Charpy vs temperature data 2

[irx]

Does anybody have a curve or data of Charpy impact values vs temperature (-50C TO 150C) for typical pressure vessel low alloy steels such as SA53, SA106B, SA216, SA516,SA105?
Thanks for your help

 

[metengr]

irx;
This type of data is not readily available, especially for free. However, I can give you some advice to ball park the data. There is a graph which is commonly referred to as CVN impact energy transition curves versus carbon content, and is referenced in many technical publications.

The graph is a compilation of transtion curves for various plain carbon steels as a function of carbon content that varies from 0.1% up to 0.80%.

For pressure vessel steels, the carbon content is less than 0.35%. So, if you locate this graph below and obtain the carbon contents for each of the carbon steels you listed above, you should be able to guesstimate the CVN upper to lower shelf energy values, and transition temperatures.

http://i15.tinypic.com/3z7nygo.jpg

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Keep in mind that for SA 516 steel, the CVN transition data would be closer to a lower carbon steel because of the fine grain heat treatment. However, using this graph will allow you to obtain worst case or more conservative data.

 

[irx]

Thanks for the info, I am trying to get a conservative value for the different materials (pressure equipment) and I want to convert Charpy to Kic to be able to calculate critical crack sizes for different cracks detected during maintenece inspections. Thanks again for the link.

 

[metengr]

irx;
You should realize that there is no direct correlation of Charpy V-notch impact energy values to fracture toughness. The equations in literature relating CVN to KI_c are only used to approximate fracture toughness (KI_c), at the upper shelf region of the CVN curve.

If you intend to use these equations, be very careful in their application. I would not rely totally on them as part of a risk-based inspection program for deciding to run or repair.

 

[stanweld]

Over 30 years ago we impact tested over 50 different heats of API 5LX-52 pipe to determine upper shelf, lower shelf, and transition zone. The 15/12 ft-lb absorbed energy values ranged from about 20F to 130F. This information was never published. While I expect that the wide range obtained at that time has narrowed due to superior steel making practice (at least in some countries), I have lately seen evidence from some international producers that would tend to invalidate my expectations.

As metengr states, you cannot directly correlate charpy values with fracture toughness.

 

[Maui]

The question of whether or not Charpy impact values can be correlated with fracture toughness values has been discussed previously. A very good and informative series of posts on this topic is contained in the following thread:
thread330-128281

Maui

 

[irx]

Maui;
Thank you for the reference, I also found a correlation in API 579 between Kic and Charpy - however I shall act with caution as proposed by Metengr.
I do not understand why data on both these parameters are not more widely published.

IRX

 

[Maui]

Irx, you're welcome. I think that you would understand why this type of data is not more widely available if you ever had the personal experience of making your own specimens and going through the process of conducting a valid fracture toughness test. I have, and the work can be quite involved. By comparison, Charpy impact tests are relatively simple and straightforward. If you are able to access this type of information at no charge, then you're very fortunate.

Maui