Effect Of Heat Input Research Articles

Effect of root welding heat input on microstructure evolution and fracture mechanism in intercritically reheat-coarse grained heat-affected zone of X80 pipeline steel

The impact toughness of X80 pipeline steel welded joints widely used in laying directly affects the service life of pipelines. The intercritically reheat-coarse grained heat-affected zone (ICCGHAZ) is an embrittlement zone in dual pass welded joints due to the existence of M-A constituents. Adjusting the heat input provides the possibility to optimize the microstructure distribution and improve the impact toughness. In this paper, microstructure, especially the M-A constituents, and fracture mechanism with different root welding heat inputs (4 kJ/cm, 6 kJ/cm, 12 kJ/cm) of ICCGHAZ in X80 pipeline steel welding joint were investigated. The results illustrated that the amount of reverted austenite decreased with increasing root welding heat input, which led to the variety of M-A constituent distribution from dense to sparse and type from island to coarse slender. With increasing root welding heat input, the impact energy of ICCGHAZ decreased (32 J→28 J→26 J) owing to the decrease of HAGBs ratio and the variety of M-A constituent types. The toughness of ICCGHAZ could be higher than the base metal at 4 kJ/cm. The impact fracture mechanism schematic diagram at 4 and 12 kJ/cm were summarized. During the impact process, cracks nucleated at the secondary thermal cycle product. Crack deflected when encountered the island-type M-A constituent. While it propagated straightly when encountered the course slender type M-A constituents. The less deflection propagation path could consume less energy and consequently decrease toughness.

Effect of Welding Heat Input on Microstructure and Properties of Coarse-Grained HAZ of 500 MPa High-Strength Low-Alloy Steel

Effect of Welding Heat Input on Microstructure and Properties of Coarse-Grained HAZ of 500 MPa High-Strength Low-Alloy Steel

Effect of electrode negativity ratio and heat input on bead and arc characteristics in submerged arc welding

The effect of electrode negativity (EN) ratio, current and welding speed on bead profile and arc stability in case of constant current square wave power source were investigated by conducting bead on plate (BOP) welding experiments on API X80 steel. In addition to this, effects of heat input on prior austenite grain (PAG) size, microstructure and hardness of coarse grain heat affected zone (CGHAZ) were also studied. Deleterious hump angle created due to EN ratio variation, decreased with increase in EN ratio and welding current. Average PAG size and spacing between bainite laths increased from 17.09 µm to 62.66 µm and 0.67 µm to 50 µm respectively with increase in heat input from 0.69 kJ/mm to 3.6 kJ/mm, which altered CGHAZ hardness. Arc stability and metal transfer mode for different EN ratios and currents were analyzed by means of probability density distribution (PDD) graphs of current and voltage transients recorded using a digital storage oscilloscope. PDD graph show better arc stability at higher currents and during the electrode positive (EP) part of current waveform.

Effect of heat input on microstructure and mechanical property of wire-arc additive manufactured Ti-6Al-4V alloy

Effect of heat input on microstructure and mechanical property of wire-arc additive manufactured Ti-6Al-4V alloy

Effect of heat input on microstructure and mechanical properties of TIG-welded semisolid cast AXE622 Mg alloy

The present study investigats the effect of heat input on the microstructure and mechanical properties of the TIG-welded semisolid AXE622 alloy. Three heat inputs, 18 kJ/mm, 21 kJ/mm, and 24 kJ/mm are used, and the corresponding joints referred to as HI18, HI21, and HI24 joints. Results showed that the average grain size in the heat-affected zone (HAZ) (~38 μm, 50 μm, and 67 μm) was more considerable than that in the fusion zone (FZ) (~15 μm, 17 μm, and 18 μm) for the HI18, HI21, HI24 joint, respectively. The volume fraction of the second phases in FZ was significantly higher concerning the HAZ. The eutectic Mg 17 Al 12 phase formed a network structure in FZ of the HI18 joint and fragmented in the HI21 joint, while less fragmentation was observed in the HI24 joint. The volume fraction, the average length, and the width of secondary phases decreased in the HAZ with increasing the heat input. The HI21 joints exhibited the largest tensile strength (~147 MPa) and elongation (~3%) and ruptured in the BM. With increasing the heat input, the hardness decreased in the HAZ and FZ. Besides, the hardness in FZ (~70 HV, 63 HV, and 58 HV) was more significant than that in the HAZ (~ 50 HV, 47 HV, 43 HV) for the HI18, HI21, and HI24 joint, respectively. The beneficial effect of semisolid processing was degraded due to the significant heat input imposed in the HAZ of the HI24 joint. • Semi-solid Mg alloy specimens were successfully produced and TIG-welded in three heat inputs • With increasing the heat input, the grain size increased more significantly in the HAZ. • The least amount of Mg 17 Al 12 phase was formed in the FZ of the HI21 joint. • The HI21 joints exhibit the largest tensile strength, yield stress, and uniform elongation. • With increasing the heat input, the hardness decreased slightly in the HAZ and FZ.

