GB2155045A - Flux cored wire electrodes - Google Patents

Abstract

There are disclosed flux cored wire electrodes for self-shielded arc-welding which comprise a steel sheath filled with a powdery flux containing as essential components thereof the following components: BaF225-70, alkali metal fluoride 1-30, compound oxide composed of the oxide of an alkaline earth metal selected from among Ca, Sr and Ba and the oxide of a metal selected from among Fe, Mn, Ni, Co, Ti, Al and Zr 1-30, Al 3-12, Mg 2-10 and Mn 0.5-10 percent by weight.

Description

SPECIFICATION Flux cored wire electrodes for self-shielded arc welding BACKGROUND OF THE INVENTION 1. Field ofthe Invention This invention relates to a flux cored wire electrode for self-shielded arc welding. More particularly, it relates to a flux cored wire electrode which is capable of providing weld metal having high toughness and free from welding defects such as pits and incomplete fusion, upon welding in any welding position.

2. Description ofthe Prior Art Flux cored wire electrodes comprise a metal sheath filled with a flux. The main components of the flux generally used in said electrodes are CaF2, which serves as a slag-forming and shielding agent, Al, which serves as a deoxidizing and denitrifying agent, and Mg, which serves as a deoxidizing and shielding agent. The use of such flux cored wire electrodes makes it unnecessary to separately supply a shielding gas and a flux, hence is advantageous in that an improvement in welding efficiency is produced. Furthermore, such electrodes are excellent in weather resistance and have various other advantages.

At present, however, said wire electrodes are used only in specific instances ofoutdoorwelding in civil engineering and construction and so on. Therefore, their advantages can hardly be said to be fully enjoyable. As the reasons for such limited use and delay in their coming into wide use in otherfields, there may be mentioned the following disadvantages: (1) Since MgO and Al203, the both having high melting point, derived, for example, from Al, which is added as a deoxidising and denitrifying agent, and Mg, which is added as a deoxidising and shielding agent, constitute the main components of the resultant slag, slag inclusion can easily take place, especialyin multilayerwelding.

(2) In addition to retention of a large amount of awl in the deposited metal, crystal grains tend to become coarser as a result of extraordinary decrease in oxygen (about 50-100 ppm), so that satisfactory notch toughness cannot be obtained.

(3) The resultant slag and molten metal assume an excessively high surface tension, so that bead dripping is aptto occur in the vertical-upward position or overhead position.

(4) The optimum arc voltage range is narrow, so that strict control ofthevoltageand/orelectrode extension is required for the elimination of pits and blowholes.

(5) Since Mg and CaF2, which have high vapor pressure, are used in large amounts as flux constituents, a large amount of fume is generated and contaminates the working environment to a consider able extent.

SUMMARY OF THE INVENTION Accordingly, it is an object of the invention to provide flux cored wire electrodes free from the drawbacks such as mentioned above. Another object is to provide flux cored wire electrodes with which their characteristic weather resistance can be made the most of.

The present invention providesflux cored wire electrodes comprising a steel sheath filled with a powderyflux containing, as essential components thereof, the following components: BaF2: 25-70 weight percent Alkali metal fluoride: 1-30 weight percent Compound oxide composed ofthe oxide of an alkaline earth metal selected from the group consisting of Ca, Sr and Ba and the oxide of a metal selected from the group consisting of Fe, Mn, Ni, Co, Ti, Al and Zr: 1-30 weig ht percent Al: 3-12 weight percent Mg: 2-10 weight percent Mn: 0.5-10 weight percent.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings; Fig. lisa graphic representation ofthe changes with time in moisture absorption by LiF, Li2SiO3 and LiBaF3; Fig. 2 is a graphic representation ofthe effect of LiBaF3 on the optimum arc voltage range; Fig. 3 is a graphic representation of the effect of Zr on the notch toughness of the weld; and Fig. 4 illustratesthe groove employed in some welding experiments.

DETAILED DESCRIPTION OF THE INVENTION The grounds on which the components of the powderyflux according to the invention have been specified are described hereinbelow.

First, BaF2 is used as a major slag-forming component in an amount of 25-70%. As compared with CaF2 SrF2, which are conventional slag-forming materials, BaF2 is superior in droplet migration and shielding capacity. Furthermore, BaF2 can effectively prevent the dripping of molten metal in the vertical-upward position. The above characteristic features become especially significant in the case of straight polarity (electrode negative) direct current arc welding. At BaF2 levels lowerthan 25%,the use of BaF2 is not so effective any more in the above aspects. More than 30% of BaF2 is used to effectively attain the shielding.

