US2963757A - Copper tube core process - Google Patents

Description

Dec. 13, 1960 R. E. HAWKINS EI'AL 2,963,757

COPPER TUBE CORE PROCESS Filed Sept. 15, 1958 2 Sheets-Sheet 1 RONALD E2: HAWKINS GENE PENDL INVENTOR$ ATTORNEY Dec. 13, 1960 R. E. HAWKINS EIAL 2,963,757.

COPPER TUBE CORE PROCESS Filed Sept. 15, 1958 2 Sheets-Sheet 2 RONALD E. HAWKINS IIIIIIIIIIIIIIIIIIIII) G PE NDL INVENTORS' AT TORNEY United States Patent COPPER TUBE CORE PROCESS Ronald E. Hawkins and Gene Pend], South Bend, IntL, assignors to The Bendix Corporation, a corporation of Delaware Filed Sept. 15, 1958, Ser. No. 760,928

12 Claims. (Cl. 22-167) This invention relates in general to molds adapted to form castings of aluminum alloy or other suitable castmgs.

Our invention is particularly directed to a core structure which, during the casting operation, prevents the formation of gas blisters on the surface of the casting; and prevents the formation of pockets of gas or any gas traces within the body of the casting.

Our invention provides an effective and simple method for producing aluminum alloy castings free of the aforementioned undesired gas filled pockets within the casting and gas produced blisters on the surface of said casting; and said process involves the use of a minimum of different elements and a minimum of simple steps in the casting operation. Our invention also includes the method of producing a permeable core which will insure a free flow of gas from a casting as it is being prepared.

An important feature of our invention lies in the provision of means, constituting a part of the mold, for conducting gases into the core of the mold, said gases being developed within the casting material as it is being poured into the mold.

Yet another object of our invention is to provide a permeable core member for a mold said core being constructed to facilitate the transfer of casting gases from the casting to the core during the molding process.

Other objects of our invention and desirable details of construction of parts will become apparent from the following detailed description of an illustrative embodiment of the invention, taken in conjunction with the accompanying drawing illustrating said embodiment, in which:

Figure 1 discloses a piece of copper tubing to be used in our invention;

Figure 2 is a view of the tube of Figure l bent at its ends to be fastened to the core of our invention and punched to locate certain holes to be made in said tube;

' Figure 3 is a view of the tube of Figure 2 drilled to provide sand receiving holes;

Figure 4 discloses the tube of Figure 3 secured to a core reinforcing wire;

Figure 5 discloses the tube and wire unit of Figure 3 secured to the body of the core of our invention;

Figure 6 discloses one-half of the casting, the product of the mold of our invention; and

Figure 7 is a view disclosing the complete casting.

' There is disclosed, in the several figures of the drawing and in the process described hereinafter, a preferred embodiment of our invention. One feature of our invention lies in the core unit disclosed in Figure 5. To produce this unit a straight piece of copper tubing, or its equivalent 10, say of one-fourth-inch outside diameter, is cut to the approximate required length. This tube, disclosed in Figure 1, is then filled with a material serving to facilitate a bending of the same whereupon the latter is then bent at its ends 12 and 14 to the shape disclosed in Figure 2; that is the ends are turned at a ice right angle to the body of the tube. Any suitable low melting point alloy such as the metal sold under the trademark Cerro Bend may be used. CerroBend is comprised of 50% bismuth, 26.7% lead, 13.3% tin, and 10% cadmium and may be removed from the tube 10 after the bending operation rather easily by virtue of its relatively low melting point.

After bending the tube is ready to be marked and punched for drilling holes in the same. Holes 16 are, in the preferred embodiment of our invention, placed two inches apart in four rows along the tube. On opposite sides the holes are opposite in pairs. The other two rows are placed so that a ring around the tube connecting each pair of holes would be midway between a ring connecting the holes in the other two rows. The tube is now ready to be heated in order to remove the aforementioned material therein. After draining this material the tube is dipped into nitric acid to make sure that it is clean both inside and out.

The copper tube, Figure 3, is now sandblasted and the aforementioned punched holes 16 are then drilled with the point of a one-eighth pilot drill which produces a three sixty-fourths-inch hole. The purpose of the sandblast is to roughen the surface of the tube to facilitate the application of a coating referred to hereinafter.

