Crankshaft Materials

fetuhoe · Post by **fetuhoe** » Wed Nov 30, 2005 4:57 pm

Does any one know the Specification of the material that 2 litre counterweighted cranks are made from.

A spec. number is OK as I have a full set of German material specifications.

Tricky question but any information would help.

Thanks

davidppp · Post by **davidppp** » Wed Nov 30, 2005 9:56 pm

Hello, Chris.

I doknow they were made by Alfinger, possibly others..may not help of course..

Why?
Thinking of gettin one rehardened?

Kind regards
David

fetuhoe · Post by **fetuhoe** » Thu Dec 01, 2005 10:07 am

David, Hi

I hear all sorts of rumours about micropolishing removing the "hard layer" as it is very thin, which surprises me if the crank has been nitrided in the first place.

Others tell me that when you re-grind you cannot reharde without significant distortion, and again if the crank has been correctly nitirded in the first place this would be a surprise.

Another guy tells me that when you re-nitirde it is never hard enough.

I am just confused and want to get to the bottom of the problem and look at the best options.

Cheers

904GTS · Post by **904GTS** » Thu Dec 01, 2005 7:14 pm

The little Porsche spec book says the following :-

After grinding, round oil passages off to 0.5r, bevel sharp edges to 0.2 - 0.5r. Subject crankshaft to Tenifer treatment - 120 minutes at 570 C; quench in warm (40 C) water. Following the Tenifer treatment polish all bearing journals and thrust surface A; test crankshaft for cracks. Maximum unbalance in crankshaft = 10 cmg.

It doesn't mention what the material is.

fetuhoe · Post by **fetuhoe** » Tue Dec 06, 2005 2:23 pm

Thanks,

I am fairly confident that the Tenifer Process is very similar to Ferritic Nitrocarburising, which is also known as Tuftriding, which is also carried out at 570 degC. I would think that there are minor differences in chemistry as Tenifer Treatments tend to produce black surfaces.

Tenifer treatments are also known as 'soft nitriding' or 'salt bath' nitriding and diffuse both carbon and nitorgen into the surface of the steel being treated.

The hard layer is probably only about 10-15 microns thick.

This process is quite different to gas nitriding which gives much deeper layers depending on time left in the nitrogen atmosphere.

It seems that both Tenifer treatment and tuftriding can be used on virtually any steel and do not need the specific alloys (such as EN40B and EN41) that are required for gas nitriding.

I assume that Porsche carnks are not manufactured from a gas nitriding steel and this could explain the poor performance that results if this process is used.