EP0321478B1 - Giesspulver bei der blockstahlerzeugung im unterguss und verfahren zu seiner verwendung - Google Patents

Giesspulver bei der blockstahlerzeugung im unterguss und verfahren zu seiner verwendung Download PDF

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Publication number
EP0321478B1
EP0321478B1 EP87905525A EP87905525A EP0321478B1 EP 0321478 B1 EP0321478 B1 EP 0321478B1 EP 87905525 A EP87905525 A EP 87905525A EP 87905525 A EP87905525 A EP 87905525A EP 0321478 B1 EP0321478 B1 EP 0321478B1
Authority
EP
European Patent Office
Prior art keywords
mold
casting powder
steel
expandable graphite
molten steel
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.)
Expired - Lifetime
Application number
EP87905525A
Other languages
English (en)
French (fr)
Other versions
EP0321478A1 (de
EP0321478A4 (de
Inventor
Maharaj Koul
Richard Paul
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.)
Atlantic Metals Corp
Original Assignee
Atlantic Metals Corp
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 Atlantic Metals Corp filed Critical Atlantic Metals Corp
Priority to AT87905525T priority Critical patent/ATE96708T1/de
Publication of EP0321478A1 publication Critical patent/EP0321478A1/de
Publication of EP0321478A4 publication Critical patent/EP0321478A4/de
Application granted granted Critical
Publication of EP0321478B1 publication Critical patent/EP0321478B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime 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
    • B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
    • B22D27/04—Influencing the temperature of the metal, e.g. by heating or cooling the mould
    • B22D27/06—Heating the top discard of ingots
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D7/00—Casting ingots, e.g. from ferrous metals
    • B22D7/12—Appurtenances, e.g. for sintering, for preventing splashing

