US2471937A - Method of making hollow poppet valves - Google Patents

Description

May 31, 1949. A. 1. COLWELL IETHOD OF MAKING HOLLOW POPPET VALVES Filed Jan. 24, 1944 w 5 6 V 12 6 m \1.2 l 2 MT ma 4 2 n .0 r W u w R a 2 2 la 7 7 7 I 2 c 7 8 I m Patented May 31, 1949 UNITED STATES PATENT oFFicE METHOD OF MAKING VAL 2 Claims. 1

This invention relates to poppet valves having cast corrosion-resistant metal head ends and forged stress-resistantand wear-resistant metal stem ends.

Specifically the invention relates to a hollow poppet valve having a hollow cast corrosionresistant metal head portion defining the hollow valve head, the hollow valve neck, and a portion of the hollow valve stem together with a hollow stress-resistant and wear-resistant forged metal stem portion welded to the cast portion throughout a weld band of greater area than the crosssectional area of the stem and located well down the length of the valve stem to be out of corroding atmospheres surrounding the valve head and neck in operation of the valve. The invention includes a process for preparing these valves.

In accordance with this invention a casting mold is provided with a mold cavity in the shape of the head end of a poppet valve. This cavity includes a poppet valve head-defining portion, a poppet valve neck-defining portion, and a segmental poppet valve stem-deflning portion. A frangible core composed of ceramic material, baked core binder impregnated sand, or the like, and having a cylindrical stem portion and an enlarged mushroom-shaped head end portion is suspended in the mold to project in the mold cavity in equally spaced relation from the walls thereof. A gate is provided in the mold surrounding the stem portion of the suspended core and communicating with the end of the stemdefining portion of the mold cavity. Metal is poured into the mold cavity around the core to produce a hollow casting from which the frangible core is readily removed. This casting is in the form of a hollow head end of a poppet valve and, in one method of casting, has a short stem portion terminating in the gate. The gate is cut from the stem portion of the casting and the end face of the casting from which the gate was cut is smooth-finished and preferably polished to present a clean, smooth, flat rim end on the castmg.

The casting is preferably composed of corrosion-resistant alloys. For example, castings composed of highly corrosion-resistant metal such as: nickel, chromium and iron alloys; nickel, molybdenum and iron alloys; non-ferrous nickelchromium alloys; and chromium-tungsten alloys HOLLOW POPPET VES Archie T. .Colwell, Cleveland, Ohio, asslgnor to Thompson Products, Inc., a corporation of Ohio Application January 24, 1944, Serial No. 519,435

2 can be used for effectively resisting the corroding gases and vapors in the'combustion chamber of an internal combustion engine. Many such alloys with highly desirable heat and corrosionresistant properties cannot be forged.

A hollow forged tube of a high strength abrasion resistant alloy is provided with a clean, smooth and preferably polished rim end. An alloy which has good resistance to valve stem guides is preferred. High heat conductivity prop; erties are also preferred. A very suitable alloy is a tungsten steel known as S. A. E. 71360 and containing 0.50 to 0.70% carbon; 3 to 5% chromium; 12 to 15%.tungsten; 0.3% manganese, and the balance iron. I

The tube can be hardened, as by nitriding, if desired.

The clean, smooth rim ends of the casting and the tube are mated together in full contacting relation, and pressure isapplied to hold the contacting surfaces together for sealing them against air, dirt and the like. Pressures of about 300 pounds per square inch of contacting surface can be used and, in some instances, these pressures may be as high as 2000 pounds per square inch.

A flame torch head is enveloped around the pressed-together members and welding flames are impinged on the members in the vicinity of the contacting surfaces to heat these surfaces by conduction radially inward from their peripheries to welding temperatures. Temperatures between 1000 C. and about 1300 C. can be used, but in no event should the metals he heated to their melting points.

A pressure weld is thereby produced and the contacting surfaces assume a concavo-convex relationship and are somewhat upset both on their inner and outer peripheries to form bulges or beads.

