WELDING RESEARCH
SUPPLEMENT TO THE WELDING JOURNAL. MARCH 1989
Sponsored by the American Welding Societv and the Welding Research Council
All papers published in the Welding Journal's Wekfalg Research Supplement undergo Peer Review before publication for: 1) originality of the contribution; 2) technical value to the welding community; 3) prior publication of the material being reviewed; 4) proper credit to others working in the same area; and 5) justification of the conclusions, based on the work performed. The names of the more than 170 individuals serving on the AWS Peer Review Panel are published periodically. All are experts in specific technical areas, and all are volunteers in the program.
Submerged Arc Welding: Evidence for Electrochemical Effects on the Weld Pool
It is hypothesized that weld metal chemistry is significantly affected by an electrochemical reaction at the weld pool-flux interface
BY J. E. INDACOCHEA, M. BLANDER AND S. SHAH
ABSTRACT. Compositional changes in toughness essentially equivalent to the occurring during heat treatment of steel. weld metal from welds made by sub base metal. However, because of the large noniso- merged arc welding of steel using CaF2- It is well established in submerged arc thermal behavior encountered in the CaO-Si02 fluxes are consistent with an welding (SAW), as in steel making, that welding processes, the circumstances electrochemical mechanism in which the low oxygen levels usually lead to better affecting the phase transformations in a filler wire is anodically oxidized to form toughness (Refs. 3-5). There seems to be weld are significantly different from those oxides and fluorides, and metals are general agreement that a microstructure occurring in steel production. For in cathodically deposited at the weld pool- normally consisting of acicular ferrite (Fig. stance, the nonmetallic inclusion volume flux interface. This speculative mecha 1) (Ref. 6) will yield the best weld metal fraction in low-carbon steel welds is nism, if correct, could make it simpler to mechanical properties in terms of much larger than that of normal steel predict flux compositions, which will strength and toughness, by virtue of its products, due to the very short time improve the quality of welds and control small grain size (typically 1 to 3 jum) and available for growth and flotation of such weld metal microstructures. high-angle grain boundaries (Ref. 7). particles (Ref. 8). For a given welding flux, The microstructural changes taking the final weld metal oxygen content has Introduction place in the weld metal on cooling been observed to be directly related to through the critical transformation tem the inclusion population (Ref. 9). On the During the past two decades, the steel perature are, in principle, similar to those other hand, oxide inclusions are known industry has experienced tremendous to strongly influence the transformation technological progress leading to many from austenite to ferrite, both by restrict alloys possessing excellent mechanical ing the austenite grain growth (Fig. 2), as and corrosion-resistant properties. Re well as by becoming nucleation sites for KEY WORDS cent developments in, for example, HSLA different ferrite morphologies. steel plate manufacturing technology Submerged Arc Welding High-temperature ferrite products, (Refs. 1, 2) have called for new formula Electrochemical Effects such as grain boundary ferrite (GF) and tions of welding consumables to produce Weld Pool Chemistry polygonal or blocky ferrite (PF) are pre weld metal deposits with strengths and CaF2-CaO-Si02 Fluxes dominant in welds with high inclusion Anodic Oxidation densities; while welds with low inclusion Weld Metal Composition densities have microstructures consisting /. £ INDACOCHEA and S. SHAH are with the Composition Changes primarily of lower temperature transfor University of Illinois at Chicago, Metallurgical Oxidized Welding Wire mation products, acicular ferrite and the Department, Chicago, III. M. BLANDER is with Cathodic Deposits Argonne National Laboratory, Chemical Tech aligned martensite-austenite-carbide (AC) Flux Predictions nology Division/Materials Science and Tech structure. These microstructures are nology Program, Argonne, III. shown in Fig. 3 (Ref. 10).
