Evidence from Inclusion Chemistry of Element Transfer during Submerged Arc Welding
Chemical factors controlling the transfer of elements into the weld pool are analyzed
BY M. L. E. DAVIS AND N. BAILEY
ABSTRACT. The complex changes in com Jackson (Ref. 1) has traced the history reached. position during the submerged arc weld and development of fluxes in arc welding This paper continues this study, using ing of C-Mn steels have been related to from the beginning of the century until additional analytical data, together with flux composition and weld metal inclu about 1972. Coe (Ref. 2) extended this information obtained from flux manufac sions, which form the final reaction prod base of knowledge and included informa turers. Other work (Refs. 6, 7) in which in ucts. High-temperature reactions in the tion on slag-metal reactions. Although a clusion types in various weld metals were arc plasma (particularly those involving good general understanding has been studied by use of the particle analyzing oxygen, fluorine, calcium and magnesium) reached of the physical and chemical scanning electron microscope (PASEM) are followed at lower temperatures by characteristics of submerged arc fluxes, has been considered since the inclusions reactions in the slag and the weld pool. some empiricism still attends flux formula represent the final reaction products. tion. In particular, because of the com However, because the welds had been plexity of the reactions occurring in the arc deposited predominantly using electrode- Introduction and weld pool, it is difficult to define un positive polarity, no attempt was made to Submerged arc welding fluxes are man ambiguously the chemical factors control examine the role of electrochemical trans ufactured in two main forms, fused and ling transfer of individual elements with port and reactions, which have been ex agglomerated, from mineral constituents. the pool and through them to predict the amined or discussed in some recent in The minerals used are also utilized in steel final weld metal composition. vestigations (Refs. 8, 9). making slags, and thus submerged arc Recent research programs involving welding fluxes bear a family resemblance submerged arc welding of carbon- and Description of Flux Composition to the slags used in steel production. carbon-manganese steels have generated However, submerged arc welding in data for both commercial and experimen Fluxes are analyzed using a combination volves very short time scales between tal fluxes from which the chemistry of the of techniques, x-ray fluorescence (XRF), melting and solidification of the weld pool, flux, wire and plate used can be compared various wet chemical methods for the while the arc temperatures achieved are with the resulting weld composition. Such lighter elements, supplemented by x-ray in excess of those in a molten steel bath. data have been used to examine the ex diffraction (XRD) for agglomerated fluxes. Fluxes for submerged arc welding must tent to which levels of elements such as In the past, the analytical convention has have special properties not required by oxygen, manganese and silicon can be been to convert the elements into their steel-making slags in order to maintain and predicted (Refs. 2-5). Although a number oxides. Thus, alkali elements have been protect the weld pool. The welding flux of trends were identified, there were no reported as their highly reactive oxides must contain minerals that will readily ion firm indications that a chemical balance and the transition elements and alkali earth ize and thus stabilize the arc current. It between slag and weld metal was, in fact, metals as their most stable oxides, al must generate, through ions and gases, an though they may be present as part of a arc plasma through which molten metal silicate lattice in which strict stoichiometry droplets may be propelled from the elec may not exist. trode to the weld pool, yet it must give In manufacturing a flux, it may be nec KEY WORDS slag fluidity to cover the solidifying weld essary to take into account the structural metal, and the slag must possess adequate Submerged Arc Welding form of constituent minerals. For example, difference in thermal contraction to de SAW C-Mn Steel Welds different flux behavior, in terms of result tach itself from the cooling metal. Submerged Arc Fluxes ant bead shape and arc stability, may be SAW Flux Types achieved by using mica rather than potas SAW Reaction Model sium, sodium and aluminosilicates. How M. L. E. DA VIS was a Senior Chemist and N. Slag-Metal Reactions ever, it would not necessarily be expected BAILEY is a Principal Metallurgist at The Welding Element Transfer that such differences would greatly influ Institute, Cambridge, England. Inclusion Chemistry ence resultant deposit composition. For Mn, Al, Si, S Reactions studying slag-metal reactions at high tem Paper presented at the 71st Annual AWS Oxygen Reactions peratures, the convention of reporting Meeting, held April 22-27, 1990, in Anaheim, Calif. oxide contents promotes a potentially
