GRAIN BOUNDARY COHESION ENHANCED SULFIDE STRESS CRACKING (SSC)-RESISTANT STEEL ALLOYS

Abstract

Alloys, processes for preparing the alloys, and articles including the alloys are provided. The alloys can include, by weight, about 0% to about 8% nickel, about 1% to about 6% tungsten, about 1% to about 4% copper, about 0.1% to about 2% chromium, about 0.01% to about 1% vanadium, about 0.01% to about 0.5% carbon, about 0.01% to about 0.1% titanium, about 0.001% to about 0.01% boron, about 0% to about 1% silicon, and about 0% to about 0.1% calcium, the balance essentially iron and incidental elements and impurities.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No. 62/259,835, filed Nov. 25, 2015, and is herein incorporated by reference in its entirety.

BACKGROUND

Sulfide stress cracking (SSC) is a primary cause of failure for steel tubing in H₂S-containing (sour) environments. In general, the higher the strength of the steel, the more susceptible the alloy is to failure in sour environments. It is observed that such SSC steel failure is mostly caused by intergranular (IG) cracking, which is related to fracture by hydrogen embrittlement (HE). In addition, it is recognized that the IG-SSC of steels can be correlated to IG stress corrosion cracking (SCC), as caused by hydrogen. As such, there is a need for cost-competitive high strength steels with enhanced resistance to SCC/SSC, since known materials that are resistant to SCC/SSC (e.g., corrosion-resistant nickel-based alloys) are expensive and hinder the economic development of projects involving sour services.

SUMMARY

The oil and gas industry has a significant need for a high strength low alloy (HSLA) steel with a yield strength of 965-1100 MPa (140-160 ksi). Existing HSLA steels suffer from either a low sulfide stress corrosion cracking toughness or yield strength, or both. Accordingly, there exists a need for an HSLA steel that can be economically manufactured and have good sulfide stress corrosion cracking toughness and good yield strength.

In one aspect, disclosed is an alloy comprising, by weight, about 0% to about 8% nickel, about 1% to about 6% tungsten, about 1% to about 4% copper, about 0.1% to about 2% chromium, about 0.01% to about 1% vanadium, about 0.01% to about 0.5% carbon, about 0.01% to about 0.1% titanium, about 0.001% to about 0.01% boron, about 0% to about 1% silicon, and about 0% to about 0.1% calcium, the balance essentially iron and incidental elements and impurities.

Other aspects of the disclosure include processes for producing the alloy, and manufactured articles comprising the alloy.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

FIG. 1 is an illustration of K1SCC versus yield strength. The points labeled “Lit. HSLA (SSC)” in the lower left are literature values for existing HSLA oil and gas SSC-resistant steels. Note that these points are reported values of KISSC (which correlates to KISCC). The bottom curve is a fit to these points. The points labeled “HyTuf”, “4340”, “300M”, and “AerMet100” are existing high strength alloys, and follow the bottom curve. The points labeled “QT S53”, “QT PH48S” and “QT M54” are existing steels and are significantly higher than the bottom curve, presumably due to the increased grain boundary cohesion. The middle curve is the bottom curve shifted up to cross the “QT S53” values. An exemplary embodiment (QT-SSC alloy) is predicted to achieve a KISSC along the middle curve with a 140-160 ksi (965-1100 MPa) yield strength. The upper curve is the bottom curve shifted up to the KIC values of “QT S53” and “4340” (which are equivalent). Since KISCC/KISSC is a fraction of KIC, the purple curve demonstrates the effect of cohesion on bringing corrosion toughness from about 20% of KIC (the bottom curve) to about 80% of KIC (the middle curve).

FIG. 2 is a CALPHAD equilibrium step diagram of phase fraction vs. temperature for an exemplary embodiment (QT-SSC alloy).

FIG. 3 is a CALPHAD metastable step diagram of phase fraction vs. temperature for an exemplary embodiment (QT-SSC alloy).

FIG. 4 is a plot of hardness vs. aging temperature for QT-SSC steel, one embodiment of the disclosed alloys.

DETAILED DESCRIPTION

Disclosed are high strength low alloy (HSLA) steels, methods for making the alloys, and manufactured articles comprising the alloys. The disclosed alloys can possess both improved processing and physical properties over existing HSLA steels, such as improved sulfide stress cracking toughness with increased yield strength, making the alloys useful in extreme environments, such as those in oil and gas applications.

The disclosed alloys have improved sulfide stress cracking (SSC) toughness, reduced hydrogen embrittlement (HE), improved corrosion resistance, and improved yield strength, relative to existing HSLA steels (FIG. 1). These improved properties may be the result of incorporating comparatively greater amounts of tungsten, nickel, and copper in the alloys, which was discovered, in part, due to the development of predictive models. Additionally, the alloy was designed to implement a variety of strategies, includingin conjunction with improved grain boundary cohesionsurface scale formation, improved hydrogen trapping, slow bulk/grain boundary hydrogen diffusion, and promotion of surface H₂ formation.

Improved grain boundary cohesion: Intergranular fracture may be a primary SSC mode in high yield strength steels. The occurrence of intergranular fracture may be reduced by improving the grain boundary cohesion with alloying additions. The change in grain boundary cohesion due to alloying (Δ2γ in J/m²) is quantified by the Rice-Wang model (Rice, J. R.; Wang, J. S. Materials Science and Engineering, A107 (1989) 23-40):

$\begin{array}{cc}\mathrm{\Delta 2\gamma }=\sum _i{\Gamma }_iE_i^{\mathrm{pot}},& \left(\mathrm{eq}.1\right)\end{array}$

where E_i^pot is the embrittling potency of element i and Γ_i is the grain boundary composition of element i. Lower (more negative) values of Δ2γ indicate a stronger cohesion between grains and a greater resistance to intergranular cracking by SSC. The grain boundary composition is predicted by the McLean Gibbs isotherm (McLean, D. Grain boundaries in metals, London: Oxford University Press; 1957):

$\begin{array}{cc}\frac{{\Gamma }_i}{1-{\Gamma }_i}=x_i^{\mathrm{Matrix}}\exp \left(-\frac{E_i^{\mathrm{GB}}}{\mathrm{RT}}\right),& \left(\mathrm{eq}.2\right)\end{array}$

where x_i^Matrix is the alloy matrix composition (calculated with CALPHAD and internal thermodynamic databases), E_GBⁱ is the grain boundary segregation energy for element i, R is the gas constant, and T is absolute temperature. See “Segregation-induced changes in grain boundary cohesion and embrittlement in binary alloys” by Gibson and Schuh, Acta Materialia 95 (2015) 145-155 and “Designing Strength, Toughness, and Hydrogen Resistance: Quantum Steel” a dissertation by Kantner, Northwestern University (2002), each of which is herein incorporated by reference.

