# US 6,723,957 B2 · Method and apparatus for welding > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,723,957 B2 - Document ID: US6723957B2 - Status: Granted - Kind: B2 - Application number: 10/112,980 - Filed: 2002-03-29 - Published: 2003-10-02 - Granted: 2004-04-20 - Earliest claimed: 2002-03-29 - Assignees: Illinois Tool Works Inc. - Inventors: Todd Holverson; Anthony Nikodym; Lin Zhang; Steven Barhorst; Jon Reynolds - Web page: https://patentgrep.com/patent/US6723957B2 ## CPC - B23K 9/0213: {Narrow gap welding} - B23K 9/092: {characterised by the shape of the pulses produced} - B23K 9/1043: {characterised by the electric circuit (B23K9/1012 takes precedence)} - B23K: SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM ## Abstract A method and apparatus for MIG welding is disclosed. When in an ac mode the output is unbalanced, or the balance may be controlled. The balance may be controlled to provide a desired deposition rate and/or to obtain a desired dilution. The frequency may be any frequency, for example 30 Hz, 60 Hz, 90 Hz, or more. The weld path may have groove with angle of less than 50 degrees. A consumable, cored, wire may be used, and provide at rates of 30 or 35 pounds per hour using a single arc. In various embodiments the balance may have a negative portion of at least 1.5 times the positive portion. The process may be started using an extended negative portion, for example 0.5 or 0.75 seconds. ## Claims ### Claim 1 A method of MIG welding comprising: providing ac power to a weld, wherein the ac power has a negative portion having a negative amperage and a positive portion having a positive amperage, and the ac power further has a frequency; wherein the negative amperage is greater than the positive amperage; wherein the frequency is at least 60 Hz. ### Claim 2 (depends on 1) The method of claim 1, wherein the frequency is between 90 Hz and 120 Hz. ### Claim 3 (depends on 1) The method of claim 1, further including providing a consumable, flux-cored, wire to the weld. ### Claim 4 (depends on 1) The method of claim 1, further including providing a consumable, metal-cored, wire to the weld. ### Claim 5 (depends on 4) The method of claim 4, wherein providing the wire includes providing a wire wherein the wire comprises a sheath encapsulating a core having a core composition, the core composition comprising a combination of graphite and one or more compounds of potassium, the combination of graphite and compounds of potassium in the core composition not exceeding approximately 5% by weight. ### Claim 6 (depends on 5) The method of claim 5, wherein providing the wire includes providing the wire electrode wherein the one or more compounds of potassium comprise K2MnTiO4. ### Claim 7 (depends on 6) The method of claim 6, wherein providing the wire wherein the combination is selected from the range from about 0.3% to about 5.0% by weight. ### Claim 8 (depends on 1) The method of claim 1, further comprising providing a weld path on at least one workpiece, wherein the weld path includes a groove having an angle of less than 50 degrees. ### Claim 9 (depends on 1) The method of claim 1, further comprising providing a weld path on at least one workpiece, wherein the weld path includes a groove having an angle of less than 30 degrees. ### Claim 10 (depends on 1) The method of claim 1, further comprising providing a weld path on at least one workpiece, wherein the weld path includes a groove having an angle of between 20 degrees and 30 degrees. ### Claim 11 (depends on 10) The method of claim 10 wherein the negative portion is at least 1.5 times the positive portion. ### Claim 12 (depends on 11) The method of claim 11 wherein the weld process begins with a first negative portion having a duration of at least 0.75 seconds. ### Claim 13 (depends on 1) The method of claim 1, including welding at a rate of at least 35 pounds per hour using a single arc. ### Claim 14 (depends on 13) A The method of claim 13 including welding at a rate of at least 40 pounds per hour. ### Claim 15 (depends on 13) The method of claim 13 wherein the negative portion is at least twice the positive portion. ### Claim 16 (depends on 1) The method of claim 1 wherein the weld process begins with a first negative portion having a duration of at least 0.5 seconds. ### Claim 17 (depends on 1) The method of claim 1 further including providing a stick-out of about 2 inches. ### Claim 18 (depends on 17) The method of claim 17 further comprising providing a shielding gas at a rate of at least 80 cubic feet per hour. ### Claim 19 A method of MIG welding comprising: providing ac power to a weld, wherein the ac power has a negative portion and a positive portion, and the ac power further has a frequency; providing at least one workpiece with a weld path thereon, wherein the weld path includes a groove having an angle of less than 50 degrees; and providing a wire comprising a sheath encapsulating a core having a core composition, the core composition comprising a combination of graphite and one or more compounds of potassium, the combination of graphite and compounds of potassium in the core composition not exceeding approximately 5% by weight. ### Claim 20 (depends on 19) The method of claim 19, wherein providing at least one workpiece includes providing the weld path with the groove having the angle between 20 degrees and 30 degrees. ### Claim 21 (depends