EP0151723B1 - Means for introducing metal in a continuous vertical casting plant for casting metal tubes, in particular from cast iron - Google Patents

Abstract

In the continuous ascending vertical casting of an iron tube T without the use of a core to form the hollow tube interior, the molten iron is contained in a crucible made up of a cooled tubular die 6, 7 and the base 1 of a syphon unit. The crucible comprises a coaxial central form 5 at least as high as the die, which creates with the latter an annular space for molten iron F. Such arrangement reduces the volume of molten iron in the crucible and thus results in considerable energy savings.

Description

The present invention relates to the vertical upward continuous casting of a metal tube, in particular of cast iron, without the use of a core for the formation of the cavity of the barrel of the tube.

The invention relates more precisely to a device for supplying liquid metal to a tubular die giving the external shape of such a tube either from a siphon block (source supply) or from a ladle under gas pressure (low pressure casting, with liquid metal rising in the mold).

In a known installation of this type, described for example in the patent application in FRANCE No. 83 11 788 of July 12, 1983 the tubular die of vertical axis forms with a support base which constitutes the bottom a crucible for the metal liquid brought in from below, either by siphon block or by swelling bag.

Thus, the crucible formed by the tubular die and the support base contains a cylindrical volume of liquid metal, which is all the more important the larger the diameter of the tube to be obtained.

The US patent ― A ― 4. 355,680, on the basis of which the preamble of claim 1 is written, describes a crucible die inside which a coaxial body of revolution is disposed, but this body is less than that of the die and serves only overflow for the removal of impurities.

The Applicant has posed the problem of considerably reducing the volume of metal, in particular liquid cast iron to be brought to the lower end of the die in an installation for continuous upward casting of a tube, despite the absence of a core, therefore to achieve significant savings in liquid metal fusion energy, in particular in liquid iron.

The solution to the problem indicated is given by the characteristics mentioned in the characterizing part of claim 1.

Thanks to this arrangement, the crucible contains only a small annular volume of liquid metal whose annular width is much greater than the thickness of the tube to be obtained but whose total volume is considerably reduced compared to that which a crucible without of central relief.

In addition, according to another important characteristic of the invention, the central relief is hollowed out by a cavity which passes right through it, which allows access, by this cavity inside the tube being formed, to above the central relief, that is to say the possibility of introducing through this cavity of the central relief control tools, for example of liquid metal level of the thickness of the tube formed.

Other features and advantages will become apparent from the following description.

• - la Fig. 1 est une vue schématique en coupe du dispositif d'alimentation en métal liquide de l'invention, pour une installation de coulée continue d'un tube sand emboîtement,
• - la Fig. 2 est une vue partielle en coupe correspondant à la Fig. 1 illustrant l'emploi d'un mannequin ou faux tube pour débuter la coulée continue,
• - la Fig. 3 est une vue en coupe analogue à la Fig. 1 du dispositif de l'invention appliquée à la coulée continue d'un tuyau en fonte à emboîtement,
• - la Fig. 4 est une vue partielle en coupe correspondant à la Fig. 1, d'une variante de relief central de l'invention à cavité le traversant de part en part,
• - la Fig. 5 est une vue en coupe analogue à la Fig. 3 illustrant la coulée continue d'un tuyau à emboîtement avec alimentation ascendante en fonte liquide par une poche de coulée sous pression,
• - la Fig. 6 est une vue partielle analogue à la Fig. 5 montrant une variante d'alimentation en métal liquide à partir d'une poche de coulée sous pression.

In the accompanying drawings, given solely by way of example,

• - Fig. 1 is a schematic sectional view of the liquid metal supply device of the invention, for an installation for continuous casting of an interlocking sand tube,
• - Fig. 2 is a partial sectional view corresponding to FIG. 1 illustrating the use of a dummy or false tube to start continuous casting,
• - Fig. 3 is a sectional view similar to FIG. 1 of the device of the invention applied to the continuous casting of an interlocking cast iron pipe,
• - Fig. 4 is a partial sectional view corresponding to FIG. 1, of a variant of central relief of the invention with a cavity passing right through it,
• - Fig. 5 is a sectional view similar to FIG. 3 illustrating the continuous casting of an interlocking pipe with ascending supply of liquid iron by a pressure casting ladle,
• - Fig. 6 is a partial view similar to FIG. 5 showing a variant supply of liquid metal from a pressure casting ladle.