Grain boundary cohesion was accomplished in the disclosed alloys by specific alloying additions that both segregate to the matrix grain boundary (E_GBⁱ<0) and improve cohesion (E_i^pot<0). Tungsten was found to be a particularly potent cohesion enhancing element, and the tungsten content of the disclosed alloys is unique compared to existing alloys. Boron was also found to be a potent cohesion enhancing element, and a significant amount of boron can be incorporated to be present at the grain boundaries of the disclosed alloys.

Surface scale formation: Absorption of H into the alloy may promote SSC failure. Therefore, modification of surface chemistry to promote the formation of protective surface scales may slow corrosion and H absorption. Scales may be made from oxides, sulfides, or other p-block elements.

Effects of copper alloying: The addition of copper in the disclosed alloys may provide BCC copper precipitates and copper in the grain boundary, which can strengthen the alloy, alter scale formation, and promote H₂ recombination at the surface.

Improved hydrogen trapping: SSC may occur when hydrogen collects at grain boundaries. Therefore, impeding hydrogen diffusion by trapping hydrogen at precipitate interfaces may reduce intergranular SSC. Modification of the alloy chemistry to promote carbide and other precipitate formation with particular morphology (e.g., fine homogenously dispersed globular carbides) may decrease SSC in the alloys. Accordingly, the disclosed alloys may possess a large volume fraction of M₂C carbide, and heat treatment can ensure a fine, homogeneous carbide dispersion.

Slow bulk/grain boundary hydrogen diffusion: Hydrogen may diffuse through alloys in sufficient quantity and speed to promote cracking. However, the disclosed alloy compositions may slow diffusion of hydrogen in the bulk and along grain boundaries.

Promotion of surface H₂ formation: Sulfides may poison the steel surface hydrogen recombination reaction, greatly increasing the steel-absorbed H content. Therefore, modification of surface chemistry may promote the recombination of the adsorbed H into H₂ gas that evolves away from the surface. Introduction of alloying elements that lower the hydrogen overvoltage (acting as effective cathodic sites) may enhance the hydrogen recombination process.

A representative composition of the disclosed alloys (alloy QT-SSC) is summarized in Table 1. The table describes the nominal composition of elements in weight and atomic percentages. In addition, the matrix and grain boundary compositions are calculated to have the values listed in Table 1 at 500° C. (an example temperature).

	TABLE 1
	Ni	W	Cu	Cr	V	C	Ti	B	Fe
Nominal Comp	6.5	4	2.5	0.5	0.1	0.1	0.02	0.0015	balance
(wt %)
Nominal Comp	6.38	1.25	2.26	0.55	0.11	0.48	0.024	0.008
(atomic %)
Matrix Comp	6.66	0.058	0.13	0.19	0.015	0.01	0	0.0075
(atomic %)
Grain Boundary	52.1	4.65	10.3	0.51	0.063	2.09	0	89.18
Comp (atomic %)

In addition, the alloy is calculated to have a Δ2γ value of −2.64 J/m², an M₂C phase fraction of 0.0129, and a BCC copper phase fraction of 0.0295. Also, a CALPHAD equilibrium step diagram of phase fraction vs. temperature (FIG. 2), and a CALPHAD metastable step diagram of phase fraction vs. temperature (FIG. 3) of the disclosed alloy were generated. As shown in Table 2, QT-SSC has a significantly lower calculated Δ2γ value compared to prior art alloys, indicating superior predicted SSC resistance.

TABLE 2
Source	Name	C	Si	Mn	P	S	Cr	Mo	Cu	Ni	W	V	Nb	Al	N	Ti	B	Δ2γ
Delattre et al. 2011	A	0.43	0.79		0.01	0.003	0.5	1.46			0.64	0.2	0.019	0.03	0.0045	0.002	0.0005	−1.47
Delattre et al. 2011	B	0.34	0.36	0.39	0.011	0.003	0.49	1.29			0.52	0.1	0.021	0.02	0.0023	0.002	0.0005	−1.48
Delattre et al. 2011	C	0.33	0.37	0.38	0.011	0.003	0.93	1.5			0.008	0.05	0.081	0.02	0.0031	0.009	0.0012	−1.57
Turconi et al. 2012	13C	0.25	?	0.41			0.98	0.71					0.024	?		?	?	−1.47
Turconi et al. 2012	14	0.25	?	0.26			0.5	0.74					0.023	?		?	?	−1.58
Turconi et al. 2012	15	0.25	?	0.19			0.5	0.74				0.15	0.022	?		?	?	−1.60
Turconi et al. 2012	16	0.24	?	0.2			0.51	0.73					0.053	?		?	?	−1.68
Turconi et al. 2012	17	0.25	?	0.2			0.53	0.73			0.021	0.031	0.031	?		?	?	−1.65
QT-SSC		0.1					0.5		2.5	6.5	4	0.1				0.02	0.0015	−2.64

I. Definitions of Terms

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In case of conflict, the present document, including definitions, will control. Preferred methods and materials are described below, although methods and materials similar or equivalent to those described herein can be used in practice or testing of the present invention. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. The materials, methods, and examples disclosed herein are illustrative only and not intended to be limiting.

The term “solvus,” as used herein, may refer to a line (binary system) or surface (ternary system) on a phase diagram which separates a homogeneous solid solution from a field of several phases which may form by exsolution or incongruent melting.

The term “solidus,” as used herein, may refer to the temperature below which a mixture is completely solid.

The term “liquidus,” as used herein, may refer to the temperature above which a material is completely liquid, and the maximum temperature at which crystals can co-exist with the melt in thermodynamic equilibrium.

As used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. The terms “comprise(s),” “include(s),” “having,” “has,” “can,” “contain(s),” and variants thereof, as used herein, are intended to be open-ended transitional phrases, terms, or words that do not preclude the possibility of additional acts or structures. The present disclosure also contemplates other embodiments “comprising,” “consisting of” and “consisting essentially of” the embodiments or elements presented herein, whether explicitly set forth or not.

The conjunctive term “or” includes any and all combinations of one or more listed elements associated by the conjunctive term. For example, the phrase “an apparatus comprising A or B” may refer to an apparatus including A where B is not present, an apparatus including B where A is not present, or an apparatus where both A and B are present. The phrases “at least one of A, B, . . . and N” or “at least one of A, B, . . . N, or combinations thereof” are defined in the broadest sense to mean one or more elements selected from the group comprising A, B, . . . and N, that is to say, any combination of one or more of the elements A, B, . . . or N including any one element alone or in combination with one or more of the other elements which may also include, in combination, additional elements not listed.

The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (for example, it includes at least the degree of error associated with the measurement of the particular quantity). The modifier “about” should also be considered as disclosing the range defined by the absolute values of the two endpoints. For example, the expression “from about 2 to about 4” also discloses the range “from 2 to 4.” The term “about” may refer to plus or minus 10% of the indicated number. For example, “about 10%” may indicate a range of 9% to 11%, and “about 1” may mean from 0.9-1.1. Other meanings of “about” may be apparent from the context, such as rounding off, so, for example “about 1” may also mean from 0.5 to 1.4.

