SU1424964A1 - Method of producing castings by oriented crystallization - Google Patents

Abstract

The invention relates to the field of foundry, in particular, to methods for producing castings by directional crystallization, and can be used to make castings of large-sized turbine blades. The purpose of the invention is to increase the density of castings and process performance. The method includes manufacturing and placing a ceramic shell mold in a graphite shaped container mounted on a refrigerator tray, filling the container around the mold with a highly heat-conducting refractory filler, uniform heating of the side surface of the container in the preheating furnace to a temperature of 1100-1500 ° C, and casting on top of the mold alloy at a temperature in excess of 80-120 ° C; liquidus temperature, and sequential removal of the container with the mold from the preheating furnace during the casting crystallization process. In this case, the filling of the container with filler is carried out in layers, using a larger fraction in each subsequent layer of filler and reducing the density and thickness of the layer of filler around the mold. S (I

Description

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The invention relates to foundry, in particular, to methods for producing directionally crystallized castings, and can be used to make castings for large-sized turbine blades.

The purpose of the invention is to increase the density of castings and process performance.

The method includes manufacturing and placing in a graphite profile container with a variable cross section cavity, installed a large base on a refrigerator tray, a ceramic shell mold for casting mainly large-sized turbine blades 300–500 m long, uniformly filled with a heat-resistant heat-resistant refractory filler. heating in the furnace of heating the side surface of the container up to 1100-1500 ° С, pouring, ku on top of the casting mold with an alloy at a temperature exceeding by 80-120 ° С te liquidus temperature, and sequential removal of the container with the mold from the preheating furnace in the process of crystallization of the casting.

In this case, the container is filled with filler in layers, using a larger fraction in each subsequent filler layer and reducing the density and thickness of the filler layer around the mold.

A change in the filler density along the height of the mold and the thickness of its layer around it allows for uniform heating of the side surface of the container to create in the mold cavity a positive temperature gradient of 12–2.0 ° C / mm, which, in combination with the upper casting of the alloy - at a relatively low temperature and a gradual drawing of the mold from the preheating furnace, it is possible to create more favorable conditions for directional crystallization and to obtain a dense directional structure ao the entire casting height. At the same time, the speed of drawing the mold from the preheating furnace is selected experimentally, based on the alloy grade, size and thickness of the casting machine and the required structure.

Example 1. A guide blade of a GT-100 turbine is cast. The height of the working part of the blade 300 mm. The metal consumption for casting is 6 kg, for the gating system - 5 kg. Shell form is set in a graphite shaped container and filled with graphite chips for the entire height in one fraction of 8-10 mm. The container is heated for 4 hours at an oven temperature of 1500 ° C. The average temperature gradient in the mold is 0.6 ° C / mm. The form is poured with alloy EY-893L at 1500 ° C (150 ° C higher than the liquidus temperature). The speed of drawing the mold from the preheating furnace is 4 mm / min. After crystallization

and cooling, the casting is separated from the ceramic shell, the core is removed and transferred to x-ray control.

Paddle rejected due to shrinkage at the transition from the pen to the castle part and shrinkage of the pen.

Example 2. In the manufacture of a blade, in contrast to example 1, the shell form is molded into layers in a container by filler: the lower part of the form is sprinkled with graphite crumb of a fraction of 2-3 mm to a height of 2/3 of the shell height, and the upper part of the form Which fraction 8-10 mm. After heating the container for 3.5 hours, the average gradient in the mold is 1.4 ° C / mm. The alloy is poured at 1430 ° (at 80 ° C, the liquidus temperature). The mold is pulled out of the oven at a speed of 5 mm / min.

Paddle tight and has no shrinkage defects.

Example 3. The casing is molded into layers in a container: the bottom layer is half of the height from the filler of a fraction of 2-3 mm, and the upper one from the filler of a fraction of 8-10 mm. The mold is heated in an oven for 3 hours. The average temperature gradient in the shell is 1.6 ° C / mm. The alloy is poured at 1450 ° C (100 ° C above the liquidus temperature). The mold is pulled at a speed of 8 mm / min.

Obtained tight casting without shrinkage defects with directional structure.

Example 4. The shell is molded in a container in layers: the bottom layer is 1/5 the height of the sheath of the filler fraction of 2-3 mm, the next layer is half the height of the filler of the fraction 5-6 mm, and the upper part of the filler is 8-10 mm. The average temperature gradient in the shell is 1.8 ° С / mm. The alloy is poured at 1470 ° С (at, 120 ° С above the liquidus temperature). The mold is pulled out of the preheating furnace at a speed of 10 mm / min.

The casting is obtained fit without shrinkage defects with a tight directional structure.

In all examples, the draw rate of the locking and lucrative parts of the casting mold is halved to improve the feed for the massive locking part of the casting.

Thus, the proposed method allows to obtain large-sized turbine blades with a dense directional structure and to increase the productivity of the process by increasing the rate of directional solidification of castings.

Claims (1)

CLAIMS A method for producing castings by directed crystallization, preferably large-sized turbine blade, comprising: placing a shell in a graphite mold -form container mounted on the pallet-cooler, the container around the mold filling of high-heat-refractory filler, uniform heating of the side surface of the container with the mold and filler preheating furnaces, pouring liquid metal from the top into the casting mold and subsequent crystallization and cooling willows in the process of extracting a container with a mold from a preheating furnace. characterized in that, in order to increase the density of castings and the productivity of the process, the container is filled in layers using a larger fraction in each subsequent filler layer and a decrease in the density and thickness of the filler layer around the mold, and the pouring is performed with liquid metal at a temperature exceeding 80 -120 ° C temperature LIQUIDUS.