Abstract
Many automotive parts, such as those used in axle, are manufactured in a forging process of special steel bars in hot and cold temperature regions. Generally, in the manufacturing process, additional heat treatment processes before and after forging such as annealing, normalizing and spheroidization annealing are necessary. Diffrential gears were used to decrease the speed and to provide moment increase for transmitting the moment coming from the engine to the wheels by turning it according to the suitable angle in vehicles and to provide that inner and outer wheels turn differently. Before cold forging process, spheroidizing annealing treatment was commonly used for cold forming ability. However, these heat treatments add production cost and manufacturing time. Because of that, there is strong demand to eliminating heat treatment process in order to achieve cost reduction and manufacturing time savings. Newly designed differential gears are subject to near net cold forging that demand steel that is capable of free forming ability. The developed Ti, Nb added Cr-Mo type case hardening steel eliminate spheroidizing annealing treatment with superior cold formability. This works examines the effect of alloying additions mainly on cold forging formability and durability. This newly developed steel was practical use in some SUV vehicle for differential gears.
KEYWORDS: Mild steel, differential gear, spheroidization annealing, case hardening steel, cost-savings