IE54202B1 - Method of manufacturing refractory magnesia-chromium product - Google Patents
Method of manufacturing refractory magnesia-chromium productInfo
- Publication number
- IE54202B1 IE54202B1 IE678/83A IE67883A IE54202B1 IE 54202 B1 IE54202 B1 IE 54202B1 IE 678/83 A IE678/83 A IE 678/83A IE 67883 A IE67883 A IE 67883A IE 54202 B1 IE54202 B1 IE 54202B1
- Authority
- IE
- Ireland
- Prior art keywords
- weight
- mixture
- magnesia
- content
- chromium
- Prior art date
Links
- 239000011651 chromium Substances 0.000 title claims abstract description 73
- 229910052804 chromium Inorganic materials 0.000 title claims abstract description 70
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 18
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims abstract description 105
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims abstract description 58
- 239000000395 magnesium oxide Substances 0.000 claims abstract description 53
- 239000000463 material Substances 0.000 claims abstract description 48
- 239000000203 mixture Substances 0.000 claims abstract description 40
- 239000011449 brick Substances 0.000 claims abstract description 39
- 238000005245 sintering Methods 0.000 claims abstract description 10
- 238000002844 melting Methods 0.000 claims abstract description 5
- 230000008018 melting Effects 0.000 claims abstract description 5
- 238000007493 shaping process Methods 0.000 claims abstract description 4
- 238000000034 method Methods 0.000 claims description 18
- 229910052742 iron Inorganic materials 0.000 claims description 9
- 229910052796 boron Inorganic materials 0.000 claims description 6
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 5
- 229910018072 Al 2 O 3 Inorganic materials 0.000 claims 1
- 235000012245 magnesium oxide Nutrition 0.000 abstract description 48
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 abstract description 34
- 229910052681 coesite Inorganic materials 0.000 abstract description 25
- 229910052906 cristobalite Inorganic materials 0.000 abstract description 25
- 229910052682 stishovite Inorganic materials 0.000 abstract description 25
- 229910052905 tridymite Inorganic materials 0.000 abstract description 25
- 239000003518 caustics Substances 0.000 abstract description 10
- 239000000377 silicon dioxide Substances 0.000 abstract description 9
- 235000012239 silicon dioxide Nutrition 0.000 abstract description 9
- 229910018404 Al2 O3 Inorganic materials 0.000 abstract 2
- 229910019830 Cr2 O3 Inorganic materials 0.000 abstract 2
- 229910017344 Fe2 O3 Inorganic materials 0.000 abstract 1
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 16
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 description 9
- 239000000047 product Substances 0.000 description 9
- QDOXWKRWXJOMAK-UHFFFAOYSA-N chromium(III) oxide Inorganic materials O=[Cr]O[Cr]=O QDOXWKRWXJOMAK-UHFFFAOYSA-N 0.000 description 7
- 239000012141 concentrate Substances 0.000 description 7
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 7
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 5
- 239000008187 granular material Substances 0.000 description 5
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 5
- 239000011159 matrix material Substances 0.000 description 5
- 239000001095 magnesium carbonate Substances 0.000 description 4
- ZLNQQNXFFQJAID-UHFFFAOYSA-L magnesium carbonate Chemical compound [Mg+2].[O-]C([O-])=O ZLNQQNXFFQJAID-UHFFFAOYSA-L 0.000 description 4
- 235000014380 magnesium carbonate Nutrition 0.000 description 4
- 229910000021 magnesium carbonate Inorganic materials 0.000 description 4
- 229910052943 magnesium sulfate Inorganic materials 0.000 description 4
- 235000019341 magnesium sulphate Nutrition 0.000 description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 238000010304 firing Methods 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- 239000007858 starting material Substances 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- TWRXJAOTZQYOKJ-UHFFFAOYSA-L Magnesium chloride Chemical compound [Mg+2].[Cl-].[Cl-] TWRXJAOTZQYOKJ-UHFFFAOYSA-L 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000011451 fired brick Substances 0.000 description 2
- 239000003500 flue dust Substances 0.000 description 2
- 239000013067 intermediate product Substances 0.000 description 2
- 239000011819 refractory material Substances 0.000 description 2
- 238000011282 treatment Methods 0.000 description 2
