. . WELDING RESEARCH

SUPPLEMENT TO THE WELDING IOURNAL, DECEMBER, 1982 ^-.^^^r Sponsored by the American Welding Society and the Welding Research Council (ffDJj

New Fluxes of Improved Weld Metal Toughness for HSLA Steels

SA W fluxes reduce Ti and B oxides, giving Ti and B microalloying additions that provide good toughness and crack opening displacement in 500-600 MPa (72.5-87 ksi) steels intended for arctic grade structures

BY R. KOHNO, T. TAKAMI, N. MORI, and K. NAGANO

ABSTRACT. Weld metals which are welding heat input is usually selected to metals was not consistent enough. In microalloyed with Ti and B can show get satisfactory toughness of the welded retrospect, these techniques may not be excellent properties even at low temper­ joints. The alloying elements in weld met­ appropriate for the addition of Ti and B to ature. However, welding consumables al, however, lead to tensile strength high­ the weld metal because they are added which can consistently add optimum er than actually needed. through a reactive welding arc cavity. amounts of Ti and B to weld metal were Suzuki, Mori and others (Ref. 1) have Recognizing the benefits of microalloy­ relatively unknown. Therefore, new pointed out that, in the SAW process, the ing weld metals with Ti and B, new fluxes Ti02-B203 bearing fluxes, which can add simultaneous addition of Ti and B to weld were developed to have the following Ti and B to weld metal by reduction of metals beneficially improves their notch characteristics: their oxides in the fluxes, were devel­ toughness. Since then, it has been recog­ oped. nized that the Ti-B can be used as 1. Good weldability, such as slag When Ti02 was a main component, it microalloys to control the microstructure detachability and arc stability. was necessary to substitute BaO, MgO or of ferritic steel welds, and Garland and 2. Optimum amounts of both Ti and B some other basic component for CaO in Kirkwood (Ref. 2) have proved that their with as low oxygen and nitrogen con­ order to eliminate the precipitation of addition is essential to assure good tents as possible. mechanical properties. perovskite (CaTi03) and have a good weldability. The new fluxes were shown Following Suzuki's lead, many re­ Weld metals were expected to obtain to be able to consistently microalloy weld searchers have studied and developed Ti and B by the reduction of Ti02 and metals with optimum amounts of Ti and B techniques to add Ti and B to ferritic steel B2O3 contained in the fluxes occuring (about 0.02% and 0.0045%, respective­ weld metals. It was found that electrodes around the arc cavity. It was conceivable ly). containing Ti and B produce these diffi­ that the oxygen content in weld metals Fracture appearance transition temper­ culties: might be reduced if the stable oxide, ature of the weld metals was sufficiently Ti02, was substituted for Si02 — Fig. 1. low and only slightly deteriorated with 1. A large fluctuation of Ti and B When weld metals are microalloyed the addition of Nb in the as-welded content in weld metals affected by com­ with Ti and B, they have an optimum metal. positions of base metal plates. composition range for obtaining good The new fluxes were successfully 2. High potential for cracking during toughness. Therefore, the composition applied to the welding of node cans of production of electrodes. of fluxes that affects Ti and B content in offshore platforms, a sea berth, LPG 3. Unstable yielding of Ti and B during weld metal was studied. tanks and ships. steel production.

When the ferroalloys of these ele­ Experimental Procedure Introduction ments were present in agglomerated Flux Preparation There is a large and growing demand fluxes, the Ti and B content in weld in the arctic regions for large welded This research focused mainly on fused structures, such as offshore platforms, type fluxes produced by fusing a mixture which require steel and joints to be highly Paper presented at the 62nd Annual AWS of intended amounts of finely powdered reliable for operating at low tempera­ Convention in Cleveland, Ohio, during April materials in either 7 or 100 kg (15.4 or tures. When submerged arc welding 5-10, 1981. 220 Ib) quantities. The 7 kg (15.4 Ib) (SAW) techniques are applied in their mixture was electrically fused for 30 R. KOHNO, T. TAKAMI, N. MORI, and K. construction, a highly basic flux with NAGANO are with the Products Research and minutes (min) using carbon electrodes in alloyed electrodes is usually selected as a Development Laboratories of Nippon Steel a water-cooled pan, after which the melt welding consumable and a low level Corporation in japan. was poured into a large water pool to

