High Welding Research Articles

Weld Seam Recognition and Tracking With Omnidirectional Wall-Climbing Robot for Spherical Tank Inspection

Abstract Weld seams of in-service pressure storage equipment, such as spherical tanks, require regular inspection to ensure safe operation. Wall-climbing robots can replace manual operations, increasing inspection efficiency and reducing maintenance costs. High precision and fast weld seam identification and tracking are beneficial for improving the automated navigation and spatial positioning of wall-climbing robots. This study proposes a weld seam recognition and tracking method with the omnidirectional wall-climbing robot for spherical tank inspection. Based on deep learning networks, the robot has a front-mounted camera to recognize weld seams and extract weld paths. Weld seam deviation data (drift angle and offset distance) were used in real time to provide feedback on the robot's relative position. For the robot to quickly correct deviations and track weld seams, a seam path-tracking controller based on sliding mode control was designed and simulated. Weld recognition experiments revealed that the robot can accurately recognize and extract weld paths, and the recognition time for each image was approximately 0.25 s. In the weld seam tracking experiments, the robot could successfully track longitudinal and transverse weld seams at different speeds (from 0.05 to 0.2 m/s). During the process of weld seam tracking, the robot angle error was kept within ±3 deg, and the maximum offset distance was less than ±35 mm. Field tests on a 3000-m3 spherical tank were conducted to verify the practicability and effectiveness of the weld seam tracking system. This robotic system can autonomously complete weld seam identification and tracking, which promotes the automation of spherical tank inspection and maintenance.

Dissimilar unbeveled aluminum to steel butt joint achieved by laser-arc hybrid welding-brazing

In this study, unbeveled butt joints of 2 mm thick steel and aluminum plates were welded using a laser-arc hybrid process. The influence of welding speed and wire feed speed on joint weld formation, microstructures, and mechanical properties were investigated. The results indicate that using a laser-arc hybrid heat source enables good weld formation of steel/aluminum dissimilar metals without groove preparation, even under high welding speed conditions. The steel side interface formed Fe₂(Al,Si)₅ near the steel and Fe(Al,Si)₃ near the aluminum. As the welding heat input decreased, the thickness of the intermetallic compounds gradually reduced. With an increase in welding speed or wire feed speed, the tensile strength of the joint first increased and then decreased, reaching a maximum of 104.47 MPa. Cracks propagated rapidly along the intermetallic compound region, resulting in brittle fracture characteristics. The three-point bending test showed a maximum longitudinal bending angle of 53.82° and a maximum transverse bending angle of 36.54°.

Study on the Electron Beam Repair Welding of 5000 Aluminum Alloys

Electron beam welding (EBW) has been attracted due to its high energy density, high depth-to-width ratio, low thermal strain, compared with arc and laser welding. In addition, it ensures high quality weld joint in structural metals in a wide range of thickness from 0.025 mm to 300 mm. Therefore, EBW is widely used in industries such as automotive, aviation, nuclear power plant, etc. Although a lot of studies on EBW for several decades have been presented, EB based repair welding with supplement of filler metal has less reported. In this work, EB repair welding for 5083 aluminum alloys was investigated because the aluminum alloys are becoming more important as a lightweight material in mobility industries. Material characterization and mechanical properties of the repair-welded specimens were evaluated, compared with characteristics of base metal and bead welding without repair. The optimized experimental conditions showed tensile strength of 294 MPa, which is a similar to base metal. Our study indicates that EB repair welding can be considered for the candidate of repair welding of aluminum alloys.

Characteristics of Solidification Cracking for Ni-P Coated Cu-Al5052 Single-Mode Fiber Laser Welds

This study fundamentally examines the characteristics of solidification cracking in Cu-Al5052 single-mode fiber laser welding by utilizing uncoated and Ni-P coated Cu plates for the high durability busbar welding of pouch-type lithium-ion battery packs. Weld solidification cracking was confirmed regardless of Ni-P coating for both weld materials. However, there were differences in the regions of crack occurrence. Unlike the uncoated Cu-Al5052 welds where cracks occurred randomly within the fusion zone, for the Ni-P coated Cu-Al5052 welds, solidification cracks were concentrated near the faying surface of the upper and lower materials, particularly near the fusion line. The effect of the Ni and P components on the solidification cracking susceptibility, i.e., the welding solidification temperature range, was considered. Diffusion-controlled Scheil’s solidification calculations revealed that the mushy zone range enlarged with the use of a Ni coating layer. It was confirmed that an extremely wide mushy zone range of 1060 K was calculated at the solidification cracking region. Furthermore, P was also identified as an element that expands the solidification temperature range based on the Cu-P binary system. Consequently, during the laser welding of Cu-Al5052 dissimilar materials, the behavior of solidification cracking in the welds is influenced by the composition of the coating material and the incorporated composition within the weld fusion zone. Hence, it is necessary to select the optimal coating material and layer thickness considering weld solidification cracking susceptibility.

