Weld Metal Research Articles

Disclosing Connection Links between Microstructure and Mechanical Performance in Pulsating Current Gas Tungsten Arc Welding of Hastelloy B-2 Superalloy

In this study, welding a Ni-Mo-based superalloy (Hastelloy B-2) was examined in order to characterize the microstructure and mechanical performance of joints along with assessing the effects of current intensity on the microstructure and mechanical responses of different weld zones. The gas tungsten arc welding (GTAW) process was used to weld the samples using ERNiCrMo-2 filler metal. The pulsed current GTAW process was used to weld the superalloy sheets of thickness of 1 mm with background current (Ib) of 20 A and 40 A and peak current (Ip) of 80 A and 60 A. Tensile and Vickers microhardness tests were conducted to evaluate the effect of pulsed current on mechanical properties of the welds along with chemistry and microstructure characterizations. Finally, the fracture surfaces after the tensile test were studied using SEM fractography analysis. The results indicated that increasing Ib and decreasing Ip led to low heat input and high cooling rate resulting in a high thermal gradient. This caused microstructure transition from the columnar dendrites to the coaxial ones in the weld zone; molten metal convection in the fusion zone led to fine grains in the weld zone during welding time. Moreover, a significant decrease in the amount of molybdenum carbides at the interdendritic regions of the weld metal was observed under these conditions. The tensile strength of the weld metal was higher than that of the base metal resulting in the fracture of all welds from the base metal. Additionally, the microhardness results indicated a significant increase for the weld metal compared to both heat-affected zone (HAZ) and base metal. The higher mechanical properties of the weld metal is attributed to the increase in background current and decrease in peak current leading to a fine grain microstructure. Fractography following the tensile test showed a completely ductile fracture.

Fracture Toughness Estimate of H-Section Steel for Offshore Structure

In this study, a novel estimating equation based on the WES2808 standard was proposed to predict fracture toughness through the transition temperature of Charpy impact toughness and CTOD (Crack Tip Opening Displacement) fracture toughness. This equation was specifically developed for 460MPa class H-section steel materials used in marine structures, including the base material (BM), heat-affected zone (HAZ), and weld metal (WM). The experimental results confirmed that the proposed estimation equation accurately predicted the fracture toughness across these different material regions. These findings demonstrate the reliability and applicability of the proposed equation in estimated fracture toughness for marine structure materials, thereby contributing to improved safety and performance in harsh environmental conditions.

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.

A Primary Study on the Applicability of Gel-Type Filler Materials to Root Pass Welds of the Thick Plate

Welding generally uses filler material to create deposited weld metal. Filler materials play a significant role in welding by providing the material needed to fill and form the joint. Existing filler materials are limited in the workspace and welding position and need help responding flexibly to welds of complex shapes. This study conducted primary research to develop a gel-type filler material with adhesion and flexibility that can cope with limited workspace and location. We attempted to provide a new approach to welding by mixing metal powder and binder to create a gel-type filler material. Root pass welding of thick plates was performed using a laser heat source. The bead appearance and cross-section of the weld zone were observed according to the type and composition of the metal powder, the binder content, and the method of synthesizing the metal powder. The physical characteristics of the weld were analyzed through observation of the hardness and microstructure of the weld.

Effect of Filler Wire Composition on Weld Metal Microstructure and Mechanical Properties in X80 Steel Laser Welds

Laser welding was performed using different filler wires, ER70S steel, commercially pure iron, and pure nickel filler, in the context of welding X80 pipeline steel to assess the microstructure and mechanical properties of the weld metal. Introducing an ER70S wire promoted acicular ferrite formation in the fusion zone, compared to a bainitic microstructure in an autogenous laser weld. The use of pure iron wire was considered as a potential strategy for reducing hardenability, as it led to the dilution of alloying elements in the fusion zone, increasing ferrite content and reducing weld metal hardness to a level compliant with API pipeline standards. The addition of pure nickel wire was used to reveal the degree of weld metal mixing imposed by the laser (thus providing an unambiguous tracer element) when it is combined with filler material dilution in the fusion zone, revealing that the upper region contained 38% wire material and the lower region only 12%. This accounts for the differences observed between the upper versus lower portions of the weld metal when other wires are used, and the use of hardness mapping and micro-indentation demonstrates the correlation between the variations in mechanical properties and microstructural differences introduced by incomplete mixing of the filler wire elements.

