INVESTIGATION OF RECYCLED SLAG IN SUBMERGED ARC WELDING FOR

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1 5 th International & 26 th All India Manufacturing Technology, Design and Research Conference (AIMTDR 2014) December 12 th 14 th, 2014, IIT Guwahati, Assam, India INVESTIGATION OF RECYCLED SLAG IN SUBMERGED ARC WELDING FOR PRESSURE VESSELS S.B. CHANDGUDE 1, S. S. ASABE 2* 1 K.K.W.I.E.E.R, NASHIK, MAHARASTRA, INDIA, ,sbchandgude@gmail.com 2* U.C.O.E.R. PUNE, MAHARASTRA,INDIA ,asabesachin@gmail.com Abstract Submerged arc welding is widely used for fabrication of pressure vessels in the industries. Flux is a major content in such welding process and it produces. Storing and disposal of this is a major problem encountered in the industries. In this study recycling of the has been carried out for one of the industry with new combinations of wire and flux during the submerged arc welding of pressure vessels. Results of chemical and mechanical analysis have been presented and compared with AWS and National Accreditation Board of Laboratories standards. The economic aspects of recycling are also discussed in this paper. Keywords: Slag, weld, recycling, flux Metal, 1. Introduction Submerged Arc Welding is the better fabrication technique in industry due to its reliability and capability of producing good quality weld. Many industries use this method of welding for fast and smooth welding for manufacturing pressure vessels. In this welding process coalescence is produced by heating the metal with an arc maintained between a bare metal electrode and the work piece. The arc is shielded by a blanket of granular fusible material known as flux placed over the welding area. Filler metal is obtained from the electrode and sometimes a supplementary welding rod or metallic addition. Flux contributes a major part towards welding cost in submerged arc welding. The Flux is converted into during welding which is treated as waste and discarded. Again submerged arc welding (SAW) is one of the most widely used processes for fabrication of thick plates, pipes, pressure vessels, rail tanks, ships, heat exchangers etc. It has become a natural choice in fabrication industries because of its high reliability, smooth finish and high productivity. Parmar had stated that it has the capability to weld thicker sections with deep penetration. Initially Mitra and Eagar, in 1984 have predicted that Mechanical and metallurgical properties of the weld metal mainly depend upon the content of manganese, silicon carbon, sulphur, phosphorous, chromium and other alloying elements in the weld metal.however, from the available literatures it is evident that the first attempt at Investigation of recycling of Slag in case of Submerged arc welding was reported by Alfred Beck and Jackson. He used a closed loop recycling process and started practicing this in However, the response from industry was very poor, because of stringent AWS and ASME codes, combined with the reluctance of fabricators to use a recycled product. By 1996 AWS and ASME codes were amended to permit the use of recycled. Beck and Jackson further revealed their finding that if it is processed properly and according to code requirements, recycled could be reliably used as a substitute to fresh flux. They further emphasized a saving up to 50 of the total cost of purchased flux by recycling the. A few researchers have also explored the possibility of using a mixture of fresh flux and. In spite of the fact that from the available literature of Singh and Pandey, it was found that is being recycled by some companies but they are professional recyclers and have not disclosed the methodology, may be due to commercial reasons. Pandey et al. found that acceptable bead geometry can be achieved using recycled and have claimed a saving of 68.6 using recycled. Many other investigators like Farias et al, Du Plessis et al. and Kanjilal et al tried to understand the role of each flux ingredients on the weld-metal properties and operational characteristics of the process by varying only the individual flux ingredient in a given flux system observed that this approach by its very nature failed to take into account the simultaneous variation of the flux ingredients as well as their interaction effects

