US 2753859 A
Description (OCR text may contain errors)
July 10, 1956 K. M. BARTLETT VALVE SEAT INSERT Filed March 7, 1952 Illllllllllll llllllllllll United States Patent VALVE SEAT INSERT Kenneth M. Bartlett, South Euclid, Ohio, assignor to Thompson Products, Inc., Cleveland, Ohio, a corporation of Ohio Application March 7, 1952, Serial No. 275,404 3 Claims. (Cl. 123188) This invention relates to a powdered metal valve seat insert having a body portion with desired expansion characteristics and a seating face portion with desired wear and corrosion resisting characteristics. Specifieally, this invention relates to a composite powdered metalvalve seat insert having a porous iron body ring carrying a porous facing ring of heat and corrosion resisting metal with a network of infiltrant metal filling the pores of both rings and integrally uniting the rings.
According to this invention, a body ring is compacted from metal having expansion characteristics compatible with the metal in an engine head or block into which the ring is to be seated. A facing ring sized for fitting in the body ring is compacted from metal powder having desired wear and corrosion resisting properties. The two rings are assembled and infiltrated with a metal having good heat conducting properties. The infiltrant metal forms a network filling the pores of both rings and creating a bond between the rings. The infiltrated rings are their solution heat treated and precipitation hardened. In this manner, the body ring can be formulated of a metal or mixture of metals which will have thermal expansio'n characteristics similar to those of the particular engine into which the ring is to be seated. At the same time, the facing ring can be formulated from refractory high temperature resisting metals, alloys, and mixtures of metal which will effectively resist the severe corrosion conditions; in an internal combustion engine caused by the presence of lead compounds in the combustion zone resulting 'from the burning of fuel containing tetraethyl lead. The refractory metal can contain high proportions of chromium and need not be weldable, since the inflltrant metal forms the bond with the body metal.
In the preferred form of the inventiomthe body metal isfihely divided iron powder obtained by reducing mill scale and containing-carbon in amounts from .01 to 1.7%
by weight. The powder has an average particle size of from -8-0 to 3-25 mesh. Ungraded fines less than 325 mesh,- and in amounts up to may be present. The iron compact is formed under pressures of from 6 to 50 tons per square inch and is porous, having a density of about 70% of the theoretical density of iron. The ring isfiat faced and has a stepped bore with a flat shoulder intermediate the flat] faces thereof. The compact is sintered: at temperatures of about 2000 to 2500 F.,- and after sintering it is cold coined to desired dimensions. At thissta'ge, the ring has a density of about 80% oftheoretica-l. The facingring is similarly prepared by compacting'; sintering, and coining. The facing ringme'tal can be obtained by atomizing molten alloy with water jets, thereby producing finely divided spherical shaped particles which are reduced to form alloy metal powder. This-powder has aboutthe. same particle size as the iron powder but the particles are more spherical in shape. Both the iron powder and the alloy powder are preferabl-ys admixed with a lubricant such as. zinc stearate in small amounts of about1% by weight to facilitate compacting steps.
The coined facing ring is seated in the stepped bore of the body ring and both rings are infiltered with a low melting metal of good heat conductivity, such as copper containing small amounts of metals such as manganese, nickel, chromium, silicon, and titanium in amounts from .1 to about 2%. The facing ring, prior to the infiltration, preferably extends above the body ring and is pressed into flush relationship with the body ring to insure a good fit between the two rings. The infiltrant metal fills the pores of both rings and forms a network which provides a bond integrally uniting the rings.
Following the infiltration step, the composite assembly is solution heat treated at temperatures around 1600 F. and then precipitation hardened. The solution heat treatment alloys the infiltrant and ring metals, while the precipitation hardening precipitates the infiltrant metal into the matrices of both metals. The resulting heat treated and precipitation hardened unit has strength and corrosion resistant characteristics not heretofore attained in valve seat inserts.
