Abstract:
Ferritic stainless steels with good oxidation resistance, and good high temperature strength and good formability are produced with Ti addition and low Al content for room temperature formability resulting from equiaxed as-cast grain structures. Columbium (niobium) and copper are added for high temperature strength. Silicon and manganese are added for oxidation resistance. The ferritic stainless steels provide better oxidation resistance than ferritic stainless steels of 18Cr-2Mo and 15Cr—Cb—Ti—Si—Mn. In addition, they are generally less costly to produce than 18Cr-2Mo.

Description:
[0001]    This application is a non-provisional patent application claiming priority from provisional application Ser. No. 61/695,771, entitled “Ferritic Stainless Steels with Excellent Oxidation Resistance with Good High Temperature Strength and Good Formability,” filed on Aug. 31, 2012. The disclosure of application Ser. No. 61/695,771 is incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    It is desirable to produce a ferritic stainless steel with oxidation resistance, high temperature strength, and good formability characteristics. Columbium and copper are added in amounts to provide high temperature strength, and silicon and manganese are added in amounts to provide oxidation resistance. The present ferritic stainless steel provides better oxidation resistance than known stainless steels such as 18Cr-2Mo and 15Cr—Cb—Ti—Si—Mn. In addition, the present ferritic stainless steel is less expensive to manufacture than other stainless steels such as 18Cr-2Mo. 
       SUMMARY 
       [0003]    The present ferritic stainless steel are produced with titanium additions and low aluminum concentration to provide room temperature formability from equiaxed as-cast grain structures, as disclosed in U.S. Pat. Nos. 6,855,213 and 5,868,875, the complete disclosures of which are each incorporated by reference herein. Columbium and copper are added to the ferritic stainless steel for high temperature strength and silicon and manganese are added to improve oxidation resistance. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0004]    The ferritic stainless steel is produced using process conditions known in the art for use in manufacturing ferritic stainless steels, such as the processes described in U.S. Pat. Nos. 6,855,213 and 5,868,875. Columbium and copper are added to the ferritic stainless steel for high temperature strength and silicon and manganese are added to improve oxidation resistance. It can be produced from material having an as-cast structure of fine equiaxed grains. 
         [0005]    A ferrous melt for the ferritic stainless steel is provided in a melting furnace such as an electric arc furnace. This ferrous melt may be formed in the melting furnace from solid iron bearing scrap, carbon steel scrap, stainless steel scrap, solid iron containing materials including iron oxides, iron carbide, direct reduced iron, hot briquetted iron, or the melt may be produced upstream of the melting furnace in a blast furnace or any other iron smelting unit capable of providing a ferrous melt. The ferrous melt then will be refined in the melting furnace or transferred to a refining vessel such as an argon-oxygen-decarburization vessel or a vacuum-oxygen-decarburization vessel, followed by a trim station such as a ladle metallurgy furnace or a wire feed station. 
         [0006]    In some embodiments, the steel is cast from a melt containing sufficient titanium and nitrogen but a controlled amount of aluminum for forming small titanium oxide inclusions to provide the necessary nuclei for forming the as-cast equiaxed grain structure so that an annealed sheet produced from this steel also has enhanced ridging characteristics. 
         [0007]    In some embodiments, titanium is added to the melt for deoxidation prior to casting. Deoxidation of the melt with titanium forms small titanium oxide inclusions that provide the nuclei that result in an as-cast equiaxed fine grain structure. To minimize formation of alumina inclusions, i.e., aluminum oxide, Al 2 O 3 , aluminum may not be added to this refined melt as a deoxidant. In some embodiments, titanium and nitrogen can be present in the melt prior to casting so that the ratio of the product of titanium and nitrogen divided by residual aluminum is at least about 0.14. 
         [0008]    If the steel is to be stabilized, sufficient amount of the titanium beyond that required for deoxidation can be added for combining with carbon and nitrogen in the melt but preferably less than that required for saturation with nitrogen, i.e., in a sub-equilibrium amount, thereby avoiding or at least minimizing precipitation of large titanium nitride inclusions before solidification. The maximum amount of titanium for “sub-equilibrium” is generally illustrated in FIG. 4 of U.S. Pat. No. 4,964,926, the disclosure of which is incorporated herein by reference. In some embodiments, one or more stabilizing elements such as columbium, zirconium, tantalum and vanadium can be added to the melt as well. 
