André Springer

Laser-GMA hybrid welding of API 5L X70 with 23 mm plate thickness using 16 kW disk laser and two GMA welding power sources

Hybrid processes have been established for the joining of thick plates. The presented approach enables single side welding of thick metal plates by combining a laser beam and two gas metal arc (GMA) welding torches in one setup. By using this hybrid process for joining high material thicknesses, manufacturing time can be significantly reduced in comparison to conventional multilayer arc welding processes. Additionally, new joint designs can be used to reduce filler metal consumption. In order to benefit from these economic advantages, and to make use of brilliant high power lasers in pipeline manufacturing, this hybrid process needs to run robustly for common gap and tolerance ranges. The process time, compared to conventional methods, will be significantly decreased, due to the use of disk lasers with a maximum output power of 16 kW combined with two high power GMA subprocesses. For process development, American Petroleum Institute (API) 5L X70 pipeline steel plates with a thickness of 23 mm have already...

Laser soldering and brazing of steel-aluminum sheets for tailored hybrid tubes

Lightweight construction plays an important role in meeting the increasing demands of the automotive industry regarding weight reduction. In this work, two approaches have been chosen: weight reduction based on material and weight reduction based on design. Steel and aluminum are used for the first approach, and hydroforming is the method used for design optimization by shaping. Mixed material seams of steel and aluminum have been generated using laser soldering and laser brazing to make steel-aluminum tailored hybrid tubes for hydroforming. The seam has to provide sufficient formability and strength. The main difficulty in joining steel and aluminum is the formation of intermetallic phases, and these hard and brittle phases have to be avoided to ensure good forming properties. Pyrometric temperature detection for power control and longitudinal beam oscillation can provide an appropriate temperature-time profile to reduce the heat input, and consequently the intermetallic phases. Tests have been performed...

Investigations on remote laser beam welding of dissimilar joints of aluminum alloys and steel with varying sheet thicknesses for car body construction

For lightweight construction, different steel and aluminum materials with various thicknesses can be welded together, depending on the dimensions and the individual functions of the workpiece. Specifically for frame and body construction, remote laser beam welding has been established as a suitable and efficient joining method for similar material seams for several years. In contrast to joining similar materials, thermal joining of steel and aluminum alloys includes different technological challenges due to the formation of hard and brittle intermetallic phases, which decreases the strength and the formability of the dissimilar joints. In the context of these requirements, the presented results show, besides the influence of different steel materials, particularly the influence of different sheet thicknesses and thickness ratios on the appropriate process parameters for remote laser beam welded lap joints of steel and aluminum alloys, respectively. Different thickness ratios, process parameters, and material properties affect the geometrical formation of the weld seam regarding penetration depth tE and weld width b, which mainly influences the composition of the molten bath and accordingly the transmittable forces. Within the scope of the presented investigations, dissimilar joints of the steel materials such as HX220LAD+Z100, 22MnB5+AS150, and 1.4301 as well as the aluminum alloy such as AA6016-T4 are characterized. Among others, the influences of the energy per unit length, material grade, and sheet thickness ratio on the achievable strengths were analyzed. The characterization of the dissimilar joints includes tensile shear tests and metallographic analyses, depending on the energy per unit length.For lightweight construction, different steel and aluminum materials with various thicknesses can be welded together, depending on the dimensions and the individual functions of the workpiece. Specifically for frame and body construction, remote laser beam welding has been established as a suitable and efficient joining method for similar material seams for several years. In contrast to joining similar materials, thermal joining of steel and aluminum alloys includes different technological challenges due to the formation of hard and brittle intermetallic phases, which decreases the strength and the formability of the dissimilar joints. In the context of these requirements, the presented results show, besides the influence of different steel materials, particularly the influence of different sheet thicknesses and thickness ratios on the appropriate process parameters for remote laser beam welded lap joints of steel and aluminum alloys, respectively. Different thickness ratios, process parameters, and mater...