Correlation of real-time thermal history with tribological properties of laser coated NiCrBSi with Ag and WS2 addition

The laser coating of NiCrBSi in pure form as well as with the addition of lubricious Ag or WS 2 has been developed on Ti6Al4V substrate. With the help of an IR pyrometer , real-time thermal history was monitored and correlated with the tribological properties of the coating. A matrix predominantly comprised of NiTi and NiTi 2 and reinforced with hard phases like CrB, TiC, TiB 2 , Cr 3 C 2 was formed for all the types of coatings. From the XRD and EDS analysis, it was observed that for the coating containing Ag, Ag was found to be present in elemental form, but in the case of coating containing WS 2 , WS 2 got dissociated during laser processing and formed TiS 2 , an anti-friction phase. Effects of heat input on the tribological behavior of both types of coatings (in-situ generated lubricating phase TiS 2 and ex-situ developed lubricating phase Ag) were analyzed with the help of real-time thermal history. For Ag-type coating, maximum hardness, minimum COF and, minimum wear rate were obtained as 968 HV, 0.25, and 2.21E-5 mm 3 /N-m respectively for lower power and higher velocity process parameters. For WS 2 coating, maximum hardness, minimum COF and, minimum wear rate were obtained as 1303 HV, 0.26, and 1.5E-4 mm 3 /N-m respectively for lower laser power and higher scan speed. Comparing both the coating, it can be stated that, low heat input led to a high cooling rate, low molten pool life, and a low peak temperature of the molten pool, which increased the lubricious phase in the coating thereby reducing the friction coefficient. The present study can be useful to develop the process maps for desired lubrication property of the coating by using real-time monitoring of the thermal histories during the laser coating process . • Correlation of real-time thermal history with performance of the laser coatings • Laser coating of NiCrBSi with addition of Ag and WS 2 as solid lubricant • Shorter molten pool life time and low peak temperature reduced friction. • Process map based on the correlation of online monitoring and tribological property • Minimum COF and wear rate of the coating was 0.25 and 2.21E-5 mm 3 /N-m respectively.

Effect of dimensionless heat input during laser solid forming of high-strength steel

Laser solid forming (LSF) technology can be used to rapidly manufacture and repair high-strength steel parts with superior performance, but the value of the heat input during operation is difficult to quantify, which has a substantial impact on the microstructure and mechanical properties of the parts. A promising method to improve the forming efficiency and quality of LSFed parts is to accurately control the heat input and explore its relationship with the microstructure and mechanical properties. To remove the interference of other variables from the experiment, the dimensionless heat input Q* was introduced. The Q* values were designed in advance to calculate the experimental parameters used to perform the LSF experiment. The microstructure was observed at different regions of the sample, and its mechanical properties were analyzed. From the results, the following conclusions were drawn. The Q* value was directly related to the cooling rate and heat accumulation in the top structure, leading to the formation of different microstructures; it also modified the original structure at the bottom, affecting the subsequent thermal cycle and indirectly changing the tempered martensite morphology. The heat input also affected the mechanical properties of the sample. The hardness of the stable zone decreased with increasing Q* value, and the lowest value was 190 HV. Similarly, the tensile strength and yield strength of the LSFed samples decreased considerably with increasing Q* value, and the lowest values were 735 and 604 MPa, respectively. Only the elongation and reduction in the area increased after a slight decrease. The Q* value had a significant effect on heat treatment. When Q* = 2.9, the increase in tensile strength and yield strength after heat treatment was the largest (29% and 44%, respectively).

Effect of heat input on microstructure and tensile properties of laser welded Ti–3Al–6Mo–2Fe–2Zr alloy joint

The heat input during laser welding process has significant influence on microstructure and properties of the joints, whereas there is currently limited research concerning the influence of heat input during laser welding process of β titanium alloys. The microstructure and tensile properties of laser welded Ti–3Al–6Mo–2Fe–2Zr (wt.%) joints under different heat inputs were investigated in this paper. Numerical simulation process was used to explain the microstructure evolution in HAZ and fusion zone. The microstructure of HAZ is divided into three different regions from fusion line to base metal. In near-HAZ, mid-HAZ, and far-HAZ, the microstructures are composed of single β phase, β + αp, and β + αp + retained αs, respectively. In fusion zone, the microstructure consists of single β phase because of the fast cooling rate and high content of β stabilizing elements. The ultimate tensile strength (UTS) of laser welded specimens is lower than that of base metal due to the lack of strengthening phase and the coarsening of β grains. Higher heat input further exacerbates the coarsening of β grains in the fusion zone and HAZ, which consequently results in the decrement of UTS of the joints.

