The Bronze Age is a historical period characterized by the use of bronze. A lot of things including a weapon were cast of this beautiful metal - bronze. I want to cast aluminum bronze dagger. Sure, aluminum bronze wasn't used that time but classic tin bronze has very similar mechanical characteristics. Nowadays, tin is pretty expensive, so aluminum is a good alternative. The most important is to use hard metal and aluminum bronze is really hard! One of the hardest bronzes.
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Step 1: Cutting a Polystyrene Foam Pattern and Making a Mold
The hardest thing in the whole process was to cut a dagger of polystyrene foam. I could make a handle, blade and even edges using hot wire cutter and sand paper. Well, I couldn't make it perfect because I've made some mistakes.
When a pattern is ready it's time to make a mold using green sand.
Step 2: Alloy Composition
For this casting I need to use really hard metal. In the past I tested aluminum bronze which contains 88% of copper and 12% of aluminum: DIY ALUMINUM BRONZE. ONE OF THE HARDEST BRONZES It's hard and pretty cheap, so I decided to use it for this project.
Step 3: Melting Metals
First of all, I need to melt copper. When it's melted I will add some aluminum bronze ingots which I've made in the past. Finally, I will add aluminum.
Step 4: Dangerous Bronze Casting
I wasn't prepared that my crucible would be heavier than usually. I've never made it full in the past :). I've spilled some bronze plus hit a mold (a riser). Everything started to burn. I always have water and a fire extinguisher near the place where I melt and cast metals! Safety first.
Step 5: Open the Mold
The result of the casting is far from to be perfect. I though that if I use high risers I can cast bronze right on the foam model. In fact it doesn't work like that. Risers should be aside from the pattern. Always! In addition, I had an issue with the edge of the polystyrene pattern. After brushing and sanding the dagger looks ancient, like it was dug out on the field of some roman battle.
Step 6: How Hard Is the Dagger
The hardness is grate. After 3 tests the best result is 24.8 HRc. Comparing aluminum bronze and brass it's 24.8 HRc vs 14.9 HRc! Basically, aluminum bronze has the similar hardness as soft steel.
Step 7: Si Vis Pacem, Para Bellum
Overall I satisfied with the result. Of course, the quality could be better. The Centurion Dagger has the weight 812 gr and hardness 24.8 HRc what is really good.