Transferability of the working envelope approach for parameter selection and optimization in thin wall WAAM

This work aims to propose and assess a methodology for parameterization for WAAM of thin walls based on a previously existing working envelope built for a basic material (parameter transferability). This work also aimed at investigating whether the working envelope approach can be used to optimize the parameterization for a target wall width in terms of arc energy (which governs microstructure and microhardness), surface finish and active deposition time. To reach the main objective, first, a reference working envelope was developed through a series of deposited walls with a plain C-Mn steel wire. Wire feed speed (WFS) and travel speed (TS) were treated as independent variables, while the geometric wall features were considered dependent variables. After validation, three combinations of WFS and TS capable of achieving the same effective wall width were deposited with a 2.25Cr-1Mo steel wire. To evaluate the parameter transferability between the two materials, the geometric features of these walls were measured and compared with the predicted values. The results showed minor deviations between the predicted and measured values. As a result, WAAM parameter selection for another material showed to be feasible after only fewer experiments (shorter time and lower resource consumption) from a working envelope previously developed. The usage of the approach to optimize parameterization was also demonstrated. For this case, lower values of WFS and TS were capable of achieving a better surface finish. However, higher WFS and TS are advantageous in terms of production time. As long as the same wall width is maintained, variations in WFS and TS do not significantly affect microstructure and microhardness.

Molten Pool Behaviors in Double-Sided Pulsed GMAW of T-Joint: A Numerical Study

The T-joint is one of the essential types of joints in aluminum welded structures. Double-sided welding is a preferable solution to maintain high efficiency and avoid significant distortion during T-joint welding. However, interactions between double-sided molten pools make flow behaviors complicated during welding. Numerical simulations regarding molten pool behaviors were conducted in this research to understand the complex flow phenomenon. The influences of wire feed rates and torch distances were simulated and discussed. The results show that droplet impinging drives the fluid to flow down to the root and form a frontward vortex. Marangoni stress forces the fluid to form an outward vortex near the molten pool boundary and flatten the concave-shaped molten pool surface. With an increased wire feed speed, the volume of the molten pool increases, and the root fusion is improved. With an increased torch distance, the width of the front molten pool decreases while the length increases, and the rear molten pool size decreases slightly. Both wire feed speeds and the torch distances have limited influences on the basic flow characteristics.

Synthesis of Fuzzy Logic Mathematical Model for Adaptive Control of the Mig/Mag Surfacing

A functional transformer with fuzzy logic is synthesized, which allows to get the estimations of weld beads height and width at the arbitrary values of entry parameters: wire feed speed and torch transverse oscillations amplitude. The influence of these input parameters on the base metal penetration and beads geometric parameters, welded using MIG/MAG process, were studied. Surfacing was performed by a robotic system with an arc power supply "Fronius TPS- 320i", which operated in the mode of arc process synergetic control. The formation of both individual beads and surfacing layers at different overlap coefficients has been studied. The arc surfacing process was realized in a mixture of protective gases (Ar+18%CO2) using a welding wire Св-08Г2С with a 1.0 mm diameter. Surfacing speed – 4 mm/s, frequency of welding torch oscillations – 1 Hz. The obtained experimental dependences of beads width and height, as well as the length of the welding pool can be used in both: creating of multi-pass MIG/MAG surfacing program for robotic restoration of critical purposes parts surfaces, and in preparing of FEM model of MIG/MAG surfacing.

A model for Manufacturing Large Parts with WAAM Technology

Wire Arc Additive Manufacturing (WAAM) is a metallic additive manufacturing process based on the fusion of metallic wire using an electric arc as a heat source. The challenge associated with WAAM is heat management and understanding bead geometry. The printing process involves high temperatures, which results in the build-up of residual stresses can often cause deformations in a component. All of the process variables, such as torch speed (TS), wire feed speed (WFS), idle time, combine to produce the geometry of the deposit bead that results in the desired component shape. So, determining a method for choosing a good combined parameter process is very important to obtain a high-quality part. This article presents a study on how to use the WAAM process to produce a complexity part of aluminium alloys. The step of the determination process parameter is concentrated to develop in this study. An experimental design is determined to study the influence between the process parameters, for example, WFS, TS, high layer, length of bead. Different samples are made using the Yaskawa robot, using the classic CMT (Cold Metal Transfer) as a manufacturing method, using zigzag filling as a manufacturing strategy with the same WFS and same idle times and different TS, different bead lengths. A new manufacturing method using the zigzag filling strategy is proposed by adding an important step in determining the process parameters. The results indicate that the length of the bead has a significant impact on another parameter of the process.

METHOD TO DEFINE MEASUREMENT UNCERTAINTY FOR DESIGN SPACE EXPLORATION IN ADDITIVE MANUFACTURING

Additive manufacturing is a process used for quick prototyping in industries. Geometrical defects are observed on printed parts. The aim of the paper is to propose a design method to implement measurements uncertainties into a Design Space for Additive Manufacturing parameters selection. To do so, two tests have been realized. The first test consists in determining the instrument’s uncertainty by measuring a standard length several times by an operator. The second test aim to determine the uncertainty within operators mesurement of geometric outputs (clad’s height, clad’s width, dilution’s height, dilution’s width and contact angle). Based on the results of our tests, uncertainties have been applied in our Design Space populated with 31 real printed clads. The uncertainties display with error bars on scatterplots allow to capitalize the knowledge for his/her exploration of the Design Space for future prints. The given information provides to ease the engineer to select the optimal solution (laser power, tool speed and wire feed speed) for his/her given Additive Manufacturing problematic among candidate points

Forming Process of Wire and Arc Additive Manufacture

The forming process of wire and arc additively manufacture (WAAM) was studied using the self-developed and designed WAAM system. The single-pass and single-layer weld bead samples were prepared with different process parameters, and the cross-sectional dimensions of the weld bead were measured. The influence rules of weld current, welding speed, wire feed speed and welding height on the weld bead size were obtained. In addition, the overlap experiment of the WAAM forming process was also carried out. The multiple and multilayer lap samples with different overlap rates were prepared, and the cross-sections of the lap samples were observed and analyzed. Finally, the overlap rate range of 35-45% with good forming effect was obtained.