         [0009]    The cast steel is hot processed into a sheet. For this disclosure, the term “sheet” is meant to include continuous strip or cut lengths formed from continuous strip and the term “hot processed” means the as-cast steel will be reheated, if necessary, and then reduced to a predetermined thickness such as by hot rolling. If hot rolled, a steel slab is reheated to 2000° to 2350° F. (1093°-1288° C.), hot rolled using a finishing temperature of 1500-1800° F. (816-982° C.) and coiled at a temperature of 1000-1400° F. (538-760° C.). The hot rolled sheet is also known as the “hot band.” In some embodiments, the hot band may be annealed at a peak metal temperature of 1700-2100° F. (926-1149° C.). In some embodiments, the hot band may be descaled and cold reduced at least 40% to a desired final sheet thickness. In other embodiments, the hot band may be descaled and cold reduced at least 50% to a desired final sheet thickness. Thereafter, the cold reduced sheet can be final annealed at a peak metal temperature of 1800-2100° F. (982-1149° C.). 
         [0010]    The ferritic stainless steel can be produced from a hot processed sheet made by a number of methods. The sheet can be produced from slabs formed from ingots or continuous cast slabs of 50-200 mm thickness which are reheated to 2000° to 2350° F. (1093°-1288° C.) followed by hot rolling to provide a starting hot processed sheet of 1-7 mm thickness or the sheet can be hot processed from strip continuously cast into thicknesses of 2-26 mm. The present process is applicable to sheet produced by methods wherein continuous cast slabs or slabs produced from ingots are fed directly to a hot rolling mill with or without significant reheating, or ingots hot reduced into slabs of sufficient temperature to be hot rolled in to sheet with or without further reheating. 
         [0011]    Titanium is used for deoxidation of the ferritic stainless steel melt prior to casting. The amount of titanium in the melt can be 0.30% or less. Unless otherwise expressly stated, all concentrations stated as “%” are percent by weight. In some embodiments, titanium can be present in a sub-equilibrium amount. As used herein, the term “sub-equilibrium” means the amount of titanium is controlled so that the solubility product of the titanium compounds formed are below the saturation level at the steel liquidus temperature thereby avoiding excessive titanium nitride precipitation in the melt. Excessive nitrogen is not a problem for those manufacturers that refine ferritic stainless steel melts in an argon oxygen decarburization vessel. Nitrogen substantially below 0.010% can be obtained when refining the stainless steel in an argon oxygen decarburization vessel thereby allowing increased amount of titanium to be tolerated and still be at sub-equilibrium. 
         [0012]    To provide the nucleation sites necessary for forming as-cast equiaxed ferrite grains, sufficient time after adding the titanium to the melt should elapse to allow the titanium oxide inclusions to form before casting the melt. If the melt is cast immediately after adding titanium, the as-cast structure of the casting can include larger columnar grains. The amount of time that should elapse can be determined by one of ordinary skill in the art without undue experimentation. Ingots cast in the laboratory less than 5 minutes after adding the titanium to the melt had large as-cast columnar grains even when the product of titanium and nitrogen divided by residual aluminum was at least 0.14. 
         [0013]    Sufficient nitrogen should be present in the steel prior to casting so that the ratio of the product of titanium and nitrogen divided by aluminum is at least about 0.14. In some embodiments, the amount of nitrogen present in the melt is ≦0.020%. 
         [0014]    Although nitrogen concentrations after melting in an electric arc furnace may be as high as 0.05%, the amount of dissolved N can be reduced during argon gas refining in an argon oxygen decarburization vessel to less than 0.02%. Precipitation of excessive TiN can be avoided by reducing the sub-equilibrium amount of Ti to be added to the melt for any given nitrogen content. Alternatively, the amount of nitrogen in the melt can be reduced in an argon oxygen decarburization vessel for an anticipated amount of Ti contained in the melt. 
         [0015]    Total residual aluminum can be controlled or minimized relative to the amounts of titanium and nitrogen. Minimum amounts of titanium and nitrogen must be present in the melt relative to the aluminum. The ratio of the product of titanium and nitrogen divided by residual aluminum can be at least about 0.14 in some embodiments, and at least 0.23 in other embodiments. To minimize the amounts of titanium and nitrogen required in the melt, the amount of aluminum is &lt;0.020% in some embodiments. In other embodiments, the amount of aluminum is ≦0.013% and in other embodiments, it is reduced to ≦0.010%. If aluminum is not purposefully alloyed with the melt during refining or casting such as for deoxidation immediately prior to casting, total aluminum can be controlled or reduced to less than 0.020%. One must be aware that aluminum can be inadvertently added to the melt as an impurity present in an alloy addition of another element, e.g., titanium. Titanium alloys may contain as much as 20% Al which may contribute total Al to the melt. By carefully controlling the refining and casting practices, a melt containing &lt;0.020% aluminum can be obtained. 
