This paper presents the main factors that cause environmental pollution in the case of the welding procedure in a protective gas environment. In the research the MIG and MAG welding processes were taken into account. The materials used in the experiments were 8TiCr170 stainless steel as the base material and as filler materials 4 types of welding wires were used, characterized by different chemical compositions. To assess the impact on the work environment of such welding processes the pollution coefficient Cp was defined based on the material balance equation as the ratio of the mass of all materials used in the welding process Mt and the effective mass of the welded performed Mu

Gh. Amza

M. Groza Dragomir

S. Paise

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Theoretical and experimental contributions regarding the impact on work environment of welding processes in MIG / MAG protective gas medium

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321METALURGIJA 52 (2013) 3, 321-324Gh. AMZA, M. GROZA DRAGOMIR, S. PAISETHEORETICAL AND EXPERIMENTAL CONTRIBUTIONS REGARDING THE IMPACT ON WORK ENVIRONMENT OF WELDING PROCESSES IN MIG / MAG PROTECTIVE GAS MEDIUMReceived – Prispjelo: 2012-10-08Accepted – Prihvaćeno: 2013-01-05Original Scientifi c Paper – Izvorni znanstveni radISSN 0543-5846METABK 52(3) 321-324 (2013)UDC – UDK 621.73.042:669.1=111Gh. Amza, M. Groza Dragomir, S. Paise, Engineering and Tehnologi-cal Systems Management Faculty, Polytehnica University of Bucharest, RomaniaThis paper presents the main factors that cause environmental pollution in the case of the welding procedure in a protective gas environment. In the research the MIG and MAG welding processes were taken into account. The ma-terials used in the experiments were 8TiCr170 stainless steel as the base material and as fi ller materials 4 types of welding wires were used, characterized by diff erent chemical compositions. To assess the impact on the work envi-ronment of such welding processes the pollution coeffi  cient Cp was defi ned based on the material balance equation as the ratio of the mass of all materials used in the welding process Mt and the eff ective mass of the welded per-formed Mu.Key words: welding, protective gases, work environment, material balance, pollution coeffi  cient.INTRODUCTIONThe use of welded structures has become increas-ingly present over the last two decades due to the ad-vantages they have in comparison with other structures obtained by other technological processes [1-2]. Deter-mining the environmental impact of the process of welding in the protective gas environment is a complex problem, which requires many years of experiments un-der different conditions and in different situations. The most important impact of the process is on the working environment, as well as on the welding operators and auxiliary operators in that department, so, the experi-ments included in the present study allowed to deter-mine that impact. Most welding processes, by the op-eration and technological equipment with which they are realized, have a major impact on the environment and pollution is not negligible [3].The main sources of environmental pollution caused by welding processes are electric discharges, electro-magnetic radiation, powders, micro powders, fumes, gases of different types and different concentrations, fog, photochemical pollution, dusts, relative organic compounds, heavy metals, decomposition of combusti-ble materials and minerals, waste and industrial waste etc. [4].In recent decades, specialized enterprises have ap-peared producing welded construction elements or large welded constructions. Welded Construction Enterprises are based on the process of welding done by different welding processes. These production sites feature a number of technological equipment for welding and other auxiliary technological equipment (for cutting, joint preparation, for cleaning, pickling and degreasing, corrosion protection, trials and testing etc.). And the en-vironmental impact is essential in designing technologi-cal process of achieving the welded construction [5-6].The environmental impact of a welding process can be analyzed in two ways, namely: the impact on the working environment, which is the indoor environment in which