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KNIFE TALK => Ed's Thoughts => : Ed Fowler May 07, 2014, 10:23:22 AM



: thoughts on grain size
: Ed Fowler May 07, 2014, 10:23:22 AM
Some thoughts on grain size from Wikipecia:

 http://en.wikipedia.org/wiki/Grain_b..._strengthening (http://en.wikipedia.org/wiki/Grain_b..._strengthening)

What you might call scientific, I have not sent it to Rex, he is buried in work this year. I invite you to give it a read and consider it.


: Re: thoughts on grain size
: Guy Gitelis May 07, 2014, 10:56:16 AM
I can't see any article...


: Re: thoughts on grain size
: Ed Fowler May 07, 2014, 01:18:11 PM
try this:

http://en.wikipedia.org/wiki/Grain_boundary_strengthening (http://en.wikipedia.org/wiki/Grain_boundary_strengthening)


: Re: thoughts on grain size
: mreich May 07, 2014, 07:13:45 PM
Thanks for posting this, Ed!

That's some interesting reading. I especially liked the part that describes the actual size of the grain in large and small grains. No wonder we need high powered microscopes to see anything remotely like a size 10 grain.

I didn't realize the size of grain had so much to do with the strength of the steel. Man, that's awesome knowledge!

Piss on anyone who says multiple hardenings are worthless. We know even better now!


: Re: thoughts on grain size
: Ed Fowler May 07, 2014, 08:12:16 PM
The fine grain coupled with the low temp forging is what sets the table. We knew we had it nailed when we tested a blade with one side showing a different pattern on the etch. When it required different forces as measured with the torque wrench to flex the blade one way then the other it took a few days for what we had just seen to soak in, then we were elated!

Wootz does not like to stretch but it does not mind compression. This is what gives us the greater toughness.

Thanks for the words of encouragement.


: Re: thoughts on grain size
: ChrisAnders August 24, 2014, 05:49:20 PM
One thing worth noting that article points out is the point where decreasing grain size starts to decrease yield strength.  Now, the sizes achieved in knives is no where near this, but it's something to note.  I was doing some research today that showed a point where toughness starts to rapidly loose the improvements from decreasing grain size.  It didn't show a reversal, but there is a point, around ASTM size 10 or 11, that the toughness levels off and doesn't show significant changes beyond that.  I am extrapolating the graph here. 

Another thing not mentioned in the article is that decreasing grain size has a drastic effect on the required quenching speed to harden the blade.  This applies mostly to plain carbon steels or very low alloy steels such as the 10xx series and steels such as 15N20, W1, W2, etc.  This could be part of the reason some people see no further gain in going beyond 2 quenches in steels like 1095.  Past that point, the grain might be fine enough that even water cannot adequately harden the steel.  It does not seem to be a problem for low alloy chromium steels like 5160 or 52100, though I'd expect more issues from the latter.  The chromium appears to allow for full hardening in anything like reasonable knife sizes (less than 3/8" thick).  I say appears because I've only seen tests done on 5150, not 52100.


: Re: thoughts on grain size
: Ed Fowler August 24, 2014, 07:43:41 PM
If the grain size is a uniform 10 (for example) the yield strength will be low. This is why a matrix can make a significant contribution, when a micrograph reveals 10 and finer you have a matrix which can be very tough. It was the matrix that we had achieved that contributed to Rex's interest.


: Re: thoughts on grain size
: ChrisAnders August 24, 2014, 08:15:41 PM
I've been thinking about that.  An array of sizes is not really avoidable.  There will always be smaller and larger grains.  An array of sizes, particularly large grains mixed with significantly smaller ones, leads to grain growth.  The larger ones absorb the smaller ones and grow at their expense.

What do you mean the yield strength will be low?


: Re: thoughts on grain size
: Ed Fowler August 25, 2014, 07:59:24 AM
Obsidian has a very fine and uniform grain size it breaks like glass. Same with hardened blades.

I was working for an outfit that was building bridges for interstate highways, I worked on the cement mix crew - we had to weigh individual wheelbarrows with 4 different sizes of gravel and sand, the mix was very specific if one was heavy the man on the scale would remove a little until it met the weight requirement, if too light he would add a little.

I asked why? It was explained: large bridges have to be flexible, they move with the air and traffic the crosses them. The matrix of the cement is what allows it to flex. If we used too much of any aggregate it would break.

