Before applying structural welds to heavy cast-iron engine blocks, mechanics preheat the surrounding metal to a uniform temperature using propane torches. While the welding torch easily melts the filler rod at the joint, applying intense localized heat to cold cast iron causes the adjacent areas to expand unevenly and crack upon cooling. By gradually warming the entire component beforehand, technicians reduce the temperature difference between the weld zone and the rest of the block.
Based on the passage, what does the author imply would happen if a mechanic welded a cold cast-iron block without preheating it?
- AThe welding filler rod would fail to melt properly at the joint.
- The engine block would be at high risk of cracking due to uneven thermal changes.Answer
- CThe surrounding metal would easily melt along with the filler rod.
- DThe propane torch would be required to cool the joint after welding.
Answer
The engine block would be at high risk of cracking due to uneven thermal changes.
The author explicitly points out that applying intense heat to cold cast iron results in uneven expansion and cracking upon cooling, which technicians prevent by warming the metal beforehand. Therefore, omitting preheating implies that the block is likely to suffer structural cracks.
Step-by-Step Solution
Key Concept
Deducing unstated outcomes from explicit cause-and-effect relationships in technical passages.
Estimated Time:45s