Conversely, at levels exceeding 70%, the slag formation becomes excessive, so that welding defects such as slag inclusion are easily formed and the welding performance is reduced.

When evaluated as a slag-forming material, BaF2 has some disadvantages. Thus, BaF2 has the property of making the weld penetration shallower as com pared with the conventional CaF2, SrF2, etc. Furth ermore, BaF2,togetherwith A1203 and MgO,which are reaction products from Al and Mg added as deoxidis ing and denitrifying materials as described hereinbe low, forms a high melting point slag, so that welding defects, such as slag inclusion and incomplete fusion, are readily developed. Moreover, the luster and appearance of beads are not always good.

The drawing(s) originally filed (were) informal and the print here reproduced is taken from a later filed formal copy.

This print takes account of replacement documents submitted after the date of filing to enable the applicant to comply with the formal requirements of the Patents Rules 1982.

To cope with these negative features of BaF2, there are combinedly used in accordance with the invention (1) an alkali metal fluoride and (2) a compound oxide composed of an alkaline earth metal oxide and a metal oxide to be described below.

The fluoride of an alkali metal (Li, K, Na, Rb, etc.) performsthefunctionsofadjustingthemelting point and viscosity of the resultant slag, potentiating and stabilizing the arc, and thereby causing deeper penetration and inhibiting flaws such as slag inclusion and incomplete fusion from occurring. For securing these functions, an amount of not less than 1% is required. However, at addition levels exceeding 30%, the flowability ofthe slag becomes excessive, so that the bead appearance of the slag becomes worsened and, in the vertical or overhead welding position, the dripping of molten metal becomes remarkable.Since the moisture in the flux causes pore formation in the weld metal, Na2ZrF6, K2SiF6, Na2SiF6, Na3AIF6, Rb2SiF6, K2TiF6, K2ZrF6, Liy and LiBaF3, which are not very hygroscopic, are suited for use as the alkali metal fluoride. They may be used eithersingly or in combination.Amongthem,LiBaF3,which is a compound alkali metal fluoride, is a flux constituent having satisfactory slag-forming, shieiding, penetration-improving and arc-stabilizing effects and furthermore is characterised in that its inherent moisture content is small and that it isvery sparingly hygroscopic. The use of a flux in which LiBaF3 is a major constituent can prevent porous and otherdefects resulting from moisture (in otherwords, hydrogen), such as pits and blowholes, to the possible utmost extent.

Fig. 1 shows the changes with time in moisture content in LiF, Li2SiO3 and LiBaF3, which are said to be relatively low in inherent moisture and hygroscopicity among alkali metal compounds. The term "inherent moisture" as used herein means the moisture content (inclusive of water crystallization, moisture absorbed, etc.) directly after manufacture. The increments in moisture content were determined by allowing each sample to stand (30"C, 80% relative humidity) for a specified period and determining the moisture released upon heating at 1,00000.

As is evidentfrom Fig. 1, LiBaF3 is very low in inherent moisture and hygroscopicity as compared with Liy and Li2SiO3. Therefore, the use of LiBaF3 as a constituent of a flux reduces the whole hydrogen contentinthefluxto a lowlevel,wherebythe formation of hydrogen-caused porous defects such as pits and blowholes can be prevented to the utmost possible extent and accordingly the arc voltage range adequate to produce satisfactoryweld zones can be enlarged.

Fig. 2 graphically shows the results of an experiment in which flux cored wire electrodes having a diameterof2 mm were produced by filling a mild steel sheath with a powderyflux prepared by adding 0-32% of LiBaF3to a basic composition consisting of 40% BaF2,7% Al, 8% Mg, 3.5% Mn, 0.5% CaO and the balance Fe (the amount oftheflux being 20% based on the whole electrode weight), followed by drawing the sheath with the flux, and used in test welding for investigating the effect of LiBaF3 on the resistance to pitformation(optimum are voltage range).The welding conditions andtest method were as follows: Welding current: 250 (A); welding speed: 20 (cm/ min); current and polarity: DC, wire (-); wire exten- sion: 25 (mm); torch angle: 00. Flat steel sheets (JIS G 3106,SM-50,25mmthickx 500 mm long) were welded together in 1 pass in the flat position underthe above conditions and the welds were subjected to radiography (JIS Z31 04). The voltage range in which the defects as judged from the radiographs were classifiable among type 1, class 1 was regarded as the optimum voltage range. The voltage at which thewire electrodes stuck out was regarded as the lower limit of said range.

