GB713381A - Welding electrode coating and method of making the same and electrodes coated therewith - Google Patents

Abstract

An electrode coating comprises flux ingredients in discrete particles bound together and to an electrode by a low melting hydrophobic water insoluble glass. The glass flows at a temperature below that at which the flux ingredients are affected and should preferably soften and flow when heated for 5 minutes at 1200 DEG F. A 200 mesh glass frit should absorb less than 1 per cent. of moisture when subjected to a 90 per cent. relative humidity for 1 week and should lose less than 3 per cent. weight when leached with pure water at 80 DEG F. for 2 days. A suitable glass has an analysis comprising 20-40 mol. per cent. of oxides of at least two of the alkali metals, sodium, potassium, lithium and rubidium, between 5 and 20 mol. per cent. of at least one of the divalent metal oxides CaO, MgO, StO, CdO, MnO, FeO, CoO and NiO, the total of the oxides being 30-55 mol. per cent. and the mol. ratio of the alkali metal oxides to divalent metal oxides being between 2 : 1 and 8 : 1, 30-60 mol. per cent. SiO2 and 2-25 mol. per cent. TiO2. The analysis may include B2O3 up to 40 mol. per cent. and Al2O3 and/or Fe2O3 up to 10 mol. per cent. Fluorine may be included up to an equivalent of 20 mol. per cent. Na2F2. The glass as a frit is prepared by mixing materials such as lithium carbonate, potassium carbonate rubidium carbonate, soda ash, lithium nitrate, potassium nitrate, sodium nitrate, sodium fluoride, potassium fluoride, lepidolite, borax, boric acid, silicates, vitanates, and cryolite together and melting. The mass is chilled and ground to less than 40 mesh. 2-40 per cent. of the frit is mixed in a mill with a flux which may comprise calcium, lithium and magnesium carbonates, dolomite, calcium, sodium and lithium fluorides, cryolite, fluorspar, hematite, magnetite, hausmannite, rutile, ilmenite, zirconium dioxide, nickel and columbium oxides, clays, mica, feldspar, pyrophyllite, lepidolite, spodumene, wollastonite, asbestos, talc, potassium titanate, ferro manganese, ferro silicon, ferro titanium, ferro chromium, ferro zirconium, ferro vanadium, ferro columbium, iron, silicon, manganese, tungsten and molybdenum in particles of less than 40 mesh. A liquid, e.g. water is added to form a plastic mass which may be brushed of extruded on to an electrode. Organic matter, e.g. resins, bituminous materials, gums and alginates may give temporary bonding. The mass is heated to say 230 DEG F. to drive off the liquid and then to 1050-1250 DEG F. to soften the glass which on cooling bonds the flux together and to the core. The core may be a steel with 0.1-0.15 per cent. carbon or a stainess steel 13 per cent. chromium, 18 per cent. chromium, 18 per cent chromium and 8 per cent. nickel or 25 per cent. chromium and 20 per cent. nickel. The analysis of each of thirteen glasses is given including; Li2O-4.8 to 16.5 mol. per cent.; Na2O-12.8 to 19.8 mol. per cent.; K2O-4.3 to 9.6 mol. per cent.; CaF2-5.3 to 7.5 mol. per cent.; MnO-2.1 to 2.5 mol. per cent.; Na2F2-3.5 to 7.5 mol. per cent.; B2O3 1.4 to 6.5 mol. per cent.; Fe2O3-0.7 to 2.4 mol. per cent.; SiO2 34.7 to 49.2 mol. per cent.; TiO2 4.2 to 13.1 mol. per cent. An example of a coating made from one of the glasses comprises a frit of analysis Li2O 10.2 mol. per cent.; Na2O 16.3 mol. per cent.; CaF2 6.1 mol. per cent.; MnO 2.1 mol. per cent.; Na2F2 6.1 mol. per cent.; B2O3 4.1 mol. per cent.; Fe2O3 2.1 mol. per cent.; SiO2 40.8 mol. per cent. and TiO2 12.2 mol. per cent. of particle size 100-200 mesh. 25 parts by weight of the frit are mixed with 8 parts FeSi; 6 parts FeMn; 35 parts CaCo3; 11.7 parts CaF3; 18 parts TiO2; 1 part sodium alginate and 15 parts of water. The mixture is extruded on to a core dried at 265 DEG F. and fired at 1200 DEG F. Five other coating examples are given which employ glasses of the specified thirteen and Mn, FeTi, rutile and SiO2 are used in addition to the fluxes already referred to.