EP0940206A1 - Oxide remover - Google Patents

Abstract

The top boundary zone of the thixotropic bar, which fully incorporates the oxide film (38), is stripped off within the boundaries of the cavity (12) of the casting chamber. The casting chamber (10) of the machine has a disk-shaped oxide knife (30) with a yoke-like edge cutout designed so that during thixoforming the top boundary zone (26) of a thixotropic metal bar (24) can be stripped off. The die (40) has a feed channel (37) incorporating a section (38) which is oriented vertically upwards and leads into the die cavity (42).

Description

The present invention relates to a horizontal die casting machine for the production of Shaped parts from thixotropic metal bolts by thixoforming, containing a mold with a mold cavity and a horizontal casting chamber with a casting chamber cavity. The invention further relates to a thixoform process for the production of molded parts from thixotropic metal bolts in a horizontal die casting machine according to the invention, with the inclusion of the oxide skin surrounding the thixotropic metal bolt in the alloy structure of the molding can be avoided.

Thixoforming relates to the production of molded parts from thixotropic metal bolts. As Metal bolts all bolts come from a convertible into a thixotropic state Metal in question.

With thixoforming, the thixotropic properties of partially liquid or partially solid metal alloys exploited. The thixotropic properties of a metal alloy mean that a suitably prepared metal behaves unloaded like a solid, under However, shear stress reduces its viscosity to such an extent that it is similar to a Metal smelt behaves. This involves heating the alloy into the solidification interval between liquidus and solidus temperature required. The temperature should be set that, for example, a structure fraction of 20 to 80% by weight is melted, the However, the rest remains in solid form.

Metallic bodies, for example bodies made of aluminum, magnesium or zinc, or their Alloys, when they come into contact with their surrounding atmosphere, coat with a natural one Oxide skin, the thickness of which is usually well below a micrometer. While the heating process of a metal bolt for transferring the same, for example, into one This oxide layer is usually already naturally present on the circumference in a thixotropic state of the metal bolt, the so-called oxide skin. The thickness of the during the heating process The oxide skin formed depends on the heating-up time required and the time surrounding the stud Atmosphere, as well as the alloy composition of the bolt in question. The The thickness of the oxide skin formed during the heating process is for aluminum bolts typically 0.1 to 10 µm. Especially with metal alloys in the molten or In the thixotropic state, impurities, such as, for example, can also be present in the oxide skin Deposit alkali and alkaline earth metals.

In the case of molded parts, the oxides formed during the heating process are usually found, i.e. Parts or particles of the oxide skin formed during the heating up again. The in the Thixotropic metal alloy existing oxidic particles form in the molded part, for example oxidic inclusions or lead to the formation of pores in the alloy structure. In addition can oxides and other non-metallic inclusions in the oxide skin in the molded part Create structural separation points. Consequently, the surface of the Thixotropic metal stud existing oxide skin, the alloy quality of the molded part and hence its mechanical properties. Especially for workpieces subject to high mechanical loads oxide inclusions are therefore undesirable or even prevent their use as mechanically strong components.

A major problem in thixoforming of thixotropic metal alloys therefore resides in the Oxide formation during the pretreatment, such as the heating process or the Transport of the metal bolt through the atmosphere surrounding it. The thickness of the formed Oxide skin can be removed by special measures during the pretreatment of the metal bolts, such as by using an inert gas atmosphere surrounding the metal bolt reduced, but not entirely avoided. They are also used to reduce the Thickness of the oxide skin measures to be taken, in particular in the case of production in industrial Scale, complex and expensive.

To include the oxide skin in the alloy structure surrounding the thixotropic metal bolt To avoid the molding, EP-A 0 718 059 describes a horizontal die casting machine for the production of molded parts from thixotropic metal bolts, which between the casting chamber and the mold an annular oxide wiper with a concentric, has annular oxide collection ring, the oxide collection ring with the Interior of the oxide wiper via a concentric, ring-shaped oxide wiper opening connected is. The thixotropic metal alloy flows through during the thixoforming process the interior of the annular oxide wiper, the thixotropic metal bolt The surrounding oxide skin is flow mechanically through the oxide wiper opening into the oxide collecting ring is directed. To despite the with respect to the longitudinal axis of the thixotropic metal bolt usually asymmetrical viscosity properties of the thixotropic metal alloy, i.e. the asymmetrical thermal and mechanical properties of the thixotropic Metal alloy to ensure stripping of a radially uniformly thick surface layer, the oxide wiper opening has a correspondingly chosen, asymmetrical opening cross section on.

The fluid mechanical stripping of the oxide skin according to EP-A 0 718 059 causes the precise control of the parameters relevant to fluid mechanics by the oxide wiper flowing, thixotropic alloy. For example, this requires precise knowledge of the Viscosity properties of the thixotropic alloy or precise control of the proportion solid / liquid, of pressure and temperature.

