Helical gear Reduction Boxes H4 ways Cement industry Concrete mixers B H4-FV25-B

Flender/Flender Gear Units/Helical gear Reduction Boxes H4

larger bevel gears. Core hardness for gears is dened at point in the gear body which lies perpendicular to the 3/C1tangent in the tooth root, at distance from the surface equal to ve times the case hardening depth. For testing, cylindrical specimen with diameter showing cooling behavior similar to that of the gear at the dened point is used. The core hardness can then be determined in reference to the measured hardness at the centre of the specimen. Fig. 3.3 Core hardness of different case hardening steels for various reference diameters9 3 Design Another aspect in material selection is related to the expected distortions during quenching. Pinions are generally quenched without support, while wheels arepreferably placed in quenching press. This is done in order to improve the run-out and atness of the gear body. quenching die consists of an expanding mandrel for the bore and clamping ring holding the wheel at (see Fig. 6.. Distortions are relatively small with xture hardening. If no quenching press isavailable, the acceptable amount of distortion must be considered in the design. Apart from specifying the composition of the material, Standard ISO 6 contains three quality classes. Table 3.9indicates attributes for the standardized qualities ML, MQ and ME. These attributes are the minimum requirements for thematerial. Especially where large bevel gears are concerned, it is usual to nd company-specic material specications which go far beyond the values listed in Table 3.9. 3.6 Choice of Lubricant 3.6.1 Introduction The lubricant is intended mainly to reduce friction and wear and to dissipate the heat generated in the gear mesh. In addition, it protects components against corrosion and is the carrier medium for various additives like oxidation inhibitors, pour pointdepressants, detergents and dispersants, whose role is to improve oil properties,along with wear and scufng protective additives to prevent gear damage. 3.6.2 Selection of the Lubricant In the grea