- -1 MgO compound Chemical class 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000002939 deleterious effect Effects 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229910052928 kieserite Inorganic materials 0.000 description 1
- 229910001629 magnesium chloride Inorganic materials 0.000 description 1
- 238000010309 melting process Methods 0.000 description 1
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 1
- 229910052753 mercury Inorganic materials 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 229910052596 spinel Inorganic materials 0.000 description 1
- 239000011029 spinel Substances 0.000 description 1
- 229910052566 spinel group Inorganic materials 0.000 description 1
- 239000004575 stone Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
- C04B35/03—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on magnesium oxide, calcium oxide or oxide mixtures derived from dolomite
- C04B35/04—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on magnesium oxide, calcium oxide or oxide mixtures derived from dolomite based on magnesium oxide
- C04B35/043—Refractories from grain sized mixtures
- C04B35/047—Refractories from grain sized mixtures containing chromium oxide or chrome ore
- C04B35/0476—Refractories from grain sized mixtures containing chromium oxide or chrome ore obtained from prereacted sintered grains ("simultaneous sinter")
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Ceramic Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Organic Chemistry (AREA)
- Compositions Of Oxide Ceramics (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
1. Method of manufacturing magnesia-chromium refractory products by preparing a mixture of a caustically burned magnesia having a grain size of less than 0.2 mm, preferably at most 0.12 mm, and of fine grained chromium ore having a FeO content of 20 to 28 % by weight , in a ratio producing in the mixture a Cr2 O3 content of 10 to 30 % by weight, preferably 15 to 25 % by weight, and a Cr2 O3 /Al2 O3 weight ratio of more than 2.5 preferably more than 3, shaping the mixture into briquettes or shaped bodies and sintering the same at temperatures of at least 2 0008C, preferably at least 2 1008C, but without melting down, and further treating the resultant magnesia-chromium sinter material to obtain burned bricks by burning at temperatures of about 1 8008C or above as well as unburned bricks or refractory masses, characterized in that the caustic magnesia having a weight content of more than 97 % MgO, at most 0.2 % SiO2 , at most 0.7 % Fe2 O3 + Al2 , preferably at most 0.3 % Fe2 03 + Al2 O3 , at most 2 % CaO, and at most 0.06 % B2 O3 and the chromium ore having a grain size up to 1.5 mm and a weight content of at most 1.5 % SiO2 , preferably at most 1.0 % SiO2 , and at most 0.2 % CaO are used in such a ratio producing in the mixture a weight content of at most 1.1 % CaO and at most 0.7 % SiO2 , the sum of the weight content of CaO + SiO2 , however, not exceeding 1.3 %.
Description
Description
The present invention relates to a method of manufacturing a refractory magnesia-chromium product by preparing a mixture of caustically burned magnesia having a grain size of less than 0.2 mm, preferably no more than 0.12 mm, and of finely granulated chromium ore having a weight content of 20% to 28% FeO, the cayti cally burned magnesia and the chromium ore being mixed in a ratio producing in the mixture a weight content of 10% to 30%, preferably 15-25%, Cr2°3* and Cr2°37A12°3 ratio of more than 2.5, preferably more than 3, shaping the mixture into shaped bodies, such as briquettes, and sintering the same without melting at a minimum temperature of 2000°C, preferably at least 2100°C, but without melting down and further treating the resultant sintered magnesia-chromium sinter material at temperatures of at least about 1800°C or above to obtain burned bricks,and unburned bricks or refractory products.
Several methods have been proposed for manufacturing pre20 reacted magnesia-chromium sintered materials and of refractories made therefrom by simultaneously sintering a material producing magnesia and chromium ore at a high ί
4 2 0 2
-3temperature, the chromium ore being dissolved during the sintering process in the periclase matrix by a reaction proceeding essentially in the solid state and being contained therein after cooling in the form of newly formed spinel precipitate so that any residue of the original chromium ore grains are present at a maximum volume of no more than 10%, preferably no more than 5%.