         [0016]    In addition to using titanium for stabilization, other suitable stabilizing elements may also include columbium, zirconium, tantalum, vanadium or mixtures thereof. In some embodiments, if a second stabilizing element is used in combination with titanium, e.g., columbium or vanadium, this second stabilizing element may be limited to ≦0.50% when deep formability is required. Some embodiments include columbium in concentrations of 0.05% or less. Some embodiments include columbium in concentrations of 0.28-0.43%. Vanadium can be present in amounts less than 0.5%. Some embodiments of the ferritic stainless steels include 0.008-0.098% vanadium. 
         [0017]    Copper improves high temperature strength. The ferritic stainless steels contain 1.0-2.0% copper. Some embodiments include 1.16-1.31% copper. 
         [0018]    Silicon is generally present in the ferritic stainless steels in an amount of 1.0-1.7%. In some embodiments, silicon is present in an amount of 1.27-1.35%. A small amount of silicon generally is present in a ferritic stainless steel to promote formation of the ferrite phase. Silicon also enhances high temperature oxidation resistance and provides high temperature strength. In most embodiments, silicon does not exceed about 1.7% because the steel can become too hard and the elongation can be adversely affected. 
         [0019]    Manganese is present in the ferritic stainless steel in an amount of 0.4-1.5%. In some embodiments, manganese is present in an amount of 0.98-1.00%. Manganese improves oxidation resistance and spalling resistance at high temperatures. Accordingly, some embodiments include manganese in amounts of at least 0.4%. However, manganese is an austenite former and affects the stabilization of the ferrite phase. If the amount of manganese exceeds about 1.5%, the stabilization and formability of the steel can be affected. 
         [0020]    Carbon is present in the ferritic stainless steel in an amount of up to 0.02%. In some embodiments, the carbon content is ≦0.02%. In still other embodiments, it is 0.0010-0.01%. 
         [0021]    Chromium is present some embodiments of the ferritic stainless steels in an amount of 15-20%. If chromium is greater than about 25%, the formability of the steel can be reduced. 
         [0022]    In some embodiments, oxygen is present in the steel in an amount &lt;100 ppm. When a steel melt is prepared sequentially in an argon oxygen decarburization refining vessel and a ladle metallurgy furnace alloying vessel, oxygen in the melt can be within the range of 10-60 ppm thereby providing a very clean steel having small titanium oxide inclusions that aid in forming the nucleation sites responsible for the fine as-cast equiaxed grain structure. 
         [0023]    Sulfur is present in the ferritic stainless steel in an amount of ≦0.01%. 
         [0024]    Phosphorus can deteriorate formability in hot rolling and can cause pitting. It is present in the ferritic stainless steel in an amount of ≦0.05%. 
         [0025]    Like manganese, nickel is an austenite former and affects the stabilization of the ferrite phase. Accordingly, in some embodiments, nickel is limited to ≦1.0%. In some embodiments, nickel is present in amounts of 0.13-0.19%. 
         [0026]    Molybdenum also improves corrosion resistance. Some embodiments include 3.0% or less molybdenum. Some embodiments include 0.03-0.049% molybdenum. 
         [0027]    For some applications, it may be desirable to include boron in the steels of the present invention in an amount of ≦0.010%. In some embodiments, boron is present in an amount of 0.0001-0.002%. Boron can improve the resistance to secondary work embrittlement of steel so that the steel sheet will be less likely to split during deep drawing applications and multi-step forming applications. 
         [0028]    In some embodiments, the ferritic stainless steels may also include other elements known in the art of steelmaking that can be made either as deliberate additions or present as residual elements, i.e., impurities from steelmaking process. 
       Example 1 
       [0029]    Embodiments of the ferritic stainless steels and comparative reference steels were made in the laboratory with the compositions set forth in Table 1 below. 
         [0030]    The materials identified as “Lab Materials” were processed on laboratory equipment according to the following parameters. Each ingot was reheated to a temperature of 2300° F. (1260° C.). It was hot rolled to a strip thickness of 0.200″ (5.08 mm). It was then hot band annealed at a temperature of 1825-1975° C. (996-1079° C.). It was then cold rolled to a thickness of 0.079-0.098″ (2.0-2.5 mm). The cold rolled strip was final annealed to a temperature of 1885-1950° F. (1029-1066° C.). 
         [0031]    The materials identified as “Plant Material” were processed on production equipment in the plant according to the following parameters. Each slab was reheated to a temperature of 2273-2296° F. (1245-1258° C.). It was then hot rolled to a strip thickness of 0.200-0.180″ (5.08-4.57 mm). The hot rolled strip was then hot band annealed to a temperature of 1950-2000° F. (1066-1083° C.). After cold rolling to 0.079-0.059″ (2.0-1.5 mm), the strip was final annealed to a temperature of 1900-2000° F. (1038-1093° C.). 
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Chemical compositions in weight %. 
               
