Vermicular cast iron alloy and internal combustion engine head

Abstract

The present invention relates to the technological field of cast iron alloys for automotive and similar applications. Problem to be solved: Presently, structural parts of internal combustion engines are made of gray cast iron alloys that rarely have a tensile strength limit range greater than 350 MPa or vermicular cast iron alloys that do not remain stable at high temperatures. Solution of the problem: It is disclosed a vermicular cast iron alloy that, due to the addition of amounts of Molybdenum, Copper and Tin, with Hot Resistance Factor from 0.5 to 1.7% (HRF=3×(% Mo)+1×(% Sn)+0.25×(% Cu)) achieves a tensile strength limit of 500 to 550 MPa at room temperature and up to 300° C., and a tensile strength limit of 430 to 450 MPa at 400° C.

Claims

1. VERMICULAR CAST IRON ALLOY, containing the usual contents of the elements carbon (3.0 to 3.9%), manganese (0.1 to 0.6%), silicon (1.5 to 3.0%), magnesium (0.005 to 0.030%), cerium (0.005 to 0.030%) and residual elements such as sulfur (less than 0.030%) and phosphorus (less than 0.050%) are also present, characterized by the fact that it comprises a vermicular cast iron alloy with the following alloy elements, in their respective proportions: Tin, existing in a range of 0.01% to 0.13% of the total amount of the alloy, Copper, existing in a range of 0.2% to 1.3% of the total amount of the alloy, and Molybdenum, existing in a range of 0.05% to 0.40% of the total amount of the alloy; these levels are balanced so that the Hot Resistance Factor (HRF) is between 0.5 and 1.7%, such factor defined by:
HRF=3×(% Mo)+1×(% Sn)+0,25×(% Cu)(percentages by weight) wherein chromium is absent in the alloy, the matrix of the microstructure of said vermicular cast iron alloy comprises a fine pearlitic matrix comprising pearlite and with graphite particles predominantly in vermicular form and with the presence of graphite nodules up to 20%, and wherein an average interlamellar spacing of the pearlite is about 0.25 μm.

2. INTERNAL COMBUSTION ENGINE HEAD, containing the usual contents of the elements carbon (3.0 to 3.9%), manganese (0.1 to 0.6%), silicon (1.5 to 3.0%), magnesium (0.005 to 0.030%), cerium (0.005 to 0.030%), and residual elements such as sulfur (less than 0.030%) and phosphorus (less than 0.050%) are also present, characterized by the fact that it comprises the following alloy elements: Tin, existing in a range of 0.01% to 0.13% of the total amount of the alloy, Copper, existing in a range of 0.2% to 1.3% of the total amount of the alloy, and Molybdenum, existing in a range of 0.05% to 0.40% of the total amount of the alloy; these levels are balanced so that the Hot Resistance Factor (HRF) is between 0.5 and 1.7%, such factor defined by:
HRF=3×(% Mo)+1×(% Sn)+0,25×(% Cu)(percentages by weight) wherein chromium is absent in the alloy, the matrix of the microstructure of said vermicular cast iron alloy comprises a fine pearlitic matrix comprising pearlite and with graphite particles predominantly in vermicular form and with the presence of graphite nodules up to 20%, and wherein an average interlamellar spacing of the pearlite is about 0.25 μm.

3. VERMICULAR CAST IRON ALLOY, comprising at least the following alloy elements, in the respective proportions: Carbon, existing in a range of 3.0% to 3.9% of the total amount of the alloy, Manganese, existing in a range of 0.1% to 0.6% of the total amount of the alloy, Silicon, existing in a range of 1.5% to 3.0% of the total amount of the alloy, Magnesium, existing in a range of 0.00% to 0.030% of the total amount of the alloy, Cerium, existing in a range of 0.005% to 0.030% of the total amount of the alloy, Sulfur, existing in a range of less than 0,030% of the total amount of the alloy Phosphorus, existing in a range of less than 0.050% of the total amount of the alloy, said vermicular cast iron alloy being especially characterized by the fact that it further comprises the following alloy elements, in the respective proportions: Tin, existing in a range of 0.01% to 0.13% of the total amount of the alloy, Copper, existing in a range of 0.2% to 1.3% of the total amount of the alloy, and Molybdenum, existing in a range of 0.05% to 0.40% of the total amount of the alloy; these levels are balanced so that the Hot Resistance Factor (HRF) is between 0.5 and 1.7%, such factor defined by:
HRF=3×(% Mo)+1×(% Sn)+0,25×(% Cu)(percentages by weight) wherein chromium is absent in the alloy, the matrix of the microstructure of said vermicular cast iron alloy comprises a fine pearlitic matrix comprising pearlite and with graphite particles predominantly in vermicular form and with the presence of graphite nodules up to 20%, and wherein an average interlamellar spacing of the pearlite is about 0.25 μm.