Definitions

  • This invention relates to mold powders employed in ingot steel production. More specifically, the present invention discloses a casting powder to be employed in bottom pour steel molds which has the unique ability to act as both a bottom pour flux and a hot topping compound.
  • a sealed bag of bottom pour flux is suspended in the mold approximately six to eighteen inches above the inlet for the molten steel.
  • the bottom pour flux consists of chemical compounds which melt and spread rapidly across the surface of the molten steel.
  • the molten slag coating the surface of the steel acts to create the correct menisus shape and prevents oxidation of steel surface.
  • the molten slag insulates the surface of the molten steel to slow solidification, and spreads a thin coat of homogenous glass between the mold and the molten steel to allow constant heat transfer and solidification and thus lessen thermally induced stresses and resultant cracking.
  • the flux absorbs impurities such as deoxidation and reoxidation products and refractory particles.
  • the bag containing the bottom pour flux burns upon the introduction of the molten steel into the mold thus automatically releasing the flux.
  • hot topping compounds are not without its detractions. Adding hot topping compound is cumbersome, labor intensive, environmentally disruptive, and may contaminate the ingot steel.
  • a method of ingot casting is known from US-A-3 934 637 including bottom pouring molten metal into an ingot mold to form an ingot wherein there is located in the ingot mold prior to the commencement of pouring, a bonded composition comprising one or more fluxing agents and expandable graphite.
  • the bonded composition is borne up on the rising metal surface.
  • the composition serves to protect the walls of the casting mold.
  • Expandable graphite means particulate graphite the particles of which on heating, intumesce to give a low density highly heat insulative vermicular structure.
  • the patent specification is silent on the exact rate of expansion of the graphite. It is only stated that the graphite is to expand to many times its original volume.
  • the expandable graphite may be present in a range of 0.5 % to 10.0 % by weight.
  • a heat-insulating antipiping composition is known from US-A-3 811 898. This molten metal is applied to the surface of the molten metal in the feeder head after the metal has been poured into the mold. The amount of antipiping composition applied is sufficient to give a layer of expanded heat insulative material on the top of the molten metal to prevent excessive piping during the solidification of the metal.
  • the first mentioned patent discloses a composition serving to protect the walls of the casting mold
  • the second mentioned patent discloses a composition serving to prevent excessive piping during solidification.
  • the composition according to the second mentioned patent is applied only after the molten metal has been poured into the mold.
  • This object is achieved by the invention by a method for increased efficiency of protecting a steelmaker's mold and a steel ingot as bottom poured into the mold, including protecting against excessive piping of the steel which tends to occur when the molten steel cools too rapidly in the mold, comprising introducing into the mold a predetermined quantity of a casting powder, comprising chemical components combined to produce a bottom pour flux, and including an expandable graphite, pouring molten steel into said mold and covered with said casting powder to cause a substantial portion of said casting powder to rise to the vicinity of the top of said mold, thinly coating the side walls of said mold as it rises, and expanding into a thick insulative blanket on top of the molten steel of a sufficient insulative quality to avoid need for a hot topping compound limiting the steel's rate of cooling and thereby minimizing the piping of the ingot, wherein an expandable graphite is used that expands to 100 - 300 times its volume and comprises 4.0 to 12.0 % by weight of the composition of said casting powder.
  • the casting powder used in this method may be automatically dispensed, is economic to produce and use, entails little environmental risk, and does not contribute to ingot contamination.
  • the casting powder provides the benefits of both the prior methods and products separately and individually serving to protect the walls of the casting mold and to prevent excessive piping during the solidification of the cast metal.
  • the method according to the invention entails introducing a compound known as "expandable graphite" in place of a portion of the carbon component of a standard bottom pour flux.
  • the resulting mixture provides all the insulative and protective benefits of standard bottom pour fluxes as well as the full insulative requirements of hot topping compounds.
  • the casting powder used in the method according to the invention is cleanly and automatically dispersed upon introduction of molten steel into the steel ingot molds. It eliminates the noxious by-products of hot topping compound and its potentially contaminating effect of "core of debris", and does not require the labor input demanded for applicatikon of hot topping compound.
  • the invention also relates to a casting powder for use in the aforementioned method.
  • This powder comprises a mixture of chemical components to produce a bottom pour flux which coats and protects the top and sides of molten steel as it is introduced into the mold and including an expandable graphite component, which expands to form a thick insulative blanket on top of the molten steel of sufficient insulative quality to avoid need for a hot topping compound, limiting the steel's rate of cooling and thereby minimizing piping of the ingot, wherein the expandable graphite is of a type that expands 100 - 300 times its volume and comprises 4.0 to 12.0 % by weight of the composition of said mixture.
  • the present invention is directed to casting powders for use in ingot steel production through bottom pour process. Instead of the bottom pour flux and the hot topping compound presently employed, the present invention substitutes a single casting powder which provides the benefits of both the prior products.
  • the present invention entails introducing a compound known as "expandable graphite" in place of a portion of the carbon component of a standard bottom pour flux.
  • the resulting mixture provides all the insulative and protective benefits of standard bottom pour fluxes as well as the full insulative requirements of hot topping compounds.
  • the present invention is cleanly and automatically dispersed upon introduction of molten steel into the steel ingot molds. It eliminates the noxious by-products of hot topping compound and its potentially contaminating effect of "core of debris,” and does not require the labor input demanded for application of hot topping compound.
  • the present invention provides a mixture of chemical components which function as a unique casting powder for bottom pour ingot steel production.
  • the present invention combines the crucial properties of both bottom pour fluxes and hot topping compounds into a single, easily dispensed, composition.
  • Bottom pour fluxes (or powders) presently employed are required to have specific qualities for covering and protecting molten steel rising in an ingot mold. These include: molten slag layer to completely coat the molten steel, to insulate, maintain a proper surface shape, protect against oxidation, and absorb deoxidation and reoxidation products; and an ability to form a thin layer of homogenous glass between the molten steel and the side walls of the mold so as to insulate, reduce thermally induced stresses and thus decrease cracking.
  • a composition of a traditional bottom pour flux may comprise the following: Constituent Percentage (%) Range by Weight Silica (SiO2) 30.0 - 35.0% Aluminum Oxide (Al2O3) 15.0 - 17.0 Calcium Oxide (CaO) 6.5 - 8.0 Iron Oxide (Fe2O3) 4.0 - 6.0 Alkali Oxide 5.5 - 8.0 Carbon (C) 5.0 - 27.0
  • Hot topping compounds have only one primary purpose: to provide a thick insulative blanket on top of the molten steel to reduce the heat loss from the top to avoid "pipe.” Pipe is a condition which occurs when there is no molten steel to feed the shrinkage cavity formed due to ingot solidification.
  • Expandable graphite is produced through treatment of high grade natural crystalline graphite through oxidation or electrolysis by various oxidising materials. It is commercially available in a number of grades from graphite suppliers.
  • expandable graphite When expandable graphite is heated rapidly it expands along the C-axis of the crystal to a magnitude of 40 to 300 times its original size.
  • Expandable graphite has different expansion rates according to its quality. It is desired to use expandable graphite that expands between 100 and 300 times its volume within the percentage weight range provided above. It is believed that ideally an expansion of 200 to 250 times its volume at a percentage weight of 6.0 to 8.0% should be employed.
  • the casting powder has a viscosity nearly identical to that of standard bottom pour flux (i.e. at 1500°C, bottom pour flux has a viscosity of approximately 50-200 poise, the present invention produces a flux with a viscosity of 50-200 poise). Moreover, under pressure the present invention produces a unique quality compressio product having anistrophy. This results in a substance perfectly suitable to properly coat between the molten steel and the side walls of the ingot mold during pouring. Thus, the casting powder produced provides superior results as both a bottom pour flux and a hot topping compound.
  • the casting powder is dispersed in the same manner as standard bottom pour flux. It is placed in a combustible container or bag, such as paper bag with grommet reinforcements, and suspended six to eighteen inches above the bottom of the ingot mold. It can also be preformed into a board and placed at the bottom of the mold. The incoming molten steel consumes the container or dissolves the board causing the release of the powder. The powder then rapidly spreads across the surface of the incoming molten steel. This is a clean, automatic process which requires little human input and supervision.
  • the benefits of the present invention are realized through the elimination of hot topping compound. Personnel are no longer required to be stationed above the molds to apply the insulative material. Atmospheric dust from the hot topping compound and "core of debris" are also eliminated. Additionally, no smoke products are produced whatsoever. Despite the somewhat higher cost of substituting expandable graphite for standard graphite, the elimination of hot topping compound and the considerable cost savings in application provide a considerable overall cost savings.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Continuous Casting (AREA)
  • Treatment Of Steel In Its Molten State (AREA)
  • Mold Materials And Core Materials (AREA)

