FR2472434A1 - METHOD AND APPARATUS FOR MOLDING PARTS BY METAL CASTING IN A PERMANENT MOLD WITH A PLUNGER WHICH SLIGHTLY COMPRISES THE MOLDED PART AT THE TIME OF ITS COOLING - Google Patents

Abstract

THE SUBJECT OF THE PRESENT INVENTION IS A PROCESS AND A DEVICE FOR MOLDING METAL PARTS. A PLUNGER 27 IS PROVIDED AT THE UPPER PART OF A CAVITY 26, A TANK 33 OF MELTED METAL IS PROVIDED ABOVE THE PLUNGER, THE PLUNGER 27 IS LOWERED INTO CAVITY 26 WHILE CONTINUING TO FEED THE TANK 33 IN MELTED METAL, WE LEAVE THE METAL CONTAINED IN CASTING CELLAR 26 TO SOLIDIFY BY TAKING THE SHAPE OF THE DESIRED PRODUCT AND THE LATTER IS DISMOLDED. APPLICATION TO THE MANUFACTURING OF FOUNDRY PARTS.

Description

2472434.

  The present invention relates to a method and an apparatus for molding cylindrical bars, plates, slabs and the like of high-melting metals and is particularly directed to the direct molding of semi-finished steel products. The classic way to make products

  semi-finished steel, for example cylindrical bars

  slabs, slabs, slabs and billets

  is to pour molten steel to

  storing an ingot, then rolling the ingot in a rolling mill to make cylindrical bars,

  slabs or slabs, slabs or billets. subse-

  In the meantime, these semi-finished products are processed into bars, tubes, tapes, strips or parts.

  of various forms that are called "finished products".

  It can take up to twenty five or more passes in various rolling mills to turn an ingot into a semi-finished product. In the passage of an ingot

  to a semi-finished product, the surface of the trans-

  of the coin decreases in the ratio of at least

  4/1. A large amount of energy as well as a

  costly measures are therefore necessary to reduce the

  ingot in the state of a semi-finished product.

  A more modern method of making slabs or other semifinished products consists of a continuous casting process in which molten steel is poured into a chute, which steel then passes into bottomlessly cooled vertical molds and then drawn by cylinders or other mechanisms

  to give a continuous piece of great length.

  In this continuous piece, sections are cut,

  which gives slabs, slabs or billets

  the shape of the vertical mold. This process is deceptively simple because in practice it presents many difficulties. A continuous casting installation is cumbersome and requires

  many places. The capital involved is consid-

  and the process is not suitable outside

mass production.

  Although the plates, slabs and billets can be cast by the continuous casting process, casting of cylindrical bars by continuous casting has not proved satisfactory, since between the various shapes of pieces, they are the cylindrical bars which, for a given volume, have the weakest surface and are difficult to cool, by behaving otherwise

  satisfactory in the continuous casting process.

  Another method of manufacturing plates,

  slabs, in particular stainless steel plates

  dable, is the bottom pressure casting process

  described in United States Patent No. 03.

  196.503 in the name of the applicant. According to this method, a casting ladle filled with molten steel is placed in

  a pressure vessel that is hermetically sealed

  with a lid. A casting tube worked

  pour this cover and go down to a distance of between ten and fifteen centimeters from the bottom of this ladle. The upper part of the pouring tube is mechanically connected to the filling end of the mold used to form the slab. The pressure of the air contained in the container causes the molten steel to rise into the pouring tube and to enter the slab forming mold by the lower end, the mold being slightly inclined. The installation is expensive and difficult

  are caused by inclusions, because the

  upper part of the slab towards which normal

  inclusions is the first part

  froidit. It is well known that ferrous metals can be cast directly into sand molds to produce commercial products. On the other hand, it is practically impossible to directly obtain commercial products in a permanent mold, since the molten ferrous metal is welded to the sidewalls of the mold and / or attacks them and, if it occurs any vertical drop, the energy of the falling molten metal may damage or even

  completely destroy the bottom of the mold.

  The invention relates to a process for directly casting semi-finished steel products and the like products of other high-melting metals, in particular cylindrical bars and

plates or slabs.

  The invention also provides an efficient and inexpensive method and apparatus for casting

  directly semi-finished products containing little

  purities and having good structural qualities of

grain and surface condition.

  In accordance with the invention, semi-finished steel products are poured directly into a permanent mold provided with a special mobile plunger which is rapidly lowered into the mold while the latter fills with molten metal and that the it is rapidly flushed upward as the molten metal solidifies, so as to lift the casting by releasing it slightly from the mold as it cools. This rise of the plunger puts the casting

  in compression and reduces cracking.

  Above the mold cavity is a molten metal tank which is always maintained.

  full while the diver descends into the mold.

  This reservoir also acts as a molten metal feeder, during the cooling of the casting. The mold cavity has a cross section

  constant, the surface of which corresponds to that of the

  it is molded. The diver has the same section

  transverse than the mold and constitutes a joint

  smoothing, impervious to molten metal, with the walls la-

  of the mold. The upper part of the diver is surrounded by a thin strip of steel and the space bounded by this band is filled with stone sand

  which hardens on the spot. The diver descends to speed

  it is between 1.3 and 10 cm / second. The descents and climbs of this plunger are advantageously ensured by a screw jack driven by an engine

to air.

  The molds for cylindrical bars are

  Vantageously consist of an inner sleeve and an outer sleeve, both steel separated by a layer of sand. The molds for making plates or slabs and other flat articles are preferably constituted by lateral blocks and by steel end blocks provided with slots, reinforced by struts. The molds can be reused many times and can be adapted at will to cast cylindrical bars or simple slabs

or multiples.

  The invention thus provides a method and apparatus for casting ferrous and other high melting metals by directly manufacturing cylindrical bars, slabs or other semi-finished products, by means of a relatively inexpensive, at a price of

  low return and high efficiency, this pre-

  the advantage of using in the best possible

  the molten metal being cast, to minimize losses and to give semi-finished products with a very good surface

  grain structure. Thanks to the invention, it is possible

  to make plates or slabs without the use of additional energy to reheat the steel or ingot as necessary to operate a rolling mill, thereby saving energy and money. The invention is particularly suitable

  the manufacture of molded products in relative quantities

  the airlock, for example, in the manufacture of stainless steel articles, which could not be ensured by continuous casting.

  because of the large imposed flow rate and the lack of flexibility.

  The invention provides molded products of excel-

  slow quality. The molten metal enters a mold after an extremely reduced contact with the air, such

  so that the oxidation of this metal is reduced to a minimum.

  The quality of the surface condition of the obtained product is better since the force directed upwards

  the plunger exerts on the reduced casting

  the volume of air between this casting and the mold and decreasing the adherence surfaces. He nty has

  splash or burrs, or deformations by flam-

  bage, nirides, and cold drops, since the metal does not fall from an appreciable height. The inclusions rise to the top of the molded product and are easily removed. The flow of metal by gravity follows trajectories imposed by

  the natural convection of the system, and not the

  jectoire imposed by the bottom pressure casting because, according to the invention, the very hot metal arrives through the upper part of the mold and 2472434i metal

  very hot rises up to this upper part of the mold.

