Abstract

  Reheating furnace is the equipment that mostly dictates the speed of production of a melt shop, since a furnace that frequently stops for maintenance forces an interruption of the plant production and, in the case of an integrated mill, can also entail an output reduction in the blast furnace. Within this important equipment on the steel production flow, the burner blocks play a crucial role in the furnace operation since they are responsible for heating the billets/plates so that they reach the temperature required for lamination. Besides compromising the reheating furnace operational safety, worn or damaged burner blocks can cause uneven heating of the steel products, consequently requiring longer residence time causing the loss of productivity and possibly the overheating of some billets/plates that can lead them to melt. On the other hand, poorly heated billets/plates can breakdown during lamination process, causing an emergency stop and the loss of production in addition to materials losses, labor waste and lost profits until the operation is resumed. The performance of Magnesita's reheating furnace burner blocks used to last for a year, when spalling and/or cracks were observed in the pre-shaped refractory castable blocks which necessarily require a furnace stoppage for their replacement. This paper presents the main characteristics and properties of a new refractory castable developed for pre-shaped burner blocks, including raw materials and grain size distribution adjusts, physico-chemical properties and thermo-mechanical behavior, which allowed to significantly improve the burner blocks performance. Tests carried out in 3 different melt shops have shown that the new refractory castable was able to endure severe and unstable reheating furnace operating conditions extending the service life of the refractory burner blocks from 1 year to more than 3 years showing perfect conditions to continue operating for a longer period.