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GB2131790A - Carbon-containing refractory - Google Patents

Carbon-containing refractory Download PDF

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Publication number
GB2131790A
GB2131790A GB08333237A GB8333237A GB2131790A GB 2131790 A GB2131790 A GB 2131790A GB 08333237 A GB08333237 A GB 08333237A GB 8333237 A GB8333237 A GB 8333237A GB 2131790 A GB2131790 A GB 2131790A
Authority
GB
United Kingdom
Prior art keywords
refractory
weight
parts
approximately
graphite
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB08333237A
Other versions
GB8333237D0 (en
GB2131790B (en
Inventor
Hiroshi Kyoden
Hideaki Nishio
Shohei Hara
Yoichiro Kawabe
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Shinagawa Refractories Co Ltd
Original Assignee
Shinagawa Refractories Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Shinagawa Refractories Co Ltd filed Critical Shinagawa Refractories Co Ltd
Publication of GB8333237D0 publication Critical patent/GB8333237D0/en
Publication of GB2131790A publication Critical patent/GB2131790A/en
Application granted granted Critical
Publication of GB2131790B publication Critical patent/GB2131790B/en
Expired legal-status Critical Current

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Classifications

    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/013Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics containing carbon

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  • 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)
  • Ceramic Products (AREA)

Abstract

A carbon-containing refractory comprises approximately 1 to 10 parts by weight of Al-Si alloy powder per 100 parts by weight of graphite (3-50 pts. by wt.) and refractory aggregate (50-97 pts. by wt.). Because the melting point of Al-Si alloy powder is as much as 80 DEG C lower than the melting points of the conventionally-used unalloyed metal powders, the oxidation-preventing effects of the Al-Si alloy powder is greater in the low temperature range (from about 400 DEG C) than the effects of unalloyed metal powders. The resulting refractory has increased hot strength and decreased weight loss after oxidizing burning. The resistance to corrosion of the present refractory is further increased by the admixture of approximately 0.3 to approximately 5 parts by weight of boron carbide per 100 parts by weight of graphite and refractory aggregate.