  The method and apparatus according to the invention can be used for the molding of articles of any ferrous metal, including stainless steel, and any high melting point metals, such as

nickel, copper and titanium.

  Other features and benefits of

  the invention will emerge from the description which will

  to follow, made with regard to the annexed drawings and giving as explanatory but not limiting, various

embodiments.

  In these drawings, Figure 1 is a side elevational and sectional view of a mold for casting cylindrical rods and using the method and apparatus of the invention; Figure 2 is a lateral section, on a larger scale, of the plunger shown in Figure 1; Figure 3 is a plan view, from above and in partial section, of the plunger and the upper part of the mold, the section being taken along the line 3-3 of Figure 2; Figure 4 is a side view and in section similar to Figure 1, illustrating the casting process

  of cylindrical bars, the diver having descended

  Viron halfway to his race; Figure 5 is a side view and in section

  similar to Figure 4, but showing the complete diver

  descended and the mold cavity filled with molten metal; Figure 6 is a sectional side view

  similar to FIGS. 4 and 5, showing the cylindrical bar

  casting and the tundish lifted and slightly disengaged from the mold as this cylindrical bar cools; Figure 7 is a plan view of the wedging strip on which we can see the slots to facilitate its winding around the perimeter of the retaining plate; FIG. 8 is a sectional and side view, on a larger scale, of a mold according to another form

  for the production of cylindrical bars

  hollow driques; Figure 9 is an end view and elevation, with some parts in section, of another embodiment of the mold according to the invention for molding a single plate or slab; Fig. 10 is a top plan view of the mold of Fig. 9; Figure 11 is a side view of the same mold, along the line 11-11 of Figure.9; FIG. 12 is a plan view, from above and on a larger scale, of a portion of the tundish and plunger of the mold shown in FIG. 9; FIG. 13 is a side elevational view and at most large scale, a portion of the tundish and plunger of the mold of Figure 9, the section being taken along the line 13-13 of Figure 12;

  FIG. 14 is an end view and elevation

  part of the tundish and the diver

  of the mold of Figure 9, in section along line 14-

  14 of Figure 13; Fig. 15 is a plan view of the motors or screw jacks and the air supply facility for the plaster mold plungers of Fig. 9; Figure 16 is a series of perspective views, representing a number of

2472434-

  semi-finished products which can be molded in accordance with the invention, namely a simple cylindrical bar, a

  hollow cylindrical bar with a thick wall, a cy-

  thin-walled, slab, plate or slab and thin plate. The permanent mold 20, as shown on

  FIG. 1 is constituted by a tubular sleeve

  21 and an outer tubular sleeve 22 concentric with the first, these two sleeves having a circular cross section, and the volume 24 they delimit being filled by a mass of sand 23. The inner wall 25 of the inner sleeve 21 constitutes the surface Lateral of a casting cavity 26. A plunger 27, attached to a lifting screw 28 can descend and mount in this cavity 26. under the action of a screw jack 29

located at the bottom of the device.

  An air motor 31 drives this screw jack 29 and forces the lifting screw 28 to lower and lift the plunger 27 with a speed that is set

at will.

  A tundish 33 is disposed at the top of the mold over the inner sleeve 21 and a ladle 34 is provided above the vessel 33 for pouring molten metal 35 therein as shown in FIG. of a casting operation, the plunger 27 is at the upper part of the casting cavity 26, as shown in FIG.

  1. Once the mass of molten metal has been released

  In said casting vessel 33, the plunger 27 is lowered at a speed set towards the bottom of the mold, so that at the end of the downward movement, the molten metal 35 fills this casting cavity 26 as shown on FIG. Figure 5. When the molten metal cools, a cylindrical bar or a semi-finished product having another shape is formed with

  the upper part, a feeder 36-which one cuts.

  If we study in more detail the mold 20, we see that the outer sleeve 22 rests on a circular base plate 38 inside an annular collar 39 to which this outer sleeve is

  soda. This collar 39 is itself fixed with the aid of

  nuts 40 and locking bolts 41 to the base plate 38, which allows to disassemble at will. To the

  upper part of the mold is a top plate

  upper plate 42, to which is welded the upper portion of the sleeve 22. This upper plate 42 has, in its center, a circular opening 43 whose diameter is slightly larger than the outer diameter of the inner sleeve 21 and an upper groove milled, circular, or

  channel 44 in which fits a ring 45 (Figure 2).

  The upper and outer part of the inner sleeve 21 is welded to the inner part of this ring 45, which enables the assembly to be placed in the opening 43

  and suspend it to the top plate 42 by applying

  cation of this ring 45 in the channel 44. The lower part of the inner sleeve 21 is not stressed and it can expand down without buckling or jamming while it absorbs heat

molten metal.

  A round plate 48 is secured by means of bolts 47 to the lower part of the inner sleeve 21, inside the outer sleeve 22. Between this round plate 48 and the sand 23 which fills the space 24 between the outside of the inner sleeve 21 and the inside of the outer sleeve 22, there is a

  layer 49 of asbestos or steel wool padding.

  There is some clearance between the outer circumference of the round plate 48 and the inner surface of the outer sleeve 22. The asbestos cushion 49 prevents the

  mass of sand 23 to escape and hinder the dilation

  necessary the inner sleeve 21 downwards.

  Preferably, the surface of the

  inner king 25 of the inner sleeve 21 to an opera-

  to any other operation to make it smooth and smooth. The inner sleeve 21 should have a thickness of at least 3.2 cm and be significantly thicker than the outer sleeve 22, since it must retain its

  resistance and cohesion when submitted directly

  to the action of molten metal, but at the same time

  this inner sleeve 21 must be as thin as possible

  to avoid the inconvenience of a thermal gradient

and the formation of cracks.

  As has been pointed out, the volume 24 between the inner sleeve 21 and the outer sleeve 22 is filled with a mass of sand 23 which is squeezed into this volume to maintain and strengthen the inner sleeve. To fill this volume 24 can be used other filling materials, for example steel balls or fine chippings. It is

  it is preferable for this filling product to be

  variable tension and is not a good conductor of heat. Figures 2 and 3 show in more detail the plunger 27; the latter is constituted by a heavy steel swivel plate 50 fixed to the upper part of the lifting screw 28 and held in a recess 51 of a cylindrical block or heavy piston 52 made of steel by a ring 53. which is secured

  at the bottom of the piston using bolts.

  54. Above this piston 52, there is a circular retaining plate 56 which is fixed to the upper part of the piston by means of bolts 57. A wedge strip 58 of steel, with a thickness of order of 0.38 mm, the normal thickness for the holds, occupies the

  around the top of the piston 52.

  This wedging band 58 is attached to the piston 52 of the plunger with nails 60 threaded into holes 61 of the retaining plate 56, in trills 62 drilled in this wedging band and in holes 63 of the piston. The lower portion 58a of this wedging band has a series of slots 64 (Figure 7), a depth of about 2.5 cm and spaced from each other by about 1.3 cm, and submit this

  bottom part to an annealing and then flap it

  to the other part, or upper part, 58b of the wedging band. This wedging strip 58 occupies the periphery of the retaining plate 56 and the latter is placed on the top of the piston 52 and subject to

  this piston with the help of bolts 57 that are tightened strongly

  at least with your fingers. This forces the holes 61 of the plate 56 to come in front of the holes

  63 of the piston 52. The nails 60 retain effectively

  cage the wedging band 58 on the piston 52 during the

descent of the latter.

