according to ISO 898, part 5:2012 table 3
The mechanical properties apply to set screws and similar, which are not subject to tension and which have threads of diameter from 1,6 to 39 mm, made from unalloyed or alloyed steel.
For further details of the mechanical properties of set screws please refer to ISO 898, part 5.
a) For hardness class 22H: if hardness is tested in Rockwell, it is necessary to test the minimum value in HRB and the maximum value in HRC.
b) No complete decarburization permitted in hardness class 45H.
c) Surface hardness shall not be more than 30 Vickers points above the measured base metal hardness of the fastener when determination of both the surface
hardness and base metal hardness are carried out with HV 0,3.