GB2079782A - Improvements in and relating to ladle covers - Google Patents

Improvements in and relating to ladle covers Download PDF

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Publication number
GB2079782A
GB2079782A GB8021532A GB8021532A GB2079782A GB 2079782 A GB2079782 A GB 2079782A GB 8021532 A GB8021532 A GB 8021532A GB 8021532 A GB8021532 A GB 8021532A GB 2079782 A GB2079782 A GB 2079782A
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GB
United Kingdom
Prior art keywords
weight
composition
aluminium
ball mill
ladle
Prior art date
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Granted
Application number
GB8021532A
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GB2079782B (en
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Bowling Back Land Co Ltd
Original Assignee
Alcan Enfield Alloys 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 Alcan Enfield Alloys Ltd filed Critical Alcan Enfield Alloys Ltd
Priority to GB8021532A priority Critical patent/GB2079782B/en
Publication of GB2079782A publication Critical patent/GB2079782A/en
Application granted granted Critical
Publication of GB2079782B publication Critical patent/GB2079782B/en
Expired legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D1/00—Treatment of fused masses in the ladle or the supply runners before casting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/10—Supplying or treating molten metal
    • B22D11/11—Treating the molten metal
    • B22D11/111—Treating the molten metal by using protecting powders

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Ceramic Products (AREA)
  • Compositions Of Oxide Ceramics (AREA)

Abstract

A ladle cover for use in foundry practice comprising a composition comprising up to 60% by weight and preferably 40 to 50% by weight of ball mill dust together with sufficient ball mill fines and/or comminuted aluminium to give a total metallic aluminium content of at least 7% by weight, up to 20% by weight of comminuted combustible cellulosic material, preferably wood chips, having a moisture content such that the total amount of free water available on combustion is not greater than 2% by weight of the composition and at least one other additive selected from expanded perlite, powdered refractory clay, pozzolan and refractory metal oxides.