In the method described in Austrian patent No. AT-B-301,433, coarse granules of chromium ore having a minor component (at most 20%, by weight) of a grain size of less than 0.1mm and a major component (at least 40%, by weight) of a grain size exceeding 1 mm, and magnesite ore of a grain size of less than 0.1 mm as the material producing the magnesia are used, the maximum acceptable limits of the SiOg and CaO contents being set forth. It is necessary in this method to use coarse granules of chromium ore to obtain a dense sintered material. When finely granulated chromium ore and magnesite ore are used, the resultant sintered grains show unfavorable porosity values. However, it is not easy to obtain coarse granules of chromium ores of the required purity since their natural occurence is limited. It is easier to obtain socalled chromium ore concentrates, i.e. chromium ores whose Si02 and CaO contents have been reduced by suitable treatments which, however, produce concentrates in finely granulated form.
-4According to the method of Austrian patent No. AT-B-290,374, a sinter material containing, by weight, no more than 2.5% SiO2 and no more than 4% CaO, with a molar ratio Ca0/Si02 of 0.6 to 2.5, is produced from such a chromium ore concentrate 20-80%, by weight, of which has a grain size below 0.12 mm and a finely granulated magnesia matrix having a MgO-content, based on the burned state, of less than 95%, by weight, of MgO, as well as, optionally, magnesite flue dust, at temperatures of at least 1750°C, for example
2000°C or more. However, the bricks made from this sinter material can be fired only at relatively low temperatures of, for example, 1560°C to 1580°C, which limits their use to correspondingly low operating temperatures and does not produce refractory properties satisfying the highest requirements.
The iron content is also a quality characteristic of the chromium ore, this value being determined by the fact that the entire iron content is present in the form of FeO in the chromium ore. Chromium ore types poor in FeO-content, for example less than 15% by weight, are considered as higher-quality ores but the iron-rich concentrates with an FeO-content of, for example, 18-27%, by weight, are obtainable at lower costs.
4 2 0 2
-5In accordance with the method of Austrian patent No. AT-B336,478, a sinter material having a weight content of 11-20% Fe203 is obtained from such an iron-rich chromium ore concentrate of an average grain size of 0.1-1.5 mm and a caustic magnesia, which may be a magnesite flue dust. The bricks shaped from this sinter material are fired at a temperature of about 1800°C, just below the softening temperature sinter material, and they show a high pyro-plasticity and good resistance to heat, which makes them suitable for operating temperatures above 1600°C but below 1800°C because they are subject to continuous wear without chipping in this temperature range. These bricks are not suitable for higher operating temperatures or for uses where they are subjected to continuous heat in this range.
German Patent DE-A-1,571,638 describes the direct production of finished refractory bricks from a granulated mixture of magnesia and chromium ore, the bricks shaped from this mixture being sintered at very high temperatures ranging between 1930° and 2095°C. The possibility of a two-stage process is also considered, whereby an intermediate product sintered at a high temperature is first produced from the mixture, and is then processed into bricks after crushing and classification. The data on the grain size only refer to the sum of grain size distribution of the mixture during the direct stone production process, but the grain size of the individual components cannot be derived therefrom. The magnesia used as a starting material for instance contains, by weight, 0.6% of Si02> but such a high proportion of this
-6impurity is unfavourable.
According to British Patent GB-A-2,002,737 a compact refractory material is produced from caustic burning of a mixture of MgO or a compound producing MgO during sintering and chromium ore or by caustically burning the MgO or
MgO compound first, then forming a mixture with the chromium ore and subsequently shaping and sintering the mixture. For this the mixture is ground extremely fine with an average particle size of below 0.05 mm. A chromium ore with a low iron content is used for example, which represents an expensive starting material, as mentioned above.
It is the object of this invention to produce a magnesiachromium sinter material from a finely granulated, iron-rich chromium ore to obtain refractory products which satisfy very high refractory requirements.
