DE2438008C2 - - Google Patents

Description

The invention relates to a coated niobium Welding electrode whose core wire is made of an alloy containing nickel consists of carbon, manganese, titanium, aluminum, May contain iron, niobium and silicon with a coating made from calcium carbonate, barium carbonate, titanium dioxide, Cryolite, manganese, niobium and possibly molybdenum.

Welding corrosion-resistant nickel alloys, for example one containing 28% chromium and 10% iron Nickel alloy, as is often used to make corrosion-resistant Tubes is used, requires special electrodes, which allows welding in all positions and also under strong pretension, crack and pore-free welded joints surrender. The weld metal must be the same Have corrosion resistance like the base material and a certain iron absorption when used as a stranger Filler metal or when coating other types Allow metals such as steel.  

From the German Ausleschrift 12 96 930 is also already a coated niobium-containing welding electrode with a covering from 10 to 35% titanium dioxide, 5 to 30% manganese carbonate, 15 to 40% alkaline earth carbonates, up to 20% manganese, up to 25% Tungsten, up to 25% molybdenum, up to 35% niobium, up to 30% iron and up to 5% compression aids, rest 10 to 35% cryolite known, whose core wire made of 10 to 25% chrome and up to 2% titanium or up to 1% aluminum or 0.5 to 2% titanium and aluminum rest there is at least 55% nickel and optionally each up to 10% iron, 0.5% silicon, 3% manganese, 0.3% magnesium, 0.1% carbon, 0.05% zirconium, 0.005% boron, 2% May contain cobalt, 8% niobium, 8% molybdenum and 4% tungsten. Individual of the cladding and core wire components are adjusted according to certain conditions.

Because the welding behavior of coated electrodes is very strong Dimensions depends on the envelope, the invention based on the task of a covered welding electrode create that guarantees particularly good welding results and especially for welding nickel alloys with 28% chrome and 10% iron. The solution to this task consists in the fact that at the beginning of a welding electrode mentioned type according to the invention the core wire made of a nickel alloy with up to 1% carbon, up to 15% Manganese, up to 50% chromium, up to 5% titanium, up to 5% aluminum, up to 70% iron, up to 90% copper, up to 10% molybdenum, up to 6% niobium and up to 1% tantalum, the rest including melting-related Contamination of nickel exists, and the cladding 10 to 26% calcium carbonate, 5 to 20% barium carbonate, 10 to 23% titanium dioxide, 20 to 30% cryolite, 4 up to 18% manganese, 1.8 to 7.2% niobium and optionally up to 4% aluminum oxide, up to 10% chromium, up to 2% chromium oxide and / or contains up to 7.2% molybdenum.  

The manganese content of the coating is preferably at least 10% and the niobium content at least 2.4%. The mixture from the aforementioned components of the envelope can pressure-relieving additives, for example bentonite and a binder, for example sodium silicate to apply the sheath to a core wire can.

It is essential that the flux forming Wrapping all active ingredients in the specified Contains salary limits to ensure that When welding, crack-free and pore-free welded joints excellent technological properties. in the With regard to a universal, especially with overhead welding usable electrode should be the wrapping Contain 24 to 26% cryolite. Advantageously contains they equal amounts of calcium carbonate, barium carbonate and Titanium dioxide.

The percentages in the following explanations refer on the total content of active ingredients.

If the calcium carbonate content is below 10%, you can there is an unstable arc, so that the slag adheres very firmly and is very difficult to remove. Removing the welding slag is also difficult, if the content of calcium carbonate  over 26% and consequently a high melting point results so that part of the flux in solid Condition at the tip of the electrode a kind of fingernail forms, which affects the arc stability and especially the vertical and overhead welding impaired. Therefore, the flux preferably contains 12 to 20%, for example 15% calcium carbonate.

Furthermore, the flux must have 5 to 20% barium carbonate contain. If the barium carbonate content is below 5% the result is a liquid that tends to drip Slag when welding out of normal position. Keep over 20% increase the melting point and lead to fingernail formation resulting in an unstable arc. Preferably the barium carbonate content is therefore 12 to 20%, for example 15%.

