Optimizing impact toughness in Q1100E steel welds via laser-arc hybrid welding energy ratio control

Hybrid welding is receiving considerable attention and is used in practical lines. And so YAG laser and MIG arc hybrid welding was performed on A5052 aluminum alloy plate to understand the mechanism of penetration and reduced welding defects as well as to investigate the effect of welding direction on the weld penetration and porosity formation level.In the case of YAG-MIG (laser-head-leading) hybrid welding, the surfaces of weld beads were by far prettier than MIG-YAG hybrid welding. The optimum distances between the laser-focused point and the MIG wire target for deeper penetration were about 2 to 4 mm, and the reason was interpreted in terms of the interaction of a laser beam to droplet, molten pool or solid plate. The penetration increased but porosity was reduced with the increase in MIG arc current. These reasons were attributed to the formation of a concave molten pool surface due to high arc pressure at a high current.In the case of MIG-YAG (MIG-nozzle-leading) hybrid welding, deeper welds were formed especially at high laser power than those made by YAG-MIG hybrid welding. However, a large amount of porosity was formed in the case of the laser beam shot perpendicularly. Such porosity was reduced by declining a laser beam just like the forehand welding, and sound deep weld beads could be produced in MIG-YAG hybrid welding. According to X-ray transmission in-situ observation, these results were interpreted by considering the formation of the wider top inlet of a keyhole produced with a YAG laser to consequently suppress the generation of bubbles. The surface of a MIG-YAG hybrid weld could be cleaned by cleaning action with DCEP-TIG heat source.Hybrid welding is receiving considerable attention and is used in practical lines. And so YAG laser and MIG arc hybrid welding was performed on A5052 aluminum alloy plate to understand the mechanism of penetration and reduced welding defects as well as to investigate the effect of welding direction on the weld penetration and porosity formation level.In the case of YAG-MIG (laser-head-leading) hybrid welding, the surfaces of weld beads were by far prettier than MIG-YAG hybrid welding. The optimum distances between the laser-focused point and the MIG wire target for deeper penetration were about 2 to 4 mm, and the reason was interpreted in terms of the interaction of a laser beam to droplet, molten pool or solid plate. The penetration increased but porosity was reduced with the increase in MIG arc current. These reasons were attributed to the formation of a concave molten pool surface due to high arc pressure at a high current.In the case of MIG-YAG (MIG-nozzle-leading) hybrid welding, deeper welds were fo...

Comparison of the welding deformation of mismatch and normal butt joints produced by laser-arc hybrid welding

In thick section laser welding, filler metal addition is usually required to improve joint fit-up tolerances or to control the chemical composition of the weld metal. With deep and narrow welds produced using an over-alloyed filler metal, it may be challenging to ensure that the filler metal and its elements are homogeneously mixed and evenly distributed throughout the fusion zone. Inhomogeneous filler metal mixing can cause unfavourable changes to weld metal chemistry and microstructure. Filler metal mixing behaviour in laser-arc hybrid and laser cold-wire welding is studied in this work. Welding tests were conducted on 10 mm thick butt-welded joints of AISI 316L austenitic stainless steel. An overmatching type 2205 duplex stainless steel filler wire was used to obtain a composition contrast between the base metal and filler metal. Energy dispersive spectroscopy (EDS) with chromium as the trace element was used for element mapping and stepwise characterization of the weld cross-section samples. Optical metallography was used to observe possible inhomogeneous filler metal mixing behaviour like local acute changes in macro- and microstructural features. The results showed a clear difference in filler metal mixing between the weld surface part (upper half) of the weld and the weld root part (lower half) in 10 mm thick welded cross-sections for closed root gap of I-groove welds or when the gap was only 0.4 mm. In narrow I-groove preparations, inhomogeneous mixing phenomena were more pronounced in laser cold-wire welds than in laser-arc hybrid welds. In both welding processes, a combination of trailing wire feeding and the use of a wider groove enabled filler metal to be introduced deeper into the bottom of the groove and improved mixing in the root portion of the welds.

