DBTT temperatures for CRES 4

[MPEngineer]

I'm a non-metals guy (Plastics, composites) in a metals world. We are supplying parts to a new aerospace program and need to ensure the metals we are using are above a certain DBTT. Is there a place where I can look these up? Thanks.

 

[mfgenggear]

http://www.ewp.rpi.edu/hartford/use...rittle transition temperature in a nickel.pdf

Mfgenggear
if it can be built it can be calculated.
if it can be calculated it can be built.

 

[metengr]

Need more information on the specific grades of CRES - 3xx or 4xx or ?

 

[EdStainless]

If it is an austenitic alloy then there is no BDTT.
If it is martensitic or ferritic then there is one.
Give us an alloy or a spec.
You can find them in alloy data sheets from various mills.

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Plymouth Tube

 

[stanweld]

Metals/alloys with face centered cubic structures, like fully austenitic stainless steels do not have a ductile to brittle transition temp. Body centered cubic structures like carbon steels, low and high alloy ferritic steels, columbium/niobium, tungsten & molybdenum do.

 

[MPEngineer]

Thanks all for your assistance. Sorry about the ambiguity, but the CRES I'm using goes from 301 all the way to PH13-8Mo.

 

[EdStainless]

The PH grades have serious DBTT issues (after all they are martensitic).
I would be concerned with anything below 32F for high strength condition (H900 or 950) while lower strength (H1050 or 1100) might be OK down to 10F.
Those temperatures should be about a 50% reduction in impact toughness.
Find out what your design limits are.

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Plymouth Tube

 

[MPEngineer]

Temperature limits are -69.7F to +160F. We also have to be sure the DBTT is less than -69.7F and recovery temperature of +180F.

 

[metengr]

Based on your service temperature limits, this rules out any martensitic stainless steel or PH alloys. I would stick with the austenitic stainless steel or nickel-containing low alloy steel grades (if corrosion is not an issue). You really need to define the minimum CVN energy value at -70 deg F. Simply referring to DBTT is of little value.

 

[MPEngineer]

metengr,
Corrosion is part of the issue, but I can figure out a way around that; i.e. use of sealants or coatings to mitigate. The customer wants the DBTT values. Is there a way to go back to the customer and ask them to reconsider? Or is there a polite way to say DBTT is little value and this is what you're really looking for?

 

[metman]

MPEngineer
The DBTT is only of value for your initial selection of material. It tells you the minimum temperature that the material will fail in a ductile mode. Like Metengr says, “austenitic stainless steel or nickel-containing low alloy steel grades” are your choices.

You can report to your customer the DBTT for the alloys from this group which you have available. Tell them, “These are the alloys which we have available that have a low enough DBTT for your application and ask them,” what is the minimum CVN energy required at -70F? We want to verify that the material will have the quantified level of ductility (in foot-pounds) necessary for your application”


Design for RELIABILITY, manufacturability, and maintainability

 

[mrfailure]

For this purpose, visual examination of the Charpy specimen after testing at -70F would be more useful than specifying Charpy energy. You can instead specify a minimum 50% shear upon testing to ensure you are at or above DBTT.

Aaron Tanzer

http://www.lehightesting.com

 

[MPEngineer]

Hi everyone, I'm back. I would like to get the DBTT for Ph13-8Mo, H1000. Can anyone help? Thanks.

 

[EdStainless]

http://www.atimetals.com/Documents/ati_13-8mo_supertough_tds_en.pdf

you can get about 1/2 of RT toughness at -40.
If you care use only the VAR remelted material.

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Plymouth Tube

 

[cloa]

Some Duplex grades (and particular batches) maybe good for such low temperatures as I've seen both -50C and -80C as toughness limit temperatures.

 

[MPEngineer]

Thanks everyone. It is much appreciated.