+

US20140065006A1 - Ferritic Stainless Steel with Excellent Oxidation Resistance, Good High Temperature Strength, and Good Formability - Google Patents

Ferritic Stainless Steel with Excellent Oxidation Resistance, Good High Temperature Strength, and Good Formability Download PDF

Info

Publication number
US20140065006A1
US20140065006A1 US14/010,646 US201314010646A US2014065006A1 US 20140065006 A1 US20140065006 A1 US 20140065006A1 US 201314010646 A US201314010646 A US 201314010646A US 2014065006 A1 US2014065006 A1 US 2014065006A1
Authority
US
United States
Prior art keywords
ferritic stainless
stainless steel
oxidation resistance
less
titanium
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US14/010,646
Inventor
Eizo Yoshitake
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Cleveland Cliffs Steel Properties Inc
Original Assignee
AK Steel Properties Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to US14/010,646 priority Critical patent/US20140065006A1/en
Application filed by AK Steel Properties Inc filed Critical AK Steel Properties Inc
Assigned to AK STEEL PROPERTIES, INC. reassignment AK STEEL PROPERTIES, INC. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: YOSHITAKE, EIZO
Publication of US20140065006A1 publication Critical patent/US20140065006A1/en
Assigned to U.S. BANK NATIONAL ASSOCIATION, AS NOTES COLLATERAL AGENT reassignment U.S. BANK NATIONAL ASSOCIATION, AS NOTES COLLATERAL AGENT PATENT SECURITY AGREEMENT Assignors: AK STEEL CORPORATION, AK STEEL PROPERTIES, INC., CLEVELAND-CLIFFS INC.
Assigned to U.S. BANK NATIONAL ASSOCIATION, AS NOTES COLLATERAL AGENT reassignment U.S. BANK NATIONAL ASSOCIATION, AS NOTES COLLATERAL AGENT PATENT SECURITY AGREEMENT Assignors: AK STEEL CORPORATION, AK STEEL PROPERTIES, INC.
Assigned to BANK OF AMERICA, N.A., AS AGENT reassignment BANK OF AMERICA, N.A., AS AGENT PATENT SECURITY AGREEMENT Assignors: AK STEEL CORPORATION, AK STEEL PROPERTIES, INC., CLEVELAND-CLIFFS INC.
Assigned to U.S. BANK NATIONAL ASSOCIATION, AS NOTES COLLATERAL AGENT reassignment U.S. BANK NATIONAL ASSOCIATION, AS NOTES COLLATERAL AGENT PATENT SECURITY AGREEMENT Assignors: AK STEEL CORPORATION, AK STEEL PROPERTIES, INC., CLEVELAND-CLIFFS INC.
Assigned to AK STEEL CORPORATION, AK STEEL PROPERTIES, INC. reassignment AK STEEL CORPORATION RELEASE BY SECURED PARTY (SEE DOCUMENT FOR DETAILS). Assignors: U.S. BANK NATIONAL ASSOCIATION
Assigned to CLEVELAND-CLIFFS STEEL PROPERTIES INC. reassignment CLEVELAND-CLIFFS STEEL PROPERTIES INC. CHANGE OF NAME (SEE DOCUMENT FOR DETAILS). Assignors: AK STEEL PROPERTIES, INC.
Assigned to CLEVELAND-CLIFFS STEEL PROPERTIES reassignment CLEVELAND-CLIFFS STEEL PROPERTIES CORRECTIVE ASSIGNMENT TO CORRECT THE RECEIVING PARTY DATA PREVIOUSLY RECORDED AT REEL: 056228 FRAME: 0566. ASSIGNOR(S) HEREBY CONFIRMS THE ASSIGNMENT. Assignors: AK STEEL PROPERTIES, INC.
Assigned to CLEVELAND-CLIFFS STEEL PROPERTIES INC. reassignment CLEVELAND-CLIFFS STEEL PROPERTIES INC. CORRECTIVE ASSIGNMENT TO CORRECT THE RECEIVING PARTY DATA FROM CLEVELAND-CLIFFS STEEL PROPERTIES TO CLEVELAND-CLIFFS STEEL PROPERTIES INC. PREVIOUSLY RECORDED AT REEL: 056313 FRAME: 0443. ASSIGNOR(S) HEREBY CONFIRMS THE CHANGE OF NAME. Assignors: AK STEEL PROPERTIES, INC.
Assigned to IRONUNITS LLC, CLEVELAND-CLIFFS INC., CLEVELAND-CLIFFS STEEL PROPERTIES, INC. (F/K/A AK STEEL PROPERTIES, INC.), CLEVELAND-CLIFFS STEEL CORPORATION (F/K/A AK STEEL CORPORATION), reassignment IRONUNITS LLC RELEASE BY SECURED PARTY (SEE DOCUMENT FOR DETAILS). Assignors: U.S. BANK TRUST COMPANY, NATIONAL ASSOCIATION, SUCCESSOR IN INTEREST TO U.S. BANK NATIONAL ASSOCIATION
Assigned to CLEVELAND-CLIFFS INC., CLEVELAND-CLIFFS STEEL PROPERTIES INC. (F/K/A AK STEEL PROPERTIES, INC.), CLEVELAND-CLIFFS STEEL CORPORATION (F/K/A AK STEEL CORPORATION) reassignment CLEVELAND-CLIFFS INC. RELEASE BY SECURED PARTY (SEE DOCUMENT FOR DETAILS). Assignors: U.S. BANK NATIONAL ASSOCIATION
Abandoned legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/002—Heat treatment of ferrous alloys containing Cr
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0236—Cold rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0273—Final recrystallisation annealing

