MXPA00001269A - High-strength, notch-ductile precipitation-hardening stainless steel alloy - Google Patents

Abstract

A precipitation hardenable, martensitic stainless steel alloy is disclosed consisting essentially of, in weight percent, about:C 0.03 max, Mn 1.0 max, Si 0.75 max, P 0.040 max, S 0.020 max, Cr 10 - 13, Ni 10.5 - 11.6, Ti 1.5 - 1.8, Mo 0.25 - 1.5, Cu 0.95 max, Al 0.25 max, Nb 0.3 max, B 0.010 max, N 0.030 max, Ce 0.001 - 0.025, the balance essentially iron. The disclosed alloy provides a unique combination of stress-corrosion cracking resistance, strength, and notch toughness even when used to form large cross-section pieces. A method of making such an alloy includes adding cerium during the melting process in a amount sufficient to yield an effective amount of cerium in the alloy product.

Description

STRUCTURALLY HARDENED STAINLESS STEEL ALLOY, HIGH STRENGTH Field of the Invention The present invention relates to martensitic, structurally hardenable stainless steel alloys and in particular to a martensitic stainless steel alloy of Cr-Ni-Ti-Mo, and an article made therefrom, which has a unique combination of resistance to cracking by stress-corrosion, resistant and tenacious to the formation of cracks.

BACKGROUND OF THE INVENTION Many industrial applications, including the aeronautical industry, require the use of manufactured parts of high strength alloys. A method for the production of such high-strength alloys has developed structurally hardened alloys. A structurally hardened alloy is an alloy where a precipitate forms within the ductile matrix of the alloy. The precipitated particles inhibit the dislocations within the ductile matrix thus reinforcing the alloy.

One of the chrono-hardened stainless steel alloys seeks to provide high strength by adding titanium and columbium and controlling chromium, nickel and copper to ensure a martensitic structure. To provide optimum toughness, this alloy is annealed at a relatively low temperature. Such a low annealing temperature is required to form a Laves phase rich in Fe-Ti-Nb before aging. Such action prevents the excessive formation of structural hardening and provides greater availability of nickel for the reversion of austenite. However, at the low annealing temperatures used for this alloy, the microstructure of the alloy does not completely recrystallize. These conditions do not promote the effective use of hardening element additions and produce a material whose strength and toughness are highly sensitive to processing. In another structurally known hardenable stainless steel, the elements chrome, nickel, aluminum, carbon and molybdenum are critically balanced in the alloy. In addition, manganese, silicon, phosphorus, sulfur and nitrogen are kept at low levels so as not to reduce the desired combination of properties provided by the alloy.

Although structurally known hardenable stainless steels have hitherto provided acceptable properties, the need has arisen for an alloy which provides better strength, together with at least the same level of toughness to crack formation and corrosion resistance provided by stainless steels. structurally hardenable, known. An alloy that has greater strength and maintains at the same time the same level of toughness to crack formation and corrosion resistance, particularly resistance to stress-corrosion cracking, would be particularly useful in the aeronautical industry, because the structural members Manufactured from such alloys could be lighter in weight than the same manufactured parts of the alloys currently available. A reduction in the weight of such structural members is desirable, since it results in greater fuel efficiency. Given the foregoing, it would be highly desirable to have an alloy that provides an improved combination of stress-corrosion resistance, strength and crack-toughness and at the same time be processed easily and reliably.

Brief Description of the Invention The disadvantages associated with structurally known martensitic, hardenable stainless steel alloys are largely solved by the alloy according to the present invention. The alloy according to the present invention is a martensitic stainless steel alloy of structurally hardenable Cr-Ni-Ti-Mo which provides a unique combination of resistance to stress-corrosion cracking, strength and cracking toughness. The broad, intermediate and preferred composition ranges of the structurally hardened artensitic stainless steel of the present invention are as follows, in percent by weight: Wide Preferred Intermediate C 0.03 max 0.02 max 0.015 max Mn 1.0 max 0.25 max 0.10 max Yes 0.75 max 0.25 max 0.10 max 0. 040 max 0.015 max 0.010 max Wide Intermediate Preferred 0. 020 max 0.010 max 0.005 max Cr 10 -13 10.5 - 12.5 11.0 - 12.0 Ni 10.5 11.6 10.75- 11.25 10.85 - 11.25 Ti 1.5 - 1.8 1.5 1.7 1.5 - 1.7 Mo 0.25 - 1.5 0.75 - 1.25 0.9 - 1.1 Cu 0.95 max 0.50 max 0.25 max At 0.25 max 0.050 max 0.025 max Nb 0.3 max 0.050 max 0.025 max B 0.010 max 0.001 0.005 0.0015 0.0035 N 0.030 max 0.015 max 0.010 max Ce to 0.025 0. 001 - 0 015 0. 002 - 0 010 The rest of the alloy is essentially iron, except for the usual impurities found in the commercial grades of such steels and minor amounts of additional elements, which can vary from a few thousandths of a percent to large quantities that do not objectionably damage the desired combination of the properties provided by this alloy. The above tabulation was provided as a convenient summary and is not therefore intended to restrict the lower and upper values of the ranges of the individual elements of the alloy of this invention to be used in mutual combination, or to restrict the ranges of the elements for used only in combination with each other. Thus, one or more of the ranges of an element of the broad composition can be used with one or more of the other ranges for the remaining elements in the preferred composition. In addition, a minimum or maximum may be used for an element of a preferred embodiment with the maximum or minimum for that element of another preferred embodiment. Through this application, unless otherwise indicated, percent (%) means percent by weight.

DETAILED DESCRIPTION In the alloy according to the present invention, the unique combination of strength, crack toughness and resistance to stress-corrosion cracking is achieved by balancing the elements chromium, nickel, titanium and molybdenum. At least about 10%, better yet at least about 10.5%, and preferably at least about 11.0% of chromium is present in the alloy to provide corrosion resistance, as compared to that of a conventional stainless steel under oxidizing conditions. At least about 10.5%, better still at least about 10.75%, and preferably at least about 10.85% of nickel is present to the alloy because it benefits the crack toughness of the alloy. At least about 1.5% of titanium is present in the alloy to benefit the strength of the alloy through the precipitation of a phase rich in nickel and titanium during aging. At least about 0.25%, still better at least about 0.75%, and preferably at least about 0.9% molybdenum is also present in the alloy, because it contributes to the crack toughness of the alloy. Molybdenum also benefits the corrosion resistance of the alloy by reducing the media and environments that promote attack by pitting and stress-corrosion cracking. When chromium, nickel, titanium and / or molybdenum are not properly balanced, the ability of the alloy to completely transform to a martensitic structure, using conventional processing techniques, is inhibited. In addition, the ability of the alloy to remain substantially totally martensitic when treated with solutions and chrono-hardens deteriorates. Under such conditions, the strength provided by the alloy is significantly reduced. Therefore, the chromium, nickel, titanium and molybdenum present in this alloy are restricted. More particularly, chromium is limited to no more than about 13%, better still to no more than about 12.5% and preferably no more than about 12.0% and nickel is limited to no more than about 11.6% and preferably to no more than approximately 11.25%. Titanium is restricted to no more than about 1.8% and preferably to no more than about 1.7% and molybdenum is restricted to no more than about 1.5%, better still, to no more than about 1.25%, and preferably no more than about 1.1%. Sulfur and phosphorus tend to segregate towards the grain boundaries of this alloy. Such segregation reduces adhesion of the grain boundary, which adversely affects fracture toughness, cracking toughness, and tensile strength of the alloy carved specimen. A product form of this alloy that has a large cross section, ie, >; 0.7 pig2 (> 4 cm2), does not undergo sufficient thermomechanical processing to homogenize the alloy and neutralize the adverse effect of sulfur and phosphorus that are concentrated in the grain boundaries. For products of large section size, a small addition of cerium is preferably made to the alloy to benefit the fracture toughness, crack toughness and tensile strength with a fitted specimen of the alloy combining with sulfur and phosphorus to facilitate its removal from the alloy. For the sulfur and phosphorus to be adequately removed from the alloy, the ratio of the amount of cerium added to the amount of sulfur present to the alloy is at least about 1: 1, better yet at least about 2: 1, and preferably at least about 3: 1. Only quantities at trace levels (ie, <0.001%) of ceria in the alloy need to be retained to realize the benefits of the addition of the cerium. However, to ensure that sufficient cerium has been added and prevent too much sulfur and phosphorus from being retained in the final product, at least about 0.001% and better still, at least about 0.002% cerium in the alloy is preferably present. Too much cerium has a damaging effect on the hot working capacity of the alloy and on its fracture toughness. Therefore, cerium is restricted to no more than about 0.025%, better still to no more about 0.15% and preferably no more than about 0.010%. Alternatively, the cerium to sulfur ratio of the alloy is not greater than about 15: 1, still better not more than about 12: 1, and preferably not more than about 10: 1. Magnesium, yttrium, or other rare earth metals such as lanthanum may also be present in the alloy instead of some or all of the cerium. Additional elements such as boron, aluminum, niobium, manganese, and silicon may be present in controlled amounts to benefit other desirable properties provided by this alloy. More specifically, up to about 0.010% boron, better still up to about 0.005% boron, and preferably up to about 0.0035% boron in the alloy, can be present to benefit the hot working capacity of the alloy. alloy. To provide the desired effect, at least about 0.001% and preferably at least about 0.0015% in the alloy is present. Aluminum and / or niobium may be present in the alloy to benefit the proportional yield strength and tensile strength. More particularly, up to about 0.25%, better still up to about 0.10%, still better up to about 0.050%, and preferably up to about 0.025% aluminum in the alloy can be present. It may also be present up to about 0.3%, better still up to about 0.10%, better still up to about 0.050%, and preferably up to about 0.025% of niobium in the alloy. Although proportional elastic limits and higher ultimate tensile strengths can be obtained when aluminum and / or niobium are present in this alloy, the increase in strength develops at the expense of crack toughness. Therefore, when an optimum cracking tenacity is desired, aluminum and niobium are restricted to the usual residual levels.

