US2162063A - Valve and a method of making the same - Google Patents

Description

June 13, 1939. F.. c CRAWFORD 2,162,063

VALVE AND METHOD OF MAKING THE SAME Filed Feb. 29. 1936 Patented June 13, 1939 UNITED STATES PATENT OFFICE I Frederick C. Crawford, Cleveland, Ohio, assignor to Thompson Products, Incorporated, Cleveland, Ohio, a corporation of Ohio Application February 29, 1936, Serial No. 66,339

Claims.

This invention relates to a valve and to a method of making the same, and more particularly to the manufacture of a valve having a layer of a surface alloy formed over the founda- 5 tion metal.

It has heretofore been proposed to provide surface alloys of metals, such as alloys of chromium and iron, by a cementation process. The patent to Kelley No. 1,365,499, dated January 11, 1921,

for instance, discloses a method for chromizing foundation metals, such as iron, nickel, molybdenum, or tungsten, according to which the foundation metal is heated in contact with powdered metallic chromium under non-oxidizing condi- 25 tions to a temperature of about 1200 Ato 1350 C.

The powdered metallic chromium may be admixed with a refractory, inert material, such as alumina or magnesia, in approximately equal proportions, or powdered aluminum may be admixed with the chromium to prevent oxidation of the chromium. The cementation takes place at a temperature below the melting point of either the chromium or of the ferrous metal or ferrous metal alloy foundation.

If such a chromizing process is applied to valves, I have found that because of the large grain structure of the chromized metal, the nished article has but little strength and hence cannot be satisfactorily used under tension or 3o where subjected to repeated stresses. It is therefore not feasible to use the process of the Kelley patent directly in the chromizing of valves because if the valve is treated in a finished condition, it would then have inherent weaknesses due to large grain size.

I have now found; however, that if a billet or slug is first chromized in accordance with the process of the Kelley patent and then severely Worked, as by extruding, forging, and the like,

such heavy mechanical work performed on the chromized foundation metal tends to break up the grain size, at the same time producing a valve having a surface layer of an iron-chromium alloy that is heat and corrosion resistant. Other surface alloys, such as those of aluminum, may be produced by the cementation process on other foundation metals, such as nickel, molybdenum, tungsten, or their ferrous alloys.

5@ It is therefore an important object of this invention to provide a method of making a valve having a surface alloy of desired characteristics.

It is a further important object of this invention to provide a valve for` internal combustion engines having a surface layer of an alloy of (Cl. Ztl-156.7

iron and chromium, which is heat and corrosion resistant.

It is a further important object of this invention to provide a method of making a chromized surface valve,l starting with a chromized surface 5 billet and forming the stem and head by a combined extrusion and forging operation.

It is a further important object of this invention to provide a valve having afsurface alloy of iron and chromium, the grain size of which has 10 been reduced by heavy mechanical working of the metal from which the valve is formed.

Other and further important objects of this invention will become apparent from the following description and appended claims. l5

This invention (in a preferred form) is illustrated in the drawing and hereinafter more fully described.

On the drawing:

Figure l is a longitudinal sectional view 20 through a die, with a plunger in elevation, showing the method of extruding a billet having a surface alloy to form a valve of my invention.

Figure 2 is a longitudinal sectional view of a chromized billet or slug. 25.

Figure 3 is a longitudinal sectional view of a partially formed valve after thel extrusion process has taken place.

Figure 4 is a longitudinal sectional view of a valve having a head thereon finished by a forging 30| operation. Y

As shown on the drawing:

The reference numeral l0 indicates a billet or slug comprising a foundation metal ll and a surface alloy l2 formed thereon by a cementation 35. process such as described in the above identified Kelley patent. The foundation metal Il may be iron or steel, nickel, molybdenum, tungsten or an alloy of any one or more of these with iron. The surface alloy l2 is an alloy of the foundation 40. metal and some other metal, such as chromium, aluminum, or the like. Since an alloy of iron and chromium has particularly good resistance to heat and corrosion and therefore is especially adapted for use in the manufacture of valves, the 45. invention willl be described with reference to a valve having a chromized surface. It will be understood, however, that other metals may be used in the forming of the surface alloy.

The heated billet l0 is placed in a recess I3 of 50, a die block l to effect the extrusion of the metal of the billet. The recess i3 is slightly larger in diameter than the diameter of the cylindrical billet it, the inner wall of the recess tapering at the bottom to provide a generally conically Ation 22.

shaped neck-portion Il and a bore I6 of reduced diameter. The die block .Il is suitably formed in two parts, an upper member I8 constituting the die proper and a lower member I1 provided with a passage I8 for the circulation of a cooling fiuid.

