Brittle Metal after Welding

[silky]

Hi,

For those with experience adding steel to locks using weld, do you find it necessary to heat treat the lock prior to filing/shaping the weld? If so, mind sharing how you do it? I have a heat treating oven.

I have used mild steel weld to add metal in a few spots of a lock, but it seems brittle as I’m trying to shape it — the new steel seems to chunk off easily. I used an oxyacetylene torch and an RG45 welding stick. I’m very new to welding so technique may be the issue. I did try annealing the parts, after welding, in the oven at 1600 degrees for thirty minutes and a slow cool, as well as heating them red-hot and letting them cool in a pile of hot ashes… still brittle.

Thank you!

- Tom

[smart dog]

Hi Tom,
When you gas weld you likely will produce some scale on the surface of the steel. That scale may be carburized and hard making filing and drilling difficult.  First, clean off any of that scale with coarse sand paper or a wire wheel.  To avoid hardening the weld and steel when welding, heat the metal to be joined very slowly with the torch with a neutral flame, add the weld at just the right temp (the point at which the metal surfaces start to become a little glossy) and then slowly back the heat away so the weld cools slowly.  If you are using mild steel rod, that should do the trick, however, the steel alloys in the lock plate and other parts may still harden somewhat.  Cleaning off any scale and then annealing in your oven should solve the problem.  Your brittle crumbling metal is likely from heating it too hot and burning the steel

dave

[silky]

Perfect. Based on what you describe as the right way, I think I was overheating and cooling too fast. To anneal, would you say 1600 for thirty minutes followed by cooling in the closed oven with power off be good? Do you have a better recipe?

Thank you so much, Dave. This helps a ton.

- Tom