Welding Chamber Research Articles

Investigation of Generatively Manufactured Components in a Sealed Welding Chamber Using the Tungsten Inert Gas Hot Wire Process

To produce additively manufactured components, various process advantages can be combined by using the tungsten inert gas (TIG) hot wire process with ohmic wire preheating. Unlike other various gas metal arc welding processes, with TIG, it is possible to influence the material properties by decoupling the energy supply and the welding filler material. Compared to the conventional TIG cold wire process, the hot wire process can achieve an increased deposition rate. To be able to use this combined process for the manufacturing of filigree components consisting of steel and titanium alloys, a system concept with a hermetically sealed welding chamber was developed. This concept is particularly designed for an individual use and is also intended to be used for producing prototypes and small quantities. In the investigations, the application of the TIG hot wire process is explored, regarding the material properties to be achieved in combination with the manufacturing plant concept developed with a sealed welding chamber. In this context, the mechanical-technological properties and detailed microstructural analyses are determined based on selected welding tests to evaluate and further develop the quality of the components produced. A final transfer of the findings to the process behavior by optimizing the interaction of the process parameters considered should lead to an increase in productivity, robustness, and reproducibility. The experimental setup’s potential for applicability in the field of additive manufacturing will be demonstrated based on this elaboration.

Numerical and experimental investigations on AA6063 extrudates: effect of number of portholes on extrusion load and weld strength

In aluminium extrusion process, metal flow is greatly controlled by the die geometry and a variety of intricate profiles can be achieved by designing dies of different configurations. In porthole die extrusion, number of portholes used for a profile is often determined by the subjective knowledge of designers. Nevertheless, extrusion load and weld strength of profile produced are not only dependent on extrusion ratio, temperature of deformation but also on the number of portholes along with other die geometry variables. In the present investigation, systematic studies were carried out on three different dies with four ports, three and two ports around die center to extrude profiles of outer diameter 29.4 mm and thickness 2 mm. Numerical simulations were carried out for estimation of pressure, temperature, strain, and strain rate parameters in the weld chamber for all the dies, followed by press trials and profiles produced were subjected to wedge expansion test. The results from numerical simulations indicated that pressure generated inside weld chamber increases with number of portholes. The surface plots indicated highest pressure of about 280 MPa for four port hole and about 276 MPa for three ports die and pressure of about 160 MPa was estimated for two port hole die at the entry of weld chamber , which is 65 mm from profile end. Similarly, temperature at profile exit was 551 °C for four portholes die and 546 °C for three portholes die and 537 °C for two portholes die. Furthermore, press trials indicated peak extrusion loads of 5241 kN, 4406 kN and 3961 kN respectively for four, three and two portholes die. Thus, the peak extrusion load decreased by about 16% for three port and about 25% for two ports die in comparison with four port die. Also, the extruded profiles in wedge expansion test indicated mean compression load of 22.70 ± 0.14 kN in four porthole die, mean compression load 22.29 ± 0.26 kN for three port die and mean compression load of 17.841 ± 0.27 kN.

Investigation of welding quality and internal elongation problem in aluminum extrusion

AA6082 aluminum alloys are particularly useful in heavy industry and machinery manufacturing given their mechanical properties, but when extruding complex profiles used in these sectors, one of the main problems is the welding problem. In order to prevent the welding defects by suitable die design, two different porthole extrusion die set were designed and manufactured using different design techniques in this study. Extrusion trials were conducted for each die. The analysis examined how die design affects profile exit temperature, stress and strain distribution, and billet interface. It also aimed to characterize the effect of die design on welding quality through tensile tests, hardness tests, and microstructural observations. The results show that tapering the mandrel and die plate parts at an angle causes compression of the material flow and reduces the volume of the weld chamber and helps to direct material to the critical regions. This design approach offers a solution for the welding problem of complicated profiles.

