Informatics Publishing Limited

Rohith Joseph ¹, M. Salai Selva Rani ², K. Devakumaran ³, P. R. Venkateswaran ³

Affiliations
1 JJ College of Engineering and Technology, Tiruchirappalli, IN
2 Sastra University, Thanjavur, IN
3 Welding Research Institute, Bharat Heavy Electricals Limited, Tiruchirappalli, IN

Abstract

Performance evaluation of the transistorized and invertor type GMAW power source under various modes of operations as continuous, pulsed and dual pulse is discussed in this paper. The performance of the power source has been evaluated with respect to the variation of current and voltage under different wire feed rates. The data is analyzed for identification of optimum working range of current and voltage with reference to less spatter, porosity and good weld bead appearance. Based on the results, the choice of the GMAW power sources for different applications is established. This study provides wider scope for introduction of automation of welding.

Keywords

GMAW, Dual Pulse, Transistorized, Inverters and Power Source Characteristics.

Full Text

     

P. K. Ghosh ¹, K. Devakumaran ¹, M. Piyush ²

Affiliations
1 Department of Metallurgical & Materials Engineering, Indian Institute of Technology Roorkee, Roorkee -247 667, IN
2 National Institute of Technology Trichy, Trichy-620015, IN

Abstract

The arc stability and performance of pulse current gas metal arc welding (P-GMAW) process under different pulse parameters (considered as their summarized influence defined by a factor Φ and shielding gas compositions have been studied through an analysis of irregularity in pulse waveform during weld deposition of low alloy steel. The arc stability has been primarily analysed as average number of peaks (N_PAJ shooting above an arbitrarily defined current (I_S) at a given interval of arcing, average deviated current (I_DC) defined as summation of shooting peak current (I_SP) beyond the I_S per peak of instability, average time interval of deviated current (T_IDC) and average duration of deviated current (T_DDC). The performance of the P-GMAW process has been analyzed with respect to its response to short circuiting. The effect of pulse parameters has been analyzed as a function of Φ, I_m and arc voltage and the shielding gas compositions has been studied with varying content of CO₂ in An It is observed that the arc stability and performance of the P-GMAW power source significantly vary with the change of pulse parameters and CO₂ content of argon gas shielding. A relatively higher Φ, I_m and arc voltage and low CO₂ content of Ar gas shielding provides better arc stability with low short circuiting.

Keywords

P-GMAW, Arc Stability, Shielding Gas, Pulse Parameters, Low Alloy Steel.

Full Text

     

P. K. Ghosh ¹, Ravi Ranjan Kumar ¹, K. Devakumaran ¹

Affiliations
1 Dept. of Met. & Mat. Engg., Indian Institute of Technology- Roorkee, IN

Abstract

Analytical studies on mode, magnitude and distribution of shrinkage stress in eight quadrants of a thick wall stainless steel pipe weld have been carried out. The studies have been conducted on GMA and pulse current GMA welds prepared by using conventional-V and narrow weld groove designs at different welding parameters. The effects of ail such variables on the said aspects of transverse shrinkage stress have been analysed. During welding, different quadrants of pipe are found to experience shrinkage stresses of non uniform mode and magnitude and they further varies as a function of welding process, procedure and parameter. Use of P-GMAW comparatively lowers and results better uniformity in transverse shrinkage stress distribution at different quadrants of the pipe weld than that observed in case of using GMAW. Keeping higher heat input and the pulse parameter giving larger value of their summarised influence defined a well known factor 0 results higher shrinkage stress. The dimensionless factor is defined as.  ϕ = [(I_I, / I_I,) f. t_h]. At a given heat input the narrow groove weld joint gives comparatively less transverse shrinkage stress. X-ray radiography of defect analysis reveals that the quadrants having compressive mode of stress gives rise to more lack of fusion at groove wall.

Full Text

     

P. K. Ghosh ¹, A. K. Saxena ², K. Devakumaran ²

Affiliations
1 Department of Metallurgical and Materials Engineering Indian Institute of Technology Roorkee - 247667, IN
2 Department o f Metallurgical and Materials Engineering Indian Institute o f Technology Roorkee - 247667, IN

Abstract

Weldability of a controlled rolled HSLA steel plates having thickness of 18, 25 and 34 mm has been studied by multipass SAW process with SMAW ischolar_main pass. The mechanical and metallurgical properties of the all weld deposit and axial weld joint have been studied. In 34 mm thick plate the weld metal microstructure has been found comparatively finer with more reheat refinement than 18 mm and 25mm thick plates, with improved properties. The weld joints are generally found to fracture from the region away from fusion line showing the strength of the weld higher than the base material. However, the presence of certain amount of inclusions may have lowered the mechanical properties of weld deposits up to certain extent. Reheat refining has been found to improve the toughness of weld metal. The toughness of HAZ mostly found comparable to that of the base metal as such the weldability of controlled rolled HSLA steel has been qualified for welding fabrication of penstock liner.

Full Text

     

P. K. Ghosh ¹, M. Ravi Reddy ¹, K. Devakumaran ¹

Affiliations
1 Dept. of Met. & Mat. Engg., Indian Institute of Technology - Roorkee, IN

Abstract

The transverse shrinkage stress generated in welding of 10, 12 and 25 mm thick steel plates using different welding processes and procedures has been estimated and its varying effect has been verified with the help of experimental measurement of distortion produced during welding. The weld joints of 10 and, 12 mm thick plates have been prepared by using the GMAW and pulsed current GMAW (P-GMAW) processes with standard V-groove design whereas the 25 mm thick plate was welded by SMAW process employing V- groove and narrow groove design. At a given heat input and weld groove size the effect of welding processes and procedures on variation of shrinkage stresses in weld deposit causing distortion of weld joint has been substantiated by estimation of bending stress developed in the weld joint through measurement of bending of the plate. It is observed that the use of PGMAW is advantageous over the GMAW with respect to reduction in stress development in weld joint. The use of narrow groove design has also been found beneficial for reduction of stresses generated in the weld joint in comparison to those observed in case of using V-groove design.

Full Text