Study of the scull composition in the blast furnace hearth of Kosaya Gora steel-works, producing ferromanganese with application of schungite (report 1)

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.

Study of composition and structure of NLMK BF No. 6 hearth scull (Report 1)

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%.

Use of Composite SiO2 (62-68)-MgO + CaO (29-39) in Ceramic Protection Mass Injection Machines in the Iron Notch and Liquid Slag Hole in Blast Furnaces

The article describes the use of protection ceramic composed of SiO2 (62-68)-MgO+CaO (29-39) in the frontal region of machines that inject refractory mass to stop pig iron running and liquid slag in blast furnaces. The new protection model (prototype) showed an annual saving of approximately R$ 32,000 compared to the compound previously used CaO-Al2O3-SiO2. It also presented lower toxicity, once it has in its morphology less amount of fiber. These fibers when inhaled cause damage to internal lungs tissues becoming harmful to health. Production rates remained, since in all the new ceramic protection samples that were tested the frontal part was preserved allowing the refractory mass to be injected in proper quantity and pressure for reconstitution of the hole length, which removes iron and slag from blast furnace. Therefore, this enables a larger internal volume in order to produce more. The protection models used were from the company Morganite-Brasil. The material morphology and crystallographic characterization were realized by Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD), respectively.

Annual Analysis of Erosion Situation of Hearth in 1000m3 Blast Furnace

For prolonging the campaign of hearth in a 1000 m3 Blast Furnace, a mathematical model is developed to compute the erosion situation of the hearth. With the model, the position of erosion line is calculated from Sep. 2011 to Apr. 2013. It is found that the dead-man zone of the hearth is eroded, and that upper the iron notch level is covered by slag.