DE102008051998A1 - Casting method comprises reducing the low pressure in a low pressure furnace after stopping casting enough so that at least one part of the cast material still in the casting column and still in the liquid state flows back into the furnace - Google Patents

Abstract

Casting method comprises reducing the low pressure in a low pressure furnace after stopping casting enough so that at least one part of the cast material still in the casting column and still in the liquid state flows back into the furnace.

Description

The The invention relates to a casting method in which liquid Casting material from a low-pressure furnace under low pressure over a pouring column against gravity to an in Sand-embedded foam model of a cast body is transported in a casting container, wherein the foam model is destroyed and a cavity leaves filled with the casting material becomes.

to Production of castings with complex shapes are casting processes with lost form in common, in which one example Wax formed mold sanded in a casting container becomes. During casting, the mold is replaced by hot casting material destroys and takes the place of form itself. Usually casting takes place in the direction of gravity. When so Lost Foam method is the form as a foam model formed of the cast body.

From the DE 10 2004 050 781 A1 is a Niederdruckvollformgießverfahren by controlled mold filling for the production of cast parts from metals and metallic alloys, in particular magnesium alloys known in which the liquid metal in the melting vessel subjected to a pressure medium, transported via a riser to the sand-embedded foam model in the mold tank and by varying the pressure in Oven vessel the mold filling speed is regulated.

It An object of the invention is an improved casting method indicate at the liquid casting material a low pressure furnace under low pressure via a pouring column against gravity to a sand-embedded foam model a cast body in a casting container is transported.

The The object is achieved by a method having the features of claim 1.

advantageous Embodiments are the subject of the dependent claims.

at a casting method according to the invention becomes liquid casting material from a low pressure furnace under low pressure over a pouring column counter gravity into a sand-embedded foam model a cast body in a casting container transported. The foam model is destroyed and leaves a cavity with the casting material is completed. The low pressure in the low pressure furnace is lowered after completion of the casting so far that at least a part of the still located in the pouring column and still liquid casting material in the low pressure furnace flowing back. In this way, a so-called Minimized circulation. Circulatory rate means that in the pouring column located casting material with the cast body solidifies together, separated from this and to return to a material cycle again must be melted. Instead, that flows in the Casting column still located, liquid casting material directly back into the low pressure furnace during the Cast body already solidified at least superficially is. In this way energy is saved. By the pressure controlled Filling the mold is a variable mold filling possible.

in the Below is an embodiment of the invention based a drawing explained in more detail.

there shows:

1 a schematic view of a portion of a casting container with a connection to a low pressure furnace.

In 1 is a casting container 1 shown. The casting container 1 is to a pouring nozzle 2 a low pressure furnace connected. For this purpose, the casting container 1 on an underside an opening into which a ceramic insert 3 is used. The ceramic insert 3 is formed in the example shown rotationally symmetrical with an opening for the passage of a casting material, but may also be formed differently. The casting container 1 becomes with the ceramic insert 3 on the pouring nozzle 2 placed. The openings in the ceramic insert 3 and in the pouring nozzle 2 form a sprue 4 , Between the pouring nozzle 2 and the ceramic insert 3 becomes a refractory nonwoven mat 5 arranged. On the ceramic insert is a foam model 6 arranged a pouring column, which is formed for example of expandable polystyrene. On the foam model 6 the pouring column becomes a foam model 7 a casting cast to be cast. Both foam models 6 . 7 are sanded, that is, the casting container 1 will with sand 8th filled and the sand 8th optionally compressed. For actual casting, the liquid casting material stored in the low-pressure furnace is forced under low pressure through the sprue 4 against gravity the foam model 6 fed to the pouring column. The penetration of the hot casting material destroys the foam. In place of the foam model 6 arises the pouring column 6 ' made of liquid casting material. In the same way, the foam model 7 of the cast body and destroyed by the cast body 7 ' replaced from the hot casting material as soon as the casting material is the foam model 7 of the cast body 7 ' reached. The low pressure in the low pressure furnace is so far after completion of the casting lowered that at least part of the still in the pouring column 6 ' located and still liquid casting material flows back into the low pressure furnace.

The ceramic insert 3 reduces heat losses in the transition from the low pressure furnace to the casting vessel 1 and thus prevents premature solidification of the casting material.

