FR2558398A1 - LARGE DIMENSION MOLD FOR METAL OR ALLOY - Google Patents

Abstract

RELATIVELY LOW EXPENSIVE MOLD FOR CASTING A LARGE-DIMENSIONAL 5 PIECE IN ALUMINUM ALLOY. IT INCLUDES A CLOSED EXTERIOR ENVELOPE 1 CORRESPONDING TO THE EXTERIOR CONTOURS OF THE CAST. THIS ENCLOSURE IS MANUFACTURED FROM THIN STEEL SHEET, BY WELDING OR RIVETING, AND IT CONTAINS CAST 3 PRIMERS AND 4 VENTS IN THE USUAL WAY. THE ENTIRE INTERIOR SURFACE OF THE STEEL ENCLOSURE IS COATED WITH A THERMALLY INSULATING MATERIAL, PREFERRED A SHEET OR FABRIC OF ASBESTOS WITH A THICKNESS UP TO 2MM, WHICH PREVENTS QUICK COOLING AND ALLOWS EASY REMOVAL OF THE MOLD.

Description

The present invention relates to the molding of

  large castings in metals and alloys, more

  especially in aluminum alloys; it aims, in part

  culier, the molding of large and complex bodies

  sion which would require, in the case of usual sand molding, complicated models and cores as well as

large casting frames.

  Two types of molds are currently used for casting non-ferrous metals, namely sand molds and metal molds. Sand casting requires a wooden or metal model which generates the required shape,

  when one or more foundation frames are filled with sand

  derie, while the interior contours and cavities

  are defined by cores inserted in the mold, these no-

  yaux also being in sand. The metal molds are

  generally used for smaller items, manufactured

  ques in series, and they are made of metal, usual-

  cast iron blocks, milled or otherwise machined

  lesson in the negative configuration required for the part

  lée, taking into account the shrinkage during solidification

  and cooling, which varies with different metals.

  The cores are similarly made of cast iron or sand and they

  are held in the mold in an appropriate way to

  create cavities in the casting.

  Both methods are suitable in the case of

  these small or medium-sized flows. However, the molds become very heavy and expensive for heavy and large pieces, which is particularly troublesome in all cases where a single piece is cast or

  when only a small number of castings are required.

  The present invention therefore relates to a mold

  for the casting of large parts, which is rela-

  very light and can therefore be obtained more economically

than the mold of the aforementioned types.

  These molds should be in one piece for unit work and should be molds of

  separable joint type when used for

  ler a small series of the same product.

  The present invention also relates to a mold, to form the outer contours, and cores to form the inner cavities by the same method.

  of manufacturing, the cores can be left in the

  this casting, due to their low weight, if desired.

  According to the present invention, a mold comprises a casing made of relatively thin sheet steel, the mold having at its upper end primers and vents while its inner surface is coated with a layer of thermally insulating material, by example an asbestos sheet or a mixture of asbestos,

  graphite and binders sprayed onto the surface of the steel.

  The configuration of the mold is obtained by preparing a plurality of elements of different shape, made of sheet steel, and assembling these elements by welding, riveting or the like. Likewise, a core is made from several sheet steel elements and it is coated on its

  outer surface with thermally insulating material.

  The mold can be composite, comprising several parts assembled by flanges and bolts, for repetitive orders, or, in the case of a single casting,

  it can be a completely closed envelope that is

  cut and removed from the casting after filling the mold and solidifying the metal. The mold may have a thin wall, even in the case of very large molds, of the

  made of the low weight of the metal, especially in the case of al-

  aluminum bonding, on the one hand, and the fact that large castings are poured in several stages because of the

  limited capacity of the oven and / or ladle, other

  be part. Between the filling stages, the first

  Cheek of poured metal solidifies, except at its upper surface

  which remains in the liquid or semi-liquid state and which is e558398

  then combine with the molten metal of the next part

  boasts. The already solidified part of the casting does not contribute to the hydraulic pressure acting on the walls of the mold and the mold is therefore exposed only to the hydraulic pressure due to the height of the molten material still liquid above the separation line between the previous layer and the new layer of metal poured into the

  mold. As a result, only a small area of the mold is supported.

  stress caused by hydraulic pressure, at

  each individual filling step, and this makes

  puts to make a thick sheet steel mold

less than 1 mm.