The object of the present invention is compared to the known prior art based on a horizontal die casting machine for the production of molded parts to provide thixotropic metal bolts that are used to manufacture oxide-free Molded parts without precise knowledge of the viscosity properties of the thixotropic metal alloy allowed, or the even stripping of the oxide skin with changing viscosity properties of the thixotropic metal alloy without making adjustments to the Horizontal die casting machine allowed.

a) die Giesskammer ein in den Giesskammerhohlraum einführbares, scheibenförmiges Oxidmesser aufweist, welches eine jochförmige Randausnehmung enthält, die derart ausgebildet ist, dass wahrend dem Thixoformen eine obere Randzone des thixotropen Metallbolzens abgestreift werden kann, und

b) die Gussform einen an den Giesskammerhohlraum angrenzenden Einguss aufweist, und die Formkavität mit dem Einguss durch einen Eingusskanal verbunden ist, wobei wenigstens der direkt vom Einguss wegführende Teil des Eingusskanales ein vom obersten Bereich des Eingusses ausgehendes, senkrecht nach oben verlaufendes Kanalstück darstellt.

According to the invention this is achieved in that

a) the casting chamber has a disk-shaped oxide knife which can be inserted into the casting chamber cavity and which has a yoke-shaped edge recess which is designed in such a way that an upper edge zone of the thixotropic metal bolt can be stripped off during the thixoforming, and

b) the mold has a sprue adjacent to the casting chamber cavity, and the mold cavity is connected to the sprue by a sprue, at least the part of the sprue leading directly away from the sprue being a vertically upwardly extending duct piece that starts from the uppermost region of the sprue.

In horizontal die casting machines, the casting chamber is the thixotropic metal bolt picks up horizontally. The concentric central axis of the casting chamber cavity becomes referred to as the longitudinal axis m of the casting chamber cavity. When thixoforming is a thixotropic metal bolts placed in the casting chamber and with a casting piston Pressure applied whereby the thixotropic metal alloy with high speed and under high pressure in a steel, in particular hot work steel, existing Mold, more precisely introduced into the mold cavity or mold cavity of the mold the thixotropic metal alloy solidifies in it.

The metal bolts can, for example, be made of any metal alloy which is used in the thixotropic state can exist. Metal alloys are preferred made of aluminum, magnesium, zinc, steel or copper, alloys made of aluminum, Magnesium or zinc are particularly preferred. The thixotropic metal bolts are cylindrical and preferably have a round or oval cross section, but can also be polygonal cross-section. The diameter of the metal bolts is, for example 50 to 180 mm, expediently 75 to 150 mm and preferably 100 to 150 mm. The length of the metal bolts is, for example, 80 to 500 mm.

The casting chamber has a trough-shaped area for inserting a thixotropic Metal bolt and a closed-shaped adjoining it in the direction of the mold Area on. The trough-shaped area expediently has a semi-cylindrical shape Recording area for the thixotropic metal bolt, and the closed The area preferably has a hollow cylindrical shape. The dimensions of the trough-shaped Range are preferably chosen such that the thixotropic metal bolts can be inserted without a necessary change in shape. The cross section of the closed area corresponds, for example, to that of the thixotropic area Metal bolt.

The oxide knife is preferably located between the trough-shaped and the closed-shaped Area, i.e. the transition area of the casting chamber.

In a further preferred embodiment of the horizontal die casting machine according to the invention has the casting chamber wall of the closed region in one upper area an oxide opening, which on the one hand the insertion, lowering and pulling out of the oxide knife and on the other hand the removal of the stripped upper Edge zone from the casting chamber cavity enables the oxide opening, for example represent a slot-like recess in the casting chamber wall.

In another preferred embodiment of the horizontal die casting machine according to the invention is the dimensions of the oxide opening such that it is only that Inserting, lowering and pulling out the oxide knife allows the oxide skin during the thixoforming process is retained in the rear bolt part until the oxide knife is pulled out of the casting chamber cavity at the end of the thixoforming process. The retained oxide skin thus remains in the bolt part whose alloy is not for the molded part is used in the so-called bolt cake, which after the thixoforming process is removed from the casting chamber cavity and disposed of.

The oxide knife is preferably essentially perpendicular to the longitudinal axis of the casting chamber cavity positioned, or more preferably with a perpendicular through the Longitudinal axis extending an acute angle of 0.5 to 20 °, for example to include a full circle of 360 °.

The yoke-shaped edge recess of the disc-shaped oxide knife is one against the Casting chamber cavity directed concave recess, the edge recess has an arched reveal. For example, the arcuate face of the yoke-shaped edge recess, i.e. the yoke-shaped edge recess in a plan view seen from the longitudinal axis of the casting chamber, a semi-circular, semi-elliptical or have a parabolic shape.