WELDING RESEARCH SUPPLEMENT I 57-s misleading view of the melt. In this report, give the average change in weld metal droplet. High-temperature stirring in the elemental analyses are given for the fluxes composition for Mn, Si, S and P and the weld pool will then keep the molten metal employed, and differences in the form in average level of Al, O and N. Table 5 also and the slag in intimate contact after the which those elements may be present are gives the level of Ti for some experimen arc has passed. Indacochea and his col discussed later in terms of differing chem tal fluxes, which contained either FeTi or leagues have commented that the system ical content of the welds. rutile (Ti02) as deliberate additions. Full contains four principal phases (wire, mol details of wire, plate, weld compositions ten flux, arc plasma and weld pool) with five interfaces between them (Ref. 8). Analysis and welding details are given in Refs. 4-7. Tables 1 and 2 give the elemental anal Hence, the model for slag metal reac Fluxes yses of fluxes, it being assumed that the tions during submerged arc welding is of remaining weight is oxygen. For consider All fluxes were analyzed using an XRF initial reactions occurring rapidly at ex ation of the chemical reactions taking technique and wet chemical methods for tremely high temperatures, exposed to an place, these weight-percent figures were ionic plasma for a short time (possibly sodium and fluorine. The fluxes are converted into the ionic fraction of individ grouped according to their main chemical <0.1 s), followed by a period when mol ual elements given in Tables 4 and 5, the ten slag is in contact with molten metal composition as shown in Tables 1 and 2. method of this calculation being similar to with the temperature decreasing. This will The XRD was carried out on the agglom that employed by Herasymenko and last for several seconds, and will depend erated fluxes to determine mineral con Speight (Ref. 10) for steel-making slags. on the size of the weld pool. Certainly, the stituents used, and these are given in Ta results of Kuwana and Sato (Refs. 11, 12) ble 3. Inclusions can be understood using this model. Thus, it will be short if a single wire is used dur Wire Plate and Weld Metal Inclusions have been analyzed qualita ing a multipass weld, longer for a single Wire, plate and weld metal chemistries tively for the number of welds (Refs. 6, 7) wire, single-pass weld, while multi-arc of test welds were obtained from The by the PASEM system (Ref. 11). The results {i.e., tandem and triple arc) welding may Welding Institute data and flux manufac are given in Tables 6-8. allow the pool to last for ^15 s. It is pos turers. All elements were determined sible that the initial reactions will depend spectrographically, apart from oxygen and on the chemical reactivity of the ionized The Submerged Arc System nitrogen, which were determined by hot species present, while the weld pool vacuum fusion. For all welds, the average During submerged arc welding, a mol reactions will depend more on kinetic change in weld metal composition from ten drop of metal from the wire electrode considerations. the value expected, considering only the passes through or around a highly ionized consumable and base metal analyses and high-temperature plasma —the welding Development of Inclusions the dilution experienced, was estimated. arc. The arc plasma will contain ions from The number of welds made with each flux wire, plate and flux, and these will react As discussed earlier (Ref. 4), it is unlikely was never less than two. Tables 4 and 5 quickly with the surface of the molten that true thermodynamic equilibrium is at-
(a) CSHS Calcium silicate, high silica. (b) CS F Calcium silicate, fused. (c) CSLS F Calcium silicate low silica, fused, 2% carbonate added and mechanically mixed after fusion. (d) B <\ Basic, agglomerated. (e) Basic, fused. (f) MS F Manganese silicate, fused. (g) AR F Alumina rutile, fused, (h) Alumina rutile, agglomerated. (i) AB A Alumina basic, agglomerated. (j) M Multipass (k) S Single-pass (I) T Single-pass tandem
CaF2 + CaO + MgO -I- '/ilFeO + MnO) (m) Bl = S1O2+ '/2(Al203 + Ti02) (n) ND Not determined
58-s I FEBRUARY 1991 Table 2-—Elemental Analysis of Experimental Fluxes
Weld j; FluxW Type Si Ti Al Fe Mn Ca Mg Na F Droduced L * HTF1 B A 6.7 <0.1 9.0 2.1 2.6 15.7 16.6 2.4 4.7 Tte) * HTF2 B A 6.3 1.3 8.8 2.1 2.5 15.4 16.8 1.6 4.5 T ce HTF3 B A 6.0 2.8 8.8 2.0 2.5 15.8 16.1 1.6 4.5 T b HTF4 B A 6.1 5.1 8.3 1.9 2.4 13.9 15.0 1.4 4.5 T u HTF5 FB A 4.8 0.1 5.4 2.1 2.0 18.0 22.7 2.0 12.5 T c b MLD1 AB A 9.0 0.4 15.8 1.5 7.6 9.4 11.4 0.6 7.9 S< > 3 MLD2 AB A 8.2 1.8 15.4 3.2 6.6 8.9 11.0 1.2 7.7 S C Q MLD3 AB A 8.4 3.1 15.1 5.0 6.3 8.3 10.4 1.2 7.1 s -Mineral Constituents Used in Table 3- < MLD4 AB A 8.7 2.8 14.9 1.6 6.7 8.6 11.0 1.3 7.7 s Agglomerated Fluxes u MLD5 AB A 8.4 0.8 15.2 1.4 7.1 9.1 11.6 1.1 8.0 s MLD6 AB A 9.3 0.8 14.6 1.5 7.1 9.6 11.3 1.1 9.1 Q s Alumina AI2O3 MLD7 AB A 9.1 0.9 14.9 1.5 6.9 9.3 11.4 1.1 8.1 s 1- MLD8 AB A 9.6 0.9 14.4 1.5 6.8 9.5 11.1 1.2 8.5 Corundu m s K 2 MLD9 B A 6.9 1.4 10.8 0.6 - 13.9 19.8 0.8 9.5 T oc Cristobalite Si02 u MLD10 B A 7.2 1.7 10.3 2.1 <0.1 13.2 19.7 0.8 10.3 T Fluorite CaF2 £ MLD11 B A 6.5 2.5 10.6 2.9 <0.1 13.4 19.2 0.9 10.5 T Hausmannite Mn304 Q MLD12 B A 6.8 2.5 10.1 0.5 <0.1 13.4 19.8 0.8 10.4 T Periclase MgO c MLD13 B A 6.6 0.5 9.8 0.3 <0.1 13.7 20.5 0.5 12.3 T Quartz Si02 u MLD14 B A 6.8 0.5 9.9 0.3 <0.1 13.8 20.6 0.5 13.6 T Rhodonite MnSi03 u MLD15 B A 7.1 0.4 8.2 0.3 <0.1 13.6 20.2 0.6 14.5 T Rutile Ti02 c MLD16 B A 7.6 0.5 9.5 0.4 <0.1 13.7 20.1 0.4 13.8 T Wollastonite CaSiQ3 I t (a) T Single pass tandem. a (b) S Single pass single wire. (c) <0.1% lr and K in all fluxes. If, LL a Table 4--Flux and Welc Chemistry, Commercial Fluxes Chang es in Weld Chemistry 2 LL from Expected, Average Average Level E a Ion Fraction ilement (wt •%) Element (wt -%) C _LL Flux Si Ti Al Mn Ca Mg F O Si Mn P S C Al O N > LL MF15 0.22 _ 0.02 _ 0.11 0.06 „ 0.58 +0,58 -1.37 +0.004 +0.026 -0.10 <0.005 0.126 0.011 a $
