US3370941A - Tungsten-containing alloy cast iron useful for internal combustion engine parts - Google Patents

Description

United States Patent Ofiice 3,370,941 Patented Feb. 27, 1968 This is a continuation-in-part of my copending application Ser. No. 496,150, filed Oct. 14, 1965, and entitled, Engine Tappet and Camshaft.

This invention relates to valve train components, particularly tappets, camshafts, and rocker arms for internal combustion engines, and more specifically relates to novel valve train components particularly suited to high compression engines having extended oil change periods.

In recent years, it has been discovered that excessive Wear and potential failure occurs not infrequently for valve train components especially tappet surfaces and cooperative cam lobes of camshafts, but also rocker arms. Closer studies have shown frequent loss of hardness in these items, to a detrimental extent. This severe loss of hardness was believed caused by excessive superficial heat on the parts. This heat was found to be generated by direct metal-to-metal contact of these parts, with such contact resulting upon lubrication breakdown occurring in present day high compression engines which frequently have long periods between oil changes.

Extensive experimetal testing was then conducted under the direction of the inventor herein, to find a solution to this problem, specifically by providing special valve train components formed of a special material. This experimentation and testing has resulted in a unique valve train material capable of retaining operative hardness even at high temperatures encountered with direct metal-to-metal contact in high compression engines.

It is, therefore, an object of this invention to provide valve train components of a material particularly suitable for high compression engines having long periods between oil changes. The novel tappets, camshafts and rocker arms are capable of maintaining operative hardness, without substantial loss of hardness even at high temperatures encountered with superficial heat caused by direct metalto-metal contact with lubricant breakdown.

Another object of this invention is to provide a novel tappet, a novel camshaft, and a novel rocker arm having excellent wear characteristics and long useful life even at excessive temperatures caused by metal-to-rnetal contact between the tappet and cam lobe with lubricant breakdown.

These and other objects of this invention will become apparent upon studying the following specification.

conventionally, tappets, camshafts and rocker arms are formed of hardenable iron. Under normal temperature conditions, hardenable iron provides a satisfactory material since it has a substantial hardness which it retains up to tempertaures of about 300 F. However, as noted pre viously herein, with high compression engines normally encountered today, particularly when coupled with long period oil changes, lubricant breakdown can occur, causing direct metal-to-metal contact between these components. This creates substantial superficial heat, elevating the temperatures a great deal above the normal 300 maximum. At these temperatures, the loss of hardness of hardenable iron becomes very significant, causing these wear surfaces to become badly damaged and prone to failure.

Through experimentation and testing, a novel valve train component material was developed which has been found to have excellent hardness retention qualities, with only insignificant loss of hardness resulting even at substantially elevated temperatures of 600-300" F. Tests of 500 or more hours duration have shown wear on the parts to be minor at elevated temperatures, with operative hardness being maintained.

The novel material is basically of the following composition range:

Element: Percent by weight Carbon 3.00-3.55 Silicon 2.00-2.90 Manganese 0.70-1.10 Phosphorous 1 0.00-0.20 Sulfur 1 000-010 Nickel 0.15-0.70 Chromium 0.40-1.25 Molybdenum 0.15-0.70 Tungsten 0.50-10.00 Iron Balance 1 1m purity.

The phosphorous and sulfur elements are normal impurities which are almost invariably present in these ferrous alloys. They are not required and should not exceed the maximum percentages indicated.

The controlled percentage of tungsten is essential and crucial in this tappet and camshaft composition. It has been found that amounts less than about /2 of tungsten are not sufiicient to prevent significant loss of hardness at elevated temperatures. It has also been found that amounts greater than about 10%, although usable, really add nothing further to the hardness retention characteristics, but merely add expense.

Experimentation has shown that a tungsten range of 3.00 to 4.00% is preferred and optimum for this novel composition. The most preferred composition is substantially as follows:

Element: Percent by weight Carbon 3.30 Silicon 2.30 Manganese 0.90 Nickel 0.50 Chromium 1.10 Molybdenum 0.50 Tungsten 4.00

. Iron Balance Here again, the sulfur and phosphorous may be present as minor impurities.

Typical examples of the novel composition tested are the following:

EXAMPLE 1 Element: Percent by weight Carbon 3.35 Silicon 2.60 Manganese 0.96 Nickel 0.25 Chromium 0.46 Molybdenum 0.27 Tungsten 2.90

Iron {and minor phosphorous and sulfur impurities) Balance This composition, when tested, showed an excellent initial hardness, and importantly, showed an excellent retention of hardness, with only insignificant 'l-oss even at temperatures of up to about 900 F. For example, with an initial hardness of about -65 points as measured on the Rockwell C. Scale, the hardness loss at 600 F. was only 1 /2 points, at 800 F. was only 3 /2 points, and at 900 F. was only 5 /2 points.

