The invention relates to a monolithic molding method of a
light duty truck weldless axle case. A weldless steel round
pipe is used, first, early hole shrinkage is conducted to two ends of the weldless steel round
pipe, two times of hydro-bugling are conducted to the middle of the weldless steel round
pipe; and then, later stage hole shrinkage is conducted to the two ends of the weldless steel round pipe to obtain a performing pipe blank which is in an
axial symmetry shape or close to an
axial symmetry shape. A die left pressure head and a die right pressure head are used on a four-way hydraulic
machine for sealing the ends of the performing pipe blank, liquid is injected into the four-way hydraulic
machine, an upper die block, a lower die block, a front die block and a rear die block are used for integral pressing and forming on the performing pipe blank from the upper direction, the lower direction, the front direction and the rear direction, an axle case semi-finished product with a hemispherical rear oil cap and an additional front cap is obtained, and an axle case product is obtained by
cutting the additional front cap. According to the monolithic molding method, the manufactured axle case is weldless, high in strength and stiffness, and high in material
utilization rate. Comparing the used technique with a traditional hydro-bugling technique, the
liquid pressure needed in manufacturing process is lowered by more than 60%, and the
tonnage of forming devices is lowered by more than 50%.