BR0309975B1 - gray cast iron alloy and cast internal combustion engine component. - Google Patents

Abstract

A substantially perlitic, grey cast iron alloy comprising, by weight, 3.2 - 3.49% carbon, 1.8 - 2.2% silicon, < 0.15% sulphur, < 0.15% phosphorus, 0.3 - 0.8% manganese, 0.2 - 0.4% chromium, 0.1 - 0.4% molybdenum, 0.03 - 0.3% vanadium, 0.3 - 1.0% copper, < 0.15% niobium, the balance iron and impurities.

Description

"GRAY Fused IRON ALLOY AND FUSED INTERNAL DECOMBUSTION ENGINE COMPONENT"

Background of the Invention

1. Field of the Invention

The present invention relates to a gray cast alloy. More specifically, the present invention relates to a substantially perlite gray cast iron further comprising binder forming elements for fatigue strength.

The invention further relates to an internal combustion demotor component cast from gray cast iron alloy according to the invention.

2. Description of the Prior Art

Gray cast iron is a more attractive material for, for example, internal combustion engine blocks for vehicles due to relatively low cost and good to excellent performance. Compositions within a wide range are previously known, such compositions usually being a compromise between properties, such as tensile strength, wear properties, etc., of the material when used and production properties, such as cost, machinability, etc.

Thus, for internal combustion engine cast blocks, a base material 0120 has a composition according to Table 1 below and a common standard alloy has a composition also according to Table 1, the standard alloyScania providing a gray cast iron with a perlite structure and a defect-free (pore-free) material due to a comparatively high carbon content.

However, although entirely acceptable in the present, a fatigue strength is currently desired as a complement to the present properties and may extend to the possible use of such a prior art gray cast iron.

It is an object of the present invention to provide a gray cast iron with a comparatively flawless structure offering good machining properties and having substantially improved fatigue strength compared to that of a standard alloy.

It is a further object of the present invention to provide a gray cast internal combustion engine component, such as an engine block, having a substantially improved fatigue strength compared to that of a standard alloy.

Brief Description of the Invention

The object of the present invention is obtained by a gray cast iron.

Further, the object of the present invention is obtained by a gray cast iron internal combustion engine component.

Brief Description of Drawing

Figure 1 shows Wöhler fatigue curves for a base alloy, a standard alloy and an alloy according to the invention.

Detailed Description of Preferred Accomplishments

In the following description all percentages given for elements in the specified alloys are given as weight percent.

The alloy according to the present invention is a gray cast iron having a substantially perlite structure, the carbon content being 3.2% to 3.49%. The comparatively high carbon content promotes a flawless structure. Additions of 0.2% to 0.4% chromium, having perlite / carbide stabilizing properties, provide a fine perlite structure.

Additions of 0.1% to 0.4% molybdenum, 0.03% to 0.3% vanadium, 0.007% to 0.015% titanium and <0.15% niobioatuam, in addition to their formation properties. carbide, as cores providing a thin perlite structure and flake graphite when fused (both as primary and secondary precipitated carbides). Molybdenum also stabilizes perlite at elevated temperatures.

Silicon is present in an amount of 1.8% to 2.2% promoting formation of gray iron.

0.3% to 0.8% manganese is present as a perlite stabilizing agent.

Copper, here in an amount of from 0.3% to 1.0%, promotes perlite formation and stabilizes perlite and also promotes fine structure formation.

Sulfur and phosphorus content should be kept below 0.15%.

Nitrogen, 0.005% to 0.017%, compresses graphite into flakes and promotes perlite formation, and aluminum, <0.01%, acts as a graphite forming agent. The gray cast iron alloy still comprises normal balance iron and impurities. The amounts of titanium, nitrogen and aluminum are in the normal range of impurities, but may be preferred.

Examples:

1500 kg batches were prepared, each batch being fused to four 300 kg engine blocks, casting starting at 1420 ° C and the temperature falling about 10 ° C during the casting procedure.

Ten different combinations, batch, demolibdenum, vanadium, titanium and niobium using a base alloy, were produced.

Also, the nitrogen and aluminum content was varied in 16 different batches with different nucleus deforming agents (inoculants).

Fatigue test samples were taken from each casting and fatigue tests were performed.

Also, batches matching the composition showing the best results from previous tests were produced and fatigue tested.

Results are shown in Figure 1, curve 3 corresponding to compositions within the decomposition ranges according to the invention, this composition also being shown in Table 1.

The gray cast irons according to the invention offer about 40% higher fatigue strength than a gray cast iron alloy and about 30% higher fatigue strength than a standard demotor block gray cast iron while still offering a satisfying gray cast iron. high performance with respect to machining, absence of defects, etc.

As mentioned above, the gray cast iron alloy according to the invention is extremely useful for cast components of internal combustion engines such as engine block components, the alloy combining machining ability, absence of defect and fatigue resistance. The alloy is also useful for other components such as cylinder heads, etc.

Table 1

Gray cast iron compositions,% by weight, according to the state of the art and the invention

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Claims (8)

1. Substantially perlite gray cast iron alloy, characterized in that it comprises by weight - 3,2% to 3,49% carbon, - 1,8% to 2,2% silicon, <0,15% sulfur, <0.15% phosphorus, - 0.3% to 0.8% manganese, - 0.2% to 0.4% chromium, - 0.1% to 0.4% molybdenum, - 0, 03% to 0.3% vanadium, - 0.3% to 1.0% copper, <0.15% niobium, - 0.007% to 0.015% titanium, - 0.005% to 0.017% nitrogen, and Iron balance and impurities. Alloy according to claim 1, characterized in that it comprises by weight - 3.3% to 3.4% carbon, - 1.8% to 2.2% silicon, <0.1% sulfur, <0,05% phosphorus, - 0,4% to 0,6% of manganese, - 0,2% to 0,4% of chromium, - 0,2% to 0,3% of molybdenum, and - 0.05% to 0.1% vanadium Alloy according to claim 1 or 2, characterized in that vanadium is present in an amount of less than 0.1%. Alloy according to claim 1, 2, or 3, characterized in that aluminum is present in an amount of less than 0.01%. Alloy according to any one of claims 1 to 4, characterized in that nickel is present in an amount of less than 0.1%. Alloy according to any one of claims 1 to 5, characterized in that the tin is present in an amount of less than 0.1%. 7. Internal combustion engine cast component, CHARACTERIZED by the fact that it is made of a substantially perlite gray cast iron alloy, said alloy, containing in% weight: - 3,2% to 3,49% of carbon, - 1,8% to 2.2% silicon, <0.15% sulfur, <0.15% phosphorus, - 0.3% to 0.8% manganese, - 0.2% to 0.4% chrome, - 0.1% to 0.4% molybdenum, - 0.03% to 0.3% vanadium, - 0.3% to 1.0% copper, - 0.007% to 0.013% titanium, <0, 15% niobium, - 0.005% to 0.015% nitrogen, <0.01% aluminum, and iron balance and impurities. Fused combustion engine component according to claim 7, characterized in that it is an engine block component or a cylinder head component.