US2552810A - Method of locating inserts in castings - Google Patents

Description

May 15, 1951 c. A. ONEILL ET AL 2,552,810

METHOD OF LQCATING INSERTS IN CASTINGS Filed May 26, 1948 2 Sheets-Sheet 1 INVENTORS. C/ayion A. 0'?! ll Wesley W. Harris BY Marius Gaga? HTTORNEY y ,1951 c. A. ONEILL ET AL 2,552,810

METHOD OF LOCATING INSERTS IN CASTINGS Filed May 26, 1948 2 Sheets-Sheet 2 INVENTORS. Clagfora A. 0W8! Wesley lMHarris BY Marius GuyoT Patented May 15, i951 METHOD OF L CA'IINGINSERTS IN CASTIN GS Application May- 26, 1948, SerialN0. 29,226

This invention relates to metal inserts embed- 'Claims. (Cl. 22- 203) Fig.1 5 isan enlarged section taken on'line-V -V of Fig. l;

ded in castings and especially a methodof maintaining the insertsin the desired position durin the casting of metal around them.

Inserts of diiierentnmetals are often usedin parts of castings to impart strength or other properties not possessed by the casting itself. In producing castings having long thininserts embedded therein trouble is often encountered in maintaining the inserts vin position during the metal pouring operation. In some cases, the inserts canbesupported in, places by cores or portions of'the mold if the shape of the castingpermits it, but if the insertis to be completely surrounded .by metal exceptfior portion protruding from the casting, a difficult positioning problem arises. 'If the insert is not too long itcan be mounted in a vertical position in themold cavity and anchored at the top and bottomv of the cavity, it can be satisfactorily locatedin .the casting. However, if the insert is thin and of considerable length, the expansion and softening of'the insertin contact with the molten metal will displaceit from'the desired locationin the casting. The problem of maintaining the location of an insert'in a mold "cavity is especially acute where Wires,'thin rodsor' tubes of considerable length are embedded'in castings poured ina horizontal orinclinedposition. In such cases the expansion of the insert as it comes in contact with the molten metal causes it to sag with resultant dislocation in the final cast product.

It is the object of our inventionto provide a method for overcoming'the aforementioned difficulty of locating inserts in castings. More particularly, it is anxobjectto provide a simple and effective method,.which can be usedin any foundry, for establishing and maintaining the position of long thin inserts in molds as the inserts expand during the pouring operation. A special object is to provide a method by which wire inserts can be accurately located in a mold and maintained in the desired location as the molten metal freezes around them.

Apparatusfor carrying out our processisillustrated in the accompanying drawingsin which:

Fig. l isa side elevational view, partially in section, of apermanent mold designed for making long rod-like castings;

Fig. 2 is an end elevation of the pouring end of the mold Fig. 3 is an elevationofthe oppositeenduof the mold;

Fig. 4 is a broken view of the .movablehalf of the mold onthe'parting face;

Fig. 6 isan enlargedsection taken on .line VI VI of Fig. 1;

Fig. '7 is a-sectiontakenonline VII-TVILof Fig. 1; and V Fig. 8 is-a longitudinal-cross sectional view of the cast rodwith a'wire insert embedded therein.

We have found thatif long thininser'ts to wbe embedded in castings areiplaced ina moldtand sufiicient tension isapplied to them'below their yield strength to producea taut -conditionprior to contact with the molten metal and this condition is maintained asthe mold. is being filled and then the tension is released ,as freezing of the metal begins, the inserts will'be properly located in the castings. Itisf important that the taiit conditionbe maintained until solidification of the molten metal has started and then' be quickly relieved .so that normal contraction can occur. as freezing is completed. "To provide'thetensibn, the'insert is gripped in any suitable manner and tension appliedthrough the grips. In referring to the inserts asbein'g long and thin, it is tobe understood that the length exceeds by many times the greatest transverse dimension aridthe thickness-cf 'theinsert is such thatitisquickly heated by the surroundingmolten=metal, usually to the temperature of the liquid metal. A taut condition isconsideredtoexist in the insert when no sagging occurs which is not corrected bythe applied tensionand' the tensicnis insumcient to cause any permanent reduction in cross "section by stretching'of the metal. The tension, there fore, should not exceed the yield'strengt'h of the metalatthetemperaturetdwhlch to -which it is exposed.

