The present invention relates to converting one metal alloy to another alloy composition. More particularly, the invention relates to converting scrap alloys into a different or target alloy for use as a new material.
Often there is a greater amount of used or scrap alloy of one formulation or composition than of other alloy compositions that are used for other purposes. This difference in the quantity of scrap alloys may be caused, for example, by more of one alloy being sent to scrap than from another alloy. Other times, improved alloys are developed and the prior alloy composition is no longer used or used in lower quantity. Those scrap alloys have, in the past, not been readily reusable. Having the ability to use any scrap alloy to produce other alloys also reduces the number of different alloys needed in inventory, When parts made of an alloy such as a nickel or cobalt superalloy used in turbine blades are taken out of service after the prescribed period of use, thus becoming what is known as “revert” alloy pieces, processes are used to reclaim those alloys because, in some cases, the alloys contain valuable elemental constituents such as rhenium. Even when small amounts of rhenium are used, the material cost of this element can have a major impact on the total cost of the alloy.
The present invention is a method and system for using a first or revert alloy having a first composition, in the manufacture of a second or target alloy having a different composition. The first alloy is cleaned and prepared for melting.
The weight percent of the elemental constituents of this first alloy and a second target alloy are obtained, e.g., from records maintained by the alloy manufacturer. The ratio of the percentage by weight of each elemental constituent in the first alloy to the second alloy is determined. The lowest ratio of the respective constituents then determines the amount of the first alloy that can be used. The first alloy is then melted and the necessary elemental constituents including aluminum are then to achieve the composition of the second alloy. The resulting second alloy is then solidified.
In the past, service revert materials have not been utilized in making the same or new alloys because of concerns regarding cleanliness of the used casting. Careful cleaning, using strong cleaning methods, to remove sufficient contaminants has made such reuse practical. Use of grit blasting and/or a high strength alkali or an autoclave to clean a scrap part, followed by an acid treatment renders the part fit for re-use. The part is melted to produce ingot for later re-melting and use in this invention.
Presented below in Table I are representations of an example of compositions of a revert alloy and a target alloy. The values for the constituent elements do not represent any actual alloy and are for illustration purposes only.
As can be seen, most of the elemental constituents are present in the target alloy in at least the same weight percent as in the revert alloy. However, note that the amount of nickel in the target alloy is less than in the revert alloy, so the ratio is only 90.1%, and the amount of tantalum is only half, so the ratio is 50% for this constituent. Thus this ratio is selected, seen in
In every case, the amount of first or revert alloy that can be used to manufacture a second or target alloy is the elemental constituent that has the lowest ratio of weight percent target alloy to weight percent first alloy. This ensures that the resulting target alloy does not have any elemental constituent that exceeds the desired, or a maximum amount allowed in the specification for that target alloy.
One method for making the determination of selecting the amount of first alloy to melt (step 19) is shown in
A wide variety of first alloys can be used in accordance with this invention to prepare second alloys having different elemental constituents, wherein the assigned quantity of first or revert alloy with the lowest ratio as described above can be added to a furnace and additional elemental constituents then added to form a melt of the second or target alloy. Casting the second or target alloy into solid form completes the process. This demonstrates that scrap alloys have increased value because they can be used in the manufacture of other alloys. More effective use of scrap alloys makes the manufacturing process more commercially economical.
Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.
This application is a divisional of application Ser. No. 12/252,754, filed on Oct. 16, 2008. All references are incorporated herein.
Number | Name | Date | Kind |
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5693159 | Athey et al. | Dec 1997 | A |
5922148 | Irvine et al. | Jul 1999 | A |
6571857 | Darolia et al. | Jun 2003 | B2 |
7329382 | Amick | Feb 2008 | B2 |
7381366 | Carter, Jr. et al. | Jun 2008 | B2 |
Number | Date | Country | |
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20120095590 A1 | Apr 2012 | US |
Number | Date | Country | |
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Parent | 12252754 | Oct 2008 | US |
Child | 13079857 | US |