Mystery steel work hardened after welding?

This is a PITA! I though it was some 1020 rod stock.......I did label it a long time ago but the rust around here soon fixed that up.

I got no idea what this stuff is as it must have been a rusty bit I picked up along the way.

I turned up 4 slugs and pre drilled them for a 1/2" tap. Welded them in place and cleaned them up. Was trying to tap them and the bloody things are rock hard! The tap just skated on it. I tried to enlarge it 11.5mm just past the lip...no luck... Any thoughts fellas? It's buried in a piece of 75 by 50 by 3 and welded both sides.... Lovely! :U

Did you quench after welding?

Anyway - just heat them up to red again and then let them air cool and you should be OK.

No water quench, they were hot and quick mig welds.. I was thinking about trying that. I might have to duck up to my neighbours place as I do not have an oxy and the part is big enough to act as it's own heat sink.
I sharpened up a masonry bit to bust through to skin an have managed to get one of the 4 tapped. Here is to hoping it's just the first 5mm that hard!

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Originally Posted by BobL

Did you quench after welding?

Anyway - just heat them up to red again and then let them air cool and you should be OK.

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I'm not so sure that is going to work.

Seeing as it air cooled from welding, trying to anneal it is a long shot.

Rob

I got lucky! Broke a sweat and chipped a tooth on the tap but I eventually got them done!
I'm going to spray the 1020 with pink paint from now on! I'm not in a hurry to do that again.

It could have been a bit of D2 I had floating around from years back. Or I just was unlucky with what was in the scrap pile...? It machined like gummy mild steel...