The flux mainly contains titanium dioxide or rutile to stabilize the arc and reduce it of the melting point. As a result, the melting point is at a level below 10% too high, so that slag beads form. Even with a titanium dioxide over 23% results too high a melting point and a tough and slag that is difficult to remove. The content of titanium dioxide is therefore preferably 12 to 20%, for example 15%.

The aluminum oxide makes it easier to remove the slag, however, is not always required. Preferred is the alumina content 1 to 2%. With a salary The melting point rises above 4% and there is a risk a fingernail formation.

The cryolite serves as a refiner and diminishes  the melting point; its proportion is preferably 24 up to 26%. Outside of these salary limits, the Melting point, so that there is a risk of melting out of the core wire consists of the sheath and the arc impaired, possibly even deleted becomes. When used for flat or horizontal welding however, the flux can also be 20% or 30% Cryolite included, because in this case with higher currents can be welded without problems with regard to the welding as with the vertical or Overhead welding result.

In addition to the other components, the flux must be 4 to 18% manganese and 1.8 to 7.2% niobium contain one To ensure melting point of a fingernail or excludes pearl formation. It also decreases with increasing levels of manganese and niobium the danger a crack. As a result, the flux contains the Welding a nickel-chromium-iron alloy with 28% Chromium and 10% iron, balance nickel preferably 13 to 16% manganese and 4.8 to 6% niobium. On the other hand, that contains Flux when welding austenitic or ferritic Steels and nickel alloys preferably 4 up to 8% manganese and 1.8 to 6% niobium. The manganese can do that Fluxes in different ways, for example added as manganese powder or ferromanganese, while the niobium preferably as ferroniobium with a niobium content from 50 to 70% or as nickel niobium and Niobium powder is added. On the other hand, manganese and niobium of course also from the core wire in the weld metal is introduced to make it susceptible to cracking to reduce.

The flux preferably also contains chromium, since chromium contents up to 10% the porosity, especially when re-igniting  of the arc. In addition, it can Chromium in the flux to replace the chromium content in the core wire.

The flux can be used without affecting welding contain up to 2% chromium oxide. At low manganese levels a chromium oxide content of, for example, 4 to 8% improves More than 2%, for example of 4%, increase the penetration effect covered electrodes too much and lead more like a burnout than a weld.

Finally, the flux can contain up to 7.2% molybdenum included to reduce the risk of cracking; in particular with relatively low manganese contents.

The flux according to the invention can in the usual way for example by extrusion followed by Dried or burned onto a core wire will. Usually the flux is made from one finely divided powder with a particle size below 0.177-0.149 mm in a dry mixture with bentonite. The mixture is then continued with Mixing a solution of sodium silicate in water until there is a homogeneous mixture for application to one Core wire obtained by extrusion. Usually contains the mixture based on 3% bentonite and 15% sodium silicate on the dry flux. After two hours Burning at 370 ° C forms a on the core wire adherent wrapping. The possible uses of the Electrode depend on its dimensions. When welding overhead for example, a short circuit can occur if the covering is too thin. Examples of typical electrode dimensions and more preferred  Current strengths are in Table I below reproduced. However, these values are by no means binding; for example, the amperage at Overhead welding can be reduced when the slag is too fluid.

Table I

Electrodes with a covering according to the invention are suitable not only for welding nickel-chromium-iron alloys, but also of nickel-chromium and nickel-copper alloys.

The flux according to the invention can be used as a coating be used. The metallic part of the electrode can be very different be composed and for example from a nickel-chromium or nickel-copper alloy with up to 50% chromium, up to 35% or even up to 70% iron, up to 90% Copper, up to 5% titanium, up to 15% manganese, up to 0.5% or else up to 1% carbon, up to 3% silicon, up to 10% molybdenum, up to 5% aluminum, up to 1% tantalum and up to 6% niobium, the rest including contamination from melting Nickel exist.  