WELDING RESEARCH SUPPLEMENT I 59-s Table 5—Flux and Weld Chemistry, Experimental Fluxes
Changes in Weld Chemistry from Expected Averag Average Level Ion Fraction Element (wt-%) Element (wt-° ») Flux Si Ti Al Fe Mn Ca Mg Na F o Si Mn c S p Ti Al o N HTF1 0.05 _ 0.07 0.01 0.01 0.09 0.15 0.02 0.05 0.55 -0.01 -0.02 -0.01 -0.002 -0.001 0.005 Experiments 0.027 0.006 HTF2 0.05 0.01 0.07 0.01 0.01 0.08 0.15 0.02 0.05 0.55 -0.05 0.00 0.00 -0.003 -0.001 0.007 to find 0.030 0.007 HTF3 0.05 0.015 0.07 0.01 0.01 0.08 0.15 0.02 0.05 0.55 -0.03 0.00 0.00 -0.003 0.000 0.010 effect of 0.026 0.007 varying Al HTF4 0.05 0.02 0.07 0.01 0.01 0.08 0.14 0.01 0.05 0.57 O.OO -0.01 0.00 -0.003 0.000 0.012 HTF5 0.04 0.05 0.01 0.01 0.10 0.21 0.02 0.14 0.42 -0.03 -0.01 -0.02 -0.006 -0.001 wire 0.031 0.007 compositior 0.020 0.008 varied MLD1 0.07 - 0.13 0.01 0.03 0.05 0.11 - 0.09 0.52 +0.04 +0.10 0.00 0.000 +0.004 0.005 0.030 0.047 0.010 MLD2 0.07 0.01 0.13 0.01 0.03 0.05 0.11 - 0.09 0.50 +0.07 +0.12 0.00 0.000 +0.004 0.010 0.031 0.042 0.011 MLD3 0.07 0.02 0.13 0.02 0.03 0.05 0.10 — 0.09 0.51 +0.09 +0.15 0.00 +0.001 +0.004 0.017 0.032 0.037 0.012 MLD4 0.07 0.01 0.13 0.01 0.03 0.05 0.10 — 0.09 0.51 +0.03 +0. 12 0.00 +0.012 +0.004 0.009 0.026 0.040 0.009 MLD5 0.07 - 0.13 0.01 0.03 0.05 0.12 — 0.09 0.51 +0.03 +0.09 -0.02 -0.006 -0.002 0.006 0.023 0.041 0.009 MLD6 0.07 — 0.12 0.01 0.02 0.05 0.10 — 0.09 0.49 +0.05 +0.13 -0.01 -0.003 +0.001 0.006 0.023 0.039 0.010 MLD7 0.07 — 0.12 0.01 0.03 0.05 0.10 — 0.09 0.51 +0.08 +0.13 -0.02 -0.001 +0.001 0.007 0.021 0.040 0.010 MLD8 0.07 — 0.12 0.01 0.03 0.05 0.10 - 0.09 0.50 +0.07 +0.11 -0.02 -0.004 -0.001 0.007 0.022 0.041 0.010 MLD9 0.05 0.01 0.08 — - 0.08 0.18 — 0.11 0.49 -0.02 -0.17 0.00 0.000 +0.001 0.005 0.027 0.017 0.009 MLD10 0.05 0.01 0.08 0.01 - 0.07 0.18 - 0.12 0.47 +0.09 -0.09 0.00 0.000 +0.002 0.017 0.023 0.015 0.012 MLD11 0.05 0.02 0.08 0.02 — 0.07 0.18 — 0.11 0.46 +0.13 -0.09 0.00 -0.001 +0.003 0.025 0.027 0.016 0.010 MLD12 0.05 0.01 0.08 - - 0.07 0.18 - 0.12 0.48 -0.02 -0.16 0.00 0.000 +0.002 0.009 0.024 0.019 0.009 MLD13 0.05 0.01 0.08 - — 0.07 0.18 — 0.11 0.47 -0.02 -0.16 0.00 -0.001 +0.003 0.005 0.020 0.024 0.009 MLD14 0.05 0.01 0.08 — — 0.07 0.18 — 0.11 0.45 +0.05 -0.12 +0.01 0.000 +0.005 0.005 0.021 0.024 0.008 MLD15 0.05 0.01 0.08 - — 0.075 0.18 - 0.11 0.46 +0.07 -0.11 +0.03 -0.003 +0.004 0.005 0.019 0.021 0.010 MLD16 0.06 0.01 0.08 - — 0.08 0.18 - 0.11 0.45 +0.11 -0.10 +0.01 -0.003 +0.003 0.007 0.020 0.020 0.010
Table 6—Summary of PASEM Analyses, Commercial Fluxes
Overall Average Weld Diameter Metal Flux Wire Elements Present, Number of Inclusions Found Total (microns) (wt-%0)
Al Al Al Al Al Al Al Al Al Al Al Al Al Al Si Si Si Si Si Si Si Si Si Si Si S S S S S S S S S S S Ti Ti Ti Ti Ti Ti Ti Ti Ti Ti Ti Ti Type Code Type Mn Mn Mn Mn Mn Mn Mn Mn Mn Mn Mn Mn Mn Mn Mn Mn
CSHS F15 S4 1 - 17 7 162 25 352 308 2 - - 12 44 39 3 985 0.81 0.126 CS F1 S3 26 26 - - 246 221 - - - 30 48 2 1 603 0.72 0.061 CSLS F2 S3 2 - 5 - 83 78 25 22 - 16 14 7 1 260 0.65 0.022
MS F5 S1 - - 2 - 325 409 - - - - 22 11 30 802 0.79 0.126 MS F3 S1 - - - - 522 262 - - - - 98 35 4 924 0.79 0.155
AR F7 S2 2-165 160 - - 10 8 10 79 77 - 1 30 71 28 55 29 52 57 126 9 1 981 0.64 0.092 AR F6 S2 45 17 - - - 2 1 52 23 2 - 113 73 32 20 22 6 200 175 11 - 796 0.69 0.066 AB F8 S3 1 - 2 1 - - - 2 2 149 58 - - 32 45 - - - - 24 24 6 - 349 0.64 0.044
F9 S3 1 - 4 - - 28 7 86 9 - 6 2- 1 1 12 19 1 - 177 0.65 0.025 F18 S3 1-35 2 - 25 3 84 8 38 13 3 6 1 50 11 1 - 292 0.59 0.019 F16 S3 2 - 4 - 2 1 - 14 2 116 3 14 2 - - - 39 7 10 1 225 0.64 0.022
CS F1 S3 - 1 110 16 7 - 122 43 - 41 22 14 - 379 0.90 0.053 CSLS F2 S3 3 - 10 1 - 113 31 27 5 221 117 5 3 - 92 49 29 - 722 0.58 0.039
MS F5 S1 - - 159 218 - - - - 39 78 3 - 498 0.88 0.064 AR F7 S2 2 3 1 3 20 13 6 1 59 53 10 12 2 2 - - - 11 1 14 25 4 33 2 1 272 0.81 0.055 AB F8 S2 1 - 13 12 166 85 2 2 78 95 - - 1 - 61 82 4 1 608 0.76 0.043 F9 S3 44 1 - 167 22 7 3 - 1 - 54 26 22 357 0.61 0.022 F16 S3 7 1 13- 24 14 95 10 1 ------17 11 15 - 213 0.70 0.024 F16 Mo-Ti-B 8 4-3 37 11 7 2 42 22 8 6 8 4 1 - 1 - 3 - 7 10 3 11 9 - 212 0.68 0.028 F16 Mo-Ti-B 4 24 7 24 4 10 5 9 1 - - 10 5 11 7 31 11 28 24 2 - 221 0.71 0.027 F17 S3Mo 1 - 27 13 2 2 7 3 57 28 2 - 46 45 5 6 4 2 74 61 13 - 404 0.68 0.028 F17 S3Mo 12 5 18 9 35 8 5 1 10 3 10 1 34 5 11 1-2123 6 13 10 1 198 0.68 0.021
Note: No.AISiSTi, SiSTi; 1 AlSiS inclusion in AB-F8-S3, CSLS-F2-S3. AB-F8-S2. B-F16-S3 and B-F17-S3MO; 1 SiTi in CSHS-F15-S4, B-F16-Mo-Ti-B, 1 Ti inclusion in AR-F7-S2, B-F16-Mo-Ti-B; 2 STi inclusions in AR-F7-S2.
