| When the novice hobby metal caster first thinks | | | | to take place. |
| about melting metal, the immediate thought is to | | | | The skin of the oxide on the molten globule has |
| collect a big box of Al bottle tops and Al drink | | | | to be "ruptured" in order to allow coalescence, i.e. |
| cans to melt. The most likely reason for this is | | | | to allow the clusters of globules to actually join |
| that the material is relatively easy to collect and | | | | together in their molten state. |
| handle, and the thinking behind the idea is that | | | | A molten flux encourages coalescence by |
| because of its lightweight it should melt quite | | | | chemical action. |
| readily. | | | | While the rotation of the furnace provides a |
| Then why is it so difficult to melt & reclaim | | | | mechanical action. |
| aluminium drink cans, bottle tops & swarf in | | | | The special fluxes; coveral 48 & 57 provide |
| a hobby gas fired crucible furnace? | | | | the chemical action,they are the best type of |
| To melt & reclaim light weight scrap | | | | fluxes to use when melting Al metal inthe region |
| aluminium requires the use of some specialised | | | | of 590 to 600 C. (Coveral 48 & 57 products |
| equipment. Most commercial scrap metalrecovery | | | | are copyright Foseco Pty Ltd) |
| foundries use what is known as a rotary type | | | | This flux may or may not provide similar results |
| meltingfurnace. This type of furnace is designed in | | | | when used in a normal crucible gas fired furnace, |
| such a way thatthe flame actually strikes the | | | | but the yield loss will still be considerable. |
| rotating furnace lining, and theheat spreads quickly | | | | The hobby foundry worker would be better off |
| around the furnace walls, which absorbthe heat. | | | | directing hisenergy towards collecting easier to |
| As the furnace rotates, the heat is also taken up | | | | source, better quality scrapto melt, such as |
| orabsorbed by the scrap metal. | | | | discarded cylinder heads, inlet manifold castings, |
| It is essential to melt the metal under a cover of | | | | auto pistons, etc. Or if the budget stretches that |
| MOLTEN FLUX, otherwise very heavy metal | | | | far, purchase commercially produced ingots, which |
| oxidation results and subsequentlyvery little metal | | | | are of a known quality. Commercial ingots will |
| is actually recovered. | | | | provide top quality metal right from the word go. |
| As each piece of small swarf or chip melts, it | | | | Trying to melt lightweight Al drink cans and bottle |
| forms a globule ofliquid metal surrounded by a | | | | tops is generally a waste of time for the hobby |
| shell of oxide. The skin tension ofthis oxidant | | | | worker, unless you use the fluxes mentioned |
| around the globule prevents coalescence, i.e. (to | | | | above, and use the correct furnace. Otherwise a |
| grow together) and because of the large surface | | | | lot of gas will be wasted heating the hobby |
| area presentedby the mass of globules, with the | | | | crucible furnace for very little gain in metal yield. |
| increase of oxide formation loss of yield is bound | | | | |