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So I hammered out and after all the grinding and hand sanding I went for an etch to show the Hamon and noticed this weird rectangle in my steel. It was on both sides in exactly the same spot. It seems like I got a bad peice of steel. T

20210811_215643.jpg

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We need a little more information here to help you.  What is the alloy that we are dealing with here and how thick is the blade in both the darker area and lighter area on the spine?  I wouldn't assume that the bar of steel was bad.

 

Doug

Edited by Doug Lester
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New steel or recycled?

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For me, the line is way to consistent for it to be a material defect.  I would think that after forging the transition from "good" steel to "bad" would be much more inconsistent.  I think I would sand it down and re-etch it and see what happens.  Did you clean it thoroughly before you etched it?  It really does look like there is residue left over by something.  I guess another possibility is that the blade is magnetized in that area and that is causing it to etch differently.  I've never experimented with whether or not that makes a difference in the FeCl, but I suppose it's possible.  Again though, I wouldn't expect to see that perfectly straight line at the back if that was the case.

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I'll be interested to hear @Jerrod Miller has to say on this one.  It looks like there is some alloy banding going on as well, but that rectangular blotch is a mystery to me.  I'd write it off as surface contamination if it didn't follow the curve of the forging. 

 

How were you holing it when you quenched it?

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4 minutes ago, Brian Dougherty said:

I'll be interested to hear @Jerrod Miller has to say on this one.

Prepare to be disappointed.  

 

4 minutes ago, Brian Dougherty said:

I'd write it off as surface contamination if it didn't follow the curve of the forging. 

I don't think it is following the forging, I think it is changing due to what is exposed from grinding.  If I understand the situation here.  I could certainly be wrong.  

 

@JASON HUBER Is your magnet rectangular?  If so, was it applied specifically at this location?  I'm thinking this is not alloy related, but process related.  If you really want to know if it is alloy related, I think I know how to test for that.  Submerge the blade in water so the entirety of the hardened material is below the water, but at least some of this patch is not.  Specifically you want the end of the patch along the spine.  Hit that spot with a torch until is is non-magnetic.  This will undo pretty much everything process related, and since the heat won't reach any martensite you won't affect the blade quality in any significant way.  If it is alloy related then you will still see that line upon re-etching, if it is process related the heat will have eliminated it (at least in the area that got hot enough).  The key being that you have to carefully hand sand only before the re-etch; no magnets, clamps, or any chemicals (including glues) near that area unless it is 100% evenly applied over the whole thing.  

 

I could see how magnetism could change an energy state and thus the etch could be changed.  I don't see how it would be that crisp though.  I'd be more inclined to think that the retained magnetism could change how it sands, with the sand paper loading up differently in a magnetized area.  But again, I wouldn't expect it to be so sharply defined.  Sure would be fun to take a look at things under a microscope, probably after a good polish and etch.  

 

It is really hard to keep such crisp lines through forging and heat treat if it is something inherent in the alloy.  But I suppose it is possible.  

 

TL;DR  Boy, that's weird.  Not sure what it could be.  

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24 minutes ago, Jerrod Miller said:

Prepare to be disappointed.  

Not at all Jerrod :)

 

Just to be clear, there isn't any sort of joinery they do in the steel mill when this stuff is getting rolled out, right?  Wire manufacturers will butt-splice a new coil of raw stock to the tail end of another to keep the drawing process running, but to my knowledge that doesn't happen in a steel mill.

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I'm certainly not an expert on steel mills (foundries yes, mills no), but it is my understanding that this would not be done.  In theory maybe a metal tag could have been rolled into the stock and fused, but that would be weird, and I think it would have distorted a bit more since then.  

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Posted (edited)

The magnet I used is rectangular but too small for this and I moved it around many times

The crazy thing is that I have grinded down so much did not see any indication until after the etch

Edited by JASON HUBER
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2 hours ago, Jerrod Miller said:

TL;DR  Boy, that's weird.  Not sure what it could be.  

 

My thoughts exactly!  :lol:  

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If it were me curiousity would beat wanting to save it and I would cut through the oddity diagonally and then polish the edge as finely as possible to see how deep it goes. 20210811_215643.jpg.31e83a2f98f72e24c3b3aa3c02e47726.jpg

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I was thinking about this the other day, but decided my hypothesis was too crazy to post.  Since the topic popped up again, I throw caution to the wind:

 

We've seen some examples on here where etching revealed where the metal had been "Stressed".  For example, sometimes you can see lines from really aggressive grinding with low grits after etching even though the surface was perfectly sanded to a proper polish before etching.

 

I don't know the metallurgy, but I assume it is the same effect that allows the police to see firearm serial numbers after they have been filed off.

 

Is it possible that this is where a gripper on the crane grabbed the roll in the steel mill to pick it up?

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3 hours ago, Brian Dougherty said:

Is it possible that this is where a gripper on the crane grabbed the roll in the steel mill to pick it up?

No, the stresses would all be relieved during heat treat.  If you were to re-heat treat a gun barrel that had the serial number removed it would also not show up for the police.  You'd be better off making a new gun barrel at that point, but that is another topic.  

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  • 2 weeks later...
Posted (edited)

Btw, I didnt use any magnets or the vice for straightening and heat treated as normal. I have made several knives in between the 2 and have had no issues. I have made contact with the distributer and they are baffled and are looking into it. This is mostly stock removal with small amount of forging on the tip area to get the length and profile. I did a hamon on both

Edited by JASON HUBER
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Is this 1095 by chance from Admiral?  Twelve or thirteen years ago they got in a batch of 1095 that was so alloy-banded it looked like wootz when etched.  AFTER forging, normalizing, and hardening.  Theoretically this should not happen, and for the longest time they refused to admit it existed.  

 

Not that this looks at all like alloy banding, but it's not the first time something odd has come up in 1095.  It actually looks like localized decarb to me.  What are you using as your hamon clay?  Could it be pulling carbon from the blade? :huh:  I remain baffled, but this looks more like it is process-related than the first one...

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Posted (edited)

Rutlands fireplace mortar. Its not from Admiral but I would like to not name the place I got it from at this time out of respect for them working with me on this. It is a very reputable place.  Its just crazy that I have used the same process with the same mortar and everything and just these 2 have done this.

Edited by JASON HUBER
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Did you get the Hamon you were looking for?  The second one really looks like a temper line.  That wouldn't explain that sharp break line on the first one though.

Edited by Alex Middleton
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