US3667535A

US3667535A - Controlled atmosphere gravity casting system

Info

Publication number: US3667535A
Application number: US83059A
Authority: US
Inventors: Marshall K Thomas Jr; James N Thompkins
Original assignee: US Department of Navy
Current assignee: US Department of Navy
Priority date: 1970-10-22
Filing date: 1970-10-22
Publication date: 1972-06-06
Anticipated expiration: 1989-06-06

Abstract

An improved system for evaluation of unique materials formed by quenching the same in their liquid state under predetermined controlled uncontaminated gaseous environment. The apparatus permits rapid solidification of the material in the desired gaseous atmosphere such that the possibility of undesirable oxidation or contamination is minimized.

Description

[451 June 6,1972

United States Patent Thomas, Jr. et al.

.164/258 X Hitchings...........................164/136 X A n m .w m tr. hk mm NN TS 7900 555667 999999 wmwmww 09968 97565 483229 680355 .7999 222223 N m w. m 3 m .m 1m H mm M J m m an 3 PS mm m G m MN K w I, t A m m DS m U 3 1 m .m WH MT T T: m mum C G .m A M .4 M U U U represented by the Secretary of the Navy Primary Examiner R Spencer Annear [22] Filed: Oct. 22, 1970 Attorney-Richard J. Miller and R. S. Sciascia [21] Appl. No.:

[57] ABSTRACT An improved system for evaluation of unique materials formed by quenching the same in their liquid state under [52] U.S.CL................. .......164/258,164/136, 164/259,

164/336 27/16 164/61, 65, 66, 68, 136, 254, predetermined controlled uncontaminated gaseous environ- 164/256, 258, 259, 335 ment. The apparatus permits rapid solidification of the material in the desired gaseous atmosphere such that the possibility of undesirable oxidation or contamination is minimized.

[51] Int. [58] Field ofSearch..................

References Cited 8 Claims, 3 Drawing Figures UNITED STATES PATENTS 1,897,589 Reeve...........,......................164/65 X PATENTEDJUH 6 I972 SHEET 10F 2 FlG.l

MARSHALL K.THOMAS,JR. JAMES M THOMPKINS War/neg PATENTED H 6M2 3.667.535 SHEET 20F 2 l/w m fags 4 I, 1

MARSHALL K. THOMAS, JR. JAMES N THOMPKINS CONTROLLED ATMOSPHERE GRAVITY CASTING SYSTEM The invention provides a method of quenching a liquid metal from a controlled gaseous environment as rapidily as possible without the contamination from ambient conditions during cooling. Both an uncontaminated quenching environment and rapid quench are essential since during the time of quenching dissolved gases in the liquid metal could be lost and gases from the atmosphere absorbed. It is also essential that the solid sample not have any detectable oxide or scale on its surface.

In the State-of-the-Art samples where prepared from a crucible, which contain liquid metal, wherein the sample was lowered from the furnace to the water quenching section and cooled therein. These samples had oxide surfaces and had scaling plus additional oxidized holes. In addition the procedure of solidification was relatively slow taking 35 to 45 seconds from the liquid state of copper at 1550 C to a solid state. It was obvious that there was contamination from the atmosphere and an additional oxide scale was produced on the surface of the sample. Removal of the sample required an additional step of grinding while in itself was not perfect since small bits of oxide could be lost. In addition oxide layers could be generated by the heat of grinding. Further, non-uniform distribution of oxygen in the sample would cause errors in analysis.

It is therefore an object of this invention to provide an improved method of quenching a liquid metal specimen in a controlled atmosphere environment.

It is a further object of this invention to provide an improved liquid sample quenching system wherein the liquid metal is poured into a mold for producing castings of predetermined configuration.

Yet another object of this invention is to provide an improved controlled atmosphere liquid metal quenching system, comprising: a container for holding a metal to be heated to the liquid state; means for heating the container and metal to the melting point of the metal; support means for maintaining the container in the heating means and for causing the metal when heated to the liquid state to leave the container under the influence of gravity; a cooling chamber for receiving the liquid metal; a mold coupled to the cooling chamber for receiving the liquid metal and to hold it ,while cooling to the solid state; and a means for providing a controlled atmosphere surround the liquid metal at all times during the heating and cooling steps until it is in the solid state and its temperature has been reduced to a point wherein rapid oxidation will not take place.

