US20110176954A1 - Ferritic Stainless Steel for Use as Conduit Members for Emission of Automotive Exhaust Gas - Google Patents
Ferritic Stainless Steel for Use as Conduit Members for Emission of Automotive Exhaust Gas Download PDFInfo
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- US20110176954A1 US20110176954A1 US13/042,542 US201113042542A US2011176954A1 US 20110176954 A1 US20110176954 A1 US 20110176954A1 US 201113042542 A US201113042542 A US 201113042542A US 2011176954 A1 US2011176954 A1 US 2011176954A1
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- 229910001220 stainless steel Inorganic materials 0.000 title claims abstract description 45
- 229910052802 copper Inorganic materials 0.000 claims abstract description 13
- 229910052720 vanadium Inorganic materials 0.000 claims abstract description 13
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 12
- 239000012535 impurity Substances 0.000 claims abstract description 7
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 3
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 3
- 229910000831 Steel Inorganic materials 0.000 abstract description 59
- 239000010959 steel Substances 0.000 abstract description 59
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- 238000012360 testing method Methods 0.000 description 19
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- 229910052717 sulfur Inorganic materials 0.000 description 2
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- 229910006291 Si—Nb Inorganic materials 0.000 description 1
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Images
Classifications
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- 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
-
- 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
- C22C38/04—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
- C22C38/18—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
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- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2530/00—Selection of materials for tubes, chambers or housings
- F01N2530/02—Corrosion resistive metals
- F01N2530/04—Steel alloys, e.g. stainless steel
Definitions
- the present invention relates to a ferritic stainless steel, which is excellent in heat-resistance, low-temperature toughness and weldability, useful as conduit members, e.g. exhaust manifolds, front pipes, center pipes and outer casings of catalytic converters in internal combustion engines of automobiles or the like, for emission of exhaust gas.
- conduit members e.g. exhaust manifolds, front pipes, center pipes and outer casings of catalytic converters in internal combustion engines of automobiles or the like, for emission of exhaust gas.
- Conduit members of automobiles for emission of exhaust gas are directly exposed to a high-temperature atmosphere containing exhaust gas during driving automobiles, and subjected to thermal stress caused by repetition of driving and stopping as well as vibration during driving. Mechanical stress is also applied to conduit members at a low temperature, when automobiles are started in winter in cold districts. Therefore, a material for use as the conduit members shall have durability in severe environments.
- conduit members are fabricated by welding or forming steel sheets or pipes to product shapes, steels necessarily have excellent heat-resistance, weldability and formability for this purpose.
- Toughness especially low-temperature toughness, is also an important property, in order to secondarily form a stainless steel sheet or pipe without cracks and to render conduit members resistant to mechanical stress at a low temperature.
- a ferritic stainless steel is often used as a material for such conduit members, due to its small thermal expansion coefficient, thermal fatigue strength and scale spalling resistance in comparison with an austenitic stainless steel. A low price is also an advantage of the ferritic stainless steel.
- JP3-274245A discloses Nb-alloyed steel and Nb, Si-alloyed steel as new SUS430J1 stainless steels
- JP5-125491A discloses Nb, Mo-alloyed steel.
- the Nb, Mo-alloyed steel is useful as parts or members exposed to severe high-temperature atmosphere due to its excellent high-temperature strength and thermal fatigue-resistance.
- poor formability and inferior low-temperature toughness are disadvantages of the Nb, Mo-alloyed steel.
- a few reports are published on improvement of formability and low-temperature toughness, the improvement is still insufficient for the purpose. Consumption of expensive Mo at a high ratio is also a disadvantage of the Nb, Mo-alloyed steel.
- high-temperature strength e.g. resistance to thermal fatigue failure
- high-temperature oxidation-resistance evaluated as a critical temperature of abnormal oxidation
- high-temperature strength is more important than high-temperature oxidation-resistance
- formability and low-temperature toughness are also important factors so as to form a stainless steel sheet or pipe to the complicated profile.
- the Nb, Mo-alloyed steel is necessarily used for such a part or member with emphasis on heat-resistance regardless of poor formability, inferior low-temperature toughness and expensiveness.
- the present invention aims at provision of a ferritic stainless steel useful as conduit members for emission of exhaust gas.
- An object of the present invention is to provide a ferritic stainless steel, which does not contain expensive Mo, with heat-resistance similar to that of Nb, Mo-alloyed steel in addition to excellent formability, low-temperature toughness and weldability.
- the present invention proposes a ferritic stainless steel, which consists of C up to 0.03 mass %, Si up to 1.0 mass %, Mn up to 1.5 mass %, Ni up to 0.6 mass %, 10-20 mass % of Cr, Nb up to 0.50 mass %, 0.8-2.0 mass % of Cu, Al up to 0.03 mass %, 0.03-0.20 mass % of V, N up to 0.03 mass % and the balance being Fe except inevitable impurities with a provision of Nb ⁇ 8(C+N).
- the ferritic stainless steel does not contain Mo as an alloying element, but optionally contains 0.05-0.30 mass % of Ti for further improvement of formability and/or 0.0005-0.02 mass % of B for further improvement of secondary formability.
- the FIGURE is a graph, which shows an effect of Cu on 0.2%-proof stress of a ferritic stainless steel at an elevated temperature.
- Such stainless steels as SUH409, SUS430J11 and SUS429 have been used as materials good of heat-resistance in an atmosphere to which conduit members are exposed.
- Such a part or member ordinarily has a complicated profile, so that it shall be made of a stainless steel good of formability and low-temperature toughness, which are never estimated from Mo-alloyed steel.
- the part or member is likely to break down due to thermal fatigue, since thermal stress is repeatedly applied to the complicated profile.
- the inventors have researched and examined effects of various alloying elements on properties of such a part or member, and discovered that a ferritic stainless steel is improved in all of high-temperature strength below 900° C., formability and low-temperature toughness by addition of both V and Cu to the same level of Nb, Mo-alloyed steel.
