The Low Temperature Annealing of 7.62 mm Brass Cartridge Cases: Stress Corrosion Susceptibility
Rept. for Sep 1978-Jan 1980
MATERIALS RESEARCH LABS ASCOT VALE (AUSTRALIA)
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This report outlines an investigation into the effects of hardening during low temperature annealing on the stress corrosion susceptibility of brass cartridge cases. The low temperature annealing occurs in the lower walls during the mouth annealing process in the production of 7.62 mm cartridge cases. In this work cartridge cases were taken from the production line prior to the mouth anneal and then annealed in an oil bath at 200 C or 250 C for a range of times. These cases were then exposed to an ammonia environment for 4 h. The tests showed that there was no evidence of enhanced stress corrosion susceptibility at higher wall hardness resulting from the artificial low temperature annealing. The degrees of cracking in the lower walls of the cartridge cases were found to decrease with increasing times of annealing with no evidence of cracking for times in excess of 6 h at 250 C. However, the trends in the results for the cases annealed at 200 C were less obvious. Reasons for this are put forward. The hardening in the cartridge cases on low temperature annealing is explained in terms of modern theories of recovery in cold worked brasses.
- Properties of Metals and Alloys
- Fabrication Metallurgy
- Ammunition and Explosives