  The wedging strip 58 is applied against the wall 25 of the inner sleeve 21 and is smoothed against this wall before drilling the holes 62. The bolts 57 can then be tightened further after having been put in place.

place the cushioning tape.

  This wedging strip 58 can be a part

  steel or any other flexible flexible metal

  resistant and resistant, able to withstand

  high levels-which are involved in this process. A good thickness for the steel cushioning strip is of the order of 0.37 mm, but this thickness can be

between 0.13 mm and 0.89 mm.

  Silica sand 65 is strongly

  ge to a binder with appropriate nuclei, in the space located

  above the retaining plate 56 to a distance of

  approximately 0.32 cm above the upper part of the cushioning band 58, so as to constitute a

  puchon or refractory lid 66 for the plunger 27.

  It is preferred that the cover 66 is concave in shape (as shown in FIG. 2), so that the sand mass is higher on the sides than in the middle. This form is easily obtained using a gland with a diameter slightly smaller than that of the inner sleeve 21 having a curved front face. The upper part of the wedging band 58 must be at least about 0.30 cm above the upper part of the sand mass, so that this sand can not scratch the inner wall 25 of the inner sleeve and dirtying the casting and / or forming cracks therein. The sand 65 is then treated with carbon dioxide, or with a "no-cooking" device, or in any other suitable manner, so as to obtain, on the plunger 27 of the piston, a refractory and hard cover 66 molded on the spot. After curing the sand, the remaining sand grains must be removed from the cover 66 and the inner wall 25 of the inner sleeve by an air jet or brush. It is absolutely essential that this refractory liner 66 made of core sand of the plunger 27 be manufactured in situ, as described, with each new casting. The piston 52 and the retaining plate 56 can be reused many times; however, it is best to use a tape of

  58 new rigging for each casting.

  It is necessary to provide, in the refractory lid 66, openings and games directed downwards so that the gases that could have arisen under the effect of the contact between the lid and the mass of molten metal can escape towards down and do not get chased up into that mass of molten metal. The lid 65 is pr.ox so that the gases, whatever they are, escaped downwards by cc lid, by the holes 61 of a -laque 56, Fr play between this plate 56.and the udder --n 52 and by O

  clearance between the inner wall 25 and a piston 52,

  penetrate inside the mold.

  The plunger 27 constituted in the manner described above forms a sliding, sealed or molten metal joint with the inner wall 25 of the inner sleeve 21, and this sleeve has, in cross-section, the same shape as the casting cavity 26 and than the article that

  we mold. The expression '' impervious to molten metal ''

  that the molten metal does not flow past the plunger or that, even if a small amount

  is not enough to trap the diver or endc--

  mage in any way, the means used to make

get off and ride this diver.

  The lifting screw 28 and the jack 29 are

  Slightly a ball cylinder, a screw jack of the type described in United States Patent No. 3,323,777 and constitute the means for lowering and raising the plunger 27. Advantageously,

  ball bearings are provided in the helical screw

  coldale housing 32, so as to form what is called a screw ball bearing cylinder. In addition, it is necessary to provide pivoting means at any point of the connection of the lifting screw 28 with the plunger 27, so that the plunger does not tend to rotate when controlling the

  screw jack for lowering or raising this diver.

  In the floor that supports the mold, there must be a bore 67, a depth at least equal to the stroke of the plunger 27, to receive the lifting screw 28 when it drops the plunger at the bottom

  of the mold. The screw jack 29 is of the type of one or the other

  be screw jack shown in Figure 15 and that one

will describe further.

  At the top of the mold 20 is mounted, over the casting cavity 26, the casting vessel

  33 (Figure 1), consisting of a metal box cy.

  lindrique 69 or a section of steel pipe, which is filled with a mass of sand with refractory cores, shaped and well aglomérée. This sand mass 70 is squeezed on the spot around a suitably shaped truncated cone having its small base at the top, then this sand is hardened. The sand 70 may comprise a silicate binder which is hardened with carbon dioxide "without cooking or a composition according to which a

  resinous binder takes under the action of a catalytic

  and hardens under the action of heat. Sharp siliceous sand of the type used in foundries for making cores can be used in

present case.

  The tundish 33 directs the molten metal into the casting cavity 26 and constitutes a

  reservoir or a counterweight 36 of molten metal

  above the plunger 27 as it descends and the casting is cooling. According to the known principles of making tapholes for molding steel parts, the casting vessel 33 can be designed with its cross-sectional area.

  lower at the top, the surface of this trans-

  downward, as represented by

  sented. Casting tanks with the largest cross-section at the top can also be used. The tundish 33 must be

  kept permanently filled with molten metal

  during the entire duration of the casting and it must be substantially full before the diver 27 begins to descend. A probe or detector 76 may be applied over the top of the tundish 33 so that, when the mass of molten metal reaches the end of the detector,

  causes a short circuit and start the

  air fan 31 which actuates the screw jack, to

descend the diver 27.

  At the beginning of a pour, the plunger 27 should find as close as possible to the upper part of the mold, and preferably within 7 inches of this upper mold, and as close as possible the bottom of the tundish 33, so that the top

  of falling of the mass of molten metal is 3a smaller.

  possible. The ladle 34 has a coating 78 made of a suitable refractory material and it has, at its lower part, an opening 77 closed by a removable plug 79. Instead of this plug, the ladle 34 may comprise a sliding door. or the steel can be dumped by a channel. When the plug 79 is lifted, the molten metal flows

  by a nozzle 80 located below the opening

  77, as shown in FIG.

  The process according to the invention is illustrated in FIGS. 1, 4, 5 and 6. In FIG. 1, the ladle 34 is at the top of the mold with its plug 79 in the closed position for

  hold the molten metal in this ladle.

  The plunger 27 is at its starting position,

top of the casting cavity 26.

  In FIG. 4, the plug 79 is already under

  and the molten metal, for example ordinary steel, stainless steel or nickel, enter the tundish 33 from the ladle 34 while the plunger 27 descends. Molten metal 35 fills the casting cavity 26 over the

  plunger 27 and also fills the tundish 33. The worker who controls this ladle must

  force to introduce the molten metal into the tub of

  33 at a speed approximately equal to that with which this metal enters the casting cavity 26 and it must continue to feed properly this

molten casting tank.

  The plunger 28 is lowered at a speed of between about 1.3 cm per second and 10.2 cm

  per second, and preferably for the cylindrical bars

  at a speed between about 3.8 and 6.35 cm per second, depending on the dimensions of the

  casting vessel 33 and the molded article, as well as

  very well known factors of the specialists. A cylindrical bar of 3m can be cast in a duration of

at 80 seconds.

  The method according to the invention makes it possible to cast cylindrical bars of great length, up to 12 m, in which case it may be good to vary the speed of descent of the diver

during the casting operation.

  In FIG. 5, the plunger 27 is shown

  at the bottom of its course, after forming a cymbal piece

  1. An insulating material 83 (for example "Ferrux" manufactured by the company Foseco, Inc.) is spread on the top of the metal mass 35 of the tundish 33 so as to maintain the metal in the molten state and allowing it to descend to the molded part at atmospheric pressure while the molded part cools down. For that, we can also appeal, if we want or if we find that this is

  necessary for an exothermic material.

