GB2034215A

GB2034215A - Mold for Continuous Casting

Info

Publication number: GB2034215A
Application number: GB7901566A
Authority: GB
Original assignee: Timex Corp
Current assignee: Timex Group USA Inc
Priority date: 1978-11-13
Filing date: 1979-01-16
Publication date: 1980-06-04
Also published as: FR2441447A1; FR2441447B3; JPS5568158A; DE2945577A1; GB2034215B; CH642575A5

Abstract

A continuous casting mold 2, e.g. of graphite, includes an inner mold body 4 having a longitudinal solidification chamber 16 therethrough, an intermediate mold body 6 surrounding and spaced from the inner mold body 4 to define an annular cooling chamber 10 therebetween and an outer mold body 8 surrounding and spaced from the intermediate mold body 6 to define an annular manifold chamber 12 therebetween communicating by a ring of radial apertures 20 with the chamber 10. Coolant such as gaseous or liquid nitrogen or liquid helium or carbon dioxide, enters the manifold chamber 12 through an opening 18 or 18'. If liquid, the coolant vaporizes so that it passes as gas into the chamber 10 to cool the mold body 4. A water cooled graphite body may be used for secondary cooling of the emerging cast product. <IMAGE>

Description

SPECIFICATION Mold for Continuous Casting.

The present invention relates to the continuous casting of metals and, more particularly, to molds and cooling techniques for use in such processes.

Continuous casting of both ferrous and nonferrous metals and alloys is a well known technique in the metallurgical are, for example, as represented by the Rossi et al patent, U.S.

3,399,716 issued September 3, 1968, among many others. Of course, in such a dynamic process which transforms hot molten metal into a solid metal shape, the mold in which solidification occurs plays an extremely important part in the process. In the continuous casting of ferrous alloys, watercooled copper molds have been successfully utilized. On the other hand, for non ferrous metals and alloys such as copper and its alloys and aluminum and its alloys, water-cooled graphite molds have found widespread use, for example, as represented by the Kolle patent, U.S.

3,592,259 issued December 10, 1971. As further illustrated in the Woodburn patent, U.S.

3,459,255 issued August 5,1 969, and the Adamec et al patent, U.S. 3,592,259 issued December 10, 1971. As further illustrated in the Woodburn patent, U.S. 3,590,904 issued July 6, 1 971, water-cooled graphite molds have also been utilized in casting slabs or ingots of metals and alloys in a noncontinuous manner.

In the continuous casting of nonferrous metals, particularly brass and aluminum, in water-cooled graphite molds, there are two serious explosion hazards. The first involves the possibility of contact between the water coolant circulating inside the mold and hot molten metal as a result of leaks and the like. The second involves a graphite steam reaction which generates explosive hydrogen gas as a reaction product. The graphite steam reaction may occur when excessive water contacts the graphite at temperatures around 10000--1 1000C. In the aforementioned Kolle patent, the exposed surfaces of the graphite mold are coated with a thin layer of silver to help avoid conditions conducive to these hazards. The coating is particularly essential when a low density graphite is employed as the mold material.

The present invention provides an improved mold for continuously casting molten metal and for overcoming the disadvantageous explosion hazards associated with the prior art. The improved mold is especially constructed for use with a coolant which is nonreactive with most any molten metal and mold material, including graphite.

Typically, the mold of the invention includes an inner mold body having a longitudinal solidification chamber therethrough with an inlet end for receiving molten metal and an outlet end through which solidified metal exits, an intermediate mold body surrounding and spaced from the inner mold body to define an annular cooling chamber therebetween along the length of the mold and an outer mold body surrounding and spaced from the intermediate mold body to define an annular manifold chamber therebetween. Preferably, the mold bodies comprise tubular graphite members of increasing diameter in concentric relationship to one another. The outer mold body preferably includes access means providing entry into the manifold chamber for a coolant which is nonreactive with the molten metal and mold, liquid or gaseous nitrogen being the preferred coolant.The intermediate mold body includes coolant access means adjacent one end of the mold, preferably the inlet end thereof, and coolant discharge means at the other end, preferably at the outlet end, the coolant access means being spaced about the periphery of the inner mold body for admitting coolant from the manifold chamber into the cooling chamber substantially uniformly around the inner mold body. In this way, the coolant enters the cooling chamber at one end of the mold and flows around and along the length of the inner mold body to the other end where it is exhausted from the chamber. The coolant absorbs heat from the inner mold body and solidifying metal therein without the risk of explosion hazards resulting from the coolant contacting the molten metal or from the coolant reacting with the mold itself.