According to the execution example illustrated in FIGS. 1 and 2, the invention is applied to the continuous upward casting of a cast iron tube T.

• - Une alimentation en fonte liquide par bloc-siphon
• - Un creuset constitué par une filière tubulaire refroidie,
• - Un extracteur non représenté du tube formé.

This installation includes:

• - Liquid iron feed by siphon block
• - A crucible consisting of a cooled tubular die,
• - An extractor not shown from the formed tube.

1.) Liquid iron supply by siphon block:

A base 1, hollow, made of refractory material, for example of the silico-aluminous type, internally comprises an L-shaped pouring duct with horizontal or slightly oblique leg 2 and with vertical chimney 3 ending at its upper part by a pouring funnel 4 .

The base 1 of the siphon block forms a support base for a tubular die described below.

According to the invention, the siphon block carries a central relief 5 of frustoconical external shape with vertical axis XX, of high height above the base 1.

Other details on the relief 5 of the invention are given below.

2. The crucible cooled externally (the die):

In axis XX, the base 1 carries a crucible consisting of a tubular die comprising a graphite jacket 6, of axis XX, the inside diameter of which corresponds to the outside diameter of the tube T to be obtained and an envelope 7.

The jacket 6 is cooled externally by an envelope 7, for example made of copper, with circulation of cooling water which enters through a conduit 8 and leaves a conduit 9. The assembly "jacket 6 and envelope 7" is therefore designated below. after under the term of "sector 6-7".

While the graphite jacket 6 rests by its lower end edge on the base 1 of the siphon block, the cooling jacket 7, in contact with the jacket 6, the jacket over almost its entire height, except for the lower end of the jacket 6 which is not cooled. The cooling water jacket 7 is therefore not in direct contact with the base 1. Optionally, but not necessarily, a refractory annular spacer block can be interposed between the cooling jacket or cooling box 7 and the base 1.

The central relief 5 of the invention, which is an integral part of the siphon block 1,2,3,4 in the present example, is also part of the crucible formed by the combination of the siphon block and the die 6-7. The central relief 5 has a height above the base 1 which is at least equal to and preferably greater than the height of the die 6-7 above said base 1.

The frustoconical central relief 5 has a large base, below the support constituted by the base 1, of diameter substantially less than the internal diameter that one wants to obtain on the tube T to be formed. A fortiori, the small upper base of the central relief 5 has a diameter substantially smaller than that of the cavity of the tube to be obtained.

In the present example, the central relief 5 is hollowed out by a lightening cavity 10, for example of frustoconical shape. But such a recess is not compulsory.

The horizontal conduit 2 of the siphon block opens below the base 1, on the wall of a crucible bottom formed by the siphon block itself, so as to bring the liquid iron to the lower end of the die 6-7, below the lower end edge of the jacket 6.

The opening of the horizontal conduit 2 for supplying liquid metal has a diameter less than the width of the annular space between the large lower base of the central relief 5 and the cylindrical cavity of the die 6-7.

In the crucible of metal or liquid iron thus formed by the die 6-7 or the jacket 6 and siphon block 1, 2, 3, 4, there is a small volume of liquid metal or liquid iron since it is annular , being between the inner wall of the jacket 6 and the outer wall of the central relief 5 of the siphon block.

The annular thickness of this annular volume of metal or of liquid iron is substantially greater than the thickness e of the tube T to be formed. In fact, in no case should the relief 5 constitute a core for the formation of the tube T. Quite the contrary, during the process of solidification of the peripheral zone of said annular volume of metal or of liquid iron, a certain annular volume of iron or liquid metal must remain between the periphery being solidified and the outer wall. In the illustrated embodiment, the annular volume of metal or liquid iron between the central relief 5 and the die 6-7 has at its lower end a radial thickness which is at least twice the thickness e of the tube T.