- Nb-alloyed ferritic stainless steels which contained V at a small ratio and Cu at various ratios, were examined by high-temperature tensile test at 700° C. and 800° C. for measurement of 0.2%-proof stress. Test results prove that high-temperature strength below 900° C. is remarkably raised to a level similar to Nb, Mo-alloyed steel by addition of V at a small ratio and Cu at a controlled ratio.
- the FIGURE shows test results of ferritic stainless steels with a basic composition of 17Cr—0.4Nb—0.1V, to which Cu is added at various ratios.
- the FIGURE also shows strength of SUS444 steel with basic composition of 18Cr—2Mo—0.4Nb as a comparative example of Nb, Mo-alloyed steel.
- Values of 0.2%-proof stress at 700° C. and 800° C. are remarkably raised in response to an increase of a Cu content, as noted in the FIGURE.
- the value of 0.2%-proof stress at 0.8 mass % or more of Cu is similar or superior to that of SUS444 steel, which contains approximately 2 mass % of Mo.
- the inventors have already confirmed from another test result that a value of 0.2%-proof stress at 900° C. is not raised to a level of SUS444 but higher than Nb-containing ferritic stainless steel by an increase of V and Cu contents.
- addition of both V and Cu is effective for improvement of high-temperature strength in a hot zone below 900° C. without significant troubles at a temperature higher than 900° C.
- a ratio of dissolved Nb for improvement of high-temperature strength is also kept at a higher value by presence of V, which converts free C and N to carbonitrides, than V-free steels containing Nb at the same ratio.
- Increase of dissolved Nb assures that high-temperature strength necessary for the purpose is attained by saved consumption of Nb in comparison with the V-free steels, resulting in improvement of formability and low-temperature toughness.
- Carbonitrides of Nb and V increase in an annealed matrix of the inventive ferritic stainless steel. Increase of the carbonitrides suppresses crystal growth to coarse grains at a weld heat-affected zone, resulting in improvement of toughness. Formation of chromium carbide, which is harmful on intergranular corrosion-resistance, is also suppressed by increase of the carbonitrides.
- C and N are generally regarded as elements effective for high-temperature strength, e.g. creep strength, but excess C and N unfavorably degrade oxidation-resistance, formability, low-temperature toughness and weldability.
- V and Nb are necessarily added at ratios corresponding to concentrations of C and N. Therefore, each of C and N contents is controlled to 0.03 mass % or less (preferably 0.015 mass % or less), in order to avoid increase of V and Nb, which causes a rise of material expense.
- Si is an element effective for high-temperature oxidation-resistance, but not so effective on high-temperature strength below 900° C. Excess Si hardens a ferritic stainless steel, resulting in degradation of formability and low-temperature toughness. In this sense, a Si content is determined at 1.0 mass % or less (preferably 0.1-0.5 mass %).
- Mn is an alloying element, which improves high-temperature oxidation-resistance, especially scale spalling resistance property, of a ferritic stainless steel, but excess Mn degrades formability and weldability.
- a Mn content is determined at 1.5 mass % or less (preferably 0.5 mass % or less).
- Ni is an austenite-stabilizing element. Excess addition of Ni to a steel containing Cr at a relatively small ratio promotes formation of a martensitic phase harmful on thermal fatigue strength and formability, as the same as Mn. Excess Ni also raises a steel cost. Therefore, a Ni content is determined at 0.6 mass % or less (preferably 0.5 mass % or less).
- Cr is an essential element for stabilization of a ferritic phase and improvement of oxidation-resistance as an important property for high-temperature use. Oxidation-resistance becomes better as increase of a Cr content, but excess Cr causes embrittlement of a stainless steel, resulting in increase of hardness and degradation of formability. In this sense, a Cr content is determined within a range of 10-20 mass %. Cr is preferably controlled to a proper value in response to a temperature on use. For instance, 16-19 mass % of Cr is favorable for oxidation-resistance at a temperature not higher than 950° C., and 12-16 mass % of Cr is favorable for oxidation-resistance at a temperature not higher than 900° C.
- Nb fixes C and N as carbonitrides, and also improves high-temperature strength in a state dissolved in a steel matrix. However, excess Nb is unfavorable for formability, low-temperature toughness and to welding hot crack-resistance. Nb not less than 8(C+N) is necessary for fixation of C and N, but an upper limit of Nb is determined at 0.5 mass % in order to maintain proper formability, low-temperature toughness and tensile type hot-cracking resistance. A Nb content is preferably controlled within a range of from 8(C+N)+0.10 to 0.45 mass %.
- Cu is the most important element in the inventive alloy system. Within a temperature range which the inventors have researched and examined, most of Cu is dissolved in an annealed steel matrix and precipitated during heat-treatment. Cu precipitates exhibit the same strengthening effect as Mo at the beginning of heating, but the strengthening effect gradually becomes weaker as the lapse of heating time. At least 0.8 mass % of Cu is necessary in order to gain high-temperature strength suitable for the purpose, as noted in the FIGURE. However, formability, low-temperature toughness and weldability are degraded as increase of a Cu content. The unfavorable effect of Cu on formability, low-temperature toughness and weldability is suppressed by controlling an upper limit of the Cu content at 2.0 mass %. The Cu content is preferably determined within a range of 1.0-1.7 mass %.
- Al is added as a deoxidizing element in a steel making process. But, excess Al degrades an external appearance of a stainless steel sheet and also puts harmful effects on formability, low-temperature toughness and weldability. In this sense, an Al content is preferably controlled at a lowest possible level, so that its upper limit is determined at 0.03 mass %.
