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
  • 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
  • B22D7/06—Ingot moulds or their manufacture
  • B22D7/10—Hot tops therefor
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S249/00—Static molds
  • Y10S249/05—Hot top

Definitions

• ABSTRACT Smokeless exothermic hot topping compositions are provided for application to the metal hot top of a cast ingot or a casting riser to improve the yield of usable metal or inhibit piping. Exothermic compositions containing aluminum, iron oxide and inert filler materials are disclosed which produce no visible smoke when used as hot topping materials.
• Hot top boards or casings usually insulate the top 1 /2 to 2 feet ofthe cast ingot sides; and exothermic materials are added to the top of the cast metal to provide heat and'insulate the metal surface. Hot top boards and exothermic topping materials together maintain a reservoir of molten metal to feed the shrinkage normally encountered in the center of a solidifying ingot top.
• Oxidizers include mill scale (Fe O iron ore (Fe O alkali metal nitrates, manganeseor chromium oxide (or other metal oxides), metal chlorates or picrates; fuels include aluminum, ferrosilicon, titanium, magnesium, silicon or alloys thereof, carbon (in the form of coke, charcoal, coal, charred oat hulls, etc.), organic compounds (resin binders), and the like; inert ingredients include sand, grog, slags, clay binders, alumina cement, perlite, vermiculite, or the like; and fluxes include sodium chloride, fluorides such as calcium fluoride or sodium fluoride. Representative prior art patents which disclose such compositions include British Pat. Nos. 673,605; 745,668; 769,719; 852,377; 870,668;
• This invention is directed to an exothermic hot topping composition for use in the primary production or casting of metal, particularly iron or steel.
• Exothermic compositions have been discovered which are completely smokeless and provide adequate feeding of an ingot hot top or cast metal riser.
• actual production runs for ingot steel castings have demonstrated that exothermic compositions of this invention perform without producing any visible smoke.
• known exothermic hot topping materials produce considerable smoke.
• compositions contain mill scale (Fe O,), aluminum and inert filler materials. These compositions contain an effective amount of an oxide of iron up to about 50% by weight and an effective amount of fuel of aluminum or aluminum alloy providing up to about 15% by weight aluminum and the balance being predominantly composed of inert filler materials. These components are proportioned to provide smokeless compositions.
• Smokeless as the term is broadly used herein to characterize compositions of this invention means no visible smoke or only trace amounts of visible smoke. However, compositions are advantageously provided as mentioned above in accord with the principles of this invention which produce no visible smoke. Smokeless as it applies to compositions of this invention can also be equated herein to a Ringelmann number less than 1 or equivalent opacity of less than 20%.
• smoke is considered to consist of the gaseous products of burning organic materials, such as wood, coal, or tobacco, rendered visible by the pres ence of small particles of carbon, which finally settle as soot.
• organic materials such as wood, coal, or tobacco
• smoke any suspension of solid particles in a gas is termed smoke.
• smoke is used to include fume, vapor, or dust that resembles smoke.
• smoke will include the latter I meanings.
• the Ringelmann Smoke Chart and equivalent opacity is used herein to read visible emissions of smoke.
• the Ringelmann Chart was developed by Maximilian Ringelmann in the late 1800s and has been a useful tool ever since, at least in controlling visible emissions, which constitutes the nuisance form of air pollution.
• the Ringelmann Chart is thoroughly covered in the Bureau of Mines Information Circular No. 8333 (May, 1967), and this Circular is incorporated herein 1 by reference to ascertain smoke emissions by Ringel mann number and opacity. Another article incorpo' rated herein by reference is Reading Visible Emission by Jerome J.'Rom, U.S. Department of Health, Education and Welfare, April 1968.
• the Ringelmann system isvirtually a scheme whereby graduated shades of gray, varying by five equal steps between white and black, may be accurately reproduced by means of a rectangular grill of black lines of definite width and spacing on a white background.
• the rule by which charts may be reproduced is as follows:
• Card 2 Lines 2.3 mm thick, spaces 7.7 mm square.
• Card 3 Lines 3.7 mm thick, spaces 6.3 mm square.