The yoke-shaped edge recess of the oxide knife is preferably designed such that through its end face a radially evenly thick, upper edge zone of the thixotropic Metal pin is stripped. The upper edge zone affects those in this sector of the Bolt cross-section of existing oxide skin. In addition, the upper edge zone can also be one the area of the thixotropic metal alloy close to the oxide skin. Accordingly corresponds the shape of the yoke-shaped edge recess preferably that of the thixotropic metal bolt, the front dimensions opposite the yoke-shaped edge recess the cross-sectional segment covered by the end face of the yoke-shaped edge recess of the thixotropic metal bolt are smaller by a constant amount. The front Opening cross section of the yoke-shaped edge recess is thus the cross-sectional shape of the adapted thixotropic metal bolt, but according to the edge zone of the thixotropic metal bolt by a predefined amount smaller.

The yoke-shaped edge recess is preferably such that the arcuate An edge layer of the thixotropic metal bolt on the face of the yoke-shaped edge recess a thickness of 0.5 to 5 mm and particularly preferably a thickness of 0.5 to 3 mm is stripped.

In the special case where the thixotropic metal bolt has a circular cross-section, the edge recess therefore expediently has an arched opening a radius r, which is preferably 0.5 to 5 mm smaller than the radius of the thixotropic Metal bolt. Usually the thixotropic in the casting chamber cavity However, metal bolts do not have a circular shape.

The yoke-shaped recess is also preferably designed such that in cross section of the thixotropic metal bolt, the upper edge zone to be stripped off Central angle from 60 ° to 200 ° and in particular from 90 ° to 180 ° of the metal bolt cross section concerns. The angle specifications here and in the following always relate to one Full circle of 360 °. The upper edge zone to be stripped preferably has one with respect to one vertical plane through the longitudinal axis of the casting chamber symmetrical shape. Therefore the yoke-shaped edge recess preferably also has a correspondingly symmetrical one Shape up.

The is located between the casting chamber cavity and the mold cavity of the casting mold Gate and the gate. The sprue preferably contains a cylindrical cavity, which adjoins the casting chamber cavity and prefers its longitudinal axis runs parallel to that of the casting chamber cavity. In the further lie the longitudinal axis m of the casting chamber cavity and the longitudinal axis of the sprue preferably in the same vertical plane. In a particularly preferred embodiment, the sprue has a circular cylindrical shape.

The dimensions and arrangement of the sprue with respect to the mold end of the Casting chamber cavity, the so-called pouring opening, are preferably such that the wall of the casting mold limiting the sprue with respect to a horizontal Level upper area represents an extension of the wall of the casting chamber cavity.

The sprue expediently has one opposite the adjacent casting chamber cavity Larger cross-sectional area, with the sprue opposite the casting chamber cavity is arranged such that the sprue - at least in a lower area - a has residual melt cavity formed as a depression. The residual melt cavity serves especially the inclusion of the thixotropic alloy pulp during thixoforming residual liquid escaping. The term residual liquid denotes a liquid Alloy content of the thixotropic metal alloy.

The residual melt cavity is very preferably designed such that it has a cross-sectional shape seen opposite the sprue opening of the casting chamber cavity Extension forms, the greatest depth of which is at the bottom of the sprue. In addition, the residual melt cavity is in relation to a vertical plane through the longitudinal axis of the sprue preferably symmetrical.

The volume of the residual melt cavity is advantageously between 1 and 10% and in particular between 3 and 8% of the volume of the thixotropic metal bolt.

The sprue, i.e. a channel-like connection of the sprue with the mold cavity, preferably begins at the top end of the sprue and preferably continues directly after the gate. In this case, at least the duct section leading away from the sprue provides of the sprue is a vertically upward channel section.

The gate is on the side facing away from the casting chamber cavity by an impact element limited, wherein the impact element is an impact surface directed against the gate and a recess formed in a lower region of the impact element, has an open impact cavity towards the gate. The impact surface is preferred arranged perpendicular to the longitudinal axis of the gate.

The impact cavity preferably relates to a horizontal plane through the Longitudinal axis of the sprue lower segment of the cylindrical sprue, the impact cavity preferred with respect to a vertical plane through the longitudinal axis of the gate is symmetrical. The measured in the longitudinal direction of the horizontal die casting machine The depth of the impact cavity is preferably 1 to 15 mm and in particular between 2 and 8 mm. In the case of a circular-cylindrical sprue, the impact cavity preferably has a circular segment-shaped cross-section.

The channel section of the sprue that runs vertically upward is preferably in one Distance a to the impact surface arranged so that between a tangent plane to the Casting chamber facing away from the vertical sprue piece, which is also vertical to the longitudinal axis of the gate or parallel to the impact surface, and the impact surface an oxide cavity is formed. The oxide cavity thus preferably describes a cylindrical one Gating cavity, which is on the one hand by the impact surface and on the other hand limited by a cross-sectional area of the sprue at a distance a from the impact surface becomes. The oxide cavity serves in particular to hold the thixotropic on the front side Metal stud existing oxide skin.