They may be present in the alloy up to about 1.0%, better still up to about 0.5%, better still up to about 0.25% and preferably up to about 0.10% manganese and / or up to about 0.75%, better still up to about 0.5%, better still up to about 0.25%, and preferably up to about 0.010% silicon as waste from scrap or scrap sources or deoxidizing additions. Such additions are beneficial when the alloy is not vacuum fused. Manganese and / or silicon are preferably maintained at low levels due to their damaging effects on toughness, corrosion resistance, and the balance of the austenite-martensite phase in the matrix material. The rest of the alloy is essentially iron, in addition to the usual impurities found in the commercial grades of the alloys intended for similar services or uses. The levels of such elements are controlled so that they do not adversely affect the desired properties. In particular, too much carbon and / or nitrogen damage the corrosion resistance and adversely affect the toughness provided by this alloy. Accordingly, no more than about 0.03%, still better not more than about 0.02%, and preferably no more than about 0.015% carbon in the alloy is present. Also, no more than about 0.030%, better yet, no more than about 0.015%, no more than about 0.010% nitrogen in the alloy is present. When carbon and / or nitrogen are present in larger amounts, the carbon and / or nitrogen bonds with the titanium to form nonmetallic inclusions rich in titanium. This reaction inhibits the formation of the phase rich in nickel and titanium which is a major factor in the high strength provided by this alloy. Phosphorus is kept at a low level due to its harmful effect on toughness and corrosion resistance. Accordingly, no more than about 0.040% is present, better still no more than about 0.015%, and preferably no more than about 0.010% phosphorus in the alloy. It is present no more than about 0.020%, still better not more than about 0.010%, and preferably no more than about 0.005% sulfur in the alloy. Higher amounts of sulfur promote the formation of non-metallic inclusions rich in titanium, which, like carbon and nitrogen, inhibit the desired reinforcing effect of titanium. Also, higher amounts of sulfur adversely affect the hot working capacity and corrosion resistance of this alloy and damage its toughness, particularly in a transverse direction. Too much copper adversely affects the tenacity of cracking, ductility and strength of this alloy. Therefore, the alloy contains no more than about 0.95%, better still no more than about 0.75%, still better not more than about 0.50%, and preferably no more than about 0.25% copper. No special techniques are required in the melting, casting, or working of the alloy of the present invention. Fusion by vacuum induction (VIM) or vacuum induction fusion followed by vacuum arc remelting (VAR) are the preferred methods for melting and refining, although other practices may be used. The preferred method to provide cerium in this alloy is through the addition of mischmetal during the VIM. The mischmetal is added in an amount sufficient to produce the necessary amount of cerium, as discussed above, in the final ingot as it was melted. In addition, this alloy can be made using powder metallurgy techniques, if desired. In addition, although the alloy of the present invention can be worked hot or cold, cold working increases the mechanical strength of the alloy. The structurally hardened alloy of the present invention is annealed in solution to develop the desired combination of properties. The annealing temperature in solution must be sufficiently high to dissolve essentially all the undesirable precipitates in the matrix material of the alloy. Nevertheless, if the temperature of the annealing in solution is very high, it will damage the toughness to the fracture of the alloy promoting an excessive growth of the grain. Typically, the alloy of the present invention is annealed in solution at 1700 ° C -1900 ° F (927 ° C - 1038 ° C) for 1 hour and then annealed. When desired, this alloy can also be subjected to a deep cooling treatment after being quenched, to develop even greater strength in the alloy. The deep cooling treatment cools the alloy to a temperature sufficiently lower than the martensite termination temperature to ensure that the transformation of the martensite is completed. Typically, a deep cooling treatment consists of cooling the alloy to below about -100 ° F (-73 ° C) for about 1 hour. However, the need for a deep cooling treatment will be affected, at least in part, by the finished temperature of the alloy martensite. If the finished temperature of the martensite is sufficiently high, the transformation to a martensitic structure will proceed without the need for a deep cooling treatment. In addition, the need for a deep cooling treatment may also depend on the size of the piece being manufactured. As the size of the piece increases, the segregation in the alloy becomes more significant and the use of a deep cooling treatment becomes more beneficial. In addition, it may be necessary to increase the time interval for the piece to be cooled, for large pieces, to complete the transformation of the martensite. For example, it has been found that in a part having a large cross-sectional area, a deep cooling treatment lasting about 8 hours is preferred to develop the high strength characteristic of this alloy. The alloy of the present invention is chrono-hardened according to the techniques used for structurally known hardened stainless steel alloys, as is known to those skilled in the art. For example, the alloys are aged at a temperature between about 900 ° F (482 ° C) and about 1150 ° F (621 ° C) for about 4 hours. The specific aging conditions used are selected considering that: (1) the final tensile strength of the alloy decreases as the aging temperature increases; and (2) the time required to chronose the alloy to a desired resistance level increases as the aging temperature decreases. The alloy of the present invention can be formed into a variety of product forms for a wide variety of uses and contributes by itself to the formation of billets, rods, rods, wires, bands, plates or sheets using conventional practices. The alloy of the present invention is useful in a wide range of practical applications, which require an alloy having a good combination of stress-corrosion cracking resistance, strength and cracking toughness. In particular, the alloy of the present invention can be used to produce structural members and fasteners for aircraft and the alloy is also very suitable for use in medical or dental instruments.

