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Allan G Offline OP
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Sending the crank away for nitriding and they wish to know what grade it is. I was under the impression that it was en14b - very much mistaken.

Any help greatly appreciated.


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I'm not sure if this helps, but in an analysis of the Golden Flash engine I have, it says the crank is 3 1/2 % nickel steel toughened to 65 tons tensie strength.

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EN16 i am nearly sure.

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Originally Posted by bon
EN16 i am nearly sure.


I think I read that triumph cranks were en16, but I didn't know if the BSA was different. Annoyingly it doesn't tell me in the parts Manual although it states other grades of special steels.

Originally Posted by Triless
I'm not sure if this helps, but in an analysis of the Golden Flash engine I have, it says the crank is 3 1/2 % nickel steel toughened to 65 tons tensie strength.


Thanks triless but I need a number.


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Found something in an A65 engine analysis re crank..."the shaft, as before, is a forging in EN 16 maganese molybdenum steel..."
REF. "The Classic Motorcycle " August 1983 . BSA A65 engine analysis article. This was an article first published in a Feb. '62 "The Motor Cycle ".

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Are you breaking cranks, Allan? I see little advantage to nitriding a crank for a road bike.


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Just trying to improve the wear resistance for the big ends


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The EN number series was supposed to be superceded by the later BS numbering system.
The Nitriding place might prefer these numbers.

Lifted this from a website," A manganese molydenum steel with good ductily and mechanical strength. Available in heat treated condition e.g (R,S,T).Supplied as black round or square bar and bright round or square, and hexagons. "
BS 970 605M36
(EN16)
All styles here,
http://www.roymech.co.uk/Useful_Tables/Matter/Strength_st.htm
Note EN16 is not specifically a Nitriding steel, whereas others such as EN40 B are brewed to be Nitrided.

Dredging the Material Science memory banks I recall that Molybdenum has very useful properties, its used for hammer heads and railway track end sections where a repeated beating will add more toughness to the alloy if Moly is part of the mix.

Last edited by gavin eisler; 07/05/16 2:47 pm.

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There is a hardening process known as Tufftriding which can be applied to a wider range of ferrous metals than nitriding , I think.

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Originally Posted by Triless
There is a hardening process known as Tufftriding which can be applied to a wider range of ferrous metals than nitriding , I think.


Tuffride is a trade name for a nitriding process.


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Originally Posted by gavin eisler
The EN number series was supposed to be superceded by the later BS numbering system.
The Nitriding place might prefer these numbers.

Lifted this from a website," A manganese molydenum steel with good ductily and mechanical strength. Available in heat treated condition e.g (R,S,T).Supplied as black round or square bar and bright round or square, and hexagons. "
BS 970 605M36
(EN16)
All styles here,
http://www.roymech.co.uk/Useful_Tables/Matter/Strength_st.htm
Note EN16 is not specifically a Nitriding steel, whereas others such as EN40 B are brewed to be Nitrided.

Dredging the Material Science memory banks I recall that Molybdenum has very useful properties, its used for hammer heads and railway track end sections where a repeated beating will add more toughness to the alloy if Moly is part of the mix.


Mn/Mo steels are all work hardening Martensitic / Bainitic steels of varying amounts depending upon the amount of Mn & Mo and their ratios.
Mn is added to forging steels to widen the working heat range and prevent grain growth during the forging process.
Mo substantially increases the toughness by the promotion of very stable bainite structure and prevents the carbide rich phases redissolving during forging thus reducing the tendency for grain growth during forging at elevated temperatures.


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"Mn/Mo steels are all work hardening Martensitic / Bainitic steels of varying amounts depending upon the amount of Mn & Mo and their ratios.
Mn is added to forging steels to widen the working heat range and prevent grain growth during the forging process.
Mo substantially increases the toughness by the promotion of very stable bainite structure and prevents the carbide rich phases redissolving during forging thus reducing the tendency for grain growth during forging at elevated temperatures."

Thanks for the refresh Trevor,what about Nitriding or Tuftriding EN 16 ?, please tell.


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Gavin,I will have to take that one on notice.
Nitriding should work well and is recommended.

I have a sneaky that carbo nitriding does not work on Mn/Mo steels
In fact I don't think you can even case harden them, the Mo binds the carbon in fairly tight, but I will have a ferret.

I was a non ferrous foundry metallurgist so most of my Iron & steel came from course work, occasional failure analyse and few conferences before I took a different career path.


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Have a read of this link Introduction to Nitriding , its very informative and gives a complete history of the process.

There appear to be varyous nitriding processes available, some better suited to British Nitriding Steels (En 40 A, En 40 B,
En 40 C, En 41 A, and En 41 B.) these were Developed for nitriding applications, and are chromium-molybdenum steels.

There is also Gas Plasma/Ion Nitriding available which apparently is not restricted to steel with nitriding forming elements.

No idea what the A65 crank is made from but if unsure maybe the Gas Plasma/Ion Niriding techneque would be better?

Hope this is of use.

Last edited by gunner; 07/08/16 11:23 pm.

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I'm not nitriding incase I break the crank. I'm nitriding to increase the journal strength.


