During calcining the aluminum hydroxide according to the Bayer process in a rotary kiln,the process of incomplete conversion to alpha alumina by soft calcination leads to a special intermediate alumina product containing microcrystalline of primary crystal alpha alumina particles less than 0.4 μm,and other alumina phases with finer microcrystalline of less than 0.2 μm particles.This special alumina powder has similar properties to silica fume or clay,such as high surface area and reactivity,fast wetting,low water demand and high stick-ability.It can partially or completely replace silica fume and clay in dry gunning mixes.It works towards improving the high temperature resistance of the gunning material matrix as well as the corrosion resistance and service life of the gunning materials.The application results show that:the ladle cementfree alumina-magnesia dry gunning mix with this special alumina sub-micro powder,compared with traditional dry gunning materials,has lower rebound loss (＜10％),better adhesion rate,higher corrosion resistance and peeling resistance;and it can replace the veneering casting repair to achieve the similar performance.A further improvement goal is to replace the initial casting linings,thus this concept will give a new revolution to the monolithic steel ladles.