We have found that this object can be accomplished with caustically burned magnesia of high MgO-content and a low content of impurities if the SiOg-content of the chromium ore and the CaO- and SiOg-contents of the sinter material are subject to certain limiting conditions, and special attention should be paid to a low boron content of the magnesia. In the aforementioned publications the boron content is ignored.
-7Therefore, according to the invention, the mixture in the first hereinabove described manufacturing method is prepared from caustically burned magnesia having a weight content of more than 97% MgO, no more than 0.2% SiOg and no more than 0.7%, preferably no more than 0.3%, of FegOg+AlgOg, a weight content of no more than 2% of CaO and a weight content of no more than 0.06% of BgOg an8 chromium ore having a grain size not exceeding 1.5 mm and a weight content of no more than 1.5%, preferably no more than 1%, of SiOg, and a weight content of no more than 0.2% of CaO used at a ratio giving the mixture a weight content of no more than 1.1% CaO and no more than 0.7% Si02, the sum of the weight content of CaO+SiOg not exceeding 1.3%,
The use of magnesia matrix in the form of the defined composition containing only minor SiOg, FegOg anc* AlgOg impurities produces a substantial increase in the refractory quality of the sinter material and the products made therefrom. The high FeO-content of the chromium ore component of the mixture has no deleterious effect on the heat resistance if its SiOg content does not exceed 1.5%, preferably 1%, by weight, and the mixture of caustically burned magnesia and chromium ore and the resultant sinter material has the indicated low CaO- and SiOg-content values and CrgOg/AlgOg weight ratio of above 2.5, but preferably 3. According to a preferred embodiment of the invention, the magnesia-chromium mixture or the sinter material has a CrgOg/FegOg weight ratio of 1.6 to 3.
-8The present invention makes it possible to use chromium ores having a high weight content of 20-28% FeO. The chromium ore is comminuted to a grain size of no more than 1.5 mm to prepare it for treatment, primarily to reduce its
SiOg-content. It is of advantage in the method of the present invention if the grain size of at least 60%, by weight, of the chromium ore is less than 0.7 mm.
In known methods for the production of sintered magnesiachromium materials, chromium ores which are relatively rich in iron have been used, and for this reason the Si02 content of the magnesia component has only a minor effect on the properties of the final product. In the method according to the invention the low SiO2 content of no more than 0.2% by weight in the magnesia starting material is adhered to, so that the SiO2 content of the sintered material is essentially only determined by the amount of chromium ore used. This means, the higher the Cr203 content of the end product, the more Si02 it will contain. If there is a higher Cr203 content, the product can, as has been found by the inventor, withstand a higher Si02 content without resultant disadvantages.
The boron content has so far only been considered detrimental in sintered magnesia and in magnesia products. In magnesiachromium products however, the B203 content has been ignored, since, because of the higher CaO and Si02 content, the boron content had little effect on the refractory properties.
-9Only the inventor recognized the fact that the low CaO and SiO2 content of the products according to the invention can only be an effective advantage, if the boron content of the magnesia is limited to a maximum of 0.06% BgOg by weight.
The caustically burned magnesia used in the method of this invention may be prepared synthetically, for example by the thermal decomposition of a purified slurry of magnesium chloride. However, it may also be obtained from lake water. While the synthetically produced magnesia will have a BgO^-content of only a few thousandths of 1%, by weight, the magnesia obtained from lake water contains higher amounts of B203>whic^ may unfavorably influence the refractory qualities of the product. Good types of lake water magnesia have a weight content of about 0.03-0.05%
BgOg and may be used for the method of the invention. Magnesia containing more than 0.06%, by weight, Bg03 is generally not desirable for this use.
A conventional binder, for example a magnesium sulfate solution which may be prepared from kieserite or Epson salt, is preferably added when the caustically burned magnesia and chromium ore mixture is prepared. The mixture is then shaped in a press, for example a roller press, to form briquettes, the applied pressures being preferably as high as can be achieved with such presses, for example pressures o of the order of magnitude of 14 to 20 N/mm . However, any type of compacting the mixture may be used. The shaped
54302
-10bodies or briquettes are dried and subsequently fired for sintering at a temperature of at least 2000°C, preferably at least 2100°C, which is obtained by the use of gaseous oxygen. The sintering furnace is preferably a shaft furnace, preferably one with at least two superposed firing zones, the gaseous oxygen being delivered to the lower zone. However, it is also possible to use a rotary kiln as long as the required high temperatures can be produced therein.
