WO2008017445A1

WO2008017445A1 - Method for producing a skim core with innoculant body

Info

Publication number: WO2008017445A1
Application number: PCT/EP2007/006943
Authority: WO
Inventors: Bernd Ebert; Henning Rehse
Original assignee: Skw Giesserei Gmbh
Priority date: 2006-08-07
Filing date: 2007-08-06
Publication date: 2008-02-14
Also published as: DE102006036840A1

Abstract

The present invention relates to a method for producing a skim core which is formed from a moulding material and on which an innoculant body is fixedly held. In order to provide a method by means of which skim cores (115), to which the innoculant body (120; 220) is securely fastened, can be produced in a simple manner in terms of production and therefore cost-effectively, a method is proposed which comprises the following steps: a) the introduction of the innoculant body (120; 220) into a core box (150; 250); b) the filling of the moulding material into the core box (150; 250), wherein the innoculant body (120; 220) is partially embedded by the moulding material; c) the hardening of the moulding material.

Description

Method for producing a sprue with

innoculant

The present invention relates to a method for producing a molding material formed from a molding material

Eingusskerns, where a Impfmittelkörper is held firmly.

Cast iron is an iron-carbon alloy with a carbon content of usually higher than 2%. ^■ Im

Unlike steel, carbon in cast iron is precipitated in the form of graphite. DIN 1693 and DIN EN 1563 differentiate depending on the graphite geometry of three types of cast iron: cast iron with lamellar graphite (abbreviated: GGL or GJL), cast iron with vermicularem graphite (abbreviated: GGV or GJV) and cast iron with nodular graphite, also called ductile iron (abbreviated : GGG or GJS).

The simplest type of gray cast iron is lamellar GJL, in which the graphite is in the form of thin, irregular platelets. These lamellae act as notches under tensile load, which is why the tensile strength of the GJL is relatively low. In addition, the GJL variety is fairly brittle. On the other hand, the lamellar graphite gives the material a good thermal conductivity and good damping properties.

The ductile cast iron GJS, in which the graphite is more or less spherical in shape, has better mechanical properties. Spheroidal graphite cast iron advantageously has steel-like mechanical properties. Because of its excellent mechanical properties, relatively low cost of manufacture and good machinability, GJS is widely used in the industry. About 45 to 50% of the world's annual production of GJS will be used for the production of castings for the

Vehicle industry consumed. Particularly in the automotive industry, previously manufactured and welded vehicle parts made of forged steel are replaced by much more economical GJS castings. In particular, so-called safety parts such as crankshafts, camshafts, connecting rods,

Multi-link, wheel hubs, truck wheel stars, axle bridges, swivel bearings, etc. made of GJS.

As raw materials for the production of GJS, GJL and GJV steel scrap, pig iron, ferrosilicon and additives such as lime, coke, quartz etc. are used. These raw materials are charged in an oven and melted. During the melting process, the chemical composition of the melt is checked and adjusted as needed by adding alloys or additives. Before casting, the melt is then treated with magnesium.

The magnesium-treated cast-iron melt is then poured into a corresponding casting mold usually by means of a pouring pond.

A Eingusstümpel is usually a placed on the upper box of molds container with spatially separated inlet and outlet point and serves to take over the liquid metal from a pan and feed it to the mold. The

Separation between inlet and outlet point causes Slag or non-metallic inclusions can accumulate on the pool surface and that it comes to avoid a suction effect, which could cause an increased gas uptake.

Gutter ponds used in large casting comprise a casting core formed from a molding material and forming a receptacle for receiving the molten iron, which as a rule is received by a frame of, for example, metal supporting the casting core. The cast pool for large-scale casting may further be provided, in addition to the frame, with a slag septum, which provides a means of retaining contaminants from entering the drainage point, as well as a plug closure for the drainage point. In contrast, pour ponds used in medium casting usually only comprise a sprue core formed from a molding material.

