ASTM G48 Method A

[Metaljon]

We are performing a ASTM G48 test Method A for a welding qualification/ welders approval on duplex steel. The client request is a 24 hour test and requiring a test result by weight loss of 4g/m2 or better. The ASTM G48 Practice A test we normally perform is a 72 hour test not 24 hrs. The standard is not precise on time but suggests 72 hours. However, the criteria for evaluation to ASTM G48 Method A is less than 1 g/m2 (minimum)for the 72 hour test and not 4 g/m2 weight loss as specified in the request. The test specification in the ASTM G48 standard is a minimum requirement and not something that the client can change. Is this an acceptable request for the client to shorten the test duration by x3 and increase the weight loss allowable by x4 for a welding qualification/ welders approval?

 

[metengr]

Agreed. However, if the client is paying for this type of revised test you might have an uphill battle or they may not be aware. Have you discussed your technical concerns this with the client?

 

[Metaljon]

Yes I have discussed with the client but they think this is acceptable for a welding qualification test. Test certificate issued would reflect that it is a client agreed specification rather than the standard ASTM criteria. Whilst some ASTM standards allow parts of the specification or tests to be agreed between the manufacturer and the client, the G48 standard does not grant such flexibility in selecting your own pass criteria.

 

[EdStainless]

First.
Did they define sample prep? ground or un-ground, pickled or not?
This is critical.

What is the test temp?

method A???? I thought that everyone had moved to using the acidified FeCl solution. It is more stable and repeatable, but slightly more aggressive.

Are they looking for pitting resistance or testing for intermetallics? These tests look nominally similar but the details are very different. You can't do both at once.



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[EdStainless]

Method E is a 24 hour test, but with the acidified solution.
There is very little difference in results at 24 and 72 hours. Pitting either initiates or not, it isn't a rate issue.

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[Metaljon]

They specified practice A to G48 but did specify that the sample was to be pickled before testing. The test temperature is 50°C. There is no sample prep specified. The test was to include a sample containing base metal, weld and HAZ. After testing to practice A they have specified no pitting at 20X magnification and weight loss to be less than 4 g/m2.

They have also specified no intermetallics or affected structure to be present to ASTM A923 Test Method A and ferrite determination to E562.

 

[SJones]

The requested testing and acceptance criteria are all normal oilfield stuff and contained in specifications such as NORSOK M-601. The temperature is a bit fiercer at 50 deg C. Very harsh to use the test for welders though.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[EdStainless]

Well at 50C this is obviously a super duplex.
Pickle it hard, this will remove any detrimental surface issues and help meet this test value.



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