The flux according to the invention is particularly suitable however for electrodes, their core wire or metallic Component made of a nickel-chromium-iron alloy with 14 to 32% chromium, 0 to 0.1% carbon, 0 to 2.5% Manganese, 0 to 2.5% silicon, 0 to 5% titanium, 0 to 5% Aluminum, up to 25% iron, 0 to 1% tantalum and 0 to 2% Niobium, balance including impurities due to melting Nickel exists. To the impurities include deoxidation and refining residues as well other impurities, as they are usually found in Find nickel-chromium-iron alloys.

For welding nickel alloys with 28% chrome and 10% iron is particularly suitable for core wires from 0 to 0.1% carbon, 0 to 2% manganese, 0 to 2.5% silicon, 24 to 32% chromium, 0 to 5% titanium, 0 to 5% aluminum and 0 to 25% iron, balance 50 to 67% nickel, preferably with at most 0.05% carbon, up to 1% manganese, up to 1% Silicon, 27 to 31% chromium, up to 1% titanium, up to 1% aluminum and 8 to 12% iron, balance 52 to 65% nickel together with 12 to 20% calcium carbonate, 12 to 20% coatings Barium carbonate, 12 to 20% titanium dioxide, 1 to 2% aluminum oxide, 24 to 26% cryolite, 13 to 16% manganese, 4.8 up to 6% niobium and 0 to 6% chromium as well as preferably 15% calcium carbonate, 15% barium carbonate, 15% titanium dioxide, 1% alumina, 24 to 26% cryolite, 13 to 16% manganese, 4.8 to 6% niobium and 0 to 6% chromium, balance iron from the Addition of ferroalloys. Also contain the wrappers 3% bentonite as a pressure-relieving agent and 15% sodium silicate as a binder.

The weld metal composition naturally depends on the Type of core wire, its sheathing and composition  of the base material. When welding an alloy with 28% chromium and 10% iron, the rest nickel with The weld metal consists of the aforementioned electrodes 50 to 67% nickel, up to 25% iron, 24 to 32% chromium, 1 up to 8% manganese, up to 0.7% titanium, 0.5 to 3% niobium, to 0.8% silicon, up to 0.1% hydrocarbon, up to 1.1% aluminum, and up to 0.1% magnesium or preferably from 52 to 65% Nickel, 8 to 12% iron, 27 to 31% chromium, 3 to 5% manganese, up to 0.2% titanium, 1 to 2% niobium, 0.2 to 0.6% silicon, up to 0.05% carbon, up to 0.1% aluminum and up 0.02% magnesium.

For welding austenitic or ferritic steels or The core wire consists of alloys with a high nickel content preferably from 0 to 0.1% carbon, 0 to 2.5% Manganese, 0 to 2.5% silicon, 14 to 18% chromium, 0 to 5% Titanium, 0 to 5% aluminum, 0 to 25% iron, 0 to 2% niobium, 0 to 1% tantalum and over 1.5% niobium + tantalum or preferably from a maximum of 0.05% carbon, a maximum of 1% manganese, at most 1% silicon, 15 to 17% chromium, up to 1% Titanium, up to 1% aluminum, 6 to 8% iron, up to 1.5% niobium, up to 0.5% tantalum and over 1.5% niobium + tantalum. For such A flux is preferably suitable for electrodes 12 to 20%, preferably 17% calcium carbonate, 12 to 20%, preferably 16% barium carbonate, 12 to 20%, preferably 16% titanium dioxide, 1 to 2%, preferably 1% aluminum oxide, 24 to 26%, preferably 25% cryolite, 4 to 8%, preferably 7% manganese, 1.8 to 6%, preferably 5.4% Niobium, 1 to 2% preferably 1% chromium oxide, 1.8 to 6%, preferably 3% molybdenum and 1 to 6%, preferably 3% Chrome, remainder iron from added ferro alloys as well additionally 3% bentonite and 15% sodium carbonate.

