DE102016124322A1 - Method for producing a casting mold for casting a highly reactive melt - Google Patents

Abstract

The invention relates to a method for producing a casting mold for casting a highly reactive melt, in particular for casting titanium, a titanium alloy or intermetallic titanium aluminides, comprising the following steps: producing a mold core from a fusible or combustible material, producing a contact layer by applying a first layer an yttria-based (YO) -based slurry on the mandrel, forming a first sanding layer by being soaked with yttria-based powder, applying a second layer of the yttria-based slurry to the mandrel, forming a second sanding layer by being sanded with one Yttria-based powder, producing a mold structure comprising a plurality of mold cores by attaching the mold cores to a base body made of the fusible or combustible material, inserting the mold structure into an auxiliary mold, producing a jacket film t by filling the auxiliary mold with a magnesium oxide-based slurry, removing the mold from the auxiliary form.

Description

The invention relates to a method for producing a casting mold for casting a highly reactive melt, in particular for casting titanium, a titanium alloy or intermetallic titanium aluminides.

Such a method is known from WO 2010/034762 A2 known. The method described therein comprises the following steps: producing a contact layer by applying a first slurry containing a first Y ₂ O ₃ powder as a substantial solid component to a mandrel, forming a first sanding layer on the contact layer by affixing the contact layer to a Y ₂ O ₃ containing as an essential component second Y ₂ O ₃ powder, wherein a first dry mass for the preparation of the first slip at least 75 wt.% Y ₂ O ₃ and contains as further solid component at least 1.0 to 25 wt.% Of a hydraulic binder ,

In this known method, a first sanding layer and then a magnesium oxide-containing intermediate layer is applied to the contact layer. Subsequently, a second sanding layer and a further intermediate layer are applied, followed by another sanding layer. This interlayer sequence is backfilled with a substantially magnesium oxide-containing cladding layer. Due to the many individual steps, this known method is very complicated, tedious and expensive.

The invention is therefore based on the object to provide a simplified method for producing a casting mold for casting highly reactive melts, which enables cost-effective production.

To solve this problem, a method having the features of claim 1 is provided.

Advantageous developments of the invention are described in the dependent claims.

The invention is based on the finding that a casting mold for casting a highly reactive melt can be produced particularly simply by producing only the contact coat (face coat) and then a cladding layer. It has surprisingly been found that it is possible to dispense with an intermediate layer. Accordingly, the process steps of producing the one or more intermediate layers and the Besandungsschichten omitted.

The method according to the invention enables a faster production of a casting mold for comparison to conventional methods, so that the method can also be used for large-scale production, for example in the automobile industry.

In the method according to the invention, provision can be made for a drying process to be carried out after the first and / or the second layer of the contact layer have been sanded.

In the simplest case, a passive drying process is carried out, which lasts between 0.5 and 10 hours. For example, a passive drying process can be performed overnight. However, if a faster drying process is desired or required, the drying can be carried out actively by means of an infrared radiator and / or by means of a fan. Such rapid drying can z. B. take one minute to five minutes.

In the context of the method according to the invention, it may be provided that the shape structure comprising a plurality of mandrels is formed like a tree by attaching the mandrels to a base body. Preferably, the base body has an elongated shape, for example, it may be cylindrical or conical. At several positions in the longitudinal direction of the body, the mandrels are attached. At a certain position in the longitudinal direction may be several, for example, two, three or four mandrels, which are distributed distributed in the circumferential direction. In this way, a mold can be produced, with which a larger number of products can be produced in a single casting process. For example, a mold may comprise four, eight, sixteen, or twenty mandrels. Accordingly, the production of products from a highly reactive melt can be carried out efficiently.

Preferably, in the method according to the invention, it is provided that the yttria-based slip from which the contact layer is produced contains a hydraulic binder, preferably calcium aluminate cement.

The inventive method is particularly well suited for the production of turbine wheels. Accordingly, it is preferable that a mandrel having the shape of a turbine wheel is used. Such turbine wheels are components of turbochargers for internal combustion engines. The above-mentioned highly reactive melts are suitable for operating temperatures of the order of 1000 ° C. Since the mold produced by the method according to the invention enables the production of particularly lightweight turbine wheels, an internal combustion engine equipped therewith can make a motor vehicle much faster accelerate. Another advantage is that CO ₂ emissions can be reduced.

In the method according to the invention, after the production of the cladding layer, the mold structure consisting of the plurality of mold cores is preferably removed by melting or burning out the material forming the mold structure. A green body formed after removal of the fusible or combustible material is then preferably sintered at a sintering temperature of more than 800 ° C and less than 1200 ° C.

