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- 1. Journal of Materials Processing Technology 176 (2006) 230–239 Effect of ﬂux cored arc welding process parameters on duplex stainless steel clad quality T. Kannana,1, N. Muruganb,∗ a Department of Mechanical Engineering, Kumaraguru College of Technology, Coimbatore 641006, Tamil Nadu, India b Department of Mechanical Engineering, Coimbatore Institute of Technology, Coimbatore 641014, Tamil Nadu, India Received 9 December 2004; received in revised form 1 March 2006; accepted 1 March 2006 Abstract The main problem faced in duplex stainless steel cladding is the selection of the optimum combination of process parameters for achieving the required quality of clad. This paper highlights an experimental study carried out to analyse the effects of various ﬂux cored arc welding (FCAW) process parameters on important clad quality parameters in duplex stainless steel cladding of low carbon structural steel plates. The experiments were conducted based on four-factor ﬁve level central composite rotatable design with full replications technique and having mathematical models developed using multiple regression method. The effects of the input process parameters on clad quality parameters have been presented in graphical form, which helps in selecting welding process parameters to achieve the desired clad quality quickly. © 2006 Elsevier B.V. All rights reserved. Keywords: Mathematical models; Duplex stainless steels; FCAW; Clad quality parameters 1. Introduction Most of the engineering applications require both high strength and corrosion resistant materials for long term relia- bility and performance. Often the strength can best be achieved by the use of steels which do not possess the required corrosion resistance. A possible materials solution to providing structural components which combine the attributes of high strength and corrosion resistance is to clad the surface of the steel with a metallurgically compatible corrosion resistant alloy. The char- acteristics desirable in such a cladding alloy are reasonable strength, weldability to the steel, resistance to general and local- ized corrosion attack, and good corrosion fatigue properties [1]. A candidate material for cladding which has excellent corrosion resistance and weldability is duplex stainless steel [2]. These have chloride stress corrosion cracking resistance and strength signiﬁcantly greater than that of the 300-series austenitics [3]. In recent years, weld cladding processes have been devel- oped rapidly and are now applied in numerous industries such ∗ Corresponding author. Tel.: +91 422 2574071; fax: +91 422 2575020. E-mail addresses: kannan kct@yahoo.com (T. Kannan), drmurugan@yahoo.com (N. Murugan). 1 Tel.: +91 422 2669589; fax: +91 422 2669406. as chemical and fertilizer plants, nuclear and steam power plants, food processing and petrochemical industries, etc. The biggest difference between welding a joint and cladding is the per- centage dilution [4] illustrated in Fig. 1. The composition and properties of cladding are strongly inﬂuenced by the dilution obtained. Control of dilution is important in cladding, where typically low dilution is desirable. When the dilution is low, the ﬁnal deposit composition will be closer to that of the ﬁller metal and the corrosion resistance of the cladding will also be maintained. Various welding processes employed for cladding are shielded metal arc welding (SMAW), submerged arc welding (SAW), gas tungsten arc welding (GTAW), plasma arc weld- ing (PAW), gas metal arc welding (GMAW), ﬂux cored arc welding (FCAW), electroslag welding (ESW), oxy-acetylene welding(OAW)andexplosivewelding[5].Amongtheprocesses employed for weld cladding, FCAW is readily accepted by the industries [6] due to the following features. • High deposition rates, especially for out-of-position welding. • More tolerant of rust and mill scale than GMAW. • Simpler and more adaptable than SAW. • Less operator skill required than GMAW. • High productivity than SMAW. • Good surface appearance. 0924-0136/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jmatprotec.2006.03.157
- 2. T. Kannan, N. Murugan / Journal of Materials Processing Technology 176 (2006) 230–239 231 Table 1 Chemical composition of base metal and ﬁller wire used Material Elements (wt.%) C Si Mn P S Al Cr Mo Ni N2 Cu IS: 2062 0.150 0.160 0.870 0.015 0.016 0.032 – – – – – E2209T1-4/1 0.023 0.760 1.030 0.024 0.002 – 23.14 3.05 9.22 0.13 0.09 Fig. 1. Weld bead geometry. • Good radiographic standard quality. • Minimum electrode wastage. This paper highlights an experimental study carried out to analyse the effects of various FCAW process parameters on important clad quality parameters in duplex stainless steel cladding of low carbon structural steel plates. The experiments were conducted based on four-factor ﬁve level central composite rotatable design with full replications technique and mathemat- ical models developed using multiple regression method. The developed mathematical models have been checked for their adequacy and signiﬁcance. 