For the next generation of nozzle bodies in the piezoinjectors of diesel engines with the common rail technology a higher tensile strength of 1400 MPa at a temperature of 350 ^оC and a hardness of 600 to 700 HV_0,5 after case hardening and stress relieving at 350 ^оC is anticipated. These condition can be fulfilled to a large extent by the steel 21 CrMoV 57. The case hardening treatment for the steel 21 CrMoV 57 is simpler and thus less costlier than the presently used steel 18 CrNi 8.