A feature of the invention is the provision of a weld area between the cast member and the forged tube which is of greater area than the cross-sectional area of either contacting surface even when the bulges or beads are removed. Because of this increased area, a stronger bond is obtained.

Since the entire welding operation is carried out with the surfaces sealed together, no burning of the metal and no flashing of the metal will occur.

It is, then, an object of this invention to provide poppet valves having cast corrosion-resistant head end portions extending well down into thestem of the valve and welded to forged stressresistant and abrasion resistant stemportions along a weld line of greater area. than the crosssectional area of the welded-together parts.

A still further object of the "invention is to provide composite hollow poppet valves having head ends composed of highly corrosion-resistant alloy and stem ends composed of wear-resistant metals with the head ends and stem ends integrally pressure-welded together at a point intermediate the ends or the stem portion of the valve.

A still further object of the invention is to provide a poppet valve having a cast corrosionresistant metal hollow head portion and a wearresistant metal stem portion welded over an increased area to the head portion in spaced relation from the neck of the valve so that in use of the valve the cast metal will be the only part of the valve exposed to the corroding atmosphere in the combustion chamber of an engine and the stem will resist abrasion of the valve guide.

A further object of the invention is to provide a process for making composite poppet valves having a cast heads and forged stems including pressure welding of the heads and stems into integral unitary relation.

A still further object of the invention is to produce a composite poppet valve having a head end portion and a stem end portion integrally joined along a sharply defined weld line positioned so that, in use of the valve, it is within the valve guide and not exposed to corroding atmospheres.

Other and further objects of the invention will be apparent to those skilled in the art from the following detailed description of the annexed sheet of drawings which, by way' of preferred example only, illustrates one embodiment of the invention.

n the drawings:

Figure 1 is an elevational view of a half of a casting mold for making cast head members for valves according to this invention and illustrating the manner in which a frangible core is suspended in the mold cavity.

Figure 2 is an elevational view, with parts shown in vertical cross section, of a cast valve head and a forged valve stem tube mounted in apparatus for pressure-welding the head and tube together.

Figure 3 is an axial cross-sectional view of a valve blank produced according to this invention.

Figure 4 is an enlarged axial cross-sectional view of the weld area of the blank of Figure 3.

Figure 5 is an axial cross-sectional view of a completed poppet valve made according to this invention.

As shown on the drawings:

In Figure 1, the reference numeral i0 designates half of a permanent casting mold having dowel pins ll projecting therefrom to receive a mating half of the mold (not shown). The mold ID has a mold cavity I2 therein defining a. valve head forming portion l2a, a valve neck forming portion l2b, and asegmental valve stem forming portion I 2c. A gate cavity 53 is formed in the mold communicating with the top end of the stem forming cavity portion i2c. This gate cavity it has an upwardly curved laterally extending passageway l3a communicating with the lower end of a pour hole I! for the mold.

1 The mold l0 also has a core suspension cavity l5 above the gate cavity l3, and a frangible core 18 is clamped in this cavity IS. The core l6 ex- Metal is poured through the pour hole l4, gate 7 passage 13a, and gate l3 into the mold cavity around the core It to form a hollow casting I I. This casting I! is readily removed from the mold by separating the mold into its component halves. The core It, being composed of frangible material, is readily broken out of the casting and the gate 18 formed in the gate cavity I3 is cut off from the casting.

As shown in Figures 2 and 3, the casting I1 has a domed head portion Ila with a central projecting lathe-centering lug llb, a beveled side wall portion llc, a curved neck portion (1, and a cylindrical fragmental stem portion He. The casting I1 has a cylindrical cavity IS in the stem portion He and an enlarged mushroom-shaped head cavity 20 communicating with the stem cavity IS. The cavities l9 and 20, of course, are formed by the core IS.

The end of the stem portion lle terminates in an annular rim I! f as shown in Figure 2 which is smooth finished as by grinding and polishing to a clean fiat surface.

