Weld Metal Research Articles

Residual mechanical properties of corroded ultra-high-strength steels and weld metals

This paper presents an in-depth investigation into the residual mechanical properties of ultra-high-strength steels and weld metals after exposure to corrosive environment. The tensile specimens of weld metals were fabricated using ER100S-G, ER110S-G, ER120S-G feedstock wires by robotic gas metal arc welding, whilst ultra-high-strength steel tensile coupon specimens were machined from the Q890 and Q960 steel plates. The high-strength steel and weld metal tensile specimens were exposed to neutral salt spray accelerated corrosion conditions. Six exposure durations were designed to achieve different corrosion degrees of specimens. A total of 23 corroded ultra-high-strength steel tensile coupon specimens and 19 corroded high-strength weld metal specimens were included. The geometric profiles of corroded steel specimens were determined via non-contact 3D laser scanning. Monotonic tensile tests were conducted to determine the stress-strain responses and key mechanical properties of corroded steel and weld specimens. Mechanical properties deterioration of corroded ultra-high-strength steels and weld metals are reported and discussed. Prediction equations on the residual mechanical properties regarding the tensile loading capacity, yield stress and ultimate tensile stress of ultra-high-strength steels and weld metals after exposure to corrosive environment were established.

Effect of Welding Process on Microstructure and Mechanical Properties of Boron Containing Modified 9Cr-1Mo Steel

The influence of Shielded Metal Arc (SMA) welding and Activated Tungsten Inert Gas (A-TIG) welding on the microstructure and mechanical properties of boron containing Modified 9Cr-1Mo steel has been investigated. The tensile strengths of SMA weld joints at room temperature and 550℃ (730, 710 MPa) are higher than those of A-TIG weld joints (520, 465 MPa); whereas A-TIG welds (66, 18J) show better impact energies at room temperature and 0℃ than SMA welds (53, 12J). Creep resistances of both the weld metals, as estimated by impression creep technique are comparable; while, the A-TIG heat affected zone (HAZ) possesses higher creep resistance than the SMA HAZ. The fracture toughness of the A-TIG weld metal is inferior (64 kJ.m-2) to that of SMA weld metal (181 kJ.m-2) and brittle fracture is seen. It has been observed that the multiple passes of SMA process are advantageous in modifying the delta ferrite present in the weld metal although they cause severe damage to the HAZ microstructure.

Transverse crack micromechanisms in high-strength steel weld metal with microstructure heterogeneity under hydrogen-containing environment

The transverse crack susceptibility for high-strength steel weld metal with microstructure heterogeneity was investigated under various environment. Transverse cracking probability (C%) increases with increasing microstructure heterogeneity and diffusible hydrogen content. The dominant transverse crack initiation are soft massive pre-eutectic ferrite (PF), the deformation-uncoordinated acicular ferrite (AF)-PF interface and inclusions aggregation. PF, AF-PF interface and inclusions acts as the principal crack extension channel during crack propagation. Transverse cracks pass AF mainly extend along {100} plane while only along {110} when passing PF. MAGBs and HAGBs impede crack propagation. The Ʃ3 boundaries promote the crack propagation, while Ʃ11, Ʃ13b and Ʃ17b hinder the crack propagation. The transverse crack of weld metal under hydrogen-containing environment is attributed to the combination of HEDE and HELP mechanisms in the presence of microstructure heterogeneity and inclusions.

Realization of Joints of Aluminosilicate Glass and 6061 Aluminum Alloy via Picosecond Laser Welding without Optical Contact.

To achieve laser direct welding of glass and metal without optical contact is hard, owing to the large difference in thermal expansion and thermal conductivity between glass and metal and an insignificant melting area. In this study, the high-power picosecond pulsed laser was selected to successfully weld the aluminosilicate glass/6061 aluminum alloy with a gap of 35 ± 5 μm between glass and metal. The results show that the molten glass and metal diffuse and mix at the interface. No defects such as microcracks or holes are observed in the diffusion mixing zone. Due to the relatively large gap, the glass collapsed after melting and caulking, resulting in an approximately arc-shaped microcrack between modified glass and unmodified glass or weakly modified glass. The shape of the glass modification zone and thermal accumulation are influenced by the single-pulse energy and linear energy density of the picosecond laser during welding, resulting in variations in the number and size of defects and the shape of the glass modification zone. By reasonably tuning the two factors, the shear strength of the joint reaches 15.98 MPa. The diffusion and mixing at the interface and the mechanical interlocking effect of the glass modification zone are the main reasons for achieving a high shear strength of the joint. This study will provide reference and new ideas for the laser transmission welding of glass and metal in the non-optical contact conditions.

