JP2018534433A - Corrosion and crack resistant high manganese austenitic steels containing passivating elements - Google Patents

Abstract

Improved steel compositions and methods for making the same are provided. The present disclosure provides an advantageous corrosion and / or crack resistant steel. More particularly, the present disclosure has high manganese (Mn) steel compositions having improved corrosion and / or crack resistance and improved corrosion and / or crack resistance (eg, via passivation). A method for producing a high manganese steel composition is provided. A method for producing a high manganese steel composition having improved corrosion resistance and / or crack resistance is also provided.

Description

(Field)
The present disclosure relates to improved steel compositions and methods of making the same, and more particularly high manganese (Mn) austenitic steel compositions having improved corrosion resistance and / or crack resistance (eg, passivating). To a method for producing a high manganese steel composition having improved corrosion and / or crack resistance. Further objects of the present disclosure may have a combination of high strength, improved sweet and sour corrosion resistance, and resistance to environment induced cracking, including sulfide stress cracking and stress corrosion cracking, It is to provide devices and components made from such austenitic high Mn steel.

(background)
Carbon steel is widely used as a structural material in the petroleum, gas, and petrochemical industries. The upstream sector of these industries is a major user of structural materials, where the use of carbon steel accounts for approximately 95% of the tonnage of all structural materials used. In general, carbon steel is a structural material that is strong, tough, weldable, widely marketed, and low cost. However, carbon steel does not have inherent corrosion resistance, and high-strength carbon steel is also prone to environment-induced cracking such as sulfide stress cracking.

  Most of the remaining 5% of the tonnage of structural materials used in the upstream sector of the petroleum, gas, and petrochemical industries is primarily corrosion resistant alloys (“CRA”) for use in harsh and corrosive environments. Among them, the most widely used is austenitic stainless steel. In general, austenitic stainless steel provides a combination of excellent corrosion resistance, crack resistance, oxidation resistance, good formability and toughness. The superior corrosion resistance of such stainless steel is typically due to high chromium (Cr) alloying, and its high ductility and toughness is typically stabilized by high nickel (Ni) alloying. This is due to the austenite phase having a face-centered cubic (FCC) atomic crystal structure. As an example, a commonly used austenitic stainless steel 304SS is about 18 wt. % Cr and 8 wt. It has a nominal composition of% Ni. Therefore, the cost of austenitic stainless steel is higher, and the cost is typically 5 to 5% that of carbon steel, mainly due to the high Ni content of expensive alloying elements that may be in short supply. 6 times. In addition, austenitic stainless steel exhibits a relatively lower strength compared to ferritic carbon steel and ferritic stainless steel and is generally prone to stress corrosion cracking.

  Driven by interest in reducing material costs and / or minimizing the impact of nickel price volatility, interest in lower cost and more cost effective stainless steels has increased. This results in, for example, 200 series austenitic Cr exemplified by types 201, 202, and 216, which are partially replaced by manganese (Mn), a less expensive austenite stabilizer and a lower cost austenite stabilizer. -Mn-Ni stainless steel was developed. In general, these 200 series stainless steels provide superior strength and equivalent ductility compared to 304SS. However, most of these Ni-reduced steels exhibit significant yield strength with the precipitation of carbides, nitrides, and / or carbonitrides when exposed to elevated temperatures in the range of about 600 ° C to about 900 ° C. Increase and a significant loss of ductility.

  High Alloy Corrosion Resistant Alloy (CRA) pipes and / or tubes for downhole applications have traditionally had higher yield and tensile strengths required to accommodate high pressures and to support high tensile loads due to pipe / tube weight Is cold worked or forged. In order to obtain a high enough strength to meet the required mechanical strength of the finished pipe / tube, the larger hollow body is drawn or stretched through a smaller die to provide an OD throughout the retained mandrel. By reducing ID at the same time, it is possible to cold deform the pipe / tube and then repeat the same process to obtain the required mechanical strength. Alternatively, pipe / tubes can be made by performing pilger rolling in which the hollow pipe / tube is mechanically forged through a die set under high pressure to substantially reduce OD and at the same time reduce ID across the mandrel. It is possible to obtain the required mechanical strength by cold deformation. The selected chemistry of the high Mn steel may exhibit dynamic strain aging (DSA) during cold deformation and / or hot deformation. DSA can be used as an effective method to improve strength and fracture toughness and can be more effective than cold deformation due to dislocation slip due to a more uniform dislocation distribution and more effective dislocation generation.

  Accordingly, there is a need for an improved steel composition that achieves improved corrosion resistance and / or crack resistance and a method of manufacturing the same. These and other inefficiencies and improvement opportunities are addressed and / or overcome by the systems and methods of the present disclosure.

(Summary)
The present disclosure provides advantageous steel compositions. More particularly, the present disclosure provides an improved high manganese (Mn) steel composition having improved corrosion / cracking resistance and a related method of manufacturing a steel composition having improved corrosion / cracking resistance. To do.

  In general, the present disclosure provides a relatively lower cost iron austenitic stainless steel composition compared to conventional austenitic stainless steel (eg, 304SS). Advantageous iron austenitic steel compositions of the present disclosure provide improved corrosion resistance (eg, against sweet and sour corrosion), crack resistance, and / or cost-effective oil (or petroleum) ) / Gas and / or petrochemical applications.

