| 摘要 |
PURPOSE:To form a coating layer which has excellent resistance to exfoliation and prevents formation of build-up on the surface of a hearth roll for heat treatment of a steel plate by spraying thermally a binding metal layer, a mixed layer of mullite and a binding metal and a mullite layer on the surface of said hearth roll. CONSTITUTION:A hearth roll in a heat treating furnace for a steel plate is formed by spraying thermally a binding metal layer consisting of an Ni or Co alloy having >=0.1mm. thickness on the suface of said roll. A mixed layer of said binding metal and mullite is thermally sprayed thereon in >=2 layers at >=0.1mm. thickness on the surface thereof. The mixing ratio of the mullite with respect to the binding metal is made larger toward the upper layer. A layer of mullite is finally thermally sprayed again at >=0.1mm. thickness. The hearth roll having the coating layer which is hardly exfoliated by thermal expansion owing to the presence of the binding metallic layer and the plural mixed layers and is free from formation of build-up by oxide of Fe, etc. is thus obtd. |