WELDING RESEARCH SUPPLEMENT 177-s TM ft v %J iV ItV .»» • -j X
> • t - >X« I % V ' i 5* i 1 '
/vg. 1 —Acicular ferrite morphology in a low-carbon-steel weld microstructure. A—A low-heat-input weld, 50.3 kj/in. (198 kj/mm); B — for a high-heat-input weld, 97.4 kj/in. (3.83 kj/mm). 25 fim
In view of the significant role of oxy weld metal. In this paper, we consider the measurements have indicated that the gen on the austenite-to-ferrite transfor possible importance of electrochemical higher the basicity indexes, the lower the mation of low-carbon steel welds, and, effects on the chemistry of weld metal oxygen content of the weld metal. The Bl consequently, its effect on notch tough produced in submerged arc welding is, however, a poor measure of the ness, an understanding of the mecha (SAW) with CaF2-CaO-Si02 fluxes. chemistry of slags. In addition, it is proba nisms that control the oxygen, in particu Thermodynamic models have been ble that equilibrium is not attained and lar, and the chemistry of the weld metal, proposed to predict the final composition that kinetic factors are important. For in general, is important for producing of submerged arc welds (Refs. 11-17). In example, Thier and Dring (Ref. 12) pro high-quality welds. view of the very high temperatures posed a diffusional model to predict the Much prior work on weld chemistry involved and small molten volumes, final content of elements in the weld has focused primarily on kinetically limit some investigators (Ref. 11) assume that metal. Thier and Dring concluded that ed thermodynamically driven reaction equilibrium is attained. Davis and Bailey the slag composition where an element mechanisms. This pyrometallurgical ap (Ref. 11) propose that the transfer of was not transferred to the metal, the proach has proven to be useful in analyz elements between the slag and the weld neutral point, is affected only by the ing some data on weld metal chemistry. metal depends on the oxide activities in current, but not by the voltage changes However, such analyses have not yet led the slag, which are directly connected to and that the neutral point is characteristic to methods of predicting the chemistry of the basicity index (Bl) of the slags. Limited for a specific type of flux. Ekstrom and Olson (Ref. 14) reported that the change in Si in weld metal is influenced by the basicity of the slag and that this influence is higher when the o D & o LOW HEAT INPUT basicity index is less than two. Dallam, ef I30 al. (Ref. 15), found that while the Si level • • A •HIGH HEAT INPUT in the weld metal was correlated with the Ui basicity index, the Mn content of the weld depends on the amount of MnO in 55 I30 the slag. Indacochea, et al. (Ref. 16), z qualitatively showed a similar correlation < between flux and weld metal composi o I 10 tion. Despite qualitative agreement among researchers regarding the flux type and direction of elemental transfer, there is \- 90 no precise determination of a "neutral z> •0° A point," the composition where a given < element is not transferred, even though rr 70 very similar types of fluxes were used in o several of these studies. This failing may rr % o°-^_ o be attributed to the possibility that the rx mechanism of elemental transfer is not so O — — 50 simple, to the influence of different weld ing parameters used, and to differences I00 300 400 700 900 IIOO I300 I300 in the wire and flux compositions. It is clear that essentially all prior studies WELD METAL OXYGEN CONTENT (PPM) have been relatively narrowly defined. A Fig. 2 —Prior austenite grain size as a function of oxygen content in the weld metal for two heat more comprehensive approach is inputsfRef. 6). The 'prior austenite" is the parent phase for the lower temperature microstructural needed in which the diverse kinetic and products thermodynamic factors involved in SAW
