Wire Manufacturing Process Research Articles

Effect of Magnetic Arc Oscillation on the geometry of single-pass multi-layer walls and the process stability in wire and arc additive manufacturing

Abstract Magnetic Arc Oscillation was applied during the construction of single-pass multi-layer walls of low carbon steel and Ti6Al4V by the Gas Tungsten Arc Welding-based Wire and Arc Additive Manufacturing process, and the influence on the geometry and the process stability was evaluated. The geometric features were assessed using transverse section macrographs and the effects of different patterns and frequencies of oscillation on the arc characteristics, metal transfer and weld pool behavior during the layer deposition were investigated using high speed and welding cameras. The results show that this technique is efficient for making thinner walls by minimizing the overflow of the weld pool and, in some conditions, increasing deposition efficiency. Furthermore, the distribution of material along the wall length becomes more homogeneous. An explanation of the effects of Magnetic Arc Oscillation on the wall geometry based on forces that act on the molten metal during layer deposition was made. Because of the swinging movement of the welding arc, the heat is distributed over a larger area, and the power density decreases. Thus, fewer previous layers are remelted, and the volume and the weight of the weld pool reduce. The weld pool temperature drops, and the surface tension force and the viscous friction increase. The distribution of arc pressure also becomes less concentrated, and the arc force on the molten metal decreases. Additionally, a magnetic force appears on the molten metal, which contributes to a change in the direction of the resultant force on the weld pool.

Effect of Sn Content on the Microstructure and Properties of Wire and Arc Additive Manufactured Al-Cu Alloy Deposits.

Al-Cu-Sn alloy deposits with different Sn contents were prepared by the wire and arc additive manufacturing process. The microstructure and mechanical properties of the deposits were examined by metallography, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and tensile tests. The results indicated that the addition of Sn significantly refined the microstructure of the deposits in their as-deposited state, and the grains were transformed from dendrites to equiaxed crystals with a uniform grain size of ∼30 μm. For the deposits with Sn ≥0.15%, the continuous and elongated θ phase on the grain boundary became block-shaped, and the size of the precipitated phase increased. After T6 heat treatment, the θ phase completely dissolved in the substrate in the deposits with Sn ≤0.1%, whereas the θ-phase solid dissolution was incomplete in the deposits with Sn ≥0.15%; the higher the Sn content, the greater the amount of θ phase remaining. After the T6 treatment, the deposits with an Sn content of 0.25% exhibited cracks distributed along the grain boundaries. The addition of Sn significantly increased the density of the θ' phase, which was diffused and uniform in size; with an increase in the Sn content, the distribution density of the θ' phase in the deposits first increased and then decreased as the peak-aging condition was reached. The addition of Sn could effectively improve the mechanical properties of the deposits, which first increased and then decreased with an increase in the Sn content. The mechanical properties of the deposits were optimal at an Sn content of 0.1%, with a tensile strength of 493 MPa, yield strength of 434 MPa, and elongation of 9.5%.

Effect of Heat Input on Formability, Microstructure, and Properties of Al–7Si–0.6Mg Alloys Deposited by CMT-WAAM Process

In order to improve the forming efficiency of Al–7Si–0.6Mg fabricated by wire and arc additive manufacturing process (WAAM), wire with a diameter of 1.6 mm was selected as the raw material. The effect of heat input on the formability, microstructure, and properties of the WAAM alloy was investigated, and the forming model was established. The WAAM alloys were characterized by electronic universal testing, scanning electron microscopy, energy spectrum analysis, and metallographic microscopy. The results show that Al–7Si–0.6Mg alloy has a large processing window under the cold metal transfer (CMT) process, and it can be well formed with a large range of heat input. The secondary dendrite arm spacing and Fe-phase in the as-deposited alloy gradually increase with an increase in heat input, and slight overburning occurs in the heat affected zone at higher heat inputs. After solid solution and aging treatment (T6 heat treatment), the size of α-Al grain and eutectic silicon grain increases with the increase of heat input. Little anisotropy in the mechanical properties is observed except at higher heat inputs. The tensile strength is 354.5 MPa ± 7.5 MPa, yield strength is 310 MPa ± 5.5 MPa, and elongation is 6.3 ± 0.7%.

