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Author Topic: thoughts on grain size  (Read 5637 times)
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Ed Fowler
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« Reply #30 on: 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.
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ChrisAnders
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« Reply #31 on: September 02, 2014, 04:49:27 AM »

I could use a smile.  What are your theories?
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John Silveira
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« Reply #32 on: September 02, 2014, 11:49:29 PM »

i second the request for follow up stories ------ Bat Guano Huh   how can we pass this up !!!    Tongue
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Ed Fowler
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« Reply #33 on: 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.

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John Silveira
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« Reply #34 on: 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 
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John Silveira
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« Reply #35 on: November 06, 2014, 10:12:37 PM »

what the hell is the story on the Bat Guano ?
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Ed Fowler
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« Reply #36 on: 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.
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mreich
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« Reply #37 on: 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.
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Ed Fowler
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« Reply #38 on: 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.
« Last Edit: February 22, 2015, 12:41:52 PM by Ed Fowler » Logged

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