Effect of SAW Parameters on Weld Element Transfer in SS316

Transcription

1 International Journal of Engineering and Technology, Vol.1, No.1 (Dec. 2011) ISSN Research Article Effect of SAW Parameters on Weld Element Transfer in SS316 Karun a*, Sandeep Jindal b, R.D. Gupta c a Department of Mechanical Engineering, TERII, Kurukshetra b Department of Mechanical Engineering, MMU, Mullana Accepted 12 Aug.2011, Available online 1 Dec Abstract Selection of welding parameters has great influence on the chemical composition of weld bead. The present study investigates the influence of submerged arc welding (SAW) parameters on weld joints based on Taguchi Method so as to obtain an optimum level for response parameter which are constituents of weld metal. Beads on plate weld were deposited on SS-316 at different welding parameter combinations. It was found that the chromium & silicon element in weld bead increases and manganese element decreases with an increase in the welding current; welding speed or the welding voltage. The results revealed that welding voltage has an appreciable influence on weld composition of above three elements. Data investigated in this paper can be used to specify welding variables for desired weld composition. Keywords: Submerged arc welding, Chemical composition, Taguchi design of experiment, S/N ratio Nomenclature SAW- Submerged arc welding V- A- Ampere S- Weld Speed (m/hr) m/hr- Meter per hour mins- Minutes KJ/mm- Kilo joule per millimeter W/p- Workpiece DOE- Design of Experiments S/N Ratio-Signal to Noise Ratios Dof- Degree Of Freedom 1. Introduction 1 Grade 316 is the standard molybdenum-bearing grade, second in importance to 4 amongst the austenitic stainless steels. The molybdenum gives 316 better overall corrosion resistant properties particularly higher resistance to pitting and crevice corrosion in chloride environments. It has excellent forming and welding characteristics. It is readily brake or roll formed into a variety of parts for applications in the industrial, architectural, and transportation fields. Grade 316 also has outstanding welding characteristics (Kannanet al, 2006). Post-weld annealing is not required when welding thin sections. Their good formability and weldability come from the low carbon content and low quantity of alloying elements SS-316 are widely used in many applications such as high pressure vessels, wind turbine towers, ships, submarines, long distance oil and gas transportation systems, bridge beams and other offshore structures. In most of these applications, welding is the primary fabrication method in industries. The most widely used welding methods in industries and research organizations are shield metal arc welding (SMAW), gas metal arc welding (GMAW), gas tungsten arc welding (GTAW) and submerged arc welding (SAW). The SAW process is often preferred because it offers high production rate, high melting efficiency, ease of automation and low operator skill requirement. It was first used in industries in the mid 19 s as a single-wire welding system. The operating variables used in the SAW process results in varying heat input in the weldment The consequence of this is the deterioration of the chemical constituents of the weld bead. Therefore, the properties of the parent metal cannot adequately match those of the weldment to ensure good performance in service, especially in low temperature services. 2. Materials and Methods 2.1 Materials In this study SS 316 was used having dimensions 100x50x5 mm. The samples were cut from SS 316 flat and were machined to get the desired dimensions. The chemical composition of the material is shown in table 1. * Corrosponding author s badhwar1985@yahoo.co.in 110

2 Karun et al International Journal of Engineering and Technology, Vol.1, No.1 (Dec.2011) Table 1 Chemical composition of SS316 Material %age by weight C 0.03 Cr 17.4 Ni 12.3 Fe Bal Mo 1.3 Mn 1.3 Si 0.8 P S 0.03 Fig. 1 Specimen 2.2 Experimental flow chart Fig.2 Welded specimens 3. Results and discussion 3.1 Responses Table 3 Responses as per Taguchi array Expt. No. V(V) I(A) Cr Mn Si Mo (m/hr) (%) (%) (%) (%) Design of experiments Selection of welding parameters Table 2 Values of parameters Machining Parameters Units Symbol Levels A A 0 V V Weld Speed m/hr S Using the trial experiments the various values given in table 2 were taken to build the L-16 array using Minitab software. The experiments were performed according to the L-16 array shown in figure 2 (Pandey et al, 1994)