60-s | FEBRUARY 1991 Table 7—Summary of PASEM Analyses, Different Al Plate Contents, Flux F17
Number of Inclusions Found
Al Al Al Al Al Al Al Al Al Al Al Al Al Si Si Si Si Si Si Si Si Si S S s S S S S S S S S Ti Ti Ti Ti Ti Ti Tl Ti Ti Ti Ti Ti No. Mn Mn Mn Mn Mn Mn Mn Mn Mn Mn Mn Mn Mn Mn Mn Mn Others Total 1 _ _ _ 3 2 _ _ _ 2 3 12 6 6 58 27 6 i 2 — 2 1 142 68 137 2 8 488 2 25 5 1 1 — 4 6 11 51 23 4 1 1 I 19 38 41 3 6 242 3 63 2 2 — — 1 — 4 11 21 1 3 2 1 I 4 28 18 3 9 175 4 2 - — 8 2 — 1 - 6 l 42 13 27 75 31 6 2 I — 4 2 67 34 38 2 15 384 5 30 2 8 8 4 1 13 2 36 10 22 5 4 12 2 I I — — 4 I 40 30 81 5 14 338 6 b6 9 1 - - - - 1 7 22 — — 2 — — - — — 1 — 3 2 39 37 — 4 194
Note: No. AISiSTi, AISTi. SiSTi inclusions; 1 AlSiS inclusion in 3 and 5, 1 AISiTi inclusion in 2. 4 and 5: 3 SiS inclusion in 4; 1 SiTi inclusion in 4; 1 S Ti inclusion in 6.
tained at any stage of welding; neverthe of the reactions occurring while the mol play only a secondary role in slag-metal less, the value of AGf, the free energy of ten slag and molten metal are in contact reactions. the reaction product (Table 9), can still be through thermal stirring. Certainly, the It is recognized that the plate also influ used to rank reactions in the order in number and type of these inclusions have ences inclusion content. Sulfur, for exam which they are likely to occur. The most been found to depend on flux type (Ref. ple, which is present only in very small common ions in the plasma will be iron 6), and PASEM analysis has shown that the amounts as an impurity in the flux, is (Fe2+Fe3+) from the steel and oxygen inclusions relate not only to the main flux present in some inclusions, particularly (O2-) from the flux. Other cations present components but also to smaller amounts those which contain manganese, while will include Ca2+Mg2+ Al3+ Ti4+ Si4+ Si02+ of elements present in the flux, such as ti aluminum pickup from the base plate can Al3+ TiO2"1" TiO+; other anions include F~, tanium. In fact, inclusions containing Al modify the inclusion population and final 2_ and to a lesser extent, possibly Si03 and Ti are found even when only low lev transformed microstructure (Ref. 7). It 4_ 4_ SiC>4 Ti04 . Because of their reactivity, els are present in the flux. In considering must be remembered that PASEM data do it is probable that fluoride ions will react the elements available from the flux, Mg not generate a complete picture of all the rapidly, and the remaining cations will then and Ca are virtually insoluble in steel, inclusions. The size range examined has compete for the available oxygen, in the whereas Mn, AI, Si and Ti are fairly soluble. generally been 0.25 nm-1.00 />m and only order indicated by the AGf value. These latter are the elements, along with the elements listed in Table 6 were deter Calcium and magnesium fluorides have S, that form the bulk of the inclusions an mined qualitatively. Iron, which is almost the largest negative AGf, and would be alyzed. certainly present in inclusions, was not expected to re-form first. Subsequently, Not all flux components are present in determined because of inevitable inter and from the practical viewpoint, the inclusions. Many fluxes have high calcium ference from the matrix, and light ele most important reactions within the arc and magnesium contents, mainly as a form ments, i.e., elements lighter than sodium, and the trailing weld pool are those that of calcium silicate and magnesia, although cannot be detected by this method of el involve oxygen. Oxygen is barely soluble neither Ca nor Mg appears in a significant emental analysis. in solid steel, but a few tenths of a percent number of inclusions made with the cal are soluble in liquid iron, and oxygen can cium silicate and basic flux types. Calcium react with any available cationic species, and magnesium are rather insoluble in Discussion separating out as the temperature falls to molten steel and both have a strong affin General Comments give nonmetallic inclusions, which can ei ity for the anions, fluorine and oxygen. It ther be absorbed by the slag or remain in is therefore likely that their ions take part In earlier work (Ref. 4), the conditions in the freezing metal as inclusions. The fate primarily in the initial arc reactions, and the weld pool were discussed with re- of the nonmetallic particle will depend on the time at which it is formed, the solubil ity of that species in the slag, and the stir Table 9—Free Energy of Formation AF for Oxides at 2000 K (cal/g-mol 0 ) ring on the weld pool. Thus, those parti 2 cles that form at the end of the life of the Reaction weld pool will have less chance of being AC absorbed by the slag. 2Cag + 02 -* 2CaOs -193,720 Zr + 0 -170,737 On this basis, the type of inclusions left s 2 — Zr02s 4/3A1, + 02 —2/3AI 0 -165,000 in the weld metal should give an indication 2 3s 2Ti, + 02 -* 2TiOs -159,400 2Mgg + 02 — 2 MgOs -157,714 4/3Tii + 02 — 2/3Ti203s -156,967 Til + 02 — Ti02s -134,908 Table 8—Elements Determined in PASEM 2Q + 02 ^2COg -137,200 Analysis Si, + o2 — Si02l -130,300