Definitions

  • 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.
  • the present ferritic stainless steel is less expensive to manufacture than other stainless steels such as 18Cr—2Mo and can be produced without a hot band annealing step.
  • 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.
  • 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.
  • 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.
  • 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 and formability.
  • 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.
  • aluminum may not be added to this refined melt as a deoxidant and in other embodiments aluminum may be added to this refined melt in a small fraction.
  • 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.
  • 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.
  • one or more stabilizing elements such as columbium, zirconium, tantalum and vanadium can be added to the melt as well.
  • the cast steel is hot processed into a sheet.
  • 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.”
  • the hot band may be annealed at a peak metal temperature of 1700-2100° F. (926-1149° C.). In other embodiments, the sheet does not undergo a hot band annealing step.
  • 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.).
  • 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 2-52 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.
  • 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.
  • titanium can be present in a sub-equilibrium amount.
  • 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.
  • 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.
  • 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%.
  • 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.
  • 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.
  • 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.
  • the amount of aluminum is ⁇ 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%.
  • Titanium alloys may contain as much as 20% Al which may contribute total Al to the melt.
  • stabilizing elements may also include columbium, zirconium, tantalum, vanadium or mixtures thereof.
  • this second stabilizing element may be limited to ⁇ 0.50% when deep formability is required.
  • Some embodiments include columbium in concentrations of 0.5% 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.
  • the ferritic stainless steels contain 1.0-2.0% copper. Some embodiments include 1.16-1.31% copper.
  • 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.
  • 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 0.97-1.00%. 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.
  • 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 0.0054-0.0133%.
  • Chromium is present in 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.
  • oxygen is present in the steel in an amount ⁇ 100 ppm.
  • 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.
  • Sulfur is present in the ferritic stainless steel in an amount of ⁇ 0.01%.
  • 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%.
  • 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%.
  • Molybdenum also improves corrosion resistance. Some embodiments include 3.0% or less molybdenum. Some embodiments include 0.03-0.049% molybdenum.
  • 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.
  • 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.
  • Embodiments of the ferritic stainless steels and comparative reference steels were made with the compositions set forth in Table 1 below.
  • Plant Material 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). Except where indicated in the examples below, 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.).
  • HT #831187 is Type 444 stainless steel
  • HT #830843 is 15 CrCb stainless steel, which is a product of AK Steel Corporation, West Chester, Ohio.
  • the oxidation resistance of several 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 using 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 #920097, eight samples were tested and the minimum, average, and maximum of these eight tests has been reported.
  • HT #930354 One plant produced hot band coil with the composition set forth in Table 1 (HT #930354, CL #681158-03) was finish-processed without hot band annealing to 1.5 mm gauge.
  • a hot band annealing step was included, the plant-produced coils of HT#930354 resulted in r-bar values of 1.34, 1.31, 1.38, and 1.34, as shown in Table 5.
  • the hot band annealing step was not included, it resulted in higher r-bar of 1.46, as shown by Table 7 below.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
  • Heat Treatment Of Steel (AREA)
  • Treatment Of Steel In Its Molten State (AREA)

Abstract

Ferritic stainless steels with good oxidation resistance, 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

