EP2823916B1 - Method of manufacturing a composite casting - Google Patents

Description

The invention relates to a method for producing a composite casting comprising an insert part and casting material, wherein the insert part is connected in a material-locking manner to the cast material according to the preamble of claim 1.

The production of composite castings allows a combination of the preferred properties of the materials in the appropriate locations. So components can be optimally assembled according to their requirements and applications due to the combination of materials. However, this requires a cohesive or metallurgical connection between the materials. When pouring steel parts into cast iron or aluminum alloys, the problem often arises of insufficient connection between cast-in steel part and enclosing or cast-in material. The early solidification of the melt due to the contact with the space-tempered insert, a metallurgical or cohesive bonding between the casting material and steel part is hindered, which can cause gaps between the composite partners.

The DE 10 2006 041 901 A1 discloses a method for producing metal composite parts from steel and / or cast iron. In this process, the einzugießende part, which is made of steel or cast iron, coated by flux. The coating aims at a reduction, that is to say that during the pouring, the oxide skin of the casting is dissolved and washed away, as a result of which the casting material can undergo a metallurgical bond.

The DE 10 2011 053 858 B3 discloses a method of using a pourable component in a lost mold, wherein a coating agent is applied to a surface of the inflowing component. The coating agent forms a separation-active surface, which prevents adhesion of the material to the component as well as corrosion before casting with casting material.

The DE 100 43 105 B4 discloses a method of forming a tough, resilient and / or at least substantially defect free bond between an insert and a cast metal material having a melting point below that of the feedstock. The insert is coated with a thin layer of a metallic material derived from the group of silver, antimony, bismuth, chromium, gold, lead, magnesium, silicon, tin, titanium and zinc. This is followed by casting of the casting material against the coated surface of the insert. The thermal expansion coefficient of the coating is greater than that of the insert and less than that of the casting material. The coated insert is also maintained at a temperature of at least 100 ° C for a period of at least 5 minutes. By this method, a part of the coating is intended to dissolve and be sacrificed to the cast metal material, while a portion of this coating remains as a diffusion barrier between insert and casting material, which is to achieve a highly tough bond between insert and casting material.

The EP 0 659 899 A1 finally also discloses a method for producing a composite casting with all the technical features of the preamble of claim 1.

Object of the present invention is to provide a method and a corresponding composite casting, which achieved over the prior art, an improved bond between an insert and casting material, and ensures economic production.

This object is achieved according to the invention that the sheathing or embedding of the insert is formed by an exothermic material which ignites by contacting with the inflowing casting material or by reaching the ignition temperature whereby the temperature gradient between solidifying melt and the insert is reduced after casting and demolding, the exothermic material is removed, the surface (s) of the insert covered by the exothermic material being / are free of casting material.

This energy is released and released to the environment, resulting in a reduced temperature gradient between the solidifying melt and the insert.

• Herstellen des Einlegeteils,
• Ummanteln bzw. Einbetten des Einlegeteils mittels exothermen Material,
• Einlegen des ummantelten/eingebetteten Einlegeteils in die Giessform,
• Füllen der Form mit Schmelze.

The method according to the invention comprises the following steps:

• Making the insert,
• Wrapping or embedding the insert by means of exothermic material,
• Inserting the coated / embedded insert into the mold,
• Filling the mold with melt.

Exothermic materials are used in addition to the use in welding (Thermitschweissgemische) in exothermic feeders in the foundry. Upon contact of the melt with the exothermic mass, a combustion reaction is triggered, which ensures in the feeder that there is the last solidifying melt and so that the changing volume during solidification in the casting can be compensated. Such materials are known in the art, which EP 1 050 354 A1 . EP 0 888 199 B1 and DE 196 42 838 A1 reveal such.

In the present invention, such a known material causing an exothermic reaction is used as a sheath for the inflowing insert. By contacting the exothermic material with the liquid casting material or by reaching the ignition temperature of the exothermic mass, the material ignites. As a result, the insert is heated from both sides, which prevents rapid solidification of the casting material in the border region to the insert, since the insert loses its quenching effect for the casting material. The temperature gradient between casting material and insert is minimized. This, in turn, promotes carbon diffusion between the casting material and the insert, whereby a cohesive or metallurgical bond can be produced.