Numerical analysis of tooling design for extruding wide aluminium hollow profiles using multi-container extrusion technology

Recently a novel multi-container extrusion method has been proposed and proved feasible to simultaneously extrude multiple billets for producing thin-walled wide profiles with reduced force by experiments. Due to its different die structure compared to conventional extrusion methods, the effects of tooling geometries on the multi-container extrusion performance should be comprehensively analysed as the base of die design optimisation. In this study, the original three-container extrusion design and six modified designs were established to investigate the influence of three key geometrical variables, including container diameter, upper die height and welding chamber height, on the extrusion performance through finite element simulation. The considered extrusion performances include metal flow uniformity, extrusion force, welding pressure, die lifetime and material yield. The drawbacks of the original die design were revealed after the primary analysis of the key influencing variables and a three-step way of design improvement was proposed accordingly. Container block and upper die were optimised for the first step; welding chamber height and die bearing length were modified during the second and third steps respectively. Compared with the original design, the final optimised design can decrease the unevenness of the extrudate front shape by 75% and double the material yield, while the extrusion force, die lifetime and welding quality were basically unchanged.

FEM Numerical and Experimental Work on Extrusion Welding of 7021 Aluminum Alloy.

Extrusion welding of AlZnMg alloys encounters great technological difficulties in practice associated with high shaping forces and the low quality of longitudinal welds. Three different chemical compositions of 7021 aluminum alloy, differing in terms of Zn and Mg contents, were used in the first stage of the research. The laboratory device modelling the behavior of metal in welding chambers of the porthole die was applied to examine the ability of 7021 alloys to produce high-quality joints. The weldability tests were carried out for different welding temperatures-400, 450 and 500 °C-and for a fixed welding pressure of 300 MPa. The microstructural effects in pressure-welds were evaluated with the use of OM and SEM/EDS. The temperature-pressure parameters in the welding chambers were analyzed by using the FEM method for original porthole dies while extruding tubes with dimensions of Ø50 × 2 mm. Finally, the industrial extrusion trials were performed with examination of the structure and strength of the seam welds. It was found that it is possible to produce high-quality high-strength welds in tubes extruded from AlZnMg alloys in industrial conditions (the strength of welds in the range of 96-101% of the strength of the basic non-welded material) through properly matched alloy chemical composition of the alloy, construction of the porthole dies and temperature-speed conditions of deformation.

Investigation of die designs on welding quality and billet material utilisation for multi-container extrusion of wide stiffened aluminium panels

Wide stiffened aluminium panels are extensively used in aerospace, marine, and civil industries due to their light-weight structure and high stiffness. In this paper, a wide stiffened aluminium panel was manufactured using the principle of the multi-container extrusion, and a comparative study was conducted using two different die designs at the same extrusion condition, in which metal flow behaviour, extrusion force, welding quality, and billet material utilisation have been investigated numerically. Additionally, the effect of extrusion speed on the extrusion process was evaluated with the modified design. It was shown that, compared with the initial design, better metal flow behaviour can be obtained in the modified design. Multi-container extrusion greatly reduces the extrusion force, and the modified design results in a more uniform extrusion force for each extrusion container. The total extrusion force for the modified design is slightly higher compared with the initial die design, due to the increased friction in the upper die channels and the second-step welding chamber. Besides, the modified design of the multi-container extrusion can obtain better welding quality evaluated by different welding criteria, and the extrusion speed has a minor effect on the welding quality. The most notable feature is that the modified design greatly improves the material utilisation, which could save 39.5% material compared to the initial design.