A folding method to increase the rigidity of paperboard tray packages

The flange of press-formed paperboard trays was reshaped in this work with a developed folding method to increase the rigidity of the trays. The tray rigidity was evaluated with compression, torsion, and storing tests. The rigidity of the folded trays and the reference trays was compared, and the quality of the trays was investigated with an optical analysis. The folding temperature was altered to 23, 60, and 90 °C to compare the effects of heat input on the tray rigidity. The compression and torsion test results linked the increased tray rigidity to the additional heat input and surface pressure induced to the material in the folding phase. The trays that were folded at 90 °C showed a 43% higher compression force and a 12% smaller torsion angle compared to the reference trays. The storing tests showed an unclear effect on the tray rigidity to the dimensional stability, and the optical analysis depicted similar quality between the folded and the reference trays. The folding method was found to enhance the stacking and end use capabilities of paperboard tray packages, and the use of higher folding temperatures was suggested to increase the strength and stiffness of the trays.

Al-steel dissimilar joining: Challenges and opportunities

Al-steel joining has a lot of use in the automotive and aerospace industries since it saves a lot of weight. The materials' physical, thermal, and metallurgical qualities differed significantly, making connecting this combination difficult. This article provides a comprehensive overview of the Al-steel joining processes. The fundamental reason for the problem in fusion joining operations is the formation of a thick intermetallic compound (IMC) layer and additional difficulties related to solidification. The effects of heat input, wettability, and IMC layer on joint formation are summarised in this article. To achieve a good joint, numerous elements like heat generation, IMC formation, and process parameters must be critically balanced in solid-state joining processes. The effects of process parameters in friction stir welding (FSW) techniques on joint's mechanical and metallographic soundness are explored in this work. Because of the steel's higher strength, there have been various attempts to soften it and make it easier to deform in order to improve weld amalgamation. The use of tungsten inert gas (TIG) welding and electrical resistance heating to achieve heat-assisted hybrid friction stir welding has been documented in the literature. The hybrid joining processes are found to be improving the joint's tensile properties.

Effects of Heat Input on Microstructure S And Mechanical Properties of Laz931 Magnesium-Lithium Alloy by Co 2 Laser Welding

Effects of Heat Input on Microstructure S And Mechanical Properties of Laz931 Magnesium-Lithium Alloy by Co 2 Laser Welding

CTOD Evaluation of API X80MO PSL2 TMCP Steel Welded Joints Used in Offshore Structures Based on API RP 2Z

Offshore structures and equipment, used both for oil extraction and wind power generation, are constantly exposed to extreme application conditions, such as low temperatures, corrosion, and cyclic loading. Thus, to ensure the integrity of such components, the use of materials with excellent mechanical properties combined with good weldability is required. In this sense, the main committees, institutes, and normative societies have created pre-qualifications, codes, and programs to evaluate and certify the weldability of steels applied in the offshore industry. API RP 2Z prequalification is one such standard that is designed to ensure that steels developed for these applications have excellent fracture toughness in the heat affected zone (HAZ). In this context, the effect of heat input on the HAZ toughness of welded joints of API X80MO steel plates was evaluated, using the CTOD (Crack Tip Opening Displacement) parameter. It was found that this steel, of 37 mm thickness, welded with heat inputs of 0.8 and 4.5 kJ/mm, presented weldability characteristics and fracture toughness behavior suitable for API RP 2Z standard specification. Therefore, API X80MO steel plates, produced by controlled rolling followed by accelerated cooling, is an option for application in the construction of offshore structures and components.

Effects of filling ratio, geometry parameters and coolant temperature on the heat transfer performance of a wraparound heat pipe

