Non-vacuum Electron Beam Welding Research Articles

Non-vacuum electron beam welding and cutting of cupper

Due to its physical properties, like high thermal and electrical conductivity copper is an indispensable material in many branches of industries. However the welding and cutting of copper and its alloys is challenging due to this properties and tendency to absorb gases resulting some defects like porosity or hot cracking. To prevent these, different requirements concerning the welding process have to be fulfilled. One requirement is the use of a highly concentrated heat input. The electron beam in atmosphere (NVEBW)is a suitable tool, which meets this requirement. This publication presents the advantages of NVEBW welding and cutting of copper. The experimental results of low-voltage (NVEBW) of copper will be shown and discussed too. The first portion studied the effects of varying power, travel speed and work distance on mechanical and electrical properties and structure of weldment at 175 kV accelerating voltage. The second portion studied the possibility of application of low-voltage 60kV NVEBW for welding of copper and influence of impurities in the copper on the welding parameters. The third portion studied the process of NVEB cutting of copper using the suction created by a local vacuum underneath the work piece. Experimental results of cutting with extremely high cutting speeds such as15m/min for 1.5 mm thick and 9m/min for 6mm thick copper will be representing.

A new 3D printing method based on non-vacuum electron beam technology

Electron beam freeform fabrication (EBF3) is one the of rapid manufacturing methods, which produces metal parts using an electron beam and wire feed unit in a layer additive fashion without need of mold or jigs. The main disadvantage of EBF3 is that the process is carried out in a chamber, which not only takes a lot of time to evacuate but also limits the size of the part being printed. Non-vacuum electron beam (NVEB) welding is widely used in industry field as a reason for its high production volumes. So a NVEB 3D printing device based on a non-vacuum electron beam welding machine from SST is designed. A serial of experiments is carried out to get a deep understand of 3D printing processing procedure using non-vacuum electron beam system and find a suitable process window. Result shows that droplet transfer mode is one of the most important parameters which determines the quality of the deposition.

Industrial Robot Automation in Solving Non-Vacuum Electron-Beam Welding Problems

The paper describes one modeling automated hardware-software system to develop additive technologically - based products. Algorithm synthesis for industrial robot control was performed. In this case, the operating tool is an electron -beam projector with plasma emitter. The model testing results of thermal processes (in 3D-enqueuing) proceeding within additive substrate material system have been described. The modeling results revealed those required parameters of emission power which would provide the melting of additive material (TiC) excluding boiling.

Economical joining of tubular steel towers for wind turbines employing non-vacuum electron beam welding for high-strength steels in comparison with submerged arc welding

Owing to restricted energy resources and the worldwide ambitions to reduce CO2 emissions, renewable energy sources, such as wind energy, are gaining economical interest and promise great growth potential. This is closely connected with the increase of plant unit sizes. The wall thickness of the tower construction is rising accordingly and leads to increasing costs for the joining technology. The rising number of weld passes for submerged arc welding (SAW) leads to rising process times and high filler material consumption. The employment of non-vacuum electron beam welding (NVEBW) can significantly reduce the number of passes, the welding time, and the filler consumption. A substantial aspect of the control of the welding process is the formation of solidification cracks. Formation mechanisms and preventions methods such as preheating, alloying, and full penetration welding will be presented and experimentally backed up. The subsequent application of the SAW and NVEBW processes will be compared to standard multi-pass SAW for an exemplary weld of 30 mm thick high-strength steel. An additional aim of current research is the overall reduction of the wall thickness of wind turbine towers applying high-strength steels. Here, it is of chief concern to preserve the advantages of the material.

Nonvacuum electron beam cutting and welding—two partnering processes for fast and highly efficient metal working

The electron beam is a tool with high energy conversion efficiency which is by and large independent of the type of metal. Its high power density qualifies the nonvacuum electron beam as an outstanding energy source for the widely used nonvacuum electron beam (NVEB) welding as well as for a new high-speed cutting tool. Advances realised by the NVEB group at the Institute of Materials Science of Leibniz University of Hannover (Germany) in the field of nonvacuum electron beam cutting (NVEBC) will be presented. Experimental results for melt cutting with conventional blow gas jets will be presented as well as a new promising cutting process using the suction created by a local low vacuum underneath the work piece. Extremely high cutting speeds such as 18.5 m/min for 2.5 mm thick stainless steel producing high-quality edges render this method a significant development for new NVEB applications. NVEB cutting and subsequent welding can be done on one integral machine realising a fast and efficient twin process.

Influence of Weld Defects on the Fatigue Resistance of Thick Steel Plates

Multi-wire submerged arc welding (SAW) process is conventionally used for long welds with large cross sections in tubular steel tower manufacturing. By applying non-vacuum electron beam welding (NVEBW), the number of passes and the heat input can be notably reduced. For plate thicknesses of 20mm or more the continuous appearance of solidification cracks inside the weld cross section rouse a great challenge. The fatigue resistance is reduced significantly and the safety of the component cannot be ensured. In this paper analytical and experimental investigations are discussed for predicting fatigue life of defective welds.

