More 1084 weirdness

Ok I contacted a past customer that had a batch of blades fail. He agreed to send one of them back to get ground and etched. What makes this blade different then the one(s) that started this thread is this steel actually has a documented receipt to be from NJSB. The customer of the first blades in this thread could not provide a receipt as it was an email that he deleted. So I did not want to start naming names and end up with another whoops it’s from eBay.

But after going through the process with this blade the blotchy pattern is remarkably similar. What is also apparent after some thought and discussion with friends is I don’t think it’s patchy alloy per say. We are thinking it’s either A: lost manganese or did not have enough to start or B: been processed and annealed so far down to the point it would require a crazy abnormal schedule to bring back normal hardenability.

I am hoping to send chunks of each blade out for alloy testing to see what is actually going on. But this blade sparked ok on the surface grinder. I removed between .025-.030 of material before polishing to 3000 grit.

Photo%20Dec%2031%2C%209%2007%2041%20PM.jpg


Photo%20Dec%2031%2C%209%2010%2041%20PM.jpg


Another thing that has me concerned is this steel is sold under the impression that all you need to heat treat it is a magnet and a bucket of something wet so to speak. Also what’s apparent from looking at all these blades is that thy would probably pass the file test as the very edge does look like it has hardened.
 
JTknives said:
Ok I contacted a past customer that had a batch of blades fail. He agreed to send one of them back to get ground and etched. What makes this blade different then the one(s) that started this thread is this steel actually has a documented receipt to be from NJSB. The customer of the first blades in this thread could not provide a receipt as it was an email that he deleted. So I did not want to start naming names and end up with another whoops it’s from eBay.

But after going through the process with this blade the blotchy pattern is remarkably similar. What is also apparent after some thought and discussion with friends is I don’t think it’s patchy alloy per say. We are thinking it’s either A: lost manganese or did not have enough to start or B: been processed and annealed so far down to the point it would require a crazy abnormal schedule to bring back normal hardenability.

I am hoping to send chunks of each blade out for alloy testing to see what is actually going on. But this blade sparked ok on the surface grinder. I removed between .025-.030 of material before polishing to 3000 grit.

Photo%20Dec%2031%2C%209%2007%2041%20PM.jpg


Photo%20Dec%2031%2C%209%2010%2041%20PM.jpg


Another thing that has me concerned is this steel is sold under the impression that all you need to heat treat it is a magnet and a bucket of something wet so to speak. Also what’s apparent from looking at all these blades is that thy would probably pass the file test as the very edge does look like it has hardened.
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how thick is that blade? 1/8” would through harden, but 1/4” probably wouldn’t.
 
It started as 3/16” and the soft spots went all the way through from surface to surface. You could see them from the moment I got the scale roughed off after a few thousands where removed. I have never had a problem with through hardening problem with any alloy is blade thicknesses. After these blades failed I ordered replacement steel from alpha knife supply and admeral steel and with the exact same treatment thy hardened flawlessly.
 
JTknives said:
All blades are checked for flatness and any bow goes up so it seats on the anvil under the diamond. If I had to guess I would say the test area is probably .01-.02 deep below surface. I had not seen the 2.5x diameter spacing before. I know I have tested really close together before and have not seen it affecting the reading but I will keep that in mind. Would that be more critical on softer material as more material is displaced upwards? I think it’s a 220grit belt I use to make the test area on a 7/8” wheel.

99.9% of the time everything goes smoothly and all RC readings are what we expect and consistent. But that .1% seams to be this carbon steel we get from time to time and it just won’t behave. I’m going to try a 1900° soak on a blade and see if that solves it. It did nothing to the last blades we got but those where from eBay.

