Heat Affected Zone Geometry Research Articles

Influence of cold-wire tandem submerged arc welding parameters on weld geometry and microhardness of microalloyed pipeline steels

Tandem submerged arc welding with an additional cold-wire (CWTSAW) is being developed for pipeline manufacturing to improve productivity in terms of deposition rate and travel speed of welding. An appropriate understanding of the welding conditions to guarantee requisite weld geometry, appearance, and mechanical properties is always essential in the development of a welding process. Currently, the effect of the cold-wire addition parameters on dilution and the geometry and properties of the weld metal (WM) and the heat-affected zone (HAZ) is not well understood. In this work, heat input, voltage, and travel speed of both electrodes along with three main cold-wire parameters are investigated and correlated with the geometry of the weld and HAZ, i.e., aspect ratio (AR), semi-penetration ratio (SPR), reinforcement area (RA), and coarse-grained heat-affected zone (CGHAZ) area, dilution, and the microhardness of the WM and CGHAZ. The results showed that varying the cold-wire parameters significantly affects the dilution, AR, SPR, and microhardness. The addition of a cold-wire at a lagging position with a feed speed of 8.5 mm/s at 63° resulted in an overall improvement in the weld geometry, dilution, and microhardness. Cold-wire addition led to a reduction in the CGHAZ area, the amount of dilution, and the microhardness of the CGHAZ. Microstructural analysis, using both optical microscopy and scanning electron microscopy (SEM), indicated the formation of finer prior austenite grains (PAGs) and less martensite-austenite (M-A) constituent within the CGHAZ of the CWTSAW samples. The appropriate process parameters are defined to control the weld and HAZ geometry, dilution, and mechanical properties.

Numerical Prediction of Fusion Zone and Heat Affected Zone in Hybrid Yb:YAG laser + GMAW Welding Process with Experimental Verification

This work concerns mathematical and numerical modelling of temperature field during hybrid welding process using Yb:YAG laser and electric arc in GMAW method. Numerical analysis is performed taking into account the motion of liquid steel in the fusion zone. Yb:YAG laser power distribution is determined on the basis of experimental research made on TruDisk 12002 laser. Geostatistical Kriging method is used in the interpolation of Yb:YAG laser power intensity distribution. Temperature field and melted material velocity field in the fusion zone of hybrid welded sheets made of S355 steel are obtained on the basis of numerical solution of continuum mechanics equations in Chorin's projection method and finite volume method. Experimental research of laser beam profile is performed in order to verify the correctness of developed heat source model. Fusion zone and heat affected zone geometry is predicted on the basis of calculated temperature field in the cross section of hybrid welded joint.

ВЛИЯНИЕ МОЩНОСТИ ЛАЗЕРНОГО ИЗЛУЧЕНИЯ И СКОРОСТИ ДВИЖЕНИЯ ЛУЧА НА ГЕОМЕТРИЮ ЗОНЫ ОПЛАВЛЕНИЯ ПРИ ЛАЗЕРНОЙ ЗАКАЛКЕ СТАЛИ 40X

The improvement of operating characteristics of the working surfaces of machine parts, tooling and metal cutting tools is important for the modern industry. Laser hardening is one of the most intensively developing methods of improvement of friction surfaces wear resistance. Laser hardening of treated surface is possible from liquid or solid state. The largest values of depth and width of a hardened layer are achieved when laser hardening from the liquid state. The application of laser hardening with surface flashing is possible for a large range of body parts. In this regard, the study of hardened zones structure and the selection of modes that cause the maximum hardened layer characteristics are important for the implementation of laser hardening technology under factory conditions. The paper presents the results of experimental study of the influence of the emission power of the quasi-continuous fiber optic ytterbium laser and laser beam velocity on the geometry of 40H steel flashing zone, not including changes in heat-affected zone geometry. Using the LK-150/1500-QCW-AC laser emitter, the authors formed on the surface of 30105 mm samples the isolated thermal wake with distinctively noticeable fluxed zone and then studied the cross-section of this wake using the LaboMet-1 microscope. In the result of the study of fluxed zone cross-section geometric characteristics, the authors determined the treatment modes at which the fluxed zone cross-section appearance changed and defined its width and depth depending on the laser emission power. Laser treatment modes are defined when the largest difference between the fluxed zone depth and the depth of the crater formed on steel surface is achieved.

Numerical Analysis of Laser Heating for Laser Assisted Micro Milling Application

The promising processing techniques of micro scale parts are very important in products miniaturization and functions enhancement. Combination of two or more processing techniques gives better processing performance especially when dealing with difficult-to-cut materials. For that reason, the combination of laser beam and micro milling process has been widely studied and proven efficient in reducing cutting force and tool life extension. However, this process needs a precise temperature control in order to eliminate heat effect generated by laser beam irradiation. In this study, temperature distributions are determined numerically to characterize the melted zone and heat affected zone geometry. From the results, the estimation of tool and micro milling cutter distance together with the allowable depth of cut are determined.

Parametric finite element model for spiral welded pipes sections loaded in tension

Spiral welded pipes gain interest for oil and gas transportation in strain based design projects. Here, the structural response of the pipe with an environmentally imposed global plastic strain is of critical importance. However, a current lack of knowledge about the structural response of a spiral welded pipeline hinders the application in a strain based design context. This response is not only influenced by material properties, but also by geometrical characteristics. To understand these complex phenomena, finite element simulations can be considered. The finite element models need to incorporate all important factors to obtain a representative analysis. This paper describes the approach and structure used to develop such model. To obtain a high degree of automation and flexibility, the authors have developed a parametric script that allows creating a three dimensional curved wide plate test geometry taken from a spiral welded pipe. The model allows to modify pipe geometry, weld and heat affected zone geometry and material properties including Hill’s 1948 yield criterion to account for anisotropic material response. Pipe geometry includes helical forming angle, diameter, pipe profile and wall thickness with possible thickness variations. Weld and heat affected zone geometry include geometrical weld reinforcement of root and/or cap, fusion line profile and misalignment. A flaw, with variable size, is introduced in the weld metal or heat affected zone. To obtain an accurate description of the actual geometry, coordinate transformation schemes are incorporated that start from a flat plate with a simplified girth weld geometry. It is concluded that the proposed model is ready for use with a good view on mesh quality and output accuracy.

La découpe de l’acier par laser CO2. Étude de la zone affectée thermiquement

The growth of laser cutting industry is well known, especially for steels. By using oxygen as assisting gas, a high cutting rate is achievable. If a lot of works have been reported on the process itself and on its efficiency, little attention has been focused on metallurgical transformation induced in the heat affected zone (HAZ) in the steel sheets, while these effects are of major importance for the further use of the laser cutted workpieces. The present paper reports results concerning the investigation of working parameters influence on HAZ geometry near the cut edges induced by heat flow during laser cutting. Materials investigated were mild steel (E24) and medium carbon steel (XC42). Beam power, oxygen pressure, thickness of the sample and travel speed of the workpiece were varied. The configuration of the HAZ geometry and microstructure observed were explained. This experimental program indicates that there is a strong effect of the experimental parameters on the HAZ geometry. Both geometrical and hardness measurements are reported.