WELDING RESEARCH SUPPLEMENT 1373-s 0.08

-100 \ non-Ti02 bearing fluxes V o 0.07 \ SiO* 30-40% \

0.06 °\ a / \ / CO Y o o \ -150 - 0.05 X] C 8 0.04 c c 'a. \ o d) 00 CO >a E

-200 o 0.03 •X \ / \ \ ro Ti02 bearing fluxes 0) 0.02 \ I /Ti02 5~35%\ \Si02 10-20%^ 0.01 I -250,_ 0.5 1.0 1.5 2.0 2.5 1000 1500 2000 Basicity index Temperature (°C) Fig. 2—Relation between the basicity index and the oxygen Fig. 1-Heat of formation for some oxides content in weld metals

granulate. Then, the granulated flux was a 16 mm (0.63 in.) root opening for semi-quantitative reignition voltage; the dried, crushed, sieved, and baked at examining all deposit weld metals. An AC latter provided an average voltage of arc 300° C (572 °F) for an hour (h) before its single electrode system was applied with as it appeared on voltage-meter on the use. The 100 kg (220 Ib) mixture was a heat input of 31 kj/cm (79 kj/in.). Cv control panel of the welding machine. fused in a 100 kg (220 Ib) fire brick-lined test bars, tension test pieces, weld sec­ furnace before the granulation proce­ tions, and chips for chemical analysis dure and was used when large amounts were sectioned from these test panels. Results and Discussion of flux were necessary. Cv test bar notch positions were selected Flux Design on the center and quarter lines of the Welding Conditions and Mechanical Tests bead width. The former were used to Initially, Ti02-CaO-CaF2AI203 fluxes test the reheated weld metal region, and containing no Si02 were used. The slag An AC tandem welding machine with a the latter were used to test the as-welded of this system did not vitrify and did not Scott connection was used. Beads initially metal region. completely detach itself from the weld were welded on mild steel plates to bead. An x-ray diffraction apparatus was examine the weldability of various fluxes. used to examine the interface region of After a rough design of flux composition Hot Cracking Susceptibility the slags. Those not completely detached became clear, high strength low alloyed were shown to consist of high amounts When the hot cracking susceptibility of (HSLA) low temperature grade steel test of perovskite (CaTiOs). Perovskite's B2O3 bearing fluxes was examined, 16 panels were used. Each was 20 mm thick, 1916-1970°C (3481-3578°F) equilibrium mm (0.63 in.) deep single V-grooves with 300 mm wide and 800 mm (0.79 X melting point is so high that it probably a groove angle of 60 deg were prepared 11.8X31.5 in.) long with double V first precipitates and then attaches itself on 36 mm (1.42 in.) thick plate. A single groove weld preparation. The chemical to the weld bead. Thus, Si02 was deter­ bead was welded in the V-groove with composition of these panels was mined to be necessary for slags to vitrify. an AC single electrode welding machine; 0.09% C, 0.28% Si, 1.40% Mn, 0.29% Ni, However, since oxygen content in weld hot cracks in weld beads were then 0.11% V, 0.042% Nb, 0.035% Al and metals increases with the Si02 content in examined using dye penetrant testing and 0.0068% N. fluxes, one requirement for the fluxes to radiography. Welding heat input was 40 kj/cm (102 have a vitrified slag of excellent weldabil­ kj/in.). After welding, slag detachability ity was that they should contain Ti02 as Arc Stability and bead shape were observed. Two one of main components and have as sets of Charpy V-notch (Cv) test bars, Arc stability in flux welding was little Si02 as possible. weld sections and chips for chemical unclear. For this reason it was necessary Welding slag detachability is improved analysis were sectioned from the HSLA to measure it using the definition that when the thermal expansion coefficient test panels. One set of Cv test bars was "the welding arc is stable when reignition largely differs from that of the steels and side-notched 6 mm (0.24 in.) thick and voltage and timing in the arc cycle are when the slags do not crystallize and taken from the reheated weld metal consistently stable." detach themselves from the weld bead region that had been affected by the The arc voltage of each electrode was surface (Ref. 3). Therefore, one of the weld thermal cycle of the following pass. measured with an adaptor. The adaptor most important problems in using the flux The other set consisted of full size Cv test consisted of two bridge-type full wave containing Ti02 was to eliminate the bars taken from the as-welded metal rectifier circuits, which had a common formation of perovskite in slags. When region. input terminal. One output terminal was CaO content in fluxes was less than 10%, A multipass weld was deposited in the crossed with a capacitor, and the other the slags were found to detach them­ single V-groove using a backing plate and remained open. The former provided a selves from weld beads.