Research on Parameters of Wire-Filling Laser Welding and Quenching Process for Joints Microstructure and Mechanical Property of BR1500HS Steel

With the aim to investigate the effect of parameter and quenching process on the joint of hot stamping steel by laser welding, the BR1500HS boron steel was welded by filling-wire laser welding with ER70-G welding wire under different parameters. The welded specimens were heated to 900℃ and held for 5min before water quenching. The universal material test machine, Optical micro-scope, Vickers hardness tester, scanning electron microscope and electron backscatter diffraction (EBSD) were used to characterize. The results showed that the macroscopic morphology of fusion zone (FZ) becomes from funnelform to hyperbolic curve shape when heat input increases and from hyperbolic curve shape to funnelform when wire-feed speed increases. The strength after quenching is more than 1557Mpa at heat input of 1040J/cm, wire feeding speed of 1.6m/min~1.8m/min and welding speed of 1.5m/min. EBSD test showed that the FZ and fine grain zone (FGZ) have more retained austenite (RA) than coarse grain zone (CGZ) before quenching and RA in FZ and heat affect zone (HAZ) decreased and distributed uniformed after quenching. The grain diameter in FZ distribute unevenly, with the maximum grain diameter larger than 40μm before quenching. After quenching, the grain diameter of FZ, HAZ and BM is more even and coarse grains in the FZ was refined. Before quenching, the microhardness of FZ and HAZ is of 450HV~500HV at different heat input and wire-feed speed and all region of joint keeps at 450HV~550HV after quenching. Most dimple and little river pattern in the joint fracture mor-phology before quenching indicates a well plasticity and most cleavage facet is observed after quenching due to the joint combine with martensite.

Multi-properties optimization of welding parameters of wire arc additive manufacture in dissimilar joint of iron-based alloy and nickel-based superalloy using grey-based Taguchi method

In order to adapt to the high temperature and heavy load process environment of large forgings, a novel die with “fist-like” structure was designed. The iron-based welding material (RMD248) as the “bone” layer and the nickel-based superalloy welding material (ERNiCr-3) as the “skin” layer were welded on the matrix by wire arc additive manufacture (WAAM). In this work, the grey based Taguchi methodology was used to optimize welding parameters (welding voltage, welding speed and wire feed speed) considering excellent multi-properties (hardness and ultimate tensile strength of high-temperature tensile test) of the dissimilar joint of RMD248 and ERNiCr-3. Further, analysis of variance was done to ascertain the influence of welding parameters on response parameters. Experimental results showed that welding speed was the most effective input parameter followed by wire feed speed and welding voltage. Finally, optimal result was verified through confirmation experiments. Meanwhile, the effect of welding speed on the microstructure and mechanical properties of joint was studied. The microstructures were characterized by optical microscopy (OM), energy dispersive spectrometer (EDS). The results indicated that the microstructure of RMD248 was consisted of more retained austenite at lower welding speed. For ERNiCr-3, the finer columnar crystal structure at higher welding speed was observed. At lower welding speed, the microhardness of RMD248 was just slightly lower, but that of ERNiCr-3 was significantly higher, and the ultimate tensile strength was higher. Therefore, the specimen at lower welding speed had better comprehensive mechanical properties.

Development of mathematical model and optimization of GMA welding parameters of IS 2062 grade A steel weldments

In this experimental works, the effect of GMA welding process parameters, such as arc voltage, wire feed speed, and gas flow rate on the mechanical quality of IS 2062 structural steel of grade A has been studied. Process parameters play an important role in determining the weld quality. In this research work response surface methodology (RSM) technique via design expert (DOE) 12 version software was applied to determining the weld quality and also to develop a mathematical model that can predict the main effect of the above said parameters on weld quality i.e. toughness and hardness. A set of experiments has been conducted to collect the data using a central composite design and ANOVA was used to predict the impact of welding parameters on toughness and hardness and Comparison also made between the actual result and predicted value and from the result that is clear that toughness and hardness of weldment is significantly affected by arc voltage, wire feed speed, and follow by gas flow rate.

Application of MIG Welding Process of Mild Steel Wire in Additive Manufacturing

The purpose of this study is to investigate the forming characteristics of single-pass Metal Inert Gas (MIG) welding wire for multi-layer additive manufacturing parts. Influences of arc current, arc voltage, arc distances, welding speed, wire feed speed, temperatures and heat input on layer formation were analyzed. The deposition of material by MIG process is controlled by a robot (ABB) controller for constructing walls of rectangular box shape. The samples were measured with a microhardness testing and tensile testing onto the welded bead created by the additive manufacturing technique. It was found that the mechanical properties of microhardness values are between 151.70 to 155.80 HV and the tensile strength values are between 472.71 to 491.12 MPa according to transverse and longitudinal sections of the specimens.