Processes of lining erosion and scull formation effect considerably the blast furnace (BF) campaign duration. Among factors, influencing the processes, impacts are distinguished, stipulated by the kind of smelted product as well as materials used for scull formation. In the BF No. 2 of Kosaya Gora steel-works within the campaign from October 1999 until November 2015, 930,000 t of high-carbon ferromanganese (mainly ФМн78 grade) and 110,000 t of foundry iron were produced. After it stoppage for overhaul, samples of the scull were picked out and studied. It was revealed, that the scull of walls of BF hearth has a laminated structure and consists of crystallization products of metal and slag melts, namely: graphite, iron carbides, manganese carbides, iron, ferromanganese, slag components. At the macro level the scull has a lamellar structure. Since during the last campaign the blast furnace apart from ferromanganese was smelting foundry iron rather long time, in the samples, picked out at the level of iron notch at some distance from the cooler, the scull metallic phase mainly consisted of iron and iron carbide. In the sample picked out at a big distance from the cooler, in the scull metallic phase the following phases were discovered by X-ray structural and Moessbauer methods: ferromanganese; complicated manganese and iron carbides, as well as α-iron. Quantity of slag components in the scull decreases in direction from iron notch level to the hearth that speaks about splitting (still in the BF hearth) slag and metallic components of the heat products. In the scull content different slag components present: silicate (38.3–47.2% SiO2) with high content of К2О + Na2O (до 32.2%), MnO (up to 7.5%) and FeO (up to 33.2%). During the quick cooling of the components on the hearth cooler, different compositions are formed: X-ray amorphous “glassy phase”, olivine composition slags of Ca(Mn,Fe,Mg)SiO4 type, wollastonite, melilite with high amount of iron and manganese. Fine inclusions of titanium nitride are presented in the scull in a small amount, as well as manganese and silicon nitrides and carbonitrides, perofskite CaTiO, the role of which is insignificant in the scull forming.

Results of study of scull and lining composition from the hearth of blast furnace No. 2 of JSC EVRAZ ZSMK after stop for capital overhaul quoted. It was determined, that due to microprobe chemical analysis data, considerable quantity different minerals and metals can be discovered in the scull and in the lining. But chemical analysis of averaged samples and their X-ray structure analysis allows to state, that the scull is formed during crystallization of heat products – cast iron and slag. Therefore the scull base is the following:– metal, in the content of which α-Fe prevails with iron carbides (Fe3C) inclusions, complicated carbides of variable composition (FeхSiyCz), iron and graphite sulfides and phosphides, as a rule, of laminar structure;– graphite in the form of separate phase;– slag components, melilite and anorthite being the base of them (minerals, formed during crystallization of slag of blast furnace heat).At the level of hot metal tap hole and higher the scull and lining are saturated by alkaline metals accompanied by forming leucite, caliofilite, calcilite, zinc (zinc oxide, ganit, willemite in samples), sulphur with forming of sulphides, phosphor (iron phosphides in metal, apatite in slag). Lower the level of tap hole the number of slag inclusions in the scull is not considerable, zinc and alkaline metals were not discovered.In all the samples content of silicon, silicon carbide, carbides, nitrides, titanium carbonitrides in total does not reach level of 5%.