The installation is completed by means of vertical guide of the tube T, partially represented by a pair of rollers or guide rollers E and is completed by an extractor not shown and consisting of a lifting device arranged to grip the upper end of the T tube formed and to gradually raise the T tube, using a stepping drive motor.

Such guide and extraction means are known per se.

OPERATION - (Fig. 1-2)

Liquid iron is introduced along arrow f into the pouring funnel 4. The filling of the siphon block and the crucible constituted by the die 6-7 with jacket 6 and the central relief 5 of the siphon block is carried out until the level of liquid iron N reaches a height slightly lower than the total height of the sector 6-7 so as not to overflow. By effect of communicating vessels, the level N of the liquid iron F is the same inside the crucible or the die 6-7 and inside the chimney 3. The jacket 7 is crossed by a current of Cold water.

To start the production of the tube T, a dummy or false tube M, consisting of a tubular steel sleeve having substantially the same internal and external diametrical dimensions, therefore substantially of the same thickness e as the tube T to be obtained, is introduced by the top of the die 6-7 using guide rollers E so as to immerse in the cast iron its lower part cut out in M1, for example in dovetail, to allow the attachment of the liquid cast iron F.

While the die 6-7 is not cooled at its lower end, it is on the contrary cooled over most of its height, up to its upper end because the jacket 6 is enveloped by the envelope of cooling 7. As a result, the cast iron solidifies on contact with the die 6-7 over the entire height which corresponds to that of the liner 7 up to the mannequin M in contact with which it solidifies. The thickness of cast iron solidified along a solidification front S is higher the lower the speed of introduction of liquid iron from below. The liquid iron F fills the notch M1 of the manikin M, solidifies, and consequently hangs on the manikin M. The manikin being pulled up by the extractor, rises in spurts and drives the part of solidified iron up, step by step.

When the mannequin M has pulled upwards a primer of tube T of sufficient height to come into engagement between the guide rollers or guide rollers E (Fig. 1), the solidification front S which forms on the periphery of the volume ring shape of liquid iron F takes the frustoconical shape and the size shown in FIG. 1 which corresponds to the total height of liquid iron F surrounded by the cooling jacket 7. The maximum solidified thickness is therefore at level N of the liquid iron.

ALTERNATIVE - (Fig. 3).

Whereas in the example of FIG. 1, the central relief 5 of the invention is applied to a die 6 intended for the formation of a tube T without interlocking, the variant of FIG. 3 is applied to the formation of a tube T1 comprising an interlocking. This variant derives from the installation described in the patent application in France 83 11 788 of July 12, 1983:

In this variant, concerning the manufacture of a cast iron pipe with interlocking, the installation is similar to that of FIG. 1, but also comprises, as described in patent application 83 11 788, means for forming the socket.

In the description which follows, the installation elements identical or similar to those of FIG. 1 and playing the same role have the same numerical references. We therefore find the same supply of liquid iron by siphon block 1, 2, 3, 4 forming a base or support for a tubular graphite die 6 wrapped by a cooling jacket 7 with circ ulation of cold water.

We find the same central relief 5 of the invention with a recess 10. Between the cooling jacket 7 and the base 1 constituted by the siphon block is interposed an insulating support plate 11. The plate 11 which supports the jacket 7 is refractory material, for example of the silico-aluminous type. It is intended to prevent cooling of the base 1 by the jacket 7.

The means to form the nesting are as follows:

The jacket 6 of the die 6-7 is surmounted or extended at its upper part by a metallic annular shell 12, for example of steel, of axis XX, flared upwards, giving the external shape of the interlocking of the pipe in cast iron to be obtained. The shell 12 is connected without discontinuity both with the inner wall and with the outer wall of the jacket 6. The shell 12 is cooled either by ambient air, or by water jets not shown.

