Delamination on san mai billet

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Ptrkgrgr

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Aug 20, 2020
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Hi guys. I am trying to forge sanmai billet out of 80crv2 core and 15n20... first I tried 1 layer 80crv2 and 2 layers of 15n20... i had just small delamination, i checked all forums and i tought that i found my mistakes. I decided to try another billet but this time 80crv2 (5mm thick core) then 15n20(3mm) then 80crv2(3mm) I clamped that and weld corners plus middle part of billet. After 4-5 cycles of forgewelding i tried if welds are good and they were perfect. Then i forged that billet to dimension which i needed. I check everything and there was no delamination. After heat treating i found delamination. Do you know guys what can be problem? Maybe when i was forging that billet temperature wasn’t high enough? Should i forge the billet still on welding temperature? Any ideas? Thank you so much :)
 
Ptrkgrgr said:
Any ideas?
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I'll defer to those who have more experience, especially when talking about 'more exotic' steels. It's a bit hard without seeing the piece and the process, but the first thing that comes to mind, especiallly if the billet was solid after the welding heats, is that you possibly did some forging of the blade too cool and sheared the weld while forging the blade.
Another thing that happens occasionally is that even when being diligent about cleaning and prepping the billet, an inclusion gets in the stack somehow and you get an area with a bad weld. And unfortunately, they might not show up until final grinding. About 2 years ago, I had a billet that looked pretty good, but a bad weld popped up when I was almost finished hand sanding, at 800g. That was a frustrating day.
 
Thank you for help. I think it could be that cold forging... But i prepared another small billet and i will see tomorrow. I cleaned everything 100% then welding and now it is waiting untill tomorrow in bottle with acetone. I will be extremely careful about temperature while forging. What do you think should i forge with welding temperature or lower? And with that your billet two years ago that had to be super annoying. I would kill someone that day
 
A forge weld can be anywhere from 1% to 99.9% welded. To get the best welds, you need to draw the billet out to twice the starting length. From there you can forge to shape. Starting with heavier stock will help.

Hoss
 
DevinT said:
A forge weld can be anywhere from 1% to 99.9% welded. To get the best welds, you need to draw the billet out to twice the starting length. From there you can forge to shape. Starting with heavier stock will help.

Hoss
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And what you recomend? When i am drawing billet should i use welding temperature or lower?
 
DevinT said:
How hot is your welding temperature?

Hoss
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I have no thermometer in my forge(i have already ordered one) but colour of my billet while welding is very bright, glowing yellow colour, borax is bubbling on the top.
 
I have found a very important aspect to continuity and success in forge welding, not often spoken about, is 'soak time' after the initial weld has been set. Get it back in the forge after the 1st welding pass, and let it sit nice and quiet at full welding heat for a few mins before you start hitting it again.

I learnt this doing crushed 'W' feather patterns. A decent soak stops the bulk of welds splitting open when they are forged 'against'
 
Why edge quench? When two different types of metal are quenched they may not move the same. This difference in movement may cause the blade to pull apart.
 
John N said:
I have found a very important aspect to continuity and success in forge welding, not often spoken about, is 'soak time' after the initial weld has been set. Get it back in the forge after the 1st welding pass, and let it sit nice and quiet at full welding heat for a few mins before you start hitting it again.

I learnt this doing crushed 'W' feather patterns. A decent soak stops the bulk of welds splitting open when they are forged 'against'
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Thank you, i will try tomorrow ☺️
 
I’m no expert but from reading your original post and your concerns about forging temperature... I can only say that I suggest you refocus on the forge welding process and temperatures at welding

I don’t do a lot Forge welding myself but I do work with a lot of laminated steel.
You seem to be thinking that you were forging and drawing out the billet at too low a temperature. I really don’t think that’s your problem based on my experience of forging laminated steels.

sorry I don’t have specific advice for you on forge welding.
 
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