• Thermal performance of a wraparound heat pipe was investigated. • An optimal filling ratio exists between 50% and 60%. • The effect of inclination angle became insignificant for larger inclination angles. • The heat pipe with an outer diameter of 16 mm has the best thermal performance. • The minimum thermal resistance value of a wraparound heat pipe is 0.027 K/W. The present work focuses mainly on the effects of heat input, filling ratio, inclination angle, tube diameter and coolant temperature on the thermal performance of a wraparound heat pipe charged with R134a. Results show that thermal resistance decreases with the increase of heat input when the filling ratio is larger than 40%. An optimal filling ratio for the heat pipe with the best performance exists between 50% and 60%. The pressure of working fluid in the heat pipe exceeds 1.6 MPa in the 70% and 80% filling ratios experiments. For larger inclination angles ( θ > 10°), the thermal resistance decreases with increasing the heat input and finally tends to a stable value. For heat loads of 420 W and greater, the values of thermal resistance are 0.056, 0.07, 0.034 and 0.027 K/W for outer diameters of 8, 10, 12 and 16 mm, respectively. No significant difference in thermal resistance at different coolant temperatures is observed for heat inputs greater than 300 W. In all experiments, for a 22° inclination angle, an outer diameter of 16 mm, and a filling ratio of 50%, the best performance of heat pipe is observed and the lowest value of thermal resistance is 0.027 K/W.

Effect of welding processes on mechanical and metallurgical characteristics of carbon steel cylindrical components made by wire arc additive manufacturing (WAAM) technique

In recent decades, Additive Manufacturing (AM) has become a viable alternative to the manufacture of metal parts. Wire arc additive manufacturing (WAAM), a welding-based AM technique is an important research area since it permits the economical manufacture of large-scale parts with relatively high deposition rates. This article compares the effect of heat input on mechanical properties of carbon steel cylindrical components fabricated by Gas Metal Arc Welding (GMAW) and Cold Metal Transferred Arc Welding (CMTAW) processes. Firstly, the influence of heat input on the grain size was analysed. Subsequently, the effect of heat input on the tensile properties, impact toughness and hardness of the cylindrical components were studied along the building direction. The cylindrical component made by CMTAW process showed superior tensile properties and higher impact toughness than GMAW component. Similarly, CMTAW component exhibited higher hardness than GMAW cylindrical component. The variations in mechanical properties are mainly due to the appreciable variations that have occurred in the microstructural features and different grain sizes evolved at different heat input levels. The bottom and top regions of the fractured tensile and impact specimens of the components are characterised by dimple structures revealing the ductile fracture.

Heat input effects on mechanical constraints and microstructural constituents of MAG and laser 316L austenitic stainless-steel welded joints

<abstract> <p>This study aims to investigate the optimum heat input required to overcome the negative consequence of the thermal properties of austenitic stainless steel to produce welded joints free of distortion. An experimental investigation using robotic-MAG and fiber-laser welding processes has been used in other to investigate angular, longitudinal distortion (bending), and microstructural constituents in the heat-affected zone (HAZ) of different welded joints. Ten 316L steel, butt-joints were made by different travel 25 speeds at the range of (7–11 mm/s). A highly sensitive 2D-laser device has been used to measure the distortion then, a microstructural investigation was done using an optical micrograph, Scanning Electron Microscopy (SEM) coupled with the Electron Dispersive Spectrometer (EDS). The laser-fiber welding process results indicated optimum parameters to prevent distortion when applying welding speed of 2.2 m/min, the power source of 2.5 kW, and the focal position of 3 mm. In MAG welding, test results revealed an increase of longitudinal distortion (bending) from 1.2 mm to 3.6 mm when raising the heat input from 0.3 to 0.472 kJ/mm. When increases welding speed (11 mm/s), angular distortion was approximately 2.1° on the left side and 1.7° on the right side. Microstructural investigations revealed the proportionality between heat input and carbides formations on the grain boundaries of HAZ. They were also the formation of etching pores and some ferrite content (10%) on the weld center.</p> </abstract>

Effect of Welding Heat Input on Microstructure and Properties of Coarse Grain Zone in Heat Affected Zone of Ultra-Low Carbon Bainitic Steel

In order to explore the effect of different the welding heat input on microstructure and impact properties in coarse grain zone in heat affected zone (CGHAZ) of ultra-low carbon bainitic steel welded joint. In this paper, Gleeble-3500 thermal simulation testing machine was used to simulate different heat input, to study the effect of linear energy on the microstructure and impact toughness of the CGHAZ of Q420qEN steel joint. The scanning electron microscope (SEM), oscillographic impact microscope and transmission electron microscope (TEM) were used. The results show that the microstructure of CGHAZ is mainly the lath bainite and granular bainite. When the welding heat input is 30kJ•cm-1, the CGHAZ grains have obvious growth phenomenon. With the increase of the welding heat input, the grain size also grows. Meanwhile, as the welding heat input increases from 18kJ•cm-1 to 30kJ•cm-1, the impact toughness of the CGHAZ of joint increases first and then decreases at -20°C.