Measuring of plasma properties induсed by non-vacuum electron beam welding

Electron beam plasma measurement was realised by means of DIABEAM system invented by ISF RWTH Aachen. The Langmuir probe method is used for measurement. The relative simplicity of the method and the possibility of dispersion of high power on the probe allow its application for the investigation of high-power electron beams. The key element of the method is a rotating thin tungsten wire, which intersects the beam transversely on its axis and collects part of the current by itself. The signals, which are registered in the DIABEAM as a voltage, were taken in the form of amplitude. The conversion of the probe current into the distribution along the beam radius was realised using the Abel’s method. A voltage-current characteristic was built for the beam current. The local electron density as well as the electron temperature, the floating potential and the plasma potential were measured and calculated by means of this characteristic.

Correlation of acoustic, physicochemical, and mechanical properties of coatings obtained using electron-beam welding deposition of chromium carbide on low-carbon steel

Multifunctional coatings have been developed using the method of nonvacuum electron-beam welding deposition of chromium carbide powder on low-carbon steel. The correlation dependences of the ultrasonic velocity, the thickness of coatings, the content of chromium in the coatings, and the loss of mass under exposure to corrosive media on the mechanical properties are constructed using the bend tests. It was shown that the observed correlation relations are mainly determined by two factors, i.e., the presence of a substitute doping agent of chromium in a solid solution and the character of a dislocation structure, which forms inside of the grain.

Setting of Gradient Material Properties and Quality Control of High Tension 3D NVEB-Weld Joints

In modern, highly loaded structures of metallic materials, particular standards are required both regarding the strength and deformation properties of individual components as well as in terms of the load carrying capacity of the bonded joints between individual components. This specific subject matter is taken up in the subproject C4 "Setting of Gradient Material Properties and Quality Control of High Tension 3D NVEB-Weld Joints" within the framework of “Collaborative Research Centre” CRC 675 "High strength, locally modified components and structures" in order to correspondingly and individually adapt a component's properties to the loading profile. For this purpose, components having specifically calibrated strength properties are joined into high quality structures. Although still quite new but powerful, and due primarily to its very favourable welding characteristics, the non-vacuum electron beam welding technology is, in this case, to be further developed with respect to an improvement in beam positioning and weld-seam defect inspection. On the other hand, a well-defined, local heat-treatment is to be carried out on individual, work-hardened components to be able to introduce targeted and structured local, load-oriented microstructural changes into the component: thereby locally changing the component's strength and deformation properties with a view to retarding crack growth.

High Strength 3D Non‐Vacuum Electron Beam Weld Joints ‐ Setting of Gradient Material Properties and Testing of Weld Quality

Highly loaded structures made of modern metallic materials are increasingly being placed under stringent standards with regard to the mechanical strength and deformation properties of their individual parts as well as with regard to the loading capacity of their joints. In order to create strain profiles in individual structural components, such components are heated with an electron beam at defined locations in order to bring in local microstructure changes and consequently the targeted local changes in the strength and deformation properties of the material with respect to a delayed crack growth. Additionally, components with specifically set tensile strength are welded to high quality structures. For this purpose the young but efficient non‐vacuum electron beam welding (NV‐EBW) method is used and further developed. Weld quality is examined especially in regard to an improved beam positioning, process control and weld joint defect detection.

Non-vacuum electron beam welding through a plasma window

The plasma window is a novel apparatus that utilizes a stabilized plasma arc as interface between vacuum and atmosphere or pressurized targets without solid material. Additionally, the plasma has a lensing effect on charged particles. This feature enables beam focusing to very small spot sizes and overcoming beam dispersion due to scattering by atmospheric atoms and molecules. Recently, the plasma window was mated to a conventional electron beam welder. And, electron beam welding in atmosphere was accomplished with electron beams of unprecedented low power and energy. Weld quality for the non-vacuum plasma window electron beam welding approached the quality of in-vacuum electron beam welding. Indications exist that electron beam attenuation is lower than theoretically predicted. Results suggest that air boring was achieved with 6–15mA, 90–150keV electron beams compared to the previously used kA, MeV electron beams. It may explain the better than expected welding results.

Non-Vacuum Electron Beam Welding

The electron beam has, for decades now, proven to be a most efficient and reliable tool for joining tasks in different application fields. Vacuum electron beam welding (EBW) has, for many years now, been a standard method for a great variety of industrial application fields. However, even out-of-vacuum (NV-EBW), the electron beam has become a high-productivity joining tool. The substantial weld depths which characterise vacuum electron beam welding are not achievable with the NV-EBW method – those weld depths characterise the vacuum electron beam and are a result of its power density. The strong points of NV-EBW lie, mainly, in high-speed production. The achievable welding speeds reach up to 60 m/min when welding aluminium sheets and up to 25 m/min when welding steel plates.

