Easy Aluminum Repair/Farbrication

[Hammered]

Could the heating problem be avoided on something like a cylinder fin by first raising the overall temp of the part in an oven?

I do some jewelery making and when fusing silver, I found that I get the most control of the process by placing the pieces I want to fuse on a hotplate and then directing my torch in the area I want to fuse.

This would require that everything be set-up and ready to go the moment the part comes out of the oven but it should reduce some of the heat sinking that seems to be the problem.

It could, but Ive found using a heat blocker works best. I use this stuff. It helps for what I do, reduce warpage. http://www.alvinproducts.com/Products/Products.asp?ID=7 It will also aid in keeping the heat right where youre putting it.

[DMorris]

But doesn't this material work by sinking heat away and dissipating it to the atmosphere so as to keep the surrounding material cooler?

What I was thinking was that if there was too much of a thermal gradient across the part, it becomes difficult to raise the temp in the work zone in a controlled way.

By bringing the temp of the whole part to a temp closer to the working temp of the bonding material, it becomes easier the add just enough heat in the work area to get the bonding material to flow.

[Hammered]

But doesn't this material work by sinking heat away and dissipating it to the atmosphere so as to keep the surrounding material cooler?

What I was thinking was that if there was too much of a thermal gradient across the part, it becomes difficult to raise the temp in the work zone in a controlled way.

By bringing the temp of the whole part to a temp closer to the working temp of the bonding material, it becomes easier the add just enough heat in the work area to get the bonding material to flow.

From all the time Ive used heat sink material, what Ive found it does best is to localize the heat. Aluminum has that great property of sinking away heat by transmitting it throughout the whole piece. This doesnt allow that transfer to happen as fast. Thus keeping the heat where youre trying to apply it. Like I said, I use it on Jon Boats to keep the rest of the area from warping. you can put your hand in the metal outside the ring of putty but not on the inside of it. Theres a huge difference in the heat on one side to the other. And as far as rebuilding fins, a piece of Stainless as a plate to allow the HTS to fllow onto works great. I use this method when filling a hole too large to span with just the filler.

[DMorris]

OK, Hammered. I'll bow to your experience but I'm still scratching my head about the physics.

Thanks for the info though!

Best, Don

[tkent02]

Welders have been preheating metals forever, it works well.

[mighty13d]

materials like cast iron and high yield steel require preheating. if not... the weld snaps in two... Thin material would be the best for totally local heat, if you're working with thicker stuff and can throw it in the oven to help, by all means, do it. just don't heat it too much and warp it like was said. and don't rapidly cool it either. that can warp it too