Patent GB-687666-A (GB)
Title: Improvements in gas-shielded electric arc welding
IPC: B23K9/173
Filed: 1949-12-29
Abstract: 687,666. Uniting by fusion. AIR REDUCTION CO., Inc. Dec. 29, 1949 [Jan. 21, 1949], No. 33247/49. Class 83 (iv). [Also in Group XXXV] In electric arc welding with a bare wire consumable electrode in which a non-oxidizing gas is supplied to shield the arc, the electrode is fed towards the arc and D.C. at reverse polarity (electrode positive) is employed. The gas which may be helium, argon or mixtures of carbon dioxide and carbon monoxide is fed in an annular non-turbulent stream to exclude air. The electrode is preferably fed at constant speed, at least 100 inches per minute, arc length being automatically regulated by the drooping characteristic of the generator and the feature that at high current densities employed the burn-off rate decreases with increasing arc length. The current density is such as to project molten metal axially as a fine spray of discrete droplets and for an argon shielded aluminium electrode the density D in amps. per square inch is given by where B is feed rate in inches per minute and C has a value between 10 and - 10. The welding of ferritic and austenitic steels, copper and magnesium is referred to. In an embodiment a wire 5 is fed by rollers 6 driven by a motor 7 through a hand gun 11 fed with gas from a cylinder 14 through a solenoid-operated' valve 17. A baffle or screen 3 is provided to provide non-turbulent flow. A generator 19 is connected across the electrode 5 and work through a switch 47a. All switches shown in the Figures are in the normal position. A circuit connected across the work and electrode 5 comprises a relay 30 which is energized at or above welding voltage; a relay 23 :which is energized at or near open-circuit voltage and a time delay relay 60 which is energized above normal welding voltage. An A.C. source supplies through switches 41a, 60a, a relay 47, a solenoid 50 for the valve 17 and the feed motor 7. A relay 41 in series with a switch 38 in the gun 11 is supplied from a low voltage transformer 35. In operation the switch 38 is pressed to energize relay 41 which closes switch 41a to energize relay 47 to close switch 47a and place open-circuit voltage across the electrode and work. Simultaneously the solenoid 50 is energized to allow gas flow. The open circuit voltage first energizes the relay 30 which momentarily closes switches 30a, 30b to put relay 60 across the supply but the time delay prevents relay 60 operating at once and relay 23 is energized to open contacts 23a, 23b and de-energize relay 30 to open switches 30a, 30b. When the electrode 5 is touched on the work the relay 23 is de-energized and contacts 23a, 23b close. When an arc is drawn the relay 30 is energized to close switches 30a, 30b and motor 7 then feeds electrode 5. Whenever shortcircuit conditions exist, the relay 30 is deenergized to stop the motor 7. When the voltage exceeds normal welding voltage the relay 60 is energized to open the switch 60a thus disconnecting feed motor 7, de-energizing relay 47 to open switch 47a and de-energizing solenoid 50 to close gas valve 17. A jog switch 43 on the gun is provided to energize a relay 46 to close contacts 46a to operate the motor 7. Reference has been directed by the Comptroller to Specification 659,015,