In a preferred embodiment of the invention for use with a vaporizable coolant the intermediate and outer mold bodies define an annular manifold and vaporizer chamber therebetween along the length of the mold. Liquid nitrogen coolant is preferably introduced into this chamber adjacent the outlet end of the mold and vaporized as it flows toward the inlet end where it enters the cooling chamber via coolant gas access means associated with the intermediate mold body. After flowing around the inner mold body along the length of the mold, the vaporized nitrogen coolant is exhausted from the cooling chamber by coolant gas discharge means adjacent the outlet end.

An embodiment of the invention is shown by way of example in the accompanying drawings and will now be described, In the drawings.

Fig. 1 is a cross-sectional view through the longitudinal axis of a mold of the invention.

Fig. 2 is a cross-sectional view along line A-A of Fig. 1 showing coolant access ports in the intermediate mold body.

A typical mold of the invention is illustrated in cross-section in Fig. 1 Although graphite is a preferred material for the mold, other refractory materials will of course be usable and can be selected as desired depending upon the nature of the metal or alloy to be cast among other factors.

The graphite mold described more fully hereinbelow has proved especially satisfactory in continuously casting leaded brass (60w/oCu,40w/o ZN, 2w/o Pb) having a soldification temperature of about 8700--8800C.

The mold 2 includes an inner mold body 4, intermediate mold body 6, and outer mold body 8 in the form of concentric graphite tubes. As shown, the intermediate mold body surrounds and is laterally spaced from the inner mold body to define an annular cooling chamber 10 therebetween along the length of the mold whereas the outer mold body is in the same relationship to the intermediate mold body to define an annular manifold chamber 12 therebetween along the length of the mold.

Annular graphite end caps 1 4a and 1 4b not only seal the ends of the graphite tubes but also serve as spacers to maintain the desired separation between the tubes. The inner mold tube 4 includes an internal wail 4a which defines a cylindrical solidification chamber 1 6 longitudinally therethrough having an inlet end 1 6a for connection to the discharge nozzle of a conventional crucible (not shown) or other vessel containing molten metal to be continuously cast and an outlet end 1 6b through which the solidified product exits.

As shown in Fig. 1, outer graphite tube 8 includes an aperture 1 8 or other coolant access means through which a vaporizable coolant which is nonreactive with the molten metal or mold can be introduced into the manifold chamber 12 adjacent the outlet end of the mold. As mentioned, liquified nitrogen is a preferred coolant exhibiting the required nonreactivity. Of course, the liquified nitrogen coolant can be obtained from a conventional storage cylinder and introduced under pressure into chamber 12 via suitable pressure fittings (not shown). When liquified nitrogen or other vaporizable coolants are employed with the mold, the manifold chamber 12 also functions as a vaporizer chamber in the following manner.As indicated by the arrows, the liquified nitrogen flows from near the outlet end 1 6b of the mold 2 toward the inlet end 1 6a along the length of the manifold and vaporizer chamber 12. During this longitudinal flow, the nitrogen absorbs sufficient heat from the intermediate and outer mold bodies to vaporize by the time it reaches the vicinity of the inlet end 1 6a. Typically, upon vaporization in chamber 12, the nitrogen expands in volume in the ratio of approximately 1 to 800. The vaporized nitrogen then flows into the cooling chamber 10 via a plurality of spaced, radial apertures 20, Fig. 2, adjacent the inlet end where molten metal enters the mold. Apertures 20 or other coolant access means are spaced around the circumference of the inner graphite tube 4 as shown to provide uniform flow of coolant therearound.Inner graphite tube 4 is provided adjacent its outlet 16b with coolant gas discharge aperture 22 or other discharge means for exhausting the vaporized nitrogen from the cooling chamber 10 after it flows along the length thereof. Of course, flow of the vaporized nitrogen from the inlet end to the outlet end of the mold in the cooling chamber 12 effects considerable heat removal from the inner graphite tube 4 and solidifying metal therein.

Aithough liquified nitrogen has been described as the coolant in the detailed embodiment of the invention, it will be apparent that other coolants such as liquified helium, liquified carbon dioxide and others may also find use in the invention.

However, it is not essential that nitrogen or any other coolant be introduced into annular chamber 12 in liquified form, although this is preferred. For example, gaseous nitrogen has been injected into manifold chamber 12, through apertures 20 and then through cooling chamber 10 for cooling purposes and produced satisfactory results in terms of effecting solidification of the molten metal in solidification chamber 1 6. Since the metal is solidified and substantially cooled in the mold 2, it is possible to further cool the solidified product exiting outlet end 1 6b by means of a water-cooled secondary graphite mold. A watercooled mold may be used for the purpose without risk of explosion since the metal is already solidified.