  • The present application claims priority from provisional patent 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, and non-provisional patent application Ser. No. 13/837,500, entitled “Ferritic Stainless Steel with Excellent Oxidation Resistance, Good High Temperature Strength, and Good Formability,” filed on Mar. 15, 2013. The disclosure of application Ser. No. 61/695,771 and application Ser. No. 13/837,500 are each incorporated herein by reference.
    • BACKGROUND
  • 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 and can be produced without a hot band annealing step.
    • SUMMARY
  • 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
  • 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.
  • 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.
  • 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 and formability.
  • 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, Al2O3, in some embodiments aluminum may not be added to this refined melt as a deoxidant and in other embodiments aluminum may be added to this refined melt in a small fraction. 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.
  • 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.
  • 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 other embodiments, the sheet does not undergo a hot band annealing step. 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.).
  • 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 2-52 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.
  • 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.
  • 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.
  • 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%.
  • 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.
  • 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 <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 <0.020% aluminum can be obtained.
  • 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 0.5% 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.
  • Copper improves high temperature strength. The ferritic stainless steels contain 1.0-2.0% copper. Some embodiments include 1.16-1.31% copper.
  • 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.
  • 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 0.97-1.00%. 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.
  • 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 0.0054-0.0133%.
  • Chromium is present in 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.
  • In some embodiments, oxygen is present in the steel in an amount <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.
  • Sulfur is present in the ferritic stainless steel in an amount of ≦0.01%.
  • 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%.
  • 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%.
  • Molybdenum also improves corrosion resistance. Some embodiments include 3.0% or less molybdenum. Some embodiments include 0.03-0.049% molybdenum.
  • 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.
  • 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
  • Embodiments of the ferritic stainless steels and comparative reference steels were made with the compositions set forth in Table 1 below.
  • 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.).
  • 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). Except where indicated in the examples below, 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.).
  • 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 <.0005 .0090 .40 16.70 1.27 1.00 .048 .019 .16 .031 .0016 1.27 .14 .071 Invention
    V3925 Lab Material .009 <.0005 .0054 .43 16.98 1.31 1.00 .049 .012 .16 .033 .0014 1.33 .21 .074 Invention
    V3926 Lab Material .010 <.0005 .0077 .43 16.90 1.28 1.00 .048 .012 .16 .031 .0016 1.31 .25 .080 Invention
    V3929 Lab Material .014 <.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 <.0005 .0085 .28 17.06 1.23 .99 .049 .0082 .14 .028 .0016 1.35 .16 .082 Invention
    V3956 Lab Material .016 <.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 <.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 #920097 Plant Material .010 .0001 .0114 .33 17.01 1.16 .98 .030 .009 .19 .026 .0015 1.30 .18 .098 Invention
    HT #930354 Plant material .007 .0009 .0133 .33 17.02 1.29 .97 .030 .0095 .15 .025 .0003 1.33 .15 .096 Invention
    V3918 Lab Material .012 <.0005 .012 .44 16.78 1.28 .28 .048 .010 .16 .031 .0015 .58 .21 .076 Reference
    V3920 Lab Material .012 <.0005 .011 .46 16.88 1.28 .28 .049 .010 .16 .031 .0017 .94 .25 .076 Reference
    V3921 Lab Material .012 <.0005 .0081 .45 16.82 1.28 .28 .049 .010 .16 .030 .0015 1.34 .27 .078 Reference
