KR20070028809A - Composition of Spheroidal Graphite Iron for Engine Exhaust Manifold - Google Patents

Abstract

A composition of spheroidal graphite cast iron for engines exhaust manifold, which improves oxidation resistance by containing Cr and Al in Fe, improves strength at high temperatures by containing Nb or V in Fe, and obtains oxidation resistance and strength at high temperatures by containing C, Si, Mn, P, S and Mo in Fe, is provided. A composition of spheroidal graphite cast iron for engines exhaust manifold comprises 0.1 to 2.0 wt.% of Cr, 0.05 to 0.4 wt.% of Al, 0.01 to 1.0 wt.% of Nb or V, 2.9 to 3.8 wt.% of C, 4.0 to 4.5 wt.% of Si, 0.5 wt.% or less of Mn, 0.04 wt.% or less of P, 0.02 wt.% or less of S, 0.5 to 1.0 wt.% of Mo, and the balance of Fe and other inevitable impurities. A composition of spheroidal graphite cast iron for engines exhaust manifolds comprises 0.1 to 2.0 wt.% of Cr, 0.05 to 0.4 wt.% of Al, 0.005 to 0.5 wt.% of Nb, 0.005 to 0.5 wt.% of V, 2.9 to 3.8 wt.% of C, 4.0 to 4.5 wt.% of Si, 0.5 wt.% or less of Mn, 0.04 wt.% or less of P, 0.02 wt.% or less of S, 0.5 to 1.0 wt.% of Mo, and the balance of Fe and other inevitable impurities.

Description

Composition of Ferritic Ductile Cast Iron for engine's exhaust manifold}

1 is a graph showing the results of the oxidation resistance test for 300 hours in an exhaust gas atmosphere of 700 ℃, 950 ℃ using the alloy of the Example and Comparative Example 1 according to the present invention.

The present invention relates to a composition of spheroidal graphite iron for an engine exhaust manifold, and more particularly, to include iron in an amount of 0.1 to 2.0% by weight of chromium (Cr) and 0.05 to 0.4% by weight of aluminum (Al) to improve oxidation resistance. Of course, in order to improve the high temperature strength, Nb or V 0.01 to 1.0% by weight, carbon (C) 2.9 to 3.8% by weight, silicon (Si) 4.0 to 4.5% by weight, manganese (Mn) 0.5% by weight or less, 0.04 wt% or less of phosphorus (P), 0.02 wt% or less of sulfur (S), and 0.5 to 1.0 wt% of molybdenum (Mo), thereby providing spherical graphite cast iron for engine exhaust manifolds having excellent oxidation resistance and high temperature strength at high temperatures. It relates to a composition.

In general, the required properties of the engine exhaust system materials were improved oxidation resistance and high temperature strength.

Therefore, even in the case of nodular graphite cast iron for exhaust manifolds, silicon-molybdenum (Si), which contains much silicon oxide (Si) and molybdenum (Mo), which is a high-temperature strength-improving element, is satisfied to satisfy the requirements. Nodular graphite iron has been used.

However, the temperature of the exhaust gas is rapidly increasing due to the change of the catalyst form due to the improvement of the engine output and the tightening of the exhaust gas regulations. As a result, the oxidation resistance and the high temperature strength requirements of the existing nodular cast iron are not satisfied. .

The present invention has been made in view of the above point, in order to improve the oxidation resistance in iron, including 0.1 to 2.0% by weight of chromium (Cr), 0.05 to 0.4% by weight of aluminum (Al), as well as improving the high temperature strength In order to contain Nb or V 0.01 to 1.0% by weight, carbon (C) 2.9 to 3.8% by weight, silicon (Si) 4.0 to 4.5% by weight, manganese (Mn) 0.5% by weight or less, phosphorus (P) 0.04 weight To provide a composition of spherical graphite cast iron for an engine exhaust manifold having excellent oxidation resistance and high temperature strength at a high temperature of 0.0% or less, sulfur (S) of 0.02% or less, and molybdenum (Mo) of 0.5% to 1.0% by weight. There is this.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The composition of spherical graphite iron for automobile engine exhaust manifold according to the present invention,