78-s|MARCH 1989 fe3?' 2%,
tJHr*f " " * • "
Sfcflf? t:. - . r. / .:. . ,J Ps l^fc*'^B 5%: /:' # . ? : 'V *c ,, SfiH - ,. ^Vi* *^ - ^ , fig. i — Typical ferrite morphologies present in low-carbon-steel weld microstructures. CE- Grain boundary ferrite; PE-polygonal or blocky ferrite; AC—aligned M-A-C (martensite-austenite-carbide); and acicular ferrite in the unlabeled micrograph (Ref. 6) (Refs. 16, 17) are examined and which have not been considered before. All In this paper, we examine the possibili also explores the possibility of mechanis welding fluxes when molten are, at least ty that the changes in chemistries of weld tic factors that have not been considered. in part, ionic and the number of cou metal with changes in the compositions Such an approach is made difficult by the lombs passed per mole of metal is very of CaF2-containing fluxes might be relat complexity of the processes in SAW. The large. If even a small fraction of the total ed to an electrochemical mechanism. DC voltages and currents are very high current (<0.01) is involved in a Faradayic (e.g., 30 V, 400 A) and lead to a system process, electrochemical effects at metal- containing the four principal phases, a flux interfaces could be a major factor Experimental Work weld wire, a molten flux, a plasma arc controlling the chemistry of weld metal Materials and a weld pool with five interfaces (Ref. 18). In addition, because the very among them. Most of the current is hot plasma is essentially electrically neu Low-carbon steel coupons of dimen transported by electrons in the plasma tral and in contact with the relatively sions 63.5 X 254.0 X 12.7 mm (2.5 X 10 from the generally cathodic weld pool to volatile fluxes, there have to be at least as X 0.5 in.) and a 2.38-mm (0.094-in.) diam the generally anodic weld wire (or filler many positive ions as there are electrons eter filler welding wire (AWS Type ER70S- wire). The electrons heat the continuous and other negatively charged particles. 3) were used to make the weld. The ly fed wire to melt it and form droplets Stable negative and positive ions formed compositions for the base plate and the that fall through the molten flux and the from flux evaporates could all participate welding wire are shown in Table 1. plasma. In addition, the temperatures are in Faradayic processes. Thus, there could The experimental fluxes were made high, and there are also large tempera also be electrochemical reactions at the from reagent-grade Si02, CaF2 and CaO ture gradients, as well as large temporal plasma-metal interfaces (Ref. 18). powders. The total of 12 different flux changes in temperature as the weld wire position is moved along the weld. An attack on such a complicated problem Table 1—Base Metal and Filler Metal Compositions (wt-%) requires some simplification. One way to simplify the approach to O such a complex system is to isolate the Material C Mn P S Si Ti Al ppm different parts of the problems. For Base metal 0.04 0.37 0.012 0.022 0.03 0.003 0.001 220 example, in this paper, we chose to Filler metal 0.09 1.18 0.007 0.013 0.58 0.002 <0.008 195 examine electrochemical effects, which WELDING RESEARCH SUPPLEMENT | 79-s In the last step before welding, all Electrochemical Mechanisms Table 2--Nominal Flux Compositions (wt-%) fluxes were baked at 700°C (1292°F) for 3 h to bum off the carbon that In SAW, the filler wire is generally anodic and the weld pool is cathodic. Flux might have been picked up during Sample Si0 CaF CaO Current is carried between these metals 2 2 melting. by the arc plasma and by the molten flux, S11 40 10 50 with the arc plasma carrying most