Steel Dissimilar Weld Research Articles

Effect of welding stability on process porosity in laser arc hybrid welding of dissimilar steel

Welding porosity is an important factor affecting the mechanical properties of welded joints. This study investigated the effect of welding stability on weld porosity to solve the problem of welding porosities in laser-arc hybrid welding of dissimilar steels. The type and formation mechanism of welding porosity were analyzed. The study results showed that the porosities generated during the welding process were process welding porosities. The generation of bubbles was closely related to the instability of the steam pressure inside laser keyhole. The droplet transfer form was an essential factor affecting the stability of the laser keyhole. When the droplet was in the projected transfer mode, the weld porosity could be effectively reduced. Penetration weld was also greatly helpful in reducing weld porosity.

Effect of Welding Parameter Conditions of 304L SS and AISI 1015 Dissimilar Steel Weld Joints to Macrostructure and Mechanical Properties

This research is focused on the effect of welding parameter conditions, using Gas Metal Arc Welding, on the macrostructure, mechanical properties, and quality of dissimilar steel weld joints. In this study, the selected joints were low carbon steel (AISI 1015) and austenitic stainless steel (304L SS). The welding current used had three different variations, such as 100, 110, and 120 A. The solid wire electrode used was ER70S6, with a diameter of 1.2 mm. Identification of the macrostructure in the heat-affected zone (HAZ), micro-Vickers hardness, and tensile tests carried out for each GMAW joint specimen. The results were then discussed. The macrostructure of dissimilar steel welded joints at a welding current of 100 A produced a good quality of welded joints and penetration compared to those using welding currents of 110 and 120 A, which had excessive penetration and caused distortion and deformation. The microhardness of the weld metal area was far higher than in other areas. At the current 100 A, the micro-Vickers hardness value of stainless steel 304L SS closing the heat-affected zone (HAZ) had increased from 209 to 226 HV. Likewise, For the welding current of 110 A, the micro-Vickers hardness value rose from 249 to 259 HV, and for the welding current of 120 A, the hardness increased from 225 to 227 HV. In the weld metal area, micro-Vickers hardness for each welding current was 318, 364, and 366 HV, while in the low carbon steel area, the hardness value decreased significantly to 180, 190, and 196 HV. At the current of 100 A, the lowest tensile strength was 359.28 MPa, and yield strength was 303.82 MPa. The tensile strength and yield strength for the current of 110 A were 367.24 MPa and 309.83 MPa, respectively. Meanwhile, at the current of 120A, the tensile strength was at the highest that is 374.86 MPa, and the yield strength value was 315.67 MPa. This study found that the dissimilar steel welded joints experienced an increase in the hardness value of the weld metal, and the tensile test results show that the welded steel joints fractured in the low carbon steel area.

Effect of friction time on heat distribution, material flow, and microstructure of friction welding of dissimilar steels

In this paper, 1045 steel is joined to Q235 steel using continuous drive friction welding. The temperature distribution and material flow during the welding process were analyzed by numerical simulation and the flow behavior was further explained by grain distribution. The microstructure and mechanical properties of the joint were investigated experimentally. The results show that with the increase of friction time, the joint temperature first increases and remains in dynamic equilibrium. The joints were divided into a central region, a 0.5R region, and an edge region along the radial direction. The highest temperature of the joint first appears in the edge region, with a relatively low temperature in the central region. The material flow rate in the edge region is faster than that in the center and 0.5 R regions, and the maximum material flow rate increases and then decreases with increasing friction time. When the friction time is suitable, the heat distribution is uniform and sufficient, and the grains show a better refinement effect, which is beneficial to the improvement of the mechanical properties of the joint. Due to the grain refinement of the joint, the highest microhardness is obtained at the weld zone in all welding conditions. All joints fractured on the Q235 steel base material side, and the fracture form was ductile fracture.

Effect of activated fluxes during welding of dissimilar stainless steels using semi-automatic setup

ABSTRACT In the present work, two dissimilar metals austenitic AISI 304 and 316 stainless steels were welded with duplex 2205 using semi-automatic bi-directional GMAW setup to appraise the microstructural and mechanical behavior of the welded joints. Three different activated fluxes i.e. SiO2, TiO2 and CrO3 were used to enhance the depth of penetration during joining of different stainless steels grades. Various process parameters such as welding current, voltage, filler wire, gas flow rate and activated flux were varied to observe their influences on joint tensile, bending strength, microhardness and microstructural properties. The experiments were designed using mixed level L18 orthogonal array of Taguchi method. Tensile strength was observed to be considerably dependent on the low gas flow rate, whereas welding current and activated flux influenced the toughness. The most significant effect on the bending strength and toughness was experienced with the use of SiO2 activated flux.

