The invention discloses a thermal bulging process for rectangular
titanium-
alloy rolled ring workpieces, which includes steps of primary bulging; primary rotation; secondary rotation; secondary bulging and
tertiary bulging. In the primary bulging, a rectangular
titanium-
alloy rolled ring workpiece which is treated by thermal rolling is sleeved on the periphery of a preheated bulging block in a bulging
machine, and the bulging block squeezes the rolled ring workpiece axially along the inner circumference of the rolled ring workpiece after the bulging
machine is started so that the primary bulging is completed, wherein the bulging temperature ranges from 780 DEG C to 830 DEG C, the bulging time ranges from 13s to 17s, the pressure
holding time ranges from 10s to 12s, and the deflection ranges from 0.3% to 0.8%. The primary rotation is completed by rotating the rolled ring workpiece along the center axis by 45 degrees. The secondary bulging is completed by processes of the primary bulging, wherein the bulging temperature ranges from 750 DEG C to 800 DEG C, the bulging time ranges from 13s to 17s, the pressure
holding time ranges from 10s to 12s, and the deflection ranges from 0.5% to 1%. The second rotation is completed by rotating the rolled ring workpiece again along the direction the same with that of the primary rotation. The
tertiary bulging is completed by the processes of the primary bulging again, wherein the bulging temperature ranges from 700 DEG C to 770 DEG C, the bulging time ranges from 15s to 20s, the pressure
holding time ranges from 12s to 14s, and the deflection ranges from 0.6% to 1%. The
dimensional precision of the rolled ring workpiece can be 1%. to 2%. of the corresponding precision after the rolled ring workpiece is bulged, and the rolled ring workpiece is mainly used for the fields of space navigation and the like.