CA1045958A - Welding electrode - Google Patents

Abstract

Abstract of the Disclosure Directed to a welding flux and covered electrode, and, more particularly, to covered electrodes having a nickel-chromium-iron alloy core and a special flux coating or covering, which electrode is capable of joining similar and dissimilar metals and which produces, in all positions, sound welds free from cracking and porosity and deposits having excellent corrosion resistance.

Description

~o4~ 8 In Canadi~n application Serial No. 186,452, certain improvements relating to covered electrodes were described, particularly covered electrodes having a nickel-chromium-iron a~loy core and a special ~lux coating or covering, which electrode is capa~le of joining similar and dissimilar metals and which produces, in all positions, sound welds free from cracking and porosity and deposits having excellent corrosion resistance.
More specifically, in my prior application I set forth that the core wire is made ofa nickel-chromium-iron alloy which contains, in per cent by weight, up to about 0.1% carbon, up to about 2% manganese, up to about 2.5% silicon, from about 24% to about 32% chromium, up to about 5~ titanium, up to about 5~ aluminum, up to about 25~ iron, and the balance, in an amount from about 50% to abau~ 67%, esslentially nickel.
Preferably, the core wire contains, in 'per cent by weight, up to about 0.05% carbon, up to about 1~ m,~nganese, up to about 1% silicon, from about 27~ to about 31~ chromium, up to about 1~; titanium, up to 1% aluminum, from abl~ut 8% to about 12 iron, and the balance, in an amount from about 52% to about 65%, essentially nickel. As will be understood by those skilled in the art, the use of the exprl3ssion "balance essen-tially" does not exclude the presence oE other elements commonly present as incidental elements, e.g., deoxidizing and cleansing elements, and impurities ~ormally associated therewith in small amounts which do not adversely affect the novel characteristics of the alloys.

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The ~lux coating contempl~ted contained, in percent, by weight of ~he dry flux, a mixture comprising from about 10~ to about 26% calcium carbonate, from about 5% to about 20%
barium carbonate, from about 10% to ~bout 23% titanium dioxide, up to about 4~ aluminum oxide (alumina), from about 20~ to !
about 30% cryolite, preferably about 24% to about 26% cryolite, ~-from about 10% to about 18~ manganese, from about 2.4% to about 7.2% columbium and up to about 10% chromium.
It has now been discovered that for the welding of austenitic and ferritic steels to each other and to high nickel alloys, there exists an advantageous combination of a colum~
bium- and/or tantalum-containing core wire and a flux coating containing in addition to those ingredients above specified, supplemental additions o~ chromium oxide and molybdenum.
It is an object of the present invention to provide a novel covered electrode having desirable characteristics for welding austenitic and ferritic steels to each other and to high nickel alloys.
Other objects and advantages will become apparent from the following description, treated as modifying the aforequoted section from application Serial No. 186,~52~ and all other parts of the disclosure of said application. `;
Generally spea~ing, in accordance with the present invention, tantalum can be present in an a~ount up to about 1%
and columbium can be present in an amount up to about 2% in the core wire of the covered electrode. The flux coating contem-plated')by the present invention contains from about 1.8~ to -about 7.2% columbium and in addition to the ingredients speci- ;
fied in the prior application, up to about 3~ chromium oxide and up to about 7.2% molybdenum. It is preferred that when the columbium is from 2.4% to 7.2~ either or both chromium I oxide or molybdenum is present.

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An illustxative exampl~ of core wire and f~ux com-positions of w~ldinq electrodes particularly suitable for the welding of austenitic ~nd ferritic citeels to each other and to high nickel alloys are shown hereinbelow in Tables I
and II, respectively.
TABLE I

:
C : Mn : Si : Cr : Ti : Al : Fe! : Ni: Cb : Ta BROAD RANGE
UT O.l:UT 2.5:UT 2.5:14-l8:Urr 5:UT S:UT 25:Bal:UT 2*:UT l* -~
PREFERRED RANGE
UT .05:UT 1 :~T iL :15 - 17:Ur~ l:UT 1: 6-8 :Bal:UT 1.5*:UT 0~5*
*Cb + Ta = 1.5-3.0 UT = up to TABLE II

_ CaCO3:BaCO3:TiO2 llA1203:Cryolite: Mn: Ck) :Cr203 : Mo Cr PREFERRED RANGE
12-20:12-20:12-20: 1-2 : 2~-26 :4-a:1.~l-6:0.5-2 :1.8-6 : 1-6 :
AIM COMPOSITION , 17 : 16 : 16 : l : 25 : 7 : 5.4 : 1 : 3 : 3 .
Note: +3~ Bentonite extrusion aid and 15% sodium silicate binder : !
It is essential that all of the far~going ~uxingredients be present in the amounts specified in cirder to provide coated electrodes suitable ~or producing sound joints which are free from cracking and porosity and which prc,vidé excellent operating characteristics in all welding position~;.
As shown, chromium oxide may be present in the flux I ~`
composition in amounts up to about 3~ It has been found, as will be shown hereinbelow in Table III, that a small addition of chromium oxide to the flux, i.e., 1%, had a varying effect on the operability of the electrodes contemlplated in this invention.