Table 1 Example / C Mn Yes P S Cr Ni Mo Cu Ti B N Nb At Ce Fe Load No. 1 0.003 0.09 0.02 .006 0.003 11.54 11.13 1.00 0.05 1.61 0.0013 0.004 < 0.01 Rest 2 0.006 0.08 0.05 0.008 0.005 11.57 11.02 1.00 0.05 1.52 0.0019 0.004 < 0.01 < 0.01 - Rest. 3 0.009 0.08 0.04 0.008 0.004 11.61 11.03 1.00 0.06 1.68 0.0021 0.005 < 0.01 < 0.01 Rest 4 0.008 0.08 0.05 0.007 0.004 11.60 11.05 1.43 0.05 1.52 0.0020 0.005 < 0.01 < 0.01 - Rest. 5 0.012 0.08 0.07 0.010 0.001 11.58 10.46 1.00 0.06 1.58 0.0024 0.004 < 0.01 < 0.01 Rest 6 0.008 0.10 0.07 0.009 0.003 11.54 10.77 1.00 0.05 1.55 0.0020 0.004 < 0.01 < 0.01 - Rest. 7 0.008 0.10 0.05 0.009 0.002 11.62 11.05 0.99 0.07 1.58 0.0030 0.003 < 0.01 0.017 Rest.1 8 0.007 0.07 0.06 0.010 0.001 11.63 10.92 0.75 0.06 1.58 0.0024 0.004 OO < 0.01 < 0.01 - Rest. 9 0.003 0.08 0.07 0.009 0.001 11.49 10.84 0.50 0.06 1.58 0.0023 0.004 < 0.01 < 0.01 - Rest. 10 0.012 0.08 0.07 0.009 0.002 11.60 10.84 0.28 O.06 1.50 0.0025 0.002 < 0.01 0.01 Rest. 11 0.007 0.10 0.05 0.010 0.001 11.62 10.99 1.49 0.06 1.67 0.0020 0.004 < 0.01 0.014 - Rest.2 12 0.006 0.08 0.05 0.007 0.005 11.58 11.08 0.98 0.05 1.52 0.0017 0.005 0.26 < 0.01 Rest 13 0.007 0.08 0.05 0.007 0.005 11.56 10.98 1.00 0.05 1.70 0.0016 0.004 0.25 < 0.01 Rest 14 0.006 0.08 0.05 0.007 0.005 11.55 11.02 1.02 0.05 1.54 0.0018 0.005 < 0.01 0.22 - Rest. 15 0.008 0.08 0.04 0.007 0.005 11.62 11.03 1.03 0.05 1.54 0.0017 0.005 0.25 0.20 - Rest .. 16 0.007 0.08 0.04 0.008 0.005 11.68 11.09 1.47 0.05 1.52 0.0017 0.004 0.26 < 0.01 Rest (Continuation Table 1) E j us / C Mn Yes P S Cr Ni Mo Cu Ti B N Nb At Ce Fe Load No. 17 0.008 0.08 0.05 0.006 0.003 11.56 10.98 1.00 0.92 1.49 0.0020 0.004 0.25 < 0.01 Rest 18 0.009 0.08 0.04 0.005 0.005 11.60 11.05 1.01 0.92 1.51 0.0024 0.004 < 0.01 < 0.01 - Rest. 19 0.011 0.09 0.05 0.008 0.0010 11.63 11.05 1.26 0.06 1.58 0.0014 0.0050 < 0.01 0.01 - Rest. 20 J 0.006 0.01 < 0.01 < 0.005 0.0012 11.60 11.07 1.26 0.02 1.60 0.0013 0.0072 < 0.01 < 0.01 - Rest. 21 J 0.004 0.05 0.04 0.005 0.0008 1.66 10.81 0.75 0.05 1.60 0.0021 0.0056 < 0.01 < 0.01 < 0.001 Rest. 22 J 0.002 0.05 0.05 < 0.005 0.0007 11.62 11.21 1.05 0.05 1.58 0.0021 0.0050 < 0.01 < 0.01 < 0.001 Rest. 23 J 0.005 0.05 0.05 < 0.005 < 0.0005 11.65 10.91 0.75 0.06 1.61 0.0020 0.0065 < 0.01 < 0.01 < 0.001 Rest. IQI 24 J 0.008 0.05 0.04 < 0.005 < 0.0005 11.64 10.89 0.05 0.05 1.58 0.0019 0.0059 < 0.01 < 0.01 < 0.001 Rest. 25 J 0.002 0.07 0.03 < 0.005 0.0006 11.63 10.99 1.00 0.05 1.56 0.0020 0.0043 < 0.01 < 0.01 ^ .OOl1 Rest. 26o-6 0.009 0.01 0.04 < 0.005 < 0.0005 11.60 11.00 1.26 0.01 1.63 0.0016 0.0042 < 0.01 < 0.01 0.006 Rest. 271-B 0.004 0.01 < 0.01 < 0.005 0.0005 11.59 11.03 1.26 < 0.01 1.60 0.0026"0.0046 <0.01 <0.01 0.002 Rest. 281-s 0.002 0.05 0.05 <0.005 <0.0005 11.61 11.14 0.90 0.05 1.60 0.0022 0.0038 <0.01 <0.01 0.004 Rest. 29J'S 0.004 0.05 0.04 <0.005 < 0.0005 11.55 10.78 0.75 0.05 1.57 0.0018 0.0044 <0.01 <0.01 0.003 Rest. 301"5 0.007 0.07 0.03 < 0.005 < 0.0005 11.70 11.08 1.00 0.05 1.53 0.0022 0.0045 < 0.01 < 0.01 0.002 Rest. A 0.030 0.02 0.02 0.004 0.006 12.63 8.17 2.13 0.03 0.01 < 0.0010 0.006 < 0.01 1.10 Rest »B 0.035 0.06 0.06 0.002 0.003 12.61 8.20 2.14 0.06 0.016 < 0.0010 0.003 < 0.01 1.14 ___ Rest.

(Continuation Table 1) Example / Mn Si Cr Ni Mo Cu Ti Nb Al Ce Fe Load No. C 0.007 0.08 0.04 0.008 0.003 11.6 8.61 0.11 2.01 1.10 0.0022 0.005 0.25 < 0.01 Rest D 0.006 0.08 0.05 0.004 0.002 11.58 8.29 0.09 2.14 1.18 0.0028 0.005 0.24 0.022 - Rest1. 1 It also contains 0.002% zirconium 2 It also contains < 0.002% zirconium 3 also contains 0.0009-0.0022 weight percent oxygen 4 Although essentially no cerium was recovered, the addition of a mischmetal was made during vacuum induction melting 5 It also contains 0.001% by weight of lanthanum 6 It also contains 0.002% by weight of lanthanum Examples To demonstrate the unique combination of properties provided by the alloy of the present, Examples 1-24 of the alloy described in the corresponding application No. 08 / 533,159 and Examples 25-30 of the present invention, having the compositions were prepared in percent by weight shown in Table 1. For comparative purposes, AD comparative fillers were also prepared with compositions outside the range of the present invention. Their compositions in percent by weight were also included in Table 1. The alloys A and B are representative of one of the structurally hardened, stainless steel alloys known and the C and D alloys are representative of another stainless steel alloy, structurally hardened, known. Example 1 was prepared as a laboratory load of 17 pounds (7.7 kg), which was vacuum melted and cast or cast as a 2.75 inch (6.98 cm) trapezoidal ingot. The ingot was heated to 1900 ° F (1038 ° C) and forged by pressing to a square bar of 1375 inches (3.49 cm). The bar was finished by wrought to a square bar of 1,125 inches (2.86 cm) and cooled with air at room temperature. The forged bar was hot rolled at 185 ° F (1010 ° C) to a 0.625 inch round bar (1.59 cubic feet) and then air dried at room temperature. Examples 2-4 and 12-18, and the comparative charges A and C were prepared as laboratory loads of 25 pounds (11.3 kg), which were melted by vacuum induction under a partial pressure of argon gas and melted or They molded as 3.5-inch (8.9 cm) trapezoidal ingots. The ingots were forged by pressing an initial temperature of 1850 ° F (1010 ° C) to square bars of 1875 inches (4.76 cm), which were then cooled with air at room temperature. The square bars were reheated, forged by pressing the temperature from 1850 ° F (1010 ° C) to square bars of 1.25 inches (3.18 cm), heated again, hot rolled from the temperature of 1850 ° F (1010 ° C) to round bars of 0.625 inches (1.59 cm), and then cooled with air at room temperature. Examples 5-6 and 8-10 were prepared as laboratory loads of 37 pounds (16.8 kg), which were melted by vacuum induction under a partial pressure of argon gas and melted or cast as 4-inch trapezoidal ingots ( 10.2 cm). The ingots were forged by pressing from an initial temperature of 1850 ° F (1010 ° C) to square bars of 2 inches (5.1 cm) and then cooled with air. A length of each square 2-inch (5.1 cm) forged bar was cut and forged from a temperature of 1850 ° C (1010 ° C) to a square bar of 1.31 inches (3.33 cm). The forged bars were hot rolled at 1850 ° F (1010 ° C) to 0.625 inch (1.59 cm) round bars and cooled with air at room temperature. Examples 7 and 11, in comparative loads B and D were prepared as laboratory loads of 125 pounds (56.7 kg), which were melted by vacuum induction under a partial pressure of argon gas and melted or molded as trapezoidal ingots. of 4.5 inches (11.4 cm). The ingots were forged by pressing an initial temperature of 1850 ° C (1010 ° C) to square bars of 2 inches (5.1 cm) and then cooled with air at room temperature. The bars were again heated and then forged from a temperature of 1850 ° F (1010 ° C) to square bars of 1.31 (3.33 cm). The forged bars were hot rolled at 1850 ° F (1010 ° C) to 0.625 inch (1.59 cm) round bars and cooled with air at room temperature.

Examples 19-30 were prepared as fillers of approximately 380 pounds (172 kg), which were vacuum melted and cast or molded as electrodes with a diameter of 6.12 inches (15.6 cm). Before melting or molding each of the electrodes, mischmetal was added to the respective VIM loads for the respective examples 25-30. The amount of each addition was selected to result in a desired retained amount of cerium after refinement. The electrodes were again cast by vacuum arc and cast or molded as ingots with a diameter of 8 inches (20.3 cm). The ingots were heated to 2300 ° F (1260 ° C) and homogenized for 4 hours at 2300 ° F (1260 ° C). The ingots were cooled in an oven at 1850 ° F (1010 ° C) and held at that temperature for 10 minutes at 1850 ° F (1010 ° C) before forging by pressing. The ingots were then forged by pressing to square bars of 5 inches (12.7 cm) as follows. The lower end of each ingot was pressed to a square of 5 inches (12.7 cm). The slab was then heated again to 1850 ° F (1010 ° C) for 10 minutes before pressing the top end to a 5-inch square (12.7 cm). The forged bars were cooled with air from the finished temperature.

