Manufacturing Practices (BT-106) - Important Questions

Explain the principle of electric arc welding. Discuss the formation and characteristics of the welding arc, factors affecting arc stability, and classification of arcs (short-circuiting, globular, spray, and pulsed).

Compare the following welding processes with respect to heat source, consumable, shielding, typical applications, advantages and limitations: Shielded Metal Arc Welding (SMAW), Gas Metal Arc Welding (MIG/MAG), Gas Tungsten Arc Welding (TIG), and Submerged Arc Welding (SAW).

Define welding heat input and derive the expression used to calculate heat input per unit length. Using the formula, calculate the heat input for a welding operation with voltage $V$, current $I$, welding speed $S$ (in mm/min) and an arc efficiency factor $\eta$. Use the standard expression and show the formula. $$Q = \eta\frac{V\times I\times 60}{S\times 1000}\left(\text{kJ/mm}\right)$$

List and describe common welding defects (such as porosity, cracks — hot and cold, lack of fusion, lack of penetration, undercut, overlap, slag inclusion). For each defect give causes and recommended remedies.

Define Heat Affected Zone (HAZ). Explain the microstructural changes that occur in the HAZ in steels during welding and discuss how welding parameters influence the size and properties of the HAZ.

Explain the principle of resistance welding. Describe the working, applications and important process parameters of spot welding, seam welding and projection welding. Discuss factors affecting weld quality in resistance welding.

Describe the principle of oxy-fuel gas welding and cutting. Explain the types of flames (neutral, carburizing, oxidizing), their identification and suitability. Describe factors affecting cutting quality.

Explain brazing and soldering. Describe filler materials, fluxes, process temperatures, and indicate the main differences between brazing, soldering and fusion welding. Give typical applications.

Explain the standard welding symbols used on engineering drawings. Interpret the following common symbols: fillet weld (single and double), V‑groove weld, square groove, and plug/slot weld. Describe how size, length, pitch and finish are indicated.

Describe methods for inspection and testing of welds. Explain the principles, advantages and limitations of Visual Testing (VT), Radiographic Testing (RT), Ultrasonic Testing (UT), Dye Penetrant Testing (PT) and Magnetic Particle Testing (MT) for weld evaluation.

Discuss the classification and selection criteria for welding electrodes and filler materials. Explain the effect of alloying elements in filler metal on weld properties (e.g., Mn, Si, C, Ni, Cr).

List the common hazards associated with welding and cutting operations and describe safety measures to control these hazards, including personal protective equipment (PPE), ventilation and workplace controls.