Gears, major components for power and motion, are widely used in industries like automotive, aerospace, ship, power, mining, etc.
Gears are subject to external forces during motion and power transfer for their working characteristics, which causes bending stresses at their teeth roots and contact stresses on their contact parts. The teeth wear by sliding friction at the contact parts. In addition, improper gear meshing causes impact. Common failures in gears include wear and scratches, pitting corrosion, abrasive wear and teeth breakage by flexural fatigue and impact fatigue.
In order to improve the mechanical properties of gear steel, alloying elements such as niobium, titanium, boron, rare earths and vanadium are microalloyed.
Jong Chung Bing, a researcher at the Faculty of Material Science and Technology, has investigated the effect of the complex microalloying of boron and RE elements on the mechanical properties of low C-Mn steel in order to achieve high performance of gear steel without the need for import-dependent chromium.
As a result, he has found that when the chemical composition of steel is C 0.23-0.27%, Mn 1.1-1.3%, Si 0.2-0.45%, P and S less than 0.03%, B 0.001-0.004% and RE 0.025-0.05%, the mechanical properties of this steel quenched and tempered at low temperature are tensile strength 1 100-1 300MPa, elongation 9-15% and impact value 90-130J/cm2, which means it meets the technical requirements of steel for gears.