Droplet Temperature Measurement in Metal Inert Gas Welding Process by Using Two Color Temperature Measurement Method

Abstract

Droplet temperature for Metal Inert Gas welding process was measured by using optical pyrometry; two colors temperature measurement method. High speed color video camera was used to capture an image of metal droplet during transfer to base metal. As a result, the movement of an arc to cover the droplet from bottom half to the entire droplet by increase of welding current had allowed the change in droplet heating process from concentrated to uniform heating. The concentrated heating in globular transfer mode had caused a higher current density at the bottom of the droplet. The change of heating process from concentrated heating in globular mode to a rather uniform heating during transition resulted in a smaller current density and reduced the heat flux into droplet, therefore decreased the droplet temperature. The further increase in welding current led the increase of droplet temperature and produced the minimum temperature in the middle of transition mode.

Study on factors affecting the droplet temperature in plasma MIG welding process

“…These differences can be attributed to the arc heating process which closely influenced the droplet temper ature. It is mentioned that the temperature largely affects the surface tension of the droplet [25][26][27].…”

Effect of Plasma Flow in Plasma MIG Welding Process to the Microstructure Refinement at Heat Affected Zone of As-Welded Carbon Steel

“…Fig. 2 shows the peak temperature of weld pool in conventional MIG welding and plasma MIG welding that was measured by using two-color temperature measurement method [6] [7]. The analysis results clearly showed that the weld pool peak temperature of conventional MIG welding was 2287 K and the one in plasma MIG welding was 1885 K. The temperature difference was about 400 K. It is suggested that the higher peak temperature of weld pool in conventional MIG welding shows the higher cooling rate.…”

Real-time monitoring of temperature field, metal transfer and cooling rate during gas metal arc-directed energy deposition

“…The mono-colour IR camera uses a single emissivity value to convert the thermal images to absolute temperature [6,13]. This poses a difficulty in determining the accurate temperature from the thermal images of a mono-colour IR camera as emissivity values depend on temperature [13]. A twocolour thermal camera measures the spectral intensities at two different wavelengths within a narrow range of wavelength bands and can directly estimate the actual temperature irrespective of variations in emissivity values over the radiating surface [13][14][15][16][17][18].…”

“…This poses a difficulty in determining the accurate temperature from the thermal images of a mono-colour IR camera as emissivity values depend on temperature [13]. A twocolour thermal camera measures the spectral intensities at two different wavelengths within a narrow range of wavelength bands and can directly estimate the actual temperature irrespective of variations in emissivity values over the radiating surface [13][14][15][16][17][18]. The two-colour thermal cameras are recently used for monitoring melt pool surface temperature for GMA brazing [6], GMAW [14] and GTAW [15] processes.…”

“…The use of mono-colour IR cameras for online monitoring of melt pool surface temperature to estimate fusion zone dimensions [7] and detect arc misalignment and mismatch between abutting edges [10] is reported for gas tungsten arc welding (GTAW), gas metal arc welding (GMAW) [8], pulsed current GMAW [11] and laser brazing [12]. The mono-colour IR camera uses a single emissivity value to convert the thermal images to absolute temperature [6, 13]. This poses a difficulty in determining the accurate temperature from the thermal images of a mono-colour IR camera as emissivity values depend on temperature [13].…”