附98版
HV2 > HV1 –30
HV3 < HV2 +30
Key
1, 2, 3 Measurement points
4 Pitch line
Figure 2 — Hardness measurements for decarburization test
Hardness determination for point 3 shall be made on the pitch line of the thread adjacent to the thread on which
determinations at points 1 and 2 are made.
The Vickers hardness value at point 2 (HV2) shall be equal to or greater than that at point 1 (HV1) minus 30 Vickers units. In
this case the height of the non-decarburized zone E is at least as specified in table 4.
The Vickers hardness value at point 3 (HV3) shall be equal to or less than that at point 1 (HV1) plus 30 Vickers units. An
increase of more than 30 Vickers units indicates that carburization is not permissible.
Complete decarburization up to the maximum specified in table 3 cannot be detected by the hardness measurement
method.
NOTE — Careful differentiation should be made between an increase in hardness caused by carburization and that due to heat treatment
or cold working of the surface.