Effect Of Heat Input Research Articles

Effect of different heat input on the microstructure and mechanical properties of laser cladding repaired 300M steel

Laser cladding repair technology is valued for its ability to repair of damaged parts with high performance. However, there are so many parameters affect the repair quality that it takes a lot of work to determine the optimal parameters. In this article, a variety of parameters were combined as dimensionless heat input (Q∗), and the effect of Q∗ on the microstructure and mechanical properties of 300M steel repaired samples were studied. Results showed that with the increase of Q∗, microstructure of heat affected zone transformed from tempered martensite to tempered martensite and low bainite. The microstructure of the repaired zone transformed from untempered martensite to untempered martensite and a small amount of retained austenite. With increasing of Q∗, residence time above the austenitizing temperature was extended, and more uniform microstructure were obtained in the repaired zone. What's more, at Q∗ = 5.1, the repair efficiency increases twice than Q∗ = 1. The tensile strength of the repaired samples reached 1017.6 MPa and the elongation reached 6.9%, which were far lower than that of forged samples. The heat treatment was carried out on the repaired parts, which eliminated the microstructure difference due to different Q∗. Compared with the repaired samples without heat treatment, the tensile strength increased by 75% to 1783.8 MPa and the elongation increased by 86% to 10.4%.

Effect of welding heat input on microstructural evolution and impact toughness of the simulated coarse-grained heat-affected zone of Q960 steel

Effect of welding heat input on microstructural evolution and impact toughness of the simulated coarse-grained heat-affected zone of Q960 steel

Heat input effect in a multipass and double-wire GMAW welding of a thick structural steel for industrial applications

Heat input effect in a multipass and double-wire GMAW welding of a thick structural steel for industrial applications

Effect of Heat Input on Hydrogen Embrittlement of TIG Welded 304 Austenitic Stainless Steel

Welds made with 304 austenitic stainless steel play an important role in high-pressure hydrogen storage systems. However, there are few investigations of the effect of heat input on the hydrogen embrittlement (HE) of tungsten inert gas (TIG) welded 304 austenitic stainless steel. In this study, the effect of heat input on the HE of TIG welded 304 austenitic stainless steel is investigated. It was found that with the increase in TIG welding heat input, the ferrite content in the weld shows a tendency to first increase and then decrease. From the perspective of morphology, it first changes from lathy ferrite and strip ferrite to dendritic ferrite, and then becomes reticular ferrite and lathy ferrite. Slow strain rate tensile (SSRT) testing shows that with the increase in heat input from TIG welding, the susceptibility of the weld to HE first increases and then decreases. Our study shows that TIG welds of 304 austenitic stainless steel exhibit the best HE resistance when the welding heat input is 0.778 kJ/mm, the relative elongation (RE) is 0.884, and the relative reduction of area (RRA) is 0.721. This work can provide a reference for the optimization of the 304 stainless steel TIG welding process.

Effect of heat input on nanomechanical properties of wire-arc additive manufactured Al 4047 alloys

Heat input is one of the most important process parameters during additive manufacturing (AM). It is of great significance to understand the effect of heat input on the microstructure and nanomechanical properties, as well as the underlying mechanisms. Wire-arc additive manufactured (WAAM-ed) Al 4047 alloys under different heat inputs were produced and studied in this work. The as-manufactured Al alloys showed hypoeutectic microstructure that consisted of primary Al (α-Al) dendrite and ultrafine Al–Si eutectic. The effect of heat input on hardness and strain rate sensitivity (SRS) were investigated through nanoindentation. The nanohardness decreased with the increasing heat input, in accordance with the trend of yield strength and microhardness in the previous studies, in which the mechanism was usually explained by the grain growth model and Hall-Petch relationship. This work suggests a distinct mechanism regarding the effect of heat input on nanohardness, which is the enhanced solid solution strengthening produced by lower heat input. In addition, the heat input had little effect on the SRS and activation volume. It is hoped that this study leads to new insights into the understanding of the relation between heat input and nanomechanical properties, and further benefits to improve the targeted mechanical properties and engineering applications of the AM-ed materials.

