Steel as a heatsink?

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It seems like most heatsinks are made of aluminum.I'm assuming that it has better thermal conductivity than steel does otherwise why use it as aluminum is more expensive than steel.I purchased a kicker zr240 board online and once i get it in working order i'm going to need to fabricate a heatsink for it so i'm wondering if steel will work or if its such a poor thermal conductor that it will only lead to the failure of the components
Steel will not conduct heat as well. According to the following site, aluminum is 4x better.

Aluminum will be easier to work with and isn't necessarily more expensive. Steel is generally rougher than aluminum so it will require much more work to get a smooth surface (needs to be smooth under the transistors for efficient heat transfer).

There are plenty of places on the net to buy aluminum stock.

Since you'll have to make something, why not cut up the sink from a cheap/junker amp? If you know someone with a bandsaw, they can quickly cut the sink to size. If the holes in the old sink fall directly under the ZR240's transistors, use a piece of 1/8" stock between the transistors and the old sink. Then drill and tap new holes.
Heat travels through aluminum fast, if you heat one end the other will warm shortly. Steel takes much longer, you can torch the end off a steel bar while holding the other end and later you will let go because it is hot....alum gets hot way faster, and cools much faster. Copper also absorbs heat well, thus you see copper CPU coolers for PCs. I would try to find a way to get some aluminum, must be able to find what you need someplace. You also have the issue of rust with steel as paint can hinder the heat transfer....though some aluminum amps are painted anyway. But I guess it also depends on how much heat you need to get rid of.
Jonny Hotnuts said:
If you want to do something really trick you might want to try liquid cooling the amp.

It is not as crazy as it might sound.

I have done liquid cooling setups with amps with great results and in the correct install looks jaw dropping.

Very easy to do

-Use hollow aluminum square tubing
-Cut into two pieces to have one for each side of the board, or bend into a "U" shape
-solder endcaps with brass compression fittings for nylon tubing screwed into them
-use 12v fuel pump and antifreeze in the coolant to keep the pump happy
-small external transmission cooler under the hood in front of the stock radiator, a reservoir would be a good idea to prevent pressure buildup and allow you to add water or drain if needed. I used a junkyard windshield washer bottle in my last setup and just removed the pump. The outlet was just drilled into the top of the reservoir.
-obviously you will also still need to use insulators between the transistors and the tubing

Everything can be purchased at Lowe's or Home Depot except the universal fuel pump.. at most auto parts stores for about $30. You will just have to decide how you want to secure the transistors to the tubes and there are many ways to do that without cutting into the tubing.
MJL21193 said:

Ever try to bend a square aluminum tube into a "u" shape? That's not easy.

Neither is soldering end caps on aluminum tubing.

Maybe I should have said "brazing", the bending requires packing the tubing with sand and crushing the ends to seal it in. Then it has to be carefully heated with a torch and bent. I've used the two piece method and it was easy for me. I helped a friend bend the tubing and that wasn't difficult either. I guess "easy" is a matter of opinion. I know people who think swapping a radio in a 99 chevrolet pickup is difficult... I can do it in about three minutes, literally.
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