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At present in the USSR and abroad wet guniting is used for hot repairs of open hearth roofs. It is used primarily as routine, general, and preventive guniting. After a certain number of heats during a campaign the moist guniting compound is applied to the whole roof or a large portion of it in a thin layer for the purpose of prolonging the service life of all elements of the roof.Local burns of roofs occur at the end of open-hearth campaigns and are accompanied by reddening of the outer surface of the roof. Reddening is observed with wearing of the roof to a thickness of less than 100 ms, after which it may collapse during any period of a heat. However, under production conditions it is not always possible to shut down an open hearth for cold repairs at the moment of reddening. Maintenance of an open hearth in normal operation for 1-5 days is an important and pressing measure form the point of view of organizing work in the open-hearth shop and in the steel plant in general.In addition, taking into consideration the high cost of cold repairs, even an insignificant (by 1-10%) increase in roof life makes it possible to obtain a significant saving in the repair of local burns.The application of moist guniting compound on the same portion of the roof leads to sharp cooling of its working surface. At this point the roof is frequently spalled, and with a small remaining thickness --caved in. The spalling is caused by thermal stresses concentrated on the boundary of the working and transition zones [1], and the caving in is caused by shrinkage of the parts in the area of guniting and failure of the bond between them.In the past decade, in our country torch guniting of converter linings has been developed and introduced [2][3][4]. In torch guniting a temperature of 1700-1900~ is developed on the surface being repaired [5]. This is approximately the same as in the second half of melting on the working surface of the open-hearth roof. Therefore, thermal shocks do not occur in the parts and the reddened portions of the roof may be welded onto without threat of caving in. This is the basic advantage of torch ganiting over moist when it is necessary to repair burns of roofs at the end of open-hearth campaigns.

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