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Castable aluminum alloy

a technology of aluminum alloy and cast aluminum, which is applied in the field of castable aluminum alloy to achieve the effects of reducing porosity, high strength, and less cos

Inactive Publication Date: 2005-09-15
GM GLOBAL TECH OPERATIONS LLC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0006] In an illustrative embodiment of the invention, a castable aluminum alloy comprises, in weight %, 0 to about 19% Si, 0 to about 5.0% Cu, 0 to about 1.5% Mg, up to about 3.0% Zn, up to about 2.0% Ni, up to about 0.3% Ti, greater than 0 to about 1.5 weight % Fe, about 0.2% to about 3.0% Mn, wherein a weight ratio of Mn / Fe is at least 0.6 when Fe is less than 0.4 weight % and weight ratio of Mn / Fe is at least 1.0 when Fe is equal to or greater than 0.4 weight % to reduce porosity and improve tensile strength of castings made from the alloy. The alloy optionally may include an appropriate amount of at least one of strontium or a rare earth metal.
[0007] Pursuant to a preferred embodiment of the invention, a castable aluminum alloy comprises, in weight %, 0 to 9.0% Si, 0 to about 5.0% Cu, about 0.15% to about 0.6% Mg, up to about 1.0% Zn, up to about 0.3% Ti, about 0.2% to about 0.8% Fe, about 0.3% to about 1.2% Mn, and balance Al, wherein the weight ratio of Mn / Fe is controlled to reduce porosity and increase tensile strength of castings made from the alloy.
[0008] Control of the Mn / Fe weight ratio pursuant to the invention can provide significantly less costly higher Fe-containing aluminum alloys (e.g. Fe content of about 0.4 weight % or greater) and / or higher Cu-containing aluminum alloys (e.g. Cu content of about 2.5 weight % or greater) for high strength while obtaining reduced microporosity and shrink porosity (macroporosity) and improved mechanical properties in castings made from the alloys.
[0010] The invention also envisions improved castings made from the above castable aluminum alloys as well as improved methods of casting same wherein both microporosity and shrinkage porosity (macroporosity) can be reduced in castings. The invention is further advantageous in that mechanical properties can be improved while achieving a reduction in casting porosity. Other advantages and features of the present invention will become apparent from the following description.

Problems solved by technology

Many commercial grade castable aluminum-silicon alloys traditionally have included iron (Fe) as an unavoidable tramp alloying element present when aluminum is produced from bauxite containing ferric oxide.

Method used

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Examples

Experimental program
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Effect test

example 1

[0036]FIG. 1 is a schematic representation of the effect of the Mn / Fe weight ratio on shrink porosity, microporosity, and tensile strength of a Cu-containing aluminum alloy having a composition, in weight %, 6.5% Si, 3.5% Cu, 0.4% Mg, 0.5% Fe, Mn as specified, and balance Al. The effect of Mn / Fe was determined by preparing a master heat of the base composition and cast into 30 pound ingots. For each value of Mn / Fe weight ratio tested in a series of Mn / Fe ratios from 0.1 to 2.0, a separate heat was prepared and Mn added in the form of Al—25 weight % Mn master alloys. In addition, pure Al was added to each of the heats except to the heat with the highest Mn / Fe ratio. This procedure was used to insure the total addition (Al—25Mn master alloy+pure Al) was a constant to dilute all of the other alloying elements by a constant amount. After melting in a clay-graphite crucible in air, each heat was degassed using a commercial rotary degasser with argon. Two sand molds were made for each hea...

example 2

[0039]FIGS. 2 and 3 illustrate practice of the invention with respect to an illustrative castable Cu-containing aluminum alloy.

[0040] In particular, FIG. 2 is a graph of showing the effect of Mn / Fe weight ratio on casting porosity at four different locations of cylinder blocks cast using the lost foam casting process. A Cu-containing aluminum alloy (319 alloy) having a composition, in weight %, 7% Si, 3.5% Cu, 0.55 Fe, 0.75% Mn, and balance Al providing a Mn / Fe weight ratio of 1.33 pursuant to the invention was cast at a melt temperature of 1430 degrees F. into a lost foam mold. The alloy was solidified in the mold at a cooling rate of about 10 degrees F / minute. For comparison, the same Cu-containing alloy with Mn of only 0.35 weight % providing a Mn / Fe weight ratio of only 0.64 was similarly cast and solidified in a lost foam mold. The Mn / Fe ratio of 0.64 is in excess of usually recommended levels but nevertheless practiced at certain commercial foundries for such alloy.

[0041] Th...

example 3

[0046] This example involves beneficial effects achieved by controlling the Mn / Fe weight ratio for aluminum alloys having silicon contents in the range of 11 to 12 weight % of the alloy. For example, FIG. 4 illustrates effects achieved with respect to castable Cu-containing aluminum alloys having a composition, in weight %, 11.75% Si, 0.4% Fe, 3.6% Cu, 0.15% Mg, 0.03% Sr, Mn as specified, and balance Al. The alloys were cast at a melt temperature of 1320 degrees F. into bonded sand molds. The alloys were solidified in the molds at a cooling rate of about 10 degrees F. / minute to produce cast bars that were heat treated to the T6 condition and then cut to make round tensile bars for testing.

[0047]FIG. 4 illustrates a significant increase in UTS of the heat treated specimens achieved by controlling the Mn / Fe weight ratio above 0.74, especially at a ratio of 1.367. The tensile elongation decreased somewhat at Mn / Fe ratios of 0.74 and 1.14 and then increased significantly at a Mn / Fe rat...

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Abstract

A castable aluminum alloy includes, in weight %, 0 to about 19% Si, 0 to about 5.0% Cu, 0 to about 1.5% Mg, up to about 3.0% Zn, up to about 2.0% Ni, up to about 0.3% Ti, greater than 0 to about 1.5 weight % Fe, about 0.2% to about 3.0% Mn, wherein a weight ratio of Mn / Fe is 0.6 or greater when Fe is less than 0.4 weight % and the weight ratio of Mn / Fe is 1.0 or greater when Fe is equal to or greater than 0.4 weight % to reduce porosity and increase tensile strength of a casting made from the alloy.

Description

RELATED APPLICATIONS [0001] This application is a continuation-in-part of copending U.S. application Ser. No. 10 / 603,086 entitled “ALUMINUM ALLOY FOR ENGINE BLOCKS” and filed Jun. 24, 2003. This application also claims benefits and priority of U.S. provisional application Ser. No. 60 / 551,997 filed Mar. 10, 2004. All of the above non-provisional and provisional applications are hereby incorporated herein by reference.FIELD OF THE INVENTION [0002] The present invention relates to castable aluminum alloys and, in particular, to aluminum casting alloys having a relatively high ratio of manganese to iron in the alloy composition to reduce porosity and improve mechanical properties of castings made therefrom. BACKGROUND OF THE INVENTION [0003] Many commercial grade castable aluminum-silicon alloys traditionally have included iron (Fe) as an unavoidable tramp alloying element present when aluminum is produced from bauxite containing ferric oxide. Manganese (Mn) has been included in such al...

Claims

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Application Information

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IPC IPC(8): B22D21/00B22D21/04C22C1/10C22C21/02C22C21/12C22C23/02C22C38/04C22C38/06
CPCC22C21/02B22D21/007
Inventor DOTY, HERBERT WILLIAM
Owner GM GLOBAL TECH OPERATIONS LLC
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