Effects of welding chamber height on properties of porthole die extrudates made of 0.5 wt.% GNPs/Al composite

In this study, porthole die extrusion was first performed on a 0.5 wt% GNP-nanoplatelet-reinforced aluminium matrix composite by using welding chambers having heights of 10, 15, and 20 mm. The effects of the welding chamber height on the microstructure and mechanical properties of the composite in the welding zone were studied. The observation results show that there are no macroscopic defects in the interface of the extrudate by the die with different welding chamber heights. The welding degree and ductility of the longitudinal weld of the extrudate increase with the increase of the height of the welding chamber. When the welding chamber height was 20 mm, the comprehensive mechanical properties of the composite along the extrusion direction and the vertical direction were the best. This was mainly because a higher hydrostatic pressure and shear force in the welding chamber with the height of 20 mm increased the recrystallisation degree of the composite, resulting in smaller sizes and an even distribution of the GNP and alumina nanoparticles inside the grain, which played positive role in hindering the dislocation slip. Further, the interface strength between GNP and the matrix was also enhanced characterized by the light and sharp tearing edge in the tensile fractography. The presence of GNP hindered the closure of micro-holes in the weld, and an increase in the welding chamber height effectively reduced the size of micro-holes, thereby improving the welding quality. So larger welding chamber height should be recommended without sacrificing stability and life of the die.

Die Design and Finite Element Analysis of Welding Seams during Aluminum Alloy Tube Extrusion

Hollow tubes are generally manufactured using porthole die extrusion. A finite element software QForm is used to analyze the material flow of aluminum alloy A6061 tubes inside a specially designed porthole die during tube extrusion. High welding pressure and shorter transverse seam length are required for a sound product. Various extrusion conditions and die geometries and dimensions affect the bonding strength of the products. In this paper, the effects of die geometries on the welding pressure are discussed using the Taguchi method. The simulation results show that a higher welding pressure is obtained with a larger porthole radius, a larger welding chamber height, and a larger bearing length, while a larger bridge width increases the welding pressure slightly. For transverse seam lengths, a shorter transverse seam length can be obtained with a smaller porthole radius and a smaller welding chamber height, and a shorter bridge width and bearing length decrease the transverse seam length slightly. The transverse seam region and flow patterns are observed. Tube expanding tests were also conducted. From the expanding test results, it is known that the fracture position did not occur at the welding line and the bonding strength could reach up to 160 MPa.

The Effect of the Bridge’s Angle during Porthole Die Extrusion of Aluminum AA6082

During the porthole die extrusion, the separated metal streams are welded together in the welding chamber. The conditions under which this occurs and the integrity of weld seam in the extrudate are impacted by the design of the bridge, including features such as its shape and dimensions. In this research, the commercial finite element method (FEM) software package, DEFORM, was used to run a series of simulation experiments in order to quantitatively understand the relationship between the bridge design and the thermal mechanical history experienced by the material during welding and the impact this has on final weld seam quality. The bridge can be roughly divided into two parts: the lower part, close to the welding chamber, and the upper part, which initially split the billet into metal streams. The results showed that increasing the lower bridge angle led to slightly higher extrusion loads and higher extrudate exit temperatures. As the lower bridge angle increased, creating a streamlined profile to a blunt profile, a dead metal zone formed under the bridge that produced higher strains near the surface of the material. In contrast, changes to the geometry of the upper bridge had little effect on the porthole die extrusion process or the thermal mechanical conditions experienced by the material.

Pengaruh Lingkungan Las terhadap Kekuatan Impak Sambungan Las Aluminum AA1100

Due to lightweight and strong, aluminum is often applied to the car bodies of an automotive and high-speed train. Welding is the main manufacturing process for these structures. Environmental conditions in welding, especially airflow velocity, humidity, and temperature, significantly affect the impact property of aluminum alloy weld joints. In this work, the welding environment is controlled by creating an insulating welding room where the airflow velocity, humidity, and temperature of the welding environment can be adjusted to obtain an ideal welding environment. The variation of welding environment conditions used was the temperature of 17°C, 22°C, and 27°C; relative humidity of 64%, 68%, and 72% and airflow velocity of 1.1m/s, 1.6m/s, and 2.1m/s. The results showed that the lower the welding environment temperature, the more toughness decreased. The lower the flow rate and the relative humidity of the surrounding air, the tougher it is. Air humidity contains a lot of water vapor (hydrogen) which can cause porosity. The low temperature of the welding chamber results in a shorter freezing time of the weld metal, resulting in cracking and porosity in the weld metal. The ambient airflow velocity interferes with the shielding gas function so that the outside air can be contaminated in the weld metal. The best welding environmental conditions will be achieved if the airflow velocity is below 1.1 m / s, the relative humidity is below 64% and the ambient temperature is 27°C.