Heretofore valve facing materials were limited to materials which had good welding characteristics enabling: them to be puddled onto a base. The available base materials were likewise limited to metals which were compatible with the puddled on facing material and V which could be suitably fabricated. The present invention, however, now makes possible the selection of metals for the base which are best suited for a particular engine block or head and metals for the facing ring which are best suited for resisting wear and corrosion. Since both the base and facing metal rings are porous, and are united by a metal of good thermal conductivity, the facing ringis better cooled. Further, the base ring, being a porous member having its pores filled with a somewhat ductileinfiltrant metal, will provide a cushion between the facingring and the engine body, thereby increasing the wear life of the facing ring due to impact by the valve.
It is, then, an object of this invention to provide avalve seat insert having a body composed of material selected for its strength and thermal expansion properties: and a facing insert selected for its hardness and corrosion resisting properties, together with a common infiltrant metal integrally uniting the facing material with the body and having good heat conductivity properties.
Another object of the invention is to provide a valve seat insert consisting of a powdered iron body ring, a powdered corrosion resistant alloy facing ring, and a common infiltrant network between the powder particles of both rings and uniting the rings into an integral structure.
A further object of the invention is to provide a composite powdered metal valve seat insert having a body ring of desired expansion properties and a facing ring of desired corrosion resisting properties in alloyed relation therewith through the media of a common infiltrant metal;
Another object of the invention is to provide a valve seat insert composed of a powdered iron body ring, a facing ring in the body ring having a high chromium content, and a copper infiltrant filling the pores of both rings and providingabond between the rings.
Another object of the invention is to provide a method of manufacturing composite powdered metal valve seat inserts.
Still another object of the invention is to provide an improved powder metallurgy method for making composite valve seat insert rings of enhanced strength andcorrosion resistance properties.
Other objects and features of the invention willbe apparent tothose skilled in the art from the following de-- tailed description of the-annexed sheet of drawings which, byway of a preferred example only, illustrates one preinsert according to this invention.
Figure 2 is a vertical cross-sectional view, with parts in elevation, illustrating the valve seat insert ofthis invention in an internal combustion engine. w
Figure 3 is an exploded vertical cross-sectional view of the components used to form the valve seat insert of this invention. 7
Figure 4 is a fragmentary vertical cross-sectional view, with parts in elevation, illustrating the manner in which the insert ring is pressed into the body ring.
Figure 5 is an exploded vertical cross-sectional view of the pressed together rings and additional components used for the infiltering operation.
Figure 6 is a vertical cross-sectional View of the stack of rings assembled for the infiltering operation.
Figure 7 is a highly magnified fragmentary view illustrating the interface between the two ring components after the infiltration step.
As shown on the drawings:
As shown in Figures 1 and 2, the valve seat insert 10 of this invention is composed of a body ring 11 and a facing ring 12. The body ring 11 has a cylindrical peripheral .wall 11a, a flat top face 11b, and a fiat bottom 110. A stepped bore 11d concentric with the periphery 11a extends inwardly from the bottom 11c to a radial shoulder He intermediate the top and bottom faces. An enlarged counterbore 11 extends from the shoulder lie to the top face 11b.
' for about 6 hours.
The facing ring 12 has a bore 12a therethrough of the same diameter as the bore 11d and a beveled mouth 12b flaring outwardly to a flat top 120. A cylindrical periphery 12d has a diameter tightly fitting the counterbore 11 of the body ring and a fiat bottom 12a is hottomed on the shoulder lle. forms a seat for the seating face 1311 around the head of a poppet valve 13.
As shown in Figure 2, the body ring 11 is press-fit into an annular recess 14 around the port 15 of an internal The beveled mouth 12b combustion engine block 16. The recess 14 has a flat bottom receiving the bottom lie of the body and a cylindrical side receiving the periphery 11a of the body ring. The facing ring 12 is thus carried by the body ring 11 in the body 16 of the engine.
As shown in Figure 3, the body ring 11 and the facing ring 12 are separately formed from powdered metal compacts 17 and 18 respectively. The compact 17 is a generally porous fiat-faced ring with the approximate size and shape of the body ring 11. The compact ring 18, however, is thicker than the finished facing ring 12 and does not have the beveled mouth 12b of the finished facing ring.
