GB1576833A

GB1576833A - Casting molten metal

Info

Publication number: GB1576833A
Application number: GB626677A
Authority: GB
Original assignee: Foseco International Ltd
Current assignee: Foseco International Ltd
Priority date: 1978-04-13
Filing date: 1978-04-13
Publication date: 1980-10-15

Description

(54) CASTING MOLTEN METAL (71) We, FosEco INTERNATIONAL LIMI TED, a British Company of Long Acre, Nechells, Birmingham, B7 5JR, England do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to casting molten metal to form ingots or other castings.

In the casting of molten metal to form ingots or other castings, it is known to provide a barrier to the loss of heat from the upper region of the body of molten metal, so-called "head metal", immediately teeming of the molten metal has terminated. In this way the head metal is kept molten and feed of metal to the body of the ingot or other casting can take place to compensate for shrinkage on solidification. The barrier to the loss of heat may be formed by the application to the exposed surface of the molten metal in the mould of a layer of heat-insulating and/or exothermic material, referred to in the art of metal casting as an anti-piping material. Such a layer may be applied by placing a board, slab, sheet or tile of suitable composition horizontally on the exposed surface of the molten metal immediately after teeming. In order to minimise the loss of heat the shape of the board slab, sheet or tile should conform substantially to the shape of the opening at the top of the mould.

Application of such a board slab, sheet or tile by hand is hazardous due to the intense heat radiated from the molten metal, which gives rise to a substantial risk of injury to an operative applying such a board to the exposed metal surface.

In the casting of ingots which are up-hill teemed, i.e. where the molten metal is introduced from the base of the ingot mould into the ingot mould cavity, hangers have been employed to support a board horizontally in the head of the ingot mould prior to teeming metal therein. This method is restricted to up hill teemed ingots and suffers from the disadvantage that the board is often dislodged or ejected from the mould due to the pressure of gases evolved during teeming, thus rendering the operation futile.

According to the invention a method of casting molten metal comprises providing a mould with an upwardly open cavity, locating adjacent the top of the cavity one or more preformed boards of heat insulating and/or exothermic material supported on one or more support devices, the support device(s) (1) having a first part extending from one inner side of the cavity to the opposite inner side of the cavity, serving to hold the device in fixed position in the cavity, (2) having a second part, extending from the first, adapted to support the board(s) in a non-horizontal position and (3) being of material which, under the action of the heat of molten metal in the upper part of the cavity, is sufficiently destroyed to cease to support the board(s), teeming molten metal into the mould to a level at which sufficient destruction of the support device(s) occurs to cause lowering of the board(s) on to the upper surface of the molten metal and allowing the molten metal to solidify in the mould.

A wide variety of possible arrangements may be adopted depending on the particular area of use and whether one or more boards are to be supported. Preferably, the or each board is supported at an angle of at least 450 to the horizontal, more preferably at least 600 in the case where molten metal is to be teemed into the mould from above, in order that the board(s) may be held well out of the way of the downward stream of molten metal. The first part of the support device is preferably positioned substantially horizontally and, therefore, the above values of preferred angles preferably apply also to the angle between the first and second parts of the device.

A specific advantage of the use of the method of the invention for casting ingots is that it may be employed both in up-hill teeming and, with suitable dimensioning of the support devices, also in cases of direct teeming.

The support device(s) may be separately to a metal casting plant, e.g. a steelworks, for assembly with the board(s) on site. In practice it is preferable to use at least two of the support devices, laterally spaced apart, for each assembly in order to provide adequate support for the anti-piping board(s).

The support device may be formed of any material which will soften or burn away at.

the elevated temperature to which it is subjected when teeming is finished. Thus, at the commencement of teeming the board is held in an inclined position and continues to be supported in this manner until the molten metal teemed into the mould reaches the top, or near the top, of the mould. The support device then softens or burns away and the board falls to a horizontal position on the surface of the molten metal. The material from the support device is manufactured may be a metal substantially the same as the metal being cast e.g. mild steel rod in the case of steel, stainless steel rod in the case of stainless steel, aluminium in the case of aluminium or alloys thereof. It is generally preferable for the first part at least of the support device to be of resilient material, e.g. spring steel, and for this part to be held in place by being sprung between the opposite sides of the cavity e.g. between opposed slabs of lining material in the top of an ingot mould. If spring steel or other resilient material is not used, the first part of the support may be flexed and then straightened to dig into opposed mould wall lining slabs.

