Abstract:
© 2020, "Ore and Metals" Publishing house. All rights reserved. Strength, durability and ultimate loads of gear teeth are determined by both the properties of steel on the working surfaces and the condition (continuity, macro-and microstructure) of the subsurface layers of the metal. Therefore, to increase the durability of gears, it is necessary to create production conditions that exclude the occurrence of defects in these areas and provide high mechanical properties (strength, hardness). One of the most unpredictable and dangerous defects in terms of consequences during the operation of gears is rolled or stamped scale-a surface defect that is interspersed with high-temperature oxides of steel, depressed during hot rolling or stamping. In this regard, the main factors that determine the quality of the surface of the gear ring during precision hot forging are described: the quality of the surface of the initial metal roll, the calcification during the heating of the workpiece, during the stamping process, and when the forging cools. Methods for improving the quality of the toothed crown surface are proposed: use of rolled metal products, lowering the temperature of the forming, use of low-oxygen heating, choice of material with increased scale resistance, selection of a rational precipitation scheme for scaling the surface of the workpiece, removing scale from the surface of the stamp engraving. Experimental technological modes of precision stamping operations and corresponding results of laboratory studies are presented. The influence of the studied factors on the quality of the forgings obtained as a result of experimental stamping was evaluated through: presence of defects (stamped scale and cavities from the scale that fell from the calibrated surface of the tooth), micro-and macrostructure of the tooth body, mechanical properties (hardness of forgings and microhardness at different depths from the tooth surface), roughness of the tooth profile surface depending on the calibration.