The oxide cavity together with the impact cavity and the residual melt cavity form one Oxide pocket. The volume of the oxide pocket serves on the one hand to accommodate the front on Bolt existing oxide skin and the residual liquid, on the other hand, this volume serves essentially to accommodate the lower edge zone of the thixotropic metal bolt. Here the lower edge zone of the thixotropic metal bolt refers to the upper edge zone essentially complementary, jacket-shaped edge region of the thixotropic metal bolt. The upper and lower edge zones together form essentially an annular Area containing mainly the oxide skin of the thixotropic metal bolt, as well optionally a region of the thixotropic alloy close to the oxide skin.

The vertically upward channel section of the sprue and its arrangement with regard to the impact surface on the one hand causes one during thixoforming curved flow of the thixotropic alloy pulp and on the other one in essentially space zone described by the oxide pocket, in which only low flow velocities occur. Through this flow pattern during thixoforming it is achieved that the oxide skin deposited in the oxide pocket on the walls of the oxide pocket sticks and does not get carried away by the flow of the thixotropic alloy pulp and is deposited in the mold cavity.

The horizontal die casting machine according to the invention thus enables the production of Molded parts made of thixotropic metal bolts without inclusions of components of the Oxide skin surrounding metal bolts in the alloy structure of these molded parts. Also happens the stripping of the oxide skin, especially in an upper edge area of the thixotropic Metal bolt, regardless of the pressure conditions in the thixotropic metal alloy, whereby a higher security and reproducibility compared to the state of the art of the thixoform process is achieved.

The invention further relates to a thixoform process for the production of moldings thixotropic metal bolts in a horizontal die casting machine according to the invention. The The object on which the method according to the invention is based is that of production of die cast parts from thixotropic metal bolts while avoiding inclusions of the the thixotropic metal stud surrounding the oxide skin in the alloy structure of the molded part, the thixoform process being essentially independent of the viscosity properties the thixotropic metal alloy should be feasible.

According to the invention, this object is achieved in that an upper edge zone of the thixotropic metal bolt, which relates to an annular sector of the metal bolt, in Stripped area of the casting chamber cavity and ejected from the casting chamber cavity or is retained in the casting chamber cavity with the stripped top Edge zone at least the existing oxide skin surrounding the metal bolt in this sector completely includes.

The amount of a metal alloy required for carrying out the method according to the invention for the production of the molded part is expediently in the form of a bolt. Suitable metal alloys for the process according to the invention are all commercially available metal alloys which can be converted into a thixotropic state. The method according to the invention is particularly suitable for processing alloys made of aluminum, magnesium, zinc, steel or copper. In particular, cast aluminum and wrought aluminum alloys are preferred. The method according to the invention is advantageously also suitable for processing particle-reinforced aluminum alloys which contain, for example, homogeneously distributed SiC or Al ₂ O ₃ particles. The method according to the invention is very particularly suitable for aluminum alloys which have a pronounced solidification interval, such as AlSi7Mg.

The alloy of the metal bolts required for the method according to the invention contains, for example homogeneously distributed, primarily solidified solid particles that degenerate from individual ones Dentrites exist. The proportion of solidified primarily solidified expediently 40% by weight or more. For example, to achieve good thixotropic behavior in the case of aluminum alloys, the alpha mixed crystal is in a globulistic form in order to achieve an even flow of melt and solid.

The degenerate dentrites generally generally have a globulistic shape, which ensures a uniform, homogeneous flow of melt and solid without segregation can be achieved. The creation of a structure with globulistic dentrites among other things through a continuous casting process, combined with an intensive electromagnetic Stir also during the solidification phase. This leads to melting and Breaking off dentrite arms that mold near the solidus temperature and that form globulistic structures.

The metal bolt required for the method according to the invention is previously used for thixoforming to a temperature above the solidus temperature and below the liquidus temperature, i.e. heated to a partially solid, thixotropic state.

The metal bolts are usually heated in a separate oven. The heating the furnace can run on fuel, such as gas or oil, or electrical energy, such as resistance heating or inductive energy input. For the process according to the invention, the metal bolt is heated in an induction furnace prefers.

The heating of the metal bolts is of great importance because the bolt condition, i.e. its partial strength, usually only in a small temperature range, Long heating times, for example the formation of a thick oxide skin or possible grain coarsening, should be avoided and to achieve a homogeneous end product the temperature distribution in the thixotropic metal bolt, the so-called Thixo blank, should be as homogeneous as possible. That is why the transfer of the Metal bolt into the thixotropic state, i.e. heating the bolt to the desired one Alloy portion is melted, preferably in an oven with a sensor regulated oven temperature.

In the semi-solid state, the thixotropic alloy, the so-called thixotropic alloy pulp, contains the reverse developed dentritic, primary solid particles in a surrounding Liquid metal matrix. The percentage of primary solid dentritic particles will expediently chosen such that the thixotropic metal bolt during the heating process, the transport into the casting chamber and in the casting chamber itself no noticeable Undergoes deformation and no noticeable loss of material due to dripping, for example of melt takes place. The thixotropic alloy slurry preferably contains a proportion primary solid particles from 40 to 80 wt .-%.