             
          
           
               
                 ID 
                 Description 
                 Al 
                 B 
                 C 
                 Cb 
                 Cr 
                 Cu 
                 Mn 
                 Mo 
                 N 
                 Ni 
                 P 
                 S 
                 Si 
                 Ti 
                 V 
                 Remarks 
               
               
                   
               
             
          
           
               
                 V3924 
                 Lab Material 
                 .007 
                 &lt;.0005 
                 .0090 
                 .40 
                 16.70 
                 1.27 
                 1.00 
                 .048 
                 .019 
                 .16 
                 .031 
                 .0016 
                 1.27 
                 .14 
                 .071 
                 Invention 
               
               
                 V3925 
                 Lab Material 
                 .009 
                 &lt;.0005 
                 .0054 
                 .43 
                 16.98 
                 1.31 
                 1.00 
                 .049 
                 .012 
                 .16 
                 .033 
                 .0014 
                 1.33 
                 .21 
                 .074 
                 Invention 
               
               
                 V3926 
                 Lab Material 
                 .010 
                 &lt;.0005 
                 .0077 
                 .43 
                 16.90 
                 1.28 
                 1.00 
                 .048 
                 .012 
                 .16 
                 .031 
                 .0016 
                 1.31 
                 .25 
                 .080 
                 Invention 
               
               
                 V3929 
                 Lab Material 
                 .014 
                 &lt;.0005 
                 .0094 
                 .40 
                 16.56 
                 1.26 
                 .98 
                 .048 
                 .014 
                 .15 
                 .030 
                 .0015 
                 1.28 
                 .17 
                 .073 
                 Invention 
               
               
                 V3954 
                 Lab Material 
                 .006 
                 .0020 
                 .014 
                 .30 
                 16.99 
                 1.27 
                 .99 
                 .048 
                 .012 
                 .14 
                 .027 
                 .0016 
                 1.33 
                 .16 
                 .008 
                 Invention 
               
               
                 V3955 
                 Lab Material 
                 .010 
                 &lt;.0005 
                 .0085 
                 .28 
                 17.06 
                 1.23 
                 .99 
                 .049 
                 .0082 
                 .14 
                 .028 
                 .0016 
                 1.35 
                 .16 
                 .082 
                 Invention 
               
               
                 V3956 
                 Lab Material 
                 .016 
                 &lt;.0005 
                 .0089 
                 .39 
                 16.92 
                 1.23 
                 .99 
                 .048 
                 .0087 
                 .14 
                 .026 
                 .0017 
                 1.32 
                 .17 
                 .078 
                 Invention 
               
               
                 V3957 
                 Lab Material 
                 .015 
                 .0017 
                 .0084 
                 .41 
                 16.90 
                 1.28 
                 .99 
                 .048 
                 .0084 
                 .14 
                 .026 
                 .0016 
                 1.32 
                 .17 
                 .075 
                 Invention 
               
               
                 V3958 
                 Lab Material 
                 .016 
                 .0017 
                 .0090 
                 .40 
                 16.93 
                 1.24 
                 .99 
                 .048 
                 .0076 
                 .14 
                 .027 
                 .0017 
                 1.32 
                 .16 
                 .078 
                 Invention 
               
               
                 V3959 
                 Lab Material 
                 .009 
                 .0020 
                 .0082 
                 .31 
                 17.35 
                 1.27 
                 .99 
                 .049 
                 .0077 
                 .13 
                 .026 
                 .0018 
                 1.31 
                 .15 
                 .078 
                 Invention 
               
               
                 V3960 
                 Lab Material 
                 .007 
                 .0007 
                 .0085 
                 .37 
                 17.40 
                 1.27 
                 .99 
                 .048 
                 .0086 
                 .14 
                 .026 
                 .0017 
                 1.33 
                 .16 
                 .078 
                 Invention 
               
               
                 V3961 
                 Lab Material 
                 .008 
                 &lt;.0005 
                 .013 
                 .29 
                 16.95 
                 1.28 
                 .99 
                 .048 
                 .011 
                 .14 
                 .025 
                 .0016 
                 1.32 
                 .16 
                 .074 
                 Invention 
               
               
                 V3962 
                 Lab Material 
                 .009 
                 .0019 
                 .0093 
                 .30 
                 16.93 
                 1.28 
                 .99 
                 .048 
                 .0082 
                 .14 
                 .026 
                 .0016 
                 1.33 
                 .17 
                 .078 
                 Invention 
               
               
                 HT 
                 Plant Material 
                 .010 
                 .0001 
                 .0114 
                 .33 
                 17.01 
                 1.16 
                 .98 
                 .030 
                 .009 
                 .19 
                 .026 
                 .0015 
                 1.30 
                 .18 
                 .098 
                 Invention 
               
               
                 #920097 
               
               
                 V3918 
                 Lab Material 
                 .012 
                 &lt;.0005 
                 .012 
                 .44 
                 16.78 
                 1.28 
                 .28 
                 .048 
                 .010 
                 .16 
                 .031 
                 .0015 
                 .58 
                 .21 
                 .076 
                 Reference 
               
               
                 V3920 
                 Lab Material 
                 .012 
                 &lt;.0005 
                 .011 
                 .46 
                 16.88 
                 1.28 
                 .28 
                 .049 
                 .010 
                 .16 
                 .031 
                 .0017 
                 .94 
                 .25 
                 .076 
                 Reference 
               
               
                 V3921 
                 Lab Material 
                 .012 
                 &lt;.0005 
                 .0081 
                 .45 
                 16.82 
                 1.28 
                 .28 
                 .049 
                 .010 
                 .16 
                 .030 
                 .0015 
                 1.34 
                 .27 
                 .078 
                 Reference 
               
               
                 V3922 
                 Lab Material 
                 .009 
                 &lt;.0005 
                 .0084 
                 .32 
                 16.86 
                 1.28 
                 .28 
                 .048 
                 .010 
                 .16 
                 .030 
                 .0014 
                 1.32 
                 .27 
                 .080 
                 Reference 
               