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For example, for the electrodes shown in my prior case~ the chromium oxide had no noticeable effect on the operability of the electrodes, whereas, or electrodes as contemplated herein-above in Tables I and II, a 1~ chromium oxide c~ddition improved arc stability. At 4% chromium oxide levels, however, it WdS
found that the penetrating characteristics of these electrodes became excessive and burning-through the plate rather than welding of the plate resulted.
Molybdenum may be added to the flux coating in amounts up to about 7.2~ to provide resistance to weld metal cracking.
Molybdenum may also be added through the core wire. Molybdenum has been found to be especially beneficial in welding electrodes as described in Tables I and II and is preferred in accordance herewith at a level of about 1.8% to about 6%.
For the purpose o~ giving those skilled in the art a better understanding of the invention, the following il-lustrative examples are given.
EXAMPLE I
-To demonstrate the excellent operability of electrodes of this invention, various flux compositions, shown herein-below in Table III, were used to coat 0.318 cm. diameter core wire, the compositions of which are shown hereinbelow in Table IV. Also shown in Table IV, are the compositions of alloys `
used in welding tests described hereinbelow. Table V correla-tes khe flux and core wires compositions of the completed electrodes.
TABLE III
:
Flux Composltlon, Weight Percent 3 3 iO2:A1203:Na3AlF6: Mn :FeCb : Cr :Cr203:FeMo No. ~
.
1 : 16 : 16 : 16 : 1 : 25 : 9 : 10 : 0 : 1 : 6

2 : 17 : 16 : 16 : 1 : 25 : 7 : 9 : 3 : 1 : 5

3 : 17 : 16 : 16 : 1 : 25 : 7 : 9 : 3 : 1 : 5 -

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~4~95~3 'rABLE IV

Alloy~ Composition in Weight Percent No. . C : Mn : Si: Cr : Al : Ti : ~lg : Fe :Cu :Ta : Cb : Ni :
.
1 :.031: .32:.22:16.4: .057: .35:.035:7.6 :.04:.50:1.08:Bal.
2 :.022: .18:.26:16.4: .055: .32:.1)30:7.1 :.02:.60:1.29:sal.
3 :.12 : .54:.32: ~ :Bal.: ~ - : 8.9 4 :.022:1.25:.34:19.5:<.01 :C.05: ~- :Bal.: -: -: - :10.2 :.03 : .86:.33:20.9: .36 : .44: :Bal,; - : - : - :31.8 6 :.05 : .12:.21:16.1: .1 : .22:0,iO2:6.6 : - : - : - :Bal.
7 :.003: .65:.07: - : - : .49: - : .46:Bal: - : - :30.5 8 :.05 : .88:.39:20.9~ Bal.: - : - : - :3Q.4 9 :.1~ : .41:<.1: - : .06 ~ :Bal : - : - : - : -: _: : :
Thé flux coating of this inveiltion can be applied to the core wire in any suitable manner, e.g., by an extrusion process, and dried on the wire surac~3 by drying and/or baking.
It has been found that satisfactory e:Lectrodes may be prepared by thoroughly dry mixing the flux ingr~edients and bentonite (consisting of ~ine powders about -80 or -100 mesh) in a suitable blending device, e.g., a mulLer, for about 2 to 3 minutes. A sodium silicate water sol!~tion is then slowly added to the mixture and the blending contii~ued until a homogenous mixture is obtained, usually about 3 Ito 5 minutes. In parts by weight of the dry ~lux, bentonite, at a level of about 3~, a~d sodium silicate ~as a 47 Baume wi~ter solution) at a level ofl about 15%, is preferxed. Bentonit~3 is a co11Oidal clay and i91 commonly used as an extrusion aid Ln the manufacture of covered electrodes and the sodium silicate is commonly used a~; a binding agent to hold together the other mineral and me~tallic ingredients of the flux coating after extrusion and b~lking. The manganese and chromium wlere added as electrolytic ¦ `

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~34595~3 powder, and the columbium as ferrocolllmbium containing 60~
columbium. The chromium oxi~e used WclS a w~lding grade powder.
The electrodes were prepared by extrusion and baked at 370~C
for 2 hours to provide a hard adherenl: coating of high mechani-cal strength relatively resistant to mechanical damage under normal handling conditions.
TABLE V

Electxode;Core Wire - Al~loy No.:Flux No.

.1 : 1 : 1 .
,2 : 1 : 2 ~ : 2 : 3 -- .
Operabili~ty tests were conducl:ed on a 1.27 cm. thick grooved metal plate, of the composition shown for Alloy No. 8, in the flat, vertical-up and overhead positions. The plate ~ ;
had a 60 V-bevel which extended to a depth of 0.95 cm., the base of the V-bev~31 being 0.48 cm. wi~le. This configuration simulates the geometry found in the s~cond weld pass of a 60 !
~-bevelled joint. All welds were conducted at 85 amperes DCRP ~Direct Current Reversed Polarity) using the same rectified power source. As will be appreciated by those skilled in the art, this weld is considered to be the most diEEicult pass in the multipass weld. The electrodes w~re found to be com-mercially operable, and comparison wil:h a commercial welding electrode showed the electrodes of th~ invention to have a more stable arc, less spatter (expulslon of molten metal from the arc) improved slag Eluidity, Eine~- txansfer size, con-siderably better final bead appearance and improved ease of slag removal. Additionally, radiographic tests for the over- -head position welds showed greater than 20 pores/cm. in the single bead deposit for the commercia-L electrode and virtually no pores for the electrode of this invention.