Fiber laser and gas metal arc hybrid welding of 440-MPa-grade high-strength marine steel was carried out at different welding speeds. The influence of welding speed on the microstructure and mechanical properties of weld metal was investigated. The weld-metal microstructure mainly consisted of pre-eutectoid ferrite, side-plate ferrite, acicular ferrite and lath bainite at a low welding speed. With the increase in welding speed, acicular ferrite and lath bainite were the dominant weld-metal microstructures. All samples failed at the base metal during tensile tests, which indicates that there is no soft zone in the hybrid welds. The welding speed had a significant effect on the impact toughness of the weld metal. The impact absorbed energy of the weld metal increased from 35 to 105 J with the increase in welding speed from 0.8 to 2.0 m/min. Large amounts of acicular ferrite and lath bainite were formed in the weld metal at a high welding speed, which resulted in an excellent impact toughness.

This study delves into the impact toughness of medium-thick (12 mm thick) titanium alloy joints crafted through a multi-layer, multi-pass welding technique that blends laser-arc (MIG) hybrid welding technology. Microstructural scrutiny, employing optical microscopy, SEM and TEM, unveils a consistent composition across weld passes, with prevailing α/α′ phases interspersed with some β phase, resulting in basket-weave structures primarily dominated by acicular α′ martensite. However, upper regions exhibit Widmanstatten microstructures, potentially undermining joint toughness. Hardness testing indicates higher values in cosmetic layers (~420 HV) compared to backing layers and bending tests manifest superior toughness in lower joint regions, attributed to smaller grain sizes induced by repetitive welding thermal cycles. Impact toughness assessment unveils diminished values in the weld metal (WM) compared to the heat-affected zone (HAZ) and base material (BM), amounting to 91.3% of the base metal’s absorption energy. This decrement is ascribed to heightened porosity in upper regions and variations in grain size and phase composition due to multi-layer, multi-pass welding. Microstructural analysis proximal to failure sites suggests one mechanism wherein crack propagation is impeded by the β phase at acute crack angles. In essence, this study not only underscores the practicality of laser-MIG hybrid welding for medium-thick TC4 alloy plates but also underscores the reliability of joint mechanical properties.

Microstructures and mechanical properties for welded joints of API X70 grade steel, using LAHW(Laser-Arc Hybrid Welding) with the combination of 2kW laser power and 1.2kW GMAW power, were investigated and compared with those of SAW(submerged arc welding) joints. In the hybrid welding experiments, the deepest penetration was obtained when the distance between laser and arc was 6.5mm. The microstructure of LAHW joint exhibited more finer than that of SAW joint. Impact absorbed energy of CGHAZ and weld deposit in the LAHW joint were 55.3J and 45.3J of minimum value at - 20 °C, respectively. The low carbon TMCP type steel used for both LAHW and SAW showed softening behaviour in the HAZ adjacent to base metal, which was known to be closely related with the SOHIC(stress oriented hydrogen induced cracking). Comparing hardness on ICHAZ, softening ratio of ICHAZ/base metal in the LAHW was measured as 0.94 which was higher than the ratio of 0.86 in SAW. By suppressing softening in the ICHAZ region, the SSCC resistance of low carbon TMCP steel welded joints could be improved.Microstructures and mechanical properties for welded joints of API X70 grade steel, using LAHW(Laser-Arc Hybrid Welding) with the combination of 2kW laser power and 1.2kW GMAW power, were investigated and compared with those of SAW(submerged arc welding) joints. In the hybrid welding experiments, the deepest penetration was obtained when the distance between laser and arc was 6.5mm. The microstructure of LAHW joint exhibited more finer than that of SAW joint. Impact absorbed energy of CGHAZ and weld deposit in the LAHW joint were 55.3J and 45.3J of minimum value at - 20 °C, respectively. The low carbon TMCP type steel used for both LAHW and SAW showed softening behaviour in the HAZ adjacent to base metal, which was known to be closely related with the SOHIC(stress oriented hydrogen induced cracking). Comparing hardness on ICHAZ, softening ratio of ICHAZ/base metal in the LAHW was measured as 0.94 which was higher than the ratio of 0.86 in SAW. By suppressing softening in the ICHAZ region, the SSCC resista...