Characterization of Microstructure and Mechanical Properties of Cr-Mo Grade P22/P91 Steel Dissimilar Welds for Supercritical Power Plant Application

Characterization of Microstructure and Mechanical Properties of Cr-Mo Grade P22/P91 Steel Dissimilar Welds for Supercritical Power Plant Application

Laser welding-brazing of NiTi/304 stainless steel wires with beam defocus and large offset

The brittleness of dissimilar NiTi-stainless steel (SS) welds caused by intermetallic compounds (IMCs) network limits their application in medical field. Inserting interlayer and special assembly are high-cost but still hard to eradicate the formation of IMCs. This work realized NiTi-SS wire joints with a high strength using laser welding-brazing mode through beam defocus and large offset. The effect of laser beam offset on joint appearance, microstructure, tensile strength and fractography was investigated. In welded-brazed joints, a fusion zone (FZ) of only one base metal formed while multilayered reaction microstructure at the brazed interface was observed. Without beam offset, a typical FZ was dominated by Ni3Ti+Fe2Ti IMCs network. The tensile strength was improved from 176.6 MPa of conventional welding mode without offset to 329.5 MPa of welding-brazing mode with 0.4-mm offset to SS side. The joint welded with large offset fractured at the brazed interface with a mixed ductile-brittle fracture; while brittle fracture inside the IMCs network of FZ was observed in the joint welded without beam offset. The enhancement of joint strength was attributed to the eradication of IMCs network in the FZ and a reaction layer with less Ti–Fe brittle IMCs. This welding-brazing mode can be applied to suppress the overall brittleness of NiTi-SS joints without using any interlayer.

Tehnologija zavarivanja čeličnog liva G18CrMo4+QT sa konstrukcionim čelikom S355J2+N

Welding technology of cast steel G18CrMo4+QT with structural steel S355J2+N is a welding of dissimilar steels. The problem of welding cast iron G18CrMo4+QT is the phenomenon of hardening of the structure due to the presence of unreleased martensite, which results in lower toughness and the formation of cold cracks. On the other hand, structural steel S355J2+N, depending on the thickness of the material, is also prone to the appearance of cold cracks. In order to prevent the formation of cracks and eliminate residuals stresses, it is necessary to perform preheating and heat treatment after welding. The paper presents welding technologies and subsequent heat treatment of G18CrMo4+QT cast iron joint with S355J2 + N structural steel with presentation of test results performed on a 12 mm thick welded sample, with V preparation of the joint, welded by MAG process in PA welding position.

Effect of Grade 5 titanium interlayer on microstructure and pitting corrosion behaviour of AA1100/A36 explosion welds

Explosion welding is a solid-state welding process that is used for the metallurgical joining of similar and dissimilar combinations of metals and alloys with varying physical and mechanical properties. In this process the metal surfaces are brought into sufficiently close contact, the valence electrons overcome the repulsive forces and result in sharing of their orbits. In recent years ocean acidification is the main problem due to a variety of pollutants. In naval applications A36 steel is used for making ship hulls that are very poor in corrosion. The present study is aimed to improve the corrosion resistance of the A36 steel by cladding aluminium alloy (AA110) using the explosion welding technique. Grade 5 titanium alloy has been used as an inter-layer between AA110 and A36 plates. The presence of Ti-6Al-4V inter-layer facilitated good bonding between aluminium and steel dissimilar weld joint with smooth bond line. The microhardness values were measured at various points start from the weld interface and towards both base metal regions. Higher hardness values were observed in the bond region and the Inter-layer regions, owing to the inherent higher hardness of Titanium and the formation of Martensitic structure near the bond region, as a result of higher and sudden impact energies. Potentiodynamic polarization tests were made in 3.5% NaCl solution. Corrosion resistance in AA1100 is higher than A36. All the observed results were correlated with microstructural features as evidenced by SEM studies.

Fracture morphology of GTAW welding of dissimilar duplex stainless steels exposed to H2S corrosion

Fracture morphology of GTAW welding of dissimilar duplex stainless steels exposed to H2S corrosion

Comparative Research of Microstructure and Mechanical Properties of Stainless and Structural Steel Dissimilar Welds.