Any recited range described herein is to be understood to encompass and include all values within that range, without the necessity for an explicit recitation.

I. Alloys

The disclosed alloys may comprise nickel, tungsten, copper, chromium, vanadium, carbon, titanium, boron, silicon, calcium, and iron, along with incidental elements and impurities.

The alloys may comprise, by weight, about 0% to about 8% nickel, about 1% to about 6% tungsten, about 1% to about 4% copper, about 0.1% to about 2% chromium, about 0.01% to about 1% vanadium, about 0.01% to about 0.5% carbon, about 0.01% to about 0.1% titanium, about 0.001% to about 0.01% boron, about 0% to about 1% silicon, and about 0% to about 0.1% calcium, the balance essentially iron and incidental elements and impurities. It is understood that the alloys described herein may consist only of the above-mentioned constituents or may consist essentially of such constituents, or in other embodiments, may include additional constituents.

The alloys may comprise, by weight, about 0.5% to about 7.5% nickel, about 2% to about 5% tungsten, about 1.5% to about 3.5% copper, about 0.1% to about 1.5% chromium, about 0.01% to about 0.5% vanadium, about 0.01% to about 0.3% carbon, about 0.01% to about 0.075% titanium, about 0.001% to about 0.005% boron, about 0% to about 0.5% silicon, and about 0% to about 0.075% calcium, the balance essentially iron and incidental elements and impurities. It is understood that the alloys described herein may consist only of the above-mentioned constituents or may consist essentially of such constituents, or in other embodiments, may include additional constituents.

The alloys may comprise, by weight, about 1% to about 7% nickel, about 2.5% to about 4.5% tungsten, about 2% to about 3% copper, about 0.1% to about 1% chromium, about 0.01% to about 0.2% vanadium, about 0.01% to about 0.2% carbon, about 0.01% to about 0.05% titanium, about 0.001% to about 0.002% boron, about 0% to about 0.2% silicon, and about 0% to about 0.05% calcium, the balance essentially iron and incidental elements and impurities. It is understood that the alloys described herein may consist only of the above-mentioned constituents or may consist essentially of such constituents, or in other embodiments, may include additional constituents.

The alloys may comprise, by weight, about 6.3% to about 6.7% nickel, about 3.8% to about 4.2% tungsten, about 2.3% to about 2.7% copper, about 0.3% to about 0.7% chromium, about 0.08% to about 0.12% vanadium, about 0.08% to about 0.12% carbon, about 0.01% to about 0.03% titanium, about 0.0013% to about 0.0017% boron, about 0% to about 0.02% silicon, and about 0% to about 0.02% calcium, the balance essentially iron and incidental elements and impurities. It is understood that the alloys described herein may consist only of the above-mentioned constituents or may consist essentially of such constituents, or in other embodiments, may include additional constituents.

The alloys may comprise, by weight, about 0% to about 8% nickel, about 0% to about 7% nickel, about 0% to about 6% nickel, about 0% to about 5% nickel, about 0% to about 4% nickel, about 0% to about 3% nickel, about 0% to about 2% nickel, about 0% to about 1% nickel, about 0% to about 0.5% nickel, about 0.5% to about 8% nickel, about 0.5% to about 7% nickel, about 0.5% to about 6% nickel, about 0.5% to about 5% nickel, about 0.5% to about 4% nickel, about 0.5% to about 3% nickel, about 0.5% to about 2% nickel, about 0.5% to about 1% nickel, about 1% to about 8% nickel, about 1% to about 7% nickel, about 1% to about 6% nickel, about 1% to about 5% nickel, about 1% to about 4% nickel, about 1% to about 3% nickel, about 1% to about 2% nickel, about 2% to about 8% nickel, about 2% to about 7% nickel, about 2% to about 6% nickel, about 2% to about 5% nickel, about 2% to about 4% nickel, about 2% to about 3% nickel, about 3% to about 8% nickel, about 3% to about 7% nickel, about 3% to about 6% nickel, about 3% to about 5% nickel, about 3% to about 4% nickel, about 4% to about 8% nickel, about 4% to about 7% nickel, about 4% to about 6% nickel, about 4% to about 5% nickel, about 5% to about 8% nickel, about 5% to about 7% nickel, about 5% to about 6% nickel, about 6% to about 8% nickel, about 6% to about 7% nickel, and about 7% to about 8% nickel. The alloys may comprise, by weight, 0%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, or 8% nickel. The alloys may comprise, by weight, about 0% nickel, about 0.5% nickel, about 1% nickel, about 1.5% nickel, about 2% nickel, about 2.5% nickel, about 3% nickel, about 3.5% nickel, about 4% nickel, about 4.5% nickel, about 5% nickel, about 5.5% nickel, about 6% nickel, about 6.5% nickel, about 7% nickel, about 7.5% nickel, or about 8% nickel.

The alloys may comprise, by weight, about 1% to about 6% tungsten, about 1% to about 5% tungsten, about 1% to about 4% tungsten, about 1% to about 3% tungsten, about 1% to about 2% tungsten, about 1% to about 1.5% tungsten, about 1.5% to about 6% tungsten, about 1.5% to about 5% tungsten, about 1.5% to about 4% tungsten, about 1.5% to about 3% tungsten, about 1.5% to about 2% tungsten, about 2% to about 6% tungsten, about 2% to about 5% tungsten, about 2% to about 4% tungsten, about 2% to about 3% tungsten, about 3% to about 6% tungsten, about 3% to about 5% tungsten, about 3% to about 4% tungsten, about 4% to about 6% tungsten, about 4% to about 5% tungsten, or about 5% to about 6% tungsten. The alloys may comprise, by weight, 1%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, or 6° A tungsten. The alloys may comprise, by weight, about 1% tungsten, about 1.5% tungsten, about 1.6% tungsten, about 1.7% tungsten, about 1.8% tungsten, about 1.9% tungsten, about 2% tungsten, about 2.5% tungsten, about 3% tungsten, about 3.5% tungsten, about 4% tungsten, about 4.5% tungsten, about 5% tungsten, about 5.5% tungsten, or about 6% tungsten.

The alloys may comprise, by weight, about 1% to about 4% copper, about 1% to about 3% copper, about 1% to about 2% copper, about 2% to about 4% copper, about 2% to about 3% copper, or about 3% to about 4% copper. The alloys may comprise, by weight, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, or 4% copper. The alloys may comprise, by weight, about 1% copper, about 1.5% copper, about 2% copper, about 2.5% copper, about 3% copper, about 3.5% copper, or about 4% copper.