2. Experimental work The experiments were conducted using UNIMACRO 501C programmable welding machine using DC electrode positive (DCEP). Test pieces of size 200 mm × 150 mm × 20 mmwerecutfromlowcarbonstructuralsteel(IS:2062) plate and its surfaces were ground to remove oxide scale and dirt before cladding. Flux cored duplex stainless steel welding wire (E2209T1-4/1) of 1.2 mm diam- eter was used for depositing the weld beads. Chemical composition of the base metal and welding wire is given in Table 1. CO2 gas at a constant ﬂow rate of 18 L/min was used for shielding. The experimental setup used consisted of a travelling carriage with a table for supporting the specimens. The carriage speed wascontinuouslyadjustablefrom6 cm/minto72 cm/min.Theweldingtorchwas held stationary in a frame mounted above the work table, and it was provided with an attachment for both up and down movement and angular movement for setting the required nozzle-to-plate distance and welding torch angle, respec- tively. The experiments were conducted by laying three beads using stringer bead technique with a constant overlap of 40%. An interpass temperature of 150 ◦C was maintained during all the cladding experiments. The experimental setup is shown in Fig. 2. Fig. 2. Experimental setup. 3. Experimental design procedure The experimental design procedure used for this study is shown in Fig. 3 and important steps are brieﬂy explained below. 3.1. Identiﬁcation of factors and responses The chosen factors were welding current (I), welding speed (S), nozzle-to- plate distance (N), and welding torch angle (T). In this study, forehand welding (push angle) technique was used. The chosen responses were weld bead width (W), average depth of penetration (P), average height of reinforcement (R), and percentage dilution (D). The chosen input and output parameters of FCAW are shown in Fig. 4. 3.2. Finding the limits of the process variables The working ranges of all selected factors were ﬁxed by conducting trial runs. This was carried out by varying one of the factors while keeping the rest of them at constant values [7]. The working range of each process parameters was decided upon by inspecting the bead for a smooth appearance without any visible defects such as surface porosity, undercut, etc. The upper limit of a factor was coded as +2 and the lower limit was coded as −2. The coded values for intermediate values were calculated using the following Eq. (1) Xi = 2[2X − (Xmax + Xmin)] Xmax − Xmin (1) Table 2 Welding parameters and their levels Parameter Unit Notation Factor levels −2 −1 0 +1 +2 Welding current A I 200 225 250 275 300 Welding speed cm/min S 20 30 40 50 60 Nozzle-to-plate distance mm N 22 24 26 28 30 Welding torch angle with reference to vertical ◦ T 20 15 10 05 00
- 3. 232 T. Kannan, N. Murugan / Journal of Materials Processing Technology 176 (2006) 230–239 Fig. 3. Experimental design procedure. Fig. 5. Typical cladded plate (Trial Nos. 14 and 29). where Xi is the required coded value of a variable X, X the any value of the variable from Xmin to Xmax, Xmin the lower limit of the variable and Xmax the upper limit of the variable. The chosen levels of the selected process parameters with their units and notations are given in Table 2. 3.3. Development of design matrix The design matrix chosen to conduct the experiment was a central compos- ite rotatable design. This design matrix [8] comprised of a full replication of 24 = (16) factorial design plus seven center points and eight star points which is shown in Table 3. All welding variables at the intermediate levels (0) constituted the center points and the combination of each welding variables at either its high- est value (+2) or lowest value (−2) with other three variables of the intermediate levels (0), constituted the star points. Thus the 31 experimental runs allowed the estimation of the linear, quadratic and two-way interactive effects of the process parameters on clad quality parameters. 3.4. Conducting the experiments as per the design matrix The experiments were conducted at the Welding Engineering Research Cen- tre in Coimbatore Institute of Technology, India. In this work, 31 deposits were made using cladding condition corresponding to each treatment combination of parameters shown in Table 3 at random. At the end of each run, settings for all four parameters were disturbed and reset for the next deposit. This was essential to introduce variability caused by errors in experimental settings [9]. A typical cladded plate is shown in Fig. 5. 3.5. Recording the responses To measure the weld bead geometry, transverse sections of each weld over- lays were cut using power hacksaw from the mid-length position of the welds, and the end faces were machined. Specimen end faces were polished and etched using a 2% nital solution and the bead proﬁles were traced using a reﬂective type optical proﬁle projector at a magniﬁcation of 10 and then the bead dimensions such as penetration, reinforcement and bead width were measured. The areas of base metal melted and the weld metal forming reinforcement were measured with the help of a digital planimeter and the percentage dilution was calcu- lated. The measured weld bead dimensions and calculated percentage dilution are given in Table 3. Fig. 4. Chosen factors and responses for FCAW process.
