Low Temp. Carbon Steel & Low Temp. Stainless Steel

[RiniEIT]

This might be a silly question...

I am aware of normal temp (min temp. = -29 deg C) vs. low temp (min temp. = -45 deg C) CARBON steel pipe and fittings, but is there a similar relationship between different types of stainless steels?

From what I see in table A-1 in B31.3, most stainless steels such as ASTM A182 & A312 can be used as low temp piping (i.e. at -45 deg C). What stainless steel piping and fittings can not be used for low temp. piping applications? (if there are any).

Thanks in advance!

 

[TGS4]

The issue with "low temperature" materials is adequately capturing the ductile-to-brittle transition. This is a property of all ferritic steels, such as carbon steel. Most stainless steels are austenitic and do not exhibit such a transition to brittle behaviour.

Not a silly question. Good question.

 

[weldstan]

Duplex stainless steels, ferritic stainless steels and martensitic stainless steels undergo a ductile to brittle transition as temperature decreases. All body centered cubic structured metals and alloys will undergo this transition.

 

[RiniEIT]

Thank you TGS4.

Weldstan, which stainless steels are you referring to? Does A182 & A312 fall into this?

Thanks.

 

[weldstan]

Both ASTM spec have numerous grades. The 3XX series are austenitic (face centered cubic). The 4XX series are ferritic or martensitic (body centered cubic/body centered tetragonal). Duplex stainless alloys have a mixed ferritic and austenitic structure (approximately 50/50.

 

[RiniEIT]

Thank you Weldstan!

 

[golbang]

Is there any difference between carbon steel and killed carbon steel welding procedure?
Thanks.

 

[LSThill]

ASME B31T 2015 This Standard provides requirements for evaluating the suitability of materials used in piping systems for piping that may be subject to brittle failure due to low-temperature service conditions

 

[weldstan]

In terms of qualification, no. However if you are qualifying a procedure requiring impact testing to be performed at low temperature, you will need to qualify your WPS with killed carbon steel made with fine grain melting practice.