• the chart as distributed by the Bureau of Mines, provides the shades of cards 1, 2, 3, and 4 on a single sheet, which are known as Ringelmann No. l, 2, 3, and 4, respectively. To use the chart, it is supported on a level with the eye, at such distance from the observer that the lines on the chart merge'into shades of gray, and as nearly as possible in line with a smoke source. The observer glances from the smoke, as it issues from the smoke source, to the chart and notes the number of the chart most nearly corresponding with the shade of the smoke, then records this number with the time of observation. A clear source is recorded as No. 0, and I percent black smoke as No. 5.
• Ringelmann Chart is only useful in evaluating black or gray emissions, a principle of equivalent opacity was developed which makes possible the application of the Ringelmann principle to other colors of smoke. Opacity simply means the degree to which transmitted light is obscured. Below is the relationship between Ringelmann number and opacity:
• Ringclmann No. Opacity Preferred operable ranges of main components are about -45% of an oxide of iron, about 91 3% aluminum fuel as aluminum metal or alloys thereof with the balance of predominantly inert materials. These main components are finely divided to permit blending for uniformity of reaction.
• the mesh sizes of iron oxide, aluminum and inert fillers can vary over wide ranges as the examples demonstrate to achieve smokeless compositions and, therefore, mesh sizes of these components are not critically limiting upon the principles ofthis invention.
• a minor amount of granular graphite can be incorporated in the exothermic composition to provide an early ignition of the exothermic reaction without deleteriously affecting I its smokelessness.
• An amount of graphite on the order of about 1 to about 4% by weight has been found to fulfill these purposes when employed in the compositions of this invention.
• the inert filler materials are selected from a class of diverse materials, particularly refractory materials in granular form such as fire clay, fire-clay grog, bauxite, olivine, perlite, expanded perlite, silica flour, silica sand and the like.
• the mesh sizeof such inert filler materials can vary over considerable ranges. It is preferred, however, to use coarse mesh sizes whose average mesh size is within the range of about l2 to about +100 to insure smokelessness. Finer particles have a tendency to cause melting or higher reaction temperatures of the exothermic compositions in use which in turn has been found to induce the formation of smoke.
• the mesh sizes for inert materials can be varied within the essential compositional parameters of this invention as willbe appreciated by the working examples and description of this invention.
• compositions of this invention when an insulating slag forming material is included with the main components.
• the inert filler material can also function as an insulating slag forming material.
• about 5-l5% by weight of expanded perlite is used as a slag forming additive which provides an insulating property to the compositions in use.
• an exothermic hot topping material that is completely smokeless is provided according to the principles of this invention when that composition consists essentially of about 35-42% by weight mill scale, I l-l3% by weight of aluminum, 30% by weight raw fire clay, about l0% by weight expanded perlite, about 5% by weight fireclay grog and about 3% by weight graphite.
• This composition is especially preferred in preparing pelletized materials as just mentioned in accordance with the above procedures.
• Each of the ingredients performs certain functions.
• the mill scale (Fe O provides the oxygen for the combustion of fuel, that is, the aluminum and the graphite.
• the expanded perlite serves to slow down the reaction and also acts as an insulator to help retain most of the heat in the steel ingot material.
• the fire clay is added as a binder to permitpelletizing of the damp mixture and the fire-clay grog is added as a compatible inert ingredient.
• the perlite, fire clay and fire-clay grog all act as inert ingredients that decrease the reaction rate and help retain the evolved heat in the steel ingot by their insulating properties in the slag.
• the compositional content of the inert refractory materials can be varied as the examples below demonstrate.
• pelletization is unnecessary to reduce dust, the fire clay could be replaced with other'materials that would improve the ignition characteristics of the mixture and the insulating properties of the resulting slag.
• pelletization has the advantage of eliminating dust and may be particularly suited where it is important to reduce the amounts of dust as well as reduction of smoke or fumes.
• a main finding in practicing this invention is the control of the compositional limits both of iron oxide oxidizer and aluminum fuels below certain critical amounts.
• An operable exothermic amount of oxide of iron up to about 50% by weight and aluminum fuel up to about 15% by weight has been found essential in providing smokelessness.
• the ratios of oxidizer and fuel will vary within these ranges of amounts.
• a stoichiometric ratio of about 3.2 to 1 of iron oxide to aluminum fuel is satisfactory, however, it is not critically essential to a practice of this invention. It has been discovered that amounts of iron oxide can be increased within the specified compositional range provided the aluminum fuel is decreased to achieve a smokeless composition.
