In the US, the round stuff is called "drill rod", and the flat stuff is called "flat stock". The water hardening type (W1 here) is cheaper, but the other varieties machine better (such as O1, which is an oil hardening, high carbon, tool steel).
I know this thread is years old, but the link didn't work because the two url's got jammed together. As of now, the first half, https://www.speedymetals.com/information/material71.html, is still a valid page. Couldn't get the other to come up.Sorry Idon't no why that link did not work. But if you click on the drill rod tab then click here for material description...........This will give all data on the drill rods they sell including harding and tempering temp.