US3672918A - Hot tops - Google Patents

Hot tops Download PDF

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Publication number
US3672918A
US3672918A US71824A US3672918DA US3672918A US 3672918 A US3672918 A US 3672918A US 71824 A US71824 A US 71824A US 3672918D A US3672918D A US 3672918DA US 3672918 A US3672918 A US 3672918A
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United States
Prior art keywords
hot top
percent
hot
exothermic
insulating layer
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
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US71824A
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English (en)
Inventor
George Rocher
Nicholas Orban
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METALLURGICAL EXOPRODUCTS CORP
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METALLURGICAL EXOPRODUCTS CORP
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    • 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
    • B22D7/06—Ingot moulds or their manufacture
    • B22D7/10—Hot tops therefor
    • B22D7/104—Hot tops therefor from exothermic material only
    • 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
    • B22D7/06—Ingot moulds or their manufacture
    • B22D7/10—Hot tops therefor

Definitions

  • Liquid metals such as steel contract during solidfication causing internal shrinkage cavities in the solidified product, generally called the ingot or casting. It is often desirable to control the exact location of these shrinkage cavities which usually form in the center portion of the ingot or casting since it is the last portion to freeze. Control of the shrinkage cavity is accomplished on most types of solidifying metals by using hot tops in or above the top of the mold to keep the metal molten as long as possible so the shrinkage cavity can be continuously filled. This then positions the shrinkage cavity at the uppermost portion of the ingot or casting where it can be removed during later processing without excessive yield loss to the product.
  • Hot tops are generally either of the permanent type or the disposable type.
  • hot top refractory brick are lined in metal castings around the top of the mold.
  • Disposable hot tops employ hot top boards which ultimately disintegrate or are otherwise disposed of during a single use, therefore, necessitating new boards for each use of the mold. These boards are generally placed in the mold and secured to the top portion of the inner mold walls to form the hot top. Disposable hot top boards can also be used in place of the permanent brick in the metal castings positioned on top of the ingot mold.
  • the disposable hot tops are generally either insulating boards comprised of materials having an appreciably lower heat conductivity than the molds which are typically cast iron or exothermic containing materials such as aluminathermic compositions which will react to initially give off heat and then retain the heat in the same manner as an insulating board.
  • Disposable composite hot top boards have also been employed. These boards consist of a layer of exothermic material press bonded to a layer of insulating material. The insulating layer is positioned against the mold wall and the exothermic layer is in contact with the molten metal.
  • Our invention improves upon the composite hot top board by increasing the insulating properties over extended periods of time. Because of the increased properties we are able to increase the yield from ingots over those yields previously obtained on comparable products. Further, our invention can be utilized in a manner so that the characteristics essential to achieving improved insulating properties are the result of in situ reactions, brought about by the molten metal environment. This ice then permits hot tops of our invention to be manufactured in a manner similar to that employed on known hot tops, yet improved results are achieved thereover.
  • Our invention is a composite hot top board of the disposable type in which a substantial amount of space exists at the interface of the exothermic and insulating layers.
  • This space is preferably in the form of randomly spaced, discontinuous and internal voids which are formed in situ under a use environment as described hereinafter.
  • FIG. 1 is a section showing an embodiment of our composite hot top
  • FIG. 2 is a photograph showing the actual structure of the hot top after in situ formation of voids.
  • FIG. 3 is a graph showing a comparison of insulating properties of our embodiment of FIG. 2 and present day hot tops.
  • FIG. 1 shows an insulating layer 10' is press bonded against an exothermic layer 11 by means well-known to those skilled in the art.
  • Exothermic layer 11 has a recess 12 along its inner surface so that a substantial amount of space 13 is formed between the layers at their interface.
  • the recess could be in the insulating layer or in both layers, and the criticality lies in the fact that a substantial amount of space must exist at the interface between the respective layers.
  • the space at the interface is formed in situ in the form of a plurality of voids.
  • FIG. 2. we show an actual piece of our composite hot top 20 after use.
  • a plurality of randomly spaced, discontinuous and internal voids 21 were formed in situ at the interface between the exothermic layer 22 and insulating layer 23.
  • the hot top boards were prepared by press bonding a flat surface of insulating layer 23 to a fiat surface of exothermic layer 22.
  • the voids 21 were formed in situ during actual use in an ingot mold teemed with molten steel.
  • the fly ash which melts at about 1900 F. decomposes to form a gas (called bloating) at the interface, thereby creating the randomly spaced, discontinuous and internal voids.
  • the temperature to accomplish this bloating is only sufficient at the immediate vicinity of the interface as can clearly be seen from FIG. 2 wherein the insulating layer 23 remains intact throughout the balance of its thickness. This temperature at the interface will be somewhere above 2500 F. due to the molten metal in the ingot mold and the exothermicity of the exothermic layer 22.
  • a fly ash content of at least 50 percent (dry ingredients) in the insulating layer is desirable to insure sufiicient voids to optimize the insulating properties.
  • Curve 1 represents the insulating properties of a standard exothermic hot top board presently produced and having a composition somewhat similar to that shown in Table I for the exothermic layer.
  • the actual composition of the hot top depicted by curve 1 of FIG. 3 difie-red from that shown in Table I by having less aluminum-containing additives, the aluminum-containing additives being replaced with grog, magnesia and 100 mesh silica sand.
  • the additional aluminum aditives in the exothermic layer of our composite hot top insures sufiicient temperature to result in the bloating and resultant voids.
  • Curve 2 of FIG. 3 is a typical curve for a standard insulating hot top board. Although many compositions are used for insulating boards, curve 2 is representative of the results obtained from insulating boards in general.
  • Curve 3 represents a composite hot top board formed of an exothermic layer and an insulating layer having compositions the same as the hot tops shown for curves 1 and 2, respectively.
  • Curve 4 represents our new composite hot top having the composition shown in Table I. It can be seen that the temperature of the molten metal (represented by the ordinate of the graph) is maintained higher and for a longer period of time by our composite hot top as compared to the other three forms of hot tops.
  • Our hot tops can be set in the ingot molds in the same manner as existing disposable hot tops.
  • the insulating layer is positioned adjacent the mold wall, thus exposing the exothermic layer to the molten metal upon teeming.
  • a composite hot top boa-rd characterized by improved insulating properties over extended periods of time comprising an exothermic layer bonded to an insulating layer, said insulating layer comprising at least fifty percent by weight fly ash, the interface between the exothermic and insulating layers having a plurality of randomly spaced, discontinuous and internal voids formed in situ.
  • the hot top of claim 2 wherein the insulating layer comprises by weight 50-80 percent fly ash, 2-12 percent perlite and 20-40 percent grog and a binder.
  • the insulating layer comprises about 62.5 percent fly ash, 32 percent grog, 5.5 percent perlite and a silica gel binder.
  • a composite hot top board characterized by improved insulating properties over extended periods of time comprising an exothermic layer and an insulating layer, said exothermic layer comprising by weight 40-70 percent aluminum additives, 10-30 percent sand additives, 5-30 percent iron oxide additives, 0-15 percent grog, 0-10 percent magnesia, 0-10 percent cryolite, 0-10 percent perlite, and 0-10 percent sodium chlorate, and said insulating layer comprising by weight 20-40 percent grog, 2-12 percent perlite, and 50-80 percent fly ash, said hot top forming a plurality of randomly spaced voids in situ at the interface of discontinuous and internal said exothermic and insulating layers.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Laminated Bodies (AREA)
  • Heat Treatments In General, Especially Conveying And Cooling (AREA)
US71824A 1970-09-14 1970-09-14 Hot tops Expired - Lifetime US3672918A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US7182470A 1970-09-14 1970-09-14

