Input Welding Research Articles

Investigating the ability of deep learning to predict welding depth and pore volume in hairpin welding

To advance quality assurance in the welding process, this study presents a deep learning (DL) model that enables the prediction of two critical welds’ key performance characteristics (KPCs): welding depth and average pore volume. In the proposed approach, a wide range of laser welding key input characteristics (KICs) is utilized, including welding beam geometries, welding feed rates, path repetitions for weld beam geometries, and bright light weld ratios for all paths, all of which were obtained from hairpin welding experiments. Two DL networks are employed with multiple hidden dense layers and linear activation functions to investigate the capabilities of deep neural networks in capturing the complex nonlinear relationships between the welding input and output variables (KPCs and KICs). Applying DL networks to the small numerical experimental hairpin welding dataset has shown promising results, achieving mean absolute error values of 0.1079 for predicting welding depth and 0.0641 for average pore volume. This, in turn, promises significant advantages in controlling welding outcomes, moving beyond the current trend of relying only on defect classification in weld monitoring to capture the correlation between the weld parameters and weld geometries.

Evolution of inclusions in DH36 grade ship plate steel during high heat input welding

In this paper, the solid solution and precipitation behavior of inclusions on the surface and 1/2 thickness of the tested steel plate under the condition of welding heat input of 400 kJ/cm is investigated by using laser confocal experiments with hot-rolled state DH36 ship plate steel as the research object, and the mechanism of the effect of inclusions on the phase transformation of an acicular ferrite is revealed. The results show that the inclusions of the tested steel are mainly composed of Oxide-MnS, MnS, Oxide, TiN, Spinel, etc. The amount of inclusions on the surface of the tested steel plate is significantly higher than that at the 1/2 thickness position. During the heating stage, the small inclusions on the surface immediately disappeared, and the large inclusions gradually solidified in the matrix; atomic diffusion occurred at the bond between the inclusions and the matrix; while the small inclusions at the 1/2 thickness position gradually disappeared at the beginning of the heating stage, and the inclusions began to precipitate and grow when the temperature was increased to 990 °C. The acicular ferrite preferentially nucleates and grows near the boundary of the inclusions during the post-weld cooling stage, and its growth ends when two acicular ferrites cross.

Influence of submerged arc welding process parameters and metallurgical behaviour in a thick carbon steel section for boiler application

AbstractThe aim of the research is to investigate the weldability of thick sections of carbon steel using submerged arc welding with varying process parameters. The experimental design for joining thick carbon steel involves manipulating input weld process parameters such as current (A), voltage (V), weld speed (mm/h), and weld electrode diameter (mm). The quality of the weld material is assessed based on transformations in microstructure, weld hardness measured by Brinell hardness number, and tensile strength (MPa). It is crucial to note that the grain structure and metallurgical behavior of other hard materials may differ significantly. The presence of carbon in the ferrite phase has led to the formation of bainite, martensite, and composites of martensite and austenite within the weld zone, as confirmed by high‐resolution microscopy. The weldment‘s hardness has increased from 242.5 HV 30 in the base metal to 316.4 HV 30 in the weldment due to metallurgical alterations in the microstructure. Weld energy input emerges as the primary factor influencing weld quality. With increasing weld current and voltage, there is a corresponding increase in the joined metal, resulting in improved characteristics in the weld structure, particularly at maximal energy input and welding speed. In the context of boiler applications, understanding the weldability of thick carbon steel sections is paramount for ensuring structural integrity and longevity under high‐temperature and high‐pressure conditions. The optimized welding parameters identified in this study can contribute to enhancing the reliability and performance of boilers, thereby promoting safety and efficiency in industrial settings.

Optimization of process parameters of cold metal transfer arc welding of AA 6061 aluminium Alloy-AZ31B magnesium alloy dissimilar joints using response surface methodology