Effect of Precipitation Behavior and Deformation Twinning Evolution on the Mechanical Properties of 16Cr–25.5Ni–4.2Mo Superaustenitic Stainless Steel Weld Metals

Effect of Precipitation Behavior and Deformation Twinning Evolution on the Mechanical Properties of 16Cr–25.5Ni–4.2Mo Superaustenitic Stainless Steel Weld Metals

The influence of cooling time on the alloy distribution in weld metals

This research explores the impact of cooling time on the distribution of alloying elements within weld metals of high-strength steel, a critical factor in optimizing welding processes for advanced structural applications. Using gas metal arc welding (GMAW) and two different filler materials, this study systematically varies cooling times to analyze the resulting chemical compositions. Energy Dispersive X-ray (EDX) analysis was employed to examine the alloy content in the weld metal, base material, and heat-affected zone (HAZ). The results demonstrate that cooling time significantly influences the concentration of alloying elements, such as chromium, nickel, and manganese, within the weld metal, revealing complex diffusion behaviours that are dependent on the thermal cycles introduced during welding. Notably, an in-depth analysis of the HAZ shows a distinct diffusion pattern for silicon, indicating intricate microstructural changes. These findings highlight the importance of controlling cooling time to optimize the microstructural and chemical properties of welded joints in high-strength steels, with implications for improving weld performance and reliability.

Comparison of destructive and non-destructive fracture toughness measurements for Q235 steel butt-welded joint

As a critical component of a welded structure, the integrity of the welded joint significantly affects the safety and reliability of the structure in service. Therefore, it is essential to investigate the integrity of welded joints. However, given the harshness of standard measurements renders them unsuitable for application to small volume zones, welded structures or in-service structures. In this study, the fracture properties of a Q235 steel butt-welded joint was evaluated by boundary effect modelling (BEM) method and the ball indentation (BI) method. The results demonstrate that the fracture toughness distribution obtained by the two methods are consistent, with the highest fracture toughness in the weld metal, followed by the heat-affected zone and the base metal, and the lowest fracture toughness in the fusion zone, which is in agreement with the results of the metallographic testing. Furthermore, the relative errors of the zones obtained by the ball indentation method and the boundary effect modelling method ranging from 10.16 to 19.05%, which indicates safety margin ought to be considered for employing the BI method to determine fracture properties of in-service structures.

Evaluation of Tensile Strength of Dissimilar Metals SS 316-pure Zn Joining by Friction Welding Method

Welding of dissimilar metals has always been a challenge in industrial applications. In this study, the joining of SS 316 and 99.9% pure zinc by continuous drive friction welding has been carried out. The welding process is carried out with parameters such as rotation speed, friction pressure, forging pressure, and burn length being kept constant for all weld joint samples. This friction time is selected through the process parameter approach carried out on aluminium alloy material. The experimental results were analysed by tensile test and microstructure using a scanning electron microscope (SEM) to characterise the microstructure. Tensile test results from friction welding with variations in friction time from 30 to 80 seconds obtained a higher tensile strength of the joint in the 30 to 50 seconds friction time range. In this experiment, the maximum joint tensile strength is obtained at 53.93 MPa, and the maximum modulus elasticity of 128.60 GPa at 35 seconds of friction. Solid-state welding makes it possible to join SS 316 and pure zinc, which is difficult to join in conventional fusion welding methods.