Laser welding of fully austenitic twinning induced plasticity (twip) steels

One of the key disciplines in today’s automotive engineering is the ever-increasing need to design lighter cars in combination with an increased crash performance. With this end in view, the use of conventional steel grades often leads to a compromise between weight and safety. In other words, designing with conventional steel grades has almost reached its limit.Fortunately, a recently introduced class of so called “twinning induced plasticity” (TWIP) steels offers promising mechanical properties, namely high tensile strength as well as high ductility. These steels can be used for complex sheet metal geometries, and they have advanced crash performance and are low weight at the same time.Nevertheless, studies have revealed limited weldability of TWIP steels, with regard to quality requirements. This is especially true for spot and inert gas welding techniques: the material characteristics can lead to hot cracking in the seams, and distortion of the workpiece [1, 2].As only little data on laser beam welding of novel TWIP steels is available, it is the task of the present study to give an overview of the laser weldability of TWIP steels.One of the key disciplines in today’s automotive engineering is the ever-increasing need to design lighter cars in combination with an increased crash performance. With this end in view, the use of conventional steel grades often leads to a compromise between weight and safety. In other words, designing with conventional steel grades has almost reached its limit.Fortunately, a recently introduced class of so called “twinning induced plasticity” (TWIP) steels offers promising mechanical properties, namely high tensile strength as well as high ductility. These steels can be used for complex sheet metal geometries, and they have advanced crash performance and are low weight at the same time.Nevertheless, studies have revealed limited weldability of TWIP steels, with regard to quality requirements. This is especially true for spot and inert gas welding techniques: the material characteristics can lead to hot cracking in the seams, and distortion of the workpiece [1, 2].As only little data on laser beam weldin...

Development of new processes for welding of thermal Al–Cu solar absorbers using diode lasers

Flat-plate solar collectors are favorable devices to generate heat from the energy of the Sun. The central part of a collector, the solar absorber, is a front-coated aluminum sheet with a copper tube fixed on the back side in order to transport heated liquid. Nowadays, the absorber is often fabricated by laser welding with two flashlamp-pumped neodymium-doped yttrium aluminum garnet (Nd:YAG) lasers which provide high peak pulse powers. A disadvantage of this procedure is the high electrical energy consumption. Research on new laser welding processes is aimed to reduce the amount of energy required. Diode lasers allow processing with higher efficiency, due to a better absorption behavior of the aluminum sheet. Accordingly, two different processes have been developed. The first one, using two laser sources in pulsed mode, is similar to the industrial process, but enables an extension of the spot welds in order to increase the joint strength. In contrast, the second process requires only one laser source to ...

Laser GMA hybrid welding for thick wall applications of pipeline steel with the grade X70

For the joining of heavy plates, hybrid processes have been established. The presented approach of one side welding of thick metal sheets combines a laser beam and two GMA welding torches in one setup. Using this hybrid process for joining high material thicknesses, manufacturing time can be significantly reduced in comparison to conventional multilayer arc welding processes. Additionally, new construction opportunities allow savings of additive materials.In order to benefit from these economic advantages and to make brilliant high power lasers in pipeline manufacturing useful, this hybrid process needs to run robustly for conventional welding practices as well as for common gap and tolerance ranges. The process time, compared to conventional methods, will be significantly decreased due to the use of disc lasers with a maximum output power of 16 kW combined with two high power GMA sub-processes. For the process development, grade X70 steel sheets with a thickness of 23 mm have already been joined in flat position within a single process step over the whole thickness.Based on these parameter studies, the process limitations have been determined with regard to energy input, gap bridgeability, vertical edge offset and a lateral position deviation of the energy sources from the weld gap. The variable applicability and the robustness of the developed hybrid process have already been approved in application oriented processes.For the joining of heavy plates, hybrid processes have been established. The presented approach of one side welding of thick metal sheets combines a laser beam and two GMA welding torches in one setup. Using this hybrid process for joining high material thicknesses, manufacturing time can be significantly reduced in comparison to conventional multilayer arc welding processes. Additionally, new construction opportunities allow savings of additive materials.In order to benefit from these economic advantages and to make brilliant high power lasers in pipeline manufacturing useful, this hybrid process needs to run robustly for conventional welding practices as well as for common gap and tolerance ranges. The process time, compared to conventional methods, will be significantly decreased due to the use of disc lasers with a maximum output power of 16 kW combined with two high power GMA sub-processes. For the process development, grade X70 steel sheets with a thickness of 23 mm have already been joined in flat ...