  In an exemplary embodiment, the microstructure of the iron-based steel composition of the present disclosure includes an austenitic phase having a predominantly face centered cubic (FCC) atomic crystal structure. In certain embodiments, exemplary ferrous steel compositions include manganese (eg, about 8 wt.% Or more), but are not limited to chromium (eg, about 11 wt.% Or more), and / or A passive film forming element comprising aluminum (eg, about 1 wt.% Or more), and / or titanium, and / or silicon (eg, about 0.5 wt.% Or more), and combinations thereof; Contains a large amount. Exemplary ferrous steel compositions include, for example, interstitial alloying elements such as carbon (eg, about 0.1 wt.% Or more) and / or nitrogen (eg, about 0.1 wt.% Or more). May further be included in large amounts.

  Thus, the present disclosure produces cost effective iron austenitic stainless steel compositions (eg, for oil (or petroleum) industry, gas industry, petrochemical industry) and cost effective iron austenitic stainless steel compositions. Provide a way to do it. The exemplary steel composition has advantages over many commonly used austenitic stainless steels such as 304SS. For example, some of these advantages are facilitated by: (i) lower material costs by replacing or reducing Ni by Mn, C, N and / or combinations thereof, (ii) high Mn alloying Higher strength due to higher nitrogen and carbon content and / or due to cold deformation and / or elevated temperature deformation, (iii) passive film-forming elements (eg Cr, Al, Ti and / or Si) improved corrosion resistance by high alloying addition, (iv) improved pitting corrosion resistance by higher nitrogen alloying promoted by Mn alloying, and / or Or (v) including one or more of maintaining toughness and cracking resistance derived from the austenitic phase, but not limited thereto Not.

  Another aspect of the present disclosure is to manufacture the device from at least partially exemplary iron austenitic stainless steel. Some exemplary uses / applications of the steel compositions of the present disclosure include oil (or petroleum), gas and petrochemical equipment / systems such as reactors, pipes, casings, packers, couplings (or fittings) ), Soccer rods, seals, wires, cables, bottom hole assemblies, tubes, valves, compressors, pumps, bearings, extruder barrels, molding dies, and combinations thereof, including but not limited to .

Exemplary Manufacturing Method The present disclosure provides a method of manufacturing an iron-based member, the method comprising:
a) providing a composition having about 8 to about 30 weight percent manganese, about 11 to about 30 weight percent chromium, and balance iron;
b) melting the composition in a controlled environment (or a controlled or controlled environment) to produce a liquid alloy steel composition;
c) cooling the liquid alloy steel composition, the step for forming an alloy steel composition;
d) hot deforming the alloy steel composition;
e) reheating the alloy steel composition for a predetermined time;
f) cooling the alloy steel composition.

  The disclosure also provides that the composition is selected from the group consisting of carbon, nitrogen, aluminum, silicon, nickel, cobalt, molybdenum, niobium, copper, titanium, vanadium, tungsten, boron, zirconium, hafnium, and combinations thereof 1 Provided is a method of manufacturing an iron-based member further comprising at least one alloying element.

  Any combination or permutation of the embodiments is envisioned. Additional advantageous steps, features, functions, and applications of the systems and methods disclosed in this disclosure will become apparent from the following description, particularly when read in conjunction with the accompanying drawings. All references listed in this disclosure are incorporated herein by reference in their entirety.

  The features and aspects of the embodiments are described below with reference to the accompanying drawings. However, the elements in the drawings are not necessarily drawn to scale.

  Exemplary embodiments of the present disclosure will be further described with reference to the accompanying drawings. The various steps, features, and process / feature combinations described below and illustrated in the drawings may be variously arranged and configured to provide embodiments that still fall within the spirit and scope of the present disclosure. It should be noted. To assist those skilled in the art in making and using the disclosed systems, assemblies, and methods, reference is made to the accompanying drawings.

FIG. 3 is an exemplary diagram showing phase stability and deformation mechanism of high Mn steel as a function of alloy chemistry and temperature. 1 represents an Fe—Cr—Mn—Ni phase diagram of an exemplary iron austenitic stainless steel composition of the present disclosure. (A) Represents a scanning electron micrograph showing a typical microstructure of an exemplary steel of the present disclosure in an as-rolled plate with secondary Cr-rich carbides in a predominantly austenitic matrix. (B) depicts a scanning electron micrograph showing a typical microstructure of an exemplary steel of the present disclosure in a solution heat treatment having a predominantly austenite microstructure. Both as-rolled and solution heat treated [20 wt. % Mn, 18 wt. % Cr, 0.6 wt. % C, 0.4 wt. % N, and the remaining Fe] alloy steel and a commercial comparative sample 304SS. Both as-rolled and solution heat treated [20 wt. % Mn, 18 wt. % Cr, 0.6 wt. % C, 0.4 wt. % N, and the remaining Fe] alloy steel and the commercially available comparative sample 304SS and carbon steel represent corrosion rates.

DETAILED DESCRIPTION The exemplary embodiments disclosed herein illustrate the advantageous steel compositions and systems of the present disclosure and their methods / techniques. However, it should be understood that the embodiments of the present disclosure are merely examples of the present disclosure that may be embodied in various forms. Accordingly, the details disclosed herein with reference to exemplary steel compositions / manufacturing methods and related processes / techniques for assembly and use should not be construed as limiting, It should be construed as merely a basis for teaching those skilled in the art how to make and use steel compositions. The drawings are not necessarily to scale, and certain drawings may be exaggerated for clarity.