Description

SPECIFICATION A carbon-containing refractory The present invention relates to carbon-containing refractories and more specifically to burned and unburned Al203-C, MgO-C, and MgO-A1203-C refractories having improved resistance to oxidation, spalling, and corrosion, in addition to improved hot strength.
Refractories containing carbon in the form of graphite are widely used in metallurgy. When in contact with molten iron, molten steel, or slag, these refractories exhibit excellent resistance to chemical corrosion. Since graphite itself is resistant to wetting by slag, its presence in refractories prevents the penetration of slag into the refractories. Further, because of the presence of graphite, the refractories can not be over-sintered, and therefore thermal spalling does not readily occur. This, too, contributes to the high durability of graphite-containing refractories.
However, graphite is very easily oxidized by oxygen in the surroundings and oxidation causes a graphite-containing refractory to lose its excellent durability. In order to obtain a refractory with good durability, it is extremely important to suppress the oxidation of graphite. Various methods have been proposed for increasing the resistance to oxidation of this type of refractory, but at present no satisfactory method has been found.
One method of preventing oxidation in carbon-containing refractories is to uniformly disperse metal powder in the refractory raw materials. Japanese Patent Laid Open No. 55-107749 discloses adding magnesium, aluminium, and silicon powder to carbon-containing refractory bricks, and Japanese Patent Laid Open No. 54-39422 discloses adding a metal powder having a greater affinity for oxygen than does carbon. In the latter case, at least one type of metal powder selected from the group consisting of Al, Si, Cr, Ti, and Mg is added. However, the resistance to oxidation and the hot strength of the resulting carbon-containing refractory, while improved, are not fully satisfactory.
The addition of metal powders to carbon-containing refractories has a number of beneficial effects. (1) From the temperature range of 200-3000C in which oxidation of the metal powders begin, carbon is protected from oxidatiori by the preferential oxidation of the metal powders. (2) When the metal powders oxidize, they expand in volume.As a result of this volume expansion, the refractory becomes more compact, and penetration of oxygen into the refractory is decreased, with a resulting decrease in oxidation of the graphite. (3) When the metal powders oxidize, they form bonds with the refractory raw materials which increase the hot strength of the refractory. (4) From about 1000C, the volatile portions of the refractory binding such as water, tar, pitch, phenolic resins, and the like employed in moulding refractories begin to volatilize, leaving pores and passageways in the refractory into which oxygen can penetrate. Once the refractory reaches a sufficient temperature and the metal powders melt, the liquid metal expands in volume and flows into and fills the pores and passageways preventing the penetration of oxygen.
However, the melting points of the metals conventionally admixed in carbon-containing refractories (e.g. 6600C for aluminium and 6490C for magnesium) are considerably higher than the temperature (around 4000C) at which oxidation of carbon begins. Accordingly, there is a temperature gap of approximately 2500C in which the ability of conventionally-used metal powders to suppress oxidation by melting and filling in pores is extremely low.
The present invention provides a carbon-containing refractory comprising approximately 3 to approximately 5 parts by weight of graphite and approximately 50 to approximately 97 parts by weight of refractory aggregate; the refractory further comprising approximately 1 to approximately 10 parts by weight of Al-Si alloy powder and, optionally, approximately 0.3 to approximately 5 parts by weight of boron carbide per 100 parts by weight of graphite and refractory aggregate.
As is well known, the melting point of a metal alloy is lower than the melting points of the metals which constitute the alloy. For example, Al-Si alloys have a eutectic point of 5770C, while unalloyed aluminium and magnesium having melting points of 6600C and 6490C, that is approximately 70-900C higher than the eutectic point.
In the present invention, Al-Si alloy powder, which has a greater affinity for oxygen than does carbon, is admixed instead of the unalloyed metal powders used in conventional carbon-containing refractories. Because of its low melting point, Al-Si alloy powder greatly increases the resistance to oxidation of the resulting refractory in the low temperature range (from about 4000 C) in which oxidation of carbon begins. Because of this incrased resistance to oxidation, the resistance to corrosion and hot strength of the refractory are increased. The resistance to corrosion is further increased by admixture of boron carbide, as will be described below.
A carbon-containing refractory according to the present invention will be described below by way of example. It significantly differs from conventional carbon-containing refractories in that it contans Al-Si alloy powder admixed with graphite and refractory aggregate.
The mechanism whereby Al-Si alloy powder increases the resistance to oxidation of a carboncontaining refractory in which it is admixed is basically the same as the mechanism whereby conventionally-used non-alloyed metal powders do so. Namely, (1) Al-Si alloy powder has a greater affinity for oxygen than carbon and is preferentially oxidized; (2) when oxidized, Al-Si alloy powder undergoes volume expansion which increases the compactness of the refractory; (3) the oxidized Al-Si alloy powder forms new bonds with the refractory aggregate, increasing the hot strength of the refractory; and (4) upon melting, the non-oxidized portion of the Al-Si alloy powder flows into and fills pores left by the volatilization of the binder used in moulding.
The big difference between the use of Al-Si alloy powder and unalloyed metal powder is the considerably lower melting point of Al-Si alloy powder. Accordingly, the range in which Al-Si alloy powder can suppress oxidation is greater than for unalloyed metal powders.