As is evidentfrom Fig. 2,the optimum arc voltage range increases with the increase in the level of addition of LiBaF3. Incorporation of LiBaF3 in an amount of 5% or more sharply enlarges the optimum arcvoltagerange.Additioninamountsofl0% or more preferably results in very good resistance to pit formation.

The compound oxide composed of the oxide of an alkaline earth metal selected from the group consisting of Ca, Sr and Ba and the oxide of a metal selected from the group consisting of Fe, Mn, Ni, Co, Ti, Al and Zr improves the appearance and luster of beads and increases the siag shielding effect and furthermore hastheeffectofimproving the notch toughness by supplying the deposited metal excessively deoxidised bystrongdeoxidising materials such Al and Mg,with oxygen.Furthermore, the compound oxides composed of Sramong them has the effect of improving the arc stability. Forthese functions to be performed efficiently, the flux should contain the above compound oxide in an amount of not less than 1 %.At levels exceeding 30%, however, droplets become excessively large, so that spatters are frequently generated in large numbers and the peelability of the slag becomes worsened.

The above-mentioned alkaline earth metal oxide easily absorbs moisture and C02 in the air and has a high melting point. Therefore, single use ofthe same may easily lead to welding defects such as pores and slag inclusion and to frequent and abundant spattering. In spite of the above, the formation of a compound oxide between the above two metal oxide classes gives a stable and sparingly hygroscopic compound.

Furthermore, the compound oxides comprising the oxides of Fe and Mn have a lower melting point as compared with the alkaline earth metal oxides alone.

The compound oxides to be used in accordancewith the invention can be represented by the general formula MxNyOzwherein M is Ca, Sr or Ba, N is Fe, Mn, Ni, Co, Ti, Al orZr and x, y and z are each a positive number. Typical examples of the compound oxide wherein M is Ca are CaFe204, Ca2FeOs, Ca2MnO4, 0amen204 and 0amen3010, typical examples of the compound oxide in which M is Sr are wsr2FeO4, Sr7Fe10022, SrFeO25, Sr2Fe2Q5, Sr3SiO5, SrSiO3, SrMnO3, Sr2MnO4, Sr3Mn207, SrNiO3, SrTiO3, Sr3A1206 and Sr2ZrO4, and typical examples of the compound oxide in which M is Ba are BaFe2O4, Ba(MnO4)2, Ba3NiO4, BaSiO4, BaSiO3 and Ba3SiO4.

However, those compound oxides which contain Si are reduced by Al and Mg, which are strong deoxidiz ing agent, to give Si, which remains in the deposited metal and causes formation of coarse ferrite crystal structure and decrease in toughness. This is the reason why Si is notfound among the essential elements to be used in accordance with the invention.

Al is an indispensable element as a strong deoxidizing and denitrifying material and atthe same time as a nitrogen-fixing agent. It captures oxygen and nitrogen invading from the atmosphere and thereby prevents pore or pit formation. For producing such effects, Al should be present in the flux in an amount of not less than 3%. However, when Al is added at an excessively high level, an excessive amount offal will remain in the deposited metal, making the crystals grains coarser and fragile. Accordingly, Al should be used in an amount not exceeding 12%. As the source of AI, there may be used not only metallic Al but also Al alloys such as Fe-Al, Al-Mg and Al-Li.

Mg performsthestrong deoxidizingfunction. Furthermore, it easily gives a metal vapor upon exposure to the heat of arc and produces an excellent shielding effect. At Mg levels less than 2%, such effects cannot produced to a satisfactory extent and, in addition, the yield of Al used combinedly decreases, whereby the denitrifying and nitrogen-fixing effects of Al are no more produced to a satisfactory extent. Conversely, an excessive amount of Mg leads to a remarkable increase in fume generation, whereby the observation ofthe molten pool becomes difficultto perform and at the sametimethe working environment is contamin- ated. In addition, the quantity of spatters increases and the shielding capacity decreases dueto increase in the viscosity of the slag.Therefore, Mg should be used in an amount of not more than 10%. Metallic Mg may also be used as the Mg source. Since, however, metallic Mg vaporizes in an explosive manner upon exposure to the heat of arc and thereby causes formation of a large number of spatters, it is preferable to add Mg intheform of an Mg alloy such as Al-Mg, Mg-Si, Mg-Si-Ca, Ni-Mg or Li-Mg.