Internally, the shell 12 supports, by an enlarged frustoconical surface 13, the flange 14 a of an annular interlocking core 14 made of refractory and air-permeable molding material, for example in a hardened mixture of sand and thermosetting resin. The core 14 gives the internal profile of the fitting of the pipe to be obtained. It comprises a tubular skirt 15, the external wall of which corresponds to the internal wall of the pipe which is to be molded. The skirt 15 extends downwards beyond the shell 12, over a certain height from the die 6-7 at the upper part thereof. The skirt 15 therefore provides, with lachemise 6 of the dies 6-7, an annular space 16 corresponding to the thickness of the pipe to be formed. Internally, the core 14 necessarily includes an internal coating 17 (tubular steel core) impermeable to air and resistant to the temperature of liquid iron.

To raise the cast iron in the annular space 16, in order to form the interlocking as will be seen below, the shell 12-core 14 assembly is completed by suction means.

The core 14 is applied to its surface 13 in the shell 12 by a metallic annular suction plate 18. The plate 18 has an annular suction groove 19 opening towards the flange 14a of the core 14, above the annular space 16. In the groove 19 there opens a conduit 20 connected through a tap 21 to a source d suction not shown. The suction plate 18 is fixed to the shell 12, for example by screws.

In this variant, the extractor of the cast iron pipe being formed is not shown. It comprises a circular metal plate 22 called a lifting plate, of axis XX, integral with the suction plate 18. The plate 22 is fixed to the plate 18 for example by screws and is connected to a lifting rod 23 of axis XX, suspended from a vertically guided lifting device, not shown.

In this variant, the central relief 5 of the invention, for example frustoconical, has dimensions of large base such that the top of the central relief 5 is located inside the cavity of the skirt 15 of the core 14, au- above the upper end of the die 6-7 or of the jacket 6. It is advantageous that the relief 5 is higher than the die 6-7, in FIG. 1 as in FIG. 3, because this makes it possible to limit the volume of liquid iron to an annular space over the entire height of the jacket 6 of the die 6-7 whereas if the central relief 5 was clearly lower than the jacket 6, there would be liquid iron above the top of the relief 5 and therefore an unnecessary excess of liquid iron.

The operation is the same as that described in patent application 83 11 788:

1.) Liquid iron supply: the tap 21 of the suction pipe 20 is closed. Liquid iron is introduced along arrow f into the funnel 4. Liquid iron F is brought to a level N located at the upper part of the jacket of the die 6-7, immersing the skirt 15 and the tubular core 17 of core 14 but remaining below the top of the central relief 5.

2.) Molding of the casing of the cast iron pipe: The shell 12 being in airtight contact with the upper edge of the jacket 6, the suction valve 21 is opened and the air contained is sucked in the annular space 16 using the duct 20 for suction of the circular groove 19 through the porous flange 14a of the core, but not through the impermeable core 17 of steel.

Liquid iron rapidly fills the annular space 16 from the socket to the porous flange 14a of the core 14.

But its level drops in the cavity of the waterproof core 17 and in the chimney 3 without descending below the skirt 15. The socket 16 thus molded solidifies from the top, that is to say from the flange 14a of the core 14.

3.) Discontinuous extraction of an interlocking pipe: In order to prepare the extraction, complete the level of liquid iron which has just fallen, by pouring iron into the funnel 4 along the arrow f during the solidification of the socket. When the socket 16 is formed and solidified, the suction valve is closed 21. The liquid iron included in the annular space between the skirt 15 and the jacket 6 of the die 6-7 as well as the shell 12, cools and solidifies both under the influence of the upper part of the cooling jacket 7 and under the influence of the shell 12. At this stage of solidification along a front S, not shown but similar to that of FIG. 1, the extractor is actuated, that is to say the assembly of the lifting plate 22 and of the shell 12 upwards (arrow f in FIG. 3) while pouring liquid iron into the 'funnel 4 to replace the solidified cast iron above the die 6-7. Care is thus taken to keep the level N of liquid iron constant during extraction, a little below the upper part of the jacket 6 at a height where the iron is still cooled by the casing 7.

The upward extraction of the solidified socket, at the same time as the raising of the shell 12, is carried out in a discontinuous step-by-step manner, as described in patent application 83 11 788. Below from the interlocking and in continuity with the latter, a barrel primer of the tube T solidifies which extends with each stroke of rise of the assembly of the shell 12 and of the core 14, according to a thickness e.

