For spot welding of two steel sheets (base metal) each of $3 m m$ thickness, welding current of $10000 A$ is applied for $0.2 s$ . The heat dissipated to the base etal is $1000 J$ . Assuming that the heat required for melting $1 m m^{3}$ volume of steel is $20, J$ and interfacial contact resistance between sheet is $0.0002 Ω$ , the volume (in $m m^{3})$ of weld nugget is
150

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Solution

The correct option is A 150
Total heat generation
$I^{2} R T = (10000)^{2} \times 0.0002 \times 0.2$
$= 4000 J$
Heat required to melt the nugget
$= 4000 - 1000 = 3000 J$
Volume of nugget
$= \frac{3000}{20} = 150 m m^{3}$

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The correct option is A 150Total heat generation I2RT=(10000)2×0.0002×0.2 =4000J Heat required to melt the nugget =4000−1000=3000J Volume of nugget =300020=150mm3

The correct option is A 150
Total heat generation
$I^{2} R T = (10000)^{2} \times 0.0002 \times 0.2$
$= 4000 J$
Heat required to melt the nugget
$= 4000 - 1000 = 3000 J$
Volume of nugget
$= \frac{3000}{20} = 150 m m^{3}$