Microstructure and mechanical properties of similar and dissimilar resistance spot welded DC04 and HRP6222 (DD11) steels

Abstract Low carbon steels are frequently preferred in the automotive industry. The most preferred welding method in vehicle body manufacturing is resistance spot welding (RSW). In this study, RSW joints of DC04 and HRP6222 steels were carried out at two different electrode forces (2.1 kN, 2.4 kN) and three different welding currents (4 kA, 6 kA, 8 kA). The effects of different welding parameters on microstructure, tensile shear force, failure mode and microhardness were investigated. So, the focus was on optimizing the welding parameters. As a result, the RSW process caused the formation of three different regions in the microstructure (the base metal, the heat affected zone and the weld metal). It was observed that the tensile shear force increased as the welding current and electrode force increased. After the tensile shear tests, two different failure modes occurred (interface and pull-out type). Hardness values showed a linear relationship with tensile shear force results. In addition, a significant increase in hardness values was observed from the base metal to the weld metal in all welding parameters.

Development of a hybrid ANFIS method for optimising laser beam welding of dissimilar metals: a virtual prototype approach

Development of a hybrid ANFIS method for optimising laser beam welding of dissimilar metals: a virtual prototype approach

Effect of Ti, Al, and Mg addition on microstructure evolution in weld metal of stainless steel solidified with F and FA modes and the tensile property

This study investigated the effect of equiaxed primary ferrite nucleation on the weld microstructure and tensile properties of two types of stainless steel solidified with primary ferrite. One was the F mode with only δ–ferrite during solidification, and the other was the FA mode with austenite formed at the end of solidification. MgAl2O4, formed after alloying of Ti, Al, and Mg and accelerated TiN formation due to the low lattice misfit of 4.88 % under their fully paralleled orientation. Primary ferrite nucleation with equiaxed solidification was achieved in both the F and FA modes. In the F mode, austenite transformed from δ–ferrite grain boundary in solid state and exhibited dependent formation with δ–ferrite morphology. Therefore, the equiaxed δ–ferrite grain promoted the refinement of austenite. Conversely, in the FA mode, austenite formed independently to δ–ferrite during solidification and grew epitaxially from the austenite phase in the base metal. As a result, austenite could not be refined by equiaxed δ–ferrite nucleation. The grain refinement could improve the tensile property. However, the brittle TiN caused the fracture initiation during tensile deformation, degrading the tensile property in both F and FA modes. This comprehensive influence of TiN and the microstructural evolution of δ–ferrite and austenite highlights the tendency of tensile properties to improve in the F mode, whereas diminished in the FA mode.

Experimental and numerical study on the material constraint effect in pipeline steel welded joint

An in-depth analysis of the material constraint effect is crucial for accurately determining the constitutive relationship and safety evaluation of pipeline steel welded joint. Therefore, this work combines experiments and finite element simulations to study the constraint effect. Through the welding method, the weld specimens with different sizes and strength mismatch conditions are prepared. The microstructure and hardness distribution of the specimens are measured, and tensile tests based on the digital image correlation (DIC) technology are conducted. Finite element models of the weld specimens with different sizes and material parameters are established, followed by tensile simulations and detailed analysis. Based on the experiments and numerical simulations, the tensile strain responses, stress-strain curves, and material parameters of different weld specimens are obtained. The results show that the smaller the weld width, the more significant the effect of the material constraint. For undermatched welds, the calculated stress of the weld metal (WM) increases with the decrease of the weld width. Additionally, the calculated stress of WM also increases with the decrease of the mismatch coefficient, where the mismatch coefficient refers to the ratio of the yield strength of WM to that of the base metal (BM). Conversely, for overmatched welds, the calculated stress of WM decreases with the decrease of the weld width. The material constraint effect is also influenced by the mismatch condition of the weld. An increase in the mismatch coefficient reduces the effective range of the stress-strain curve obtainable for WM. To analyze the effect of the mismatch condition, it is necessary to comprehensively compare the yield strength and strain hardening capacity of each material. The width-to-thickness ratio of the weld specimen has little effect on the calculated stress of WM. The finite element simulation method can be used to correct the stress-strain curves obtained from the tests to achieve accurate constitutive relationships.

