EP0597129A1 - Fe-cr-legierung mit hervorragender beabeitbarheit - Google Patents

Fe-cr-legierung mit hervorragender beabeitbarheit Download PDF

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Publication number
EP0597129A1
EP0597129A1 EP93911960A EP93911960A EP0597129A1 EP 0597129 A1 EP0597129 A1 EP 0597129A1 EP 93911960 A EP93911960 A EP 93911960A EP 93911960 A EP93911960 A EP 93911960A EP 0597129 A1 EP0597129 A1 EP 0597129A1
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alloy
content
weight
meets
member selected
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French (fr)
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EP0597129A4 (en
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Mitsuyuki Kawasaki Steel Corporation Fujisawa
Yasushi Kawasaki Steel Corporation Katoh
Yoshihiro Kawasaki Steel Corporation Yazawa
Satoshi Kawasaki Steel Corporation Ohwada
Keiichi Kawasaki Steel Corporation Yoshioka
Fusao Kawasaki Steel Corporation Togashi
Susumu Kawasaki Steel Corporation Satoh
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JFE Steel Corp
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Kawasaki Steel Corp
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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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium

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  • the present invention relates to an Fe-Cr alloy having a significantly improved workability.
  • the present invention also relates to an Fe-Cr alloy having an improved workability as well as an excellent acid resistance.
  • the present invention relates to an Fe-Cr alloy having an improved workability as well as an excellent oxidation resistance.
  • the present invention relates to an Fe-Cr alloy having an improved workability as well as excellent acid resistance and oxidation resistance.
  • Fe-Cr alloys are generally known to be materials of excellent corrosion resistance. Various improvements in the corrosion resistance, workability, and other physical properties have been proposed for such Fe-Cr alloys including the following proposals.
  • Japanese Patent Publication No. 63-58904 proposes a ferritic stainless steel having a Cr content of from 11.0 to 16.0% by weight, wherein Ti is added to a predetermined amount. This material has excellent bulging properties as well as secondary workability.
  • Japanese Patent Publication No. 64-6264 proposes a bright annealed stainless steel plate having a Cr content of from 8.0 to 35.0% by weight, wherein Si, Mn and Nb are respectively added to a predetermined amount. This material has an excellent rust resistance.
  • Japanese Patent Publication No. 2-1902 proposes an Fe-Cr alloy having a Cr content of more than 20.0% by weight and up to 25% by weight, wherein Mo, Mn and Nb are respectively added to a predetermined amount.
  • This material is a ferritic stainless steel having an excellent high-temperature cracking resistance upon welding as well as weld toughness.
  • Japanese Patent Application Kokai No. 61-186451 proposes an Fe-Cr alloy having a Cr content of from 25 to 50% by weight, wherein Si, Mn and Mo are respectively added to a predetermined amount.
  • This material is an alloy having an excellent acid resistance.
  • Japanese Patent Application Kokai No. 62-267450 proposes an Fe-Cr based alloy having a Cr content of from 16 to 19% by weight wherein Mo is added to a predetermined amount.
  • This material is a high-purity ferritic stainless steel having an excellent intergranular corrosion resistance.
  • Japanese Patent Application Kokai No. 1-287253 proposes an Fe-Cr-AI alloy having a Cr content of 15 to 26% by weight and an AI content of from 4 to 6% by weight, wherein a rare earth element is added to a predetermined amount.
  • This material is an AI-containing ferritic stainless steel having an excellent oxidation resistance as well as production feasibility.
  • Japanese Patent Application Kokai No. 2-232344 proposes an Fe-Cr based alloy having a Cr content of from 25.0 to 30.0% by weight, wherein Mo is added to a predetermined amount.
  • This material is a ferritic stainless steel having an excellent resistance to adhesion of organisms as well as a high resistance to sea water corrosion.
  • Japanese Patent Application Kokai No. 3-2355 proposes an Fe-Cr alloy having a Cr content of from 16.0 to 25.0% by weight, wherein Nb is added to a predetermined amount determined in relation to the total content of C and N.