- 4. T. Kannan, N. Murugan / Journal of Materials Processing Technology 176 (2006) 230–239 233 Table 3 Design matrix and the observed values of clad quality parameters Trial no. Design matrix Clad quality parameters I S N T W (mm) P (mm) R (mm) D (%) 01 −1 −1 −1 −1 29.50 0.61 4.97 07.86 02 +1 −1 −1 −1 36.62 0.73 5.00 12.10 03 −1 +1 −1 −1 24.20 0.63 4.23 11.35 04 +1 +1 −1 −1 28.00 0.77 4.27 11.98 05 −1 −1 +1 −1 30.00 0.57 5.00 06.54 06 +1 −1 +1 −1 34.98 0.67 5.29 08.82 07 −1 +1 +1 −1 25.59 0.58 4.18 09.69 08 +1 +1 +1 −1 29.51 0.70 4.20 11.16 09 −1 −1 −1 +1 28.34 0.73 5.00 08.97 10 +1 −1 −1 +1 34.50 0.97 5.10 13.75 11 −1 +1 −1 +1 24.00 1.00 4.00 18.52 12 +1 +1 −1 +1 27.80 1.20 4.34 20.58 13 −1 −1 +1 +1 29.26 0.60 5.08 07.46 14 +1 −1 +1 +1 34.80 0.80 5.28 09.14 15 −1 +1 +1 +1 25.30 0.97 4.00 18.00 16 +1 +1 +1 +1 27.70 1.00 4.20 14.80 17 −2 0 0 0 20.15 0.40 3.98 05.86 18 +2 0 0 0 31.00 1.07 4.90 16.48 19 0 −2 0 0 39.53 0.70 5.68 05.31 20 0 +2 0 0 23.10 1.00 3.63 17.35 21 0 0 −2 0 25.10 0.83 4.32 11.71 22 0 0 +2 0 28.00 0.63 4.81 09.01 23 0 0 0 −2 30.20 0.56 4.17 10.54 24 0 0 0 +2 26.00 0.87 4.87 13.98 25 0 0 0 0 27.88 0.70 4.55 10.33 26 0 0 0 0 29.42 0.83 4.34 13.60 27 0 0 0 0 28.00 0.77 4.50 10.73 28 0 0 0 0 27.90 0.87 4.50 11.71 29 0 0 0 0 29.20 0.83 4.32 13.76 30 0 0 0 0 27.80 0.79 4.58 10.99 31 0 0 0 0 27.80 0.80 4.57 10.67 W, width; P, penetration; R, reinforcement; D, dilution %; I, welding current; S, welding speed; N, nozzle-to-plate distance; T, welding torch angle. 3.6. Development of mathematical models The response function representing any of the clad quality parameters can be expressed using Eq. (2) Y = f(X1, X2, X3, X4) (2) where Y is the response (e.g. weld bead width), X1 the welding current (I) (A), X2 the welding speed (S) (cm/min), X3 the nozzle-to-plate-distance (N) (mm) and, X4 the welding torch angle (T) (◦). The second order response surface model [10] for the four selected factors is given by Eq. (3) Y = βo + 4 i=1 βiXi + 4 i=1 βiiX2 i + 4 i = 1 i<j βijXiXj (3) The above second order response surface model equation could be expressed as follows: Y = β0 + β1I + β2S + β3N + β4T + β11I2 + β22S2 + β33N2 + β44T2 +β12IS + β13IN + β14IT + β23SN + β24ST + β34NT (4) where β0 is the free term of the regression equation, the coefﬁcients β1, β2, β3 and β4 are linear terms, the coefﬁcients β11, β22, β33, and β44 the quadratic terms, and the coefﬁcients β12, β13, β14, β23, β24, and β34 the interaction terms. The values of the coefﬁcients of the polynomial Eq. (4) were calculated [11] using following Eqs. (5)–(8) β0 = 0.142857 Y − 0.035714 (XiiY) (5) βi = 0.041667 (XiY) (6) βii = 0.03125 (XiiY) + 0.035714 (XiiY) − 0.035715 Y (7) βij = 0.0625 (XijY) (8) The coefﬁcients were calculated using QA six sigma software (DOE-PCIV) and the same was veriﬁed by using the software SYSTAT 10.2. After determining the