Theinser'tsmaybe made of anyoftheeonventional metals, the choice -'depend'mg *uponth'e purpose of the insert "and the character of the casting metal. The *inserts, nbviously, should have a higher melting point" than the metal sur-' rounding them and they should not be "readily soluble in 'the molten metal or attackedto' "such an extent as -to-destroy or s1ibst-anti'ally their usefulness; Metals commcnly used as inserts are i copper, brass, 1 bronze, iron,-s'teel, stainlesszsteeLtMonel metal, chrome-nickel alloys-anti low expansion ialloys. Although the inserts may have any :desired :eross sectional-shape, -those of uniform :shape :such :as 3 bars, wires, or tubes are most easily hand'led.

The long uthin .insents :may he employed in eithe ferrous ior non-.ferrous :eastings, Ebut ther find special application #in light 'rmetal fcastings 3 because of the favorable combination of properties gained by their use. In referring to light metals, it is to be understood thatthis term includes aluminum, magnesium and the alloys in which these metals predominate. As a practical matter those compositions containingat least 70% aluminum or magnesium find the greatest utility.

The shape of the casting may introduce problems in applying tension to the long insert; however, apparatus can be designed to meet the requirements of any particular mold. The castings may be solid bars or tubes, or of more intricate shape. It is essential, in any case, that the insert be so placed in the mold cavity as to permit the application of tension without collapsing the mold or distorting the cast product. An example of a difficult casting in which to place a long thin insert is that of a magnesium base alloy anode rod having a ratio of length to cross section V greater than 15 to 1. '-To embed a steel wire in the center of such a rod ofiered many practical difiiculties. It was found, however, that by grip-. ping opposite ends of the insert, tautening it, maintaining the wire taut during pouring of the molten metal and then releasing the tension as freezing started a concentrically located wire was obtained in the cast rod. The wire extended beyond the ends of the casting thus providing a convenient place for gripping the wire and applying tension thereto. An apparatus suitable for making such anode castings is described hereinbelow.

The inserts should be clean and dry, of course, to'insure good contact with the Surrounding meta1; It may be desirable to clean or pickle the inserts as well as to dry them prior to placement in the mold or the drying may be done after the inserts have beenplaced in the mold. In making the foregoing anode rods having bare steel wire inserts, it was found that the wires should be pickled in conventional acid baths or otherwise cleaned and then preheated to establish the proper contact between the insert and the cast'magnesium base alloy.

The tension applied to the insert should only be'high enough to keep it taut, as mentioned hereinabove, during the pouring operation. The tension may be maintained at a constant value or itmay bevaried especially where there is danger ofdelforming the insert at an elevated temperature. Thus, as the insert becomes heated through contact with the molten metal, it will be kept taut without danger of acquiring a permanent set. A convenient means of applying the desired tension is to use a constant load which is of such a magnitude that it does not exceed the yield strength of the insert at the temperature of the molten metal poured around the insert. Any suitable means may be employed to anchor the ends of the insert and to provide the desired tension. Usually hydraulic or pneumatic means will befound to be best suited to operate clamps and the movable head member. Only that portion of the insert which is to be embedded in the casting need be placed under tension but generally it is most convenient to grip the ends of the insert.

Once the mold cavity has been filled and freezing of the molten metal has started, the applied tension should be discontinued providing a solidification continues. Thus, freezing can be completed without further application of tension to the insert. The tension should not be terminated until the insert will remain in the desired location. On the other hand, the tension should not be retained until solidification is complete for undesirable strains can be created that may lead to loosening of the insert or warpage of the casting. We have found that by releasing the tension as freezing begins and progresses the insert can contract normally as the surrounding metal cools, a firm bond between insert and casting is established and no strains are left which would tend to loosen the insert.

The process of our invention may be carried out in any type of mold with suitable apparatus. It is most easily effected on a so-called permanent mold because means for clamping the insert in position and applying tension can be mounted directly upon the mold. Where a sand mold is employed a rigid frame outside the mold will generally be required for holding the insert and maintaining it under the desired tension. The same situation exists where plaster molds or molds made of similar material are employed. It will be understood, therefore, that the type of mold does not limit our invention.