2 INVESTIGATION OF RECYCLED SLAG IN SUBMERGED ARC WELDING FOR PRESSURE VESSELS More recently after 2010 researchers like Dr.Kulwant Singh, Jatinder Garg, and Jasvinder Singh have made effort regarding mechanical property testing with recycled and also supported the ecological aspect of recycled. Again in 2011 through conference paper Mukesh, J.S. Randhava, N.M. Suri made an attempt regarding comparative analysis of the weld beads lead by both original flux and developed S.S. flux. The famous publisher Elsevier in 2012 focused an ecological aspect of recycled through journal named Journal of Hazardous material. A quantity of information is also available in the in which recycling and disposing methodologies have been given. In view of the strong support found from review of available literature for the recycling, one common recommendation witnessed that submerged arc welding Slag can be recycled with adding certain quantities of additives for economical and ecological benefits. 1.1 Aim of Study As per detail literature review and Methodology an attempts were made with the same objective of Economical and ecological benefits of recycling; one industry where near about 20 bags of fresh flux used daily was selected for execution of same process. where it was possible to analyse that whether the recycling is practically possible for selected industry. though there is cost saving through recycling process; it must follow AWS specification and should give sound weld. For the same it was decided that as per AWS classification i.e. for all flux- solider composite electrode multiple pass classification in the chemical analysis weld metal readings for carbon, manganese, silicon, sulphur and phosphorus should to take in account. For the same weldment it was decided to check it for different testing s such as tension test, Impact test and radiographic test with comparison of standard AWS values. 2.3 Sample weld with crushed The crushed and sieved was then used to produce a bead on mild steel plate as shown in fig.4.2 the size of the base plates was kept to be 280 X28 X 16 mm. The weld bead was deposited using 4 mm diameter EH-14 wire electrode in combination with crushed. A constant potential transformer-rectifier type power source with a current capacity of 1250 amperes and an open circuit voltage upto 51 volts. The welding parameters of the SAW machine were kept as shown in Table 1 the welding wire Specifications can be given as AWS SFA 5.17/EH 14 whose net weight per pack is 25x10 3 g with cost Rs 3000 per packet. This copper coated SAW welding wire was taken from regular supplier named Anand Arc Ltd; with 4mm diameter. The Flux Specification of Anand Arc Saw fluxes in this testing are F7A4EH14/F7P4EH14. Table 1 Welding parameters used for experiment 2. Experimental Analysis The details of the process can be explained as below. Parameter Units Symbol Value 2.1 Slag collection Slag collection was done from Artson Engineering Limited of Ambad M.I.D.C. Nashik. The collections have made only for the testing purpose in such a way that it will fulfill requirement of making weld pads for testing.(1500g for single test) Open circuit voltage Volts V 36 Current Ampere I Mechanical crushing Collected was then crushed mechanically and sieved in such a way that it will match the exact grain size provided through submerged arc welding machine.(as per the grain size of original flux).as per the amount of flux used in present industry it was decided to Investigate recycling method and determine the cost saving for production of pressure vessels. The analysis was done in such a way that Travel speed m/s S Nozzle to plate distance mm N

3 5 th International & 26 th All India Manufacturing Technology, Design and Research Conference (AIMTDR 2014) December 12 th 14 th, 2014, IIT Guwahati, Assam, India 2.4 Sample weld with fresh flux A weld bead on a similar plate as was prepared with original fresh flux in combination with EH-14 filler wire maintains the same welding parameters as were used in case of preparing the weld using crushed. This wire-flux combination was selected as the Artson engineering uses this combination and collected is also of same combination. 2.5 Comparison of weld metal composition Weld samples were removed from the middle and Explained in above illustration of weld plates. The samples removed thus with Specification SA 516 Gr 70 of condition of carbon steel were subjected for all testing mentioned in sample Methodology. 2.6 Slag Processing the weld material for better results. Skilful labour and proper cleaning will solve these obstacles. Figure 1 Weld pad and sample for testing Table 2 Chemical investigation results As Per the Details of results of samples from NEPPTUNE Metallurgical Laboratories, the further processing of have done with information of addition of alloying elements/deoxidizers for Recycling. In this chemical processing the of weight 980g was mixed with calcium carbonate and silicon dioxide of weight 120g and 10g respectively; This addition was important to add Carbon and its reaction with silicon dioxide were created good balance of sulphur and oxygen as well for further recycling. Then in the same mixture alloy i.e. Ferro-manganese and Ferro-titanium were added in trace amount to satisfy the Manganese AWS requirement. Potassium silicate is used as a binder. 