The nickel-chromium-iron electrodes described result  a healthy weld metal with mechanical properties and a corrosion resistance that the base material made of a nickel alloy with 28% chromium and 10% iron corresponds. To ensure optimal corrosion resistance should reach the carbon content of the weld metal kept below 0.05%, preferably below about 0.03% and the chromium content is at least 26% or 27%, preferably about 28%. A low susceptibility to cracking is guaranteed if the weld metal at least 0.5%, preferably about 1% niobium and at least 1%, preferably contains about 3% manganese.

In numerous comparison attempts, the superiority has of provided with an envelope according to the invention Electrode shown. It had in these experiments Fluxes from Table II below resulting compositions, of which the wrappings 1 to 18 fall under the invention while the wrappings A to F are outside the invention. All Fluxes contained 3% bentonite and 15% sodium silicate as a 47% tree solution, based on dry weight, and were made on a 3.2 mm core wire from 0.02% Carbon, 0.16% manganese, less than 0.02% sulfur, 29.8% Chromium, 0.29% aluminum, 0.14% titanium, 0.14% magnesium and 0.014% iron, balance nickel applied by extrusion. All electrodes were on for two hours Fired at 288 ° C.

The electrodes were used for overhead welding with direct current reverse polarity and a current of 85 A. used. When welding were done in a single pass 60 ° V joints with a root width of 9.5 mm in 12.7 mm thick sheets of the same composition as that Core wire filled. That way a second  Passage of a 60 ° V joint can be simulated, as is well known as extremely difficult when welding with several Passages applies. The tests proved the excellent Suitability of the electrode according to the invention, one of which with the coating 11 showed optimal behavior. The arc stability was both long and Excellent in the event of a short arc, without tendency to short circuit or fingernail formation. The welding slag could be removed with a hammer and chisel, so that no pretreatment before the next run, for example, grinding was required. The Weld was completely even with excellent transition to the side walls of the joint and had a cross-section a flat, only slightly convex contour. In contrast were the results of the welding tests with the electrodes the envelopes A to F are all insufficient. In particular one showed with the envelopes A and E. strong tendency to form fingernails.  

Table II

Further tests were carried out with electrodes from some of which are wraps according to Table I, but others Core wires possessed for strength and corrosion resistance to investigate. The compositions of the Core wires and base materials result from the following Table III while the data of the electrodes can be seen from Table IV. The alloy rest consisted of nickel with the exception of steel 4. All Alloys in Table III are exceptions of soft steel 4 to the group of nickel alloys 28% chrome and 10% iron. From Table V are the Welding conditions and results can be seen while Table VI except the compositions of the welding wires the nickel as the rest and Table VII their Room temperature properties including those of the alloy 2 listed last digit. At the A normal U-joint was used for welding in normal position a bevel of 15 °, a radius of 6.4 mm, a web flank of 2.4 mm and a root gap of 3.2 mm filled. When surfacing in normal position 10 adjacent welding beads were applied. During overhead welding, a 60 ° V butt weld was made in a 25.4 mm thick plate, the first Run in normal position and the following runs in the overhead position. The pipe welding was done in a forced position on a pipe with an inner diameter of 66.7 mm and an outer diameter of 79.4 mm and a joint, the bevel 45 ° and the web surface 1.6 mm amounted to. The first run was using Alloy 5 as filler material using the TIG process executed.

The welded joints were examined by X-ray. In addition, 6 or 7 cross samples were made and polished, etched with Lepito etchant and at  microscopically examined ten times magnification. At the bending tests on which Table V was based two 9.5 mm thick cross samples of each welded joint using a mandrel with a diameter of 38 mm bent by 180 °. Each time there was an attempt in sweat condition and another try after a twenty hour glow at 904 ° C and cooling in Air carried. The number of cracks per cross section according to Table V represents an average of the sample pairs.  