The alloys may comprise, by weight, about 0.1% to about 2% chromium, about 0.1% to about 1.5% chromium, about 0.1% to about 1% chromium, about 0.1% to about 0.5% chromium, about 0.5% to about 2% chromium, about 0.5% to about 1.5% chromium, about 0.5% to about 1% chromium, about 1% to about 2% chromium, about 1% to about 1.5% chromium, or about 1.5% to about 2% chromium. The alloys may comprise, by weight, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2% chromium. The alloys may comprise, by weight, about 0.1% chromium, about 0.2% chromium, about 0.3% chromium, about 0.4% chromium, about 0.5% chromium, about 0.6% chromium, about 0.7% chromium, about 0.8% chromium, about 0.9% chromium, about 1% chromium, about 1.1% chromium, about 1.2% chromium, about 1.3% chromium, about 1.4% chromium, about 1.5% chromium, about 1.6% chromium, about 1.7% chromium, about 1.8% chromium, about 1.9% chromium, or about 2% chromium.

The alloys may comprise, by weight, about 0.01% to about 1% vanadium, about 0.01% to about 0.8% vanadium, about 0.01% to about 0.6% vanadium, about 0.01% to about 0.4% vanadium, about 0.01% to about 0.2% vanadium, about 0.01% to about 0.1% vanadium, about 0.01% to about 0.05% vanadium, about 0.05% to about 1% vanadium, about 0.05% to about 0.8% vanadium, about 0.05% to about 0.6% vanadium, about 0.05% to about 0.4% vanadium, about 0.05% to about 0.2% vanadium, about 0.05% to about 0.1% vanadium, about 0.1% to about 1% vanadium, about 0.1% to about 0.8% vanadium, about 0.1% to about 0.6% vanadium, about 0.1% to about 0.4% vanadium, about 0.1% to about 0.2% vanadium, about 0.2% to about 1% vanadium, about 0.2% to about 0.8% vanadium, about 0.2% to about 0.6% vanadium, about 0.2% to about 0.4% vanadium, about 0.4% to about 1% vanadium, about 0.4% to about 0.8% vanadium, about 0.4% to about 0.6% vanadium, about 0.6% to about 1% vanadium, about 0.6% to about 0.8% vanadium, or about 0.8% to about 1% vanadium. The alloys may comprise, by weight, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1% vanadium. The alloys may comprise, by weight, about 0.01% vanadium, about 0.02% vanadium, about 0.03% vanadium, about 0.04% vanadium, about 0.05% vanadium, about 0.1% vanadium, about 0.2% vanadium, about 0.3% vanadium, about 0.4% vanadium, about 0.5% vanadium, about 0.6% vanadium, about 0.7% vanadium, about 0.8% vanadium, about 0.9% vanadium, or about 1% vanadium.

The alloys may comprise, by weight, about 0.01% to about 0.5% carbon, about 0.01% to about 0.4% carbon, about 0.01% to about 0.3% carbon, about 0.01% to about 0.2% carbon, about 0.01% to about 0.1% carbon, about 0.1% to about 0.5% carbon, about 0.1% to about 0.4% carbon, about 0.1% to about 0.3% carbon, about 0.1% to about 0.2% carbon, about 0.2% to about 0.5% carbon, about 0.2% to about 0.4% carbon, about 0.2% to about 0.3% carbon, about 0.3% to about 0.5% carbon, about 0.3% to about 0.4% carbon, or about 0.4% to about 0.5% carbon. The alloys may comprise, by weight, 0.01%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5% carbon. The alloys may comprise, by weight, about 0.01% carbon, about 0.05% carbon, about 0.1% carbon, about 0.15% carbon, about 0.2% carbon, about 0.25% carbon, about 0.3% carbon, about 0.35% carbon, about 0.4% carbon, about 0.45% carbon, or about 0.5% carbon.

The alloys may comprise, by weight, about 0.01% to about 0.1% titanium, about 0.01% to about 0.075% titanium, about 0.01% to about 0.05% titanium, about 0.01% titanium to about 0.025% titanium, about 0.025% to about 0.1% titanium, about 0.025% to about 0.075% titanium, about 0.025% to about 0.05% titanium, about 0.05% to about 0.1% titanium, about 0.05% to about 0.075% titanium, or about 0.075% to about 0.1% titanium. The alloys may comprise, by weight, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1% titanium. The alloys may comprise, by weight, about 0.01% titanium, about 0.02% titanium, about 0.03% titanium, about 0.04% titanium, about 0.05% titanium, about 0.06% titanium, about 0.07% titanium, about 0.08% titanium, about 0.09% titanium, or about 0.1% titanium.

The alloys may comprise, by weight, about 0.001% to about 0.01% boron, about 0.001% to about 0.0075% boron, about 0.001% to about 0.005% boron, about 0.001% to about 0.0025% boron, about 0.0025% to about 0.01% boron, about 0.0025% to about 0.0075% boron, about 0.0025% to about 0.005% boron, about 0.005% to about 0.01% boron, about 0.005% to about 0.0075% boron, or about 0.0075% to about 0.01% boron. The alloys may comprise, by weight, 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, or 0.01% boron. The alloys may comprise, by weight, about 0.001% boron, about 0.002% boron, about 0.003% boron, about 0.004% boron, about 0.005% boron, about 0.006% boron, about 0.007% boron, about 0.008% boron, about 0.009% boron, or about 0.01% boron.

The alloys may comprise, by weight, about 0% to about 1% silicon, about 0% to about 0.75% silicon, about 0% to about 0.5% silicon, about 0% to about 0.25% silicon, about 0.25% to about 1% silicon, about 0.25% to about 0.75% silicon, about 0.25% to about 0.5% silicon, about 0.5% to about 1% silicon, about 0.5% to about 0.75% silicon, or about 0.75% to about 1% silicon. The alloys may comprise, by weight, 0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1% silicon. The alloys may comprise, by weight, about 0% silicon, about 0.1% silicon, about 0.2% silicon, about 0.3% silicon, about 0.4% silicon, about 0.5% silicon, about 0.6% silicon, about 0.7% silicon, about 0.8% silicon, about 0.9% silicon, or about 1% silicon.

The alloys may comprise, by weight, about 0% to about 0.1% calcium, about 0% to about 0.075% calcium, about 0% to about 0.05% calcium, about 0% to about 0.025% calcium, about 0.025% to about 0.1% calcium, about 0.025% to about 0.075% calcium, about 0.025% to about 0.05% calcium, about 0.05% to about 0.1% calcium, about 0.05% to about 0.075% calcium, or about 0.075% to about 0.1% calcium. The alloys may comprise, by weight, 0%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1% calcium. The alloys may comprise, by weight, about 0% calcium, about 0.01% calcium, about 0.02% calcium, about 0.03% calcium, about 0.04% calcium, about 0.05% calcium, about 0.06% calcium, about 0.07% calcium, about 0.08% calcium, about 0.09% calcium, or about 0.1% calcium.

In one embodiment, the alloys comprise, by weight, about 6.5% nickel, about 4.5% tungsten, about 2.5% copper, about 0.5% chromium, about 0.1% vanadium, about 0.1% carbon, about 0.02% titanium, about 0.0015% boron, about 0% silicon, and about 0% calcium, the balance essentially iron and incidental elements and impurities.

The alloys may comprise, by weight, a balance of iron and incidental elements and impurities. The term “incidental elements and impurities,” may include one or more of niobium, ruthenium, lanthanum, zirconium, manganese, cerium, magnesium, and nitrogen.