The fabrication of dissimilar metal joints, particularly between AA 6061 aluminum alloy (Al) and AZ31B magnesium alloy (Mg), poses significant technical challenges due to their distinct metallurgical characteristics and the inherent difficulties associated with welding such materials. These challenges include the propensity for intermetallic compound formation, thermal cracking, and differences in thermal and mechanical properties between the two alloys. Cold Metal Transfer (CMT) welding, known for its low heat input and controlled metal transfer, offers a potential solution to these issues. However, optimizing the process parameters to ensure strong, defect-free joints requires a systematic approach. This study aims to optimize CMT welding parameters using parametric mathematical modeling (PMM) to produce high-strength Al and Mg dissimilar joints and to study the effects of CMT parameters on tensile strength (TS) and weld metal hardness (WMH), as well as the microstructural features of AA 6061 aluminum alloy/AZ31B magnesium alloy (Al/Mg) dissimilar joints. Al/Mg dissimilar butt joints were produced by the CMT process using ER4043 as filler wire. CMT, a low-heat input welding technique, was used to mitigate issues such as intermetallic compounds (IMCs), wider heat-affected zone (HAZ), and distortion. The CMT parameters, particularly wire feed speed (WFS), welding speed (WS), and arc length correction (ALC), were optimized using response surface methodology (RSM) to maximize the TS and WMH of the Al/Mg dissimilar joints. Polynomial regression was employed to create PMMs that integrated these CMT parameters to forecast the TS and WMH of the joints. An analysis of variance (ANOVA) was applied to assess the feasibility of the PMMs. The results indicated that the Al/Mg dissimilar joints, produced using a WFS of 4700 mm/min, a WS of 280 mm/min, and an ALC of 10%, exhibited higher TS and WMH values of 33 MPa and 95.8 HV, respectively. The PMMs provided precise forecasts for the TS and WMH of the Al/Mg joints with an error rate of less than 1% and a confidence level of 97%.

Effect of Ti/N Ratio on TiN Particles, Microstructures, and Toughness of Heat‐Affected Zone After High Heat Input Welding of the Ca‐Treated Steel Plates

The high heat input welding (HHIW) can greatly enhance the welding efficiency of the steel plates. However, coarse grains and brittle microstructures will be formed in the heat‐affected zone (HAZ) during the HHIW process, which deteriorates the toughness of HAZ. In the present study, the effect of the Ti/N ratio on the size and distribution of titanium nitride (TiN) particles, microstructures, and toughness of HAZ after HHIW of 400 kJ cm−1 is investigated for the Ca‐treated steels with different Ti/N ratios of 1.61, 3.79, and 5.00 for TN16, TN38, and TN50 steels. The TN38 steel has the highest number density of the TiN particles with the sizes between 20 and 25 nm and the highest pinning force of the particles in three steels, resulting the smallest grain sizes in its HAZ. In addition, in three steels, the TN38 steel has the main microstructure of intragranular aciculate ferrites with the highest high‐angle grain boundaries density in its HAZ, thereby obtaining the highest value of low‐temperature impact toughness of the HAZ.

Inclusions Evolution of Ca‐Treated Steel During High‐Heat Input Welding

This article has investigated a 60 mm Ca‐treated Q550 steel used for high‐heat input welding. The results have shown that the Ca‐type inclusions account for 70% of the inclusions in the steel which are mainly CaAlMg type, Ca–Al type, and a small amount of CaS type while the non‐Ca‐type inclusions are mainly FeCO. After undergoing the welding thermal cycle, the number of Ca‐containing inclusions above 2 μm in size is decreased while the number of non‐Ca‐containing inclusions below 1 μm (mainly FeO) is increased significantly. However, the total area of inclusions is decreased. It has been found out that the CaAlSO‐type inclusions undergo “diffusion” of O element to the surroundings during the thermal cycle, forming a ring‐shaped oxygen‐rich zone and carbon‐rich zone which promotes the nucleation of acicular ferrite. In contrast, the CaAlMgSO‐type inclusions undergo “decomposition” during the thermal cycle which forms a group of inclusions with different sizes and types, promoting nucleation of multioriented acicular ferrite.

Multicriteria decision-making for optimization of welding parameters in cold metal transfer and pulse metal-inert gas weld bead of AA2099-T86 alloy using CRITIC and ROV methods

PurposeThe criteria importance through intercriteria correlation (CRITIC) and range of value (ROV) combined methods were used to determine a single index for all multiple responses.Design/methodology/approachThis paper used cold metal transfer (CMT) and pulse metal-inert gas (MIG) welding processes to study the weld-on-bead geometry of AA2099-T86 alloy. This study used Taguchi's approach to find the optimal setting of the input welding parameters. The welding current, welding speed and contact-tip-to workpiece distance were the input welding parameters for finding the output responses, i.e. weld penetration, dilution and heat input. The L9 orthogonal array of Taguchi's approach was used to find out the optimal setting of the input parameters.FindingsThe optimal input welding parameters were determined with combined output responses. The predicted optimum welding input parameters were validated through confirmation tests. Analysis of variance showed that welding speed is the most influential factor in determining the weld bead geometry of the CMT and pulse MIG welding techniques.Originality/valueThe heat input and weld bead geometry are compared in both welding processes. The CMT welding samples show superior defect-free weld beads than pulse MIG welding due to lesser heat input and lesser dilution.

