Project ForgeManufacturing Engineering
Machining Processes
GATE 2008
Hard
A researcher conducts electrochemical machining (ECM) on a binary alloy (density 6000 kg/m³) of iron (atomic weight 56, valency 2) and metal P (atomic weight 24, valency 4). Faraday's constant=96500 coulomb/mole. Volumetric material removal rate of the alloy is 50 mm³/s at a current of 2000 A. The percentage of metal P in the alloy is closest to
- A40
- 25
- C15
- D79
Explanation
Mass removal rate=MRR×ρ=50×10⁻⁹×6000=3×10⁻⁴ kg/s=0.3 g/s. Alloy equivalent weight Eeq=(dm/dt)F/I=0.3×96500/2000≈14.48 g/equiv. With E_Fe=56/2=28 and E_P=24/4=6, and mass fraction wP of P: 1/Eeq=wP/6+(1-wP)/28. Solving: wP≈0.255≈25%.
Source: GATE ME 2008 (2008)
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