The refractory nonwoven mat 5 has at least low deformability and / or compressibility, so that a contact area between the casting nozzle 2 , which may also be formed of a ceramic material and the ceramic insert 3 is sealed, even if the surfaces of the casting nozzle 2 and the ceramic insert 3 in the contact area are not one hundred percent plan.

The lowering of the low pressure is preferably carried out after an at least partial solidification of the casting material of the cast body 7 ' in the cavity, so casting material only from the pouring column 6 ' but not from the casting 7 ' flows back into the low pressure furnace.

The foam model 6 the pouring column 6 ' becomes so on the ceramic insert 3 put on that it is fixed by this in its position. This is due to the design of the ceramic insert 3 and the foam model 6 and achieved their mating in the manner of a sleeve. This is the foam model 6 fixed during the subsequent Einsandens and does not slip. The sleeve is formed in the figure so that the foam model 6 outside on the ceramic insert 3 is plugged. Alternatively, the sleeve can also be formed conversely so that the foam model 6 in the ceramic insert 3 is inserted.

The foam model 7 of the cast body 7 ' can with the foam model 6 the pouring column 6 ' be formed in one piece. A casting system formed in this way is also called grape.

On the foam model 6 the pouring column 6 ' can be provided at a transition to the foam model of the casting a constriction (not shown), which causes by their small cross-sectional area and high heat radiation that the casting material is cooled faster at the bottleneck and at least superficial faster solidifies than in the pouring column 6 ' , In this way, the low pressure can already be lowered when the casting material of the casting 7 ' not yet frozen, without this can flow back into the low-pressure furnace. Such an Engestelle is also called a freezing module.

The foam models 6 . 7 can be formed as molds, as in 1 shown. Likewise, also full forms for the foam models 6 . 7 be used.

The height of the low pressure used depends in particular on a required height of the pouring column 6 ' from.

Instead of of expandable polystyrene (EPS) may also be another foam be used.

1

gooseneck

2

casting nozzle

3

ceramic insert

4

sprue

5

refractory nonwoven mat

6

foam model a pouring column

6 '

Eingusssäule

7

foam model a cast body

7 '

cast body

8th

sand

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 102004050781 A1 [0003]

Claims (7)

Casting method in which liquid casting material from a low-pressure furnace under low pressure via a pouring column ( 6 ' ) against gravity to one in sand ( 8th ) embedded foam model ( 7 ) of a cast body ( 7 ' ) in a casting container ( 1 ), wherein the foam model ( 7 ) is destroyed and a cavity is left, which is filled with the casting material, characterized in that the low pressure in the low-pressure furnace after completion of the casting is lowered so far that at least a part of the still in the pouring column ( 6 ' ) and still flowing liquid casting material flows back into the low-pressure furnace. Casting method according to claim 1, characterized in that the lowering of the low pressure after at least partial solidification of the casting material of the cast body ( 7 ' ) is performed in the cavity. Casting method according to one of claims 1 or 2, characterized in that the casting container to a pouring nozzle ( 2 ) of the low-pressure furnace is connected, wherein a ceramic insert ( 3 ) in an opening at a bottom of the casting container ( 1 ) is used, wherein a foam model ( 6 ) of the pouring column ( 6 ' ) on the ceramic insert ( 3 ) is placed and fixed by this in its position and wherein the casting container ( 1 ) with the ceramic insert ( 3 ) on the pouring nozzle ( 2 ) is placed so that through an opening in the ceramic insert ( 3 ) and the pouring nozzle ( 2 ) a sprue ( 4 ) is formed for the casting material. Casting method according to claim 3, characterized in that the ceramic insert ( 3 ) and the foam model ( 6 ) of the pouring column ( 6 ' ) are put together in the manner of a sleeve. Casting method according to one of claims 3 or 4, characterized in that a fireproof nonwoven mat ( 5 ) between the pouring nozzle ( 2 ) and the ceramic insert ( 3 ) is arranged. Casting method according to one of claims 3 to 5, characterized in that a foam model ( 7 ) of the cast body ( 7 ' ) used with the foam model ( 6 ) of the pouring column ( 6 ' ) is integrally formed. Casting method according to one of claims 3 to 6, characterized in that a foam model ( 6 ) of the pouring column ( 6 ' ) used at a transition to the foam model ( 7 ) of the cast body ( 7 ' ) has a constriction, wherein the casting material is cooled faster at the bottleneck and at least superficial faster solidifies than in the pouring column ( 6 ' ).