Role of Si element in the IMC formation and tensile-shear property of the laser welding-brazing steel-Al dissimilar joints

A comparative investigation was conducted to explore the role of Si in the intermetallic compound (IMC) formation and tensile-shear property of steel-Al joints fabricated via laser welding-brazing (LWB) technique. Three filler wires including ER5356, ER4043 and ER4047 were employed to join the DP780 steel and 5754 Al alloy. The results exhibited that the presence of Si could improve the tensile-shear property of steel-Al joints. With increasing the Si addition, the failure locations of the joints changed from the interface, weld metal to Al alloy base metal. For the joints fabricated with ER5356 filler, the IMCs consisted of Fe2Al5 and Fe4Al13. On the contrary, Fe4(Al, Si)13 and Al8Fe2Si was detected for the joints prepared with ER4043 and ER4047 filler wires. The Si could suppress the generation of brittle Fe2Al5. In addition, Fe4(Al, Si)13 and Al8Fe2Si could resist the crack propagation, guaranteeing the qualified tensile-shear strength of the joints.

Effect of welding parameters on microstructure and mechanical properties of dissimilar AISI 304/ductile cast iron fusion welded joints

Problems associated with dissimilar fusion welding are mainly originated from the differences in melting points, coefficients of thermal conductivity and thermal expansion, …etc., and carbon content when welding dissimilar ferrous materials. In this study, the problems associated with dissimilar fusion welding of stainless steel AISI304 with ductile cast iron DCI grade A536 were investigated. Using shielded metal arc welding (SMAW) process, various welding parameters were studied to investigate the successful/accepted dissimilar welded joint(s). Welding electrodes and welding techniques were the main studied parameters. Microstructural and mechanical investigations were carried out for welded joints under different welding parameters. Tensile, impact and hardness tests coupled with optical and scanning electron microscopic examinations with EDX analysis were made for metallurgical and mechanical evaluations of welded joints. This extensive study could solve the problem of dissimilar welding between ductile cast iron and 304 stainless steel. The main results showed that joints welded by ENiCrFe-3 electrode in root pass and ENiFe-CI in filling passes were the successful dissimilar welded joints with 422 MPa tensile strength which represents 104% of annealed DCI base metal and without any changes in toughness properties, where toughness at HAZ of DCI was 18 J. High Ni content in weld metal increased the strength, ductility and reduced the weld metal dilution.

Tensile testing of S690QL1 HSS welded joint heterogeneous zones using small scale specimens and indentation methods

Abstract The welded joints are structures with significant heterogeneity, indicated by their fundamental segmentation into base metal (BM), heat affected zone (HAZ), and weld metal (WM). The heat affected zone, having width in millimeter scale for fusion welding processes, is further segmented into several characteristic regions, having differences in grain structure and size. The microstructural heterogeneity results in significant differences in mechanical properties of individual welded joint zones. Mechanical testing of such small material volumes is inconvenient, or even impossible, using the standard size specimens proposed in testing standards. Requirement to precisely position the specimens, even ones with subsize dimensions, and investigate mechanical properties of specific narrow HAZ regions presents certain challenge. This work investigates the X welded joint of S690QL1 grade high strength steel (HSS), welded with slightly overmatching filler metal. The material tensile properties are tested, using small scale specimens and indentation methods. Small scale specimens are ASTM E8 round tensile subsize and flat sheet mini tensile specimens (MTS). The indentation methods include hardness testing and profilometry-based indentation plastometry (PIP) method, to gain additional insights into material stress–strain behavior. Finally, paper evaluates the testing methods, comparatively processes the collected experimental data, and provides guidelines for heterogeneous structures testing.

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.

