RU2284244C2 - Method for producing shaped castings of aluminum alloys and apparatus for performing the same - Google Patents

Abstract

FIELD: manufacture of shaped castings, namely pistons of aluminum alloys.

SUBSTANCE: method comprises steps of casting melt metal into cavity of casting mold through funnel and runner by action of centrifugal force at revolution number of casting mold in range 200 - 300 rev/min. Metal is poured through central runner and supply ducts into non-split casting mold for simultaneously filling two or more separate cavities. Doze of cast metal corresponds to total volume of cast pistons. After metal pouring, castings are impregnated with metal being in supply ducts. Casting mold is in the form of non-split structure including funnel, runner, supply ducts and cavities of castings.

EFFECT: possibility for making high-density pistons with lowered quantity of gas bubbles and slag inclusions.

2 cl, 2 dwg

Description

The invention relates to foundry, and in particular to a method and apparatus for centrifugal casting of shaped castings, for example pistons, from aluminum alloys.

A casting device is known for centrifugal casting of castings in molds rotating about an axis passing outside the mold (copyright certificate No. 414048, class B 22 D 13/06, 05.11.74), through a casting funnel and two gate systems.

A centrifugal foundry machine with a vertical axis of rotation is known (copyright certificate No. 700279, class B 22 D 13/06, dated November 30, 79), in which there is a housing with molds, a metal receiver, gateways and a circulation system.

However, the known devices for centrifugal casting of castings have a complex and laborious design, since the manufacture of molds involves significant energy consumption, and the casting technology does not allow castings of the required density to be obtained.

Closest to the claimed invention in terms of essential features, is a method and apparatus for centrifugal casting of a rotor of a brake disc (according to Japanese patent No. 4-9627, CL 22 D 13/00 of 02.20.92, see w / w Inventions of the world , 1993, issue 16, No. 8, p. 30), in which for the implementation of the method a mold is used containing an annular peripheral cavity located in the lower part of the mold and farthest from its axis, a central cavity located near the axis, narrow curvilinear cavity located vertically to the axis, sprues a bowl located on the upper surface of the mold and remote from its axis at a distance that does not allow extrusion of the melt from the gate channel; a certain amount of melt from one material is poured into the cavity of the fixed form and only after pouring is completed, the form is rotated around its axis at a speed of 200-300 rpm, forming a disk in it, after it has hardened, the melt from another material is poured into the mold and so gradually form a product from a melt of various material.

However, the known analogue has an extremely complex casting structure with a complex technological process of pouring the melt and a set of different materials to obtain a casting. In addition, this design does not provide the necessary density of the structure in the Central part of the casting adjacent to the axis of rotation.

The technical task of the invention is the creation of a structurally simple casting structure with the possibility of producing shaped castings with a high density and with a minimum percentage of castings.

To solve the technical problem, the proposed invention, which includes a method for producing castings, pouring molten metal into the cavity of the mold through the casting funnel and the gate by centrifugal force at a mold rotation speed of 200-300 rpm (features similar to the closest analogue), are introduced new signs, namely, that the liquid metal is poured into the mold and simultaneously into two or more cavities of the mold independent from each other, moreover, in a given dose, corresponding to the total volume of exfoliation The flow in one technological cycle, passing the melt in a continuous stream through the feed channels of the mold, and the action of centrifugal force with a gravity coefficient of 15-35 support until the castings are completely crystallized. According to the device for implementing this method, which includes a metal mold with cavities, a casting funnel and a gate (signs similar to the closest analogue), new design features have been introduced, consisting in the fact that the mold is an integral structure consisting of two or more autonomous cavities of castings located radially along the lateral sides of the mold and at the same distance from the axis of rotation of the mold, mold cavities are made with a given bias towards the front parts of the mold, and they have locking devices fixed coaxially with the cavities, which are connected by the supply channels to the central gate, located on the same axis with the casting mold, the feed channels being made with an expanding section in the direction of the casting for its free extraction from the mold, and the sections of the supply channels - profits have dimensions corresponding to the volume of the passing melt in the mold cavity, mounted coaxially with the axis of rotation of the platform.

Analyzing the totality of the essential features of the claimed invention in comparison with the above analogues, as well as in comparison with the prior art in the field of foundry, the applicant has not identified technical solutions with the totality of features inherent in the proposed patenting of the invention.

The results of the experiments at a specialized plant for the production of pistons confirm the possibility of implementing the claimed invention with features characterizing it, since several pistons made of aluminum alloys with a dense crystallization structure were obtained at once in one technological process.

The essence of the invention is illustrated by the drawing, in which Fig. 1 shows a device in general view, in Fig. 2 is the same, in cross section along AA in Fig. 1.

The device comprises a platform 1 with a vertical axis of rotation, on which, on the same axis (coaxially) with it, a metal casting mold is rigidly mounted, which is an integral structure consisting of a central gate 2, located on the same axis with the casting mold, two or more cavities 4 castings autonomously located in the radial direction along the sides of the mold and at the same distance from the axis of rotation of the mold. The cavities 4 are connected to the central gate 2 by supply channels 3, which simultaneously perform the function of profits, which in their cross section have dimensions corresponding to the volume of the passing melt in the cavity 4, and are also made with an expanding cross section in the direction of the casting to freely remove it from the mold. Cavities 4 also for free extraction of castings are made with a given slope towards the end parts, and they have locking devices 5 fixed on the same axis with cavities 4 of the mold. A casting funnel 6 is installed vertically and on the same axis as the platform in the upper part of the metal integral mold.