• 1 einen Querschnitt einer nach dem erfindungsgemäßen Verfahren hergestellten Gussform, und
• 2 eine Seitenansicht einer mehrere Formkerne umfassenden Formstruktur.

The invention will now be described by way of example with reference to the drawings. The drawings are schematic representations and show:

• 1 a cross section of a mold produced by the process according to the invention, and
• 2 a side view of a plurality of mold cores comprising mold structure.

1 shows a cross section of a mold, which is produced by the described method. First, a mold core 1 produced. In this embodiment, the mandrel is made 1 made of wax as a fusible material. The outer contour of the mandrel corresponds to the outer contour of the product to be produced by means of the casting mold.

In this embodiment, it is in the mold core 1 around a trained as a wax turbine wheel. The mold core 1 is coated with a slip based on yttria (Y ₂ O ₃ ). The painting can be done either manually or alternatively by an automatic method, for example by a robot, by spraying. The slurry contains calcium aluminate cement.

By painting the mold core 1 with the slip becomes a first contact layer 2 generated. Subsequently, this first contact layer 2 sanded with a yttria containing as an essential ingredient powder, whereby a first Besandungsschicht 3 is formed. The first contact layer 2 and the first sanding layer 3 are then dried. Passive drying (air drying) can take eight to ten hours. An alternatively possible rapid drying by means of an infrared radiator and fans can be carried out for one minute to five minutes.

Subsequently, a second contact layer 4 applied, followed by a second sanding layer 5 , The second contact layer 4 and the second sanding layer 5 consist of the same materials as the first contact layer 2 and the first sanding layer 3 that is, from the yttria-based slurry or the yttria-containing powder as an essential ingredient.

The method thus successively the two contact layers 2 . 4 of yttrium oxide, also referred to as a "face coat" applied.

Subsequently, several such, two contact layers 2 . 4 having mandrels 1 a shape structure 6 composed. In this embodiment, the shape structure 6 tree-shaped, wherein the mandrels 1 at a central, longitudinally extending body 7 be attached.

2 is a side view and shows the shape structure 6 passing through several cores 1 and a central, longitudinally extending body 7 is formed. At a certain position in the longitudinal direction of the body 7 There are four each distributed over the circumference arranged mandrels. 1

The tree-like shape structure 6 allows the simultaneous production of several identical or even different products through a single casting process.

The mold produced by this process has no intermediate layer. Instead, the shape structure 6 in an auxiliary form 8th then the auxiliary form is used 8th with a slurry based on magnesium oxide (MgO) 9 filled. After the slurry has dried, it becomes the one of the several mold cores and the central body 7 existing tree-like shape structure 6 by melting the mold core consisting of wax 1 removed, whereby a green body is formed. The green body is sintered at a sintering temperature of more than 800 ° C and less than 1200 ° C, then the finished mold from the auxiliary form 8th be removed, whereby the process is completed.

LIST OF REFERENCE NUMBERS

1

mold core

2

contact layer

3

sanding

4

contact layer

5

sanding

6

shape structure

7

body

8th

auxiliary layer

9

Schlicker

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2010/034762 A2 [0002]

Claims (7)

Method for producing a casting mold for casting a highly reactive melt, in particular for casting titanium, a titanium alloy or intermetallic titanium aluminides, comprising the following steps: producing a mold core from a fusible or combustible material, producing a contact layer by applying a first layer of a Yttria (Y ₂ O ₃ ) based slurry on the mandrel, - forming a first sanding layer by being soaked with yttria based powder, - applying a second layer of the yttria (Y ₂ O ₃ ) based slurry to the mandrel, - preparing a Second Besandungsschicht by Besanden with an yttria-based powder, - Producing a multiple mold cores comprising mold structure by attaching the mandrels to a made of the meltable or combustible material body, - Inserting the mold structure in an auxiliary form, - Man by filling the auxiliary form with a magnesium oxide-based slip, - removing the mold from the auxiliary form. Method according to Claim 1 , characterized in that after Besanden the first and / or the second contact layer, a drying operation is performed. Method according to Claim 1 or 2 , characterized in that the shape structure is formed like a tree. Method according to one of the preceding claims, characterized in that an yttria-based slurry is used which contains calcium aluminate cement. Method according to one of the preceding claims, characterized in that a mold core having the shape of a turbine wheel is used. Method according to one of the preceding claims, characterized in that after the production of the cladding layer, the existing of the plurality of mandrels mold structure is removed by melting or burning out of the forming structure of the forming material. Method according to Claim 6 , characterized in that a green body formed after removal of the fusible or combustible material is fired at a sintering temperature of more than 800 ° C and less than 1200 ° C.

Images