Metallurgical, mechanical, and corrosion behavior of AISI 304L joints welded using variable arc energy inputs and subjected to thermal aging

The effect of three levels of welding arc energy input on the metallurgical, mechanical, and corrosion behavior of AISI 304L stainless steel was studied with the aim of investigating and recommending the most useful range of process parameters for improved performance of engineering structures made from this industrially important alloy. The gas tungsten arc welding process was employed, and all the joints were butt-welded using a single-V groove design. With an increase in heat input, the δ-ferrite phase changed from lathy to vermicular, besides the heat-affected zones of all the welds exhibiting grain coarsening effects. Postweld thermal aging led to the preferential occurrence of carbides in the interdendritic regions, which degraded their corrosion performance. Thermal aging did not affect the tensile strength of these welds, but their ductility was significantly impacted. The extent of segregation of Cr and C, especially, was observed to be the least in the case of low heat input welds. This study establishes that while designing welding procedures for AISI 304L structures, low welding arc energy should be used as it promotes better mechanical as well as corrosion properties.

Inclusions and microstructures in coarse-grained heat-affected zone of Al–Ti–Ca deoxidized shipbuilding steels with different Al contents after high-heat input welding

The inclusions, microstructure evolution and impact toughness of the coarse-grained heat-affected zone (CGHAZ) of Al–Ti–Ca deoxidized shipbuilding steel plates with different Al contents after high-heat input welding of 400 kJ cm−1 are investigated. The characteristics of inclusions and their influence on the refinement of microstructure and impact toughness in CGHAZ was elucidated. Increasing the Al content from 0.016 wt% to 0.022 wt% and 0.043 wt% results in an increase in the average size of prior austenite grain and the brittle phase fractions, while decreasing the content of intragranular acicular ferrites (IAFs). The results of the thermodynamic calculations, high-temperature laser scanning confocal microscopy and differential scanning calorimetry all show that increasing the Al content can diminish the austenitic stable region, elevate the transition temperature from austenite to ferrite and suppress the nucleation of IAF. In the present steels, the IAF formation is successfully induced by the specific inclusions, namely Al2O3–CaO–Ti2O3–MnS(-CaS), in which the calcium aluminate inclusions are embedded with Ti-oxides and CaS–MnS precipitates. The effective inclusions have the number density of 93 mm−2 in 16Al steel and 27 mm−2 in 22Al steel, but they are rarely found in 43Al steel. On average, an effective inclusion can induce 3.4 IAFs in 16Al steel and 2.8 IAFs in 22Al steel. Thus, as the Al content increases from 0.016 wt% to 0.22 wt% and 0.043 wt%, the impact toughness of CGHAZ at −40 °C decreases from 134 J to 78 J and 24 J with the welding heat input of 400 kJ cm−1.

Experimental studies on fillet weldment joints by artisans in Ghana’s Western Region

Constant progress, demand in the manufacturing of mechanisms parts, and the ability to join parts together is another critical aspect of manufacturing for assemblers. Joining methods plays a significant role and welding must be constantly improved, experimented with, and upgraded due to its increasing use in all aspects of manufacturing. The quality of a weld joint is highly dependent on the process parameter. Welds are examined to ensure that they meet specifications through various experimental processes ranging from computational networks, evolutionary algorithms, non-destructive testing (NDT) and destructive testing (DE) to ascertain the quality of joints. The main objective of the study was to ascertain the quality of welded joints through non-destructive evaluation (NDE). To achieve this goal, an experimental method of four (4) NDE methods were employed to evaluate the quality of weldment joints on a mild steel material joined using manual metal arc welding (MMAW) process in selected fabrication shops in Takoradi-Kokompe, Ghana. Steel specimens were prepared and taken to the artisans to be created into corner joints using the fillet method. The specimens were tested using non-destructive testing techniques. The results on the welded joints were evaluated using the AWS D1.1 code of acceptance for structural steels. The results revealed that all welded joints from fabricators failed to meet the AWS D1.1:2000 acceptance criteria and, thus, had to be rejected. The results implies that through the artisans have worked for many years in the welding trade, their lack of competence and skills in the selection of right input welding parameters contributed to the results. The results implies that, the finished artefacts may look fine but internal structures may contribute to future failure of the fabricated artefacts.