• the aluminum fuel should be decreased from about 15% by weight towards about 10% by weight to achieve smokelessness.
• EXAMPLES 1l l Exothermic hot topping compositions of this invention were prepared as lOOO-gra'm samples in Examples ll 1 containing ingredients in weight percent as listed in Table I as follows. All compositions of Table I additionally contained 30% raw fire clay, except Examples 5 and '6' in which 27% raw fire clay was used. These compositions were ignited on IOO-pound inductionfurnace heats of carbon steel maintained at about 29003000F by supplying a small amount of power to the induction coil.
• the mill scale (Fe O,) was first screened through a /2-inch-mesh screen, heated to about 650F to dry and degrease it, pulverized in a ball mill, and screened through a ZO-mesh screen.
• the ball mill used for pulverizing the mill scale was 20 inches in diameter and was loaded about half full with 2-inch-diameter steel balls.
• The-mill scale was ground for to minutes.
• the aluminum metal (grindings and turnings) was 5 these examples, i.e., much less smoke than was produced by the bare steel surface by comparison. Such a trace corresponds to a smoke rating considerably less than Ringelmann No.
• Example 3 was considered to be the best from the standpoint of no visible smoke being produced and, from a standpoint of overall performance of reaction time and temperature.
• the densities of the pelletized /2-inch-mesh screen to break up any large pellets and mixtures of Examples 3-5 and 8-1 1 were about 3943 30 then dried at 350F.
• the dried, partially pelletized mixpounds/cubic foot and Examples 6-7 were about 8386 ture was packaged in lO-pound lots in polyethylene pounds/cubic foot.
• the %-inch or smaller pellets were bags. I r
• Example 12 was evaluated on comping compositions and the results are reported in Table flashal steel ingots having a hot top cross sectional l. area of approximately 24 inches square.
• EXAMPLES 13-20 Compositions containing mill scale, aluminum and fire clay in varying percentages by weight were formulated as listed in Table II.
• the mill scale particle sizes were of about 2+l0 mesh and the aluminum particle sizes were about 10+30 mesh.
• the fire clay'particle sizes were approximately -12 mesh.
• the mill scale particle sizes were such that the particles passed through a 2 mesh screen and were retained on a 10 mesh screen, whereas the aluminum particles'passed through a 10 mesh screen and were retained on a 30 mesh screen.
• Table II demonstrates that when the mill scale was varied between 30% and 50% by weight with the aluminum varying between about 10-1 by weight, an exothermic reaction was observed between about 21003 100F. Inthe case of Examples 13-15, no visible smoke was observed. A trace or a faint trace of smoke was observed in Examples 16-17, respectively, but such an amount was less than the bare surface of the metal itself. Furthermore, in connection with Examples 16-17, the negligible amounts of smoke were comparable to the trace amounts of the preceding examples.
• exothermic hot topping materials are prepared which perform in a satisfactory manner and which will not smoke or only negligible amounts of smoke considerably less than a Ringelmann EXAMPLES 21-27
• Examples 21-27 80% of the mill scale particle sizes were about l0+ 50 mesh and the-balance was approximately 70% of about l0+l50 mesh and 30% of about l50 mesh.
• the aluminum particle sizes of Examples 21-27 comprised 85% of about 30+l00 mesh with the balance of 15% being approximately -12+30 mesh. All the test runs in this series were made by placing the exothermic hot topping material on molten steel as in Examples 13-20 above and the temperatures of the reactions recorded by an optical pyrometer as above. The results are reported in Table ll-las follows.
• mill scale aluminum -Continued 307 raw fire clay 107: expanded perlitc tire-clay grog 3% graphite on the metal top than the pelletized mixtures used in Examples l-l l. Eliminating the pelletizing step however tends to increase the dust created when the exo thermic hot topping compound was handled.
• Examples I I I I 5 30-33 also employed the addition ofiron oxide (F8203) Furthermore, the mesh size of the m ll scale in this exf part or a" fth mil] Scale (F3304).
• the raw fire clay and bauxite 15 were calcined before use.