374-s | DECEMBER 1982 A region where slags attached them­ Alkali metal oxide not contained Flux (a) Alkali metal oxide contained Flux (b) selves to weld beads corresponded with Semi-quantitative-reignition the perovskite precipitating area in the

CaO-Si02-Ti02 ternary system (Ref 4). Therefore, other basic components, such as BaO and MgO were substituted for

CaO. Trial fused fluxes of Ti02-BaO-

CaO-CaF2-AI203-Si02 (A system) seemed to give much better weldability than those of Ti02-MgO-CaO-CaF2-Al203- Si02; for this reason, our efforts concen­ trated on the A system fluxes. We also determined that fluxes which contained equiweight of BaO and Ti02 were able to give good slag detachability. This can be explained by use of BaO-Ti02 Lead and BaTi03-CaTiO phase diagrams (Ref. 3 Trail 4). The region of perovskite precipitation disappears when BaTi03 content is more time Lead time than 80 mole-%, while the BaO-Ti02 system has a eutectic point when BaO ® and Ti02 are nearly the same weight. This also confirms that fluxes having similar SlOO eutectic composition have good weld­ ability. Slag detachability became noticeably 50 better when AI2O3 content increased, which might be caused by the unusual thermal behavior of alumina-titanate at Flux A Type JZ nearly 500°C (932°F) (Ref. 5). The highest 20 Electrode 2%Mn + 0.5%Mo M ° applicable welding current also increased EXPECTED VALUE with AI2O3 content. by mixing of only electrodes and plate

Oxygen and Nitrogen Content in Weld Metal

Oxygen content was some 0.04% and 10 100 0.02% when the basicity index was 0.5 and 1.3 respectively, with A system fluxes of Ti02 content ranging from 5% to 35% and Si02 content ranging from 10% to 20%. Fluxes which did not contain TO2, showed an oxygen content of 0.065% at the basicity indexf of 1.25 and 0.02% at 70 80 90 100 -75 -60 -45 -30 -15 the basicity index of 2. Nitrogen content in weld metal Test temperature (C) The A system fluxes clearly give less (ppm) oxygen content than that of fluxes which © do not contain Ti02, given the same © basicity index —Fig. 2. When the basicity Fig. 3 — Effect of alkali metal oxide in fluxes on: A—arc stability; B - weld metal nitrogen: C—Cv index is replaced with the IIW index}, the toughness difference in the oxygen content of weld metals only slightly decreased. The basic­ with an increased basicity index —Fig. 4. ity indices were not applicable for these Fig. 3A. fluxes, if the indices are intended to With the stabilization of the welding The reduction ratio for A type fluxes predict oxygen content in weld metals. arc, nitrogen content in the weld metal was about 0.001; these contained 30% decreased by an amount nearly the same Al203 and had a basicity index of 1.0. The Arc stability of the A system fluxes was as that of the absorbed content; this was Ti content in the weld metal remained at not as good as that of commonly avail­ defined as the difference between the approximately 0.020 ~ 0.025% when able Si02-CaO-MgO type flux. There­ measured N content in the weld metal changing the welding parameters as fol­ fore, alkali metal oxides were added to and the expected N content calculated lows; current from 400 to 800 amperes stabilize the arc —namely, arc reignition from the nitrogen content of the base (A), voltage from 25 to 40 volts (V), and peak voltage. The trail electrode was metal, electrodes, and average dilution of welding speed from 5 to 11.7 mm/s (11.8 affected more than the lead electrode — the base metal —Fig. 3B. to 27.6 ipm) for A system fluxes. B in the weld metal was successfully added by reduction of B 0 in fluxes and Ti and B Content in Weld Metal 2 3 proportionally increased by increasing fin this paper, the basicity index is defined The effect of flux composition on the B2O3 content in them. The partition coef­ as: reduction ratio of Ti0 was also studied ficient did not change when fluxes (0.108*CaO + 0.068*MnO + 0.10*MgO + 2 where the reduction ratio was defined as belonged to the same flux system. The 0.078*CaF2 + 0.10*BaO) -t- (0.105*SiO2 + weld metal flux a ratio of the total Ti content in the weld partition coefficient (B /B203 ) 0.002*AI2O3 + 0.08*TiO2) metal to the Ti0 content of the slags. was 0.009 for the A type fluxes —Fig. fBi = (CaO + CaF2 + MgO + K20 + Na20 + 2 5A. 1/2 (MnO + FeO)) + (Si02 + '/2(AI203 The reduction ratio increased with + TiO + Zr02)) increased Al203 content in the flux and The content of Ti and B in each bead

WELDING RESEARCH SUPPLEMENT 1375-s - 200 Basity index o 2.0 <0.72 A 0.73-1.1 " 150 X >1.1 100