Investigations on laser welding of dissimilar joints of steel and aluminum using a high-power diode laser

Lightweight construction is currently of high interest, not only for the automotive sector, but also for the maritime industry, due to various benefits. On the one hand, CO2 emissions can be reduced as a result of lower fuel consumption, and on the other hand a higher speed can be achieved, especially for yachts. Hence, hybrid joints of steel and aluminum parts are in great demand for yachts. Presently, these parts are joined using explosive welding adapters, which are complex, time-consuming, and costly to manufacture. For efficient manufacturing of such adapters, a high-power laser welding process is predestined. Aluminum alloy EN AW-6082 (t = 8 mm) and steel S355 (t = 5 mm) are welded in a lap joint configuration using a diode laser with a laser beam power of 10.4 kW. The challenge of welding this dissimilar material combination is the formation of hard and brittle intermetallic compounds within the weld seam, which may lead to cracks and negative effects on mechanical properties of the joint. To meet the required mechanical properties, the mixing ratio of the intermetallic compounds can be limited, as determined in the context of the presented welding process development. Using suitable mixing ratios, the weld seam quality can be increased as shown in metallography analysis, hardness tests, and tensile shear tests. Among other things, the welded samples provide a shear force of approximately 9 kN.Lightweight construction is currently of high interest, not only for the automotive sector, but also for the maritime industry, due to various benefits. On the one hand, CO2 emissions can be reduced as a result of lower fuel consumption, and on the other hand a higher speed can be achieved, especially for yachts. Hence, hybrid joints of steel and aluminum parts are in great demand for yachts. Presently, these parts are joined using explosive welding adapters, which are complex, time-consuming, and costly to manufacture. For efficient manufacturing of such adapters, a high-power laser welding process is predestined. Aluminum alloy EN AW-6082 (t = 8 mm) and steel S355 (t = 5 mm) are welded in a lap joint configuration using a diode laser with a laser beam power of 10.4 kW. The challenge of welding this dissimilar material combination is the formation of hard and brittle intermetallic compounds within the weld seam, which may lead to cracks and negative effects on mechanical properties of the joint. To meet ...

Method for evaluating the behavior of laser welded dissimilar material seams in single overlap configuration under impact loads by the example of twinning induced plasticity steels

Due to increasingly more stringent environmental and safety regulations as well as the globally increasing but locally different customer demands, automanufacturers are in search of measures to meet these requirements. In order to do so, research and development departments particularly focus on sustainable, light weight solutions. Based on material and load adapted design, an economic way of using new materials must be realized. This integral method of construction results in a diversified use of materials in automobiles. Consequently, dissimilar material combinations are increasing in number and importance, including crash-relevant structural parts. Concerning joining technology, light weight design is a challenge, because the ability to join dissimilar material combinations is often accompanied by small tolerance windows for the production process. In other words, minimum variation of process parameters may lead to a significant quality change of the properties of the seam. The present study deals with...