               
                 HT 
                 Plant Material 
                 .009 
                 .0060 
                 .010 
                 .17 
                 17.58 
                 .09 
                 .35 
                 1.90 
                 .0114 
                 .23 
                 .022 
                 .0005 
                 .44 
                 .20 
                 .066 
                 Reference 
               
               
                 #831187 
               
               
                 (444) 
               
               
                 HT 
                 Plant Material 
                 .010 
                 .0002 
                 .0086 
                 .37 
                 14.32 
                 .08 
                 1.01 
                 .010 
                 .0077 
                 .14 
                 .022 
                 .0010 
                 1.27 
                 .25 
                 .045 
                 Reference 
               
               
                 #830843 
               
               
                 (15 Cr-Cb) 
               
               
                   
               
             
          
         
       
     
         [0032]    The materials identified as “Invention” in the remarks are embodiments of the ferritic stainless steels of the present disclosure. The materials identified as “Reference” are not embodiments of the ferritic stainless steels of the present disclosure. In fact, two are well-known prior products: HT #831187 is Type 444 stainless steel and HT #830843 is 15 CrCb stainless steel, which is a product of AK Steel Corporation, West Chester, Ohio. 
       Example 2 
       [0033]    The oxidation resistance of several of the steel compositions described in Example 1 and Table 1 above was tested at 930° C. for 200 hours in air. The results of the tests are set forth in Table 2 below. The individual compositions are each identified by their respective ID number. The oxidation resistance was evaluated two factors. One was the amount of weight gain, and the other was degree of spalling. For each material, except HT #920097, the reported weight gain value is an average of two tests. For HT #9200097, eight samples were tested and the minimum, average, and maximum of these eight tests has been reported. 
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Oxidation resistance test results at 930° C. for 200 hours in air. 
               
             
          
           
               
                   
                 Chemical Composition (weight %) 
                 Weight Gain 
                 Spalling 
               
             
          
           
               
                   
                 C 
                 Cb 
                 Cr 
                 Cu 
                 Mn 
                 N 
                 Si 
                 Ti 
                 (mg/cm 2 ) 
                 (Scale Off) 
                 Remarks 
               
               
                   
                   
               
             
          
           
               
                 V3954 
                 .014 
                 .30 
                 16.99 
                 1.27 
                 .99 
                 .012 
                 1.33 
                 .16 
                 1.34 
                 No 
                 Invention 
               
               
                 V3924 
                 .0090 
                 .40 
                 16.70 
                 1.27 
                 1.00 
                 .019 
                 1.27 
                 .14 
                 1.40 
                 No 
                 Invention 
               
               
                 V3929 
                 .0094 
                 .40 
                 16.56 
                 1.26 
                 .98 
                 .014 
                 1.28 
                 .17 
                 1.44 
                 No 
                 Invention 
               
               
                 V3956 
                 .0089 
                 .39 
                 16.92 
                 1.23 
                 .99 
                 .0087 
                 1.32 
                 .17 
                 1.14 
                 Partial* 
                 Invention 
               
               
                 V3955 
                 .0085 
                 .28 
                 17.06 
                 1.23 
                 .99 
                 .0082 
                 1.35 
                 .16 
                 1.15 
                 Partial* 
                 Invention 
               
               
                 V3961 
                 .013 
                 .29 
                 16.95 
                 1.28 
                 .99 
                 .011 
                 1.32 
                 .16 
                 1.17 
                 Partial* 
                 Invention 
               
               
                 V3960 
                 .0085 
                 .37 
                 17.40 
                 1.27 
                 .99 
                 .0086 
                 1.33 
                 .16 
                 1.19 
                 Partial* 
                 Invention 
               
               
                 V3958 
                 .0090 
                 .40 
                 16.93 
                 1.24 
                 .99 
                 .0076 
                 1.32 
                 .16 
                 1.20 
                 Partial* 
                 Invention 
               
               
                 V3957 
                 .0084 
                 .41 
                 16.90 
                 1.28 
                 .99 
                 .0084 
                 1.32 
                 .17 
                 1.21 
                 Partial* 
                 Invention 
               
               
                 V3959 
                 .0082 
                 .31 
                 17.35 
                 1.27 
                 .99 
                 .0077 
                 1.31 
                 .15 
                 1.22 
                 Partial* 
                 Invention 
               
               
                 V3962 
                 .0093 
                 .30 
                 16.93 
                 1.28 
                 .99 
                 .0082 
                 1.33 
                 .17 
                 1.37 
                 Partial* 
                 Invention 
               
               
                 V3925 
                 .0054 
                 .43 
                 16.98 
                 1.31 
                 1.00 
                 .012 
                 1.33 
                 .21 
                 1.43 
                 Partial* 
                 Invention 
               
               
                 V3926 
                 .0077 
                 .43 
                 16.90 
                 1.28 
                 1.00 
                 .012 
                 1.31 
                 .25 
                 1.47 
                 Partial* 
                 Invention 
               
               
                 HT #920097 
                 .0114 
                 .33 
                 17.01 
                 1.16 
                 .98 
                 .009 
                 1.30 
                 .18 
                 1.63 Min 1.70 Ave 
                 No 
                 Invention 
               