When a sufficient barrel length has thus been obtained for the pipe T being formed, the pouring of liquid iron is stopped in the funnel 4 and the annular space between the die 6-7 and the central relief 5, for example by a lower orifice not shown, from which the shutter is removed. It then suffices to completely lift the pipe formed above the die 6-7 and to disengage its fitting out of the shell 12 and of the core 14 and of the suction plate 18.

Another variant: In Figs. 1 and 3, instead of being an integral part of the siphon block 1-2-3-4, the central relief 5 can be a body attached to said siphon block and sealed thereon.

ALTERNATIVE from FIG. 4.

In an example of execution similar to that of FIG. 1, the blind recess internal recess of the central relief 5 is replaced by an open cavity 10a passing right through, axially, the relief 5, opening at the top of the central relief 5, and opening towards the outside on the underside from socket 1 of the siphon block 1-2-3-4.

It advantageously follows that, by this cavity 10a opening a passage from the outside to the inside of the tube T in formation, it is possible to introduce a CN tool for controlling the level of liquid metal or else a CE tool for measuring the thickness of the tube formed by measuring its internal diameter since its external diameter is known, or else a CT bath temperature measurement tool. The tools CN, CT and CE symbolically represented by dashed lines are given as examples to illustrate the possibility of access or visit inside the tube T, thanks to this passage cavity 10a. With regard more particularly to the measurement or detection of the level N, since it is in this example a supply of liquid metal by a siphon block with communicating vessels constituted by the crucible 6-7 on the one hand and the vertical chimney 3 on the other hand, it is certain that one can detect or measure the level N from the outside, by the chimney 3, at least outside the periods of reloading in liquid iron according to the arrow f But we will see in other variants where there is no system of communicating vessels, that it is useful to be able to access the level of liquid iron from the inside.

ALTERNATIVE from FIG. 5:

The liquid iron supply system is modified: the siphon block 1-2-3-4 is replaced by a pressure casting ladle 24 of the teapot type with oblique filling chute closed by a cover 25. A pouring tube vertical 26 made of refractory material passes through the upper wall of the closed pocket 24. It plunges almost to the bottom of the pocket 24 and protrudes above the upper wall of the pocket 24 over a short length along which it is surrounded and reinforced with a frustoconical nozzle 27 of axis XX of connection with an interlocking complementary frustoconical 28 of axis XX to the lower part of the base la to make the pouring tube 26 communicate with the cavity 10b or 10c of the central relief 5. In this example, it is mandatory that the central relief 5 is hollowed out leaves by a cavity to allow the rising crossing of the liquid iron and its discharge inside the crucible formed by the die 6-7 and the base la over the top of the central relief 5.

The relief 5 can be given a hollow frustoconical shape of constant thickness with a recess cavity such as 10b. There is thus an enlarged mass of hot liquid iron at the bottom and axial part of the central relief 5.

It is also possible to give the central passage cavity, that is to say through the relief 5, a cylindrical shape of the same diameter as the inside diameter of the ascending pouring tube 26, according to the profile in phantom 10c. A conduit 29 in communication with the interior of the pocket 24 at the top of the latter, above the level of the liquid metal F is connected to a source of compressed gas or to a discharge under the control of a tap 30.

The variant of FIG. 5 has the advantage of allowing better control and even automatic control of the supply of liquid iron under low pressure of a gas which may be air or an inert gas such as nitrogen or argon.

ALTERNATIVE from FIG. 6:

In a supply of liquid metal by a ladle under low pressure, similar to that of FIG. 5, the single vertical tube 26 of upward casting is replaced by a pair of tubes 26a and 26b of upward vertical casting which pass through the base 1b of the crucible formed by the die 6-7 is the base 1b and which open at the bottom of the crucible, in the annular space between the central relief 5 and the die 6-7. In this example, the frustoconical connection nozzle 27 is replaced by annular support and spacers 31 surrounding each tube 26a, 26b and interposed between the ladle 24 and the base 1b. The annular wedges 31 of support and spacing allow the axial cavity 10c of the central relief 5 to open at its lower part towards the outside and therefore to offer a passage for a tool to access the interior of the crucible by example using a CN level control tool.