As is disclosed in Figure 4 the ends of the tube or core element are now brazed to a length of core wire 18 of suitable material such as steel. The tube is now sprayed with a ceramic coating having a refined aluminum oxide base; a suspension of alumina and sodium silicate in water is preferred. This makes a protective nonmctallic coating less than five-thousandt-hs of an inch thick which prevents the molten metal of the casting from eroding the tube.

The holes 16 are now preferably filled with shell mold sand to keep the molten metal of the casting from flowing into the interior of the tube; however the permeable sand will allow gases from the casting metal to enter the tube and escape into the interstices of a generally rodlike core member 20, Figure 5. This member, shaped to effect the desired cavity, that is, bore, of the casting to be made, is fabricated in the usual manner except that the bent ends 12 and 14 of the copper tube are embedded, that is, printed in the core during said fabrication. The core 20 and tube 10 secured thereto to gether provide a core unit which will insure a free flow of gas from the casting as it is being formed. The core element 20 is preferably made of sand or its equivalent and a suitable binder such as corn flour. The wire 18- reinforces the core element 20 and facilitates the handling of the core unit without breaking the same.

As to the casting operation the core unit 10, 2G is placed in the usual mold box 21 whereupon the molten aluminum alloy at 1290 F. to 1300 F. temperature is poured into said mold to form a casting 22. The cavity of the casting is indicated in Figure 6 by the reference numeral 24. The mold is then shaken to crumble the sand core 20 and the fragments of said core are then dumped out of the mold through an opening not shown. The casting 22 is then trimmed by a band saw, then immersed in nitric acid for destruction of the copper tube 10, then flushed in water, and lastly subjected to a jet of air to dry the cavity 24. The wire 18 is removed from the casting after the destruction of the sand core 20. The casting may then be X-rayed to determine the presence, if any, of remaining portions of the tube.

There is thus provided, by our invention, a hollow casting free of gas blisters, blows on the surfaces of the casting and gas pockets within the body of said casting. The whole casting unit is shown in Figure 7 and onehalf of a split in two unit is shown in Figure 6. Import 3 tant features of our invention lie in (1) the severalsteps for making the core unit 10, 20 and (2) the virtues of said core unit itself as an article of manufacture. The perforated U-shaped tube serves to draw'the gasout of the mold cavity during the molding operation'said gas being lodged in the sand core member and the water soluble and therefor easily washed off nonmetallic alumina, sodium silicate coating for the tube 10 prevents an erosion of the tube by the molten metal forming the casting.

While the preferred embodiment of the invention has been described in considerable detail, we do not wish to be limited to the particular construction shown which may be varied within the scope of the invention,'and it is'the intention to cover hereby all adaptations, modifications andarrangements thereof which come within the practice of those skilled in the art to which the invention relates. a

We claim:

1. A mold adapted to form hollow castings free of gas and imperfections, said mold including'a core unit comprising a core member predominantly of a sandy material, a foraminous tubular member having its ends anchored into the body of the core member and operable to drain gas from the casting metal into the latter mem her during the casting operation.

2. A mold adapted to form hollow castings free of gas and imperfections, said mold including a core unit com prising a core member predominantly of sand, a foraminous tubular member soluble in nitric acid having its ends anchored into the body of the core member and operable by virtue of its foramens to drain gas from the casting metal into the latter member during the casting operation, together with a water soluble nonmetallic coating on the tube, said coating serving to prevent erosion of the tube during the casting operation.

3. A mold adapted to form hollow castings free of gas and imperfections, said mold including a core unit comprising a core member predominantly of sand, a U-shaped foraminous tubular member soluble in nitric acid having its ends anchored into the body of the core member and operable to drain gas from the casting metal into the latter member during the casting operation, together with a water soluble non-metallic coating on the tube,

said coating serving to prevent erosion of the tube during the casting operation.

4. A mold adapted to form hollow castings free of gas and imperfections, said mold including a core unit comprising a core member predominantly of a sandy material, a perforated tube member soluble in nitric acid havingits ends anchored into the body of the core member and operable to drain gas from the casting metal into the latter member during the casting operation, to gether with a water soluble non-metallic coating of aluminurn and sodium silicate sprayed on the tube, said coating serving to prevent erosion of the tube during the casting operation.

