| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide an inexpensive, high strength invar alloy which has low thermal expansion and excellent hot workability, and is used for a shadow mask of a cathode ray tube, and to provide a production method therefor. SOLUTION: The alloy has a composition which contains one or more kinds of strengthening elements selected from C and Nb, Ni, Co, Al and Ca, and, if required, which further contains B, and in which the contents of Si, Mn, P, S, Mg, Cu, Cr, V, Mo, Ti, N and O are controlled to specified values or lower, in which the content of Mg inclusion is controlled to a specified value or lower, and also, Ca/O is 0.1 to 2.0, or the proportion of Mg, Al and Ca in oxide inclusions is controlled to a specified ratio to allow Ca sulfide to precipitate incidentially to oxide inclusions, and which contains the balance being substantially Fe. In the production of the alloy, the ratio of CaO to Al2 O3 in slag to be used in secondary refining is controlled to 1.4 to 2.2, and the content of SiO2 and the content of MgO in the slag are controlled and then slag refining is performed. Thereafter, a Ca alloy is added thereto by the start of casting.</p> |