The insert is preferably made of steel, copper, bronze, brass, aluminum or an aluminum alloy. The process or the composite casting is versatile due to the wide choice of materials.

The exothermic material preferably has an easily oxidizable metal, in particular aluminum and / or magnesium.

In addition, it is advantageous that the exothermic material has an oxidizing agent for the readily oxidizable metal, in particular iron (III) oxide.

The backfill material used is preferably an oxide, in particular SiO ₂ . The backfill material serves as a filling material, which is mixed with the other substances such as aluminum and / or magnesium and an oxidizing agent.

The exothermic material preferably comprises a binder which serves the cohesion of the exothermic material. The preferred binder is an alkali silicate in use.

A preferred embodiment is that a cast iron is used as the casting material, preferably GJS, GJL and / or GJV. Through the cast-in insert, a high strength and elongation at break can be achieved at designated locations in the cast component, or additional, positive properties for a subsequent further treatment can be given to the composite cast component.

In composite castings produced by methods known in the art, the connections between the cast material and the insert are usually insufficient. Composite castings which have been produced by the method according to the invention have an improved cohesive connection between the materials.

The use of such manufactured composite castings offers a good alternative to substituting cast steel or steel welded constructions with the advantage of the known cast iron alloys and their method of manufacture.

As a preferred embodiment, an aluminum alloy is used as the casting material, thereby, for example, aluminum components can be combined with various metallic materials, whereby the advantage of the weight reduction can be used by the light aluminum.

Preferably, the inventive method is used with lost molds.

By this method, it is possible to use an insert, which has a sufficient thickness or wall thickness, which allows the insert after the casting process still a heat treatment or welding process to undergo. Methods which are known from the prior art, allow only the pouring of a steel part, which is very thin-walled, in order to counteract the rapid solidification and the impeded carbon diffusion by the contact of the room temperature-controlled steel part with the casting material something.

Preferably, a hollow body is used as an insert. The cavity fills with the casting material and connects cohesively with the insert. The outer surface of the insert is coated with the exothermic material or embedded in the material. Due to the exothermic reaction of the mass after contact with the melt, the mass also gives off heat to the insert, resulting in a unified temperature gradient between the solidifying melt and the insert. The insert can also be unilaterally, or in hollow execution from the inside with the exothermic material in combination.

After the casting and demolding, the exothermic material can be easily removed and the outer surface or inner surface of the insert emerges. Post-processing is then possible, but in some cases not necessary because the dimensional accuracy and the surface finish are already of good quality. Also by the possible savings of further processing steps, the inventive method is economically highly interesting. Furthermore, these methods provide extended possibilities to after-treat the cast component, such as e.g. Welding or heat treatment (even partially on the insert).

Such composite castings produced by the method according to the invention are particularly suitable for general mechanical engineering, construction machinery and vehicle construction. It can thereby different materials economically combined with each other and the preferred properties of the individual materials are combined with each other, without the problem of insufficient connection of the materials by early solidification of the casting material occurs.

• Fig. 1 einen Teilschnitt einer Giessform mit eingesetztem ummantelten Einlegeteil,
• Fig. 2 eine fotographische Abbildung eines mit exothermem Material ummantelten Stahlrohrs,
• Fig. 3 ein Schliffbild durch einen Ausschnitt des Verbundgussteils und
• Fig.4 ein Ausschnitt eines Verbundgussbauteil mit eingegossenem Stahlteil

Embodiments of the invention will be described with reference to the figures, wherein the invention is not limited to the embodiments. It shows:

• Fig. 1 a partial section of a mold with inserted jacketed insert,
• Fig. 2 a photographic image of a steel tube encased with exothermic material,
• Fig. 3 a microsection through a section of the composite casting and
• Figure 4 a section of a composite cast component with cast steel part

Fig. 1 shows a partial section of a mold in which a composite casting 1 was shed. The casting material 2 flows into the casting mold formed by the molding material 5 in which an insert 3 is inserted in order to form a cohesive or metallurgical bond with the casting material 2. The casting material 2, preferably GJS, GJL or GJV, flows into the casting mold formed by the molding material 5. At the points where the casting material 2 touches the exothermic material 4, this ignites, whereby heat is released to the environment. The insert is thereby heated and the temperature gradient between the solidifying melt and the insert is reduced. In addition, the carbon diffusion between casting material 2, which directly touches the insert 3, and the insert 3 is driven forward. Thus, a cohesive or metallurgical connection at the direct contact points between insert 3 and casting material 2 is achieved. After molding, the exothermic material 4 can be easily removed from the insert 3. The area covered by the exothermic material 4 / n of the insert 3 is free of casting material, thus a reworking of the surface of the insert is not necessarily necessary, which in turn makes the inventive method economically very interesting.