  • This material is a ferritic stainless steel having excellent cold workability, toughness and corrosion resistance.
  • the Fe-Cr alloys as described above contain a relatively large amount of Cr since corrosion resistance was of prime importance in these alloys. As a result, these alloys occasionally suffered from poor ductility, and hence, insufficient workability. When such materials are used in such application as automobile exterior material or a building exterior material wherein the material should be press-worked, they suffer from such problems as cracking upon working, or an extreme difficulty in working due to strict working conditions. As set forth above, there is a strong demand for an improvement of such materials in their workability.
  • an object of the present invention is to provide an Fe-Cr alloy which has an improved workability as well as sufficient acid resistance and oxidation resistance.
  • the inventors of the present invention have made an extensive study and surprisingly found that an Fe-Cr alloy wherein the contents of impurities including C, N, O, P and S, which had been present in conventional Fe-Cr alloys, are reduced to an extremely low level would have a markedly superior ductility.
  • the present invention is based on such a finding.
  • a novel Fe-Cr alloy having an excellent workability characterized in that the alloy comprises 3 to 60% by weight of Cr; and 100 ppm or less in total content of C, N, O, P and S; the balance being Fe and inevitable impurities.
  • an Fe-Cr alloy having excellent workability and acid resistance characterized in that the alloy comprises 5 to 60% by weight of Cr; 100 ppm or less in total content of C, N, O, P and S; and at least one member selected from Ni, Co and Cu at a content that meets the following relation (1): the balance being Fe and inevitable impurities.
  • an Fe-Cr alloy having excellent workability and oxidation resistance characterized in that the alloy comprises 3 to 60% by weight of Cr; 100 ppm or less in total content of C, N, O, P and S; and at least one member selected from Si, Mn and AI at a content that meets the following relation (2): and/or at least one member selected from Ca, Mg and rare earth metals (REM) at a content that meets the following relation (3): the balance being Fe and inevitable impurities.
  • the alloy comprises 3 to 60% by weight of Cr; 100 ppm or less in total content of C, N, O, P and S; and at least one member selected from Si, Mn and AI at a content that meets the following relation (2): and/or at least one member selected from Ca, Mg and rare earth metals (REM) at a content that meets the following relation (3): the balance being Fe and inevitable impurities.
  • an Fe-Cr alloy having excellent workability, acid resistance, and oxidation resistance characterized in that the alloy comprises 5 to 60% by weight of Cr; 100 ppm or less in total content of C, N, O, P and S; at least one member selected from Ni, Co and Cu at a content that meets the following relation (1): and at least one member selected from Si, Mn and AI at a content that meets the following relation (2): and/or at least one member selected from Ca, Mg and rare earth metals (REM) at a content that meets the following relation (3): the balance being Fe and inevitable impurities.
  • the alloy comprises 5 to 60% by weight of Cr; 100 ppm or less in total content of C, N, O, P and S; at least one member selected from Ni, Co and Cu at a content that meets the following relation (1): and at least one member selected from Si, Mn and AI at a content that meets the following relation (2): and/or at least one member selected from Ca, Mg and rare earth metals (REM) at a content that meets the following relation (3): the
  • the Fe-Cr alloys as described above contain a relatively large amount of Cr since corrosion resistance is of prime importance in these alloys. As a result, these alloys may occasionally suffer from poor ductility, and hence, insufficient workability to render working of the alloy material into the shape required by the specific application difficult, or in some cases, impossible. For example, when such materials are worked into a pipe and used in pipeworking after bending, the pipe often undergo such troubles as breaking upon bending. As set forth above, there is a strong demand for an improvement of such materials in their workability.
  • an object of the present invention is to provide an Fe-Cr alloy which has an improved workability as well as an excellent high-temperature strength.
  • Another object of the present invention is to provide an Fe-Cr alloy which has sufficient acid resistance and/or oxidation resistance in addition to the improved workability and high-temperature resistance.