Of course, other modifications to the preferred embodiment can also be made and will be apparent to those skilled in the art. For example, the coolant access aperture 1 8 through the outer mold body may be positioned nearer to the inlet end 1 6a of the mold body as indicated by the dashed lines 18'. In addition, the shape of the mold bodies 4, 6 and 8 may be other than tubular and the cross-sectional shape of the solidification chamber can be varied to produce most any desired product shape. It is intended to cover these and other modification which will occur to those skilled in the art in the claims appended hereto.

Claims

Claims.

1. A mold for continuously casting molten metal, comprising: a) an inner mold body having a longitudinal solidification chamber therethrough with an inlet end for receiving molten metal and an outlet end through which solidified metal exits; b) in intermediate mold body laterally surrounding and spaced from the inner mold body to define an annular cooling chamber therebetween along the length of said inner and intermediate mold bodies; c) an outer mold body laterally surrounding and spaced from the intermediate mold body to define an annular manifold chamber therebetween along the length of said intermediate and outer mold bodies;; d) at least one of said intermediate and outer mold bodies including first coolant access means providing entry for coolant into said manifold chamber, said intermediate mold body including second coolant access means adjacent one end of the mold and spaced around the periphery of the inner mold body for admitting coolant from said manifold chamber into the annular cooling chamber substantially uniformly around said inner mold body and coolant discharge means adjacent the other end of said mold, whereby coolant can flow along the length of the cooling chamber around the inner mold body from one end thereof to the other, absorbing heat from said inner mold body as it flows through said cooling chamber, and then can be exhausted from said cooling chamber through said coolant discharge means.

2. The mold of claim 1 wherein said inner mold body, intermediate mold body and outer mold body comprise tubular members of increasing diameter concentrically disposed relative to one another.

3. The mold of claim 1 wherein said second coolant access means comprises a plurality of access ports through the intermediate mold body connecting the manifold chamber to the cooling chamber, the access ports being spaced uniformly around the periphery of the inner mold body.

4. The mold of claim 1 wherein said coolant discharge means includes an exit port through the intermediate mold body and outer mold body connecting the cooling chamber to the outside atmosphere.

5. The mold of claim 1 wherein the second coolant access means for admitting coolant into the cooling chamber is disposed adjacent the inlet end of the mold and the coolant discharge means is disposed adjacent the outlet end of the mold.

6. A continuous casting mold adapted for use with a vaporizable liquid coolant which is nonreactive with the metal being solidified or with the mold, comprising: a) an inner mold body having a longitudinal solidification chamber therethrough with an inlet end for receiving molten metal and an outlet end through which solidified metal exits; b) an intermediate mold body laterally surrounding and spaced from the inner mold body to define an annular cooling chamber therebetween along the length of said inner and intermediate mold bodies; c) an outer mold body laterally surrounding and spaced from the intermediate mold body to define an annular manifold and vaporizer chamber therebetween along the length of said intermediate and outer mold bodies;; d) at least one of said intermediate and outer mold bodies including liquid coolant access means in the vicinity of the outlet end of the mold providing entry for the vaporizable coolant into said manifold and vaporizer chamber through which the coolant flows toward the inlet end of the mold and is vaporized as it travels therethrough, said intermediate mold body including coolant gas access means adjacent the inlet end of the mold for admitting the vaporized coolant from said manifold and vaporizer chamber into the annular cooling chamber around said inner mold body and coolant gas discharge means adjacent the outlet end of the mold, whereby the vaporized coolant can flow along the length of the cooling chamber around the inner mold body from the inlet end to the outlet end thereof, absorbing heat from said inner mold body, and then can be exhausted from the cooling chamber through said gas discharge means.

7. The mold of claim 6 wherein said inner mold body, intermediate mold body and outer mold body comprise tubular members of increasing diameter disposed concentrically relative to one another.

8. The mold of claim 6 wherein said coolant gas access means includes a plurality of access ports through the intermediate mold body connecting the manifold chamber to the cooling chamber, the access ports being spaced uniformly around the periphery of the inner mold body.

9. The mold of claim 6 wherein said coolant gas discharge means includes an exit port through the intermediate and outer mold bodies connecting the cooling chamber to the outside atmosphere.

10. A continuous casting mold substantially as hereinbefore described with reference to the accompanying drawings.