Dimensions Of Heat-affected Zone Research Articles

Effect of CO2 Laser Fluence on Cladding Geometrical Dimensions Alternations

Geometrical dimensions could play a potential role in the function of laser cladding of nickel-base powder on the cold-rolled carbon steel substrate. The geometrical dimensions and their impact on the efficiency of the process of laser cladding of nickel-base powder (Ni -10wt% Al) on cold rolled 0.2% carbon steel substrate was investigated. This work focused on the effect of laser-specific energy input of CO2laser. The geometrical dimensions of cladding regions are including cladding width, cladding height, depth of dilution, contact angle, dilution area, cladding area, and heat-affected zone dimensions determinations. The laser power (1.8 kW) was used at different traverse speeds (1.5, 3.6, 5, 7.1, 8.6, 12.5 mm/s) with (3mm) laser beam diameter. The feed rate was kept constant after many preliminary claddings at approximately 11 g/min. Fluence values ranged from (48-400J/mm2), and the power density value was (255W/mm2). A minimum dilution percentage (25%) was obtained at the highest fluence value (400 J/mm2). Observations were measured using an optical microscope, scanning electron microscopy, and Image software. Obtained results indicated that the increase in the fluence leads to an increase in height of cladding, HAZ region but lower depth of dilution

Improved grain structure prediction in metal additive manufacturing using a Dynamic Kinetic Monte Carlo framework

This work describes a Dynamic Kinetic Monte Carlo numerical modeling framework that can predict the microstructure of metals during powder bed fusion (PBF) and directed energy deposition (DED) additive manufacturing (AM) while considering significant variations in thermal history and heat accumulation that occur during the build. Although the conventional Kinetic Monte Carlo (KMC) method is well-established, it does not accommodate variation in the spatial domains of the melt pool (MP) and heat affected zone (HAZ) with time. Thus, the predicted microstructure remains relatively similar even over large AM build domains. While the existing KMC approach may suffice over spatial regions in which the MP and HAZ remain relatively unchanged, this circumstance is largely contrary to what experimentalists have recently found when imaging different regions in PBF and DED AM builds, thus raising issues with scalability and versatility of the method. The Dynamic KMC framework proposed in this work addresses these concerns by implementing discretized, spatially-varying MP and HAZ at every time increment during the grain structure prediction. The new framework operates in two stages; stage one establishes the 3D spatial MP and HAZ dimensions using either thermal finite element (FE) simulation or through experimental 3D thermal imaging; stage two subsequently integrates these time-varying MP and HAZ dimensions into the KMC algorithm at every time increment during the build. Thus, the Dynamic KMC framework captures the effects that rapid thermal cycles and heat accumulation have on grain nucleation and growth. The method is demonstrated through a case study involving a thin-walled Inconel 625 structure made by the selective laser melting (SLM) type of laser-based powder bed fusion (PBF-LB). The numerically predicted microstructures at various regions and scan layers within the build show strong agreement with experimentally observed trends reported in literature. Significant variations in grain morphology predicted by the Dynamic KMC framework can, according to specific thermal histories, provide investigators with new capabilities in assessing mechanical property variations across different regions of AM parts. • A Dynamic Kinetic Monte Carlo (KMC) framework for microstructure prediction in metal additive manufacturing is demonstrated. • Microstructure evolution is captured based on dynamic melt pool and heat affected zone behavior due to 3D heat accumulation. • Microstructure results using the novel framework for a thin-walled Inconel 625 SLM build agree with experimental observation. • More realistic microstructures in laser-based powder bed fusion and directed energy deposition can therefore be predicted.

Numerical and Experimental Investigations of Trajectory Effects into Temperature Distribution and Distortion in the Slot Welding of Steel S235JR

One of the significant factors that impresses on welded parts’ performance is welding trajectory. Slotted samples with loop and parallel trajectories welded by two steel plates by S235JR and GMAW process. Temperature distributions were registered by the four K type thermocouples. Heat affected zone dimensions were measured on polished and etched cross-sections of each sample. Induced distortions by dial indicators were gauged along welding process and cooling. To evaluate temperature field and distortion in the welding process, three-dimensional FE models were performed. There was good agreement between the FE model predictions and experimental measurements. The most temperatures, distortions and induced longitudinal and transverse residual stresses by welding in the loop trajectory were more than the parallel.