Description

SPECIFICATION Improvements in and relating to ladle covers This invention relates to ladle covers for use in foundry practice and especially for use in the casting of steel.
Ladle covers are used in foundry practice to prevent heat loss from ladles of molten metal and comprise flowable powdery materials which are cast over the surface of the molten metal to form a heat insulating layer thereupon. Some such powders simply form a heat insulating layer and others, known as "exothermic" covers contain ingredients that undergo exothermic reaction at the temperature to which they are subjected thereby not only preventing abstraction of heat by radiation from the exposed surface of the molten metal but also providing an additional input of heat from the exothermic reaction.
During the smelting of aluminium a certain amount of dross is produced consisting mainly of aluminium oxide but also containing a certain proportion of metallic aluminium. This dross is usually collected and subjected to a ball milling operation which allows the separation of relatively large lumps of metallic aluminium that can be returned for smelting.The residue has a range of particle sizes and is normally separated into different fractions by sieving. The larger particles which are known as "fines" contain enough residual metallic aluminium to make them usable for a number of purposes, but the smaller particles known as ''ball mill dust" are generally of little use and must be dumped. Even the dust, however, contains a small proportion of aluminium. Hitherto no satisfactory large scale use for ball mill dust has been found.
This invention is based on the observation that ball mill dust can be used in an amount of up to 60% by weight in exothermic ladle covers for use in foundry practice.
According to the invention a ladle cover comprises up to 60% by weight of ball mill dust together with sufficient ball mill fines and/or comminuted aluminium such that the total metallic aluminum content of the cover is at least 7% by weight up to 20% by weight of comminuted combustible cellulosic material having a moisture content such that the total amount of free water available on combustion is not greater than 2.0% by weight of the composition, and at least one other additive selected from expanded perlite, powdered refractory clay, pozzolan and refractory metal oxides.
In the ladle covers of the invention the amount of ball mill dust is preferably within the range of from 40 to 50% by weight, with ball mill fines being added to bring the metallic aluminium content of the composition to at least 11%. It is not normally necessary to add comminuted aluminium to the ladle cover composition but if desired metallic aluminium can be added if a higher exothermic output is required.
The combustible cellulosic material is preferably finely divided wood and may be in the form of wood flour or saw dust but is preferably in the form of wood chips. Wood flour and saw dust frequently contain relatively large amounts of water (often up to 15%) which flashes to steam on contact with the molten metal. This steam can cause blowing of the finely powdered ingredients of the ladle cover and, accordingly, it may be desired to keep the amount of steam produced to a minimum. When wood flour or saw dust is used in the covers of the invention it is frequently necessary to limit their content to a maximum of 8 to 9% to limit the amount of steam produced. Waste wood chips, for example, as produced in the production of chip board are pre-dried and usually have a moisture content not exceeding 6 to 9%.Consequently the amount of steam produced from a given weight of this material is very much less than that produced from undried wood material and such wood chips can be used in an amount of up to 20% by weight of the ladle cover material.
The ladle covers of the invention are extremely efficient and generally form a solid self-supporting layer over the surface of the molten metal. The aluminium content burns with high exothermic output and the combustible cellulosic material burns away to produce a structure with a large number or relatively fine pores which have a good insulating effect. Once the exothermic heat of combustion of the aluminium has been disipated the ladle covers of the invention will maintain the surface temperature of molten steel in a ladle for a considerable period of time to the extent that even the slag may remain molten for periods of up to and, even in excess of 3/4 of an hour.
A typical example of the composition of a ladle cover according to the invention was made by intimately mixing the following components: Wood chips (9% water) 14% Fines 30% Perlite 6% Pozzolan 6% Ball mill dust 44%
CLAIMS 1. A composition comprising up to 60% by weight of ball mill dust together with sufficient ball mill fines and/or comminuted aluminium such that the total metallic aluminiun content is at least 7% by weight, up to 20% by weight of comminuted combustible cellulosic material having a moisture content
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements in and relating to ladle covers This invention relates to ladle covers for use in foundry practice and especially for use in the casting of steel. Ladle covers are used in foundry practice to prevent heat loss from ladles of molten metal and comprise flowable powdery materials which are cast over the surface of the molten metal to form a heat insulating layer thereupon. Some such powders simply form a heat insulating layer and others, known as "exothermic" covers contain ingredients that undergo exothermic reaction at the temperature to which they are subjected thereby not only preventing abstraction of heat by radiation from the exposed surface of the molten metal but also providing an additional input of heat from the exothermic reaction. During the smelting of aluminium a certain amount of dross is produced consisting mainly of aluminium oxide but also containing a certain proportion of metallic aluminium. This dross is usually collected and subjected to a ball milling operation which allows the separation of relatively large lumps of metallic aluminium that can be returned for smelting.The residue has a range of particle sizes and is normally separated into different fractions by sieving. The larger particles which are known as "fines" contain enough residual metallic aluminium to make them usable for a number of purposes, but the smaller particles known as ''ball mill dust" are generally of little use and must be dumped. Even the dust, however, contains a small proportion of aluminium. Hitherto no satisfactory large scale use for ball mill dust has been found. This invention is based on the observation that ball mill dust can be used in an amount of up to 60% by weight in exothermic ladle covers for use in foundry practice. According to the invention a ladle cover comprises up to 60% by weight of ball mill dust together with sufficient ball mill fines and/or comminuted aluminium such that the total metallic aluminum content of the cover is at least 7% by weight up to 20% by weight of comminuted combustible cellulosic material having a moisture content such that the total amount of free water available on combustion is not greater than 2.0% by weight of the composition, and at least one other additive selected from expanded perlite, powdered refractory clay, pozzolan and refractory metal oxides. In the ladle covers of the invention the amount of ball mill dust is preferably within the range of from 40 to 50% by weight, with ball mill fines being added to bring the metallic aluminium content of the composition to at least 11%. It is not normally necessary to add comminuted aluminium to the ladle cover composition but if desired metallic aluminium can be added if a higher exothermic output is required. The combustible cellulosic material is preferably finely divided wood and may be in the form of wood flour or saw dust but is preferably in the form of wood chips. Wood flour and saw dust frequently contain relatively large amounts of water (often up to 15%) which flashes to steam on contact with the molten metal. This steam can cause blowing of the finely powdered ingredients of the ladle cover and, accordingly, it may be desired to keep the amount of steam produced to a minimum. When wood flour or saw dust is used in the covers of the invention it is frequently necessary to limit their content to a maximum of 8 to 9% to limit the amount of steam produced. Waste wood chips, for example, as produced in the production of chip board are pre-dried and usually have a moisture content not exceeding 6 to 9%.Consequently the amount of steam produced from a given weight of this material is very much less than that produced from undried wood material and such wood chips can be used in an amount of up to 20% by weight of the ladle cover material. The ladle covers of the invention are extremely efficient and generally form a solid self-supporting layer over the surface of the molten metal. The aluminium content burns with high exothermic output and the combustible cellulosic material burns away to produce a structure with a large number or relatively fine pores which have a good insulating effect. Once the exothermic heat of combustion of the aluminium has been disipated the ladle covers of the invention will maintain the surface temperature of molten steel in a ladle for a considerable period of time to the extent that even the slag may remain molten for periods of up to and, even in excess of 3/4 of an hour. A typical example of the composition of a ladle cover according to the invention was made by intimately mixing the following components: Wood chips (9% water) 14% Fines 30% Perlite 6% Pozzolan 6% Ball mill dust 44% CLAIMS
1. A composition comprising up to 60% by weight of ball mill dust together with sufficient ball mill fines and/or comminuted aluminium such that the total metallic aluminiun content is at least 7% by weight, up to 20% by weight of comminuted combustible cellulosic material having a moisture content such that the total amount of free water available on combustion is not greater than 2% by weight of the composition, and at least one other additive selected from expanded perlite, powdered refractory clay, pozzolan and refractory metal oxides.
2. A composition as claimed in claim 1 containing all mill dust in an amount within the range of from 40 to 50% by weight with ball mill fines to bring the metallic aluminium content of the composition to at least 11%.
3. A composition as claimed in claim 1 or claim 2 wherein the combustible cellulosic material is finely divided wood.
4. A composition as claimed in claim 3 wherein the finely divided wood is wood flour or saw dust.
5. A composition as claimed in claim 4 wherein wood flour or saw dust are present in the composition in a maximum amount of 8 to 9% by weight of the composition.
6. A composition as claimed in claim 3 wherein the finely divided wood is wood chips.
7. A composition as claimed in claim 6 wherein wood chips are present in an amount of up to 20% by weight of the composition.
8. A composition as claimed in claim 1 having a formulation substantially as set forth in the Example herein.
GB8021532A 1980-07-01 1980-07-01 Improvements in and relating to ladle covers Expired GB2079782B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB8021532A GB2079782B (en) 1980-07-01 1980-07-01 Improvements in and relating to ladle covers

