US3098270A - Die casting method and article - Google Patents

Description

July 23, 1963 A. F. BAUER 3,098,270

DIE CASTING METHOD AND ARTICLE I Filed April 18, 1961 4 Sheets-Sheet 1 INVENTOR. ALFRED F. BAUER BY/ f :6

ATTOR NEYS July 23, 1963 A. F. BAUER 3,098,270

Filed April 18, 1961 DIE AR LE 4 Sheets-Sheet 2 x 332 HVVENTO ZF E ALFRED F. 5 BY ATTORNEYS July 23, 1963 A. F. BAUER DIE CASTING METHOD AND ARTICLE 4 Sheets-Sheet 3 Filed April 18. 1961 IN VEN TOR.

ALFRED F. BAUER AT TOR N EYS July 23, 1963 A. F. BAUER 3,

DIE CASTING METHOD AND ARTICLE Filed April 18, 1961 4 Sheets-Sheet 4 12 .517." E12 -Il INVENTOR. RI ALFRED F. BAUER ATTORNEYS 3 ,fi-98,Z70 Patented July 23, 1963 3 098,270 DIE CASTING lvmruon AND ARTICLE Alfred F. Bauer, Toledo, Ohio, assignor to National Lead glompany, New York, N.Y., a corporation of New ersey Filed Apr. 18, 1961, Ser. No. 103,867 Claims. (Ql. 22-264) This invention relates to a method of making a diecasting having an insert of a metal other than the principal metal of which the casting is made. The invention is particularly directed to a method of die-casting a body such as an aluminum or other light metal, internal combustion engine cylinder block having cylinder liners of gray iron or similar wear resistant metal.

At the present time, die-cast engine blocks are just being introduced in this country. These blocks are made of aluminum alloy castings with gray iron cylinder liners cast in place and bonded to the aluminum by a rough interfacial surface. Preferably the liner is made as thin as possible to improve the heat transfer into the aluminum, but there is a limit on the thinness of the liner wall since it must first withstand the die-casting pressure, which usually runs in excess of 8000 psi. If the liner is made as thin as the engine designer would like to have it, the liner will crack under the heavy metal pressure, while if stock is added to the bore to make the liner thick enough to withstand the pressure in a virtually unsupported condition, the increased weight and the necessity for removing the extra stock in the bore result in increased machining cost. If stock is added on the outside of the liner, in an elfort to reduce the machining time, it results in unnecessarily increasing the weight of the casting. The added weight tends to defeat one of the prime advantages of the die-cast aluminum engine block.

Further, it is highly desirable that the gray iron liners be made with a taper-free, cylindrical interior. Thus, a section of a centrifugally cast tube may be used advantageously and little machining of the bore will be required or the liner may be initially machined to the cylindrical form and the subsequent boring and honing required can be kept to a minimum.

It has been found that a taper-free, relatively thin gray iron cylinder liner may be cast in place in an aluminum die-casting, .such as an engine block, only if the liner is properly supported during the casting step. In accordance with the present invention, the proper support is derived by placing the liner, in a heated condition, over a heated (but cooler) holder outside of the die and then inserting the holder into the die. Attempts to shrink a heated liner onto a holder which is an immovable part of the die will not be successful, for reasons which will be hereinafter explained.

It is also of the utmost importance that the holder be removed from the completed casting in such a manner that the casting is not damaged or distorted by the force required for the separation of the parts. The liner which was shrunk onto the holder before the latter was inserted into the die has been, by the casting operation, united with the aluminum of the casting by a mechanical bond which must not be disturbed or altered by the removal of the holder. It has been found that a hollow holder, made of a metal of relatively good heat conductivity, and having a wall thickness suflicient to support the liner without distortion, but no greater, can be removed by differential expansion. The present invention includes as steps in the process, supporting the casting, on a suitable base, while it is hot, injecting a cooling fluid into the inside of the hollow holder to cause it to contract away from the hot liner and casting, and then applying a mechanical force acting axially of the holder to urge the holder outwardly of the completed casting.

The primary object of the present invention, therefore, is to provide a method of die-casting a sleeve or hollow object of a higher melting metal into a body of a relatively lower melting metal and :to support the body of higher melting metal in such a manner as to assure that it will withstand the high pressures resulting from the die-castmg operation.

Another object of the invention is to provide a method of die-casting a composite piece, such as an aluminum engine block having a gray iron cylinder liner, which will greatly facilitate the operation and increase the speed with which the completed castings can be made since many steps of the method are carried on outside of the die-casting machine which is thus made available for more frequent operation and increased production.

