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
  • B22D7/102—Hot tops therefor from refractorial material only

Definitions

• the present invention concerns casting metals in an ingot mold with the use of a so-called hot-top positioned on th.e mold to reduce pipe-formation in the solidified ingot.
• the present invention consists in a method of casting metal ingots comprising teeming the molten metal in an ingot mold with a hot-top, the hot-top having a metal inner wall which is thin co pared to the thickness of the mold wall and which is surrounded by a heat insulating barrier, the resulting thermal expansion of the hot-top forming a gap between the inner wall of the hot-top and the shell of solidified metal on the ingot without external manipulation.
• the invention in a second aspect consists in a hot-top for use with an ingot mold in the casting of metal ingots, the hot-top comprising a hollow body having a base adapted to be positioned at the upper end of an ingot mold and comprising an inner wall of heat conductive metal surrounded by a heat insulating barrier.
• the invention consists in the combination of a hot-top as set forth inbefore with an ingot mold, where- in the thickness of the inner wall of the hot-top is chosen in relation to the capacity of the ingot mold in such a manner as to prevent melting or fusion of the inner wall during casting molten material in the mold, and wherein the inner wall is thin compared to the thickness of the mold wall.
• the invention consists in an ingot mold comprising a hot-top, the hot-top having an inner wall which is thin compared to-the thickness of the mold wall and is made of heat conductive material having a higher melting point than the material of the mold wall, said inner wall being surrounded by a heat insulating barrier and being positioned inside the upper part of the ingot mold, the said heat insulating barrier being formed between said inner wall and the wall of the said upper part of the ingot mold.
• Figure 1 is a cross section through an ingot mold and an associated hot-top according to a first embodiment of the invention
• figure 2 is a cross section through an ingot mold with a hot-top according to another embodiment of the invention
• figure 3 is a cross section through an ingot mold with incor- porated hot-top according to still another embodiment of the invention.
• Figure 1 shows an ingot mold 1, a hot-top 2 and a cover plate 3 and is divided into two by a line A so that two stages of the casting process can be shown.
• the left hand side of the figure shows the mold just after molten metal 4 has been poured into the mold.
• the molten metal will normally be steel or iron, though non-ferrous metals may also be cast in a similar manner.
• the hot-top 2 has a metal inner wall 5 having a thickness which is small compared to that of the mold walls.
• the inner wall 5 is surrounded by a heat barrier 6 made from a (heat resistant) ceramic fiber material. It is essential that the thickness of the inner wall 5 be chosen in relation to the capacity of the mold 1 such that the wall will not melt or become fused with the poured molten metal.
• the inner wall 5 should have a melting point which is not more than 300 C below the casting temperature of the molten metal.
• the inner wall 5 may be 10 to 30 mm thick.
• a suitable metal is cast iron but of course the material of the inner v / all will depend on the metal being cast. As shown in figure 1 the hot-top tapers from its base to its open top which is closed by the top cover 3. This taper is not, however, essential.
• An additional heat barrier 9 is provided around the lower edge of the inner wall 5 to prevent heat transfer between the inner wall and the ingot mold. This additional heat barrier may not always be needed.
• the hot-top is surrounded by a metal head case 10 provided with lifting lugs by means of which the hot-top and head case can be mounted on or removed from the ingot mold.
• the metal may be poured either uphill or downhill.
• the cover plate 3 which may be as described in U.K. patent specification No. 1,496,348, is placed on the hot-top after pouring.
• FIG. 1 shows the molten metal immediately after teeming. Shortly after the poured metal contacts the inner wall 5 a thin outer layer or shell of solidified metal is formed on the poured metal due to heat being conducted away from the molten metal by the mold 1 and the inner wall 5 of the hot-top.
• the metal is then allöwed to cool until it is solid. This is the situation shown in the right hand side of figure 1.
• the hot-top 2 and the cover 3 re ain in position throughout the en- tire cooling process.
• the gap 7, together with the insulation provided by the heat barrier 6, ensure that the upper portion of the ingot does not cool too rapidly with respect to the re-mainder of the ingot. Furthermore, there is no need to intro- cute exothermic material into the gap 7 during cooling of the cast metal because of the thermal insulation provided by the gap 7 and heat barrier 6.
• the hot-top described is reusable and also avoids the necessity of Special Provision being made to move the hot-top mechanically during the casting Operation.
• the hot-top may be advantageous to position means for causing extra thermal expansion of the hot-top when it is heated during teeming.
• the sections of the hot-top may be separated by Strips of a material having a high degree of thermal expansion such as copper, or a bimetallic substance.
• the inner surface of the hot-top may be coated with a heat reflective or a parting agent.
• Figure 2 shows a hot-top positioned inside the upper part of an ingot mold 21.
• An inner wall part 51 rests on a shoulder
• the mold wall and is surrounded by a heat insulating barrier 61 corresponding to heat barrier 6 described above.
• the outer wall of the hot-top is constituted by the wall of the ingot mold itself, which leads to a simplified structure of the co-combination.
• a heat barrier " 91 can be inserted between the lower edge of wall 41 and the shoulder of the ingot mold.
• the wall part 51 of the hot-top is made of a material such as steel hav ⁇ ing a higher melting point than the material of the input mold itself which is generally cast-iron.
• Figure 3 shows an embodiment si ilar to that of figure 2 where ⁇ in an inner wall part 52 has a base part 53 which is incorporating in the wall of the ingot mold 22.
• the inner wall of the hot-top is maintained at its lower edge in a given position with respect to the ingot mold, but its upper edge can expand to achieve the desired effect.
• a heat barrier 62 is again inserted between the ingot mold wall and the inner wall part 52.
• the embodiment of figure 3 provides an ingot mold in which the hot-top wall is incorporated at the time of making the ingot mold itself and does therefore not require an additional manufacturing step.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Continuous Casting (AREA)
• Molds, Cores, And Manufacturing Methods Thereof (AREA)
• Casting Support Devices, Ladles, And Melt Control Thereby (AREA)
• Cooling Or The Like Of Semiconductors Or Solid State Devices (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

Family

ID=9787080

Family Applications (1)

Country Status (8)

Cited By (2)

Families Citing this family (1)

Citations (4)

Family Cites Families (2)

• 1978
  • 1978-02-07 GB GB4957/78A patent/GB1595737A/en not_active Expired
• 1979
  • 1979-01-25 JP JP50037179A patent/JPS55500084A/ja active Pending
  • 1979-01-25 BR BR7906448A patent/BR7906448A/pt unknown
  • 1979-01-25 DE DE792934887T patent/DE2934887T1/de active Granted
  • 1979-01-25 WO PCT/EP1979/000003 patent/WO1979000596A1/de unknown
  • 1979-08-28 EP EP79900170A patent/EP0009028A1/en not_active Withdrawn
  • 1979-10-05 SE SE7908283A patent/SE431833B/sv not_active IP Right Cessation
• 1980
  • 1980-04-24 FR FR8009293A patent/FR2448951A1/fr active Granted

Patent Citations (4)

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