    V3922 Lab Material .009 <.0005 .0084 .32 16.86 1.28 .28 .048 .010 .16 .030 .0014 1.32 .27 .080 Reference
    HT #831187 Plant Material .009 .0060 .010 .17 17.58 .09 .35 1.90 .0114 .23 .022 .0005 .44 .20 .066 Reference
    (444)
    HT #830843 Plant Material .010 .0002 .0086 .37 14.32 .08 1.01 .010 .0077 .14 .022 .0010 1.27 .25 .045 Reference
    (15 Cr-Cb)
  • 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
  • The oxidation resistance of several 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 using 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 #920097, eight samples were tested and the minimum, average, and maximum of these eight tests has been reported.
  • 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/cm2) (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 No Invention
    1.70 Ave
    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
    15 Cr-Cb .0086 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
  • 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:
  • 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
  • The longitudinal tensile properties of several of the steel compositions of Example 1 were tested according to the procedure of ASTM Standard E8/E8M. 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:
  • TABLE 4
    Longitudinal tensile properties (ASTM E8/E8M), stretch r-values,
    and ridging resistances.
    Longitudinal ASTM Tensile
    Gauge .2% YS UTS EL Stretch r- Ridging
    Lab ID (mm) (MPa) (MPa) (%) HRB 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 5
  • 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:
  • 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
    • EXAMPLE 6
  • Four hot band samples of A, B, C, and D from heat #920097 were produced in the plant. A laboratory study was conducted in order to examine the effect of hot band annealing process and the hot band annealing temperatures for higher r-bar (drawability or drawing capability), the results of which are set forth in Table 6. Lower hot band annealing temperature and processing without hot band annealing resulted in higher r-bar with slightly lower tensile elongation and lower resistance to ridging, but all within an acceptable range.
  • TABLE 6
    Longitudinal tensile properties (ASTM E8/E8M), stretch r-values, and ridging resistances.
    Longitudinal ASTM Tensile
    Gauge .2% YS UTS EL Ridging
    Lab ID HBA Temp (mm) (MPa) (MPa) (%) HRB r-bar (0-6) Remarks
    A1 No HBA 2.01 412 543 31.4 86.5 1.44 1 Invention
    2.01 413 543 31.7 87.0
    A2 1825° F. 1.99 407 538 31.7 86.6 1.20 0 Invention
    1.99 407 537 31.7 87.2
    A3 1900° F. 1.97 407 537 32.2 86.7 1.15 0 Invention
    1.97 407 537 32.1 86.8
    A4 1975° F. 1.97 406 536 32.0 86.8 1.15 0 Invention
    1.97 405 536 32.2 86.8
    B1 No HBA 2.02 414 541 31.9 86.8 1.29 1 Invention
    2.02 413 541 31.3 86.4
    B2 1825° F. 1.99 409 538 33.2 87.2 1.24 0 Invention
    1.99 408 539 32.5 85.0
    B3 1900° F. 1.98 408 537 32.9 85.6 1.19 0 Invention
    1.98 407 536 31.7 86.4
    B4 1975° F. 1.98 406 536 32.8 85.7 1.25 0 Invention
    1.99 405 535 32.1 86.5
    C1 No HBA 1.51 419 556 29.3 86.6 1.70 1 Invention
    1.50 418 556 29.4 86.4
    C2 1825° F. 1.50 414 545 30.8 86.7 1.61 0 Invention
    1.50 412 545 31.1 85.7
    C3 1900° F. 1.49 407 541 31.3 86.0 1.45 0 Invention
    1.49 410 541 30.4 85.9
    C4 1975° F. 1.49 410 540 31.3 85.8 1.45 0 Invention
    1.49 409 540 31.1 86.0
    D1 No HBA 1.55 418 548 29.1 86.7 1.57 1 Invention
    1.55 419 549 29.6 86.6
    D2 1825° F. 1.53 411 541 31.0 86.2 1.48 1 Invention
    1.53 413 543 31.4 85.8
    D3 1900° F. 1.54 413 538 31.0 86.4 1.33 0 Invention
    1.53 416 543 30.6 86.2
    D4 1975° F. 1.52 410 539 31.4 86.6 1.32 0 Invention
    1.54 408 536 32.1 86.3
    • EXAMPLE 7
  • One plant produced hot band coil with the composition set forth in Table 1 (HT #930354, CL #681158-03) was finish-processed without hot band annealing to 1.5 mm gauge. When a hot band annealing step was included, the plant-produced coils of HT#930354 resulted in r-bar values of 1.34, 1.31, 1.38, and 1.34, as shown in Table 5. When the hot band annealing step was not included, it resulted in higher r-bar of 1.46, as shown by Table 7 below.
  • TABLE 7
    Longitudinal tensile properties (ASTM E8/E8M), stretch r-values, and ridging resistances.
    Longitudinal ASTM Tensile
    Gauge .2% YS UTS EL Ridging
    Plant ID HBA (mm) (MPa) (MPa) (%) HRB r-bar (0-6) Remarks
    HT# 930354 CL# No 1.55 439 565 27.4 89.9 1.46 2 Invention
    682158-03 1.55 441 566 28.4 89.5 2
  • 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.