A Review On Multi objective Optimisation of Process Parameters in Shielded Metal Arc Welding For Joining Stainless Steel 3041 And Mild Steel 1018

Due to Mechanical properties of the welding metal and heat affected zone (HAZ) is quality of welding in this research work the review of Multi-objective optimization of welding process parameters for obtaining best weld strength with good mechanical properties of dissimilar metals like stainless steel 3041 and Mild steel 1018 is done. This process used for welding is shielded Metal Arc welding and dissimilar metal are stainless steel 3041 and mild steel 1018. Welding speed, depend on electric property like current Voltage electrode angle, feed rate, Arc length are taken as controlling variables. The weld strength (N/mm2) and Bead geometry variables and Heat Affected Zone are obtained by set of experiment, the possible best outcomes and best method has been chosen by this research. Keywords: HAZ, Multi objective optimization, Response surface Methodology, Shielded metal arc welding

Novel approach for in-line process monitoring during ultrasonic metal welding of dissimilar wire/terminal joints based on the thermoelectric effect

AbstractUltrasonic metal welding (USMW) is a manufacturing technique widely employed in the automotive and aerospace industries due to its efficiency in joining similar as well as dissimilar metals. Despite its prevalence, the lack of effective in-line process monitoring methods has resulted in high scrap rates, product recalls due to unrecognized scrap or financial losses due to pseudo-scrap, limiting its application in more sensitive industries. This paper presents a novel thermoelectric effect-based method for in-line process monitoring of USMW processes. This approach utilizes the thermoelectric properties, that manifest at the junctions of dissimilar metals during welding to accurately measure the temperature of the weld zone without the need of additional thermocouples, pyrometers or infrared cameras. An experimental setup was developed to validate the thermoelectric-based temperature measurement methodology. Key to this approach is the detection of thermoelectric voltage developed due to thermo diffusion when dissimilar materials are joined. The experiments showed a strong correlation between the thermoelectric voltage and the mechanical strength of the welds, suggesting that this parameter can effectively predict the quality of the weld. In the trials, a series of welded samples was created under controlled conditions to measure the generated thermoelectric voltage and correlate it with ultimate tensile strength tests. The data were analyzed using Spearman’s correlation coefficients to determine the correlation of the thermoelectric signals and joint strength. Results indicate that the thermoelectric voltage measurements correlate highly with the joint strength, with a Spearman’s correlation coefficient of over 0.94, thereby providing a promising predictive metric for assessing weld quality.

Revealing the embrittlement phenomena after post-weld heat treatment of high-strength weld metal using high-resolution microscopy

High strength combined with sufficient toughness is a fundamental prerequisite for steel in the field of lightweight construction. Joining high-strength steels by means of welding requires the use of highly advanced filler metals and a stress-relief post-weld heat treatment (PWHT) for optimum performance of the joint. However, such a heat treatment can lead to embrittlement in the weld metal. In this context, the present work deals with the influence of different PWHT holding temperatures on the microstructure and mechanical properties of a high-strength multipass all-weld metal to reveal the embrittlement phenomena. The all-weld metal was fabricated via gas metal arc welding using a metal cored wire with a minimum yield strength of 690 MPa. Charpy V-notch impact testing and tensile testing were carried out to characterize the strength and toughness of the all-weld metal in the as-welded condition and after a 2 h stress-relief PWHT at 520 °C, 580 °C, and 620 °C. The microstructure was characterized utilizing high-resolution techniques such as atom probe tomography and high-energy X-ray diffraction. The strength and toughness of the all-weld metal both decrease after PWHT with different holding temperatures. The cause for the observed embrittlement was found to be the formation of Mn-rich cementite precipitates. These carbides increase in size and phase fraction with increasing holding temperature and lead to a brittle transcrystalline cleavage fracture. Consequently, it was concluded that a gas metal arc welded joint with the investigated filler metal should not be exposed to stress-relief PWHT at temperatures higher than 580 °C.