the welders and workers who participate in the general technological process operate (health and its evolution); the impact on the natural environment, which is the external environment in which the indus-trial organization of welded constructions has an infl u-ence by means of the substances occurring in the manu-facturing process [7-8]. The main polluting factors gen-erated by the welding technological processes are: the powder and micropowder of different substances with sizes between 1-7µm and lower sizes by 2µm; the parti-cles of heavy metals: Cu, Sn, Mn, Si, Ni, Sb, V, Zn etc.; carbon oxides: CO, CO2, COx; nitrogen oxides: NO, NO2, NOx; sulfur oxides: SO2, SO3, SOx; hydrogen sulfi de H2S; acid aerosols: Cl, F, SO4, NO3; tropospheric ozone: O3; volatile organic compounds; saturated hy-drocarbons, chlorates, acetones etc.; the persistent or-ganic pollutants: trichlorethan, tetrachlorethilene, xy-lene, aromatic hydrocarbons etc.; powder; fumes and fog; solid debris (electrode ends, wires, bars, pipes, pro-fi les, slag). [9-10].MATERIALSThe input about the basic material and the steps needed to achieve environmental experiments for weld-322  METALURGIJA 52 (2013) 3, 321-324Gh. AMZA et al.: THEORETICAL AND EXPERIMENTAL CONTRIBUTIONS REGARDING THE IMPACTing in a protective gas environment MIG / MAG was chosen so as to determine by comparison the nature of cases occurring and the quantities of gas and micro par-ticles/particles arising from the application of the weld-ing process.For a relevant and comparative analysis, numerous experiments were performed by going through the fol-lowing steps:choice of the base material subject to experiments. • The basic materials on which the deposits were made was a steel from the class of stainless steels, type 8TiCr170;stablishing the methods for cleaning, degreasing and • etching on the surface so that where the welding fi ller will be added there aren’t any impurities;choice of fi ller material.• The fi ller materials were chosen so as to allow a quantitative and qualitative comparison of results;determining the main parameters of deposition by • welding technology;comparative analysis of the results obtained;• determination of the coeffi cient of pollution and en-• vironmental quality indicator.The basic material onto which the weld seams for experiments were deposited was 8TiCr170 steel, a fer-ritic stainless steel, whose chemical composition is shown in Table 1.Also, we used as protective environment to achieve welded joints Ar for the MIG procedure and Ar+CO2 for the MAG process.RESULTS AND DISCUSSIONEstablishing the impact of the work environment was done using the materials balance equation. Material balance equation, in the case of welding processes in the protective gas environment MIG/MAG, is: M el + Mgp=Mmd+Mpa+Mps+Mpnd  (1)where: Mel is the mass of electrode wire used in weld-ing; Mmd – the mass of the metal or alloy deposited in the welding bead, which is determined by weighing; Mgp – protective gas mass, which is known; Mpa – mass of the losses in the atmosphere, that includes all the sub-stances released in the welding process, which remain in the atmosphere, determining the relationship:Mpa=MCO+MCO2+MNO+MNO2+MNOX+MSO2+ +MH2S+MH2+Magn  (2)where: MCO is the mass of carbon oxides released into the atmosphere; MCO2 - mass of CO2, released into the atmosphere; MNO mass of NO, released into the atmos-phere; MNO2 mass of NO2, released into the atmosphere; MNOX - mass of other nitrogen oxides, released into the atmosphere; MSO2- mass of SO2, released into the at-mosphere; MH2S- mass of H2S, released into the atmos-phere; MH2- mass of H2, released into the atmosphere; Magn - mass of other undetectable gases, released into the atmosphere and which can be calculated with the equation: Magn = (0,005...0,008)MCO (3)Depending on the nature of the base and fi ller mate-rials, as well as on the protective gas function, Mps - mass of the soil losses includes all substances deposited on the ground after the welding process, which is calcu-lated by the equation: Mps=Mmp+Mss  (4)where: Mmp este is the mass of the particles and micro-particles arising from the welding process and deposited on the soil; Mss – mass of the metal splash leaving the weld bath and deposited to the ground. In the