Parametric Investigation of Closed Loop Pulsating Heat Pipe with Cerium Oxide Nanofluid

In this study, a closed-loop pulsating heat pipe experimental investigation was done with 1% wt concentration of cerium oxide/EG-water (60-40) nanofluid. The unsteady state measurement was done to determine the effect of heat input, filling ratio and evacuation pressure on the thermal performance of the closed-loop pulsating heat pipe. The thermal performance is assessed in terms of temperature variation, thermal resistance and effective thermal conductivity of the pulsating heat pipe. The most appropriate behaviour is observed at 0.0799 bar evacuation pressure with 50% FR. The lowermost thermal resistance of 0.116598K/W was observed at 0.0799 bar evacuation pressure and 50% FR. The effective thermal conductivity value was observed as 5078.34 W/mK at 50% FR, 0.0799 bar for 80W heat input which is 12 to 13 times better than pure copper. The pulsation action inside the pulsating heat pipe is verified with the power spectral density analysis. This study supports the better performance of the heat pipe at 50% FR with a lower evacuation pressure of 0.0799 bar.

Effect of equivalent heat input on WAAM Al-Si alloy

Heat input is a critical parameter in wire arc additive manufacturing (WAAM). A large number of studies have been carried out on the heat input of WAAM. However, the current research only focuses on the influence of different heat input values on the structure and performance of components, and the influence of equivalent heat input on the structure and performance of components is totally overlooked. In this paper, a new understanding of heat input is gained through analysis of the forming, microstructure and properties of WAAM components. Through the design of energy parameters (welding current, welding voltage, and traverse speed), three sets of the same heat input are obtained with different parameter combinations during the WAAM of aluminum-silicon alloy as the research object. The wire feeding speeds of Samples A, B, and C are 4, 6, and 8 (unit: m/min), respectively. The traverse speeds of Samples A, B, and C are 6, 11, and 16 (unit: mm/s), respectively. The results showed that the forming morphologies, microstructure and mechanical properties of thin-walled parts obtained under different parameters are significantly different with the same heat input. Under the interaction of wire feeding speed and traveling speed, the forming height of the sample decreases and the width increases, and the grain size increases with the increase of the two parameters. Sample A has the best mechanical properties, with an average tensile strength of 208.85 MPa and an average hardness of 71.66 HV. Compared with those of Sample C, the microhardness and tensile strength increased by 18.4 HV and 17.5 MPa, respectively.

A novel compression-assisted energy storage heat transformer for low-grade renewable energy utilization

Thermal energy storage is a promising method to balance the timing mismatch between the intermittent energy sources and time-variable user loads but cannot address the low-grade issue, which results in the underutilization of low-temperature renewable energy. An absorption-based energy storage heat transformer (ESHT) can achieve temperature upgrading with satisfactory storage performance. To further improve the system performance, a novel compression-assisted ESHT (CESHT) is proposed. The dynamic characteristics of the basic ESHT and CESHT cycles are analyzed and compared. Then, the effects of heat output, heat input, and heat sink temperatures on the cycle performance are investigated. Results show that significant enhancements are achieved by the CESHT cycle for both energy storage performance and temperature upgrading ability. With auxiliary compression, the temperature lift is increased from 30 °C to 65 °C, and the required input temperature is decreased from 60 °C to 45 °C. Moreover, the performance indexes are greatly improved, e.g., the energy storage efficiency, energy storage density, and exergy efficiency are respectively increased from 0.24 to 0.43, from 35.2 kWh/m3 to 282.7 kWh/m3, and from 0.32 to 0.54 with a temperature lift of 30 °C. The proposed cycle demonstrates the advantages of enhanced storage performance and large temperature lift.

Effect of Heat Input on Microstructure and Corrosion Resistance of X80 Laser Welded Joints

Using fiber laser welding technology, X80 pipeline steel welded joints with different welding heat inputs were obtained. Their microstructure, mechanical properties, and corrosion resistance (in NACEA solution saturated with hydrogen sulfide) were studied. Findings indicated that with the increase in heat input, the proportion of ferrite, strength, elongation, and corrosion resistance increased within a certain range and the sum of the proportion of martensite and bainite and hardness decreased. The heat input has a greater effect on the microstructure of weld metal (WM) and coarse-grained heat-affected zone (CGHAZ), while that of fine-grained heat-affected zone (FGHAZ) is basically unchanged. Obvious differences are also found in the corrosion resistance of different regions of the welded joints, among which FGHAZ has the strongest corrosion resistance, followed by WM and CGHAZ. The heat input mainly affects the microstructure type of the welded joint to affect the corrosion resistance. Therefore, we model the heat input as a function of Rct and icorr from this relationship. In addition, the corrosion products film produced by the long-term immersion of the welded joint in the saturated H2S NACEA solution can hinder the development of corrosion and enhance the corrosion resistance to a certain extent.