2Mn, + 02 — 2MnOs -112,000 Aluminum 3/2Mni + 02 -* '/2Mn304| -80,475 Sulfur 4/3Mm + o2 -* 2/3Mn203 -68,534
Silicon 1.894Fei + 02 — Fe0.947Oi -67,920
Titanium 3/2Fei + 02 -* '/2Fe304i -59,454 Manganese 4/3Fei + 02 — 2/3Fe203 -50,200 Calcium Mni + 02 — Mn02 -38,100 Chromium 4Nag + 02 — 2Na20, -10,400
WELDING RESEARCH SUPPLEMENT 161-s spect to two flux types having varying conditions. Oxygen levels are highest with number of Al inclusions occurring with the amounts of the deoxidant additions fer- single wire multipass welds, and some former. Basic fluxes also showed a higher rotitanium, Fe-Ti, and calcium disilicide, what lower with single-pass welds, pre proportion of inclusions containing Al than
CaSi2. This discussion is now broadened to sumably as a result of increased base plate those that did not. consider all flux types, and the initial find dilution. However, tandem wire welds Aluminum is present in the base plate ings are adjusted from the consideration give appreciably lower oxygen values, and the wire, as well as in the flux. From of additional data obtained from The implying that chemical and physical reac the elements found in the inclusions by Welding Institute and flux manufacturers. tions within the extended weld pool are of PASEM, Al is likely to be in the form of As before, the free energies of formation major significance. aluminosilicates, aluminates and mixed ox of the mineral oxides (given in Table 9) are As considered previously (Ref. 4), the ides, probably of random stoichiometry. used in the prediction of likely reactions. cations Mg2+ and Ca2+, which are virtually The reaction of aluminum with oxygen to insoluble in steel and have highly negative form alumina may be values for the formation of their oxides, Reactions Involving Oxygen 2AI3+ + 302- — Al 0 (1) will probably react first with oxygen in the 2 3 Fluorine reactions will remove some Ca arc. CaO and MgO are readily absorbed or an initial reaction with oxygen may lead and Mg and also possibly some Si (Ref. 12) by the molten slag where their chemical to a cationic or anionic species being de from the arc plasma, forming CaF2, MgF2 activity is relatively high, and occur in weld veloped: and SiF . However, most reactions occur inclusions to only a limited extent. 4 Al3+ + O2" ->• AIO+ ring in the arc will involve oxygen, and Aluminum has the next highest value of Al3+ + 202" — AI0 (2) these will determine following reactions in AGf for the formation of a stable oxide of 2 both the weld pool and the slag. The gen the metallic cations present in the flux. These charged species may be dissolved eral effect of flux type on weld metal ox Earlier work on the composition of weld in the weld pool or the molten slag where ygen content is well recognized, a high metal inclusions (Ref. 6) using similar base they can react further, as discussed in a oxygen level being associated with acid materials showed the number and type of later section. fluxes. Eagar (Ref. 15) has differentiated Al-containing inclusions depended on flux Inclusions containing only Al (presum between the roles of Si02 and FeO in the type —Table 6. Manganese silicate fluxes ably with oxygen or perhaps nitrogen) are flux or slag, pointing out that weld metal gave no Al inclusions, although one flux found exclusively in welds made with Al- oxygen content is not a simple function of contained 5.3 wt-% Al. Calcium silicate treated base plate. If the Al level is in the flux oxygen potential. Nonetheless, a fluxes gave some inclusions containing Al, creased artificially by depositing a root general correspondence between weld provided the Al content of the flux was pass with a self-shielded flux cored wire metal oxygen and flux oxygen anion con greater than 2 wt-°o Al. Alumina-based containing Al powder, the number of such tent exists, as indicated by Fig. 1. This fig fluxes showed a variation between ag inclusions increases (Ref. 7). Reaction (1) ure also indicates an effect of welding glomerated and fused fluxes, a higher above could involve Al from the flux or
10 x Multipass welds * Multipass welds o Tandem art welds o Tandem arc welds a Single pass welds 0 Single pass welds 0 120-
Multipassj 0 110 webs OS
0 100
0090- •a °B § j1j 080- > 0 070-
§0 060- £ -05
0050 1
0040 . Tandem / arc welds -10 0030
0 020-
-05 0-35 040 045 050 055 060 0 005 010 015 Ion fraction, (01 in flux Ion fraction,IMnl influx Fig. 1 — The effect of oxygen in the flux on weld metal oxygen content. Fig. 2 - Effect of Mn in the flux on change in weld metal Mn.