Preliminary Research for Development of MW-TIG Hybrid Welding System

The paper aims to report preliminary researches towards to development of new hybrid welding system by coupling a microwave beam with a TIG torch. The main research was focused on the designing of hybrid system as well as to establish the heating/welding mechanism by coupling two different thermal sources. Therefore, a specific welding chamber was designed taking into consideration the limitations provided by microwave waveguide technical specs, geometrical shape and dimensions of the TIG torch as well as the temperature monitoring during welding process and video surveillance for data recording. A microwave generator with adjustable power from 0 to 1250 W was coupled with a TIG torch and welding power source in order to establish the main parameters for hybrid system. The preliminary researches reported that the MW-TIG hybrid welding could be applied to eutectic joining of materials using low power (up to 600 W) injected from microwave generator as well as low welding current (up to 20 A). The flow of shielding gas have been established initially to 2 l/m. The research related to stabilization of MW-WIG plasma arc have been studied by increasing the flow of shielding gas up to 10 l/m. The results have shown that the microwave generator and TIG torch can be coupled to obtain hybrid-welding process without any matching tuning devices but with risks for damaging the microwave generator. Further researches will be done in order to design auxiliary devices to optimize the hybrid-welding process and to avoid any unwanted plasma arc discharge from welded base materials to microwave generator. In terms of temperature monitoring, an infrared pyrometer has been used. The IR pyrometer was targeted to the base materials in order to be able to measure their temperature without any influences from plasma arc. The results obtained have shown a stable plasma at average microwave power around 400 W even without any TIG current.

A Critical Review on Fume Extraction System for Pipe and Plate Welding

In general, for both pipe and plate welding fixtures plays a crucial role. The current study investigates exposure among welders employed in the shop floor area. This welding fumes extractor has a exhaust ventilation setup to track sensitivity to welding fumes using glass fiber filter paper. The trick to acquiring the most effective system fitted to the closed atmosphere so that the gases do not disperse beyond the welding chamber is by learning the fundamentals of ventilation and airborne contaminant extraction. In previous tests, fixtures outside the fumigation hood were installed for both pipe and platform welding. By using a lathe chuck with 4 jaws fixed at both ends that keep the pipe up to 30 mm in diameter, a basic concept of the fixture is constructed. A horizontal rotating stand that is movable only in the y-axis can be set according to the area to be welded without any deflections. This device will be rotated with minimum speed, where the welding can be done effectively without press and dislocations. The main vision is to control the welding fumes in a closed chamber and to fabricate a lightweight fume extraction hood with pipe and plate welding fixtures. This research comes up with good social benefits to reduce blowout of fumes in industries and visibility during welding.

Homogenization of 7075 and 7049 Aluminium Alloys Intended for Extrusion Welding

During the extrusion of aluminum alloys profiles using porthole dies, the temperature of the material in the welding chamber is one of crucial parameters determining the quality of longitudinal welds. In order to extend the permissible temperature range, the billets intended for this process should be characterized by the maximum attainable solidus temperature. Within the present work, the homogenization of AlZnMgCu alloys DC-cast (Direct Chill-cast) billets was investigated, with the aim of solidus temperature maximization. Conditions of soaking and cooling stages were analyzed. The materials were homogenized in laboratory conditions, and the microstructural effects were evaluated on the basis of DSC (Differential Scanning Calorimetry) tests and SEM/EDS (Scanning Electron Microscopy/Energy-Dispersive Spectroscopy) investigations. For all examined alloys, the unequilibrium low-melting microstructure components were dissolved during soaking, which led to the significant solidus temperature increase, in comparison to the as-cast state. The values within the range of 525–548 °C were obtained. In the case of alloy with highest Cu concentration, the application of two-step soaking was necessary. In order to take advantage of the high solidus temperature obtained after soaking, the cooling rate from homogenization must be controlled, and the effective cooling manner is strongly dependent on alloy composition. For high-Cu alloy, the solidus decreased, despite the fast cooling and the careful billets preheating being necessary.