Effect of Heat Input on Microstructure and Corrosion Resistance of CP-Ti Laser Beam Welded Joints

The TA1 welded joints with different heat inputs were obtained by a fiber laser and their microstructure, mechanical properties and corrosion resistance in simulated saliva solution were studied. The results show that the microstructure in fusion zone (FZ) is needle-like α′ martensite and lath-shape α′ martensite, and that of the heat-affected zone (HAZ) is zigzag α phase. With the increase of heat input, the volume fraction of needle-like α′ martensite decrease and the microstructure is coarsened in FZ, but there is almost no change in the microstructure of the HAZ. The order of the corrosion resistance of welded joints with different heat inputs is the same as FZ > HAZ > base material (BM), and the heat input has a more influence on the corrosion resistance of FZ. The binary multiple linear regression relationship between the corrosion current density/charge transfer resistance and the length/width of α′ martensite was established, indicating that the width of α′ martensite is the main factor affecting the corrosion resistance.

Effect of heat input and post weld heat treatment on the texture, microstructure and mechanical properties of laser beam welded AISI 317L austenitic stainless steel

In this study, AISI 317L austenitic stainless steel sheets were welded using laser beam welding method and post-welding heat treatment (PWHT) was applied to the joints. The effect of PWHT and welding heat input on texture, microstructure and mechanical properties was examined. According to the results obtained in the study, it was observed that the microstructure of the weld metal of the samples welded with the lowest and highest heat input consisted largely of austenite and a small amount of ferrite grains. Mechanical properties were directly affected by such microstructural changes. With the exception of impact notch results, higher tensile strength and micro-hardness was observed for most welded joints compared to the base metal for heat-treated and non-heat-treated conditions. It was found that the bending strength decreased due to softening of the microstructure after heat treatment. High mechanical properties were achieved in the samples joined with low heat input thanks to the microstructure with finer grains. According to the electron backscatter diffraction result (EBSD); the austenite (FCC) ratio in the base metal and weld metal of the sample welded with the highest heat input was found to be approximately 98% and 92%, while the ferrite (BCC) ratio in the base metal and weld metal was determined as 2% and 8%. It was determined that austenite volume ratio increases with PWHT. Austenite grains showed a random orientation in the base metal, while in the weld metal they showed orientation in the direction of [111] and more often [100]. Generally K–S and N–W orientation relationship (OR) was observed in the samples. In the weld metal of the C4H sample, transmission electron microscopy (TEM) determined the spinodal decomposition of ferrite, but G-phase was not observed.

Numerical Simulations of the Effect of Heat Input on Microstructural Growth for MIG-Based Wire Arc Additive Manufacturing of Inconel 718

Numerical Simulations of the Effect of Heat Input on Microstructural Growth for MIG-Based Wire Arc Additive Manufacturing of Inconel 718

Metallurgical Characteristics of Low Carbon Steel Cylindrical Components Made by Wire Arc Additive Manufacturing (WAAM) Technique

Fabrication of metal parts by wire and Arc Additive Manufacturing (WAAM) has received an increased interest in recent years, as it allows high design flexibility and reduction of material wastage compared to other traditional manufacturing routes. This article compares the effect of heat input on metallurgical characteristics of wire arc additive manufactured low 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 analyzed. Subsequently, the effect of heat input on the metallurgical characteristics of the cylindrical components was studied along the building direction. The microstructure of the built cylindrical-walled component varies from the top to the bottom regions and can be distinguished into two regions: lamellar structures (widmanstatten ferrite and grain boundary ferrite) in the top regions; and equated grains of fully ferrite in the bottom region in GMAW. In the CMT-WAAM cylindrical component samples have been noted two different regions: the bottom region characterized by a ferritic structure with thin strips of pearlite and the top region characterized by a lamellar structure typically bainite with acicular ferrite.