A further object of this invention is to. provide an improved controlled atmosphere liquid metal quenching system, comprising: furnace means having a hollow portion; a sample holder for liquid metal positionable in the hollow portions; actuating rod support means in the furnace rotatable between two positions, the first position supportingthe sample holder, the second position releasing the sample holder from within the furnace; a cooling chamber coupled to the furnace and directly below the hollow position; means in the cooling chamber for mounting the sampler holder to release the liquid metal; a molding means coupled to the cooling chamber to receive the liquid metal; means for cooling the cooling chamber and the molding means to bring the liquid sample to a solid state temperature; and an atmosphere control means coupled to the furnace, drop chamber and the mold for cleaning and purging the system and for providing an inert atmosphere during the heating, cooling and solidifying phases of the quenching system to prevent oxidization and impurity inclusion.

Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings wherein:

FIG. 1 is a schematic layout of the system;

FIG. 2 is a detailed drawing of the furnace, cooling chamber and mold; and

FIG. 3 is a further detail of that portion of the furnace containing the crucible, and crucible support.

Referring now generally to the Figures, a furnace 10 is shown having a hollow section 11 connected to a tube 12, through a connector 13 to a drop or cooling chamber 14. A mold section 15 is provided and a set of cooling coils l6 surrounds the cooling section-of both the mold section and the cooling chamber. An atmospheric control system is generally designated as 20 to include a series of

stopcocks

21, 22, 23 and 24, interconnecting a source of vacuum 25, not shown, a vacuum gauge 26, a source of inert gas 27, a water manometer 28, and a water bubbler 29. This system is coupled through a pair of connections 30, 31 to the furnace and the drop chamber.

FIG. 3 shows a partial cross-sectional view of the details of that portion of the furnace wherein there is supported a crucible 40, containing a liquid metal 41 and a gas delivery tube 42. The entire unit 41 supported upon an actuatable rod 44 having at least two positions, the first position being that which supports the crucible in a stationary position during the heating of the metal to the liquid state. The second position of the rod 44 is a position rotated away from the support position so that the crucible 40 is released for free fall.

FIG. 2 shows the crucible in two stages of free fall after hav ing been released by the rod 44. The first stage, the crucible has followed a path down through the upper position of the quenching or cooling chamber 14 and in position shown, designated as 50, the crucible has hit the pair of copper pins 51, 52, positioned such that the center of moment about the base of the crucible 40 is such that it rotates into the position shown as 55. It should be noted that in any given molding operation there is only one crucible within the quenching chamber, but for the sake of clarity, two are showninto successive positions 50 and 55. The liquid metal 41 is shown descending into the inner portion 58 of the mold. In one embodiment of the invention where specimens are being prepared for further gas analysis the exact shape of the specimen is not critical, however, it should be noted that if a casting operation is to be performed the mold portion 58 would have a specific configuration such as to provide the desired casting. After a predetermined cooling period mold 15 is removed and the specimen removed from portion 58.

The general operation of the apparatus is as follows. Initially all of the

stopcocks

21, 22, 23 and 24, and the vacuum type ball 59, in FIG. 3, are in the closed position. The system is evacuated by opening stopcock 21, which is connected to the vacuum system 25, and two way stopcock 23 is positioned so that it is open to the vacuum line. Pressure is monitored with the vacuum gauge 26 and in one instance when the vacuum reached 200 microns or less the stopcock-23 is open to admit argon gas which has been purified by passing over fine copper tumings at 600 C and the vacuum line is blocked off from the quenching chamber. Time is allowed to elapse to further purify and purge the system, the platinum rod is positioned in its support position with a crucible having a metal sample to be melted and the quenching chamber is attached, as shown in FIG. 1. Stopcock 22 is opened and adjusted to provide a slight pressure of 0.5 centimeters of water at the bottom furnace 12. This procedure flushes any residual air in the bottom of the furnace. Valve 23 is opened to relieve the high pressure of the argon gas in the quenching chamber through bubbler 29. The ball valve 59 is slowly opened while stopcock 22 is manipulated to maintain a slight positive pressure.

When the ball valve is completely opened the crucible 40 is dropped by rotating the platinum 44 from its first to its second position. The crucible'is dropped and a temperature change at the water cooled mold indicates that in fact the crucible has tipped.

After the sample has been dropped, ball valve 59 is rotated to the closed position, valve 22 is closed, the clamps 13 are released and the quenching chamber is removed from under the furnace allowing the next succeeding sample to be inserted into the bottom of the furnace.

The quenching chamber is allowed to stand for a period of time, in one successful embodiment of the invention 15 minutes, to make certain that the sample has reached room temperature and that there is no chance of oxidation.