Other objects and advantages of the invention Will become apparent from the following description of the new method, reference being had to the accompanying drawings, in which:

FIG. 1 is a perspective view of a typical insert holder used in the method of the present invention;

FIG. 2 is a perspective view of a typical cylinder liner or insert;

FIG. 3 is a perspective view of an insert holder loaded with the liner shown in FIG. 2 prior to its insertion in the die-casting machine;

FIG. 4 is a fragmentary diagrammatic sectional view of a die-casting machine in the die-open position showing a loaded holder in position to be received over a part of the ejector die;

FIG. 5 is a view of the machine shown in FIG. 4 with the dies closed and the insert holder located by coaction with the cover die;

FIG. 6 is a view similar to FIG. 5 showing the parts immediately upon completion of the casting operation;

FIG. 7 shows the dies again open and the casting and holder ejected;

FIG. 8 is a sectional view of a completed casting with the insert holder still in place;

FIG. 9 is a sectional view taken on line 9-9 of FIG. 8 of a completed casting placed in a fixture for removal of the insert holder;

FIG. 10 shows the step of spraying a cooling fluid into the interior of the hollow insert holder to cause its contraction; and

FIG. 11 shows the contracted insert holder forced axially away from the completed casting by the removal .fiX- ture.

The drawings are to be used solely as illustrative of the steps of the method of the present invention, and hence are diagrammatic. As indicated therein, an insert hold-er, shown in FIG. 1, is loaded with an insert shown in FIG. 2, the resulting combination being shown in FIG. 3. The method of the present invention is shown in conjunction with die-casting a part such as an aluminum cylinder block for an internal combustion engine. While a single cylinder is shown in the process of formation, it will be readily understood that multi-cylinder engines are made by the same process, either in the in-line or V-form. In order that the disclosure may not be unduly complicated, details of the die-casting machine and the associated dies are omitted.

It is preferred that the insert holder, designated 20 in the drawings, be at a somewhat elevated temperature, preferably about 500 F. and that the insert designated 21 be about F. hotter than the holder. The temperatures indicated above are illustrative of a typical die-casting practice which requires that the die and its associated parts shall be pro-heated to approximately the temperatures to be encountered during a prolonged production run, taking into account, of course, the cooling action of the various cooling cavities provided in the die. Any

suitable furnace may be used to retain a supply of the holders and inserts at the proper temperatures, and the step of bringing the two parts together may be accomplished manually or by any automatic loading device.

It is of great importance in the practice of my new method that the holders 20 be loaded outside of the diecasting machine and that they are separate parts capable of independent temperature control and manipulation. By loading the holders apart from the die-casting machine it becomes possible to support a cylindrical liner, for example, on the cylindrical holder by a precisely controlled shrink fit which assures that the liner is completely backed by the holder and can thus withstand the tremendous pressures of the ensuing die-casting operation. If the liner were to be slipped over a holder with the parts at the same temperature, suflicient clearance would be required between the parts that the liner would not be properly supported and would be in danger of failing under the pressure of the casting operation unless its wall thickness were to be increased to such an extent that the unit pressures were within the limits which the sleeve-like liner could withstand. In many instances it is highly undesirable to use a thick liner. For example, if the liner is to become a part of an aluminum cylinder block for an internal combustion engine and is, therefore, of a wear resistant metal such as cast iron, it is desirable in the eyes of the engine designer to make this liner as thin as possible. A thick walled liner such as would be necessary to with stand the die-casting pressures in a virtually unsupported condition has one of two disadvantages. Either the liner requires excessive machining on the inside to reduce the wall thickness, or it adds unnecessary and undesirable weight to the casting. The first of these disadvantages results in a higher cost of production by prolonging the machining time, while the second results in a heavy engine which defeats in part the purpose of using aluminum for the block.

The holder 20 is preferably made of steel which has a relatively good heat conductivity and is made hollow with one end open. The wall thickness of the holder is selected to be great enough to withstand the crushing pressure of the die-casting operation that will be transmitted to it through the sleeve-like liner 21, and thin enough to cool and shrink away from the insert in a predetermined time when subjected to cooling fluid as hereinafter described. At its solid end the holder is provided with a locating dowel 24 which cooperates with the cover die portion as hereinafter described.

When the holder 20 has been loaded, it is placed manually or automatically over the nose of a core pin 26 which is part of the ejector die set in a die-casting machine, as shown in FIG. 4. The ejector die is designated 28 and moves towards and away from a stationary cover die 30. The die cavity is completed by side slides, two of which are shown at 32 and 34 in the drawings. The interior of the holder 20 is somewhat larger than the outer diameter of the pin 26 to provide an easy mounting of the loaded holder on the pin, although a rather good fit can be obtained between these parts due to the conical configuration of the pin nose which aids in locating the holder as it is moved over the pin 26 by the loading device or by manual manipulation.