Preferably the second part of the support device extends from one end of the first part and there may be a second part extending from each end of the first part, the second parts of the or each support device supporting two of the boards at opposite sides of the cavity.

According to another aspect of the invention there is provided an assembly of a mould, for casting metal, having an upwardly open cavity and, located adjacent the top of the cavity, one or more preformed boards of heat insulating and/or exothermic material supported on one or more support devices as described above.

By way of example the invention is more particularly described with reference to the accompanying drawings, in which: Figure 1 is a vertical section of a mould having one form of hot top arrangement shown prior to teeming, Figure 2 is a plan view from above of the mould of Figure 1, Figure 3 is the same as Figure 1 but after teeming, Figure 4 is a vertical section of a mould having another form of hot top arrangement shown prior to teeming, and Figure 5 is a plan view from above of the mould of Figure 4.

The assembly shown in Figure 1 comprises an ingot mould body 1, having secured in the open end a hot top assembly made up of a set of hot lining slabs 2. Two board support devices (only one of which is shown in Figure 1), each comprise a first part 3 which is sprung between opposite slabs 2 of the hot top lining, and a second part 4 which extends upwardly from one end of part 3 at an angle of about 45". An exothermic anti-piping board 6 is supported on the two parts 4 of the two support devices. The support devices are formed of 4mm diameter spring steel rod.

In use, molten metal is poured into the mould from below, and as the metal rises the heat softens the support devices and under the influence of gravity the board 6 falls onto the metal 7, into the position shown in Figure 3.

Figure 4 shows a support device having upwardly inclined second parts 9, 11 at each end of a first part 8 held sprung between the two hot top lining slabs 2. Parts 9 and 11 are sufficiently long and sufficiently inclined that boards 10 and 12 can rest thereon without toppling, as shown. This type of arrangement is particularly suitable for use in direct teeming of ingots; boards 10 and 12 are supported at an angle still small enough to ensure that they will fall onto the exposed surface of the molten metal ingot at the end of teeming, and yet the angle is large enough that the opening at the top of the mould is sufficient to permit uninterrupted teeming of the metal from above into the mould. Arrangements of this type are also particularly useful in cases where there is restricted access space above the top of the mould.

The above examples illustrate that the method of the present invention enables a board to be applied to the exposed surface of the head metal in an ingot or other casting mould at the end of teeming without the need for an operative to work in close proximity to the molten metal in the mould.

The support devices are advantageous in that they are simple to make and easy to put in position. Furthermore different designs are not needed for moulds having different wall thickness or configuration at their top ends.

WHAT WE CLAIM IS: 1. A method of casting molten metal which comprises providing a mould with an upwardly open cavity, locating adjacent the top of the cavity one or more preformed boards of heat insulating and/or exothermic material supported on one or more support devices, the support device(s) (1) having a first part, extending from one inner side of the cavity to the opposite inner side of the cavity, serving to hold the device in fixed position in the cavity, (2) having a second part, extending from the first, adapted to support the board(s) in a non-horizontal position and (3) being of material which under the action of the heat of molten metal in the upper part of the cavity, is sufficiently destroyed to cease to support the board(s),