The square bars of 5 inches (12.7 cm) resulting from Examples 19-24 and 26-29 were cut in half with the billets of the upper and lower ends being identified separately. Each billet from the lower end was heated again to 1850 ° F (1010 ° C), and held at that temperature for 2 hours, forged by pressing to 4.5 inch (11.4 cm) by 2.75 inch (6.98 cm) bars and cooled with air at room temperature. Each billet from the upper end was heated again to 1850 ° F (1010 ° C) and kept at that temperature for 2 hours. For Examples 19-24 and 27-29, each billet from the top end was forged by pressing then to 4.5 inch (11.4 cm) by 1.5 inch (3.8 cm) bars and cooled with air at room temperature. For Example 26, the top end billet was forged into bars 4.75 inches (12.1 cm) by 2 inches (5.1 cm), heated again to 1850 ° F (1010 ° C) for 15 minutes, forged by pressing bars 4.5 inches (11.4 cm) by 1.5 inches (3.8 cm) and then cooled with air at room temperature. The square bars of 5 inches (12.7 cm) of Examples 25 and 30 were cut into thirds and halves, respectively. The billets were then heated to 1850 ° F (1010 ° C), kept at that temperature for 2 hours, pressed by pressing into 4.5 inch (11.4 cm) by 1.625 inch (4.13 cm) bars, and then cooled with air at room temperature. With reference to Examples 1-18 and the AD loads, the charges of each Example and the Comparative Load were roughened to produce tensile-resistant specimens, resistant to stress-corrosion, and tensile resistant with notched specimen, uniforms, having the dimensions indicated in Table 2. Each specimen was cylindrical with the center of each specimen being reduced in diameter with a minimum radius by connecting the central section to each end section of the specimen. The stress-corrosion specimens were polished to a nominal larger diameter with a surface finish with a 400 grain.

Table 2 Central Section Type of Length Diameter Length Diameter Minimum radius Diameter Specimen inches / inches / inches / inch / inches / cm larger cm cm cm inches / cm Traction 3.5 / 8.9 0.5 / 1.27 1.0 / 2.54 0.25 / 0.64 0.1875 / 0.476 Uniform Effort-5.5 / 14.0 0.436 / 1.11 1.0 / 2.54 0.25 / 0.64 0.25 / 0.64 0.225 / 0.5 corrosion 7 Action with 3.75 / 9.5 0.50 / 1.27 1.75 / 4.4 0.375 / 0.95 0.1875 / 0.476 the notched specimen (1) A notch was provided around the center of the tensile specimen with notched specimen. The diameter of the specimen was 0.252 inches (0.64 cm) at the base of the notch; the root radius of the notch was 0.0010 inches (0.0025 cm) to produce a stress concentration factor (Kt) of 10.

The test specimens of Examples 1-18 and Charges A-D were heat treated according to the Table 3 below. The heat treatment conditions used were selected to provide a peak resistance.

Table 3 Treatment in Solution Treatment of Enve j ecimiento Examples 1-18 1800 ° F (982 ° C) / 1 hour / Q1 '2 900 ° F (482 ° C) / 4 hours / AC3 Loads A and B 1700 ° F (927 ° C) / 1 hour / WQ4 950 ° F (510 ° C) / 4 hours / AC Loads C and D 1500 ° F (816 ° C) / 1 hour / WQ 900 ° F (482 ° C) / 4 hours / AC 1 WQ = water tempered 2 Cold treated at -100 ° F (-73 ° C) for 1 hour, then heated in air. 3 AC = cooled with water. 4 Treated cold at 33 ° F (0.6 ° C) for 1 hour and then heated in air.

The mechanical properties of Examples 1-18 were compared with the properties of Comparative Loads A-D. The measured properties included the proportional elastic limit of 0.2% (.2% of YS), the final tensile strength (UTS), the percent elongation in four diameters (% of Alarg.), The percent reduction in the area (% Red.), and the tensile strength with notched specimen (NTS). All properties were measured along the longitudinal direction. The results of the measurements are given in Table 4.

• Table 4 Example / Cr Ni Mo Ti .2% YS ÜTS% of% Network in NTS NTS / UTS Load (Ksi / Mpa) (Ksi / MPa) Alarg. Area (Ksi / MPa) No. 1 11.54 11.13 1.00 1.61 253.7 / 1749 264.3 / 1822 12.0 50.5 309.0 / 2130 * 1.17 1 2 11.57 11.02 1.00 1.52 244.7 / 1687 256.2 / 1766 14.7 53.5 341.2 / 2352 * 1.33 3 11.61 11.03 1.00 1.68 246.8 / 1702 260.1 / 1793 12.6 49.4 324.9 / 2240 * 1.25 4 11.60 11.05 1.43 1.52 244.2 / 1684 256.7 / 1770 14.4 58.8 352.5 / 2430 * 1.37 5 11.58 10.46 1.00 1.58 248.5 / 1713 * 266.0 / 1834 * 11.5 * 49.6 * 288.3 / 1988 * 1.08 6 11.54 10.77 1.00 1.55 251.4 / 1734 * 268.3 / 1850 * 11.7 * 51.7 * 324.9 / 2240 * 1.21 7 11.62 11.05 0.99 1.58 240.5 / 1658 * VO 261.6 / 1804 * 11.5 * 51.1 * 344.5 / 2375 * 1.32 8 11.63 10.92 0.75 1.58 250.4 / 1726 * 267.9 / 1847 * 12.4 * 54.5 * 361.4 / 2492 * 1.35 9 11.49 10.84 0.50 1.58 251.4 / 1733 * 267.9 / 1847 * 11.3 * 50.6 * 3393/2339 * 1.27 10 11.60 10.84 0.28 1.50 248.4 / 1713 * 264.5 / 1824 * 12.1 * 57.0 * 347.3 / 235 * 1.31 11 11.62 10.99 1.49 1.67 227.6 / 1569 * 255.6 / 1762 * 11.6 * 47.9 * 332.8 / 2295 * 1.30 12 11.58 11.08 0.98 1.52 250.7 / 1728 262.4 / 1809 12.2 52.4 312.2 / 2153 * 1.19 13 11.56 10.98 1.00 1.70 255.8 / 1764 270.2 / 1863 13.2 50.2 281.6 / 1942 * 1.04 14 11.55 11.02 1.02 1.54 248.7171 262.9 / 1813 13.9 50.7 262.2 / 1808 * 1.00 (Continuation Table 4) Example / Cr Ni Mo Ti .2% YS UTS% of% Network in NTS NTS / UTS Load (Ksi / MPa) (Ksi / MPa) Alarg. Area (Ksi / MPa) No. 15 11.62 11.03 1.03 1.54 247.8 / 1708 262.4 / 1809 12.4 48.3 289.3 / 1995 * 1.10 16 11.68 11.09 1.47 1.52 238.3 / 1643 251.2 / 1732 15.9 56.0 318.6 / 2197 * 1.27 17 11.56 10.98 1.00 1.49 239.2 / 1649 254.6 / 1755 12.7 39.6 289.0 / 1993 * 1.14 18 11.60 11.05 1.01 1.51 235.3 / 1622 250.0 / 1724 11.8 42.4 311.9 / 2150 1.25 A 12.63 8.17 2.13 0.01 210.1 / 1449 224.4 / 1547 14.4 59.4 346.9 / 2392 * 1.54 B 12.61 8.20 2.14 0.016 209.2 / 1442 230.1 / 1586 15.9 65.4 349.8 / 2412 1.52 CA. OR C 11.66 8.61 0.11 1.10 250.5 / 1727 254.3 / 1753 12.2 52.0 319.6 / 2204 * 1.26 D 11.58 8.29 0.09 1.18 251.0 / 1731 259.3 / 1788 10.7 46.7 329.7 / 2273 1.27 The reported value is an average of two measurements, The data in Table 4 show that Examples 1-18 of the present invention provide a proportional yield strength and superior tensile strength as compared to loads A and B, while providing acceptable levels of toughness to the formation of cracks, according to what is indicated by the NTS / UTS relationship, and ductility. Thus, it is noted that Examples 1-18 provide a superior combination of strength and ductility relative to Loads A and B. In addition, the data in Table 4 also show that Examples 1-18 of the present invention provide a tensile strength that is at least as good, up to significantly better than that of Loads C and D, while providing an acceptable yield strength and ductility, as well as an acceptable level of crack toughness according to what is indicated by the NTS / UTS relationship. The stress-corrosion cracking properties of Examples 7-11 in a chlorine-containing medium were compared with those of Comparative Loads B and D via a low velocity deformation test. For the stress-corrosion cracking test, the specimens of Examples 7-11 were treated in solution in a manner similar to the specimens for traction and then over-aged at a selected temperature to provide a high level of strength. The specimens from Comparative Loads B and D were treated in solution in a manner similar to their respective traction specimens, but over-aged at a selected temperature to provide the level of stress-corrosion cracking resistance typically specified in the aeronautical industry. More specifically, Examples 7-11 were chrono-hardened at 1000 ° F (538 ° C) for 4 hours and then cooled in air and Comparative Loads B and D were time-hardened at 1050 ° F (566 ° C) during 4 hours and then cooled in air. The stress-corrosion cracking resistance was tested by subjecting sets of specimens of each example / load to a tensile stress by means of a constant extension speed of 4 x 10 ~ 6 inches / sec (1 x 10 ~ 5 cm / sec. ). The tests were conducted in each of four different media: (1) a boiling solution of 10.0% NaCl acidified to pH 1.5 with H3P04; (2) a boiling solution of 3.5% NaCl at its natural pH (4.9-5.9); (3) a boiling solution of 3.5% NaCl acidified to pH 1.5 with H3P04; and (4) air at 77 ° F (25 ° C). The tests conducted in air were used as a reference against which the results obtained in the medium containing chlorine could be compared. The results of the stress-corrosion test are given in Table 5 including the time to fracture the test specimen (Total Test Time) in hours, the percent elongation (% Alarg.), And the reduction in the cross-sectional area (% Network. in Area).

