Experimental Measurements of Fall Voltages and Droplet Temperature in GMAW

• Author / Creator

  McIntosh, Cory L

• Heat distribution measurements in Gas Metal Arc Welding (GMAW) were concurrently measured at the cathode and anode giving increased insight and prediction capabilities. A calorimeter and water cooled cathode were used to determine energy partitions in GMAW for various electrodes, currents, shielding gases, and waveforms. Fall voltage, droplet temperature, and thermal efficiency measurements were inferred from the heat distribution measurements at the cathode and anode. Secondary and less dominant voltage losses were directly measured or modelled. The simultaneous measurements of all voltage loss regions allowed the determination of arc column voltage potential. All fall voltage measurements were comparable with those found in literature. Measurements show overall cathode fall voltage is independent from current and waveform selection and appears to be the first time to be experimentally verified for both steel and aluminum. Overall cathode fall voltage was measured to be 12.7 V and 10.9 V for steel and aluminum electrodes respectively. Results indicate that arc composition and temperature could be influencing overall cathode fall voltages. Overall anode fall voltage was independent on current and waveform selection and averaged at 4.7 V and 6.1 V for steel and aluminum respectively. Droplet temperature results indicate that a minimum in temperature exists at the transition point between globular and spray metal transfer in a steel electrode. By modifying small amounts of CO2 in the shielding gas, droplet temperature can be lowered while still maintaining a similar deposition rate. Values of cathode and anode fall voltages were used to determine deposition rates with results correlating well with other literature. The experiments performed in this study were able to give consistent measurements when spatter was not an issue and were representative of typical GMAW parameters. Voltage loss and deposition rate calculations correlate well with other literature indicating that fall voltage and droplet temperature measurements are correct. These experimental results in conjunction with models will grant greater understanding and comprehension pertaining to metal transfer, droplet temperature, fume formation, deposition rates, and heat distribution in GMAW.

• Subjects / Keywords

  • Arc Physics
  • Potential Drop
  • Fall Voltage
  • Droplet Temperature
  • GMAW
  • Welding

• Graduation date

  Spring 2017

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3J38KW2J

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.