               
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 1.74 Max 
               
               
                 V3918 
                 .012 
                 .44 
                 16.78 
                 1.28 
                 .28 
                 .010 
                 .58 
                 .21 
                 −0.14 
                 Severe 
                 Reference 
               
               
                 V3920 
                 .011 
                 .46 
                 16.88 
                 1.28 
                 .28 
                 .010 
                 .94 
                 .25 
                 −1.77 
                 Very Sever 
                 Reference 
               
               
                 V3922 
                 .0084 
                 .32 
                 16.86 
                 1.28 
                 .28 
                 .010 
                 1.32 
                 .27 
                 −1.98 
                 Very Sever 
                 Reference 
               
               
                 V3921 
                 .0081 
                 .45 
                 16.82 
                 1.28 
                 .28 
                 .010 
                 1.34 
                 .27 
                 −2.48 
                 Very Sever 
                 Reference 
               
               
                 444 
                 .010 
                 .17 
                 17.58 
                 .09 
                 .35 
                 .0114 
                 .44 
                 .20 
                 0.88 
                 Severe 
                 Reference 
               
               
                 15Cr-Cb 
                 .0086 
                 .37 
                 14.32 
                 .08 
                 1.01 
                 .0077 
                 1.27 
                 .25 
                 1.29 
                 Severe 
                 Reference 
               
               
                   
               
               
                 *“Partial” means that spalling occurred just around the edges of the specimens and a few small spots away from the edges. 
               
             
          
         
       
     
       Example 3 
       [0034]    The longitudinal high temperature tensile properties of several of the steel compositions of Example 1 were tested according to the procedure of ASTM Standard E21 tensile test. The results of these tests are set forth below: 
         [0000]    
       
         
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Longitudinal high temperature tensile properties. (ASTM Standard E21 tensile tests). 
               
             
          
           
               
                   
                 600° C. 
                 700° C. 
                 800° C. 
                 Average 
                   
               
             
          
           
               
                   
                 Gauge 
                 .2% YS 
                 UTS 
                 Gauge 
                 .2% YS 
                 UTS 
                 Gauge 
                 .2% YS 
                 UTS 
                 .2% YS at 
                   
               
               
                 ID 
                 (mm) 
                 (MPa) 
                 (MPa) 
                 (mm) 
                 (MPa) 
                 (MPa) 
                 (mm) 
                 (MPa) 
                 (MPa) 
                 Three Temp. 
                 Remarks 
               
               
                   
               
             
          
           
               
                 V3924 
                 2.03 
                 260 
                 372 
                 2.00 
                 116 
                 126 
                 2.03 
                 37.2 
                 46.9 
                 138 
                 Invention 
               
               
                 V3925 
                 2.01 
                 241 
                 391 
                 2.05 
                 151 
                 160 
                 2.01 
                 41.0 
                 50.6 
                 144 
                 Invention 
               
               
                 V3926 
                 2.00 
                 265 
                 385 
                 2.03 
                 142 
                 150 
                 2.00 
                 39.3 
                 49.6 
                 149 
                 Invention 
               
               
                 V3929 
                 2.01 
                 262 
                 381 
                 2.01 
                 125 
                 135 
                 2.01 
                 37.9 
                 48.9 
                 141 
                 Invention 
               
               
                 V3954 
                 2.02 
                 244 
                 348 
                 2.04 
                 135 
                 165 
                 2.03 
                 24.1 
                 35.1 
                 134 
                 Invention 
               
               
                 V3955 
                 2.04 
                 239 
                 352 
                 2.05 
                 147 
                 178 
                 2.06 
                 32.0 
                 44.1 
                 139 
                 Invention 
               
               
                 V3956 
                 2.05 
                 245 
                 354 
                 2.06 
                 134 
                 150 
                 2.05 
                 40.7 
                 49.3 
                 140 
                 Invention 
               
               
                 V3957 
                 2.05 
                 257 
                 376 
                 2.05 
                 100 
                 122 
                 2.06 
                 38.6 
                 50.0 
                 132 
                 Invention 
               
               
                 V3958 
                 2.02 
                 246 
                 369 
                 2.04 
                 107 
                 121 
                 2.04 
                 40.0 
                 50.0 
                 131 
                 Invention 
               
               
                 V3959 
                 2.03 
                 238 
                 352 
                 2.05 
                 96 
                 120 
                 2.05 
                 34.5 
                 45.8 
                 123 
                 Invention 
               
               
                 V3960 
                 2.03 
                 252 
                 370 
                 2.05 
                 102 
                 118 
                 2.05 
                 36.9 
                 49.3 
                 130 
                 Invention 
               
               
                 V3961 
                 2.02 
                 244 
                 353 
                 2.03 
                 160 
                 185 
                 2.03 
                 31.0 
                 43.1 
                 145 
                 Invention 
               
               
                 V3962 
                 2.03 
                 243 
                 356 
                 2.04 
                 108 
                 126 
                 2.05 
                 34.8 
                 46.2 
                 129 
                 Invention 
               