On the Influence of Welding Parameters and Their Interdependence During Robotic Continuous Ultrasonic Welding of Carbon Fibre Reinforced Thermoplastics.

Ultrasonic welding of fibre-reinforced thermoplastics is a joining technology with high potential for short welding times and low energy consumption. While the majority of the current studies on continuous ultrasonic welding have so far focused on woven reinforcements, unidirectional materials are preferred for highly loaded aerospace components due to their better mechanical performance. Therefore, this paper investigates the influence and interdependence of the welding speed, amplitude, and energy director thickness on the weld quality of adherends made of unidirectional composites. The quality of the welded joints is assessed by a single-lap shear strength and fracture surface analysis complemented by the microscopic analysis of cross-sections and comparison to a co-consolidated reference. The results showed that the welding process is highly affected by changing welding speeds for a given amplitude. Furthermore, while lower amplitudes lead to significant scatter in the welding quality, higher amplitudes result in increased heating rates and a fully molten energy director even for high welding speeds. Nevertheless, insufficient consolidation at high welding speeds results in porosity in the weld line. Finally, it was observed that thicker, and therefore more compliant, energy directors lead to more uniform melting of the energy director and less deviation in the weld quality for a wider range of welding speeds.

Resistance of the Steel Lap Joints Connected by Spot Welding and Brazing

Welding technologies are constantly evolving, and their applicability is expanding, considering also the construction domain. Steel structures benefit from the advances in welding technologies due to the use of thin gauge steel sheets which can now be connected at high quality and automatically. The resistance of the connection between the thin steel sheets is crucial for the durability and safety of a structure made of built-up thin-walled cold-formed steel elements. Generally, self-drilling screws or bolts are used for the connection between thin-walled elements, but the quantity of time and manpower necessary for a large number of connections demands an improved solution. Conventional welding techniques are unsuitable for joining thin sheets, ranging from 0.4 to 1.0 mm to thicker ones measuring 1.0 to 3.5 mm. This article compares the results of an experimental investigation into lap joints connected by spot welding and MIG brazing with the design code provisions. The study examines single-lap joints in steel sheets of 0.8, 1.0, 1.2, 1.5, 2.0 and 2.5 mm thickness, connected using these welding technologies. The results obtained are then compared with analytical relations and processed according to EN 1990. Depending on the thickness of the connected sheets, spot welding can lead to two failure modes: button pull-out fracture and interfacial fracture. MIG brazing, a welding technology that deposits material below the melting point of the base material, is known for its advantages, such as low energy consumption, spatter-free operation, high welding speed, and compatibility with thin sheet metals. However, its application in the structural engineering of cold-formed elements lacks documentation. In the study, the MIG brazed specimens failed in the heat-affected zone of the connection. The results indicate the dependence of the spot weld lap joint resistance on the connected sheets' thickness, while the resistance of the MIG brazed lap joints is influenced by the minimum thickness of the connected steel sheet. The study aims to demonstrate the feasibility of the proposed solutions, evaluate their performance, and establish the limits of their applicability. A statistical interpretation of the results highlights the precision and reliability of joint resistance.

Investigations on opportunities and challenges of brilliant high-power laser beam welding with 24 kW and adjustable power distribution for different materials

Solid-state laser beam sources offer the possibility of generating high-brilliance laser beams with low expansion and high usable intensity at the focal point. New approaches include beam shaping with the use of core and ring fiber and, therefore, variable power distribution in the laser beam focal point and material interaction area. Particularly, high-power laser beam welding benefits from beam shaping because of the stabilizing effect on the weld pool. Furthermore, the technical progress achieved with regard to beam quality also allows one to achieve high Rayleigh lengths and, therefore, a more uniform beam diameter over the whole material thickness. In this study, investigations on high-power laser beam welding with a 24 kW disk laser beam source are conducted for three different materials (mild steel, aluminum alloy, and copper), which are of high interest for welding in different sectors. The influence of power distribution between the core and the ring as well as welding speed on weld geometry (depth and width), weld pool stability, and the resulting weld seam quality is investigated. It is shown that the welding process cannot just be scaled up in comparison with welding with lower laser beam power but has its own challenges. It is possible that high welding depths (12 mm for copper, more than 12 mm is possible for aluminum, and 25 mm for mild steel) could be achieved in one pass. To achieve this, aluminum needs the lowest energy per unit length per mm of sheet thickness and copper the highest.