For the thixoform process, a thixotropic metal bolt is placed in the trough-shaped Area of the casting chamber cavity inserted and by means of a casting piston with pressure acted on, so that the thixotropic metal bolt through the closed-shaped area of the casting chamber cavity is pushed, with an upper edge zone of the thixotropic Metal pin is stripped. Then the pressurized thixotropic alloy pulp arrives via the sprue and the sprue into the mold cavity. The mold cavity can are or can be under ambient pressure during the method according to the invention be evacuated.

The pressurization of the thixotropic metal bolt by the casting piston is preferred chosen such that turbulence in the thixotropic metal alloy and thus the formation of gas and oxide inclusions in the molded part should be avoided if possible, i.e. the Pressurization of the casting piston is preferably done in such a way that a laminar one Flow of the thixotropic metal alloy with the surrounding oxide skin. Of the pressure exerted by the casting piston is, for example, between 200 and 1500 bar, expediently between 500 and 1000 bar. The resulting flow velocity the thixotropic alloy pulp is, for example, 0.2 to 3 m / s, expediently 0.3 to 2 m / s.

A thixoform process is also preferred, in which the process on the end face of the thixotropic Existing oxide skin, as well as a lower edge zone of the thixotropic metal bolt when hitting the impact surface of the impact element, together with the during the thixoforming of residual liquid emerging from the thixotropic alloy the oxide pocket located in the gate is passed, the lower edge zone being annular Sector of the metal bolt, which corresponds to the corresponding annular sector of the upper edge zone is complementary, and the stripped lower edge zone at least that in oxide skin present in this sector and completely surrounding the metal bolt.

The stripping of the upper edge zone of the thixotropic metal bolt can be further preferred happen continuously throughout the duration of the thixoforming process, so that the pro Unit of time stripped material quantity proportional to the feed speed of the casting piston is. At the beginning of the thixoforming process, the oxide knife is inserted into the Casting chamber cavity inserted and held in a vertical position that in the upper Edge zone of the thixotropic metal bolt is a radially uniformly thick layer of the oxide skin and the area close to the oxide skin of the thixotropic metal alloy is stripped off, the oxide knife being pulled out of the casting chamber cavity before the casting piston reached the position of the oxide knife.

Figur 1

zeigt schematisch eine Teilansicht eines vertikal durch die konzentrische Mittelachse des Giesskammerhohlraumes verlaufenden Längsschnittes einer erfindungsgemässen Horizontal-Druckgiessmaschine.

Figur 2

zeigt eine Teilansicht eines vertikal durch die konzentrische Mittelachse des Giesskammerhohlraumes verlaufenden Längsschnittes einer erfindungsgemässen Horizontal-Druckgiessmaschine während der Formfüllung.

Figur 3

zeigt einen Querschnitt durch die Giesskammer entlang der Linie A-A in Fig.1, d.h. einen Querschnitt durch die Giesskammer am Ort des Oxidmessers.

Figur 4

zeigt einen Querschnitt durch den Einguss der Gussform entlang der Linie B-B in Fig. 1, d.h. einen Querschnitt durch den Einguss am Ort der Aufprallfläche.

Further advantages, features and details of the invention result from the preferred exemplary embodiments shown in FIGS. 1 to 4 and from the description of the figures.

Figure 1

schematically shows a partial view of a longitudinal section of a horizontal die casting machine according to the invention, running vertically through the concentric central axis of the casting chamber cavity.

Figure 2

shows a partial view of a vertical section through the concentric central axis of the casting chamber cavity of a horizontal die casting machine according to the invention during the mold filling.

Figure 3

shows a cross section through the casting chamber along the line AA in Figure 1, ie a cross section through the casting chamber at the location of the oxide knife.

Figure 4

shows a cross section through the casting of the mold along the line BB in Fig. 1, ie a cross section through the casting at the location of the impact surface.

Figure 1 shows an example of a partial view of a vertical through the concentric central axis m of the casting chamber cavity 12 extending longitudinal section of an inventive Horizontal die casting machine, with a part of the horizontal lying in this longitudinal section Casting chamber 10 and the mold 40 can be seen.

The casting chamber 10 has a casting chamber cavity 12 which is cylindrical Casting chamber wall 14 is encased, the casting chamber 10 being a trough-shaped Area and a closed-shaped area 11. In Figure 1 is only a part of the closed region 11 is shown. The casting chamber 10 serves the one hand Inclusion of a thixotropic metal bolt 24 and on the other hand the pressurization the same through a casting piston 20.

The casting chamber cavity 12 represents a substantially cylindrical through which Giesskammerwandung 14 limited volume with a concentric central axis, the Longitudinal axis m, represents. The casting chamber cavity 12 is only in a mold side Area, i.e. the closed region 11 of a closed hollow cylindrical Casing, the casting chamber wall 14, surrounds and points to the mold 40 opposite side, for example a semi-cylindrical half-shell - not shown - On, which is used to insert the thixotropic metal bolt 24. The one through the hollow cylindrical Casting chamber wall 14 caused closed-shaped casting chamber cavity 11 has, for example, a round, oval or polygonal cross section. The diameter of the closed-shaped casting chamber cavity 11 preferably corresponds to 103 to 115% of the diameter of the thixotropic metal bolt, so that the metal bolt 24 after the insertion into the trough-shaped region of the casting chamber cavity 12 usually only on its underside a mechanical and thermal contact with the casting chamber wall 14 has.