  The numerical values included in the detailed description and claims of this specification are all modified by “about” or “approximately” as indicated, taking into account experimental errors and variations that would occur to those skilled in the art.

  Where a range of values is provided, each intervening value between the upper and lower limits of the range (up to 1/10 of the lower limit unless the context clearly dictates) and any other value within that specified range Designated or intervening values are understood to be included within the scope of the present disclosure. A range from any lower limit to any upper limit is contemplated. The upper and lower limits of these smaller ranges that may be independently included within the smaller ranges are also encompassed within the scope of this disclosure subject to any specifically excluded limits within that specified range. . Where the specified range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the disclosure.

  Although methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present disclosure, the preferred methods and materials are now described. All publications cited herein are hereby incorporated by reference as if the relevant methods and / or materials set forth in the cited publication are disclosed and described.

  As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” have specific definitions that are specifically contextual. It should be noted that it includes plural references unless otherwise indicated.

  Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terminology used in the description of the disclosure herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. All publications, patent applications, patents, drawings, and other references cited herein are expressly incorporated by reference in their entirety.

Definition CRA: Corrosion resistant alloy may mean, but is not limited to, a material that is specially formulated to have good corrosion resistance to produce equipment used in corrosive environments. Corrosion resistant alloys can be formulated to suit a wide range of harsh corrosion conditions.

  Ductility: can mean a measure of a material's ability to undergo perceptible plastic deformation prior to failure, but is not limited thereto and can be expressed as percent elongation (% EL) or percent area reduction (% AR).

  Corrosion resistance: may mean, but is not limited to, the inherent resistance of a material to degradation caused by exposure to a reactive or corrosive environment.

  Toughness: can mean resistance to crack initiation and propagation, but is not limited thereto.

  Stress corrosion cracking (SCC): It can mean, but is not limited to, cracking of a material due to the simultaneous action of stress and reaction and corrosive environment.

Sulfide stress cracking (SSC): It can mean, but is not limited to, cracking of a material by exposure to a fluid containing hydrogen sulfide (eg, H ₂ S).

  Yield strength: can mean the ability of a material to withstand a load without deformation, but is not limited in any way.

  Cooling rate: may mean, but is not limited to, the cooling rate of a piece of material that is generally measured at or near the center of the piece of material.

  Austenite: may mean, but is not limited to, the metallurgical phase of steel having a face-centered cubic (FCC) atomic crystal structure.

  Martensite: can mean the metallurgical phase of steel that can be formed by a non-diffusible phase transformation (not limited) with a parent phase (typically austenite) and product phase having a specific orientation relationship However, it is not limited to it.

  ε (epsilon) martensite: It can mean a specific form of martensite having a hexagonal close-packed atomic crystal structure caused by cooling or distortion of the austenite phase, but is not limited thereto. ε-martensite typically forms on the close-packed (111) face of the austenite phase and is morphologically similar to deformation twins or stacking fault clusters.

  α '(alpha prime) martensite: may mean a specific form of martensite having, but not limited to, a body-centered cubic (BCC) or body-centered square (BCT) atomic crystal structure caused by cooling or distortion of the austenite phase Is not to be done. α 'martensite is typically produced as a platelet.

_Ms temperature: It can mean a temperature at which transformation from austenite to martensite is started during cooling, but is not limited thereto.

_Mf temperature: It can mean a temperature at which transformation from austenite to martensite is completed during cooling, but is not limited thereto.

_Md temperature: may mean the maximum temperature at which a specified amount of martensite is produced under defined deformation conditions, but is not limited thereto. The _Md temperature is typically used to characterize the austenite phase stability during deformation.

  Carbide: may mean a compound of iron / metal and carbon, but is not limited thereto.

Cementite: It may mean a compound of iron / metal and carbon having an approximate chemical formula of M ₃ C having an orthorhombic atomic crystal structure, but is not limited thereto.

Perlite: Typically refers to a two-phase lamellar mixture composed of alternating layers of ferrite and cementite (M ₃ C), but is not limited thereto.

  Particle: Can refer to an individual crystal in a polycrystalline material, but is not limited thereto.

  Grain boundary: can mean, but is not limited to, a narrow zone in the metal corresponding to a transition from one crystal orientation to the other, ie, separation of one particle from the other.

  Quenching: can mean, but is not limited to, accelerated cooling by any means in which the selected fluid is utilized to show a tendency to increase the cooling rate of the steel relative to air cooling.

  Accelerated cooling start temperature (ACST): It can mean the temperature reached on the plate surface at the start of quenching, but is not limited thereto.

  Accelerated cooling end temperature (ACFT): may mean, but is not limited to, the maximum temperature or substantially the maximum temperature reached by the plate surface after quenching is stopped by heat conduction from the intermediate thickness of the plate.

  Slab: A piece of steel having an arbitrary dimension.

  Recrystallization: The formation of new strain free particle structured particles from cold worked metal achieved by heating through a critical temperature.

T _nr temperature: An upper limit temperature at which austenite does not recrystallize.

