The invention provides a cold
extrusion process of a
planet gear sun gear of a transmission of a heavy-load
truck. The cold
extrusion process includes the following steps that a
raw material bar is saw-
cut into a specified size; the saw-
cut bar is rapidly heated to 950 DEG C + / - 20 DEG C, upsetting and inner hole
impact extrusion are completed, a cup-shaped blank is formed, and
forging waste heatis saved; spheroidizing annealing treatment of a
forging blank is completed, and the
hardness of the blank is reduced to be smaller than or equal to 120 HB;
punching is completed, and an annular blankis formed;
polymer lubricant soaking treatment is carried out after turning is completed, and the blank is air-dried and then prepared for extrusion; tooth form cold extrusion forming is completed; an inner hole and the two end faces of a cold extrusion part are turned, a tooth form is chamfered so that burrs can be removed, an internal spline of the sun gear is broached, and part
machining before heat treatment is completed;
carburizing and
quenching treatment is carried out,
carbon potential is controlled at 1% at a strong
carburizing stage, the
carbon potential is controlled at 0.8% at a
diffusion stage, and the surface
hardness, the core
hardness, the carburized layer depth and the grain size of the quenched part meet the technical requirements; and after a
tooth surface is ground, the design requirements are met. The cold extrusion process is low in
machining cost and
environmentally friendly, and the abrasion resistance is improved.