  • the inventors of the present invention have made an extensive study and surprisingly found that an Fe-Cr alloy wherein the contents of impurities including C, N, O, P and S, which had been present in conventional Fe-Cr alloys, are reduced to an extremely low level would have a markedly superior ductility. Furthermore, the inventors of the present invention found that high-temperature strength of the resulting product may be significantly improved by adding a predetermined amount of at least one member selected from Ti, Nb, Zr, V, Ta, W and B to the above-mentioned Fe-Cr alloy of a reduced impurity content. The present invention has been achieved on the basis of such findings.
  • an Fe-Cr alloy having excellent workability and high-temperature strength characterized in that the alloy comprises 3 to 60% by weight of Cr; 100 ppm or less in total content of C, N, O, P and S; and at least one member selected from Ti, Nb, Zr, V, Ta, W and B at a content that meets the following relation (1): the balance being Fe and inevitable impurities.
  • an Fe-Cr alloy having excellent workability, high-temperature strength, and acid resistance characterized in that the alloy comprises 5 to 60% by weight of Cr; 100 ppm or less in total content of C, N, O, P and S; at least one member selected from Ti, Nb, Zr, V, Ta, W and B at a content that meets the following relation (1): and at least one member selected from Ni, Co and Cu at a content that meets the following relation (2): the balance being Fe and inevitable impurities.
  • an Fe-Cr alloy having excellent workability, high-temperature strength, and oxidation resistance characterized in that the alloy comprises 3 to 60% by weight of Cr; 100 ppm or less in total content of C, N, O, P and S; at least one member selected from Ti, Nb, Zr, V, Ta, W and B at a content that meets the following relation (1): and at least one member selected from Al, Si and Mn at a content that meets the following relation (3): and/or at least one member selected from Ca, Mg and rare earth metals (REM) at a content that meets the following relation (4): the balance being Fe and inevitable impurities.
  • the alloy comprises 3 to 60% by weight of Cr; 100 ppm or less in total content of C, N, O, P and S; at least one member selected from Ti, Nb, Zr, V, Ta, W and B at a content that meets the following relation (1): and at least one member selected from Al, Si and Mn at a content that meets the following relation (3): and/or at least one member selected from
  • an Fe-Cr alloy having excellent workability, high-temperature strength, acid resistance, and oxidation resistance characterized in that the alloy comprises 5 to 60% by weight of Cr; 100 ppm or less in total content of C, N, O, P and S; at least one member selected from Ti, Nb, Zr, V, Ta, W and B at a content that meets the following relation (1): at least one member selected from Ni, Co and Cu at a content that meets the following relation (2): and at least one member selected from Al, Si and Mn at a content that meets the following relation (3): and/or at least one member selected from Ca, Mg and rare earth metals (REM) at a content that meets the following relation (4): the balance being Fe and inevitable impurities.
  • the alloy comprises 5 to 60% by weight of Cr; 100 ppm or less in total content of C, N, O, P and S; at least one member selected from Ti, Nb, Zr, V, Ta, W and B at a content that meets the following relation (1): at least one member selected from Ni,
  • the Fe-Cr alloys as described above contain a relatively large amount of Cr since corrosion resistance is of prime importance in these alloys. As a result, these alloys occasionally suffer from poor ductility, and hence, insufficient workability. When such materials are used in such application as automobile exterior material or a building exterior material wherein the material is required to have a sufficient workability, they may suffer from such problems as cracking upon working, or an extreme difficulty in working due to strict working conditions. As set forth above, there is, a strong demand for an improvement of such materials in their workability.
  • main object of the present invention is to provide an Fe-Cr alloy which has an improved workability as well as a sufficient pitting resistance.
  • Another object of the present invention is to provide an Fe-Cr alloy which has an improved acid resistance in addition to the above-mentioned improved properties.
  • a further object of the present invention is to provide an Fe-Cr alloy which has an improved oxidation resistance in addition to the improved workability and acid resistance.