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. it is preferable to use at least two of the support devices, laterally spaced apart, for each assembly in order to provide adequate support for the anti-piping board(s). The support device may be formed of any material which will soften or burn away at. the elevated temperature to which it is subjected when teeming is finished. Thus, at the commencement of teeming the board is held in an inclined position and continues to be supported in this manner until the molten metal teemed into the mould reaches the top, or near the top, of the mould. The support device then softens or burns away and the board falls to a horizontal position on the surface of the molten metal. The material from the support device is manufactured may be a metal substantially the same as the metal being cast e.g. mild steel rod in the case of steel, stainless steel rod in the case of stainless steel, aluminium in the case of aluminium or alloys thereof. It is generally preferable for the first part at least of the support device to be of resilient material, e.g. spring steel, and for this part to be held in place by being sprung between the opposite sides of the cavity e.g. between opposed slabs of lining material in the top of an ingot mould. If spring steel or other resilient material is not used, the first part of the support may be flexed and then straightened to dig into opposed mould wall lining slabs. Preferably the second part of the support device extends from one end of the first part and there may be a second part extending from each end of the first part, the second parts of the or each support device supporting two of the boards at opposite sides of the cavity. According to another aspect of the invention there is provided an assembly of a mould, for casting metal, having an upwardly open cavity and, located adjacent the top of the cavity, one or more preformed boards of heat insulating and/or exothermic material supported on one or more support devices as described above. By way of example the invention is more particularly described with reference to the accompanying drawings, in which: Figure 1 is a vertical section of a mould having one form of hot top arrangement shown prior to teeming, Figure 2 is a plan view from above of the mould of Figure 1, Figure 3 is the same as Figure 1 but after teeming, Figure 4 is a vertical section of a mould having another form of hot top arrangement shown prior to teeming, and Figure 5 is a plan view from above of the mould of Figure 4. The assembly shown in Figure 1 comprises an ingot mould body 1, having secured in the open end a hot top assembly made up of a set of hot lining slabs 2. Two board support devices (only one of which is shown in Figure 1), each comprise a first part 3 which is sprung between opposite slabs 2 of the hot top lining, and a second part 4 which extends upwardly from one end of part 3 at an angle of about 45". An exothermic anti-piping board 6 is supported on the two parts 4 of the two support devices. The support devices are formed of 4mm diameter spring steel rod. In use, molten metal is poured into the mould from below, and as the metal rises the heat softens the support devices and under the influence of gravity the board 6 falls onto the metal 7, into the position shown in Figure 3. Figure 4 shows a support device having upwardly inclined second parts 9, 11 at each end of a first part 8 held sprung between the two hot top lining slabs 2. Parts 9 and 11 are sufficiently long and sufficiently inclined that boards 10 and 12 can rest thereon without toppling, as shown. This type of arrangement is particularly suitable for use in direct teeming of ingots; boards 10 and 12 are supported at an angle still small enough to ensure that they will fall onto the exposed surface of the molten metal ingot at the end of teeming, and yet the angle is large enough that the opening at the top of the mould is sufficient to permit uninterrupted teeming of the metal from above into the mould. Arrangements of this type are also particularly useful in cases where there is restricted access space above the top of the mould. The above examples illustrate that the method of the present invention enables a board to be applied to the exposed surface of the head metal in an ingot or other casting mould at the end of teeming without the need for an operative to work in close proximity to the molten metal in the mould. The support devices are advantageous in that they are simple to make and easy to put in position. Furthermore different designs are not needed for moulds having different wall thickness or configuration at their top ends. WHAT WE CLAIM IS:

1. A method of casting molten metal which comprises providing a mould with an upwardly open cavity, locating adjacent the top of the cavity one or more preformed boards of heat insulating and/or exothermic material supported on one or more support devices, the support device(s) (1) having a first part, extending from one inner side of the cavity to the opposite inner side of the cavity, serving to hold the device in fixed position in the cavity, (2) having a second part, extending from the first, adapted to support the board(s) in a non-horizontal position and (3) being of material which under the action of the heat of molten metal in the upper part of the cavity, is sufficiently destroyed to cease to support the board(s),

teeming molten metal into the mould to a level at which sufficient destruction of the support device(s) occurs to cause lowering of the board(s) on to the upper surface of the molten metal and allowing the molten metal to solidify in the mould.

2. A method according to claim 1 in which the first part of the or each support device is of resilient material and is held in place by being sprung between the opposite sides of the cavitv.

3. A method according to either preceding claim wherein the or each board is supported at an angle of at least 45" to the horizontal.

4. A method according to claim 2 wherein the angle is at least 60".

5. A method according to any preceding claim wherein the board or boards are supported on at least two of the support devices laterally spaced apart.

6. A method according to any preceding claim in which the or each support device is of a metal substantially the same as the metal being cast.

7. A method according to any preceding claim wherein the second part of the or each support device extends from one end of the first part.

8. A method according to any of claims 1 to 6 wherein there is a second part extending from each of the first part of the or each support device and the second parts of the or each support device support two of the boards at opposite sides of the cavity.

9. A method according to claim 1 and substantially as described with reference to the accompanying drawings.

10. An assembly of a mould, for casting metal, having an upwardly open cavity and, located adjacent the top of the cavity, one or more preformed boards of heat insulating and/or exothermic material supported on one or more support devices as set forth in claim 1.

11. An assembly according to claim 10 and substantially as described with reference to the accompanying drawings.