Subhash Chandra Saha

Optimization of the effect of welding heat input on the microstructure and mechanical properties of submerged arc welded joints by fuzzy-based multiobjective threshold acceptance algorithm

This article investigates the influence of welding heat input on the microstructure, hardness, ultimate tensile strength and toughness of submerged arc welding of plain carbon steel. An attempt was also made to find an optimal welding heat input conditions using Fuzzy logic–based multiobjective threshold acceptance algorithm. Phase analysis of weldments was evaluated at different welding conditions varying from 7.806 to 17.955 kJ/cm. Results revealed that the percentage of ferrite increases with the heat but pearlite percentage decreases and significant grain coarsening was observed in weld zone. Mechanical properties of the weld joints decrease with the increase of heat input. Fuzzy interference system has been adopted to solve the multiobjective problem to avoid the imprecision and uncertainty in weights of the responses. Threshold acceptance method has been introduced for finding optimal welding heat input condition. Finally, a confirmatory test was carried out using the optimal result to verify the effectiveness of this approach.

Process Parametric Optimization of Submerged Arc Welding by Using Utility Based Taguchi Concept

Achieving optimal weld parameters with desired quality features is very difficult because these quality features are highly correlated. There are several control parameters which directly or indirectly affect the response parameters. In the present study, an attempt has been made to search an optimal parametric combination, capable of producing desired high quality joint in submerged arc weldment by Taguchi method coupled with Utility theory. In the present investigation three process variables viz. Wire feed rate (Wf), stick out (So) and traverse speed (Tr) have been considered and the response parameters are hardness, tensile strength (Ts), toughness (IS).

3-D Modeling & Numerical Simulation of Friction Stir Welding Process

A 3D thermal pseudo mechanical model formulated in an Eulerian frame considering a quassisteady approach to Friction Stir welding modeling of AA6061 Aluminium alloy is proposed and implemented using nonlinear finite element code in Comsol Multiphysics v 4.1. The effect of different operating parameters on the temperature distribution was analyzed. The material flow is found to be enhanced with the increase in traverse speed and angular velocity of the pin with a pronounced swirl on the advancing side. The distribution of equivalent plastic strain and dynamic viscosity was found to correlate with the distribution of the microstructure zones in the weld.

Modelling and multi-response optimization of wire electric discharge machining parameters using response surface methodology and grey–fuzzy algorithm:

Wire electric discharge machining is a non-conventional machining wherein the quality and cost of machining are influenced by the process parameters. This investigation focuses on finding the optimal level of process parameters, which is for better surface finish, material removal rate and lower wire consumption for machining stainless steel-316 using the grey–fuzzy algorithm. Grey relational technique is applied to find the grey coefficient of each performance, and fuzzy evaluates the multiple performance characteristics index according to the grey relational coefficient of each response. Response surface methodology and the analysis of variance were used for modelling and analysis of responses to predict and find the influence of machining parameters and their proportion of contribution on the individual and overall responses. The measured values from confirmation experiments were compared with the predicted values, which indicate that the proposed models can be effectively used to predict the responses in the wire electrical discharge machining of AISI stainless steel-316. It is found that servo gap set voltage is the most influential factor for this particular steel followed by pulse off time, pulse on time and wire feed rate.

Evaluation of microstructure and mechanical properties of P91 steel weldment due to addition of boron trioxide into flux during submerged arc welding

The present investigation studied the effect of boron trioxide (B2O3) addition into flux on the microstructure and mechanical properties of modified 9Cr-1Mo (P91) steel in submerged arc welding (SAW) process. Boron trioxide powder was mixed with commercial flux in different ratios to change the weld metal chemical composition. Optical emission spectroscopy results showed that weight percentage of boron varies from 0.00 to 0.0068 with the addition of boron trioxide into welding flux. Weld metal microstructure without the addition of boron reveals the presence of tempered martensite and ferrite phase, whereas boron-added microstructures highlighted the dominating nature of tempered martensite. Scanning electron microscope analysis also showed that the dispersed carbides especially M23C6 were increased with the addition of boron. Weld metal macrohardness profile reveals that boron has the significant effect on the weld metals. The maximum hardness of 342 HV was found for the 12.5% B2O3, whereas weld of without boron shows the hardness of 240.8 HV. Boron addition has a positive effect on the tensile strength of weld joints except for the 12.5% B2O3. But the toughness of weld zone decreases with the addition of boron.