The castin I I is preferably composed of highly corrosion-resistant and heat-resistant alloys such as those specified hereinabove.

A forged cylindrical metal tube 2|, preferably composed of forged stress-resisting and wearresisting material, has a thickened nubbin end portion 2la on one end thereof and a flat clean smooth finish rim end Zlb on the other end thereof. A- straight cylindrical bore 22 extends through the tube 28.

As shown in Figure 2, the casting I1 is mounted in a base block 23 of a press 24. This base block 23 has a recess'23a therein snugly receiving the head dome Ila and the lug lib of the casting so that the casting can be mounted in an upright position with the flat rim end I'If thereof disposed in a horizontal plane.

The press 24 also has a recessed block 25 receiving the nubbin end 2la of the tube 2i so that the tube depends vertically with the fiat rim end 2|b thereof resting on and mating with the flat rim ll} of the casting. The contacting rim ends "I and 2|b are pressed together in full contacting relation by the press 24 at high pressures which will seal the contacting surfaces.

A torch head 26 in the form of an annular ring envelopes the stem portion We of the casting I1 and the tube 2!. This torch head 26 defines an annular gas chamber 26a. receiving gases from a nipple 2'5. An oxygen supply tube 28 and an acetylene supply tube 29 are connected to the nipple 2? for supplying oxygen and acetylene to the annular passageway 26a.

The inner periphery of the torch head 26 has a plurality of small radial holes 26b therein providing jets for issuing gases from the chamber 26a around the entire periphery of the tube 26 and stem portion [1c of the casting l7. Jets of flame 30 issue from the holes 26b and impinge upon the casting and tube to heat the contacting surfaces Hi and Mo radially inward from their outer peripheries to welding temperature. As indicated by the arrows 3| the torch head 26 is reciprocated axially along an area of the stem ing the reciprocation Jets II will ing temperatures.

' area portion "e and the tube 2| on either side of the contacting surfaces thereof. As indicated by the arrow 32, the torch head" is also oscillated durthereof so that the flame not constantly impinge upon the the tube and casting.

flames impinge upon and same spot of The oily-acetylene I heat the casting and tube adjacent the contacthaust valves for internal combustion engines, the corrosive gases surrounding the valve head and valve neck do not reach the forged stem portion of the valve because the weld area is spaced sufficiently from the neck of the valve to v be in or near the valve stem guide and not exing surfaces thereof and heat is conducted by inward along the entire conbring thes surfaces to weld- The temperatures of the surfaces will depend largely upon the type of metal to be welded. but suitable welding temperatures will never reach the melting points of the metal and are normally in the nature of 1000 C. to 1300 C.

Pressure from the press 24 is continually applied during. the welding operation and. as shown in Figures 3 and 4, the metal on each side of the contacting surfaces is upset to form an outer bead 33 and an inner bead ll. During the heating, the contacting surfaces will be pressed down around their peripheries into a concave-convex relationship and the weld line 35 produced by the pressure welding operation will have an arouate contour which has a greater area than the of the initially contacting surfaces even when the beads 33 and 34 are removed.

The blank of Figure 3 is thus produced and from this blank the finished valve 38 of Figure 5 is formed by machining and forging operations. Thus the thickened nubbin portion Ila of the tube II is inwardly collapsed to form a solid end 31 on the valve stem closing the valve cavity 30. This valve cavity receives coolant (not shown) such as metallic sodium or the like for dissipating heat from the head of the valve along the length of the valve stem. The beads 33 and 34 of the blank are machined off. but the final valve 35 still has the curved weld line 35 of greater area than the cross-sectional areas of either the cast stem portion He or the tube 2|. This increased weld area is highly desirable to increase the strength of the bond between the cast head and the forged stem.

The valve 36 thus has a cast head portion 38a extending down through the neck of the valve to the weld line 35 which is intermediate the ends of the valve stem and is in spaced relation from the neck of the valve.