In the design of sprues is generally to ensure that the transition between the bottom of the sprue and sprue is characterized by soft contours, so that an always continuous flow is present in the sprue. To ensure this, the pouring capacity of the pan should be such that the sprue core is always filled with metal.

However, to achieve optimum material properties and high metallurgical quality, both the GJS, GJV and GJL cast iron melts must be seeded before casting or during casting. Through the vaccination, nuclei are created, which compel for the excretion of graphite from the melt are required, among other things, the formation of cementite is suppressed.

Among the different vaccination methods, the so-called inoculation with inoculants is particularly effective. In the inoculation, the molten cast iron is poured into the mold via a sprue with a sprue core, at the bottom of which an inoculant body is fixed. The molten iron passing through the gate core continuously dissolves the inoculant body and is thereby inoculated with its contents. Especially in medium and large castings, the application of this method is very effective and therefore very common.

Inoculant bodies are bodies that consist of inoculants or contain inoculants. They are usually offered as a shaped body in the trade and have different shapes and dimensions depending on the purpose. Examples of inoculum bodies include so-called vaccinees sold under the trademarks Germalloy® or Optigran® and based on an iron / silicon alloy.

An essential prerequisite for the use of the molding is that a caused by its low density floating of the Impfmittelkörpers is prevented in the molten iron during casting, otherwise the Impfmittelkörper in iron does not dissolve and the intended ImpfWirkung therefore does not occur. For this reason, a secure attachment of the Impfmittelkörpers must be ensured in the sprue. In large-scale casting, the inoculant bodies are partially embedded by hand for secure attachment of the inoculant bodies in and around the pouring basin into the soils of the manually formed pouring basins.

In medium casting, on the other hand, prefabricated and hardened cores which are preferably produced on core casting machines are often used as the pouring basins. The problem with the use of finished trained cores is that a sufficient assurance of

Inoculant body against a floating the same subsequently as good as not given. Although there are efforts to attach the Impfmittelkörper subsequently, for example by means of adhesive to the sprue core. However, the adhesives used only withstand the high temperatures during the casting process for a short time, so that a secure attachment of the inoculant body to the sprue core over the entire casting process can not be guaranteed.

Object of the present invention is therefore to provide a method by means of which can be produced in a simple and therefore cost-effective manner from a molding material formed Eingusskerne on which an Impfmittelkörper is securely attached.

This object is achieved on the basis of a method of the generic type by a method which comprises the following steps:

a) introducing the Impfmittelskörpers in a core box; b) filling the molding material into the core box, wherein the Impfmittelkorper is partially embedded by the molding material;

c) the curing of the molding material.

It has been found that an inoculant body can be securely fixed to a gate core by placing the seed body in the core box for the gate core, filling the molding material into the core box, only partially embedding the seed body of the molding material, and curing the molding material becomes. The inventive method provides Eingusskerne to which the Impfmittelkorper by partially embedding in the molding material against

Floating are secured during the casting process and which allow safe use of the inoculation process.

Moreover, according to the inventive method, a manual partial embedding of the Impfmittelskorpers in the Exngusskern or a nachtragliches attach the Impfmittelkorpers to an already finished Eingusskern no longer necessary. Rather, the method according to the invention can be carried out fully automatically, for which reason corresponding sprue cores can be produced in a particularly cost-effective manner by means of the method according to the invention.

Under a core box is in the context of the present invention as in the foundry technology, a one- or multi-part mold for molding of cores and Core shapes, for example by means of core forming machines according to the usual core molding processes understood. In general, a core box is a multi-part mold, which can be removed after opening the molded body.

In order to achieve a particularly secure hold of the inoculant body at the sprue, the seed body is preferably fixed to the sprue core.

By means of the method according to the invention, it is possible in particular to produce high-quality sprue cores with inoculant bodies for use in medium casting. In accordance with a further preferred embodiment of the method according to the invention, it can therefore be provided that the sprue core and the inoculant body have dimensions which are suitable and typical for medium casting. Corresponding dimensions are adequately described in the prior art and known to the person skilled in the art.

