EP0648563B1 - Method to cast a piece of cast iron or another metal with high melting point - Google Patents

Description

Technical area

The subject of the present invention is a process for casting cast iron parts or all other metal with a melting temperature high.

It finds applications in many areas of industry requiring parts made of cast iron or another metal having a temperature of high fusion. In particular, she finds a application in the nuclear industry for the recycling of ferrous metals likely to be radioactive.

State of the art

Many parts molding processes cast iron are currently known.

A first method consists in using a sand mold into which the cast iron is poured. This process is generally implemented to carry out large volumes requiring a unit manufacturing. Now sand is a material likely to be contaminated in contact with cast iron radioactive. Also, to be used in a nuclear installation ventilated and continuously in depression, the cast iron parts thus molded must have their radioactivity checked. This process therefore leads to a large amount of waste including disposal is expensive.

A second method consists in using a shell mold having an internal shell and an outer shell between which the melting. The shells are then cooled, generally by a circulation of fluids, for allow the part to be removed from the mold. The purpose of this process is disadvantage of being rigid; so it cannot be put only for simple forms and preferably for mass production. In in addition, the shells being cooled by the circulation of a fluid, risks of contact with the fluid with molten iron are to be expected; as well, such a method cannot be implemented in a nuclear installation.

A third molding process consists of project molten iron onto a central shell rotating rapidly and cooled by a fluid. he it is a centrifugal molding process. This process has significantly disadvantages identical to those of the second method presented above. In addition, this process presents a risk of rupture of the rotating part whose consequences could be considerable. The implementation of such a process does not therefore cannot be envisaged in an installation nuclear because of its unreliability.

Furthermore, it is known to mold lead parts using formwork collaborators, i.e. formwork of which at least part of said formwork adheres to lead to form the desired part.

Lead with a melting point significantly lower (325 ° C) than the melting point of the cast iron (1,200 ° C), as well as steel and well other metals, it cannot be used for make pieces of cast iron or any other metal having a high melting temperature.

Statement of the invention

The present invention has precisely for object a process for casting cast iron parts (or other metals with a high melting point) at means of collaborating formwork, also called envelopes; for application to industry nuclear, the metal used to mold the part can be a more or less radioactive recycled metal.

• réaliser une enveloppe par assemblage de tôles en un premier métal,
• disposer des granulats autour de cette enveloppe,
• couler un second métal en fusion dans ladite enveloppe,
• après refroidissement et solidification du second métal, retirer les granulats, ledit second métal solidifié collaborant avec l'enveloppe en premier métal pour réaliser la pièce.

More precisely, this process for molding metal parts having high melting temperatures consists, for each part to be molded, of:

• make an envelope by assembling sheets of first metal,
• dispose of the aggregates around this envelope,
• pour a second molten metal into said envelope,
• after cooling and solidification of the second metal, remove the aggregates, said second solidified metal collaborating with the envelope of first metal to produce the part.

According to the invention, the realization of the envelope may consist of welding sheets to inside which the second metal is poured.

It also consists in welding metal inserts on the sheets to keep them in fixed position when casting the second metal.

According to the preferred embodiment of the invention, the first metal is steel and the second metal is cast iron.

The aggregates are preferably steel balls.

According to an application of the invention, this process allows the creation of waste containers radioactive from recycled ferrous metals.

Brief description of the drawings

• Figure 1 shows a perspective view partially cut from a collaborating formwork for implementing the method according to the invention;
• FIG. 2 schematically represents a view cross section of a radioactive waste container produced according to the method of the invention.

Detailed description of an embodiment

In the following description, the process of the invention will be described in its application to the production of a cast iron container. It can, however, be implemented to achieve all kinds of very shaped and weighty pieces various, cast iron or any other metal with a high melting temperature.

Figure 1 therefore represents the formwork collaborating 1, or envelope 1, used to produce, according to the method of the invention, a container capable of receive, for example, radioactive waste. The envelope produced for the implementation of this method of the invention, comprises an outer sheet 2 cylindrical and an inner sheet 4 cylindrical and concentric with the outer sheet 2.

According to another embodiment of the invention, not shown in the figure, the envelope may be of parallelepiped shape or of a whole other form.

The lower ends of these sheets 2 and 4 are closed by bottoms 2a and 4a. To their upper ends a sheet 2b ensures a closure of the envelope. This sheet 2b, however, includes filling holes 3.

All sheets 2, 4, 2b, 2a, 4a, made of a first metal, are welded together to form the envelope.

According to the preferred embodiment of the invention, this first metal is steel, steel having the property of being tensile and compression.

Sheets 2 and 4 are kept in a fixed position relative to each other by means metal inserts. According to the example in Figure 1, sheets 2 and 4 are maintained at their ends upper, by six inserts welded on the one hand on the sheet 2 and secondly on sheet 4. At the ends lower panels 2 and 4, four inserts 8 are welded, on the one hand on the face outside of the bottom 4a of the sheet 4 and on the other hand on the bottom 2a of the sheet 2.

