3.2.2 Limitations One limitation of hot wire GTA welding is that it is not normally used for manual welding. There are also additional equipment costs for the hot wire power supply in addition to the cold wire GTAW equipment. The power supplies are not especially compact and portable for moving around in the field. In going from cold wire to hot wire GTAW, it may be necessary to change the groove design to one more suitable to hot wire and the increased deposition rate. There are some consumable costs such as the hot wire feed guide tube contact tips and tungsten electrodes. The cost of helium or helium argon mixes used as shield gas for some applications are greater than for straight argon and more gas is consumed. And there may be increased costs for training welding personnel.
3.2.3 Orbital hot wire Perhaps the biggest limitation in the application of hot wire technology is that it is not suitable for welding small pieces and it is limited with respect to welding position. The most practical welding position is 1G, or downhand welding on plate or welding of pipes when the pipe can be rotated, followed by 2G. While it would be tempting to apply hot wire technology to true out-of-position orbital welding, the significant increase in deposition that can be achieved in downhand hot wire welding will not be seen in orbital applications. There are often difficulties in welding at the 6 to 8 o’clock positions. When welding downhill, the puddle tends to run into the tungsten electrode unless the travel speed is very slow. When welding uphill the puddle tends to sag. However, some metallurical benefit may be achieved in orbital applications at the expense of greater complexity.
Regardless of the application, techniques and equipment configuration, hot wire must be controlled with the principals similar to cold wire welding.
4. Hot wire power supplies
Several manufacturers have developed power supplies for hot wire GTAW welding. Some use sine wave AC for heating the wire, some use square wave and even DC. The Arc Machines, Inc. Hot Wire Power Supply Model 501 has controls for (heating) current and (hot wire) voltage. The standard mode of operation for the Model 501 is Constant AC Voltage (0 - 10 Volts), but Constant Current mode (Max output 250 Amps) is also available. The Model 501 implements advanced technology. AC current is used to minimize magnetic interference (arc blow). The AC current of the Model 501 is very close to a true sine wave. To control the hot wire power the voltage is sensed where the power cable is attached to the guide tube. By measuring the voltage at the guide tube, the effects of cable length (voltage drop) are controlled.
The accuracy of true RMS provided by these measurements make it possible to duplicate production conditions from one set-up to the next with excellent repeatability of process.
3.2.2 Limitations One limitation of hot wire GTA welding is that it is not normally used for manual welding. There are also additional equipment costs for the hot wire power supply in addition to the cold wire GTAW equipment. The power supplies are not especially compact and portable for moving around in the field. In going from cold wire to hot wire GTAW, it may be necessary to change the groove design to one more suitable to hot wire and the increased deposition rate. There are some consumable costs such as the hot wire feed guide tube contact tips and tungsten electrodes. The cost of helium or helium argon mixes used as shield gas for some applications are greater than for straight argon and more gas is consumed. And there may be increased costs for training welding personnel.
3.2.3 Orbital hot wire Perhaps the biggest limitation in the application of hot wire technology is that it is not suitable for welding small pieces and it is limited with respect to welding position. The most practical welding position is 1G, or downhand welding on plate or welding of pipes when the pipe can be rotated, followed by 2G. While it would be tempting to apply hot wire technology to true out-of-position orbital welding, the significant increase in deposition that can be achieved in downhand hot wire welding will not be seen in orbital applications. There are often difficulties in welding at the 6 to 8 o’clock positions. When welding downhill, the puddle tends to run into the tungsten electrode unless the travel speed is very slow. When welding uphill the puddle tends to sag. However, some metallurical benefit may be achieved in orbital applications at the expense of greater complexity.
Regardless of the application, techniques and equipment configuration, hot wire must be controlled with the principals similar to cold wire welding.
4. Hot wire power supplies
Several manufacturers have developed power supplies for hot wire GTAW welding. Some use sine wave AC for heating the wire, some use square wave and even DC. The Arc Machines, Inc. Hot Wire Power Supply Model 501 has controls for (heating) current and (hot wire) voltage. The standard mode of operation for the Model 501 is Constant AC Voltage (0 - 10 Volts), but Constant Current mode (Max output 250 Amps) is also available. The Model 501 implements advanced technology. AC current is used to minimize magnetic interference (arc blow). The AC current of the Model 501 is very close to a true sine wave. To control the hot wire power the voltage is sensed where the power cable is attached to the guide tube. By measuring the voltage at the guide tube, the effects of cable length (voltage drop) are controlled.
The accuracy of true RMS provided by these measurements make it possible to duplicate production conditions from one set-up to the next with excellent repeatability of process.
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