50

1.5 C = 0.09. Si=0.22. Mn = 1.25. Ti = 0.02 N = 0.008. 0 = 0.032 50 100 £ B content in weld metal (X10"%) &

o &A A '-aJ CO L. C o 1.0 o A /*> AA, ° TD A A „

Fig. 5 — Relation between B20) in flux and B in 0.5 weld metal and optimum B content in weld metal

(Cinfinity/Cfirst pass) the apparent partition coefficient(L) and a weight ratio of the L-O X 10 15 20 25 30 35 fused slag to the weld metal(Y) are re­ lated by: Amount of Al203 in flux {%) (-infinity/f-first pass /-l _L Y*L)/ % 4 - Effect of Al20} content and basicity of fluxes on reduction ratio of Ti02 = (1 + Y*L-a) (D of all-deposited weld metal were chemi­ This clearly showed that Ti and B can be where a is a dilution. cally analyzed to determine the consis­ consistently added to weld metal by The coefficients for Cr, V, Nb, B and Ti tency of Ti and B content in multipass reducing their oxides in fluxes even when were measured for agglomerated fluxes welds. Dilution of the base metal plate base metal dilution changes with each of the Ti0 -MgO-Si02-AI 03-CaF2 sys­ was also checked by Ni and Mo which pass —Table 1. 2 2 tem with direct-current electrode posi­ were added from the base metal and The apparent partition coefficient, tive. The result is qualitatively explained electrode, respectively. The weld metal which differed from the reduction ratio at with equation (1) and Fig. 6 (Ref. 6). The of each pass consistently contained a convenience, was defined as the ratio apparent partition coefficients of Ti and B 0.018% Ti and 0.0046% B, while Ni con­ of an element's content in the fused slag for the A type flux was also plotted on tent decreased and Mo content to the content in the weld metal; the Fig. 6. By comparing their formation ener­ increased with decreasing dilution, i.e., condensing factor was defined as the gies, the order of stability of the oxides each successive pass. The composition of ratio of the final concentration to the was found to be Ti02, B2O3 and O2O3 flux #151 was 37% Si02 + Ti02, 18% concentration of the first pass. As shown (Ref. 7, 8). Nb203 and V205 would Al20, 30% CaO + BaO and 15% CaF2. in the Appendix, the condensing factor appear between B2O3 and O2O3 (Ref. 9), and the partition coefficients are related by comparing the element affinities to Table 1—Compositional Change of Ni, Mo, Ti and B with Each Pass of Deposited Weld oxygen. Therefore, Ti and B can be Metal, % stably added to the weld metals by reduction of their oxides even for multi­ Weld pass pass welding. On the other hand, ele­ no. Ni Mo Ti Fi ments such as Cr, Ni, and Mo, which have low apparent partition coefficients, 1 5.16 0.21 0.017 0.0042 increase their content in weld metal as 2 3.40 0.32 0.017 0.0040 3 2.10 0.39 0.017 0.0048 the pass number increases, even when 4 1.65 0.41 0.017 0.0043 their oxides are added to the fluxes. 5 1.29 0.42 0.019 0.0047 6 1.02 0.46 0.017 0.0045 7 0.% 0.45 0.018 0.0046 Hot Cracking Susceptibility 8 0.80 0.46 0.018 0.0047 B is known to have a high hot cracking 9 0.68 0.46 0.019 0.0045 10 0.94 0.44 0.016 0.0045 susceptibility so that an optimum amount 11 0.63 0.44 0.017 0.0049 of B2O3 contained in flux #151 was mea­ sured. Hot cracking susceptibility of Ti Base metal plate 8.82 <0.02 - - Electrode 0.0 0.54 — — and B bearing welds did not differ from usual Si-Mn type welds when the base

376-s I DECEMBER 1982 »Cr203 • aggromerated Ti02 beaing fluxes

O fused Ti02 beaing • V205 fluxes

If)c 0) Ti02 •o c o equation (1) B2O3 j^~2000 o fY = 0.17 1200 U=0.7

10 20 30 40 50 60 Partition coefficient Fig. 7 (left) — Comparison of hot Fig. 6- Relation between a condensing factor cracking susceptibility of Ti-B bearing and an apparent partition coefficient 20 30 40 50 weld metal with Si-Mn type weld Welding speed (cm/min) metal