In the sinter, the chromium ore is dissolved in the periclase matrix in a process proceeding pratically in the solid state since a melting of the material is neither required nor desired, except for a minor amount of a molten phase derived from any impurities in the type of chromium ore used. When the sinter material is cooled, the chromium ore components are pratically completely precipitated in the magnesia matrix as newly formed spinels. The structure of the sinter material approaches that of a molten granular material without, however, requiring an expensive melting process for its manufacture. Residues of the original chromium ore granules, if present at all, should be limited to a maximum volume 10%, preferably no more than 5%.
The sinter material, which is an intermediate product of the method of the present invention, has a low open grain porosity of an average of about 7%, by volume, measured in a grain size of 3 to 4 mm, the grain volume including all
-npores being determined by the mercury reception in a vacuum pycnometer with an input pressure (initial pressure) of about 265 mbar according to DIN (German Industry Norm) 51 065,
Part 2, and the solid grain volume including the closed pores being determined by an air comparison pycnometer. This measuring method is also used for the values of the open sinter grain porosity in the examples and comparison tests.
The bricks produced by the method of this invention may be fired without damaging them at temperatures up to
2000°C and higher, and they exhibit a very high resistance to heat. The values of the resistance to pressure under heat, measured at 1600°C, lie in the range of 15 N/mm2 and higher.
The invention will be elucidated further in the following operating examples and comparison tests.
Example 1
Fifty-seven weight percent of caustic magnesia A having a grain size up to 0.1 mm and 43%, by weight, chromium ore concentrate (chromium ore A) having a grain size up to 1.5 mm of which 90%, by weight, had a grain size of less than
0.7 mm were mixed, with the addition of a magnesium sulfate solution. The mixture was then pressed to form briquettes, the briquettes were dried and then fired in a shaft furnace at a temperature of 2100°C to produce magnesia-chromium
5420 3
-12sinter material A. The composition of the raw materials and the resultant sinter material was as follows, all percentages being by weight:
Caustic Magnesia A Chromium Ore A Sinter Material Si02 0.01% 0.91% 0.45% FeO - 25.93 -Fe2°3 0.02 - 12.20 ai2o3 0.02 14.90 6.50 10 Cr203 - 47.03 20.10 CaO 1.35 0.07 0.77 MgO 98.60 10.90 59.90
Sinter material A had the Ca0+Si02 Ca0/Si02 Cr203/Fe203 Coarse grain density Sinter grain porosity, following properties:
1.22% by weight 1,71
1.65
3.60 g/cm3 open 6.1%/volume
A brick mixture was prepared from this sinter material A according to the following recipe, all percentages being by weight:
3.0 - 5.0 mm 20% 1.0 - 3.0 mm 45% 0.1 - 1.0 mm 10% up to 0.1 mm 25%
-1354202
This mixture was mixed with 3.7%, by weight, of magnesium sulfate solution, pressed to bricks under a pressure of 110 N/mm , the bricks were dried and then fired for four hours (not counting the heating up and cooling period) at 1800°C. Resultant bricks A had the following properties:
Coarse brick density 3.20 g/cm
Brick porosity, open 17.3%, by volume
Resistance to pressure at room temp. 55.4 N/mm
Resistance to pressure at 1600°C 23.9 N/mm2
For purposes of comparison, a sinter material B was prepared in the identical manner but with the use of a chromium ore concentrate (chromium ore B) poorer in iron and of a grain size up to 1.5 mm, 80%, by weight, being smaller than 0.7 mm. Caustic magnesia A was again used as the magnesia component. Chromium ore B and the resultant magnesia-chromium sinter material B had the following composition, all percentages being by weight:
Chromium ore B Sinter material B
Si02 0.36% 0.30% FeO 15.00% -Fe2°3 - 5.75% AlgOg 11.70% 4.17%Cr2°3 57.70% 20.47% CaO 0.15% 0.83% MgO 14.90% 68.40%
-1434202
Fired bricks 8 were prepared from this sinter material B under the identical conditions as hereinabove described, producing the following properties:
Coarse grain density
Sinter grain porosity, open
Coarse brick density
Brick porosity, open
Resistance to pressure at room temp
Resistance to pressure at 1600°C
3.61 g/cm3 6.1%, by vol. 3.20 g/cm3 17.5%, by vol. 45.5 N/mm2 23.3 N/mm2
The comparison shows that bricks A prepared in accordance with the invention have properties generally equivalent to those of comparison bricks B prepared from the more expensive chromium ore B, even slightly surpassing them with respect to their resistance to pressure.
