I am going to be melting aluminum cylinder head and some soda cans in the home foundry. I am aware the sulphur and the hydrogen present in the melt can make aluminum prone to cracks and brittle.

Are there recommended ingredients that can be put inside the molten aluminum besides flux that precipitates or remove undesirables?

  • $\begingroup$ welcome to SE, remember that soda cans would have carbon due to coatings and carbon tends to make aluminium brittle. I am not sure how can you get rid of carbon because passing oxygen to form $CO_2$ might also oxidize your aluminium. I would suggest adding pure aluminium ingot to atleast dilute your melt of the undesirables. $\endgroup$ – gfdsal Aug 9 '20 at 10:50
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    $\begingroup$ well I didn't know that. This is crucial information. I am more interested in not having to buy pure aluminum ingot because that will un-motivate me for the purpose I am recycling the aluminum. $\endgroup$ – metron Aug 9 '20 at 10:52

I never encountered S or C as problems in Al. The problem with hydrogen is that it can cause porosity as it is dissolved in the molten Al and comes out as a gas during freezing. Engine blocks and heads are usually Si alloys ( 5 to 12 %) like the wheels. They may have some Cu to make it hardenable. I expect contamination problems would be more likely Fe and Cu ( getting too high ). The cans usually have very little alloy.

  • $\begingroup$ acknowledged. Is there any remedy to mitigate the hydrogen? Also Si,Cu are good in my opinion for giving aluminum some strength so they are not considered undesirable right? Also what is the source of hydrogen in Aluminum, is it the coatings on aluminum cans? $\endgroup$ – metron Aug 9 '20 at 21:31
  • $\begingroup$ I was just pointing out that H does not embrittle Al, it causes porosity. If it is present ,I would suspect moisture in the furnace atmosphere ; oxidizing the Al and releasing H to dissolve in the melt. $\endgroup$ – blacksmith37 Aug 9 '20 at 21:52
  • $\begingroup$ alright. I think this answers the question about the fact S or C isn't undesirables. $\endgroup$ – metron Aug 10 '20 at 15:35

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