62-s I FEBRUARY 1991 * Multipass welds o Tandem arc welds ° Single pass welds 08 -
0-7
0 6 -
X £ 05
to X J 04 D 6Qi I 03 " .c: X X I 0-2 D" ° 0 5 o X O 0 1-- 5 8 D X M*° -0 1- * " « Multipass welds o Tandem arc Melds -0 2 - - a Single pass welds • ' -3 -2 -1 0 1 23 4 5 6 7 01 02 ! Flux Mn parameter IMn)(0)-(Sil(0)'',xlO' Ion fraction, (Sil in flux Fig. 3—Effect of flux Mn parameter on the resultant change in weldmetal Fig. 4 — Effect of Si in the flux on change in weld metal Si. Mn content. plate. In the former case, the absence of lated for Ti. The absence of inclusions cussed later. alumina inclusions from the weld metal in containing only Ti should not be surpris Carbon monoxide has the highest neg dicates the reaction occurs rapidly in the ing, as the amount of Ti present in fluxes ative value of AGf at high temperature arc, and the inclusions are then absorbed is far less than the amount of Si, and the but, as the temperature falls, so does the by the slag. In contrast, it seems the reac suboxides of Ti are more reactive than stability of this oxide. Hence, dissociation tion of dissolved oxygen with plate Al those of Si. will occur, with competition of metallic takes place in the weld pool, with less ef The reactions of manganese with oxy cations for the oxygen: fective removal of the reaction product gen may be diverse. Manganese exhibits into the slag. variable valency and may form many ox CO —C+'/202 (11) Silicon and titanium are both soluble in ides and oxide radicals from MnO to the In the majority of single-arc welds studied, steel and react readily with oxygen to manganate anion Mn02f: The divalent the carbon level is lower than expected. form stable dioxides but can react with state is generally the most stable, and thus, However, in some more recent welds less or more oxygen to give reactive an MnO forms readily, but the mineral haus- (Ref. 4), no significant difference was ions and cations: mannite used in flux manufacture is a found between weld carbon levels and 2 2 spinel with Mn present in both the divalent those expected, although this could be a Si0 + ll lll + 0 " (3) and trivalent states (Mn Mn 04). The al feature of the type of experimental fluxes 4+ 2 ternative minerals manganite (MnO(OH)) used, i.e., alumina basic. Si + 20 ~ -*Si02 (4) and bixbyite (Mn 0 ) also contain divalent sio2+ + o2- 2 3 — Si02 (5) and trivalent manganese. Thus reactions Further Reactions Involving Manganese 2+ 2 Si0 + 20 " — SiOj2 (6) such as: Although the amount of Mn present in 2+ 2 4 2+ 2 SiQ + 30 " — Si04 (7) Mn + O " — MnO (8) the flux determines to some extent the Mn transfer into the weld pool, it is obvious which will react with elements present in Mn3+ + O2- •MnO+ (9) from Fig. 2 that this is not the only factor the weld pool. The PASEM data show that 2 determining the weld Mn content. From Si is found in inclusions without any other MnO+ + O " -MnOl (10) the reactions involving oxygen, MnO is analyzed elements, as would be predicted can be postulated. Manganese is found in the most stable oxide formed down to from Reactions (3)-(7), above. Silicon is inclusions together with S, Si, Al and Ti in ~530°C (986°F). However, many of the also found in inclusions containing Mn, Ti all combinations. Manganese is also inclusions containing Mn also contain Si, and Al and in all combinations, i.e., man present in the steel and wire, and it is un and this would suggest that reactions such ganese silicates, manganese aluminosili- likely that the inclusions containing Mn as: cates, etc. have resulted from Mn in the flux alone. A similar set of reactions may be postu 2+ 2 Other reactions involving Mn are dis Mn + Si0 3 -* MnSi03 (12)
WELDING RESEARCH SUPPLEMENT 163-s x Multipass welds x Multipass welds on plates of similar Al contents ° Tandem arc welds a Single pass welds 0 8
07 0 020
0-6 / * 05 3 0 015 X / X /
X X / 5 0-3 L^ s Single pass welds 0 010 / x
07
K /
0 005 -o;
-0 2
0 i ' 005 010 0 15 020 010 020 0-30 2 (ShUir* 4/3AI))-itSi*j (Tr+4/3AI))\(0) Ion fraction (All in flux Fig. 5-Effect of a flux silicate lattice parameter on the change In weld Fig. 6 - Effect of Al content in the flux on the level of Al in the weld. metal 51. (Multipass welds on plate with a similar Al level.)
Fig. 7— The effect of IMU also occur in the weld pool. basic flux ingredients x Mult/pass welds The silicates formed will be more solu on weld metal sulfur o Tandem arc welds a Single pass weids ble in the slag than in the weld pool, and levels. " it may be postulated that two reactions, the formation of MnO and the formation of manganese silicates, work in opposition 0 02 - to each other, the former transferring Mn to the weld and the latter removing it while thermal mixing continues. Figure 3 is a graph of the change from expected Mn content against a parameter, which indi cates the ability of the flux to produce 001 - MnO and the silicate anion. A reasonable o \ o \ trend is apparent for the different weld types and again, as for oxygen, minimal
X X variation in Mn is associated with tandem \x o arc welding, implying reactions in the pool to be dominant. This theory explains why 0 \ 1 0 two fluxes, neither of which contains Mn, 0F3 ^w o o remove Mn from the weld to different 0 \ cnx D extents, i.e., Flux F15 with its high silicon xF3 X. o o c o o and oxygen contents removes more man ganese than F9, which contains lower amounts of these elements. X 001 - *F5 X Further Reactions Involving Silicon The transfer of Si from flux to weld de pends broadly on the amount of Si in the flux —Fig. 4. Earlier work (Ref. 5) estab 01 02 lished a relationship between the Si trans fer and the total slag lattice network Excess base parameter (Ca*Mgrl(Mn*Fell- (Sifl(71r4/3 All) formers, {i.e., the amount of Al + Ti + Zr)
64-s | FEBRUARY 1991 present in the flux. These network form tained during submerged arc welding, or will take place to form inclusions contain ers have the ability to release Si for trans whether a pseudo-equilibrium can be pos ing Mn, Ti, Al, S and Si, but the silicate re fer into the weld by substitution of them tulated to identify those reactions control action is fairly dominant — Fig. 3. selves into the silicate lattice. Titanium, Al ling weld metal chemistry. There has been Transfer of Si from flux to weld metal and Zr do, however, compete with Si for implicit acceptance that welding condi depends broadly on the amount present available oxygen in the arc and will, as the tions are important, for example, high arc in the flux, although competing reactions oxides, be more readily absorbed by the voltage and increased arc length can mod with Al and Ti and substitution in the sili slag than the weld pool. Figure 5 shows ify element transfer and deposit chemis cate lattice by the same two elements also the