Metal founding – Process – Shaping liquid metal against a forming surface
Reexamination Certificate
2000-04-26
2001-11-06
Dunn, Tom (Department: 1725)
Metal founding
Process
Shaping liquid metal against a forming surface
C164S444000
Reexamination Certificate
active
06311762
ABSTRACT:
TECHNICAL FIELD
The present invention relates to the hot-top continuous casting of metals, particularly steel. It relates more especially to the constituent components of the mould, their relative positioning having to be meticulously adjusted during set-up of the assembly.
BACKGROUND OF THE ART
Hot-top continuous casting may be seen as a development of conventional continuous casting, which is manifested by the fact that the meniscus (free surface of the cast metal) is pushed back upwards with respect to the level where the solidification of the metal against the cooled copper of the mould is initiated, whereas these two levels are virtually coincident in conventional continuous casting. This novel arrangement is obtained by placing, on the cooled copper part of the mould, a contiguous feed head made of thermally insulating refractory material, intended to contain the cast liquid metal and on the wall of which feed head any corresponding spurious solidification must be avoided. Consequently, the solidification of the cast metal can start correctly on the upper edge of this copper part. For this reason an inert gas (argon, for example) is injected along the first inner perimeter of the mould between the copper part and the feed head, in the form of jets intended to shear any undesirable solidified film which would have a tendency to be already formed in contact with the refractory feed head. This type of arrangement is described in document FR-A-2,703,609, the content of which is incorporated into the present specification by way of reference.
As taught by Patent Application FR-A-2,747,061, it is therefore advantageous for the bottom of the feed head to consist of a part made of a dense refractory having good mechanical strength, such as Sialon®. This part acts as a transition region between the cooled copper of the mould and the thermally insulating fibrous refractory of the feed head placed above it, which would degrade too rapidly if it were placed directly in contact with the upper edge of the cooled copper body, at the point where definite solidification of the cast metal starts. On the other hand, the risk of spurious premature solidification on this intermediate part is increased, but remains of no consequence because of the shearing gas blown into the interface with the copper, which interrupts the downward propagation of this undesirable process.
The stream of shearing gas is injected via a thin slot (a few tenths of a millimetre barely suffice), which is produced by compressing a bead of fibrous refractory material placed between the Sialon insert and the copper body of the mould. Using clamping means, the bead is compressed until the desired slot thickness is obtained, this being calibrated using controlled shims.
However, it proves to be necessary for correct execution of the casting process for there to be uniform distribution of the flow of gas around the inner perimeter of the mould. Now, despite every care that may be taken in controlling the slot thickness “when cold” (in the absence of cast metal), this good linear distribution is not in general correctly provided. Moreover, account cannot be taken of local disparities in the pressure drop at the copper/refractory interface, which disparities are associated, inter alia, with local variations in the microroughness of the two facing surfaces which define the injection slot. Furthermore, there is even less uniformity when operating “hot” (in the presence of cast metal) because of the phenomena of differential expansion of the materials involved.
SUMMARY OF THE INVENTION
The object of the present invention is to allow uniform linear distribution of the flow of shearing gas injected into the “refractory feed head/cooled metal body of the mould” interface by dispensing with having to adjust the thickness of the injection slot, and preserving this uniform distribution “when hot”.
With this objective in mind, the subject of the invention is a process for adjusting the injection, during casting, of a fluid through an injection slot made at the “cooled metal body/refractory feed head” interface of a mould for the hot-top continuous casting of metals and emerging on the inner perimeter of this mould, the latter being provided with means for locally adjusting the thickness of the slot, which process is characterized in that, outside casting periods, an inflammable fluid is injected through the said slot, the fluid being ignited as it leaves the slot, and in that the said adjustment means are acted upon in such a way that the height of the flames leaving the slot is approximately constant around the inner perimeter of the mould.
As will have been understood, the basic idea behind the invention is that it is no longer a question of seeking to have a uniform slot thickness over the entire shearing-gas injection perimeter, but to have a uniform distribution of the flow of gas around this perimeter, this being manifested by a curtain of flames whose height at any point is adjusted.
The subject of the invention is also a device for implementing the process and intended for a mould for the hot-top continuous casting of metals having, made at the “cooled metal body/refractory feed head” interface, a slot for injecting a fluid which emerges around the inner perimeter of the mould, which device is characterized in that it comprises:
a line for feeding a fluid into the said injection slot, provided with a flow-regulating valve and with a supply selector which can be connected to the outlet of different fluid-supply sources; and
elastic-clamping means making it possible to adjust the width of the injection slot around the inner perimeter of the mould.
REFERENCES:
patent: 4157728 (1979-06-01), Mitamura et la.
patent: 5325910 (1994-07-01), Schneider et al.
patent: 5676195 (1997-10-01), Vassilicos
patent: 5743323 (1998-04-01), Ohguro et al.
patent: 0 620 062-A1 (1994-10-01), None
patent: 2 703 609 (1994-10-01), None
Edouard Weisseldinger
Perrin Eric
Salaris Cosimo
Ascometal
Dunn Tom
Tran Lee
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