Mn increases the strength of deposited metal. It also causes a reduction in the surface tension of molten metal and thereby adjusts the shape of beads. Mn should be added at least in an amount of 0.5%.

However, at Mn levels exceeding 10%, the strength of the deposited metal becomes excessively high, so that the deposited metal becomes poor in ductility and resistanceto cracking. As the Mn source, there may be used metallic Mn and Mn alloys such as Fe-Mn and Fe-Si-Mn. In addition, MnO, MnO2 and the like oxides as well as Li2MnO3, SrMnO3, Ba(MnO4)2 and the like compound oxides may also be used as the Mn source.

The reason isthatthefluxto be used in accordance with the invention contains large amounts ofthose elements (Al, Mg) which have higher affinity to oxygenthanto Mn and such elementsdeoxidisethe Mn oxides to convert the same to metallic Mn.

The essential components of the flux to be used in the practice ofthe invention are as those mentioned hereinabove. However, for use in fields where notch toughness at lowtemperature (generally -IO"to -60"C) is required, such as in the field of offshore constructions, it is effective to further incorporate one or more of Ni (in an amount of 0.5-20%), Zr (0.1-4%),Ti (0.01-0.5%) and B (0.01-0.2%). For increasing the stability of arc, it is also effective to add the rare earth elements Ce and/or La in a total amount of 0.01-0.5%.

The rear earth elements, when used in an amount of not less than 0.1%, are effective in improving the stability of arc. At addition levels lessthan 0.1%, they are not significantly effective in the above aspect, whereas, at levels exceeding 0.5%, adverse effects are produced.

Thus, for instance, the covering of the slag decreases or marked spattering takes place. As the compounds containing said rare earth elements, there may be mentioned mixed metals and alloys, such as (Ce, La)-Fe-Si and (Ce, La)-Ca-Si, and oxides such as CeO2, Ce203 and La203. In the following, brief mention is made of such secondary additives.

Ni is an austenite-forming element and has the effect of increasing the notch toughness of deposited metal by inhibiting the coarsening offerrite crystal grains resulting from retention of a large amount of Al.

Such effect is efficiently produced at an addition level of not less than 0.5%. However, at addition levels exceeding 20%, the strength becomes excessive and the resistance to cracking becomes poor. As the Ni source, there may be mentioned metallic Ni as well as Ni alloys, such as Fe-Ni-Cr and Ni-Mg, and oxides and compound oxides of Ni, such as NiO and Ba2NiO4.

Zr possesses the effect of improving the notch toughness of deposited metal by making crystal grainsfinerandfixingtheinvading nitrogen. This effect is produced efficiently at an addition level of not less than 0.1%. When the addition level exceeds 4%, the burning/adhesion of slag becomes remarkable, whereby the peelability is worsened. Moreover, the notch toughness rather decreases.Fig. 3 is a graphic representation of the relationship between the Zr contentintheflux and the notch toughness as revealed in an experiment in which flux cored wire electrodes were produced by drawing a mild steel sheath filled with a powderyflux prepared by adding 0.1-5% of Zr in the form of Fe-Zr (Zr: 30%)to a base composition consisting of 50% BaF2, 3.5% LiF, 6% SrMnO3, 9.2% Al, 7% Mg,0.2% Mn, 5% Ni and the balance Fe,to a diameter of 1.6 mm and used in experimental welding.The welding conditions were as follows: Test conditions: Base metal: SM-sOA,sheetthicknessl9mm Welding position: flat position, 7 layers, 13 passes Welding current: 250 A, DC (-) Welding voltage: 21 V Welding speed: 15-22cm/minute Wire extension: 25 mm Notch toughness test: 2 mm V notch Charpy test according to JIS Z 12.

As is evident from Fig. 3, the addition of 0.1-4% of Zrto the flux improved the notch toughness and, especially when 0.5-3% of Zr is added, the improvement is remarkable. As the Zr source, there may be mentioned alloys such as Fe-Zr and Zr-Si, fluorides such as K2ZrF6 and Na2ZrF6, and oxides and compound oxides such as ZrO2, ZrSiO4 (zircon sand) and Li2ZrO3.

