RU2267378C1 - Bimetallic castings making method - Google Patents

Abstract

FIELD: manufacture of cast products.

SUBSTANCE: method comprises steps of making bimetallic casting of two alloys having different chemical contents and melting temperature values; preliminarily casting blank of easy-to-melt alloy such as bronze; placing it into casting mold; pouring hard-to-melt alloy such as cast iron into mold at temperature that exceeds by 10 - 20° C its zero fluidity temperature and at speed of melt motion in mold equal to 0.5 m/s; then slightly melting surface layer of bronze for forming interface layer Fe-Cu in order to provide reliable joining of bronze and iron.

EFFECT: enlarged manufacturing possibilities of process for making bimetallic castings with thin easy-to-melt layers.

2 ex

Description

The invention relates to the field of foundry and can be used in the manufacture of castings with special service properties, for example bimetal plain bearings.

A known method of manufacturing bimetallic castings, in which the surface layer of the cast iron is subjected to decarburization, then this layer is impregnated with aluminum, after which the castings are installed in a mold and cast from the outside with aluminum alloy to obtain finning (Japan Patent No. 51-25214, CL 11 B 083 claimed on 02/09/73).

The closest analogue to the claimed technical solution adopted for the prototype is a method for the manufacture of bimetallic castings from two dissimilar in chemical composition and with different melting point alloys, soaking to solidify the melt in the mold and removing the finished bimetallic casting from the mold (SV 33049 A, B 22 D 19102, 10.31.1933).

The disadvantages of the method include the limited technological capabilities for producing bimetallic castings with thin fusible layers due to the possible mixing of bimetals, and therefore, increased material consumption for machining allowances, restrictions on the range of low-melting workpiece alloys, prone to segregation.

The aim of the invention is to eliminate the noted drawbacks, namely, expanding the technological capabilities of obtaining bimetallic castings with thin fusible layers, expanding the range of castings, including through the use of fusible alloys, prone to segregation, reducing material consumption.

This goal is achieved by the fact that in the method of manufacturing bimetallic castings from two alloys of different chemical composition and with different melting points, a more refractory alloy is poured onto a billet cast from a more fusible alloy and installed in a mold at a temperature of 10-20 ° C higher its temperature is zero fluidity, with a melt velocity in the form of 0.1-1.0 m / s.

The temperature and time parameters of the casting are established from the conditions of ensuring non-mixing of bimetals during pouring and the formation of a transition layer that firmly binds two dissimilar in chemical composition, with different melting points of the casting alloys.

The proposed sequence of foundry operations and their modes allow, due to technological capabilities, to obtain such castings as steel-bronze, cast-iron-bronze with thin layers of bronze without the danger of mixing bimetals, since a high-melting alloy is frozen until the workpiece is melted from a more low-melting alloy.

The solution to the problem of using blanks from more fusible alloys, prone to segregation, for example, lead bronzes, is simplified. At the same time, it becomes possible to expand the range of bimetallic billets obtained by non-centrifugal casting methods.

Examples of the method.

Example 1

Bimetal plain bearing made of gray cast iron-bronze BrOTsS 5-5-5 is prepared as follows.

A bronze layer of 3 mm thickness is frozen onto a permanent rod with a diameter of 200 mm, it is placed in a casting mold and cast from the outside with cast iron at a temperature of 1220 ° C with a melt velocity of 0.5 m / sec.

If there is a solid phase in the cast iron, immediately after filling the mold, the process of its crystallization begins with the simultaneous melting of the surface of the more fusible bronze layer (bronze melting temperature 915 ° С) and the formation of the Fe-Cu transition layer.

When the cast iron shrinks, the inner bronze layer is compressed.

After the bimetallic casting has hardened and cooled to 900 ° C, a permanent core is removed, the casting is removed from the mold and the process is repeated.

The finished casting (outer diameter - 280 mm, height - 500 mm) has allowances of 1 mm to the side in diameter and 5 mm to the ends. The consumption of bronze on the bearing is reduced by more than 10 times.

Example 2

Bimetallic chill mold from gray cast iron (bearing case) and bronze BrAZh 9-3 (working layer) are obtained in the following sequence.

Gasified polystyrene foam models receive casting of the working layer of chill mold from bronze with a thickness of 8 mm, set it vertically in a mold with gaps from the walls: 30 mm for cast iron pouring and 10 mm from the working side of the chill mold, which is filled with calcined dusty quartz.

Cast iron is poured into the assembled mold at a temperature of 1280 ° C at a speed of 0.1 m / s, maintained until the cast iron solidifies and the bimetallic castings are cooled to 800 ° C, and then the casting is knocked out and finishing operations are performed.

In the process of casting iron, the bronze layer is melted (the melting point of bronze is 1040 ° C) with the formation of a transition Fe-Cu layer, which firmly binds bronze and cast iron.

The obtained bimetallic chill mold has an increased resistance compared to a conventional one made of cast iron, due to the fact that bronze has a relative elongation 10 times higher than that of cast iron, therefore it better resists the formation of a heat network.

The use of the invention improves the technical and economic indicators of foundry in the manufacture of bimetallic castings and the chill casting of non-ferrous and ferrous alloys.

Claims (1)

A method of manufacturing bimetallic castings from two alloys that are heterogeneous in chemical composition and with different melting points, characterized in that a more refractory alloy is poured onto a billet cast from a more low-melting alloy and installed in a mold at a temperature of 10 ÷ 20 ° C above its zero temperature fluidity with a melt velocity in the form of 0.1 ÷ 1.0 m / s.