“S” shaped cast in wire

Details “S” shaped cast in wire “S” shaped cast in wire

2002-03-26

2004-03-23

McHenry, Kevin L (Department: 1725)

Metal fusion bonding

With means to deform work, filler, or flux portion before...

C228S056300, C228S246000, C219S137800

Reexamination Certificate

active

06708864

ABSTRACT:

The present invention pertains to the art of welding, and more particularly to welding wires used in welding machines.
INCORPORATION BY REFERENCE
U.S. Provisional Application Ser. No. 60/298,555 filed Jun. 15, 2001 entitled “‘S’ Shaped Cast In Wire” is incorporated herein by reference.
BACKGROUND OF THE INVENTION
One of the lingering problems in the field of welding is the consistent formation and placement of a quality weld bead. Various measures have been employed to achieve this goal. For instance, the waveform of the welding current has been closely controlled to achieve better weld bead formation and weld bead quality. In addition, the feed rate of a weld wire has been controlled to produce a higher quality weld bead. The composition of the consumable weld wire and various types of shielding gases used during the welding process have been employed to achieve higher quality weld beads. Although many of these techniques have significantly improved weld bead quality, consistent weld bead placement on a workpiece has remained illusive.
One of the remaining problems with obtaining a consistent weld bead placement on a workpiece is the position of the weld wire relative to the workpiece as the weld bead is being formed. It has been found that when the position of the tip of the weld wire varies relative to the welding tip of a welder, the consistency of the weld bead placement degrades. It is common industry practice to feed a “killed” weld wire to a welder during the welding process. A “killed” weld wire is a weld wire that has had its shape memory removed prior to the weld wire being wound onto a reel, spool, container, or the like. When the weld wire is wound on the reel, spool, container, or the like, the weld wire adopts a new shape as it is being wound. When the weld wire is unwound from the reel, spool, container, or the like, the weld wire adopts a new shape during the unwinding process. As a result, the shape of the unwound wire will vary along the longitudinal length of the unwound weld wire. Once the unwound weld wire is cut into various sections, the unwound wire retains its adopted shape obtained when being unwound from the reel, spool, container, or the like. Further modifications to the shape of the weld wire can result during the cutting process and/or while the weld wire is positioned for being cut and/or as the weld wire is fed into the welding machine. Since the weld wire has no memory, the weld wire constantly modifies its shape as it passes through the weld gun, thus resulting in inconsistent positioning of the weld wire as it exits the welding tip of the welding gun or torch. This inconsistent positioning of the weld wire results in inconsistent placement of the weld bead onto a workplace.
Various techniques have been used by operators to minimize this attribute of the weld wire. One technique is for the operator to cut the weld wire in certain positions relative to the unwound weld wire to obtain a desired weld wire profile for the cut weld wire section. The operator can further modify the shape of the weld wire by hand as he/she deems fit. Although these techniques can improve weld bead placement on a workpiece, the weld bead placement consistency varies widely between operator and from the use of different cut sections of the weld wire.
When the weld wire is automatically fed into a welding machine, such as in a robotic welder, problems with consistent weld bead placement can be severe. Typically, robotic welders follow a predefined path when forming a weld bead. The varying position of the weld wire as it exits the welding tip of the robotic welder can cause significant weld bead placement deviation during the welding process. During manual welding, the operator has the ability to attempt to correct and/or compensate for weld bead placement; however, such techniques are inapplicable to robotic welders.
In addition to the problems associated with the use of “killed” wire in obtaining consistent weld bead placement, the “killed” wire is more susceptible to bending and the formation of kinks in the weld wire as the weld wire travels through the weld gun, thereby resulting in undesired weld bead placement and the possibility of a low quality weld bead.
In view of the persistent problems of weld bead placement during a welding operation, there is a demand for an improved weld wire which addresses the problem associated with consistent weld bead placement onto a workpiece.
SUMMARY OF THE INVENTION
The present invention pertains to an improved weld wire and a process for making the improved weld wire for use in various types of welding machines. These welding machines can include automated welders and manual welders. In addition, the weld wire can be used in various types of welding processes such as MIG, MAG, or STT welding, or in other types of welding processes wherein a consumable electrode is utilized to form a weld bead onto a workpiece. The improved weld wire in accordance with the present invention involves the utilization of a weld wire that has a shape memory imparted onto the weld wire prior to and/or at the time the weld wire is wound onto a reel, spool, container, or the like, and which shape memory is fully or partially retained by the weld wire as the weld wire is unwound from the reel, spool, container, or the like. The use of weld wire with a shape memory is a deviation from common industry practice that teaches that weld wire that is fed into a welding machine should have little or no shape memory. The common practice in the industry was to “kill” the wire or otherwise remove the shape memory of the wire prior to winding the weld wire onto a reel, spool, container, or the like. It was commonly believed that a weld wire having a shape memory would adversely affect the unwinding of the weld wire from the reel, spool, container, or the like during the welding process and would further be more susceptible to kinks, bends and other problems as the weld wire is fed through the welder during the welding process. Furthermore, it was commonly believed that a weld wire with shape memory would aggravate the problem associated with consistent weld bead placement. Surprisingly, the use of a shape memory weld wire in accordance with the present invention results in the formation of a weld bead having better consistent placement during the welding operation and the formation of higher quality weld beads than weld beads formed by “killed” weld wires. The use of a weld wire with shape memory has also been found to form a more robust weld bead during the welding process. Furthermore, the use of a weld wire with shape memory has been found to reduce the occurrence of bends and kinks in the welding wire as it is being cut for use during the welding process and/or during the feeding of the weld wire through a welding machine during the welding process. It has also been found that the use of a weld wire with shape memory reduces or substantially eliminates the operator's control over the weld wire shape. In the past, weld wire that has been “killed” could be cut at various locations to help improve the weld bead placement. However, the shape of the cut weld wire was inconsistent from one operator to the next, and furthermore the shape of the weld wire was inconsistent from one cut section to another. As a result, the operator had significant control over the resulting consistency of weld bead placement. The use of a weld wire with shape memory in accordance with the present invention overcomes this inconsistency problem since similar cut weld wire sections will have substantially the same shape from one cut section to the next. In addition, the weld wire with shape memory will resist further shape modifications during the cutting process and as the weld wire is fed through a welder. Consequently, as the weld wire with shape memory is fed through the contact tip of a welding gun, the weld wire will be similarly positioned relative to the tip from one cut section to the next, thus forming a more consistent weld bead placement during the welding operation.
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