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De, A.
- An Investigation on Effect of Process Parameters on Weld Bead Profile of Modified 9Cr-1Mo Steel by Pulsed GMAW
Authors
1 Larsen & Toubro Limited, Heavy Engineering IC, Powai Campus, Mumbai 400072, IN
2 Department of Mechanical Engineering, Indian Institute of Technology Bombay, Mumbai 400072, IN
Source
Indian Welding Journal, Vol 47, No 4 (2014), Pagination: 23-23Abstract
Environmental regulations requiring reduced C02 emissions coupled with demand for greater efficiency are demanding greater use of advanced creep resisting steels such as modified 9Cr-lMo (P91) for high temperature components in the power generation industry. Traditionally, modified 9Cr-lMo steels are welded using gas tungsten arc welding, shielded metal arc welding and submerged arc welding processes. In order to reduce costs and downtime, particularly for site repairs, recently there is much interest in the use of high productivity welding processes; particularly gas shielded welding processes such as Gas Metal Arc Welding (GMAW). However, the situation with GMAW, particularly with active gas mixtures, is more complex because of the variable recovery of key elements such as Mn, Si, and Nb/Cb. It has been reported that the solid wire Gas Metal Arc Welding (GMAW) process has not found widespread use in the industry mainly due to concerns over lack-of-fusion, sensitivity to welder error and demands for more sophisticated power sources. However, in recent past, as a process of potentially high productivity, interest in GMAW for welding P91 materials is increasing for Industrial applications.
In the present investigation, bead-in-groove trials are performed on a 12mm thick modified 9Cr-lMo material by pulsed current gas metal arc welding (GMAW-P) process. Two primary parameters like current and weld travel speed are considered in the present experiment and their effect on weld bead geometry, weld metal toughness and weld metal microstructure are discussed. The samples are also subjected to chemical analysis, oxygen content measurement, and inclusion level&hardness survey after PWHT. Response surface methodology (RSM) design approach is used to develop a mathematical relation between the input variables (current and speed) and responses. The developed model is then compared with the experimental results; it is found that the deviation falls within the limit of a 95% confidence level. The direct and interactive effects of the process parameters are also discussed in the present paper.
- Three-Dimensional Heat Transfer Analysis of Laser-Arc Hybrid Welding Process
Authors
1 Mechanical Engineering Department, Indian Institute of Technology Bombay, Mumbai – 400076, IN
Source
Indian Welding Journal, Vol 47, No 4 (2014), Pagination: 57-64Abstract
Laser-arc hybrid welding process employs a laser beam and a welding arc concurrently for the joining of thick plates at high welding speeds. Systematic quantitative studies to understand the role of welding conditions on the rate of heat input and weld pool profile are important but rarely reported for hybrid welding process. The current work presents a three-dimensional heat transfer analysis of hybrid welding process using finite element method. The computed results are validated using experimentally measured results that are reported in the independent literature. The model is used further to examine the effect of welding speed, laser and arc power, and the separation distance between laser beam and welding arc on the weld pool profile. The computed results show that the weld width will reduce with increase in welding speed and the separation distance while the penetration increases with the laser power.Keywords
Laser-Arc Hybrid Welding, Numerical Model, Heat Transfer Analysis, Weld Pool Profile.- Reliable Estimation of Volumetric Heat Source in Numerical Simulation of Fusion Arc Welding Process
Authors
1 Department of Mechanical Engineering, Indian Institute of Technology Bombay, Mumbai - 40006, IN
Source
Indian Welding Journal, Vol 45, No 4 (2012), Pagination: 51-65Abstract
In recent times, the conduction heat transfer based numerical process models have been able to provide reliable quantitative understanding of the peak temperature, thermal cycle and weld bead dimensions in several fusion welding systems. However, the reliability of the computed results from these models depends significantly on the presumed dimensions of typical volumetric heat source that accounts for the arc heat input into the workpiece. We present here an analytical procedure to estimate the dimensions of the volumetric heat source as function of welding conditions and weld joint geometry in single and two-wire arc welding processes with electrode material deposition. The computed results of thermal cycle and weld bead dimensions are validated extensively with corresponding experimentally measured results from single wire gas metal arc welding and two-wire submerged arc welding processes.- Three-Dimensional Heat Transfer Modeling of Laser Beam Welding using Adaptive Volumetric Heat Source and GA based Optimization of Absorption Coefficient
Authors
1 Mechanical Engineering Department, IIT Bombay, Powai, 400076, IN
Source
Indian Welding Journal, Vol 42, No 2 (2009), Pagination: 43-48Abstract
An accurate estimation of the temperature field in weld pool and its surrounding area is important for a priori determination of the weld pool and heat affected zone dimensions, and the weld thermal cycle. The present work reports a finite element based three-dimensional quasi-steady heat transfer analysis for prediction of temperature field and weld dimensions in laser welding process. The novel feature introduced in the model is that a volumetric heat source term is used to account for the energy absorbed by the molten weld pool. However, the volumetric heat source is defined in an adaptive manner by mapping it with the computed weld pool dimensions such that there is no need to predefine the heat source dimensions. The heat transfer model further considers temperature dependent material properties and the latent heat of melting and solidification. The numerical heat transfer model is further integrated with a genetic algorithm (GA) based optimization tool to optimize the value of absorption coefficient that is usually not known with confidence and required to calculate the net heat input into the workpiece. The predicted weld pool dimensions from the overall integrated model are validated successfully against similar experimentally measured results reported in independent literatures for laser beam welding process.