A casting piston 20 is located on the side of the casting chamber 10 facing away from the casting mold 40 introduced the thixotropic alloy 24 with high pressure during the thixoforming the mold cavity 42 of the mold 40 presses. The thixotropic metal alloy 24 loses the initially existing bolt shape, so that the in the closed region 11 of the Casting chamber 10 located thixotropic metal alloy 24 the entire cross section of the Filling chamber cavity 12 fills; at least in the area of the casting chamber close to the mold 10. In this text, reference number 24 applies equally to the thixotropic metal bolts and the thixotropic metal alloy.

FIG. 1 also shows the disk-shaped oxide knife 30 essential to the invention, which is arranged here in the closed region 11 of the casting chamber 10. To the Inserting, lowering and pulling out the oxide knife 30 by means of an oxide knife guide 32 has the horizontal casting chamber wall 14 of the closed area 11 an oxide opening 22. The oxide knife 30 contains a yoke-shaped edge recess 31, which is designed such that an upper edge zone 26 of the thixotropic metal bolt 24 is stripped. The upper edge zone 26 relates to the jacket-shaped or hollow cylindrical oxide skin 28 of the thixotropic metal bolt 24 in a cross-sectional, upper sector of the bolt cross-section. In addition to introducing, Lowering and pulling out the oxide knife 30 further serves the oxide opening 22 for Removing the stripped top edge zone 26 from the casting chamber cavity 12.

The mold 40 shown in Figure 1 consists of a fixed mold half 44 with a Mold half recess 43 and a movable mold half 46 with a mold half recess 47, the mold halves recesses 43 and 47 of the two mold halves 44 and 46 together form the mold cavity 42 of the mold 40.

The gate is located between the casting chamber cavity 12 and the mold cavity 42 36 and the sprue 37. Here, the mold cavity 42 with the sprue 36 through one Sprue 37 connected. The part of the sprue leading directly from the sprue 36 37 relates to a tubular channel piece 38 which is in the uppermost region of the sprue 36 begins and runs vertically upwards. That to the vertical channel piece 38 of the sprue 37 adjoining channel piece tapers towards the mold cavity 42.

The gate 36 has the shape of a cylindrical cavity, which adjoins the casting chamber cavity 12 and one to the longitudinal axis m of the casting chamber cavity 12 has parallel concentric longitudinal axis. The longitudinal axis m of the casting chamber cavity 12 and the longitudinal axis of the gate 36 are in the same vertical plane.

The arrangement of the gate 36 with respect to the mold-side end of the casting chamber cavity 12, the so-called sprue opening 39, is such that the wall of the sprue 36 represents an extension of the casting chamber wall 14 in an upper region.

The gate 36 has a larger one than the adjacent casting chamber cavity 12 Cross-sectional area, wherein the gate 36 with respect to the mold-side end of the casting chamber cavity 12, the so-called pouring opening 39, is arranged such that the Wall of the sprue 36 in the uppermost region an extension of the casting chamber wall 14 and the gate 36 opposite the casting chamber cavity 12 in one lower region forms a residual melt cavity 62 designed as a depression. Therefore is the longitudinal axis of the sprue 36 with respect to the longitudinal axis m of the casting chamber cavity 12 shifted vertically downwards.

In the present text, the terms above and below always refer to a horizontal one Plane through the longitudinal axis m of the casting chamber cavity 12 or through the longitudinal axis of the gate 36.

The gate 36 is on the side facing away from the gate 39 by an impact element 50 limited, the impact element 50 directed towards the gate 36 Impact surface 52 and one as a recess in a lower region of the impact element 50 formed impact cavity 54 open towards the gate 36. The impact surface 52 is arranged parallel to a cross-sectional area of the gate 36 and is therefore perpendicular to the concentric longitudinal axis of the gate 36.

The vertically upward-extending channel piece 38 of the sprue 37 is on the one hand in a distance a to the impact surface 52 and, on the other hand, directly to the sprue opening 39 then arranged. The volume of the gate 36 between the cross-sectional area by the boundary of the vertical duct piece 38 closest to the impact surface 52 and the impact surface 52 describes the oxide cavity 56. The oxide cavity 56 forms together the oxide pocket 60 with the impact cavity 54 and the residual melt cavity 62.

