RU2585881C2 - Method for evacuation of moulds and device therefor - Google Patents

Abstract

FIELD: metal processing.

SUBSTANCE: invention relates to metallurgy and can be used in casting grinding bodies in centrifugal machines with vertical rotation axis. Method is characterised by that above mold 6 with ventilation channels 12 is placed disk-like screen 5 to make slot-type channel 10. Screen is made with annular ledges 11 to make circular zones narrowing in slot-type channel above ventilation channels 12. Through slotted nozzle 9 is air cooling agent fed to periphery of slot channel 10. Above rotating mold vortex space of alternating low pressure is formed to create negative pressure in zones of narrowing of slot channel and exhaust of air and gases from mold.

EFFECT: higher quality of casts due to elimination of gas porosity.

2 cl, 1 dwg

Description

The invention relates to the field of foundry and can be used for mass production of grinding media in foundry vibrocentrifugal machines with a vertical axis of rotation. A known method for producing metal castings, including filling the molds with a melt during vibrocentrifugal vacuum casting process (1).

However, there are no machines for mass casting of castings in which all types of casting would be simultaneously used: vibration, centrifugal, vacuum, no.

Known foundry machines (2) and (3) for producing grinding media by vibrocentrifugal method. The proposed device is installed, for example, on a machine (2) in order to ensure pouring molds without backpressure and to eliminate the appearance of signs of gas porosity in the obtained castings.

The basis of the invention is the task of creating a method of evacuating molds on the basis of a new device, which allows to improve the quality of castings and expand the technological capabilities of existing machines.

The task is achieved in that a region of vortex space of variable-reduced pressure is created above the mold, rarefaction is carried out in the zone of the narrowed slot channel, which is formed between the wave plane of the disk-shaped screen and the surface of the mold, and a disk-shaped screen with a wave surface in shape size is introduced into the device with a central hole for the funnel, around which there is a collector with a slot nozzle for purging the zone of a narrowed slot channel, which is formed between the top disc-shaped screen and molds.

Figure 1 shows a device for implementing the proposed method of evacuation of the mold. The device comprises a frame 1, brakes 2, a movable beam 3 with a vibratory chute 4, into which a disk-shaped screen 5 of the size of the casting mold 6 is inserted, which has a central hole for the casting funnel 7 and a manifold 8 with a slot nozzle 9 for purging a limited narrowed slot channel with air refrigerant 10 formed during the assembly of mold 6 with a table 13 between the surfaces of the screen 5 and mold 6, and on the lower surface of the shield 5, annular, smoothly rounded protrusions 11 are made at the same radii from the axis of rotation of mold 6, on which you edeny ventilation channels 12 of connector cavities flooded. The frame is mounted above the working table 13, which performs vertical vibrations and horizontal rotations in the operating machine (2), to which all the above mechanisms are connected. The claimed method of evacuation is carried out using a device mounted in frame 1 as follows: compressed air, like air refrigerant, is blown through a slot nozzle 9 to the periphery of the slot channel 10, bounded below by the upper surface of the mold 6, and above by the lower surface of the disk-shaped screen 5, where -flat speed stream obeys Bernoulli's law. In the lower part, the circumferential component of the flow velocity of the disk friction pump, which discards the flow from the center to the periphery, is superimposed on the flow along the entire surface of the rotating form 6.

The radial movement of the pressure flow, in channel 10, bends with increasing absolute velocity of the flow at the surface of the smooth wall of form 6, approaching the vortex. The addition of two flows increases the decrease in static pressure in the slotted channel 10 in the annular zones of the narrowing of the flow, where the ventilation ducts are removed from the cavities and the mold connector.

The device itself on machine 2 operates as follows. The movable beam 3 with the vibratory chute 4, the screen 5 and the idle funnel 7 is displaced, freeing access to the working table 13, on which the form 6 is mounted and fixed, after which the movable beam 3 is set in the filling position by the working stroke, as shown in FIG. one.

Includes: vibration of the trough 4 for the period of pouring a portion of the melt, vertical vibration and horizontal rotation of the mold 6 on the table 13 with a purge of the formed slot channel 10 from the center to the periphery by a cooling stream of compressed air.

Air and gases are sucked out of the cavities of the mold 6, which are poured into the narrowed annular protrusions of the channel 10 from the mold 6 through the extracted ventilation ducts 12. The process ends when crystallization of the casting is completed. According to the program, the brakes 2 are turned on and off, the channel 10 is purged. The movable beam 3 is idled to the side, freeing up access to form 6 on table 13, where the process of replacing the filled mold is in progress.

The casting process continues.

Adding a vacuum device to vibration-centrifugal casting machines, thereby expanding their technological capabilities, using three types of casting at the same time, which did not exist before, and vacuuming is carried out in a new way. In addition, this device can be used independently, where vacuum is required during centrifugal casting.

Thus, acting on the melt with a vacuum, vibration and centrifugal force, we obtain high-quality castings without defects in gas porosity with a high structure of abrasion resistance and impact loads, as well as expanding the technological capabilities of existing machines.

Information sources

1. Patent of Ukraine No. 93812, MKI V22D, 2011

2. Patent of Ukraine No. 89598, MKI V22D, 2010

3. RF patent No. 2026140, publ. 01/09/95

Claims (2)

1. A method of evacuating a casting mold for centrifugal casting, characterized in that a disk-shaped screen is placed above the casting mold with ventilation channels to form a slotted channel with annular zones of narrowing above the ventilation ducts, a vortex space of variable-reduced pressure is created above the casting mold with the creation of rarefaction in the zones narrowing the slotted channel by supplying air refrigerant through the slotted channel from the center to its periphery. 2. A device for evacuating a mold for centrifugal casting, comprising a disk-shaped screen placed above the mold to form a slot channel and made with annular protrusions forming narrowing zones in the slot channel and with a central hole for the filling funnel, a collector with a slot nozzle, located around the funnel and ensuring the supply of air refrigerant through the slotted channel, while the annular protrusions of the disk-shaped screen are located above the ventilation ducts of the mold.

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