Bolt nil ductility temperatures 1

[Ibreakstuffdigitally]

Is there a specified requirement for structural bolt ductility at low temperatures?

I've been unable to find a reference for transition temperatures.

I'm looking for data on grade 8 bolts, as well as data on A325 and A490.

I'd assume the A325 and A490 would be superior, however I dont really have any basis for this...

Thanks in advance for any information

 

[TVP]

The chemical composition ranges, steelmaking practices, and mechancial properties allowed by standards such as ASTM A 325 and A 490 are too variable to define a single transition temperature. Stated another way, a bolt with a hardness/strength at the low end of the spec coupled with superior melting, very low S & P, CaSi inclusion modification, and extremely fine prior austenite grain size will have a substantially lower (more than 20 degrees C) transition than coarse grain, high S & P, high hardness bolts.

 

[Ibreakstuffdigitally]

Thanks, although that's rather bad news for me. Is there a relatively standard source for controlled toughness bolts for structural applications at various low temperatures? (-20, 30 and 40 degrees C respectively)

I'm not interested in using stainless if I can avoid it, and I know that such steels as 4340 can maintain decent impact properties down to -40 or so.

does anyone offer this sort of thing off the shelf, and (hopefully) at a moderate price?

 

[TVP]

ASTM A 320 is the standard specification for low temperature bolts. There are a number of different product grades, with both conventional martensitic (quenched & tempered) alloys as well as austenitic stainless steels being described. 4140, 4037, 4137, 8740, and 4340 are all grades that are referenced in this standard. FYI, the standard uses notation like Grade L7A or L71 for 4037, L43 for 4340, etc.