SU510313A1 - Method of coating a metal mold - Google Patents

Description

one

The invention relates to foundry, in particular, to the coating of the inner surface of a rotating mold, especially on its face parts.

Methods are known for coating a mold under pressure by spraying, by pouring, by pouring a liquid or molten lining.

A disadvantage of the known methods is that the coating is applied only to the cylindrical part of the mold. Due to the high speed of rotation of the mold and the resulting significant linear speed of movement of its end parts, the coating falling on them under the action of centrifugal forces rolls onto the cylindrical part of the mold.

When casting cylindrical billets from gray and high-strength cast iron into molds, painted with one of the above methods, the end parts of the billets have a significant chill and require additional high-temperature annealing to obtain the required microstructure. If castings are obtained using such coating methods on a mold and are not subjected to annealing, they are performed with profits, which are then cut off with the bleached ends, which leads to increased metal consumption and increased costs.

It is known to use the lining of the front cover of a metal mold with a rod of a material with lower thermophysical properties or the insertion of special asbestos gaskets. Performing a single lining reduces the productivity of the machine, is not amenable to mechanization and increases the cost of the technological process of producing castings.

The aim of the invention is to improve the coating of the metal mold, especially of its end parts, which will allow eliminating the chipping of the end parts of the iron castings. This is achieved by applying a coating at a speed of rotation of the mold 200 to 450 rpm, ensuring a linear speed on its end walls in the range of 1.4-1.7 m / s. Coverage time is approximately equal to

2.5-6 s and depends on the size of the painted area. Due to the high adhesion and cohesive properties of the coating and the relatively low level of centrifugal forces, the coating suspension enters the end walls of the mold heated to 140-420 ° C, covers them and creates a layer 0.2-0.4 mm thick. The thickness of the layer depends on the heating temperature of the mold, the speed of its rotation, the properties of the coating and the conditions for its supply to the mold. Normally coverage falls

on the end parts of the mold dod pressure 0.05-2.5 atm.

After finishing the coating, the machine switches to full speed required to pour the metal into the mold. This contributes to a more even distribution of the coating layer in the cylindrical part of the mold.

Example. The coating is fed to the end parts of the mold under a pressure of 0.3 atm. Coverage consumption 0.4-0.5 l. When the speed of rotation of the mold is 450 rpm and the linear speed of 1.7 m / s in its end parts, the coating is demolished in small quantities under the action of centrifugal forces on the cylindrical part of the mold, and due to the high adhesive and cohesive properties of the binder coating evenly colors the end parts molds. Under such application conditions, the thickness of the coating on the front cover and the flange of the pusher is 0.2-0.4 mm, which completely prevents chipping at the ends of the cast-iron sleeves.

When the rotation speed is less than 200 rpm, the end parts are covered relatively

well, but on the cylindrical part of the mold, there will be sags up to 1-1.2 mm thick, which requires an increase in the machining allowance of the casting. At a rotational speed greater than 500 rpm, the coating of the end portions of the mold is uneven. The thickness of the coating in some places reaches 0.1 mm and less. At a rotational speed of more than 900 rpm, the coating practically does not paint the end walls of the mold and the ends of the castings of 10-12 mm are bleached.

Claims (1)

Invention Formula The method of coating a metal mold during centrifugal casting of billets such as tractor sleeves, including the supply of a liquid coating to a heated rotary mold, characterized in that, in order to improve the coating, it is applied at a rotational speed of the mold 200-450 rpm to obtain a linear speeds on its end walls of 1.4-1.7 m / s.