I made these hooks for my Dad. No, they aren't pretty, yes they'll work. They will be hung in his shop, used for extension cords, air hoses, etc. Should I heat treat them? If so, what method should I use? 

Good Morning,

No Heat Treat required. They will not be receiving any impact. They will be 'Hanging Around'.

Paint a tiny face on them, with a goofy smile. Give them Life.

Neil

Now you do know that heat treat does NOT mean harden right?  Annealing is a heat treat that makes the steel very soft. So when you ask if you need to heat treat them you need to tell us if you were thinking of making them soft, or tough, or hard or what?

If they were made from mild steel then heat treating usually doesn't do anything---you can quench very low carbon steel in water and it won't harden!

If they were made from high carbon steel I would normalize them to make them tough but not brittle.

So you need to give us what alloy they are to know if the heat treat result you want is even possible.

If you will be hanging stuff from them you may want to round the contact edges to decrease wear on the hoses.

ThomasPowers

I'm relatively new to the craft, I was under the impression that heat treating meant hardening. Thanks for correcting me! Also, I don't know the alloy, I think it's just mild steel. The metal just appeared in my project bucket one day, I don't even know where it came from or who put it there. Also, thanks for the tip about rounding out the edges. I'll make sure to do that. 

heat treatment means using heat to change the properties of the metal

In general high carbon steel is not used except where it's properties are needed as it's more expensive to make and work and requires heat treatment after working to get the results wanted. Businesses tend not to like paying more unless they absolutely have to.   

On the other hand I have had High C scrap sneak into what I thought was only Low C stuff.  So when working with scrap metal of unknown provenance you may want to test it with either the spark test or the heat past critical and quench and try to break test. (USE PPE! If it was HC; then it can shatter sending shrapnel!)

Thank you for the instruction!