Application of 2 3 Factorial Design Experiments for Gas Tungsten Arc Welding Parameters on ASTM A36 Steel Welds Prachya Peasura 1, a

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1 Applied Mechanics and Materials Online: ISSN: , Vols , pp doi:0.4028/ 203 Trans Tech Publications, Switzerland Application of 2 3 Factorial Design Experiments for Gas Tungsten Arc Welding Parameters on ASTM A36 Steel Welds Prachya Peasura, a Department of Production Technology Education, Faculty of Industrial Education and Technology, King Mongkut s University of Technology Thonburi, Thongkru, Bangkok Thailand 040 a prachya.pea@kmutt.ac.th Keywords: 2 3 factorial designs, Carbon steel, Hardness, Penetration Abstract. ASTM A36 carbon steel is the most commonly available of the hot-rolled steels. This specification covers carbon steel shapes, plates, and bars of structural quality for use in riveted, bolted, or welded construction of bridges and buildings, and for general structural purposes. The research was to study the in effected of gas tungsten arc welding parameters which effects the hardness and physical characteristics of welding for carbon steel ASTM A36. The specimen was carbon steel sheet metal 6 mm thick. The 2 3 factors experiment was used polarity direct current electrode negative (DCEN) and alternating current (AC), welding current at 90 and00 amperes with tungsten electrode angles at 30 and 60degree. The weld sample was test by hardness and penetration. The result showed that polarity, welding current and tungsten electrode angle had on interaction on hardness and penetration at 95% confidence (p-value < 0.05).The factors made maximum hardness was polarity AC, welding current 00 amp. and tungsten angle 60 of HV. The factors made maximum penetration was polarity DCEN, welding current 00 amp. and tungsten angle 60 of 2.7mm. The research data can be used to determine the appropriate gas tungsten arc welding process of carbon steel weld. Introduction Carbon steels containing form about 0.5 to 0.30 percent carbon are commonly called mild steel. Underbead cracking or lack of toughness in the heat affected zone is not usually encountered when welding mild steel containing no more than 0.2 percent carbon and percent manganese. Such steel can be welded without preheat, postheat, or special welding procedures when the joint thickness is less than in., and joint restrain is not sever.[-2] ASTM A36 steel is the most commonly available of the hot-rolled steels. This specification covers carbon steel shapes, plates, and bars of structural quality for use in riveted, bolted, or welded construction of bridges and buildings, and for general structural purposes. The mild carbon steel can be gas tungsten arc welding (GTAW) without preheat but proper welding procedures must be used. The amount of energy produce by the arc is proportional to the current and polarity [3-4] The 2 k design is particularly useful in the early stages of experimental work, when there are likely to be many factors to be investigated. It provides the smallest number of runs with which k factors can be studied in a complete factorial design. Because there are only two levels for each factor, we must assume that the response is approximately linear over the range of the factor levels chosen. [5] The research was used study of welding parameter selected in polarity, welding current and electrode angle to GTAW on the important factor. Because the selection condition on access to inappropriate, would have affected the mechanical and physical property which reduced the optimum of weld sample. Quality requirements used in this research were mechanical property test and physical property being the criteria for considering the quality of specimens. The results of this research could be the basic data in making research or being the information for quality control GTAW process. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-06/03/6,0:6:2)

2 708 Computer-Aided Design, Manufacturing, Modeling and Simulation II Experimental Welding Methods and Materials Test The sample tested was ASTM A36 chemical showed in Table which a thickness of 6 mm. The samples were welded by using gas tungsten arc welding without filler metal addition. The tungsten electrode was used EW-Th2 with electrode diameter mm. Welding current was set constant 90 and 00 Amps, direct current electrode negative (DCEN) and alternating current(ac). The welding spot was at 4 sec. Argon was selected as a shielding gas with the flow rate of 2 liters / minute. After welding of experiment, specimen were tested the penetration of a weld by testing following ASTM E3 - standard guide for preparation of metallographic specimens [6]. Mechanical properties were tested by vicker hardness following ASTM E92-82(2003) standard test method for Vickers hardness of metallic materials [7]. Table Chemical composition of carbon steel ASTM A 36 by weight (%) C Mn Si P Mo Experimental of Design The experiment was to study in main effects and interaction on hardness and penetration. The experimental design was used 2 3 factorial designs to be the main factors affecting significantly. The hypothesis test that level of confidence 95 %( P-value< 0.05). The factors used in the study are as follows excremental treatment was to 3 replicate. Hypothesis of experimental. H0 ;(αβ) ij =0 is polarity, welding current and electrode angle no interaction hardness and penetration H; (αβ) ij 0 is polarity, welding current and electrode angle interaction hardness and penetration Table 2 Experimental factor and two levels Factor Symbol Level Unit Low(-) High (). polarity A AC DCEN - 2. Welding current B Amp 3. Electrode angle C degree Experimental Result Results of Hardness The welding sample was the test on hardness for measuring which using 24 sample for each testing according to ASTM E92-82(2003) standard test method for vickers hardness of metallic materials. Plots for Hardness Normal Probability Plot of the s s Versus the Fitted Values Percent Fitted Value Histogram of the s s Versus the Order of the Data Frequency Observation Order Fig. plot for hardness

