Annealing process for sapphire crystal bar

The invention provides an annealing process for a sapphire crystal bar. The process comprises five stages, namely rapid heating, slow heating, heat preservation, slow cooling and rapid cooling, wherein the highest temperature in the heat preservation stage can reach 1900 DEG C. By the adoption of the process, internal stress generated in the drawing-out process of the sapphire crystal bar can be remarkably reduced, the phenomena of warping and corner chipping in a subsequent sapphire wafer machining process are reduced, dislocation density in a sapphire crystal growth process can be reduced, and the crystal bar becomes colorless and transparent. Through verification, after the annealed sapphire crystal bar is processed into a wafer, the warp reject ratio of the wafer is 0 and the bow reject ratio of the wafer is 0.9%, respectively reduced by 100% and 70% compared with a warp reject ratio and a bow reject ratio before annealing, and transmittance in a visible light wave band reaches 86%. The annealing process