2.7 Chemical analysis and Weld Quality testing After the preparation of recycled the weld pad samples were taken for the further chemical analysis and weld qualification test as per the requirement of AWS standards. Condition of weld metal AWS requirement (Max.Value) With fresh flux With pure With recycled C Mn Si S P Results Analysis The Investigation of Recycled can be processed as per the Information in the references which involves Chemical analysis of weld metal and weld Qualification assurance with Radiographic, Tension and Impact testing. for the same weld pad and specimens for testing s were made as shown in figure 1.samples were tested for fresh flux, and recycled ; with reference to standard reference values in table no.1.thus there was no problem in case of chemical analysis; only it was necessary to have a correct and careful attempt with the help of proper instrumental and chemical setup. More thing necessary to concentrate are to verify the welding parameter well before the sample weld preparation as well as to avoid mechanical impurities in 3.1 Chemical analysis of weld metal From the above investigation it was very much clear that the chemical percentage for Carbon was increased by 0.02 from to recycled which was better than fresh flux and satisfying AWS requirement value of 0.20 (which shows max. range of values for carbon).similarly in case of manganese increment observed was 0.21 which satisfies the range of maximum value of 1.60 in case of Silicon there was also an increment with 0.05 percentage and found satisfactory as Max AWS value is In case of Sulphur and phosphorus it was only minor incremental change than original values but which was also permitted as per requirement of AWS i.e Thus 258-3

4 INVESTIGATION OF RECYCLED SLAG IN SUBMERGED ARC WELDING FOR PRESSURE VESSELS there was no problem in case of chemical analysis; only it was necessary to have a correct and careful attempt with the help of proper instrumental and chemical setup. 3.2 Weld Qualification Tests and Results The next step in the analysiss after chemical satisfaction was to undergo the tests for weld qualifications to ascertain its performance. As per explanation given in previously the three tests i.e., Tension, Impact and Radiographic were conducted and the results Explained as below. Table 2 Results of Mechanical Testing YS UTS Heading N/mm 2 N/mm 2 Elongation AWS Requirement minimum minimum With fresh flux With pure Cost Analysis Practically it s very difficult to predict the fluctuation in the prices; again according to demand there are some chances of change in true cost. But before implementation of recycling process cost analysis is essential. Considering this view cost analysis of Recycled for 100X10 3 g was calculated and compared with the fresh flux available in the market. This comparison had done according to principal of market value method which as similar to the technique of product revenue deducted from production cost. Mathematical calculation for 100X10 3 g recycled is with details of sample preparation which need total 1500g quantity of Slag/flux. Extra tolerance cost and profit consideration are taken as 10 and 12 the respectively as per the standardd norm which are expected to be followed by the company. Actually in the present analysis impact cost of recycling on environment has not considered and calculated. But in practical case this recycling saves lot of environmental hazards and pollutions, which are going to create an adverse effect on quality of life. Again in this case the possible cost of handling and Storing in free land spaces when it was not supposed to be recycled has not considered. For the selected industry with the present rates of consumables it is showing increment in the cost as compared with the value of fresh flux by the major difference of cost is due to large increment in cost of chemicals than previous attempts. Recycled Slag Graphical analysis 1.8 Table 3 Results of weld qualification testing Heading AWS Requirement Charpy Impact (J) 20 J minimum. With fresh flux With pure Radiography Observation NSD NSD C Mn Si S P Recycled Slag IP 0 AWS requ. fresh flux pure recy. Figure 2 Chemical Comparison of weld metal 258-4

