US2875104A - Slag-forming welding electrode - Google Patents

Description

' S. S. BERGH ETAL SLAG-FORMING WELDING ELECTRODE Feb. `24, 1959 Filed May 16, 1955 weld ng elecTrode Tube .9v agnTm n l ng Slgmphase slgnors to Wargns Aktiebolag, Vargon, Sweden, a Swedishompany y Apl'inaabi May is, 1955; sei-'ral No. 508,766 v 4claims priority, appliatia sweden July 31, 195s 17 claims. (c1. 117`2os) This application isa continuationin-part of our application Serial No.l380,862, filed September 17,1953, Slag forming welding electrodes are Vofntwo types, namely those having a core of iron or iron alloy witha slag' forming coating and those having a 1shell or tube of iron or `iron alloy lledwiththe slag forming material. In both cases metals and erally are lincluded with the slag formingmaterial. lhe purpose of such metal or metal alloy additionsis to alloy with the coreor shell metal and also to effect deolgidation, Eor this purpose bothV pure metals 4and `metal alloys such asironv alloys e.; g. ferromnganese and ferrosiliconfor leoxidation and. purenickel, ferrochromium and ferromolybdenum fc'Jr'alloying have been used. It :hsbee'n shown. tl'ratlthel commercial lon/,carbon ferrochrome with a chromium content of 65773% is very diflcult to pnlverize which makes the resulting' po wder relatively expensive and limits its use Yin welding electrodes., i.

The object of 'thep'resent invention is to producerjless expensive weldingl electrodes bythe use of powderof iron alloyI with a lower'chromium content thantheplow, carbon arent alibi/S in powdered form gen- 1 ferrolchr'orne referred4 to above butnot asflow as ,thatn of the :well known steels, A. ,1 v g: n

`ironchro'inirnn alloys, in p state; of sigma phase,` having' l l 60% and the customary silicon and carbon contents have beerrioundrto lbe lvery brittle prsapableoffbeing made brittle,` With purei irori-febrornium necessary to` subject' rhein'to heat:v eatmenete develop brittlenessbit brittlen'esscanbe developed also by additions 0f fsttain elements su ca fase;Si,` A1,.M, W, V, Ti, Zr, Cb, 'I`,a, a nril iand M Y Veseelements may be added in sucllA substantial" ani nts" that',` Awithout noteworthy lossfof the `brittle property, other alloying metals may be used-such .as.Cu, i persepare indifferentorwhich `counteract the sigma phase formation; A highcontent ofnickel'eor manganese `counteracts Cthe sigma .phase formation. "It4 is possible, khowever; to add nickel andmanganese in high quantitiesprovided thatone or more ofthe aforesaid sigma promoting elementsispresent in asufcient quantity. u WAccording tothe invention,.saidsigmaphase formation is utilized in order to simplify the pulverization for manufacturing a powder to be used in welding electrodes and thereby lower the cost of the electrodes, and improve their quality. Some metals, e. g. nickel, cobalt and copper, are in pure form too soft to be ground into powder. When incorporated into a brittle sigma phase alloy, however, said soft metals may easily be ground together with the other elements contained in the alloy.

A phosphorus content of up to 1%, preferably 0.1% to 1%, a silicon content of up to 10%, preferably 1% to 10%, a molybdenum content of up to 10%, and a nickel content of 5% to 30% has been found suitable. It has been found that nickel may be replaced, wholly or partially, by manganese. Thus, e. g. in an alloy of the kind stainless and heat resisting iron-'chromiumV llos/.S it generally isa chromium content between about 30% and about Y `Co-and other metals, which vcrentlybrittle, the 'desiredybrittleness can be imparted b'ye heattreatment at a temperature within the range 600,-8S 04C. -,Aswilllbeseen from -the above, .the vbrittle alloys, .the powders otfwhichv are to be used in weldingelectrodes, depending upon .their compositions, arey either brittle as they are formed without any special embrittling treatment, orthey are 'cooled from the liquid state under conditions designed to develop brittleness i. e. by cooling more or less slowly through-the range Ifrom 880 C. to 600 C. orY they are embrittled by being heated up for a sulficiently long time to within the range 600 C. to 880 C., preferably about 800 C. and then cooled. The brittle alloys are then pulverized and incorporatedinto the weld-v ing electrodes as cores or shells along with the slag forming materials n the customary way.

