Over recent years, owing to the need to increase productivity, it has been necessary among other things to increase the hot metal temperature in the blast furnace hearth. As a result, refractory lining wear becomes more intense. While publications present a host of comparative tests for hearth refractories and their performance, hardly any information is available in such publications regarding reaction mechanisms and further deterioration of these materials. Based upon comparative laboratory test results using two carbon materials of different concepts, the various reaction mechanisms and enhanced refractory lining deterioration for the blast furnace hearth have been identified. From an understanding of these wear mechanisms acting upon the hearth lining, it has been decided to introduce some practical operating measures, with a view to extending the blast furnace campaign.

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In this work it is presented a methodology applied by Companhia Siderúrgica Nacional (CSN, Brazil) in order to assess its blast furnace 3 carbon refractory hearth lining conditions. The aim of the investigation was the gathering of critical data base for blast furnace refractories life cycle follow up and eventual repair decision taking.The sample drilling locations were chosen around the tap holes and hearth bottom areas. The advancing drilling depths were based on local temperature profiles. The isotherm limit of 500 °C was elected as a control parameter to assess the critical carbon refractory condition. The guidelines for sampling and testing as well as the results obtained through the physical and chemical characterizations of the cored samples are presented. The condition of the refractory lining is discussed under the light of the different known wear mechanisms of blast furnace hearth carbon refractories.

This paper looked into hot metal corrosion behavior for graphite refractory used in blast furnace hearth, consisting of 50% graphite and 50% anthracite, impregnated with TiO 2 , ZrO 2 carrying solutions. The method used for corrosion was the Finger Test, which was conducted in an induction furnace with 30 Â 30 Â 280 mm bar-shaped test specimens, and the hot metal and slag used were taken from the CSN #2 Blast Furnace runner, the test temperature was 1470 8C with a sixty-minute isotherm. After the corrosion test, the specimens were characterized by their dimensional variation, X-ray diffractometry and Scanning Electronic Microscopy (SEM).

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