Optimizing CO2 laser beam welding parameters for magnesium hybrid metal matrix composites (ZE41A)

ABSTRACT The current work is the investigation of optimizing input welding parameters of CO2 laser welding of two stir squeeze casted magnesium (ZE41A) matrix silicon nitride and alumina-reinforced hybrid metal matrix composites (MMCs). Two similar hybrid MMC plates were joined by the CO2 laser beam welding process and were investigated for input welding parameters influencing the metallurgical and mechanical properties. The identified parameters were subjected to optimization by Box-Behnken experimental design of Response Surface Methodology (RSM) and the experimental trials were validated by Analysis of Variance (ANOVA). With increases of 16% and 23%, the microhardness and tensile strength peaked at 207 MPa and 78 HV, respectively. The ideal input welding settings were 3500W of laser power, 4 mm/minute welding speed, and a focus length of 1.5 mm.

Thermal analysis of AISI 1020 low carbon steel plate agglutinated by gas tungsten arc welding technique: a computational study of weld dilution using finite element method

An important goal in a number of optimization studies is a high-quality weld joint. Thermal analysis of AISI 1020 low carbon steel plate agglutinated by gas tungsten arc welding technique was carried out using S 2021 version. With SOLIDWORKS Premium, the simulation was run. The simulation was performed using the Thermal Simulation programme with 20 weld runs. With the findings of the initial study serving as a sensor, a design study was conducted. A total of 15 runs were completed, and the weld dilution and thermal conductivity responses were available. A range of welding temperatures including 3397 to 3688 °C were experimentally applied in the joining process of AISI 1020 low carbon steel plate of 10 mm thickness, and a strain gauge indicator was used to measure the thermal stresses induced in the steel plate. However, minimum and maximum weld dilution values of 73.1 and 46.8% were obtained with FEM at an input of arc heat of 66.4 and 37.2 J/mm, while the minimum and maximum weld dilution values of 71.55 and 45.5% were computed using experimental approach at the same heat input. On the other hand, maximum and minimum weld dilution of 71.55 and 44.5% were computed from experimental process at minimum and maximum welding current of 199.77 and 250.23 A, while 73.1 and 46.8% were obtained for the maximum and minimum weld dilution through FEM procedure at the same welding input variables. Hence, gas tungsten arc welding input parameters should be properly selected and controlled during welding operation, in order to minimize thermal effects and welding flaws such as high dilution rate.

The Influence of the Second Phase on the Microstructure Evolution of the Welding Heat-Affected Zone of Q690 Steel with High Heat Input.

Q690 steel is widely used as building steel due to its excellent performance. In this paper, the microstructure evolution of the heat-affected zone of Q690 steel under simulated high heat input welding conditions was investigated. The results show that under the heat input of 150-300 kJ/cm, the microstructures of the heat-affected zone are lath bainite and granular bainite. The content of lath bainite gradually decreased with the increase in heat input, while the content of granular bainite steadily increased. The proportion of large-angle grain boundaries decreased from 51.1% to 40.3%. Overall, the average size of original austenite increased, and the precipitates changed from Ti (C, N) to Cr carbides. During the cooling process, the nucleation position of bainitic ferrite was from high to low according to the nucleation temperature, and in order of inclusions at grain boundaries, triple junctions, intragranular inclusions, bainitic ferrite/austenite phase boundaries, twin boundaries, grain boundaries, and intragranular inclusions at the bainitic ferrite/austenite phase interface. The growth rate of bainitic ferrite nucleated at the phase interface, grain boundary, and other plane defects was faster, while it was slow at the inclusions. Moreover, it was noted that the Mg-Al-Ti-O composite inclusions promote the nucleation of lath bainitic ferrite, while the Al-Ca-O inclusions do not facilitate the nucleation of bainitic ferrite.