effect of the competing processes, try, but the present study suggests that play a major role —Fig. 5. i.e., the release of silicon and the absorp other factors may be more significant than Aluminum transfer appears to depend tion of silicon in the flux on the transfer of generally recognized. Not only must dif on the amount of Al in the flux (Fig. 6), al Si. Although general agreement has been ferentiation be made between arc plasma though Al-containing inclusions may be shown, it must be expected that other re and weld pool reactions (Ref. 14), but also formed also from Al in the base plate. It is, actions, such as the reaction of Mn2+ with the overall time scale of the welding op however, likely that reactive alumino-ox- silicate (Si044~) ions discussed above and eration can influence weld metal compo ide radicals are formed in the arc plasma, that considered below with Al, also play a sition and must be considered. This is in which dissolve in the weld pool and react dicated by Figs. 1 and 3. Presumably, the role in the transfer of silicon. The series of to give aluminates and alumino-silicates, extended pool with tandem arc welding reactions proposed by Christensen and whereas dissolved Al metal present (either allows more time both for reactions to Grong involving the volatile compound from the flux or present in the base plate) occur in the pool, and for removal of re SiO (Ref. 16) is based on a scheme that reacts only in the pool to give alumina or action products to the slag. On this basis, does not appear to consider droplet/ AIN inclusions. predictive systems for weld metal chem plasma reactions. The sulfur content of a weld metal de istry must be regarded as to some extent specific to the welding procedure em pends on the amount of basic slag ingre Further Reactions Involving Al ployed in their derivation. dients. Because reaction can take place in the In a previous section, it was postulated The present observations regarding el weld pool, overall time scale of the weld that the initial reaction of aluminum with ement transfer are generally consistent ing operation may be important in deter oxygen may lead to cationic or anionic with other workers' findings. It is, how mining weld metal composition, since time radicals being dissolved in the molten ma ever, remarked that the inclusion analyses will determine the extent to which reac terial, i.e.: employed clearly show considerable in tions occur and which reaction products Al3+ + O2- — AIO+ teraction between deoxidant elements. A are removed by the slag. 3+ 2 number of trends have been identified, Al + 20 - — AI02 but the relationships obtained all show These will be free to react further with scatter, and more work is required to de species encountered in the molten pool in velop an overall picture. A ckno wledgments reactions similar to the following: 2 AIO+ + AI0 f— Al203 The work presented in this report was 2 _ 2AIO+ + Si0 3 — AI2Si05 Summary and Conclusions financed jointly by Research Members of 2 2AIO+ + MnSi0 4"— MnAI2Si06 The Welding Institute and the Materials 2+ A study has been made of distribution 2AIQT+ Mn — MnAl204 and Chemicals Requirements Board. + of elements between fluxes and weld TiO + AlOi;— TiAI03, etc. metal during the submerged arc welding The authors would like to thank The From the inclusion contents found in weld of steel. Analytical data have been exam Welding Institute staff and all commercial metal, most weld pool reactions involving ined in relation to results of PASEM analy flux manufacturers for helpful discussion Al will also involve Mn and/or Si — Table 6. sis of weld metal inclusions. and assistance. In general, as the flux Al content increases, A model of slag-metal reactions was so also does the weld Al content (Fig. 6), taken of initial reactions occurring rapidly References although further work is necessary on the at high temperatures in the arc plasma, 1. lackson, C. E. 1973. Fluxes and slags in relationship between Al, Mn and Si. followed by a longer time when molten welding. WRC Bulletin, No. 190. slag is in contact with molten metal at 2. Coe, F. R. 1978. Fluxes and slags in arc Reactions Involving Sulfur lower temperatures. welding. The Welding Institute Report No. 75/ Welding fluxes contain S only as an im Reactions involving oxygen and fluorine 1978/M. purity. In earlier work (Ref. 3), the amount take place in the arc plasma. This is prob 3. Davis, M. L. E„ and Coe, F. R. 1977. The chemistry of submerged arc welding fluxes. of basic ingredients present in the flux ably the case with Ca and Mg in particu The Welding Institute Report 39/1977/M. compared with the amount of acidic in lar. During these reactions, neutral com pounds and reactive oxide radicals are 4. Davis, M. L. E„ and Bailey, N. 1982. gredients was found to influence the Element transfer of deoxidant additions to sub removal of S from the weld pool. Figure 7 formed involving other deoxidant ele ments. These reactive oxides can react merged arc fluxes for welding ferritic steels. The shows a plot of change in weld metal S Welding Institute Report 185/1982. further in the slag, or in the molten weld from expected against an excess base pa 5. Davis, M. L. E., and Bailey, N. 1979. How pool, provided they are soluble. If they rameter. At least with the low dilution submerged arc flux composition influences el multipass welds, a good general agree react in the weld pool, they may be ement transfer. The Welding Institute Conf. on ment is seen, except for the manganese absorbed by the slag or may remain in the Weld Pool Chemistry and Metallurgy. silicate fluxes F3 and F5, suggesting that solidifying metal as inclusions. 6. Pargeter, R. |. 1987. Investigation of sub Mn may act in a more basic manner in such Transfer of Mn from flux to weld pool, merged arc weld metal inclusions. TMS/AIME fluxes than expected from a basicity for or removal of Mn from weld pool to slag, Symp. Welding Metallurgy of Structural Steels. Denver, Colo. mula as in Ref. 17. is determined not only by the amount of Mn in the flux, but also by reaction with 7. Terashima, H., and Hart, P. H. M. 1983. Effect of flux Ti0 and wire Ti content on tol silicate anions, the product of which is 2 Implications erance to high Al content of submerged arc more readily absorbed by the slag than by welds made with basic fluxes. Paper 27, The In the past, there has been debate as to the metal, although some manganese sil Welding Institute Conf. The Effects of Residual, whether thermodynamic equilibrium is at icate inclusions remain. Other reactions Impurity and Micro-Alloying Elements on Weld-