An online surface height measurement method for GTAW-based additive manufacturing

Wire and arc additive manufacturing (WAAM) process control is critical to forming dimensional accuracy. The online surface height measurement technology is one of the key technologies to achieve closed-loop control of the WAAM surface height. Measurement equipment such as charge-coupled device (CCD) or infrared cameras have difficulties in meeting the requirements for high-frequency online layer height measurement of multi-directional complex paths. In this paper, an online surface height measurement model (OSHMM) based on welding current, voltage, arc length signal, and motion system height displacement data is proposed that can measure the height value of the surface just below the tungsten electrode. The influence of large surface height deviation and the change of wire-feed rate, corner, and inclined edge on measurement accuracy were analysed. The experimental results show that the proposed method can guarantee the accuracy of ± 1.5 mm in the above cases.

Process planning for adaptive contour parallel toolpath in additive manufacturing with variable bead width

Lightweight structures with slender features and thin walls can be fabricated by the additive manufacturing process. The fabrication process utilizes a contour parallel toolpath, where sets of parallel contours are offset from the boundaries of a geometric structure at predefined intervals to deposit the material layer by layer. Currently, these intervals are set to be constant, which limits its capability to produce near net-shape parts. In recent research, the feasibility to fabricate parts using contour parallel toolpaths with variable bead widths has been explored to increase the production speed, to improve the geometry accuracy, and to manufacture void-free parts. However, existing process planning methods are computationally inefficient and challenging to implement. To resolve these issues, this paper proposes a comprehensive process planning framework for adaptive contour parallel toolpath with variable bead widths. More specifically, this framework includes a toolpath planning algorithm using the level-set method and a process planning algorithm for generating the desired bead geometry using a Gaussian process regression model. To validate the proposed framework, a case study has been demonstrated in the fabrication of benchmark features with a wire and arc additive manufacturing process.

Effect of microtextures on the intermediate temperature fracture behavior of additive-manufactured Ni-based overlay

Texture components with specific orientations are found to play important roles in crack and fracture phenomena. In this study, nickel-based alloy overlays with different texture intensities were directly produced by wire and arc additive manufacturing (WAAM) processes. Results of hardness and tensile tests from room to elevated temperatures showed global differences in strength, ductility and cracking susceptibility between the deposit with the Cube texture and the deposit with the Brass texture. The formation mechanism of different textures during WAAM processes was elucidated. Then the deformation of individual texture grains and incompatible deformation among them were analyzed, and their effects on the fracture mechanism at the intermediate temperature were also investigated. During the deformation, the Brass grains, with relatively lower Schmid factors compared to the Cube grains, were hard to activate (111)<1–10> system slip without rotation, which led to significant strain accumulation at the grain interior and boundaries. The incompatible deformation and discontinuous slip transfer between differently orientated grains, especially the Brass grains, induced cracking and exacerbated the ductility within the intermediate temperature range.

Phase field study of spacing evolution during wire and laser additive manufacturing under transient conditions

Understanding the dynamic evolution of primary dendritic spacing in the laser melt pool is significant from a technological viewpoint because primary spacing is one of the foremost parameters that control the final mechanical properties of additive manufactured products. In this work, a multi-scale computational framework that couples FEM and a developed quantitative phase field method is employed to simulate the evolution of microstructure and primary spacing of a nickel-based superalloy during wire and laser additive manufacturing (WLAM) solidification. Transient conditions in the laser melt pool are considered in which both temperature gradient G and solidification speed VP are made time-dependent. Through the use of this model, the dendritic morphology, tip velocity and spacing evolution during the solidification are investigated to provide the relationship between the laser processing parameters and the final spacing. Moreover, we attempted to clarify the intrinsic mechanism of spacing adjustment under different laser processing parameters from a novel perspective. This work provides meaningful understanding of spacing evolution in nickel-based superalloy and demonstrates the potential of controlling the complex microstructure morphologies and final primary spacing during wire and laser additive manufacturing process.

Effect of wire and arc additive manufacturing (WAAM) process parameters on bead geometry and microstructure

This paper discusses the effects of process parameters in TIG based WAAM for specimens created using Hastelloy X alloy (Haynes International) welding wire and 304 stainless-steel plate as the substrate. The Taguchi method and ANOVA were used to determine the effects of travel speed, wire feed rate, current, and argon flow rate on the responses including bead shape and size, bead roughness, oxidation levels, melt through depth, and the microstructure. Travel speed and current were found to have the largest effect on the responses. Increasing travel speed or decreasing current caused a decrease in melt through depth and an increase in roughness. Printing strategies were tested using specimens of multiple layers and no significant difference was found between printing layers in the same direction and printing layers in alternating directions. No observable interface between the layers was present suggesting a complete fusion between layers with no oxidation. Three distinct zones were identified within the three- and eight-layer samples. The zones were characterized by the size and distribution of the molybdenum carbide formations within the matrix grain formations.