• the olivine was about 1OO EXAMPLE 29 mesh and composed of magnesium silicate and 7% iron
• the procedures of Example 28 were repeated except z'
• the g contlfmed allow l that a mesh size for the aluminum was about -30+150, was a out T 3 AS slerve y ij F; in other words the aluminum particles passed through 20 l i s can use a mesh screen and were retained on a 150 mesh t e OX1 a urt t Z naturfe'o screen.
• the hot topping composition of Example 29 Sl ag g ance lllsubsmut' had a reaction temperature of about 2950F and exhibhgher li re ractorly men materiel; oa a ited a faint trace of smoke comparable to the trace f zi l chun y or g i pm 15 amounts of the preceding examples.
• This example fur- 75 we or more easy remova Tom t 6 0t meta ther illustrates the wide latitude of mesh sizes for the EXAMPLES 4 4g oxidizer and the fuel for use in the hot topping compositions of this invention to achieve smokelessness.
• Example 43 the topping material smoked considerably under the conditions of test, whereas in Example 44, the coarser bauxite did not smoke.
• Example 47-48 even though the bauxite was ofa coarser grain size (16+80 mesh) with increasing amounts of aluminum from about 16 to 20% by weight in the presence of 40% mill scale the hot topping material developed considerable smoke and melted.
• the Ringelmann number smoke rating for Examples 47-48 was greater than 1, i.e., about 2 or more.
• the balance being predominantly composed of inert finely divided filler material, said oxide, fuel and inert material components proportioned to provide said smokeless composition.
• composition of claim 1 which has a Ringelmann number smoke rating of less than one.
• composition of claim 2'wherein said metal is iron or steel.
• composition of claim 11 wherein said oxide of iron is present in an amount of about 25% to about 45% by weight and said fuel is present in an amount to provide about 9% to about 13% by weight aluminum.
• composition ofclaim 5 wherein said inert material contains an insulating refractory material contains an insulating refractory material.
• composition of claim 7 wherein said insulating material is expanded perlite.
• composition of claim 1 as a hot topping for iron or steel.
• composition of claim lv wherein said filler material is a refractory material.
• composition of claim 11 wherein said refractory material is selected from the group consisting of raw fire clay, silica flour, silica sand. fire-clay grog, perlite, expanded perlite, olivine, and bauxite.
• composition of claim 1 wherein said inert filler material has an average grain size of about 1 2 to about +100 mesh. 7
• a smokeless exothermic hot topping composition for iron or steel consisting essentially of about to about 45% by weight finely divided mill scale, about 9% to about 13% by weight finely divided aluminum, and the balance being predominantly composed of inert refractory material, said mill. scale, aluminum and refractory material components proportioned to provide said smokeless composition.
• the composition of claim 14 which contains about 1% to about 4% by weight of graphite.
• composition of claim 14 which contains about 5% to about 15% perlite.
• composition of claim 14 which contains about 40% mill scale and about-12% aluminum.
• composition of claim 14 which produces no visible smoke during'reaction upon the surface of a molten metal.
• a smokeless exothermic hot topping composition for iron or steel having a Ringelmann number smoke rating of less than one which consists essentially of about 35-42% mill scale, about 11-13% aluminum, about 14% graphite and the balance inert refractory material.

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Citations (4)

• 1973
  • 1973-10-31 US US411401A patent/US3867155A/en not_active Expired - Lifetime
• 1974
  • 1974-10-09 GB GB43775/74A patent/GB1489600A/en not_active Expired
  • 1974-10-11 CA CA211,286A patent/CA1011948A/en not_active Expired
  • 1974-10-25 NO NO743855A patent/NO140548C/no unknown
  • 1974-10-28 FI FI3149/74A patent/FI314974A/fi unknown
  • 1974-10-30 DE DE19742451968 patent/DE2451968A1/de not_active Withdrawn
  • 1974-10-30 NL NL7414170A patent/NL7414170A/xx not_active Application Discontinuation
  • 1974-10-30 DK DK565474A patent/DK565474A/da not_active Application Discontinuation
  • 1974-10-30 FR FR7436351A patent/FR2249940B1/fr not_active Expired
  • 1974-10-30 SE SE7413639A patent/SE410285B/xx unknown
  • 1974-10-30 BR BR9096/74A patent/BR7409096A/pt unknown
  • 1974-10-30 JP JP49125320A patent/JPS5074525A/ja active Pending

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