点溶接機電極の先端部の温度上昇の実測と計算

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The maximum temperature rise in electrode tip is estimated from the measured heat input to the electrode during one spot welding. It reaches as high as about 700℃ for ordinary spot welding conditions of steel plates of 0.8∿3.2mm thickness. For calculation the electrode cross section is assumed constant along the electrode length, and the effect of wave form of heat flow from the tip is investigated. Q in Table 1 is the measured heat input to each side of the electrode per one welding under the conditions shown in the table. θ_2 in the table shows the calculated results using the equation (9) under the following assumption, i.e. the heat flow wave form is taken as Fig. 11(a), heat flow time T_H is assumed as equal to current flow time T_0 shown in the table, the cross section of the electrode is taken as S_2 corresponding to the root diameter of the electrode. Fig. 14 shows the temperature distribution curves along the length when a constant heat H=1000cal/(cm)^2 sec flows in from the electrode tip for the duration T_H=0.25,0.5,1.0,1.5sec. Curves A∿D show the temperature rise when the distance x_0 of cooling end from the tip is infinity and A, B'∿E' for x_0=1cm. For the calculation of the effect of cooling water, it is assumed that equation (33) holds, according to the model shown in Fig. 13 (h is taken as 1 for Fig. 14 and 18). Heat flow time T_H is divided into two parts as shown in Fig. 17 and the temperature at the moment C is calculated as the sum of the parts. Temperature due to the part AB is calculated using equation (49), T_1 being time constant defined as in equation (43) and the period of (BC)^^^- is chosen far longer than time constant T_2. It is easily shown that the magnitude of temperature fluctuation at a point 1cm distant from the tip is negligible when intermittent heat input cycle is less than 1sec/spot and we see that the cooling effect of cooling water is only effective to reduce the average temperature rise in the electrode under intermittent welding. Table 3 shows the temperature rise at the tip for cyclic heat flow from the tip for various combinations of x_0,h, T_H and T_w (i.e. cyclic period). The value shows the temperature at the moment C in Fig. 19 for H=1000cal/(cm)^2 sec. Fig. 2,4 shows the oscillogram of the temperature rise at 2mm distant from the tip (Fig. 1). Electrode pressure is also shown in Fig. 2.
1966-11-25

点溶接機電極の先端部の温度上昇の実測と計算

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