of the S12 40 20 40 Welding Procedure S13 40 30 30 current. S14 40 40 20 The welds were single-pass, laid on top At the interface between flux and S15 30 30 40 of the test coupons in a horizontal posi cathodic weld pool, metals in the flux S16 30 40 30 tion. The welding was done automatically tend to deposit by reactions such as S17 30 50 20 with a programmable microprocessor 2+ S18 30 60 10 controlling the power supply and amount Ca (flux) + 2e — Ca (metal) 4+ S19 20 40 40 of filler metal deposited. The electrode Si (flux) + 4e -* Si (metal) (1) S20 20 50 30 extension and electrode-to-workpiece The products, which are formed metasta- S21 20 60 20 distance were maintained in all the welds bly at the interface, tend to simultaneous S22 20 70 10 produced. Two heat inputs were used, ly diffuse into the metal and back react and the corresponding welding process with the slag components by reactions ing parameters are given in Table 3. The such as stability of the arc as a function of flux Table 3—Welding Process Parameters composition and heat input was moni Si02 + 2Ca ** 2CaO 4- Si (2) tored during welding. It was found that Thus, the balance between the differ Voltage 33 V 31 V the stability of the arc decreased as the ent elements that might be deposited is Current 600 A 330 A level of silica decreased from 40 to 20%. controlled by the relative rates of the Travel speed 12.2 ipm 12.2 ipm In addition, the welds produced with electrodeposition process, of the back Wire speed 75 ipm 40 ipm the high-heat inputs showed greater reactions (or volatilities), and of the diffu Heat input 97.4 kj/in. 50.3 kj/in. arc stabilities than the low-heat input sive processes that carry the interfacial 3.83 kj/mm 1.98 kj/mm welds. materials away from the interface. Because of the high volatility of Ca and its Chemical Analyses compositions listed in Table 2 were used relative insolubility in steel, Ca is likely to in this study. All the flux samples were The analyses for oxygen were per vaporize through the flux and to partly accurately weighed, mixed thoroughly formed using a LECO oxygen analyzer. react according to Equation 2. In addition, for 2 h, melted in a graphite crucible using For this, the weld samples were extracted Ca is soluble in CaF2-rich melts. a 50-kW induction furnace, and then from the middle of the weld metal. For The most important anodic reaction poured into a vessel containing tap the other chemistries, atomic absorption is water. This quenching procedure caused was used for the filler metal and emission nO2- + M (metal) -» MO + 2ne (3) the flux to break into small pieces spectrometry was employed for the n which were dried at 260°C (500°F) weld specimens. The compositions of all where M is a metal at the weld wire-flux for 2 h before being crushed further the weld samples are summarized in interface and 2n is the valence of the and sized between —14 and 200 mesh. Table 4. metal in the oxide. Fluoride is probably Table 4--Chemical Analysis of Weld Specimens Composition (wt-%) Weld O Sample C Mn P S Si Ti Al (ppm) S11L 0.088 0.53 0.010 0.015 0.54 0.002 <0.008 400 S12L 0.084 0.46 0.012 0.017 0.59 0.002 <0.008 432 S13L 0.076 0.34 0.012 0.020 0.65 0.002 <0.008 405 S14L No Sample S15L 0.106 0.58 0.010 0.013 0.40 0.002 <0.008 240 S16L 0.094 0.45 0.010 0.016 0.51 0.002 <0.008 262 S17L 0.083 0.36 0.010 0.017 0.59 0.002 <0.008 289 S18L 0.094 0.41 0.010 0.016 0.51 0.002 <0.008 250 S19L 0.110 0.69 0.009 0.007 0.35 0.002 <0.008 207 S20L 0.104 0.64 0.009 0.009 0.35 0.002 <0.008 173 S21L 0.101 0.53 0.009 0.014 0.38 0.002 <0.008 204 S22L 0.092 0.52 0.009 0.014 0.54 0.002 <0.008 196 S11H 0.100 0.50 0.011 0.018 0.35 0.002 <0.008 500 S12H 0.092 0.42 0.010 0.018 0.40 0.002 <0.008 554 S13H 0.090 0.40 0.009 0.018 0.43 0.002 <0.008 521 S14H(b> No Sample S15H 0.105 0.53 0.009 0.014 0.30 0.002 <0.008 243 S16H 0.099 0.46 0.010 0.017 0.37 0.002 <0.008 326 S17H 0.100 0.40 0.009 0.015 0.38 0.002 <0.008 336 S18H 0.096 0.42 0.009 0.016 0.36 0.002 <0.008 311 S19H 0.099 0.68 0.009 0.008 0.28 0.002 <0.008 191 S20H 0.106 0.63 0.010 0.008 0.30 0.002 <0.008 154 S21H 0.106 0.50 0.010 0.014 0.33 0.002 <0.008 201 S22H 0.102 0.50 0.009 0.013 0.40 0.002 <0.008 190 (a) L designates low heat input; H designates high heat input. (b) Excessive weld porosity. 