- the additive V improves high-temperature strength of a ferritic stainless steel in co-presence of Nb and Cu. Addition of V together with Nb is also effective for formability, low-temperature toughness, intergranular corrosion-resistance and toughness at a weld heat affected-zone. These effects are noted at 0.03 mass % or more of V, but excess V above 0.20 mass % is rather unfavorable for formability and low-temperature toughness. In this sense, a V content is determined within a range of 0.03-0.20 mass % (preferably 0.04-0.15 mass %).
- Ti is an optional element, which raises Lankford value (r) and improves formability of a ferritic stainless steel, and its effect is noted at 0.05 mass % or more of Ti.
- excess Ti promotes formation of TiN harmful on external appearance of a stainless steel and also degrades formability and low-temperature toughness.
- Ti shall be held at a smallest possible ratio, even when Ti is added for improvement of formability. Therefore, an upper limit of a Ti content is determined at 0.30 mass % (preferably 0.20 mass %).
- B is another optional element for improving secondary formability of a stainless steel and suppressing cracking during multi-stepped forming.
- the effect on formability is noted at 0.0005 mass % or more of B, but excess B causes degradation of productivity and weldability.
- a B content is determined within a range of 0.0005-0.02 mass % (preferably 0.001-0.01 mass %).
- the inventive alloy system is designed on the assumption that expensive Mo is not added as an alloying element, but Mo is likely to be included as an impurity during steel making. Since inclusion of Mo at a relatively high ratio is harmful on formability, low-temperature toughness and weldability, it shall be controlled at a ratio less than 0.10 mass %.
- P, S and O are preferably controlled at lowest possible levels. Accounting hot-workability, oxidation-resistance and so on, upper limits of P, S and O are preferably determined at 0.04 mass %, 0.03 mass % and 0.02 mass %, respectively. At least one of W, Zr, Y and REM (rare earth metals) may be added for heat-resistance, or at least one of Ca, Mg and Co may be added for hot-workability.
- W, Zr, Y and REM rare earth metals
- Table 1 Each ferritic stainless steel with chemical composition shown in Table 1 or 2 was melted in a vacuum furnace and cast to a 30 kg ingot. The ingot was forged, hot-rolled, annealed, cold-rolled to a thickness of 2.0 mm or 1.2 mm, and finish-annealed.
- Table 1 shows compositions according to the present invention, while Table 2 shows comparative compositions.
- a steel No. 11 corresponds to SUS430J11
- a steel No. 15 corresponds to SUH1409L
- a steel No. 16 corresponds to a 14Cr—Si—Nb steel
- a steel No. 17 corresponds to SUS444. Any of these steels has been used so far as a material for an exhaust manifold.
- Each annealed cold-rolled steel sheet of 2.0 mm in thickness was examined by a high-temperature tensile test, a high-temperature oxidation test, a room-temperature tensile test and Charpy impact test.
- Each annealed cold-rolled steel sheet of 1.2 mm in thickness was examined by a tensile type hot-cracking test.
- a test piece was heated at each temperature of 850° C., 900° C., 950° C., 1000° C. and 1100° C. for 200 hours under conditions regulated in JIS Z2281.
- the heated test piece was observed by naked eyes to detect occurrence of abnormal oxidation (i.e. growth of knobby thick oxide through a steel sheet).
- a critical temperature, at which the test piece was heated without abnormal oxidation, was determined from the observation results.
- each annealed cold-rolled steel sheet of 2.0 mm in thickness was shaped to a test piece No. 13B and stretched under conditions regulated in JIS Z2241 to measure its elongation after fracture.
- any of the inventive steels Nos. 1-10 has 0.2%-proof stress at 800° C., fairly higher than the Nb, Si-alloyed steel No. 16 and similar or superior to the Nb, Mo-alloyed steel No. 17.
- Values of elongation by the room-temperature tensile test, a ductile-brittle transition temperature by Charpy impact test and a critical strain by the tensile type hot-cracking test were also similar or superior to the Nb, Mo-alloyed steel No. 17.
- the Mo-containing comparative steel No. 17 had the same properties as the inventive steels Nos. 1-10, but its low-temperature toughness was relatively inferior. A cost of the steel No. 17 is inevitably higher than the inventive steels Nos. 1-10, due to consumption of Mo at approximately 2 mass %.
- a ferritic stainless steel is improved in formability, low-temperature toughness and weldability without degradation of heat-resistant by specified alloying design, especially control of V and Cu contents, without necessity of expensive Mo.
- the newly proposed stainless steel is useful as members or parts for automotive engines or conduit members, e.g. exhaust manifolds, front pipes, center pipes, outer casings of catalytic converters for emission of exhaust gas.
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Abstract
A ferritic stainless steel useful as conduit members for emission of automotive exhaust gas consists of C up to 0.03 mass %, Si up to 1.0 mass %, Mn up to 1.5 mass %, Ni up to 0.6 mass %, 10-20 mass % of Cr, Nb up to 0.50 mass %, 0.8-2.0 mass % of Cu, Al up to 0.03 mass %, 0.03-0.20 mass % of V, N up to 0.03 mass % and the balance being Fe except inevitable impurities with a provision of Nb≧8(C+N). The steel may further contain 0.05-0.30 mass % of Ti and/or 0.0005-0.02 mass % of B. Mo as an inevitable impurity is controlled to be less than 0.10 mass %. The steel has excellent formability, low-temperature toughness and weldability as well as the same heat-resistance as Nb, Mo-alloyed steel.
Description
- This application is a continuation of co-pending U.S. patent application Ser. No. 12/689,824 filed Jan. 19, 2010, which is a continuation of U.S. patent application Ser. No. 12/233,122 filed Sep. 18, 2008, now abandoned, which is a continuation of U.S. patent application Ser. No. 10/482,718 filed Jan. 2, 2004, now abandoned, which is a national phase of International Patent Application No. PCT/JP02/06768 filed Jul. 4, 2002, which claims priority to Japanese Patent Application No. JP 2001-204444 filed Jul. 5, 2001.