Table III

Table IV

Table V

Table VI

Table VII

The data in Table V clearly show that the electrodes a healthy weld metal with the coating according to the invention surrender. Welding tests 4 and 5 were shown apart from normal position only minimal porosity. The Properties of the weld metal of tests 3A and 6 show that the electrode is insensitive to iron absorption Weld metal results. As a result, the Electrode for surfacing an alloy with a higher Corrosion resistance and for the production of alien species Use connections as they are often used in container construction or occur with other welded constructions, that require a carrier. Although with the electrode L weld metal produced S was healthy, was the behavior this electrode lying outside the invention unsatisfactory because it forms fingernails and a weld metal with raised edges resulted. That too with an electrode outside the invention produced weld metal T proved at radiographic examination as healthy; it resulted but there is difficulty removing the slag, because the weld metal is not flat but raised Showed edges.

To investigate the corrosion resistance, were transverse samples of the weld metal enclosing the base material 1, 2, 7 and 10 every eight-eight hourly rhythm immersed in boiling 65% nitric acid. The respective Weight loss with different test duration result from Table VIII and are for better assess a weight loss of 20 to 30 mg / dm² / day of a 28% chromium and 10% iron containing Wrought nickel alloy.

The somewhat stronger corrosion of the weld metal in the tests 1 and 2 is due to the relevant levels of carbon  and chrome conditional. The electrode of the welding test 1 had a core wire with a carbon content of 0.067% and a chromium content of 28.9% while wrapping contained no chromium. The resulting one Carbon content of 0.062% and the chromium content of 26.2% of the weld metal caused an undesirably strong Corrosion.

The weld deposit from Experiment 2 was used an electrode of the same composition as in the experiment 1 produced, but the coating contained 3% chromium. The The weld metal concerned contained 0.052% carbon and 28% chromium; it was subject to markedly less corrosion as the weld deposit of trial 1. The difference the carbon content of the weld metal from experiments 1 and 2 can be traced back to segregation in the core wire. The use of core wires with little less Carbon content of 0.021% and 0.005% in the frame Tests 7 and 10 showed significantly lower carbon contents of the weld metal and one accordingly better corrosion resistance than the weld metal of the Experiments 1 and 2. The corrosion resistance holds you Comparison with the corrosion resistance of the kneaded Base material. None of the attempts could be a preferred attack in the weld metal or in the heat-affected zone.

Further Huey tests on annealed samples showed that a four-hour sensitization at 593 ° C with air cooling and sensitizing for twenty hours 704 ° C with air cooling not the corrosion resistance impaired.  

Table VIII

The following experiments illustrate the effect of the Niobs in the flux. Five electrodes 11 to 14 with different niobium contents in the coating used. In any case, a core wire came with one Diameter of 4 mm with an electrode diameter of 6.1 mm for use. The core wire consisted of 0.021% Carbon, 1.16% manganese, 8.6% iron, 0.02% silicon, 29.8% chrome, 0.29% aluminum, 0.14% titanium and 0.014% Magnesium, balance nickel.

The coating consisted of a flux with 15% calcium carbonate, 25% cryolite, 1% aluminum oxide, 15% manganese, 4% chromium and 15% barium carbonate and titanium dioxide each Trap of electrodes 11 to 13 and 14% barium carbonate each and titanium oxide in the case of electrode 14 as well as in all Cases 3% bentonite and 15% sodium silicate in addition to nickel and ferroniobium with 60% niobium in those shown in Table IX Amounts.

The electrodes were used for butt welding of 25.4 mm  thick plates made of a nickel alloy with 0.031% carbon, 0.14% manganese, 9.6% iron, 0.06% silicon, 30.8% chromium, 0.15% aluminum, 0.16% titanium and 0.018% Magnesium, rest nickel used. The welding was done in normal position with a 15 ° U-diagonal joint with a web flank of 2.4 mm, a radius of 6.3 mm and one Root gap of 3.2 mm. The fugue was in eighteen Passages filled in, leaving the welding slag between the individual runs with hammer and chisel easily removed. The data listed in Table X. of the experiments clearly show the beneficial effect of the niobium in the coating for susceptibility to cracking.