Induction assisted GMA-laser hybrid welding of high-strength fine-grain structural steels

The huge range of application for high-strength fine- grain structural steels is increasing because of the advantages concerning the mechanical properties and welding suitability for this material. Thick sheets up to 10 mm are used e.g. for offshore applications, mobile crane-, concrete pump-, pipeline- and shipbuilding. Conventionally, fine-grain structural steels are joined using arc welding methods in multi-layer processes, and at a comparatively low welding speed. Edge pretreatment time and high consumption of additional materials are typical for arc welding methods. Induction assisted GMA-laser hybrid welding is more efficient because of the advantages in terms of the high welding speed, a reduction of the edge pretreatment with lower flank angles and a smaller heat affected zone (HAZ). In the course of this research, a process has been developed for a single-layer seam for fine- grain structural steels with the grades S700MC, X70 and S690QL in a thickness range from 10 to 15 mm. For this configuration, a reproducible process has been achieved. The high quality welding seams were characterized by metallographic analyses, tensile tests, notched-bar impact tests and hardness tests. In addition, the use of inductive preheating provides advantages regarding the process and the metallurgy. It is possible to increase the welding speed, and to obtain homogeneous mechanical properties around and in the welding seam. A simulation model was developed for both the preheating process and the GMA-laser hybrid welding process, to accompany the experimental research.The huge range of application for high-strength fine- grain structural steels is increasing because of the advantages concerning the mechanical properties and welding suitability for this material. Thick sheets up to 10 mm are used e.g. for offshore applications, mobile crane-, concrete pump-, pipeline- and shipbuilding. Conventionally, fine-grain structural steels are joined using arc welding methods in multi-layer processes, and at a comparatively low welding speed. Edge pretreatment time and high consumption of additional materials are typical for arc welding methods. Induction assisted GMA-laser hybrid welding is more efficient because of the advantages in terms of the high welding speed, a reduction of the edge pretreatment with lower flank angles and a smaller heat affected zone (HAZ). In the course of this research, a process has been developed for a single-layer seam for fine- grain structural steels with the grades S700MC, X70 and S690QL in a thickness range from 10 to 15 mm. For this configurati...

Laser welding of dissimilar low-alloyed steel-steel butt joints and the effects of beam position and ultrasound excitation on the microstructure

There are many different steel grades available for various purposes and applications. For semi-finished workpieces with different, specific local requirements with regard to mechanical or chemical properties, a strong joint between the different steel grades is necessary. Additionally, workpieces subject to forming require a sufficient plasticity in the area of the joint. In thermal welding of different metals, a new alloy always appears in the weld itself. This means, for example, that due to different properties, grain growth and interfaces with graded transitions, and induced negative or restrictive consequences, the tendency for crack initiation may increase. Therefore, heat input and the molten area of the weld have to be kept as small as possible. The main part of the work deals with butt welding of round bars with a diameter of 30 mm made of C22 (1.0402) and 41Cr4 (1.7035). For this application, a laser welding process using a high power disk laser is an appropriate tool. First, a controlled melting ratio can be achieved by varying the beam position relating to the gap. Further, the problem of cracking, due to the inhomogeneous alloy formation in the weld, is countered by the introduction of an ultrasonic vibration into the joining zone. With low amplitudes and a frequency of 18 kHz, the homogeneity and the microstructure formation could be influenced. Therefore, the risk of cracking can be reduced. The impact of this approach is tested using metallographic methods.There are many different steel grades available for various purposes and applications. For semi-finished workpieces with different, specific local requirements with regard to mechanical or chemical properties, a strong joint between the different steel grades is necessary. Additionally, workpieces subject to forming require a sufficient plasticity in the area of the joint. In thermal welding of different metals, a new alloy always appears in the weld itself. This means, for example, that due to different properties, grain growth and interfaces with graded transitions, and induced negative or restrictive consequences, the tendency for crack initiation may increase. Therefore, heat input and the molten area of the weld have to be kept as small as possible. The main part of the work deals with butt welding of round bars with a diameter of 30 mm made of C22 (1.0402) and 41Cr4 (1.7035). For this application, a laser welding process using a high power disk laser is an appropriate tool. First, a controlled melti...