As molding material for the formation of the sprue core, any molding material described in the prior art can generally be used, which satisfies the conditions occurring during the casting process. According to a preferred embodiment of the method according to the invention, the molding material is a sand mixed with a binder, wherein the binder may be both inorganic and organic in nature. Sand / binder mixtures can be processed very well to moldings such as cores and in them partially embedded Impfmittelkörper be kept very strong in the corresponding cured mixtures. The seed body to be used in the process according to the invention may generally have any outer shape. For example, the seed body may have a square, rectangular, triangular, trapezoidal, parallelogram, circular or hexagonal shape

Have cross-section or be formed for example as a sphere, pyramid, cylinder, cone, cube or cuboid. In order to further improve the hold of the inoculant body at the sprue core, it may further be provided that the part of the inoculant body to be embedded in the molding material is provided, for example, with a corrugation, with pins or with a roughened surface.

Preferably, the Impfmittelkörper has an outer shape, which leads to the formation of one or more undercuts in the molding material with appropriate embedding of the body. As a result, a particularly firm hold of the inoculant body is ensured at the Eingusskern, the body can be removed from the hardened Eingusskern in this case only when the latter is broken.

According to a further preferred embodiment of the method according to the invention, the seed body has a triangular or trapezoidal cross-section or is in the form of a pyramid or a cone. If the inoculant body has, for example, a trapezoidal cross-section, then the body is to be embedded in the molding material in such a way that the wider of the two of its parallel aligned base sides is directed counter to the sprue core floor. Such an arrangement leads in the

Mold material for forming two opposing one another Undercuts, which are engaged behind by the Impfmittelkörper and thus guarantee a firm grip of the Impfmittelkörpers at the Eingusskern.

According to a further embodiment of the method according to the invention, the inoculant body is partially embedded in the sprue core, namely in a form-locking manner. As a result, in addition to a firm hold of the inoculant body at the sprue, it is ensured that no liquid iron can enter when using the sprue core resulting from the method according to the invention between the inoculant body and the adjoining molding material, which dissolves the inoculum body in the embedding area and consequently loosens and swells the inoculant body could cause.

It may be preferred that the seed body is releasably fixed after insertion into the core box and prior to filling of the molding material, preferably at the core box. This ensures that, regardless of the manner in which the molding material is filled into the core box, the seed body is arranged in the desired position on the casting core resulting from the method according to the invention.

Further, it may be preferable that the filling of the molding material into the core box is performed under a high pressure. The filling of the molding material in the core box under high pressure causes a high compression of the molding material, whereby a very good hold of the

Inoculant body is ensured at the Eingusskern. According to a further preferred embodiment of the method according to the invention can be provided that the method further comprises a step in which a filter element is introduced into the core box, wherein the filter element is partially embedded after the filling of the molding material of the molding material. It has been found that a filter element can also be securely fastened to a sprue core by inserting the filter element into the core box for the sprue core

Mold material is filled into the core box, wherein the filter element is embedded by the molding material only partially, and the molding material is then cured. This embodiment of the method according to the invention provides sprue cores to which both inoculant bodies and also

Filter element are securely fixed by partial embedding in the molding material. It will be appreciated that a filter element may be securely attached to the sprue core without securing an inoculant body to the sprue core in parallel.

According to a further preferred embodiment of the method according to the invention, the filter element has a trapezoidal cross section and is preferably designed as a round filter element. In this case, the filter element is preferably arranged in the outlet for the liquid metal.

The design of the filter element with trapezoidal cross-section allows the formation of undercuts in the mold material, which are engaged behind by the filter element can be and thus ensure a firm grip of the filter element at the Eingusskern.

According to a further preferred embodiment of the method according to the invention, it is preferred that the

Filter element after insertion into the core box and before filling the molding material in the core box is releasably fixed, preferably on the core box. This ensures that, regardless of the manner in which the molding material is filled into the core box, the filter element is arranged in the desired position on the casting core resulting from the method according to the invention and does not assume a position displaced from the desired position.