F E n n Q. 120 cn -120 , nTnfiTm ' . 100 ® r T 7r r ® b I 100 <-30 **<$&& a 80 -15 1 80 * .-27 C 60 ^-56 -5S77 j^ V-36X y* c 60 c c 40 (1) 4U to -50 s /—\Jl •4-a -t-» c /A O ?n o 20 AS @ 3 -«3 O o /^} 7 C=0.1, Si = 0.26, Mn=U7"UTi=0.p28 - "*^>^| ^ -42y -11 CQ 0, 00 0 y 50 100 150 200 0/eft* 50 *,10 0 150 200 N content in weld metal (ppm) N content in weld metal (ppm) Fig. 8 - Effect of N and B content in weld metal on FA TT. Heat input was 45 kj/cm. Notch was located at as welded area (A) and at reheated area (B). Numbers in figures are FA TT plate contained 0.12% C. Ti and B bearing of about 15 kj/cm (38.1 kj/in.). The A when B was approximately equivalent in welds did not practically differ from Si- system fluxes were also able to alloy weld molar content with N. FATT scarcely Mn bearing welds when welding currents metals with this value. changed when the notch position was ranged from 500 to 800 A and welding The B203 content in the A type flux changed from as welded region to the speed ranged from 20 to 60 cm/min, i.e., #151 was varied from 0 to 1.0% to find reheated region. The lowest possible 3.3 to 10 mm/s (7.9 to 23.6 ipm)-Fig. the most favorable B content in weld FATT and the most favorable content of 7. metals — Fig. 5B. Results showed that N and B were not clear —Fig. 8 —(Ref. 0.0040 to 0.0050% was best for the 12). Features as-welded metal, and 0.0040% to The FATT came down to -80°C Mechanical Properties and Toughness of 0.0060% for the reheated weld metal. (—112°F) at a Mn content of about 1.8% Weld Metal The optimum contents of B were practi­ for as-welded metal and to —70°C It was of primary importance to find cally the same for both metals. Respec­ (-94°F) at a Mn content of about 1.5% the optimum content of Ti and B in weld tive Cv absorption energies were 165 ) for stress relief heat treated weld metal — metals that give good Cv absorption and 90 ) (6 mm subsize test bars for Fig. 9. FATT deteriorated at 10 to 20°C energy when weld metals were micro- reheated weld metals) at -60°C (50 to 68°F) with the addition of 0.07% alloyed with the Ti and B. Ti in weld (-76°F). Nb to the weld metal and deteriorated metals was investigated with the agglom- The fracture appearance transition more with stress-relief heat treatment. arated fluxes, because it was difficult for temperature (FATT) was lowered more The deterioration of as-welded metal the fused A type fluxes to make the Ti than 15°C (27°F) with reducing N con­ was much less than Si-Mn type weld content in weld metal scatter over a wide tent in weld metal 0.0010% - Fig. 3C. metals —Fig. 10. Further detail descrip­ enough range with a same weldability The effects of Mn, N and Nb on Ti- and tions can be found elsewhere (Ref. 13, and O content in weld metals. When B-bearing weld metals were studied using 14). one-side-welding was applied to 32 mm all-deposited weld metals and applying When weld metals were microalloyed 2 (1!4 in.) thick 50 kg/mm (71.1 ksi) class Ti02-B203 bearing agglomerated fluxes. with optimum amounts of Ti and B, the steel using a high heat input of 197 kj/cm The content of Mn, N and Nb in the weld weld metals contained the least amount (500 kj/in.), the most favorable Ti con­ metal was controlled by varying the con­ of proeutectoid ferrite —Fig. 11. The tent was found to be about 0.02% where tent of Fe-Mn-N and Fe-Nb in the fluxes. quantity of proeutectoid ferrite increased B content was from 0.0030 to 0.0050% B content was controlled by changing the when the B content decreased from the (Ref. 10, 11). This value was also con­ amount of B2O3. optimum amount, but did not change firmed with another Ti02-B203 bearing The FATT improved with decreasing when the B content was increased. This agglomerated flux using a low heat input nitrogen content and was minimized may explain the drop in Cv absorption

WELDING RESEARCH SUPPLEMENT I 377-s P.W.H.T. -10 Weld metal AW SR -20 Si-Mn-Ti-B -o- —• — P.W.H.T. Weld metal -20 AW SR Si-Mn-Ti-B —o— —•— -30 -40 o O £-40 if < -50 -60 -60