  In FIG. 6, the plunger is shown at the position which it occupies after having been lifted to expel mold 30 and casting vessel 33 from the mold 20 with a short distance B at least 1.9 cm. and which can reach 7.6 to 10.2 cm. The plunger 27 is held in this position as the casting cools and contracts and this plunger can be lifted a second or third time to accommodate the shrinkage and prevent the bottom of the casting mold 33 from coming to rest. on the top of the mold 20. It is important to apply a lifting force to the lower part of the casting during cooling thereof,

  in order to maintain contact between the room

  30 during solidification and the inner wall of the mold, to remove all areas of adhesion between the wall of the mold and the surface of the molded part

  and to delay the formation of a volume filled with air.

  The hydrostatic pressure exerted by the metal in the state

  fade is compensated by the diver and the developer.

  horizontal and vertical cracks are prevented. The longer the time during which the faces of the casting during solidification can be held against the wall of the mold is long, the more this casting can cool, the more the structure of its grain is fine and better is its

surface condition.

  The lifting force is obtained by inverting the plunger 27 for a short time until the tundish 33 begins to clear the part.

upper part of the mold 20.

  The plunger 27 is then stopped, the casting is allowed to contract and the tundish 33 can return to the upper part of the mold 20. The plunger 27 is again lifted and the force directed towards the plunger 27 is applied again. up, until this tundish 33 rises again by disengaging from the top of the mold 20. These operations can be repeated two or three times, or more as needed, until the contraction of the room

  casting 30 be completed. The rise or operation of

  version can begin immediately after-that the

  27 has reached the bottom of the cell, and preferably begins within one minute of the moment when the

  diver has reached the bottom of his race.

  At the last stage of the process, the feeder 36 formed in the casting vessel 33 is separated from the cast cylindrical piece 30 by burning or cutting it at the upper part of the casting and this bar is lifted from the mold.

  cylindrical end using appropriate lifting means.

  For example, pliers carried by a crane, this cylindrical bar being at the same time pushed to its lower part by the plunger 27. At this stage, the molded object is solidified and it has cooled and contracted by disengaging itself. the inner wall 25

  of the mold, which allows to unmold.

  In order to prevent the molten metal from being welded to the inner sleeve 21, a coating can be applied

* zirconium oxide 55 or any other anti-

  appropriate welding, at the top 37 of the man-

  21 inside and inside wall 25 of this inner sleeve down to the plcngeur, to

its highest position.

  In the case of steel mold, it is good to form and maintain, on the inner wall 25, an oxide coating serving as an insulating layer between

  the molten metal mass 35 and the inner sleeve 21.

  The oxide is rapidly forming in the temperature range

  from about 930.degree. C. to about 10.sup.-10.degree. C. and for this purpose a sand having fairly good insulating properties (for example a mass of siliceous sand) in the volume 24 between the inner sleeve 21 is used. and the outer sleeve 22, of

  way that the temperature of this inner sleeve has

  ringworm sufficient value for oxide formation.

  Given the obvious limitations imposed by the

  construction, the inner sleeve 21 is advantageously

  relatively thin wall to wall,

  It can quickly reach the temperatures at which the insulating oxide forms when exposed to the molten metal. Another advantage provided by a thin inner sleeve is that a warmer sleeve expands further and, therefore, decreases the pressures on the casting. For a 20.3 cm cylindrical bar, the inner sleeve 21 should have a thickness of about 3.8 cm.

  So that the inner sleeve 21 can reach

  At temperatures on which an insulating oxide layer is formed on its inner face, the weight of this inner sleeve should be preferably between about 1.25 and 1.5 times the weight of the molded article. We can possibly send a jet of air,

  through the mass 23 of siliceous sand for

  cool down in the event that it reaches a temperature above 10901C and begin to lose strength and cohesion. If you wish

  increase the thermal conductivity of the material -

  contained in volume 24 between the sleeve

  inside and the outer sleeve -: - we can mix -

  sand from steel shot or similar material. Apart from the screw jack described, it is t i to ensure the vertical displacement of the plunged 27, rere call any mechanical, pneumatic or electrical. It is also possible to fix a rod to the upper part of the plunger 27 or to a piston in -n

  cylinder at the bottom, this rod being co-

  pneumatically or by steam. It is also possible to use a rack and pinion device actuated by a pneumatic motor or by an electric motor. Oil devices are not

  not advisable because of the risk of fire.

  Figure 8 shows a form of realization

  suitable for the manufacture of hollow cylindrical bars. The permanent mold 20 is the same as that of Figures 1 to 6. The plunger 100 is similar to the plunger 27 of Figures 1 to 4, in that it comprises a piston 101 and a cushioning band 102 filled with a mass 103 hardened stone sand intended to constitute

the cover 104 of this plunger.

  With a view to the manufacture of a cylindrical bar

  that digs, is fixed to the pioneer 100 a soul 106 of which? the length is a little longer than that of the cylindrical bar to be molded, increased by the height of the

  Pouring tank 105. The soul is controlled and guided

  This core 106 comprises a hollow steel tube 108 filled with a dry siliceous sand 109. The lower part of this core 106 is welded to a plate of '10. This plate 110 is itself attached to the piston 101 of the plunger with the aid of four bolts 111 regularly distributed, at the rate of one bolt.

  in each frame of this plate. As the

  specialists, it is possible to use

  very good means to fix the soul to the diver.

  A ceramic sleeve 113 from the template 107 is applied over the core 106 to protect it against the impact of the molten metal mass 35 and also to guide the core. The molten metal 35 that

  laon pours into a tray 114 coated with brick bricks.

  fractaries enter the pouring well 105 that it fills. This ceramic sleeve 113 is adjustable and it

  has a length sufficient to protect the core 106

  be the action of molten metal. We can also introduce

  to draw the molten metal into the mold above the

  plunger 100, using a side-door device

or lower.

  The means for setting up the jig 107 consists of a pair of tabs 117 and 118, welded

  to the box 69 of the tundish 105 and which supports

  a vertical rod 119. A horizontal piece 120 is welded to the upper part of the rod 119 and

  it retains the template 107 and the sleeve 113 in part.

  ramic by an end above the center of the casting cavity 26. A bolt 121 in the leg 118

  holds the rod in a adjustable way.

  The plunger 100 is lowered to about the same speed as in the case of solid cylindrical bars, or a little faster as the metal cools down a little faster. Depending on the size and shape, it may not be necessary to exert a reverse lifting force at the bottom of the plunger 100 to avoid similar cracks or defects. We can call on

  diver 100 to unmold the article after the mas-

  has solidified and cooled sufficiently

  to disengage from the inner wall 25 of the mold

the effect of his contraction.

  Core 106 should be considered expandable and should not be reused. This core 106 can be separated from the casting after demolding.

the latter.

  To combine hollow cylindrical bars,

  we can also use souls of another form.

  For example, a massive ceramic core can be used.

  than. One can still call upon a soul reinforced with a rod and a bar or by binding. The type of soul that should be used depends on a large number of practical factors, which will become clear.

to specialists.