coefﬁcients, the mathematical models were developed. The insigniﬁcant coefﬁcients were eliminated without affecting the accuracy of the developed model by using t-test. This was done by back elimination technique, which is available in QA six sigma software (DOE-PCIV) and the same was veriﬁed by using the software SYSTAT 10.2. The signiﬁcant coefﬁcients are given in Table 4. The ﬁnal mathematical models were constructed by using only these coefﬁcients. The developed ﬁnal models with welding variables in coded form are given below. Bead width (W) (mm) = 27.775 + 2.494I − 3.244S + 0.415N − 0.610T −0.303I2 + 1.066S2 + 0.316T2 − 0.616IS. Average depth of penetration (P) (mm) = 0.764 + 0.104I + 0.074S − 0.048N + 0.110T + 0.021S2 + 0.061ST.
- 5. 234 T. Kannan, N. Murugan / Journal of Materials Processing Technology 176 (2006) 230–239 Table 4 Estimated values of the signiﬁcant coefﬁcients of the models Coefﬁcient Clad quality parameters W P R D βo 27.775 0.764 4.535 11.702 β1 2.494 0.104 0.128 1.466 β2 −3.244 0.074 −0.475 2.730 β3 0.415 −0.048 0.054 −1.037 β4 −0.610 0.110 0.052 1.608 β11 −0.303 – – – β22 1.066 0.021 0.053 – β33 – – – – β44 0.316 – – – β12 −0.616 – – −0.751 β13 – – – −0.593 β14 – – – – β23 – – −0.052 – β24 – 0.061 – 1.482 β34 – – – – Average height of reinforcement (R) (mm) = 4.535 + 0.128I − 0.475S + 0.054N + 0.052T + 0.053 S2 − 0.052SN. Percentage dilution (D) = 11.702 + 1.466I + 2.730S − 1.037N + 1.608T − 0.751IS − 0.593IN + 1.482ST. It was found that the reduced models are better than the full models because the reduced models have higher values of R2 (adjusted) and lesser values of standard error of estimates than that of full models. The values of R2 (adjusted) and standard error of estimates for full and reduced models are given in Table 5. 3.7. Checking the adequacy of the developed models The adequacies of the developed models were tested using the analysis of variance (ANOVA) technique [12]. As per this technique, if the calculated F- ratio values for the developed models do not exceed the standard tabulated values of F-ratio for a desired level of conﬁdence (95%) and the calculated R- ratio values of the developed models exceed the standard tabulated values of R-ratio for a desired level of conﬁdence (95%), then the models are said to be adequate within the conﬁdence limit. These conditions were satisﬁed for all the developed models, which are given in Table 6. The validity of these models, were again tested by drawing scatter diagrams as shown in Fig. 6a–d which show the observed and predicted values of clad quality parameters. 3.8. Conducting the conformity test Conformity tests were conducted using the same experimental setup to con- ﬁrm the results of the experiment and demonstrate the reliability of the predicted values. The conformity tests show the accuracy of the models developed, which is above 96%. This is shown in Table 7. 