1997 年 15 巻 2 号 p. 247-253
In this paper we studied the loci and the velocities of scattering spatters in shielded metal arc welding with high titanium oxide type electrode. We examined only spatters that flew off in the right-angle direction to the weld line and passed through the slit of 4 mm by 75 mm. The loci of the spatters were photographed when they scattered in the air, and their velocities were calculated using their times of photographing. And we simulated the loci and velocities of the spatters. The experimental data and calculated values were compared.
In the experiment we examined 110 spatters, and their particle diameters range from 0.1 to 1 mm. The spatters flew around on the surface of base metal within a 500 mm radius circle. They flew in the air for less than about 0.5 seconds. And the highest velocity was 6 m/sec. The Reynolds numbers of the spatters were less than 7. They were given by Re=d×V/ν (d is the diameter of a spatter, V is the velocity of the spatter, ν is coefficient of kinematic velocity). And the coefficient of kinematic viscosity of the air was calculated using the temperature. The temperature was determined by the arithmetic mean of the temperature of spatters (given they were 1637 K) and the temperature of the air (293 K). To simulate the loci and the velocities of the spatters, the equation of motion was set up under a certain condition. The condition is that the temperatures of the scattering spatters are constant and their drag coefficients (Cd) are given by the Stokes equation for a sphere (Cd=24/Re). The calculated value by this equation matches well the experimental results, though the former was a little larger than the latter in almost all the cases.