Improvement of stability of Nb3Sn superconductors by introducing high specific heat substances

High-Jc Nb3Sn conductors have low stability against perturbations, which accounts for the slow training rates of high-field Nb3Sn magnets. While it is known that adding substances with high specific heat (C) into Nb3Sn wires can increase their overall specific heat and thus improve their stability, there has not been a practical method that is compatible with the fabrication of long-length conductors. In this work, we put forward a scheme to introduce such substances to distributed-barrier Nb3Sn wires, which adds minimum difficulty to the wire manufacturing process. Multifilamentary wires using a mixture of Cu and high-C Gd2O3 powders have been successfully fabricated along this line. Measurements showed that addition of Gd2O3 had no negative effects on residual resitivity ratio or non-Cu Jc, and that flux jumps were remarkably reduced, and minimum quench energy values at 4.2 K, 14 T were increased by a factor of three, indicating that stability was significantly improved. We also discussed the influences of the positioning of high-C substances and their thermal diffusivity on their effectiveness in reducing the superconductor temperature rise against perturbations. Based on these results, we proposed an optimized conductor architecture to maximize the effectiveness of this approach.

Measuring the qualitative factors on copper wire surface

This paper is focused on improvement of quality of copper wire manufacturing process. Through the Design of Experiment (DOE) method, it presents the way to keep the thickness of oxide layer during rolling copper wire at the level requested by customer. Variation coefficient of measurement replications performed in each test within the planned experiment was used as the response in the DoE method. Settings for the selected process parameters of copper wire rolling that have a significant effect on the thickness of the surface oxide layer, and were obtained on the basis of the planned experiment, were verified in the production conditions.

Effect of continuous hybrid process on mechanical and electrical properties of rectangular pure copper wire

In this study, a continuous hybrid (CH) process applied with newly designed dies was proposed to manufacture a high strength and high electrical conductivity rectangular copper wire in a continuous way. The 2nd pass CH process with different processing routes, A and C, was numerically and experimentally carried out to check the practicality of the process and to investigate the deformation behavior of the commercially pure copper wire. Electron backscatter diffraction, tension and Vickers micro-hardness tests were employed to study the changes in the microstructure and mechanical properties of the wire. Electrical conductivity was also measured by a four-point probe method. According to the current investigation, the CH process with the new concept dies could impose relatively high plastic deformation without die change during the process and promote the accumulation of dislocation, resulting in grain refinement of the wire compared to the conventional wire drawing (WD) process. The mechanical strength and hardness values of the processed rectangular pure copper wire by the CH process were increased, and the electrical conductivity was relatively maintained compared to the one processed by the WD process. In particular, route C could produce wire with relatively uniform strength distribution. Route A might be adequate for the manufacturing of one-sided hardened rectangular wire such as the contact wire for rail electrification. It is demonstrated that the CH process can be applied to the rectangular wire manufacturing process and might be beneficial to produce high strength and high electrical conductivity copper wire for various applications.

Experiment study on electroplated diamond wire saw slicing single-crystal silicon

This paper conducted the slicing experiments of single-crystal silicon using a reciprocating electroplated diamond wire saw. The machined wafer topography and wire wear were observed by using scanning electron microscope (SEM). The influences of process parameters and cutting fluids on single-crystal silicon wafer surface roughness (SR), subsurface micro-crack damage (SSD) depth, total thickness variation (TTV) and warp were investigated. The bonded interface sectioning technique was used to examine the cut wafers SSD depth. Study results show that a higher wire speed and lower ingot feed speed can produce lower wafer SR and SSD; the lower warp of wafer needs lower wire speed and ingot feed speed; and low wafer TTV can be obtained by an appropriate matching relationship between wire speed and ingot feed speed. The synthetic cutting fluid has a better total effect to improve the wafer quality. The pulled-out of diamond abrasives is the main wear form of wire, which indicates that more research on improving the abrasives retaining strength on wire surface should be investigated in fixed-abrasive wire manufacturing process, in order to improve the wire life and wire saw machining process.