3 EXAMPLE 2 Element: Percent by weight Carbon 3.32 Manganese 1.02 Molybdenum 0.26 Silicon 2.69 Chromium 0.69

Nickel 0.23

Tungsten 4.60 Iron (and minor amounts of phosphorous and sulfur impurities) Balance This particular composition had a higher percentage of tungsten than the previous example, and showed greater hardness retention characteristics. For example, at 600, hardness loss was only 1 /4 points, at 800 was only 2 /2 points, at 900 was only 4 /4 points, and at 1000 was only 6 /2 points.

EXAMPLE 3 Element: Percent by weight Carbon 3.30

Silicon 2.30-

Manganese 0.90 Nickel 0.50

Chromium 1.10

Molybdenum 0.50 Tungsten 4.00 Iron Balance As indicated previously, in the preferred tungsten range of 3.00 to 4.00 loss of hardness of the tappet or camshaft is at a minimum. At 600", the loss of hardness Was 1 point, and at 800 the loss of hardness was 3 points.

Preferably, the complete tap-pet, complete camshaft, and complete rocker arm are formed of the novel material. Alternatively, just the bearing surfaces could conceivably be formed of the special material.

The components may be formed by any known technique, such as casting. The material may be melted by any standard melting method, then poured into suitable molds, such as sand molds, carbon dioxide molds, shell molds, or permanent molds. It can even be chilled against a carbon plate or similar heat extracting medium. It may be hardened by normal heat treating techniques such as those conventionally used on hardenable iron, a typical heat treatment including heating to 1,580 F. holding about thirty minutes, then quenching in oil. Since these latter melting, casting, cooling and heat' treating steps are all conventional, they are not described in further detail.

It is conceivable that certain minor variations from the specific compositions noted may be made within the concept presented. The invention is intended to be limited only by the scope of the appended claims and the reasonable equivalents thereto.

I claim:

1. An internal combustion engine valve train component comprising a body having at least a bearing surface consisting essentially of the following composition:

Element: Percent by weight Carbon 3.00-3.55

Silicon 200-290 Manganese 0.70-1.10 Nickel 0.15-0.70

Chromium 0.40-1.25

Molybdenum 0.15-0.70 Tungsten 0.50-10.00

Iron (plus minor sulfur and phosphorous impurities) Balance 2. The internal combustion engine valve train component in claim 1 wherein said entire body is of said composition.

3. The structure in claim 1 wherein said component is a tappet.

4. The structure in claim 1 wherein said component is a camshaft.

5. The structure in claim 1 wherein said component is a rocker arm.

6. The internal combustion engine valve train component wherein said com-position consists essentially of:

Element: Percent by weight Carbon 3.00-3.55

Silicon 2.00-2.90

Manganese 0.70-1.10 Nickel 0.15-0.70

Chromium 0.40-1.25

Molybdenum 0.15-0.70 Tungsten 3.00-4.00 Iron (plus minor sulfur and phosphorous impurities) Balance 7. The internal combustion engine valve train component in claim 6 wherein said entire body is of said composition.

8. The structure in claim 6 wherein said component is a tappet.

9. The structure in claim 6 wherein said component is a camshaft.

19. The structure in claim 6 wherein said component is a rocker arm.

References Cited UNiTED STATES PATENTS 1,876,724 9/1932 Mitchell et al. 75l28 1,876,725 9/1932 Mitchell et al. 7512 8 XR 1,910,034 5/1933 Mitchell et al. 75-128XR 1,973,263 9/1934 Mitchell et al. 75l28 2,171,083 8/1939 Ervin 75-128 XR 2,227,065 12/1940 Charlton 75128 XR 2,962,397 11/1960 Thompson 148-35 XR 3,073,292 1/1963 Behnke et al. 75-'128 XR 3,198,631 8/1965 Jones 75-128 DAVID L. RECK, Primary Examiner.

P. WEINSTEIN, Assislant Examiner.

Claims (1)

1. AN INTERNAL COMBUSTION ENGINE VALVE TRAIN COMPONENT COMPRISING A BODY HAVING AT LEAST A BEARING SURFACE CONSISTING ESSENTIALLY OF THE FOLLOWING COMPOSITION: ELEMENT: PERCENT BY WEIGHT CARBON 3.00-3.55 SILICON 2.00-2.90 MANGANESE 0.70-1.10 NICKEL 0.15-0.70 CHROMIUM 0.40-1.25 MOLYBDENUM 0.15-0.70 TUNGSTEN 0.50-10.00 IRON (PLUS MINOR SULFUR AND PHOSPHOROUS IMPURITIES) BALANCE