  With this same general arrangement, it is also conceivable to mold a cylindrical bar made of copper reinforced with steel, which can then be rolled and possibly stretched.

  to make it a steel-reinforced copper wire.

  It is then necessary to mount a steel rod on the plunger instead of the core 106 and to pour copper around this rod. As another variant, a series of steel rods could be mounted on the plunger, these rods being guided by a template located at the upper part, and thus molding a cylindrical bar made of copper comprising a whole series of

reinforcing steel parts.

  In the same way, reinforced or multi-metal objects can be molded from other high-melting metals. For example, room 106 could have a more

  large diameter and be steel-clad steel

  stainless, so as to have externally a stainless steel coating and, internally, a steel core

low carbon.

  Figures 9 to 15 show another embodiment for the manufacture of plates or slabs. Referring to FIG. 9, it can be seen that a mold 150 is constituted by two identical lateral blocks or side portions 151 and 152 which lie parallel and vertically on a base plate 153 and which are effectively held at this position by a series of hydraulic cylinders 154 which exert a pressure against the outer faces of these lateral blocks. Advantageously, the whole assembly is disposed in a concrete well 155 and the hydraulic cylinder and piston mechanism 154 or the cylinders are fixed.

at the side walls of this well.

  As shown in FIG. 10, the side blocks 151 and 152 are separated from one another by two pairs of vertical end blocks 157, 158, 159, 160 which are identical to each other. For a first casting, the end blocks 157 and 158 separate the lateral blocks

  151 and 152 and, in association with the diver 161,

  limit a casting cavity 162 for a plate or slab. For the next casting, the side block 151 is raised above the side block 152 and lowered to the other side as indicated at 151 'by dashed lines in FIG. side blocks 152 and 151 'are

  separated by the extreme blocks 159 and 160, and in

  with a diver 163, they delimit a second

  cavity 164 for the molding of slabs. A lifting crane

  ge is attached to rings 165 (Figure 12) on either side of the block, to lift and put it

place as described above.

  The reason for moving the side block 151 in this manner is that it is desired to successively subject each of the faces of each of the blocks 151 and 152 to the action of the molten metal during the successive castings, so that the thermal stresses neutralize each other, instead of accumulating as 247243t4

  would pass if only one side of each of the blocks la-

  The metals were exposed to the heat of the molten metal. The

  side blocks would warp and crack

  molds if they were only exposed by one face to the extremely high heat of the molten metal.

  The lateral blocks 151 and 152 are advantageously

  cast iron and of a thickness between

  25 and 30 cm, with faces that have been machined to be flat and smooth. The

  Cast iron side blocks are preferable for the manufacture of

  large slabs. But for the manufacture of small slabs, billets and slabs, it is possible to

  use split steel side blocks, reinforcing

  by props, of the type described in

  United States Patent No. 3,948,311 to

the applicant.

  The extreme blocks 157 to 160 are all identical

  between them and we will only describe block 157.

  As clearly seen in FIGS. 12 and 13, the end block 157 consists of a narrow plate 168 made of steel, with a thickness of about 6 cm, comprising a series of horizontal slots 169 that are regularly spaced apart, on its outer face . A strut 170 in the form of I-beams is fixed to the outer or rear face of the plate 168, by means of a series of Nelson pins 171 welded to this plate and which pass through the holes 172 made in this beam I Several cylindrical rollers 173 are arranged horizontally

  in a channel 174 of great length in the form of a U,

  above and below each of the pins 171 so as to allow all the necessary movements and adjustments when the metal in the molten state touches the very hot face of the plate 168 and forces it to expand. Slots 169 support all dilations

  the I-beam stay 170 resists.

  Each of the pins Nelson 171 has a nut 175 which blocks the piece 174 in the form of a channel against the rollers 173. In order to avoid galling, a large clearance is provided in the holes 172 of the stay in the form of an I-beam. in which are threaded the goup l- the Nelson 171. We assemble each of the extreme blocks by arranging horizontally the plate 168 and the stay in the form of beam I, distributing the rollers

  173, ep disposing the piece 174 in the form of a channel

  above these pebbles and by subjecting these various parts

  these to each other by applying the nuts 175 to the ends of the pins 171. Optionally, one can place the rollers 173 on axes or consoles

  housed in the channel-shaped room 174.

  The outer blocks 157 and 171 are attached to the

  edge of the side block 172 which is not raised,

  to be able to be adjusted in one direction and the other and to allow the manufacture of plates or slabs of different widths. Considering FIG. 10, it can be seen that three consoles 177 are welded to each end of the lateral block 152. The upper console and the lower bracket are identical and one plate 17B is welded, in a horizontal position, to each of

  these consoles. A housing 179 is mounted at each ex-

  upper console and inboard console

  177, in the vicinity of one of the extreme blocks 157 to 160. If we consider FIG. 11, it can be seen that at each of the extreme blocks at least two

  screw 180de set up. Each of these 180 screws

  One of the housings 179, in which there is a pinion centered by a worm 181. One of the worm 181 drives the gears of the two set screws 180 attached to each end block. A flywheel 182 controls a second gear contained in another housing 183 for rotating the worm 181 and forcing the two set screws 180 to move towards and away from the end block to which they are attached. There is thus provided a steering wheel 182 for each. blocks 157 to 160. The flywheels 182 from the housing 183 are mounted side by side in pairs on a plate 184 (Figure 9) welded to the intermediate console 177. It is obvious that one could appeal to other means for the implementation

  place and adjustment of extreme blocks.

  Since the divers 161, 163 are identical and only one plunger is used at

  At the same time, we will describe in detail only the plunge

  161. Referring to FIG. 11, it can be seen that the plunger 161 of the mold intended for the manufacture of a simple plate or slab consists of a block 187

  attached to two lifting screws 188 and 189 which hold it.

  This block 187 corresponds to the piston 52 of the plunger 27 of FIG. 2. In FIGS. 12 to 14, a wedge strip 192 with, in cross-section, the shape of an L, whose lower arm is housed in a horizontal slot. 190 of block 187. Holes 191 drilled in

  block 187 receive nails 194 which also pass

  in the holes 196 drilled in the wedging band 192, after application of this wedging band against the inner walls of the mold 150. The core sand 193 is stacked in the space above the block, delimited by the wedging band 192, and the sand is cured to form an expandable flat refractory cover 195 for protecting the plunger 161. The base plate 153 (Fig. 11) advantageously has holes 197, each of which is provided large enough to receive the plunger. one of the lifting screws 188 or 189, without being able to contain the plunger 161, so that this plunger remains permanently above the lower edge of the side blocks 157 to and does not need to be put back in front of these blocks for each new casting. In order to facilitate the manufacture of various floor plates or slabs, the plunger plate 187 is designed with a central portion 198 and two end portions 199 as shown in FIG.

  can vary the size of the plunger 151 by

  raising one of the end portions 199, or both of the central portion 198. As shown in Fig. 13, each of the end portions 199 is attached to the central portion 198 by means of a horizontal bolt

  * 200. Threaded washers 201 are attached to the ex-

  the lower part of the central portion 198 and are attached to the upper part of the lifting bolts 188 and 199 so as to

plunger 161 to these lifting screws.