Microstructural and Mechanical Characterization of the Laser Beam Welded SAF 2507 Super-Duplex Stainless Steel

The influence of laser beam welding parameters (power, welding rate, focusing, head oscillation, shielding gas) on the microstructure, mechanical properties and corrosion resistance of the super-duplex stainless steel SAF 2507 was studied in this paper. The presented results clearly report the effects of welding parameter changes on the character of the steel’s microstructure. The presence of secondary phase M2N in weld metals has an important influence on their mechanical properties. Optimal mechanical properties, an acceptable ferrite/austenite ratio, and the minimum content of M2N nitride required in the weld metal were acquired in the case the following application: 1100 W power, welding speed of 10 mm/s, focusing of 4 mm, and pure nitrogen shielding gas (20 L/min).

Effect of Cr addition on microstructure, mechanical properties, and corrosion behavior of weld metal in weathering steel of high-speed train bogie

Effect of Cr addition on microstructure, mechanical properties, and corrosion behavior of weld metal in weathering steel of high-speed train bogie

Microstructure and mechanical properties of ultrasonically welded aluminum to Zn–Mg–Al coated and uncoated mild steels

The gaining popularity of aluminum alloys in the automotive industry demand the development of energy efficient joining methods of Al with other metals such as steel. Among such joining methods, ultrasonic welding is advantageous because it is cost effective and prevents metallurgical defects because of the low welding energy involved. This study evaluates the microstructural changes and mechanical properties of dissimilar ultrasonic welding of Al to Zn–Mg–Al-coated and uncoated mild steels. Various intermetallic compounds (IMCs), such as FeAl3, and Fe2Al5 with different thicknesses and morphologies were observed at the joint interfaces. The Al-to-Zn-Mg-Al-coated steel exhibited mechanical properties that are superior to those of Al-to-uncoated mild steel. The results are discussed in terms of microstructure evolution, joint characteristics, and interfacial reactions in the welds. This study contributes to the understanding of the mechanisms behind strong ultrasonic welding of dissimilar metals.

Nrf-2/HO-1 activation protects against oxidative stress and inflammation induced by metal welding fume UFPs in 16HBE cells

As one of the main occupational hazards, welding fumes can cause oxidative damage and induce series of diseases, such as COPD or asthma. To clarify the effects of the metal fume ultrafine particulates (MF-UFPs) of welding fumes on oxidative damage, UFPs were collected by melt inert gas (MIG) and manual metal arc (MMA) welding, and the composition was confirmed. Human bronchial epithelial 16HBE cells were treated with 0–1000 µg/cm2 MF-UFPs to analyse the cytotoxicity, oxidative stress and cytokines. The protein and mRNA expression of Keap1-Nrf-2/antioxidant response elements (AREs) signalling pathway components were also analysed. After 4 h of treatment, the cell viability decreased 25% after 33.85 and 32.81 µg/cm2 MIG/MMA-UFPs treated. The intracellular ATP concentrations were also decreased significantly, while LDH leakage was increased. The decreased mitochondrial membrane potential and increased ROS suggested the occurrence of oxidative damage, and the results of proteome profiling arrays also showed a significant increase in IL-6 and IL-8. The expression of AREs which related to antioxidant and anti-inflammatory were also increased. These results indicate that the MF-UFPs can cause oxidative stress in 16HBE cells and activate the Nrf-2/ARE signalling pathway to against oxidative damage.