Table 5 Ex / Charge Environment Total Time of% of% Network. Do not . Test (hours) Lengthening in area Boiling 10.0% NaCl 8.5 4.9 21.5 at pH 1.5 9. 4 5.4 25.0 3.5% boiling NaCl at 13.5 11.3 53.7 pH 1.5 13. 6 11.1 58.6 12. 6 11.5 53.9 3.5 boiling NaCl at 14.4 12.0 62.0 pH 5.8 Table 5 (continued) Ej / Charge Environment Total Time of% of% Red. No. Test (hours) Lengthening in Area 13. 0 11.7 60.2 Air at 77 ° F (25 ° C) 14.4 12.6 60.4 12. 6 10.6 58.6 14. 2 12.8 56.1 Boiling 10.0% NaCl 8.2 5.4 23.8 at pH 1.5 1. 3 5.3 21.4 Boiling 3.5% NaCl at 13.0 11.0 54.4 pH 1.5 13. 3 11.0 53.4 3.5% boiling NaCl at 13.9 13.8 64.8 pH 5.9 14. 1 13.8 64.1 14. 0 13.4 62.4 Air at 77 ° F (25 ° C 14.6 14.3 63.7 14. 0 13.6 63.2 Boiling 10.0% NaCl 10.0 6.2 20.6 at pH 1.5 . 3 10.6 20.7 Table 5 (continued) Ej / Charge Environment Total Time of% of% Red. No. Test (hours) Lengthening in Area 3.5% boiling NaCl at 12.6 10.6 50.1 pH 1.5 12. 8 12.0 49.5 3.5% boiling NaCl at 13.6 12.2 55.8 pH 4.9 13. 6 12.0 54.4 Air at 77 F (25 ° C) 13. 12.6 59.6 14. 0 12.8 58.5 NaCl at 10.0% boiling 9.6 7.0 27.9 at pH 1.5 . 4 7.7 17.9 3.5% boiling NaCl at 13.7 11.8 58.1 pH 1.5 13. 8 11.5 54.0 3.5% boiling NaCl at 13.5 13.3 61.8 pH 5.9 14. 3 14.6 61.7 14. 0 11.9 52.8 Air at 77 ° F (25 ° C) 14.4 13.1 63.8 14. 4 12.7 63.9 Table 5 (continued) Ej / Charge Environment Total Time of% of% Red. No. Test (hours) Elongation in area 11 NaCl at 10.0% boiling 9.5 6.5 20.8 at pH 1.5 9. 5 5.0 22.2 11. 3 7.2 22.9 3.5% boiling NaCl at 13.5 10.8 58.6 pH 1.5 13. 9 11.0 56.5 13. 0 11.6 53.2 3.5% boiling NaCl at 14.6 12.3 62.8 pH 5.8 14. 1 12.7 61.6 Air at 77 ° F (25 ° C) 14.4 12.7 61.5 13. 4 11.5 58.5 13. 6 11.3 53.8 .0% boiling NaCl 14.9 14.5 51.7 at pH 1.5 . 2 16.6 65.2 13. 7 12.9 59.8 3.5 boiling NaCl at 14.2 13.3 69.9 pH 1.5 Table 5 (continued) Ej / Charge Environment Total Time of% of% Red. No. Test (hours) Lengthening in Area 13. 5 14.0 69.9 13. 6 14.5 68.4 3.5% boiling NaCl at 13.4 13.9 67.6 pH 5.8 13. 6 15.1 69.9 Air at 77 ° F (25 ° C) 14.1 15.1 69.9 (i) 15.1 15.7 69.7 . 4 15.4 69.3 Boiling 10.0% NaCl 7.4 3.7 6.9 at pH 1.5 9. 6 8.3 15.6 . 2 10.0 19.2 3.5% boiling NaCl at 13.4 11.3 49.6 pH 1.5 13. 2 10.1 46.1 12. 8 10.7 44.9 3.5% boiling NaCl at 13.4 11.5 51.3 pH 5.8 13. 4 11.9 52.0 Table 5 (continued) Ex / Charge Environment Total Time of% of% Network. No. Test (hours) Lengthening in Area Air at 77 ° F (25 ° C) 14. 1 15. 2 56. 0 . 1 14. 4 54. 4 . 8 35. 4 59. 6 (1) These measurements represent the reference values for the test conditions with boiling 10.0% NaCl only.

The effort at stress corrosion cracking relative to the alloys tested can be better understood by referring to a ratio of the parameter measured in the corrosive medium to the parameter measured in the reference medium. Table 6 summarizes the data in Table 5 by presenting the data in a relationship format to facilitate comparison. The values in the column marked "TC / TR" are the ratios of the average time for the fracture under the corrosive condition to the average time for the invoice under the reference condition. The values in the column marked "EC / ER" are the ratios of the% elongation average under the corrosive condition indicated at the% elongation average under the condition of r 69 57 36 11 75 .55 .39 B 96 94 85 D 59 49 24 (3.5% NaCl boiling at pH 1.5) .92 .90 .92 .92 .79 85 Table 6 Ex / Charge No. TC / TR (i) EC / ER (2) RC / RR (3) 91 89 .84 95 90 11 94 91 B 98 92 .99 D 93 .70 (3.5% NaCl boiling at pH 4.9-5.9] .98 94 1.0 98 98 1.0 98 95 .93 97 1.0 92 11 1.0 98 1.0 B .96 .90 96 D .95 .77 .92 m TC / TR = Average time for fracture under corrosive conditions divided by the average time for fracture under reference conditions. ! 2) EC / ER = Average elongation under corrosive conditions divided by the average elongation under reference conditions. (3) RC / RR = Average reduction in the area under corrosive conditions divided under the average reduction under reference conditions. The mechanical properties of Examples 7-11 and Loads B and D were also determined and plotted in Table 7 including 0.2% yield strength (.2% YS) and final tensile strength.

(UTS) in ksi (MPa), the percent elongation in four diameters (% of Alarg.), The reduction in the area (% Red. In Area), and the tensile strength with notched specimen (NTS) in ksi (MPa).

Table 7 Ex / Load Condition .2% YS UTS%% Network. In NTS No. (ksi / MPa) (ksi / MPa) Alarg. Area (ksi / MPa) H1000 215.8 / 1495 230.5 / 1589 15.0 62.5 344.6 / 2376 H1000 223.0 / 1538 233.6 / 1611 14.5 64.0 353.0 / 2434 H1000 223.4 / 1540 234.8 / 1619 14, 64.3 349.6 / 2410 H1000 219.3 / 1512 230.0 / 1586 14.4 65.0 348.6 / 2404 Table 7 (continued) Ex / Load Condition .2% YS UTS%% Network. In NTS No. (ksi / MPa) (ksi / MPa) Alarg. rea (ksi / MPa) 11 H1000 210.5 / 1451 230.9 / 1592 15.0 63.0 344.2 / 2373 H1050 184.1 / 1269 190.8 / 1316 17.9 72.3 303.4 / 2092 H1050 182.9 / 1261 196.9 / 1358 17.6 62. 296.3 / 2043 When considered together, the data presented in Tables 6 and 7 show the unique combination of strength and resistance to stress-corrosion cracking provided by the alloy according to the present invention, as presented by means of Examples 7-11. . More particularly, the data in Tables 6 and 7 show that Examples 7-11 are capable of providing significantly greater strength than Comparative Loads B and D, while providing a level of stress-corrosion cracking resistance which is comparable to those of alloys. Additional specimens of Examples 7 and 11 were aged at 1050 ° F (538 ° C) for 4 hours and then cooled in air. These specimens provided final tensile strengths at room temperature of 214.3 ksi and 213.1 ksi, respectively, which are still significantly better than the strength provided by Loads B and D when they were similarly aged. Although not tested, it would be expected that the stress-corrosion cracking resistance of Examples 7 and 11 would be at least the same or better as it aged at a higher temperature. In addition, it should be noted that the boiling 10.0% NaCl conditions are more severe than the recognized standards for the aviation industry. With reference to Examples 19-30, the bars of each example were roughened to produce tensile and tensile specimens with uniform notched test specimens, having the dimensions indicated in Table 2. Each specimen was cylindrical with the center of the specimen. each specimen being reduced in diameter and a minimum radius by connecting the central section to each end of the specimen. In addition, CVN test specimens (ASTM E 23-96) and compact tensile blocks for testing fracture toughness (ASTM E399) were machined from the annealed bar. All test specimens were treated in solution at 1800 ° F (982 ° C) for 1 hour and then annealed, cold treated at -100 ° F (-73 ° C) for 1 to 8 hours and then heated in air, and were aged at 900 ° F (482 ° C) or 1000 ° F (538 ° C) for 4 hours and then cooled in air. I i Measured mechanical properties include peak resistance of 0.2% (.2% YS), final tensile strength (UTS), percent elongation in four diameters (% Alarg.), Percent reduction in area (% Red.), tensile strength with notched specimen (NTS), resistance with specimen carved Charpy V at room temperature (CVN), and fracture tenacity at room temperature (Kic) - The results of the measurements are given in Tables 8-11.