The present study utilized a metal inert gas welding (MIG) to make a dissimilar weld of stainless steel AISI 304, 314, 316L, 420 grades and a standard structural steel S355MC. It refers to a weld joining two materials from different alloy systems commonly used in heat exchangers, pressure vessels, and power plant systems. Obviously, maintaining the integrity of such welds is of paramount importance to the safety issues. Therefore, detailed microscopic and experimental studies were performed to evaluate the reliability of these welds. The microscopic analysis did not reveal any presence of weld defects such as porosity or cracks, which ensured that MIG process parameters were properly selected. The performance of dissimilar welds was assessed by hardness and tensile tests. The hardness profiles revealed differences between austenitic and martensitic steel welds that later showed extremely high values in the heat-affected zone (HAZ), which caused fractures in this zone during tensile test. The welds of all austenitic steel grades withstood the tensile test, showing an average tensile strength of 472 MPa with fractures observed in the base metal zone. It made clear that the use of a filler rod 308LSI is suitable only for the austenitic stainless and structural steel dissimilar welds and not appropriate for martensitic-structural steel welds. The achieved results revealed that the higher hardness of the martensitic phase in the HAZ of AISI 420 is closely related with the formation of untempered coarse martensitic structure and higher carbon content.

Experimental investigation on microstructure, mechanical properties, and residual stresses of dissimilar welded joint of martensitic P92 and AISI 304L austenitic stainless steel

In this study, microstructural characteristics and mechanical properties of martensitic steel P92 and AISI 304L austenitic stainless steel (ASS) dissimilar metal weld (DMW) have been examined. The welding was performed using the multipass gas tungsten arc welding (GTAW) process. The ERNiCrMo-3 (Inconel 625) filler metal was used due to its excellent compatibility with the P92 and AISI 304L ASS metals. The microstructure characterization performed with an optical microscope and scanning electron microscope revealed the presence of an unmixed zone in the form of beach, peninsula, and island at the base metal and weld fusion zone interface. Secondary phases enriched with Nb and Mo, and migrated grain boundaries (MGBs) were also observed at the weld fusion zone. The microstructural characterization at the P92 side revealed the presence of a soft ferrite zone and delta ferrite at the weld and P92 interface. The different peak temperature experienced by the P92 metal during the welding process results into the formation of three distinct zones with diverse mechanical and microstructural properties namely coarse grain heat affected zone (CGHAZ), fine grain heat affected zone (FGHAZ), and inter-critical heat affected zone (ICHAZ). The post weld heat treatment (PWHT) at 760 °C for 2 h followed by air cooling was performed to homogenize this heterogeneous microstructure formed toward the P92 side. It was observed that this PWHT does not have any significant effect on weld fusion zone and 304L SS heat affected zone (HAZ) microstructure. But, PWHT modifies the microstructure of P92 side HAZ. The tensile test, Vickers micro-hardness test, and charpy impact test were carried out to determine the mechanical properties of the DMW. The tensile strength was found as 587.709 MPa in the as-welded condition and 594.515 MPa in PWHT condition. The tensile test results indicated that specimens were failed from 304L stainless steel (SS) base metal (BM) in as-welded and PWHT condition. The charpy impact toughness test results showed that the toughness of the weld joint was very low in as-welded and PWHT condition (47J) compared to the P92 (190J) and SS 304L (285J) BM. From the microhardness examination, it was observed that the ICHAZ was the weakest zone among all the other regions due to its lower micro-hardness value compared to the other regions. After welding process, residual stresses were measured in as-welded and after PWHT condition at the center of the weld and at the HAZ of P92 and SS 304L (through the thickness of the plate) using experimental-based deep hole-drilling (DHD) strain-gauge method. The results showed that both circumferential (hoop stress) and axial (longitudinal stress) welding residual stresses were decreased after PWHT.

Evaluation of bond interface characteristics of rotary friction welded carbon steel to low alloy steel pipe joints

In the present investigation, rotary friction weld joints were prepared between carbon steel and low alloy steel pipes. These types of similar and dissimilar configurations are in general, used for drill pipe joining. Low alloy steel for the friction welding in dissimilar configurations were used in two different microstructure state; a) as-received and b) quenched and tempered. The friction weld joints showed three distinct weld microstructure characteristics; a) radial plastic flow, b) axial plastic flow and, c) partial heat affected zone, for joining configurations. In general, microstructure characterization revealed grain size refinement and carbide precipitation in the vicinity of bond interface for all types of similar and dissimilar steel joining conditions. A characteristic bond layer width of ~2 μm was developed between the dissimilar steel weld joints whereas it was found to be absent for the similar weld joints. These weld joints were evaluated for their mechanical properties by using conventional tensile tests and furthermore by automated ball indentation technique. The study has also shown that in the case of dissimilar steel joints the mechanical properties of the bond interface can be obtained aptly by using an automated ball indentation technique. The quench and temper treatment given to the low alloy steel resulted in the improved bond interface strength. The improvement of the mechanical properties of the weld joints was attributed to the synergistic effect of grain size refinement and tempered martensite microstructure.

