American Welding Society Forum
In AWS A5.1-91 Page 24, Figure 12, Note 2 states " The notched surface and the surface to be struck shall be parallel within 0.002 in. (0.05 mm) and have at least 63 u in. (1.6 um) finish."
Does "The notched surface" refer to the notch its self, or to the surface ajacent to the notch?
For what it's worth, this is my take on it:
Since it refers also to the "surface to be struck", it implies that it is talking about the flat sides of the specimen, not the notch.
I do not have a copy of A5.1. I have a copy of ASTM A370-97a Standard Test Methods and Definitions for Mechanical Testing of Steel Products in front of me. Figure 11, Note 1 says "Finish requirements - 2 um (63 uin.) on notched surface and opposite face; 4 um (125 uin.) on other two surfaces". This indicates to me the entire notched side and the entire opposite side. Adjacent sides hold lower requirements.
It has been many years since I have performed charpy testing. It is difficult to find a machinist who can consistently machine accurate charpys until they understand what you want. Have trashed countless charpy specimens (and thus the test plates) because of inaccurate charpy specimens. Angle, radius and remaining thickness below the notch contribute greatly to consistent results.
Since the results from charpy testing is only meaningful if all variables are kept within tolerance, machine and specimens are critical. Be sure the specimens are made correctly and be sure the charpy machine holds a current certification. This is not as easy as it would seem on the surface that is why charpy testing is not cheap.
Thanks for your replies. I also arrived at the interpretation that it was the specimen sides that were being referred to rather than the notch its self. It seems to me that the surface finish of the notch is far more critical and it's surprising that it's not specified.
My reason for raising the subject is the suspicion that a charpy notch broach is dragging swarf during the cut and marking the notch surface.
It is difficult to prove this without knowing the surface finish requirements of the notch.
The charpy specimens are otherwise within tolerance.
Any futher comments would be appreciated.
I would like to obtain some information on the proper way to perform a charpy v- notch test on materials. Any suggestions.
Check out ASTM A370. It should give you info on what to do.
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