Another embodiment is by the Fig. 2-4 demonstrated.

As insert 3, a cylindrical steel tube made of a high-carbon steel with wall thicknesses of 5 mm is used and molded into exothermic material 4 with a defined wall thickness. This steel pipe 3 with surrounding exothermic material 4 is inserted into the mold 5 to be cast as from Fig. 2 seen. The closed mold 5 is filled with melt 2 for producing a GJS, wherein the interior of the steel pipe 3 is flowed through by melt 2 and a Part of the exothermic material has 4 direct melt contact. After the ignition temperature of the exothermic material 4 is reached, this gives off heat to the environment and the steel pipe 3. This is greatly heated and the temperature gradient between the steel pipe 3 and solidifying melt 2 is reduced. This has a favorable effect on the structure formation and the carbon diffusion between the casting material 2 and the steel pipe 2, which is due to the concentration differences take place from. Due to the incorporation of the carbon atoms in the interstices of the steel, the melting temperature is lowered and the tube wall of the steel pipe 3 dissolves. Areas of the steel are carburized and replaced by castings. Thus, a seamless transition from the casting 2 and steel 3 takes place in Fig. 3 is shown. In Fig. 4 is a section of the component with cast steel pipe 3 shown.

LIST OF REFERENCE NUMBERS

1

Composite casting

2

cast material

3

Insert / steel tube

4

Exothermic material

5

Casting mold made of molding material

Claims (12)

1. Process for producing a composite cast part (1) containing an insert part (3) and casting material (2), wherein the insert part (3) is integrally bonded to the casting material (2) and the process comprises the following steps:

   producing the insert part (3),

   encapsulating or embedding the insert part,

   inserting the encapsulated/embedded insert part into the casting mould,

   filling the mould with molten mass,

   characterized in that the encapsulation/embedding of the insert part is formed by an exothermic material (4) which ignites through the contact with the inflowing casting material or as a result of the ignition temperature of the exothermic mass being reached, as a result of which the temperature gradient between the solidifying molten mass and the insert part (3) is reduced, wherein, after the casting and removal from the mould, the exothermic material (4) is removed, wherein the face(s) of the insert part covered by the exothermic material (4) is or are free from casting material (2).
2. Process for producing a composite cast part (1) according to Claim 1, characterized in that the insert part (3) consists of steel, copper, bronze, brass, aluminium or an aluminium alloy.
3. Process for producing a composite cast part (1) according to either of Claims 1 and 2, characterized in that the exothermic material (4) comprises a readily oxidizable metal, in particular aluminium and/or magnesium.
4. Process for producing a composite cast part (1) according to one of the preceding claims, characterized in that the exothermic material (4) comprises an oxidant for the readily oxidizable metal, in particular iron(III) oxide.
5. Process for producing a composite cast part (1) according to one of the preceding claims, characterized in that the exothermic material (4) comprises a back-fill material, preferably an oxide.
6. Process for producing a composite cast part (1) according to Claim 5, characterized in that the oxide is preferably SiO₂.
7. Process for producing a composite cast part (1) according to one of the preceding claims, characterized in that the exothermic material (4) comprises a binder, preferably alkali silicate.
8. Process for producing a composite cast part (1) according to one of the preceding claims, characterized in that the casting material (2) is a cast iron, in particular GJS, GJL and/or GJV.
9. Process for producing a composite cast part (1) according to one of the preceding claims, characterized in that the casting material (2) is an aluminium alloy.
10. Process for producing a composite cast part (1) according to one of the preceding claims, characterized in that the casting mould (5) is a lost casting mould.
11. Process for producing a composite cast part (1) according to one of the preceding claims, characterized in that the composite cast part (1) can be subjected to a heat treatment or to a welding process at least on the insert part (3).
12. Process for producing a composite cast part (1) according to one of the preceding claims, characterized in that the insert part (3) is a hollow body or a free-form part.

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