Steel chemisty for bearing grade steels...some useful information

scottickes

scottickes

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Oct 27, 2005
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Fellow knifemakers,

As most of you know, I work for Timken Bearings. There had been some discussion in previous threads about bearing steels for knife forging material. It was pointed out that not all through hardened bearing steels are 52100. This is true. For the thinnest cross sections ( up to about 1/2"), Timken bearings are made from 52100. For cross sections from about 1/2" to about 7/8" ASTM 485-1 is used. For cross sections thicker than that, ASTM485-2 is used.

The reason for the different grades of through hardened steel in bearings is for hardenability. For example, 52100 won't satisfactorily harden completely through on cross sections greater than 1/2". For those of you that understand the term "staying ahead of the nose", this will make sense. I'll let Mr. mete or Mr. Cashen explain "staying ahead of the nose", as they have a better grasp of how to explain it than I do.

The changes in the chemistry allow the other steels to "stay ahead of the nose" on thicker cross sections. I'm attaching the chart of the steel chemistries that was supplied to me. In addition, there are many other steel chemistries on the chart. The ones used for through hardened bearings are in "red".

Basically, according to our metallurgist who supplied this information to me, as far as forging and heat treating the three steels (52100, ASTM 485-1 and ASTM 485-2), you can use the same heat treating processes for all three that you use for 52100 and get good results, since the cross sections will always be thin enough to "stay ahead of the nose".

If you need to know if a particular bearing is through hardened or case carburized, please feel free to email me or Private Message me with the part number and I'll let you know if it is a good steel for knifemaking.
 

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Wow Scott that is good information! I learned something that I did not know. You see I have a little yet limited experience with 52100 (I am still rather concerned about what may burn out of it and get into smiths brains) and I had no idea that 1/2" would be a limitation on it's depth of hardness, I knew it wasn't O1 or L6 but I just assumed that it was deeper hardening than that. Very good information to file away for the future. Thank you!
 
Yes , pick the right one ! When I was at Timken I had a project because the customer hadn't picked the right type within the 52100 family. Large cylinders weren't getting hard enough . I was able to work out a procedure that saved most of the parts. It was a dual quench ,first into water [to get below the nose ] then into slower oil to prevent cracking.Took some doing but it was an interesting experiment !
 
Gabe Newell said:
Googling about, I found this patent from 1974:

http://www.google.com/patents?id=jr...&hl=en&sa=X&oi=book_result&resnum=5&ct=result
Click to expand...

Wow, how many different variations on that same process have been patented or studied? Grange patented a similar process back in 66 and then Stickles expanded on it in his research, then there is this one. The one common thread in them is in order to avoid retained austenite due to high carbon levels and still get fine carbide dispersion the typical spheroidal condition is replaced with a finer one for the condition prior to hardening. Bainite, very fine pearlite etc... the only one they avoid before making martensite is martensite;) ;) If ultra fine grain size in 1966 is too unbelievable perhaps 1974 is new enough, or perhaps any date in the second half of the 20th century.:)
 
Would it be possible "the-lines-that-are-called-Wootz-that-aren't-Wootz" a person sees pictures of in 52100 blades that have had a lot of low temp. heat cycling and/or multiple quenching is segregating the large amounts of silicon in A485-1 & 2... maybe causing planes of weakness similar to planes of weakness found in wrought iron (silicon inclusions?) ???

Mike
 
Mike Krall said:
Would it be possible "the-lines-that-are-called-Wootz-that-aren't-Wootz" a person sees pictures of in 52100 blades that have had a lot of low temp. heat cycling and/or multiple quenching is segregating the large amounts of silicon in A485-1 & 2... maybe causing planes of weakness similar to planes of weakness found in wrought iron (silicon inclusions?) ???

Mike
Click to expand...

Silicon inclusions in modern bearing grade steels? That isn't happening. Modern steel making processes for bearing grade steels, have led to very little (in the amount of) and very small inclusions in the modern steels. The cleanest steels made in the world today are bearing steels.