The operation of our process is illustrated in connection with the apparatus shown in the accompanying drawings for casting magnesium base alloy anodes of rod-like proportions. In Figs. 1, 2 and 3 is a book type permanent (iron) mold composed of parts I and 2 pivotally joined together through hinges 8 and 9 and hinge pin It. The mold half I is'stationary being supported by vertical channel columns 3 and associated angle braces 5 attached to a base I. The other mold half 2, which is movable, carries counterweight I2 to facilitate opening and closing the mold. The mold is held in closed position by the clamping pins I I having rack teeth thereon and moved upwardly or downwardly by pinions within the housing and pin guides I3 on the top edge of the stationary mold half 2. The pinions are actuated simultaneously through movement of the bar I5 and associated le'gs leading to each pinion shaft. The mold is mounted at a slight inclination to the horizontal and the mold cavity I8, seen in Fig. 4, is fed through pouring sprue I6 in the upwardly extending portion Id of the mold at the upper end of the mold. Themold cavity is gated on its underside close to the upper end thereof.

The means for applying tension to thewire insert 20 comprise two air operated clamping devices for gripping opposite ends of the insert, one of the clamping devices being movable. At the upper end of the mold is mounted an air diaphragm I! attached to the mold by brackets I9. Clamping pin 2|, actuated by the diaphragm, operates in a suitable bore provided in the mold body adapted to receive and support the pin. This pin in extended position contacts the bent portion of wire insert 20 in hole 23 which is at right angles to the clamping pin. At the other end of the mold is a guide and supporting U- shaped bracket 25 attached to the stationary mold part I. A movable head 2! carrying wire clamping means is slidably mounted in the parallel arms of the bracket 25, the movement'of the head being controlled through piston rod 39 operated by air cylinder 3'! also attached to bracket 25. The wire clamping means mounted on the movable head 21 is similar to that at the other end of the mold and consists of an air diaphragm 29 attached by brackets 3| to the said movable head with clamping pin 33 passing into the head and contacting the wire inhole 35 at right angles to said pin. Compressed air for' operation of the diaphragmsandnir cylinder is :obtained from a suitable-source.

In operation the cleaned and preheated wire with a right angle bend close to one end is placed inthe mold cavity, the bent end being inserted in=the hole 23 and the other end in hole 35 in the movable head 2'1. Compressed air isadmitted to the diaphragms thereby causing the clamping pins to lock the wire in position. The wire is then tautened by introduction of air at a predetermined pressure to the air cylinder 31. Generally it is most convenient tokeep the pressure constant throughout theperiod that the-wireris held under :tension. For example, in a 2+inch diameter cylinder an air pressure of 80 p. s. i. will exert enough tension to hold taut a 0.100 inch diameter steel wire during the casting of a magnesium base alloy rod. After the wire has been tautened the mold is closed and molten metal introduced in conventional manner. The wire expands as it is surrounded by liquid metal but any tendency to sag is prevented by movement of head 27. As soon as the pouring has stopped freezing will have started and the air supply to diaphragms and air cylinder is cut off. Freezing of the molten metal continues and is completed as the wire contracts of its own accord. The insert will be found to be concentrically positioned in the casting. The mold may then be opened and the casting removed.

Having thus described our invention, we claim:

1. The method of locating a long thin metallic insert within the body of a light metal casting, said insert having a higher melting point than the light metal, said method comprising providing a thin insert of sufiicient length to extend through the casting and protrude from opposite sides thereof, placing said insert in the mold with a portion of said insert passing through the mold cavity in said mold, gripping opposite ends of said insert and solely supporting it outside of the mold cavity, applying a tension to said insert below its yield strength at the highest temperature to which it is exposed but sufficient to produce a taut condition, introducing molten metal into the mold cavity and around said insert, maintaining the taut condition of the insert as its temperature rises through contact with the molten metal, releasing said tension after the molten metal has begun to freeze around the insert and before all of the metal has solidified, and allowing the remaining molten metal to freeze and encase the insert.