This arrangement is particularly advantageous since it allows access to an invisible interior space since, in this example, it is between the central relief 5 and the core 17 of the skirt 15 of the nesting core 14.

Claims (14)

1. Feed apparatus for molten metal for an installation for the continuous vertical casting of a metal pipe (T, T1) in particular of cast-iron, of the type comprising an inlet for molten metal at the lower end of a cooled die (6-7) resting on a stand (1, 1 a, 1b), the die (6-7) forming a crucible with the stand (1, 1a, 1b) in order to contain the molten metal and of the type which comprises inside the die (6-7) and on the vertical axis (X-X) of the latter, a coaxial body of revolution of height corresponding to that of the die (6-7) in order to provide with the latter an annular volume of molten metal (F) in the lower part of which is located the mouth of at least one pipe (2, 26, 26a, 26b) for feeding molten metal, characterised in that the coaxial body of revolution is a central relief (5), the height of which is greater than that of the die (6-7), in order to prevent the presence of molten metal above central relief (5), and to limit the volume to be filled with molten metal to the annular space comprised between the die (6-7) and the central relief (5).

2. Apparatus according to Claim 1, characterised in that the central relief (5) has a frustoconical shape with a large lower base.

3. Apparatus according to Claim 1, characterised in that in the case where the die (6-7) is surmounted and extended in the upwards direction by an arrangement for casting a socket of a cast-iron pipe (T1 comprising a chill-mould (12) and an annular core (14) of refractory material which is permeable to air, as well as means (18-19-20-21) for creating reduced pressure in the annular space comprised between the chill-mould (12) and the core (14), the central relief (5) penetrates inside the annular core (14) by providing with the latter an annular space for the molten cast-iron.

4. Apparatus according to Claim 1, characterised in that the central relief (5) consists of refractory material.

5. Apparatus according to Claim 1, characterised in thatthe central relief (5) is recessed internally by a cavity (10, 10a, 10c) opening out towards the outside on the lower face of the stand (1,1 b) of the siphon unit (1, 2, 3, 4).

6. Apparatus according to Claim 5, characterised in that the cavity (10) of the relief (5) is blind.

7. Apparatus according to Claim 5, characterised in that the cavity (10a, 10b) of the central relief (5) is open and opens out at the top of the central relief (5).

8. Apparatus according to Claim 5, characterised in that in the case where the crucible formed by the die (6-7) and the stand (1) is fed by a siphon unit (1, 2, 3, 4), the central relief (5) forms an integral part of the siphon unit (1, 2, 3, 4).

9. Apparatus according to Claim 1, characterised in that the central relief (5) is attached to the stand (1, 1a, 1b).

10. Apparatus according to Claims 5 and 7, characterised in that the cavity (10a, 10c) which is open to the atmosphere, opens out on the lower face of the stand (1, 1b) on the outside of the latter.

11. Apparatus according to Claim 7, characterised in that in the case where the crucible formed by the die (6-7) and the stand (1a) is fed by a pressurised casting ladle (24) situated below said crucible (6-7-1a) and comprising a single bottom casting tube (26) immersed in the casting ladle (24), the cavity (10b) of the central relief (5) is located as an axial and vertical extension of the bottom casting tube (26).

12. Apparatus according to Claim 7, characterised in that in the case where the crucible formed by the die (6-7) and the stand (1 b) is fed by a pressurised casting ladle (24) comprising two vertical bottom casting tubes (26a, 26b) immersed in the casting ladle (24) and opening out at their upper end at the bottom of the annular space between the central relief (5) and the die (6-7), the lowerface of the stand (1 b) supporting the die (6-7) is spaced from the casting ladle (24) by support and spacing wedges (31) and the cavity (10b, 10c) of the central relief (5) opens into the atmosphere on the lower face of the stand (1 b).

13. Apparatus according to Claim 5, characterised in that the cavity (10, 10a, 10b) ofthecentral relief (5) has a frustoconical shape.

14. Apparatus according to Claim 11, characterised in that the cylindrical cavity (10c) of the central relief (5) has the same diameter as the inner diameter of the bottom casting tube (26) from the pressurised casting ladle (24).

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