Section 2 Materials

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 3, 2.1 Material properties 2.1.1, the specified minimum tensile strength is to be selected within the following limits:

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.

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

2.2.1 An ultrasonic examination is to be carried out on all gear blanks where the finished diameter of the surfaces, where teeth will be cut, is in excess of 200 mm.

2.2.2 Magnetic particle or liquid penetrant examination is to be carried out on all surface-hardened teeth. This examination may also be requested on the finished machined teeth of through-hardened gears.