- The present invention relates to a ferritic stainless steel, which is excellent in heat-resistance, low-temperature toughness and weldability, useful as conduit members, e.g. exhaust manifolds, front pipes, center pipes and outer casings of catalytic converters in internal combustion engines of automobiles or the like, for emission of exhaust gas.
- Conduit members of automobiles for emission of exhaust gas are directly exposed to a high-temperature atmosphere containing exhaust gas during driving automobiles, and subjected to thermal stress caused by repetition of driving and stopping as well as vibration during driving. Mechanical stress is also applied to conduit members at a low temperature, when automobiles are started in winter in cold districts. Therefore, a material for use as the conduit members shall have durability in severe environments.
- Since conduit members are fabricated by welding or forming steel sheets or pipes to product shapes, steels necessarily have excellent heat-resistance, weldability and formability for this purpose. Toughness, especially low-temperature toughness, is also an important property, in order to secondarily form a stainless steel sheet or pipe without cracks and to render conduit members resistant to mechanical stress at a low temperature.
- A ferritic stainless steel is often used as a material for such conduit members, due to its small thermal expansion coefficient, thermal fatigue strength and scale spalling resistance in comparison with an austenitic stainless steel. A low price is also an advantage of the ferritic stainless steel.
- Various improvements have been proposed so far in order to improve a high-temperature strength of a ferritic stainless steel, which is intrinsically lower than an austenitic stainless steel. For instance, JP3-274245A discloses Nb-alloyed steel and Nb, Si-alloyed steel as new SUS430J1 stainless steels, and JP5-125491A discloses Nb, Mo-alloyed steel. Especially, the Nb, Mo-alloyed steel is useful as parts or members exposed to severe high-temperature atmosphere due to its excellent high-temperature strength and thermal fatigue-resistance. However, poor formability and inferior low-temperature toughness are disadvantages of the Nb, Mo-alloyed steel. Although a few reports are published on improvement of formability and low-temperature toughness, the improvement is still insufficient for the purpose. Consumption of expensive Mo at a high ratio is also a disadvantage of the Nb, Mo-alloyed steel.
- By the way, high-temperature strength (e.g. resistance to thermal fatigue failure) and high-temperature oxidation-resistance (evaluated as a critical temperature of abnormal oxidation) are not necessarily balanced at high level for some parts or members. In the case of a part or member, which has a complicated profile but does not come in contact with high-temperature exhaust gas, high-temperature strength is more important than high-temperature oxidation-resistance, and formability and low-temperature toughness are also important factors so as to form a stainless steel sheet or pipe to the complicated profile. However, the Nb, Mo-alloyed steel is necessarily used for such a part or member with emphasis on heat-resistance regardless of poor formability, inferior low-temperature toughness and expensiveness.
- The present invention aims at provision of a ferritic stainless steel useful as conduit members for emission of exhaust gas. An object of the present invention is to provide a ferritic stainless steel, which does not contain expensive Mo, with heat-resistance similar to that of Nb, Mo-alloyed steel in addition to excellent formability, low-temperature toughness and weldability.
- The present invention proposes a ferritic stainless steel, which consists of C up to 0.03 mass %, Si up to 1.0 mass %, Mn up to 1.5 mass %, Ni up to 0.6 mass %, 10-20 mass % of Cr, Nb up to 0.50 mass %, 0.8-2.0 mass % of Cu, Al up to 0.03 mass %, 0.03-0.20 mass % of V, N up to 0.03 mass % and the balance being Fe except inevitable impurities with a provision of Nb≧8(C+N).
- The ferritic stainless steel does not contain Mo as an alloying element, but optionally contains 0.05-0.30 mass % of Ti for further improvement of formability and/or 0.0005-0.02 mass % of B for further improvement of secondary formability.
- The FIGURE is a graph, which shows an effect of Cu on 0.2%-proof stress of a ferritic stainless steel at an elevated temperature.
- Such stainless steels as SUH409, SUS430J11 and SUS429 have been used as materials good of heat-resistance in an atmosphere to which conduit members are exposed. Some parts or members, which are heated up to 800-900° C. at highest, need high-temperature strength fairly higher than conventional steels. Such a part or member ordinarily has a complicated profile, so that it shall be made of a stainless steel good of formability and low-temperature toughness, which are never estimated from Mo-alloyed steel. Moreover, the part or member is likely to break down due to thermal fatigue, since thermal stress is repeatedly applied to the complicated profile.
- The inventors have researched and examined effects of various alloying elements on properties of such a part or member, and discovered that a ferritic stainless steel is improved in all of high-temperature strength below 900° C., formability and low-temperature toughness by addition of both V and Cu to the same level of Nb, Mo-alloyed steel.
- Several Nb-alloyed ferritic stainless steels, which contained V at a small ratio and Cu at various ratios, were examined by high-temperature tensile test at 700° C. and 800° C. for measurement of 0.2%-proof stress. Test results prove that high-temperature strength below 900° C. is remarkably raised to a level similar to Nb, Mo-alloyed steel by addition of V at a small ratio and Cu at a controlled ratio.
- The FIGURE shows test results of ferritic stainless steels with a basic composition of 17Cr—0.4Nb—0.1V, to which Cu is added at various ratios. The FIGURE also shows strength of SUS444 steel with basic composition of 18Cr—2Mo—0.4Nb as a comparative example of Nb, Mo-alloyed steel.
- Values of 0.2%-proof stress at 700° C. and 800° C. are remarkably raised in response to an increase of a Cu content, as noted in the FIGURE. The value of 0.2%-proof stress at 0.8 mass % or more of Cu is similar or superior to that of SUS444 steel, which contains approximately 2 mass % of Mo. The inventors have already confirmed from another test result that a value of 0.2%-proof stress at 900° C. is not raised to a level of SUS444 but higher than Nb-containing ferritic stainless steel by an increase of V and Cu contents. In short, addition of both V and Cu is effective for improvement of high-temperature strength in a hot zone below 900° C. without significant troubles at a temperature higher than 900° C.