3 Mean of SN ratios Karun et al International Journal of Engineering and Technology, Vol.1, No.1 (Dec.2011) Table 4 S/N ratio Expt. No. V(V) I(A) S Cr Mn Si Mo S/N ratio S/N ratio S/N ratio S/N ratio Analysis of experimental data The chemical composition elements chromium (Cr), manganese (Mn), molybdenum and silicon (Si) along with the input process parameters is given in table 3. Minitab 15 software was used to analyze the measured response (Indacochea et al, 1985) Effect of input factors on Cr: The response table for signal to noise ratio for Cr is shown in table 4 and the responses in table 3. For Cr, the calculation of S/N ratio follows Larger the Better model. Therefore, voltage (V) has the maximum effect Table 5 Effect of input factors on Cr Level W. Speed Delta Effect of input factors on Mn: The response table for signal to noise ratio (Davis et al, 1977) for Mn is shown in table 4 and the corresponding table is shown in table 6. For Mn, the calculation of S/N ratio follows Larger the Better model. Therefore, voltage (V) has the maximum effect on Manganese element in the weld bead Table 6 Effect of input factors on Mn Level W. Speed Fig.3 Effect of Cr Delta

4 Mean of SN ratios Mean of SN ratios Mean of SN ratios Karun et al International Journal of Engineering and Technology, Vol.1, No.1 (Dec.2011) Fig. 4 Effect of Mn 0 Effect of input factors on Mo: The response table for signal to noise ratio for Mo is shown in table 4 and the corresponding table is shown in Table 8. For Mo (Chan et al, 1994), the calculation of S/N ratio follows Larger the Better model. Therefore, voltage (V) has the maximum effect on Molybdenum element in the weld bead. Table 8 Effect of input factors on Mo Level W. Speed Delta Effect of input factors on Si: The response table for signal to noise ratio for Si is shown in table 4 and the corresponding table is shown in Table 7. For Si, the calculation of S/N ratio follows Larger the Better model. Therefore, voltage (V) has the maximum effect on Silicon element in the weld bead (Chandel et al, 1987). Table 7 Effect of input factors on Si Level W. Speed Delta Rank Fig. 6 Effect of Mo Optimization of parameters: Optimal Parameters of Input Factors Fig. 5 Effect of Si 0 Physical Optimal Combination Requirement V(V) I(A) W.S(m/hr) Cr Mn Si Mo ( LEVEL-4) 0(LEVEL-4) (LEVEL-4) ( LEVEL-1) (LEVEL-1) (LEVEL-1) ( LEVEL-4) 0(LEVEL-4) (LEVEL-4) ( LEVEL-4) 0(LEVEL-4) (LEVEL-4) It can be seen from the graphs that for Cr, Mo & Si to be maximum factor V (V) has to be at high level 4, current (A) has to be at high level 4 & weld speed has to be at high level 4. For maximum Mn, factor V (V) has to be at low level 1, current (A) has to be at low level 1 &weld speed has to be at low level 1. is the most critical 113

5 Karun et al International Journal of Engineering and Technology, Vol.1, No.1 (Dec.2011) factor affecting composition of weld bead then, &W. Speed (Basu, et al, 2002). 4. Conclusion The combined effect of welding parameters on weld metal composition in SAW process was examined. Accordingly, the following conclusions can be drawn: It is interesting to note that chromium, molybdenum & silicon elements displaying a increasing trend & manganese element displaying a decreasing trend with an increase in any parameter, viz voltage, current & speed. An attempt was made to determine important welding parameters for composition of weld like Cr, Mn & Si in the SAW process. For controlling the weld metal composition, welding voltage is more effective than is welding current. Future scope of the work In this present study only four parameters have been studied in accordance with their effects. Keeping the view of future scope, other elements like carbon, sulphur, phosphorous etc. can be studied. 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