Optimization of welding parameters on weld deposits area in pulsed gas metal arc welding

This paper presents a methodology for optimising pulsed gas metal arc welding parameters on Stainless Steel GRADE 410. Most sectors favour the economic welding technique for its favourable outcomes, such as enhanced strength and reduced corrosion. Compared to conventional welding methods, pulsed gas metal arc welding has the advantage of reducing current consumption and increasing the rate at which metal is deposited. An optimisation technique is employed to forecast the weld bead's accurate geometry, penetration depth, and reinforcement height, considering the welding input parameters such as welding speed, current rate, and frequency level. The Taguchi technique uses experimental analysis by considering input and output parameters. A multiple regression analysis model has been developed for SS Grade 410 Stainless steel to determine the bead geometry's correctness.

Refinement mechanism of large heat-input welding CGHAZ microstructure by N addition and its effect on toughness of a V-Ti-N microalloying weathering steel

The large heat input welding performance of uncoated weathering steel remains a great challenge since their coarse grain heat-affected zones (CGHAZs) are usually occupied by coarse and brittle microstructure consisting of granular bainitic ferrite (GBF) and martensite/austenite (M/A) constituents. In this article, a V-Ti-N microalloying weathering steel suitable for large heat input welding was achieved through the N addition, and the mechanism dominating the modified microstructure and the enhanced impact toughness of CGHAZ was deeply elucidated mainly by HRTEM. The results indicated that in the simulated CGHAZ with large heat input of 80 kJ/cm, the increase of N content from 0.0030 wt% to 0.0075 wt%, and 0.0115 wt% elevated the density of nano- and submicron-sized particles of (Ti, V)(C, N) containing VN, which in turn resulted in the refinement of prior austenite grains (PAGs) by the improved grain boundary pinning effect and the enhancement in heterogeneous nucleation of intragranular ferrite (IGF) by the decreased lattice disregistry (δ) between (Ti, V)(C, N) and IGF. The fraction of high-angle grain boundaries (HAGBs) with misorientation tolerance angles (MTAs) higher than 15° was thereby increased while the mean equivalent diameter (MED) of ferritic grains with HAGBs was decreased. Simultaneously, the N addition scattered the M/A constituents, promoted the internal substructure of dislocation-type M/A at the expense of twin-type M/A, and accordingly reduced the hardness difference between the M/A constituents and the matrix. All these factors retarded brittle crack initiation and propagation, and low-temperature impact toughness of simulated CGHAZ increased from 62.8 J to 141.2 J.

Effects of preheating on laser beam–welded NSSC 2120 lean duplex steel

AbstractDuplex stainless steels show sustainable alternative for the conventional austenitic grades, with higher strength, higher resistance against stress corrosion cracking, and lower purchase cost. Thus, duplex stainless steel gains more attention in construction, oil and gas, and chemical industries. Among duplex stainless steels, low nickel and low molybdenum alloyed lean duplex stainless steel are a cost-effective substitution of austenitic grades. However, keeping the balanced ferrite/austenite phase ratio in the weld metal can be challenging, mostly for autogenous and low heat input welding processes. In our research, a newly developed NSSC 2120 lean duplex stainless steel grade was welded autogenously by fiber laser welding process. Different welding parameters and preheating temperatures were used during the experiments. The welds were evaluated by microscopic and metallographic techniques, and also by electrochemical corrosion measurements. The welding parameters and the preheating temperature greatly influenced the weld shape and the austenite content in the weld metal. It was found that the focus point distance from the sheet surface had significant effect on the weld geometry. Changing the focus point distance to + 2 mm, the penetration depth increased from 4.96 to 5.53 mm, and increased the austenite content by 2.6%. Due to the preheating the welds became wider and shallower, e.g., from 4.96 to 4.08 mm penetration depth, while the cross-section are increased from 5.10 to 6.12 mm2 at the same sample. The preheating resulted in more intergranular austenite formation, which meant maximum 4% increase in the weld metal. The increasing austenite content resulted in increasing pitting corrosion resistance in 3.5% NaCl electrolyte, the highest increase was 90 mV.