After the pin 26 is loaded the die halves can be closed to the position shown in FIG. 5. It will be noted that the dowel extension 24 has entered a mating recess 36 in the cover die 30 so that the sleeve or liner 21 is properly and accurately located in the die with respect to the several cores that are necessary to form the finished part, and that it is not necessary to rely on the core pin 26 as the sole locating element for the liners which must be precisely positioned in the final casting.

When the die parts have been closed, the shot can be made, metal being forced into the die from a shot sleeve 38 by a shot plunger 40 as shown in FIG. 6. It has been found that pressures in the order of 8000 to 10,000 psi.

are required properly to fill the die and this pressure is,

communicated to the sleeve or insert 21. In accordance with the method of the present invention, the compressive forces set up by the die-casting pressure are communicated through the material of the insert to be absorbed as compressive stress in the holder 20. Thus, the liability of cracking the relatively brittle gray iron insert or cylinder liner is greatly reduced or eliminated.

After a predetermined cooling time, the dies can again be opened and the casting ejected as indicated in FIG. 7. It will be noted that the holder 20 is ejected with the casting and that the liner 21 is now an integral part of the casting and supports the holder 20, the two parts being at substantially the same temperature.

The holder 20 is separated from the casting at a station which may be remote from the die-casting machine so that production may continue during the time the holder 20 is being removed from a completed casting. In accordance With the present invention, the casting is sup ported in such a position that the open end of the holder 20 faces downwardly (see FIG. 9). A source of cooling fluid such as a spray head 41 is then raised into the hollow holder and water or mixed water and air is sprayed into the interior of the holder. Since the parts are still hot from the casting operation, the contraction of the holder caused by the extraction of heat by the cooling fluid will release the holder from the interior of the sleeve. The holder may then fall out or be pushed out of the sleeve by any suitable device such as a fluid operated ram 42 (as indicated in FIG. 10). The holder is then ready to be used again in a subsequent casting cycle.

The die-casting machine can be operated during the time required for loading a set of holders for a multicylinder engine and also during the time required for removing the holders from a completed casting, since it is only necessary to supply several sets of holders for the process to be made substantially continuous.

If it is attempted to cast the liner 21 into the engine block without utilizing the holder 20, great difficulty is experienced in placing the sleeve properly on the core nose 26 because in practice this die part is inaccessible and the placement of the sleeve is slow and cumbersome. In addition, a casting is much more difficult to eject if it is necessary to strip the liner from the core 26 directly. The present process has led to substantial increases in production and substantial savings in costs and in rejected castings.

While the invention has been described in connection with the die-casting of cylinder blocks for internal combustion engines, it obviously has great advantages in the manufacture of other die-cast parts. The invention therefore includes such modifications as are defined by the appended claims.

What I claim is:

1. A method of making a composite die-cast article having an insert of a metal of higher melting point than the remainder of the casting comprising, heating the insert to a temperature higher than that of a holder therefor, positioning the heated insert over the holder, decreasing the temperature difference between the insert and the holder to establish a shrink fit between the two over the entire area of the insert subject to die casting pressures, supporting the holder with the insert shrunk thereon relative to other parts of a die so that an outer face of the insert defines a part of the die cavity, closing the die, casting metal of lower melting point than the metal of the insert under elevated die-casting pressure into the die and around the insert, cooling the die-cast metal to cause shrinkage thereof around the insert, removing the solidified casting with the insert united therewith, and the holder from the die, cooling the holder to cause shrinkage thereof away from the insert, withdrawing the holder from the casting, and passing the holder for reuse with another insert for a subsequent casting.

2. The method in accordance with claim 1 in which said step of cooling the holder to cause shrinkage thereof away from the insert comprises spraying water into the interior of the holder while maintaining the casting at an elevated temperature.

3. A method of making a composite die-cast article having an insert of a metal of higher melting point than the remainder of the casting comprising, heating the insert to a temperature of 100 F. to 200 F. higher than that of a holder therefor, positioning the heated insert over the holder, decreasing the temperature difference between the insert and the holder to establish a shrink fit between the two over the entire area of the insert subject to die casting pressures, supporting the holder with the insert shrunk thereon relative to other parts of a die so that the outer face of an insert defines a part of the die cavity, closing the die, casting metal of lower melting point than the metal of the insert under elevated diecasting pressure into the die and around the insert, cooling the die-cast metal to cause shrinkage thereof around the insert, removing the solidified casting with the insert united therewith, and the holder from the 'die, cooling the holder to cause shrinkage thereof away from the insert, withdrawing the holder from the casting, and passing the holder for re-use with another insert for a subsequent casting.