The present invention further relates to a core box for producing a sprue core formed of a molding material to which a seed body is firmly held by partially embedding in the molding material of the sprue core, the core box being provided with a holder by means of which the seed body is fixed and / or so can be positioned that the Impfmittelkörper is partially embeddable in the molding material.

According to a preferred embodiment of the core box according to the invention, the holder is designed as a receptacle which can receive the non-embeddable part of the Impfmittelkörpers positive fit.

Further, it may be preferred if the core box is provided with a fixing device for releasably fixing the Impfmittelkörpers in the and preferably on the core box. According to a further preferred embodiment of the core box according to the invention, it is provided that the core box is further provided with a second holder, by means of which a filter element is positionable such that the filter element is partially embeddable in the mold material.

Furthermore, it can be provided according to a further preferred embodiment of the core box according to the invention that the core box is provided with a fixing arrangement for releasably fixing the filter element in the core box. By this measure, it can be avoided that the filter element is displaced during filling of the molding material and is in an unwanted position in the hardened sprue core.

The invention further relates to a sprue made according to the method of the invention or produced using the core box according to the invention.

The drawing is used in conjunction with the following description of the explanation of the invention. Show it:

Fig. 1: Schematic representation of a known

Gutter ponds for large-scale casting with inoculant body A) in cross-section; B) in plan view;

Fig. 2: Schematic representation of a produced by the method according to the invention Eingusskerns for medium casting with Impfmittelkörper A) in cross section; B) in plan view;

Fig. 3: Schematic representation of a first embodiment of a core box according to the invention in cross section A) without and B) with inoculated Impfmittelkörper;

Fig. 4: Schematic representation of a second embodiment of a core box according to the invention in cross section A) without and B) with inoculated seed body and filter element.

FIG. 1 shows a manually produced casting pond for large casting, generally designated by the reference numeral 10, as known from the prior art. Of the

Eingusstümpel 10 includes one of a

Sand / binder mixture mixture formed as a molding material

Casting core 15, which is received in a frame 35 made of metal. In the bottom of the sprue core 15 is an inoculant block

20 embedded as Impfmittelkörper and arranged a drain 25 for liquid metal.

The Eingußümpel 10 is equipped with a slag septum 21, which provides a way to retain contaminants from entering the drain 25. The Eingußümpel 10 is further provided at the outlet 25 with a plug closure 30, which is opened only when the pool is filled. FIG. 2 shows a pouring basin for the central casting, which is designated overall by the reference numeral 100. The pouring pool 100 comprises one of a

Sand / binder mixture mixture formed as a molding material Eingusskern 115, in the bottom of a Impfmittelblock 120 embedded as Impfmittelkörper and a drain 125 is arranged for liquid metal.

The Eingusstümpel 100 and the Eingusskern 115 with the Impfmittelblock 120 and the drain 125 was prepared by the method according to the invention using the first embodiment of a core box 150 according to the invention shown in FIG. To produce the sprue core 115 with seed block 120, the seed block 120 was first inserted into the trapezoidal socket 155 as a holder. The receptacle 155 and the Impfmittelblock 120 have such dimensions that the narrow base of the Impfmittelblocks 120 comprehensive section 122 positively engages the receptacle 155, while the broad base of the Impfmittelblocks 120 comprehensive

Section 124 freely projects into the sand / binder mixture mixture to be filled space 160.

Thereafter, a sand / binder mixture mixture was filled in the space 160 of the core box 150 by means of a core shooting machine. In the filling process, section 124 of inoculum block 120 was embedded in the mixture. The embedding of the portion 124 results in the formation of two opposing undercuts in the cured sand / binder mixture, which are formed by corresponding parts of the portion 124 of Inoculation block 120 are engaged behind and so ensure a firm grip of Impfmittelblocks 120 at Eingusskern 115.

After the filling process, the sand / binder mixture mixture was cured and the sprue 115 was removed from the mold.