Claims (2)

What is claimed is:
1. A ferritic stainless steel comprising the following elements by weight percent:
0.020% or less carbon
0.020% or less nitrogen
15-20% chromium
0.30% or less titanium
0.50% or less columbium
1.0-2.00% copper
1.0-1.7% silicon
0.4-1.5% manganese
0.050% or less phosphorus
0.01% or less sulfur
0.020% or less aluminum
2. The ferritic stainless steel of claim 1, further comprising at least one of the following elements by weight percent:
3.0% or less molybdenum
0.010% or less boron
0.5% or less vanadium
1.0% or less nickel
US14/010,646 2012-08-31 2013-08-27 Ferritic Stainless Steel with Excellent Oxidation Resistance, Good High Temperature Strength, and Good Formability Abandoned US20140065006A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US14/010,646 US20140065006A1 (en) 2012-08-31 2013-08-27 Ferritic Stainless Steel with Excellent Oxidation Resistance, Good High Temperature Strength, and Good Formability

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US201261695771P 2012-08-31 2012-08-31
US13/837,500 US20140065005A1 (en) 2012-08-31 2013-03-15 Ferritic Stainless Steel with Excellent Oxidation Resistance, Good High Temperature Strength, and Good Formability
US14/010,646 US20140065006A1 (en) 2012-08-31 2013-08-27 Ferritic Stainless Steel with Excellent Oxidation Resistance, Good High Temperature Strength, and Good Formability

Related Parent Applications (1)

Application Number Title Priority Date Filing Date
US13/837,500 Continuation US20140065005A1 (en) 2012-08-31 2013-03-15 Ferritic Stainless Steel with Excellent Oxidation Resistance, Good High Temperature Strength, and Good Formability

Publications (1)

Publication Number Publication Date
US20140065006A1 true US20140065006A1 (en) 2014-03-06

Family

ID=49151344

Family Applications (2)

Application Number Title Priority Date Filing Date
US13/837,500 Abandoned US20140065005A1 (en) 2012-08-31 2013-03-15 Ferritic Stainless Steel with Excellent Oxidation Resistance, Good High Temperature Strength, and Good Formability
US14/010,646 Abandoned US20140065006A1 (en) 2012-08-31 2013-08-27 Ferritic Stainless Steel with Excellent Oxidation Resistance, Good High Temperature Strength, and Good Formability

Family Applications Before (1)

Application Number Title Priority Date Filing Date
US13/837,500 Abandoned US20140065005A1 (en) 2012-08-31 2013-03-15 Ferritic Stainless Steel with Excellent Oxidation Resistance, Good High Temperature Strength, and Good Formability

Country Status (19)

Country Link
US (2) US20140065005A1 (en)
EP (1) EP2890825B1 (en)
JP (1) JP6194956B2 (en)
KR (2) KR20150080485A (en)
CN (2) CN104769147A (en)
AU (1) AU2013308922B2 (en)
BR (1) BR112015004228A2 (en)
CA (1) CA2882361C (en)
ES (1) ES2728229T3 (en)
HR (1) HRP20190864T1 (en)
HU (1) HUE043997T2 (en)
MX (1) MX377538B (en)
MY (1) MY172722A (en)
PL (1) PL2890825T3 (en)
RS (1) RS58807B1 (en)
RU (1) RU2650467C2 (en)
SI (1) SI2890825T1 (en)
WO (1) WO2014036091A1 (en)
ZA (1) ZA201502075B (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20140065005A1 (en) * 2012-08-31 2014-03-06 Eizo Yoshitake Ferritic Stainless Steel with Excellent Oxidation Resistance, Good High Temperature Strength, and Good Formability

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017021565A1 (en) 2015-08-05 2017-02-09 Gerdau Investigacion Y Desarrollo Europa, S.A. High-strength low-alloy steel with high resistance to high-temperature oxidation
CN107675075A (en) * 2017-09-05 2018-02-09 王业双 A kind of high-performance high temperature resistant ferritic stainless steel and preparation method thereof
JP6420893B1 (en) * 2017-12-26 2018-11-07 日新製鋼株式会社 Ferritic stainless steel
CA3163544A1 (en) * 2019-12-18 2021-06-24 Oerlikon Metco (Us) Inc. Iron-based high corrosion and wear resistance alloys

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA899A (en) * 1871-03-24 D. Cameron Composition of matter for making fire brick, and in the art of burning the same
US6426039B2 (en) * 2000-07-04 2002-07-30 Kawasaki Steel Corporation Ferritic stainless steel
US20060163231A1 (en) * 2005-01-26 2006-07-27 Nippon Welding Rod Co., Ltd. Ferritic stainless steel welding wire and manufacturing method thereof
CA2762899A1 (en) * 2009-06-15 2010-12-23 Nisshin Steel Co., Ltd. Ferritic stainless steel material for brazing and heat exchanger member
WO2012036313A1 (en) * 2010-09-16 2012-03-22 新日鐵住金ステンレス株式会社 Heat-resistant ferrite-type stainless steel plate having excellent oxidation resistance