               
                 HT #920097 CL 
                 2.00 
                 247 
                 373 
                 2.00 
                 148 
                 167 
                 2.01 
                 36.6 
                 46.9 
                 144 
                 Invention 
               
               
                 #F06626 
               
               
                 HT #920097 CL 
                 2.03 
                 256 
                 373 
                 2.03 
                 144 
                 172 
                 2.02 
                 38.0 
                 47.6 
                 146 
                 Invention 
               
               
                 #F06629 
               
               
                 V3918 
                 2.01 
                 245 
                 370 
                 2.02 
                 153 
                 166 
                 2.02 
                 40.0 
                 51.3 
                 146 
                 Reference 
               
               
                 V3920 
                 2.02 
                 251 
                 382 
                 1.99 
                 167 
                 195 
                 2.02 
                 38.9 
                 49.6 
                 152 
                 Reference 
               
               
                 V3921 
                 2.01 
                 260 
                 383 
                 2.00 
                 137 
                 151 
                 2.00 
                 36.5 
                 47.5 
                 145 
                 Reference 
               
               
                 V3922 
                 2.05 
                 247 
                 373 
                 2.03 
                 146 
                 154 
                 2.04 
                 40.3 
                 49.3 
                 144 
                 Reference 
               
               
                   
               
             
          
         
       
     
       Example 4 
       [0035]    The longitudinal tensile properties of several of the steel compositions of Example 1 were tested according to the procedure of ASTM Standard E8/E8M test. In addition, the stretch-r values were tested according to the procedure of ASTM Standard E517. Ridging resistance of the compositions was also determined on a qualitative scale of 0-6, where 0 is the best and 6 is unacceptable. The results of these tests are set forth below: 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 Longitudinal tensile properties (ASTM E8/E8M), 
               
               
                 stretch r-values, and ridging resistances. 
               
             
          
           
               
                   
                 Longitudinal ASTM Tensile 
                   
               
             
          
           
               
                   
                 Gauge 
                 .2% YS 
                 UTS 
                 EL 
                   
                 Stretch 
                 Ridging 
                   
               
               
                 Lab ID 
                 (mm) 
                 (MPa) 
                 (MPa) 
                 (%) 
                 HRB 
                 r-bar 
                 (0-6) 
                 Remarks 
               
               
                   
               
               
                 V3926 
                 2.02 
                 475 
                 613 
                 27.5 
                 93.0 
                 1.01 
                 3 
                 Invention 
               
               
                   
                 2.02 
                 476 
                 614 
                 27.7 
                 92.8 
                   
                 2 
               
               
                 V3925 
                 2.02 
                 465 
                 598 
                 27.6 
                 92.4 
                 1.21 
                 2 
                 Invention 
               
               
                   
                 2.02 
                 466 
                 600 
                 28.6 
                 92.0 
                   
                 2 
               
               
                 V3929 
                 2.03 
                 432 
                 563 
                 31.4 
                 89.8 
                 1.37 
                 1 
                 Invention 
               
               
                   
                 2.03 
                 430 
                 563 
                 31.4 
                 89.6 
                   
                 2 
               
               
                 V3924 
                 2.05 
                 451 
                 579 
                 29.9 
                 90.5 
                 1.24 
                 2 
                 Invention 
               
               
                   
                 2.04 
                 452 
                 580 
                 30.0 
                 89.9 
                   
                 1 
               
               
                 V3955 
                 2.01 
                 425 
                 552 
                 31.2 
                 88.0 
                 1.16 
                 1 
                 Invention 
               
               
                   
                 2.02 
                 422 
                 547 
                 30.5 
                 88.2 
               
               
                 V3956 
                 2.01 
                 411 
                 542 
                 31.3 
                 87.7 
                 0.98 
                 1 
                 Invention 
               
               
                   
                 2.02 
                 407 
                 538 
                 30.4 
                 87.5 
               
               
                 V3961 
                 2.05 
                 449 
                 572 
                 29.0 
                 89.8 
                 1.31 
                 1 
                 Invention 
               
               
                   
                 2.04 
                 443 
                 569 
                 29.4 
                 90.0 
               
               
                 V3954 
                 2.04 
                 447 
                 571 
                 28.8 
                 90.4 
                 1.16 
                 1 
                 Invention 
               
               
                   
                 2.04 
                 446 
                 570 
                 29.0 
                 89.6 
               
               
                 V3962 
                 2.07 
                 451 
                 580 
                 28.8 
                 90.5 
                 1.29 
                 1 
                 Invention 
               
               
                   
                 2.07 
                 451 
                 577 
                 30.1 
                 90.0 
               
               
                 V3957 
                 2.01 
                 454 
                 587 
                 27.1 
                 91.6 
                 1.16 
                 1 
                 Invention 
               
               
                   
                 2.01 
                 448 
                 581 
                 28.7 
                 90.8 
               
               
                 V3958 
                 2.05 
                 428 
                 570 
                 27.9 
                 89.2 
                 1.14 
                 1 
                 Invention 
               
               
                   
                 2.05 
                 429 
                 569 
                 29.5 
                 89.1 
               