  Dynamic strain aging (DSA): A material due to increased stress required for dislocation motion due to strain due to interaction between solute atoms (eg, carbon and / or nitrogen) and dislocations or dislocation pinning by solute atoms. This is a phenomenon related to an increase in yield strength and hardness.

  The present disclosure provides advantageous steel compositions (eg, those having improved corrosion / cracking resistance). More particularly, the present disclosure provides improved high manganese (Mn) steel compositions having improved corrosion resistance / crack resistance and methods for producing high manganese steel compositions having improved corrosion resistance / crack resistance. To do.

  In an exemplary embodiment, the present disclosure provides a relatively lower cost iron austenitic stainless steel composition compared to conventional austenitic stainless steel (eg, 304SS). Thus, the advantageous iron austenitic steel compositions of the present disclosure provide for petroleum where improved corrosion resistance (eg, against sweet and sour corrosion), crack resistance, and / or cost effectiveness is desired / required. / Available for gas / petrochemical applications.

  In certain embodiments, the microstructure of an exemplary ferrous steel composition includes an austenitic phase having a predominantly FCC atomic crystal structure. In some embodiments, exemplary steel compositions include manganese (eg,> 8 wt.%), But are not limited to Cr (eg,> 11 wt.%), And / or Al (eg, ,> 1 wt.%), And / or Si (eg,> 0.5 wt.%), And / or Ti (eg,> 1 wt.%), And combinations thereof, and combinations thereof Contains a large amount. Exemplary steel compositions may contain large amounts of interstitial alloy elements such as, for example, carbon (eg,> 0.1 wt.%) And / or nitrogen (eg,> 0.1 wt.%).

  Thus, the present disclosure provides a cost effective iron austenitic stainless steel composition (eg, for the petroleum industry, gas industry, petrochemical industry) and a method for producing a cost effective iron austenitic stainless steel composition. To do. Exemplary steel compositions have advantages over many commonly used austenitic stainless steels (eg, 304SS). Some of these benefits include lower material costs by replacing or reducing Ni by Mn, C, N, and / or combinations thereof, higher nitrogen promoted by high Mn alloying and / or pre-deformation Higher strength due to content and carbon content, improved corrosion resistance due to high alloying addition of passivating film forming elements (eg Cr, Al, and / or Si), higher nitrogen promoted by Mn alloying This may include, but is not limited to, improved pitting corrosion resistance due to alloying and / or maintenance of toughness and crack resistance from the austenite phase.

  Steel compositions described or encompassed by this disclosure may be used in many systems / applications (eg, petroleum, gas, and / or petrochemical equipment / systems such as reactors, pipes, casings, packers, couplings (or Joints), soccer rods, seals, wires, cables, bottom hole assemblies, tubes, valves, compressors, pumps, bearings, extruder barrels, molding dies, etc.), especially where corrosion / crack resistance is important / desired / It can be advantageously used in applications.

  In an exemplary embodiment, the present disclosure provides an iron-based member / composition containing manganese. In certain embodiments, the member / composition comprises about 5 to about 40 weight percent manganese, about 0.01 to about 3.0 weight percent carbon, and the balance iron. The member / composition may also include one or more alloying elements such as, but not limited to, about 0-30% chromium, about 1-15% aluminum, about 0.01-10% % Silicon, and combinations thereof. The member / composition may also include one or more additional alloying elements such as, but not limited to, nickel, cobalt, tungsten, molybdenum, niobium, copper, titanium, vanadium, nitrogen, boron, and their Combinations can be included. An exemplary iron-based member / composition containing manganese (and optionally other alloying elements) is described in US 2012/0160363, the entire contents of which are hereby incorporated by reference in their entirety. And incorporated in the specification).

Member Composition In some embodiments, as noted above, the iron-based composition comprises about 5 to about 40 weight percent manganese (preferably about 8 to about 30 weight percent manganese), about 0.01 to about It may contain about 3.0 wt% carbon (preferably about 0.1 to about 1.50 wt% carbon) and the balance iron.

  The member / composition may also include one or more alloying elements such as, but not limited to, about 0 to about 30 wt. % Chromium (more preferably 11-30 wt.%), About 1 to about 15 wt. % Aluminum (more preferably 2 to 10 wt.%), About 0.01 to about 10 wt. % Silicon (more preferably 1.5-5 wt.%), About 0.01 to about 10 wt. % Titanium (more preferably 1.5-5 wt.%), And combinations thereof.

  The member / composition may also include one or more alloying elements such as, but not limited to, silicon, nickel, cobalt, molybdenum, niobium, copper, titanium, vanadium, tungsten, nitrogen, boron, zirconium, hafnium. , And combinations thereof. The weight percent is based on the total weight of the part / composition.

  Nickel is from about 0 to about 20 wt. % Can be included in the member. Cobalt is about 0 to about 20 wt. % Can be included in the member. Molybdenum is about 0 to about 10 wt. % (More preferably 0.3 to 5% by weight). Niobium, copper, titanium, tungsten, and / or vanadium are each about 0.2 to about 10 wt. % (More preferably 0.3 to 5% by weight). Nitrogen is about 0.01 to about 3.0 wt. % (More preferably, 0.1 to 1.5% by weight). Boron is about 0 to about 0.1 wt. % (More preferably 0.001 to 0.1% by weight).