3 Applied Mechanics and Materials Vols Fig. shows residual plot for hardness. It is know that the probability of normal distribution type data was the linear. Then, perform the inspection at a fixed variance. The residual versus the fitted values showed in graph the relationship of the error and the average in factor. The residual versus the order of the data was relationship in error and order of the experimental. The results showed that the data are randomness. Therefore concluded that the data from the experimental results for hardness. Fig. 2 (A) Pareto chart of the standardized effects for hardness, (B) Normal probability plot of the standardized effects for hardness Fig.2 (A) showed in pareto chart of the standardized effects at α = The value the presented an absolute value higher than 2.2(α = 0.05), which were located at right of the line, were significant. The factor AC, ABC and BC is less than 2.2 are not significant. The absolute standardized value of the effect of each factor and its interaction appeared at the right of each bar. The factors interaction which were represented as a square were significant at α = 0.05 show in Fig.2 (B) while the effect represented by a circle were not significant Table 3 General linear models: Hardness versus polarity, welding current and tungsten angle Term Effect Coef SE Coef T P Constant Polarity Current Tungsten angle Polarity*Current Polarity*Tungsten angle Current*Tungsten angle Polarity*Current*Tungsten angle S = R-Sq = 97.52% R-Sq(adj) = 96.44% According to Table 3, Analysis of variance for hardness versus is polarity, welding current and tungsten angle. Found that the polarity, welding current and tungsten angle no interaction hardness at the level of confidence 95% (P-Value <0.05). This fit of model was checked with the coefficient of determination R 2 (adj), indicating 96.44% of the response factor could explain the variability on the response of hardness. Main Effects Plot (data means) for Hardness Polarity Current Mean of Hardness Tungsten angle Fig. 3 Main effects plot for hardness

4 70 Computer-Aided Design, Manufacturing, Modeling and Simulation II Fig. 3 shows main effects plot of hardness. The result showed that analysis of variance no interaction on the hardness. Therefore, in analyzing the effects of factors must be considered from the main effects plot. The pull factors that result in hardness most polarity AC, welding current 00 amp. and tungsten angle 60. The results were used to study the factors that will affect the maximum hardness of HV. Results of Penetration The welding sample was the test on physical property for measuring depth penetration width which using 24 specimens for each measuring microscope number E.7302 Resolution = µ. Brand MITUTOYO. Plots for Penetration 99 Normal Probability Plot of the s 0.0 s Versus the Fitted Values Percent Fitted Value Frequency Histogram of the s s Versus the Order of the Data Observation Order Fig. 4 plot for penetration The model adequacy checking to examine the appropriateness and accuracy of the data obtained from experiments. The residual plot for penetration indicates that the probability of normal distribution type data was the linear show in Fig4. Then, perform the inspection at a fixed variance. The residual versus the fitted values showed in graph the relationship of the error and the average in factor. The residual versus the order of the data was relationship in error and order of the experimental. The results showed that the data are randomness. Fig. 5 (A) Pareto chart of the standardized effects for penetration, (B) Normal probability plot of the standardized effects for penetration Fig.5 (A) showed in pareto chart of the standardized effects at α = The value the presented an absolute value higher than 2.2(α = 0.05), which were located at right of the line, were significant. The factor C, BC and ABC is less than 2.2 are not significant. The absolute standardized value of the effect of each factor and its interaction appeared at the right of each bar. The factors interaction which were represented as a square were significant at α = 0.05 show in Fig.5 (A) while the effect represented by a circle were not significant Table 4 General linear models: Penetration versus polarity, welding current and tungsten angle Term Effect Coef SE Coef T P Constant Polarity Current Tungsten angle Polarity*Current Polarity*Tungsten angle Current*Tungsten angle Polarity*Current*Tungsten angle S = R-Sq = 98.37% R-Sq(adj) = 97.65%

5 Applied Mechanics and Materials Vols The result showed that analysis of variance for penetration versus is polarity, welding current and tungsten angle. Found that the polarity, welding current and tungsten angle no interaction penetration at the level of confidence 95% (P-Value <0.05) show in table 4. This fit of model was checked with the coefficient of determination R 2 (adj), indicating % of the response factor could explain the variability on the response of penetration. Main Effects Plot (data means) for Penetration Porality Current 2.6 Mean of Penetration Tungsten Angle Fig. 6 Main effects plot for hardness Fig. 6 present the main effects plot of penetration. The factors was the analysis of variance no interaction on the penetration. Therefore, to analyze the effects of factors must be considered from the main effects plot. The pull factors that result in high penetration on polarity DCEN, welding current 00 amps. And tungsten angle 60. The results were used to study the factors that will affect the high penetration of 2.7mm. Conclusions The research studies the factor polarity, welding current and tungsten angle on mechanical and physical property in ASTM A36 welds. This study shows that 2 3 factorial designs was the interaction welding parameters. A 2 3 factorial design was successfully employed for experimental design and result. The conclusion showed that polarity, welding current and tungsten electrode angle had on interaction on hardness and penetration at 95% confidence (p-value < 0.05).The factors made maximum hardness was polarity AC, welding current 00 amp. and tungsten angle 60 of HV. The factors made maximum penetration was polarity DCEN, welding current 00 amps. And tungsten angle 60 of 2.7mm. The research data can be used to determine the appropriate gas tungsten arc welding process of steel weld. Reference [] American Welding Society, Welding Handbook seventh edition, Volume4 Metals and Their Weldability, American welding society, (982), pp.0-5 [2] American society for metal, Metals hand book ninth edition volume 9, American society for metal, (985), pp [3] R.L. O Brien, Welding Handbook eighth edition, Volume2 Welding Process, American welding society, (992), pp [4] The Lincoln electric company, The procedure handbook of arc welding, The Lincoln electric company,(994), pp.section6 [5] Douglas C. Montgomery, Design and analysis of experiments, John Wiley and son, (99), pp.97 [6] The American society of testing and materials, ASTM E3 - Standard Guide for Preparation of Metallographic Specimens, The American society of testing and materials, (202). [7] The American society of testing and materials, ASTM E92-82 standard test method for vickers hardness of metallic materials, The American society of testing and materials, (2003).

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