Ni-Fe-Cr-Mo Alloy

Abstract

The invention relates to an alloy comprising (in mass %) Ni 33-35%, Cr 26-28%, Mo 6-7%, Cu 0.5-1.5%, Mn 1.0-4%, Si max. 0.1%, Al 0.01-0.3%, C max. 0.01%, N 0.1-0.25%, B 0.001-0.004%, SE>0 to 1%, and Fe remainder, including unavoidable impurities.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation of and Applicant claims priority under 35 U.S.C. §120 of U.S. application Ser. No. 13 / 881,851 filed on May 29, 2013, which application is a national stage application under 35 U.S.C. §371 of PCT Application No. PCT / DE2011 / 001875 filed on Oct. 20, 2011, which claims priority under 35 U.S.C. §119 from German Patent Application No. 10 2010 049 781.9 filed on Oct. 29, 2010, the disclosures of which are incorporated by reference. A certified copy of priority German Patent Application No. 10 2010 049 781.9 is contained in parent U.S. application Ser. No. 13 / 881,851. The international application under PCT article 21(2) was not published in English.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The invention relates to an Ni—Fe—Cr—Mo alloy, especially a modified alloy in accordance with EN Material No. 1.4562 as well as its use.[0004]2. Description of the Related Art[0005]The alloy with Materia...

AI Technical Summary

Benefits of technology

[0030]Surprisingly, it has been found that the high solution annealing temperature range of 1150 to 1180° C. or higher mentioned initially can be significantly lowered when the nickel content of this alloy is increased to 33.0 to 35.0 mass %. For an average nickel content of 34 mass % in comparison with previously 31 mass %, the solution annealing temperature range can be lowered by at least 30° C. to at least 1120 to 1150° C. Furthermore, it has been found that an increase of the manganese content by increase of the solubility of nitrogen acts positively on the metallurgical stability. Both manganese and also nitrogen itself act as stabilizers of the austenitic microstructure. In addition, manganese binds sulfur which impairs the hot workability of the material. Usually, the Material 1.4562 is manufactured with a manganese content of approximately 1.7 mass % on the average. It has now been found that an increase of the manganese content to 1.8 to 2.6 mass % in combination with an alloying of nitrogen facilitates the solution annealing treatment by the additional austenite stabilization, in that the necessary temperature can still be somewhat further lowered and the necessary time shortened. However, too high manganese contents impair the corrosion resistance, which is apparent, for example, during the measurement in the “Green Death” test solution.

[0032]The nitrogen solubility increased by the manganese addition defined according to the invention leads to a weaker binding of the nitrogen to chromium as a metal nitride. Hereby the effective content of chromium Creff, which is available for the increase of the corrosion resistance, is increased.Creff=Cr−10 Cr (C+N)

[0036]For the improvement of the processability, especially for the hot forming, it is proposed, starting from a diversely usable nickel-iron-chromium-molybdenum alloy (EN Material No. 1.4562), to optimize the nickel content and the manganese content. In this way, the solution annealing temperature of the sigma phase can be significantly lowered, without diminishing the resistance of the alloy to technical phosphoric acid and other technical acids as well as to pitting corrosion and stress corrosion cracking.

Problems solved by technology

In addition, manganese binds sulfur which impairs the hot workability of the material.

However, too high manganese contents impair the corrosion resistance, which is apparent, for example, during the measurement in the “Green Death” test solution.

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