- Improvement of high-temperature strength by addition of both V and Cu to Nb-alloyed steel is probably explained as follows: When a metallurgical structure of the inventive stainless steel is observed after heating a short or long while, distribution of fine particles of Nb and Cu compounds is detected. The observation result means that particles of V compounds are preferentially precipitated at the beginning of heating so as to keep Nb and Cu in a dissolved state and that Nb and Cu compounds are finally precipitated as fine particles effective for precipitation-hardening. The precipitates, which are uniformly distributed as fine particles in a steel matrix at the beginning of heating, do not aggregate together during long-term heating, so that precipitation-hardening is maintained effective a long while.
- A ratio of dissolved Nb for improvement of high-temperature strength is also kept at a higher value by presence of V, which converts free C and N to carbonitrides, than V-free steels containing Nb at the same ratio. Increase of dissolved Nb assures that high-temperature strength necessary for the purpose is attained by saved consumption of Nb in comparison with the V-free steels, resulting in improvement of formability and low-temperature toughness.
- Carbonitrides of Nb and V increase in an annealed matrix of the inventive ferritic stainless steel. Increase of the carbonitrides suppresses crystal growth to coarse grains at a weld heat-affected zone, resulting in improvement of toughness. Formation of chromium carbide, which is harmful on intergranular corrosion-resistance, is also suppressed by increase of the carbonitrides.
- Individual effects of alloying elements in the inventive ferritic stainless steel will become apparent from the following explanation.
- C up to 0.03 mass %, N up to 0.03 mass %
- C and N are generally regarded as elements effective for high-temperature strength, e.g. creep strength, but excess C and N unfavorably degrade oxidation-resistance, formability, low-temperature toughness and weldability. In the inventive alloy system, which contains V and Nb for fixation of C and N as carbonitrides, V and Nb are necessarily added at ratios corresponding to concentrations of C and N. Therefore, each of C and N contents is controlled to 0.03 mass % or less (preferably 0.015 mass % or less), in order to avoid increase of V and Nb, which causes a rise of material expense.
- Si up to 1.0 mass %
- Si is an element effective for high-temperature oxidation-resistance, but not so effective on high-temperature strength below 900° C. Excess Si hardens a ferritic stainless steel, resulting in degradation of formability and low-temperature toughness. In this sense, a Si content is determined at 1.0 mass % or less (preferably 0.1-0.5 mass %).
- Mn up to 1.5 mass
- Mn is an alloying element, which improves high-temperature oxidation-resistance, especially scale spalling resistance property, of a ferritic stainless steel, but excess Mn degrades formability and weldability. Excess addition of Mn to a steel containing Cr at a relatively small ratio causes formation of a martensitic phase harmful on thermal fatigue strength and formability, since Mn is an austenite-stabilizing element. Therefore, a Mn content is determined at 1.5 mass % or less (preferably 0.5 mass % or less).
- Ni up to 0.6 mass %
- Ni is an austenite-stabilizing element. Excess addition of Ni to a steel containing Cr at a relatively small ratio promotes formation of a martensitic phase harmful on thermal fatigue strength and formability, as the same as Mn. Excess Ni also raises a steel cost. Therefore, a Ni content is determined at 0.6 mass % or less (preferably 0.5 mass % or less).
- 10-20 mass % of Cr
- Cr is an essential element for stabilization of a ferritic phase and improvement of oxidation-resistance as an important property for high-temperature use. Oxidation-resistance becomes better as increase of a Cr content, but excess Cr causes embrittlement of a stainless steel, resulting in increase of hardness and degradation of formability. In this sense, a Cr content is determined within a range of 10-20 mass %. Cr is preferably controlled to a proper value in response to a temperature on use. For instance, 16-19 mass % of Cr is favorable for oxidation-resistance at a temperature not higher than 950° C., and 12-16 mass % of Cr is favorable for oxidation-resistance at a temperature not higher than 900° C.
- From 8(C+N) to 0.50 mass % of Nb
- Nb fixes C and N as carbonitrides, and also improves high-temperature strength in a state dissolved in a steel matrix. However, excess Nb is unfavorable for formability, low-temperature toughness and to welding hot crack-resistance. Nb not less than 8(C+N) is necessary for fixation of C and N, but an upper limit of Nb is determined at 0.5 mass % in order to maintain proper formability, low-temperature toughness and tensile type hot-cracking resistance. A Nb content is preferably controlled within a range of from 8(C+N)+0.10 to 0.45 mass %.
- 0.8-2.0 mass % of Cu
- Cu is the most important element in the inventive alloy system. Within a temperature range which the inventors have researched and examined, most of Cu is dissolved in an annealed steel matrix and precipitated during heat-treatment. Cu precipitates exhibit the same strengthening effect as Mo at the beginning of heating, but the strengthening effect gradually becomes weaker as the lapse of heating time. At least 0.8 mass % of Cu is necessary in order to gain high-temperature strength suitable for the purpose, as noted in the FIGURE. However, formability, low-temperature toughness and weldability are degraded as increase of a Cu content. The unfavorable effect of Cu on formability, low-temperature toughness and weldability is suppressed by controlling an upper limit of the Cu content at 2.0 mass %. The Cu content is preferably determined within a range of 1.0-1.7 mass %.
- Al up to 0.03 mass %
- Al is added as a deoxidizing element in a steel making process. But, excess Al degrades an external appearance of a stainless steel sheet and also puts harmful effects on formability, low-temperature toughness and weldability. In this sense, an Al content is preferably controlled at a lowest possible level, so that its upper limit is determined at 0.03 mass %.
