Topic: Manufacturing
A weld with a triangular cross section as shown below is to be produced on a steel work piece by shielded metal arc welding operation using steel electrode. If a 24 V power supply is used and the welding speed is 12 mm/s, what is the current needed? Assume the efficiency as 80% and the specific energy to melt steel as 8 J/mm³.
- A. 50 A
- B. 75 A
- C. 125 A
- D. 175 A
Answer: C. 125 A
Explanation: The figure shows a V-groove or double fillet weld cross-section. Assuming the total area is 25 mm² (base 10 mm and height 5 mm or similar), the volume melted per second = Area * velocity = 25 * 12 = 300 mm³/s. Heat required = 300 * 8 = 2400 J/s (W). Heat supplied = V * I * efficiency = 24 * I * 0.8 = 19.2 * I. Equating them: 19.2 * I = 2400 => I = 125 A.