  Manganese-containing iron-based members / compositions can also include other alloying elements selected from the group consisting of zirconium, hafnium, and combinations thereof. Each of these other alloying elements is about 0 to about 6 wt. % (More preferably 0.2 to 5 wt.%) In the member / composition.

Alloying for Strain Induced Transformation In general, the mechanical properties of the disclosed high Mn steels typically depend on the properties of the strain induced transformation controlled by the chemical composition of the steel and / or the processing temperature. Unlike conventional carbon steel, high Mn steel includes a metastable austenite phase having a face centered cubic (FCC) atomic crystal structure at ambient temperature (eg, 18-25 ° C.). When strain is applied, the metastable austenite phase can be transformed into several other phases via strain-induced transformation. More specifically, the austenitic phase is dependent on the chemistry and / or temperature of the steel, depending on the microtwin (matrix aligned FCC twins), ε martensite (hexagonal lattice), and α ′ martensite (body It can be transformed into a heart square lattice. These transformation products can impart a range of unique properties to high Mn steel. For example, fine micro twins effectively segment primary particles and act as obstacles with strong dislocation motion. This results in effective grain refinement, resulting in an excellent combination of high ultimate strength and ductility.

  It is known that the chemical composition and temperature of steel are the main factors controlling the strain-induced phase transformation pathway as shown in FIG. In general, high Mn steels are divided into four groups, eg, highly stable (A), mildly metastable (B), and moderately metastable (C), depending on the stability of the austenite phase with respect to strain and temperature. And highly metastable (D) Mn steels. The metastability of these phases is affected by both temperature and strain. These steels will tend to increase metastability at higher temperatures and higher strains (eg, higher transformation tendencies).

  FIG. 1 is an exemplary diagram showing the phase stability and deformation mechanism of high Mn steel as a function of alloy chemistry and temperature. The letters (A, B, C, and D) represent various transformation paths during deformation. In this figure, Steel A will be deformed by dislocation slip, but will not transform into a different phase (a phase similar to other metals and alloys). On the other hand, steels BD will transform upon deformation.

  The steel in region A having stable austenite and deformed primarily by dislocation slip due to mechanical strain can be produced with a high Mn content (eg, about 25 wt.% Or more). In general, steels with a well-stabilized austenitic structure exhibit lower mechanical strength but maintain toughness at cryogenic temperatures, provide low magnetic permeability, and have high resistance to hydrogen embrittlement.

  Region B steels having a mildly metastable austenitic phase can be produced with medium manganese content (eg, about 15 to about 25 wt.% Mn and about 0.6 wt.% C). These steels form twins when deformed. In general, this type of steel can achieve greater plastic elongation for the formation of a wide range of deformation twins associated with dislocation slip (a phenomenon known as twin induced plasticity (TWIP)). Twinning results in high work hardening rates when the microstructure is effectively refined because twin boundaries act like grain boundaries and strengthen the steel by the dynamic Hall-Petch effect. TWIP steel combines very high tensile strength (eg, greater than 150 ksi) with very high uniform elongation (eg, greater than 95%), making it very attractive for many applications.

  Region C steels having a moderately metastable austenitic phase can be produced at lower manganese contents (eg, about 10 to about 18 wt.% Mn). In general, this type of steel can be transformed into ε-martensite (hexagonal lattice) by strain. When subjected to mechanical strain, these steels will deform mainly due to the formation of ε-martensite accompanying dislocation slip and / or mechanical twinning.

  Region D steels with highly metastable austenitic phases can be produced with even lower manganese contents (eg, about 4 to about 12 wt.% Mn). In general, this type of steel will transform into a strong phase having a body-centered cubic crystal structure (called α 'martensite) when deformed. This strong phase can also provide wear and erosion resistance.

  Thus, the chemistry of high Mn steel can be tailored to provide a range of properties by controlling their transformation during deformation.

Other Alloying Concepts for High-Mn Steel Alloying elements in high-Mn steel determine the austenite phase stability and strain-induced transformation paths. In general, manganese is the main alloying element in high Mn steels and is important for stabilizing the austenitic structure both during cooling and during deformation. In the Fe-Mn binary system, when the austenite phase is stabilized by increasing the Mn content, the strain-induced phase transformation path changes from α 'martensite to ε martensite and then to micro twin formation. To do.

  Carbon is also an effective austenite stabilizer, and the solubility of carbon is high in the austenite phase. Thus, carbon alloying can also be used to stabilize the austenite phase during cooling from the melt and during plastic deformation. Carbon also increases the strength of the austenite matrix by solid solution strengthening. As described, the carbon in the member / composition of the present disclosure is about 0.01 to about 3.0 wt. % Range.

  Since aluminum is a ferrite stabilizer, it destabilizes the austenite phase during cooling. However, the addition of aluminum to high Mn steel stabilizes the austenite phase against strain-induced phase transformation during deformation. Furthermore, austenite is strengthened by solid solution strengthening. The addition of aluminum also increases the corrosion resistance of the high Mn content iron-based members disclosed herein by promoting the formation of a passive film. Aluminum in the members / compositions of the present disclosure is about 0.0 to about 15 wt. % Range.

  Silicon is a ferrite stabilizer that maintains α 'martensite transformation and promotes ε martensite formation during deformation at ambient temperature. Due to solid solution strengthening, the addition of Si is 1 wt. Strengthen the austenite phase by about 50 MPa per% addition. Silicon in the members / compositions of the present disclosure is about 0.01 to about 10 wt. % Range.