Family Cites Families (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01165752A (en) * 1987-12-22 1989-06-29 Kawasaki Steel Corp Ferritic stainless steel having superior corrosion resistance in highly concentrated halide solution
JPH02115346A (en) * 1988-10-21 1990-04-27 Kawasaki Steel Corp Ferritic stainless steel with excellent corrosion resistance in high concentration halides
US5426039A (en) * 1993-09-08 1995-06-20 Bio-Rad Laboratories, Inc. Direct molecular cloning of primer extended DNA containing an alkane diol
FR2720410B1 (en) * 1994-05-31 1996-06-28 Ugine Savoie Sa Ferritic stainless steel with improved machinability.
JP3439866B2 (en) * 1995-03-08 2003-08-25 日本冶金工業株式会社 Ferritic stainless steel with excellent corrosion resistance and weldability
JP3886785B2 (en) * 2001-11-22 2007-02-28 日新製鋼株式会社 Ferritic stainless steel for petroleum fuel reformers
JP3942876B2 (en) * 2001-11-22 2007-07-11 日新製鋼株式会社 Ferritic stainless steel for hydrocarbon fuel reformer
JP3989790B2 (en) * 2002-07-30 2007-10-10 新日鐵住金ステンレス株式会社 Ferritic stainless steel sheet with excellent press formability and manufacturing method thereof
JP3920185B2 (en) * 2002-09-27 2007-05-30 日新製鋼株式会社 Stainless steel tire rim material and motorcycle frame material with excellent flexibility
JP4463663B2 (en) * 2004-11-04 2010-05-19 日新製鋼株式会社 Ferritic steel material excellent in high temperature steam oxidation resistance and method of use thereof
JP5236158B2 (en) * 2005-01-26 2013-07-17 日本ウエルディング・ロッド株式会社 Ferritic stainless steel welding wire and manufacturing method thereof
JP4302678B2 (en) * 2005-09-01 2009-07-29 日新製鋼株式会社 Ferritic stainless steel sheet for fuel tanks
JP4761993B2 (en) * 2006-02-14 2011-08-31 日新製鋼株式会社 Manufacturing method of ferritic stainless steel welded pipe for spinning
JP4948998B2 (en) * 2006-12-07 2012-06-06 日新製鋼株式会社 Ferritic stainless steel and welded steel pipe for automotive exhaust gas flow path members
RU2415963C2 (en) * 2009-07-13 2011-04-10 Открытое акционерное общество "Научно-производственное объединение "Центральный научно-исследовательский институт технологии машиностроения", ОАО НПО "ЦНИИТМАШ" Heat resistant steel
US20140065005A1 (en) * 2012-08-31 2014-03-06 Eizo Yoshitake Ferritic Stainless Steel with Excellent Oxidation Resistance, Good High Temperature Strength, and Good Formability

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA899A (en) * 1871-03-24 D. Cameron Composition of matter for making fire brick, and in the art of burning the same
US6426039B2 (en) * 2000-07-04 2002-07-30 Kawasaki Steel Corporation Ferritic stainless steel
US20060163231A1 (en) * 2005-01-26 2006-07-27 Nippon Welding Rod Co., Ltd. Ferritic stainless steel welding wire and manufacturing method thereof
CA2762899A1 (en) * 2009-06-15 2010-12-23 Nisshin Steel Co., Ltd. Ferritic stainless steel material for brazing and heat exchanger member
WO2012036313A1 (en) * 2010-09-16 2012-03-22 新日鐵住金ステンレス株式会社 Heat-resistant ferrite-type stainless steel plate having excellent oxidation resistance
US20130149187A1 (en) * 2010-09-16 2013-06-13 Nippon Steel & Sumikin Stainless Steel Sheet Corporation Heat-resistant ferritic stainless steel sheet having excellent oxidation resistance

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
' 899 *
US 2013/0149187 A1 of Inoue et al. is the English equivalent of WO 2012/036313 A1 with publication date of 03/22/2012. *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20140065005A1 (en) * 2012-08-31 2014-03-06 Eizo Yoshitake Ferritic Stainless Steel with Excellent Oxidation Resistance, Good High Temperature Strength, and Good Formability

Also Published As

Publication number Publication date
EP2890825B1 (en) 2019-04-03
WO2014036091A1 (en) 2014-03-06
PL2890825T3 (en) 2019-09-30
KR20150080485A (en) 2015-07-09
ZA201502075B (en) 2016-03-30
RU2650467C2 (en) 2018-04-13
CA2882361C (en) 2019-06-18
HUE043997T2 (en) 2019-09-30
KR20200028502A (en) 2020-03-16
MX377538B (en) 2025-03-10
EP2890825A1 (en) 2015-07-08
MX2015002677A (en) 2015-05-12
JP6194956B2 (en) 2017-09-13
JP2015532684A (en) 2015-11-12
BR112015004228A2 (en) 2017-07-04
CA2882361A1 (en) 2014-03-06
RS58807B1 (en) 2019-07-31
AU2013308922A1 (en) 2015-03-05
CN104769147A (en) 2015-07-08
HRP20190864T1 (en) 2019-06-28
US20140065005A1 (en) 2014-03-06
RU2015108849A (en) 2016-10-20
MY172722A (en) 2019-12-11
ES2728229T3 (en) 2019-10-23
AU2013308922B2 (en) 2016-08-04
CN104769147A8 (en) 2018-10-09
CN108823509A (en) 2018-11-16
SI2890825T1 (en) 2019-06-28

