Increasing the life of the walls and roof of 100-ton electric-arc furnaces

Abstract

A DSP-IO0 electric arc furnace was placed in service in Orsk-Khalilova Metallurgical Combine in 1981. In accordance with the design the arched roof of the furnace is laid dry with PKhSE-3 and PKhSE-5 refractories.In the first campaigns the life of the roof was low (43 heats), which was the reason for conducting investigations on improving the lining.The work was done in two directions, by selection of the composition of mortar for the lining and by changing the method of lining and design of the roof.Four variations of the mortar composition were tested.All of the mixtures of powders were mixed with an aqueous solution of magnesium sulfate with a density of 1.25 g/cm s ~Table i).The introduction of even the first three variations of the mortar (series of campaigns No. 2-4) made it possible to increase the average life of the roof by i0 heats.The mortar with a filler of a mixture of magnesite powder and SMZh provided a further increase in life to an average of 84 heats.An increase in the rise of the roof from 920 to 1020 mm and laying the lining by the ring method made it possible to not only significantly reduce the bricklaying labor but also to increase the life of the roof to 103 heats per campaign.Ring lining of the roof was done in the following manner.Fourteen rings or parts placed on edge were laid and then two rings laid flat, after which the templates were placed in the electrode holes and two rows of parts were laid on edge around them.The laying was done using amortar of a mixture of magnesite powder and SMZh and the thickness of the joints was 3-5 mm. Between the second and third and the third and fourth rings joints 1-2 mm thick of roofing felt were laid.In 7 out of 55 cases there were failure of the roof support rings and flooding of the roof lining with water and, as the result, early failure of the roof.Therefore at present work is being done on selection of the optimum number of expansion joints and the points of their location.It should be noted that the new roof design operates under more severe conditions in relation to the period compared in connection with the introduction of vacuum treatment of the metal and the 20-25~ increase in the temperature of the steel before tapping.The wall lining was laid in two layers.The reinforcing layer was laid with KhM-I (GOST 5381-72) parts and the working layer with PKhS-23 and PKhS-17 (GOST 10888-76) parts 460 and 380 n~ thick, respectively.The wall life in the initial period was an average of 56 heats.To increase the wall life PKhP-80 (fused periclase--chromite) and KhPT-23 (heat resistant chromite-periclase) parts were used in nine campaigns for lining the working layer, which made it possible to increase the service life of the walls to 65-73 heats (Table 2).Orsk-Khalilova Metallurgical Combine.