WELDING RESEARCH SUPPLEMENT | 65-s ability and Weld Properties, London, England. Mn on oxygen absorption by steel weld metal taining CaF2. WIC Conf., Welding for Challeng 8. Indacochea, |. E., et al. 1989. Submerged during arc welding. IIW Doc 1X-1593-90. ing Environments, Toronto, Canada, pp. 325- arc welding: evidence for electrochemical ef 12. Kuwana, T., and Sato, Y. 1989. Effect of 332. fects on the weld pool. Welding journal Si on oxygen absorption by steel weld metal 15. Eagar, T. W. 1978. Sources of weld 68(3):77-s to 83-s. during arc welding. IIW Doc IX-1555-89. metal oxygen contamination during submerged 9. Indocochea, |. E.„ et al. 1989. Electro 13. Ekelund, S., and Werlefors, T. 1970. A arc welding. Welding lournal 57(3):76-s to 80-s. chemical transport of Mn between the flux and system for the quantitative characterization of 16. Christensen, N., and Grong, O. 1986. the weld metal in submerged arc welding. ASM microstructure by combined image analysis and Reactions of acid and weakly basic submerged Conf., Recent Trends in Welding Science and x-ray discrimination in the scanning electron arc fluxes. Scand. j Met. 15(1):30-40. Technology, Gatlingburg, Tenn., pp. 581-586. microscope. Proceedings of the Symposium on 17. Tuliani, S. S., Boniszewski, T. T, and 10. Herasymenko, P., andSpeight.CE. 1950. Scanning Electron Microscopy, IIT Research In Eaton, N. F. 1969. Notch toughness of com Ionic theory of slag-metal equilibria — part 1. JISI, stitute, 1, p. 417. mercial submerged arc weld metal. Weld, and 106(11):169-183. 14. Lau, T. W., and Vasudevan, R. 1985. Met. Fab. 37(8):327-339. 11. Kuwana, T., and Sato, Y. 1990. Effect of Gas-metal-slag interactions of binary fluxes con
WRC Bulletin 332 April 1988
This Bulletin contains two reports that characterize the mechanical properties of two different structural shapes of constructional steels used in the pressure vessel industry. (1) Characteristics of Heavyweight Wide-Flange Structural Shapes By J. M. Barsom and B. G. Reisdorf
This report presents information concerning the chemical, microstructural and mechanical (including fracture toughness) properties for heavyweight wide-flange structural shapes of A36, A572 Grade 50 and A588 Grade A steels. (2) Data Survey on Mechanical Property Characterization of A588 Steel Plates and Weldments By A. W. Pense This survey report summarizes, for the most part, unpublished data on the strength toughness and weldability of A588 Grade A and Grade B steels as influenced by heat treatment and processing. Publication of this Bulletin was sponsored by the Subcommittee on Thermal and Mechanical Effects on Materials of the Pressure Vessel Research Committee of the Welding Research Council. The price of WRC Bulletin 332 is $20.00 per copy, plus $5.00 for postage and handling. Orders should be sent with payment to the Welding Research Council, Suite 1301, 345 E. 47th St., New York, NY 10017.
WRC Bulletin 357 September 1990
Calculation of Electrical and Thermal Conductivities of Metallurgical Plasmas
By G. J. Dunn and T. W. Eagar
There has been increasing interest in modeling arc welding processes and other metallurgical processes involving plasmas. In many cases, the published properties of pure argon or helium gases are used in cal culations of transport phenomena in the arc. Since a welding arc contains significant quantities of metal vapor, and this vapor has a considerably lower ionization potential than the inert gases, the assumption of pure inert gas properties may lead to considerable error. A simple method for calculating the electrical and thermal conductivities of multicomponent plasmas is presented in this Bulletin. Publication of this report was sponsored by the Welding Research Council. The price of WRC Bulletin 357 is $20.00 per copy, plus $5.00 for U.S. or $10.00 for overseas postage and handling. Orders should be sent with payment to the Welding Research Council, 345 E. 47th St., New York, NY 10017.
66-s I FEBRUARY 1991 WRC Bulletin 336 September 1988
Interpretive Report on Dynamic Analysis of Pressure Components—Fourth Edition
This fourth edition represents a major revision of WRC Bulletin 303 issued in 1985. It retains the three sections on pressure transients, fluid structure interaction and seismic analysis. Significant revisions were made to make them current. A new section has been included on Dynamic Stress Criteria which emphasizes the importance of this technology. A new section has also been included on Dynamic Restraints that primarily addresses snubbers, but also discusses alternatives to snubbers, such as limit stop devices and flexible steel plate energy absorbers.
Publication of this report was sponsored by the Subcommittee on Dynamic Analysis of Pressure Components of the Pressure Vessel Research Committee of the Welding Research Council. The price of WRC Bulletin 336 is $20.00 per copy, plus $5.00 for postage and handling. Orders should be sent with payment to the Welding Research Council, Suite 1301, 345 E. 47th St., New York, NY 10017.
WRC Bulletin 355 July 1990
Programming and Control of Welding Processes—Experience of the USSR
By V. Malin
This report is an in-depth look at technical welding studies and their implementation in the USSR, a country that has a long history of welding automation development. More than 300 articles published in the USSR over the last three decades were examined, and 177 are referenced in this report. Publication of this report was sponsored by the Interpretive Reports Committee of the Welding Research Council. The price of WRC Bulletin 355 is $35.00 per copy, plus $5.00 for U.S. and $10.00 for overseas postage and handling. Orders should be sent with payment to the Welding Research Council, 345 E. 47th St., Room 1301, New York, NY 10017.
WRC Bulletin 354 June 1990
The two papers contained in this bulletin provide definitive information concerning the elevated tem perature rupture behavior of 2V4Cr-lMo weld metals.
(1) Failure Analysis of a Service-Exposed Hot Reheat Steam Line in a Utility Steam Plant By C. D. Lundin, K. K. Khan, D. Yang, S. Hilton and W. Zielke
(2) The Influence of Flux Composition of the Elevated Temperature Properties of Cr-Mo Submerged Arc Weldments By J. F. Henry, F. V. Ellis and C. D. Lundin
The first paper gives a detailed metallurgical failure analysis of cracking in a longitudinally welded hot reheat pipe with 184,000 hours of operation at 1050°F. The second paper defines the role of the welding flux in submerged arc welding of 2V4Cr-lMo steel. Publication of this report was sponsored by the Steering and Technical Committees on Piping Systems of the Pressure Vessel Research Council of the Welding Research Council. The price of WRC Bulletin 354 is $50.00 per copy, plus $5.00 for U.S. and $10.00 for overseas postage and handling. Orders should be sent with payment to the Welding Research Council, 345 E. 47th St., Room 1301, New York, NY 10017.
WELDING RESEARCH SUPPLEMENT 167-s