Table 8 Example / Size of the Orientation .2% YS UTS% of Network. In NTS NTS / UTS CVN (feet- Klt or Kq Bar Load (Ksi / MPa (ksi / Mpa) ñlarg Area (Ksi / MPa) (Ksi / MPa) lb / J) (Ksi / MPa / No. (inches / cra) 26 4.5x2.75 / 11x7.0 Longitudinal 231. "3/1595 249.0 / 1717 13. 55.7 328.6 / 2266 1.32 10/14 t 72.6 / 79.

Transversal 227 .1 / 1566 245, .3 / 1691 10 .9 40, .8 318. .5 / 2196 1. .30 9/12 t 68.7 / 75.5 4. 5x1.5 / 11x3.8 Longitudinal 236 .4 / 1630 254 .2 / 1753 13 .3 54 .6 342, .3 / 2360 1. .35 12/16 t 74.6 / 82.0 Transversal 230 .3 / 1588 255,. 4/1761 12 .3 51, .9 320. .1 / 2207 1. .25 12/16 t 74.9 / 82.3 27 4.5x2.75 / 11x7.0 Longitudinal 224 .0 / 1544 246 .4 / 1699 14 .8 59 .0 349, .9 / 2412 1. .42 21/28 t 90.9 / 99.9 Transversal 211 .4 / 1458 239 , .2 / 1649 14 .0 50 .9 343. .9 / 2171 1. .44 14/19 t 79.9 / 87.8 4. 5x1.5 / 11x3.8 Longitudinal 221 .2 / 1525 242 .9 / 1675 14 .5 61 .1 348, .4 / 2402 1, .43 19/26 t 95.5 / 105 Transversal 213. 7/1473 * 245. 8/1695 * 13. 8 * 51. 1 * 348. .1 / 2400 1. .42 18/24 04.0 / 92.3 28 4.5x2.75 / 11x7.0 Longitudinal 234 .8 / 1619 253, .6 / 1748 12 .5 54, .9 332, .0 / 2289 1, .31 11/15 t 69.4 / 76.2 Transversal 232, .7 / 1604 252, .8 / 1743 12 .1 51, .7 335. .3 / 2312 1. .33 10/14 + 71.9 / 79.0 4. 5x1.5 / 11x3.8 Longitudinal 231 .1 / 1593 252, .0 / 1738 12 .6 54 .4 328. .5 / 2265 1, .30 11/15 t 78.8 / 86.6 4. 5x1.5 / 11x3.8 Transversal 228, .8 / 1578 253, .6 / 1748 12 .4 53, .6 330. .2 / 2277 1. .30 9/12 73.7 / 81.0 19 4.5x2.75 / 11x7.0 Longitudinal 223 .6 / 1542 244, .3 / 1684 14 .3 56, .9 341. .3 / 2353 1, .40 15/20 + 89.9 / 98.8 Transverse 224, .0 / 1544 243, .0 / 1681 10 .8 43, .0 313. .3 / 2160 1, .29 8/11 t 71.2 / 78.2 (Continuation Table 8) Example / Size of Orientation .2% YS UTS% of Network. In NTS NTS / ÜTS CVN (feet-K? Or Kq Load Bar (Ksi / MPa (ksi / Mpa) Area Alarg (Ksi / MPa) (Ksi / MPa ) lb / J) (Ksi / MPa / No. (inches / cm) 4.5xl.5 / l? x3T8 Longitudinal 222.7 / 1536 243.2 / 1677 15.0 60, .0. 343, .3 / 2367 1, .41 19 / 26 t 94.0 / 103 Transversal 215.7 / 1487 241.0 / 1662 11.6 43, .5 325, .4 / 2244 3, .35 11/15 82.1 / 90.2 4.5x2.75 / 11x7.0 Longitudinal 229.8 / 1584 247.8 / 1708 13.7 57. .5 343, .8 / 2370 1, .39 9/12 t 74.0 / 81.3 Transversal 229.2 / 1580 249.2 / 1718 12.6 49, .8 324 .9 / 2240 1, .30 10/14 t 70.3 / 77.2 4. 5x1.5 / 11x3.8 Longitudinal 225.9 / 1558 244.5 / 1606 14.3 59. .2 339, .2 / 2339 1, .39 11/15 t 82.6 / 90.8 Transversal 229.3 / 1581 249.1 / 1718 12.1 48, .7 334, .2 / 2304 1, .34 11/15 81.4 / 89.4 21 4.5x2.75 / 11x7.0 Longitudinal 242.6 / 1673 260.4 / 1795 11.8 53, .8 234, .1 / 1624 0. .90 5/7 t 47.0 / 51.6 Transversal 245.2 / 1691 263.5 / 1817 10.3 43, .7 218 .8 / 1509 0, .83 6/8 t 47.0 / 51.6 4. 5x1.5 / 11x3.8 Longitudinal 240.8 / 1660 258.9 / 1785 12.2 51. .3 262, .8 / 1812 1, .02 5/7 t 55.8 / 61.3 Transversal 243.1 / 1676 262.4 / 1809 10.8 47, .4 235. 5/1624 0, .90 5/7 53.3 / 56.6 22 4.5x2.75 / 11x7.0 Longitudinal 227.0 / 1565 246.5 / 1700 13.4 56, .0 332 .1 / 2290 1, .35 10/14 t 76.4 / 84.0 Transversal 226.8 / 1564 248.8 / 1715 12.3 50. .4 322 , .7 / 2225 1, .30 10/14 t 74.0 / 81.3 4. 5x1.5 / 11x3.8 Longitudinal 226.2 / 1560 246.3 / 1698 13.3 55, .7 329 .3 / 2270 1, .34 12/16 t 89.6 / 94.1 Transversal 223.0 / 1538 247.4 / 1706 11.6 47. .9 318.9 / 2199 1, .29 11/15 75.4 / 82.8 The test specimens were treated in solution at 1800 ° F (982 ° C) for 3 hours and then annealed in water, treated cold at -100 ° F (-J3 ° C) for 1 hour and then heated in air, they were aged at 900 ° F (482 ° C) by 4 hours and then cooled in air. The reported values are an average of two measurements, except for the values indicated by an "*" which form a single measurement and the values indicated by "t" which are an average of three measurements.

