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

Definitions

• This invention relates to compositions for use in pouring molten metals, particularly to the casting of ferrous ingots.
• a principal aim of casting pit practice is to produce ingots which have a minimum of surface and internal d fects, such as cavities or inclusions.
• the former may be avoided, as is well known, by correct hot topping procedures.
• the removal of both surface and internal inclusions is still a major problem.
• the amount of inclusion depends on many factors, and much attention is at present paid to correct teeming speeds and temperatures, teeming nozzle diameters, and the correct use of suitable coatings on the internal walls of the mould.
• slag cover provides an insulating cover to the ingot and accordingly a reduction in the quantity of anti-piping insulation required.
• Such slags as are used for bottom pouring are, however, unsuitable for top pouring since their viscosity is too high and only partial melting occurs at steel making temperatures.
• a suitable material for top pouring must have a low viscosity and a low melting point.
• the alkali and alkaline earth metal fluorides have these properties.
• a process for the production of steel ingots which comprises top-pouring molten steel through a flux composition comprising one or more fluorides and one or more alkali metal carbonates.
• Preferred fluorides are alkaline earth metal fluorides, notably calcium fluoride, possibly in admixture with only minor proportions of sodium aluminum fluoride (cryolite) or alkali metal fluorides in order to reduce fume to a minimum. These have melting points about 200 C. below steel making temperatures, and are thus very fluid at such temperatures. They also dissolve silica, alumina and manganese dioxide (common deoxidation products in steel) at this temperature, and on cooling a solid solution is formed, rather than the dissolved matter coming out of solution.
• alkali metal carbonates sodium carbonate is preferred.
• the flux compositions may contain other ingredients for special purposes.
• the inclusion is the flux of anthracene or other polynuclear aromatic compound (e.g. naphthalene, acenaphthene, diphenyl, diphenylmethane, indene, fluorene, or phenanthrene.
• anthracene or other polynuclear aromatic compound e.g. naphthalene, acenaphthene, diphenyl, diphenylmethane, indene, fluorene, or phenanthrene.
• anthracene or other polynuclear aromatic compound has two important advantages. First its combustion leads to a reducing atmosphere over the molten metal, which protects the metal stream. In addition, anthracene vapour sublines on the cold walls of the mould, ahead of the rising metal surface. If any splashes of molten metal impinge on the mould wall, they do not remain there to form scabs on the side of the finished ingot, but are blown off the wall by the immediate volatilisation of the anthracene on the wall. This leads to a much improved surface finish.
• the surface quality is further improved by the presence of the fluid flux.
• the flux runs into and fills any imperfections such as cracks, or crazing in the mould walls, which prevents the metal entering into such cracks.
• the fume level of the composition of the present invention is sufliciently low to allow normal foundry use.
• compositions are preferably applied in powdered form. It has been found that pelleted material, though effective, sometimes tends to become undesirably trapped in the molten metal.
• Preferred flux compositions for use in the process of the present invention include the following ingredients in the proportions by Weight indicated:
• Percent Alkaline earth metal fluorodie 25-90 Alkali metal carbonate 1-30 Alkali metal fluoride or complex fluoride 0-10 3 Percent Anthracene or other polynuclear aromatic compound -20 Calcium oxide 0-35 Ferrosilicon 0-20
• All parts and percentages are by weight.
• the method of the invention may of course be employed in continuous casting, giving cast strands of improved quality.
• a process for the production of steel ingots comprising the steps of top-pouring molten steel into an ingot mould through a flux composition, said flux composition including at least one fluoride, at least one alkali metal carbonate, and a polynuclear aromatic compound, and subsequently allowing the poured molten steel to solidify in the ingot mould.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Continuous Casting (AREA)
• Curing Cements, Concrete, And Artificial Stone (AREA)
• Treatment Of Steel In Its Molten State (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=10389819

Family Applications (1)

Country Status (5)

Cited By (12)

• 1966
  • 1966-08-16 GB GB36626/66A patent/GB1156845A/en not_active Expired
• 1967
  • 1967-07-31 US US657063A patent/US3567432A/en not_active Expired - Lifetime
  • 1967-08-04 BR BR191855/67A patent/BR6791855D0/pt unknown
  • 1967-08-14 SE SE11450/67A patent/SE333042B/xx unknown
  • 1967-08-16 JP JP42052266A patent/JPS524253B1/ja active Pending

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