Experimental study on diffusion absorption refrigerator achieving 0.2 coefficient of performance using low global warming potential refrigerant and low-grade heat source

The commercial model of diffusion absorption refrigeration operated purely via thermal energy utilizes ammonia as a refrigerant. Ammonia is not only a toxic substance but also reacts with copper; thus, most commercialized diffusion absorption refrigerator is fabricated using carbon steel instead of copper. In the previous research, copper cannot be used in the diffusion absorption refrigerator because of the ammonia. However, in this study, via the newly proposed low global warming potential refrigerant R600a, copper absorber can be employed to improve the coefficient of performance of diffusion absorption refrigerator. R600a, n-octane and helium are used as the refrigerant, absorbent, and auxiliary gas, respectively. Simultaneously, the bubble pump and absorber are fabricated from copper to improve the heat transfer rate. As a result, a high coefficient of performance is achieved despite the use of a low global warming potential refrigerant. In particular, the experimental analysis is conducted with a focus on how the effectiveness and performance of the absorber vary by comparing carbon steel and copper as the absorber material. The configuration of the two diffusion absorption refrigerators is exactly the same but the absorber material is changed. When employing copper, the effectiveness of the absorber is improved by 9.09–35.71% compared to that of carbon steel absorber under the same heat input. In addition, an experimental investigation is conducted by changing the pressure to 400 kPa, 465 kPa, 530 kPa, and 600 kPa for heat input in the range of 30–100 W to analyze the effect of heat input and operating pressure. By utilizing copper for diffusion absorption refrigerator with R600a, a coefficient of performance of 0.20 is achieved at a low generator temperature of 71.07 °C, which is the highest coefficient of performance and the lowest generator temperature with low global warming potential, so that solar energy can be utilized as the heat source in the present diffusion absorption refrigerator system.

Evaluation of the Effect of Heat Input and Cooling Rate of Rail Flash-Butt Welding using Finite Element Method Simulation

Abstract Simulations using the finite element method (FEM) were done to understand the effects of heating/cooling rates on the distribution of residual stresses. Two material parameters from rails were used while the boundary conditions remained constant: heat-affected zone size, maximum temperature and heating extraction rate. To complement the analysis, a flash-butt weld of a Premium rail was done with welding parameters adjusted to obtain a narrow HAZ, without forced cooling, to examine the microstructure formed in the critical regions in the web and the edge of the rail foot. The results showed that there was a concentration of vertical residual stresses in the web region, while the presence of horizontal compression residual stresses was mostly superficial in the rail head region. The main result from the simulation sets was that when using two simulation parameters with similar materials (rails) substantially different results were obtained. Metallographic examinations showed that there was no presence of acicular microconstituents (martensite/bainite). In the rail web, proeutectoid ferrite was observed in the central region, cementite in a previous austenitic grain boundary, in the region that reached temperatures close to AC3, and almost complete spheroidization in the region of maximum spheroidization. In contrast, in the rail foot edge region, there was a completely pearlitic microstructure, in the central region and in the zone that reached temperatures close to AC3, and a lower volume of spheroidization in the region where maximum spheroidization is typically observed, probably due to the higher cooling rate in this region.

Coupling Effect of Heat Input and Path on the Deposition Quality and Microstructure of Multiple Beads Laps Al-Mg Alloys by Wire Arc Additive Manufacturing

Coupling Effect of Heat Input and Path on the Deposition Quality and Microstructure of Multiple Beads Laps Al-Mg Alloys by Wire Arc Additive Manufacturing

Effect of heat input and heat treatment on the microstructure and toughness of pipeline girth friction welded API 5L X65 steel

High-strength low-alloy steels (HSLA) have been considered key materials for the petroleum industry for the construction of pipelines to move oil and gas for long distances. Conventional welding processes may produce important microstructural changes, which negatively impact the mechanical behavior of the pipeline material. Alternatively, pipeline girth friction welding is an excellent choice to lessen the detrimental effect on microstructure since it is a one-shot low heat input process. This work aims to optimize impact toughness – the most affected mechanical property - to qualify pipeline girth friction welded API 5L X65 steel joints according to the requirements of the DNV OS F101: 2013 international standard. The impact toughness optimization process relied on the evaluation of the welding parameters' effect on heat input and on post-weld heat treatment (PWHT). The results indicated that even though the single thermal cycle imposed lowered the size and fraction of martensite-austenite (M/A) constituent in the as-welded condition, impact toughness was notably reduced due to previously austenite grain growth and unfavorable crystallographic texture. However, at least part of the original base material's impact toughness can be restored by decreasing the heat input, although not sufficient to qualify the weld. Otherwise, PWHT led to grain size refinement and reduced crystallographic texture, which in turn improved impact toughness beyond the minimum level specified by the technical standard.