Claims (7)

  1. Verfahren zum Erzielen eines besseren Schutzes einer Stahlkokille und eines Stahlblocks beim Bodenguß und zum Schutz vor übermäßiger Lunkerbildung des Stahls, was bei einem zu schnellen Abkühlen der Stahlschmelze in der Kokille auftritt, bestehend aus
       Eingeben einer vorgegebenen Menge eines Gießpulvers in die Kokille bestehend aus chemischen Bestandteilen kombiniert zum Erzeugen eines Bodengußflußmittels und aus einem expandierbaren Graphit,
       Eingießen von geschmolzenem Stahl in die Kokille und abgedeckt mit dem Gießpulver um zu bewirken, daß ein wesentlicher Teil des Gießpulvers bis in den Bereich des oberen Endes der Kokille ansteigt, dünnes Beschichten der Seitenwände der Kokille beim Ansteigen und Expandieren in eine dicke isolierende Decke auf der Oberseite der Stahlschmelze mit ausreichender isolierender Qualität zum Vermeiden der Notwendigkeit einer hot topping-Verbindung, was die Abkühlgeschwindigkeit des Stahls begrenzt und damit die Lunkerbildung des Stahlblocks herabsetzt,
       wobei ein expandierbarer Graphit verwandt wird, der auf das 100- bis 300-fache seines Volumens expandiert und 4 bis 12 Gewichts-% der Verbindung des Gießpulvers ausmacht.
  2. Verfahren nach Anspruch 1, gekennzeichnet durch die Verwendung eines expandierbaren Graphits, der um das 200- bis 250-fache seines Volumens expandiert und 6 bis 8 Gewichts-% der Verbindung des Gießpulvers ausmacht.
  3. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß das Gießpulver in einen mindestens 150 mm über dem Boden der Kokille aufgehängten brennbaren Behälter eingebracht wird.
  4. Verfahren nach Anspruch 3, dadurch gekennzeichnet, daß der brennbare Behälter ein brennbarer Beutel ist.
  5. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß das Gießpulver in eine Tafel verformt und am Boden der Kokille eingesetzt wird.
  6. Gießpulver zur Verwendung bei dem Verfahren gemäß irgendeinem der vorhergehenden Ansprüche, bestehend aus
       einer Mischung von chemischen Bestandteilen zum Erzeugen eines Bodengußflußmittels, das die Oberseite und die Seiten der Stahlschmelze während des Einfüllens in die Kokille schützt und expandierbaren Graphit enthält,
       der unter Bildung einer dicken isolierenden Decke auf der Oberseite der Stahlschmelze von ausreichend isolierender Qualität expandiert zum Vermeiden der Notwendigkeit einer hot topping-Verbindung, was die Abkühlgeschwindigkeit des Stahls begrenzt und damit die Lunkerbildung des Stahlblocks herabsetzt,
       wobei es sich um einen expandierbaren Graphit handelt, der um das 100- bis 300-fache seines Volumens expandiert und 4 bis 12 Gewichts-% der Verbindung des Gemisches ausmacht.
  7. Gießpulver nach Anspruch 6, dadurch gekennzeichnet, daß es sich um einen expandierbaren Graphit handelt, der um das 200- bis 300-fache seines Volumens expandiert und 6 bis 8 Gewichts-% der Verbindung des Gemisches ausmacht.
EP87905525A 1986-08-13 1987-08-10 Giesspulver bei der blockstahlerzeugung im unterguss und verfahren zu seiner verwendung Expired - Lifetime EP0321478B1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT87905525T ATE96708T1 (de) 1986-08-13 1987-08-10 Giesspulver bei der blockstahlerzeugung im unterguss und verfahren zu seiner verwendung.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US89606786A 1986-08-13 1986-08-13
US896067 1992-06-09

