Development of Minimally Alloyed Structural Steel for Large Module Gears of Transmissions

Abstract

In the world practice of manufacturing gears for automotive equipment, a search is being made for new, more effective steel grades and ways to realize their advantages, achieved both during smelting and during further thermal, deformation and chemical-thermal treatment. There is a tendency to reduce the nickel content in structural steel grades and replace them with sparingly alloyed, microalloyed with strong carbide-forming elements. The condition for using sparingly alloyed structural steels is the ability to find a compromise between increasing the reliability and durability of machine parts and saving deficient alloying materials. Based on this, the article formulates the main provisions that should be taken into account when developing minimally alloyed structural steel compositions for manufacturing highly stressed gears of mobile machine transmissions. It is shown that the introduction of new sparingly alloyed steel grades leads to the need to develop new technologies with the solution in each case of the problem of assessing the impact of alloying elements and microadditives on the hardenability of steel. The method of minimum doping of steel for gears with a module of 10 mm is given. Based on the application of a new approach, a new minimally alloyed structural steel has been developed that provides high strength, fatigue and technological characteristics of large module gears. The hardenability of the core and cemented layers of the developed steel is determined, which provides the life of the gears for at least 1,000 hours in operating conditions at contact stresses in the engagement pole σН = 1,800 MPa.

Keywords

• sparingly alloyed structural steels
• hardenability
• minimal alloying
• calculation method