Ductile iron

Inactive Publication Date: 2011-09-01
MITSUBISHI HEAVY IND LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0025]According to the present invention, by adopting the composition described above, a ductile iron having superior high-temperature strength and oxidation resistance as well as excellent ductibility can be produced at low cost.
[0026]A turbine housing, exhaust manifold, and turbine housing-integrated exhaust manifold produced using the ductile iron of the present invention are able to satisfactorily withstand usage under high-temperature conditions of 800° C. or higher.

Problems solved by technology

In recent years, improvements in fuel consumption driven by environmental regulations have resulted in a tendency for increased engine exhaust gas temperatures.
However, these materials include large amounts of Ni and Cr within the raw materials, meaning the raw material costs are high.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0040]Table 1 shows the element composition of ductile iron test pieces of sample numbers 1 to 13.

TABLE 1Sam-pleNum-Composition (mass %)berCSiMnMoVWCrMg12.984.680.420.410.29—0.320.04322.974.670.390.220.28—0.320.04233.034.620.400.820.30—0.300.04042.994.640.401.830.28—0.280.04252.924.650.390.100.30—0.290.04263.074.680.382.200.30—0.310.04072.974.620.380.390.29—0.100.03983.014.670.400.400.31—0.820.04292.994.660.410.400.30—0.050.043103.004.650.410.390.31—1.200.040113.064.630.390.400.30——0.042121.804.620.400.390.30—0.300.040133.063.300.400.390.28—0.280.042

[0041]Raw materials were blended and melted to achieve the element compositions detailed in Table 1, and each composition was then cast in the shape of a Y-block B-type test piece prescribed in JIS G 5502, thus completing preparation of test pieces for sample numbers 1 to 13. Subsequently, each test piece was subjected to a heat treatment at 915° C. for 3 hours to effect ferritization.

[0042]Using the method prescribed in JIS G 5502, the ...

example 2

[0053]Table 2 shows the element composition of ductile iron test pieces of sample numbers 1 and 14 to 18.

TABLE 2Sam-pleNum-Composition (mass %)berCSiMnMoVWCrMg12.984.680.420.410.29—0.320.043142.994.620.400.400.290.180.300.039153.014.680.400.410.290.310.330.043163.034.600.410.400.300.950.320.045172.984.640.420.390.290.070.300.043183.014.680.400.410.291.210.310.044

[0054]Using the same method as example 1, test pieces were prepared using sample numbers 14 to 18 and subsequently subjected to ferritization. Measurement of the spheroidization rate using the method described in JIS G 5502 revealed a spheroidization rate of at least 90% for each of the test pieces.

[0055]Each of the test pieces from sample numbers 14 to 18 was measured for 0.2% yield strength and oxidation weight loss at 800° C. FIG. 5 illustrates the 0.2% yield strength ratio for each test piece, referenced against the ductile iron test piece of sample number 1. In this figure, the vertical axis represents the 0.2% yield st...

example 3

[0058]Table 3 shows the element composition of ductile iron test pieces of sample numbers 1 and 19 to 22.

TABLE 3Sam-pleNum-Composition (mass %)berCSiMnMoVNbCrMg12.984.680.420.410.29—0.320.043193.034.580.410.410.310.040.320.041203.004.630.400.410.290.090.310.040213.034.610.400.390.300.270.320.045223.044.600.430.390.300.350.310.041

[0059]Using the same method as example 1, test pieces were prepared with the element compositions detailed for sample numbers 19 to 22. Following a homogenized heat treatment for one hour at 1,200° C., a heat treatment was performed at 915° C. for 3 hours to effect ferritization. Measurement of the spheroidization rate using the method described in JIS G 5502 confirmed a spheroidization rate of at least 90% for each of the test pieces. Subsequently, each of the test pieces was measured for 0.2% yield strength and oxidation weight loss at 800° C.

[0060]FIG. 8 illustrates the 0.2% yield strength ratio for each test piece, referenced against the ductile iron tes...

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Abstract

A ductile iron having superior high-temperature strength and oxidation resistance at temperatures exceeding 800° C. compared with conventional high Si and Mo ductile iron. The ductile iron comprises, in terms of mass ratio, carbon: 2.0 to 4.0%, silicon: 3.5 to 5.0%, manganese: not more than 1.0%, chromium: 0.1 to 1.0%, molybdenum: 0.2 to 2.0%, vanadium: 0.1 to 1.0%, and magnesium: 0.02 to 0.1%, with the remainder being composed of iron and unavoidable impurities.

Description

TECHNICAL FIELD[0001]The present invention provides a ductile iron having superior high-temperature strength and oxidation resistance.BACKGROUND ART[0002]Ductile iron exhibits excellent high-temperature strength and oxidation resistance, and is used in turbine housings and exhaust manifolds of turbocharger in the diesel engines of passenger vehicles and industrial machinery, and the like. In recent years, improvements in fuel consumption driven by environmental regulations have resulted in a tendency for increased engine exhaust gas temperatures. Turbine housings and exhaust manifolds are used under conditions where they are subjected to rapid temperature variation as a result of repeated exposure to high temperatures generated by the exhaust gases, and therefore require superior levels of high-temperature strength and oxidation resistance.[0003]A high Si and Mo ductile iron (ductile cast iron) is conventionally used as the material for turbine housings, and the service temperature ...

Claims

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Application Information

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IPC IPC(8): C22C37/06C22C37/04C22C37/10
CPCC22C37/04C22C37/10C22C37/06C21D5/00
Inventor ARAI, TAKASHI
Owner MITSUBISHI HEAVY IND LTD
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