US2742356A - Cast valve seat insert - Google Patents

Description

April 17, 1956 H. F. PRAssE ETAL 2,742,356

CAST VALVE SEAT INSERT Filed Ooi. 7, 1954 Y vloosel in the engine.

Y f k2,142,356 CssrfvALvE' SEAT INSERT Herbert F. Prasse, Gates Mills, and Adna A. Armstrong,

Mentor, Ohio, assignorsto Thompson Products, Inc., Cleveland, Ohio, a corporation of Ohio t A Application October 7, 1954, Serial No, 460,872 4 claims. (ci. '7s- 171) y The present invention relates. to valve `seat inserts of ,the type employed in internal combustion engines.

While the valve seat'insertisa relatively simple struc-V One of theprirnary,l problems ofthe iselection `of a suitable metal or alloy for use in valve seat insertsl arises from what is known as collapse resistance.

Itis known that :when metals or alloys are heated to very high 'temperatures for extended periodsof time,'they nidStean-:S w Patent o i 2,742,356' Patented Apr. 17, 1956 Inline'with the above, a good valve seat insert should also maintain its hot hardness properties, i. e., it should retain a substantial amount of its hardness even at the elevated temperatures at which the engine is operating. This ability to maintain its hardness governs to a large extent the degree of Contact which canbe Vmaintained between the valve face and the valve seat insert atthe operating temperatures of the engine. i

. y The characteristics of the valve seat insert also have aV pronounced effect upon the valve lash changes evident I during voperation of the engine. VThese changes accumu late inthe valve train due to wear and the pounding down of the valve seat insert during use. It is desirable that the valve seat insert have characteristics which minimize these changes, as it is undesirable to make frequent adjustments on the valve lash during operation of the engine.l f

,willqcongeal or set in an expanded state and willnot Y contract to their original dimensions when cooled.` Since engine. valve ,seat inserts are normally press-itted in recesses in engine cylinder heads or blocks, the valve seat inserts become heated in theoperation'of the engine and mayexpand to a point where further expansion is` restrictedby .thel cylinder metal itself. When this point is reached, continued expansion'due to increased temperatures .will cause the insert to bow inwardly away'from the restraining shoulder or wall of the engine head, or block. If the bowed inserts reach the setting temperatureand are then ,cooled from .this temperature, the insert metal shrinks jaway from the insert recess and the insert becomes The lbowed and set inserts are known asV co1lapsed`inserts and the temperature at which such yinsertstake apermanent set is known as the collapse temperature.A l f in the past, valve lseat inserts for-the most part have been producedby expensiveforging, machining, and heat treating procedures.v The `best of these prior known inserts had to be annealed, hardened, quenched, tempered, and drawn to a Rockwell hardness of about 35 on the C scale'. The micro-structure of thesev inserts generally exhibited an aggregatefof Vcarbideswitli some martensite oriented in an'interdendritic pattern andh/aving some of the carbides in the grain boundaries and scattered throughout `l y the matrix. This structure, however, did not provide adequate collapse 'resistance at temperatures above `about Another problem which manifests itself particularly/'in engines employing gasolines having a relatively high percentage ofrtetraethyl lead is that of surfaceresistance.

A good insert must have a smooth face which resists deposit build up, corrosion, erosion, pitting, or excessive wear. Otherwise, an unsatisfactory seal will result between the valve seating face and the valve seat insertring.

y'A lcharacteristic possessed by a good valve insert ring is that of lack of anity for the carbonaceous materials and lead deposits present in the combustion chamber. These materials tend to become deposited on valve seat insert rings and act as effective heat dams, thereby increasy ing the valve head'temperatures.

`.All of the above factors indicate that the problem of selecting a suitable alloy for `valveseat insert ringsis quite substantial. 1

In view of the foregoing, the need still remains in the art for a more satisfactory valve seat insert ring, and the satisfaction of that need is the primary object of the present invention. j

vAnother object of the present invention is to provide an `improvedvalve seatinsert ring whichpis less expensive andmore convenient to manufacture than the type of p valve seat `insert rings being presently employed in many types of internal combustion engines.

. Other and further objects of this invention will be apparent to those skilled in the `art in the foregoing detail description of the annexed sheet of drawings which, by way of example only, illustrates a valve seat insert of s this invention.