  Titanium is a ferrite stabilizer and is often alloyed to stabilize carbon by forming titanium carbide. Stabilization of carbon through the formation of titanium carbide prevents the formation of chromium carbides that can affect the formation of "passive" layers. Titanium in the members / compositions of the present disclosure is about 0.01 to about 10 wt. % Range.

  Since chromium is a ferrite stabilizer, it promotes the formation of a ferrite phase during cooling. The addition of chromium also promotes the formation of a passive film by increasing the corrosion resistance of the high Mn content iron-based members disclosed herein. Furthermore, the addition of Cr to the Fe—Mn alloy system reduces the thermal expansion coefficient. Chromium in the member / composition of the present disclosure may be about 0.5 to about 30 wt. % Range.

  Copper is an austenite stabilizer and improves strength by solid solution hardening. The copper in the member / composition of the present disclosure is about 0.5 to about 10 wt. % Range.

  Sulfur is used in the case of sulfide inclusions to improve machinability (eg, FeS, MnS, and / or combinations thereof act as a chip breaker). Sulfur generally has a potential to reduce pitting corrosion resistance, so generally 0.02 wt. Maintained at a low level of less than%.

By understanding the effects of these alloying elements, it is possible to design a suitable steel chemistry for a specific application. Some design criteria for high Mn steel can be critical martensitic transformation temperatures, eg, M _s and M _εs . M _s is an upper critical temperature at which transformation from austenite to α ′ martensite occurs, and M _εs is an upper critical temperature at which transformation from austenite to ε martensite occurs.

Exemplary Composition and Microstructure An exemplary steel composition concept of the present disclosure is shown in FIG. In an exemplary embodiment, the steel composition is Cr alloyed to promote corrosion film formation to obtain corrosion resistance, and Mn and / or Ni alloyed to obtain toughness and / or crack resistance. Is used to stabilize the austenite (also known as γ) phase. However, Cr is a ferrite (also known as α) stabilizer. Thus, as Cr alloying increases, more Mn and / or Ni alloying additions may be required to stabilize the austenite phase.

  In the embodiments that follow, a number of various alloying additions of the iron austenitic stainless steel composition provided by the present disclosure are described.

  In an exemplary embodiment, an exemplary steel composition replaces the more expensive Ni alloying of conventional austenitic stainless steel with a lower cost Mn (eg, about 8 to about 30 wt.% Mn). , Mainly to achieve the crystal structure of austenite. This allows cost reduction, but still achieves an austenitic crystal structure with high ductility and toughness.

  In an exemplary embodiment, the steel composition may contain a sufficient amount of Cr (eg, about 11 to about 30 wt.%). The Cr alloying additive provides corrosion resistance, including sweet corrosion resistance and sour corrosion resistance.

  In certain embodiments, exemplary steel compositions may include high carbon and / or high nitrogen alloying (eg, when the carbon content ranges from about 0.1 to about 1.5 wt.%). And / or if the nitrogen content is in the range of about 0.1 to about 1.5 wt.%). As noted above, exemplary iron austenitic stainless steel compositions have improved nitrogen solubility in the melt and in steel due to the addition of manganese alloys.

  In certain embodiments, exemplary iron austenitic stainless steel compositions can include Al alloying (eg, Al addition in the range of about 1 to about 15 wt.%, Preferably about 2 to about 10 wt.%). .

  In some embodiments, exemplary iron austenitic stainless steel compositions may include Si (eg, Si alloying is in the range of about 0.5 to about 10 wt.%, Preferably about 1.5 to about 5 wt.% Range).

  In some embodiments, exemplary iron austenitic stainless steel compositions may include one or more of niobium (Nb), titanium (Ti), vanadium (V), tungsten (W), and molybdenum (eg, When the total content of each of these elements is in the range of about 0.3 to about 5 wt.%).

  In an exemplary embodiment, the iron austenitic stainless steel composition includes a primary austenitic phase and a secondary phase of carbide, nitride, and / or carbonitride and combinations thereof. The carbon and nitrogen content of an exemplary steel composition provides a strength level within a range (eg, within a range of about 50 ksi to about 120 ksi as manufactured without cold deformation). Selected. Exemplary steel compositions can achieve even higher yield strengths, for example, greater than 100 ksi, by performing cold deformation.

Applications Another aspect of the present disclosure is to make devices and the like from partially or fully exemplary iron austenitic stainless steel. Such exemplary equipment may include, but is not limited to, oil / gas and / or petrochemical equipment, including, but not limited to, reactors, pipes, casings , Packers, fittings, soccer rods, seals, wires, cables, bottom hole assemblies, tubes, valves, compressors, pumps, bearings, extruder barrels, molding dies, and combinations thereof.

Processing The steel compositions / members of the present disclosure are subject to various processing techniques including, but not limited to, various exemplary thermomechanical control processing ("TMCP") techniques, processes, or methods. Can be manufactured or produced.

  The present disclosure further provides exemplary process steps for manufacturing / producing exemplary iron austenitic stainless steel.

  Initially, an exemplary steel element / member may be melted to produce a liquid alloy steel in a controlled environment (eg, at about 1600 ° C. for about 30 minutes and under control of evaporation loss of N and / or Mn).

