A device for arc welding is provided in which a continuously-fed electrode wire is in electrical contact with a contact tube. The contact tube is improved by using a substantially oxygen-free conductive alloy in order to reduce the amount of electrical erosion

Pike, James F.

NASA Technical Reports Server

United States Patent [19] 
US005192852A 
[ill Patent Number: 5,192,852 
Pike MI Date of Patent: Mar. 9. 1993 
SUBSTANTIALLY OXYGEN-FREE 
CONTACT TUBE 
Inventor: Junes F. Pike, Newport News, Va. 
Assignee: Tbe United Statea of Ameria as 
represented by the Adminiahtor of 
the National Aeronautics md Space 
A m t i o n ,  Washington, D.C. 
Appl. No.: 791,728 
Filed: Nor. 14,1991 
Int. c1.5 ................................................ B23K 9/24 
U.S. c1. ................................................ 219/137.61 
Field of seprcb ......................... 219/137.2, 137.61 
[561 Referenas Cited 
FOREIGN PATENT DOCUMENTS 
50-59245 5/1975 Japan .............................. 219/137.61 
52-31924 3/1977 J w  .............................. 219A37.61 
52-31923 3/1977 Japan .............................. 219A37.61 
52-31925 3/1977 Japan .............................. 219A37.61 
1123816 11/1984 U.S.S.R. ......................... 219A37.61 
primary Examiner-ClifFord C. Shaw 
Attorney, Agent, or Finn-Kevin B. Osbome 
A device for arc welding is provided in which a con- 
tinuously-fed electrode wire is in electrical contact with 
a contact tube. The contact tube is improved by using a 
substantially oxygen-free conductive alloy in order to 
reduce the amount of electrical erosion. 
1571 ABSTRACJ: 
18 Claims, 1 Drawing Sheet 
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US. Patent 
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Mar. 9,1993 
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5,192,852 
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SUBSTANTLALLY OXYGEN-FREE CONTACT 
TUBE 
ORIGIN O F  THE INVENTION 5 
The invention described herein was made by employ- 
ecs of the United States Government and may be manu- 
factured and used by or for the Government for govern- 
mental purposes without the payment of any royalties 
thereon or therefor. 
BACKGROUND OF THE INVENTION 
10 
1. Field of the Invention 
This invention relates generally to arc welding and 
more specifically to a contact tube improvement to 
reduce the degree of electrical erosion. 
2. Description of the Related Art 
Arc welding processes such as gas metal arc welding 
(GMAW), flux cored arc welding (FCAW) and sub- 2o 
merged arc welding (SAW) use continuously-fed con- 
sumable electrodes. These electrodes are guided 
through and maintain contact with a contact tube which 
also acts to transfer current to the electrode. Because of 
their function in transferring current, the tubes must 25 
have high conductivity and therefore are generally 
manufactured from copper alloys. Contact tubes are 
considered an expendable component which must be 
periodically replaced as a result of abrasive wear and 
electrical erosion which cause deterioration of the 30 
tubes. Because of this deterioration, the welding indus- 
try has long sought various means for increasing the 
useful life of the contact tubes. Although electrical 
erosion has been identified in the art as a source of 
deterioration, applicant is unaware of related art identi- 35 
fying the underlying cause of this phenomenon. 
SUMMARY OF THE INVENTION 
It is a primary object of the present invention to pro- 
vide a device for transferring current to a continuously- 40 
fed consumable electrode which has an increased wear 
life due to a reduction in electrical erosion. Additional 
objects and advantages of the present invention are 
apparent from the specifications and drawings which 
The foregoing objects are achieved by manufacturing 
the contact tube from a substantially oxygen-free cop- 
per alloy. Selection of an oxygen-free copper was based 
on results of metallurgical analyses conducted by the 
applicant of contact tubes presently used in the art. 50 
These analyses revealed high concentrations of oxides 
in the regions of the contact tubes affected by electrical 
erosion. 
Beneficial results have been obtained by limiting the 
oxygen content to a maximum of approximately 0.001% 55 
by weight. Use of this type of alloy has been shown to 
increase the wear life of a specific contact tube by ap- 
proximately 37%. 
Contact tubes manufactured with this substantially 
oxygen-free copper alloy are suited to a variety of arc 60 
welding processes such as GMAW, FCAW and SAW 
which use contact tubes to transfer electrical current to 
a continuously-fed consumable electrode wire. 
BRIEF DESCRIPTION OF THE DRAWING 
FIG. 1 is a schematic drawing of a portion of a weld- 
ing gun containing a contact tube and a continuously- 
fed electrode wire. 
follow. 45 
65 
DESCRIPTION OF THE PREFERRED 
