US2904863A

US2904863A - Method of moulding metal cylinders

Info

Publication number: US2904863A
Application number: US592379A
Authority: US
Inventors: Schmid Christoph
Original assignee: Deutsche Erdoel AG
Current assignee: Wintershall Dea Deutschland AG
Priority date: 1955-06-25
Filing date: 1956-06-19
Publication date: 1959-09-22
Anticipated expiration: 1976-09-22

Description

Sept. 22, 1959 c. sci-1WD METHOD OF MOULDING METAL CYLINDERS Filed June 19. 1956 lNVENTOR WW ATTORNEYS United States Patent 2,904,863 .1 METHOD OF MOULDING METAL CYLINDERS Christoph Schmid, Wietze, Kreis Celle, Germany, assignor to Deutsche Erdiil-Aktiengesellschaft, Hamburg, Germany Application June 19, 1956, Serial No. 592,379

Claims priority, application Germany June 25, 1955 1 Claim. (Cl. 22-202) It is occasionally necessary in industry to have cylinders made of low melting metals or alloys, and such cylinders cannot be made satisfactorily by the customary methods.

Such cylinders are useful, for example, in the mineral oil industry for liquid-tight casings to enclose sample cores which are to be subjected to flooding tests under the conditions existing in rock strata from which the sample cores have been obtained. These flooding tests are carried out at high pressures, which may be up to several hundred atmospheres, and at high temperatures of 100 C. or higher, and there are used for making the casings low melting metals or alloys, because these materials are capable of expanding in accordance with the changes in shape that the sample cores undergo when subjected to the aforesaid conditions. During the flooding the pressure acting on the exterior of the casing is kept a few atmospheres higher than the flooding pressure in the interior of the casing. In this manner bursting of the casing outwardly from the interior is prevented, and throughout the test the casing is kept in close contact with the sample core.

Cylinders of easily fusible metals or alloys are usually made by casting the molten metal into a suitably prepared mould and then bringing about solidification, if desired, by means of suitable cooling devices. The sample core itself is used as the core of the mould, in order to produce a casing that very closely fits the external surface of the sample core. In this manner there is obtained a cylinder having a porous and bubbly structure which cannot withstand the conditions of pressure and temperature used when the flooding tests are carried out under the conditions existing in the rock strata. Furthermore, the liquid metal penetrates into the porous rock of the sample core.

In order to produce a pore-free finely crystalline metal casing, and to ensure that the metal does not penetrate into the core during casting, it has been recognised that immediate solidification of the molten metal at the external surface of the rock sample is essential, but that, to ensure pore-free solidification of the metal casing, the external surface of the rock sample must itself be preheated to a temperature above ordinary temperature but below the melting point of the metal. The term metal is used in the appended claim to include a metal alloy.

In the method of the present invention the casting mould with the rock sample forming the core of the mold is placed in a temperature controlling device and preheated to a temperature above ordinary temperature ice and below the'melting-point'of the-metal or-alloy. Into themould,-'-of which the temperature has thus been adjusted, the metal or alloy is introduced at atempera'ture somewhat above, for example, about 15 C. above, its melting point. The difference in temperature between the mould and the melt is sufficient to cause immediate solidification of the melt at the outer surface of the core without the formation of pores. The molten metal or alloy is introduced into the mould by means of a preheated funnel. The temperatures at which the mould with its core and the moulten metal or alloy should be maintained depend on the melting point of the metal or alloy and on the size and petrographic properties of the rock sample to be enclosed in the casing. These temperatures are so chosen that, after the molten metal or alloy has been introduced, it solidifies immediately at the surface of the rock core so that it cannot penetrate into the porous rock core. The rapid solidification of the metal or alloy also prevents the penetration of bubbles of air or gas from the rock core into the metal or alloy, and a finely crystalline metal structure is obtained. Since the metal solidifies very rapidly when the correct temperatures for carrying out this invention are used, the pouring funnel must be withdrawn during the casting operation at a rate corresponding with the rate at which the molten metal or alloy is introduced, but care must be taken that the outlet end of the tube of the funnel remains continuously below the level of the melt.

The method of the invention is described by way of example with reference to the accompanying drawing. In this example, an alloy having a melting point of 135 C. is used for casting a casing round a rock core of 55 millimetres diameter having a permeability of about 350 millidarcy and a porosity of about 23 percent. The rock core 1 is held in position in the centre of a casting mould 2 by means of a clamping screw 6 mounted in a bracket 7 fixed to the mould. The mould and core are then placed vertically, for example, in a tubular electric oven 3 of suitable dimensions and heated to a temperature C. below the melting point of the alloy. A funnel 5 having a long outlet tube 4 is heated to a temperature about 50 C. above the melting point of the alloy, and is inserted immediately before the casting operation into the space between the rock core and mould until the lower end of the tube 4 is almost on the bottom of the mould. The alloy is melted and heated to a temperature 15 C. above its melting point. The molten alloy is poured into the funnel, and care is taken that the latter is always partially filled with alloy. During the casting operation the funnel is withdrawn progressively from the space between the core and the mould, while taking care that the outlet end of the tube 4 remains continuously immersed in the melt. By this procedure the escape of easily volatile substances from the core and through the molten metal, and the consequent formation of pores and bubbles in the cast cylinder, are avoided.

I claim:

A method of moulding a pore-free cylindrical casing of low melting metalabout a sample core of a rock stratum to be subjected to a flooding test, which method comprises preheating a mould and sample core of rock, which forms the core of the mould, in a temperature controlling device to a temperature above ordinary temperature and below the melting point of the metal, heating the metal to a temperature above its melting point, slowly introducing the molten metal into the mould by means of a funnel heated above the said melting point and with its tube extending substantially to the bottom of the mould, and during the casting operation gradually withdrawing the funnel from the mould at a rate corresponding to that at which the molten metal is introduced and While maintaining the end of the tube of the funnel continuously immersed in the rising melt, the difference in temperature between the preheated core and the molten metal during the casting operation being *about 90 C. and-such as to cause immediate solidification of the melt at the outer surface of the core.

References Cited in the file of this patent UNITED STATES PATENTS Wheeler Apr. 26, 1887 Peck Apr. 30, 1889 Ensslen Apr. 30, 1912 Donaldson Feb. 26, 1929 Townhill Sept. 3, 1957 OTHER REFERENCES