Crystallographic study on microstructure and impact toughness of coarse grained heat affected zone of ultra-high strength steel

The significant effect of welding heat input on microstructure evolution and toughness of coarse grained heat affected zone (CGHAZ) in ultra-high strength steel was studied from the aspect of crystallography. Charpy impact test confirmed the optimum toughness of CGHAZ was obtained at the heat input of 20 kJ/cm, which was related to the cumulative contribution of its well-refined bainitic structure and the highest density of high angle grain boundaries (HAGBs). Analysis on crystallography shows that the weakest variant selection occurs at the nose temperature of bainite transformation curve, inducing the staggered configuration of different Bain groups, and thus obtaining the highest density of HAGBs, especially the block boundary dominated by V1/V2 variant pair. From the establishment of the relationship between impact toughness and crystallographic structure, the variation in toughness of CGHAZ is primarily correlated to the block size.

Heat treatment and heat input effects on the dissimilar laser beam welded AISI 904L super austenitic stainless steel to AISI 317L austenitic stainless steel: Surface, texture, microstructure and mechanical properties

In this study, AISI 904L super austenitic - AISI 317L austenitic stainless steel sheets were successfully welded by laser welding method using six different heat inputs. Welded samples went through 1 h of post-weld heat treatment (PWHT) at 1100 °C and then left to cool at room temperature. The effect of PWHT and welding heat input on surface, texture, microstructure and mechanical properties has been examined. According to the results obtained in the study, it was observed that the weld metal microstructure of the samples welded at the lowest and highest heat input values consisted entirely of austenite (dendritic + interdendritic) grains. With PWHT, Cr23C6 precipitation was observed in both grain boundaries and austenite grains. In addition, austenite as well as dislocation and stacking fault formations were observed in the microstructure. While the highest austenite content was observed in the microstructure of AISI 317L, the content of austenite increased in all samples with PWHT. It was observed that most of the grains that were orientated in the [111] direction were orientated in the direction of [101] and [001] after PWHT. However, the KAM values of the dislocation in grain boundaries decreased with the effect of PWHT. In addition, with the reduction of the ratio of dark grains and the effect of re-crystallisation, (112) <111> components representing austenite grains appeared in FCC/BCC texture. It was identified that due to these textural changes, the tensile strength and resistance to bending of the samples were negatively affected but their toughness was positively affected. AB3 sample with the highest tensile strength, hardness, bending strength and lowest toughness had values of 615 MPa, 214 HV, 1100 N and 57 J, respectively, while these values changed to 550 MPa, 181 HV, 720 N and 60 J with the effect of PWHT. Due to the presence of the chromium-oxide layer, it was identified that the density of O− ion and H− ion was at high levels on the surface of the weld metal. It was identified that the density of these ions decreases with increasing depth, while Fe−, Cr− and Ni− ions increase. Excellent K–S and N–W orientation relationship (OR) was observed between FCC/BCC-structured grains present in the microstructure of without PWHT base metals and weld metal, while Bain OR was also observed in weld metal with or without PWHT. In the microstructure of the base metals with PWHT, there was no OR relationship between grains with FCC/BCC structures.

Comparative study on strength of TMCP and QT high-strength steel butt-welded joints

The strength of high-strength steel butt-welded joints with a similar steel grade may be quite different due to their discrepancies in the processing methods of high-strength steel. The process methods mainly include quenching and tempering (QT) and thermo-mechanically controlled process (TMCP). These differences in the strength of high-strength steel butt-welded joints with different processing methods of steel have not been quantitatively determined and considered in several design codes, which may lead to the unsafe design for the high-strength steel butt-welded joints. This research demonstrated a comparative and quantitative study on the strength of double-V butt-welded joints made of QT550, QT690, TMCP 550, and TMCP690. The true stress-strain behavior of various zones within these welded joints, including the hardened heat affected zone (HHAZ), softened HAZ (SHAZ), weld metal (WM), and base metal (BM), were investigated based on the test and simulation results of the round notched specimens and the flat grooved specimens in tension. The developed true stress-strain models were validated against the test results of high-strength steel butt-welded joints. The strength of QT and TMCP high-strength steel butt-welded joints were then numerically analyzed considering the effect of different heat inputs of 1.0, 1.5 and 1.9 kJ/mm. The results show that strength ratios of SHAZ to BM of butt-welded joints made of TMCP steel were lower than those made of QT steel when the heat input was <1.9 kJ/mm. The strength of each zone in the TMCP high-strength steel butt-welded joint may not necessarily decrease with increasing heat inputs.