Dissimilar metal deposition with a stainless steel and nickel-based alloy using wire and arc-based additive manufacturing

The wire and arc-based additive manufacturing process applies arc welding technology; the wire material is melted by the arc discharge, and is then accumulated successively in this process. The wire and arc-based additive manufacturing process directly and locally adds material to the molten pool. By changing the material locally during the process, more than one kind of material can be used simultaneously in a single manufactured component. In this study, two kinds of dissimilar metal deposition were conducted. A combination used was a stainless steel and Ni-based alloy. Mechanical properties near the interface such as hardness and bond strength were investigated. As a result, it was found that the mechanical properties of the manufactured alloy were comparable to those of a bulk material. In addition, an additive manufacturing system and a torch path planning method for using more than two kinds of material were proposed. By using this method, highly functional shapes whose surfaces and inner structures are made of different material could be made.

Determining the velocity of a moving rod and the thickness of its coating using natural frequencies of flexural vibrations

Research has been performed on natural transverse vibrations of a portion of a constant length in a straight thin coated rod moving along the neutral line of a non-deformed state. The movement takes place between two rigidly fixed coaxial guides (clamps), the distance between them equalling the length of the rod moving portion. The longitudinal force is assumed to constantly act along the neutral line. It has been found that a decrease in the natural frequencies of flexural vibrations of the rod occurs with an increase in the velocity parameter. It is also shown that a decrease in the natural frequencies of flexural vibrations of the rod occurs with an increase of the coating thickness. Using two frequencies of flexural vibrations, we can determine the velocity parameter of the moving rod and the thickness of its coating. The results of the research work can find technological use in the problems on dynamics and strength of machines and mechanisms in manufacturing the coated products: in textile industry, wire manufacturing process, metallurgy (especially for rolling metal bars and strips), wire drawing, plastic products and paper rolls manufacturing and can be used to determine the velocity and the coating thickness of a moving rod, strip or wire using two frequencies of flexural vibrations.

Electrochemical Polishing of Nitinol and Other Medical Alloys in Aqueous Electrolytes Using Pulse/Pulse Reverse Electric Fields

Nitinol is an important medical alloy, and its unique properties have allowed advancement of minimally invasive procedures for medical and orthodontic applications. Nitinol is a near equiatomic alloy of nickel and titanium whose properties, namely superelasticity, shape memory effect and self-passivity, are particularly important for medical applications. However, surface preparation plays a significant role in the surface properties of Nitinol and consequently influences corrosion behavior in a physiological environment. Surface treatments including mechanical polishing, chemical polishing, electropolishing, anodization and heat treatments have been investigated for corrosion behavior in physiological environments, especially in terms of nickel ion release from the device surface, which is an important consideration for medical applications owing to nickel’s toxicity. Electropolishing is attractive for the preparation of Nitinol surfaces due to improvements in corrosion resistance, biocompatibility and surface quality when compared with other surface preparation methodologies.[i] Traditionally, processing of these materials has been carried out in hazardous chemicals such as hydrofluoric acid, or fluoride salts that convert to hydrofluoric acid,[ii] to electropolish and passivate the device and achieve the surface finish required for insertion into the body. The inclusion of hydrofluoric acid, in addition to concentrated sulfuric-phosphoric acids, makes for an extremely hazardous working environment. Alternatively, non-aqueous electrolytes such as methanol-perchloric acid[iii] or methanol-sulfuric acid[iv] mixtures have been suggested, but these require low-moisture environments and low-temperatures (-10 °C) and industrial implementation is difficult. The current work demonstrates that Nitinol surfaces may be electropolished in simple, aqueous electrolytes using pulse and pulse/reverse electric fields. Electropolishing of Nitinol has been done in dilute sulfuric acid solutions (5-10%) as well as salt electrolytes using pulse/pulse reverse voltage fields under ambient conditions. This work has been demonstrated for Nitinol coupons, wires and shape sets; processing of these surfaces will be discussed. Implementation of a Nitinol wire manufacturing process is an important step in the fabrication of these devices for medical use. Scale up of Nitinol wire electropolishing in terms of apparatus is also currently underway and will be discussed. In the current work, a reel-to-reel apparatus will be utilized to facilitate scale-up activities. A schematic of the reel-to-reel apparatus is shown in the accompanying image. The apparatus design is straight-forward due to limited considerations needed for processing under ambient conditions in simple aqueous electrolytes. Important cell considerations such as cathode configuration and residence time will be discussed along with processing considerations. This method is applicable to other medical alloy wires, devices and implants. [i] R. Steegmueller, T. Fleckenstein, and A. Schuessler, Proceedings of the Materials and Processes for Medical Devices, 163-168 (December 1, 2006). [ii] Dr. James Carlson, Senior Metallurgical Engineer, Cook Medical, private communication, November 2010. [iii] W. Miao, X. Mi, M. Zhu and H. Li, J. Ceramic Processing Research, 7 (4), 367-370 (2006). [iv] K. Fushimi, M. Stratmann and A.W. Hassel, Electrochimica Acta, 52, 1290-1295 (2006). Figure 1