The incidental elements and impurities may include one or more of niobium (e.g., maximum 2%), ruthenium (e.g., maximum 2%), lanthanum (e.g., maximum 2%), zirconium (e.g., maximum 2%), manganese (e.g., maximum 2%), cerium (e.g., maximum 2%), magnesium (e.g., maximum 2%), and nitrogen (e.g., maximum 0.02%).

The alloys may comprise, by weight, 6.5% nickel, 4.5% tungsten, 2.5% copper, 0.5% chromium, 0.1% vanadium, 0.1% carbon, 0.02% titanium, 0.0015% boron, 0% silicon, and 0% calcium, the balance essentially iron and incidental elements and impurities. The incidental elements and impurities may include one or more of niobium (e.g., maximum 2%), ruthenium (e.g., maximum 2%), lanthanum (e.g., maximum 2%), zirconium (e.g., maximum 2%), manganese (e.g., maximum 2%), copper (e.g., maximum 2%), vanadium (e.g., maximum 2%), cerium (e.g., maximum 2%), magnesium (e.g., maximum 2%), and nitrogen (e.g., maximum 0.02%).

The alloys may consist of, by weight, 6.5% nickel, 4.5% tungsten, 2.5% copper, 0.5% chromium, 0.1% vanadium, 0.1% carbon, 0.02% titanium, 0.0015% boron, 0% silicon, and 0% calcium, the balance essentially iron and incidental elements and impurities. The incidental elements and impurities may include one or more of niobium (e.g., maximum 2%), ruthenium (e.g., maximum 2%), lanthanum (e.g., maximum 2%), zirconium (e.g., maximum 2%), manganese (e.g., maximum 2%), copper (e.g., maximum 2%), vanadium (e.g., maximum 2%), cerium (e.g., maximum 2%), magnesium (e.g., maximum 2%), and nitrogen (e.g., maximum 0.02%).

The alloys may have a 42y value of about −4 J/m² to about 0 J/m², about −4 J/m² to about −1 J/m², about −4 J/m² to about −2 J/m², about −3 J/m² to about −2 J/m², about −3 J/m² to about −1 J/m², about −3 J/m² to about 0 J/m², or about −2.8 J/m²to about −2.5 J/m². The alloys may have a Δ2γ value of less than or equal to 0 J/m², less than or equal to −0.5 J/m², less than or equal to −1 J/m², less than or equal to −1.5 J/m², less than or equal to −2 J/m², less than or equal to −2.1 J/m², less than or equal to −2.2 J/m², less than or equal to −2.3 J/m², less than or equal to −2.4 J/m², less than or equal to −2.5 J/m², less than or equal to −2.6 J/m², less than or equal to −2.7 J/m², less than or equal to −2.8 J/m², less than or equal to −2.9 J/m², or less than or equal to −3 J/m². The alloys may have a Δ2γ value of 0 J/m², −0.5 J/m², −1 J/m², −1.5 J/m², −2 J/m², −2.1 J/m², −2.2 J/m², −2.3 J/m², −2.4 J/m², −2.5 J/m², −2.6 J/m², −2.64 J/m², −2.7 J/m², −2.8 J/m², −2.9 J/m², −3 J/m², −3.1 J/m², −3.2 J/m², −3.3 J/m², −3.4 J/m², −3.5 J/m², or −4 J/m². The alloys may have a Δ2γ value of about 0 J/m², about −0.5 J/m², about −1 J/m², about −1.5 J/m², about −2 J/m², about −2.5 J/m², about −2.64 J/m², about −3 J/m², about −3.5 J/m², or about −4 J/m².

The alloys may have a yield strength of about 800 MPa to about 1300 MPa, about 800 MPa to about 1200 MPa, about 800 MPa to about 1100 MPa, about 900 MPa to about 1100 MPa, or about 965 MPa to about 1100 MPa. The alloys may have a yield strength of greater than or equal to 800 MPa, greater than or equal to 825 MPa, greater than or equal to 850 MPa, greater than or equal to 875 MPa, greater than or equal to 900 MPa, greater than or equal to 925 MPa, greater than or equal to 950 MPa, greater than or equal to 975 MPa, greater than or equal to 1000 MPa, greater than or equal to 1025 MPa, greater than or equal to 1050 MPa, greater than or equal to 1075 MPa, greater than or equal to 1100 MPa, greater than or equal to 1150 MPa, greater than or equal to 1200 MPa, greater than or equal to 1250 MPa, or greater than or equal to 1300 MPa. The alloys may have a yield strength of 800 MPa, 810 MPa, 820 MPa, 830 MPa, 840 MPa, 850 MPa, 860 MPa, 870 MPa, 880 MPa, 890 MPa, 900 MPa, 910 MPa, 920 MPa, 930 MPa, 940 MPa, 950 MPa, 960 MPa, 965 MPa, 970 MPa, 980 MPa, 990 MPa, 1000 MPa, 1010 MPa, 1020 MPa, 1030 MPa, 1040 MPa, 1050 MPa, 1060 MPa, 1070 MPa, 1080 MPa, 1090 MPa, 1100 MPa, 1150 MPa, 1200 MPa, 1250 MPa, or 1300 MPa. The alloys may have a yield strength of about 800 MPa, about 900 MPa, about 1000 MPa, about 1100 MPa, about 1200 MPa, or about 1300 MPa. The yield strength may be measured according to ASTM E8 or ASTM E21.

The alloys may have a sulfide stress corrosion cracking toughness (K1SSC) value of about 30 MPa*m^1/2 to about 60 MPa*m^1/2, about 40 MPa*m^1/2 to about 60 MPa*m^1/2, about 50 MPa*m^1/2 to about 60 MPa*m^1/2, about 40 MPa*m^1/2 to about 50 MPa*m^1/2, or about 40 MPa*m^1/2 to about 45 MPa*m^1/2. The alloys may have a sulfide stress corrosion cracking toughness (K1SSC) value of greater than or equal to 30 MPa*m^1/2, greater than or equal to 33 MPa*m^1/2, greater than or equal to 35 MPa*m^1/2, greater than or equal to 38 MPa*m^1/2, greater than or equal to 40 MPa*m^1/2, greater than or equal to 43 MPa*m^1/2, greater than or equal to 45 MPa*m^1/2, greater than or equal to 48 MPa*m^1/2, greater than or equal to 50 MPa*m^1/2, greater than or equal to 55 MPa*m^1/2, greater than or equal to 58 MPa*m^1/2, or greater than or equal to 60 MPa*m^1/2. The alloys may have a sulfide stress corrosion cracking toughness (K1SSC) value of 30 MPa*m^1/2, 31 MPa*m^1/2, 32 MPa*m^1/2, 33 MPa*m^1/2, 34 MPa*m^1/2, 35 MPa*m^1/2, 36 MPa*m^1/2, 37 MPa*m^1/2, 38 MPa*m^1/2, 39 MPa*m^1/2, 40 MPa*m^1/2, 41 MPa*m^1/2, 42 MPa*m^1/2, 43 MPa*m^1/2, 44 MPa*m^1/2, 45 MPa*m^1/2, 46 MPa*m^1/2, 47 MPa*m^1/2, 48 MPa*m^1/2, 49 MPa*m^1/2, 50 MPa*m^1/2, 51 MPa*m^1/2, 52 MPa*m^1/2, 53 MPa*m^1/2, 54 MPa*m^1/2, 55 MPa*m^1/2, 56 MPa*m^1/2, 57 MPa*m^1/2, 58 MPa*m^1/2, 59 MPa*m^1/2, or 60 MPa*m^1/2. The alloys may have a sulfide stress corrosion cracking toughness (K1SSC) value of about 30 MPa*m^1/2, about 35 MPa*m^1/2, about 40 MPa*m^1/2, about 45 MPa*m^1/2, about 50 MPa*m^1/2, about 55 MPa*m^1/2, or about 60 MPa*m^1/2.