To accommodate the axial, i.e. in the direction of flow of the thixotropic metal alloy 24 in the direction of the sprue 36 acting forces, the fixed mold half 44 of the mold 40 at one Shield 18, i.e. a strong wall element of the die casting system. The shield 18 and the fixed mold half 44 have a continuous opening for receiving the casting chamber 10 on. The shield 18 also has a directed against the continuous opening and groove-shaped recess 17 arranged at the edge of the mold 40. This groove-shaped Recess 17 serves to receive a complementarily shaped stop rib 16 of the casting chamber 10. The groove-shaped recess 17 of the shield 18 and the molded one Stop rib 16 of the casting chamber 10 are expediently radially symmetrical educated. Now the casting chamber 10 in the through opening of the shield 18th inserted so far that the stop rib 16 completely into the groove-shaped recess 17th engages and the fixed mold half 44 is also set flush with the shield 18, so takes the shield 18 the axial during thixoforming in the casting chamber 10 Powers up.

Figure 1 shows the horizontal die casting machine in the initial state of the thixoforming process represents, i.e. the filling of the mold cavity 42 has not yet started. The thixotropic metal alloy 24 is located in the casting chamber cavity 12 and has its outer bolt shape already lost, i.e. the thixotropic metal alloy 24 and the oxide skin 28 surrounding it essentially fill the entire cross-sectional area of the casting chamber cavity 12. Seen in longitudinal section through the horizontal die casting machine, the oxide skin 28 is on to recognize the lower and upper edge of the thixotropic metal alloy. Through the oxide knife 30, an upper edge zone 26 of the oxide skin 28 is stripped off and through the oxide opening 22 excreted from the casting chamber cavity 12. Seen in the printing direction, is therefore missing the metal alloy 24 located after the oxide knife 30 in an upper edge zone the oxide skin, due to the thixotropic state of the metal alloy and the Because of pressure, the thixotrope located after the oxide meter, viewed in the direction of flow Alloy porridge immediately again the entire available cross section of the casting chamber cavity 12 occupies.

Figure 2 shows a partial view of a vertically through the concentric central axis m of the casting chamber cavity running longitudinal section of a horizontal die casting machine according to the invention during mold filling. The horizontal die casting machine shown in Figure 2 corresponds to that in FIG. 1, the casting piston 20 being up to shortly before the oxide knife 30 introduced and the mold cavity 42 already partially with thixotropic alloy is filled. In the drawing, the thixotropic metal alloy 24 is shown with dots.

FIG. 2 also shows the part which is partially filled with parts of the oxide skin 28 and residual melt See oxide pocket 60. The lower edge zone of the oxide skin 28 is together with the thixotropic alloy 24 pushed into the gate 36, the oxide skin 28, i.e. the Oxide skin on the face of the metal bolt and the lower edge zone, due to the impact on the impact surface 52 essentially into the impact 54 and oxide cavity 56 of the Oxide pocket 60 is passed. Part of the oxide skin 28 is - along with that during the Thixoforms from the thixotropic alloy slurry 24 emerging residual melt - into the Residual melt cavity 62 passed. Due to the design of the gate 36 shown here an oxide pocket 60 is formed, in which only a very low speed field in terms of amount of the flow filling the mold cavity. The mainstream the thixotropic metal alloy 24 runs horizontally from the pouring opening 39 coming streamlined vertically upwards to the sprue 37. Because of the low Velocity field in the oxide pocket 60 is avoided that already in the oxide pocket 60 deposited components of the oxide skin 28 entrained with the main flow and be deposited in the mold cavity 42.

Figure 3 shows a cross section through the casting chamber 10 along the line A-A in Figure 1. This corresponds to a section through the horizontal die casting machine perpendicular to Longitudinal axis m of the casting chamber cavity 12 at the location of the oxide knife 30, the Section A-A runs along the end face 33 of the oxide knife 30. 3 shows this a cross section through the hollow cylindrical casting chamber wall 14 of the closed Area 11 of the casting chamber 10, the thixotropic metal bolt located therein 24, the oxide knife 30, and a portion of the oxide knife guide 32. The casting chamber cavity 12 has a circular cross section and the yoke-shaped edge recess 31 of the Oxide knife 30 has an arcuate cross section. The radius r of the yoke-shaped The edge recess 31 is smaller by the dimension b than the radius of the casting chamber cavity 12. This creates a jacket-like upper edge zone during the thixoform process 26 of the thickness b of the thixotropic metal bolt 24 stripped.

Seen in cross section, the yoke-shaped edge recess 31 comprises a central angle of 180 °, or an arc length of r · π, so that the stripped, upper edge zone 26 likewise comprises a central angle of 180 ° and the upper edge zone 26 has a cross-sectional area of b.π. (r + b / 2) having. The yoke-shaped edge recess 31 and thus also the upper edge zone 26 are symmetrical with respect to the vertical plane through the longitudinal axis m of the casting chamber cavity 12.