Ti, in very small amounts, is effective in increasing the notch toughness. The effect is produced efficiently at an addition level of not less than 0.01%. In this case, the use of Zr in the above-mentioned addition level range and/or 0.01-0.2% of B in combination with Ti can make the above effect more significant.

However, when the addition level of Ti exceeds 0.5%, the adhesion of burnt slag becomes persistent and the appearance of beads and the welding perform ance become worsened. As the Ti sou rce, there may be used not only metallic Ti and such as Fe-Ti but also oxides such as TiO2 and Ti203 and compound oxides such as Li2Ti03, CaTi204 and CaTiO3.

When used alone, B is little effective in improving the notch toughness. However, when used in combination with an appropriate amount of Ti, B potentiates the effect of Ti, as mentioned above. While such effect is efficiently producible at an addition level of not less than 0.01 %,the addition of B in escess of 0.2% leads to decrease in resistance to cracking due to hardening and to decrease in notch toughness. As the source of B, there may be mentioned alloys such as Fe-B, oxides such as B203, and compound oxides such as Li2B407 and Na2B407.

Thefluxmayfurthercontain,as slag4orming agents added either singly or in combination, oxides such as Awl203, MgO, FeO, Fe203, Na 220, K20, LiFe02, Li2MnO3, Li2SiO3 and Six2, fluorides otherthan the alkali metal fluorides, such as CaF2, SrF2, MgF2, BaSiF6, Al F3, MnF2, CeF3 and LaF3, and carbonates such as Li2CO3, Na2CO3, BaCO3, CaCO3, MgCO3, SrCO3 and MnCO3, each in an amount not causing slag inclusion ordecreasein welding performance, preferably in a total amount (inclusive ofthe above-mentioned slag-forming materials, namely BaF2, alkali metal fluoride and compound oxide composed of the oxide of an alkaline earth metal selected from among Ca, Sr and Ba and the oxide of a metal selected from among Fe, Mn, Ni, Co, Ti, Al and Zr) or not more than 18% based on the whole wire weight. For improving mechanical properties, such as hot strength, and corrosion resistance of the deposted metal, there may also be added such elements as Cr, Mo, Cu, Nb, V, Co and P.

Furthermore, iron powder may also be added for increasing the deposition rate or for improving the flowability ofthe powdery flux in the step offilling a steel sheath therewith in the manufacture of wire electrodes.

In theforegoing, the description has been focused on the composition of the flux for use in filling steel sheaths therewith. Another very importantfactorfor efficiently producing the effects ofthe respective components is the rate offilling the flux. The rate of filling should be selected within the range of 15-30% based on the whole wire weight. If the rate offilling is less than 15%, the contents of the respective flux constituents specified hereinabove become insufficient, hence satisfactory effects cannot be obtained.

On the other hand, at a rate of filling exceeding 30%, the deposited metal becomes excessively abundant in Al and other alloys and consequently intended mechanical properties cannot be obtained in some cases and, in other cases, the amount of the resultant slag becomes excessive, whereby problems are encountered, such as marked slag inclusion or decrease in welding performance.

The most common material of the sheath is mild steel. Depending on the intended use, low alloy steels and high alloy steels may also be used. The sectional structure of the slag is not particularly limited although the relatively simple cylindrical form is generally used in cases where the wire diameter is 2 mm or less and a structure made by tucking in the sheath in a complicated manner is generally used for manufacturing wire electrodes having a larger dia meter of about 2.4-4 mm.

In the foregoing, the constitution of the present invention has been outlined. As a result of selecting specific components as the constituents ofthe flux to be filled in steel sheaths, it is now possible to provide flux cored wire electrodes for self-shielded arc welding which can give, in any welding position, excellent weld metals freefrom welding defects such as pits and incomplete fusion and having good mechanical properties (especially toughness).

Thefollowing examples illustrate the effects of the present invention.

EXAMPLES A steel sheath having the chemical composition shown in Table 1 was filled with a powdery flux having the composition shown in Table 2 (filling rate: 20%) and drawn to give a flux cored wire electrode having a diameter of 2 mm.

Using each wire electrode thus obtained, experimental welding was performed underthe conditions given below. The results obtained are shown in Table 3.