80-s I MARCH 1989 also involved in an anodic reaction, but D & O LOW HEAT INPUT forms relatively volatile products, which 0.7 need not be considered here. Because of 3 • 40% Si02 _B A #HIGH HEAT INF>UT a * 30% Si02 / large overpotentials, all of the metals at D 0 • 2 0% Si02 / the interface, principally Fe, will oxidize. The less noble elements in the alloy, such as Mn and Si, will diffuse toward the I- 0.6 interface and react with the FeO by reactions such as (- z FeO + Mn ; ' MnO + Fe (4) UJ 2FeO -I- Si = : Si02 4- 2Fe 5 Also, some oxide will diffuse into the 3 ° metal and some will dissolve in the flux. o The overall effect is to greatly increase o the oxygen content of the weld wire tip o and to decrease the less noble elements, such as Mn and Si, somewhat. When i 0.4 heated for a sufficiently long time, the tip forms a droplet which will have a high < oxide content near the surface and tend to lose some of its less noble elements to 2 the flux. Measurements of such droplets 0.3 by Lau, etal. (Refs. 19, 20), in CaO-AI 0 2 3 UJ based fluxes have shown their very high oxygen contents. When these oxide-rich droplets fall 0.2 into the weld pool, the oxides can react 10 20 30 40 50 60 70 with the more active metals, including CaF2 IN THE FLUX (WT%) those that have been cathodically elec- trodeposited at the surface of the weld 50 40 30 20 pool. In the measurements of Lau, ef al. CaO IN THE FLUX(WT%),40%Si02 Fig. 4 —Silicon (Refs. 19, 20), a large fraction of the oxide content in the welds associated with the droplets is removed 40 30 20 10 produced with the THE FLUX(WT%),30%Si0 Si0 -CaO-CaF before being incorporated in the weld, CaO IN 2 2 2 submerged arc probably by back reactions with the most 40 30 20 10 welding fluxes for active elements in the weld, such as Ca or CaO IN THE FLUX (WT%),20%Si02 two heat inputs Si (or Al in their measurements). An understanding of the electrochem istry of the plasma is limited by the increase in the Si02 content of the CaF2- which are too numerous to discuss here. sparsity of information on plasma species. CaO-Si02 mixtures, but decrease with an Further work on the effect of current is Most of the current is carried by elec increase in the current density. Since the needed to completely define the mecha trons. However, because of the con silica in the fluxes tends to form anionic nism, which probably involves concen straint of approximate electroneutrality species (chain silicates or fluorosilicates), it tration polarization of silica and diffusion- of the dense plasma, the number of is probable that the kinetics of direct controlled deposition of Si. positive ions is at least as large as the electrochemical deposition of silicon at As can be seen from Fig. 5, the manga number of electrons, and these ions can the cathodic weld pool is not as favor nese content of the weld metal is fairly carry a small but significant fraction of the able as that for the deposition of the close to that expected for mixtures of current. Metals such as Fe, Ca and Mn are volatile Ca. Consequently, a small weld wire and base plate metal for the relatively volatile and are probably ion amount of Si would be directly formed lowest contents of