'5. A method of producing a hollow metal casting free of gas and imperfections in the casting caused by gas, said method including the successive steps of filling a copper tube with a low melting point alloy, bending said tube to a desired shape, heating and removing the low melting point alloy from the tube, drilling a plurality of relatively small spaced apart holes in the tube, filling the holes in the tube with a material permeable to gas evolved from casting metal during the casting operation, spraying the tube with a suspension of aluminum and sodium'silicate in water, embedding the tube ends in a core member, placing the core member with its attached 'tube in a mold box, pouring molten casting metal into the mold box, removing the core member, and removing the copper tube by destroying the same with nitric acid or its equivalent.

ing the casting operation to be freed of gas and imperfections caused by gas, said method including the successive steps of filling a substantially straight copper tube with a low melting point alloy, bending said tube to a desired shape, heating and removing the low melting point alloy from the tube, drilling a plurality of relatively small-diametered spaced apart holes in the tube, spraying the tube with a ceramic coating having an aluminum oxide base embedding the tube ends in a tubular shaped core member during the process offorming said member, and filling the holes in the tube with a material permeable to the aforementioned gas evolved from the casting metal during the casting operation.

7. A method of making a core unit used in a mold adapted to make an aluminum casting said casting, during tne casting operation, to be freed of gas and imperfections caused by gas, said method including thesucessive steps of filling a substantially straight copper tube with a low melting point alloy, bending said; tube at its two end portions heating and removing the low melting point alloy from the tube, drilling a plurality of relatively small-diametered spaced apart holes in the tube, attaching a substantially straight core reinforcing metal rod to the ends of the tube so that the rod is substantially parallel to the tube, and filling the holes in the tube with a material permeable to the aforementioned gas evolved from the casting metal" during the casting operation, spraying the tube with a suspension of aluminum and sodium silicate in water, and embedding the rod and tube ends in a rodlike core member'during the process of forming said member.

8. A method of producing a hollow metal casting free of gas and imperfections in the casting caused by gas,

said method including'the successive steps of drilling a plurality of relatively small spaced apart holes in a metal tube, coating the exterior of the'tube with a protective material, embedding the tube ends in a core member,

placing the core member with its attached tube in a mold box, pouring molten casting metal into the mold box, removing the'core member, and removing the metal tube by destroying the same with a suitable acid.

9 A method of producing a hollow metal casting free i of gas and imperfections in the'casting caused by gas,

said method including the successive steps of forming a plurality of relatively small'spaced apart holes in a tubu-' lar member, filling the plurality of holes in the. tube with a material permeable to'gas evolved during the casting operation, coating the exterior of the tube with'a protec-' 10. A mold adapted to form hollow castings free of.

gas and imperfections, said mold including a member made predominately of a sandy material, a tubular mem ber having a plurality of relatively small openings formed in the wall thereof through which the gas evolved during the casting operation can flow into the tube,'a protective ceramic coatingdeposited on the exterior wall of the tube to prevent erosion of thetube duringthe casting operation, said tubular member having 'its ends anchored in said sandy member and being operative to drain said gas from the casting: metal into said member during the casting operation. a

11. A mold adapted to form hollow castings free of gas and imperfections, said-mold including a core unit comprising a sand core, a-foraminous tubularmember having at least one open end, said open end being anchored into said sand core, said tubular member being operative to drain gas from the casting metal'into the sand core dur- 7 ing the casting operation.

12. A mold adapted to form hollow castings free of comprising a sand core, a tubular member having a plurality of spaced apart openings formed in the wall thereof, means permeable to the gas evolved during the casting operation disposed in said plurality of relatively small openings, said tubular member having opposite open ends anchored into said sand core and being operative to drain said gas from the casting metal into said core unit during the casting operation.

References Cited in the file of this patent UNITED STATES PATENTS 818,413 Caldwell Apr. 24, 1906 6 2,045,556 Almen June 23, 1936 2,812,562 Dalton Nov. 12, 1957 2,844,855 Gadd et al July 29, 1958 OTHER REFERENCES Trans. Am. Foundrymens See, pages 483 to 487 of vol. 65 (1957).

Woldman: Engineering Alloys, page 170, first edition, revised 1954.

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