Oh dear, I've done it again ....

Picked up some 2" steel bar yesterday thinking it was mild steel and it's not....
Funny thing is I'm lost to what it might be. The power hacksaw and bandsaw won't touch it, after scratching the surface the teeth are gone, well half gone.
But it files ok ... that's what stumps me

With tungsten tips it lathes beautifully, fantastic finish very much like the lorry half shafts I machined some time ago. But the finish is not as chrome like and a tad more even. That could be the lathe though.
When lathing the swarf comes off in one long piece with each cut and rarely breaks. I'm talking 15ft of swarf 'ere in one long string. It's tough too like a spring.
What else? Oh yes, I got roughly two pieces 3ft long, these were cut from 6m lengths of which there were plenty of in the yard. So it's not halfshafts this time. This is bar stock...but what

Does machine nice though, just can't cut it .....

Edit: Just remembered sumut, it doesn't seem to have a soft core, same all the way through.