Before 1984, bearing steels were much dirtier and damage to bearings from inclusions was much more prevelant. In my 11 years in the field now, looking at damaged bearings, I have not seen an inclusion related damage mode. This is not to say that there are no inclusions in bearing grade steel, only to say that the amount of inclusions and the size of the inclusions has been reduced to an amount that is nearly insignificant.

I've seen only two inclusion related bearing failures, and both happened in test labs with bearings operating under perfect conditions. Both bearings had been tested well past 90 million revolutions before the tiny inclusion led to a fracture.

Basically, what I'm saying is that if you're looking for inclusions to add or detract from the appearance of a knife, or to contribute negatively to a knifes performance, you're following a dead end.

Now, there are supplies of 52100 that may not be made with the processes that result in super clean bearing grade steel. For example, the steel used by Ed Fowler is 52100 steel and of very high quality, as can be attested to by the high performance that he gets from his knives. However, I do not know what melting processes were used in the manufacture of that particular steel. It may not have been made with the same processes used for bearing grade steels.

Since knives don't receive millions of flexes like a bearing does, I doubt that a silicon inclusion would lead to a knife failure, or least it would be a very rare occurance.

Just some of my thoughts on the subject.
 
We didn't make dirty steels in the old days !!...In the '60s we were developing vacuum degassing and other processes all toward reducing the amount of inclusions.The've gotten much better now.We don't talk much here about quality levels but different industries require different quality levels .The highest quality steels were always for the bearing and aircraft industries....BTW we sometimes do want inclusions . For various free machining grades such as 416 sulfur is added.The sulfides break the chips making it easier to machine.
 
mete said:
...BTW we sometimes do want inclusions . For various free machining grades such as 416 sulfur is added.The sulfides break the chips making it easier to machine.
Click to expand...

Wrought iron is also pure bliss to machine, the chips just flake and get out of the way. I have seen many inclusions in 10XX and 5160, carbides and alloying tend to just ignore them so they are not a path, catalyst or apparent contributer to the alloy or carbide banding that we often get when segregating things out of solution in cycling. For the most part silicon treats carbon much like nickel does, it just ignores it. Much of the banding we see when our heating cycles get out of hand are probably a result of chromium segregation in steels such as O1 or 52100 where they so often crop up. It is possible to get macroscopic effects from carbide in the grain boundaries where it would certainly contribute to brittleness, but if we heat high, cool fast and then keep it low thereafter it may not take that route. If it does a good and proper normalization above Accm is our best bet at saving things.
 
Kevin "The one common thread in them is in order to avoid retained austenite due to high carbon levels and still get fine carbide dispersion the typical spheroidal condition is replaced with a finer one for the condition prior to hardening. Bainite, very fine pearlite etc... the only one they avoid before making martensite is martensite

Kevin, I guess they don't do the triple quench.
I do need to study the pdf file a bit more and "Many Thanks" to you, scottickes. I appreciate it. Now maybe Kevin will want to try some of it. :)
 
raker said:
...Kevin, I guess they don't do the triple quench.
Click to expand...
:thumbup::)

raker said:
... Now maybe Kevin will want to try some of it. :)
Click to expand...
:eek: Oh nooo! You may have some sort of natural immunity to whatever it is Ray since you seem pretty lucid whenever we speak, but I aint going to submit myself to any long term exposure to that stuff! With my equipment I could really get crazy and go places man was never meant to meddle! In no time at all I could be wearing a tin foil hat and taking 5 years to finish the heat treatment on one blade. When the authorities finally investigated the complaints of the smell of rancid quenchant they would take me away one day after discovering three freezers full of frozen blade parts and half eaten tangs sitting a vat of acid from my panicked attempts to dispose of the evidence. While they brought in heavy equipment to remove all the rope scraps from my back yard, I would wiggle my way to the hole in my cell door and rant about the number 19! The only clue the therapist would get out of me about this cryptic number would be… ASTM!
 
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