INVESTIGATION OF THE MUTUAL INFLUENCE OF WELDING TECHNOLOGY AND HEAT TREATMENT OF WELDED JOINTS MADE OF DISSIMILAR GRADES OF STEEL

The work is devoted to the study of welding and heat treatment modes of dissimilar steels: low-alloyed manganese-silicon and heat-resistant chromium-molybdenum to ensure the strength of the welded joint in accordance with the requirements of the current NTD. To achieve this goal, special welding processes were developed, which consist in changing the geometry of the preparation of the edges of the welded joints and tightening the tolerance for the temperature limits of heat treatment. The presented measures make it possible to ensure the mechanical and operational properties of welded joints at the required level.

Application of Artificial Neural Networks in Predicting Output Parameters of Gas Metal Arc Welding of Dissimilar Steels

Application of Artificial Neural Networks in Predicting Output Parameters of Gas Metal Arc Welding of Dissimilar Steels

Wire-feed assisted A-TIG welding of dissimilar steels

This study investigates the activated flux-tungsten inert gas welding (A-TIG) welding of dissimilar P92 steel-304H ASS using ‘wire feed’ (patent pending) in terms of weld pool mixing behavior, microstructure and mechanical properties of the weld joint. ErNiCrMo-3 wire was fed during welding and three-wire feeding configurations were analyzed in view of filler wire melting and weld pool mixing behavior. The metal from filler wire is transferred into the weld pool in the form of ‘interrupted liquid bridge’ and ‘uninterrupted liquid bridge.’ The ‘uninterrupted liquid bridge’ melting resulted in homogeneous mixing of filler wire into the weld pool. The weld joint produced using the best wire feeding configuration was characterized and compared with the weld joint developed without wire feed. Microstructure alterations were realized with the use of wire feed. The weld zone with wire feed exhibited a fully austenitic structure, whereas; the completely martensitic structure was obtained using A-TIG welding without wire feed. The microstructural transformation led to the improvement of ductility and impact toughness of weld joint without substantial loss of tensile strength. The total elongation and impact toughness of the A-TIG weld joint with wire feed was 45.9% and (89 ± 2) J, respectively, which were significantly higher in contrast to the A-TIG weld joint without wire feed [total elongation: 37.4% and impact toughness: (30 ± 2) J].

Effects of welding technique, filler metal and post-weld heat treatment on stainless steel and mild steel dissimilar welding joint

Joining of two materials having different physical, chemical, and thermal properties and to make the joint tough and stiff, special attention and investigation are required. In this research, the welding joint between stainless steel (SS) of grade AISI 304 and mild steel (MS) of grade AISI 1020, was accomplished by using shielded metal arc welding (SMAW) and tungsten inert gas (TIG) welding process. To investigate the effect of filler material in the dissimilar welding joint, both MS and SS filler material was exercised. For post-weld heat treatment (PWHT), three distinct temperatures of 600 °C, 630 °C, and 650 °C were investigated over the welded specimens. To explore the optimum welding process and PWHT process for this dissimilar joint, both tensile and bending tests were carried out. Destructive tests have suggested that PWHT at 630 °C is better for the SMAW process with both MS and SS electrodes and PWHT at 600 °C is more suitable for TIG welding process with both MS and SS filler rod. Both optical and SEM micrographs showed that the amount of δ ferrite and martensite is higher in the as-welded situation. The coarser grain structure was observed in the heat-affected zone (HAZ) which makes the sample susceptible to failure. This is the region where the hardness values were the smallest. The hardness values have decreased after PWHT which justified the achievement of higher ductility after heat treatment. After conducting fracture analysis by SEM, it has been noticed the specimen becomes more ductile after PWHT. The best solution based on the mechanical, microstructural, and fracture analysis concluded that TIG welding with MS filler rod and PWHT at 600 °C is the optimum condition for joining SS AISI 304 with MS AISI 1020.