Investigation on metal vapor characteristics and keyhole/melt pool dynamics in high-power laser welding with side gas flow

High-power laser welding processes involve intense interactions between the laser beam and the base material, resulting in severe welding defects such as humping, spattering, and undercutting. Utilizing side gas flow may provide an effective approach for minimizing these defects. However, the effects of side gas flow on the dynamic behavior and weld formation necessitate further investigation. In this study, an innovative analysis of metal vapor characteristics and keyhole/melt pool dynamics in high-power laser welding with side gas flow is presented, combining experimental and simulation results. A three-dimensional transient fluid flow model was developed, uniquely integrating an adaptive heat source, evaporation-condensation processes, and metal vapor energy attenuation to provide a novel perspective on the effects of side gas flow in high-power laser welding. The results display that side gas flow could suppress plasma, increase thermal input to the melt pool, and intensify the flow of liquid metal toward the pool bottom during high power laser welding, thereby enhancing weld seam penetration. The numerical results indicate that variations in flow rate significantly impact metal vapor morphology, with higher flow rates reducing both the average area and height of the metal vapor and effectively suppressing the size of metal vapor/plasma. When the side gas flow rate is 20 l/min, with the gas flow impact point located at the keyhole opening and the nozzle height set to 3 mm, the side gas flow significantly enhances the depth-to-width ratio of the weld seam in 316L stainless steel laser welding. This work can provide guidance for suppression of weld defects in high-power laser welding of medium-thick steel components, which has important theoretical significance and application value.

Modelling of cracking during beam oscillation laser welding of a creep-resistant nickel alloy

During high power laser welding of Inconel 740H, horizontal solidification cracks form at locations between approximately 70–80% of the weld depth. With the integration of circular beam oscillation, the laser energy density distribution and underlying thermo-mechanical conditions were altered. By coupling three-dimensional heat transfer, fluid flow, and stress modelling tools, the role that circular beam oscillation plays in the formation of the strain rates and stresses driving this cracking phenomenon was identified. While the addition of a circular oscillation pattern appeared to lower the stress levels along the solidification front, it did not eliminate the appearance of horizontal cracking. Only when the beam amplitudes reached 1.6 mm did solidification cracking disappear, but the weld depths were also significantly reduced.

Microstructure and mechanical properties of thin-walled TA1 titanium pipes fabricated by high-frequency induction welding

High frequency induction welding (HFIW) was effectively employed for the high-speed fabrication of thin-walled TA1 titanium pipes (TWTPs) with a nominal wall thickness of ∼0.6 mm. The microstructure and mechanical properties of TWTPs manufactured under varying welding parameters were investigated. The weld zone (WZ) exhibits a waist shape measuring ∼622 μm in width, and the width of the heat-affected zone (HAZ) spans between 763 and 864 μm. Both the WZ and HAZ are composed of a mixture of coarse serrated α grains with fine acicular and twins, while the BM retains equiaxed grains. This unique microstructure was resulted from the thermal cycling during HFIW, contributing to a notable increase in microhardness within the WZ compared to both the HAZ and the BM. Optimal manufacturing conditions were identified at a welding power of 14.4 kW, a welding speed of 60 m/min, an opening angle of 6°, and a squeeze displacement of 0.2 mm, yielding the TWIP with a tensile strength of ∼307 MPa and tensile elongation of ∼27%. Tensile fracture analysis revealed that failure predominantly occurred within the BM, underlining a ductile fracture mode characterized by pronounced dimple formations. The enhanced mechanical performance of the weld joints can be attributed to the heterogenous microstructure in the WZ, where the presence of large serrated α-grains enhances ductility, and the fine martensite and twins contribute to the high strength.

Simulation of Friction Stir Welding of AZ31 Mg Alloys.