Part 1 Characteristics of hybrid laser-arc welding: Advantages and disadvantages of arc and laser welding Fundamentals of hybrid laser-arc welding Heat sources of hybrid laser-arc welding processes Effect of shielding gas on hybrid laser-arc welding Properties of joints produced by hybrid laser-arc welding Quality control and assessing weld quality in hybrid laser-arc welding. Part 2 Applications of hybrid laser-arc welding: Hybrid welding of magnesium alloys Shipbuilding applications of hybrid laser-arc welding Industrial robotic application of laser-GMAW and laser-Tandem hybrid welding Hybrid laser-arc welding of aluminium Hybrid laser-arc welding of dissimilar metals. Part 3 Hybrid laser-arc welding of steel: Hybrid laser-arc welding of steel.

A laser beam is still a relatively expensive energy source. Therefore, hybrid processes are getting more and more popular. The word “hybrid” is derived from the Latin and means “mixing or putting things together from different sources”. The laser hybrid welding and cladding process describes the combination of the laser process and a conventional process to a new one. The first laser hybrid process was the laser oxygen cutting which is a combination of laser energy and a chemical energy coming from an exothermal reaction of the oxygen with the heated steel. The first known laser hybrid welding process was an arc process stabilized by a laser (M. Eboo et. al. 1978); the first laser welding process supported by or combined with an arc jet was presented by E. Beyer et. al. at the ICALEO Conference in 1994. Since that time different papers in laser arc and laser plasma hybrid welding have been presented by Fraunhofer followed by laser induction welding and cladding process. This process has been running in production for years now.The latest laser hybrid processes are the combination of CO2, Nd:YAG lasers or diode lasers and plasma spraying or plasma cladding. These processes were first presented at the Diode Laser Workshop in Dresden in 1999. The Fraunhofer-Gesellschaft took out patents on these processes as well.The interest in hybrid process technologies is demonstrated in the high number of papers presented e. at WLT-Conference “Lasers in Manufacturing” in Munich and at the past years’ ICALEO Conferences [1 - 12].A laser beam is still a relatively expensive energy source. Therefore, hybrid processes are getting more and more popular. The word “hybrid” is derived from the Latin and means “mixing or putting things together from different sources”. The laser hybrid welding and cladding process describes the combination of the laser process and a conventional process to a new one. The first laser hybrid process was the laser oxygen cutting which is a combination of laser energy and a chemical energy coming from an exothermal reaction of the oxygen with the heated steel. The first known laser hybrid welding process was an arc process stabilized by a laser (M. Eboo et. al. 1978); the first laser welding process supported by or combined with an arc jet was presented by E. Beyer et. al. at the ICALEO Conference in 1994. Since that time different papers in laser arc and laser plasma hybrid welding have been presented by Fraunhofer followed by laser induction welding and cladding process. This process has been running in pr...

In this paper, after a brief overview on principle, properties and applications of laser arc hybrid welding, a few topics from current research are given a closer look. These topics include basic research into the interactions between laser beam and arc as well as applied research into new hybrid welding processes and applications. As an example for the latter, laser GMA hybrid welding with good gap bridging in the thin sheet range using a single-mode fibre laser is presented. Moreover, results from an extended study into laser GMA hybrid welding of aluminium to steel are reported. It is concluded that - although interesting applications have already been implemented - there still remain lots of open questions and unexplored, challenging applications in stock for hybrid welding.