  • an Fe-Cr alloy wherein the contents of impurities including C, N, O, P and S, which had been present in conventional Fe-Cr alloys, are reduced to an extremely low level would have a markedly superior ductility in addition to a sufficient corrosion resistance.
  • pitting resistance of the resulting product may be significantly improved by adding a predetermined amount of Mo to the above-mentioned Fe-Cr alloy of a reduced impurity content, and that acid resistance of the resulting product may be significantly improved by further addition of at least one member selected from Ni, Co and Cu in a predetermined amount.
  • oxidation resistance of the resulting product may be significantly improved by further addition of a predetermined amount of at least one member selected from Al, Si and Mn and/or a predetermined amount of at least one member selected from Ca, Mg and REM.
  • the present invention has been completed on the basis of such finding.
  • an Fe-Cr alloy having excellent workability and pitting resistance characterized in that the alloy comprises 5 to 60% by weight of Cr; 100 ppm or less in total content of C, N, O, P and S; and 0.5 to 20% by weight of Mo; the balance being Fe and inevitable impurities.
  • an Fe-Cr alloy having excellent workability, pitting resistance, and acid resistance characterized in that the alloy comprises 5 to 60% by weight of Cr; 100 ppm or less in total content of C, N, O, P and S; 0.5 to 20% by weight of Mo; and at least one member selected from Ni, Cu and Co at a content that meets the following relation (1): the balance being Fe and inevitable impurities.
  • an Fe-Cr alloy having excellent workability, pitting resistance, and oxidation resistance characterized in that the alloy comprises 5 to 60% by weight of Cr; 100 ppm or less in total content of C, N, O, P and S; 0.5 to 20% by weight of Mo; and at least one member selected from Al, Si and Mn at a content that meets the following relation (2): and/or at least one member selected from Ca, Mg and rare earth metals (REM) at a content that meets the following relation (3): the balance being Fe and inevitable impurities.
  • the alloy comprises 5 to 60% by weight of Cr; 100 ppm or less in total content of C, N, O, P and S; 0.5 to 20% by weight of Mo; and at least one member selected from Al, Si and Mn at a content that meets the following relation (2): and/or at least one member selected from Ca, Mg and rare earth metals (REM) at a content that meets the following relation (3): the balance being Fe and inevitable impurities.
  • an Fe-Cr alloy having excellent workability, pitting resistance, acid resistance, and oxidation resistance characterized in that the alloy comprises 5 to 60% by weight of Cr; 100 ppm or less in total content of C, N, O, P and S; 0.5 to 20% by weight of Mo; at least one member selected from Ni, Cu and Co at a content that meets the following relation (1): and at least one member selected from Al, Si and Mn at a content that meets the following relation (2): and/or at least one member selected from Ca, Mg and rare earth metals (REM) at a content that meets the following relation (3): the balance being Fe and inevitable impurities.
  • the alloy comprises 5 to 60% by weight of Cr; 100 ppm or less in total content of C, N, O, P and S; 0.5 to 20% by weight of Mo; at least one member selected from Ni, Cu and Co at a content that meets the following relation (1): and at least one member selected from Al, Si and Mn at a content that meets the following relation (2): and/or at least one member selected from Ca,
  • the Fe-Cr alloys as described above contain a relatively large amount of Cr since corrosion resistance is of prime importance in these alloys. As a result, these alloys may occasionally suffer from poor ductility, and hence, insufficient workability. When such materials are used in such application as a basin compartment of a home kitchen sink, a building exterior material or an automobile exterior material wherein the material is required to have a sufficient workability, they may suffer from such problems as cracking upon working, or an extreme difficulty in working when strict working conditions are required. As set forth above, there is a strong demand for an improvement of such materials in their workability.
  • first object of the present invention is to provide an Fe-Cr alloy which has an improved workability as well as sufficient pitting resistance and weld-zone corrosion resistance.
  • Second object of the present invention is to provide an Fe-Cr alloy which has an improved acid resistance and/or oxidation resistance in addition to the above-mentioned improved properties.