- 0.03-0.20 mass % of V
- The additive V improves high-temperature strength of a ferritic stainless steel in co-presence of Nb and Cu. Addition of V together with Nb is also effective for formability, low-temperature toughness, intergranular corrosion-resistance and toughness at a weld heat affected-zone. These effects are noted at 0.03 mass % or more of V, but excess V above 0.20 mass % is rather unfavorable for formability and low-temperature toughness. In this sense, a V content is determined within a range of 0.03-0.20 mass % (preferably 0.04-0.15 mass %).
- 0.05-0.30 mass % of Ti
- Ti is an optional element, which raises Lankford value (r) and improves formability of a ferritic stainless steel, and its effect is noted at 0.05 mass % or more of Ti. However, excess Ti promotes formation of TiN harmful on external appearance of a stainless steel and also degrades formability and low-temperature toughness. In this regard, Ti shall be held at a smallest possible ratio, even when Ti is added for improvement of formability. Therefore, an upper limit of a Ti content is determined at 0.30 mass % (preferably 0.20 mass %).
- 0.0005-0.02 mass % of B
- B is another optional element for improving secondary formability of a stainless steel and suppressing cracking during multi-stepped forming. The effect on formability is noted at 0.0005 mass % or more of B, but excess B causes degradation of productivity and weldability. In this sense, a B content is determined within a range of 0.0005-0.02 mass % (preferably 0.001-0.01 mass %).
- 0-0.10 mass % of Mo
- The inventive alloy system is designed on the assumption that expensive Mo is not added as an alloying element, but Mo is likely to be included as an impurity during steel making. Since inclusion of Mo at a relatively high ratio is harmful on formability, low-temperature toughness and weldability, it shall be controlled at a ratio less than 0.10 mass %.
- There are no restrictions on elements other than the above, but ordinary impurities such as P, S and O are preferably controlled at lowest possible levels. Accounting hot-workability, oxidation-resistance and so on, upper limits of P, S and O are preferably determined at 0.04 mass %, 0.03 mass % and 0.02 mass %, respectively. At least one of W, Zr, Y and REM (rare earth metals) may be added for heat-resistance, or at least one of Ca, Mg and Co may be added for hot-workability.
- There are not special restrictions on manufacturing conditions, as far as Cu is dissolved in a steel matrix beforehand in order to gain excellent heat-resistance as an annealed state after hot-rolling. In the case where a ferritic stainless steel can not be hot-rolled to predetermined thickness, a steel sheet bestowed with the same heat-resistance as an annealed hot-rolled steel sheet is manufactured by repetition of cold-rolling and annealing. High-temperature strength is further improved by dispersion of Cu as fine particles at any stage of a manufacturing process. The excellent properties are maintained as such, even after the annealed hot-rolled or cold-rolled steel sheet is formed or welded to a certain profile (involving production of a steel pipe).
- The other features of the present invention will be apparent from the following examples.
- Each ferritic stainless steel with chemical composition shown in Table 1 or 2 was melted in a vacuum furnace and cast to a 30 kg ingot. The ingot was forged, hot-rolled, annealed, cold-rolled to a thickness of 2.0 mm or 1.2 mm, and finish-annealed. Table 1 shows compositions according to the present invention, while Table 2 shows comparative compositions.
- In Table 2, a steel No. 11 corresponds to SUS430J11, a steel No. 15 corresponds to SUH1409L, a steel No. 16 corresponds to a 14Cr—Si—Nb steel, and a steel No. 17 corresponds to SUS444. Any of these steels has been used so far as a material for an exhaust manifold.
-
TABLE 1 Chemical Compositions of Inventive Ferritic Stainless Steels Alloying elements (mass %) No. C Si Mn Ni Cr Nb Ti Mo Cu Al B V N [Nb] 1 0.015 0.31 0.15 0.10 17.09 0.35 — 0.01 0.85 0.01 — 0.10 0.009 0.16 2 0.010 0.28 0.17 0.11 17.13 0.36 — 0.01 1.50 0.01 — 0.11 0.008 0.22 3 0.008 0.32 0.05 0.10 17.02 0.33 — 0.01 1.93 0.01 — 0.10 0.010 0.19 4 0.012 0.33 0.22 0.09 10.71 0.35 — — 1.42 0.01 — 0.12 0.011 0.17 5 0.011 0.39 0.50 0.09 14.01 0.38 — — 1.45 0.01 30 0.12 0.006 0.24 6 0.007 0.21 0.16 0.21 19.52 0.33 — — 1.51 0.01 20 0.11 0.008 0.21 7 0.007 0.81 0.18 0.12 12.03 0.31 0.15 0.04 1.50 0.03 10 0.06 0.006 0.21 8 0.011 0.30 1.21 0.10 17.44 0.36 0.20 0.03 1.53 0.03 50 0.03 0.009 0.20 9 0.011 0.36 0.12 0.11 17.42 0.21 0.11 0.09 1.51 0.02 150 0.04 0.007 0.07 10 0.028 0.33 0.31 0.11 17.40 0.45 0.07 0.02 1.48 0.01 20 0.04 0.021 0.06 The B content is represented by ppm unit. [Nb] is calculated as Nb − 8[C + N]. The mark (—) means a value below detection limit. -
TABLE 2 Chemical Compositions of Comparative Ferritic Stainless Steels Alloying elements (mass %) No. C Si Mn Ni Cr Nb Ti Mo Cu Al B V N [Nb] 11 0.008 0.30 0.28 0.14 17.00 0.37 — 0.02 0.60 0.03 — — 0.011 0.22 12 0.010 0.36 0.28 0.17 16.99 0.38 — 0.01 4.08 0.01 — 0.04 0.012 0.20 13 0.008 1.38 0.26 0.17 17.06 0.41 0.01 0.01 1.48 — — — 0.013 0.24 14 0.009 0.35 0.32 0.31 17.24 0.74 — 0.01 2.48 0.02 — 0.01 0.013 0.56 15 0.020 0.42 0.39 0.10 12.16 0.01 0.23 0.02 — 0.02 — — 0.014 −0.26 16 0.011 1.10 0.98 0.10 14.75 0.50 — 0.01 0.03 — — — 0.012 0.31 17 0.012 0.40 0.70 0.22 18.28 0.50 — 1.94 0.24 0.01 20 0.04 0.011 032 18 0.011 0.82 0.25 0.11 17.42 0.45 0.01 0.02 1.69 0.34 20 0.01 0.021 0.19 19 0.012 0.31 0.29 0.11 19.55 0.20 0.01 — 0.82 — — 0.02 0.008 0.04 The B content is represented by ppm unit. [Nb] is calculated as Nb − 8[C + N] The mark (—) means a value below detection limit. The underlined figures are out of the ranges defined by the present invention. - Each annealed cold-rolled steel sheet of 2.0 mm in thickness was examined by a high-temperature tensile test, a high-temperature oxidation test, a room-temperature tensile test and Charpy impact test. Each annealed cold-rolled steel sheet of 1.2 mm in thickness was examined by a tensile type hot-cracking test.