on 19) The method of claim 19, wherein providing at least one workpiece includes providing the weld path with the groove having the angle less than 30 degrees. ### Claim 22 (depends on 21) The method of claim 21 wherein: the negative portion is greater than the positive portion; and the negative portion is at least 1.5 times the positive portion. ### Claim 23 (depends on 22) The method of claim 22, wherein the frequency is between 90 Hz and 120 Hz. ### Claim 24 (depends on 23) The method of claim of claim 23, wherein providing the wire includes providing the wire electrode wherein one or more compounds of potassium comprise K2MnTiO4, and the combination is selected from the range from about 0.3% to about 5.0% by weight. ### Claim 25 (depends on 19) The method of claim 19, wherein providing the wire includes providing the wire electrode wherein the one or more compounds of potassium comprise K2MnTiO4, and the combination is selected from the range from about 0.3% to about 5.0% by weight. ### Claim 26 A method of MIG welding comprising: providing ac power to a weld, wherein the ac power has a negative portion and a positive portion and the ac power further has a frequency; and providing a consumable wire to the weld at a rate of at least 35 pounds per hour using a single arc. ### Claim 27 (depends on 26) The method of claim 26, wherein providing the wire further comprises providing a wire comprising a sheath encapsulating a core having a core composition, the core composition comprising a combination of graphite and one or more compounds of potassium, the combination of graphite and compounds of potassium in the core composition not exceeding approximately 5% by weight. ### Claim 28 (depends on 27) The method of claim 27, wherein providing the wire includes providing the wire electrode wherein the one or more compounds of potassium comprise K4MnTiO4, and the combination is selected from the range from about 0.3% to about 5.0% by weight. ### Claim 29 (depends on 26) The method of claim 26 including providing a consumable to the weld at a rate of at least 40 pounds per hour. ### Claim 30 (depends on 29) The method of claim 29, further comprising providing the weld path on at least one work piece, wherein the weld path includes a groove having an angle of less than 30 degrees. ### Claim 31 (depends on 26) The method of claim 26 wherein the negative portion is at least twice the positive portion. ### Claim 32 (depends on 31) The method of claim 31 wherein the duration of the negative portion is at least 1.5 times the duration of the positive portion. ### Claim 33 A method of MIG welding comprising: providing ac power to a weld having a negative portion having a negative amperage and a positive portion having a positive amperage, and the ac power further having a frequency; and wherein the negative amperage is at least 1.5 times the positive amperage portion. ### Claim 34 (depends on 33) The method of claim 33 wherein the duration of the negative portion is at least 1.5 times the duration of the positive portion. ### Claim 35 (depends on 33) The method of claim 33 wherein the weld process begins with a first negative portion having a duration of at least 0.5 seconds. ### Claim 36 (depends on 33) The method of claim 33 wherein the weld process begins with a first negative portion having a duration of at least 0.75 seconds. ### Claim 37 An apparatus for MIG welding a substrate of low carbon steel having a thickness of at least ½ inch comprising: a table for holding the substrate; a MIG gun; a carriage for traversing the MIG gun over the substrate and providing a deposition rate of at least 30 pounds per hour; a source of shielding gas disposed to provide the shielding gas to the MIG gun; and a power source, connected to the MIG gun, capable of providing a substantially square AC current at the MIG gun, with the average current being at least 300 amps. ### Claim 38 A MIG welding system comprising: power means for providing ac power to a weld, wherein the ac power has a negative portion and a positive portion, and the ac power further has a frequency; and control means for controlling the power means, wherein the negative portion has a negative amperage and the positive portion has a positive amperage, wherein the control means causes the negative amperage to be greater than the positive amperage, and wherein the frequency is at least 60 Hz. ### Claim 39 (depends on 38) The system of claim 38, wherein the control means includes means for providing the frequency to be between 90 Hz and 120 Hz. ### Claim 40 (depends on 38) The system of claim 38, further including a consumable, flux-cored, wire, disposed to be provided to the weld. ### Claim 41 (depends on 40) The system of claim 40, wherein the wire is metal-cored. ### Claim 42 (depends on 41) The system of claim 41, further comprising a weld path on at least one work piece, wherein the weld path includes a groove having an angle of less than 50 degrees. ### Claim 43 (depends on 38) The system of claim 38, further comprising a weld path on at least one workpiece, wherein the weld path includes a groove having an angle of less than 30 degrees. ### Claim 44 (depends on 43) The system of claim 43 wherein the control means for includes means for causing the negative amp-seconds to be at least twice the positive amp-seconds. ### Claim 45 (depends on 38) The system of the claim 38 wherein