Process chain for the manufacture of hybrid bearing bushings

The current study presents a novel Tailored Forming process chain developed for the production of hybrid bearing bushings. In a first step, semi-finished products in the form of locally reinforced hollow profiles were produced using a new co-extrusion process. For this purpose, a modular tool concept was developed in which a steel tube made of a case-hardening steel, either C15 (AISI 1015) or 20MnCr5 (AISI 5120), is fed laterally into the tool. Inside the welding chamber, the steel tube is joined with the extruded aluminum alloy EN AW-6082. In the second step, sections from the compound profiles were formed into hybrid bearing bushings by die forging. In order to set the required forming temperatures for each material—aluminum and steel—simultaneously, a tailored heating strategy was developed, which enabled successful die forging of the hybrid workpiece to the desired bearing bushing geometry. Using either of the case-hardening steels in combination with aluminum, this novel process chain made it possible to produce intact hybrid bearing bushings, which showed both macroscopically and microscopically intimate material contact inside the compound zone.

The Effect of Ejectors on Reduction of Indoor Air Pollution in the Welding Room

In this study, the ejector installation has been designed and processed according to the plan and further investigated the effect of the ejector’s performance on reducing air pollutants in a welding chamber. This is done after gas and dust particles appear during the welding process. The measurement of air pollutants was carried out in two conditions. The first condition during the welding process was without using the ejector and the second condition is when the welding process continues and the ejector runs simultaneously. The measurements were made for carbon monoxide (CO) gas, nitrogen monoxide (NO) gas and total suspended particles. The ambient gas sampler was used in measuring CO and NO gases, while the Staflex air sampler measures dust particles. The results show that when the ejector is run or in the second condition, carbon monoxide and nitrogen monoxide and total dust particles are lower in concentration compared to the situation when the ejector is not running.

Automation of Welding Fumes based on MQ-2 Sensor in Welding Laboratory.

In practical welding activities, there are potential hazards that must be addressed. These potential hazards include exposure to toxic fumes and dust. Fumes in the welding process contain a lot of metal oxides and can cause chronic effects in the form of eye irritation, sensory irritation, and impaired lung physiological function. Therefore, an air intake sistem is needed to minimize the volume of fumes in the welding chamber . This study aims to design an automation of exhaust smoke using the sensor module, microcontroller and actuator. The resulting tool is equipped with a display of detected air quality conditions, and an alarm indicating that the air quality is in a dangerous level. The method used is experimental development with 3 main stages, namely: designing hardware and software, testing the tools and analyzing their work functions. The results obtained are that the MQ-2 sensor is able to detect changes in the concentration of welding smoke and can be used as an analog input to control the work of the indicator lights, alarms and exhaust fans. The average ability of the exhaust fan to absorb the smoke concentration in the welding chamber is 26.85 seconds for 33 ppm at 40 mm long welding and 29.51 seconds for 37 ppm at 80 mm long welding process. With this capability, this tool can be used as a technical solution related to Occupational Health and Safety in welding laboratories.

