Question

During resistance spot welding of 2 mm thick steel plates (Density 7800 Kg/$m^2$), certain amount of current is passing through the plates for 0.15 sec. The resultant weld nugget formed is having the volume of 220 ${\text{mm}}^3$. The latent heat of fusion of steel is 1380 kJ/kg and effective resistance in the welding operation is 200 $\mu \Omega$. The current passing through the electrodes is
approximately

• A. 8885 A
• B. 280 A
• C. 3946 A
• D. 1973 A

Answer 1

The correct option is A 8885 A

t = 2 mm,

$\rho =7800{\text{kg/m}}^2$

$T=0.15\sec$

$V=220{\text{mm}}^3=220\times {10}^{-6}{m}^3$

$L=1380\text{KJ/kg,}R=200\times {10}^{-3}\Omega ,I=?$

$m_n=\rho \times V_n$

$=7800\times 220\times {10}^{-9}$

$=1.716\times {10}^{-3}\text{kg}$

Heat used = heat generated

$I^2\times R\times T=\text{mL}$

$I^2\times 200\times {10}^{-6}\times 0.15=1.716\times {10}^{-3}\times 1380\times {10}^3$

$I=8885A$