  Figures 11 to 14 show an arrangement for covering the upper part of the mold and to have a tundish integrally with the assembly. The tundish 203 comprises a box 204 inside which there is a ceramic sleeve 2G8. The upper part of the casting cavity 162 is covered by a layer 210 of sand

  core, packed in a thin metal tub 211

  held by below by the plunger 161; this sand is then hardened. A ceramic sleeve 212 is installed on this metal tank 211 before forming the sand layer 210, and this sleeve is then surrounded with packed sand comprising a binder as indicated above. A hole 213 having a diameter of, for example, 2.5 cm is drilled in the metal tank 212, so that when the molten metal is introduced into the sleeve 212, it rapidly burns around the holes 213 and flows without being impeded into the casting cavity 162 above the plunger 161. Of course, other arrangements could be made to cover the upper part of the casting cavity and to constitute a reserve of molten metal above of the cavity and to have access to this cavity. For example, it is possible for metal plates to be applied to the lateral blocks 151 and 152 and to insert a tank of

casting.

  Before proceeding with a casting operation, it is necessary to lower the plunger 161 so that it is no longer in direct contact with the bottom of the metal tank 211 which supports the layer 210 of stone sand away from at least 1.3 cm. It is thus formed between the refractory core sand applied to the plunger 161 and the metal rod 211, a space

  in which the molten metal can flow.

  The plunger 161 is lowered and lifted by means of two screw jacks 216 and 217 connected to the lifting bolts 188 and 189 as shown in FIG. 11. A single pair of screw jacks 218 and 219 lowers and lifts the plunger 163 (FIG. 10). There is therefore a single plunger and a single pair of screw jacks for each casting cavity, so that the same pair of jacks is used at a rate of

casting on two.

  The control members are the same for all the screw jacks 216 to 219, so that only those corresponding to the screw jacks 216 and 217 will be scored. As shown in FIG. 15, an air motor 220 rotates a tree 221, so

  worms 222 and 223. mounted at both ends.

  Means of this shaft 221, engaged with the pinions 228 and 229, raise and lower the lifting bolts

  188 and 189. The air motor 220 is reversible.

  sible and at variable speed. At one end

  of the shaft 221 there is a limit switch 224

  upper and lower control controlled by this tree.

  This limit switch 224 is electrically connected to an electromagnetic coil 225 which controls a four-way valve 226 and is connected to appropriate electrical controls so that this valve 226 can raise and lower the screws.

lift 168 and 189.

  A brake 227 controlled by electromagnetic coil

  -tic is mounted at the end 221 opposite the end o is the limit switch 224 and the brake is electrically connected to this switch which provides control. When this limit switch 224 detects that the plunger 161 has arrived at the upper or lower end of its stroke, the switch automatically actuates the valve 226 and controls the

  brake 227 so that it stops the plunger.

  One of the advantages of using an air motor as a source of power for driving the screw jacks is that when the plunger is forced to lift at the end of its descent. to apply an expulsion force, the air motor does not stall and provides appreciable lifting force with each slow or even non-rotational rotation of the

worm.

  In the tundish 203, a probe or detector 230 (FIG. 9) is installed which is adjusted in such a way that, when this tundish is

  practically full of molten metal, the provocative detector

than the descent of the diver.

  The well 155 in which the mold 150 is placed has vertical plates 232 (FIG.

  the jacks 154 are fixed; these plates rise above

  above ground level, up to about one third of the depth of the well. The parts of the plates 232 which are above the ground level are supported

  by vertical support plates 233, mounted perpendicularly

  in particular to the plates 232 of the well and arranged on horizontal mounting plates 234. The means for supplying hydraulic fluid and the control means of the cylinders 154 are outside the well, at a distance from the latter.The cylinders 154

  compress against each other the lateral blocks-

  151 and 152 and the extreme blocks 157 to 160 at each casting and i-b are loosened when the force ends

  upward expulsion from the diver 161.

  As shown in FIG. 11, the screw jacks 216 to 219 are mounted on a plate 236 located at the bottom of the well. A cylindrical hole 237 is dug into the ground just below the lifting screw of each screw jack, this hole being intended to receive the corresponding lifting screw when one makes

go down the diver.

  With the apparatus shown in Figures 9 to 15, plates or slabs are molded by the same operations as those applied for the manufacture of cylindrical bars. The plunger 161 is raised to the upper part of the casting cavity 162 and is provided with the

  setting 192 and the cover 195, as explained previously.

  dement, so that this diver forms a joint

  metal-tight sliding door with internal walls

  The casting vessel 203 or molten metal reservoir is placed and / or formed over the casting cavity 162. With the ladle 34, molten metal 35 is poured into the casting vessel 203 and, as soon as this tank is full, the plunger 161 is lowered to the speed of between about 1.3 and 10 cm per second until it reaches the bottom of the casting cavity; at this point, the diver stops and begins to ascend by exerting at least one force of expulsion and, better, a force this

  lifting on the plate or slab, being solidified

  tion. This plate or slab is pushed up

  and, in this way, raises and chases the upper

  150 of the casting mold 203. The rise of the plunger 161 then stops temporarily and, as the molded piece contracts, the casting vessel 203 tends to return to the upper part of the mold 150. The force of The upwardly directed lift is then applied again to maintain the tundish 203 disengaged from the top of the mold 150 and to keep the metal that cools in compression. Then, after about 10 to 15 minutes, the molded plate or slab cools down and can then be unmolded by relaxing the pressure exerted by the hydraulic cylinders 154 and lifting the plunger 161. We can chase the weight that s' is formed in the tundish 203 while the casting is still in the mold or can be lifted from the mold

  this molded piece and cut it into a separate place.

  In view of the following casting, one of the lateral blocks (ie, in the case of the apparatus shown in FIGS. 9 to 15, the lateral block 151) is raised over the other lateral block (namely the lateral block 152) and reassembled to form a second casting cavity 164 in which the very hot face of each of the side blocks 151 and 152 subjected to the molten metal is the face other than that exposed to the metal in question. melting during the previous casting. The diver 163 is commanded in the same way as was explained

of the plunger 161 of the cavity 162.

  Figure 16, as indicated above, represents

  various objects of various shapes that can be made by applying the method according to the invention. FIG. 16A shows a cylindrical bar 241 that can be manufactured using the apparatus shown in FIGS. 1 to 7. The cylinder constituting this bar has a diameter of between 10 and 50 cm and a length of 3 at 9 m. Figure 16B shows a thick-walled hollow cylindrical bar 242, which can be manufactured using the apparatus shown in Figure 8; Figure 16C shows a thin-walled hollow bar 243 that can be manufactured using the same apparatus; FIG. 16D shows a billet or slab that can be manufactured using the apparatus of FIGS. 9 to 15. A billet is normally of square cross-section, the sides of which are each 5 to 38 cm long, the length of the billet being

  at least 3 m. A slab also has a transpor-

  square-shaped and each side has a length of between 15 and 30 cm, the length of the piece being at least 3 m; however, billets and slabs may also have a rectangular section. FIG. 16E shows a plate or slab 245 made using the apparatus shown in FIGS. 9 to 15. A slab is a fairly flat piece of elongated shape, of which two opposite faces constitute a rectangle whose width is from 60 to 203 cm or more and whose length is between 3 and 9 m, the thickness of this part being between 5 and 25 cm. A plate is similar to a slab with this difference that it is thinner. Figure 16F shows a plate 246 that can be made with the apparatus of Figures 9 to 15; FIG. 16G shows a cylindrical bar 239 with a bulging head, which can be manufactured by means of the apparatus of FIGS. 1 to 7. The head 240 of this part is formed in the casting vessel. Indeed, a large tundish has a lower portion for the formation of the head 240, the remaining upper part constituting the mrcelelotte that is removed. The present method of making such articles constitutes

  to push a cylindrical bar to form the head.

