How significant is the selection of the temperature for Charpy tests, comparing the -40° C (-40° F) of A 923 and the ASME minimum design metal temperature?
ASTM A 923 and ASME UHA 51 have in common only that they both use Charpy tests. However, the purpose on the tests for the two procedures are quite different. The purpose of A 923 was to demonstrate that the heat treatment applied to a duplex stainless steel mill product had eliminated the intermetallic phases. The Charpy test was chosen because it was familiar to producer and user. As shown in the appendix of ASTM A 923, an acceptance criterion of 40 ft-lb at -40° C (-40° F) was found to correlate with the appearance of the intermetallic phase in a metallographic examination and a loss of corrosion resistance. Impact energy was selected as the acceptance criterion because of its intuitive meaning and the fact that it is so readily measured in an impact test. A 923 was not intended to demonstrate suitability for use at this temperature. The test was chosen to demonstrate the absence of the intermetallic phase. The high impact energy and low test temperature were necessary in order to ge