- In the high-temperature tensile test, a test piece was stretched at 800° C. under conditions regulated in J1S G0567, so as to measure its 0.2%-proof stress.
- In the high-temperature oxidation test, a test piece was heated at each temperature of 850° C., 900° C., 950° C., 1000° C. and 1100° C. for 200 hours under conditions regulated in JIS Z2281. The heated test piece was observed by naked eyes to detect occurrence of abnormal oxidation (i.e. growth of knobby thick oxide through a steel sheet). A critical temperature, at which the test piece was heated without abnormal oxidation, was determined from the observation results.
- In the room-temperature tensile test, each annealed cold-rolled steel sheet of 2.0 mm in thickness was shaped to a test piece No. 13B and stretched under conditions regulated in JIS Z2241 to measure its elongation after fracture.
- In Charpy impact test, an impact was applied to a sub-sized test piece of 2.0 mm in thickness at each temperature of −75° C., −50° C., −25° C., 0° C. and 25° C. under conditions of ITS Z2242, to detect a ductile-brittle transition temperature.
- In the tensile type hot-cracking test, a test piece of 40 mm in length and 20 mm in width was clamped at its both ends and TIG-welded under the condition that a tensile stress was applied to the test piece along its longitudinal direction, so as to detect a minimum strain at which the test piece began to crack. Tensile type hot-cracking resistance was evaluated by the critical strain detected in this way. Test results are shown in Table 3.
- It is noted from Table 3 that any of the inventive steels Nos. 1-10 has 0.2%-proof stress at 800° C., fairly higher than the Nb, Si-alloyed steel No. 16 and similar or superior to the Nb, Mo-alloyed steel No. 17. Values of elongation by the room-temperature tensile test, a ductile-brittle transition temperature by Charpy impact test and a critical strain by the tensile type hot-cracking test were also similar or superior to the Nb, Mo-alloyed steel No. 17. These results prove that objective performance is attained without necessity of Mo as an alloying element. When results of the steels Nos. 4, 5 and 12 are compared with each other, it is understood that a critical temperature for occurrence of abnormal oxidation becomes lower as decrease of a Cr content. Due to the effect of Cr on abnormal oxidation, the Cr content shall be determined at a proper value in response to a temperature at which a steel member or part will be exposed.
- The comparative steels Nos. 11, 15, 16 and 19, which lacked of V and Cu, had formability, low-temperature toughness and weldability at levels required for the purpose but poor high-temperature strength at 800° C. The comparative steel No. 12, which contained excess Cu, was good of high-temperature strength but inferior in formability and weldability to the Nb, Mo-alloyed steel No. 17, so that it was hardly formed or welded to a product shape.
- The comparative steel No. 13, which contained Cu within a range defined by the present invention but excess Si, and the comparative steel No. 14, which contained excess Nb, were good of high-temperature strength but inferior in formability, low-temperature toughness and weldability to the inventive steels Nos. 1-10.
- The comparative steel No. 18, which contained less V and excess Al, had the same heat-resistance and formability as the inventive steels Nos. 1-10 but poor low-temperature toughness, which led to occurrence of troubles during manufacturing or on use. The comparative steel No. 19 was poor of high-temperature strength due to shortage of V.
- The Mo-containing comparative steel No. 17 had the same properties as the inventive steels Nos. 1-10, but its low-temperature toughness was relatively inferior. A cost of the steel No. 17 is inevitably higher than the inventive steels Nos. 1-10, due to consumption of Mo at approximately 2 mass %.
-
TABLE 3 Evaluation of Test Results 0.2%-proof stress A critical temperature (° C.) Elongation after A transition A critical No. at 800° C. (N/mm2) of abnormal oxidation fracture (%) temperature (° C.) strain 1 35 1000 34 −50 ◯ Inventive 2 45 1000 32 −50 ◯ Examples 3 47 1000 31 −50 ◯ 4 43 850 34 −50 ◯ 5 44 900 33 −50 ◯ 6 44 1000 32 −50 ◯ 7 45 950 32 −50 ◯ 8 43 1000 34 −50 ◯ 9 36 1000 35 −50 ◯ 10 35 1000 32 −50 ◯ 11 24 1000 34 −50 ◯ Comparative 12 50 950 29 −25 X Examples 13 45 1100 28 0 X 14 47 1000 30 0 X 15 18 850 37 −75 ◯ 16 25 950 35 −50 ◯ 17 35 1000 32 −25 ◯ 18 40 1000 31 0 ◯ 19 30 1000 32 −25 ◯ A critical strain of 3% or more is evaluated as the mark ◯, and less than 3% is evaluated as the mark X. The underlined figures do not meet with objective property. - According to the present invention as the above, a ferritic stainless steel is improved in formability, low-temperature toughness and weldability without degradation of heat-resistant by specified alloying design, especially control of V and Cu contents, without necessity of expensive Mo. The newly proposed stainless steel is useful as members or parts for automotive engines or conduit members, e.g. exhaust manifolds, front pipes, center pipes, outer casings of catalytic converters for emission of exhaust gas.