  The liquid alloy steel can then be cooled to about room temperature or a suitable low temperature to form a predominantly austenitic structure of the alloy steel (eg, continuously in the form of a cast ingot or as a slab, billet, and / or bloom) Cast into). For example, liquid alloy steel can be placed in a mold (eg, water-cooled copper mold) and ingot cast or continuously cast to form a cast ingot / slab while suppressing Mn segregation.

  The alloy steel ingot / slab is then hot deformed (eg, above about 800 ° C.) to control the particle size and / or shape of the alloy steel into bars, sheets, tubes, and the like.

  In some embodiments, the alloy steel (e.g., alloy steel bar / sheet) is then optionally reheated or subjected to a solution treatment (e.g., greater than about 1000 <0> C for about 1 hour), The secondary phase formed in the previous hot deformation process can be substantially dissolved.

  The reheated / solutionized alloy steel is then rapidly cooled (eg, at least about 10 ° C./second) to a suitable cooling stop temperature (eg, typically below about 300 ° C. or about room temperature). It can form a predominantly austenitic structure of alloy steel (eg, in a water quenching bath).

  In some embodiments, the alloy steel (eg, alloy steel bar / sheet) is optionally cold deformed (eg, rolled or forged) to further increase the strength of the alloy steel by causing strain-induced transformation. Can be increased.

  The disclosure is further described with reference to the following examples, which do not limit the scope of the disclosure. The following examples illustrate improved systems and methods for producing or producing improved steel compositions (eg, improved high Mn steel compositions having improved corrosion resistance and / or crack resistance). To do.

Example 1
Exemplary alloys of the present disclosure were made by vacuum induction melting. Prior to melting, the nominal chemistry of the steel composition is about 20 wt. % Mn, 18 wt. % Cr, about 0.6 wt. % C, about 0.4 wt. % N and the remaining Fe. A liquid alloy steel was produced by producing a steel composition by reduced pressure induction melting in a controlled environment in which the evaporation loss of N and Mn was controlled.

  The liquid alloy steel was then poured into a water-cooled Cu (copper) mold to form a uniformly cast ingot (while suppressing Mn segregation) and then cooled to approximately ambient temperature.

  Next, the ingot was hot deformed at a temperature above about 800 ° C. to control the particle size, and the alloy steel was shaped as a cylindrical bar. Then, some of the bars were reheated / solution heat treated for about 1 hour at about 1200 ° C. to substantially dissolve the secondary phase formed during hot deformation. The solution heat treated sample was then rapidly cooled to about room temperature in a water quench bath (eg, at least about 10 ° C./second) to form a predominantly austenitic structure of the alloy steel.

  The as-rolled sample (ie non-solution heat treated sample) exhibited secondary Cr-rich carbide as shown in FIG. 3A. This microstructure should be avoided to ensure improved corrosion resistance.

  As shown in FIG. 3B, mainly the austenite structure was achieved in the solution heat treated sample. This sample is a solution heat-treated at about 1200 ° C. for about 1 hour and then cooled in water.

Electrochemical polarization curves were obtained with exemplary steels and commercially available 304 grade stainless steel (19 wt.% Cr, 8 wt.% Ni, residual Fe). 50.2 g / L NaHCO ₃ and 3 wt. A test aqueous solution with% NaCl was made from analytical grade reagent and deionized water. During the test, the test aqueous solution was purged with about 1 bar of carbon dioxide (CO2) gas at a rate of about 100 cc / min. Before the test, the surface of the steel sample was polished with silicon carbon paper having a particle size of # 600. FIG. 4A illustrates an exemplary steel of the present disclosure at about 25 ° C. and a commercially available 304SS polarization curve. The solution treated steel of the present invention exhibited similar corrosion resistance compared to 304SS, as shown in FIG. 4B.

  While the present disclosure has been described primarily in the context of steel compositions for use in petroleum, gas, and / or petrochemical industry / system / application components, such description is merely used for disclosure purposes. And is not intended to limit the present disclosure. In contrast, it should be appreciated that the steel compositions of the present disclosure may be useful in a variety of applications, systems, operations, and / or industries.

  Although the systems and methods of the present disclosure have been described with reference to exemplary embodiments, the present disclosure is not limited to such exemplary embodiments and / or implementations. More precisely, the system and method of the present disclosure are capable of many implementations and applications, as will be apparent to those skilled in the art of the present disclosure. This disclosure expressly includes such modifications, improvements, and / or variations of embodiments of the present disclosure. Since many variations to the above arrangement can be made and many different embodiments of the present disclosure can be made without departing from the scope thereof, everything contained in the drawings and the specification is illustrative only. And is not intended to be construed in a limiting sense. In the above disclosure, additional modifications, changes, and substitutions are contemplated. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the disclosure.

