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It's been a long time but now I have a Damascus problem.


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I haven't been on this forum for a long time but I am now getting into making kitchen knives. I have welding problems with my Damascus blades. The first weld of a billet goes smoothly. I have done it both with and without flux with little trouble. But the second and subsequent welds tend to be problematic. I always grind the scale off and the only thing I I don't always do is let it cool completely before stacking it. So often there is blue oxidation when I try subsequent welds. I am using a reducing gas forge and weld between 2150- 2200.  Usually I can get it to weld to set but it takes far more effort than I think it should. And the last feather pattern I made I can't get it to completely weld after it is split with the wedge. Any thoughts? Thanks Todd

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What steels are you using, and which ones are on the outside of your first stack?  There are some that work in a stack, but don't like to weld to themselves.

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Brian- I am using 1080 and 15n20 and the. 1080 is on the outside. 

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1080 and 15n20 are an easy weld. There should be no problem of having the same steel on the weld.

 

Without more data it is hard to troubleshoot. From what you describe you should be getting good welds. However, feather pattern by its very nature wants to delaminate all the time. You probably already know this, but keep it HOT, because if you try to move the steel in a feather billet when its even a little too cold and it'll split up like a celebrity couple. 

 

You're not getting flux trapped inside your welds, are you? Make sure you are grinding the layers to a crowned shape rather than a cup shape between welds.

 

Luck.

 

Dave

 

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Yeah Dave, that's what I find frustrating they should be easy to weld. I don't think flux entrapment is the problem. In fact where I welded the split back together it is welded in the center but not the edges. The Ws are holding up fine. Do others let their billets cool between welds so there is no oxidation?

 

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The way my shop and forge are positioned I have to either fold and reweld all while hot, or I have to cool the material down and grind it clean to re-stack.  (there is 400' between my forge and the nearest power tool)  So if I am doing something that involves precise restacking, it is al pretty cool and clean when it goes back together.

 

I wouldn't have thought a little blue oxide would be an issue with the proper forge environment, but can't say that I have welded something that was truly "Blue".  However, I no longer grind off the mill scale from my 1084 and 15N20 pieces when I do my first stack.  I just use them as they came from the steel supplier, and I would have thought those oxides would be harder to weld through.

 

Can you explain your process a bit more?  

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Posted (edited)
3 hours ago, Brian Dougherty said:

but can't say that I have welded something that was truly "Blue". 

I finally got some forge time and welded up a few pieces of 15N20 together that I had TIG welded the seams together about 2 months ago.  The outer pieces developed the blue heat oxidation color so I'm assuming the inside pieces did too, but it seemed to weld up fine:  

 

 

Edited by billyO
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I always cut and stack hot, and I've never noticed the blue affecting anything.

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 A little more detail on my process. Like I mentioned the first weld of the stack seems to go easily. I just use the steel the way it comes from Kelly Cupples. The 15n20 is shiny and the 1080 is cold rolled so it is pretty clean too. After the first weld Then I draw it out and grind it down to clean metal which goes blue from the heat. After cutting I stack and tack weld the corners. Heat to glowing and flux with borax. Heat to 2150ish and give it a light squeeze on the press. Heat again and squish harder with the press. Heat again and hand hammer around the edges. Then I have gotten paranoid so I often grind it some to see if it has welded. If it hasn't completely welded then I repeat the above in no particular order, just trying everything. Usually that eventually works but not on this feather billet. 

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That's confounding.  If it wasn't for the fact that you get the first stack weld to stick, I would have guessed that you are not letting it soak long enough.  However, I doubt that is the issue here since the problem seems isolated to the second stacking.

 

I will say that 2150F is kind of on the low end of the range I shoot for.  I like to get over 2200F.

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Hi Todd, sorry to hear the frustration, but I'm a bit confused.  Are you saying you're having difficulties with subsequent stacks after the first stack and weld, or just when you are doing a feather pattern. 

If the former, then I have no ideas and can only offer you positive thoughts and wishes of luck.  

If the latter, I'd agree with the comments about probably getting a little too cold when splitting the final stack.  One thing I do to try to prevent this is to squish the stack a little each heat when using the blunt chisel to split, to try to 're-set' the edge welds where they tend to start to spread apart.  Even though this shortens the stack a little, it doesn't matter when you forge the billet out into the blade. 

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I have just read through this thread twice. Here are my observations and opinions.

 

On 5/26/2021 at 11:44 AM, Todd Miller said:

I am using a reducing gas forge and weld between 2150- 2200.

How is the temp determined? A thermocoupler can be off by a couple hundred degrees one way or the other, depending on where in the forge it is located.. In any case, I think you are too cold. Get it over 2200 and keep it there for all the welding and forging operations. 

 

On 5/26/2021 at 4:46 PM, Todd Miller said:

The Ws are holding up fine.

This leads me to believe that you are trying to make a Ws patterned billet and then do a feather split. The stacking of the Ws is going well and the split is where you have the trouble rewelding? So I would reiterate Billy O.'s question.

 

If the subsequent stacking to create the Ws is a problem, I would say it's the heat and soak time that is causing the delams. 

23 hours ago, Todd Miller said:

After the first weld Then I draw it out and grind it down to clean metal which goes blue from the heat. After cutting I stack and tack weld the corners. Heat to glowing and flux with borax. Heat to 2150ish and give it a light squeeze on the press.

Again, the temp is too low. I also do full squeezes on three welding presses every time I stack and weld. Grinding clean MUST be done across the billet, not lengthwise and no coarser than say, 100 grit to prevent creating oxidation and flux tunnels between layers. Like Alan, 

On 5/27/2021 at 8:46 AM, Alan Longmire said:

I always cut and stack hot,

 

23 hours ago, Todd Miller said:

Heat to glowing and flux with borax

Less is more. I only use enough flux to read the temp. When it is boiling vigorously, flip the billet upside down and check the other side. When both sides are  boiling, it's time to weld. 

 

Ultimately, I think your process is good. You just need to add more heat and soak time. Remember to do all of your drawing out at welding temp. This reinforces the welds as you forge. Draw out in small increments. Don't try to move a lot of steel quickly, as that only encourages delamination at the edges. I have started to do my drawing out of Damascus with flat dies rather than rounded ones, and I draw out in the press. This way, the drawing out process is really just more welding operations.

 

My initial billets are typically 1.5" wide and 5.5" long. My welding dies for the press are 2"x6". The first three welding presses happen along the entire billet with the billet inline with the dies. The next few passes are done with the billet perpendicular to the dies and done in overlapping 2" bites. This begins the drawing out process. I will also turn the billet on edge and draw it out to keep it fairly square as I go. If there is any edge delamination, it will appear instantly during this pass. 

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Thanks for the responses. I'll check my thermocouple and try soaking longer. Those seem to be the most likely culprits. 

 

Todd

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On a side note, I have found that by placing the 15N20 on the outsides of the stack, it pits much less than the 1080 from scale. This makes grinding much easier and less steel wasted.

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