EMBODIMENTS 
Referring to FIG. 1, a contact tube 10 is housed 
within a welding gun nozzle 30. The contact tube 10 
acts both to guide a continuously-fed electrode wire 20 
and to transfer current to the electrode wire 20. Current 
is provided by means of a conventional power supply. 
Although FIG. 1 depicts a hollow, cylindrical 
contact tube 10 through which the electrode wire 20 is 
guided, this is only a illustrative design. The present 
invention applies to any t* and shape of contact tube 
which maintains contact with the wire in order to trans- 
fer current. Any suitable guiding mechanism can also be 
employed. 
Metallographic examination by the applicant of a 
contact tube 10 made from a conventional copper alloy 
indicated the occurrence of electrical erosion at the 
contact tip 1Oa of the tube. This region of erosion was 
associatad with an increased incidence of oxides. To 
reduce the oxide occurrence, contact tubes 10 were 
manufactured from a substantially oxygen-free copper 
alloy in which the oxygen content was maintained 
below approximately 0.001% by weight. The reduced 
oxygen content resulted in an approximately 37% in- 
crease in the wear life of contact tubes which were 
tested. Further decreases in the concentration of oxy- 
gen may be used to achieve higher levels of wear life. 
According to the present invention, substantially reduc- 
ing the oxygen in any conductive alloy susceptible to 
electrical erosion due to the formation of oxides should 
significantly enhance the wear life of the contact tube 
10. 
Although the present invention has been described in 
detail with respect to certain preferred embodiments 
thereof, it is understood by those of skill in the art that 
variations and modifications in this detail may be made 
without any departure from the spirit and scope of the 
present invention, as defmed in the hereto-appended 
claims. 
What is claimed is: 
1. A device for arc welding, comprising: 
(a) a continuously-fed consumable electrode wire; 
and 
(b) a contact tube which is in electrical contact with- 
said electrode wire, wherein said tube is comprised 
of a substantially oxygen-free conductive alloy for 
reducing electrical erosion of said contact tube. 
2. The device according to claim 1, wherein said 
contact tube guides said electrode wire. 
3. The device according to claim 1, wherein said 
contact tube is comprised of a substantially oxygen-free 
copper alloy for reducing electrical erosion of said 
contact tube. 
4. The device sccording to claim 3, wherein said 
contact tube guides said electrode wire. 
5. The device according to claim 1, wherein said 
contact tube is comprised of a copper alloy containing a 
maximum of approximately 0.001% osygen by weight 
for reducing electrical erosion of said contact tube. 
6. The device according to claim 5, wherein said 
contact tube guides said electrode wire. 
7. A device for arc welding, including a continuous- 
ly-fed consumable electrode wire and a contact tube 
which is in electrical contact therewith, wherein the 
improvement comprises: 
- - 
3 
5,192,852 
4 
a substantially oxygen-free conductive alloy forming 
said contact tube for reducing electrical erosion of 
said contact tube. 
8. The improvement according to claim 7, wherein 5 
said contact tube guides said electrode wire. 
9. The improvement according to claim 7, wherein 
said contact tube is comprised of a substantially oxygen- 
free copper alloy for reducing electrical erosion of said 10 
contact tube. 
10. The improvement according to claim 9, wherein 
said contact tube nuides said electrode wire. 
13. A contacting member for use in arc welding, 
wherein a continuously-fed electrode wire is in electn- 
contact with said contacting member, comprising: 
a contact tube for transferring electric current to the 
electrode, wherein said contact tube is comprised 
of a substantially oxygen-free conductive alloy for 
reducing electrical erosion of said contact tube. 
14. ne contacting member according to claim 13, 
wherein said contact tube guides said electrode wire. 
15- The conat ing member according to Claim 139 
wherein said contact tube is comprised of a substantially 
oxygen-free copper alloy for reducing electrical erosion 
of said contact tube. 
16. The contacting member according to claim 15, 
ing a maximum of approximately 0.001% oxygen by 
weight for reducing electrical erosion of said contact 
tube. 
containing a maximum of approximately O.Obi% oxy- 
gen by weight for reducing ektrical  erosion of said 
18. The contacting member according to claim 17, 
20 contact tube. 
12. The improvement accordmg to claim 11, wherein wherein said contact guides electrode wire. 
said contact tube guides said electrode wire. * * * * *  
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Substantially oxygen-free contact tube

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