Friction stir welding has been extensively applied for the high-quality bonding of Mg alloys. The welding temperature caused by friction and plastic deformation is essential for determining the joint characteristics, especially the residual stress and weld microstructure. In this work, a modified moving heat source model was proposed by considering the variations in heat generation caused by friction shear stress at both the side and bottom surfaces of the tool. The application of this model was further extended to the entire welding process, especially in the plunging stage. The relative errors between the experimental and simulated peak temperatures at characteristic points were small, with a maximum of 10%, thereby validating the model for accurate temperature prediction. Furthermore, the influence of welding and rotational speed on temperature fields was systematically investigated. At relatively low welding and rotational speeds, the welding temperature increased significantly with either an increase in rotational speed or a decrease in welding speed. However, this effect gradually diminished at higher welding and rotational speeds. These results provide some valuable guidelines for controlling heat generation to improve the quality of Mg alloy welds.

Evaluation of corrosion properties of TA2-Q345 explosive composite plate at different heat treatment temperatures

This study investigated the effects of post-weld heat treatment (PWHT) at 500 °C, 600 °C, 700 °C, and 800 °C on the microstructure and corrosion performance of the TA2-Q345 explosive composite plate, with TA2 as the flyer plate and Q345 as the base plate. X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) analyses were performed, alongside electrochemical experiments. The explosive welding interface of the TA2-Q345 composite plate exhibited a characteristic wavy structure, which indicated high welding quality. The XRD results indicated that the PWHT temperature significantly affects both the phase structure and the intensity of the diffraction peaks of the oxide film. Additionally, the porosity calculations demonstrated that the sample subjected to PWHT at 500 °C exhibited the lowest porosity in the surface oxide film, resulting in a denser oxide film that effectively enhanced corrosion resistance. However, as the temperature continued to rise, defects such as craters, bulges, and delamination between the oxide film and the titanium matrix were observed. The results of the electrochemical analysis indicated that, compared to untreated samples, the PWHT samples demonstrated improved corrosion resistance. Specifically, the sample with PWHT at 500 °C has the lowest corrosion current density (icorr) of 6.1892E-06 A/cm2, while the untreated sample has the highest icorr of 6.3577E-05 A/cm2, indicating that 500 °C is the optimal temperature. The corrosion process involved the hydrolysis of titanium chloride to form a TiO2 film and localized corrosion of the TiO2 protective film. The corrosion products composed of mainly C, O, and Ti were dispersed on the surface of PWHT samples.

Effects of heat input on microstructures and mechanical properties of LAZ931 magnesium-lithium alloy in High-Speed TIG welding

LAZ931 magnesium-lithium (Mg-Li) alloy is a novel ultra-light alloy material. This research investigates the Tungsten Inert Gas (TIG) welding process of a 2.15 mm thick LAZ931 magnesium-lithium alloy thin plate without wire filling. The objectives are to determine the appropriate heat input range, achieve welded joints with good forming quality, and examine the effect of heat input on the microstructure and mechanical properties of the welded joints. The results show that post-TIG welding at high welding speed, the melt width of the entire welded joints is very narrow only about 9 mm, and a small amount of MgLiAl2 (θ) phase and AlLi (γ) phase precipitate in the weld seam zone(WSZ), while a significant amount of θ phase precipitates in the heat-affected zone (HAZ), making the HAZ the highest in strength due to precipitation strengthening. With increasing heat input, the quantity of θ phase decreases, resulting in reduced strength and hardness but increased plasticity in the HAZ. The highest hardness in the HAZ was measured at 87.6 HV, with the base material (BM) exhibiting the lowest hardness. The tensile strength of the joint reaches 163.2 MPa, with an elongation of 23.9 %, and the fracture mode is a mixed ductile–brittle fracture.