Similar Documents

Publication Publication Date Title
TWI404808B (en) Boron steel sheet with high quenching property and manufacturing method thereof
JP5362582B2 (en) Ferritic stainless steel with excellent corrosion resistance and stretch formability and method for producing the same
CN111433381B (en) High Mn steel and method for producing same
TW201333223A (en) Duplex stainless steel, duplex stainless steel slab, and duplex stainless steel material
CN113166885B (en) High-strength steel material having excellent ductility and low-temperature toughness, and method for producing same
CA2882361C (en) Ferritic stainless steel with excellent oxidation resistance, good high temperature strength, and good formability
CN113631733A (en) Bar-shaped steel
JP6842257B2 (en) Fe-Ni-Cr-Mo alloy and its manufacturing method
CN113412337A (en) High Mn steel and method for producing same
CA2254584C (en) Non-ridging ferritic chromium alloyed steel
US9816163B2 (en) Cost-effective ferritic stainless steel
EP3872216B1 (en) Cryogenic austenitic high-manganese steel having excellent shape, and manufacturing method therefor
KR101764990B1 (en) High-strength, low-specific gravity steel plate having excellent spot welding properties
JPH0551633A (en) Production of high si-containing austenitic stainless steel
RU2262549C1 (en) Medium-carbon steel with elevated cutting ability
KR101505299B1 (en) Steel and method of manufacturing the same
KR100605719B1 (en) Manufacturing method of soft thin steel sheet for deep processing and thin steel sheet manufactured by this method
AU2003200957B2 (en) Non-ridging Ferritic Chromium Alloyed Steel
JPH06207244A (en) Thin steel sheet excellent in balance of strength and ductility
JPH10265892A (en) Iron base alloy excellent in ductility

Legal Events

Date Code Title Description
AS Assignment

Owner name: AK STEEL PROPERTIES, INC., OHIO

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:YOSHITAKE, EIZO;REEL/FRAME:031459/0672

Effective date: 20131004

STCV Information on status: appeal procedure

Free format text: EXAMINER'S ANSWER TO APPEAL BRIEF MAILED

STCV Information on status: appeal procedure

Free format text: ON APPEAL -- AWAITING DECISION BY THE BOARD OF APPEALS

AS Assignment

Owner name: BANK OF AMERICA, N.A., AS AGENT, ILLINOIS

Free format text: PATENT SECURITY AGREEMENT;ASSIGNORS:CLEVELAND-CLIFFS INC.;AK STEEL CORPORATION;AK STEEL PROPERTIES, INC.;REEL/FRAME:052162/0782

Effective date: 20200313

Owner name: U.S. BANK NATIONAL ASSOCIATION, AS NOTES COLLATERAL AGENT, OHIO

Free format text: PATENT SECURITY AGREEMENT;ASSIGNORS:AK STEEL CORPORATION;AK STEEL PROPERTIES, INC.;REEL/FRAME:052162/0691

Effective date: 20200313

Owner name: U.S. BANK NATIONAL ASSOCIATION, AS NOTES COLLATERAL AGENT, OHIO

Free format text: PATENT SECURITY AGREEMENT;ASSIGNORS:CLEVELAND-CLIFFS INC.;AK STEEL CORPORATION;AK STEEL PROPERTIES, INC.;REEL/FRAME:052162/0865

Effective date: 20200313

AS Assignment

Owner name: U.S. BANK NATIONAL ASSOCIATION, AS NOTES COLLATERAL AGENT, OHIO

Free format text: PATENT SECURITY AGREEMENT;ASSIGNORS:CLEVELAND-CLIFFS INC.;AK STEEL CORPORATION;AK STEEL PROPERTIES, INC.;REEL/FRAME:052432/0166

