A Study of the Submerged Arc Welding of Titanium

A Study of the Submerged Arc Welding of Titanium Submerged arc welding of titanium is technologically feasible; the major problem today is the operability of the flux BY D. C. HILL AND C. L. CHOI ABSTRACT. This report presents the lurgical compatibility and structural CaCI2 CsCI-CaCI, RbCI-CaCI, results of a study of halides as can integrity. didate materials for submerged arc The technical tasks associated with welding of titanium alloys. Criteria are this program involve identification of defined for optimum performance candidate flux systems, formulation of and tests are performed to screen fluxes, and welding tests. Identifica candidate fluxes. CaF2-base fused tion of candidate systems includes fluxes are found to offer preferred consideration of oxygen activity, welding characteristics. Four promis moisture resistance, and slag char ing compositions are identified: CaF2, acteristics. Formulation of these flux CaF2-(5%) BaCI2, CaF2-(5%) es requires the development of new SrF2«SrCI2 and CaF2-(5%) BaCI2- process technology. The successful (2%) LiF. completion of the program is demon Groove welds made with CaF2 flux strated by welding tests. and Ti-6AI-2Cb-1Ta-1 Mo electrodes Most of the literature dealing with 2 4 6 8 10 12 produce strength-toughness com the formulation of fluxes for the sub EXPOSURE TIME (hours) binations of 1082 MPa_^ 47 merged arc welding of titanium has 2 MN\m/m (157 ksi — 41 kskin.) with been published in the Soviet Union by Fig. 1 — Moisture absorption data for no auxiliary shielding and 999 MPa — S. M. Gurevich and co-workers at the selected fused chlorides and chloride 69 MNvm/m2 (145 ksi — 60 kskin.) Paton Welding Institute (Ref. 1). In ad compounds with auxiliary argon shielding. Heat dition, Gurevich has US Patent 3,551 ,- treating the welds at 535 C for 1 h 218 "Flux for Welding Titanium and its resulted in small decreases in Alloys" (Ref. 2). Gurevich has con welding applications. The preferred strength and corresponding small in centrated on developing a CaF2 base flux compositions are CaF2-(5- creases in toughness. flux to which small amounts of BaCI2, 21%)BaCI2-(1-5%)NaCI-(0.5-1.5%)NaF NaCI and NaF are added. The (Ref. 2). Introduction applicable quaternary phase di The only extensive study of fluxes agram has not been developed, but for the submerged arc welding of The high reactivity of titanium pre since the quantities of NaF involved in titanium conducted in the United vents the use of oxide-base sub the flux are small, the system may be States was done by H. F. Petsch of merged arc fluxes such as those represented by the CaF2-BaCI2-NaCI Electric Boat under contract to the developed for ferrous welding. In ternary diagram. This diagram has Naval Applied Science Laboratory order to develop fluxes suitable for been established (Ref. 3) and shows (Ref. 5). It is not known whether any titanium welding, investigators have that all of the fluxes covered by the patents were issued as a result of this built on a CaF2 base. While satis Gurevich patent are single phase work. Petsch also concentrated on factorily providing a medium for CaF2 solutions with melting points in developing a CaF2 base flux. The maintaining a stable arc, these fluxes excess of 1000 C. The Gurevich fluxes composition with the best operability have not been capable of fulfilling the are reported to produce high quality was CaF2-(5%)BaCI2-(2%)LiF. additional requirements of metal- welds with no porosity and good Minimum weldmetal oxygen was ob mechanical properties (Ref. 4). It is tained with C a F 2 - (5 %) L i F - not clear from the patent whether (3.5%)SrCI2«SrF2. Both of these fluxes these fluxes must be fused or whether can be expected to solidify as single D. C. HILL is Group Leader and C. L. CHOI simple mechanical mixtures of the is Senior Research Metallurgist, Linde Re phase CaF2 solutions at tem search Department. flux components will suffice for peratures in excess of 1000 C. These 152-8 I