I have always remembered his thoughts. The bridge is still in use, after almost 60 years on interstate 6 & 40 Idaho Springs Colo. It is weathered but as good as new.

Next time you see some cement that is failing, note the sizes of the aggregate and you will probably understand why. The cement curb at our post-office is nothing but broken cement and 1 inch rock. Had they used the right mix it would be solid.

We got lucky when we developed the matrix in our 52100 and quality 5160. It all depends on everything from the chemistry to the final blade.  Other than the above explanation I don't feel I need to know, I just enjoy the performance qualities.


: Re: thoughts on grain size
: ChrisAnders August 25, 2014, 09:06:31 AM
I am more familiar with concrete than I should be.  Other than that, you lost me.


: Re: thoughts on grain size
: Ed Fowler August 25, 2014, 09:20:03 AM
OK I will try again. Blades break when the fracture runs through grains, it is called a tear when it goes around grains. The object is develop a matrix and temper and naturally more to force it to tear instead of break. Rate of reduction, grain size and grain flow also contribute. Does this make sense?


: Re: thoughts on grain size
: Ed Fowler August 25, 2014, 10:22:59 AM
I will add another attempt at explanation:
Fill a bucket with1 inch marbles, is it full?
Then add some 1/2 inch marbles and shake it, is it full?
Keep adding smaller marbles and shake it, is it full?
Then add find sand, shake it - is it full?
Then add talcum powder, is it full?
Then add water, is it full?
This is an old demonstration the kind of applies.

The 1 inch marbles have obvious fracture lines, easily to run a wedge down through and separate them.
As the matrix becomes more complex the fracture line has a tougher course to run providing it cannot fracture objects in the matrix.


: Re: thoughts on grain size
: ChrisAnders August 25, 2014, 06:10:27 PM
OK I will try again. Blades break when the fracture runs through grains, it is called a tear when it goes around grains. The object is develop a matrix and temper and naturally more to force it to tear instead of break. Rate of reduction, grain size and grain flow also contribute. Does this make sense?

That kinda sounds backwards.  Tearing sounds like it goes through the grains, while breaking sounds like it would go around them.  I've seen pictures of grain boundary fractures; they don't look like they tore at all. 

The concrete and marble analogy kinda makes sense, but there aren't any voids in steel like the marbles one and, as above, the grains in steel will always have a variety of sizes, at least in knife blades.  There are ways to get single grains, but they are rare and specialized.

Can you elaborate on what you mean by matrix?


: Re: thoughts on grain size
: Ed Fowler August 26, 2014, 07:58:26 AM
Matrix: That which contains and gives shape or form to anything. This definition is from the dictionary.


: Re: thoughts on grain size
: ChrisAnders August 27, 2014, 03:39:16 AM
That is what I would call unconstitutionally vague, at least for purposes of our discussion here.

On another note, how different were the torques from one side to the other on the wootz blade referenced in the beginning of the thread?


: Re: thoughts on grain size
: Ed Fowler August 27, 2014, 08:32:34 AM
The torque readings going one way were 45 - 50 ft lbs, going the other way were 65 - 70 foot pounds. It took us a while to realize what we had witnessed, then it was a day for celebration.


: Re: thoughts on grain size
: John Silveira August 27, 2014, 10:38:12 AM
nothing has been mentioned about the Subgrains ? 

i suppose it's not an aspect of grain refinement and matrix that we necessarily need to involve ourselves with and just accept it as part of the structure of the grains themselves - the important aspect is basically grain sizes and matrix ? 


: Re: thoughts on grain size
: ChrisAnders August 27, 2014, 01:14:15 PM
Subgrains are most important in low carbon and microalloyed structural steels.  I have not seen them referenced in quenched and tempered steels. 

With regard to the wootz blade, do I understand correctly that the wootz structure was evident on one side and not the other?


: Re: thoughts on grain size
: Ed Fowler August 27, 2014, 01:39:28 PM
Yes, the two sides were different, you could see it in the etched blade. The difference was confirmed by the torque values. Evidently one side got a little hotter than the other somewhere down the line. What we wish to achieve occurs in a very narrow thermal band.


: Re: thoughts on grain size
: ChrisAnders August 27, 2014, 06:56:46 PM
Was this with repeated bends?  Have you been able to replicate this again?  So, which side was on the inside of the blade during the lower torque bend?