The alloys may have an M₂C phase fraction of about 0.01 to about 0.015, about 0.01 to about 0.013, or about 0.012 to about 0.013. The alloys may have an M₂C phase fraction of 0.01, 0.011, 0.012, 0.0125, 0.0126, 0.0127, 0.0128, 0.0129, 0.013, 0.0131, 0.0132, 0.0133, 0.0134, 0.0135, 0.014, or 0.015. The alloys may have an M₂C phase fraction of about 0.01, about 0.011, about 0.012, about 0.0129, about 0.013, about 0.014, or about 0.015.

In certain embodiments, M is selected from the group consisting of Fe, Cr, Cu, Ni, W, V, and Ti, or any combination thereof. In certain embodiments, M is selected from the group consisting of Cr, W, V, and Ti, or any combination thereof. In certain embodiments, M is selected from the group consisting of Cr, W, and V, or any combination thereof.

The alloys may have a BCC copper phase fraction of about 0.025 to about 0.035, about 0.025 to about 0.033, about 0.025 to about 0.03, about 0.027 to about 0.033, or about 0.027 to about 0.03. The alloys may have a body centered cubic copper phase fraction of 0.025, 0.026, 0.027, 0.028, 0.029, 0.0295, 0.03, 0.031, 0.032, 0.033, 0.034, or 0.035. The alloys may have a body centered cubic copper phase fraction of about 0.025, about 0.026, about 0.027, about 0.028, about 0.029, about 0.0295, about 0.03, about 0.031, about 0.032, about 0.033, about 0.034, or about 0.035.

II. Methods of Manufacture

Also disclosed are methods of manufacturing the disclosed alloys. The alloys may be produced by vacuum melt practices or air melt practices. Calcium or silicon may be added to the melt for the purpose of decreasing impurities such as sulfur, phosphorous, or nitrogen. Calcium or silicon may be added in minute quantities. Additional titanium may be added to the melt for the purpose of converting nitrogen to TiN. The alloys may be produced by methods including, but not limited to, single melting, double melting, casting, centrifugal casting, additive manufacturing, or powder production.

A method for producing the disclosed alloys may include, but are not limited to, steps such as preparing a melt, melting, casting, homogenization, hot rolling, hot working, cold rolling, cold working, solutionizing, quenching, quenching with oil, cooling, subzero cooling, warming, aging, hardening, or softening. These steps may be performed in a different order. These steps may be performed more than once, in a cycle. Not all steps are required. Other common preparation techniques and variations upon the methods disclosed herein will be apparent to one of ordinary skill in the art.

III. Articles of Manufacture

Also disclosed are manufactured articles including the disclosed alloys. Exemplary manufactured articles include, but are not limited to, steel pipes or tubes. The steel pipes or tubes may be used in oil or gas drilling, extraction, transport, or other services. The steel pipes or tubes may be formed by various methods, including piercing followed by hot rolling, extruding, forging, and other techniques, including those that form a tube or a pipe with no seam.

IV. Examples

A steel alloy was prepared and tested for physical properties. Table 3 shows the design and composition of the exemplified alloy (QT-SSC).

TABLE 3
Nominal composition (weight percentage) of exemplified alloy
	Ni	W	Cu	Cr	V	C	Ti	B	Fe
QT-SSC	6.5	4	2.5	0.5	0.1	0.1	0.02	0.0015	balance

Example 1: QT-SSC

A melt was prepared with the nominal composition of 6.5 Ni, 4 W, 2.5 Cu, 0.5 Cr, 0.1 V, 0.1 C, 0.02 Ti, 0.0015 B, and balance Fe, in wt %. From the melt, the QT-SSC alloy was prepared. Steel was melted and cast by vacuum induction melting at a weight of about 50 pounds. The steel was subjected to homogenization at 1204° C. for 8 hours, and hot rolled from an initial 4 inch round cross section to 0.75 inch by 2.75 inch plate. Test samples of the QT-SSC alloy were excised from the hot rolled plate and solutionized at 950° C. for 1 hour, quenched with oil, subzero cooled at −73° C. for about 1 hour, and warmed in air to room temperature.

In the as-solutionized state, the hardness of the QT-SSC steel was measured at about 38 on the Rockwell C scale. Samples were then subjected to isochronal aging heat treatments at secondary hardening temperatures in the range of 450 and 625° C. for 5 hours. As shown in FIG. 4, hardness was increased by aging in the range of 450 to 550° C., followed by softening by over-aging at above 550° C. Additional testing of room temperature mechanical properties indicated a range of achievable strength-toughness combinations with different aging conditions, as shown in Table 4.

TABLE 4
				%		Hardness
Aging	UTS	TYS	%	Reduction	CVN	(Rockwell	KIC	KISCC	Ratio
Condition	(ksi)	(ksi)	Elongation	in Area	(ft-lb)	C)	(ksi√in)	(ksi√in)	K1SCC/K1C
450° C./5 hr	190	170	16	53	26.5	41	103	—
550° C./5 hr	178	160	20	67	71	39	101	≧90.7	≧0.898
625° C./5 hr	157	138	20	66	79.5	30	93	—
Test	ASTM	ASTM	ASTM E8	ASTM E8	ASTM	ASTM	ASTM	ASTM
Specification	E8	E8			E23	E18	E399	F1624
Typical									~0.2-0.3
High-strength
Steel

Aging at 550° C. for 5 hours was shown to result in an optimal balance between tensile yield strength and fracture toughness for the exemplified alloy. The tensile yield strength in this condition was about 160 ksi and ultimate tensile strength was about 178 ksi. The ambient impact toughness in this condition was about 71 ft-lb, and the plain strain fracture toughness was about 101 ksiIin. Stress corrosion cracking testing in accordance with ASTM F1624 test methods indicated a fracture toughness of about 90.7 ksiIin in a 3.5% NaCl solution at an open circuit potential of about −0.571 VSCE.