0.1 to 2.0% Cr, 0.05 to 0.4% Al, 0.01 to 1.0% Nb or V, 1.0 to 1.0% C, 2.9 to 3.8% C, 4.0 to 4.5% Si, 0.5% or less Mn, 0.04% or less P, S It is characterized by consisting of 0.02% by weight or less, Mo 0.5 ~ 1.0% by weight, and the balance of Fe and other unavoidable impurities.

As a preferred embodiment, Cr 0.1 ~ 2.0%, Al 0.05 ~ 0.4%, Nb 0.005 ~ 0.5%, V 0.005 ~ 0.5%, C 2.9 ~ 3.8%, Si 4.0 ~ 4.5%, Mn 0.5% % Or less, P 0.04% or less, S 0.02% or less, Mo 0.5 to 1.0% by weight, and the balance of Fe and other unavoidable impurities.

In general, the cast iron used for the engine exhaust system of the automobile uses an alloy of carbon, silicon, manganese, phosphorus, molybdenum and the like.

Table 1 below shows the composition and content of spherical graphite iron for automobile engine exhaust manifolds according to the present invention.

As shown in Table 1, 0.1 to 2.0% by weight of chromium (Cr), 0.05 to 0.4% by weight of aluminum (Al), 0.01 to 1.0% by weight of Nb (niobium) or V (vanadium), and 2.9 to 3.8 of carbon (C) Weight%, silicon (Si) 4.0-4.5 weight%, manganese (Mn) 0.5 weight% or less, phosphorus (P) 0.04 weight% or less, sulfur (S) 0.02 weight% or less, molybdenum (Mo) 0.5-1.0 weight%, And residual amounts of iron (Fe) and other unavoidable impurities.

In the present invention, in order to increase the oxidation resistance of the material and to ferrite the structure, the content of silicon (Si) is constantly adjusted to the above composition, and chromium (Cr) and aluminum (Al) are added in combination.

At this time, the content of chromium is appropriate in the range 0.1 to 2.0% by weight. This is because, if the content of chromium is lower than 0.1% by weight, the oxidation resistance is insufficient, and if the content of chromium is higher than 2.0% by weight, it is not preferable due to a decrease in ductility.

In addition, the content of aluminum (Al) is preferably added to 0.05 to 0.4% by weight of the total content. Because, when the aluminum content is less than 0.05% by weight, the oxidation resistance is insufficient, and when the aluminum content is higher than 0.4% by weight, brittleness rapidly increases due to dispersion precipitation of iron aluminum carbide (FeAlC).

The content of silicon (Si) is preferably in the range of 4.0 to 4.5% by weight. This is because, when the silicon content is lower than 4.0% by weight, the oxidation resistance is insufficient, and when the silicon content is higher than 4.5% by weight, it is not preferable due to increased brittleness.

In addition, carbon (C) is suitable 2.9 ~ 3.8% by weight. Because, when the carbon content is lower than 2.9% by weight, the workability is lowered due to the increase in hardness, and when the carbon content is higher than 3.8% by weight, the process becomes overprocess due to overexposure, resulting in a significant decrease in physical properties. Because it becomes.

In addition, the present invention adds 0.01 to 1.0% by weight of niobium (Nb) or vanadium (V) in order to improve the high temperature strength of the material. Niobium and vanadium combine with carbon to form fine carbides and improve high temperature strength and thermal fatigue resistance.

In addition, the niobium and vanadium suppress carbide production of carbon to improve oxidation resistance and machinability. For this purpose, the content of niobium and vanadium is preferably 0.01% by weight or more.

However, when a large amount of niobium and vanadium is added, carbides are formed at the grain boundaries, and carbon is depleted by the formation of carbides of niobium and vanadium, so that castability is lowered. Thus, when niobium and vanadium are simultaneously added, 0.5 wt. It is preferable to set it as% or less (total 1.0 weight% or less).