relation (1) there is also Mpnd, which is the mass of other unde-tectable substances, which close the balance equation, and can be calculated with the formula: Mpnd=(0,06...0,09)(Mpa+Mps)   (5)Thus the pollution coeffi cient Cp was defi ned as the ratio of the mass of all materials used in the welding In order to conduct experiments to determine the quantities and types of gases resulting from burning dif-ferent types of fi ller materials used for the welding in protective gas environment was chosen one of 4 types of fi ller wire whose composition is presented in Tables 2-5.Table 1 Chemical composition of steel 8TiCr170/ %MaterialChemical elementsC Cr Si Mn8TiCr170 0,09 16,5 1,0 1,0Table 2 Chemical composition of fi ller material ER70S-6 / %MaterialChemical elementsC max. Mn SiER70S-6 0,09 1,53 0,92Table 3 Chemical composition of fi ller material ER70S-3 / %MaterialChemical elementsC max. Mn SiER70S-3 0.1 1,1 0,6Table 4  Chemical composition of fi ller material E70C-6M / %MaterialChemical elementsC max. Mn SiE70C-6M 0,06 1,5 0,6Table 5  Chemical composition of fi ller material ER 80S-G / %MaterialChemical elementsC max. Mn Si Mo ER 80S-G 0,1 1,1 0,7 0.5323METALURGIJA 52 (2013) 3, 321-324Gh. AMZA et al.: THEORETICAL AND EXPERIMENTAL CONTRIBUTIONS REGARDING THE IMPACTprocess Mt and the effective mass of the welded joint performed Mu meaning:   (6)The welding system parameters were varied in a wide range of values, to fi nally be able to optimize the technological process of welding in terms of working environment pollution, Table 6.To establish dependencies between types and quan-tities of resulting fumes and welding parameters, we have measured, during the experiments, the following parameters: welding current, welding voltage and weld-ing time. After the conclusion of the experiments we have determined the length of the cord, and based on the computing relationship – the linear energy value was determined for each experiment. The experimental re-sults obtained by variable selection of welding process parameters are presented in Tables 7 and 8. The quanti-tative determination of the fumes resulting during the welding process was done using the equipment MA-DUR GA40 PLUS and were processed using special-ized software called “STATISTICA”. The MADUR GA40 PLUS analyzer is a device that can be endowed with between 2 to 6 sensors able to detect different gas concentrations. What is worth mentioning is the fact that just one nitrogen sensor can detect the following types of gas O2, CO, NO, CO2, NOx, H2S. The fi rst three of them are directly determined, while the rest of them are directly calculated by the analyzer.The experimental stand was endowed with various elements enabling us to monitor the welding process, and to completely absorb the welding resulting sub-stances, as follows: in the upper part an opening was built in, enabling the measurement device to be insert-ed; in order for the welder to monitor the electric arc (especially its stability), we had a small part cut out and replaced with a special piece of glass providing protec-tion against the light of the electric arc; in order to cre-ate access for the fi ller material, the port electrode, the welding pistol and the initiation of the welding process, in the bottom part, the stand was provided with an ac-cess system of corresponding dimensions. This area was sealed in order to reduce any potential gas or fume leaks.The experimental stand was designed to meet the following criteria: material: steel; thickness: 5 mm; ad-ditional requirement: air tightness; access to the weld-ing space; maximal dimensions of the welded pieces: 750x300x50mm; maximum weight: 80Kg; predeter-mined volume; a certain degree of universality enabling the realizing of welding joints by the welded analyzed process. In order to realize the welded seams of sheet metals or thicker profi les we used the welding equip-ment ESAB-LAF 1250 DC. The power source used for automatic submerged arc welding is a power source for triphase welding, operated by a remote control, de-signed for increased performance in MIG/MAG proce-dures. This source was also combined with the ESAB, A2-A6 Process Controller (PEH).CONCLUSIONFollowing the experimental results obtained, we can draw the following conclusions– the highest