Welding electrodes of the two types referred to'are illustrated in the accompanying drawings in which: ....Fig. ..1 is .a-longitudinal section ofa welding electrode havingfa solid core and aYslag-formingcoating containing thesigma phasealloy, and Fi g 2 i?? longitudinal gestion 0f a weldirialelectrcde having `a shell or tube of the welding metal and an inner Slasffcrmina matins'. Contaiuiiigilhei s igralnhse alloy- Whensuch an electrode is used, the brittle alloy powder contained in thleshelbwill be reinelted and `simultaneously dilutedwith thecore metal, e.-g. iron or nickeLjto'such annlentengt'thatgthe brttleness disappears, i. e. the compositionfoflthe resultingY alloy does not lie within the sigma phrange. Y i If the electrode consistsof an iron or nickel tube anda. slag forming core containing an alloypowder in the sigma form, the same thing will occur when the electrode is used. Y

Qwing tothe ternary, quaternary or still more complexcompositiori of sigma alloy, itsfmelting point is generally essentially lower compared to that ofbrinary alloys. This isylof very greep-importance whenthe ,alloyL is usedl for the manufacture Aof.,welding Aelectrodes and particularly when the electrf'deh is to' contain powders'of metals melting atv high temperature, e. g. tungsten. When usingthe'electrode, the .powder, the core: material and possible iluxing agents are melted in the arc,and the meltsare mixed in afshort time, a low. melting point being of the greatest importance.: .f A N f Y v y l By practicing the fundamental idea of the invention it is, possible'. directly wh `ch when used for welding electrodes of the types stated herein, `c'oiribine .in themselves the properties ofA previously addeddeoxidants, e. g. ferrosilicon and ferromanganese,

A porated inthe weld and to improve its properties in one wayforanothenme. g. forincreasing the yresistance to corros'inor erosion, increasing the refractoryy properties, improving the hardness, tenacity, or the like. These properties areV obtained by suitably adapting the alloying elements in the powder, while considering the general rule that the composition shall be chosen so that a phase transformation can be obtained, which effects the brittleness. Thus, by suitably increasing the contents of silicon and manganese, it is possible to obtain a desired deoxidizing effect without loss of more expensive alloying elements. Further, by suitably adapting the nobler alloying ingredients, such as chromium, nickel, molybdenum, copper, cobalt, tungsten and carbide forming elements such as titanium, vanadium, columbium, tantalum and zirconium, it is possible to obtain such a composition of to mea'mi'factlvireY uniform powders,V

with an unalloyed or alloyed core or case, on melting of the electrode there is produced a weld of corrosion-resisting or refractory properties and with a content of alloying elements which is at least as high as in the material, e. g. stainless steel, which is to be welded with said electrode, and consequently with at least as good properties as this material. If, according to these directions, there is to be manufactured a powder for use in electrodes with a low alloyed or unalloyed core, and the electrodes are to give a material in the Weld of the so-called 18/8- type, i. e. a material containing about 18% chromium and 8% nickeland possibly also containing other metals which improve the properties, such as manganese, molyb'- denum, copper, aluminum, tungsten and carbide forming elements and others, the alloy from-which the powder is manufactured according to the invention shall contain chromium and nickel and other alloying elements in such a ratio that the weld obtains the desired composition. When welding, there is usually a loss of chromium and, therefore, the ratio chromium to nickel should preferably be somewhat higher in the sigma alloy than what is desired in the weld.

As examples of compositions of alloys of the kind referred to herein which are brittle, the following may be cited.

