A Comparison Study on Relationship Between Welding Current and Penetration for Plasma Enhanced Shielded Metal Arc Welding(PESMAW).

For open root pass girth welds, manual welding with cellulosic electrodes is still the most widely used process in spite of its susceptibility to hydrogen-induced defects. Barring considerable losses due to productiondelays and failures, the pipeline industry has learnt to live with these defects, as cellulosic electrodes are capable of producing low cost, high penetration welds- a prerequisite for pipe welding. Nevertheless, attempts have been made by researchers to reduce hydrogen levels in pipeline weldments either by altering the procedure techniques or by adopting different processes or by introducing new fabrication materials and methods. The Plasma Enhanced Shielded Metal Arc Welding (PESMAW), a modified version of the conventional Shielded Metal Arc Welding (SMAW) is one among these attempts, aimed to amplify penetration levels in general-purpose, rutile-coated electrodes at comparatively lower currents. It employs gas carrying tubular covered electrodes with a specially designed Universal Electrode Holder (UEH), which has provisions for external gas supply through the orifice of the electrodes. The gas introduced at the tip of the electrode gets ionized in the arc column and develops auxiliary plasma. This enhances the heat content of the weldment and yields high penetration weld beads at low currents. This paper presents an investigation on the performance of PESMAW by applying it to the welding of mild steel sheet of thickness 5 mm. The effect of welding current on bead geometry & shape relationships of welds, micro hardness analysis andweld microstructure were studied. Flat position ‘bead on plate’ technique was used to deposit weld beads in a mechanized manner. CO2 was used as the orifice gas through the general-purpose rutile coated tubular electrodes. It was observed that the flow of orifice gas during welding resulted in the increase in weld penetration, while the absence of plasma gas resulted in flatter and wider weld beads

An investigation on relationship between process control parameters and weld penetration in robotic CO2 arc welding using factorial design approach

Weld penetration is an important physical characteristic of a weldment that affects the stress carrying capacity of the weld joint. Several welding parameters seem to influence weld penetration. This paper presents the relationship between weld penetration and four direct welding process parameters of robotic CO2 arc welding process on structural carbon steel. Two level, full factorial design was applied to investigate and quantify the direct and interactive effects of four process parameters on weld penetration. The upper and lower limits of the process control variables were identified through trial and error methodology, and the experiments were conducted using ‘bead on plate’ mode. The performance of the model was then tested by using analysis of variance technique and the significance of the coefficients was tested by applying student’s‘t’ test. Commercial computer programs were used for statistical analysis. The main and interactive effects of different welding parameters are studied by presenting it in graphical form

Rheocasting and Thixocasting: Semi-Solid Casting Technologies

The new trend in the automotive industry and aerospace industry to produce more fuel-efficient automotive vehicles and lightweight engineering components has resulted in the increased use of aluminium and magnesium alloys. Currently, high-pressure die-casting process fulfils the bulk requirement of the automotive industry as well as aerospace industry needs. However, the increasing demands on quality and weight reduction have driven the development of new casting processing technologies. The problems associated with liquid metal high-pressure die-casting have resulted in the increased interest in semi-solid forming processes. Such processes are rheocasting and thixoforming technologies. Rheocasting and thixocasting are potential semi-solid casting techniques. Both are potential foundry processes capable to manufacture lightweight aluminium and magnesium alloy castings. In this article, various aspects on rheocasting technology and thixoforming process are discussed in a simplified manner

Effect of Lead Addition in LM6 Alloy Castings

In this research work, lead is added in the LM6 alloy melt and casting samples in the form of a slab are made by pouring the treated alloy in the sand moulds. Lead is added in the range from 2% to 14% in the chosen LM6 alloy. The chosen pouring temperature was around 800 degree centigrade. In this work, effect of lead on the hardness, microstructure and impact strength are discussed. Besides, corrosion resistance tests are conducted and the results are discussed. Fracture surface studies are also conducted on the samples after the impact test and fractographs are captured to analyse the type of failure

A PREDICTION OF WELDING PROCESS CONTROL VARIABLES BY PREDICTION OF WELD BEAD GEOMETRY USING FACTORIAL DESIGN APPROACH

Plasma Enhanced Shielded Metal Arc Welding(PESMAW) is a modified version of the age old manual metal arc welding (MMA) where the cellulose based flux coated solid wires are replaced by tubular low hydrogen flux coated electrodes. PESMAW process is aimed to eliminate the usage of cellulose in the electrode coating so as to save some trees and hence make the welding process partially green. The high heat content of the cellulose supported arc is achieved by controlled supply of auxiliary plasma gas through the tubular wire directed into the arc. This paper discusses the influence of the welding process parameters to the weld bead characteristics of weldments made by PESMAW process using mild steel as base metal. Two level fractional factorial design was adopted to investigate and quantify the direct and interactive effects of four major control parameters. “Bead on plate” technique was used to lay weldments and bead geometry was measured using standard metallurgical procedures. Statistical models were made from the obtained results and were analyzed and tested by using analysis of variance technique and students‘t’ test. The estimated and obtained values were compared. The main and interactive effects of control parameters were studied and presented in graphical form

Establishing a Hybrid Laser Lathing Technology

Traditional contact lathing is greatly challenged by the rapidly being developed super hard engineering materials. Being the earliest machining process, lathing operation captures 60 % of the total machining processes in most metal cutting industries. This paper reviews the literature related to the available technological solutions for non-contact laser lathing process. It also aims to establish a novel methodology to propose a hybrid non-contact lathing operation using a flatbed CO laser cutting machine.While exposing 2 the various techniques of laser lathing, preliminary empirical work conducted shows a promising future of hybridizing CO laser flat cutting into laser lathing process. The summary of this paper is expected to create a 2 leap in laser machining process towards developing a hybrid laser processing of materials involving transformation of 2D flat cutting into 3D laser turning to cater the market of precision machining