               
                 V3959 
                 2.07 
                 461 
                 585 
                 28.0 
                 90.9 
                 1.19 
                 1 
                 Invention 
               
               
                   
                 2.07 
                 459 
                 583 
                 28.7 
                 90.2 
               
               
                 V3960 
                 2.06 
                 458 
                 586 
                 29.1 
                 90.5 
                 1.15 
                 1 
                 Invention 
               
               
                   
                 2.06 
                 452 
                 581 
                 28.8 
                 90.7 
               
               
                 V3918 
                 1.99 
                 379 
                 508 
                 33.4 
                 84.9 
                 1.45 
                 1 
                 Reference 
               
               
                   
                 1.99 
                 381 
                 510 
                 33.5 
                 84.8 
                   
                 1 
               
               
                 V3920 
                 2.05 
                 426 
                 556 
                 30.5 
                 89.4 
                 1.13 
                 1 
                 Reference 
               
               
                   
                 2.05 
                 424 
                 555 
                 31.1 
                 89.3 
                   
                 1 
               
               
                 V3921 
                 2.02 
                 477 
                 618 
                 26.9 
                 92.7 
                 1.04 
                 2 
                 Reference 
               
               
                   
                 2.02 
                 474 
                 616 
                 26.5 
                 92.4 
                   
                 3 
               
               
                 V3922 
                 2.04 
                 416 
                 543 
                 33.1 
                 88.4 
                 1.21 
                 1 
                 Reference 
               
               
                   
                 2.03 
                 414 
                 543 
                 32.4 
                 88.2 
                   
                 1 
               
               
                   
               
             
          
         
       
     
       Example 4 
       [0036]    The longitudinal tensile properties of several of the steel compositions of Example 1 were tested according to the procedure of ASTM Standard E8/E8M test. In addition, the stretch-r values were tested according to the procedure of ASTM Standard E517. Ridging resistance of the compositions was also determined on a qualitative scale of 0-6, where 0 is the best and 6 is unacceptable. The results of these tests are set forth below: 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 5 
               
             
             
               
                   
               
               
                 Longitudinal tensile properties (ASTM E8/E8M), 
               
               
                 stretch r-values, and ridging resistances. 
               
             
          
           
               
                 HT #920097 
                 Longitudinal ASTM Tensile 
                   
               
             
          
           
               
                 Coil ID 
                 Gauge 
                 .2% YS 
                 UTS 
                 EL 
                   
                   
                 Ridging 
                   
               
               
                 Position 
                 (mm) 
                 (MPa) 
                 (MPa) 
                 (%) 
                 HRB 
                 r-bar 
                 (0-6) 
                 Remarks 
               
               
                   
               
               
                 681730-02 
                 2.01 
                 403 
                 534 
                 33.1 
                 86.3 
                 1.22 
                 0 
                 Invention 
               
               
                 Head 
                 2.01 
                 404 
                 535 
                 32.6 
                 86.2 
                   
                 0 
               
               
                 681730-02 
                 1.97 
                 402 
                 532 
                 32.8 
                 86.4 
                 1.24 
                 0 
                 Invention 
               
               
                 Tail 
                 1.97 
                 402 
                 532 
                 32.6 
                 86.3 
                   
                 0 
               
               
                 681730-05 
                 2.03 
                 400 
                 530 
                 32.4 
                 86.0 
                 1.37 
                 0 
                 Invention 
               
               
                 Head 
                 2.03 
                 398 
                 529 
                 32.7 
                 86.2 
                   
                 0 
               
               
                 681730-05 
                 2.03 
                 404 
                 534 
                 32.7 
                 86.4 
                 1.20 
                 0 
                 Invention 
               
               
                 Tail 
                 2.03 
                 404 
                 534 
                 33.8 
                 86.6 
                   
                 0 
               
               
                 681727-02 
                 1.51 
                 405 
                 537 
                 31.8 
                 86.4 
                 1.34 
                 0 
                 Invention 
               
               
                 Head 
                 1.51 
                 406 
                 537 
                 31.0 
                 86.4 
                   
                 0 
               
               
                 681727-02 
                 1.61 
                 401 
                 530 
                 32.6 
                 86.0 
                 1.31 
                 0 
                 Invention 
               
               
                 Tail 
                 1.61 
                 401 
                 530 
                 32.3 
                 86.3 
                   
                 0 
               
               
                 681727-01A 
                 1.53 
                 398 
                 530 
                 31.8 
                 85.8 
                 1.38 
                 0 
                 Invention 
               
               
                 Head 
                 1.53 
                 401 
                 532 
                 32.1 
                 86.0 
                   
                 0 
               
               
                 681727-01A 
                 1.56 
                 401 
                 532 
                 31.7 
                 86.2 
                 1.34 
                 0 
                 Invention 
               
               
                 Tail 
                 1.56 
                 401 
                 532 
                 32.5 
                 85.9 
                   
                 0 
               
               
                   
               
             
          
         
       
     
         [0037]    It will be understood various modifications may be made to this invention without departing from the spirit and scope of it. Therefore, the limits of this invention should be determined from the appended claims.