12crni3a is the most widely used carburizing steel, its strength, ductility, hardenability sexual high. Mainly used for heavy-duty conditions, under the requirements of high strength, high hardness and high toughness toughness of the spindle and the centers are required to withstand shock loads, surface abrasion, heat treatment changed the small shaft, rod, and a variety of high-speed and impact load transmission gear, adjusting screw, camshaft