4. Results and discussions The models developed above can be used to predict the clad qualityparametersbysubstitutingthecodedvaluesoftherespec- tive process parameters. The responses calculated from these models for each set of coded welding parameters are represented in graphical form in Figs. 7–16. Also by substituting the values of the desired clad quality parameters, the values of the process parameters, in coded form can be obtained. 4.1. Direct effects of process parameters on clad quality parameters 4.1.1. Direct effect of welding current (I) on clad quality parameters Fig. 7 shows all the clad quality parameters W, P, R, and D increase with increase in welding current. This is due to the increase in welding current density and the weight of wire fused per unit of time [13]. Also with increase in welding current the arc becomes stiffer and hotter which penetrates more deeply and melting more base metal. 4.1.2. Direct effect of welding speed (S) on clad quality parameters From Fig. 8, it is evident that the clad quality parameters R and W decrease with increase in welding speed but P and D Table 5 Comparison of R2 values and standard error of estimates for full and reduced models Clad quality parameter R2 values Standard error of estimates Full models Reduced models Full models Reduced models Width (W) 0.856 0.889 1.552 1.365 Penetration (P) 0.816 0.839 0.075 0.070 Reinforcement (R) 0.884 0.900 0.165 0.153 %Dilution (D) 0.793 0.836 1.707 1.515 Table 6 Analysis of variance for testing adequacy of the models Parameter 1st order Terms 2nd order Terms Lack of ﬁt Error terms F-ratio R-ratio Whether model is adequate SS d.f. SS d.f. SS d.f. SS d.f. W 414.845 4 48.00 10 26.016 10 12.499 6 1.249 15.870 Adequate P 0.732 4 0.010 10 0.073 10 0.018 6 2.477 20.149 Adequate R 6.164 4 0.400 10 0.368 10 0.066 6 3.353 42.719 Adequate D 318.38 4 56.142 10 34.20 10 12.24 6 1.677 13.119 Adequate F-ratio (10, 6, 0.05) = 4.09; SS, sum of squares; R-ratio (14, 6, 0.05) = 3.96; d.f., degrees of freedom.
- 6. T. Kannan, N. Murugan / Journal of Materials Processing Technology 176 (2006) 230–239 235 Table 7 Comparison of predicted and actual values of clad quality parameters Process parameter in coded form Predicted values of clad quality parameters Actual values of clad quality parameters Error (%) I S N T W P R D W P R D W P R D −0.11 −0.22 0.09 −0.3 28.9 0.72 4.7 10.6 28.6 0.67 4.8 10.3 −1.04 −2.86 2.13 −2.80 −0.79 −0.35 0.94 1.02 27.3 0.72 4.8 10.3 27.7 0.71 4.6 10.2 1.47 −1.39 −4.17 −0.97 −0.66 0.03 0.90 1.03 26.3 0.77 4.6 11.5 26 0.78 4.7 11.8 −1.14 1.30 2.17 −2.61 %Error = actual value−predicted value predicted value × 100. Fig. 6. Scatter diagram of (a) weld bead width model; (b) depth of penetration model; (c) percentage dilution model; and (d) height of reinforcement model.
