High-chromium nitrogen containing castable alloy

Abstract

A corrosion and erosion resistant alloy comprising as mandatory elements besides iron, in % by weight, about 31 to about 48 chromium, about 0.01 to about 0.7 nitrogen, about 0.5 to about 30 manganese and about 0.3 to about 2.5 carbon. This abstract is neither intended to define the invention disclosed in this specification nor intended to limit the scope of the invention in any way.

Description

[0001] This application is a continuation-in-part of U.S. application Ser. No. 10 / 040,357 filed Jan. 9, 2002, the entire disclosure whereof is expressly incorporated by reference herein.[0002] 1. Field of the Invention[0003] This invention relates generally to the art of alloys and more particularly to a high-chromium, nitrogen containing alloy having high corrosion resistance. The instant invention also relates to a high-chromium, nitrogen containing castable alloy, a high-chromium nitrogen content alloy, and a process for producing the high-chromium, nitrogen containing alloy, and articles prepared from the same.[0004] 2. Discussion of Background Information[0005] Equipment used in highly corrosive environments typically is made of alloys such as stainless steel and other highly alloyed materials. These alloys must be able to withstand the extremely corrosive environments created by chemicals such as concentrated sulfuric acid or concentrated phosphoric acid. A particularly diffic...

AI Technical Summary

Problems solved by technology

A particularly difficult environment is encountered in the production of phosphate fertilizer.

The crude phosphoric acid produced can be extremely corrosive and contains some residual sulfuric acid.

A particularly corrosive environment is encountered during the concentration of the crude phosphoric acid.

The most severe corrosive environments are typically encountered in the processing of deposits of phosphate rock which contains a high content of halides, such as chloride or fluoride.

However, both alloys exhibit poor mechanical properties, especially low toughness, brittleness, sensitivity to heat, and low notched impact resistance, thereby limiting their usefulness.

The ferritic structure comprised in these alloys is inherently very brittle, and the carbide phase embedded in such a brittle phase results in a very low toughness, high notch sensitivity, as well as sensitivity to heat.

Additionally, the ferritic structure is supersaturated with chromium, resulting in a formation of the sigma phase, which drastically lowers toughness and corrosion resistance.

The alloy of the '801 patent possesses good toughness, but exhibits very poor hardness and very poor wear resistance and low tensile strength.

Its hardness of 208 to 354 HB is similar to that of CD4MCU stainless steel (260-350 HB), which has excellent corrosion resistance, but poor wear resistance.

The alloy disclosed in U.S. Pat. No. 5,320,801 is similar to austenitic, high-nickel stainless steels in that it has good toughness, but very low tensile strength and hardness, as well as poor wear resistance.

The nickel

Images