As the Al-Si alloy powder used in the present invention, commercial Al-Si powder is satisfactory. From the standpoint of reactivity and dispersibility, it is desirable that the grain size of the Al-Si alloy powder be no greater than approximately 0.1 > 25 mm. The amount of Al-Si alloy powder used per 100 parts by weight of graphite and refractory aggregate should be approximately 1 to approximately 10 parts by weight. If less than approximately 1 part by weight is used, the effectiveness of the Al-Si alloy powder is small, and if more than approximately 10 parts by weight are used, resistance to corrosion is decreased.
The refractory aggregare employed in the present invention comprises oxides such as magnesia, spinel, alumina, silica, zircon, and zirconia, and non-oxides such as silicon carbide, silicon nitride, and boron nitride. There are no particular limits on the components, but it is desirable that the main components be magnesia, spinel, and alumina.
The graphite portion of the refractory maybe a natural graphite such as amorphous graphite or crystalline graphite, or it may be an artificial graphite such as that derived from electrode scraps, petroleum coke, or carbon black. However, it is preferable to use crystalline graphite with few impurities The relative portion of graphite used depends upon the type of refractory aggregate used and the intended use for the refractory. However, it is generally preferable to employ 3 to 50 parts by weight of graphite in 100 parts by weight of refractory aggregate and graphite. If the amount of graphite is less than approximately 3 parts by weight, the graphite will not exhibit good resistance to wetting by slag, in which case the entire refractory will have poor resistance to slag.Furthermore, if the graphite exceeds approximately 50 parts by weight, the desired strength can not be obtained and it becomes difficult to obtain a compact constitution.
The resistance to corrosion of a carbon-containing refractory according to the present invention is further increased by admixture of boron carbide. When the surface of a carbon-containing refractory containing boron carbide is exposed to molten metal, boron carbide is oxidized and forms boron oxide.
Boron oxide, together with the refractory aggregate and the oxides of the metal alloy powder, forms a melt of a high viscosity which covers the surface of the refractory and prevents oxidation of the graphite in the refractory.
In the present invention, it is mandatory that boron carbide be admixed not alone but in combination with Al-Si alloy powder. When boron carbide is mixed with the refractory aggregate and graphite either by itself or with unalloyed metal powder, the hot strength and the strength after heating of the refractory are low, and thus the beneficial effects produced by the present invention can not be achieved.
Commercial boron carbide abrasive material is satisfactory for use as the boron carbide in a carbon-containing refractory according to the present invention. In order to achieve good reactivity and uniform dispersion of the boron carbide, it is desirable that the grain size by at most 0.125 mm. Per 100 parts by weight of graphite the refractory aggregate, approximately 0.3 to approximately 5 parts by weight of boron carbide should be used. If less than approximately 0.3 parts by weight of boron carbide are used, its addition has no effect. If it exceeds approximately 5 parts by weight, the refractory exhibits excellent resistance to oxidation, but its hot strength and durability decrease.
An unburned carbon-containing refractory according to the present invention may be produced by first blending the graphite, the refractory aggregate, and the grain-size regulated metal alloy powder in the ratios mentioned above. At this time, boron carbide may also be admixed. A binder such as tar, pitch, phenolic resin, or furan resin is added. Using conventional methods, this mixture is moulded. After drying at around 2000C, an unburned refractory is obtained. If it is burned at 900-1 5000C in a reducing atmosphere, a burned refractory is obtained.
The following examples of a refractory according to the present invention illustrated the effects produced by various combinations of the components.
EXAMPLE 1 80 parts by weight of magnesia, 20 parts by weight of graphite, 2 parts by weight of aluminium silicon alloy powder, 1 part by weight of boron carbide, and 5 parts by weight of resol-type phenolic resin as a binder were blended together and then moulded under a pressure of 1000 kg/cm2 into standard bricks (230 x 114 x 65 mm) which were then dried at 2000C for 5 hours. At 1 4O00C, the completed unburned bricks had a high hot modulus of rupture of 205 kg/cm2. After oxidizing burning at 10000C for 3 hours, the bricks had a decrease in weight of only 3.1%.
EXAMPLES 2-4 Using the same method as was used for Example 1 , three additional examples of a carbon containing refractory having various compositions were mixed and formed into unburned standard bricks. The components and physical properties of these refractories are shown in Table 1.
COMPARATIVE EXAMPLES 1'-3' For the purpose of comparison, three refractories having the compositions shown on the right side of Table 1 were blended and moulded into standard bricks using the same methods as was used in preparing Example 1.
Comparative Examples 1' and 3' contained metal powders in unalloyed form. These refractories also had much lower hot strength and greater weight loss after oxidizing burning than did Examples 4 containing Al-Si alloy powder.
Comparative Example 2' contained boron carbide as an admixture without Al or Si powder, either in alloyed or unalloyed form, with the result that the hot strength was lower and the weight loss after oxidizing burning was higher than for any of the other examples.
TABLE I
Example Number The present invention Comparative Examples 1 2 3 4 1' 2' 3' magnesia 80 60 80 80 -spinel 30 20 0 F alumina 60 85 90 z w, B silicon carbide 10 crystalline graphite 20 10 20 5 20 20 10 zm 0") i;;; t Al-Si alloy powder 2 4 5 3 cnQ Al Al powder I 2 3 8 Si powder 1 boron carbide 1 1 2 1 1 1 1 % weight loss after Co oxidizing burning at 3.1 2.0 1.6 1.3 3.2 4.5 4.2 F 1OOO0Cfor3 hours rr hot modulus of rupture tkg/cm2) at 14000C 205 195 180 200 175 155 160