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Nitriding does not really increase the strength.
It increases the stiffness and more importantly it increases the fracture toughness.

Put simply fracture toughness is the ability of the steel to resist a crack getting bigger.
It is another by product of WWII when it was noticed that some cracks would develope while you watched then yet other parts could be riddled with cracks but never failed.

The nitrogen atoms sit in holes in the lattice and key layers of atoms together preventing them from sliding over each other.
They also block the path of hydrogen atoms traveling through the lattice ( which is how cracks actually form & grow ).

Hence the use of the word TOUGH in the descriptions.
Not significantly harder,
Not significantly stronger

But
Massively tougher.

No metal object is stable.
All of the atoms in the lattice are moving all the time and over time forged cranks get weaker and more brittle thus the strong suggestion to get them nitrided.
Salt dip or controlled atmosphere nitriding is cheap.
Other more exotic methods are a lot more expensive.


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Very interesting thread, I wish I knew more about metalurgy.


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Originally Posted by NickL
A65 = EN16 Strong as buggery, with a throw that small and journals that size no need for any nitriding/tufftriding etc. Never heard of anyone breaking one.


Come off it Nick.
Every second A 65 from the USA has a big weld down the front left side of the crankcase and it wasn't done to fix a casting defect.

Yes A65 cranks are very strong even by modern standards, but they do break and they don't get stronger with age


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Originally Posted by Allan Gill
I'm not nitriding incase I break the crank. I'm nitriding to increase the journal strength.


It won't materially increase the strength of your crank.
It will inhibit the formation of cracks and if cracks are there resists then getting bigger.


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Originally Posted by BSA_WM20
Every second A 65 from the USA has a big weld down the front left side of the crankcase and it wasn't done to fix a casting defect.

Yes A65 cranks are very strong even by modern standards, but they do break and they don't get stronger with age

That's thrown rods, not busted crankshafts


... and probably due to a combination of shot big end shells from the motors having been lugged and sludged up sludge traps rather than timing side bush wear smile

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Originally Posted by gunner
Have a read of this link Introduction to Nitriding , its very informative and gives a complete history of the process.

There appear to be varyous nitriding processes available, some better suited to British Nitriding Steels (En 40 A, En 40 B,
En 40 C, En 41 A, and En 41 B.) these were Developed for nitriding applications, and are chromium-molybdenum steels.

There is also Gas Plasma/Ion Nitriding available which apparently is not restricted to steel with nitriding forming elements.

No idea what the A65 crank is made from but if unsure maybe the Gas Plasma/Ion Niriding techneque would be better?

Hope this is of use.


Interesting article, and as a base line high school level introduction quite good a bit USA jingoistic and a bit short on production facts but useful just the same.
Most of the work he refers to is strait laboratory work, not commercial and there is a big difference.
Commercially putting a batch of steel into a controlled atmosphere furnace for a few hours a 500 C is neither easy nor cheap which despite what he says is why nitriding is not a production line process and still plays second fiddle to standard case hardening or even flame / induction hardening.
As for vacuum plasma nitriding we are talking defence & high end medical uses only big big $$$$$.
Up until USA coal sweam gas production took off more American made parts were heat treated in Australia than in the USA due to the energy costs in the USA and lack of security of energy supply.

Al-Fe alloys are in the exotic category and generally frowned upon because Al in steel makes it near impossible to recycle.
Professor Walwark developed a whole range of very high strength high temperature lightweight Al- fe alloys back in the 70's to replace the Ni-Fe alloys and despite gaining another ACTA Metallurgia ( worlds highest accolade for metallurgy) for Australia the alloy system never went into commercial production mainly due to the difficulty in sorting scrap for recycling back in those days


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As a matter of interest, where did the fractures occur on the Nourish cranks? If at the drive end, could that have been due to belt primaries being run too tight ?

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Originally Posted by NickL
Get that nitriding process wrong and you make the crank more brittle.
Then the arguments start about who's fault that was if and when it breaks.....,,,

Broken rods are the cause of welded cases, mainly due to oiling problems. Not broken cranks.
I've seen a few broken nourish cranks made of nitrided EN40 they can snap like carrots.


Nitriding can not make the steel more brittle, that is the beauty of the process.
CARBO- NITRIDING can as it is a case hardening process.

Any yes I was wrong
So I will go & stand in the naughty corner.
Thrown rods , not broken cranks.


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Thanks trevor, I was going to say the same thing till I saw your reply. The company who are doing my motor ( and do a lot of Motorsport cranks) they told me a lot about the process etc ( most of which was understandable but too much information to try and repeat)

In a nutshell the process is like cooking a top notch steak!


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Hi Nick

I was looking in my "machinery Handbook" under engineering terms and couldn't find your term brick ****house. It is quite an old copy so may only be in some of the newer versions!

I tend to agree with your comments though, end-feed an A65 crank and keep pumping oil to the shells and they can take a lot of punishment. Even most of the rod failures were caused due to the lack of oil.

And thanks Trevor for his explanations and knowledge of metrology.

Off to the library

John

Last edited by JER.Hill; 07/11/16 1:56 am.
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