Method and apparatus for welding

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.

1 .- 38 . (canceled) 
   
   
       39 . A method of MIG welding comprising:
 providing ac power to a weld through a center topper inductor with a plurality of EN windings and a plurality of ED windings wherein there are more EP windings than EN windings, and wherein the ac power has a negative portion provided through the EN winding and a positive portion provide through the EP windings, and the ac power further having a frequency; and   wherein the negative portion is at least 1.5 times the positive portion.   
   
   
       40 . The method of  claim 39  wherein the duration of the negative portion is at least 1.5 times the duration of the positive portion. 
   
   
       41 . The method of  claim 39  wherein the weld process begins with a first negative portion having a duration of at least 0.5 seconds. 
   
   
       42 . The method of  claim 39  wherein the weld process begins with a first negative portion having a duration of at least 0.75 seconds. 
   
   
       43 . 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;   wherein the negative portion is greater than the positive portion; and   wherein the weld process begins with the negative portion of at least 0.5 seconds duration.   
   
   
       44 . The method of  claim 43  wherein the weld process begins with a first negative portion having a duration of at least 0.75 seconds. 
   
   
       45 . 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.   
   
   
       46 .- 48 . (canceled) 
   
   
       49 . A MIG welding system comprising:
 power means for providing ac power to a weld through a center topper inductor with a plurality of EN windings and a plurality of ED windings wherein there are more EP windings than EN windings, and wherein the ac power has, wherein the ac power has a negative portion provided through the EN winding and a positive portion provide through the EP windings, and the ac power further has a frequency; and   control means for controlling the power means, wherein the negative portion has a negative amp-seconds and the positive portion has a positive amp-seconds, wherein the control means causes the negative amp-seconds to be greater than the positive amp-seconds, and wherein the frequency is at least 60 Hz.   
   
   
       50 . The system of  claim 49 , wherein the control means includes means for providing the frequency to be between 90 Hz and 120 Hz. 
   
   
       51 . The system of  claim 49 , further including a consumable, flux-cored, wire, disposed to be provided to the weld. 
   
   
       52 . The system of  claim 51 , wherein the wire is metal-cored. 
   
   
       53 . The system of  claim 52 , 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. 
   
   
       54 . The system of  claim 49 , 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. 
   
   
       55 . The system of  claim 54  wherein the control means for includes means for causing the negative amp-seconds to be at least twice the positive amp-seconds. 
   
   
       56 . The system of  claim 49  wherein the control means includes means for causing the negative amp-seconds to be at least 1.5 times the positive amp-seconds. 
   
   
       57 . The system of  claim 56  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. 
   
   
       58 . The system of  claim 49  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. 
   
   
       59 .- 79 . (canceled) 
   
   
       80 . A method of controlling dilution in MIG welding comprising:
 providing ac power to a weld provided through the EN winding, wherein the ac power has a negative portion provided through the EN winding and a positive portion provide through the EP windings, and the ac power further has a frequency;   controlling the balance of the negative portion and the positive portion to obtain a desired dilution.   
   
   
       81 . The method of  claim 80  wherein the negative portion is greater than the positive portion. 
   
   
       82 . The method of  claim 80  wherein the negative portion is less than the positive portion.