A plunger I8 carrying a cylindrical head 20 of substantially the same diameter as that of the recess I3 is adapted to be forced down into said recess to snugly fit the same and extrude metal from the billet l0 through the throat I5 and bore I6. In its extreme lower position, the head of the plunger assumes the position indicated in dotted lines in Fig. l, the length of travel of the plunger being such as to leave a portion, indicated by the reference numeral 2|, of the billet unextruded.

After the extrusion process, the partially formed valve is in the form illustrated in Fig. 3 and comprises a head portion 2l and a stem por- 'I'he surface alloy layer I2 of iron and chromium extends over the partially formed head portion 2| and down along the stem portion 22, the thickness of the layer tapering off toward the extremity of the stem portion. Although the surface layer I2 is shown in Fig. 3 as extending the full length of the stem 22 and over the end thereof, it will be understood that it is not necessary for the surface alloy layer to completely cover the stem. Also, for purposes of illustration,

the relative thickness of the surface alloy layer is greatly exaggerated. In the case of the original billet, for instance, the depth of the penetration of the iron-chromium alloy may be only between 0.030 and 0.040 inch. This amount of penetration can be obtained in the case of an iron -or steel foundation metal by heating the billet under non-oxidizing conditions or in a g vacuum in contact with powdered metallic chromium to a temperature of from 1200 to 13507 C. for about four hours or more.

The partially finished valve head 2I is next subjected to a forging operation, or a combined upsetting and forging operation to produce an enlarged head portion 23 (Fig. 4) having a conical seat engaging surface 24. The usual machining operations may be performed to provide a finished valve and a portion of the stem may be milled out, as at 25, to provide a reduced portion for receiving the valve spring retainer lock. In the nshed valve, the layer of surface alloy I2 will be slightly thicker over the top of the head portion and the thickness will slightly diminish toward the extremity of the stem protion 22.

Due to the heavy mechanical work performed in the extruding and forging operation, the grain size of the iron-chromium alloy and of the ferrous foundation metal or alloy is considerably reduced, refining the metal to give maximum strength and fatigue resistance.

I'he resulting valve is therefore strong and, on the head and part of the stem at least, heat and corrosion resistant. Furthermore, the chromized surface of the valve possesses considerable hardness, which reduces wear in the valve stem guides.

The foundation metal of the billet used in forming a valve of my invention may suitably be a chrome-nickel steel,l such as SAE specifications No. 3140, or a common carbon steel, such as SAE specifications No. 1020. Other metals, however, may be used for a foundation metal, or alloys of such other metals as nickel, molybdenum, or tungsten. In fact any of the metals commonly used in the commercial manufacture of valves may be employed in my method as the foundation metal.

I am aware that many changes may be made and numerous details of construction 'may be varied through a wide range without departing from the principles of this invention, and I, therefore, do not purpose limiting the patent granted hereon otherwise than necessitated by the prior art.

I claim as my invention:

l.. The method of making a chromized` valve, which comprises chromizing a cylindrical billet to a depth of 0.03 to 0.04 inch and extruding said billet to form a stem and head having a chromized surface layer tapering off in thickness from the head toward the stern.

2. The method of making a one-piece valve having a thin surface alloy, which comprises providing a metal billet or slug with the desired thin surface alloy by a cementation process and extruding said billet to form said valve and reduce the grain size of the metal thereof and of the surface alloy.

3. A one-piece poppet valve comprising a head and a stern of ferrous foundation metal having a thin cementized surface alloy thereon different from said foundation metal, said stem having been extruded down from a billet of the foundation metal and the surface alloy to reduce the grain size of the alloy.

4. A one-piece poppet valve comprising a head and a stem of ferrous foundation metal having a chromized surface alloy of only a few hundredths of an inch in thickness and of inwardly decreasing chrome content, said stem having been worked down from a billet of the-foundation metal and surface alloy, and the head formed therefrom by a forging operation to greatly reduce the grain size of the chromized alloy.

5. The method of making a one-piece poppet valve having a thin surface alloy which comprises chromizing a metal billet to a depth of a few hundredths of an inch, and extruding said billet to form a stem and head having a chromizedsurface of a reduced grain size.

FREDERICK C. CRAWFORD.

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