with the hearth, and the impact of the transfer of convective and radiative heat.

Influence of heat input on HAZ liquation cracking in laser welded GH909 alloy

In this paper, we describe influence of heat input on HAZ liquation cracking in laser welded GH909 alloy. The results demonstrated that more cracks were produced using high laser power and welding speed. The presence of cracks greatly weakened the hot ductility of this material and the binding force between the adjacent grains, resulting in reducing the tensile strength of welded joints. The occurrence of HAZ cracking was mainly attributable to the coarseness of microstructures and large tensile stresses. A new method was proposed to prevent HAZ liquation cracking using low laser power and welding speed at a constant heat input. The simulated results were consistent with the experimental results, verifying the correctness and feasibility of the method.

Studies on the pore formation in super duplex stainless steel welds

When welding super duplex stainless steels, a non-admissible pore formation can occur even if recommended processing guidelines are strictly followed. To investigate this phenomenon and to determine the influencing factors, different bead-on-plate welds were produced using gas metal arc welding and submerged arc welding. The welding consumables, the shielding gas, and the welding flux were varied. Additionally, the influences of heat input and interpass temperature were examined. The studies have shown that the shielding gas, the welding flux, and the filler metal have great influence on the pore formation. Even small variations in the chemical composition of the welding consumables lead to different results. In addition, the ferrite number and the chemical composition of the bead-on-plate welds strongly depend on the used shielding gases and filler metals. Furthermore, it became clear that the porosity of the weld metal can be affected by the welding speed.

Effect of Heat Input on Mechanical and Metallurgical Properties of Gas Tungsten Arc Welded Lean Super Martensitic Stainless Steel

Welding of 6mm thick AISI: 410S lean super martensitic stainless steel (LSMSS) under different heat input of 7.97, 8.75 and 10.9 kJ/cm was carried out by gas tungsten arc welding process. The influence of heat input on metallurgical and mechanical properties in weld and HAZ region was studied. The tensile tests were carried out at different temperatures, namely at room temperature, at 600oC, 7000C and 8000C. It is observed that rise in the heat input and temperature decreased the tensile strength of the weld joint. Further it is noticed that rise in the heat input enhanced the toughness of weld deposit but hardness of weld joints showed insignificant variation in it. This was primarily due to the increase in ferrite content in the matrix of martensite by enhancement of the heat input. In general, the microstructures of weld consisted of mixture of martensite and austenite as well as some amount of ferrite. Whereas, HAZ near to the fusion line consisted of larger and more elongated bright phase of banded delta ferrite in a matrix of martensite irrespective of change in heat input.

Geohazards and thermal regime analysis of oil pipeline along the Qinghai–Tibet Plateau Engineering Corridor

This paper investigates the influence of geohazards on the existing oil pipeline and the potential interaction between the proposed new oil pipeline and preexisting transportation structures along the Qinghai–Tibet Plateau Engineering Corridor. The current Golmud–Lhasa oil pipeline has been seriously affected by retrogressive thaw slumps caused by surface water being channeled through culverts causing serious erosion problems. Climate data show that the air temperature increased at a rate of 0.0281 °C/a for the past 60 years along the corridor. To design the new pipeline, the effects of revegetation, climate warming and pipe insulation on permafrost have been simulated using numerical modeling. A warm oil pipeline would potentially lead to significant thawing of the permafrost foundation. When climate warming is not considered, insulation of the buried pipe could keep the permafrost stable. Revegetation and the use of utilidors could counteract the influence of heat input from the oil pipe, and even a 1.1 °C/50a climate-warming rate. However, for the 2.6 °C/50a climate-warming-rate scenario, they are inadequate to keep the permafrost stable. Vegetation cover is important to reduce the effect of climate warming on both the natural and the human-impacted permafrost. Revegetation after construction is important to protect the permafrost environment as well as the oil pipeline itself.

Effect of Heat Input During Disk Laser Bead-On-Plate Welding of Thermomechanically Rolled Steel on Penetration Characteristics and Porosity Formation in the Weld Metal

The paper presents a detailed analysis of the influence of heat input during laser bead-on-plate welding of 5.0 mm thick plates of S700MC steel by modern Disk laser on the mechanism of steel penetration, shape and depth of penetration, and also on tendency to weld porosity formation. Based on the investigations performed in a wide range of laser welding parameters the relationship between laser power and welding speed, thus heat input, required for full penetration was determined. Additionally the relationship between the laser welding parameters and weld quality was determined.

Influence of multiple thermal cycles on microstructure of heat-affected zone in TIG-welded super duplex stainless steel

The influence of heat input and multiple welding cycles on the microstructure of the heat-affected zone in autogenously TIG-welded 6 mm 2507 type super duplex stainless steel plates was investigate ...

Influence of Heat Input and PWHT on the Microstructure and Mechanical Properties in Dissimilar (IS2062-EN8) Welded Joints

In the research work we evaluated the effect of heat input and PWHT on dissimilar metal joints influencing their mechanical properties and microstructure. Dissimilar metal joints of Mild steel and EN8 are prepared by using MIG welding process. This melting is possible because a sufficient amount of energy transferred per unit time and energy density is supplied to the wire. Tensile strength, impact, hardness was tested and Microstructure was studied. The heat input transferred along the transverse length of the welded joint will affect the entire weldment zone. Across the traverse length the hardness values are used to identify different zones of the welded joint. This heat input is varied with input parameters such as voltage, current and speed of wire. In the present research work heat input is considered as low and high heat input cases. The microstructure and the mechanical properties at different zones of each plate of weldment with low and high heat input cases are analysed with out and with post weld heat treatment.

