Magnesia Refractories Research Articles

World Production of Steel and Magnesia Refractories: State of the Art and Trends of Development

The state of the art and the trends of development of the world production of steel, nonferrous metallurgy, and the cement industry -- the chief users of magnesia refractory materials -- are considered. A new generation of magnesia refractories developed for oxygen converters, electric furnaces, post-furnace and continuous steel-casting technologies, nonferrous metallurgy, and the cement industry provide conditions for environment-friendly, competitive, and effective applications in various branches of industry.

Current state of steel-melting production and the technology for and raw-materials base of magnesia refractories in Ukraine

Current state of steel-melting production and the technology for and raw-materials base of magnesia refractories in Ukraine

Current state of steel-melting production and the technology for and raw-materials base of magnesia refractories in Ukraine

The state of steel-melting production in Ukraine in 1991–1995 is considered. About 50% of the steel is produced in open-hearth furnaces. The imperfect structure of steel-melting production, the low quality of the refractory materials used, and the unstable operating conditions of steel-melting equipment determine the high specific consumption of magnesia refractories which exceeds that in the leading industrial countries by a factor of 2–3. The volume of out-of-furnace treatment of steel by the LF, AOD, ACEA—CKF, and VKO processes does not exceed 1% of the total yield.

Synthesis of rare-earth chromates in the presence of certain oxides

The effect of Al2O3, SiO2, MgO, 3Al2O3·2SiO2 on the synthesis of LnCrO3 (where Ln=Nd, Sm, Yb) at high temperatures is considered. Chromium oxide in all the compositions Ln2O3−Cr2O3−Al2O3 (SiO2, MgO, 3Al2O3·2SiO2) reacts mostly with Ln2O3, i.e., silicon oxide alumina, magnesium oxide, and mullite do not interfere with formation of rare-earth chromates. This makes it possible to predict high durability for LnCrO3 electric heaters operating in contact with corundum, dinas, aluminosilicate, and periclase refractories in laboratory and industrial furnaces.

Magnesia refractories from Slovakian periclase

The Nikitovsk Dolomite Plant has produced an experimental industrial batch of magnesia articles based on Slovakian periclase. Results have shown that the articles made of Slovakian periclase correspond to the requirements of GOST 10888-76 for periclase-chromite refractories and GOST 4689-74 for periclase refractories.

Structure of the production and use of magnesia refractories

The expediency of changing the structure of the production and use of magnesia refractories and modifying the refractory industry with orientation on refractories of a new generation is indicated.

Periclase refractories from imported powders

Ten charges with different compositions were obtained from periclase refractories and used to investigate the parameters of periclase articles. The properties of articles of industrial size prepared from imported powders did not differ from those prepared from Satkinsky periclase.

Production of refractories from Chinese periclase

Periclase refractories from Chinese periclase are produced by the Chasovo-Yarsky Refractory Plant. The refractories have been tested with positive results at a number of metallurgical works, and specifications have been established for articles.

Increasing the strength of green magnesia refractories by using combined binders

The effect of the pH of the lignosulfonate (LST) medium on the strength of the green and the qualitative parameters of magnesia parts is established. LST with a weak alkaline medium are recommended for periclase parts, and LST with a weak acid medium are recommended for chrome-containing parts. The effect of some modifying additions to LST is investigated with testing of it in batch production. Combined binders (mixtures of LST with sodium and ammonium bases) are shown to have a positive effect on the properties of the green and ready parts.

Relation between Corrosion Rate of Magnesia Refractories by Molten Slag and Penetration Rate of Slag into Refractories

Corrosion tests on magnesia refractories in molten CaO-SiO2-CaF2-Al2O3 slags have been conducted at 1873K in a high frequency induction furnace. By combining the corrosion rate with the microstructures of tested specimens and the theoretical analysis of the slag penetration, a penetration resistance coefficient of refractory, Rp was introduced as an index for evaluating the corrosion behavior of the refractory. Using this index the penetration behavior of the slag into the refractory was evaluated and the penetration rate of slag into the refractory was related to the corrosion rate, which suggests the possibility of developing a refractory resistant to both spalling and corrosion.