Claims (8)
1. A ferritic stainless steel for use as a conduit member for emission of automotive exhaust gas, consisting essentially of C up to 0.03 mass %, Si up to 1.0 mass %, Mn up to 1.5 mass %, Ni up to 0.6 mass %, 10-20 mass % of Cr, 0.50 mass % or less of Nb, 0.8-2.0 mass % of Cu, Al up to 0.03 mass %, 0.03-0.20 mass % of V, N up to 0.03 mass % and the balance being Fe except inevitable impurities with a provision of Nb≧8(C+N).
2. The ferritic stainless steel defined by claim 1 , wherein Mo as an inevitable impurity is controlled to be less than 0.10 mass %.
3. The ferritic stainless steel defined by claim 1 , which further contains 0.05-3.0 mass % of Ti.
4. The ferritic stainless steel defined by claim 1 , which further contains 0.0005-0.02 mass % of B.
5. The ferritic stainless steel defined by claim 2 , which further contains 0.05-3.0 mass % of Ti.
6. The ferritic stainless steel defined by claim 2 , which further contains 0.0005-0.02 mass % of B.
7. The ferritic stainless steel defined by claim 3 , which further contains 0.0005-0.02 mass % of B.
8. The ferritic stainless steel defined by claim 5 , which further contains 0.0005-0.02 mass % of B.
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US13/632,418 US20130263979A1 (en) | 2001-07-05 | 2012-10-01 | Ferritic Stainless Steel for Use as Conduit Members for Emission of Automotive Exhaust Gas |
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PCT/JP2002/006768 WO2003004714A1 (en) | 2001-07-05 | 2002-07-04 | Ferritic stainless steel for member of exhaust gas flow passage |
US12/233,122 US20090053093A1 (en) | 2001-07-05 | 2008-11-06 | Ferritic Stainless Steel for Use as Conduit Members For Emission of Automotive Exhaust Gas |
US12/689,824 US20100119404A1 (en) | 2001-07-05 | 2010-01-19 | Ferritic Stainless Steel for Use as Conduit Members For Emission of Automotive Exhaust Gas |
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JP2696584B2 (en) * | 1990-03-24 | 1998-01-14 | 日新製鋼株式会社 | Ferrite heat-resistant stainless steel with excellent low-temperature toughness, weldability and heat resistance |
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JP3536567B2 (en) * | 1997-01-24 | 2004-06-14 | Jfeスチール株式会社 | Ferritic stainless steel for engine exhaust components with excellent heat resistance, workability and muffler corrosion resistance |
-
2002
- 2002-07-04 EP EP02743819A patent/EP1413640B1/en not_active Expired - Lifetime
- 2002-07-04 CN CNB02813138XA patent/CN1225566C/en not_active Expired - Lifetime
- 2002-07-04 DE DE60204323T patent/DE60204323T2/en not_active Expired - Lifetime
- 2002-07-04 US US10/482,718 patent/US20040170518A1/en not_active Abandoned
- 2002-07-04 JP JP2003510470A patent/JP4197492B2/en not_active Expired - Lifetime
- 2002-07-04 KR KR10-2004-7000076A patent/KR20040007764A/en not_active Application Discontinuation
- 2002-07-04 WO PCT/JP2002/006768 patent/WO2003004714A1/en active IP Right Grant
- 2002-07-04 ES ES02743819T patent/ES2240764T3/en not_active Expired - Lifetime
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2008
- 2008-08-18 JP JP2008209904A patent/JP5138504B2/en not_active Expired - Lifetime
- 2008-11-06 US US12/233,122 patent/US20090053093A1/en not_active Abandoned
-
2010
- 2010-01-19 US US12/689,824 patent/US20100119404A1/en not_active Abandoned
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US10030282B2 (en) | 2012-02-15 | 2018-07-24 | Nippon Steel & Sumikin Stainless Steel Corporation | Ferrite-based stainless steel plate having excellent resistance against scale peeling, and method for manufacturing same |
US9885099B2 (en) | 2012-03-09 | 2018-02-06 | Nippon Steel & Sumikin Stainless Steel Corporation | Ferritic stainless steel sheet |
US11384405B2 (en) | 2012-11-20 | 2022-07-12 | Outokumpu Oyj | Ferritic stainless steel |
US10385429B2 (en) | 2013-03-27 | 2019-08-20 | Nippon Steel & Sumikin Stainless Steel Corporation | Hot-rolled ferritic stainless-steel plate, process for producing same, and steel strip |
Also Published As
Publication number | Publication date |
---|---|
DE60204323D1 (en) | 2005-06-30 |
JP5138504B2 (en) | 2013-02-06 |
KR20040007764A (en) | 2004-01-24 |
EP1413640B1 (en) | 2005-05-25 |
DE60204323T2 (en) | 2006-01-26 |
CN1524130A (en) | 2004-08-25 |
JP2008297631A (en) | 2008-12-11 |
EP1413640A1 (en) | 2004-04-28 |
US20040170518A1 (en) | 2004-09-02 |
JPWO2003004714A1 (en) | 2004-10-28 |
CN1225566C (en) | 2005-11-02 |
EP1413640A4 (en) | 2004-12-15 |
US20090053093A1 (en) | 2009-02-26 |
JP4197492B2 (en) | 2008-12-17 |
ES2240764T3 (en) | 2005-10-16 |
US20100119404A1 (en) | 2010-05-13 |
WO2003004714A1 (en) | 2003-01-16 |
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