FR2711329A1 - Process for molding parts made of cast iron or any other metal having a high melting temperature. - Google Patents

Abstract

The invention relates to a method for molding cast iron parts using a cooperating steel casing. This process consists of: - making a casing by assembling and welding steel sheets, - placing the aggregates around a casing, - pouring the molten iron in said casing, and - after cooling and solidification of the cast iron, removing the aggregates to obtain a cast iron part working with the steel sheets. Application to the production of radioactive waste containers, structural and biological protection elements.

Description

PROCESS FOR MOLDING CAST IRON OR OTHERWISE

  METAL HAVING A HIGH MELT TEMPERATURE

DESCRIPTION

  TECHNICAL FIELD The present invention relates to a method for molding parts of cast iron or any other metal having a high melting temperature. It finds applications in many areas of the industry requiring cast iron parts or other high melting temperature metal. In particular, it finds 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 in which the cast iron is cast. This method is generally used to produce large volume parts requiring unit manufacture. Sand is a material that can be contaminated by contact with radioactive smelting. Also, to be used in a ventilated nuclear installation and continuously in depression, the cast iron parts thus molded must undergo a control of their radioactivity. This process therefore leads to a large amount of waste

disposal is expensive.

  A second method is to use a shell mold having an inner shell and an outer shell between which the cast is cast. The shells are then cooled, generally by a circulation of fluids, to allow the demolding of the part. This method has the disadvantage of being rigid; it can therefore be implemented only for simple shapes and, preferably, for the manufacture of parts in series. In addition, the shells being cooled by the circulation of a fluid, risks of fluid contact with the molten iron are expected; also, such a method can not be implemented in a

nuclear installation.

  A third molding process involves casting molten cast iron onto a rapidly rotating, fluid-cooled central shell. This is a centrifugal molding process. This process has disadvantages substantially

  identical to those of the second method presented above.

  In addition, this method has a risk of rupture of the rotating part whose consequences could be considerable. The implementation of such a method can not therefore be envisaged in an installation

  because of its unreliability.

  Furthermore, it is known to mold lead parts using collaborating formwork, that is to say, forms at least a portion of said formwork adheres to the lead to form

the desired piece.

  Since lead has a much lower melting point (325 ° C) at the melting point of cast iron (1,200 ° C), as well as steel and many other metals, it can not be used to achieve cast iron or other metal parts

  having a high melting temperature.

  SUMMARY OF THE INVENTION The present invention relates to a process for molding cast iron parts (or other high melting temperature metals) by means of collaborating formwork, also called envelopes; for application to the nuclear industry, the metal used to mold the part may

  to be a recycled metal more or less radioactive.

  More specifically, this process for molding metal parts having high melting temperatures consists, for each piece to be molded, in: - producing a shell by assembling sheets into a first metal, - arranging aggregates around this envelope pouring a second molten metal into said envelope; after cooling and solidifying the second metal, removing the aggregates, said second solidified metal collaborating with the envelope first;

metal to make the piece.

  According to the invention, the realization of the envelope may consist of welding plates to

  inside which is poured the second metal.

  It also consists in welding metal inserts on the sheets to keep them in place.

  fixed position during the casting of the second metal.

  According to the preferred embodiment of the invention, the first metal is steel and the

second metal is cast iron.

  Aggregates are preferentially

steel balls.

  According to one application of the invention, this method allows the production of radioactive waste containers from recycled ferrous metals.

Brief description of the drawings

  FIG. 1 represents a partially cut-away perspective view of a collaborating formwork for implementing the method according to the invention; FIG. 2 represents, schematically, a sectional view of a radioactive waste container

  performed according to the method of the invention.

  Detailed presentation of an embodiment

  In the description that follows, the

  method of the invention will be described in its

  application to the realization of a cast iron container.

  It can, however, be used to make all kinds of shapes and weights very varied, cast iron or any other metal with a

high melting temperature.

  FIG. 1 thus represents the collaborating formwork 1, or envelope 1, used to produce, according to the method of the invention, a container capable of

  for example, receive radioactive waste.

  The envelope produced for the implementation of this method of the invention comprises a cylindrical outer sheet 2 and a cylindrical inner sheet 4 and

  concentric to the outer sheet 2.

  According to another embodiment of the invention, not shown in the figure, the envelope may be of parallelepipedal shape or of a whole

other form.

  The lower ends of these sheets 2 and 4 are closed by funds 2a and 4a. At their upper ends a sheet 2b ensures a closure of the envelope. This sheet 2b however has

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, the steel having the property of being resistant in tension and in compression. The sheets 2 and 4 are held in a fixed position relative to each other by means of metal inserts. According to the example of Figure 1, the sheets 2 and 4 are held at their upper ends by six inserts welded on the one hand on the sheet 2 and on the other hand on the sheet 4. At the lower ends of the sheets 2 and 4, four metal inserts 8 are welded, on the one hand on the outer face 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 holding the two sheets is, of course, given by way of example and may vary depending on the resistance

  metals used and the shape of the parts to be molded.