The compact 17 is fabricated from iron powderprepared by reducing iron oxide mill scale in a reducing atmosphere to form metallic iron. The metallic iron powder is ball milled to a particle size in the range from about 80 to about -325 mesh with additional ungraded fines passing through the 325 mesh screen.v These lines may constitute as much as 20% of the powder. Carbon in amounts up to 1.7% by weight is admixed with the iron powder to achieve higher strength properties. Carbon should be present in amounts at least equivalent to about .0l% by weight. A molding lubricant such as zinc stearate, in amounts of about 1% by weight, is admixed into the iron powder. The resulting carbon and lubricant containing iron powder is then compacted in a die under pressures ranging from about 6'to about 50 tons per square inch. The coherent compact 17 is thereby formcd. This compact 17 has a porosity of about being about 70% theoretical density and with a porosity range of 15 to being generally acceptable.
. The compact 17 isthen sintered in a feed through'fur nace at temperatures between about 1650 to 2500 F., Actually the compact is only at the sintering temperature for about 1 hour, the remaining time being consumed by bringing the compact up to temperature and by cooling the compact as it leaves the furnace. A preferred sintering temperature is 2100 F. and the preferred sintering time at this temperature is 1 hour.
After sintering, the compact has a porosity of about 20% or a density of 80% of theoretical. A porosity range of about 10 to about 35% is suitable. During the sintering step, the carbon in the compact combines with the iron to form iron-carbon combinations depending upon the relative proportions of iron and carbon in the compact to thereby produce a steel of the desired expansion characteristics compatible with the body metal of the engine body 16.
After sintering, the compact 17 is cold coined in shaping dies at pressures of from 15 to 50 tons per square inch to shape the sintered unit into conformity with the final dimensions of the body ring 11.
The compact 18 is formed from powdered refractory corrosion resistant metal or alloy preferably produced by atomizing wherein the molten metal or alloy in fine stream form is contacted by high pressure water jets whichform rounded, odd shaped particles including small spheres of the metal. Since the metal may be oxidized in the atomizing treatment, the spheres are reduced in a hydrogen or other reducing zone to form the metal. The metal spheres are ball milled if necessary to the desired particle size within the same range as the powdered iron for making the compact 17. The resulting powder is admixed with a molding lubricant such as zinc stearate in amounts of about 1% by weight.
Many types of metals can be used to form the powder for the facing ring, and these metals preferably contain high amounts of chromium to effectively resist corrosion. Such high chromium content metals do not possess good welding characteristics, but this is not a drawback in the present process. Alloys of the Stellite series, such as Stellite No. 6, containing from 63% to 68% cobalt; 27 to 30% chromium; and 2 to 6% tungsten are highly desirable. Alloys of the Ni-Chrome series, particularly those alloys containing from 15 to 16% chromium; 59 to 62% nickel; about 24% iron; and about .1% carbon are also suitable. A mechanical mixture of 50% powdered iron and 50% powdered chromium by weight is also useful. A very suitable alloy is an alloy having the following composition:
Per cent Nickel 50 to 65 Chromium 20 to 35 Tungsten and/or molybdenum 6 to 9.5 Carbon 1 to 2.5 Silicon .05 to .50 Zirconium .01 to .10 Iron Balance Compacting pressures of about 6 to 50 tons per square inch are used to compact the powder of the facing ring, but since the metal powder is preferably formed by the atomizing process and the particles are therefore of rounded, odd shapes, the thus compacted facing ring will only have a density of about 60% of theoretical. The odd shaped particles are desirable to enhance the infiltration step, because they provide a network of cavities there-' The sintered compact 18 is then cold cpined in shaping dies at pressures of about 15 to 25 tons per square inch and the resulting coined ring will have a height A greater than the distance B between the shoulder and the top face of the compact 17, so that when the ring 18 is seated in the counterbore of the ring 17, it will project slightly above the top face of the ring 17. The height A is preferably within the range of about to inch greater than the height B.
The ring 18 fits snugly in the counterbore of the ring 17 and the assembly is placed in a die shown in Figure 4 having a female member 19 with an ejector bottom 20 having a recess 21 therein. A punch 22 has a projecting mandrel portion 23 fitting into the recess 21. The assembled rings 17 and 18 are placed in the die 19 on the bottom 20 and the punch 22 is inserted to seat the mandrel 23 in the recess 21 and to then move theactive face 24 of the punch againsttheprojecting portion 18a of the facing ring 18 Pressures of about 25 to 50 tons per square inch are exerted on the assembled rings in the die to force the rings 17 and 18 into full conforming relation with the ring 18 being pressed down to the same level as the top face of the ring 17, thereby producing the assembly 25 shown in Figure 5. The rings 17 and 18, at the same time, are sized close to the dimensions of the finished insert 10.