The removal of the sample is accomplished by closing stopcock 23, cutting off the flow or argon, in thiscase the inert atmosphere. The cooling water to the quenching chamber is turned ofi permitting the copper mold to warm up to room temperature before it is sealed to quenching chamber for the next run. One additional advantageof this is that the sealing compound, coupling the furnace to the quenching chamber seals better if the temperature is 25 C or higher. The quenching chamber is then inverted and the sample removed.

If it were desirable to cool the liquid sample even more rapidily it should be noted that instead of cooling water circulating about the quenching chamber it would be possible to design the system to provide liquid nitrogen or some other coolant as the temperature controller of the mold. Further the entire quenching chamber could be immersed in a container to provide more efficient cooling of the chamber.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings it is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

We claim:

1. An improved controlled atmosphere liquid metal quenching system, comprising:

a. a container for holding a metal to be heated to said liquid state capable of free fall:

b. means for heating said container and metal to the melting point of said metal:

c. support means having first and second positions, said first position supporting said container in an upright position and said second position causing said container to free fall for maintaining said container in said heating means and for causing said metal when heated to said liquid state to leave said container under the influence of gravity;

. a cooling chamber for receiving said liquid metal;

e. a mold coupled to said cooling chamber for receiving said liquid metal and to hold it while cooling to the solid state; and

. a means for providing a controlled atmosphere surrounding said liquid metal at all times during the heating and cooling stages until it is in the solid and its temperature has been reduced to a point wherein rapid oxidation will not take place.

2. The system of claim 1 wherein said container is a crucible having an open end and the supporting means is a rod rotatable between first and second positions, said first position supporting said crucible in the upright position and in the second position allowing said crucible to fall.

3. The system of claim 2 wherein said cooling chamber has means positioned therein to rotate said crucible to a position where the liquid metal freely falls therefrom.

4. The system of claim 3 wherein a cooling jacket is provided about said cooling chamber.

5. The system of claim 4 wherein the coolant in said cooling jacket is water.

6. The system of claim 4 wherein there is provided a vacuum system coupled to said controlled atmosphere system for cleansing and purging the atmosphere in the heating means, the cooling chamber and the mold.

7. The system of claim 6 wherein said crucible is made of aluminium the said support rod of platinum.

8. An improved controlled atmosphere liquid metal quenching system, comprising:

a. furnace means having a hollow portion;

b. a sample holder for liquid metal positioned in said hollow portion;

c. actuating rod support means in said furnace rotatable between two positions, said first position supporting said sample holder, said second position releasing said sample holder from within said furnace;

d. a cooling chamber coupled to said furnace and directly below said hollow position;

e. means in said cooling chamber for mounting said sample holder to release said liquid metal; f. a moulding means coupled to said cooling chamber to

Claims

1. An improved controlled atmosphere liquid metal quenching system, comprising: a. a container for holding a metal to be heated to said liquid state capable of free fall: b. means for heating said container and metal to the melting point of said metal: c. support means having first and second positions, said first position supporting said container in an upright position and said second position causing said container to free fall for maintaining said container in said heating means and for causing said metal when heated to said liquid state to leave said container under the influence of gravity; d. a cooling chamber for receiving said liquid metal; e. a mold coupled to said cooling chamber for receiving said liquid metal and to hold it while cooling to the solid state; and f. a means for providing a controlled atmosphere surrounding said liquid metal at all times during the heating and cooling stages until it is in the solid and its temperature has been reduced to a point wherein rapid oxidation will not take place.

5. The system of claim 4 wherein the coolant in said cooling jacket is water.

8. An improved controlled atmosphere liquid metal quenching system, comprising: a. furnace means having a hollow portion; b. a sample holder for liquid metal positioned in said hollow portion; c. actuating rod support means in said furnace rotatable between two positions, said first position supporting said sample holder, said second position releasing said sample holder from within said furnace; d. a cooling chamber coupled to said furnace and directly below said hollow position; e. means in said cooling chamber for mounting said sample holder to release said liquid metal; f. a moulding means coupled to said cooling chamber to receive said liquid metal; g. means for cooling said cooling chamber and said molding means to bring said liquid sample to a solid state temperature; and h. atmosphere control means coupled to said furnace, drop chamber and said mold for cleaning and purging said system and for providing an inert atmosphere during the heating, cooling and solidifying phases of said quenching system to prevent oxidization and impurity inclusion.