Welding hard spots

[Jeff64]

A question for the welders in the group.  I bought a flux core MIG welder. I know it's not a TIG, but I couldn't justify the money as my need, for now, is occasional.  Filled in some low spots on butt plate and it appears that in some places, but not all, the metal has hardened.  You can feel the file glide over it.  So did I do something wrong?  It's not everywhere that I welded just a couple of spots.  Can I anneal to make it soft so it can be filed? Thanks in advance.

[jsb30]

Heat area up with ox-acetylene torch to a bright blue color. Remove torch slowly from heated area and let it slowly cool.

[Tim Ault]

Don’t know about flux core  but the migs we use at work use regular wire /gas and the bead is always pretty darn soft welding plain mild galv steel .

[john bohan]

You should check the filler wire to see if it's for mild steel which would be on the 60's. Stronger steels start in the 70's series,no worry you can still anneal. Did you cool this repair fast?

[Jeff64]

I guess it cooled a bit too fast first time around.  Heated it to blue and put it in my tub of vermiculite.  Worked like a charm, hard spots gone.  Thanks all.

[Dphariss]

A question for the welders in the group.  I bought a flux core MIG welder. I know it's not a TIG, but I couldn't justify the money as my need, for now, is occasional.  Filled in some low spots on butt plate and it appears that in some places, but not all, the metal has hardened.  You can feel the file glide over it.  So did I do something wrong?  It's not everywhere that I welded just a couple of spots.  Can I anneal to make it soft so it can be filed? Thanks in advance.

Annealing should work. Not uncommon at all
First something like a Hobart 135 that is gas shielded will cause a lot less grief. Its about 95-98% of  TIG and TIG will REALLY cause hard spots that will not anneal since they can add tungsten in the weld. My little Hobart (I think the current model is a 145 or some such) has welded up all sorts of new and old gun parts. The last thing I did was the trigger on a 1st gen 1873 Win. Can't get this part ANYWHERE since the sear and trigger are one piece. The only time flux wire is good is outside welding something like stake pockets on a trailer when the wind is up.
One never knows what one will run into in a casting and especially OLD gun parts. And I used to work at a place with a TIG and used it. Definite advantages for small parts. But the little Hobart will do it too. May take longer and need more cleanup, but usually can do this with a file not a belt sander. If you hit a hard spot heat to cherry and put in wood ash till cool (or I use my little gas forge and let it cool in the forge) and pray there were not too much chrome from too many old Buick bumpers or chunks of tank armor in the melt.

Making a lock to fit an old inlet when converting a 1960s(?) chunk gun to flint.