FIG. 4 shows a core box 250 according to a second embodiment. With this core box 250, cores can be produced by means of the method according to the invention, which comprise both an inoculant body and a filter element in the region of the outlet for the metal.

In order to produce a sprue core with an inoculum block 220 as an inoculant body and ceramic filter 230 as a filter element, the inoculant block 220 is inserted into the trapezoidal receiver 255 as a holder. Thereafter, the ceramic filter 230 is clamped between the surfaces 232 and 234 of the core box 250 as a second holder. The receptacle 255 and the inoculant block 220 have dimensions such that the section 222 comprising the narrow base area of the inoculum block 220 positively engages the receptacle 255, while the section 224 comprising the broader basal area of the inoculum block 220 is exposed to the sand / binder layer. Merging mixture to be filled space 260 protrudes.

Subsequently, a sand / binder mixture is introduced as a molding material by means of a core shooter in the space 260 of the core box 250. In the filling process, the section 224 of the seed block 220 and the free annular section 236 of the circular ceramic filter 230 embedded in the mixture with a trapezoidal cross-section. The embedding of the portion 224 and the portion 236 of the inoculant block 220 and the ceramic filter 230 leads to the formation of opposing undercuts in the cured sand / binder mixture, which are engaged by parts of the section 224 and 236, and thus a firm grip of the Ensure inoculant block 220 and the ceramic filter 230 on the Eingusskern thus produced.

Claims

claims

1. A process for producing a sprue core formed from a molding material, on which an inoculant body is firmly held, characterized in that the process comprises the following steps:

a) introducing the seed body (120; 220) into a core box (150; 250);

b) charging the molding material into the core box (150; 250), wherein the seed body (120; 220) is partially embedded by the molding material;

c) the curing of the molding material.

2. The method according to claim 1, characterized in that the molding material is a staggered with a binder sand.

3. The method according to any one of the preceding claims, characterized in that the Impfmittelkörper (120; 220) has a trapezoidal cross-section.

4. The method according to any one of the preceding claims, characterized in that the Impfmittelkörper (120; 220) in the Eingusskern (115) is partially embedded, in a form-fitting manner.

5. The method according to any one of the preceding claims, characterized in that the Impfmittelkörper (120; 220) after insertion into the core box (150; 250) and before filling of the molding material is releasably fixed.

6. The method according to any one of the preceding claims, characterized in that the filling of the molding material in the core box (150; 250) takes place under a high pressure.

A method according to any one of the preceding claims, characterized in that the method further comprises a step in which a filter element (230) is introduced into the core box (250), the filter element (230) after filling of the molding material from the molding material is partially embedded.

8. The method according to claim 7, characterized in that the filter element (230) has a trapezoidal cross section.

9. The method according to claim 7 or 8, characterized in that the filter element (230) after insertion into the core box (250) and before filling of the molding material in the core box (250) is releasably fixed.

10. core box for producing a sprue core formed from a molding material, to which an inoculant body is firmly held by partially embedding in the molding material of the sprue core, the core box (150, 250) being provided with a holder (155; by means of which the seed body (120; 220) is positionable such that the seed body (120; 220) is partially embeddable in the die material.

11. core box according to claim 10, characterized in that the holder (155; 255) is designed as a receptacle which can receive the non-embeddable part of the Impfmittelkörpers (120; 220) positively.

A core box according to claim 10 or 11, characterized in that the core box (150; 250) is provided with a fixing means for releasably fixing the seed body (120; 220) in the core box (150; 250).

13. core box according to one of the preceding claims, characterized in that the core box (250) is further provided with a second holder (232, 234) by means of which a filter element (230) is positionable such that the filter element (230) partially in the mold material can be embedded.

14. core box according to claim 13, characterized in that the core box (250) is provided with a fixing arrangement for releasably fixing the filter element (230) in the core box (250).

15. Eingusskern prepared by a method according to any one of claims 1 to 9 or manufactured under Use of a core box (150; 250) according to one of claims 10 to 14.