The gas velocity by the fluid dynamic method (shown in Fig.6 and the expression 2), the temperature distribution (shown in Fig. 14) and the mixing rate of air (as measured by the Orsat apparatus) (shown in Fig. 11) into the jet along the jet axis at various distances from the nozzle under the ordinary operating conditions for spraying process are experimented and some considerations of the results are made. Moreover, the flying velocities of the spraying powders (Al2O3, Mo and Nickelbase alloy) in the jet are measured by using the turning disc (shown in Fig. 1). The results can be summarized as follows. Under the conditions of the flow rate of operating gas 30l/min and the operating currents 450 and 550 A. (1) At the 50 mm' distance from the nozzle (i) Flying velocity of spraying powder Al2O3: 150-160 m/sec Mo: 100-105 m/sec Nickel-base alloy: 70 m/sec (ii) Gas velocity: 120-140 m/sec (iii) Temperature under current 550 A: 2, 200°C under current 450 A: 1.700°C (iv) Mixing rate of air: 55-65% (2) At the 100 mm' distance from the nozzle (i) Flying velocity of spraying powder A12O3: 140-150 m/sec Mo: 95-100 m/sec Nickel-base alloy: 60-70 m/sec (ii) Gas velocity: 40-50 m/sec (iii) Temperature (under current 450, 550 A): 800-900°C (iv) Mixing rate of air: about 90%
It is pointed out that the calorimetric estimation of the welding pool temperature described in Christensen and Chipman's report concerning slag-metal interaction in the pool is based on the misuse of the result of Wells's paper which treats the two dimensional heat flow in welding. Wells's paper shows that M=q/c pvdTf approaches 2 when vd/2α takes large values. Using this fact, they calculated the temperature considering q/2 is the heat content of the nugget when the nugget is in molten state, q being measured calorimetrically. It is clear, however, that the above mentioned Wells's result does not mean that q/2 is the heat content of the molten pool.