Claims (4)

1. A carbon-containing refractory comprising: approximately 3 to approximately 50 parts by weight of graphite; approximately 50 to approximately 97 parts by weight of refractory aggregate; and approximately 1 to approximately 10 parts by weight of Al-Si alloy powder per 100 parts by weight of graphite and refractory aggregate.
2. A carbon-containing refractory as claimed in claim 1, further comprising approximately 0.3 to approximately 5 parts by weight of boron carbide per 100 parts by weight of graphite and refractory aggregate.
3. A carbon-containing refractory substantially as described in any of Examples 1 to
4.
GB08333237A 1982-12-13 1983-12-13 Carbon-containing refractory Expired GB2131790B (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP57217056A JPS59107961A (en) 1982-12-13 1982-12-13 Carbon-containing refractories

Publications (3)

Publication Number Publication Date
GB8333237D0 GB8333237D0 (en) 1984-01-18
GB2131790A true GB2131790A (en) 1984-06-27
GB2131790B GB2131790B (en) 1986-07-30

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Family Applications (1)

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GB08333237A Expired GB2131790B (en) 1982-12-13 1983-12-13 Carbon-containing refractory

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JP (1) JPS59107961A (en)
DE (1) DE3344851A1 (en)
FR (1) FR2537565B1 (en)
GB (1) GB2131790B (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0669293A1 (en) * 1994-02-25 1995-08-30 North American Refractories Company Resin bonded ceramic-carbon-metal composite comprising boron source and a combination of at least two metals
WO2023132948A1 (en) * 2022-01-06 2023-07-13 HarbisonWalker International Holdings, Inc. Refractory lining design and steel practice for low refractory waste, and refractory based on reclaimed low-impurity magnesia-carbon aggregate

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH06661B2 (en) * 1988-02-12 1994-01-05 品川白煉瓦株式会社 Refractory bricks containing silicon nitride for hot metal treatment
RU2151123C1 (en) * 1998-06-04 2000-06-20 Санкт-Петербургский государственный технологический институт (технический университет) Composition and method of formation of compound for carbonized refractory materials

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2040911A (en) * 1979-02-09 1980-09-03 Kyushu Refractories Carbon-containing refractory bricks

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL251128A (en) * 1959-09-22
GB1058461A (en) * 1962-10-02 1967-02-08 Int Minerals & Chem Corp Refractory and cupola operation
JPS55115917A (en) * 1979-02-28 1980-09-06 Nippon Steel Corp Wall structure of converter
JPS55116655A (en) * 1979-02-28 1980-09-08 Tokyo Yogyo Kk Refractories
JPS5727968A (en) * 1980-07-17 1982-02-15 Kurosaki Refractories Co Plate brick for sliding nozzle
JPS57166362A (en) * 1981-04-06 1982-10-13 Tokyo Yogyo Kk Refractories containing carbonaceous matter

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2040911A (en) * 1979-02-09 1980-09-03 Kyushu Refractories Carbon-containing refractory bricks

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0669293A1 (en) * 1994-02-25 1995-08-30 North American Refractories Company Resin bonded ceramic-carbon-metal composite comprising boron source and a combination of at least two metals
WO2023132948A1 (en) * 2022-01-06 2023-07-13 HarbisonWalker International Holdings, Inc. Refractory lining design and steel practice for low refractory waste, and refractory based on reclaimed low-impurity magnesia-carbon aggregate

Also Published As

Publication number Publication date
GB8333237D0 (en) 1984-01-18
JPS6152099B2 (en) 1986-11-12
FR2537565B1 (en) 1991-10-31
FR2537565A1 (en) 1984-06-15
DE3344851A1 (en) 1984-06-14
GB2131790B (en) 1986-07-30
JPS59107961A (en) 1984-06-22
DE3344851C2 (en) 1988-04-07

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PCNP Patent ceased through non-payment of renewal fee

Effective date: 19951213