The assembly 25 is now ready for infiltration.
To facilitate infiltration, without necessitating extensive finish grinding operations, an infiltration bridge ring 26 is provided. This ring 26 is a porous sintered iron compact having a porosity adapted to soak up and pass molten infiltrant metal therethrough by capillary action. A porosity of from 20 to 40% is satisfactory. The ring 26 has a fiat bottom face with a plurality of radial circumferentially spaced legs 27 therearound for resting on the assembly 25. The ring 26 has a bore therethrough at least as large as the bore through the assembly and has an outer diameter extending beyond the facing ring 18 to overlap the body ring 17. The legs 27 only contact the assembly 25 along narrow lines, as shown in Figure 6 for a purpose to be more fully hereinafter described.
A ring 28 of infiltrant metal is molded from powder to a size for overlying the top face of the bridge 26. The infiltrant is metal having good heat conductivity properties, such as copper. A preferred metal is a copper alloy composed of about 95% copper and the remainder selected from the group consisting of manganese, nickel, chromium, silicon, and titanium, with manganese being a preferred ingredient.
As shown in Figure 6, the bridge 26 is placed on the assembly 25 with the legs 27 preferably contacting both rings 17 and 18 of the assembly and the copper ring 28 is placed on the ring 26. The assembly is then introduced into an infiltrating furnace maintained at temperatures above the melting point of the infiltrant. When the copper alloy is the infiltrant material, temperatures of around 2000 to 2300 F. are used. As the infiltrant metal melts, it passes through the porous bridge 18 and enters the assembly 25 through the legs 27 of the bridge. These legs thus provide a channeling effect which directs the molten infiltrant into the porous assembly 25 along relatively narrow lines. As a result, any excess infiltrant metal remaining after infiltration is complete does not present a problem of removal, because the infiltrating bridge is readily broken off after solidification of the infiltering metal without leaving massive surface deposits of the infiltrant.
Since the body ring 17 has a porosity of about 20%, While the facing ring 18 may have a slightly higher porosity, and since the infiltrant metal fills all of the pores of both rings 17 and 18, the resulting assembly will contain about 20% copper. It should be understood, however,
that the copper content may be varied through a wide range controlled by the porosities of the compacts, and that copper contents of from to 35% are useful.
To improve the strength and wear properties of the infiltrated ring assembly, the assembly is solution heat treated which difluses the ,cuprous metal into the ferrous matrix of the body ring, and the alloy matrix of the seat ring in alloyed condition therewith. In addition, the alloy and ferrous matrices of the two rings are diffused into the cuprous infiltrant phase. The solution heat treatment can be eifected at temperatures within the range of 1000 to 2000" F., and preferably at 1600 F. for a relatively short period of time, such as /2 hour. After the solution heat treatment, the composite ring assembly is oil quenched and reheated to effect precipitation hardening. The precipitation treatment will precipitate both iron and alloy from the copper phase, and copper from the iron and alloy phase forming an integral bonding trinary system of the infiltrant, iron and the refractory alloy at the interface between the rings. The precipitation hardening is effected at temperatures of around 900 to 1200", and preferably at 925 for 1 hour, followed by air cooling.
The incorporation of manganese into the infiltrant metal results in the production of a fluify or spongy residue at the interface between the legs 27 of the bridge and the top faces of the rings 17 and 18. This residue can easily be broken off without necessitating appreciable finishing operations. The infiltrated and heat treated assembly need only be finished by a light grinding operation to form the taper or seating face 12b and to bring the periphery 11a into exact desired diameter dimensions. This light grinding operation is easily effected and, if desired, the seating face 12b can be initially formed in the compacting and coining operations to further minimize the finish grinding. step.