A tool-path generation strategy for wire and arc additive manufacturing

This paper presents an algorithm to automatically generate optimal tool-paths for the wire and arc additive manufacturing (WAAM) process for a large class of geometries. The algorithm firstly decomposes 2D geometries into a set of convex polygons based on a divide-and-conquer strategy. Then, for each convex polygon, an optimal scan direction is identified and a continuous tool-path is generated using a combination of zigzag and contour pattern strategies. Finally, all individual sub-paths are connected to form a closed curve. This tool-path generation strategy fulfils the design requirements of WAAM, including simple implementation, a minimized number of starting-stopping points, and high surface accuracy. Compared with the existing hybrid method, the proposed path planning strategy shows better surface accuracy through experiments on a general 3D component.

Synthesis and characterization of SiO2 nano- and microwires by a non-catalytic technique

In this paper, we report on the synthesis of pure silica (SiO2) nano- and microwires by a non-catalytic process. The structure, morphology and properties of the products were examined by scanning electron microscopy, transmission electron microscopy, and energy dispersive spectroscopy. The microstructural analysis shows that the SiO2 wires are high purity silica and are completely amorphous; their diameter ranges from 70 nm to 2 μm. The fiber length varies from 100 μm to several mm. The wire manufacturing process involves reduced temperatures and times (1000 °C, 30 min) compared to other processes, without needing any catalyst and has been carried out on different kinds of substrates (SiC and Si). Successful growth of SiO2 wires on the surface of silicon microcantilevers has been demonstrated; they could be used as an alternatively way to enhance the sensor performances.

Thermo-mechanical analysis of Wire and Arc Additive Layer Manufacturing process on large multi-layer parts

Wire and Arc Additive Layer Manufacturing (WAALM) is gaining increasing popularity as the process allows the production of large custom-made metal workpieces with high deposition rates. The high power input of the welding process, causes significant residual stress and distortion of the workpiece. This paper describes the thermo-mechanical behaviour of the multi-layer wall structure made by the WAALM process. A 3D thermo-elastic–plastic transient model and a model based on an advanced steady-state thermal analysis are employed in this study. This modelling approach shows a significant advantage with respect to the computational time. The temperature simulations and distortion predictions are verified by comparing with the experimental results from thermo-couples and laser scanners, while the residual stresses are verified with the neutron diffraction strain scanner ENGIN-X. The stress across the deposited wall is found uniform with very little influence of the preceding layers on the following layers. The stress redistributed after unclamping with a much lower value at the top of the wall than at the interface due to the bending distortion of the sample.

Control crucial to copper rod quality

Dieter Klefoth and Stefan Seemer look at a demand-based speed-controlled pump system. This, with new submersible pumps together with state-of-the-art control systems, has been instrumental in lowering the power consumption and raising the reliability and quality of a copper wire manufacturing process in Germany.

Non-Uniform Bronze Formation in Internal Tin ${\rm Nb}_{3}{\rm Sn}$ Wire

The bronze phase transformations during the heat treatment of two multifilamentary internal tin Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn wires for high field applications made by Luvata are investigated and compared with some model single core wires. Non-uniform bronze profiles, non-uniform Sn distributions in different bundles, and Sn concentration gradient inversion were observed. Their possible formation mechanisms and consequences are discussed in relation to crystal orientation, Ti addition and microstructure. Wire manufacturing processes such as wire drawing impart preferred orientations on the components. The effect of wire texture on Cu-Sn interdiffusion and non-uniform bronze formation was investigated and believed not to be the cause of the non-uniform bronze profiles. 3-dimensional X-ray microtomography is applied to explain the non-uniformity in different bundles by analyzing the porosity formed during reactive diffusion of the low-melting phases. Ti is often added as a ternary addition, either in the Sn core or as Nb-Ti. In the Luvata wires investigated, Ti is present in Sn as the intermetallic compound Ti <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> Sn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> . Its dissolution through a ternary CuSnTi phase, possibly via reaction with CU <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> , has been observed. EDS mapping of the Ti distribution suggests that it is likely to be responsible for the inversion of the Sn concentration gradient. The potential advantage of adding Ti in Sn over using Nb-Ti alloy is discussed. Critical temperature measurements were performed to relate superconducting properties to the phase transformations, composition changes and non-uniform bronze formation.