pollution coeffi cient Cpmax = 1,33, was obtained when using the following parameters : Is = 252 A; Ua = 22 V; t = 60 s; lc = 27 cm; vs = 0,45 cm/s; El = Table 8 Pollution coeffi  cient Cp values calculatedFiller material nameMt /gMu /g CpER 70S-6 1 556,66 1 286,50 1,211 602,08 1 292,02 1,241 635,85 1 298,39 1,26ER70S-3 1 636,01 1 288,26 1,271 613,75 1 291,77 1,251 637,62 1 299,79 1,26E 70C-6M 1 637,46 1 289,34 1,271 577,19 1 282,27 1,231 615,76 1 303,04 1,24ER80S-G 1 659,02 1 276,17 1,301 727,07 1 298,55 1,331 655,75 1 293,56 1,28Table 6 Values regime welding parametersFillermaterialnameWelding parameters regimeIs /AUa /VLc /cmt /sVs /cm/sEl /kJ/cmER 70S-6 198 21,0 26 60 0,43 8,6212 22,2 26 60 0,43 9,8288 24,0 29 60 0,48 12,9ER70S-3 229 21,2 28 60 0,47 9,4246 22,8 27 60 0,45 11,2265 24,7 36 60 0,60 9,8E 70C-6M 200 21,5 28 60 0,47 8,3210 22,5 26 60 0,43 9,8286 24,0 28 60 0,47 13,2E80S-G 231 21,0 29 60 0,48 9,0252 22,0 27 60 0,45 11,1272 24,5 35 60 0,58 10,3Table 7  Weight values resulting gas during the welding process / ppmFiller material name CO NO NO2 NOx SO2 H2S H2ER 70S-6 516 0 0 0 0 1 8607 0 0 0 0 1 7609 0 0 0 1 1 16ER70S-3 599 0 0 0 1 1 39663 0 0 0 1 1 21651 0 0 0 1 1 31E 70C-6M 516 0 0 0 0 1 5607 0 0 0 0 1 7609 0 0 0 1 1 16ER80S-G 599 0 0 0 1 1 39663 0 0 0 1 1 21651 0 0 0 1 1 31324  METALURGIJA 52 (2013) 3, 321-324Gh. AMZA et al.: THEORETICAL AND EXPERIMENTAL CONTRIBUTIONS REGARDING THE IMPACT11,1 kJ/cm, electrode E805-6, with rutile coating, diam-eter of the metal rod DVM = 1,2 mm;– the lowest pollution coeffi cient Cpmin = 1,21, was obtained when using the following parameters: Is = 198 A; Ua = 21 V; t= 60 s; lc = 26 cm; vs = 0,43 cm/s; El = 8,6 kJ/cm, electrode E705-6, without coating, metal rod  diameter DVM = 1,2 mm;– the highest concentration of carbon monoxide COmax = 1215 ppm, was obtained when using the fol-lowing welding mode: Is = 193 A; Ua = 24,7 V; t = 60 s; lc = 25 cm; vs = 0,42 cm/s; El = 10,3 kJ/cm, electrode E715-1M, with rutile coating, diameter of the metal rod DVM = 1,2 mm;– the lowest concentration of carbon monoxide COmin = 0,16 ppm, was obtained when using the follow-ing parameters of the welding regime: Is = 198A; Ua = 21 V; t = 60 s; lc = 26 cm; vs = 0,43 cm/s; El = 8,6 kJ/cm, electrode E705-6, without coating, metal rod diameter DVM = 1,2 mm and with electrode E70C-6M; – the largest amount of hydrogen H2max = 56 ppm, was obtained when using the following parameters of the welding regime: Is = 195 A; Ua = 24,5 V; t = 60 s; lc = 26 cm; vs = 0,43 cm/s; El = 9,9 kJ/cm, electrode E715-5M, with base coating, metal rod diameter DVM = 1,2 mm;– the lowest concentration of hydrogen H2min = 5 ppm, was obtained when using the following welding mode: Is = 200 A; Ua = 21,5 V; t = 60 s; lc = 26 cm; vs = 0,47 cm/s; El = 8,3 kJ/cm, electrode E70C-6M, with base coating, metal rod diameter DVM= 1,2 mm;– in most experiments concentrations of NO, NO2, NOx, SO2 and H2S were not detected.REFRENCES[1]  D. Dobrotă, G. Chirculescu, Proceedings of a Conference “Modern Technologies Quality and Restructuring – TMCR”, Chişinău, (2005) 2, 373-376.[2]  D. Dobrotă, L. M. Cîrtînă, Proceedings of a Conference “Modern Technologies Quality and Restructuring – TMCR”, Chişinău, (2005) 2, 377-380.[3]  L. Henning et al., EPA contract no. 68-Do-123, Midwest Research Institute, Kansas City, (1994).[4]  American Welding Society, Fumes and gases, Safety and Health Fact Sheet, (2005) 1.[5]  T. Karkoszka et al., Metalurgija, 51 (2012) 2, 145 – 288.[6]  A. M. Leman, A.R. Omar and M.Z.M Yusof, 2010, Moni-toring of Welding Work Environment, 5 (2010) 1, 18-26.[7]  H. S. Ashby, Welding Fumes in the workplace: preventing Potential Health Problems Through Proactive Controls, Professional Safety, (2002) 55-60.[8]  P. J. Hwitt, 2001, Annals Ocuppational. Hygiene, 45 (2001) 4, 295-298.[9]  EN ISO 14001, Environmental management systems – Re-quirements with guidance for use, (2004).[10]  EN ISO 14717, Welding and allied processes – Environ-mental check list, (2005).Note:  The responsible translator for English language is S.C. PURTRAD S.R.L., Targu Jiu, Romania

Theoretical and experimental contributions regarding the impact on work environment of welding processes in MIG / MAG protective gas medium

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