Si02 in the flux. With ized to form positive ions. Oxygen can electrochemically, but more is likely to an increase in the concentration of Si02, be present as 0+ and possibly as O-, and form by the evaporation of Ca, which one would expect an increased amount the presence of some oxyions ions would then reduce Si02 in the flux to Si. of oxide produced at the anode and a derived from SiO, Si02, FeO or MnO Later back reactions of the Si with the larger loss of Mn from the filler wire, vapor molecules is likely, but there is no oxides on weld wire droplets entering the which contains the majority of the Mn information on numbers or distributions weld pool would reduce the total expected in the weld. This can lead to the of such positively and negatively charged amount of metallic Si produced by this observed decrease in Mn with increased ions. All of these ions can participate in mechanism. The higher the ratio of CaO Si02 in the flux. Faradayic processes, which will, to a first to CaF2 in the melt, the greater the The compositional changes of most approximation, parallel the Faradayic pro amount of oxide produced at the weld concern are those related to oxygen. The cesses involving the slag. wire tip and the greater the amount of Si physical properties and quality of welds which would be reoxidized and redis- are strongly influenced by the amount of solved in the flux. Of course, one also Interpretation of the Experiments oxygen. Figure 6 exhibits the changes in expects that the amount of metallic Si oxygen content for the different flux produced would be larger the greater the As can be seen in Fig. 4, the silicon compositions. It is obvious that the con Si02 content of the flux. This is consistent contents of the weld metals are generally centration of oxygen in the weld with the results in Fig. 4. The decrease of higher than the nominal values expected decreases with a decrease in the amount Si content in weld metal with an increase from simple mixing of roughly equal of silica in the flux. For the lowest concen of current could be understood by any amounts of the base metal and filler wire. trations of silica, the concentration of one of a number of possible mechanisms, These silicon contents increase with an oxygen differs little from that of the WELDING RESEARCH SUPPLEMENT 181-s ~ 0.8 600 0.7 a • 40% Si02 i- 560 z 5 A A 30% Si0t UJ a. O • 20% Si0 I- a. 520 2 z 0.6 O A o LOW HEAT INPUT o z 480 o UJ I- • * • HIGH HEAT INPUT UJ z 440 o CO 0.5 o UJ 400 z z < UJ CD o 360 z > 0.4 X < o 320 2 _l < 280 H < 0.3 UJ 240 u Si02-CaO-Cori FLUX SYSTEMS 2 5 a •40%Si02 • A OL0W HEAT INPUT 200 h A A30%Si0 « A •HIGH HEAT INFUT UJ 0.2 2 5 160 UJ O •20%Si0- 120 5 10 20 30 40 50 60 70 0. I CaF2 IN THE FLUX (WT%) 10 20 30 40 50 60 70 CaF£ IN THE FLUX (WT%) 50 40 30 20 CaO IN THE FLUX(WT%),40%Si0 50 40 30 20 2 CaO IN THE FLUX (WT%), 40%Si02 I 1 i I 40 30 20 10 40 30 20 10 CaO IN THE FLUX (W T%),30% Si02 CaO IN THE FLUX (WT%),30%Si02 , t l_ I I 40 30 20 10 40 30 20 10 CaO IN THE FLUX (WT%),20%Si02 CaO IN THE FLUX 82-s|MARCH 1989 References 9. Jang, ). W.. and Indacochea, ]. E. 1987. 1985. Flux composition dependence of micro- 1. Dolby, R. E. 1983. Advances in welding Inclusion effects on submerged arc weld structure and toughness of submerged arc metallurgy of steels. Metal Tech. 19(9): microstructure. journal of Materials Science HSLA weldments. Welding journal b4(S)AA0-s 349. 