: Re: thoughts on grain size
: Ed Fowler August 27, 2014, 07:55:55 PM
It did 10 90 degree flexes. the torque values were consistent. The hardened area of the blade did not tear.

We have not done it again. If some time in the future we get a similar etch patterns we will test it.

Butch tested another blade at a hammer in in front of a bunch of bladesmiths.  This blade cut exceptionally well, until no one wanted to cut any more, then Butch put a torque wrench on her and she completed 35 90 degree flexes, consistent torque value at 65 foot pounds.

The Wootz side, it did not mind compressing, resisted stretch.


: Re: thoughts on grain size
: ChrisAnders August 30, 2014, 07:30:05 PM
So what are the benefits of a finer grain size?  I've not seen them in one place, and figured this would be the thread to do it.  I'll list the ones I know, as well as some possible detriments, but it all depends on what you want to do if it hurts or hinders.

1) greater impact toughness - this levels off and appears to possibly hit a maximum around an ASTM size of 11-12.

2) greater yield strength - this has been discussed earlier in this thread.  There is a maximum point, and beyond that, the strength starts going back down, but even an ASTM size of 15 isn't nearly that fine.  In steels with less than 0.8% carbon, coarser grained steels can be stronger, but that only applies to steels not quenched and tempered and is certainly not universal.  I'm also not sure that finer grains mean noticeably increased strength in quenched and tempered steels tempered at less than about 450 F.  The strength of the martensite pretty much overshadows everything else at that point.

3) less warpage during quenching - this has been known for a long time, since before 1939. 

4) decreased quench cracking - this is a real problem, and finer grains help prevent microscopic quench cracks.  Even stuff you'd never think of will crack if you give it a chance.  I cracked some round rod made of 4140 once, so higher carbon and more complicated shapes need all the help they can get.

5) decreased ductility - this might be a detriment, but it depends on what you want to do.  Steels being processed that require high ductility, where strength is secondary, will have better properties with larger grains

6) decreased hardenability - this was also discussed above, but for completeness I'll put it here.  Steels with finer and finer grains require faster and faster quenches to reach full hardness.  This really only applies to the 10xx and a handful of other steels, as even the small amount of Chromium in 5160 will allow essentially full hardness in the center of a 1" round bar.

OK, that's all I got.  Anything else I missed?


: Re: thoughts on grain size
: davidm August 30, 2014, 09:25:02 PM
I asked on another thread with no response.. I think since this thread is about steel, grain, etc..
Can someone give an explanation to the following excerpts /claims, is this a superior product or process?  And why promote the forged knife, made on a "custom" or individual basis, if the same or better level of performance is available in the production knife market? 

 "Although hardened INFI knives are 58-60 Rc we have yet been able to chip an edge. The edge can be dented or misaligned but its high level of malleability at such high hardness has never been duplicated by any other steel that we are aware of or have tested."

"Tougher, by an enormous margin, than any other steel we've ever tested. It has unparalleled edge holding under high impact and in cutting tests, and shock resistance that begs you to "bring it on". INFI has an ease of re-sharpening that you have to see to believe and higher levels of lateral strength at high hardness than have ever been achieved by any other steel."

http://www.bussecombat.com/about-our-steel-infi/ (http://www.bussecombat.com/about-our-steel-infi/)







: Re: thoughts on grain size
: ChrisAnders August 31, 2014, 06:56:41 AM
Infi has a low carbon level, something like 0.55-0.6%.  Impact toughness is highly dependent on carbon content, the lower the carbon the higher the impact toughness.  However, part of that is marketing and words like "enormous margin" are highly subjective. 


: Re: thoughts on grain size
: Ed Fowler August 31, 2014, 04:11:31 PM
Chris you put me back into research mode, been reading about grain size most of the day. I will respond to your post. At this point I believe that it is tough to generalize the influence of grain size to all steels. So far I have studied read about grain direction and grain size. One author reported an endurance limit of 78.000 on specimens cut with the grain and one of about 58,000 on specimens cut across the grain, for a steel of 139,000 tensile.

Grain size is  which is extremely important in respect to the ability of a notched specimen to resist impact, seems of relatively minor importance in fatigue.


: Re: thoughts on grain size
: ChrisAnders August 31, 2014, 07:45:03 PM
I think you may be getting grain direction and grain size mixed up there Ed. 