It is understood that the disclosure may embody other specific forms without departing from the spirit or central characteristics thereof. The disclosure of aspects and embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the claims are not to be limited to the details given herein. Accordingly, while specific embodiments have been illustrated and described, numerous modifications come to mind without significantly departing from the spirit of the invention and the scope of protection is only limited by the scope of the accompanying claims. Unless noted otherwise, all percentages listed herein are weight percentages.

For reasons of completeness, various aspects of the present disclosure are set out in the following numbered clauses:

Clause 1. An alloy comprising, by weight, about 0% to about 8% nickel, about 1% to about 6% tungsten, about 1% to about 4% copper, about 0.1% to about 2% chromium, about 0.01% to about 1% vanadium, about 0.01% to about 0.5% carbon, about 0.01% to about 0.1% titanium, about 0.001% to about 0.01% boron, about 0% to about 1% silicon, and about 0% to about 0.1% calcium, the balance essentially iron and incidental elements and impurities.

Clause 2. The alloy of clause 1 comprising, by weight, about 6% to about 7% nickel, about 3.5% to about 4.5% tungsten, about 2% to about 3% copper, about 0.1% to about 1% chromium, about 0.01% to about 0.2% vanadium, about 0.01% to about 0.2% carbon, about 0.01% to about 0.05% titanium, and about 0.001% to about 0.002% boron, the balance essentially iron and incidental elements and impurities.

Clause 3. The alloy of clause 1, wherein the alloy has a calculated Δ2γ value of less than or equal to −2 J/m².

Clause 4. The alloy of clause 1, wherein the alloy has a yield strength of greater than or equal to 965 MPa (140 ksi), measured according to ASTM E8.

Clause 5. The alloy of clause 1, wherein the alloy has a sulfide stress corrosion cracking toughness (K1SSC) value of greater than or equal to 44 MPa*m^1/2 (40 ksi*in^1/2).

Clause 6. The alloy of clause 1, wherein the alloy has an M₂C phase fraction of 0.01 to 0.015, wherein M is selected from the group consisting of W, Cr, V, and Ti, or any combination thereof.

Clause 7. The alloy of clause 1, wherein the alloy has a body centered cubic copper phase fraction of 0.025 to 0.035.

Clause 8. The alloy of clause 1 comprising about 6.5% nickel.

Clause 9. The alloy of clause 1 comprising about 4% tungsten.

Clause 10. The alloy of clause 1 comprising about 2.5% copper.

Clause 11. The alloy of clause 1 comprising about 0.5% chromium.

Clause 12. The alloy of clause 1 comprising about 0.1% vanadium.

Clause 13. The alloy of clause 1 comprising about 0.1% carbon.

Clause 14. The alloy of clause 1 comprising about 0.02% titanium.

Clause 15. The alloy of clause 1 comprising about 0.0015% boron.

Clause 16. The alloy of clause 1 comprising, by weight, about 6.5% nickel, about 4.5% tungsten, about 2.5% copper, about 0.5% chromium, about 0.1% vanadium, about 0.1% carbon, about 0.02% titanium, and about 0.0015% boron, the balance essentially iron and incidental elements and impurities.

Clause 17. A method for producing an alloy comprising:

preparing a melt that comprises, by weight, about 0% to about 8% nickel, about 1% to about 6% tungsten, about 1% to about 4% copper, about 0.1% to about 2% chromium, about 0.01% to about 1% vanadium, about 0.01% to about 0.5% carbon, about 0.01% to about 0.1% titanium, about 0.001% to about 0.01% boron, about 0% to about 1% silicon, and about 0% to about 0.1% calcium, the balance essentially iron and incidental elements and impurities.

Clause 18. The method of clause 17, wherein the melt comprises, by weight, about 6% to about 7% nickel, about 3.5% to about 4.5% tungsten, about 2% to about 3% copper, about 0.1% to about 1% chromium, about 0.01% to about 0.2% vanadium, about 0.01% to about 0.2% carbon, about 0.01% to about 0.05% titanium, and about 0.001% to about 0.002% boron, the balance essentially iron and incidental elements and impurities.

Clause 19. The method of clause 17, wherein the melt comprises, by weight, about 6.5% nickel, about 4.5% tungsten, about 2.5% copper, about 0.5% chromium, about 0.1% vanadium, about 0.1% carbon, about 0.02% titanium, and about 0.0015% boron, the balance essentially iron and incidental elements and impurities.

Clause 20. The method of clause 17, wherein the alloy has a calculated Δ2γ value of less than or equal to −2 J/m².

Clause 21. The method of clause 17, wherein the alloy has a yield strength of greater than or equal to 965 MPa (140 ksi), measured according to ASTM E8.

Clause 22. The method of clause 17, wherein the alloy has a sulfide stress corrosion cracking toughness (K1SSC) value of greater than or equal to 44 MPa*m^1/2 (40 ksi*in^1/2).

Clause 23. The method of clause 17, wherein the alloy has an M₂C phase fraction of 0.01 to 0.015, wherein M is selected from the group consisting of W, Cr, V, and Ti, or any combination thereof.

Clause 24. The method of clause 17, wherein the alloy has a body centered cubic copper phase fraction of 0.025 to 0.035.

Clause 25. The method of clause 17, wherein the alloy is produced by vacuum melt or air melt practices.

Clause 26. A manufactured article comprising an alloy that comprises, by weight, about 0% to about 8% nickel, about 1% to about 6% tungsten, about 1% to about 4% copper, about 0.1% to about 2% chromium, about 0.01% to about 1% vanadium, about 0.01% to about 0.5% carbon, about 0.01% to about 0.1% titanium, about 0.001% to about 0.01% boron, about 0% to about 1% silicon, and about 0% to about 0.1% calcium, the balance essentially iron and incidental elements and impurities.

Clause 27. The article of clause 26, wherein the alloy comprises, by weight, about 6% to about 7% nickel, about 3.5% to about 4.5% tungsten, about 2% to about 3% copper, about 0.1% to about 1% chromium, about 0.01% to about 0.2% vanadium, about 0.01% to about 0.2% carbon, about 0.01% to about 0.05% titanium, and about 0.001% to about 0.002% boron, the balance essentially iron and incidental elements and impurities.

Clause 28. The article of clause 26, wherein the alloy comprises, by weight, about 6.5% nickel, about 4.5% tungsten, about 2.5% copper, about 0.5% chromium, about 0.1% vanadium, about 0.1% carbon, about 0.02% titanium, and about 0.0015% boron, the balance essentially iron and incidental elements and impurities.

Clause 29. The article of clause 26, wherein the alloy has a calculated Δ2γ value of less than or equal to −2 J/m².

Clause 30. The article of clause 26, wherein the alloy has a yield strength of greater than or equal to 965 MPa (140 ksi), measured according to ASTM E8.

Clause 31. The article of clause 26, wherein the alloy has a sulfide stress corrosion cracking toughness (K1SSC) value of greater than or equal to 44 MPa*m^1/2 (40 ksi*in^1/2).