Air boring and nonvacuum electron beam welding with a plasma window

The plasma window is a novel apparatus that utilizes a stabilized plasma arc as interface between vacuum and atmosphere or pressurized targets without solid material. Additionally, the plasma has a lensing effect on charged particles. This feature enables beam focusing to very small spot sizes and overcoming beam dispersion due to scattering by atmospheric atoms and molecules. Recently, the plasma window was mated to a conventional electron beam welder. And, electron beam welding in atmosphere was accomplished with electron beams of unprecedented low power and energy. Weld quality for the nonvacuum plasma window electron beam welding approached the quality of in-vacuum electron beam welding, without the use of helium as process gas. Weld widths were independent of stand-off distance for up to 5cm, which along with visual observations suggest that pinched beam propagation might have been achieved with 6–25mA, 90–150KeV electron beams. That may explain the better than expected welding results. By comparison previously demonstrated self-pinched propagation used kA MeV electron beams.

Non Vacuum Electron Beam Welding of Light Sheet Metals and Steel Sheets

Material treatment using high-energy beams is an established process. In the field of welding, the most used processes are laser beam and vacuum electron beam welding. This paper describes the possibilities of the Non Vacuum Electron Beam Welding (NV-EBW) process. Fundamental investigations were made: beam power density measurements, Arata beam tests as well as penetration tests for aluminum alloy AlMg3, magnesium alloy AM50 and stainless steel X4CrNi18–10. Due to high achievable welding speeds (<20 m/min) and to the high automation grade, mainly sheet metal and aluminum alloys up to a thickness of 5 mm can be welded economically. Welding tests were made to check the applicability of the process to the welding of tailored blanks in AlMg3 and AlMgSi0.8 as well as to DC04 steel sheet. Furthermore it is possible to weld different materials and tailored blanks (tests were made on Mg alloys AZ31, AZ61, AZ91 and AM50) as well as flanged joints, plain butt joints, lap joints and fillet welds. For welding flanged joints, the process is characterized by a high gap bridging ability. The influence of linear misalignments and of gaps between the plates on the quality of edge welds was also investigated.

Laser- und Elektronenstrahlschweißen von Magnesiumwerkstoffen

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High-pressure arcs as vacuum-atmosphere interface and plasma lens for nonvacuum electron beam welding machines, electron beam melting, and nonvacuum ion material modification

Atmospheric pressure plasmas can be used to provide a vacuum-atmosphere interface as an alternative to differential pumping. Vacuum-atmosphere interface utilizing a cascade arc discharge was successfully demonstrated and a 175 keV electron beam was successfully propagated from vacuum through such a plasma interface and out into atmospheric pressure. Included in the article are a theoretical framework, experimental results, and possible applications for this novel interface.

A major advance in high-power electron-beam welding in air

A major extension of the capabilities of nonvacuum electron-beam welding follows from the development of a machine with higher beam power. Tests with a new atmospheric electron gun operating at 60 kW have shown that the advantages of nonvacuum electron-beam welding must be reevaluated. Gas heating produced by the beam itself becomes very pronounced, so that electron scattering is reduced causing the high-power density of the beam to be retained over larger working distances. Single-pass butt welds with a depth-to-width ratio of 4 : 1 can be made in 3.8-cm-thick steel at a speed of 0.77 cm/sec, while the ultimate welding depth exceeds 5 cm. Medium thick material, e.g., 1.3-cm steel, can be welded at a 5-cm work distance, with a depth-to-width ratio of 3 : 1. The large work distance permits access to more complex structures and interior corners such at T sections, which can now be fabricated from a plate, 1.3 cm thick, at a speed of 2–3 cm/sec, making a full through weld from one side. Also, seam welds of two 3-mm-thick hot-rolled steel sheets can be produced at speeds of up to 15 cm/sec. High-power machines need not be significantly larger or costlier than low-power guns, and the present 60 kW does not represent any technical limit. Welding efficiency improves with higher power; when welding steel of 2 cm thickness or more the energy efficiency of the process at 60 kW is better than 50%, while at 40 kW it is merely 30%. In addition, the high power permits greater welding speed. These developments translate directly into improved cost justification for electron-beam welding and a broad expansion of its possible applications.

Electron-beam welding of sheet metal steel with particular reference to tubular shapes

The application of electron-beam welding and the justification for its use in production are illustrated by reviewing in detail two applications: one utilizing a cheap, general purpose machine which demonstrates the fundamental principle of using one component per machine cycle to minimize tooling costs and the second concerned with a more sophisticated equipment for semi-continuous production in an area formerly considered to be exclysively the field of the non-vacuum electron-beam welding process. The problems of introducing the process are considered, with an approach to assessing the economics of potential applications.