Effects of Autogenous Gas Tungsten Arc Welding (GTAW) on Corrosion Resistance of Stainless Steel 316L

The autogenous manual gas tungsten arc welding (GTAW) process was used for cladding austenitic stainless steel 316L using a single pass with various contact tip-to-work distances (CTWDs). Immersion and electrochemical tests were used to evaluate the corrosion resistance of the welded specimens, and a microstructural analysis was conducted to investigate the chemical composition of the molten pool and the heat-affected zone of welding. The key findings of this study indicate that the corrosion resistance improved under a CTWD of 5 mm due to the optimal distribution of ferrite and a refined microstructure. Additionally, the highest hardness was observed in specimens with a CTWD of 3 mm, attributed to the increased ferrite content in the weld metal. As the CTWD increased, the ferrite fraction decreased, and the hardness also diminished. However, in the CTWD 7 mm case, the higher heat input influenced the microstructure and molten pool shape significantly through the Marangoni effect, resulting in a lower corrosion resistance. These results suggest that optimizing the CTWD can enhance the corrosion resistance of welded 316L stainless steel.

COMPARATIVE STUDIES ON MICROSTRUCTURE AND TOUGHNESS OF 9 % Ni STEEL JOINTS WELDED BY SMAW AND GTAW

The microstructure and impact toughness of 9 % Ni steel joints welded by shielded metal arc welding (SMAW) and gas tungsten arc welding (GTAW) were investigated. The two kinds of weld metal were mainly composed of cellular dendrites and a granular precipitated phase. The grains and cellular dendrites of the GTAW weld metal were smaller than those of the SMAW weld metal. The precipitates in the SMAW weld metal were stripe-shaped while those in the GTAW weld metal were rod-shaped; the number of precipitates in the GTAW weld metal was lower than in the SMAW weld metal. The low-temperature impact toughness of the GTAW weld metal was better than that of the SMAW weld melt.

Investigation on the fatigue crack growth behavior of welded joints in EH690 high-strength marine steel

EH690 high-strength steel (HSS) is extensively utilized in marine engineering due to its exceptional strength. The fatigue crack growth (FCG) behaviors of EH690 HSS welded joints in different zones (base metal (BM), heat-affected zone (HAZ), and weld metal (WM)) were investigated by conducting FCG tests with various stress ratios (R). The results demonstrate that the WM and HAZ materials exhibit enhanced resistance to FCG compared to the BM material. The higher stress ratios result in increased fatigue crack growth rates (FCGRs). The welded residual stress (WRS) distribution in the welded joints was predicted considering solid-state phase transformation (SSPT). Subsequently, a comprehensive analysis of the WRS influence on FCG behavior shows that the residual compressive stress enhances the material’s resistance to FCG. Additionally, the effect of R on the FCG behavior of the material was investigated by employing the Walker model, and the applicability of the Walker model was discussed as well. Finally, the FCG mechanisms of the different zones in the welded joint were investigated from a microscopic perspective, further exploring the influence of R on the FCG behavior.

Crucial effects of plasma gas on the weld and microstructural characteristics of plasma arc welded aero engine Ti6Al4V alloy joints

This study explores the influence of plasma gas flow rate (PGFR) on the defects, microstructure evolution and mechanical properties during plasma arc welding of Ti6Al4V titanium alloy thin sheets using microscopic analysis, spectroscopic analysis, tensile and microhardness tests. The variation in PGFR affects the welding arc in terms of its stability, pressure and constriction which results in transformation of arc from conduction mode to keyhole mode and changes in microstructure as well. All the other welding process parameters were kept constant except for PGFR which was varied to investigate its significance. Excess weld metal was observed under the weld bead is an attribute of keyhole formation. Macrographs exhibits increments in weld geometry measurements whereas weld defects such as lack of penetration and porosity decreased with increased PGFR. The microstructural examination showed a variety of phase formations that includes majorly with acicular α and Widmanstätten α morphologies. Tensile strength and hardness at the weld region of the welded joints increases with increase in PGFR. An oxygen rich brittle subsurface layer called α-case morphology was observed at the weld region of 1 L/min joint causes significant reduction in ductility.

