A study conducted by the German Institute for Machine Elements (FZG) in Munich, Germany, on behalf of the International Molybdenum Association (IMOA) has found that a newly-developed molybdenum-alloyed carburising steel has out-performed existing gear steels without increasing alloy cost.
Modern gearboxes must deal with increasing load stresses while offering high reliability, requiring exceptionally strong, high-performance steel. Combining alloying elements with heat treatment produces the optimal blend of high surface hardness and high base strength required for safe operation in large, highly-loaded gears.
Compared to the standard high-end gear steel grade (18CrNiMo7-6), the new steel contains slightly more carbon, twice the amount of molybdenum (0.55%) but only about half the addition of nickel (0.9%).
The IMOA-sponsored study, conducted in association with a German special steel producer, found that hardenability and strength were greatly improved, with the new steel clearly out-performing all reference steel grades in two DIN standard benchmark tests. However there was no increase in alloy cost.
Dr. Nicole Kinsman, IMOA technical director, said: “This superior performance means that gears made from this new grade could support either higher torque, or for equivalent loads, could be built smaller and lighter. Possible applications include wind turbines, heavy machinery, trucks and cars.”