Clause 32. The article of clause 26, wherein the alloy has an M₂C phase fraction of 0.01 to 0.015, wherein M is selected from the group consisting of W, Cr, V, and Ti, or any combination thereof.

Clause 33. The article of clause 26, wherein the alloy has a body centered cubic copper phase fraction of 0.025 to 0.035.

Clause 34. The article of clause 26, wherein the article is a steel pipe or steel tube.

Claims

1. An alloy comprising, by weight, about 0% to about 8% nickel, about 1% to about 6% tungsten, about 1% to about 4% copper, about 0.1% to about 2% chromium, about 0.01% to about 1% vanadium, about 0.01% to about 0.5% carbon, about 0.01% to about 0.1% titanium, about 0.001% to about 0.01% boron, about 0% to about 1% silicon, and about 0% to about 0.1% calcium, the balance essentially iron and incidental elements and impurities.

2. The alloy of claim 1 comprising, by weight, about 6% to about 7% nickel, about 3.5% to about 4.5% tungsten, about 2% to about 3% copper, about 0.1% to about 1% chromium, about 0.01% to about 0.2% vanadium, about 0.01% to about 0.2% carbon, about 0.01% to about 0.05% titanium, and about 0.001% to about 0.002% boron, the balance essentially iron and incidental elements and impurities.

3. The alloy of claim 1, wherein the alloy has a calculated Δ2γ value of less than or equal to −2 J/m2.

4. The alloy of claim 1, wherein the alloy has a yield strength of greater than or equal to 965 MPa (140 ksi), measured according to ASTM E8.

5. The alloy of claim 1, wherein the alloy has a sulfide stress corrosion cracking toughness (K1SSC) value of greater than or equal to 44 MPa*m1/2 (40 ksi*in1/2).

6. The alloy of claim 1, wherein the alloy has an M2C phase fraction of 0.01 to 0.015, wherein M is selected from the group consisting of W, Cr, V, and Ti, or any combination thereof

7. The alloy of claim 1, wherein the alloy has a body centered cubic copper phase fraction of

0. 025 to 0.035.

8. The alloy of claim 1 comprising about 6.5% nickel.

9. The alloy of claim 1 comprising about 4% tungsten.

10. The alloy of claim 1 comprising about 2.5% copper.

11. The alloy of claim 1 comprising about 0.5% chromium.

12. The alloy of claim 1 comprising about 0.1% vanadium.

13. The alloy of claim 1 comprising about 0.1% carbon.

14. The alloy of claim 1 comprising about 0.02% titanium.

15. The alloy of claim 1 comprising about 0.0015% boron.

16. The alloy of claim 1 comprising, by weight, about 6.5% nickel, about 4.5% tungsten, about 2.5% copper, about 0.5% chromium, about 0.1% vanadium, about 0.1% carbon, about 0.02% titanium, and about 0.0015% boron, the balance essentially iron and incidental elements and impurities.

17. A method for producing an alloy comprising:

preparing a melt that comprises, by weight, about 0% to about 8% nickel, about 1% to about 6% tungsten, about 1% to about 4% copper, about 0.1% to about 2% chromium, about 0.01% to about 1% vanadium, about 0.01% to about 0.5% carbon, about 0.01% to about 0.1% titanium, about 0.001% to about 0.01% boron, about 0% to about 1% silicon, and about 0% to about 0.1% calcium, the balance essentially iron and incidental elements and impurities.

18. The method of claim 17, wherein the melt comprises, by weight, about 6% to about 7% nickel, about 3.5% to about 4.5% tungsten, about 2% to about 3% copper, about 0.1% to about 1% chromium, about 0.01% to about 0.2% vanadium, about 0.01% to about 0.2% carbon, about 0.01% to about 0.05% titanium, and about 0.001% to about 0.002% boron, the balance essentially iron and incidental elements and impurities.

19. The method of claim 17, wherein the melt comprises, by weight, about 6.5% nickel, about 4.5% tungsten, about 2.5% copper, about 0.5% chromium, about 0.1% vanadium, about 0.1% carbon, about 0.02% titanium, and about 0.0015% boron, the balance essentially iron and incidental elements and impurities.

20. The method of claim 17, wherein the alloy has a calculated Δ2γ value of less than or equal to −2 J/m2.

21. The method of claim 17, wherein the alloy has a yield strength of greater than or equal to 965 MPa (140 ksi), measured according to ASTM E8.

22. The method of claim 17, wherein the alloy has a sulfide stress corrosion cracking toughness (K1SSC) value of greater than or equal to 44 MPa*m1/2 (40 ksi*in1/2).

23. The method of claim 17, wherein the alloy has an M2C phase fraction of 0.01 to 0.015, wherein M is selected from the group consisting of W, Cr, V, and Ti, or any combination thereof

24. The method of claim 17, wherein the alloy has a body centered cubic copper phase fraction of 0.025 to 0.035.

25. The method of claim 17, wherein the alloy is produced by vacuum melt or air melt practices.

26. A manufactured article comprising an alloy that comprises, by weight, about 0% to about 8% nickel, about 1% to about 6% tungsten, about 1% to about 4% copper, about 0.1% to about 2% chromium, about 0.01% to about 1% vanadium, about 0.01% to about 0.5% carbon, about 0.01% to about 0.1% titanium, about 0.001% to about 0.01% boron, about 0% to about 1% silicon, and about 0% to about 0.1% calcium, the balance essentially iron and incidental elements and impurities.

27. The article of claim 26, wherein the alloy comprises, by weight, about 6% to about 7% nickel, about 3.5% to about 4.5% tungsten, about 2% to about 3% copper, about 0.1% to about 1% chromium, about 0.01% to about 0.2% vanadium, about 0.01% to about 0.2% carbon, about 0.01% to about 0.05% titanium, and about 0.001% to about 0.002% boron, the balance essentially iron and incidental elements and impurities.

28. The article of claim 26, wherein the alloy comprises, by weight, about 6.5% nickel, about 4.5% tungsten, about 2.5% copper, about 0.5% chromium, about 0.1% vanadium, about 0.1% carbon, about 0.02% titanium, and about 0.0015% boron, the balance essentially iron and incidental elements and impurities.

29. The article of claim 26, wherein the alloy has a calculated Δ2γ value of less than or equal to −2 J/m2.

30. The article of claim 26, wherein the alloy has a yield strength of greater than or equal to 965 MPa (140 ksi), measured according to ASTM E8.

31. The article of claim 26, wherein the alloy has a sulfide stress corrosion cracking toughness (K1SSC) value of greater than or equal to 44 MPa*m1/2 (40 ksi*in1/2).

32. The article of claim 26, wherein the alloy has an M2C phase fraction of 0.01 to 0.015, wherein M is selected from the group consisting of W, Cr, V, and Ti, or any combination thereof

33. The article of claim 26, wherein the alloy has a body centered cubic copper phase fraction of 0.025 to 0.035.

34. The article of claim 26, wherein the article is a steel pipe or steel tube.