Grain direction comes from the rough shaping operations of the cast billets.  It is caused by inclusion in the steel.  These are typically oxides, nitrides, and sulfides.  The sulfides are typically used as examples.  These inclusions are drawn out in the direction of rolling or forging and give the steel different properties in different directions.  This is called grain direction, a term I have abandoned because of it's potential for confusion.  I use mechanical fibering now.  The term originated before the actual grains were known, almost certainly coming from man's familiarity with the different properties of wood based on the direction of the grain.  This leads to a great deal of confusion.  The effects of mechanical fibering are evident in the example you gave.  The fatigue limit is 26% less in the transverse direction (58,000) vs. the longitudinal direction (78,000).  I'd definitely call that significant.  Whenever possible, steel is used with the longitudinal direction in line with the greatest stress.  If this is not possible, then the weaker mechanical properties are taken into account.  The longitudinal direction is parallel to the direction the billet was rolled or parallel to the direction of greatest deformation for large forgings.  The transverse direction is across the direction of rolling or forging at 90 degrees.  A third direction is also possible.  This is the through thickness direction, running through the thickness of the plate.  This is the weakest direction. 

Grain size is the average size of the steel grains, which are the little bits of steel that you see under the microscope and the multiple quenches refine to smaller and smaller size.  These are the things Rex is measuring for ASTM grain size.  These grains are independent of the mechanical fibering (grain direction) discussed above.  The grains change each time the steel is heat treated.  The mechanical fibering is virtually unaffected by heat treatment.  As to your example, I do not know how grain size effects fatigue limits.  My guess is that finer grain size increases the fatigue limit, though I can't say how much. 

The specific effects of grain size are steel and use specific.  However, the Hall-Petch relationship in the Wikipedia link in the beginning of this thread applies to all metals, and can be used to predict the strength increase from grain refinement.  It may, in modified form, apply to all materials that have grains, though I've not looked into it. 


: Re: thoughts on grain size
: Ed Fowler August 31, 2014, 09:03:19 PM
That post was just a comment on what I was reading while exploring grain size. I thought it was interesting and while I had the reference figured I would post it up. 


: Re: thoughts on grain size
: ChrisAnders September 01, 2014, 07:04:41 AM
It was quite interesting.  I have some references here that I'll check.  I've never looked into it before.


: Re: thoughts on grain size
: Ed Fowler September 01, 2014, 06:21:01 PM
Chris:
Your description of fine grain pretty well covers it.

I believe I found where the part about decreased harden ability in fine grain comes from. I feel it is from long soak times and  found a chapter titled decremental hardening, where in steels are only partially brought to critical temp and quenched. The reason for this was because fine grain will grow with long soak times.

Multiple quench as we do it does not require long soak times, and we can then temper our blades to achieve the ductility we want.

I also found where US Steel had a patten on "multiple quench", they went to four quenches. I have found that with the steel we are working with 3 quenches is where we get the best "bang for our buck". The part about their patten is on page 1264 of the 10th edition of the US Steel handbook. The part that was not included in the write up was called the "properly designed cycles".  I feel our team figured "properly designed" cycles out.

If you take the time to read from different arenas covered in the handbook you will find that there is really nothing new, just putting knowledge from one area to another.

Again the decreased ductility can be avoided by a high rate of reduction at the right temperature etc.


: Re: thoughts on grain size
: ChrisAnders September 01, 2014, 06:50:06 PM
I'm not sure what you mean on the decreased hardenability from increased soak times.  This would possibly cause the grains to grow, though the times would have to be extremely long.  I've see pictures of O1 soaked at austenizing temperature (1450-1475) for nearly an entire shift (5-6 hours).  No grain growth was evident.  To be sure it had issues, but grain growth was not one of them.  Undissolved carbides, which O1 has from Tungsten and some other elements, prevent grain growth by acting as speed bumps to the grain boundaries.  But I digress.

Bigger grains mean better hardenability.  Finer grains mean less hardenability.  The grain boundaries are great places for all kinds of stuff to happen.  One of the things that happens is that is where pearlite starts to form when steels are cooled from austenizing temperatures.  The more grain boundaries (due to finer grains), the easier it is to form pearlite during quenching instead of the martensite we all want.  I've seen 1095 quenched in a highly recommended fast commercial quenchant just for steels like it, and it still had a few little spots of pearlite in it.  Now, they were not detrimental, and the as quenched hardness was still around HRc 66, but they were there. 