Welding conditions: Test sheets: JIS G 3106, SM-SOA, 45 mm thick x 500 mm long Shape of groove: X (Fig. 4) Welding current: 250 (A), DC [wire (-)1 Welding voltage: 21-22 (V) Welding speed: 13-24 (cm/minute) Wire extension: 20 [ UNASSIGNED CODE 3D ] -25 (mm) Method of building up: 8 layers and 14 passes for each oftheface and back Welding position: flat position Back chipping: mill scale removal with a grinder afterarc air gouging Testing methods: Tensile test: JIS Z31 11 Impacttest: JIS Z31 12 Side bend test: JIS Z 312Z Ultrasonictest: JIS Z 3060 Table 1 Composition of steel sheath C Si Mn P S 0.05 0.Q1 0,42 0.007 0.010 (weight percent; the balance being Fe and unavoidable impurities) As is evident from Table 2 and Table 3, the deposited metals obtained in a smooth manner by using the wire electrodes (Nos. 1-7) which met the requirements according to the invention were free of defects, such as blowholes, slag inclusion and incomplete fusion, and had good mechanical properties. In particular, the deposited metals obtained by using the wire electrodes (Nos. 6 and 7) with appropriate amounts of Ti and Zr added to thefluxes and the wire electrode (No.3) with Ti and B added to the flux were very excellent in notch toughness at low temperature (-30 C).On the contrary, the wire electrodes for comparison which failed to meet any of the requirements according to the invention gave deposited metals inferior in at least one of the welding performance, ultrasonic test results and mechanical properties and thus failed to accomplish the objects of the invention.

Table Wire Flux composition (%) Electrode No. BaF2 LiF K2SiF6 LiBaF3 CaFeO4 SrFeO4 Li2MnO3 Al Al-Mg (Mg 60%) 1 (invention) 45 - 5 - - 8 - 3.5 12 2 (") 70 - 1 - - - - 7 3.4 3 ( " ) 25 ~ ~ 8 30 3 6 9 4 (") 32 10 - 20 5 - - 3.5 12 5 (") 45 10 - - - 1 - " " 6 (") " - - 7 - 8 - " " 7 (") " - - " - " - " " 8 (for com- 56 3 - - - - - " 14 parison) 9 (") 54 2 - - - - - " 9 10 (") 55 0.5 - - - 1 - " 12 11 (") 44 32 - - - " - " " 12 (") 55 - 5 - - 0.5 - " " 13 (" ) ! 44 - " - - 32 - " 14 ( " ) # 45 - I 5 - - * 8 - " 15 Table 2 continued Wire Flux composition (%) Electrode no.Mn Ni Fe-Zr ZrSiO4 Fe-Ti TiO2 Al2O3 MgO FeO (Zr 30%) (Ti 40%)2 2 5 1 3 - - - - - - 3 3 2 " - - - - - - 5 " 3 1.6 4 0.5 - - - 4 4 3 " - - - - 2 2 5 s " n n 6 " " - 1.5 - 0.3 " " 2 7 " 2.5 ~ 0.2 " " 8 5 - - - - - - 8 9 " - - 3 3 - - - 15 10 " 4 - - - - - - 11 " " - - - - - - 12 " - - - - - - - 13 " - - - - - - - 14 14 " 4 - - - - - - Table 2 continued Table 3 Table 3 Wire Chemical Composition of deposited metal (%) Elecrode No.

C Si Mn P S Al Ni Zr Ti 1 (invention) 0.05 0.13 0.94 0.007 0.002 0.62 1.42 - 2 (") 0.04 0.06 0.92 0.008 0.001 0.41 - - 3 (") 0.05 0.04 0.90 0.08 0.003 0.52 0.82 - 0.03 4 (") 0.04 0.03 0.93 0.007 0.003 0.88 0.83 - 5 (") 0.05 0.04 0.90 0.008 0.001 0.92 0.85 - 6 (") 0.04 0.05 0.87 0.007 0.002 0.64 0.81 0.01 0.02 7 (") 0.05 0.04 0.91 0.008 0.002 0.66 0.83 0.02 0.02 8 (for comp- 0.10 0.14 0.89 0.007 0.001 0.70 1.04 - arison) 9 (") 0.07 0.15 0.91 0.007 0.003 0.61 - 0.03 0.02 10 (") 0.04 0.03 0.92 0.007 0.003 0.90 0.81 - 11 (") 0.05 0.05 0.89 0.008 0.001 0.98 0.85 - 12 (") 0.04 0.03 0.87 0.008 0.004 0.90 - - 13 (") 0.04 0.03 0.90 0.007 0.001 0.56 - - 14 (") 0.05 0.05 0.95 0.009 0.002 1.43 0.85 - - Table 3 continued Table 3 continued Table 3 continued