Example 2
Sinter materials and bricks fired from such materials were prepared in the same manner as in Example 1 from caustic magnesia A and chromium ores with different SiOg contents. Sinter material C and resultant bricks C were made from chromium ore C which satisfies the conditions of the present invention. Sinter material D and comparison bricks D were prepared from chromium ore D having a larger SiOg content. The chromium ores and resultant sinter materials had the following compositions, all percentages being by weight:
Chromium ore C Sinter material C Chromium ore 0 Sinter material D Si02 0.41% 0.30% 1.52% 0.66% FeO 25.51% - 23.63% - Fe2O3 - 12.07% - 11.90% Al2°3 15.77% 6.33% 14.22% 6.63%Cr2°3 46.89% 19.60% 46.99% 19.95% CaO 0.11% 0.73% 0.06% 0.74% MgO 10.21% 60.90% 14.40% 60.10%
Sinter materials and bricks C and D had the following properties, all 10 percentages being by weight:
Sinter C Sinter D Ca0+Si02 1.03% 1.40% Cao/Si02 2.43 1.12 Cr203/Fe203 1.62 1.68 Coarse grain density 3.62 g/cm3 3.66 g/cm3 Sinter grain porosity, open (by vol .) 7.6% 7.1% Bricks C Bricks D Coarse brick density 3.18 g/cm3 3.19 g/cm3 Brick porosity, open (by vol.) 18.4% 18.1% Resistance to pressure (room temp., 59.0 N/mm2 60.8 N/mm2 Resistance to pressure (1600°C) 20.9 N/mm2 14.4 N/mm2 It was shown that the comparative quality D with a CaO+SiOg-content above 1.3%, by weight, indicated a : 30% lower resistance to heat of tl
fired bricks than that of quality C obtained according to the invention.
-16Example 3
Sinter material and resultant bricks C produced in accordance with the present invention in the manner of Example 2 were compared to sinter material and resultant bricks E produced with caustic magnesia E containing an amount of Fe203ln excess that required by this
invention. Chromium ore E had a grain size up to 1.5mm, of which 80%, by weight, had a grain size smaller than 0.7 mm, to satisfy the conditions of the invention. Caustic 10 magnesia E and chromium ore E were mixed in a weight ratio of 62:38, with the addition of magnesium sulfate solution as a binder. The mixture was shaped into briquettes, dried and fired in a shaft furnace in the presence of gaseous oxygen at a temperature of about 2100°C to obtain sinter 15 material E :, the indicated substances having the following compositions, all percentages being by weight: Caustic Chromium Sinter Magnesia E Ore E Material E Si02 0.19% 1.32% 0.68% 20 FeO - 23.79 -Fe2°3 3.22 - 13.09 ai2o3 0.43 14.23 6.36 ^Γ2θ3 - 47.15 20.27 CaO 1.05 0.14 0.66 25 MgO 95.11 13.37 58.94 CaO+SiO 2 1.34
1.54
Cr2O3/Fe2O3
-1754202
Bricks C and E, respectively, were produced in the manner described in Example 1 from sinter material C of the invention (Example 2) and comparison sinter material E but
portions of these bricks were fired at different 5 temperatures. The resistance to pressure (DF) of these bricks at 1600°C was measured in the following manner in N/mm2: Brick firing temperature 1700°C 1800°C 1900°C 2000°C Bricks C DF at 1600°C N/mm2 10.4 20.9 26.4 33.8 10 Bricks E DF at 1600°C N/mm2 4.8 10.5 * * *could not be measured because it was not possible to
produce the bricks (completely deformed and fissured)
It can be seen that bricks may be readily fired from sinter material C prepared according to the invention even at very high temperatures, i.e. 2000°C. However, with sinter material E outside the scope of this invention, the highest firing temperature is about 1800°C. Furthermore, these bricks show a considerably lower resistance to heat than corresponding bricks C, prepared according to the invention.