JUNE 1 97 6 fluxes performed best when made as melt. Time-temperature data was chloride mixture or chloride com mechanical mixtures of the flux com taken using a Houston Instruments y-t pound was found with a melting point ponents. In general, the overall per recorder. For casting, the melt was above 1000 C. This disputes the find formance of these fluxes could be poured into a graphite mold and ings of E. P. Dergunov et al (Ref. 6) judged inferior to the claimed per allowed to solidify. The flux was who found a significant region of high formance of the Gurevich fluxes. crushed in a Bico Pulverizer. melting point chloride mixtures in the This program seeks to re-examine The fused fluxes were analyzed for RbCI-CsCI-CaCI2 system. The high- the application of submerged arc carbon content, as contamination welding to titanium by considering the from the crucible would be unaccep fundamental requirements for a flux table. Typical carbon analyses were: system and by experimentally measuring the physical char Melt Wt % Carbon acteristics of candidate fluxes. NaCI 0.02 RbCI 0.02 Flux Studies RbOCaClj 0.02 Fused Flux Preparation CaF2 0.01 Note that the carbon content did not Fused fluxes were prepared by exceed 0.03%. charging into a high purity graphite crucible and melting in a 30 kW Elec Melting Point Studies trotherm Induction Furnace. Flux lots were 250 grams and 2000 grams. The Melting point determinations on 0 2 4 6 8 10 flux was melted under air for 15 halide fluxes were made using a ther EXPOSURE TIME (hours) minutes. For thermal arrest studies, a mal arrest technique. Those systems Fig. 2 — Moisture absorption data for se Pt-Pt/Rh thermocouple shielded with studied included RbCI-CsCI-CaCI2 lected fused fluorides and fluoride com an alumina tube was immersed in the and RbCI-CsCI-BaCI2. No chloride, pounds Table 1 — Welding Parameter Study for Fused CaF, Flux Wire Volt Cur Exten Travel Wire Elec Flux Slag Bead size, age, rent, sion, speed, feed, trode burden, remo smooth Bead Bead mm V A mm mm/s mm/s angle mm val ness shape color 1.6 28 205 20 6.3 108 vert 20X13 — P P shiny 1.6 33 215 20 6.3 108 vert 20X13 — F F yellow 1.6 32.5 210 20 6.3 94 vert 20X18 — G G lustrous 1.6 31.5 210 20 6.3 94 vert 20X26 — G G dull 1.6 34.5 200 20 6.3 87 vert 20X26 — G G blue 1.6 34.5 200 20 6.3 87 vert 20X26 G G P shiny 3.2 35.5 420 20 6.7 36 vert 26X26 F G P yellow 3.2 36 400 20 6.7 33 vert 26X26 F — — — 1.6 34 240 20 6.3 108 vert 26X26 F G F — 1.6 34 245 20 6.3 108 vert 20X26 F G VG Yellow 1.6 34 260 20 6.3 138 vert 20X26 F G G dull 1.6 34 260 20 6.3 138 vert 20X26 F G G yellow 1.6 34.5 220 20 5.1 94 vert 20X26 G G G yellow 1.6 34 245 13 6.3 99 vert 20X26 G G G yellow 1.6 30 240 13 6.3 110 10°lead 20X26 G G G — 1.6 34 245 13 6.3 97 vert 20X26 G G G — 1.6 34 240 13 6.3 97 vert 20X26 G G G — 1.6 34 240 13 6.3 97 vert 20X26 G G G — 1.6 34 235 13 6.3 97 vert 20X26 G G G yellow 1.6 34 240 13 6.3 97 vert 20X26 G G G — 1.6 34 240 13 6.3 97 vert 20X26 G G G — 1.6 34 220 13 6.3 76 vert 20X26 G P P — 3.2 32 400 13 8.5 40 vert 26X26 G G G yellow 3.2 34.5 440 20 8.5 36 vert 26X26 G G G yellow 3.2 34.5 390 20 8.5 42 10° lead 26X26 G G G yellow 3.2 34.5 405 26 8.5 42 vert 26X39 G G G dull 3.2 34 435 26 8.5 47 vert 26X39 F F G yellow 3.2 35 415 26 8.5 42 vert 26X39 F G G dull 3.2 33.5 445 19 8.5 48 vert 20X26 F F F yellow 3.2 34 425 19 8.5 42 vert 33X39 F G G yellow 3.2 36 430 19 8.5 42 vert 33X39 F G G yellow 3.2 35 450 19 8.5 48 vert 26X26 F G F yellow 3.2 34 600 19 8.5 70 vert 26X26 P G G yellow 3.2 35 425 19 8.5 42 vert 26X26 G G G blue 3.2 35 430 19 8.5 42 10° lag 26X26 G G G yellow 3.2 35 430 19 8.5 42 10° lag 26X26 G F P yellow 3.2 34 390 26 8.5 38 vert 26X33 G G G yellow 3.2 36 425 26 8.5 44 vert 26X33 G G G yellow 3.2 34 390 26 8.5 38 vert 26X33 G G G dull 3.2 34 380 26 8.5 38 vert 26X39 G F P yellow 3.2 34.5 220 19 8.5 22 vert 26X39 VG VG VG yellow WELDING RESEARCH SUPPLEMENT! 153-8 est melting point found in this system C.

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