P.S. is there a SOP on hardness testing that I can get ahold of?
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the platen on your rockwell tester has to be dead flat too. I was getting funky readings at work on our nuclear stuff. Turned out the platen had to be ground as it was beat up. as for the scale issue, i haven't made my first blade yet so i have no idea
 
JTknives said:
It started as 3/16” and the soft spots went all the way through from surface to surface. You could see them from the moment I got the scale roughed off after a few thousands where removed. I have never had a problem with through hardening problem with any alloy is blade thicknesses. After these blades failed I ordered replacement steel from alpha knife supply and admeral steel and with the exact same treatment thy hardened flawlessly.
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Sounds like out of spec steel. do you get PMI reports with your steel?. I used to do QA at a manufacturer and sometimes the steel was not what the supplier said it was
 
JTknives said:
It started as 3/16” and the soft spots went all the way through from surface to surface. You could see them from the moment I got the scale roughed off after a few thousands where removed. I have never had a problem with through hardening problem with any alloy is blade thicknesses. After these blades failed I ordered replacement steel from alpha knife supply and admeral steel and with the exact same treatment thy hardened flawlessly.
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probably low manganese, low carbon, or excessively fine grain structure. My guess is the carbon is locked up in large carbides, and you have a carbon depleted matrix. (Based on previous experience with this vendor.)
 
I wonder what it would look like if you ground in the bevels.

I know many folks have had hardening issues with NJSB 1084 due to coarse spheroidizing. I haven't... perhaps because forge to shape? 1800F - 2000F temps and mechanical deformation might break up the nasty stuff?
 
Rick Marchand said:
I wonder what it would look like if you ground in the bevels.

I know many folks have had hardening issues with NJSB 1084 due to coarse spheroidizing. I haven't... perhaps because forge to shape? 1800F - 2000F temps and mechanical deformation might break up the nasty stuff?
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in the worst examples, people have normalized at 1900f to breakup the course spheroids. Forging solves that issue.
 
So where do we go from here? Think I'm going to go with 1075 or 80CRV2 my next steel purchase. Feel like I am taking chances ordering the 1084.

Has anyone else had problems with the 1084?
 
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R.C.Reichert said:
So where do we go from here? Think I'm going to go with 1075 or 80CRV2 my next steel purchase. Feel like I am taking chances ordering the 1084.

Has anyone else had problems with the 1084?
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I have some 1084 from December '18/January '19 that hardens just fine in my 2 brick forge. It could be way off but the knives hold a sharp edge. I ordered some more 1084 a couple months back and now I'm worried it won't harden when I start working with it.

I'm not sure where to go for steel at this point. I had a good experience with admiral's 1075 last year, but it's labeled 1075/1080, which concerns me. How can you sell a knife without really knowing what the alloy is?
 
If we can pin down (convincingly) a problem with a source ... then we make a LOT of noise directly to that source. It is our responsibility to give convincing evidence to that source. It is their responsibility to convince us they have solved the problem. Sorry .. a lifetime of supply chain management driving that comment.

yell LOUD to them
 
N.W. Gean said:
I have some 1084 from December '18/January '19 that hardens just fine in my 2 brick forge. It could be way off but the knives hold a sharp edge. I ordered some more 1084 a couple months back and now I'm worried it won't harden when I start working with it.

I'm not sure where to go for steel at this point. I had a good experience with admiral's 1075 last year, but it's labeled 1075/1080, which concerns me. How can you sell a knife without really knowing what the alloy is?
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Alpha Knife Supply. Everything I've bought from there has been exactly as described and hardened reliably and consistently.
 
Cushing H. said:
If we can pin down (convincingly) a problem with a source ... then we make a LOT of noise directly to that source. It is our responsibility to give convincing evidence to that source. It is their responsibility to convince us they have solved the problem. Sorry .. a lifetime of supply chain management driving that comment.

yell LOUD to them
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they are aware, and have changed the requested annealing from the mill. Until the new stock comes in, in 1+ year, we will be guessing which batch we are working with.
 
R.C.Reichert said:
So where do we go from here? Think I'm going to go with 1075 or 80CRV2 my next steel purchase. Feel like I am taking chances ordering the 1084.

Has anyone else had problems with the 1084?
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The 80crv2 has had known hardening issues for some time.
 
I wonder if a couple of normalising heats at 1900 would help it harden as with their w2?
 
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