The reliability of a steel-melting object operation depends to a considerable extent on the state of the furnace hearth refractory lining. Prolonged and partial furnace stoppages lead to loss of integrity of the sintered layer whose restoration requires performance of several necessary operations. Timely repair of the sintered layer reduces hot lost time and periclase material consumption.The hearth is one of the main elements of the workspace of an open-hearth furnace. It consists of a bottom, within whose central part there is steel delivery opening, longitudinal banks over the side of the furnace and transverse in the direction of the front and rear walls. During operation of a hearth it should exhibit sufficient impact strength in order to withstand mechanical damage during loading with charges of categories A and B of form No. 1 -3 (GOST 2787), and also physicochemical action of a gas atmosphere, slag and metal, hydrodynamic action of poured molten iron, delivered steel, etc. The lining of the hearth should be of rational thickness in order to provide sufficient heat insulation and reliable resistance to possible penetration of liquid metal.Normally a hearth consists of successively placed layers of refractory material, laid on a metal sheet. The first layer is asbestos board (GOST 2850). A layer chamotte objects (GOST 8693) is placed upon it, and then there is a layer of periclase powder, that is the so-called sintered layer. The design thickness of the furnace hearth with a capacity of 200 -300 tons is 1080 -1170 mm, including, mm: sintered layer 225 -250, layer of periclase objects 690 -805, chamotte 120, asbestos board about 20 [1]. Laying of the bottom, longitudinal and transverse banks is also made with horizontal rows. The slope of the hearth bottom surface in the direction of the steel-pouring opening is made due to the sintered layer to a value of 0.05. The axis of the steel-pouring opening is arranged at an angle of 7°to the horizontal surface. Transverse banks of the hearth of the rear and front walls to the level of the charging doors is made at an angle of 45°, and the longitudinal banks from the direction of the port are made at an angle of about 35°. Expansion joints are filled with periclase powder grade DMPK-75 with a gap.Thermal expansion joints in the hearth periclase layer have a thickness of 10 mm per running meter with laying on end and 4.5 -6.0 mm with laying at the edge. Thermal expansion joints are not considered in the layer of chamotte objects in laying the bottom and banks. In rows of periclase objects in the longitudinal bank from the direction of the port the thermal expansion joints are 9 mm per 1 running meter of laying. Joints are staggered in the banks.The temperature of the inner surface of the hearth during melting varies within wide limits. On direct contact with molten metal before delivery its rises to 1660°C and on contact with the slag to 1700°C. In the period of repairing banks and the hearth bottom the temperature falls below 1000°C. The heat resistance of the linin...

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