Effect of B2O3 containing fluxes on the microstructure and mechanical properties in submerged arc welded mild steel plates

This paper represents a study on the effect of B2O3 additions in fluxes on the microstructure and mechanical properties of the weld metal formed during Submerged Arc Welding of Mild Steel plates. Five fluxes with about 2.5, 5, 7.5, 10 and 12.5% B2O3 were used with a low carbon electrode. Welding process parameters were kept constant for all the conditions. The microstructure of weld metal for each flux consisted mainly of acicular ferrite, polygonal ferrite, grain boundary ferrites and equiaxed pearlite. It was noted that the Vickers hardness value was a function of boron content and shows a mixed trend. Impact Energy and Tensile Strength were increased with the increase in boron content in welds this can be attributed to relation with the higher acicular ferrite percentage. However an optimum level of toughness and tensile strength was available with 7.5% and 5% of B2O3 respectively. A qualitative comparison has also be done with fresh flux by means of full metallography and mechanically.

On the Issues of Asymmetry Observed in Heat Transfer & Material Flow in Friction Stir Welding

In this paper, a standard CFD code, COMSOL is used to describe the 3-dimensional modeling of friction stir welding using threaded tool and based on fully sticking friction. A standard threaded tool profile is used for the full flow analysis including heat generation and heat flow. Temperature distribution is analyzed for full sticking and sliding condition. The effect of different operating parameters on the temperature distribution was performed.The importance of cell Peclet number is also investigated in the temperature distribution on advancing and retreading side. The results are in reasonable agreement with the predictions.

Optimization of Process Parameters for Submerged Arc Welding by Weighted Principal Component Analysis Based Taguchi Method

In submerged arc welding (SAW), weld quality is greatly affected by the weld parameters such as welding current, traverse speed, arc voltage and stickout since they are closely related to weld joint. The joint quality can be defined in terms of properties such as weld bead geometry and mechanical properties. There are several control parameters which directly or indirectly affect the response parameters. In the present study, an attempt has been made to search an optimal parametric combination, capable of producing desired high quality joint in submerged arc weldment by Taguchi method coupled with weighted principal component analysis. In the present investigation three process variables viz. Wire feed rate (Wf), stick out (So) and traverse speed (Tr) have been considered and the response parameters are hardness, tensile strength (Ts), toughness (IS).

A Simplified Numerical Approach for Finding the Temperature Distribution in Submerged arc Welding Process

The quality of joining has assumed a greater role in fabrication of metal in recent years, because of the development of new alloys with tremendously increased strength and toughness. Submerged arc welding is a high heat input fusion welding process in which weld is produced by moving localized heat source along the joint. The weld quality in turn affected by thermal cycle that the weldment experiences during the welding. In the present study a simple comprehensive mathematical model has been developed using a moving heat source and analyzing the temperature on one section and then the temperature distribution of other section are correlated with time delay with reference analyzed section.

The Use of Taguchi Method Based on Desirability Function Approach for Optimization of Process Parameters in Submerged Arc Welding

In this paper, the Taguchi method coupled with desirability function approach is used for the optimization of response parameters in submerged arc welding (SAW). Desirability function (DF) approach has been introduced to convert the multi- response objective to single objective. Weld quality is greatly influenced by the weld parameters which directly or indirectly affect the response parameters. In the present investigation three process variables viz. Wire feed rate (Wf), stick out (So) and traverse speed (Ts) have been considered and the response parameters are hardness (H), tensile strength (TS), toughness (IS). Finally a confirmatory test has been carried out with the optimal process parameters for validation of the experiment.