  For molding parts of very simple form, the envelope may comprise only one

  sheet metal, no metal insert is necessary.

  When this formwork collaborating, or envelope, is made, it is introduced into a box 10 whose bottom 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 inside the envelope. In particular, for the example of the envelope of FIG. 1, aggregates

  are introduced inside the inner sheet 4.

  These aggregates ensure the maintenance of the envelope during

of the introduction of the cast iron.

  These aggregates 12, which may for example be steel balls, make it possible to prevent any deformation of the sheets 2 and 4 during the casting of the molten cast iron, the sheet temperature being able to reach about 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.

  Aggregates 12 have, moreover, a preponderant role in the evacuation of the calories resulting from the casting of the molten cast iron, these aggregates having

a high heat capacity.

  In addition, the collaborating forms, of the type described above, may, as required, include reinforcements, inserts, reserves, notches, etc.. When the aggregates have been introduced, the molten cast iron is, in turn, introduced into the casing 1 and, in particular, between the sheets 2 and 4

  for the example of Figure 1, by a few orifices 3.

  According to one embodiment of the method, the melt casting is divided into several jets distributed on the surface of the envelope. Such a distribution of the cast iron ensures a better distribution of the forces due to the pressure of the molten iron on the sheets as well as calories due to the high temperature of the molten cast iron. Such an embodiment makes it possible to mold thin pieces using jets of

  molten cast iron of small diameter.

  In addition, the casting speed of the cast iron can be adapted to allow faster solidification of the cast iron, which reduces the pressure experienced by the sheet 4 of the casing 1 (ferrostatic pressure effect). When the cast iron thus cast is cooled, the aggregates are discharged (by tilting

  or aspiration) and the molded part is recovered.

  In order to allow an easier evacuation of the aggregates 12, and thus to limit the risks of sticking the aggregates against the envelope, the walls, respectively, external of the sheet 2 and internal of the sheet 4 may be previously coated with a product

of poteyage.

  The embodiment, according to the method of the invention, of a cast iron container has been described previously. A cover can be made, by the same method, to fit on the container shown on the

figure 1.

  FIG. 2 shows, in section, the container of FIG. 1, with its lid, obtained

by the process of the invention.

  The references, shown in this FIG. 2, which are identical to the references of FIG.

  represent identical elements.

  The container represented in this FIG. 2 thus comprises the envelope 1 made of steel sheets collaborating with the solidified cast iron 3. The combination steel / cast iron / sandwich steel has excellent strength characteristics, the cast iron having good compressive strength and the steel having good tensile and compressive strength and a good elongation capacity allowing to absorb shocks. This combination is, in addition, a good protection against radioactivity. FIG. 2 also shows the groove 14 for gripping the container (of type

  ANORA shell C), as well as metal inserts 6.

  In addition, the lid 16 of the container is shown. This cover has an envelope 18 in

  steel sheets collaborating with a layer of cast iron 20.

  According to the example shown in this Figure 2, the cover 16 is fixed on the container by means of a screw system. This screw system consists of several threaded holes made in the lid and in the container, inside which are introduced screws. FIG. 2 shows two tapped holes 22 and two screws 24 inserted in

said tapped holes 22.

  In another example, the fixing of the lid on the container can be achieved by means of a weld bead deposited between the lid and the container, this fastening further ensuring

the tightness of the whole.

  In addition to the application to the radioactive waste container, the method of the invention may be

  to make all kinds of anti-

  radiation such as doors, walls, floors, etc., the thickness of which may vary from about 40 to 350 millimeters. This method therefore makes it possible to provide protection against radiation by using the recycled ferrous metals of the nuclear industry.

Claims (7)

  1. A method for molding metal parts having high melting temperatures, characterized in that it consists, for each piece to be molded, to: - produce a formwork collaborating, or envelope, (1) by assembling sheets in one first metal, - arranging the aggregates (12) around the casing, - casting a second metal (3) melt in said casing, - after cooling and solidification of the second metal, removing the aggregates, said second solidified metal collaborating with the envelope first metal to make the piece.   2. Method according to claim 1, characterized in that the realization of the envelope consists of welding plates within which is cast the second metal.   3. Method according to claim 2, characterized in that the embodiment of the envelope further comprises welding metal inserts (6, 8) on certain sheets to maintain a fixed position   said sheets relative to each other.   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 aggregates are steel balls.   7. A process for molding containers of radioactive waste, characterized in that it consists   in a process according to any one of the claims 1 to 6.