Fatigue of A4-80 bolt

[AndyLake]

Hi all,

Does anybody know the fatigue limit of the A4-80 bolt? A4-80 is made of acid-proof steel. I have found the fatigue limit value for the 8.8 steel bolt, but not for the A4-80 acid-proof bolt.

 

[TVP]

It will depend on how it is manufactured (cold headed, rolled threads vs. hot headed, cut threads, etc.). Since bolt fatigue is best stated as a mean stress plus an alternating stress, it is best to consult with manufacturers that have the capability to perform this type of testing. Bufab Stainless is one such supplier.

http://www.bulten-stainless.se/eng/index.htm

 

[CoryPad]

VDI 2230 states that the fatigue resistance of austenitic steel bolts is provided in the following references:

42] Turlach, G.: Verbindungselemente aus Titan und Titanlegierungen. Draht-Welt (1980) 5

[43] Kellerman, R.; Turlach, G.: Schrauben aus ultrafesten Stählen und Titanlegierungen für den Leichtbau. Draht-Welt 56 (1970) Nr. 1, S. 51/75; Nr. 2, S. 107/112; Nr. 3, S. 189/192 (Beilage Schrauben, Muttern, Formteile)

[44] Wiegand, H.; Illgner, K.H.; Beelich, K.H.: Festigkeit und Formänderungsverhalten von Schraubenverbindungen insbesondere aus austenitischen Werkstoffen. Draht 18 (1967) S. 517/526

[45] Beelich, K.H.: Gesichtspunkte zur Deutung des Relaxationsverhaltens und zur Auslegung temperaturbeanspruchter Schraubenverbindungen. Draht-Welt 56 (1970), S. 3/8

[46] Wiegand, H.; Beelich, K.H.: Einfluss überlagerter Schwingbeanspruchung auf das Verhalten von Schraubenverbindungen bei hohen Temperaturen. Draht-Welt 54 (1968), S. 566/570

[47] Wiegand, H.; Flemming, G.: Hochtemperaturverhalten von
Schraubenverbindungen. VDI-Z 16 (1971), S. 415/421

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[AndyLake]

TVP: The bolt supplier is reluctant to rummage the fatigue value. I have asked the fatigue value directly from the bolt manufacturer -> no answer (?!)

CoryPad: Thaks! I’ll try to find those sources.


Nowadays almost everything is standardized. I really wonder if the fatigue limit of the acid-proof bolt hasn’t been standardized. I’m sure that you can find much more needless things from the standards...

 

[yates]

You don't say to what standard your bolkt was made. A4-80 sounds like an EN definition, which does not necessarily require either a rolled thread nor a forged head nor underhead radius cold rolling. Without these three items, an austenitic stainless steel bolt (which you appear to have) has precious little fatigue resistance. With any appreciable ammount of repeated dynamic load, a aerospace-type bolt (rolled thread, forged head, cold-rolled underhead radius) in INCO 718 for example, would have been a better choice.

 

[yates]

Cory,
The references mentioned in VDI 2230, are a bit ancient. The influence of structure, for example, on fatigue resistance of titanium alloys is much better understood now than in the seventies when titanium bolts were in their infancy. Gerhard Turlach, who is one of the authors mentioned, and who continues to be active in standardisation circles, has written much more recent papers on the subject.

 

[CoryPad]

A4-80 is a designation within ISO 3506-1 Mechanical properties of corrosion-resistant stainless steel fasteners — Part 1: Bolts, screws and studs. It is similar to type 316. These are commercial quality fasteners, and I am sure the "ancient" references will be adequate.

If I were working on more critical parts, with newer materials and/or production techniques, I would look into more recent publications, or more likely, conduct new testing.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[AndyLake]

Thanks yates! Sorry, I forgot to mention the standard. A4-80 is made of AISI 316.

Could you please tell me more about Inconel 718 bolts? Do you know exact fatigue values of 718? A4-80 (316) has good enough corrosion resistance in our case and I think Inconel 718 is at least as good as A4-80? Is the Inconel 718 bolt much more expensive than “common” acid-proof bolt A4-80?

Can anybody recommend me the bolt, which has higher fatigue limit than A4-80 has. The corrosion resistance has to be as good as the corrosion resistance of A4-80. The price should be low enough.

 

[CoryPad]

Inconel 718 is in an entirely other cost category than A4-80. This alloy is nickel-based and intended for high temperature applications like turbine engine parts.

Austenitic stainless steels can have higher strength (including fatigue) if it is strain hardened. Ask some suppliers.

Other alloys to consider are A-286, 17-4 PH, and a few new ones from Carpenter Technology:

http://crswnew.cartech.com/wnew/techarticles/TA00060.html

Also check out the articles on cold heading:

http://crswnew.cartech.com/wnew/techarticles/TechLibrarySelector.html

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.