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Remediation of Sensitization in Metals

a sensitization and metal technology, applied in the field of metal sensitization remediation, can solve the problems of base metals being more susceptible to grain modification produced, and achieve the effects of effective remediation, reducing tensile stress, and reducing or eliminating substantially

Inactive Publication Date: 2014-10-02
PROGRESS RAIL SERVICES
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AI Technical Summary

Benefits of technology

The present invention relates to a method for effectively remedying the effects of metal sensitization or repairing sensitized metals using conventional welding procedures. The invention involves introducing a treatment zone of plastic material into the sensitized metal by applying a multiplicity of shock pulses in the form of ultrasonic energy to the area of sensitized metal. The treatment results in a modified grain structure that slows the rate of enrichment of alloying elements at grain boundaries, causes intergranular diffusion of alloying elements, and reduces or eliminates substantially straight intergranular paths through the workpiece. The invention also provides a method for treating metal in a way that makes it less susceptible to stress corrosion cracking.

Problems solved by technology

The ultrasonic wave energy is believed to ultrasonically excite the base metal and relax stresses therein thereby making the base metal more susceptible to grain modification produced by the impact of a set of indenters coupled between the metal surface and the ultrasonic transducer.

Method used

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  • Remediation of Sensitization in Metals
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  • Remediation of Sensitization in Metals

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Embodiment Construction

[0022]The present invention is directed to the application of UIT to sensitized metals for effectively remediating the effects of metal sensitization and / or repairing the sensitized metals using conventional and emergent welding methods. As used herein, sensitized metal refers to metal having an alloying element precipitate out of solution and congregate at the metal grain boundaries thereby forming a continuous or solid film of the alloying element along the metal grain boundaries. The film may extend to the surface of the metal. By forming a continuous or solid film, interconnected intergranular pathways are formed along the grain boundaries of the metal.

[0023]An exemplary metal that is susceptible to sensitization is 5456-H116 aluminum. 5XXX aluminum alloys are commonly used in naval ship structures. These alloys provide high strength-to-weight ratios while maintaining good as-welded strength and excellent corrosion resistance. However, alloys like 5XXX aluminum alloys with above...

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Abstract

An ultrasonic impact treatment method for remediating metal sensitization including introducing ultrasound compression wave energy through ultrasonic mechanical impulse impacts into an area of sensitized metal in a workpiece. The ultrasound compression wave energy and impulse impacts impart compressive residual stress to the workpiece thereby decreasing tensile stresses in the sensitized metal and modifying the grain structure of the workpiece. These changes to the structure of the workpiece combine to slow the rate of enrichment of alloying elements at grain boundaries within the area of sensitized metal, cause intergranular diffusion of alloying elements in the area of sensitized metal, return a portion of alloying elements in the area of sensitized metal to solution and reduce or eliminate substantially straight intergranular paths through the workpiece.

Description

FIELD OF THE INVENTION[0001]The present invention is directed to a method for remediating sensitization in metals, and more particularly, to remediating sensitization in metals by application of ultrasonic impact treatment (UIT).BACKGROUND OF THE INVENTION[0002]Sensitized metals are those that when exposed to high temperatures for extended periods have alloying phases precipitate to the grain boundaries of the metal. Precipitation of the alloying phases makes the materials very susceptible to cracking and material failure. Stress corrosion cracking (SCC) refers to the growth of a crack in a susceptible material that is subjected to tensile stress above a threshold value and exposed to either a gaseous or liquid corrosive environment. A non-exhaustive list of examples of materials susceptible to SCC include carbon steels, low alloy steels, high strength steels, all 300-series stainless steels (including Types 304, 304L, 304H, 321, and 347), aluminum alloys from the 5XXX alloy family ...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C21D10/00
CPCC21D10/00C21D9/50C21D2211/004C21D2221/00
Inventor SHARMAN, DAVID JOHNABSTON, II, SAMUEL B.HANES, TAYLOR
Owner PROGRESS RAIL SERVICES
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