Metallurgical apparatus – Means sealing or opening aperture in vessel – By means plugging aperture
Patent
1994-03-23
1995-09-19
Andrews, Melvyn
Metallurgical apparatus
Means sealing or opening aperture in vessel
By means plugging aperture
222597, 29508, 29515, 29516, C21C 546
Patent
active
054510368
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a so-called dart, as used in the metallurgical industry in the tapping of furnaces to control, or preclude, slag exit and hence slag contamination of the steel etc. being cast.
Conventional darts consist basically of a head and an attached tail, the head being an enlarged body of refractory material and the tail being a relatively slender, elongate member, e.g. of 1 m length, with at least a portion of the tail extending below the head and being adapted to engage in the tap hole of the furnace, the head acting in effect as a float valve member and eventually closing off the tap hole as the level of the melt falls, to prevent slag exiting via the tap hole.
Conventionally, the head and tail of a dart are supplied as two separate components and are either assembled on site, or alternatively are assembled elsewhere and delivered as a single, assembled unit, although the latter arrangement creates problems with regard to packaging and transport.
In one known construction, the tail consists of a refractory concrete sleeve surrounding, and keyed to, a central reinforcing bar, the latter protruding from the upper end of the sleeve for engagement by a gripper of a lifting and lowering mechanism, and having--towards what in use is its upper end--a shoulder on which the body is adapted to be seated and there secured by air setting cement. Care must be taken to ensure that no excessive cement is used, and furthermore, a hardwood wedge must firstly be cut and then hammered into a gap at the side of the reinforcing bar, but not to an extent that would over-stress the body and result in cracking.
In another known construction, the protruding upward end of the reinforcing bar is screw threaded, being passed through, and projecting beyond, a central hole of the head, with the latter seating on the upper end of the dart, and with the head being secured in position on the tail by a nut applied to the threaded projection.
Clearly, the above operations require a relatively skilled operator, is time consuming, and despite the care being taken in assembly, sometimes results in a damaged dart and hence the production of a scrap dart as the tail is relatively fragile, despite the presence of the reinforcing bar.
The basic object of the invention is to provide an improved dart, and an improved method of dart assembly, compared with prior art proposals.
According to a first aspect of the present invention, there is provided a metallurgical dart comprising: through hole extending from top to bottom of the head and lined with a metallic sleeve, with a portion of the lining sleeve projecting beyond the top and/or bottom of the head; internal metallic element and of external diameter slightly less than the internal diameter of the lining sleeve, such that the tail can pass, as a close fit, through the lining sleeve of the head; and element of the tail and the projecting portion of the lining sleeve, to fix the head and tail together.
According to a second aspect of the invention of independent significance, there is provided a method of assembling a two-part metallurgical dart comprising an enlarged head having a metallic element, and an elongate tail also having a metallic element, wherein two metallic elements are brought into close proximity and a crimped or other deformed metal joint is formed between them.
Preferably, the head also has a through hole, wherein the tail is inserted through the hole of the head, or alternatively the head is passed along the tail, and thereafter the crimped or other deformed metal fixing joint is made between the two metallic elements.
The invention also includes a metallurgical dart assembled by these methods.
Thus, with the dart in accordance with the invention, a substantially simplified assembly operation is possible, resulting not only in more rapid assembly but in minimized risk of failures, with attendant cost savings. Furthermore, as the tail, or at least a portion of the tail, passes completely through the head, the latter may be fixed at a selected location along the
REFERENCES:
patent: 4399986 (1983-08-01), Collins
patent: 4709903 (1987-12-01), LaBate
Andrews Melvyn
Monocon International Limited
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