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB8021532A GB2079782B (en) 1980-07-01 1980-07-01 Improvements in and relating to ladle covers

Publications (2)

Publication Number Publication Date
GB2079782A true GB2079782A (en) 1982-01-27
GB2079782B GB2079782B (en) 1984-04-11

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1984003460A1 (en) * 1983-03-08 1984-09-13 Ferrox Co Ets Int Process for thermal insulation of the surface of a molten mass of steel and thermally insulating board used as a cover plate for carrying out said process
US4670018A (en) * 1985-09-03 1987-06-02 Cornwell James H High BTU fuel element

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1984003460A1 (en) * 1983-03-08 1984-09-13 Ferrox Co Ets Int Process for thermal insulation of the surface of a molten mass of steel and thermally insulating board used as a cover plate for carrying out said process
TR22526A (en) * 1983-03-08 1987-10-01 Ferrox Co Ets Int THERMAL MAINTENANCE ISOLATED USED AS A COVER BOARD FOR THERMAL INSULATION OF THE SURFACE OF ERIMIS STEEL MASS.
US4670018A (en) * 1985-09-03 1987-06-02 Cornwell James H High BTU fuel element

Also Published As

Publication number Publication date
GB2079782B (en) 1984-04-11

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PCNP Patent ceased through non-payment of renewal fee