Effect of Mg Addition on Inclusions in the Welding Heat-Affected Zone of Pressure Vessel Steels

With the development of the pressure vessel industry, high-energy wire welding has a great future. However, this means higher demands on the weldability of pressure vessel steels. Controlling inclusions via oxidative metallurgy is a reliable method of improving the weldability of pressure vessel steels. Hence, in this paper, experimental steels with different Mg element mass fractions were prepared using vacuum metallurgy. Simulated welding for high-heat input welding was carried out using the Gleeble-2000 welding thermal simulation test machine. The inclusions in the welding heat-affected zone (HAZ) in the experimental steels were observed using an optical microscope (OM) and scanning electron microscope (SEM). The compositions of the inclusions were analyzed using an energy-dispersive spectrometer (EDS). The research results indicated that the addition of Mg could increase the number density of the inclusions in the welding HAZ. With the addition of Mg from 0 to 5 wt.%, the total number density of the inclusions increased from 133 to 687 pieces/mm2, and the number density of the inclusions with a size of 0–5 μm2 increased from 122 to 579 pieces/mm2. The inclusions in the experimental steel welding HAZ with Mg elements were mainly elliptical composite inclusions composed of (Mg-Zr-O) + MnS. Moreover, MnS precipitated on the surface of the Mg-containing inclusions in the welding HAZ. Intragranular acicular ferrite (IAF) nucleation was primarily induced via the minimum lattice mismatch mechanism, supplemented with stress-strain energy and inert interface energy mechanisms.

Review on mechanical and micro-structure properties of dissimilar joining of IS 2062 mild steel

Most steel and aluminum alloys can be fused using the MIG and TIG welding methods, which provides higher mechanical properties and microstructure at optimized input settings. Several studies tested the effectiveness of MIG and TIG welding for connecting a wide range of alloys used in a variety of applications. MIG and TIG welding process parameters are critical aspects that determine weld quality. The goal of this review study is to synthesize the published literature on various MIG and TIG welding variants and to investigate the effect of various welding input process parameters on the microstructure, hardness, tensile strength, and impact strength of the weldment. The results showed that changing the value of any of the parameters had a considerable impact on the weld qualities. Welding current and welding speed are the two most essential welding input factors. Lowering the welding voltage and gas flow rate while increasing the welding speed and wire feed rate results in the highest ultimate tensile strength of the weldment. When compared to traditional weld methods, TIG produces better mechanical characteristics and lower residual stresses. To increase weld quality, there is a greater scope of research on the mechanism of residual stresses and their association with microstructure and mechanical properties.

ANALISIS PENERAPAN ISO 14001 UNTUK MENUNJANG KESELAMATAN KERJA PADA PT. UNITED STEEL CENTER MENGGUNAKAN METODE HAZARD IDENTIFICATION, RISK ASSESMENT AND RISK CONTROL (HIRARC)

PT. United Steel Center Indonesia-Karawang is a company engaged in manufacturing that focuses on blanking steel coins for automotive or non-automotive. The TKG and TWB departments were chosen to be the object of research based on data regarding the highest number of work accident incidents in 2021 and there are still manual processes involving humans. The method used is the HIRARC method, a method that combines hazard identification, risk assessment, and risk control to avoid or minimize work accidents. There are 3 problems that occur in the TKG department and 2 problems in the TWB department. Therefore, it is necessary to update the SOP, especially regarding the use of PPE, which replaces the safety hand and safety leg with a universal size so that it can adjust to the size of each employee's hands and feet, adding earmuff PPE for noisy work, wearing a Gas Respirator mask for anti-oiling work. rust, and the use of safety hands during the input welding process.Keywords: HIRARC; Work Accident ;PPE.

Influence of Ti/N Ratio on Inclusions, Microstructures, and Toughness in Heat‐Affected Zone of Shipbuilding Steel Plates with Mg Deoxidation after High Heat Input Welding

The inclusions, microstructures, and toughness in heat‐affected zone (HAZ) of the shipbuilding steel plates with Mg deoxidation and the different Ti/N ratios are studied after the high heat input welding of 400 kJ cm−1. With increasing the Ti/N ratio from 3.00 to 5.67, the average size of inclusions increases, the mass fraction of total TiC inclusions increase from 2.8% to 5.0%, and the average size of MgO–TiN–MnS increases from 2.82 to 5.49 μm, while the number density that can induce intragranular acicular ferrite (IAF) nucleation decreases from 87 to 62 mm−2. These changes in inclusions are detrimental to induce the IAF nucleation. The HAZ microstructures are composed of the IAFs, polygonal ferrites, and upper bainites (UBs). With increasing the Ti/N ratio, the area fraction of the IAFs decreases from 44% to 14%, and the area fraction of UBs increases from 1.8% to 9.5%. The HAZ fracture mode changes from ductile fracture to brittle fracture after the high heat input welding of 400 kJ cm−1, and the HAZ toughness decreases from 183.3 to 48.7 J at −20 °C.