A technician removes a box of 2024-T4 solid rivets from cold storage (icebox) to install in a wing skin repair. Which statement correctly describes how these rivets must be handled?
- AThey may be left at room temperature indefinitely without any effect on their hardness
- BThey should be placed in an oven and artificially aged before installation to increase strength
- CThey must be driven within the time specified by the manufacturer (typically about 10 to 20 minutes) or returned to refrigeration before natural aging makes them too hard to buck
- DThey can be freely substituted for 2017-T4 rivets with no time restriction since both are icebox rivets
Show answer & explanationAnswer & explanation
Correct answer: C. They must be driven within the time specified by the manufacturer (typically about 10 to 20 minutes) or returned to refrigeration before natural aging makes them too hard to buck
2024-T4 icebox rivets are solution heat treated, quenched, and refrigerated to delay natural aging. Once removed from cold storage they begin to age harden at room temperature and become too hard to drive properly if not used within the specified short time window (much shorter than 2017-T4 rivets), so they must be driven quickly or re-refrigerated.
Why the other options are wrong
- A. Room temperature exposure causes natural aging that hardens the rivet over time.
- B. Artificial aging in an oven increases hardness further and is not the correct handling step for driving rivets.
- D. 2017-T4 and 2024-T4 have different allowable room-temperature times and are not interchangeable without limitation.
Icebox (Heat-Treated) Rivets
2017-T4 and 2024-T4 aluminum rivets are solution heat treated, quenched, and stored refrigerated to keep them soft and workable until installation, since they naturally age harden at room temperature.
- Stored below freezing to slow natural aging
- 2017-T4 usable roughly 1 hour at room temperature
- 2024-T4 usable only about 10-20 minutes
- Must be re-refrigerated or re-heat-treated if the time limit is exceeded
Memory trick: Icebox rivets are like ice cream — melt (warm up) too long and they harden and spoil the job.