Publications (1)

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US3672918A true US3672918A (en) 1972-06-27

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US71824A Expired - Lifetime US3672918A (en) 1970-09-14 1970-09-14 Hot tops

Country Status (9)

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US (1) US3672918A (enrdf_load_stackoverflow)
AT (1) AT318157B (enrdf_load_stackoverflow)
BE (1) BE772415A (enrdf_load_stackoverflow)
CA (1) CA942926A (enrdf_load_stackoverflow)
DE (1) DE2108052A1 (enrdf_load_stackoverflow)
FR (1) FR2106489B1 (enrdf_load_stackoverflow)
GB (1) GB1295599A (enrdf_load_stackoverflow)
LU (1) LU63893A1 (enrdf_load_stackoverflow)
NL (1) NL7101442A (enrdf_load_stackoverflow)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3923526A (en) * 1972-07-22 1975-12-02 Aikoh Co Heat-insulating board for covering the top surface of a feeder head
US4036282A (en) * 1974-09-04 1977-07-19 Foseco International Limited Process of ingot casting
US4201606A (en) * 1977-07-19 1980-05-06 Foseco Trading Ag. Refractory exothermic heating insulating articles

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102012019802B4 (de) 2012-10-10 2023-07-27 Mercedes-Benz Group AG Verfahren zur Herstellung eines Gusskörpers

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1256395A (fr) * 1960-05-06 1961-03-17 Berk Exothermics Ltd Tête exothermique pour moules de coulée des métaux

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3923526A (en) * 1972-07-22 1975-12-02 Aikoh Co Heat-insulating board for covering the top surface of a feeder head
US4036282A (en) * 1974-09-04 1977-07-19 Foseco International Limited Process of ingot casting
US4201606A (en) * 1977-07-19 1980-05-06 Foseco Trading Ag. Refractory exothermic heating insulating articles

Also Published As

Publication number Publication date
BE772415A (fr) 1972-01-17
DE2108052A1 (de) 1972-03-16
FR2106489A1 (enrdf_load_stackoverflow) 1972-05-05
CA942926A (en) 1974-03-05
GB1295599A (enrdf_load_stackoverflow) 1972-11-08
AT318157B (de) 1974-09-25
FR2106489B1 (enrdf_load_stackoverflow) 1976-05-28
LU63893A1 (enrdf_load_stackoverflow) 1972-02-03
NL7101442A (enrdf_load_stackoverflow) 1972-03-16

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