RU2184010C1 - Apparatus for making castings with monocrystalline structure - Google Patents

Abstract

FIELD: machine engineering, possibly manufacture of castings of refractory alloys with monocrystalline structure, for example castings of turbine blades. SUBSTANCE: apparatus includes ceramic envelope formed by applying layer-by-layer of ceramic suspension onto model. In envelope there are arranged successively: seed cavity with predetermined-orientation seed, cavity with insert-crystal sampler and cavity for forming casting. Seed cavity is arranged directly in base of insert; in upper portion of insert there is seat providing vertical alignment of insert and model. After application of ceramic suspension there are no gaps between walls of insert-crystal sampler and envelope. It provides elimination of foreign crystal formation at process of oriented crystallization. EFFECT: increased yield of high quality monocrystalline castings. 3 cl, 4 dwg, 1 ex

Description

 The invention relates to mechanical engineering and can be used to obtain castings with a single crystal structure from heat-resistant alloys, in particular castings of turbine blades of gas turbine engines and plants.

A device for producing single-crystal castings is known, containing a ceramic shell with a starting cavity, a crystal sample cavity in the form of a spiral gate — a helicoid used to select one crystal from a plurality of columnar grains, and a cavity for casting formation (US patents 3519083, 4133368). However, the use of such a device - a shell casting mold requires pouring the melt directly onto the water-cooled refrigerator, which creates significant difficulties when mounting the mold on the refrigerator. In addition, such a device allows to obtain castings only with the orientation [001] with an accuracy of only 10-15 ^o .

 A device for producing single crystals is also known, comprising a ceramic shell with a cavity in which a seed is mounted, connected by a gate with a casting cavity (US Pat. No. 4,714,101). The disadvantage of this device is the difficulty of obtaining perfect single crystals in it, due to the fact that when the mold is heated to fill, a coating forms on the seed, which prevents the transfer of the structure to casting.

 Closest to the claimed one is a device for producing single-crystal castings (RF patent 2080209 class B 22 D 27/04), which contains a ceramic shell formed by layer-by-layer application of a ceramic suspension on a model in which a seed cavity is sequentially made with a single crystal seed set in it orientation, a cavity with an insert-crystal sampler and a cavity forming a casting. The disadvantage of this device is the difficulty of creating a tight connection between the end of the insert, the crystal and the top of the cavity where this insert is located. During directed crystallization, foreign crystals can form in this gap, which grow into the cavity of the casting, as a result of which the latter is rejected.

 The technical task of this invention is to increase the yield of single-crystal castings in structure.

 To accomplish this task, a device is proposed for producing castings with a single-crystal structure, including a ceramic shell formed by successively applying layers of ceramic suspension to a model in which a seed cavity is placed sequentially with a single crystal seed placed in it with a given crystallographic orientation, a cavity with a crystal-sample insert and a cavity, forming a casting, while according to the invention, the seed cavity is made at the base of the insert crystal a sampler, while in the upper part of the insert-crystal sampler a socket is made to ensure vertical alignment of the insert and the model during assembly.

To obtain castings with a given axial crystallographic orientation, the top of the seed cavity, adjacent directly to the crystal, is made at an angle of 0-55 ^o to the vertical axis.

 To obtain castings with a given spatial crystallographic orientation, a plane is made on the lateral surface of the nest of the crystal-insert insert to ensure its and model's alignment in the horizontal plane.

 For the same purpose, planes are made on the lateral surfaces of the seed cavity and the seed.

 The proposed device allows to increase the yield of single crystal castings in structure, since the seed cavity is made at the base of the insert, the crystal, while in the upper part of the insert, the crystal is made a socket to ensure vertical alignment of the insert and the model during assembly.

 In the manufacture of the mold, a ceramic suspension is applied directly to the ceramic insert attached to the casting model, wetting the latter well. As a result, the gaps between the walls of the crystal insert and the mold are completely eliminated. Due to the absence of these gaps, which are the place of formation of foreign crystals in the process of directional crystallization, the yield of single-crystal castings increases sharply.

The inclination of the top of the seed cavity relative to the vertical axis allows you to get a given deviation of the orientation of the casting from any crystallographic axis, for example, [111] from the seed [001]. The maximum angle of such a deviation in g. K. the structure is 55 ^o .

 To obtain a given spatial orientation, it is necessary to orient the geometric axis of the casting relative to the crystallographic axis of the seed. Using planes made on the lateral surfaces of the seed cavity and the seed, the latter is oriented relative to the insert-crystal. The crystal sampling insert is oriented relative to the casting axes by installing and fixing in its nest with the protrusion plane of the model on the side surface during assembly.

 The insert itself is oriented relative to the crystallographic axes of the seed using planes made on the lateral surfaces of the seed cavity and the seed.