  As will be readily understood by those skilled in the art, the method and apparatus according to the invention make it possible to manufacture still other semifinished articles. The

  applicant considers that the process according to the

  also makes irregular pieces

having for example the shape of a bone.

  As has been pointed out, the casting tanks,

  the refractory lids for the diver, the neck

  of molds for making slabs and cores for the manufacture of hollow round bars, consist of mixtures of sand and binder

  like those used in foundries for

  kernel fection. As a composition of carbon dioxide and sodium silicate binder, mention may be made of

  Carsil 700, sold by the company Foseco Foundry Pro-

  ducts Group, Cleveland, Ohio, United States of America.

  There may also be mentioned a composition which is "without cooking", in which a sodium silicate binder has been taken under the effect of a catalyst or an agen:

  chemical hardening (which is not carbon dioxide)

  the product sold by Thiem Division of Koppers Company in Milwaukee, Wiscorsin, United States of America, under the trademark "Thiem Chem

  Bond 31. Compositions can also be used.

  for the production of foundry cores, preferably with inorganic binders, such as refractory clay, western bentonite, Portland cement or iron oxide.Resin binders, such as phenolic resins, give off a great deal of of

gas and are less to advise.

  In the case of compositions give off water during the curing operation, it is good to blow the refractory lid and / or the tundish with the torch in order to remove this water. It can be done with a welding torch taking

  take care not to damage the hardened stone sand.

  As will be readily understood by those skilled in the art, the invention makes it possible to use divers of another shape comprising a refractory lid and a wedging strip or equivalent means constituting a sliding seal that is impermeable to the molten metal with the

side walls of the mold.

  Some parts of the sand may be replaced by prefabricated ceramic discs or blocks, but it is advisable to drown them in the sand so that there remains between the wedging strip and the ceramic disk or block a layer of sand. a thickness of at least 1.27 cmi ensuring a buffer effect. This is because the ceramic parts have, for the most part, high coefficients of expansion and may expand ern applying against the wedging band and jam the diver or prevent him from descending. The forces acting on the wedging band are important and this wedging band must be firmly attached to the diver. Instead of the wedging band shown in FIG. 7, it is possible to form a suitable wedging band by welding

  to the band a row of Nelson pins, these pegs

  allowing them to keep the tape in place and

  thinking of slitting and folding. The pins are welded perpendicular to a flat face of the strip in a row that occupies the entire length of this strip, at a distance from one of the edges equal to about one third of the width. To moriir the wedging band on the piston or block d_

  plnjur, we have this vertical

  The pins then extend horizontally from the lower portion of the wedging band and rest on the piston or block. A metal retaining plate clamps and retains pins on the pistzn or plunger block and thereby holds the chock band. The refractory lid hardened on

  place is on top of this retaining plate.

  The ladles are shown to fill the molds with molten metal because, with

  pockets, the molten metal is exposed the least pos-

  to the atmosphere gas. In some cases, however, spilling molten metal with a channel may be preferable because it allows

  a larger volume of metal in a shorter time.

  As noted, a significant lifting force must be applied to the lower

  of the molded part, very quickly after the plunge-

  He has reached the limit of his downward course, a'r.

  that the tension forces that arise in a molded part during its cooling are

  greatly reduced or even abolished and that

  Preferably, the casting is in a compression state.

  When the molded part is lifted slightly off the mold, it is clearly in the state of

  compression under the effect of its own weight,

the weight of the tundish.

  If the molded part is not lifted and released from the mold, the lifting force must be equivalent to at least half, and more preferably two-thirds, the weight of that part. Once the diver has stopped descending, the moment at which the lifting force must be applied may vary depending on the metal that

  flowing, the type of article to be molded and the

  metal in the process of solidification to adhere to the inner walls of the mold. Similarly, the value of the lifting force can vary according to the same

  factors. For example, some items such as

  hollow cylindrical bars or slabs of small size, the application of a lifting force at the end

  casting may not be necessary. We think

  the application of a lifting force at the end of the casting always improves the surface

  molded part and the structure of its grain.

  Molds for making articles

  according to the method according to the invention are advantageously

  sowing enacier or enfonte. However, they can be made from other materials, such as copper or graphite, but the copper molds must be water-cooled and the graphite molds are very expensive. If steel and cast iron molds can

  reused many times, they are not

  times not indestructible. However, they are called "permanent molds" to distinguish them from molds that are unusable after a single pour or molds that could only be used for a number

  relatively small quantities of castings, for example

  ts. We can possibly cool the molds

  with water to speed up the cycle of operations.

  However, although this is slower, the cooling

  air is preferable because it does not have the water cooling complications. We can

  air-cooled the molds of Figures 1 to 8 into

  to pass a jet of air in the sand.

  In the particular case of molds for the manufacture of cylindrical bars, the applicant considers that it is advantageous to regularly smooth the surface of the inner wall so that it remains clean. In the case of molds for manufacturing

  plates or slabs, we can wash the faces int -

  from time to time by neuLagPe or brushing.

  In most cases, the applicant Persian that the present invention can be used for the manufacture of semi-finished products of ferrous metal, steel

  low carbon or various stainless steels

* dables. The invention can also be used by the manufacturer

  cation of products of other high-melting metals, for example nickel. More generally, the applicant considers that the present invention finds its application in the molding of any part having a uniform cross-section, in any metal Ln with a melting point higher than 1000 ° C.,

  so especially copper objects. We must

  understand that a process that allows for

  objects in a ferrous metal can certainly mold copper objects, since copper

  is a low-melting metal, easy to work with.

  The opposite is not true because a process that molds copper objects may not allow

  to cast ferrous metal objects.

  Because of the very nature of the process according to the invention and as is obvious

  of the description which precedes the molded objects

  have a regular cross section or a configuration that corresponds to that of the mold and that of the diver. But one can vary at will the length of the molded object by changing the stroke of the plunger. If the lion wants to make an object of short length, we can stop the descent of the diver to a level higher than the bottom of the mold and the length of the object is thus determined by the limit imposed on the descent of the diver. The applicant considers that the process according to the invention makes it possible to mold relatively long cylindrical bars, slabs and billets, up to 12 m

or more.