The other alloying ingredients which may be incorporated with the infiltrant metal, such as chromium, nickel, titanium, and silicon, are desirable to alloy with the main metals to increase the hardness and wear resisting properties of the product. Metals such as molybdenum and vanadium can also be used to alloy with the final body.
The structure resulting from the infiltration and heat treatments is illustrated in the magnified view of Figure 7 of the drawings wherein the interface I between the facing ring 18 and the body ring 17 is indicated generally by the dotted line. The sintered facing ring 18 includes spherical particles 29 with pores therebetween. These particles may be partially fused together along their boundaries. The base ring 17 is composed of particles 30 of alloy material. These particles are more irregular than the spherical particles 29, since the particles 29 are formed by the atomizing process which produces spherical bodies. A skeleton 31 fills the pores between the particles 29 and 30 and extends through the interface I to form a continuous copper phase bonding both of the rings into an integral structure. It will be noted that the copper bond 32 at the interface I is actually a part of the skeleton 31 and is anchored firmly in the voids between the particles 29 and 30.
From the above descriptions it will therefore be understood that this invention provides a powdered metal composite valve seat insert with a facing ring composed of metal that is best suited for valve facing purposes, and a body ring composed of metal which is best suited for its compatibility with the engine body or block in which it is mounted. Both of these metals are integrally united through a common infiltrant metal which has good heat transfer properties, so that the facing metal is in good heat transfer relation with the engine body, even though it is isolated from the engine through the body ring. This body ring forms a cushion, and, being compatible with the engine body, it need not have any special anchoring shape or be equipped with additional fastening means, since a press fit relationship can be maintained throughout the operating temperatures of the engine. The sintering, solution treating, and precipitation treating steps provide physical properties for the composite valve seat insert but they also effect alloying of the incorporated metals and carbon.
It Will be understood that modifications and variations may be effected Without departing from the scope of the novel concepts of the present invention.
I claim as my invention:
1; A valve seat insert for an internal combustion engine which comprises a first ring having a 70% to 90% powdered ferrous metal matrix, a second ring seated in one face of said first ring and having a 70% to 90% heat and corrosion resistant metal alloy matrix, from 30% to 10% cuprous infiltrant metal filling said pores and forming a continuous network extending throughout said pores and across the rings to integrally unite the rings, and said infiltrant and matrix phases being alloyed and each containing matrix metal from the copper phase and copper from the matrix phase with said rings being integrally bonded together at the ring interface by iron and corrosion resistant alloy precipitated from the copper phase and copper precipitated from the iron and corrosion resistant alloy phases. I V
2. A valve seat insert for an internal combustion engine of known thermal expansion properties which comprises a powdered iron metal body ring having substantially the same thermal expansion properties as the engine to receive the ring, a powdered metal alloy facing ring having high temperature corrosion resisting properties, a continuous skeleton of a copper alloy infiltered through both of said rings and integrally uniting the rings with said rings being integrally bonded together at the ring interface by the iron and corrosion resistant alloy precipitated from the copper phase and the copper precipitated from the iron and corrosion resistant alloy phases.
3. A valve seat comprising a base ring including compacted iron particles, a corrosion resistant facing ring seated within the'confines of said base ring, said facing ring consisting of a powdered metal alloy compact containing about 63 to 68% cobalt, about 27 to 30% chromium, and about 2 to 6% tungsten, and a cuprous infiltrant skeleton extending through and uniting both of said rings with said ring being integrally bonded together at the ring interface by iron and a corrosion resistant alloy precipitated from the copper phase and copper precipitated from the iron and corrosion resistant alloy phases.
References Cited in the file of this patent UNITED STATES PATENTS 1,959,068 Stoll May 15, 1934 1,993,489 Stoll Mar. 5, 1935 2,004,259 Weiger June 11, 1935 2,136,690 Jardine Nov. 15, 1938 2,401,483 Hensel June 4, 1946 2,456,779 Goetzel Dec. 21, 1948 2,549,939 Shaw Apr. 24, 1951 2,566,752 Stern Sept. 4, 1951 2,606,831 Koehring Aug. 12, 1952 FOREIGN PATENTS 565,520 Great Britain Nov. 14, 1944 OTHER REFERENCES Peters: Cemented Steels, published in Materials and Methods, April 1946.