Semi in-situ local structure observation during PWHT of Cr–Mo weldments extent of the PWHT on local structure changes in heat affected zone microstructure

Soft zone formation in dissimilar Cr–Mo welding occurs during post weld heat treatment that could compromise the integrity of the weldment. The decomposition of martensite could cause this formation at the weld heat affected zone adjacent to the fusion boundary. There could not yet determine the actual width of this zone. The extent of martensite decomposition in soft zone Cr–Mo steel dissimilar weld was observed in semi in-situ stages using the x-ray absorption spectroscopy (XAS) at Synchrotron facility. 2.25Cr–1Mo was welded using ER90S–B9 using GTAW process. PWHT was performed at 730 °C for 0.5 h and 2.0 h in a chamber with opening for Synchrotron light analysis at various locations away from the fusion boundary. This was complemented by microstructure and grain size analysis. The results showed the decomposition of martensite started at the fusion boundary and could extend beyond 1000 microns covering both CGHAZ and FGHAZ. Since the experiment was performed in normal atmosphere, the oxide film could form during PWHT on the surface of the specimen. More oxide formed was observed more in the location with high carbide contents. There was more oxide formation at the locations further distance from fusion boundary due to less martensite decomposition. Therefore, the extent of the phenomena could be stated by using information from oxide formation and martensite decomposition which could help to determine the risk on both creep life and oxidation.

Insights into the microstructure evolution and crystallographic texture of API X-65 steel/UNS S32750 stainless steel dissimilar welds by EBSD analysis

In this study, the microstructural features and microtexture evolution of API X-65 steel welded to UNS S32750 stainless steel were evaluated. The weldments were produced with the different heat input (HI) values: 0.68 and 0.78 kJ/mm. The samples were then characterized by means of the electron backscatter diffraction analysis. The obtained results showed that the microtexture components formed in the UNS S32750 heat-affected zones (HAZs) and the UNS S32750 base metal were the same. However, the microtexture of the API X-65 HAZs was significantly affected by the HI values in comparison to that of the API X-65 parent metal. A random orientation of grains and also a non-uniform distribution of both austenite and ferrite phases were observed in the weld zones. It was revealed that with decreasing the HI value, the austenite’s fractions decreased; hence, almost equal fractions of austenite and ferrite phases were formed in the weldment employing the HI value of 0.68 kJ/mm. It was inferred that the kernel average misorientation and fractions of the especial boundaries were not influenced by the changes in the HI values. Moreover, it was observed that the weld metals showed slightly better impact resistance in comparison to the base metals.

Microstructural characterization of low alloy steel A508 – 309/308L stainless steel dissimilar weld metals

In this study, the microstructure and microhardness of low alloy steel A508 welded with 309/308L stainless steel are investigated. The microstructure evaluations show that the heat affected zone of the A508 base metal changes, from tempered bainite to an uneven mixture of bainite and martensite, depending on the intensity of the heat flow from the welding process. Different recrystallization processes at the heat affected zone of the base metal are responsible for the changes of the microstructure, which lead to differences in the grain sizes, strain level, and yield strength in this region. The greatest deformation level is observed in the grain refined region with the highest heat influx, which leads to a high level of grain refinement and stress in this region, followed by the partial grain refined region and base metal matrix region, respectively. The interface region between the base metal and weld metal is observed to be very complex. At some regions of the 309/308L, adjacent to the fusion boundary type II boundaries, resulting from the allotropic δ – γ transformation and migration of steel phases/boundary at high temperature of welding were observed, alongside the type I boundaries. The 309/308L stainless steel consists of vermicular ferrite distributed along the austenite matrix, while ternary sigma secondary phase was observed to precipitate at the interface of the ferrite/austenite boundary. The yield strength of the grain refined region, partial grain refined region, and base metal matrix in A508 were estimated to be 598 MPa, 600 MPa, and 595 MPa, respectively. Finally, the heat affected zone of the base metal showed the highest hardness followed by the base metal matrix and weld metal, respectively.

Research on the Relationship between Carbon Precipitation and Mechanical Properties of Dissimilar Steel Welds

After the room temperature tensile test of the pearlite heat-resistant steel and austenitic stainless steel welds after operation, it was found that 75% of the fracture locations were on the austenite side weld line and 25% of the fracture locations were on the austenite side. The maximum tensile strength of the pipe wall under the operating temperature of 530°C and 540°C is 480 MPa and 580 MPa, respectively. Metallographic examination found that there was a “uphill diffusion” near the weld. Through theoretical calculations, after 90,000 hours of operation, on the austenite side of the weld, the difference in carbon increase in the “uphill diffusion” per unit area under the two conditions is about 1.3833E + 8. Based on the analysis of the relationship between the difference in carbon increment and the mechanical properties, it can be deduced that the dissimilar steel weld of this type of screen superheater tube can continue to serve for about 25,000 hours.