Mild Steels at -80¦C?

[JMOwen]

I am currently evaluating the design of some large but lightly stressed welded storage frames. We have many years of experience of similar designs fabricated in mild steel (S275/43A) operating in a -20°C environment.

My concern is that that the new generation of frames will be in service at -80°C and must have a 25 year design life.

Brittle fracture is obviously the main concern. There is no stress cycling to speak of of fatigue is unlikely to be an issue. Specifiying 304 stainless steel would solve the problem but adds significant cost. Aluminium is prohibitively expensive because of the welding costs.

Does any one know of other less expensive low temperature steels that are readiliy available?

Alternately is there any data on the fracture toughness / stress limits for mild steels at -80°C?

 

[flamby]

I don't think structural steel will work. Check out following specifications.

ASTM A516
ASTM A517
ASTM A537

Ciao.

 

[jahawker]

I found your post whilst I have been searching for information regarding the use of 43A steel down to -15 degrees C.

The application is within a Crane and I'm looking to justify its use at low temperatures with regard to Brittle failure.

Do you have any information regarding Brittle Transition Temeprature or Nil-Ductility Temperature or Fracture Toughness for 43A steel at these temperatures? Do you have any Charpy Impact data or ideally a BTT curve showing a spread of data? Any information you may have could be useful.

Thanks.

 

[JMOwen]

Jahawker,

My application was at -80°C and as mild steels appear loose any fracture toughness below ~-40°C I didn't pursue them any further.

There is however a lot of data on the web from steel manufacturers / suppliers. I'd advise you to contact them directly.