In addition, since niobium and vanadium have different temperature ranges for generating carbides, a precipitation strengthening action can be expected over a wide temperature range.

Therefore, a great effect can be anticipated by adding either niobium and vanadium or compound addition.

In addition, it is preferable to include molybdenum in the range of 0.5 to 1.0% by weight of the total content.

At this time, when the molybdenum is lower than 0.5% by weight, the lack of high temperature strength occurs, and when higher than 1.0% by weight, the possibility of shrinkage defects is high.

Because molybdenum (Mo) is thermodynamically stable at high temperatures, the molten metal (carbide with carbon) is first generated in the molten metal during casting production, depleting carbon.

In addition to the above components, the present invention includes 0.5 wt% or less of manganese, 0.04 wt% or less of phosphorus (P), and 0.02 wt% or less of sulfur (S) in the composition of cast iron for automobile engine exhaust systems. The manganese, phosphorus and sulfur are impurity introduced during the injection of molten metal and are regulated below the above range.

Hereinafter, the present invention will be described in more detail based on the following examples, but the present invention is not limited by the following examples.

Example

Using the materials of the composition and content shown in Table 2 below, conventional nodular cast iron for engine exhaust manifold (Comparative Example 1 and Comparative Example 2) and nodular graphite cast iron for engine exhaust manifold according to the present invention (Example) Was produced.

Test Example 1 : Oxidation Resistance Test

The results of the oxidation resistance test for 300 hours using the alloy of Example and Comparative Example 1 in a 700 ℃, 950 ℃ exhaust gas atmosphere are shown in Table 2 below.

As shown in Table 1, it was observed that the amount of oxidation is significantly reduced compared to the alloy of the comparative example.

Test Example 2 : High Temperature Strength Experiment

Table 1 shows the results of the high temperature tensile test at 700 ° C., 800 ° C., and 900 ° C. using the alloys of Example and Comparative Example 2.

As shown in Table 3, in the case of the embodiment according to the present invention it was observed that the high temperature strength is improved compared to the alloy of the comparative example.

As described above, according to the composition of the spheroidal graphite iron for the engine exhaust manifold according to the present invention, the present invention has been devised in view of the above-mentioned, chromium (Cr) 0.1 ~ to improve the oxidation resistance to iron 2.0 wt%, aluminum (Al) 0.05 ~ 0.4 wt%, as well as Nb and V 0.01 to 1.0 wt% to improve the high temperature strength, carbon (C) 2.9 ~ 3.8 wt%, silicon ( Si) 4.0-4.5 wt%, manganese (Mn) 0.5 wt% or less, phosphorus (P) 0.04 wt% or less, sulfur (S) 0.02 wt% or less, and molybdenum (Mo) 0.5-1.0 wt% It is possible to improve the oxidation resistance and high temperature strength.

Claims (2)

0.1 to 2.0% Cr, 0.05 to 0.4% Al, 0.01 to 1.0% Nb or V, 1.0 to 1.0% C, 2.9 to 3.8% C, 4.0 to 4.5% Si, 0.5% or less Mn, 0.04% or less P, S A composition of spheroidal graphite iron for an engine exhaust manifold, comprising 0.02% by weight or less, Mo 0.5-1.0% by weight, and residual amounts of Fe and other unavoidable impurities. 0.1 to 2.0 wt% Cr, 0.05 to 0.4 wt% Al, 0.005 to 0.5 wt% Nb, 0.005 to 0.5 wt%, C 2.9 to 3.8 wt%, Si 4.0 to 4.5 wt%, Mn 0.5 wt% or less, P 0.04 A composition of nodular graphite cast iron for an engine exhaust manifold, comprising by weight percent or less, S 0.02 weight percent or less, Mo 0.5 to 1.0 weight percent, and a balance of Fe and other unavoidable impurities.

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