2.1.1 In the
selection of materials for pinions and wheels, consideration is to
be given to their compatibility in operation. Except in the case of
low reduction ratios, for gears of through-hardened steels, provision
is also to be made for a hardness differential between pinion teeth
and wheel teeth. For this purpose, the specified minimum tensile strength
of the wheel rim material is not to be more than 85 per cent of that
of the pinion.
2.1.2 Subject
to Pt 5, Ch 5, 2.1 Material properties 2.1.1, the specified minimum
tensile strength is to be selected within the following limits:
| Pinion and pinion sleeves
|
550 to 1050 N/mm2
(56
to 107 kgf/mm2)
|
| Gear wheels and rims
|
400 to 850 N/mm2
(41
to 87 kgf/mm2)
|
A tensile strength range is also
to be specified and is not to exceed 120 N/mm2 (12 kgf/mm2) when the specified minimum tensile strength is 600 N/mm2 (61
kgf/mm2) or less. For higher strength steels, the range
is not to exceed 150 N/mm2 (15 kgf/mm2).
2.1.3 Unless
otherwise agreed, the full specified minimum tensile strength of the
core is to be 800 N/mm2 (82 kgf/mm2) for induction-hardened
or nitrided gearing and 750 N/mm2 (76 kgf/mm2)
for carburised gearing.
2.1.4 For
nitrided gearing, the full depth of the hardened zone is to be not
less than 0,5 mm and the hardness is to be not less than 500 HV for
a depth of 0,25 mm.