Claims (22)

a. Providing a composition having 8-30 wt% manganese, 11-30 wt% chromium and the balance iron;
b. Melting the composition in a controlled environment, producing a liquid alloy steel composition;
c. Cooling the liquid alloy steel composition, forming the alloy steel composition;
d. Hot deforming the alloy steel composition;
e. Reheating the alloy steel composition for a predetermined time;
f. Cooling the alloy steel composition;
g. A method for producing an iron-based member, the method comprising cold-deforming the alloy steel composition.   The method for producing an iron-based member according to claim 1, wherein step b) comprises melting the composition at 1600 ° C. for 30 minutes.   The method for producing an iron-based member according to claim 1, wherein step c) is a step of cooling the liquid alloy steel composition to an ambient temperature, the step comprising forming the alloy steel composition.   The method for producing an iron-based member according to claim 1, wherein step d) includes hot-deforming the alloy steel composition at 800 ° C or higher.   The method for producing an iron-based member according to claim 1, wherein step e) includes reheating the alloy steel composition at 1000 ° C or higher for 1 hour.   The method for producing an iron-based member according to claim 1, wherein step e) comprises a step of reheating the alloy steel composition at 1200 ° C or higher for 1 hour.   The method for producing an iron-based member according to claim 1, wherein step f) includes a step of cooling the alloy steel composition to less than 300 ° C.   The method of manufacturing an iron-based member according to claim 7, wherein step f) comprises cooling the alloy steel composition at a rate of at least 10 ° C / second until the alloy steel composition is less than 300 ° C.   One or more alloys wherein the composition is selected from the group consisting of carbon, aluminum, silicon, nickel, cobalt, molybdenum, niobium, copper, titanium, vanadium, tungsten, nitrogen, boron, zirconium, hafnium, and combinations thereof The method for producing an iron-based member according to claim 1, further comprising a chemical element. a. Each of the nickel or cobalt is in the range of 0.5-20% by weight of the total composition;
b. The aluminum is in the range of 0.1 to 15% by weight of the total composition;
c. Each of the molybdenum, niobium, copper, titanium, tungsten or vanadium is in the range of 0.2 to 10% by weight of the total composition,
d. The silicon is in the range of 0.01 to 10% by weight of the total composition;
e. The nitrogen ranges from 0.01 to 3.0% by weight of the total composition;
f. The boron is in the range of 0.001 to 0.1% by weight of the total composition;
g. Each of the zirconium or hafnium is in the range of 0.2 to 6% by weight of the total composition.
A method for manufacturing the iron-based member according to claim 9. The composition is
a. 8-30 wt% manganese, 11-30 wt% chromium,
b. One or more alloying additives comprising 0.10 to 1.5 wt% carbon, 0.10 to 1.5 wt% nitrogen and combinations thereof;
c. 0.5-10 wt% silicon, 1.0-15 wt% aluminum and combinations thereof;
d. The method of manufacturing the iron-type member of Claim 1 containing remainder iron. a. Providing a composition having 8-30 wt% manganese, 11-30 wt% chromium and the balance iron;
b. Melting the composition in a controlled environment, producing a liquid alloy steel composition;
c. Cooling the liquid alloy steel composition, forming the alloy steel composition;
d. Hot deforming the alloy steel composition;
e. Reheating the alloy steel composition for a predetermined time;
f. Cooling the alloy steel composition;
g. The iron-type member manufactured by the process including the process of cold-deforming the said alloy steel composition.   The iron-based member according to claim 12, wherein step b) comprises melting the composition at 1600 ° C for 30 minutes.   13. The iron-based member according to claim 12, wherein step c) is a step of cooling the liquid alloy steel composition to ambient temperature, the step comprising forming the alloy steel composition.   The iron-based member according to claim 12, wherein step d) includes a step of hot-deforming the alloy steel composition at 800 ° C or higher.   The iron-based member according to claim 12, wherein step e) includes a step of reheating the alloy steel composition at 1000 ° C or higher for 1 hour.   The iron-based member according to claim 12, wherein step e) includes a step of reheating the alloy steel composition at 1200 ° C or higher for 1 hour.   The iron-based member according to claim 12, wherein step f) includes a step of cooling the alloy steel composition to less than 300 ° C.   The iron-based member of claim 18, wherein step f) includes cooling the alloy steel composition at a rate of at least 10 ° C./second until the alloy steel composition is below 300 ° C.   One or more alloys wherein the composition is selected from the group consisting of carbon, aluminum, silicon, nickel, cobalt, molybdenum, niobium, copper, titanium, vanadium, tungsten, nitrogen, boron, zirconium, hafnium, and combinations thereof The iron-based member according to claim 12, further comprising a chemical element. a. Each of the nickel or cobalt is in the range of 0.5-20% by weight of the total composition;
b. The aluminum is in the range of 0.1 to 15% by weight of the total composition;
c. Each of the molybdenum, niobium, copper, titanium, tungsten or vanadium is in the range of 0.2 to 10% by weight of the total composition,
d. The silicon is in the range of 0.01 to 10% by weight of the total composition;
e. The nitrogen ranges from 0.01 to 3.0% by weight of the total composition;
f. The boron is in the range of 0.001 to 0.1% by weight of the total composition;
g. The iron-based member according to claim 20, wherein each of the zirconium and hafnium is in the range of 0.2 to 6% by weight of the entire composition. The composition is
a. 8-30 wt% manganese, 11-30 wt% chromium,
b. One or more alloying additives comprising 0.10 to 1.5 wt% carbon, 0.10 to 1.5 wt% nitrogen and combinations thereof;
c. 0.5-10 wt% silicon, 1.0-15 wt% aluminum,
d. The iron-based member according to claim 12, comprising the remaining iron.

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