C = 0.1, Si=0.26, Mn = 1.27 -70 Ti = 0.028, B =0.050 Ti=0.022% 0 0.02 0.04 0.06 -80 B-50 ppm Nb '%) 0.5 Fig. 10 - Effect of Nb content in weld metal on FA TT. Weld beads were welded on 20 mm (0.79 in.) thick plate with SA W. Heat input Mn content in weld metal was 31 kj/cm (78.7 kj/in.). Stress was relieved at 630°C (1166°F) for Fig. 9-Effect of Mn content in weld metal on FATT 1 h energy when B content in weld metal decreased from the optimum level; how­ ever, it may have also been affected by the boron constitutions at austenite grain boundaries when the B content in­ creased. Ti content is a necessary condition for wmm j . | ill l&W§- weld metals to obtain high Cv absorption energy; without it, B is almost entirely oxidized and with it, B is nitrified. This is because inclusions containing titanium oxides seemed to act as nucleation sites Hv-'l^*' of acicular ferrite in the austenite grains. It is concluded, therefore, that fine acicular •^•>7--#>K^ ferrite structures can be formed by stabi­ lizing austenite grain boundaries with seg­ :AA$&% regated B and by early nucleation of 5* ^A^aV acicular ferrite mainly by titanium oxides. • -"SS&'-.^ar Nitrification of B is also important to fix free-N in weld metal that deteriorates the Cv toughness of weld metals (Ref. 12). 4.0 Qi"-- i A A_B1 • 1 Samples taken from all 93 all-deposited "•fTcr.i"'^ l r '. .1-vX 4L~.X-n weld metals were analyzed by step wise regression analysis for tensile strength. Independent variables and their ranges were carbon equivalent (Ceq = C + Mn/ 6 + Si/24) at 0.173-0.509%, 0-0.27% Mo, 0.0-0.030% Nb, 0.000-0.009% B and 0.0030-0.0180% N. Tensile strengths(TS) were:

i- 7* •'**'/•• -v;.'\ • TS = 82.9*Ceq + 25.1*Mo + 165*Nb + 220*Ti + 126*N + 28.4 (kg/mm2) (2) iCWfia?

:• a>" . I. ? ,<~r' V /i with a standard deviation of 2.7 for , - • . 1 a »• a as-welded metals, and:

TS = 58.2*Ceq + 33.3*Mo + 283*Nb + 326*Ti + 189*N + 30.3 (kg/mm2) (3) \.r D A U _. .'^rt with a standard deviation of 2.4 for Fig. 11 — Microstructure of Ti bearing weld metal (A, B) and Ti-B bearing weld metal (C, D). A and C stress-relief heat treated weld metal. sized at 400M (as shown in A), and B and D sized at 100M (as shown in B)

378-s I DECEMBER 1982 Regression coefficients were more than and from the sub-surface. The axis of the tanks. The plates were Al killed low 0.91. It was clearly shown that B content test pieces were set along the weld bead temperature grade steel with a typical in weld metal did not significantly affect direction. Full size COD test pieces were chemical composition of 0.072% C, tensile strength (Ref. 13). cut according to British Standard DD-19, 0.19% Si, 1.07% Mn, 0.014% P, 0.002% S and notches were located to cross the and 0.24% Ni. The plates were prepared axis of weld metal. with single V-groove welds and welded Applications The chemical composition of the weld in a horizontal position with heat input of metals was 0.09% C, 0.26% Si, 1.3- about 20 kj/cm (51 k)/in.). The groove of Developed Ti02-B203 bearing fluxes 1.5% Mn, 0.025% V, 0.010% Nb, 0.021% the final side was prepared by arc goug­ can be used to build the node cans of Ti, 0.0060% B, 0.0040% N and ing before welding. offshore platforms, LPG tanks, ships, and 0.025% O. Cv, tension and COD tests and chemi­ line pipes. The tensile strengths were about 585 cal analysis of weld metals were carried MPa (84.8 ksi) for as-welded metal and out. The side-notched Cv test bars and Node Cans of Offshore Platform were about 570 MPa (82.7 ksi) for stress- tension test pieces were cut from the relief heat treated weld metal. Average backing side of the weld metals. Full BS4360-50D class steel, which is 63 mm Cv absorption energy was not less than thickness COD test specimens were cut (2V2 in.) thick, is used for offshore plat­ 110 ) for as-welded metals and not less according to British Standard 5162:1979. forms. The chemical composition of such than 70 ) for stress-relieved weld metal An example of the chemical composi­ a plate was 0.14% C, 0.46% Si, 1.41% Mn, even at -60°C (-76°F)-Fig. 11 A. The tion of weld metals was 0.07% C, 0.12% 0.006% P, 0.002% S, 0.023% Al, 0.03% root areas showed slightly lower Cv val­ Si, 1.37% Mn, 0.014% P, 0.004% S, 0.07% Nb, 0.05% V and 0.0056% N. The plate ues than the sub-surface area. Minimum Ni, 0.027% Ti, 0.003% B and 0.036% O. was prepared with a double V-groove COD value was not less than 0.2 mm Tensile strength was 609 MPa, (88 ksi) weld and was welded with the new A (0.008 in.) for as-welded metal and not and average Cv absorption energy was type flux #151 using a heat input of about less than 0.7 mm (0.03 in.) for stress- 193 ) at -50°C (-58°F); COD values at 45 k)/cm (114 kj/in.). Some weld joints relieved weld metal at -60°C (-76°F)- -50°C (58°F) were not less than 2.7 mm were given stress relief heat treatment at Fig. 11B. (0.106 mm). 630°C (1166°F) for 2Vi hours (h) after Although the COD value increased weiding. with the stress relief, the Cv absorption Cv, tensile strength, and crack opening energy slightly decreased for reasons not Ships displacement(COD) tests were per­ yet clear. formed as well as analysis of the weld The other sector of application for The flux can also be applied to sea metal. Side-notched Cv test bars were Ti0 -B 03 bearing fluxes is in ship build­ berths using multipass techniques. 2 2 cut from root areas and from sub-surface ing. Single pass submerged arc welding areas where the center axis of the test with flux-copper backing was used to LPG Tanks bar coincided with the quarter thickness join 50 kg/mm2 (71 ksi) class ship steel (32 ] line from the surface. The tension test An agglomerated Ti02-B203 bearing mm or 1 A in. thick) at a heat input of pieces were taken both from the root flux was applied to weld walls of LPG 197 k)/cm (500 kj/in.). The tensile