Publications (3)

Publication Number Publication Date
EP0321478A1 EP0321478A1 (de) 1989-06-28
EP0321478A4 EP0321478A4 (de) 1990-04-10
EP0321478B1 true EP0321478B1 (de) 1993-11-03

Family

ID=25405572

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Application Number Title Priority Date Filing Date
EP87905525A Expired - Lifetime EP0321478B1 (de) 1986-08-13 1987-08-10 Giesspulver bei der blockstahlerzeugung im unterguss und verfahren zu seiner verwendung

Country Status (9)

Country Link
EP (1) EP0321478B1 (de)
JP (1) JPH01501536A (de)
KR (1) KR880701599A (de)
AU (1) AU604503B2 (de)
BR (1) BR8707766A (de)
CA (1) CA1285461C (de)
DE (1) DE3788067T2 (de)
MX (1) MX169019B (de)
WO (1) WO1988001210A1 (de)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0875320B1 (de) * 1997-04-30 2004-01-21 Stopinc Aktiengesellschaft Schiebeverschluss für ein Metallschmelze enthaltendes Gefäss
JP5366896B2 (ja) * 2010-07-07 2013-12-11 株式会社神戸製鋼所 下注ぎ造塊方法
JP5807910B2 (ja) * 2011-11-15 2015-11-10 山陽特殊製鋼株式会社 下注ぎ造塊用の被覆剤
JP6609139B2 (ja) * 2015-08-24 2019-11-20 山陽特殊製鋼株式会社 下注ぎ造塊法のための被覆剤

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3308514A (en) * 1965-01-07 1967-03-14 Dow Chemical Co Method of hot topping using vermicular graphite
GB1298701A (en) * 1969-11-12 1972-12-06 Foseco Int Heat-insulating antipiping compounds
GB1431787A (en) * 1973-03-28 1976-04-14 Foseco Int Casting of molten metals
JPS5253727A (en) * 1975-10-28 1977-04-30 Fuoseko Japan Rimitetsudo Yuug Formed additive for mold
JPS6038201B2 (ja) * 1978-09-04 1985-08-30 石川島播磨重工業株式会社 圧延材端部形状制御装置

Also Published As

Publication number Publication date
KR880701599A (ko) 1988-11-04
BR8707766A (pt) 1989-08-15
JPH01501536A (ja) 1989-06-01
AU7856787A (en) 1988-03-08
DE3788067D1 (de) 1993-12-09
DE3788067T2 (de) 1994-05-19
CA1285461C (en) 1991-07-02
EP0321478A1 (de) 1989-06-28
MX169019B (es) 1993-06-17
EP0321478A4 (de) 1990-04-10
AU604503B2 (en) 1990-12-20
WO1988001210A1 (en) 1988-02-25

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