control means includes means for causing the negative amp-seconds to be at least 1.5 times the positive amp-seconds. ### Claim 46 (depends on 45) The system of the claim 45 wherein the control means includes means for causing the weld process to begin with a first negative portion having a duratiOn of at least 0.5 seconds. ### Claim 47 (depends on 38) The system of claim 38 wherein the control means includes means for causing the weld process to begin with a first cycle portion having a duration of at least 0.75 seconds. ### Claim 48 A system of MIG welding comprising: power means for providing ac power to a weld, the ac power having a negative portion having a negative amperage and a positive portion having a positive amperage, and the ac power further having a frequency; and means for controlling the power means such that the negative amperage is at least 1.5 times the positive amperage. ### Claim 49 (depends on 48) The system of claim 48 further comprising means for controlling the power means such that the weld process begins with a first negative portion having a duration of at least 0.5 seconds. ### Claim 50 A system of MIG welding comprising: an ac power source having a MIG output with a positive portion having a positive amperage and a negative portion having a negative amperage; a controller controllably connected to the power source; a feedback circuit disposed electrically between the power source and the controller; a source of consumable wire, disposed to provide wire to the MIG output; wherein the controller provides that the negative amperage is greater than the positive amperage, and further wherein the MIG output has a frequency of at least 60 Hz. ### Claim 51 (depends on 50) The system of claim 50, wherein the power source is a step-up cycloconverter and the frequency is between 90 Hz and 120 Hz. ### Claim 52 (depends on 50) The system of claim 50, wherein the wire is a flux-cored wire. ### Claim 53 (depends on 52) The system of claim 52, further comprising providing a weld path on at least one work piece, wherein the weld path includes a groove having an angle of less than 50 degrees. ### Claim 54 (depends on 52) The system of claim 52, further comprising providing a weld path on at least one work piece, wherein the weld path includes a groove having an angle of less than 30 degrees. ### Claim 55 (depends on 52) The system of claim 52 wherein the negative portion is at least 1.5 times the positive portion. ### Claim 56 (depends on 52) The system of claim 52 wherein the controller includes a start circuit, a control output and a timing circuit, that provides a negative portion having a duration of at least 0.5 seconds at the start of the weld process. ### Claim 57 (depends on 50) The system of claim 50, wherein the wire comprises a sheath encapsulating a core having a core composition, the core composition comprising a combination of graphite and one or more compounds of potassium, the combination of graphite and compounds of potassium in the core composition not exceeding approximately 5% by weight. ### Claim 58 (depends on 57) The system of claim 57, the one or more compounds of potassium comprise K2MnTiO4. ### Claim 59 (depends on 58) The system of claim 58, wherein the combination is selected from the range from about 0.3% to about 5.0% by weight. ### Claim 60 A system of MIG welding comprising: a MIG torch; an ac power source disposed to provide ac power to the MIG torch; a source of consumable wire, disposed to provide wire to the MIG torch; and wherein the wire comprises a sheath encapsulating a core having a core composition, the core composition comprising a combination of graphite and one or more compounds of potassium, the combination of graphite and compounds of potassium in the core composition not exceeding approximately 5% by weight. ### Claim 61 (depends on 60) The system of claim 60, the one or more compounds of potassium comprise K2MnTiO4. ### Claim 62 (depends on 61) The system of claim 61, wherein the combination is selected from the range from about 0.3% to about 5.0% by weight. ### Claim 63 (depends on 60) The system of claim 60 further comprising a controller operatively connected to the power source, and including a start circuit having a time delay and a control output, wherein the weld process begins with a first negative portion having a duration of at least 0.5 seconds. ### Claim 64 A system of MIG welding comprising: an ac power source having a control input and a MIG output, wherein the MIG output has a negative portion having a negative amperage and a positive portion having a positive amperage; a controller, including a balance circuit and a feedback circuit, operatively connected to the control input such that the negative amperage is at least 1.5 times the positive amperage. ### Claim 65 A method of controlling dilution in MIG welding comprising: providing ac power to a weld, wherein the ac power has a negative portion having a negative amperage and a positive portion having a positive amperage, and the ac power further has a frequency; controlling the balance of the negative amperage and the positive amperage to obtain a desired dilution. ### Claim 66 (depends on 65) The method of claim 65 wherein the negative amperage is greater than the positive amperage. ### Claim 67 (depends on 65) The method of claim 65 wherein the negative portion is less than the positive portion.