  The thermally insulating inner layer serves, on the one hand, to prevent rapid cooling of the metal to

  through the steel walls, and consequently its harmful effect

  ble on the final quality of the casting, and it

  on the other hand easily separates the mold from the part

  casting, since asbestos or projection mixtures

  do not adhere to aluminum alloys.

  It is obvious that, for relatively small parts and large series, the usual casting method

  in sand by means of wooden or metal models, in particular

  tying in foundry machines is preferable. Any-

  times, the present process is better and more economical for the casting of large parts, such as bridge elements, support pillars for buildings, submerged foundations for sea dikes, molds for pressing sheet metal in the aviation industry and

  automotive, etc. The present process is particularly suitable for

  rement for casting molds used in manufacturing

  pressing prototypes, while studying new ones

airplanes or motor vehicles.

  The sheet steel mold is suitable for obtaining

  complicated configurations, since the difficulties

  wood models do not exist when using this process. Sand casting requires, first of all, a draft along the opposite surfaces, in order to allow an easy extraction of the model out of the sand mold, while the present method allows to cast pieces with parallel sides. Model molding

  forces to form the incoming and protruding parts at the

  yen of joint models whose separate parts are extracted separately from the mold, while with the present process the entire mold can be destroyed in the case of

  unique castings, or you open the composite mold

  site along the flanges and the various parts of the mold are removed from the casting. This method of removing a mold is similar to that used with permanent molds made of a metal block, except that molds of the latter type would be very heavy and of

extremely cottony manufacturing.

  A preferred material for the manufacture of molds is sheet steel with a thickness of 0.5 mm or

  more, which can be easily riveted or welded. Com-

  preferred coating material, a film may be used

  2 mm asbestos, or an asbestos fabric which can be thinner but can be obtained up to a thickness of 2 mm; these two materials can be curved to the shape of the mold, in particular when they are wet,

  and they adhere well to the metal surface of the mold a-

  after having been fixed there by riveting or gluing. Another method of insulation is to spray on the inner surface of the mold an insulating material, of the type used for coating permanent steel molds in order

  to be able to easily separate the casting from the mold.

  Likewise, the cores are made from

  preformed elements of sheet steel which should be coated

  on the outside in order to be easily separated from the part

  this casting. On the other hand, since they are light in weight,

  they can be left in the casting, if desired

  sire or if they are intended for hollow spaces without

munication with the outside.

  The invention will be better understood in the light of

  the description of its non-limiting embodiments

  ves, shown in the accompanying drawings in which: FIG. 1 is a vertical section through a mold used for the casting of a hollow column,

  Fig. 2 is an enlarged view of the

  tail "A" of FIG. 1, and FIG. 3 is a section through a mold for a

piece of different type.

  It can be seen in FIG. 1 that a sheet metal mold of a-

  cier comprises an outer casing 1 and an inner casing 2 defining the core, their respective shapes corresponding to the outer and inner contours of the part to be cast in the mold. The upper part of the mold has primers 3 for pouring the metal into the mold, while several vents 4 are provided.

  in the upper part and the side walls to allow

put on the exhaust gas.

  FIG. 2 represents a part of the walls of the exterior and interior envelopes which are made of coated steel sheets 10 and 20, on their face intended

  in contact with the molten material, a thermal layer

  only insulating asbestos sheet 11 and 21, respectively-

  is lying. The metal casting is designated by the reference 5.

  The method of manufacturing a mold of this type consists in first preparing the outer envelope from cut and preformed elements, of sheet steel, which are

  assembled in the final configuration by welding or ri-

  and to coat the interior surfaces with a

  thermally insulating. It is assumed that the outer envelope has a sufficient size for a worker to enter it and fix the insulating layer by gluing or riveting. However, if the interior space is too narrow for a worker to perform this work, the coating is

  applied to individual elements, before they are assembled

  which can be done by welding since asbestos

  resists heat. In the case of a composite mold, each

  that separate element is coated internally, before assembly

  clamping by means of flanges and bolts.

  The inner envelope or core 2 is manufactured in a similar manner and it is clear that there is no difficulty in coating with the material thermally

  insulating since this operation is carried out on the

  external faces after complete assembly of the envelope.

  In the mold shown in Figure 1, it will be impossible

  ble to insert the core through the lower opening of the

  outer velope, since the large diameter parts of the core cannot pass into the small internal diameter parts of the outer casing. In this case, the insertion of the core is made possible by manufacturing the outer casing in at least two parts which are assembled after their positioning around the core, with a correct gap between the walls, by means of a connection. permanent or removable. The distance between

  the two envelopes is determined and maintained by

  tretoises or rivets 6, preferably made of the same material as the casting. Lost spacers are inserted

  during or after the complete assembly of the mold.