4. A method of making a composite die-cast article having an insert of a metal of higher melting point than the remainder of the casting comprising, heating the insert to a temperature of approximately 150 F. higher than that of a holder therefor, positioning the heated insert over the holder, cooling the insert to establish a shrink fit between the insert and holder over the entire area of the insert subject to die casting pressures, supporting the holder with the insert shrunk thereon relative to other parts of a die so that an outer face of the insert defines a part of the die cavity, closing the die, casting metal of lower melting point than the metal of the insert under elevated die-casting pressure into the die and around the insert, cooling the die-cast metal to cause shrinkage thereof around the insert, removing the solidified casting with the insert united therewith, and the holder from the die, cooling the holder to cause shrinkage thereof away from the insert, withdrawing the holder from the casting, and passing the holder for re-use with another insert for a subsequent casting.

5. A method of making a composite die-cast article havin an insert of a metal of higher melting point than the remainder of the casting comprising, heating the insert to a temperature higher than that of a holder therefor, positioning the heated insert over the holder, decreasing the temperature difference between the insert and the holder to establish a shrink fit between the two over the entire area of the entire area of the insert subject to die casting pressures, supporting the holder with the insert shrunk thereon relative to others parts of a die so that an outer face of the insert defines a part of the die cavity, closing the die and at the same time establishing a support between the holder and both the movable and stationary portions of the die, casting metal of lower melting point than the metal of the insert under elevated die-casting pressure into the die and around the insert, cooling the die-cast metal to cause shrink-age thereof around the insert, removing the solidified casting with the insert united therewith, and the holder from the die, cooling the holder to cause shrinkage thereof away from the insert, withdrawing the holder from the casting, and passing the holder for re-use with another insert for a subsequent casting.

References Cited in the file of this patent UNITED STATES PATENTS 116,408 Britten June 27, 1871 1,727,119 Troeger Sept. 3, 1929 1,886,396 Hainlen Nov. 8, 1932 2,219,471 Davis Oct. 29, 1940 2,580,816 Morin Ian. 1, 1952 OTHER REFERENCES Practical Consideration in Die Casting Design, copyright 1948, by the New Jersey Zinc Co., printed by Marbridge Printing Co., Inc., New York 14, NY. pp. 152, 159, 169, 173 relied on.

Die Casting for Engineers, copyright 1953, by the New Jersey Zinc Co., printed by Marbridge Printing Co., Inc., New York, N.Y., pp. 47, 50, 128-129 relied on.

Transplant Coated Aluminum Cylinder Bores, by Bauer, A.F., 1961, summer meeting, Society of Automotive Engineers, 485 Lexington Avenue, New York 17, NY.

Claims (1)

1. A METHOD OF MAKING A COMPOSITE DIE-CAST ARTICLE HAVING AN INSERT OF A METAL OF HIGHER MELTING POINT THAN THE REMAINDER OF THE CASTING COMPRISING, HEATING THE INSERT TO A TEMPERATURE HIGHER THAN THAT OF A HOLDER THEREFOR, POSITIONING THE HEATED INSERT OVER THE HOLDER, DECREASING THE TEMPERATURE DIFFERENCE BETWEEN THE INSERT AND THE HOLDER TO ESTABLISH A SHRINK FIT BETWEEN THE TWO OVER THE ENTIRE AREA OF THE INSERT SUBJECT TO DIE CASTING PRESSURES, SUPPORTING THE HOLDER WITH THE INSERT SHRUNK THEREON RELATIVE TO OTHER PARTS OF A DIE SO THAT AN OUTER FACE OF THE INSERT DEFINES A PART OF THE DIE CAVITY, CLOSING THE DIE, CASTING METAL OF LOWER MELTING POINT THAN THE METAL OF THE INSERT UNDER ELEVATED DIE-CASTING PRESSURE INTO THE DIE AND AROUND THE INSERT, COOLING THE DIE-CAST METAL TO CAUSE SHRINKAGE THEREOF AND AROUND THE INSERT, REMOVING THE SOLIDIFIED CASTING WITH THE INSERT UNITED THEREWITH, AND THE HOLDER FROM THE DIE, COOLING THE HOLDER TO CAUSE SHRINKAGE THEREOF AWAY FROM THE INSERT, WITHDRAWING THE HOLDER FROM THE CASTING, AND PASSING THE HOLDER FOR RE-USE WITH ANOTHER INSERT FOR A SUBSEQUENT CASTING.

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