The number of metal inserts now the two sheets is, of course, given as example and may vary depending on resistance the metals used and the shape of the parts to be molded.

For very shaped molded parts simple, the envelope can have only one sheet metal, no metal insert is necessary.

When this collaborating formwork, or envelope, is made, it is introduced into a box 10, the bottom of which is covered with aggregates. A multitude of aggregates 12 are then deposited in the box 10, all around the envelope.

Depending on the shape of the parts to be molded, aggregates can also be introduced to inside the envelope. Especially for the example of the envelope of figure 1, aggregates are introduced inside the inner sheet 4. These aggregates maintain the envelope during from the introduction of cast iron.

These aggregates 12, which can be by example steel balls, prevent all deformations of sheets 2 and 4 during casting of molten iron, the temperature of the sheets possibly reach approximately 1000 C. At such a temperature, the sheets may, in fact, deform under the pressure of the cast iron.

These steel balls have a size of about 0.3 to 5 mm in diameter.

The aggregates 12 also have a role predominant in the evacuation of calories resulting casting molten iron, these aggregates having a high heat capacity.

In addition, the collaborating formwork, type described above, can, as required, include reinforcements, inserts, reserves, notches, etc.

When the aggregates have been introduced, molten iron is, in turn, introduced into envelope 1 and, in particular between plates 2 and 4 for the example of FIG. 1, through a few orifices 3.

According to one embodiment of the method, the molten cast iron is divided into several jets distributed over the surface of the envelope. Such a distribution of the cast iron ensures better distribution of the forces due to the pressure of the cast iron molten on the sheets as well as calories due to the high temperature of molten iron.

Such an embodiment makes it possible to mold thin pieces using jets of small diameter molten iron.

In addition, the casting speed of the cast iron can be adapted to allow solidification faster melting, reducing pressure undergone by the sheet 4 of the casing 1 (pressure effect ferrostatic).

When the cast iron thus cast is cooled, the aggregates are removed (by tilting or suction) and the molded part is recovered.

To allow easier evacuation of aggregates 12, and therefore of limiting the risks of bonding of the aggregates against the envelope, the walls, respectively, external of sheet 2 and internal of sheet 4 can be previously coated with a product poteyage.

We previously described the realization, according to the method of the invention, of a container in melting. A cover can be made, by this same process, to fit on the container shown on the figure 1.

In FIG. 2, there is shown, in section, the container of Figure 1, with its lid, obtained by the method of the invention.

The references, shown in this figure 2, which are identical to the references of FIG. 1 represent identical elements.

The container shown in this figure 2 therefore comprises the casing 1 made of steel sheets collaborating with solidified cast iron 3. The association steel / cast iron / sandwich steel has excellent strength characteristics, cast iron having good compressive strength and steel having good tensile strength and compression as well as good elongation capacity to absorb shocks. This association also constitutes good protection against radioactivity.

Also shown in Figure 2 the container gripping groove 14 (of the type ANORA® shell C), as well as the metal inserts 6.

In addition, the cover 16 is shown. of the container. This cover has an envelope 18 in steel sheets working with a layer of cast iron 20.

According to the example shown in this figure 2, the cover 16 is fixed to the container by means a screwing system. This screwing system consists in several tapped holes made in the cover and in the container, inside which are introduced screws. In Figure 2, there is shown two tapped holes 22 and two screws 24 inserted in said tapped holes 22.

According to another example, the fixing of the lid on the container can be achieved by a weld bead deposited between the cover and the container, this attachment further ensuring the tightness of the assembly.

In addition to application to the waste container radioactive, the method of the invention can be implemented works to achieve all kinds of radiation protection such as doors, walls, floors, etc., the thickness of which can vary from approximately 40 to 350 millimeters.

This process therefore makes it possible to carry out radiation protections using ferrous metals recycled from the nuclear industry.

Claims (7)

1. Process for casting parts made of metals having high melting points, characterized in that it consists, for each part to be cast:

   in producing a collaborating form, or casing, (1) by joining together metal sheets made of a first metal;

   in placing granulates (12) around the casing;

   in pouring a molten second metal (3) into the said casing;

   in removing the granulates after the second metal has cooled and solidified, the said solidified second metal collaborating with the casing made of the first metal in order to produce the part.
2. Process according to Claim 1, characterized in that the production of the casing consists in welding metal sheets into which the second metal is poured.
3. Process according to Claim 2, characterized in that the production of the casing furthermore consists in welding metal inserts (6, 8) onto some of the metal sheets in order to keep the said metal sheets in a fixed position, one with respect to the others.
4. Process according to any one of Claims 1 to 3, characterized in that the first metal is steel.
5. Process according to any one of Claims 1 to 4, characterized in that the second metal is cast iron.
6. Process according to any one of Claims 1 to 5, characterized in that the granulates are steel balls.
7. Process for casting containers for radioactive waste, characterized in that it consists of a process according to any one of Claims 1 to 6.

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