Section 6 Materials

6.1.1 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 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.

6.1.2 Subject to Vol 2, Pt 3, Ch 1, 6.1 General 6.1.1, the specified minimum tensile strength is to be selected within the following limits:

1. Pinion and pinion sleeves: 550 to 1050 N/mm².

2. Gear wheels and rims: 400 to 850 N/mm².

A tensile strength range is also to be specified and is not to exceed 120 N/mm² when the specified minimum tensile strength is 600 N/mm² or less. For higher strength steels, the range is not to exceed 150 N/mm².

6.1.3 Unless otherwise agreed by LR, the specified minimum tensile strength of the core is to be 800 N/mm² for induction-hardened or nitrided gearing and 750 N/mm² for carburised gearing.

6.1.4 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.

6.2.1 Specifications for materials of pinions, pinion sleeves, wheel rims, gear wheels, and quill shafts, giving chemical composition, heat treatment and mechanical properties, are to be submitted for approval with the plans of gearing.

6.2.2 Where the teeth of a pinion or gear wheel are to be surface hardened, i.e,. carburised, nitrided, tufftrided or induction-hardened, the proposed specification and details of the procedure are to be submitted for approval.