Effects of Welding Heat Input on Microstructure and Corrosion Characterization in CGHAZ of X80 Pipeline Steel

Effects of Welding Heat Input on Microstructure and Corrosion Characterization in CGHAZ of X80 Pipeline Steel

A multi-tier layer-wise thermal management study for long-scale wire-arc additive manufacturing

High heat input during layer-wise deposition in the Gas Metal Arc-based Wire-Arc Additive Manufacturing (GMA-WAAM) process leads to significant defects such as high residual stress and distortion. However, the choice of layer-wise heat input is constrained due to the requirement of an optimal set of weld parameters. It is essential to study the effect of heat input on the evolution and control of residual stress in the long-scale WAAM fabricated components. Therefore, this study investigates a novel multi-tier heat input strategy represented by four levels for a GMA-WAAM fabricated long-scale thin-walled component. Accordingly, a layer-wise single-, two-, three-, and four-tier heat input strategy in a twelve-layered long-scale thin-walled component is investigated for transient thermal and residual stress distributions through Finite Element Modelling (FEM). Further, a set of validation experiments was performed, which agreed with the predicted results. It is concluded that a reduced heat input during successive layer deposition greatly influences the cumulative heat input into the system. The two-tier heat-input (case 2) system is found suitable among proposed case studies as an appropriate thermal management system with a variation of 6.98% in peak (melt pool) temperature and 198.4 °C increase of minimum temperature during complete deposition. Also, the four-tier heat input (case 4) produced the component's lowest longitudinal and transverse stresses by 13.07% and 25.83%, respectively.

The effect of heat input on microstructure and HAZ expansion in dissimilar joints between API5L X80 / DSS 2205 steels using thermal cycles

In this research, the effect of the shielded metal arc welding (SMAW) process heat input upon the microstructure and development of the heat-affected zone in the dissimilar joint of API 5L X80/DS5 2205 steels was investigated by recording the thermal cycles with thermocouple implantation in the perpendicular direction of the weld line. The filler metal used (electrode) is DSS 2209. The microstructure of the base and weld metals and their interfaces at different heat inputs were investigated using the scanning electron microscopy/energy-dispersive spectroscopy analysis technique (SEM/EDS) and optical microscopy (OM). The results indicated that the interface between the base metals and the weld metal has excellent consistency and that there is no evidence of cracks at different heat inputs. By increasing the heat input, it was determined that the amount of secondary austenite in the weld metal and heat-affected zone of 2205 steel had been increased. There occurred an epitaxial growth at the interface of 2209/2205, and there were a fine transition zone and Type II boundaries at the interface of 2209/ API 5L X80. The areas containing coarse, fine, and partially fine grains were detected in the heat-affected zone of the X80 steel. The thermal cycle results determined that the temperature peak in the areas away from the fusion line had increased by increasing the heat input and that the heat-affected zone of the two base metals, particularly the X80 steel, had been extended further.

Effect of welding parameters on the mechanical and metallurgical properties of armor steel weldment

The effect of welding parameters on the mechanical and metallurgical properties of armor steel weldment was studied using gas tungsten arc welding process with two filler wires: carbon steel and austenitic stainless-steel filler wires (AWS A5.18 ER 70S-6 and AWS A5.9 ER 307, respectively). The joint configurations were mainly single V and single bevel grooves. Using both AWS A5.18 ER70S-6 carbon steel filler wire and AWS A5.9 ER307, austenitic filler wire for the two joints passed the required tensile strength by the military standard. The joints successfully regained the base metal hardness at a distance of less than 15 mm. The ultimate tensile strength of the joints welded in a single bevel groove is 906 MPa which is higher than the joints welded using a single V groove is 865 MPa. This could be attributed to the increase in dilution percentage with the single bevel joints. Both single V joint and single bevel joints passed the required Charpy V-notch impact test whether using both carbon and stainless-steel wires. The effect of heat input and cooling rate on the mechanical and microstructure of welded joints was studied. The reduction of heat input caused a narrow HAZ with a small reduction in its hardness values with much reduction in the width of softening microstructure zone. SEM observations show that the base metal has a martensitic structure, but the weld metal microstructures depend on the filler: carbon steel or austenitic steel types. Using a single bevel groove with an austenitic steel filler metal, the weld metal shows a martensitic/austenitic microstructure by SEM observation, and this was verified by the Schaeffler diagram which showed a high dilution percentage (about 35% dilution). This resulted in a significant increase in joint strength and a higher weld metal impact resistance.