'2. The method of locating a long thin metallic insert within the body of a light metal casting, said insert having a higher melting point than the light metal, said method comprising providing a thin insert of sufficient length to extend through the casting and protrude from opposite sides thereof, placing said insert in the mold with a portion of said insert passing through the mold cavity in said mold, gripping opposite ends of said insert and solely supporting it outside of the mold cavity, applying a predetermined constant tension to said insert below its yield strength at the highest temperature to which it is exposed but sufficient to produce a taut condition, introducing molten metal into said mold cavity and around said insert, maintaining the same tension as the temperature of the insert rises through contact with the molten metal, releasing said tension after the molten metal has begun to freeze around the insert and before all the metal has solidified, and allowing the remaining molten metal to freeze and encase the insert.

:3. l'lhecm'ethod ofilocating' a. longitudinally disposed'wire insertin predetermined position with respect to the axis of an elongated light metal casting, said wire having a higher melting point than the light metal, said method comprising providing a wire of suflicient length to extend through said casting and protrude from opposite .ends thereof, placing said wire in themold with a portion of said wire passing through the mold cavity in said mold, securing one end of said Wire insert in fixed position and the other end in axially movable position outside the mold cavity and thereby solely supporting said insert, axially moving the said second end a sufficient distance to establish a tension in said wire insert less than its yield strength at the maximum temperature to "which it is heated by contactwith the molten light metal but sufiicient to create a taut condition, introducing molten metal into the mold cavity and around said wire insert maintaining said taut condition as the temperature of the wire rises through contact with the molten metal by further axial movement of said second end of the wire insert, releasing said second end of the wire insert after the molten metal has begun to freeze around the insert and before all of the metal has solidified, and thereafter allowing the remaining molten metal to freeze and encase the wire insert.

4. The method of concentrically locating a longitudinally disposed iron wire insert within the body of a rod shaped light metal casting, said method comprising providing a wire of sufficient length to extend through the castin and protrude from opposite ends thereof, placing said wire in the mold with a portion passing through and in concentric position with respect to the mold cavity in said mold, gripping opposite ends of said wire insert and solely supporting it outside of the mold cavity, applying a predetermined constant tension to said wire below its yield strength at the highest temperature to which it is exposed but sufficient to produce a taut condition whereby the wire is firmly held in said concentric position within the mold cavity, introducing molten metal into said mold cavity and around said wire, maintaining the same tension as the temperature of the wire rises through contact with the molten metal, releasing said tension after the molten metal has begun to freeze around it and before all the metal has solidified, and thereafter allowin the remaining molten metal to freeze and encase the wire insert.

5. The method of concentrically locating a longitudinally disposed iron wire insert within the body of a rod shaped magnesium base alloy casting, said method comprising providing a wire of sufficient length to extend through the casting and protrude from opposite ends thereof and through at least one end wall of the mold wherein the casting is formed, placing said insert in the mold with a portion of said insert passing through and in concentric position with respect to the mold cavity in said mold, securing one end of said insert in fixed position and the other end in axially movable position outside the mold cavity and thereby solely supporting said insert, axially moving the said second end a sufiicient distance to establish a predetermined constant tension in said wire insert less than the yield strength of said wire at the maximum temperature to which it is heated by the molted metal but sufiicient to create a taut condition whereby the wire insert is firmly held in concentric position within the mold cavity, introducing molten tension as the temperature of the wire rises by contact with the molten metal by further axial movement of said second end of the wire insert,

abruptly releasing said second end of the wire insert after the molten metal has begun to freeze around the wire insert and before all the metal has solidified, and. thereafter allowing the remaining molten metal to freeze and encase the wire insert.

CLAYTON A. ONEIIL.

WESLEY W. HARRIS.

MARIUS GUYOT.

REFERENCES CITED The following references are of record in the file of this patent:

Number UNITEDSTATESPA'IENTSj Name Date Osgood Jan. 13, 1852 Haas Oct. 26, 1909 Anderson Mar. 8, 1910 Tidnam et a1 Nov. 29, 1910 Burley May 31, 1927 Muse Dec. 7, 1937 McCullough et al.' Dec. 9, 1941 Miller et a1 Sept. 24,1946

FOREIGN PATENTS Country Date Number France Nov. 14, 1925

Images