Ultrasonic *3 Welding performance *4 ' Wire Test Electrode Defects Flat position Vertical Ascending Position :No. slag | Slag inclus- earanon Quantity Slag Auaeexance Quantity Slag holes ion, inoampl- anf shape 1 of Peela- - and shape of Peela ete fusion ofbeaas spatters bility of be rts ~ Spatters bility 1 none none 0 0 0 0 2 1 tg (3 o ---O--------O '~~O O O 3 none " ~~ 0 O G O O (9 I O O 0 0 0 5 1 1 " 0 t 0 O 6 1 0 0, 0 0 0 0 7 ', ,, t O O t Zo O 8 4 112 mm O A O O t O 220 mm r A ' t~~ ~ 0' 'A o 10 none 150 mm ' A '0' ~ 0 A 0 0 O 11 A A O A A 12 3 1 mum A QX Qf n h 13 2 none O A a n t A A 14 j none , 12 mm 8 o 8 6) 0 0 *1 Tensile test pieces: subjected to ageing treatment at 100 C for 24 hours after mechanical processing but priorto testing.

*2 Side bend test: bending angIe 180" bending diameter 19 mm *3 Ultrasonictest: for blowholes, total number; for slag inclusion and incompletefusion,total length.

*4 Evaluation of welding performance; 8 excellent; 0 good; A poor Welding current x welding voltage: Flat position: 250A x 21 V Vertical position: 170A x 20V Other conditions were the same as those in joint welding in flat position.

Claims (1)

1. A flux cored wire electrode for self-shielded arc welding which comprises a steel sheath and a powdery flux containing as essential components the components given below, said sheath being filled with said flux and the amount of said flux being 15-30 percent by weight based on the whole wire electrode weight: BaF2: 25-70 percent by weigh Alkali metal fluoride: 1-30 percent by weight Compound oxide composed of the oxide of an alkaline earth metal selected from the group consisting of Ca, Sr and Ba and the oxide of a metal selected from the group consisting of Fe, Mn, Ni, Co, Ti, Al and Zr: 1-30 percent by weight Al: 3-12 percent by weight Mg: 2-10 percent by weight Mn: 0.5-10 percentbyweight.

2. Aflux cored wire electrode as setforth in Claim 1, wherein the alkali metal fluoride comprises at least one member selected from the group consisting of Na2ZrF6, K2SiF5, Na2SiF6, Na3AlF6, Rb2SiF6, K2TiF5, K2ZrF5, LiF and LiBaF3.

3. Aflux cored wire electrode as setforth in Claim 2, wherein the alkali metal fluoride is LiBaF3.

4. A flux cored wire electrode as setforth in Claim 3, wherein the flux contains LiBaF3 in an amount of not less than 5%.

5. Aflux cored wire electrode as setforth in Claim 3, wherein the flux contains LiBaF3 in an amount of notlessthan 10%.

6. Aflux cored wire electrode as setforth in Claim 1, wherein the flux further contains at least one metal selected from the group consisting of Ni (0.5-20% ), Zr (0.1-4% ), Ti (0.01-0.5%) and B (0.01-0.2%).

7. Afluxcoredwireelectrodeassetforth in Claim 1 wherein the flux contains at least one rare earth element selected from the group consisting of Ce and La in a total amount of 0.01-0.5%.

8. Aflux cored wire electrode as setforth in Claim 6, wherein the flux contains Zr in an amount of 0.5-3%.

Amendments to the claims have been filed, and have the following effect: *(b) New ortextually amended claims have been filed as follows:

1. Aflux cored wire electrode for self-shielded arc welding which comprises a steel sheath and a powderyflux containing the components given below, said sheath being filled with said flux and the amount of said flux being 15-30 percent by weight based on the whole wire electrode weight: BaF2: 25-70 percent by weight Alkali metal fluoride: 1-30 percent by weight Compound oxide composed of the oxide of an alkaline earth metal selected from the group consisting of Ca, Sr and Ba and the oxide of a metal selected from the group consisting of Fe, Mn, Ni Co, Ti, Al and Zr: 1-30 percent by weight Al: 3-12 percent by weight Mg: 2-10 percent by weight Mn: 0.5-10 percent by weight.