Effect of process temperatures on joining aluminum alloy (AA5052) to polypropylene (PP) by friction lap welding

The joining of aluminum alloy 5052 (AA5052) and polypropylene (PP) by friction lap welding (FLW) was investigated under different process temperature conditions. Welding experiments were conducted at different tool rotational speeds, and the process temperatures were monitored using an infrared camera and thermocouples. The temperature distribution at the cross-section was determined using a validated numerical model. The joint quality was assessed by measuring tensile shear strength and examining the joint morphology. It was found that interfacial temperatures in the range of 156 °C–316 °C were optimal for achieving effective mechanical interlocking, attributed to the appropriate flow of molten PP into the textured aluminum alloy surface. Temperatures below 130 °C resulted in inadequate PP flow, leading to poor joint formation, while temperatures above 316 °C caused over-melting of PP, bubble formation, and approached the PP initial decomposition limit. Raman spectroscopy showed that the process temperatures did not cause significant chemical bonding and that mechanical interlocking was the main contributing joining mechanism. The results showed that dissimilar welding of metals and non-polar polymers can be optimized by the precise monitor and control of the temperature of the process.

SiO2-Bearing Fluxes Induced Solidification Path Transition in Weld Metals of EH36 Shipbuilding Steel

SiO2-Bearing Fluxes Induced Solidification Path Transition in Weld Metals of EH36 Shipbuilding Steel

Theoretical and experimental research on the critical buckling pressure of the thin-walled metal liner installed in the composite overwrapped pressure vessel

Composite overwrapped pressure vessels (COPVs) are widely used in the field of high-pressure gas storage and transportation because of their light weight and high strength. In engineering, autofrettage is usually used to improve the fatigue life of composite pressure overwrapped vessels with metal liners. However, excessive pressure of autofrettage could cause buckling damage to the metal liner. In order to determine the upper limit of autofrettage (critical buckling pressure) and analyze its influence on the safety factor of COPVs, a theoretical calculation model of the critical buckling pressure about the metal liner was established based on classical laminated plate theory and the confined buckling theory. Then, a COPV with thin-walled welded metal liner was prepared by fiber winding process. In order to monitor and judge the buckling damage mode of the liner, the circumferential strain of the COPV's cylinder was measured by loading and unloading step-by-step. Finally, the influence of materials and dimensions of the metal liner on the pressure ratio (the ratio of the first layer failure pressure to the critical buckling pressure of the COPV's metal liner) was discussed. When the diameter to thickness ratio (R/t) of the metal liner was greater than 35, the pressure ratios of the 6063-T5 aluminum alloy liner and the S30408 stainless steel liner both exceeded 2.25. However, the pressure ratio of 6061-T6 aluminum alloy liner with R/t ≤ 60 was lower than 1.85, which shows that the metal liner with higher yield strength and lower elastic modulus has higher utilization rate of fiber winding layers. Due to the fact that the current design standards only ensure the reliability of COPVs through safety factors and various type testing with their evaluation methods, the proposed theoretical calculation method can reduce the uncertainty of COPVs during the design and testing rounds.

Microstructural and mechanical properties evolution for 9Cr[sbnd]Si heat resistant steel deposited metals under different heat treatment states

To develop the matched filler metal for the structural materials in Generation IV lead-cooled fast reactor (LFR), the microstructural evolution and mechanical property variation of 9CrSi heat resistant steels deposited metals were investigated both for the as-welded and as-aged (at 550 °C) weld metals. The experimental results indicate two precipitates in the as-welded deposited metals: the bigger M23C6 and the smaller MX. Si facilitates the nucleation of M23C6. The chain-like precipitates (consisting of M23C6) form at the boundaries of prior austenite and martensitic laths in high-Si specimens. They deteriorate not only the strength but also the impact energy. Meanwhile, a few δ ferrites form in high-Si deposited metal deteriorating the impact energy. Precipitates tend to nucleate at the interface between the δ ferrite and the martensite after aging. New types of precipitates (Mo-rich M6X and Laves) with rapid coarsening rate form in as-aged high-Si deposited metals as time increases. Coarse precipitates deteriorate the pinning effect, which causes the recovery of laths and dislocations. Subgrain pinned by M23C6 forms in deposited metals with post-weld heat treatment (PWHT) during aging. The structure hinders the formation of M6X and facilitates the formation of nano-sized MX. Therefore, the mechanical properties of deposited metals with PWHT are stable during long-term (up to 10,000 h) aging treatments.