Table 9 Example / Orientation Size .2% YS UTS Network%. In NTS NTS / UTS CVN (feet- K1 or Kq Load Bar (Ksi / MPa (ksi / Mpa) Area Alarg (Ksi / MPa) lb / J) (Ksl / MPa / No (inch / cm) 26 4.5x2.75 / 11x7.0 Longitudinal 209.1 / 1442 225.1 / 1552 15.2 63.9 340.3 / 2346 1.51 29/39 t 108.9 / 119.0 tt. • ^ 1 Transversal 210.0 / 1448 225.2 / 1553 13.4 54 .5 332.9 / 2295 1.48 19/26 + 98.2 / 108 4.5x1.5 / 11x3.8 Longitudinal 211.2 / 1456 227.9 / 1571 15.1 63.0 342 .4 / 1361 1.50 28/38 t 113.6 /124.8 Transversal 212.1 / 1462 225.0 / 1551 13.3 56.2 300.7 / 2328 1.50 22/30 97.0 / 106 27 4.5x2.75 / 11x7.0 Longitudinal 204.8 / 1412 220.0 / 1517 1 .0 67.8 343.9 / 2371 1.56 47/64 t 109 6 / 120.4 Transversal 201.1 / 1386 2'20.1 / 1518 15.1 62.2 322.5 / 2224 1.47 30/41 t 103.2 / 113.4 4.5x1.5 / 11x3.8 Longitudinal 205.7 / 1418 219.4 / 1513 17.4 68.2 343.5 / 2368 1.57 50/68 t 115.8 / 127.2 Transverse 206.9 / 1426 221.3 / 1526 14.3 57.7 112.8 / 2295 1.50 34/46 106.3 / 116.8 28 4.5x2.75 / 11x7.0 Longitudinal 209.9 / 1447 224.8 / 1550 15.2 65.0 340.0 / 2344 1.51 39/53 t 106 1/116. 6 (Continuation of Table 9) • Example / Orientation Size .2% YS OTS% of% Network. In NTS NTS / UTS CVN (feet-K? 4 or K, Load Bar (Ksi / MPa (ksi / Mpa) Area Alarge (Ksi / MPa) lb / J) (Ksi / MPa / No. (inch / cm) Transversal 210.5 / 1451 225.7 / 1556 14.5 62.2 338.8 / 2336 1.50 31/42 97.9 / 108 4.5x1.5 / 11x3.8 Longitudinal 210, .6 / 1452 224, .7 / 1549 15. .4 66 335.9 / 2295 1.48 39/53 t 111.7 / 122.7 4.5x1.5 / 11x3.8 Transversal 206, .3 / 1422 221. .8 / 1529 14. .1 61.6 327.0 / 2255 1.47 31/42 105.6 / 116.0 19 4.5x2.75 / 11x7.0 Longitudinal 201 .2 / 1387 217, .0 / 1496 16, .1 64.5 335.5 / 2313 1.55 31/42 t 112.4 / 123.5 Transversal 197 .1 / 1359 213. .3 / 1471 16, .9 66.3 328.9 / 2268 1.54 40/54 t 101.6 / 111.6 4.5x1.5 / 11x3.8 Longitudinal 197, .1 / 1359 213. .3 / 1471 16, .9 66.3 328.9 / 2268 1.54 10/54 t 101.6 / 111.6 Transversal 196 .9 / 1358 211, .4 / 1458 14, .9 53.2 300.4 / 2071 1.42 17/23 93.3 / 103 20 4.5x2.75 / 11x7.0 Longitudinal 209 .3 / 1443 223, .5 / 1541 16, .5 67.0 347.8 / 2398 1.56 33/45 t 105.4 / 115.8 Transversal 211 .0 / 1455 225, .6 / 1556 12, .7 49.9 337.9 / 23 30 1.50 22/30 t 99.7 / 110 co 4. 5x1.5 / 11x3.8 Longitudinal 200, .4 / 1382 219. .5 / 1513 16. .2 66.6 343.0 / 2365 1.56 36/49 t 111.3 / 122.3 Transversal 207 .2 / 1429 221. .8 / 1529 14, .3 59.4 340.0 / 2344 1.53 23/31 103.6 / 113.8 21 4.5x2.75 / 11x7.0 Longitudinal 216. 4/1492 * 229, .4 / 1582 14, .8 65.6 342.0 / 2350 1.49 20/27 t 89.3 / 98.1 Transversal 219, .2 / 1511 231. .6 / 1597 13. .2 59.4 342.1 / 2359 1.48 17/23 t 86.0 / 94.5 4.5x1.5 / 11x3.8 Longitudinal 217 .6 / 1500 230, .3 / 1588 14, .8 64.4 343.2 / 2366 1.49 23/31 t 100.0 / 109.9 Transversal 218 .5 / 1506 230. .7 / 1591 12, .0 54.8 340.6 / 2348 1.48 17/23 92.4 / 02 22 4.5x2.75 / 11x7 .0 Longitudinal 203 .8 / 1405 219. .6 / 1514 15, .5 65.5 329.8 / 2274 1.50 42/57 95.6 / 105 Transversal 202 .7 / 1398 219, .2 / 1511 13, .6 55.4 324.3 / 2236 1.48 28/38 t 97.7 / 107 4.5x1.5 / 11x3.8 Longitudinal 202 .6 / 1397 218, .4 / 1506 16, .0 66.1 325.6 / 2245 1.49 44/60 t 110.0 / 120.9 Transversal 202 .2 / 1394 219 , .6 / 1514 13, .7 57.1 327.0 / 2555 1.49 25/34 99.8 / 110 The test specimens were treated in solution at 1800 ° F (982 ° C) for 1 hour and then annealed in water, treated cold at -100 ° F (-73 ° C) for 1 hour and then heated in air, they were aged at 1000 ° F (538 ° C) for 4 hours and then cooled in air. The -values reported are an average of two measurements, except for the values indicated by a "*" which form a single measurement and the values indicated by "t" which are an average of three measurements.

Table 10 Example / Orientation Size .2% Y? UTS% of% Network in NTS NTS / UTS CVN (ft- K? 4 O Kq Bar Load (Ksi / MPa (ksi / Mpa) Area Alarge (Ksi / MPa) lb / J) (Ksi / MPa / No. (inches / cm) 27 4.5x2.75 / 11x7.0 Longitudinal 234.8 / 1619 259.8 / 1791 13.2 58.2 352.4 / 2430 * 1.36 28 4.5x2.75 / 11x7.0 Longitudinal 233.8 / 1612 254.7 / 1756 12.8 56.3 336.5 / 2320 1.32 - 239.0 / 1648 258.8 / 1784 12.8 56.3 336.5 / 2320 1.32 - Transversal 234.1 / 1674 256.3 / 1767 12.1 51.3 320.8 / 2212 1.25 - 70.7 / 77.7 4. 5x1.5 / 11x3.8 Longitudinal 238.4 / 1644 258.0 / 17779 12.8 55.8 335.5 / 2313 1.30 - 29 4.5x2.75 / 11x7.0 Longitudinal 241.3 / 16664 260.2 / 1794 12.6 56.0 297.2 / 2049 1.14 6/8 t 56.5 / 62.1 Transverse 246.5 / 1700 264.8 / 1826 10.3 45.3 305.3 / 2705 1.15 6/8 t 55.5 / 61.0 (Continuation of Table 10) Example / Orientation Size .2% YS ÜTS% of% Network in NTS NTS / UTS CVN (ft- Kl4 0 Kq Load Bar (Ksi / MPa (ksi / Mpa) Area Extension (Ksi / MPa) lb / J) (Ksi / MPa / No. (inches / cm) 4.5x1.5 / 11x3.8 Longitudinal 239.8 / 1553 258.9 / 1785 12.9 56.7 331.0 / 2282 1.28 8/11 t 62.9 / 69.1 Transversal 238.5 / 1644 257.4 / 1775 11.6 49.5 314.5 / 2168 1.22 6/8 62.8 / 69.0 30 4.5x1.62 / 11x4.11 Longitudinal 236.2 / 1628 255.8 / 1764 13.3 58.6 358.8 / 2474 1.40 - 81.2 / 89.2 • 19 4.5x2.75 / 11x7.0 Longitudinal 227.6 / 1569 256.5 / 1768 13.0 57.9 346.2 / 2387 1.35 20 4.5x2.75 / ll? .0 Longitudinal 236.6 / 1631 257.4 / 1775 12.9 56.8 346.1 / 2386 1.34 - 21 4.5x2.75 / 11x7.0 Longitudinal 242.9 / 1675 263.1 / 1814 12.1 52.5 241/1664 0.92 - 22 4.5x2.75 / 11x7.0 Longitudinal 231.7 / 1598 254.1 / 1752 13.6 58.8 344.1 / 2372 1.35 23 4.5x2.75 / 11x7.0 Longitudinal 238.8 / 1646 258.9 / 1785 12.6 55.0 291.3 / 1940 1.09 5/7 t 58.8 / 64.3 L? Transversal 240.4 / 1658 259.2 / 1787 10.7 43.9 294.2 / 2028 1.14 6/8 t 56.0 / 61.5 or 4. 5x1.5 / 11x3.8 Longitudinal 235.1 / 1621 254.5 / 1755 12.7 54.6 316.0 / 2179 1.24 7/9 t 66.7 / 73.3 Transverse 236.4 / 1630 256.5 / 1768 11.3 48.4 280.9 / 1934 1.10 7/9 60.1 / 66.0 24 4.5x2. 75 / 11x7.0 Longitudinal 237.7 / 1639 257.3 / 1774 12.9 56.2 339.9 / 2344 1.32 7/9 t 63.3 / 70.0 Transversal 240.0 / 1655 260.8 / 1798 9.5 39.1 307.4 / 2120 1.10 8/11 t 58.7 / 64.5 4.5x1.75 / 11x3.8 Longitudinal 233.9./1621 254.5 / 1755 12.7 54.6 316.0 / 2179 1.24 7/9 t 66.7 / 73.3 Transversal 233.8 / 1612 254.3 / 1753 11.4 47.7 310.5 / 2141 1.22 8/11 66.6 / 73.2 25 4.5x1.62 / 11x4 .11 Longitudinal 238.6 / 1645 257.4 / 1775 13.2 58.2 332.2 / 22 + 90 1.29 - 69.0 / 75.8 Transversal 232.9 / 1606 258.3 / 1781 13.0 51.4 325.0 / 2241 1.26 - 67.2 / 73.8 The test specimens were treated in solution at 1800 ° F (982 ° C) for 1 hour and then annealed in water, treated cold at -100 ° F (-73 ° C) for 8 hours and then heated in air, they were aged at 900 ° F (482 ° C) for 4 hours and then cooled in air. The • reported values are an average of two measurements, except for the values indicated by an "*" which form a single measurement and the values indicated by "t" which are an average of three measurements.