Comparisons of laser and laser-arc hybrid welded carbon steel with beam oscillation

Laser-arc hybrid welding heat source has high energy density, and the temperature field is very uneven and unstable. It is impossible to systematically study the welding temperature field only through process tests. For this reason, the calculation of the thermal process of hybrid welding is of great significance to the systematic study of the temperature field of hybrid welding. In this paper, the laser-arc hybrid welding process of 8mm thick austenitic stainless steel was simulated by SYSWELD software. The results indicate that with the increase of laser energy, the melting time increases, and the peak temperature rises from 1,230°C to about 2,000°C; When the laser energy is 3.0 kW, the welding deformation reaches the minimum value of 0.68 mm, but the peak value of equivalent stress is high, which is 476.8193 MPa. When the arc voltage increases, the peak temperature rises from 1,650°C to 1,850°C, and the melting time increases. The arc voltage has little effect on the equivalent stress of the weld and has a clear impact on the welding deformation. When the voltage is 18 V, the maximum deformation reaches 2.191 mm.

Role of arc mode in laser-metal active gas arc hybrid welding of mild steel

Hybrid welding was carried out on Type 304 stainless steel plate under various conditions using a YAG laser combined with a TIG arc, and the effects of various welding conditions on the penetration and porosity formation were investigated for respective arrangements of a YAG laser beam or TIG torch ahead in hybrid welding, and the welding results were compared with the ones obtained with a TIG arc only or a YAG laser alone. In most cases the hybrid weld beads were deeper and wider in comparison with the YAG laser ones; however, this fact did not always take place. It was consequently found that a laser beam should be shot inside the molten pool made readily with a TIG arc alone to produce deeper weld beads effectively. It was also confirmed that, under the focused condition, the hybrid weld beads at the arc current of 200 A had a smaller amount of porosity than the YAG laser ones. The behavior of arc plasma and laser-induced plume as well as the relationship between a laser-shot spot and the molten pool made with TIG arc only was observed through a CCD camera and a high-speed camera during arc and hybrid welding to understand the hybrid welding phenomena and factors affecting penetration.

Recently laser arc hybrid process is actively researched as a new heat source of welding. Laser arc hybrid welding is combination of laser characterized by the high energy density and electric arc characterized by the high energy efficiency. Metal is vaporized by irradiation of high power laser and this laser induced metal vapor makes path of electron because it has lower ionization energy than argon. Therefore the laser irradiation affects on temperature distribution of arc plasma. In this paper, measurement method of temperature of laser arc hybrid welding plasma is introduced and the effect of laser on the arc plasma is observed. For real-time measurement intensity distribution of plasma is obtained by CCD and abel inversion is accomplished for conversion from two dimensional data to three dimensional one. As a result of observation, plasma is concentrated by the laser and high temperature region is generated above the laser irradiated area.Recently laser arc hybrid process is actively researched as a new heat source of welding. Laser arc hybrid welding is combination of laser characterized by the high energy density and electric arc characterized by the high energy efficiency. Metal is vaporized by irradiation of high power laser and this laser induced metal vapor makes path of electron because it has lower ionization energy than argon. Therefore the laser irradiation affects on temperature distribution of arc plasma. In this paper, measurement method of temperature of laser arc hybrid welding plasma is introduced and the effect of laser on the arc plasma is observed. For real-time measurement intensity distribution of plasma is obtained by CCD and abel inversion is accomplished for conversion from two dimensional data to three dimensional one. As a result of observation, plasma is concentrated by the laser and high temperature region is generated above the laser irradiated area.

The interaction between laser and arc plasma is a central issue in laser-arc hybrid welding. We report a new interaction phenomenon called laser destabilizing arc dynamics in kilowatt fiber laser-TIG hybrid welding of 316L stainless steel. We found the laser action significantly oscillates the arc tail with a 1–3 kHz high frequency. Direct numerical simulation demonstrates that the destabilization mechanism is due to the high-speed oscillated metal vapor ejecting from the mesoscopic keyhole. More interestingly, the high-speed metal vapor could contrict the arc plasma by physical shielding. This provides a fundamentally different explanation from the generally adopted metal vapor ionization theory for laser constrict arc plasma phenomenon. Also, the results substantiate that the arc plasma cannot easily enter into the keyhole because of the violent metal vapor.