Austenitic paramagnetic corrosion resistant material

Abstract

The alloys of the present invention provide austenitic, paramagnetic materials with high strength, ductility, and yield strength and good corrosion resistance in media with high chloride concentrations. Alloys of the present invention were developed because of the need by oilfield industries for superior materials. The alloys of the present invention may be used in drilling string components, and the tests performed demonstrate that such alloys exhibit properties balanced for very high yield strength, magnetic permeability, and corrosion resistance superior in every respect to presently available paramagnetic, high strength, corrosion resistant austenitic stainless steels.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application No. 60 / 816,213, filed Jun. 23, 2006, which provisional application is incorporated herein by reference in its entirety.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates generally to austenitic, paramagnetic and corrosion-resistant materials having high strength, yield strength, and ductility for use in media with high chloride concentrations, and, more particularly, to steels suitable for use in non-magnetic components in oilfield technology, especially in directional drilling of oil and gas wells. [0004] 2. Description of the Related Art [0005] High-strength materials that are paramagnetic, corrosion-resistant and which, for economic reasons, consist essentially of alloys of chromium, manganese, and iron are used for manufacturing chemical apparatuses, in devices for producing electrical ene...

AI Technical Summary

Benefits of technology

"The present invention provides a new material that can be used in high-chloride environments, such as in oilfield technology. This material has high strength, ductility, and corrosion resistance. The material can be used in non-magnetic components in oil and gas wells. The material has a specific composition that includes specific amounts of carbon, silicon, manganese, nitrogen, chromium, nickel, molybdenum, copper, boron, sulfur, and phosphorous. The material also has a specific PREN value and yield strength at 0.2 offset. The technical effect of this invention is to provide a new material that can withstand high chloride concentrations and has good strength and corrosion resistance."

Problems solved by technology

However, increasingly higher demands are being placed on the chemical corrosion properties as well as the mechanical characteristics of materials used in this manner.

However, their magnetic permeability values prevent their use in parts used in connection with magnetic measurements and exclude their use for drill stems.

On the other hand, available paramagnetic materials with good strength characteristics cannot resist attacks by corrosion and, for the most part, paramagnetic parts with high corrosion resistance often do not have the necessary high mechanical values.

Use of nitrogen to improve mechanical and chemical corrosion properties of substantially Cr—Mn—Fe alloys is known, however, this requires expensive metallurgic processes operating at elevated pressure.

However, molybdenum, like chromium, is a ferrite former and can lead to unfavorable magnetic characteristics in the material in segregation areas.

While increased nickel contents stabilize the austenite, possibly in conjunction with increased copper concentrations, it has been believed that increased nickel content may have a detrimental effect on the mechanical characteristics and intensify crack initiation.

However, at these low levels of nickel and copper (these two elements being austenite formers), low levels of molybdenum and / or chromium (being ferrite forming elements) must be present for a stable metallurgical structure, and therefore this steel fails to meet the desired level of pitting corrosion resistance.

None of the steels discussed above have all of the desired properties of yield strength and pitting corrosion resistance necessary for acceptable performance under these more exacting operating conditions.