22:689-700. to 151-s. 2. Suzuki, H. 1982. Yield strengths of metals 10. Abson, D ).. Dolby, R. E., and Hart, P. 16. Indacochea, J. E., Blander, M., Christen and alloys. Welding in the World 20:121- M. H. 1978. Proceedings of the International sen, N., and Olson, D. L. 1985. Chemical 148. Conference on Trends in Steel and Consuma reactions during SAW with FeO-MnO-Si02 3. Tuliani, S. S., Boniszewski, T., and Eaton, bles for Welding. The role of nonmetallic fluxes. Metall. Trans., Vol. 16B, pp. 237-245. N. F. 1961. Notch toughness of commercial inclusions in ferrite nucleation in carbon steel 17. Blander, M„ and Olson, D. L. 1984. submerged arc weld metal. Welding and Metal weld metals. Paper 25. The Welding Institute, Thermodynamic and kinetic factors in the Fabrication 8:327. Cambridge, U.K. pyrochemistry of submerged arc flux welding 4. Lewis, W. )., Faulkner, C. E., and Rieppel, 11. Davis, M. L. E.. and Bailey, N. 1980. of iron-based alloys. Second International Sym P. J. 1961. Flux and filler wire developments for How submerged arc flux composition influ posium on Metallurgical Slags and Fluxes, eds. submerged arc welding HY80 steel. Welding ences element transfer. Weld Pool Chemistry A. Fine and D. R. Gaskell, TMS-AIME, Warren journal40(8):337-s to 345-s. and Metallurgy Conference, pp. 289-302, The dale, Pa., pp. 271-277. 5. Kubli R. A., and Sharav, W. W. 1961. Welding Institute, Cambridge, U.K. 18. Blander, M„ and Olson, D. L. 1986. Advancements in submerged arc welding of 12. Thier, H., and Dring. 1980. Metallurgical Electrochemical effects on weld pool chemis high impact steels. Welding journal 40(11):497- reactions in SAW. Weld Pool Chemistry and try in submerged arc and D.C. electroslag s to 502-s. Metallurgy Conference, pp. 271-278, The welding. Proceedings of the International Con 6. Shah, S. 1986. The influence of flux Welding Institute, Cambridge, U.K. ference on Trends in Welding Research (Ad composition on the microstructure and 13. Chai, C. S., and Eagar, T. W. 1985. vances in Welding Science and Technology), mechanical properties of low-carbon steel Slag-metal equilibrium during SAW. Metallurgi Gatlinburg, Tenn., pp. 363-366. weld metal. M.S. Thesis, University of Illinois, cal Transactions B, Vol. 16-B, pp. 539-547. 19. Lau, T., Weatherly, G. C, and McLean, Chicago, III. 14. Ekstrom, V., and Olson, K. 1980. The A. 1985. The sources of oxygen and nitrogen 7. Ricks, R. A., Howell, P. R., and Barrite, G. influence of ferrite and oxygen contents on contamination in submerged arc welding using S. 1982. The nature of acicular ferrite in HSLA weld metal mechanical properties of sub CaO-AI203 based fluxes. Welding journal weld metals, journal of Materials Science merged arc welded stainless steel. Weld Pool 64(12):343-s to 347-s. 47:732-740. Chemistry and Metallurgy Conference, pp. 20. Lau, T., Weatherly, G. C, and McLean, 8. Cloor, K., Christensen, N., Maehle, G., 323-332, The Welding Institute, Cambridge, A. 1986. Gas/metal slag reactions in sub and Simonsen, T. 1963. Nonmetallic inclusions U.K. merged arc welding using CaO-AI203 based in weld metal. IIW DOC II-A-106-63. 15. Dallam, C. B., Liu, S., and Olson, D. L. fluxes. Welding journal 65(2):31-s to 38-s. WRC Bulletin 326 August 1987 Suggested Arc-Welding Procedures for Steels Meeting Standard Specifications—Revised August 1987 By C. W. Ott and D. J. Snyder This revised WRC Bulletin (formerly No. 191) contains the text covering the third updating of the tables "Suggested Practices for the Shielded Metal-Arc" and "Submerged-Arc Welding of Carbon and Low-Alloy Steels" that are contained in the WRC book Weldability of Steels—Fourth Edition, by R. D. Stout. Since the tables are so extensive (constituting 107 pages in the book), they are not reproduced in this bulletin. Bulletin 326 will be sold with the book Weldability of Steels—Fourth Edition for $40.00 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 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 ot 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. WELDING RESEARCH SUPPLEMENT 183-s