Effective date: 20200417

STCV Information on status: appeal procedure

Free format text: BOARD OF APPEALS DECISION RENDERED

STPP Information on status: patent application and granting procedure in general

Free format text: NON FINAL ACTION MAILED

AS Assignment

Owner name: AK STEEL CORPORATION, OHIO

Free format text: RELEASE BY SECURED PARTY;ASSIGNOR:U.S. BANK NATIONAL ASSOCIATION;REEL/FRAME:055587/0118

Effective date: 20210312

Owner name: AK STEEL PROPERTIES, INC., OHIO

Free format text: RELEASE BY SECURED PARTY;ASSIGNOR:U.S. BANK NATIONAL ASSOCIATION;REEL/FRAME:055587/0118

Effective date: 20210312

STPP Information on status: patent application and granting procedure in general

Free format text: FINAL REJECTION MAILED

AS Assignment

Owner name: CLEVELAND-CLIFFS STEEL PROPERTIES INC., OHIO

Free format text: CHANGE OF NAME;ASSIGNOR:AK STEEL PROPERTIES, INC.;REEL/FRAME:056228/0566

Effective date: 20210202

AS Assignment

Owner name: CLEVELAND-CLIFFS STEEL PROPERTIES, OHIO

Free format text: CORRECTIVE ASSIGNMENT TO CORRECT THE RECEIVING PARTY DATA PREVIOUSLY RECORDED AT REEL: 056228 FRAME: 0566. ASSIGNOR(S) HEREBY CONFIRMS THE ASSIGNMENT;ASSIGNOR:AK STEEL PROPERTIES, INC.;REEL/FRAME:056313/0443

Effective date: 20210202

AS Assignment

Owner name: CLEVELAND-CLIFFS STEEL PROPERTIES INC., OHIO

Free format text: CORRECTIVE ASSIGNMENT TO CORRECT THE RECEIVING PARTY DATA FROM CLEVELAND-CLIFFS STEEL PROPERTIES TO CLEVELAND-CLIFFS STEEL PROPERTIES INC. PREVIOUSLY RECORDED AT REEL: 056313 FRAME: 0443. ASSIGNOR(S) HEREBY CONFIRMS THE CHANGE OF NAME;ASSIGNOR:AK STEEL PROPERTIES, INC.;REEL/FRAME:057941/0376

Effective date: 20210202

STCB Information on status: application discontinuation

Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION

AS Assignment

Owner name: IRONUNITS LLC, OHIO

Free format text: RELEASE BY SECURED PARTY;ASSIGNOR:U.S. BANK TRUST COMPANY, NATIONAL ASSOCIATION, SUCCESSOR IN INTEREST TO U.S. BANK NATIONAL ASSOCIATION;REEL/FRAME:063272/0001

Effective date: 20220510

Owner name: CLEVELAND-CLIFFS STEEL PROPERTIES, INC. (F/K/A AK STEEL PROPERTIES, INC.), OHIO

Free format text: RELEASE BY SECURED PARTY;ASSIGNOR:U.S. BANK TRUST COMPANY, NATIONAL ASSOCIATION, SUCCESSOR IN INTEREST TO U.S. BANK NATIONAL ASSOCIATION;REEL/FRAME:063272/0001

Effective date: 20220510

Owner name: CLEVELAND-CLIFFS STEEL CORPORATION (F/K/A AK STEEL CORPORATION),, KANSAS

Free format text: RELEASE BY SECURED PARTY;ASSIGNOR:U.S. BANK TRUST COMPANY, NATIONAL ASSOCIATION, SUCCESSOR IN INTEREST TO U.S. BANK NATIONAL ASSOCIATION;REEL/FRAME:063272/0001

Effective date: 20220510

Owner name: CLEVELAND-CLIFFS INC., OHIO

Free format text: RELEASE BY SECURED PARTY;ASSIGNOR:U.S. BANK TRUST COMPANY, NATIONAL ASSOCIATION, SUCCESSOR IN INTEREST TO U.S. BANK NATIONAL ASSOCIATION;REEL/FRAME:063272/0001

Effective date: 20220510

AS Assignment

Owner name: CLEVELAND-CLIFFS STEEL PROPERTIES INC. (F/K/A AK STEEL PROPERTIES, INC.), OHIO

Free format text: RELEASE BY SECURED PARTY;ASSIGNOR:U.S. BANK NATIONAL ASSOCIATION;REEL/FRAME:067025/0974

Effective date: 20240403

Owner name: CLEVELAND-CLIFFS STEEL CORPORATION (F/K/A AK STEEL CORPORATION), OHIO

Free format text: RELEASE BY SECURED PARTY;ASSIGNOR:U.S. BANK NATIONAL ASSOCIATION;REEL/FRAME:067025/0974

Effective date: 20240403

Owner name: CLEVELAND-CLIFFS INC., OHIO

Free format text: RELEASE BY SECURED PARTY;ASSIGNOR:U.S. BANK NATIONAL ASSOCIATION;REEL/FRAME:067025/0974

Effective date: 20240403

点击 这是indexloc提供的php浏览器服务，不要输入任何密码和下载