RU2647975C1 - Method of producing cast steel by centrifugal casting - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to a foundry, in particular to the production of castings by centrifugal casting. In the rotating molding around the vertical axis, the casting is performed by casting the melt and simultaneously feeding refractory dispersed particles with a density of more than 8,000 kg/m³, such as tungsten carbide, to harden the outer surface of the casting. After pouring 50 % of the melt, the supply of tungsten carbide is stopped and to harden the inner surface of the casting delivering particles of density less than 8,000 kg/m³ , for example silicon carbide, until the melt is cast.

EFFECT: provides the production of castings with high mechanical properties of the external and internal surfaces.

4 cl, 2 dwg

Description

The invention relates to the manufacturing technology of castings obtained by centrifugal casting with hardening of the external and internal and parts of the casting with dispersed carbide phases, which can be used in metallurgical and other industries.

A known method of forming a steel tubular billet by centrifugal casting, comprising pouring the melt into a mold rotating around a horizontal axis and hardening the surface of the billet by feeding refractory dispersed particles through a batcher into the pouring trough into the melt jet, while dispersed particles with a density of more than 6000 kg / m ³ with the first end portions and a melt flow of 75% after pouring of the melt, and for hardening the inner surface is carried out feeding tug fusible particles having a density less than 5000 kg / m ³ after 25% of the melt flow and the end with the end of the casting process (RU №2381087, B22D 13/00, publ. 10.02.2010.). The method provides the possibility of hardening the outer and inner surfaces of the resulting workpiece. However, in this way it is possible to obtain only a steel pipe billet hardened from the inside and outside and it is impossible to obtain a casting with a hardened inner surface of the "glass" type.

As the closest analogue, the method of centrifugal casting on machines with a vertical axis of rotation is selected, which includes pouring the melt into a mold and rotating it around the vertical axis, pouring the melt into a stationary form, and it starts to rotate until the melt is filled after the bottom of the casting has solidified.

The method allows to obtain castings of the type "glass" (RU No. 2235001, B22D 13/00, publ. 08/27/2004.).

The disadvantage of this method is the need for additional technological operations in order to harden the outer, inner and end surfaces of the casting.

The objective of the invention is to obtain steel castings by centrifugal casting with high strength properties of the outer and inner surfaces of the casting.

This problem is solved in that when implementing the method of hardening the external and internal parts of the surface of the casting, including pouring the melt into a mold and rotating it around a vertical axis, pouring the melt into a rotating mold, while supplying refractory particles with a density of more than 8000 kg / m ³ , after hardening of the preform according to the invention, the supply of particles having a density of more than 8000 kg / m ³ stops and the supply of particles with a density of less than 8000 kg / m ³ begins, while the flow of refractory particles with a density of more than 8000 k g / m ³ begins with pouring the melt and ends after pouring 50% of the melt, and the supply of particles with a density of less than 8000 kg / m ³ begins after pouring 50% of the melt and continues until the end of the smelting.

In the proposed method for hardening the outer parts of the workpiece with refractory particles with a density of more than 8000 kg / m ³ , they begin to be fed simultaneously with the beginning of pouring the melt into the mold and continue to feed particles until 50% of the mass of the melt is filled, and for hardening the inner part of the workpiece with refractory particles with a density less than 8000 kg / m ³ , their flow begins after pouring 50% of the mass of the melt and continues until the end of the casting process. If the supply of dispersed particles with a density of more than 8000 kg / m ^{3 is completed} before pouring 50% of the melt, the number of particles is insufficient to ensure uniform properties along the height of the outer surface of the casting. In the case of feeding dispersed particles with a density of 8000 kg / m ³ throughout the entire casting time, particles introduced after pouring 50% of the melt, due to the crystallization of the side surfaces and the bottom of the casting, are distributed over the entire volume of the casting, without changing the strength properties of the outer surface of the casting, but to significant costs of dispersed particles. In the case of the beginning of the supply of dispersed particles with a density of less than 8000 kg / m ³ before pouring 50% of the melt, the particles are distributed throughout the casting volume, without substantially changing the strength properties of the inner surface of the casting, but also leading to significant costs of the dispersed particles.

The technical result of the invention is to obtain a steel casting by centrifugal casting with the possibility of providing the external and internal parts of the casting with high strength properties.

The technical result is achieved by the fact that the steel casting is formed by pouring the melt into a mold and rotating it around a vertical axis, pouring the melt into a rotating mold, while at the same time the flow of dispersed particles with a density of more than 8000 kg / m ³ starts, the flow is stopped after 50% of the mass melt, after which they begin to feed dispersed particles with a density of less than 8000 kg / m ³ and end it simultaneously with the end of the casting process.

The essence of this method is illustrated in the drawing, where in FIG. 1 shows a scheme for producing hardened castings by centrifugal casting: 1 - mold, 2 - melt, 3 - steel pouring ladle, 4 - rotation mechanism, 5 - dispenser, 6 - refractory dispersed phase. FIG. 2 illustrates the distribution of dispersed particles upon completion of melt casting.

An example of the method

The casting was obtained from steel grade 20 smelted in an induction furnace. The outer diameter of the workpiece is 150 mm, the inner diameter is 110 mm, the height is 70 mm, and the bottom thickness is 30 mm. As the hardening phase we used tungsten carbide (WC), with a density of 15800 kg / cm ³ in an amount of 200 g, and also silicon carbide (SiC), with a density of 3210 g / cm ³ in an amount of 200 g. The melt with a temperature of 1650 ° С was poured from a steel ladle into a mold rotating at a speed of 600 rpm, while WC flow was started into the steel stream using a dispenser. The flow of WC was stopped after pouring 50% of the melt. After supplying 50% of the mass of the melt, the supply of SiC was started. The supply of SiC ceased simultaneously with the end of the casting process. After complete solidification and stopping the rotation of the mold, the casting was removed. The resulting casting had a satisfactory surface quality with a dense body structure and without shrinkage defects. The proposed method made it possible to obtain a casting with high mechanical properties: hardness (compared to the "glass" casting obtained without the introduction of dispersed particles), on the outer surface it increased by 45-50 HB, and on the inside it increased by 30-35 HB.

Claims (1)

A method of producing steel castings by centrifugal casting, comprising pouring the melt into a rotating mold and simultaneously supplying refractory dispersed particles, characterized in that first, refractory dispersed particles are supplied with a density of more than 8000 kg / m ³ , they are stopped after pouring 50% of the melt and refractory is fed dispersed particles with a density of less than 8000 kg / m ³ until the pouring of the melt into the mold.

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