Figure 4 shows a cross section through the sprue 36 of the mold 40 along the line B-B in Fig. 1. This corresponds to a section through the horizontal die casting machine vertically to the concentric longitudinal axis of the sprue 36 at the location of the impact surface 52 3 shows a cross section through the movable mold half 46 and the sprue 36. The sprue 36 is circular cylindrical. The dashed line c represents that shown in FIG. 4 Cross-sectional area projected circumference of the casting chamber cavity cross-section. The cross section shown in FIG. 4 also shows the residual melt cavity 62, which versus the cross-sectional area of the casting chamber cavity, i.e. compared to that of the Dashed line c enclosed area, has a crescent shape. Thereby the residual melt cavity 62 forms a crescent-shaped enlargement of the casting chamber cavity 12, which at the bottom of the gate 36, i.e. at the bottom of the in Figure 4 shown cross-sectional area, which has the greatest depth.

4 shows the impact cavity 54, which is a lower segment of the cylindrical Socket 36 relates, wherein the impact cavity 54 with respect to a vertical is formed symmetrically through the center of the gate 36. In the further the Impact cavity 54 is superimposed in its lower region by the residual melt cavity 62.

Claims (10)

Horizontal die casting machine for the production of molded parts from thixotropic metal bolts (24) by thixoforming, comprising a casting mold (40) with a mold cavity (42) and a horizontal casting chamber (10) with a casting chamber cavity (12),
characterized in that a) the casting chamber (10) has a disc-shaped oxide knife (30) which can be inserted into the casting chamber cavity (12) and which has a yoke-shaped edge recess (31) which is designed such that an upper edge zone (26) of the thixotropic metal bolt is formed during thixoforming (24) can be stripped, and b) the mold (40) has a gate (36) adjacent to the casting chamber cavity (12), and the mold cavity (42) is connected to the gate (36) by a gate (37), at least that directly from the gate (36 ) part of the sprue (37) leading away from the uppermost region of the sprue (36) is a vertically upward duct piece (38). Horizontal die casting machine according to claim 1, characterized in that the Casting chamber (10) a trough-shaped area for inserting the thixotropic metal bolt (24) and a closed-shaped one adjoining it in the direction of the mold (40) Area (11), wherein a casting chamber wall (14) of the closed Region (11) has an oxide opening (22) in an upper half, which allows the insertion, lowering and removal of the oxide knife (30). Horizontal die casting machine according to claim 1, characterized in that the Casting chamber (10) a trough-shaped area for inserting the thixotropic metal stud (24) and a closed-shaped one adjoining it in the direction of the mold (40) Area (11), the oxide knife (30) in the transition area is positioned between the trough-shaped and the closed area (11). Horizontal die casting machine according to one of claims 1 to 3, characterized in that the yoke-shaped edge recess (31) is designed such that through the end face (33) a radially uniformly thick, upper edge zone (26) of the thixotropic metal bolt (24) is stripped. Horizontal die casting machine according to one of claims 1 to 4, characterized in that the gate (36) is opposite the adjacent casting chamber cavity (12) has a larger cross-sectional area, the sprue (36) being opposite the casting chamber cavity (12) is arranged such that the sprue (36) - at least in a lower area - a residual melt cavity designed as a depression (62). Horizontal die casting machine according to claim 5, characterized in that the Residual melt cavity (62) has a crescent-shaped cross-sectional area, whereby the greatest depth of the residual melt cavity (62) at the lower edge of the gate (36) located. Horizontal die casting machine according to one of claims 1 to 6, characterized in that the gate (36) facing away from the casting chamber cavity (12) Side is limited by an impact element (50), the impact element (50) an impact surface (52) directed against the gate (36) and one as a recess in a lower area of the impact element (50) designed against the gate (36) has open impact cavity (54). Horizontal die casting machine according to claim 7, characterized in that the Inlet (36) is designed in such a way that the channel piece leading away from the inlet (36) (38) of the sprue (37) at a distance a from the impact surface (52) is such that between the impact surface (52) and a distance a from it Cross-sectional area of the gate (36) an oxide cavity (56) is formed. Thixoform process for the production of molded parts from thixotropic metal bolts in a horizontal die casting machine according to one of Claims 1 to 8, in which inclusions of the oxide skin (28) surrounding the thixotropic metal bolt (24) are avoided in the alloy structure of the molded part,
characterized in that
an upper edge zone (26) of the thixotropic metal bolt (24), which relates to an annular sector of the metal bolt (24), is stripped off in the region of the casting chamber cavity (12) and ejected from the casting chamber cavity (12) or retained in the casting chamber cavity (12), wherein the stripped upper edge zone (26) completely encompasses at least the oxide skin (28) present in this sector and surrounding the metal bolt (24). A method according to claim 9, characterized in that one on the end face of the thixotropic metal bolt (24) existing oxide skin and a lower edge zone of the thixotropic metal bolt (24) when hitting the impact surface (52) of the impact element (50), along with that during thixoforming from the thixotropic Alloy remaining liquid emerging in an oxide pocket in the gate (36) (60), the lower edge zone being an annular sector of the Metal bolt (24) relates to the corresponding annular sector of the upper Edge zone (26) is complementary, and the stripped lower edge zone at least that in this sector existing oxide skin (28) surrounding the metal bolt completely includes.

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