SU1558554A1 - Method of producing bimetallic castings - Google Patents

Abstract

The invention relates to foundry and is aimed at improving the quality of centrifugally cast bimetallic castings. The metal is poured after insertion of the reinforcing insert into the rotating form in two stages. At the first stage, the metal is poured in the amount of 0.85-1.0 volume of casting. After aging 1-4 with the metal topped up to 1.05-1.15 volume of the casting. 1 il.

Description

The invention relates to the field of foundry, in particular to the production of bimetallic castings with a reinforcing insert by centrifugal casting.

The aim of the invention is to improve the quality of castings by reducing non-metallic inclusions in the transition zone from the reinforcing insert to the base metal.

The drawing shows a mold for carrying out the method.

Casting molds and consists of a mold 1, insert 2, a pusher 3 with a stem 4, a cover 5, a transverse partition 6. A sleeve 7 is used as the reinforcement insert introduced into the form, centered on the protrusion of the transverse partition 6 and kept from displacement by stallions 8 and a ring insert 9. The sleeve 7 is provided with an inner conical surface 10. The base metal is poured through the opening 11 of the cover 5 along the filling chute 12.

The proposed method is made roll of high strength alloy 25OH24VZT. The method is carried out on a centrifugal casting machine. The reinforcement insert is inserted and installed into a mold, the elements of which are used to equip the centrifugal machine. The rig, along with the reinforcement insert, is heated to 700 ° C and is driven into rotation at a speed of 600 rpm. After that, the base metal (alloy 25OX24VT) is cast in the amount of 0.85-1.0 of the volume of the casting. After a pause of 1-4 seconds, during which the non-metallic inclusions and slag ascend, the base metal is refilled to 1.05-1.15 casting volume from the periphery to the center of the casting. A part of the metal on the reinforcing insert side is pushed out of its base by refilling the base metal. In this part of the metal, located on the side of the reinforcing insert, there are floating up non-metallic inclusions (slag, flux particles, air bubbles, etc.). Thus, surfaced nonmetallic inclusions are derived. At the same time, topping up the metal dose to 1.05-1.15 of the volume of the casting makes it possible to displace nonmetallic inclusions beyond the limits of the casting when waste-free use of the metal to be added.

Removal of inclusions occurs under the action of the hydrostatic pressure of the metal, the direction of circulation of which is indicated by arrows. Metal topped up under

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the action of centrifugal forces tends to get to the periphery of the casting and displaces the metal located at the axis of the casting. Along with it, nonmetallic inclusions are superseded, which have emerged during the pause in the transition zone from the reinforcing insert to the base metal and in contact with the reinforcing insert. Making the surface 10 of the reinforcing insert with the base metal of the conical additionally, with a pause of less than 1 s, the proportion of breaks of casting due to defects in the transition zone increases due to an increase in the number of nonmetallic inclusions in the transition zone, the time of which ascent during the pause is insufficient metal. With duration

It facilitates the displacement and removes 10 pauses more than 4 s. The number of non-metallic inclusions increases due to the increase in viscosity of the initially cast base metal, which makes it difficult for the inclusions to move beyond the reinforcement insert, resulting in casting rejects. This leads to a decrease in the quality of castings, which is reflected in an increase in the proportion of their failures due to defects in the transition zone.

A 1–4 s pause improves the quality of castings by reducing the number of nonmetallic inclusions in the transition zone.

The economic efficiency of the proposed method for producing bimetallic castings with a reinforcing insert is achieved by reducing the number of breakdowns of products obtained from bimetallic castings - mill rolls.

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non-metallic inclusions outside the transition zone. This is due to the fact that the force of the emergence of inclusions directed by the radial axis of rotation of the form is decomposed into two components, 15 one of which is perpendicular to the surface of the cone, and the second is directed along this surface and pushes the inclusions out of the transition zone.

The amount of poured base metal less than 0.85 of the volume of the casting leads to the content of non-metallic inclusions in the transition zone over 30%. The number of breakdowns in the transition zone of rolls made from castings obtained by the proposed method (turning the reinforcement insert, cracking, and so on) exceeds the number of roll breaks for other reasons.

The amount of the casting of the base metal poured into the cavity cannot exceed 1.0 in volume of the casting, since the metal poured above this volume inevitably pours out of the bounds of the cavity, which leads to excess metal consumption.

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Claims (1)

Invention Formula A method of producing bimetallic castings, including heating a reinforcing insert, inserting it into a mold, initial pouring into a rotating base metal form, holding and refilling into a base metal form, characterized in that, in order to improve the quality of castings by reducing nonmetallic inclusions in the transition zone from the reinforcing insert to the base metal, the initial casting of the base metal and the subsequent topping up are performed respectively in an amount of 0.85-1.0 and up to 1.05-1.15 of the casting volume, and the duration The holders are 1-4 s. , Topping up the base metal to less than 1.05 and more than 1.15 of the casting volume results in a non-metallic inclusions content in the transition zone of over 30% and exceeding the level of breakdowns in the transition zone for other reasons. Fill the base metal in the amount of 0.85-1.0 volume of the casting, followed by refilling of the base metal to 1.05-1.15 casting volume improves casting quality by reducing the number of nonmetallic inclusions in the transition zone. With a pause of less than 1 second, the proportion of breaks in the casting due to defects in the transition zone increases due to an increase in the number of non-metallic inclusions in the transition zone, the time of which is not enough during the pause and which float when topping up the base metal. With duration pause more than 4 s, the number of non-metallic inclusions increases due to the increase in viscosity of the initially cast base metal, which makes it difficult for the inclusions to move beyond the reinforcement insert, resulting in casting rejects. This leads to a decrease in the quality of castings, which is reflected in an increase in the proportion of their failures due to defects in the transition zone. Invention Formula A method of producing bimetallic castings, including heating a reinforcing insert, inserting it into a mold, initial pouring into a rotating base metal form, holding and refilling into a base metal form, characterized in that, in order to improve the quality of castings by reducing nonmetallic inclusions in the transition zone from the reinforcing insert to the base metal, the initial casting of the base metal and the subsequent topping up are performed respectively in an amount of 0.85-1.0 and up to 1.05-1.15 of the casting volume, and the duration The holders are 1-4 s. , v /// W //// y / 77, but /