Effect of Inverter Power Source Characteristics on Welding Stability and Heat Affected Zone Dimensions

The paper presents results the research in the effect of power sources dynamic characteristics on stability of melting and electrode metal transfer to the weld pool shielded metal arc welding. It is proved that when applying inverter-type welding power sources, heat and mass transfer characteristics change, arc gap short-circuit time and drop generation time are reduced. This leads to reduction of weld pool heat content and contraction of the heat-affected zone by 36% in comparison the same parameters obtained using a diode rectifier.

COMPUTER ANALYSIS OF THE GMAW AND GMAW-CW WELDING THERMAL CYCLES

A novel process of welding GMAW-CW (Gas Metal Arc Welding-Cold Wire) had been developed with it resemblance to the GMAW (Gas Metal Arc Welding), the GMAW-CW has an additional wire fed into de weld pool, allowing better deposition rates, while maintaining weld characteristics. However, there is a more complex situation related to the HAZ (Heat Affected Zone) and weld geometry prediction than the GMAW conventional. The welding energy is a high metallurgical important parameter because together with the geometric characteristics of the gasket and the preheat level is decisive in thermal cycles imposed to the material, and therefore in the possible microstructural transformations and behavior of the joint. The behavior of representative curves of thermal cycling reflects important aspects regarding the conditions used in welding. Usually such factors as the type of process, use or non- pre or post- heating, heat input, multipass welding, are able to establish differences in the form of a heat cycle curve. In this work, it was applied the dual ellipsoidal model of heat input, adapted to the GMAW-CW and compared to the same model over the GMAW, using existing experimental data and predicting the HAZ dimensions in function of weld and welding parameters. The results found had less than 10% error from experimental data in a more refined version of the model, whereas the difficulties to predict cold wire addition influences were not trivial.

Process Parameter Selection for Resistance Spot Welding through Thermal Analysis of 2 mm CRCA Sheets

An attempt is made to arrive at suitable process parameters for resistance spot welding through thermal analysis. 2mm Closed Rolled Closed Anealing (CRCA) sheet metal is selected as work piece. Nugget and electrode diameter are evaluated from emperical relations. Full factorial Design Of Experiment (DOE) is applied for weld current and time. Thermal analysis is carried out for selected DOE values using SYSweld. Temperature distribution, nugget and Heat Affected Zone dimensions are obtained from the analysis. Weld strenght is analysed through experimental trails. Optimum process parameter for spot welding of 2mm CRCA sheet is arrived by comparing simulation and experimental results.

Modeling and prediction of HAZ using finite element and neural network modeling

A B S T R A C T A R T I C L E I N F O With the increasing demands for product variety and quality level the need to eliminate human operator from the feedback path for welding process correction is evident. Of the several manufacturing methods welding alone has defined true automation. Success of automation depends on effective and efficient decision making tools. Neural network is applied to intelligent weld control. In Submerged Arc Welding (SAW), selecting appropriate values for process variables is essential to control heat affected zone (HAZ) dimensions and get the required bead size and quality. Also, conditions must be selected that will ensure a predictable and reproducible weld bead. This paper proposes the modeling and prediction of dimensions of Heat-Affected Zone for SAW process using Finite Element Analysis (FEA) and Artificial Neural Network (ANN). The dimensions of HAZ for SAW are modeled are simulated using FEA using the process variables such as welding current, arc voltage, arc efficiency and welding speed and the results are used as the learning file for ANN model. The developed ANN model is forwarded to predict the dimensions of HAZ and the results are compared with simulated FEA results. The developed method is found to be time consuming, competent and cost effective.

Laser surface alloying of medium carbon steel with SiC (P)

Laser surface alloying (LSA) is increasingly recognised as a powerful surface modification tool to enhance the wear and corrosion resistance of engineering components. The present work deals with laser alloying of medium carbon steel with silicon carbide using a high-power CO 2 laser. A processing regime, identifying an appropriate laser power-scan speed combination for achieving defect-free alloyed layers, has been established during the study. The influence of repetitive scans on the alloyed layer properties was also subsequently investigated in a comprehensive manner. Repetitive scanning was found to affect substantially the laser-alloyed zone (LAZ) and heat-affected zone dimensions, as well as the phase constitution of the laser-alloyed layers. The microstructure in the LSA layers was also observed to vary significantly with the number of scans, besides changing quite distinctly with depth in the LAZ. Tribological tests revealed considerable improvement in abrasive wear performance by laser surface alloying, and the results also emphasise the need to control the number of repetitive scans to achieve optimum performance.