In projection welding, which characteristic determines where heat will be generated?

In projection welding, which characteristic determines where heat will be generated?

• A. The design of the parts
• B. The operator's mood
• C. The ambient humidity
• D. The color of metal

Answer: (A)

In projection welding, heat is generated where the electrical resistance is highest, which is at the projections engineered into the parts. The projections create a very small contact area, so the current density there is concentrated and the local resistance is high. Since heat from resistance welding is proportional to the current squared times the resistance, most heating occurs at these projections, causing the metal to fuse at those points when the proper current and clamping force are applied. The rest of the pieces remains relatively cooler because their contact areas are larger and their resistance is lower. The other factors listed don’t determine where heat builds up. The operator’s mood, ambient humidity, or the color of the metal don’t set the heat generation location; only the part design and the electrical conditions do.

In projection welding, heat is generated where the electrical resistance is highest, which is at the projections engineered into the parts. The projections create a very small contact area, so the current density there is concentrated and the local resistance is high. Since heat from resistance welding is proportional to the current squared times the resistance, most heating occurs at these projections, causing the metal to fuse at those points when the proper current and clamping force are applied. The rest of the pieces remains relatively cooler because their contact areas are larger and their resistance is lower.

The other factors listed don’t determine where heat builds up. The operator’s mood, ambient humidity, or the color of the metal don’t set the heat generation location; only the part design and the electrical conditions do.