Low and High Gas Tungsten Arc Welding Heat Inputs Influence on Corrosion of Stainless Steel Weldments

In this study, influence of low and high heat inputs on corrosion susceptibility of 304L austenitic stainless steel (ASS) in simulated 0.5 molar solution of NaCl was investigated. Gas tungsten arc welding (GTAW) was used to generate low and high levels welding heat input. Microstructures of the weldments were examined, using metallurgical optical microscope (OMM) (Olympus GX51), while the corrosion behaviours were evaluated by potentiodynamic polarization tests, and corrosion data were recorded, using a computer-based data logging system – Autolab PGSTAT 204N. From the results, the evolving microstructures of the weldments before corrosion were characteristically heterogeneous; austenite (γ) was the leading phase, while ferrite (α) grains were dispersed within the γ matrix. Fusion zone (FZ) and heat affected zone (HAZ) microstructures after corrosion were characterised by pits of varying sizes with different alignments. And at GTAW speed, current and voltage of 7.2 mm/s, 200A and 40V, corresponding to low heat inputs, there were few number and size of pits relative to 1.7 mm/s, 200A and 40V, corresponding to high heat input. Shift in corrosion potentials (Ecorr) toward less negative direction, that is more nobility was observed at the low heat inputs induced GTAW parameters as compared to the corresponding high heat inputs induced GTAW parameters. In general, corrosion susceptibility of 304L ASS in the simulated 0.5 molar solution of NaCl was heightened at high heat inputs induced GTAW parameters as compared to the corresponding low heat inputs parameters.

Reducing capillary depth fluctuations in high-speed laser welding of stainless steel using multi-core laser technology

Laser welding was carried out in AISI304 (X5CrNi18-10) stainless steel using a multi-core fiber laser. High-speed X-ray imaging was used to monitor the process. When employing core-power only (400W) at high welding speeds (12m/min), the capillary depth was found to be inconsistent. The capillary penetration into the material varied from approximately 0.8 mm to approximately 0.2 mm, with fluctuation periods of between single milliseconds and tens of milliseconds. Employing a 0.5:0.5 ring-core power distribution (390W:390W) to achieve the same penetration (0.8mm) was found to reduce fluctuations in the depth of the welding process and the capillary penetration. Possible reasons for this reduction in depth fluctuations are discussed together with a detailed description of the resulting changes in weld cross-section.

Characterization and modeling of laser transmission welded polyetherketoneketone (PEKK) joints: Influence of process parameters and annealing on weld properties

Welding high-performance thermoplastics has gained popularity across various industries such as automotive, aerospace, and medical. Laser transmission welding (LTW) has emerged as an effective method for joining thermoplastic parts due to its precise control and high joint quality. PAEK (polyaryletherketone) are wide spreading over various industrial applications as a substitute to metals and thermosets when high durability and performance are required. Polyetherketoneketone (PEKK) is one of these PAEK and it has received less attention than PEEK until now. PEKK, being a semi-crystalline thermoplastic, requires additional care during processing due to its propensity to crystallize. This study presents both experimental and numerical investigations into LTW of PEKK molded parts, aiming to understand the influence of welding parameters and crystallinity on weld joint morphology and mechanical properties. PEKK plates, prepared in amorphous and semi-crystalline states, are subjected to LTW using a 975 nm diode laser. Material characterization confirms differences in crystallinity between the samples, which affect their thermal and optical properties, which are crucial for welding. Welding tests are conducted with varying laser power (between 75 and 95 W) and semi-transparent part thickness (2 and 4 mm). The morphology of joints is analysed. Assemblies undergo post-weld annealing treatment to examine its influence on weld crystallinity and consequent mechanical properties. Results reveal an anisotropic distribution of crystallinity within the heat-affected zone (HAZ). The depths of the molten layer (ML) and semi-crystalline layer (scL) vary with laser power and assembly type. A notable decrease in weld strength with laser power is highlighted, while annealing leads to enhanced crystallinity and improved weld strength. Despite variations, high weld strengths are achieved with annealing. Computational modelling elucidates the complex interplay between laser irradiation, temperature distribution, and crystallization kinetics observed experimentally. Overall, this comprehensive investigation provides valuable insights into optimizing LTW parameters for PEKK parts.

Fatigue strength of repair‐welded headed studs

AbstractWelded connections of headed studs are highly stressed details in bridge structures in steel‐concrete composite construction and are largely responsible for the functionality of the supporting structures. At the same time, this detail requires a lot of resources due to the high welding effort and therefore has a major influence on the economic success. An important criterion for the economic and ecological balance of the structure is the durability of the welded joint, which is quantified by the fatigue strength. The welding of headed studs for composite bridges is usually carried out using fully mechanised drawn arc stud welding in accordance with EN ISO 14555. Due to the process, stud welds that do not fulfil the standard requirements for flawless condition may occur in individual cases. The design rules for stud load‐bearing capacity in accordance with EN 1994‐2 are based on tests and only apply to connections produced using drawn arc stud welding. In the past, there were practicable and tacitly accepted solutions for repairing such sporadically occurring faulty welds, but these were never systematically investigated. Particularly against the background of fatigue loading, repair‐welded stud connections are now to be systematically investigated in a project funded by the AIF. The article provides an overview of the execution of stud welded joints and presents the tests planned in the project in order to achieve a practicable recommendation for the repair welding of headed studs.