The remainder of the valve stem 36b is composed of the forged stress-resistant and wearresistant metal from the tube 2i. The stem portion 36b of the valve does not extend into chambers containing corrosive gases when the valve is in operation in an engine, since the cast part of the valve extends sllfflcient-ly down th length of the valve stem so that it is the only portion exposed to the corroding gases.

The beveled side wall I 1c of the casting l1, as shown in Figure 5, can be recessed to receive a puddled-in or welded-in ring 39 of alloy steel to provide a seating face for the valve.

From the above descriptions it will be understood that this invention provides a po pet valve having a hollow head end, a hollow neck portion, and a hollow short stem portion composed of cast corrosion-resisting metal together with a forged main stem portion, having stressand wear-resistance, welded to the stem portion of the head by a pressure-welding operation to produce a bond area of greater cross-sectional area than the stem portion.

In use of the valves of this invention as exthe metal radially tacting surfaces to pet valve head posed to the gases. The stem metal being wear resistant will withstand abrading action of the guide and, being highly heat conductive, will dissipate heat from the valve head. The weld between the stern and head portions 'is sharp and uniform with an area greater than the transverse cross section areas of either the stem or head at the weld line. The increased area caused by pressure welding produces a stronger bond.

It will, of course. be understood that various details of construction may be varied through a wide range without departing from the principles of this invention and it is, therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claims.

I claim as my invention:

1. The method of producing composite hollow valves having cast hollow head ends and forged hollow stem ends which comprises forming a hollow heat and corrosion resisting alloy casting having a hollow poppet valve head and neck with a cylindrical'stem portion extending from the neck and havin a flat end face, forging a strong abrasion resisting steel blank to form a hollow cylindrical tube with a thickened end portion and a reduced-diameter stem-defining portion with a flat end face, cleaning the flat end faces of the reduced-diameter stem defining portion of the tube and the stem portion of the casting, axially pressing said end faces together into full contacting relation under pressures from about 300 to 2000 pounds per square inch of contacting surface, impinging flames around the casting and tube on each side of the contacting surfaces for heating said surfaces by conduction to temperatures from about 1000 C. to about 1300 C., continuing the application of pressure on said surfaces during said heating for deforming and pressure welding the surfaces together along an arcuate weld line of greater area than the area of the initial contacting surfaces, ma-

chining the resulting blank into final poppet valve shape, and inwardly collapsing the thickened end portion of the tube part of the blank to seal the hollow interior of the valve.

2. The method of making hollow poppet valves which comprises forming a casting of highly corrosion-resistant metal having a hollow popportion, a curved converging hol low neck portion, and a short hollow cylindrical stem portion having a flat end face, cleaning and polishing the flat end face of said stem portion of the casting, forming a hollow tube of forgeable steel with a fiat end face, cleaning and polishing a flat end face of said tube, axially pressing the cleaned and polished end faces of the tube and casting together under pressures sufficient to seal the contacting surfaces, and heating the casting and tube in the vicinity of the contacting surfaces while said surfaces are being pressed together to temperatures sufficiently high for welding the surfaces and thereby producing a composite valve blank having a cast corrosion-resistant head portion extending into the stem portion of the valve and a forged stress-resisting hollow stem welded to the head portion throughout a curved area of greater size than the thickness of either the stem portion of the casting or the tube at the weld line.

REFERENCES CITED ARCHIE T. COLWELL.

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

UNITED STATES PATENTS Number Mldgley Feb. 25, 1930 Number Number 15 4,767

8 Name Date Ford Aug. 12, 1930 Taub Apr. 19, 1932 Lewis, Jr. Feb. 27, 1934 Sterling Feb. 19, 1935 Fllnterman July 23, 1935 Halle Sept. 15, 1936 Miner Aug. 23, 1938 Colwell Mar. 3, 1942 Roth 1 Apr. 13, 1943 Scherl Feb. 18, 1947 FOREIGN PATENTS Country Date Great Britain 1903

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