For any given property, there is more than one way to get there.  Many times, one way will completely overshadow the others.  The decrease in ductility from very fine grains can be more than overcome by proper tempering.  Also, realize that pearlitic steels, as in the spine of one of your blades, are still very ductile when compared to hardened and tempered steels.  Making very fine grained pearlite will decrease ductility, but it might be like taking a cup of water from a bathtub, its just not that big a deal.

Can you explain the mechanism behind higher ductility from high reduction rates by forging?  I think this might also be one of the things that, while it contributes, it's not the major factor and is overshadowed by the annealing steps prior to hardening.  The annealing steps are done to the entire blade right?  Then the edge is hardened?

Again, I don't believe that the fine grain sizes found in HEPK style blades will lower the hardenability in any practical way, unless one chooses to use a 10xx or similar plain carbon steel with essentially no alloying other than carbon, iron, and standard manganese (0.25% to 0.75%).  Hardenability is critical in industrial application, and they generally use much thicker sections than knife makers.  With that in mind, even the hardenability drop from ultrafine grain in something like a 2" diameter bearing of 52100 could be detrimental, provided through hardening is a requirement. 


: Re: thoughts on grain size
: Ed Fowler September 01, 2014, 10:25:05 PM
Our typical blade starting with a 6 1/2 inch round bar of steel goes through 50 or more thermal cycles, with a top end of 1,725 f. at the very top end. The rate of reduction is over 98 %. Most of the final forging is accomplished at 1,625 f. and naturally lower, until the steel resists forging. We have very little time to forge before it must go back in the forge. This process, many low temp thermal cycles, with quality 52100 sets the table for the final thermal cycles.

We could not have achieved what we have without a consistent steel, after Rex joined us we only used steel from one pour.
Rex and his associates provided a lot of brain power to get us were we are now.

After forging, post forging quenches and two flash normalizing cycles then a full normalizing cycle to room temperature in 70 degree still air (as close as we can get) the blades go through what I call  high temperature temper cycles, 988 degrees for two hours, cool down slow in Paragon to room temp, then into the house hold freezer for three cycles.

Following this process we have never had a blade warp significantly in heat treat.

Only the bottom 1/3rd of the blade is hardened. Inside of the blade there is a pyramid shaped cone of martensite, the top of the paragon is surrounded by softer steel. The spine is usually around 32 RC, then as you progress down the side of the blade it gets harder quick. The transition zones mirror the pyramid and structure of the surrounding steel. This is the part that is of great interest to me, but we have no way of investigating exactly what is happening.

When the hardened section finally tears, the tear will radiate toward the spine, then bifurcate when it meets the softer steel. This is exactly what we want to happen, the blade with a tear in it can be straightened and you still have a knife.

I have theories, but when I talk about them I just get smiles.

When I tried to work with 01, quality control was not what I needed, thus the switch to 52100. I tried 52100V and was never able to get the ductility we get with 52100. The blades with vanadium always chipped out requiring too high a temper to get the cutting performance I could achieve with 52100.

When attempting to forge blades out of flat stock with a minimum of rate of reduction the blades fall way short in the performance qualities we can achieve from working down larger stock. I had many blades forged from 3" ball bearing out cut blades from 2" ball bearings, I never had a blade from a 2" out perform a 3". Thus my belief that the higher rate of reduction is significant. Naturally the bearings themselves varied in chemistry as I had no way to know if they were from the same pour of steel or steel mill for that matter.

For example I sent Rex some blades forged from 3" ball bearings, two of them had come from a pour that had been alloyed with nitrogen instead of manganese. These bearings probably came from WWII vintage Germany when we had shut off their supply of manganese, they learned how to substitute nitrogen for manganese, their bearings lasted longer than the ones the allies were making. The Germans imported bat guano in transport submarines. If you want to know the rest of the story I will relate it to you.

Rex found an article written my some Russian students who duplicated Wootz, their work coincides with what we are doing.

I industry could not afford to put this much time into their product, it is not economical on a large scale, I believe this is why US Steel abandoned their process.


: Re: thoughts on grain size
: ChrisAnders September 02, 2014, 04:49:27 AM
I could use a smile.  What are your theories?


: Re: thoughts on grain size
: John Silveira September 02, 2014, 11:49:29 PM
i second the request for follow up stories ------ Bat Guano ???   how can we pass this up !!!    :P


: Re: thoughts on grain size
: Ed Fowler September 07, 2014, 07:24:50 AM
OK I have been very busy for a couple of days but back now.