On ythe drawings: f

Figure lisa plan view of the valve seat insert ring of the present` invention; s

- Figure 2 is a fragmentary view, with parts inl elevation, of the valve port area of an internal combustion engine, showing the valve seat insert in its normal condition;

Figure 3 is a greatly enlarged fragmentary view of the valve port area, illustrating theinsert ring in its normal condition; l f

Figure 4 is a view similar to FigureA 3, but illustrating the ring in its collapsed condition;

Figure 5 is a graphic reproduction of a micro-structure of the alloy constituting the insert, at a magnilcation of about 500 times.

Asrshown on the drawings:

From Figures l to 4, it will be seen that the engine valve port assembly 10 Vmay include an engine block or cylinder head 11 normally composed of cast iron, and a cast valve seat insert 12 press fitted intoa. recess 13 of the engine,block or cylinder head 11. A bore 14 concentric with the recess 13 is provided to receive avalve stem l guide 16 in the usual manner. A'valve 17 is shown in 'seatedrelation in the valve seat .insert ring 12 (Fig. 2),

'the valve 17 having a stem 17a slidably received withinV the valve stem guide 176. j g

The valve seat insert-ring 12 may consist of a ring having a cylindricalrouter peripheral Wall 12a, a llat bot- V tom 12b, a ilat top 12e and a tapered seating face 12d convergingfrom the ilat top 12e to a cylindrical inner peripheralvwall 12e.

The peripheral wall 12a is in snug fitting relation with In normal operation, the valve seat insert ring 12 mainstantially the same degree as the metal in which-the recess 13 is formed. However, when the valve seat insert 1 2 isl heated to'a point where it can expand no further due to the restraining effect of the walls of the` recess, it may become Vbowed as illustrated in Figure 4. This bowing may create a gap illustrated at 19 in an exaggerated form in Figure 4Q If the insert 12 is Afcollapsed in the condition shown in Figure 4, then the gap 19 will remain void underk lower operating temperatures. `As a result, the insert 12 will remain loose in the recess 13.

We have now found that the collapse temperature of valve seat inserts can be increased, and other desirable properties of the inserts enhancedby employing a cast valve seat insert having the following composition:

' y l i -Percent Carbon l Y 2.25 to 2.75 Nickel 37 to 43 Chromium Y 18v to 22 Cobalt l0 to l4 Tungsten, molybdenum or mixtures thereof 5 to 7 Iron- Substantially the balance A particularly preferred composition forvalve insert rings has the following analysis:

1 Percent n lron Substantially the balance For the purposes of this invention, molybdenum and tungsten are substantially intt-zrchangeable.A Where the hardness of the insert is of prime importance, tungsten Carbon 2.5 Nickel` 40. Chromium 20 `Cobalt. 12 Tungsten 6 Y The insert is heated rst torabout 300 F. for several hundred cycles of operation. It is then cooled and cheeked for looseness. The temperature is then increased in increments and the heating is repeated for several hundred cycles. The procedure is continued until the insert under test loosensrin the cast iron cup. The nal temperature is then recorded as the loosening temperature or collapse temperature. The collapse resistance of four insert rings having compositions Within the ranges given The resistance of the insert rings to corrosion by lead oxide was determined in 'a standard test in which the samples are packed in lead oxide and maintained at a temperature of 1675 F. for one hour irranY oxidizing atmosphere The decrease in weight after thetest, expressed in grams per square decimeter, is taken as the lead oxide corrosion loss. When tested under the conditions given, valve seat insert rings having compositions within the ranges indicated above showed an average loss of only 3.5 grams per square decimeter. In contrast, samplesof various commercial valve seat inserts of compositions different from that of the present inventions alone may be employed as in the above preferred com- .n

position. Where toughness is the objective, molybdenum alone VYmay be used.V If desired, a mixture of the two metals may be used to secure the benefit of each, as in the following composition:

y p Percent Carbon Y 2.5 Nickel 40 Chromium 20 Cobalt 1 2 Tungsten 3 Molybdenum Y 3 Y lron Substantially the balance and cast in suitable molds for `producing the insert ring vl2. Thec'arsting process employedV may includejconven` tional sand casting, shell molding, investment casting, 0r other casting techniques capable of producing smooth, accurate castings free from cracks, blow holes, shrinks and the like.