4. INTERNAL COMBUSTION ENGINE HEAD, being characterized by the fact that it is made of a vermicular cast iron alloy comprising the following alloy elements, in the respective proportions: Carbon, existing in a range of 3.0% to 3.9% of the total amount of the alloy, Manganese, existing in a range of 0.1% to 0.6% of the total amount of the alloy, Silicon, existing in a range of 1.5% to 3.0% of the total amount of the alloy, Magnesium, existing in a range of 0.00% to 0.030% of the total amount of the alloy, Cerium, existing in a range of 0.005% to 0.030% of the total amount of the alloy, Sulfur, existing in a range of less than 0,030% of the total amount of the alloy Phosphorus, existing in a range of less than 0.050% of the total amount of the alloy, Tin, existing in a range of 0.01% to 0.13% of the total amount of the alloy, Copper, existing in a range of 0.2% to 1.3% of the total amount of the alloy, and Molybdenum, existing in a range of 0.05% to 0.40% of the total amount of the alloy; these levels are balanced so that the Hot Resistance Factor (HRF) is between 0.5 and 1.7%, such factor defined by:
HRF=3×(% Mo)+1×(% Sn)+0,25×(% Cu)(percentages by weight) wherein chromium is absent in the alloy, the matrix of the microstructure of said vermicular cast iron alloy comprises a fine pearlitic matrix comprising pearlite and with graphite particles predominantly in vermicular form and with the presence of graphite nodules in up to 20%, and wherein an average interlamellar spacing of the pearlite is about 0.25 μm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will be described in greater detail based on the following figures, which:

(2) FIG. 1 illustrates graphics of mechanical properties results and microstructure of vermicular iron connected with Sn, Cu and Mo, compared to the conventional class #450. Block Y of 25 mm of thickness; and

(3) FIG. 2 illustrates the vermicular iron typical microstructure containing Sn, Mo and Cu, with HRF=1.15% (vermicular graphite particle and refined pearlite).

DETAILED DESCRIPTION OF THE INVENTION

(4) Thus, in order to achieve the above-mentioned technical objects and effects, it is described the vermicular cast iron alloy, according to the present invention.

(5) In this sense, it is the general merit of the invention to add molybdenum, copper and tin in balanced and suitable proportions to the list of alloy elements already conventionally used in vermicular cast iron, without the addition of other elements capable of forming hard phosphides such as, for example, chromium associated with high levels of phosphorus (>0.05%) and others.

(6) Among the possible alloy elements already used in vermicular cast iron, in their typical compositions and usual contents, such as carbon (3.0 to 3.9%), manganese (0.1 to 0.6%), silicon (1.5 to 3.0%), magnesium (0.005 to 0.030%), cerium (0.005 to 0.030%), and residual elements such as sulfur (less than 0.030%) and phosphorus (less than 0.050%), it is added to the vermicular cast iron alloy, object of the present invention: Molybdenum, Tin and Copper.

(7) More particularly, such alloy elements are especially added in the following proportions: Molybdenum, in a range of 0.05% to 0.40% of the total amount of the alloy. Tin, in a range of 0.01% to 0.13% of the total amount of the alloy. Copper, in a range of 0.2% to 1.30% of the total amount of the alloy.

(8) These quantities of molybdenum, copper and tin should be balanced, so that the Hot Resistance Factor (HRF) is between 0.5 to 1.7%. Such factor is defined here as:
HRF=3×(% Mo)+1×(% Sn)+0.25×(% Cu)(percentages by weight)

(9) Obviously, the vermicular cast iron alloy, object of the present invention, may contain still further typical impurities of cast irons, which do not alter or impair the desired features.

(10) As previously mentioned, said desired results—tensile strength limit of 500 to 550 MPa at ambient temperature and up to 300° C., and tensile strength limit of 430 to 450 MPa at 400° C.—are particularly achieved due to the addition of Molybdenum, Tin and Copper, in the aforementioned ranges and within the aforementioned Hot Resistance Factor. These additions of molybdenum, copper and tin may be carried out in the melting furnace, in the transport or pouring pan, in the pouring furnace, or in the pouring jet.

(11) As a final result of the addition of the above-listed alloy elements, in the proportions given above, by means of the process explained above, a vermicular iron is obtained, whose microstructure comprises a fine pearlite matrix, with predominantly vermicular form graphite particles and with the presence of graphite nodules of up to 20%, being the average interlamellar spacing of the pearlite reduced, for example, in a block Y of 25 mm of thickness, from 0.32 μm to 0.25 μm, as illustrated in the FIG. 1.

(12) It is also worth highlighting that the decrease in the average interlamellar spacing of the pearlite (FIG. 2) comprises one of the main causes of the increase in mechanical strength of the vermicular cast iron alloy, object of the present invention.

(13) Consequently, it becomes possible to manufacture an internal combustion engine head (and, incidentally, other structural parts of internal combustion engines) with said cast iron alloy containing the usual contents of carbon (3.0 to 3.9%), manganese (0.1 to 0.6%), silicon (1.5 to 3.0%), magnesium (0.005 to 0.030%), cerium (0.005 to 0.030%), and residual elements, such as sulfur (less than 0.030%) and phosphorus (less than 0.050%), being especially added Tin, in the range of 0.01 to 0.13% of the total amount of alloy, Copper, in a range of 0.2% to 1.3% of the total amount of the alloy, and Molybdenum, in a range of 0.05% to 0.40% of the total amount of the alloy, percentages expressed by weight. These quantities of molybdenum, copper and tin must be balanced, so that the Hot Resistance Factor (HRF) is between 0.5 to 1.7%. Such factor is defined by:
HRF=3×(% Mo)+1×(% Sn)+0.25×(% Cu)(percentages by weight)

(14) In any case, the same features of the microstructure matrix of the vermicular cast iron alloy (fine pearlite matrix with graphite particles predominantly in vermicular form and presence of graphite nodules in up to 20%), as well as the results desired (tensile strength limit of 500 to 550 MPa at room temperature and up to 300° C. and tensile strength limit of 430 to 450 MPa at 400° C.) are fully present in the internal combustion engine head.

(15) Consequently, these high values of hot strength allow a long life of the component and, alternatively, allows to revise the design of the dimension of the head, reducing section thicknesses, which also results in improved heat extraction conditions, important aspect in internal combustion engine heads.

(16) This means that the invention in question enables the development of superior performance engine heads, suitable for high engine operating temperatures and high levels of mechanical stress.