Rods get pulled from wells during workovers or abandonment activities. Then inspected for anything that might cause future issues - pits, defects, bad threads, bent... Anyways for chopping up into little lathe projects, sounds like a good source of 4xxx series steel. Maybe not the easiest stuff to turn on small machines, but its pretty tough stuff & can be nicely surface finished with the right technique. You can also heat treat (harden) some of these alloys too if you're set up for that. Hard to go wrong for the price.
The scrap to avoid or at least be aware of is chromed or semi hardened material, usually shafting or big pins. It can be ugly on our cutting tools. Some people will try & anneal semi-hard chunks in their BBQ but now you're trading gas for mystery metal.