Table 11 Example / Size of Orientation .2% YS UTS% of% Network in NTS NTS / UTS CVN (feet- Kl4 O Kq cp Bar Load (Ksi / MPa (ksi / Mpa) Area Alarg (Ksi / MPa) lb / J) (Ksi / MPa / I-1 No. (inches / cm) 28 4.5x2.75 / 11x7.0 Longitudinal 214.0 / 1476 228.9 / 1578 15.2 65.9 335.2 / 2311 1.46 35/47 218.2 / 1504 232.1 / 1600 15.1 66.2 335.2 / 2311 1.46 36/49 - Transverse 212.5 / 1465 227.0 / 1565 34.6 62.2 346.3 / 2388 * 1.53 - 108.0 / 118.7 4.5x1.5 / 11x3.8 Longitudinal 213.8 / 1474 227.9 / 1571 14.9 64.1 - - - 30 4.5x1.62 / 11x4.11 Longitudinal 216.2 / 1491 230.3 / 1508 15.7 66.0 353.4 / 2437 1.53 - 120.8 / 132.7 Transversal 210.3 / 1450 226.5 / 1562 14.3 * 58.6 * 350.0 / 2413 1.55 308.2 / 118.9 23 4.5x1.62 / 11x4.11 Longitudinal 216.2 / 1491 228.7 / 1577 14.9 65.1 344.2 / 2373 1.51 27/37 t 102.3 / 112.4 Transversal 217.9 / 1502 231.0 / 1593 12.6 53.5 336.4 / 2319 1.46 22/30 t 91.1 / 100.1 (Continuation of Table 11) Example / Orientation Size .2% YS UTS% of% Network in NTS NTS / UTS CVN (feet- Kl4 O Kq Load Bar (Ksi / MPa (ksi / Mpa) Area Extension (Ksi / MPa) lb / J) (Ksi / MPa / No. (inches / cm) 4.5x1.5 / 11x3.8 Longitudinal 214.6 / 1480 227.6 / 1569 14.9 65.7 347.7 / 2197 1.53 28/38 t 107.5 / 110.1 Transverse 212.5 / 1465 226.0 / 1558 12.8 56.7 339.1 / 2338 1.50 21/28 97.8 / 107.5 24 4.5x2.75 / 11x7.0 Longitudinal 214.5 / 1479 * 227.3 / 1567 * 14.9 * 64.6 * 344.2 / 1273 1.51 32/43 t 102.5 / 112.6 Transverse 215.4 / 1485 228.7 / 1577 12.8 53.3 334.8 / 2308 1.46 23/34 t 96.2 / 105.7 4.5x1.5 / 11x3.8 Longitudinal 210.9 / 1454 224.7 / 1549 15.5 66.4 347.5 / 2396 1.55 30/42 t 109.4 / 120.2 Transverse 212.2 / 1463 225.9 / 1558 12.2 53.0 338.1 / 2331 1.50 21/28 95.8 / 105.2 25 4.5x1.62 / 11x4.11 Longitudinal 218.2 / 1504 232.0 / 1600 15.1 64.4 350.3 / 2415 1.51 29 4.5x2.75 / 11x7.0 Longitudinal 215.8 / 1488 228.5 / 1576 14.7 64.3 342.8 / 2364 1.50 28/38 t 102.5 / 112.6 L? Transversal 221.0 / 1524 * 232.8 / 1605 * 12.0 * 52.9 * 342.4 / 2361 1.47 26/35 t 100.3 / 110.2 4.5x1.5 / 11x3.8 Longitudinal 217.0 / 1496 229.4 / 1582 14.9 65.4 347.9 / 2399 1.52 28/38 t 107.8 / 118.4 Transverse 215.7 / 1487 228.5 / 1576 13.4 59.5 338.9 / 2337 1.48 24 / 32 104.8 / 115.2 The test specimens were treated in solution at 1800 ° F (982 ° C) for 1 hour and then annealed in water, treated cold at -100 ° F (-73 ° C) for 8 hours and then heated in air, they were aged at 1000 ° F (538 ° C) for 4 hours and then cooled in air. The reported values are an average of two measurements, except for the values indicated by an "*" which form a single measurement and the values indicated by "t" which are an average of three measurements. cp co The terms and expressions that have been used here were used as terms of description and not limitation. There is no intent in the use of such terms and expressions to exclude any equivalents of the described features or any portions thereof. It is recognized, however, that various modifications are possible within the scope of the claimed invention. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (18)

CLAIMS Having described the invention as above, the content of the following claims is claimed as property:

1. An alloy of martensitic stainless steel, structurally hardenable, characterized in that it has a unique combination of resistance to stress-corrosion cracking, resistance and crack-toughness, consisting essentially of, in percent by weight, approximately C 0.03 max Mn 1.0 max Yes 0.75 max P 0.040 max s 0.020 max Cr 10 - 13 Ni 10.5 - 11.6 Ti 1.5 - 1.8 Mo 0.25 - 1.5 Cu 0.95 max Al 0.25 max Nb 0.3 max B 0.010 max N 0.030 max Ce 0.001 - 0.025 the remainder is essentially iron. The alloy according to claim 1, characterized in that it contains no more than about 0.015 weight percent cerium. 3. The alloy according to claim 1, characterized in that it contains not more than about 0.010 weight percent cerium. 4. The alloy according to claim 1, characterized in that it contains at least about 0.002 weight percent cerium. 5. The alloy according to claim 1, characterized in that it contains no more than about 0.75 weight percent copper. 6. The alloy according to claim 5, characterized in that it contains not more than about 0.015 weight percent cerium. The alloy according to claim 5, characterized in that it contains no more than about 0.010 weight percent cerium. The alloy according to claim 5, characterized in that it contains at least about 0.002 weight percent cerium. 9. A method for preparing a structurally hardenable martensitic stainless steel alloy having a unique combination of stress-corrosion cracking resistance, strength and cracking toughness, the alloy consists essentially of the following elements in the following by approximate hundred weight: C 0.03 max Mn 1.0 max Yes 0.75 max P 0.040 max S 0.020 max Cr 10 - 13 Ni 10.5 - 11.6 Ti 1.5 - 1.8 Mo 0.25 - 1.5 Cu 0.95 max Al 0.25 max Nb 0.3 max B 0.010 max N 0.030 max and the rest is essentially iron, the method is characterized in that it comprises the steps of: melting the filler materials containing the elements in sufficient proportions to provide the amounts in percent by weight; and adding cerium to the alloy during melting thereof, the ratio of the amount of cerium added to the amount of sulfur present in the alloy is at least about 1: 1. The method according to claim 9, characterized in that the step of adding cerium to the alloy comprises the step of adding cerium to the alloy in an amount such that the ratio of the amount of cerium added to the amount of sulfur present in the the alloy is at least about 2: 1. The method according to claim 10, characterized in that the step of adding cerium to the alloy comprises the step of adding cerium to the alloy in an amount such that the ratio of the amount of cerium added to the amount of sulfur present in the the alloy is at least about 3: 1. The method according to claim 9, characterized in that the step of adding cerium to the alloy comprises the step of adding cerium to the alloy in an amount such that the ratio of the amount of cerium added to the amount of sulfur present in the the alloy is no more than about 15: 1. The method according to claim 12, characterized in that the step of adding cerium to the alloy comprises the step of adding cerium to the alloy in an amount such that the ratio of the amount of cerium added to the amount of sulfur present in the the alloy is not more than about 12: 1. 14. A martensitic stainless steel alloy product, structurally hardenable, having a unique combination of stress-corrosion cracking resistance, strength, and cracking toughness, the alloy is characterized in that it consists essentially of, in percent by weight, approximately: C 0.03 max Mn 1.0 max Yes 0.75 max P 0.040 max S 0.020 max Cr 10 - 13 Ni 10.5 - 11.6 Ti 1.5 - 1.8 Mo 0.25 - 1.5 Cu 0.95 max Al 0.25 max Nb 0.3 max B 0.010 max N 0.030 max Ce up to 0.025 and the rest is essentially iron , the product of the alloy is prepared by: melting fillers containing C, Mn, Yes, P, S, Cr, Ni, Mo, Cu, Al, Nb, B, N, and Fe in sufficient proportions to provide the amounts in percent by weight; and adding cerium to the alloy during melting thereof, the ratio of the amount of cerium added to the amount of sulfur present in the alloy is at least about 1: 1. 15. The product according to claim 14, characterized in that it is prepared by adding cerium to the alloy in an amount such that the ratio of the amount of cerium added to the amount of sulfur present in the alloy is at least about 2: 1. 16. The product according to claim 15, characterized in that it is prepared by adding cerium to the alloy in an amount such that the ratio of the amount of cerium added to the amount of sulfur present in the alloy is at least about 3: 1. 17. The product according to claim 14, characterized in that it is prepared by adding cerium to the alloy in an amount such that the ratio of the amount of cerium added to the amount of sulfur present in the alloy is no more than about 15: 1. . 18. The product according to claim 17, characterized in that it is prepared by adding cerium to the alloy in an amount such that the ratio of the amount of cerium added to the amount of sulfur present in the alloy is no more than about 12: 1. .