Аннотация. Продолжительность кампании современных доменных печей составляет 15-20 лет. Достигнутая длительность их эксплуатации в значительной мере определяется стойкостью футеровки лещади и горна. С целью изучения процессов, влияющих на скорость ее эрозии, осуществлено исследование состава и структуры гарнисажа на футеровке стен горна и лещади доменной печи № 2 ЕВРАЗ ЗСМК после остановки на капитальный ремонт. Приведены результаты визуального осмотра состояния футеровки нижней части горна и лещади. Представлена макроструктура отобранных проб, показан общий вид штуфных образцов и аншлиф-брикетов. Исследован минеральный состав проб и химический состав их отдельных минеральных фаз. Установлено значительное увеличение плотности проб, отобранных ниже уровня чугунной летки, что, по мнению авторов, обусловлено увеличением содержания металлической фазы в гарнисаже по высоте горна в направлении от уровня фурм к лещади и значительным изменением пористости гарнисажа как по его горизонтальному сечению, так и по высоте горна. Пористость образцов, отобранных ниже уровня чугунной летки, незначительна и находится на уровне 2,73-3,73 %. Содержащиеся в доменных расплавах газы (кислород, азот, водород) приводят к формированию пористой структуры гарнисажа незначительной толщины в верхних горизонтах горна и леточном канале. Установлено, что на лещади наблюдается накопление цинка, а также его сплавов с железом и свинцом. Макроструктура проб имеет достаточно четко выраженную слоистость. Цинк в пробе существует в виде двух минеральных фаз: оксидной (цинкит) и металлической, часто с примесью железа и редкосвинца. Полученные результаты, наряду с результатами ранее выполненных работ по изучению состояния гарнисажа и футеровки горна доменных печей, лягут в основу теоретического анализа механизма формирования гарнисажа и изменения свойств футеровки, влияющих на продолжительность кампании доменных печей.Ключевые слова: доменная печь, футеровка стен горна и лещади, макроструктура, состав и структура проб гарнисажа, содержание металлической фазы в гарнисаже, содержание газов в расплавах, пористость гарнисажа, накопление цинка на лещади.

Analysis of blast furnaces running experience in Japan, Europe and North America shows, that duration of their operating period determines to a great extent by hearth and bottom lining endurance. Study of structure change of scull and hearth walls and bottom lining at different burden compositions and BF heat conditions will enable to elaborate organization and technical solutions for BF efficiency increasing. Study of hearth scull composition at the level of iron notch and lower at PAO NLMK BF No. 6 after 2nd category overhaul stoppage from 26.08.2016 through 29.09.2016. Lump samples of mass from 10 up to 70 kg were taken with careful visual inspection to exclude oxidized and hydrated pieces. Based on visual inspection of samples as well as petrographic, chemical, X-ray structural and microprobe analysis it was determined, that the scull base comprises products formed during crystallization of heat products. They included a metal, in which a magnetic part (α-iron) is prevailed with iron carbide and graphite inclusions, graphite as a separate phase, slag components with a base of melilite at the level of iron notch and silicates (X-ray amorphous) of variable content of СaO–K2O–Na2O–SiO2–Al2O3system. The quantity of metal and graphite in the hearth walls scull increases from iron notch to the bottom and reaches a value >85 % at the level 300 mm lower than iron notch. Content of titanium compounds in oxide form in all the samples as well as nitrides, carbo-nitrides totally does not exceeds 1–2%.

Results of study of lining and scull of the hearth of blast furnace No. 2 of JSC EVEAZ ZSMK presented, done after BF stop for major overhaul. It was determined, that the scull has a zonal structure, due to different conditions of the forming of it during the furnace running and blowing-down. The scull consists of isolations of graphite, metal and slag inclusions having distinctly lamellar structure. Number of slag inclusions in the scull of the hearth walls lower the hot metal tap hole is not big and sharply arises in samples at levels above the tap hole. In metal structure within the scull ferrite (a-Fe) prevails, also there are some lamellar graphite isolations and perlite. Quantity and thickness of metal isolations in the samples increases from the scull periphery to the center of blast furnace (from 20–30% and tens of microns to 70–90% (mass) and 30–50 microns correspondently) and decreases from the lower part of the hearth wall to the upper one. Titanium nitride (osbornite) TiN and titanium oxide (rutile) TiO2, sulfides of calcium, iron, manganese, silicon carbide SiC present in the scull in a small quantity (less 2%). In samples taken higher the hot metal tap hole, in the scull slag isolations there are a considerable amount of alkali metals oxides and sulfides, and phosphide and iron sulfides were exhibited in the metal phase. It speaks about considerable evaporation/sublimation of compositions of potassium, sodium, Sulphur and phosphorus in the blast furnace hearth following by their condensation/crystallization at the cooled lining of hearth walls.