Recent brittle behavior of carbon steel (A105/A106/A234/A53)
Recent brittle behavior of carbon steel (A105/A106/A234/A53)
(OP)
I've been reading a few reports and bulletins on recent brittle failures of carbon steel components that have occurred during hydrotests. Materials discussed include A105/A106/A234/A53. Here are a couple of links to bulletins:
NCPWB Technical Bulletin May 2016
ABSA Information Bulletin No. IB16-018
Reference is made to failed impact tests with absorbed energy values as low as 3 ft-lbs at 70°F, where the material otherwise appears to meet all requirements of the specifications! It sounds as though one of the major contributing factors is the direction microalloying has taken at the mills in recent years, with the Mo:C ratio being highlighted.
These low energy values are concerning, how do you foresee the code committees reacting?
NCPWB Technical Bulletin May 2016
ABSA Information Bulletin No. IB16-018
Reference is made to failed impact tests with absorbed energy values as low as 3 ft-lbs at 70°F, where the material otherwise appears to meet all requirements of the specifications! It sounds as though one of the major contributing factors is the direction microalloying has taken at the mills in recent years, with the Mo:C ratio being highlighted.
These low energy values are concerning, how do you foresee the code committees reacting?





RE: Recent brittle behavior of carbon steel (A105/A106/A234/A53)
The MN to C ratio that is being proposed is not that simple to explain away the problem. I believe this is a local sourcing issue rather than a wide spread materials problem. Once BPV VIII decides on a plan going forward we can pursue under BPV I. Otherwise, nothing will be done. Impact testing will not be used by BPV I because boilers operate well above any DBTT for carbon steel. If anything, ASTM should do something regarding chemical composition limits or on tramp elements.
RE: Recent brittle behavior of carbon steel (A105/A106/A234/A53)
RE: Recent brittle behavior of carbon steel (A105/A106/A234/A53)
I am certainly not trying to downplay this thing but until I hear from others on my code committees and subgroup, I intend to gather more information before I jump on the revision band wagon.
RE: Recent brittle behavior of carbon steel (A105/A106/A234/A53)
RE: Recent brittle behavior of carbon steel (A105/A106/A234/A53)
RE: Recent brittle behavior of carbon steel (A105/A106/A234/A53)
I don't pretend to be a materials engineer and so won't comment on the science. I will say that I'm now familiar with several occasions in recent months in which flanges for new construction of pressure vessels were destructively tested. The test results did not meet energy values which Section VIII would have led me to expect. Taking a "usual suspects" country of origin approach does not explain the failures. The jury is definitely out on this. I'm looking forward very much to either B16 or B31 or BPV to getting some more definitive results out on this. This issue is being taken rather seriously by some.
RE: Recent brittle behavior of carbon steel (A105/A106/A234/A53)
RE: Recent brittle behavior of carbon steel (A105/A106/A234/A53)
It is not clear what your intent was with the quote you posted. Some commentary from you would be helpful when posting stuff. If your intent was to draw people's attention to the known and well documented issue of MDMT or MPT and that codes and standards exist which address this then great. But the issue in this thread is not solved by the application of known MDMT design. That's precisely the problem: New (so no in service degradation) steel has been failing in a brittle fracture mode at temperatures well warmer than Code determined MDMT.