During WWII the allies shut down the supply of manganese into Germany feeling that this would shut down their steel industry as manganese was needed to harden steel. Germany had no viable source of manganese in their boarders. But the tanks kept rolling, the planes kept flying, the war machine kept moving, even thought they knew Germany had to be out of manganese.

A Messerschmidt was shot down over England and the boys from Roll's Royce did a metallurgical autopsy on it. They found that the bearings were alloyed with Nitrogen instead of Manganese. They also found that their performance was better when compared with what the allies were using.

They decided to alloy a batch of steel with Nitrogen, and poured some fertilizer into a vat of molten steel, it exploded killing many workers and destroying the plant. Naturally they blamed the explosion on a V2 rocket.

After the war they found a large number of Transport U Boats that had been transporting Bat Guano from South America to their steel industry.  This information was classified for years and may still be.

We were just lucky finding this out:
I sent Rex 5 blades I had forged and heat treated form 5 different 3" ball bearings, Rex found 5 different chemistries.  This is why I had to test a blade out of every ball bearing, I had no idea where they came from other than a scrap yard in Casper Wyo. On e of the blades was alloyed with Nitrogen.

Rex asked the other men in the lab about it and one of the senior metallurgists had worked with Roles Royce in the lab during the war. He remembered the Nitrogen incident. It was not just the nitrogen that made their bearings better, their science was far ahead of ours at the time.

What this incident told me was that when experimenting with a steel you must be positive of the origin of your steel or you will be chasing ghosts trying to understand what is happening.



: Re: thoughts on grain size
: John Silveira September 07, 2014, 09:12:40 AM
OK I have been very busy for a couple of days but back now.

During WWII the allies shut down the supply of manganese into Germany feeling that this would shut down their steel industry as manganese was needed to harden steel. Germany had no viable source of manganese in their boarders. But the tanks kept rolling, the planes kept flying, the war machine kept moving, even thought they knew Germany had to be out of manganese.

A Messerschmidt was shot down over England and the boys from Roll's Royce did a metallurgical autopsy on it. They found that the bearings were alloyed with Nitrogen instead of Manganese. They also found that their performance was better when compared with what the allies were using.

They decided to alloy a batch of steel with Nitrogen, and poured some fertilizer into a vat of molten steel, it exploded killing many workers and destroying the plant. Naturally they blamed the explosion on a V2 rocket.

After the war they found a large number of Transport U Boats that had been transporting Bat Guano from South America to their steel industry.  This information was classified for years and may still be.

We were just lucky finding this out:
I sent Rex 5 blades I had forged and heat treated form 5 different 3" ball bearings, Rex found 5 different chemistries.  This is why I had to test a blade out of every ball bearing, I had no idea where they came from other than a scrap yard in Casper Wyo. On e of the blades was alloyed with Nitrogen.

Rex asked the other men in the lab about it and one of the senior metallurgists had worked with Roles Royce in the lab during the war. He remembered the Nitrogen incident. It was not just the nitrogen that made their bearings better, their science was far ahead of ours at the time.

What this incident told me was that when experimenting with a steel you must be positive of the origin of your steel or you will be chasing ghosts trying to understand what is happening.



Well --------------------------------------------SHIT !!!! ROFLMAO 


: Re: thoughts on grain size
: John Silveira November 06, 2014, 10:12:37 PM
what the hell is the story on the Bat Guano ?


: Re: thoughts on grain size
: Ed Fowler November 08, 2014, 09:10:51 AM
You know as much about it as I do. If we wanted to really know the information is probably documented in some WWII German research paper that may still exist or was destroyed.


: Re: thoughts on grain size
: mreich February 22, 2015, 11:15:32 AM
what the hell is the story on the Bat Guano ?

The Germans needed nitrogen to harden their steel. Bat shit is high in nitrogen, which makes it the best natural fertilizer...or steel hardening agent.

Maybe natural nitrogen works better than refined nitrogen? I don't know.

I know that nitrogen rich processed fertilizer mixed with fuel oil (I think that means diesel fuel) is highly explosive.

I'm not sure what conclusions could be drawn from an exploding steel mill, but I'm guessing pure(er?) nitrogen can be reactive to high temperature too.


: Re: thoughts on grain size
: Ed Fowler February 22, 2015, 12:39:14 PM
Most who participated in the English experiment did not survive the event. Rex and I figure they tried to add the nitrogen in the form of fertilizer to molten steel.


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