In FIG. 1a shows a General view of a device for producing castings with a single crystal structure, where:
1 - ceramic shell;
2 - insert-crystal;
3 - curved sprue course;
4 - a seed cavity, the top of which is tilted at an angle of 0-55 ^o ;
5 - seed;
6 - ceramic mass, fixing the seed;
7 - socket in the insert;
8 - the cavity forming the casting.

On figb shows a model of the casting, where:
9 - casting model;
10 - centering protrusion;
11 - plane on the centering protrusion.

On figv shows a cross section of the insert and shell through the socket, where:
12 is a plane on the side surface of the nest.

Figure 1g shows a section through a seed cavity, where:
13 - a plane made on the seed;
14 - a plane made on the lateral surface of the seed cavity.

In the ceramic shell 1, formed by layer-by-layer deposition of layers of ceramic suspension on the casting model 8, there is an insert 2 with a crystal sampler in the form of a curved gate 3 with a seed cavity 4 made in it, the top of which is inclined at an angle of 0-55 ^o . In the upper part of the insert there is a centering socket 7 connected to the cavity 8 forming the casting. In the seed cavity 4, a seed 5 is installed, which is fixed in the cavity 4 by a ceramic mass 6. When assembling on the protrusion 10 of model 9, insert 2 is inserted, which ensures their vertical alignment. To ensure alignment of the model of the casting 9 and insert 2 in a horizontal plane, the planes 11 and 12 are made on the lateral surface of the socket 7 and the protrusion 10. To ensure the alignment of the seed 5 and the crystal insert 2, the planes 13 and 14 are made on their lateral surfaces.

 Example.

В обоих случаях для отливки монокристальных образцов использовались затравки с аксиальной ориентацией [001], полученные ориентированной вырезкой из заготовок произвольной ориентации. На боковой поверхности затравок выполнялись плоскости, параллельные направлению [100] для получения отливок [001] и

для получения отливок [111]. На моделях прямоугольных слитков выполнялся цилиндрический выступ длиной 8 мм и диаметром 6 мм, на котором параллельно узкой стороне слитка располагалась плоскость. Во вставке-кристаллоотборнике выполнялось гнездо ответной конфигурации, а в затравочной полости формировалась плоскость, параллельная плоскости, расположенной в центрующем гнезде. Для отливки образцов [001] были изготовлены вставки без наклона верха затравочной полости, а для отливок [111] - вставки с наклоном 55^o.The invention was tested when casting flat rectangular single-crystal samples of size 15x30x120mm in two orientations: 1) vertical axis - [001], horizontal, perpendicular to the wide side of the sample - [100]; 2) respectively, [001] and

In both cases, for casting of single-crystal samples, we used seeds with an axial orientation [001] obtained by oriented cutting from blanks of arbitrary orientation. On the side surface of the seeds, planes were made parallel to the [100] direction to produce [001] castings and

for castings [111]. On models of rectangular ingots, a cylindrical protrusion of 8 mm in length and 6 mm in diameter was performed on which a plane was located parallel to the narrow side of the ingot. A nest of the reciprocal configuration was made in the crystal insert, and a plane parallel to the plane located in the centering nest was formed in the seed cavity. For casting samples [001], inserts were made without tilting the top of the seed cavity, and for castings [111], inserts with an inclination of 55 ^{o were made} .

 The single-crystal samples were cast on a UVVNK-8P directed crystallization unit from the heat-resistant alloy ZhS36-VI in blocks of six.

Swimming trunks mode: temperature lower. heater - 1600-1610 ^o C
temperature top. heater - 1550-1570 ^o С
alloy pouring temperature - 1550-1560 ^o С
mold drawing speed - 4-5 mm / min.

As shown by visual and x-ray control of the obtained castings, all of them had a single crystal structure of a given orientation with an accuracy of 5-7 ^o .

 Testing of this device under industrial conditions when casting single-crystal turbine blades of aircraft gas turbine engines and stationary installations showed that it provides an increase in the yield of suitable castings in the structure up to 90-95%.

Claims (3)

 1. A device for producing castings with a single crystal structure of a given crystallographic orientation, comprising a ceramic shell formed by layer-by-layer deposition of a ceramic suspension on a model, and in which a seed cavity with a single crystal seed of a given orientation placed in it, a cavity with a crystal-sample insert and a cavity forming casting, characterized in that the seed cavity is made at the base of the insert, the crystal, while in the upper part of the insert and-socket kristallootbornika configured to provide vertical alignment and insertion of the model is assembled. 2. The device according to p. 1, characterized in that the top of the seed cavity is made with an angle of 0-55 ^o to the vertical axis.  3. The device according to claim 1 or 2, characterized in that a plane is made on the lateral surface of the nest of the crystal-insert insert to ensure alignment of it and the model in the horizontal plane.