Fracture toughness and microstructural analysis of rotary friction welded S355J2 and SS316L steels for critical applications

Dissimilar metal welding is seeing growing adoption across industries to enhance structural functionality and efficiency. Achieving high-quality, defect-free dissimilar weld joints requires a comprehensive understanding of the interrelationships between the welding-induced microstructural changes and the material's performance characteristics, particularly its fracture-related properties. This study investigates the impact of microstructural changes on the fracture toughness of dissimilar welds between structural low-carbon steel (S355J2) and austenitic stainless steel (SS316L) prepared using the Rotary Friction Welding (RFW) technique. Welding preforms were created from respective pipe pup pieces. The evaluation involves microstructural analysis, tensile testing, hardness testing, and fracture toughness testing using compact tension specimens derived from various zones of the weld joints. Results revealed significant microstructural differences across the weld joint. The weld region exhibited stable hardness with a maximum of 208 HV1 in S355J2′s thermo-mechanically affected zone (TMAZ). High tensile strength (Ultimate Tensile Strength 540 MPa, Yield Strength 367 MPa) with failures mainly on the S355J2 side. The fracture toughness (KQ) matched parent metal values, with the RFW weld centre line (WCL) showing superior crack tip opening displacement (CTOD) of 0.35 mm. Fractography generally indicates ductile failure.

Computational modeling and virtual analysis using a moving heat source to join AZ61A and AA7075 alloys with the application of a titanium alloy interlayer

Laser beam welding (LBW) uses a concentrated laser beam to fuse materials, providing benefits such as a smaller heat-affected zone (HAZ), speed, accuracy, adaptability across multiple materials, and seamless adoption into automation processes. Achieving optimal weld quality with LBW remains difficult due to the need to select the appropriate welding process variables and proper interlayer between dissimilar materials. Due to the high cost and safety risks to operators and equipment in LBW, it is challenging to use the practical experiment. Additionally, welding materials with high thermal conductivity and lower melting temperatures, such as AZ61A and AA7075, is a considerable challenge. Previous research focused on process parameters in laser beam welding of various metals, but not enough consideration has been given to the effect of a titanium interlayer on AA7075 and AZ61A using virtual data. This study aims to fill these gaps by using simulation data to assess the effects of process parameters and the titanium interlayer during LBW of dissimilar materials. A backpropagation neural network with the gradient descent learning rule was used for optimization, and a central composite design was used to predict the optimal process parameter interaction. The result indicates the optimum equivalent strain is obtained at the values of beam radius between 4.5 to 5 mm. The maximum equivalent stress reached during welding speed is between 4 to 4.5 mm/s. The maximum residual stress was obtained at the number of segments of 160. The predicted maximum and average anticipated errors for peak temperature are 0.1655 % and 0.0210 %, while for residual stress it is computed as 0.1766 % and 0.0754 %. The Ti-interlayer in magnesium and aluminum laser welding reduces peak temperatures, allows for uniform energy distribution, minimizes localized heating, and enhances weld quality while lowering residual stress.

Hardness and Microstructure Characterization of Hardfacing Alloys Deposited by The Shielded Metal Arc Welding (SMAW) on AISI 1045 Medium Carbon Steel

A ring frame is a machine used for yarn production in the textile industry. Continuous use of the machine results in wear on the shaft timing pulley on the ring frame machine. To improve this condition, repairs are needed, one of which uses the hardfacing method. This study aims to determine the effect of hardfacing on the microstructure and hardness of the shaft timing pulley made from AISI 1045. The hardfacing process used the shielded metal arc welding (SMAW) method with welding current variations of 115 A, 125 A, 135 A, 145 A, and 155 A. In this study, the electrode used was AWS A5.1 E7018 with a diameter of 3.2 mm. The hardfacing product obtained was then finished with a lathe to produce a shaft with a final diameter of 30 mm. In this study, microstructure and hardness tests were carried out on specimens before and after finishing. The results of this study showed that an increase in current caused an increase in the number of pearlite phases in the weld metal and HAZ (heat-affected zone) areas. While in the base metal, the increase in current increased the number of ferrite phases. The highest hardness value was found in specimens that were hardfaced with a current of 145 A. However, the hardness of the hardfacing layer will decrease with the use of currents greater than 145 A. The hardness of the specimens with hardfacing treatment at a current of 145 A resulted in hardness in the weld metal, HAZ, and base metal of 225 HV, 209 HV, and 203 HV, respectively. After the finishing process, the weld metal, HAZ, and base metal in this specimen produced a hardness of 225 HV, 217 HV, and 208 HV, respectively.

Investigation of Process Parameters on the Mechanical Strength in Ultrasonic Metal Welding of Aluminum to Copper Dissimilar Joints

Investigation of Process Parameters on the Mechanical Strength in Ultrasonic Metal Welding of Aluminum to Copper Dissimilar Joints