2.0

ii oi- uu

E

gl.O o

-75 -60 -45 -30 -15 0 -60 -50 -40 -30 -20 -10 Temperature (°C) Temperature (°C)

Fig. 12 - Toughness of weld metal when Ti02-B203 bearing flux applied to BS4360-50D class thick plate. A-Cv toughness; B - COD value

WELDING RESEARCH SUPPLEMENT 1379-s strength of welded metals was about 540 even at low temperature; this is usually For simplicity of calculation, a direct MPa (78 ksi), and the Cv absorption difficult to obtain with commonly mar­ pile up weld bead is assumed, namely, energy of the weld metal was about 100 j keted fluxes. the n-th pass formed with a part of at -10°C, i.e., 14°F(Ref. 10). (n-1)th weld metal and (1-a) part of the References electrodes. It is also assumed that neither Line Pipes the base metal plate nor the electrode 1. Suzuki, H.; Sekino, S.; Mori, N.; Tanigaki, contain a considered element. Flux of this family is applied to weld H.; and Sugioka, I. Development of CaF -Ti-B 2 Where the apparent partition coeffi­ seams of AP1-5LX-70 class arctic-use line- type submerged-arc tubular wire with high cient (L) is a ratio of the element content pipes using single-pass techniques on notch toughness. IIW Doc. 11-583-71, in the slag (Cs) to the element in the weld each side of the weld. IX-750-72. 2. Garland, |. G., and Kirkwood, P. R. 1975. metal (CM), the mass conservation rule Towards improved submerged arc weld met­ requires: Conclusion al, part 2. Metal Construction and British Weld­ ing lournal 7(6):720. The object of the research discussed in aCtf*W + Q*W = Ga*W + Cs' W 3. Wanke, R. 1973. Lineare thermisher aus- M S M 5 this paper was to develop fluxes which dehnungs koefficient von schweisspulver- (1) can consistently microalloy weld metal schaken und berechnung ausden ausdehnung- with Ti and B. The most probable way sweiwerten. Schweissen und Schneiden 25 H7: where CM = the element content in n-th seemed to be the addition of Ti and B to S252-254. pass weld metal; CF = the element con­ the weld metal by reducing their oxides 4. Reser, M. K. ed. 1974. Phase diagrams tent in the flux; WM = weight of fused (Ti02 and B2O3) in fluxes during welding. for ceramists, 3rd ed. American Ceramic Soci­ weld metal to n-th pass weld metal; ety. After discovering the design principle of Ws = weight of fused slag; Ti02-B203 bearing fluxes, new fluxes 5. Buessen, W. R.; Thielke, N. R.; and Sara- e |a,e kavskas, R. V. 1952. Thermal expansion hyster- One can assume Q5p P = 0 so that with the following characteristics were isis of aluminum titanate. Ceramic Age by solving the recurrence equation (1), successfully developed and applied: 60(10):38-40. the element content of n-th pass weld is 6. Nagano, K.; Takami, T.; and Koyama, K. given as: 1. Weld metals deposited using these 1980. On the behaviour of partition reaction fluxes contain less oxygen than those of Ti and B in SAW. Preprint of IWS Spring CF*Y n using other marketed fluxes at the same Conference: 78-79 (in Japanese) C n — [1-(a/(1+Y*L)) ] (2) ^M — (1+Y*L-a basicity index, because the stable oxides 7. Kubaschewski, O; Evans, E. Ll.; and of Ti02 are used as a main component Alcock, C. B. A. 1967. Metallurgical thermo­ chemistry, 4th ed. instead of Si0 . 