In upset welding, fusion occurs across the entire abutting surfaces, not just at localized points.

• A. True
• B. False
• C. Sometimes
• D. Not specified

Answer: (A)

In upset welding, resistance heating at the interface occurs as current passes while the pieces are pressed together. Because the contact is intended to be across the full cross-sectional area of the joint, heat is generated along the entire abutting surfaces rather than at isolated points. As the temperature rises and the metal yields under pressure, it can plasticly flow and diffuse to form a bond over the whole interface. This is why the joint fuses across the entire abutting surfaces, not just at limited spots. Clean, intimate contact is essential; any oxides or contaminants that prevent full-area contact can cause localized bonding, but with proper surface prep the fusion extends across the entire interface.