Investigation of the failure behaviour of equiatomic AlCrCuNiFe based high entropy alloy TIG weld cladding

The present research focuses on the development of an equiatomic AlCrCuNiFe high entropy alloy (HEA) cladding using the TIG welding process. The influence and contribution of TIG cladding process parameters (welding current, welding speed, and SOD) on the microhardness and flexural stress have been investigated using the response surface methodology (RSM) and analysis of variance (ANOVA), respectively. The indentation fracture toughness test has been conducted over the claddings exhibiting minimum, maximum, and optimum microhardness values. The result revealed that welding current has the highest effect on the mechanical performance of the HEA cladding. The FE-SEM, optical microscopy, XRD and EDS analysis were performed to characterize the claddings. The cladding deposited at the S12 test run offered the least flexural resistance, microhardness, and indentation fracture toughness which was about 812 MPa, 494.97 HV0.3, and 1.29 ± 0.04 MPa.m1/2, respectively. In contrast, the optimized S5 cladding specimen exhibited good flexural resistance, appreciable microhardness and indentation fracture toughness of about 1543.92 MPa, 712 HV0.3, and 1.63 ± 0.03 MPa.m1/2 respectively. The optimum cladding exhibited flexural stress, microhardness, and fracture toughness enhancement of 46.77 %, 30 %, and 26.35 % compared to the least resistance cladding (S12) due to the high-retained alloying elements leading to enhanced solid solution strengthening. The three-point bend-tested cladding specimens’ optical microscopy images revealed that the cladding failure was primarily due to cohesive failure, crack progression, and delamination.

Research Progress on the Microstructure Evolution Mechanisms of Al-Mg Alloys by Severe Plastic Deformation.

Al-Mg alloys are widely used as important engineering structural materials in aerospace engineering, transportation systems, and structural constructions due to their low density, high specific strength, corrosion resistance, welding capability, fatigue strength, and cost-effectiveness. However, the conventional Al-Mg alloys can no longer fully satisfy the demands of practical production due to difficulties caused by many defects. The high strength of Al-Mg alloys as non-heat treatment precipitation-strengthened alloys is achieved primarily by solid solution strengthening along with work hardening rather than precipitation strengthening. Therefore, severe plastic deformation (SPD) techniques can be often used to produce ultrafine-grained structures to fabricate ultra-high strength aluminum alloys. However, this approach often achieves the strengthening of material at the cost of reduced ductility. This paper comprehensively summarizes the various approaches of ultrafine/nanocrystalline materials for enhancing their plasticity, elaborates on the creation of a bimodal microstructure within the alloy, and discusses the formation of a nanotwin microstructure within the alloy and the incorporation of dispersed nanoparticles. The mechanisms underlying both the strengthening and toughening during large plastic deformation in aluminum alloys are summarized, and the future research direction of high-performance ultrafine crystalline and nanocrystalline Al-Mg aluminum alloys is prospected.

Effects of stabilized heat treatment on stress rupture properties of high Si-bearing austenitic stainless steel weld metal

The 15Cr-9Ni-Nb austenitic stainless steel weld metal with a Si content of 3.5 wt% was prepared via gas tungsten arc welding and then held at 900 °C for 3 h for the stabilized heat treatment (SHT). The stress rupture properties of the as-welded (AW) and SHT weld metals at 550 °C were evaluated via the Larson-Miller parameter. The microstructure evolution was discussed during the 550 °C stress rupture process. The coarse σ-phase and relatively fine G-phase formed on the δ-ferrite during aging at 550 °C. In the AW weld metal, the continuous δ-ferrite with a large amount of coarse σ-phase led to the formation and expansion of cracks during the stress rupture process, which accelerated the eventual rupture and damaged the stress rupture properties. The SHT decreased the δ-ferrite content and formed a large amount of nanoscale NbC precipitated in the matrix. The decreased δ-ferrite content avoided the rapid formation and expansion of cracks and the nanoscale NbC blocked the dislocation movement during the stress rupture process, which improved the stress rupture properties.