Claims (11)
1. A method of manufacturing a refractory magnesiachromium product by preparing a mixture of caustically burned magnesia having a grain size of less than 0.2 mm 5 and of fine grained chromium ore having a weight content of 20% to 28% FeO, the mixture having a weight content of 10% to 30% Cr 2 O 3 and a Cr 2 0 3 /Al 2 0 3 weight ratio of more than 2.5, shaping the mixture into shaped bodies, sintering the same without melting at a minimum temperature of 2000°C, 10 and further treating the resultant sintered magnesia-chromium material to obtain burned bricks by burning at temperatures of at least about 1800°C as well as unburned bricks or refractory masses,, wherein the improvement comprises preparing the mixture from caustically burned magnesia 15 having a weight content of more than 97% MgO, no more than 0.2% Si0 2 , no more than 0.06% B 2 O 3 , no more than 2% CaO, cind no more than 0.7% Fe 2 O 3 +A1 2 O 3 and a chromium ore having a grain size not exceeding 1.5 mm and a weight content of no more than 1.5% SiO 2 and no more than 0.2% CaO, 20 the mixture having a weight content of no more than 1.1 % CaO and no more than 0.7% SiO 2 , the sum of the weight content of CaO + SiO 2 not exceeding 1.3%.
2. The manufacturing method of claim 1, wherein the caustically burned magnesia has a grain size of no more 25 than 0.12 mm. -193. The manufacturing method of claim 1, wherein the weight content of Fe 2°
3 +A1 2®3 in the caustically burned magnesia is no more than 0.3%.
4. The manufacturing method of claim 1, wherein the 5. Cr 2°3 wei 9 ht content in the mixture is between 15% and 25%.
5. The manufacturing method of claim 1, wherein the Cr 2 O 3 /Al 2 O 3 weight ratio in the mixture is more than 3.
6. The manufacturing method of claim 1, wherein the SiO 2 weight content in the chromium ore is no more than 1%. 0
7. The manufacturing method of claim 1, wherein the minimum sintering temperature is 2100°C.
8. The manufacturing method of claim 1, wherein the grain size of at least 60%, by weight, of the chromium ore is less than 0.7 mm. 1g