- 7. 236 T. Kannan, N. Murugan / Journal of Materials Processing Technology 176 (2006) 230–239 Fig. 7. Effect of welding current on clad quality parameters. increases with increase in welding speed. Decrease in R and W can be obviously attributed to the reduced heat input per unit length of weld bead as welding speed is increased and less ﬁller metal is applied per unit length of the weld [13]. The percentage dilution of base metal in the pool increases with the increase in welding speed, since the weight of deposited metal per unit of length decreases with the cross section of the bead decreases very little. With low welding speed the arc is almost vertical and in this instance the weld pool cushions the effect of arc and prevents deeper penetration. 4.1.3. Direct effect of nozzle-to-plate distance (N) on clad quality parameters It is evident from Fig. 9 that P and D decrease slightly with increase in nozzle-to-plate distance but W and R increases Fig. 8. Effect of welding speed on clad quality parameters. Fig. 9. Effect of nozzle-to-plate distance on clad quality parameters. with increase in nozzle-to-plate distance. Increase in nozzle- to-plate distance increases the circuit resistance, which reduces the welding current. This decrease of welding current reduces the penetration of arc and hence reduces the dilution. With increase in nozzle-to-plate distance the arc length is increased hence the bead width is increased due to wider arc area at the weld surface and this consequently increases the reinforce- ment height because the same volume of ﬁller metal is added [14]. 4.1.4. Direct effect of welding torch angle (T) on clad quality parameters From Fig. 10 R, P and D decrease with increase in weld- ing torch angle but W increases with increase in welding torch angle. The reason is when the angle is increased in fore- hand welding the arc force pushes the weld metal forward, i.e. Fig. 10. Effect of welding torch angle on clad quality parameters.
- 8. T. Kannan, N. Murugan / Journal of Materials Processing Technology 176 (2006) 230–239 237 Fig. 11. Interaction effects of welding current and welding speed on bead width. towards the cold metal, which reduces the penetration, reinforce- ment and percentage dilution but width of the weld increases [15]. 4.2. Interaction effects of process parameters on clad quality parameters 4.2.1. Interaction effects of welding current (I) and welding speed (S) on bead width (W) From Fig. 11 it is clear that the W increases with increase in welding current. It also increases with decrease in welding Fig. 12. Interaction effects of welding torch angle and welding speed on pene- tration. Fig. 13. Interaction effects of nozzle-to-plate distance and welding speed on reinforcement. speed. These effects are due to welding current having a pos- itive effect but welding speed having negative effect on bead width. The increasing trend of weld bead width with increase in welding current decreases with the increase in welding speed. 4.2.2. Interaction effects of welding torch angle (T) and welding speed (S) on average depth of penetration (P) Fig. 12 shows that the P decreases with increase in welding torch angle. This decreasing trend of P with increase in welding torch angle gradually decreases with decrease in welding speed. Fig. 14. Interaction effects of welding current and welding speed on percentage dilution.
- 9. 238 T. Kannan, N. Murugan / Journal of Materials Processing Technology 176 (2006) 230–239 Fig. 15. Interaction effects of nozzle-to-plate distance and welding current on percentage dilution. This is because welding torch angle has negative effect and welding speed has positive effect on penetration. 4.2.3. Interaction effects of nozzle-to-plate distance (N) and welding speed (S) on average height of reinforcement (R) From Fig. 13, it is evident that R increases with the increase in nozzle-to-plate distance when welding speed is from 20 cm/min to 50 cm/min and the rate of increase in R also decreases with the increase in welding speed. But when welding speed is at 60 cm/min, R decreases with increase in nozzle-to-plate dis- tance. Fig. 16. Interaction effects of welding speed and welding torch angle on per- centage dilution. 4.2.4. Interaction effects of welding current (I) and welding speed (S) on percentage dilution (D) From Fig. 14, it is clear that D increases with increase in weld- ing current for all values of welding speed. But this increasing trend of D with the increase in welding current decreases grad- ually with the decrease in welding speed. These effects occur because both welding current and welding speed have a positive effect on percentage dilution. 