Table Percent Per- Per- Per- Per- Per- Per- Per- 'Per- Per- Cr cent cent cent cent cent cent cent cent;l cent N1 M0 Cu Al Si Ti Cb C0 P The rest in each case consists of iron with the accessory elements or impurities usually contained therein.

As a rule it can be said that the necessity for heat treatment decreases with increasing contents of elements such as silicon, molybdenum, tungsten, titanium and vanadium.

The invention is not limited with respect to theV nature of the slag forming ingredient or the binder when the alloy powder is used in a welding electrodecoating. The coating may be acid, neutral or basic.`

We claim:

1. A welding electrode consisting essentially of a rod consisting principally of a metal selected from the group consisting of iron and nickel and a slag forming coating thereon, said coating` containing a, brittle sigma phase iron-chromium alloy having a chromium content of E10-60%, the ingredients of the coating and the rod being capable of forming an alloy which does not contain sigma phase when the electrode is used -for welding.

2. Electrode as defined in claim 1, in which the ironchromium alloy also contains nickel in quantity amounting to from to 30%. Y

3. Electrode as defined in claim 2, in which at least Y part of the nickel content is replaced by manganese, 1%

of manganese replacing about 0.5% of nickel.

4. Electrode as defined in claim 1, in which the ironchromium alloy also contains molybdenum in quantity up to 10%.

5. Electrode as defined in claim 1, in which the ironchromium alloy also contains silicon in quantity up to 10%.

6. Electrode as defined in claim 1, in which the iron? chromium alloy also contains phosphorus in quantity up to 1%.

7. Electrode as defined in claim 1, in which thewiron chromium alloy consists essentially of 58% of chromium, 2.0% of silicon and 40% of iron.

8. Electrode as defined in claim l, in which the ironchromium alloy consists essentially of 51% of chromium, 1.5% of silicon and 47.5% of iron.

9. Electrode as defined in claim l, in which the ironchromium alloy consists essentially of of chromium, 7% of nickel and 48% of iron.

l0. Electrode as defined in claim l, in which the ironchromium alloy consists essentially of 47% of chromium, 12% of nickel and 41% of iron.

11. Electrode as defined in claim 1. in which the ironchromium alloy consists essentially of 42% of chromium, 19% of nicke14% of silicon, 0.2% of phosphorus and 34.8% of iron.

12. Electrode as defined in claim l, in which the ironchromium alloy consists essentially of 47% of chromium, 19%V of nickel, 4% of molybdenum and 30% of iron.

13. Electrode as defined in claim l, in which the ironchromiumalloy consists essentially of 43% of chromium, 19% of nickel, 5% of molybdenum, 4% of copper and 29% of iron.

14. Electrode as defined in claim l, in which the ironchromium alloy consists essentially of 43% of chromium, 21% of nickel, 2% of titanium, 4% of columbium and 30% of iron.

l5. Electrode as defined in claim l, in which the ironchromium alloy consists essentially of 44% chromium, 18% of nickel, 6% of molybdenum, 8% of copper and 24% of iron.

16. Electrode as defined in claim 1, in which the ironchromium alloy consists essentially of 45% of chromium,

12% aluminium, 8% of silicon, 12% of cobalt and 23% of iron.

l7 Electrode as defined in claim l, in which the ironchromium alloy consists essentially of 35% of chromium, 51% of titanium, 45% of cobalt and 15% of iron.

Claims (1)

1. A WELDING ELECTRODE CONSISTING ESSENTIALLY OF A ROD CONSISTING PRINCIPALLY OF A MENTAL SELECTED FROM THE GROUP CONSISTING OF IRON AND NICKEL AND A SLAG FORMING COATING THEREON, SAID COATING CONTAINING A BRITTLE SIGMA PHASE IRON-CHROMIUM ALLOY HAVING A CHROMIUM CONTENT OF 30-60%, THE INGREDIENTS OF THE COATING AND THE ROD BEING CAPABLE OF FORMING AN ALLOY WHICH DOES NOT CONTAIN SIGMA PHASE WHEN THE ELECTRODE IS USED FOR WELDING.

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