SU1079353A1 - Method of casting into sand-clay moulds in autoclave - Google Patents

Abstract

METHOD OF CASTING IN SANDY-GLY, BREAKED FORMS IN AUTOCLAVE, mainly aluminum alloys, including the pouring of metal into formulas and the creation of stepped pressure at an autoclave during pressure casting, characterized in that, in order to eliminate the welding pressure during the casting of the splicing, the casting, characterized in that, in order to eliminate the welding pressure during the casting of the splicing, the casting, characterized in that, in order to eliminate the welding pressure during the casting of the splicing, the casting, which is used for the purpose of removing the welding pressure during the casting of the splicing, casting, characterized by the fact that in order to eliminate the welding pressure during the casting of the splicing, the casting is different, in order to eliminate the welding pressure during the casting of the grinding of the casting, which is used to remove the welding pressure during the casting of the splicing, casting, which, in order to eliminate the welding pressure during the casting process density, pressure increase at each stage is carried out by a value of 0.1-0.2 MPa for 0.2-0.4 s and maintains the pressure reached for 1.0-5.0 s. about co

Description

The invention relates to foundry, in particular, to methods for producing castings that solidify at elevated pressure in a single sand-clay mold.

A known method for producing reflux under high pressure, in which a sandy-clay mold is placed in an autoclave and molten metal is poured into it through an opening in the autoclave. After this, the opening is closed with a lid and an overpressure is created in the autoclave. The application of overpressure to the casting during the crystallization period prevents porosity in it from 1J.

One way, along with a positive effect — the high density of castings achieved when casting by this method — overpressure leads to a scrap of a mechanical burn.

The closest to the proposed method is to cast in an autoclave, including the filling of the metal into a sandy-clay form and creating a stepped-rising pressure C2J in the autoclave during crystallization.

In the known method, the stepwise increasing pressure increases the density of the crystallized casting, but does not eliminate the surface defects of the castings, namely, burns.

The cause of the burn is the difference in h: Pitch between the pressure in the autoclave acting on the surface of the melt in the gating system and the pressure at the metal-form contact. The pressure difference occurring is due to the filtration of air (gas) through the pores of the mold. The magnitude of the pressure difference first increases and then decreases. The highest value of the occurrence of the pressure difference reaches after 0.15 s, after the beginning of the application of pressure. The resulting pressure drop together with the hydrostatic pressure of the melt promotes the penetration of the liquid metal into the pores of the foundry mold. The formation of carbide occurs when the total pressure from the liquid metal exceeds the critical pressure at which melt penetrates the pores of the mold. The magnitude of the critical pressure depends on the surface tension forces, the radius of the capillary, and the wetting angle.

The purpose of the invention. is the elimination of burns on the surface of the casting and an increase in its density.

This goal is achieved by the fact that according to the method of casting into sand-clay forms in an autoclave, mainly aluminum alloys, including pouring metal into molds and creating a stepping pressure in the autoclave during the crystallization of the casting, pressure is increased at each step by 0.1- 0.2 MPa for 0.2-0.4 s and maintain pressure achieved within 1.0-5.0 s.

5 In FIG. 1 shows a device for casting sand and clay forges in FIG. 2 - graphs of pressure changes in the autoclave during the casting of the casting versus time.

The device consists of a mold 1, an autoclave 2 with a hole 3 for pouring metal, a cover 4 and a valve 5.

The method is as follows.

5 way.

The mold 1 is placed into the autoclave 2 and the melt is poured through the hole 3. After this, the hole is closed with a lid 4 and, using ventilated type 5, is created from (Cyclic stepped-increasing pressure in the autoclave. The pressure is increased in steps of 0.1-0 , 2 MPa per 0.20, 4 p. Moreover, each subsequent

lifting is done after

the pressures in the autoclave P and on the junction-form P contact are compared, and the difference between the values of dP will be equal to zero. The number of pressure stages is chosen as

In this way, the difference in the 4P solutions at each degree does not exceed the value of the critical pressure P ,. When this pressure is maintained for 1.0-5.0 s.

5 As an example of using the casting method, the castings of specimens from the AL9 alloy were cast. The pressure is raised in three stages of 0.2-0.4-0.5 MPa. After the pressure is raised at the Ksssda stage, an exposure of 5-6 seconds is made to achieve equality between the pressure in the autoclave and the metal-form contact. Castings are obtained without a burn.

5 The use of the proposed method of casting in an autoclave provides a reduction in marriage reject by 5%. The economic effect of introducing a casting method in an autoclave is 97 rubles. per 1 ton of suitable castings.

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T.S.

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Claims (1)

METHOD FOR SANDING IN SAND-CLAY FORMS IN AUTOCLAVE, mainly aluminum alloys, including pouring metal into forges and creating stepwise increasing pressure in the autoclave during crystallization of the casting, characterized in that, in order to eliminate burn-in on the surface of the casting and increase its density, raising the pressure at each stage is carried out at a value of 0.1-0.2 MPa for 0.2-0.4 s and withstand the achieved pressure for 1.0-5.0 s. figure 1