4.2.5. Interaction effects of welding current (I) and nozzle-to-plate distance (N) on percentage dilution (D) From Fig. 15, it is clear that D decreases with increase in nozzle-to-plate distance for all values of welding current. But this decreasing trend of D with the increase in nozzle-to-plate distance decreases gradually with decrease in welding current. These effects occur because welding current has a positive effect whereas nozzle-to-plate distance has a negative effect on D. 4.2.6. Interaction effects of welding torch angle (T) and welding speed (S) on percentage dilution (D) From Fig. 16, it is evident that D decreases with the increase in welding torch angle when welding speed is from 30 cm/min to 60 cm/min and the rate of decrease in D also increases with increase in welding speed from 30 cm/min. But when welding speed is 20 cm/min D increases with the increase in welding torch angle. 5. Conclusions • Aﬁvelevelfourfactorfullfactorialdesignmatrixbasedonthe central composite rotatable design technique can be used for the development of mathematical models to predict the clad quality parameters for duplex stainless steel cladding using FCAW. • Dilution increases with the rise in welding current and weld- ing speed and decreases with the rise in nozzle-to-plate dis- tance and welding torch angle. • Reinforcement increases with the rise in welding current and nozzle-to-platedistanceanddecreaseswiththeriseinwelding speed and welding torch angle. • Weld bead width increases with the rise in welding cur- rent, nozzle-to-plate distance and welding torch angle and decreases with the rise in welding speed. • Penetration increases with the rise in welding current and welding speed and decreases with the rise in nozzle-to-plate distance and welding torch angle. • Bead width increases with the increase in welding current at all levels of welding speed. But the rate of increase in bead width with the increase in welding current decreases signiﬁ- cantly with the increase in welding speed. • Increase in welding torch angle decreases penetration when welding speed is high but penetration slightly increases with the increase in welding torch angle when welding speed is low. • Percentage dilution decreases with the increase in nozzle- to-plate distance at all levels of welding current. But the rate of decrease in percentage dilution with the increase in
- 10. T. Kannan, N. Murugan / Journal of Materials Processing Technology 176 (2006) 230–239 239 nozzle-to-plate distance decreases signiﬁcantly with decrease in welding current. Acknowledgements The authors wish to thank M/S Bohler welding, Austria for providing ﬂux cored welding wire for this work. The ﬁnan- cial support for this work from All India Council of Techni- cal Education and University Grant Commission is gratefully acknowledged. The authors also wish to thank the management of Coimbatore Institute of Technology and Kumaraguru College of Technology for having provided all the necessary facilities to carryout this work. References [1] D.F. Hasson, C. Zanis, L. Aprigliaho, Fraser, Surfacing of 3.25% nickel steel with Inconel 625 by the gas metal arc welding-pulsed arc process, Weld. J. 57 (1978) 1s–8s. [2] L. Karlsson, L. Ryen, S. Pak, Precipitation of intermetallic phases in 22% duplex stainless steel weld metals, Weld. J. 74 (1995) 28s–40s. [3] Report on Practical Guidelines for the Fabrication of Duplex Stainless Steel, International Molybdenum Association, 2001. [4] Welding, Brazing, and Soldering, vol. 6, ASM Handbook, USA, 1993. [5] N. Murugan, R.S. Parmar, Effects of MIG process parameters on the geometry of the bead in the automatic surfacing of stainless steel, J. Mater. Process. Technol. 41 (1994) 381–398. [6] L. Juffus, Welding Principles and Applications, fourth ed., Delmar Pub- lishers, New York, 1999. [7] N. Murugan, R.S. Parmar, Mathematical models for bead geometry pre- diction in automatic stainless steel surfacing by MIG welding, Int. J. Joi. Mater. 7 (1995) 71–80. [8] W.G. Cochran, G.M. Cox, Experimental Designs, second ed., John Wiley & Sons, New York, 1987. [9] P. Harris, B.L. Smith, Factorial technique for weld quality prediction, Met. Construct. 15 (1983) 661–666. [10] D.C. Montgomery, Design and Analysis of Experiments, ﬁfth ed., John Wiley & Sons (ASIA) Pte Ltd., 2003. [11] V. Gunaraj, N. Murugan, Application of response surface methodology for predicting weld bead quality in submerged arc welding of pipes, J. Mater. Process. Technol. 88 (1999) 266–275. [12] V. Gunaraj, N. Murugan, Prediction and comparison of the area of the heat affected zone for the bead on plate and bead on joint in submerged arc welding of pipes, J. Mater. Process. Technol. 95 (1999) 246–261. [13] J. Cornu, Advanced Welding Systems, vol. 2, IFS (Publications) Ltd., UK, 1988. [14] J.W. Kim, S.J. Na, A study on the effect of contact tube-to-work piece distance on weld pool shape in gas metal arc welding, Weld. J. 74 (1995) 141s–152s. [15] F. Rieber, Hand Book of Welding, PWS–KENT Publishing Company, USA, 1985.