Thecast insert rings need no special heatV treatment, 'i5 making them considerably. easier and less expensive toY manufacture than commonly used insert rings which frequently require hardening and drawing steps incidnt to their manufacture. Y

Y The micro-,structure `of ythe finished valve seat insert rings is illustrated in Figure 5 of the drawings. It will be observed that the structure'may include dendrites 21 surrounded by a solid solution 22 consisting of an eutectic matrix. l

A convenient collapse test for the rings consists in inserting the ring under Vtest in cast iron cup receiving a lhigh frequency induction coil in the hollow interior of the ring.- The cast iron cup isrsurroundedv by a water ring. The insert lis then'intermittently heated by the induction coil and cooled by a water spray on theicast cup.

lost up toseveral hundred grams per square decimeter under the identical test conditions. v 'ln addition to the' foregoing, valve seatl inserts made in accordance -with the present invention did not accumulate a signicant amount of combustion chamber deposits' on their' faces and evidencedno measurable loss .in hardness at the operating temperature of the engine. This, again, was in marked contrast to several commercial valve seat inserts which had a substantial affinity for the combustion chamber deposits and lost a substantial amount iof their strength at the operating temperature of the engine. i. i

A very significant advantage of the present invention arises from the valve lash properties observed when valve seatA inserts of the present invention are employed in operating engines. In onesuch test, a heavy duty truck engine was provided withseveralvalve seat insert rings produced according to the present invention in several of its cylinders. The accumulated lash change. in the cylinders after 400 hours Vof operation was Van increase of 0.004. inch. in other cylinders, high nickel alloy in; sert rings containing 58.7% nickel, .2.6% chromium, about 4% iron, and about 2.0% carbon were employed. The accumulated valve lash change for these inserts, in the sametest, was in excessvof 0.010 inch.

From the foregoing, it will beaPPIeciated that the valve seat inserts of the present invention have exceptional r esistance to collapse, resistance to lash loss, and excellent corrosion resistance. The'additional properties of. good hot strength and resistance to deposits make the alloys of the present invention considerably more satisfactory for the intended use than heretofore known more experisive inserts. j

' While thealloy of the present invention has properties making it particularly suitable in the' manufacture of `valveseat` inserts, it will be appreciated that the alloy willhave more general applicability ,for articles requiring wear and corrosion resistance properties. l

` It will be understood that modifications and variations maybeetected without departing from the scope and novel concepts of the present invnntiom 'Y Y n i We claim as our invention: i

t l. A cast valve seat insert comprising a ring having the p following composition:

2. A cast valve seat insert comprising airing having the following composition:

Percent Carbon 2.5 Nickel 40 Chromium 20 'Cobalt 12 Tungsten 6y Iron Substantially the balance 3. The method of making Va valve seat insert having enhanced wear resisting and corrosion resisting properties which comprises forming a molten mixture of the following composition:

Percent Carbon 2.25 to 2.75 Nickel 37 to 43 ,Chromium 18 to 22 "Cobalt 1o to 14 Metal selected from the group consisting of tungsten, molybdenum, and mixtures thereof 5 to 7 Iron Substantially the balance and casting said mixture into the shape of a ring.

4. A method of making a valve seat insert having enhanced wear resisting and corrosion resisting properties which comprises forming a molten mixture of the following composition:

t Percent Carbon 2.5

Nickel 40 Chromium 20 Cobalt 12 Tungsten 6 Iron Substantially Ythe balance and casting lsaid mixture into the shape of a ring.

References Cited in the iile of this patent Y UNITED STATES PATENTS Y Y 2,214,810 Chesterfield Sept. 17, 194() 2,296,460 McDonald Sept. 22, 1942 FOREIGN PATENTS 637,786 Great Britain May 24, 1950

Claims (1)

1. A CAST VALVE SEAT INSERT COMPRISING A RING HAVING THE FOLLOWING COMPOSITION: PERCENT CARBON --------------2.25 TO 2.75 NICKEL --------------- 37 TO 40 CHROMIUM ----------------- 18 TO 22 COBALT ------------------- 10 TO 14 METAL SELECTED FROM THE GROUP CONSISTING OF IRON ------------ SUBSTANTIALLY THE BALANCE

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