Claims (20)

  - 1. A method for molding high melting point metal products of constant cross-section in a permanent mold (20) having a casting cavity whose cross-section corresponds to that of the product, characterized by the fact that comprises the following steps: a) a plunger (27) is provided at the upper part of a casting cavity (26) capable of withstanding a high melting point molten metal and also capable of remaining in sliding contact and sealed with the inner walls of the mold; b) there is provided a reservoir (33) for the molten metal above the plunger (27); c) pouring melted high melting metal into the reservoir (33); d) when this reservoir is substantially filled, the plunger (27) is lowered relative to the mold towards the bottom of the cavity (26) at a set speed, while continuing to supply the reservoir (33) with molten metal so that the molten metal enters the cavity above the plunger (27) and fills it; e) allowing the metal contained in the casting cavity (26) to solidify in the form of the desired molded product; and f) the latter is demolded.   2. Method according to claim 1, characterized in that the plunger is lowered (27).   at a set speed between 1.5 cm and 10 cm / sec.   3. Process according to any one of the claims   1 and 2, characterized by the fact that the metal   High melting point is a ferrous metal.   4. Process according to any one of the   cations 1 and 2 characterized in that it comprises the complementary step of causing the plunger (27), in the minute following the end of descent, to exert a compressive force on the product in progress solidification.   5. Method according to claim 4 caractériFe in that, for the diver (27) exercises this   compression force, it is lifted relative to the mold.   6. Process according to any one of the claims   1 and 2, characterized in that it comprises the complementary step of forcing the plunger (27) within one minute after the end of its descent, to exert a force directed upwards on the lower part of the product. molded so as to lift it off of the mold.   7. Process according to any one of the   cations 1 and 2 characterized by the fact that the plunger (27) is placed in the cavity (26) with a refractory lid (66) constituting the upper part of this plunger, formed on the spot in the mold and with a metal shim (58) surrounding the lid (66) and   attached to the lower part of the diver.   8. Method according to claim 7, characterized in that the lid of the plunger 27 is made in situ in the mold, by compacting a compound of hardenable sand in the space delimited by   the shim (58) and then hardening this compound.   9. A process for directly casting a semi-finished product of ferrous metal, characterized by the   it includes the following steps: -   a) there is a plunger (27) at the top of a permanent mold of regular cross section whose inner faces are smooth,   the shape of the cross-section of this mold corresponds to   to the one of the semi-finished product that is to be molded, the plunger (27) being sealingly applied against the inner faces of the mold so as to keep the molten ferrous metal above the plunger, b) available a reservoir (33) for the molten ferrous metal above the plunger (27); c) filling the reservoir (33) with molten ferrous metal and then lowering the plunger (27) relative to the mold towards the bottom of the mold while maintaining the reservoir (33) substantially full of molten metal, so the molten metal enters the mold-defined space above the plunger (27) and fills this space as the plunger descends to form a semifinished product in the mold; and   d) this semi-finished product is demolded.   10. The method of claim 9, characterized in that it comprises the complementary step which consists, after the plunger (27) has reached the bottom of its race and while the molded product cools and solidifies, to back up the plunger (27) and apply to the molded product sufficient force to lift it off the mold, at least on a low height.   11. A method according to claim 9, for casting hollow cylindrical bars of a ferrous metal, characterized in that it comprises the following complementary steps of: attaching a rod-shaped core to the upper part of the plunger (27). ) and after allowing the molten metal in the mold to solidify to form   a cylindrical bar, to unmold this cylindrical piece.   12. Apparatus for directly casting semi-finished products into a high melting point metal having a constant cross-sectional area   apparatus which implements the process according to any one   conque of claims 1 to 11 being characterized   in that it comprises: a) a mold having smooth vertical interior walls which define a casting cavity (26) having a constant cross-section corresponding to that of the molding products; b) a plunger (27) which can up and down in this casting cavity (26), this plunger having, in transverse, a shape and dimensions that are the same as those of the casting cavity and being in sliding and sealing contact with the inner walls of the mold c) means (28, 29) for lowering and mounting the plunger (27) relative to the mold at a set speed; and d) a reservoir (33) for the molten metal, disposed at the top of the mold, over the   casting cavity (26), this reservoir for feeding   melted metal the cavity above the diver (27).   Apparatus according to claim 12   characterized in that the plunger (27) comprises a) a block held by the descent means; b) a wedging band (58) disposed around and above the block to which it is attached; and c) a refractory lid (66) filling the space delimited by this cushioning band (58) and   attached to the top of this block.   Apparatus according to claim 12   rised by the fact that the refractory couviercle (66) is in agglomerated stone sand.   15. Apparatus according to claim 12   in that the refractory liner (66) is constituted by core sand packed in situ within the wedge strip (58) in the casting cavity (26) and cured to provide a   adjustment with close tolerance but with soft friction.   16. Apparatus according to claim 12, characterized in that the means for lowering and mounting the plunger (27) comprising a   screw jack (29) located at the bottom of the mold.   17. Apparatus according to claim 12 for directly molding cylindrical bars, characterized in that its mold comprises an inner sleeve (21) of circular cross section and whose inner surface is smooth; an outer sleeve (22) surrounding the inner sleeve (21) to which it is concentric; and a filling material (23) introduced between this inner wall (21) and an outer wall (22). Apparatus according to claim (12) for directly molding cylindrical or other rods, characterized in that the plunger (27) is provided to have at its upper part a rod-shaped core, which core the inner sleeve (21), and in that there is provided means for maintaining the upper part of this core   (106) when the diver (27) goes up and down.   Apparatus for molding cylindrical bars directly from a molten metal having a high melting point, characterized in that it comprises: a) an upper plate (42)   - b) an inner sleeve (21) of trans-   circular diaphragm and whose inner surface is smooth, this sleeve being fixed to the upper part of this upper plate (42) and able to expand freely downwards c) an outer sleeve (22) surrounding the inner sleeve (21) to which it is concentric, this outer sleeve being fixed to the upper part of the upper plate (42) d) a lower plate (38) to which is fixed the bottom of the outer sleeve (22); e) a ring-shaped inner plate (48) fixed to the lower part of the inner sleeve (21) and covering substantially the entire area between the inside of the outer sleeve (22) and the outside of the inner sleeve (21); ), this ring-shaped plate being located above the lower part of the outer sleeve (22); f) a filling material (23) serving as a support and insulation, disposed between the inner sleeve (21) and the outer sleeve (22) g) a sealing means (49) disposed at the upper part of the ring-shaped inner plate (48), said sealing means having the role of preventing the loss of this filler material (23) between the outer periphery of said ring-shaped inner plate (48) and the interior the outer sleeve (22); h) a plohgeur. (27) mounted smoothly and against the inner surface of the inner sleeve in a molten metal seal; i) means for lowering and mounting the plunger (27) at a set speed; and j) a tank (33) for the molten metal, which tank is located at the top of the top plate (42) and is connected to the inner sleeve (21), the tank having the role of introducing molten metal in the space delimited by the inner sleeve (21), above the plunger (-27), while the latter goes down.   20. Apparatus for directly casting plates or slabs, a high-melting metal, characterized in that it comprises: a) two vertical side blocks (151, 152), parallel to each other; b) two vertical end blocks (157, 158), parallel to each other at the ends of the two lateral blocks (151, 152) and between them, so as to define a cavity for molding a plate or a slab; c) a plunger (127) housed in this cavity and having approximately the same shape as the latter, in cross section, the plunger being mounted to fit smoothly against the faces of the blocks which delimit the cavity, sealingly to the molten metal ; d) means for lowering the plunger (27) at a set speed; and e) a reservoir (33) for the molten metal, located above the cavity and connected thereto.