According to Toller :

Has anyone else used these bits on steel?

I have heard it doesn't work, but your experience obviously shows it does.

From your description you were drilling the steel dry? That isn't going to
work.

Carbide drills once they're used, have fairly rounded tips - they "cut"
largely by bashing their way thru masonry. Which is why hammer
drills make masonry drilling so much easier, but does almost nothing
for wood or metal.

Mild steel drilling is with sharp-edged tools - ordinary twist
drills with proper edges and relief angles. In a drill press with
a good bit, you see these nice continuous swirls of metal swarf
coming off the drill bit. A carbide tripped drill ain't sharp.

_However_, particularly with hardened steel (which can't really be "cut"
at all with edged tools), you can cut with a fairly dull bit - by
melting your way through. Problem being that the drill bit tip has to
stay hard while the stuff you're drilling gets soft. With an ordinary
drill bit, the tip just deforms and you don't get anywhere, and you
feel like you're trying to push cooked spaghetti thru a cinder block.

Carbide has a considerably higher melting/softening point than steel.
So, in some cases a carbide drill bit would work fine. If you use
a lubricant or coolant, this won't work at all, because the work
simply won't get hot enough.

There are special drill bits specifically designed to get hot and melt
their way through hardened steel. Had a shop instructor demonstrate one
once - piece of hardened steel could not be scratched by a file or a
normal cutting tool. With the special bit in a hand drill, he got
through it in seconds. Threw droplets of molten steel, sparks, and the
hole glowed for a few minutes... Eye protection _definately_ advised.
--
Chris Lewis,

Age and Treachery will Triumph over Youth and Skill
It's not just anyone who gets a Starship Cruiser class named after them.