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 flax 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.
• 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 know as "expandable graphite" in place of a portion of the carbon component of a standard bottom pour flux.
• the resulting mixtur 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 ingo 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.
• composition of a traditional bottom pour flux may comprise the following:
• 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. Due to the expansion of the steel while molten, this discrepancy leaves the sides too high in respect to the core. Thus, without proper insulation, the center of the steel ingot will solidify in a sunken position or with severe imperfections — creating an entire segment of the ingot which must be excised and discarded. To accomplish the necessary insulation, a wide variety of compositions have been utilized. Typical ranges are as follows: Constituent Percentage ( % ) Range by wen-m
• Expandable graphite is produced through treatment of high grade natural crystalline graphite through oxidation or electrolysis by various oxidizing 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.
• Iron Oxide (Fe2 ⁇ 3. 4.0 - 6.0
• the present invention is prepared in the same manner as standard bottom pour flux.
• 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)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

Family

ID=25405572

Family Applications (1)

Country Status (9)

Cited By (1)

Families Citing this family (3)

Citations (2)

Family Cites Families (3)

• 1987
  • 1987-08-10 AU AU78567/87A patent/AU604503B2/en not_active Ceased
  • 1987-08-10 EP EP87905525A patent/EP0321478B1/de not_active Expired - Lifetime
  • 1987-08-10 BR BR8707766A patent/BR8707766A/pt not_active Application Discontinuation
  • 1987-08-10 DE DE3788067T patent/DE3788067T2/de not_active Expired - Fee Related
  • 1987-08-10 WO PCT/US1987/001958 patent/WO1988001210A1/en active IP Right Grant
  • 1987-08-10 JP JP62505033A patent/JPH01501536A/ja active Pending
  • 1987-08-12 CA CA000544344A patent/CA1285461C/en not_active Expired - Fee Related
  • 1987-08-18 MX MX007790A patent/MX169019B/es unknown
• 1988
  • 1988-04-13 KR KR1019880700405A patent/KR880701599A/ko not_active Application Discontinuation

Patent Citations (2)

Non-Patent Citations (1)

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