  The shape of the core shown in Figure 1 does not allow it to be separated from the finished casting. It can therefore be left in the room, since it will not greatly increase the total weight, or it can be cut into several parts which can themselves be removed

of the room.

  Figure 1 also illustrates the overflow

  several stages. We see in the figure that the metal has been

  dried in three stages, so as to reach levels I, II and III, respectively. To understand the process

  of casting, it is assumed that the part is of such a dimension

  the metal brought by a single pocket is just enough

  fisant to fill the mold successively at different levels. After having poured the first pocket, we reach level "I" and the mass of the metal located below the level

  calf I solidifies before the next pocket is

  with the exception of the top layer which is still in the molten state. When pouring the metal to level "II", the solid part below level "I"

  exerts no hydraulic pressure on the walls of the mold

  the surrounding, due to the contraction of the flow.

  For this reason, the maximum hydraulic pressure acts on the wall of the mold at the height of level "I", this pressure being p = yH, oy is the density of the molten metal (kg / cm3) and H is the distance between the levels "I" and "IV" (cm). Newly poured metal easily combines

  on the molten or semi-liquid surface of the lower layer

  re. The same pressure situation is found during the

  subsequent filling weights, up to the upper level, and it is clear that the maximum pressure on any region of the mold is exerted at the lower end of each

part of liquid metal.

  The mold shown in Figure 4 includes a

  outer casing 1 'in the shape of a truncated cone and a

  2 'inner velvet in the shape of a truncated cone of the same length

  size and diameter smaller than that of the envelope ex-

  3 'casting primers and 4' vents are pre-

  seen in the upper part and the side walls of the outer envelope, in the same way as in the mold shown in FIG. 1. The inner envelopes and

  outside of the mold are connected at their upper ends

  respective lower and lower with annular plates

  res 7 'and 8' which close the mold. The entire interior space of the mold is coated with an insulating material. Connections

  between the two envelopes are preferably of a de-

  mountable, so that the mold can be separated without

have to destroy it.

  It is easy to understand that it is simple to assemble

  block the parts of the mold and remove them from the solidified casting and that this type of mold is well suited for the casting of long and hollow mats, hollow columns

and similar parts.

  It is understood that modifications of detail can be made in the shape and construction of the device according to the invention, without departing from the scope

of it.

 558398

Claims (10)

Claims   1. Mold for the casting of a large piece   metal die, which is particularly suitable for the casting of a large piece of aluminum alloy, characterized in that it comprises a closed external envelope (1) corresponding to the external contours of said part (5) and the walls of which are made of relatively thin sheet steel, this casing comprising at least one casting starter (3) and at least one vent (4) and being coated   on its inner side with a thermally iso-   lante which resists the heat of molten metal to ver- serve in the mold.   2. Mold according to claim 1, for the casting of a large part having at least one   inner cavity, characterized in that it comprises a no-   yau in the form of an inner envelope (2) corresponding   corresponding to the configuration of said cavity and the walls of which are made of relatively thin sheet steel, this core being connected to the outer casing and fixed to the distance   required from the outer shell walls, the ex-   the inside of the core walls being coated with a material   thermally insulating which resists the heat of the ma-   third molten to pour into the mold.   3. Mold according to claim 1 or 2, characterized   in that it comprises a unitary external envelope, used   made for a single casting of a part.   4. Mold according to claim 1 or 2, characterized in that it comprises a composite outer envelope, consisting of several wall elements connected to each other in a removable manner, by assembly means   such as flanges, bolts and nuts.   5. Mold according to one of claims 1 to 4, ca-   characterized in that it has a coating resistant to   heat, attached to the surface of the casing by riveting.   6. Mold according to one of claims 1 to 4, charac-   terized in that it has a coating resistant to   heat, fixed to the surface of the envelope by gluing.   7. Mold according to one of claims 1 to 4, ca-   characterized in that it comprises a layer resistant to   heat, sprayed on the surface of the envelope.   8. Mold according to claim 5 or 6, characterized   in that the covering consists of a sheet of a-   crumbling. 9. Mold according to claim 5 or 6, characterized   in that the covering consists of an asbestos fabric.   10. Mold according to claim 7, characterized in that the heat-resistant layer consists of a mixture of asbestos, graphite and binder, sprayed on the envelope wall surface.