2 8. Caughlin |. P. 1954. Contributions to the where Y is the fused weight ratio of the 2. The fluxes can consistently microal­ data on theoretical metallurgy: XII heat and fused slag to the fused weld metal. loy weld metals with optimum amounts free energy of formation of inorganic oxides. Since a/(1 + Y*L) is usually less than 1, of Ti and B over a wide range of heat Bulletin 542. Bureau of Mines. when n goes to infinity, CM converges to inputs. 9. Elliott, ). F. and Crleiser, M. 1960. Ther­ the coefficient before the square bracket 3. The fluxes have good arc stability so mochemistry for steel making. Vol. II. Addision- in right hand side of equation (2). There­ that the N content in weld metal can be Wesley Publication Co. fore, one can define the condensing reduced. 10. Horigome, T.; Kanazawa, S.; Tsunetomi, factor as: E.; Mimura, H.; Nakashima, A.; Shinmyo, K.; and 4. The slags of these fluxes easily Okamoto, K. 1967. Newly developed 50kg/ 2 detach themselves from weld beads mm ship steel and its welding material. Pro­ Cinfin,ty/Cl = (1 + Y*L)/(1 + Y*L-<*) (3) even at a root pass of multipass welding ceedings of we/ding of HSLA [microalloyed] because of successful elimination of the structural steels: 679-705, 786-788. Metals One can see from equations (2) and (3) formation of perovskite (Ti02CaO). Park, Ohio: American Society for Metals. that the changing of element content 5. The optimum amount of Ti content 11. Horigome, T.; Tsunetomi, E.; Shinmyo, with pass number is practically negligible in weld metal ranges from 0.015 to K.; Nagano, K.; Mori, N.; and Kato, T. 1978. Study of Ti-B type welding material for high when the element is added by reducing 0.025%, and for B content it is the equiv­ its oxide in the flux and when the appar­ alent molar weight of N in weld metals. heat input submerged arc welding of 50kg/ mm2 class steel, jnl jpn Welding Soc. 47:18-25 ent partition coefficient is large enough. 6. The FATT lowers with decreasing N (in lapanese). On the other hand, when Ni in the content. 12. Mori, N.; Homma, H.; Okita, S.; and base metal plate and Mo in the electrode Wakabayashi, M. 1981. Mechanism of notch are considered, one has to replace equa­ When optimum amounts of Ti and B toughness improvement in weld metals con­ tion (1) with. are added to weld metals, the weld met­ taining Ti and B. jnl jpn Welding Soc. 50 #2:35-42 (in Japanese). als have following the characteristics: Cw = aCW + (l-a)Cw (4) 13. Mori, N.; Homma, H.; Wakabayashi, M.; and Okita, S. Ti-B kei yosetsu kinzoku no where Cw = the element content in the 1. High Cv absorption energy with zaishitsu tokusei. jnl jpn Welding Soc. 50 n-th pass weld metal, and Cw = the ele­ appropriate tensile strength of weld met­ #8:74-81 (in lapanese). ment content in the electrode. al. 14. Homma, H.; Mori, N.; Saito, S.; and For Ni and Mo in this paper, equation 2. Only slight deterioration of FATT in Shinmyo, K. Effects of titanium-boron and (4) can be rewritten as: niobium additons on the mechanical proper­ as-welded metal with the addition of ties of submerged arc weld metals. IIW Doc. 1 n base pla,e Nb. Oaji = a CNl IX-1072-78; Doc XII-E-10-78. CMS = O-^Cf, (5) When new flux was applied to weld Appendix: The Effect on Composition of Therefore, one can see from equation BS4360-50D class steel and to Al killed Weld Metals of the Reduction Ratio of (5) that Ni in the weld metal decreases low temperature steel, as-welded metals Oxide in Flux and the Dilution of a Base and Mo increases with an increasing weld showed a good minimum COD value Metal Plate. pass number.

380-s | DECEMBER 1982