A combined basic lining of steel teeming ladles of units for composite treatment of steel

The use in steel-teeming ladles of a combined lining of periclase-chromite parts in the zone of the metal and periclase parts in the slag belt provided a lining life of up to 14–18 heats and a minimum quantity of nonmetallic inclusions and metallic chromium in teeming of cord steel. During service zone formation accompanied by change in texture, structure, and phase composition of the refractory occurs. Wear of the periclase-chromite parts in the zone of the metal is caused by mechanical breaking away of the dense working layer from the less dense one at boundary with the transition or least changed zone. Wear of the periclase refractories occurs as the result of chemical interaction with the slag with formation of lowmelting compounds with subsequent passage of them into the slag.

Magnesia refractories from Korean periclase with magnesium sulfate bond

Investigations showed that by using Korean periclase powders, and magnesium sulfate as the bond, it is possible to obtain periclase, periclase-chromite and chromite-periclase refractories whose properties meet the requirements of the existing standards of the USSR. The main parameters of the technology for making such articles were worked out.

Magnesia refractories for ladles with ladle treatment of steel (Discussion)

Laboratory and production investigations with production and testing of experimental lots of magnesia-type ladle parts have shown the promise of use in the slag belt of ladles with ladle treatment of the steel of chromite-periclase-forsterite and periclase-spinellide (with synthesized magnesioalumina spinel) parts.

Magnesium Aluminate Hydrate as a Chemical Bond of Magnesia Refractories—Part III: Thermomechanical Properties

The present paper is the third of a series of papers on a new chemical bond on magnesia refractories. Results of the compressive creep testing of the chemically bonded samples at elevated temperature up to 1500°C, prepared from sea-water magnesia (Japan) and natural magnesite (Salem, India), cured at 110°C for 24 hrs, have been presented in this part. Samples prepared with the bond (0.25 wt%) evaluated by creep experiments with a compressive load of 3 kg.cm−2 up to 1500°C for 30 hrs showed a maximum strain rate of 0.2% per hour without failure. This makes it an acceptable chemical bond of the future for magnesia refractories. The deformation mechanism suggested a diffusion controlled Nabarro-Herring creep, while a grain-boundary diffusion process might also be a possibility.

Testing reagents IUM-465 and dichlorocarbonic acids in magnesite flotation

The existing raw-material base for magnesite minerals does meet the requirements of the iron and steel industry for high-grade magnesia refractories without preliminary benefication. The Siberian Electrosteel Factory in 1988 investigated the flotation of magnesites from the Satkinsk deposits using the IUM-465 reagent and dichlorocarbonic acid

Use in the lining of electric furnaces of increased quality magnesia refractories

On examine la composition, la granularite et les proprietes physicomecaniques de briques refractaires de magnesie fondues ou frittees et utilisees dans les fours electriques

Magnesium Aluminate Hydrate as a Chemical Bond of Magnesia Refractories—Part II: Bond Formation

Magnesium aluminate hydrate (MAH) which is synthesized as a gelly like material, retains its combined water over a wide range of temperature and undergoes a series of changes with the rise of temperature. A strong bond is maintained between periclase grains and MAH which does not weaken during the gradual decomposition of the latter. By analogy with the mechanism postulated in the phosphate bond, formation of contacts between grains and the bond during hardening of the binder may involve hydrogen bonds. The strength in the so-called “weak zone” is maintained by generation of anion and cation vacancies in the binder, producing a reactive non-stoichiometric spinel, which interacts in the solid state with periclase grains.

Laboratory-scale technological studies on periclase refractories

Laboratory-scale technological studies were carried out for developing the technology of periclase products based on different magnesite powders. Our studies showed the possibility of producing periclase refractories meeting the property specifications of GOST 4689-74 from certain imported powders.

Use of large magnesiospinellide concrete parts soaking pit hearths

A method of production of large magnesiospinellide concrete parts for soaking pit hearths based on slag- and iron-impregnated scrap of magnesia refractories has been introduced in Khristoforovka Refractory Block and Concrete Plant.

Obtaining magnesia and periclase refractories from bischofite from the volgograd deposits

Experimental work was carried out to obtain from bromine liquors of bischofite of the Volgograd deposits magnesium oxide, using low capacity industrial equipment for chemical purification of magnesite, including a recuperator, a tank-collector, a spray-reactor, a cyclone, an absorption column, spray traps, a vacuum pump, and a filter press.