Effect of die structure on extrusion forming of thin-walled component with I-type longitudinal ribs

The thin-walled component with I-type longitudinal ribs is widely used in aerospace and defense equipment due to its advantage of high-performance and lightweight, yet this complex structure is difficult to manufacture. One method is to form a simple thin-walled tube and I-type longitudinal ribs respectively and then connect them together by welding or riveting. Another method is to form a simple thick-walled tube firstly and then cut out the I-type longitudinal ribs. However, welding or riveting will weaken the component performance and cutting will waste lots of material. In this paper, the extrusion forming process is tried to manufacture the seamless thin-walled components with I-type longitudinal ribs. By FE simulation and experiment of the initial extrusion forming process scheme, it can be found that the metal flow velocities in the thin wall and longitudinal ribs areas are different, which lead to the deformation instability, even producing cracking. To solve the deformation instability, the effects of die structure including the porthole, the baffle-block, and the secondary welding chamber on the metal flow in extrusion process are studied. It reveals that increasing the area of the porthole will increase the metal flow velocity, increasing the height of the baffle-lock will decrease the metal flow velocity, and decreasing the height of the secondary welding chamber will improve the metal flow uniformity. Thus, the velocity uniformity of the metal flow at different position can be controlled in a better level to guarantee stable deformation by selecting appropriate die structure parameters. Finally, an optimized die structure is designed and the extrusion experiment is carried out, which obtain a good forming quality. The research work can provide an important guidance for improving the manufacturing level of thin-walled component with I-type longitudinal ribs.

Influence of hydrogen, oxygen, nitrogen, and water vapor on the formation of pores at welding of copper using laser light at 515 nm wavelength

Due to increased absorptivity of laser light at 515 nm wavelength in copper materials, welds with low formation of spatters and homogeneous weld depths can be performed.1 However, depending on the used process parameters, a process regime with strong formation of pores is observed. These pores are not resulting from instabilities of the capillary (process pores), but they are observed to result from the interaction of ambient gas with the melted material in the welding zone. Different gaseous elements such as nitrogen, hydrogen, oxygen, and water vapor, therefore, were applied to the welding process to investigate their influence on the resulting weld seam porosity. For this purpose, all welds were performed in a welding chamber. It is found that the reaction of ambient nitrogen with ambient oxygen during the welding process has a strong influence on the resulting weld seam porosity. Furthermore, pores are observed in the weld seam when the raw copper material contains an increased amount of oxygen. Depending on which copper material is used, strategies are derived to perform welds with low or no formation of pores.

A Design Approach of Porthole Die for Flow Balance in Extrusion of Complex Solid Aluminum Heatsink Profile with Large Variable Wall Thickness

In this study, porthole die used for extrusion of a solid heatsink profile with wall thickness variation ratio up to 15.3 was designed using finite element (FE) simulations. To improve the flow balance in the die, a design approach was introduced to find the appropriate die structure, which includes the porthole and pocket geometry correction, the bearing length adjustment, and the port bridge structure modification. Using the proposed die, the predicted velocity relative difference (VRD) and the maximum velocity difference (ΔV) of extrudate were significantly lower than those of an initial die, which was preliminarily designed based on general design experiences. The required extrusion force and the residual stress in the product were also reduced significantly. Then, the effects of the port bridge structure and welding chamber height on the behavior of the metal flow in the die were investigated. To verify the proposed die design, experimental extrusions were conducted on a 930-ton extruder. The experiment results showed that the extruded product fulfilled the requirements for dimensional tolerances. The design approach presented in this paper can be useful for practical implementation of die design when extruding similar solid heatsink profiles with large wall thickness variation.

Estimation of Extrusion Welding Conditions for 6xxx Aluminum Alloys

Extrusion of hollow shapes containing longitudinal welds from easy-to-weld aluminum alloys is realized in industrial practice by using porthole dies. In the work, an original method and a special modified device is presented that simulates conditions occurring in a welding chamber of the porthole dies. The weldability tests were performed for low and medium-component 6xxx alloys – in a wide range of welding temperatures and pressures. The seam welds strength were examined. The microhardness test was performed perpendicularly to the surface of welding. The microstructure of the material both in the welds region and outside them were examined by using light microscope and scanning microscope SEM. The chemical composition was examined used the EBSD method. Most favorable welding conditions for the tested alloys, allowing for obtaining high-strength welds were defined.