Table IX

Table X

As part of another experiment, an electrode from an envelope according to the invention and another Core wire with 0.03% carbon, 2.2% manganese, 8% iron, 0.1% silicon, 16% chromium, 0.1% aluminum and 3% titanium, Rest of nickel used. The core wire had a diameter of 4 mm with an electrode diameter of 6.1 mm as well as a coating made of 17% calcium carbonate, 16% Barium carbonate, 16% titanium dioxide, 25% cryolite, 1% Aluminum oxide, 15% manganese and 10% ferroniob with 60% Niobium, based on dry weight. The coating was by mixing the flux components with 3% bentonite and 15% sodium silicate. The covered electrode was used for butt welding a 30.2 mm thick plate made of Inconel 600 with 0.04% carbon, 0.20% manganese, 7.2% iron, 0.20% silicon and 15.8% chromium, Rest of nickel used. The welding was carried out in the normal position and a bevelled 15 ° U-joint with a web flank of 2.4 mm, a radius of 6.4 mm and one Root gap of 3.2 mm. The joint was made in the course of twenty passages filled to a thickness of 30.2 mm, with the welding slag between the individual Effortless passes with hammer and chisel had it removed. During the X-ray examination the weld metal turned out to be healthy; Cross samples were completely error-free, even when trying to bend even after one Harden.

In another experiment, a 3.2 mm thick core wire was used the aforementioned composition with a 1.9 mm thick coating of 16% calcium carbonate, 14% barium carbonate, 17% titanium dioxide, 25% cryolite, 1% aluminum oxide, Add 15% manganese and 10% ferro-niobium with 60% niobium. The The electrode in question was used for butt welding a 12.7 mm thick plate made of Inconel 600 with nine Passages used. The plate had a bevel 60 ° V joint with a root gap of 3.2 mm and one  Bridge flank of 2.4 mm. During the X-ray examination were only two pores with a diameter less than 0.8 mm determined on a length of 15.4 cm. Cross samples proved after a bending test both in the welded as well as completely crack-free in the hardened state.

The absorption capacity of the weld metal for iron was in the Another experiment using the aforementioned Examined core wires with a diameter of 4 mm, the one with a 2.1 mm thick covering of the aforementioned type was provided. At ten beads were placed on a 12.7 mm thick test Soft steel sheet with 0.2% carbon and 0.4% Manganese, remainder iron welded on. The radiographic Investigation revealed no errors. There were also cross samples after bending around a mandrel with a diameter of 25.4 mm completely crack-free.

The excellent welding properties of electrodes with a molybdenum-containing coating with a lower manganese content as the wrapping shown in Table II with further sweat attempts. The electrodes passed from a 3.2 mm thick core wire of the composition of the Runs 7 and 8 from Table XII and an envelope according to table XI; they had a diameter of 3.2 mm. The welding tests were carried out with the electrode combinations Table XIII below using the Envelopes according to Table II on a 12.7 mm thick Alloy 14 plate performed.

The electrodes can be welded in normal and Use vertical position and overhead welding and resulted in comparison with commercially available welding electrodes a much more stable arc, a better one Flowability of the slag, a better transition, a  much better weld metal appearance and a lighter removable slag. During the X-ray examination who showed over head-welded connections there are practically no pores, while conventional pores Welding with more than 2 pores per mm in one Sweat bead resulted.

The suitability of electrodes 11 to 13 for welding to show alloys of the same or an alien type Alloy 9 to 15 plates according to Table XII used. The process conditions and results are compiled in the following tables XIV and XV. The welding in normal position was done in the manner explained in connection with Table V, while with overhead welding a 9.6 mm thick 60 ° V butt weld was placed, the first pass took place in normal position. For filling up the Butt welds required a total of eight passes each deliberately interrupted and continued with a new electrode. When cladding were two beads of sweat on a plate made of soft steel or alloy 15 applied. The X-ray examination and the bending tests were described in the context of Table V. Way performed.  

Table XI

Table XII

Table XIII

Table XIV

Table XV

In the bending test 18 there were small cracks in the Melting line with the plate 1, while in the bending test 19 all cracks occurred in the weld metal and in the welded Condition to break in the weld metal and in the hardened Condition led to breakage in the melting line.