The device operates as follows.

The platform 1 is imparted a rotational movement about a vertical axis and, together with the platform, the entire structure of the metal mold is rotated. Upon reaching a rotation speed of 200-300 rpm, liquid metal (melt) is poured through the pouring funnel in a predetermined dose corresponding to the total volume of castings obtained in one production cycle, while the melt passes into the central gate 2, where the melt comes into contact with its walls acquires rotational motion and under the action of centrifugal force with a gravity coefficient of 15-35, the melt with a continuous stream passes through the supply channels 3 in the cavity 4, at the same time fills the cavity of the castings and part of the cavities of the supply channels - profits 3 having a given surface slope towards castings, and the volume of supply channels - profits provides power to the castings during their crystallization. Since the cavities 4 are located radially on the lateral sides of the mold, the melt fills all the cavities simultaneously in the radial direction and part of the cavities of the supply channels — profits 3, as a result of which the liquid metal gradually crystallizes under the action of centrifugal force with the formation of a fine-grained casting structure. Due to the fact that the cavities 4 are closed on the outside of the mold by the locking device 5, the formation of shaped castings takes place inside the cavities. Due to the fact that the cross section of the supply channels 3 are 2-4 times smaller than the cross sections of the central gate 2, the jet of the passing melt does not interrupt when filling all the cavities 4 of the permanent mold, and is poured with a continuous stream into all cavities of the mold, which eliminates the formation of non-slit and nonsense. At the end of casting in the cavities of 4 castings, the process of crystallization of the metal and the formation of the casting takes place, and in the supply channels - profits 3, the formation of shrinkage shells occurs.

A method for producing shaped castings is implemented by the claimed device in such a way that a liquid metal in a predetermined dose corresponding to the total volume of castings obtained in one production cycle is poured into an integral mold that rotates on the same vertical axis as the platform. For example, when casting VAZ 2103-1004015N pistons in double form, the dose of liquid metal to be poured is 375 cc, and the volume of metal in one casting is 187 cc. At a rotation speed of 200-300 rpm and a gravity coefficient of 15-35, the molten metal flows in a continuous stream into the central gate 2 and simultaneously into two or more cavities 4, which are independent and radially located in the mold, through the supply channels 3. The action of centrifugal force is maintained up to complete crystallization of the castings, after which they stop rotation and easily remove castings that are not interconnected by the gate system. This ends the technological cycle. The finished casting has a compacted structure without gas and slag shells. With this casting process, the operation of trimming sprues is excluded.

An experimentally selected gravity coefficient within 15-35 under the action of centrifugal force provides accelerated solidification of the melt, since the action of centrifugal force is maintained until the castings are completely crystallized in all mold cavities rotating around a common axis. The high density of the structure of shaped castings of aluminum alloys obtained by the claimed method is priority for alloys of ectectic composition that crystallize intensively in the claimed range (minimum and maximum) of the gravity coefficient, i.e. in the range of 15-35, since at this quantitative value of the gravity coefficient there occurs accelerated crystallization of shaped castings under the action of centrifugal force, which prevents the growth of dendrites and contributes to intensive grain refinement, which in turn allows one to obtain higher strength properties of the casting metal and a higher value elongation

In addition, during the crystallization process, no segregation of impurities is observed.

An advantage of the claimed invention in comparison with known analogues is that this method and device that implements it provides accelerated crystallization of castings in mold cavities, as well as obtaining shaped castings, for example pistons, with a dense fine-grained structure and high physical and mechanical properties due to the impact in the process of their crystallization of centrifugal force, many times greater than the force of gravity.

Finished shaped castings, for example pistons, obtained by the present invention have higher performance properties compared to castings obtained by the closest analogue, as well as in comparison with other technologies known in the foundry industry.

The proposed device for producing shaped castings in comparison with the known similar technical solutions has a simplified design with the lowest labor and energy costs, in addition, it allows you to completely eliminate the foundry marriage of pistons in the form of "gas and slag shells".

Claims (2)

1. The method of producing shaped castings in the form of pistons made of aluminum alloys, including centrifugal pouring of liquid metal in the cavity of the mold through the casting funnel and the gate operation under the action of centrifugal force with a mold rotation speed of 200-300 rpm, characterized in that the liquid metal is poured into an integral mold through the central gate and feed channels, and then the crystallized castings are impregnated with metal located in the feed channels, and the dose of the cast metal is determined accordingly vuyuschey total volume obtained castings pistons. 2. A device for producing shaped castings in the form of pistons from aluminum alloys, containing a rotating platform, a metal casting mold, a casting funnel, a central gate, feed channels and cavities of castings, characterized in that the metal casting mold is integral with the casting funnel, gating stroke, feeding channels and cavities of castings.

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