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EXAMP~E II
To clemonstrate the ~bility of electrodes o~ this invention to weld simiIar and dissimilar alloys, various plate materials, shown hereinabove in Table IV, were welded. The welding details and result of tests are shown here~nbelow in Table VI. The "flat" position shown in Table VI consisted of welding a single U-groove (15 bevl21, 0.6 cm. radius, 0.24 cm. root ~ace and 0.31 cm. root opening) weld. The "c,verhead" position consisted of a 0.95 cm. thick butt weld (60 V-butt joint) in which the first pass was made in the flat position. Eight-passes were reqllired to fill the 60 V-butt joint and intentional restrikei3 (weld bead inter-rupted and a fresh electrode started) were made in each pass.
The welded joints were radiographical;Ly examined, cut into transverse slices (about 6 or 7 slice~; per welded joint) polished, etched with Lepito's reagent: and microscopically examined for defects at lOX. The bencl tests were performed by bending two 0.95 cm. thick transvexse slices from each weld 180 about a 3.8 cm. diameter pin.
The results of tensile and Charpy V-notch impact tests on coupons cut fom the transverse slices from weld Nos. 2, 4 and S are shown in Table VII and illu~ltrate the excellent tensile properties and toughness of wellds made with the covered electrode o this invention.

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TABLE; VI I

Weld: o.o 2 % . U . T . S .,: Elong ., : R . A .: Fracture: Charpy v-Notch @-195C.
No.: Y.S.,:
: 2 2 :(2.54cm): :Location:Con- :Touyh-:Laterial N/~un N/mm 96 : 96 : :di-tion:nesc., :Expan-: : : : :joule :sion, cm :
2 : 337.1: 555.7 : 27.5 :71.2: Plate : - : N.T. : N.T.
4 : 310.3 493.0 : 18.5 :51.2: Pla~e : - : N.T. : N.T.

5 : 434.4: 685.3 : 14.5 :38.0: Weld : As- : 8a : .142 : : : : : :Welded:
: : : : : :Aged 2:100 : .170 : : :hrs./ :
: : : : : :565C : : ~.
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Although the present invent on has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope o the invention, as those skilled in the art will readily understand. Such modi~ications and variations are consiclered to be within the purview and scope of the invention and appended claims. For example, the composition of the core wire may contain up to about 1~ carbon, up to about 15% manganese, up to about 50% chromium, up to about 5% titanium, up to about 2% aluminum, up to about 70~
iron, up to about 90~ copper, up to about 10% molybdenum, up to about 6% columbium, up to about 3~ silicon and the balance essent~ally nickel~

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Claims (8)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A flux composition containing, in weight percent, from about 10% to about 26% calcium carbonate, from about 5% to about 20% barium carbonate, from about 10% to about 23% titanium dioxide, up to about 4% aluminum oxide, from about 20% to about 30% cryolite, from about 10% to about 18% manganese, up to about 10% chromium, from about 1.8% to about: 7.2% columbium, from 0%
to about 3% chromium oxide, and from 0% to about 7.2% molybdenum with the proviso that when the columbium is from about 2.4% to about 7.2%, either or both chromium oxide or molybdenum is also present.

2. A flux composition in accordance with claim 1, wherein chromium oxide is from about 0.5% to about 3%.

3. A flux composition in accordance with claim 1, wherein molybdenum is from about 1.8% to about: 6%.

4. A flux composition in accordance with claim 1, wherein the columbium is from about 1.8% to less than about 2.4%.

5. A flux composition in accordance with claim 1, wherein the cryolite is from about 24% to about 26%.

6. A flux composition in accordance with claim 1, which comprises from about 12% to about 20% calcium carbonate, from about 12% to about 20% barium carbonate, from about 12% to about 20% titanium dioxide, from about. 1% to about 2% aluminum oxide, from about 24% to about 26% cryolite, from about 4% to about 8% manganese, from about 1.8% to about 6% columbium, from about 1% to about 6% chromium, from about 0.5% to about 2%
chromium oxide and from about 1.8% to about 6% molybdenum.

7. An all-position welding electrode having a core wire containing, by weight, up to about 1% carbon, up to about 15%
manganese, up to about 50% chromium, up to about 5% titanium, up to about 2% aluminum, up to about 70% iron, up to about 90% copper, up to about 10% molybdenum, Up to about 6% columbium, up to about 3% silicon and the balance essentially nickel, and a flux coating of the composition defined in claim 1.

8. An all-position welding electrode in accordance with claim 7, wherein the cryolite is from about 24% to about 26%.