Classifications

• • 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

• the wall material is made from a mixture of granular or powdered aerated concrete or porous concrete and organic fibre material such as Wood meal, sawdust, mechanical wood pulp and a binder, and according to the invention the mixture also comprises sand of such a rate of refractability that the melting temperature of the sand is lower than the temperature of the molten metal, said sand, under the influence of the heat from the molten metal, providing a thin vitreous mineralic layer.
• This invention relates to hot tops for casting steel and to a Wall material particularly suited to such hot tops.
• hot tops from exothermic, combustible, ceramic and refractory material. Furthermore, it is known to manufacture hot tops from porous insulating materials such as aerated concrete, kieselguhr, asbestos or vermiculite and to provide these hot tops, on the side facing the steel or metal, with a surface layer of refractory material such as chamotte meal, quartzite powder or dolomite powder.
• molten steel when tapped into the chill has a temperature of between -1600" C. it is natural that in constructing hot tops an effort should be made to use material having as high a melting point as possible in order to prevent the material of the hot top from melting. For this reason refractory material such as quartzite powder, dolomite powder, etc., is often used.
• the basic idea of the invention is to provide a wall material for the hot top having such a composition that the surface contacting the molten steel or other metal will be covered with a smooth, gastight, thin vitreous mineralic layer when contacting the molten steel or metal.
• the wall material of the hot top is made from a mixture of granular or powdered aerated concrete or porous concrete and organic fibre material such as wood meal, sawdust, mechanical wood pulp and a binder, and according to the invention the mixture also comprises sand of such a rate of refractability that melting temperature of the sand is lower than the temperature of the molten metal, said sand, under the influence of the heat from the molten metal, will define a thin vitrous, mineralic layer.
• the sand may, for example contain felspar, preferably having finer particles than the aerated concrete.
• the upper limit of the melting temperature or melting temperature interval of the steel is 1570-1610 C.
• the liquidus temperature (melting temperature interval) of the steel may vary, for example, between 1450 and 1550 C.
• the melting temperature of the sand should be lower than this lquidus temperature or melting temperature interval.
• the melting process is limited to a thin zone since the vitreous mineralic layer contains a large number of porous relatively coarse concrete particles which render the vitreous layer extremely heat-insulating and since a large number of such coarser, unmelted grains of porous concrete in the vitreous layer will cause the melting point of the vitreous layer to be much higher than the average analysis of the ceramics would in fact indicate.
• the vitreous layer will protect the steel or metal against carburization and other impurities and will impart a smooth surface to the hot top and the billet. Normally no remnants of the hot top will stick to the resultant smooth casting or billet surface. The heat radiation from the smooth surface will also become less than from the normal, somewhat rough surface.
• Suitable particle sizes are, for non-refractory sand of the kind now defined, max. 1.5 mm. and at least lower than 0.5 mm. and for porous concrete max. 6 mm. and at least 80% lower than 3 mm.
• the particle size of the porous concrete exceeds that of the sand.
• the ratio by weight between sand and porous concrete should be between 1:2 and 4:1, suitably 2:1.
• the best quantity of sawdust or other organic fibre material is between 5-10% by weight.
• the binder should be of organic nature.
• An extremely suitable binder is an emulsion of polyvinyl acetate. It can be used alone, but can also very well be combined with dextrine, molasses, sulphite lye, core oil and phenolic resins.
• Hot tops made in one integral piece or in the form of slabs of this material can be manufactured by mixing the dry materials with binder in conventional way and then pressing the mixture in moulds. The material is then allowed to dry in a drying furnace at 200 C. It is possible to produce hot top material having a low volume weight as low as 0.7-0.8 g./cm. which means an extremely high insulating capacity.
• Wall material for hot tops for chill casting of steel or other metal comprising a mixture of granular and powdered porous concrete having a particle size not exceeding about 6 mm., at least one of a group of organic fibre materials selected from wood meal, sawdust and mechanical wood pulp, a binder for said organic fibre material comprising an emulsion of polyvinyl acetate, and sand having a particle size not exceeding about 0.5 mm., said organic fibre material comprising between 5% and 10% by weight of the entire mixture, the ratio by weight of sand to porous concrete being between 1:2 and 4:1, the ratio of refractability of said sand being such that the melting temperature of the sand is lower than the temperature of the molten metal, said sand, under the influence of heat from the molten metal, providing a thin vitreous, mineralic layer at the surface of the wall material contacting the molten metal.
• said binder consists of an emulsion of polyvinyl acetate combined with an element from the group consisting of dextrine, molasses, sulphitic lye, core oil and phenolic resin.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Moulds, Cores, Or Mandrels (AREA)
• Curing Cements, Concrete, And Artificial Stone (AREA)
• Mold Materials And Core Materials (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=20257999

Family Applications (1)

Country Status (5)

Cited By (1)

Families Citing this family (2)

• 1970
  • 1970-02-02 SE SE01322/70A patent/SE352256B/xx unknown
• 1971
  • 1971-01-22 DE DE19712103028 patent/DE2103028A1/de active Pending
  • 1971-01-25 US US109647A patent/US3706682A/en not_active Expired - Lifetime
  • 1971-02-02 FR FR7103414A patent/FR2080948B3/fr not_active Expired
  • 1971-04-19 GB GB2014271A patent/GB1304982A/en not_active Expired

Also Published As

Similar Documents