AN EXPERIMENTAL STUDY OF ARC WELDING PARAMETERS FOR ULTIMATE STRENGTH IN BENDING & HARDNESS ON DMR 249A & OPTIMIZATION

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1 AN EXPERIMENTAL STUDY OF ARC WELDING PARAMETERS FOR ULTIMATE STRENGTH IN BENDING & HARDNESS ON DMR 249A & OPTIMIZATION 1 ARJUN A ABHYANKAR, 2 DNYANESH M NIKAM, 3 SHIVAM S PAWAR, 4 JANMESH SHAH 1,2,3,4 SRTTC, kamshet 1 arjun.abhyankar@yahoo.com, 2 dnyanesh133@gmail.com, 3 pawarshivam44@gmail.com, 4 shahjanmesh10@gmail.com Abstract Arc welding is a fusion welding process having wide applications in ship building industry. In this process proper selection of input welding parameters is necessary in order to obtain a weld ultimate strength and hardness.therefore, necessary to control the input welding parameters. ARC welding parameters are the most important factors affecting the quality, productivity and welded joint Ultimate Strength (bending), Weld bead Hardeness, shape and depend on number of parameters. Inadequate weld bead hardness & poor Ultimate strength in Bending may failure of a welded structure since the effect of various welding parameters on the weld ability of DMR 249 A Steel specimen having dimensions 200mm 50 mm 13 mm, welded by ARC welding were investigated. Joint is directly influenced by the welding input parameters i.e welding current, electrode angle, welding speed. The Hardness & Ultimate Strength (bending ) were measured for each specimen after the welding operation is done on Single v butt joint and the effects of welding speed, current, voltage parameters on Hardness & Ultimate Strength (bending) were investigated.. In this research using Taguchi's method of design of experiments a mathematical Model was developed using parameters such as, welding current (A), Electrode Angle (E), welding speed (S) and output is Hardness (H) & Ultimate Strength (bending) (UTS b). After collecting data, signal-to-noise ratios (S/N) were calculated and used in order to obtain the optimum levels for every input parameter. Keywords Arc Welding, Bending Ultimate Strength, Hardness, Taguchi Method, Minitab14 Software, DMR 249A. I. INTRODUCTION DMR249A steel is high strength low alloy (HSLA) steel. This structural grade steel DMR 249 is standardized by the American Bureau of Shipping and is being used in the construction of the hulls of various naval vessels with specific weight and resilience qualities. Arc welding processes are used during construction and fabrication of bridges, vessels, ships and off shore drills.ultimate Strength of single V butt weld is improved by the application of taguchi method. The aim of our research was to find out the influence of input parameters electrode angle, current, welding speed on DMR 249 material hardness and ultimate strength by the application of bending load. Traditionally, it has been necessary to study the weld input parameters for welded product to obtain a welded joint with the required specification. Butt weld is examined whether they meet the requirement or not. Finally the welding parameters can be chosen to produce a welded joint with desired specification. Design of experiment (DoE) techniques has been applied to carry out such optimization. Taguchi method have been adapted for this research purpose. By using the Taguchi method, industries are able to greatly reduce product cycle time for both design and production, therefore decrease costs and increasing profit. The objective of the taguchi method is to optimize the welding process parameter reading for improving performance characteristics and to identify the product parameter reading under the optimal process parameter reading. The steps in the Taguchi parameter design are: 1) Selecting the proper orthogonal array (OA) 2) performing experiments based on the( OA); 3) analyzing data; identifying the optimum condition; and performing confirmation runs with the optimal levels of all the parameters II. PROBLEM DESCRIPTION Welding defect (crack) is occurred in fabrication area of mazgaon dock which is visible after painting, Why-Why Analysis is done to find out reason for crack generation and failure. Table:2.1why-why Analysis for Welding Defect Sr. No. Cause Why Why Why 1 Welding break (In bending) Welding parameters not ok (i.e Current,electrode angle,welding speed) Welder is not skilled Excessive bending load 2 Small crack in welding is visible after painting Why - Why Analysis Welding strength and hardness not ok Proper inspection method for crack detection not available 33

