Can you repair or fix forge weld delams?

[Simon Thibault]

Hey! I had a success doing a 5-layer 3/4" wide welded billet and i'm on to my next one, a 3-Layer 1.5" wide billet. I'm using a charcoal pit forge at very high heats (seems to be a big advantage of charcoal) and did both of these without flux, opting for keeping the billets too hot to form scale instead. 

 

So on this billet, which is about 3" long, the lower 1.5" or so seems nicely welded, but there are failed welds or delams on the upper section, the part that didn't get placed into the depths of the firepit.

 

 What do you folks suggest to close the failed welds in the upper section? or is it not something i can fix? I've got it soaking in salted vinegar in the hopes that that will get rid of the scale and other debris, but not sure how to close it up.

Edited September 24 by Simon Thibault

[Alan Longmire]

You can certainly try rewelding it.  Vinegar alone should work, not sure why the salt?  Clean the seams with a wire brush, flux, and try.  As an absolute last resort, if the delams are open, pry them open further and pack with sugar mixed with cast iron filings.  Do this hot.  The sugar adds carbon and helps hold the iron filings in the crack, which also adds carbon.  The higher the carbon content, the lower the welding temperature.  Doesn't always work, but when it does it's a neat trick.

[Brian Dougherty]

14 hours ago, Simon Thibault said:

... opting for keeping the billets too hot to form scale instead. 

 

I'm not sure this part works the way you think it does.  Reducing scale is about keeping the oxygen away, either by being in the right part of the fire, or with a gloopy flux that coats the metal.  For the most part, the hotter something is, the faster it will oxidize.  However, I'm sure someone will come along to chime in if I'm leading you astray.

 

That being said, it is common to not get things hot enough when welding, so more heat is generally a good strategy as long as you aren't burning up the steel.

[Simon Thibault]

15 minutes ago, Brian Dougherty said:

 

I'm not sure this part works the way you think it does.  Reducing scale is about keeping the oxygen away, either by being in the right part of the fire, or with a gloopy flux that coats the metal.  For the most part, the hotter something is, the faster it will oxidize.  However, I'm sure someone will come along to chime in if I'm leading you astray.

 

That being said, it is common to not get things hot enough when welding, so more heat is generally a good strategy as long as you aren't burning up the steel.

 

Thank you for this Brian, what I read somewhere was that scale forms at around 1600F, I believe, so keeping it real hot to avoid that and assumed this was correct as on my first billet seemed to have few delams. However that does not necessarily mean that my understanding is correct, so i'm very interested in learning more about the intracacies of flux-less forge welding and how to avoid scale, because i think this might be a new addiction for me,

[Simon Thibault]

1 hour ago, Alan Longmire said:

You can certainly try rewelding it.  Vinegar alone should work, not sure why the salt?  Clean the seams with a wire brush, flux, and try.  As an absolute last resort, if the delams are open, pry them open further and pack with sugar mixed with cast iron filings.  Do this hot.  The sugar adds carbon and helps hold the iron filings in the crack, which also adds carbon.  The higher the carbon content, the lower the welding temperature.  Doesn't always work, but when it does it's a neat trick.

Not sure, in my excitement i may have just salted my vinegar! i assumed salt makes more corrosive vinegar? i'll switch it to plain vinegar.

 That is so cool about the cast iron fillings!

 I'll obtain a wire brush, brush it real good, then flux it. Laundry borax powder for the flux? I don't have flux or a wire brush yet!

 One thing i love about forge welding is that it has really reduced my need for tongs as I can weld handles of mild steel onto my blade steel now, which is amazing. 

Edited September 25 by Simon Thibault

[Alan Longmire]

58 minutes ago, Simon Thibault said:

scale forms at around 1600F

 

More like 1400 F, and it forms faster and thicker the hotter you get. I missed that part of your original question, sorry.  As Brian said, the only way to keep scale from forming is to keep oxygen away from the steel.  A reducing fire and flux both do that, and borax fluxes absorb some iron oxide.  That's why it's black when it spatters off the steel during the weld and subsequent forging. 

 

55 minutes ago, Simon Thibault said:

i assumed salt makes more corrosive vinegar?

 

It probably does, but you don't want corrosive here.  You just want gentle oxide removal.

[Simon Thibault]

Thank you, i believe i've got the oxygen free fire - pile of charcoal with flames shooting up out of it - so, ensure the steel doesn't drop to 1400F? What i do is i try to really keep it hot like out of the fire, gentle hammer taps, right back into the forge. Maybe 5 seconds out of the fire at a time.

 But back on topic, i'm looking up flux now and am watching YT videos as to how to apply and use that

Edited September 25 by Simon Thibault

[Alan Longmire]

If the flames are blue, you are in reduction, meaning all the oxygen has been consumed and you're seeing the combustion of carbon monoxide.  If the flames are yellow, you're oxidizing and getting scale.  And I think you missed the bit about scale forming at all temperatures above 1400F.  It forms faster the hotter you go.  You'll see it falling off the steel as dust while forging, bigger flakes the colder it gets.  Scale goes liquid just above welding heat, but that doesn't help since by then the steel itself is burning out the carbon.  Flux liquifies the oxides at lower temperatures.  Borax, anhydrous borax, and boric acid are the best known fluxes.  

[Simon Thibault]

Greatly appreciated Alan thank you kindly!