5 5 th International & 26 th All India Manufacturing Technology, Design and Research Conference (AIMTDR 2014) December 12 th 14 th, 2014, IIT Guwahati, Assam, India fresh flux pure The major difference of cost is due to large increment in cost of chemical than previous attempts. Increment in Production may give better results of recycling for selected industry. Another Method of Recycling such as addition of fresh flux into may be best option for industry with less flux consumption Obs.values. Figure 3 Weld qualification testing comparison The results of chemical comparison and weld qualification testing are will be easier to understand with graphical representation as above. 4. Conclusions As per the detail literature review on Recycling of with the help of exact methodology with some predictions and investigation have been done on recycling of with further conclusions. Slag in the submerged arc welding can be recycled with proper application of prescribed methodology. Chemical analysis and mechanical testing was given satisfactory value which are again acceptable by AWS. But for the selected industry with the present rates of consumables it is showing increment in the cost as compared with the value of fresh flux by References 240 Min Min 20 J Min YS UTS Elong. Req.values C.I.test Recycled Slag Eagar, T.W. (1979), Oxygen and Nitrogen Contamination during Arc Welding, Journal of Proc. Of weldments: Physical Metallurgy and Failure Phenomena. Beck, H.P., and Jackson A.R. (1996), Recycling Saw Slag Proves Reliable and Repeatable, Welding Journal, pp Discussions Slag in submerged arc welding can be possible to recycle with the proper attempts of recycling. Results of recycled starting with chemical analysis are very positive and well acceptable by AWS standards. for the proper recycling it becomes necessary to follow the exact methodology as instructed.due care Should be taken at the time of collection of if there are more than one combination of wire and flux are in working; because definitely for different combination of wire and there are variation in contents of chemical percentage in. To avoid the mixing of clay particles and metallic particles into the necessary arrangement of collectors and magnetic separator s will be very much essential. Preservation of collected in dry and cool space before it goes for recycling will avoid the further complications of oxidation and other chemical reactions. In actual practice the cost of handling pure and consideration of environmental affection will give the better saving in case of industry with mass production. So the industry with maximum daily consumption of fresh flux can still accommodate the loss and have desired saving. In case of industries of whose daily consumption of fresh flux is less; for them it is difficult to sustain with this recycling. In spite of all these circumstances industries with less flux consumption can go for recycling for the sake of ecological benefits. ESAB, Handbook (2003), a full line of submerged arc flux and wire for every application, industry and environment, pp Murugana, N., Gunaraj, V. (2005),Prediction and Control of Weld Bead Geometry and Shape Relationships in Submerged Arc Welding of Pipes, Journal of Materials Processing Technology Vol.168, pp Kanjilal, P., Pal T.K. Majumdar, S.K. (2006), Prediction of Element Transfer in Submerged Arc Welding, Journal of Materials Processing Technology, Vol.171, pp

6 INVESTIGATION OF RECYCLED SLAG IN SUBMERGED ARC WELDING FOR PRESSURE VESSELS Singh, K., Pandey, S. (2009), Recycling of to act as a flux in submerged arc welding, Resources Conservation and Recycling, Vol.53, Elsevier, pp singh, K., Sahani, V., Pande, S. (2009),Slag Recycling in Submerged Arc Welding and its Influence on Chemistry of Weld Metal, Asian Journal of Chemistry, Vol.21,pp.47-51, pp Garg, J., Dr. Singh, K. (Feb.2010),Recycling Of Submerged Arc Welding Slag For Economy and Environment, National Conference on Advancements and Futuristic Trends in Mechanical and Materials Engineering. Singh, K., Singh, J. (February 2010), Influence of Slag Flux Mixture on Mechanical Properties of Welds in Submerged Arc Welding, National Conference on Advancements and Futuristic Trends in Mechanical Engineering. Mahto, D., Kumar, A. (September 2010), Novel Method of Productivity Improvement and Waste Reduction through Recycling of Submerged Arc Welding Slag, Jordan Journal of Mechanical and Industrial Engineering. ISSN Vol.4, pp Randhava, J.S. Suri, N.M. et al. (December 2011), Comparative Analysis Of The Weld Beads laid By Both Original S.S. Flux and Developed S.S.Flux, International Journal of Materials Science and Engineering, Vol.2, pp.1-2. Singh, J., Singh, K., Garg, J. (December 2011), Reuse of Slag as Flux in Submerged Arc Welding and its Effect on Chemical Composition, Bead Geometry and Microstructure of The Weld Metal, National Conference on Advancements and Futuristic Trends in Mechanical and Materials Engineering,vol.1. Annonia, R., Souzaa, P. et al. (November-2012), Submerged-arc welding s: Characterization and leaching strategies for the removal of aluminum and titanium, Journal of Hazardous Materials, Elsevier, pp