9. The manufacturing method of claim 1, wherein the mixture has a CrgOg/FegOg weight ratio of 1.6 to 3.
10. A method substantially as hereinbefore described with reference to the Examples.
11. A refractory magnesia-chromium product whenever 20 manufactured according to a method as claimed in any of claims 1 to 10.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT0141082A AT373229B (en) | 1982-04-08 | 1982-04-08 | METHOD FOR PRODUCING A FIREPROOF MAGNESIACHROME SINTER MATERIAL |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| IE830678L IE830678L (en) | 1983-10-08 |
| IE54202B1 true IE54202B1 (en) | 1989-07-19 |
Family
ID=3513283
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| IE678/83A IE54202B1 (en) | 1982-04-08 | 1983-03-28 | Method of manufacturing refractory magnesia-chromium product |
Country Status (14)
| Country | Link |
|---|---|
| EP (1) | EP0091704B1 (en) |
| JP (1) | JPS58185476A (en) |
| AT (1) | AT373229B (en) |
| BR (1) | BR8301745A (en) |
| CA (1) | CA1197267A (en) |
| DD (1) | DD209614A5 (en) |
| DE (1) | DE3364146D1 (en) |
| ES (1) | ES8405749A1 (en) |
| GR (1) | GR78156B (en) |
| IE (1) | IE54202B1 (en) |
| IL (1) | IL68226A (en) |
| MX (1) | MX156507A (en) |
| TR (1) | TR21803A (en) |
| YU (1) | YU42620B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3527789C3 (en) * | 1985-08-02 | 1994-02-24 | Refratechnik Gmbh | Coarse ceramic molded body and its use |
| JPS63110929U (en) * | 1987-01-06 | 1988-07-16 |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1571638B2 (en) * | 1966-12-24 | 1972-01-05 | International Minerals and Chemical Corp., Skokie, 111. (V.StA.) | METHOD OF MANUFACTURING A FIRE-RESISTANT BODY FROM A GRANULATED MIXTURE OF CHROME SPINEL AND PERICLAS |
| AT290374B (en) * | 1969-04-03 | 1971-05-25 | Oesterr Amerikan Magnesit | Process for the production of refractory chromium and chromium magnesite bricks |
| DE2015566C3 (en) * | 1969-05-15 | 1975-07-24 | General Refractories Co., Philadelphia, Pa. (V.St.A.) | Process for the production of directly bonded, refractory moldings |
| AT336478B (en) * | 1972-09-29 | 1977-05-10 | Veitscher Magnesitwerke Ag | METHOD OF MANUFACTURING FIRED REFRACTORY BRICKS |
| AT353154B (en) * | 1973-10-03 | 1979-10-25 | Pickford Holland & Company Lim | MATERIAL FOR THE MANUFACTURE OF REFRACTORY STONES AND THE LIKE |
| HU176631B (en) * | 1977-06-10 | 1981-03-28 | Veszpremi Vegyipari Egyetem | Process for preparing compact simultaneous sinters of direct bond |
-
1982
- 1982-04-08 AT AT0141082A patent/AT373229B/en not_active IP Right Cessation
-
1983
- 1983-03-24 IL IL68226A patent/IL68226A/en unknown
- 1983-03-25 EP EP83200420A patent/EP0091704B1/en not_active Expired
- 1983-03-25 DE DE8383200420T patent/DE3364146D1/en not_active Expired
- 1983-03-28 IE IE678/83A patent/IE54202B1/en unknown
- 1983-03-30 CA CA000424891A patent/CA1197267A/en not_active Expired
- 1983-04-04 GR GR70982A patent/GR78156B/el unknown
- 1983-04-06 YU YU808/83A patent/YU42620B/en unknown
- 1983-04-06 BR BR8301745A patent/BR8301745A/en not_active IP Right Cessation
- 1983-04-06 TR TR21803A patent/TR21803A/en unknown
- 1983-04-06 DD DD83249611A patent/DD209614A5/en not_active IP Right Cessation
- 1983-04-07 JP JP58061512A patent/JPS58185476A/en active Granted
- 1983-04-07 ES ES521297A patent/ES8405749A1/en not_active Expired
- 1983-04-08 MX MX196873A patent/MX156507A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| ATA141082A (en) | 1983-05-15 |
| YU42620B (en) | 1988-10-31 |
| DE3364146D1 (en) | 1986-07-24 |
| YU80883A (en) | 1986-02-28 |
| ES521297A0 (en) | 1984-06-16 |
| TR21803A (en) | 1985-07-18 |
| DD209614A5 (en) | 1984-05-16 |
| EP0091704B1 (en) | 1986-06-18 |
| JPS58185476A (en) | 1983-10-29 |
| IE830678L (en) | 1983-10-08 |
| JPS6331428B2 (en) | 1988-06-23 |
| IL68226A0 (en) | 1983-06-15 |
| AT373229B (en) | 1983-12-27 |
| IL68226A (en) | 1986-03-31 |
| GR78156B (en) | 1984-09-26 |
| CA1197267A (en) | 1985-11-26 |
| ES8405749A1 (en) | 1984-06-16 |
| BR8301745A (en) | 1983-12-13 |
| MX156507A (en) | 1988-09-05 |
| EP0091704A1 (en) | 1983-10-19 |
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