2 III. EXPERIMENT SET UP / UNDERTAKEN WORK 3.1In the present work, Ultimate strength (Bending) test analysis of a V-butt jointed specimen is conducted in a normal environment: 3.2 Work piece material specification: The material used for the analysis is DMR-249A, whose composition is listed in Table. Table: 3.1 chemical composition Fig:3.1 Undertaken work The experimental setup consists of Arc Welding Machine,stopwatch,DMR-249 A Specimen for conducting experiment. DMR-249 is used as the work piece material for the experimentation to optimize the Ultimate strength in Bending and Hardness. The plate with dimension 100mm *50mm *13mm is used in this experiment. Fig: 3.4 Work piece materials (DMR-249A) Fig:3.2 Experimental set up 3.3 Hardness Testing: Hardness is defined as resistance to indentation. Brinell hardness test results are expressed in terms of pressure generated due to load (P). It is calculated by the ratio of load applied and projected contact area. Load in the range of 500 to 3000 kg can be applied depending upon the type of material to be tested. 3.3 Electrode Material & composition :- Fig :3.3 (a) Fig:3.3(b) 34

3 Fig :3.5 hardness testing (BHN) 3.4 Ultimate bending strength Testing bend test is one of the most important and commonly used destructive tests to determine the ductility and soundness of the weld joint produced using under one set of welding conditions. Fig:3.8 Root bending test in UTM IV. DESIGN OF EXPERIMENT 4.1 Orthogonal Array Taguchi: This study, L9(3) orthogonal array of Taguchi experiment was selected for three parameters (current, electrode angle, welding speed ) The experiment consists 3 factors,then total number of experiment is Table: 4.1 Process Parameters Fig:3.6 Root bending test in UTM 4.2 Taguchi Orthogonal Array: Taguchi orthogonal array is designed with three levels of welding parameters with the help of software Minitab 14. Table: 4.2 Taguchi Orthogonal Array Fig: 3.7 Root bending test in UTM 4.3 Observation: Nine experiments are performed with different current, electrode angle & welding speed and ultimate strength in bending and hardness is calculated. The observation tables are given below: 35

4 Table:4.3 Observation "Bending strength & hardness Graph 4.3 stress vs strain (UTM) V. RESULTS For the maximum ultimate strength in bending and hardness, the solution is Larger is better and S/N ratio is determined according to the following equation: Graph 4.1 stress vs strain (UTM) S/N = -10 log10 {n-1σy-2} where, S/N = Signal to Noise Ratio,n = No. of Measurements, y = Measured Value The ultimate strength and hardness values measured from the experiments & their corresponding S/N ratio values : Table :5.1 S/N ratio values and mean Graph 4.2 stress vs strain (UTM) 36

5 Main Effects Plot (data means) for SN ratios CURRENT ELECTRODE A Mean of SN ratios WELDING SPEED Signal-to-noise: Larger is better Fig:5.1 Effect plot for SN ratio Fig -6.2 : Surface plot of current with respect to Ultimate strength in bending and Welding Speed. Main Effects Plot (data means) for Means 96.0 CURRENT ELECTRODE A Mean of Means WELDING SPEED Fig:5.2 Effect plot for mean CONCLUSION An experimental study has been done for finding optimal input parameters in the Arc Welding i.e, current, electrode angle and welding speed, to achieve maximum ultimate bending strength and hardness for DMR-249 are as follows: Fig -6.3 : Surface plot of current with respect to hardness and ultimate strength in bending. REFERENCES [1] Kamal, residual stress studies on arc welding joint of naval steel(dmr249), Rishi pamnani, Govind k sherma, s mahadevan, T jayakumar, M. vasudevan journal of manufacturing process volume 20, part 1,oct [2] Parametric Optimization of Gas Metal Arc Welding Process by Taguchi Method on Weld Dilution M. Aghakhani, E. Mehrdad, and E. Hayati. [3] PARAMETERS TO PREDICT MAXIMUM YIELD STRENGTH IN AISI 1040"International journal of Mechanical Engineering and Roboting Research, INDIA, October 2012, [4] A.R.Bahman and E.Alialhosseini "CHANGE IN HARDNESS,YIELD STRENGTH AND UTS OF WELDED JOINTS PRODUCED OF ST37 GRADE STEEL " Indian journal of Science and Technology, Dec [5] S. R. Patil, C. A. Waghmare "OPTIMIZATION OF MIG WELDING PARAMETERS FOR IMPROVING STRENGTH OF WELDED JOINTS", Patil et al, International Journal of Advanced Engineering Research and Studies, July-Sept., 2013,14-16 Fig: 6.1 Surface plot of current with respect to Electrode angle & Welding speed 37