Influence of heat input in microwelding of titanium alloy by micro plasma arc

In the present work, an investigation is carried out on microwelding of Ti6Al4V alloy with 500μm thin plate in butt joint configuration. The effect of welding speed and current are analysed to estimate the feasible range of process parameters for a successful joint. The role of fixture to minimize the oxidation and weld induced distortion has been demonstrated in joining of titanium alloy. The critical assessment on the performance of the weld joint is evaluated by micro-tensile, micro-hardness and metallographic analysis. The feasible range of process parameters like welding speed of 2–7mm/s and current of 8–13A produces the high quality weld joint using several other favourable conditions for titanium alloy. A three-dimensional finite element model is developed to simulate the temperature distribution and weld induced distortion of the joint. The sequentially coupled thermo-mechanical model predicts the distortion using large-displacement theory. The shape and size of computed macrograph are well agreed with experimentally measured values and indicates the robustness of the present numerical model used for micro scale welding process.

Investigation on parameter optimization for laser welded butt joint of TA15 alloy

The butt joints of TA15 alloy plates with 3- and 5-mm thickness were welded by fiber laser. By utilizing the representative and comparative of orthogonal test, considering factors such as laser power, welding velocity, and defocus distance, titanium alloy laser welding orthogonal testing was performed. The relationships between macromorphology and heat input, fusion depth, and welding width were obtained. And then, the welding parameters were optimized. Microstructure was analyzed by optical microscope, and the influence of heat input on microstructure was discussed. Range analysis on hardness and tensile test of 3- and 5-mm-thick titanium alloy was performed, and optimized combination was carried out. Finally, the reasonable laser welding parameters of TA15 alloy were proposed.

Influence of Heat Input on Microstructure and Toughness Properties in Simulated CGHAZ of X80 Steel Manufactured Using High-Temperature Processing

To determine and demonstrate the weldability of high-Nb high-temperature processed (HTP) steels and provide extremely valuable information for future line pipe steel design and general steel manufacture, in the current study the toughness in simulated coarse-grained heat-affected zone (CGHAZ) of an X80 grade steel manufactured using HTP was evaluated. The simulated CGHAZs subjected to thermal cycles with various heat inputs (HIs) (0.8 to 5.0 kJ/mm) were produced using a Gleeble 3500 simulator. The microstructures and corresponding mechanical properties were investigated by means of optical microscopy, scanning electron microscopy, electron backscatter diffraction, hardness testing, and Charpy V-notch (CVN) testing. The microstructural examination shows that the simulated CGHAZs consisted of a bainite-dominant microstructure and relatively low amount (<2 pct) of martensite–austenite (M–A) constituent. The prior austenite grain size was controlled to be 45 to 55 µm at HIs of 0.8 to 3.5 kJ/mm, and remarkably increased to 85 µm at an HI of 5 kJ/mm. The results of CVN testing suggest that superior toughness can be achieved in the studied range of HIs (0.8 to 5 kJ/mm). This is thought to be associated with the combined effects of bainitic microstructure and low M–A fraction as well as comparatively fine austenite grain size in the studied CGHAZs.

Selective Laser Post-Treatment on Titanium Cold Spray Coatings

The aim of the present work is to investigate the feasibility and effects of a selective postdeposition laser treatment on titanium coatings. Commercially pure titanium grade 2 powders were deposited by means of a cold spray process on aluminum alloy AA2024-T3 sheets. The surface treatment of the coating was realized using a 220 W diode laser. The influence of heat input and dimensional features of coating layer and substrate was assessed by an experimental campaign conducted following a design of experiments approach. Optical and scanning electron microscopy analysis of the microstructure of the deposited and treated material as well as microhardness measurements showed the formation of a compact layer of titanium oxide on the coating surface and the preservation of the temper state of the aluminum substrate.

A NUMERICAL APPROACH FOR MODELLING THERMAL PROFILES AND EFFECTS OF PROCESS PARAMETERS ON IT IN SUBMERGED ARC WELDING OF AISI 1518 GRADE STEEL

A comprehensive methodology for the analysis of thermal analysis due to welding has been studied in this present investigation. A finite volume methodology (FVM) among term of the basic heat transfer equation was enforced to simulate the temperature profiles in submerged arc welding (SAW) of AISI 1518 grade steel. The supply of the arc is assumed to be a moving conicoidal heat supply with a Gaussian distribution. The obtained results from the simulation methodology are compared with experimental results and determined a good agreement with experimental results, with associate degree overall proportion of error calculable to be between 5.23%. The influence of welding current and speed of temperature analysis has been evaluated and located that each one those parameters are playing a necessary role in moving the temperature distribution of the assembly, i.e.when current inflated, the temperature conjointly inflated with constant speed yet like higher speed temperature is decreased for constant current . Finally, the influence of heat input on peak temperature variations in various welding parameters has been evaluated and shown that the higher heat input in higher temperature is obtained.