Instead of the cryolite you can of course also equivalent amounts of sodium and aluminum fluoride used will.

Claims (11)

1. Coated niobium-containing welding electrode, the core wire of which consists of a nickel-containing alloy, which can contain carbon, manganese, titanium, aluminum, iron, niobium and silicon, with a coating of calcium carbonate, barium carbonate, titanium dioxide, cryolite, manganese, niobium and optionally molybdenum , characterized in that the core wire made of a nickel alloy with up to 1% carbon, up to 15% manganese, up to 50% chromium, up to 5% titanium, up to 5% aluminum, up to 70% iron, up to 90% copper, up to 10 % Molybdenum, up to 3% silicon, and up to 1% tantalum, the remainder including melting-related impurities nickel, and the coating 10 to 26% calcium carbonate, 5 to 20% barium carbonate, 10 to 23% titanium dioxide, 20 to 30% cryolite, 4 to Contains 18% manganese, 1.8 to 7.2% niobium and optionally up to 4% aluminum oxide, up to 10% chromium, up to 2% chromium oxide and / or up to 7.2% molybdenum. 2. Electrode according to claim 1, characterized in that the coating is at least 10% manganese and at least Contains 2.4% niobium.   3. Electrode according to claim 1 or 2, characterized in that that the coating contains 24 to 26% cryolite. 4. Electrode according to claim 1, characterized in that the coating is 12 to 20% calcium carbonate, Barium carbonate and titanium dioxide, 1 to 2% aluminum oxide, 24 to 26% cryolite, 13 to 16% manganese, 4.8 to Contains 6% niobium and a maximum of 6% chromium. 5. Electrode according to claim 4, but the same amounts contains calcium carbonate, barium carbonate and titanium dioxide. 6. Electrode according to claim 1, characterized in that the coating 12 to 20% calcium carbonate, barium carbonate and titanium dioxide, 1 to 2% aluminum oxide, 24 up to 26% cryolite, 4 to 8% manganese, 1.8 to 6% niobium, 1 up to 2% chromium oxide, 1.8 to 6% molybdenum and 1 to 6% Contains chromium.   7. Electrode according to one or more of claims 1 to 6, characterized in that the core wire 0 to 0.1% carbon, 0 to 2.5% manganese, 0 to 2.5% silicon, 14 to 32% chromium, 0 to 5% titanium, 0 to 5% Aluminum, 0 to 25% iron, 0 to 1% tantalum and 0 to 2% niobium, the rest including melting-related Contains impurities nickel. 8. Electrode according to claim 7, characterized in that the core wire 0 to 0.1% carbon, 0 to 2% Manganese, 0 to 2.5% silicon, 24 to 32% chromium, 0 to 5% titanium, 0 to 5% aluminum and 0 to 25% iron, the rest including contamination from melting Contains 50 to 67% nickel.   9. Electrode according to claim 8, characterized in that the core wire 0 to 0.05% carbon, 0 to 1% Manganese, 0 to 1% silicon, 27 to 31% chromium, 0 to 1% aluminum, 0 to 1% titanium and 8 to 12% iron, the rest including contamination from melting Contains 52 to 65% nickel. 10. Electrode according to claims 6 to 7, characterized in that that the core wire 0 to 0.1% carbon, 0 to 2.5% manganese, 0 to 2.5% silicon, 14 to 18% Chromium, 0 to 5% titanium, 0 to 5% aluminum, 0 to 25% Iron, 0 to 2% niobium and 0 to 1% tantalum in one Total niobium and tantalum content of at least 1.5%, Remainder including contamination from melting Contains nickel. 11. Electrode according to claim 10, characterized in that that the core wire 0 to 0.05% carbon, 0 to 1% Manganese, 0 to 1% silicon, 15 to 17% chromium, 0 to 1% titanium, 0 to 1% aluminum, 6 to 8% iron, 0 to 1.5% niobium and 0 to 0.5% tantalum with a total content of niobium and tantalum of at least 1.5%, the rest including contamination caused by melting Contains nickel.