  • an Fe-Cr alloy wherein the contents of impurities including C, N, O, P and S, which had been present in conventional Fe-Cr alloys, are reduced to an extremely low level would have a markedly superior ductility in addition to a sufficient corrosion resistance.
  • pitting resistance of the resulting product may be significantly improved by adding a predetermined amount of Mo to the above-mentioned Fe-Cr alloy of a reduced impurity content, and that weld zone-corrosion resistance (intergranular corrosion resistance) may be significantly improved by further addition of at least one member selected from Ti, Nb, Zr, V, Ta, W and B in a predetermined amount.
  • the inventors of the present invention found that acid resistance of the resulting product may be significantly improved by further addition of at least one member selected from Ni, Co and Cu in a predetermined amount.
  • the inventors of the present invention also found that oxidation resistance of the resulting product may be significantly improved by further addition of a predetermined amount of at least one member selected from Si, Mn and AI and/or a predetermined amount of at least one member selected from Ca, Mg and REM.
  • the present invention is based on such a series of findings.
  • an Fe-Cr alloy having excellent workability, pitting resistance, and weld corrosion resistance characterized in that the alloy comprises 5 to 60% by weight of Cr; 100 ppm or less in total content of C, N, O, P and S; 0.5 to 20% by weight of Mo; and at least one member selected from Ti, Nb, Zr, V, Ta, W and B at a content that meets the following relation (1): the balance being Fe and inevitable impurities.
  • an Fe-Cr alloy having excellent workability, pitting resistance, weld corrosion resistance, and acid resistance characterized in that the alloy comprises 5 to 60% by weight of Cr; 100 ppm or less in total content of C, N, O, P and S; 0.5 to 20% by weight of Mo; at least one member selected from Ti, Nb, Zr, V, Ta, W and B at a content that meets the following relation (1 ): and at least one member selected from Ni, Cu and Co at a content that meets the following relation (2): the balance being Fe and inevitable impurities.
  • an Fe-Cr alloy having excellent workability, pitting resistance, weld corrosion resistance, and oxidation resistance characterized in that the alloy comprises 5 to 60% by weight of Cr; 100 ppm or less in total content of C, N, O, P and S; 0.5 to 20% by weight of Mo; at least one member selected from Ti, Nb, Zr, V, Ta, W and B at a content that meets the following relation (1): and at least one member selected from Si, Mn and AI at a content that meets the following relation (3): and/or at least one member selected from Ca, Mg and rare earth metals (REM) at a content that meets the following relation (4): the balance being Fe and inevitable impurities.
  • the alloy comprises 5 to 60% by weight of Cr; 100 ppm or less in total content of C, N, O, P and S; 0.5 to 20% by weight of Mo; at least one member selected from Ti, Nb, Zr, V, Ta, W and B at a content that meets the following relation (1): and at least one member selected from Si, Mn
  • an Fe-Cr alloy having excellent workability, pitting resistance, weld corrosion resistance, and oxidation resistance characterized in that the alloy comprises 5 to 60% by weight of Cr; 100 ppm or less in total content of C, N, O, P and S; 0.5 to 20% by weight of Mo; at least one member selected from Ti, Nb, Zr, V, Ta, W and B at a content that meets the following relation (1): at least one member selected from Ni, Cu and Co at a content that meets the following relation (2): and at least one member selected from Si, Mn and AI at a content that meets the following relation (3): and/or at least one member selected from Ca, Mg and rare earth metals (REM) at a content that meets the following relation (4): the balance being Fe and inevitable impurities.
  • the alloy comprises 5 to 60% by weight of Cr; 100 ppm or less in total content of C, N, O, P and S; 0.5 to 20% by weight of Mo; at least one member selected from Ti, Nb, Zr, V, Ta, W and B
  • the present invention comprises four categories of inventions as described below. Description will be given in accordance with the order of the categories. The description is also given in accordance with the order of the categories in the sections of "Summary of the invention", “Examples”, and “Industrial Utility”.
  • FIG. 1 diagrammatically shows increase in elongation and decrease in proof stress (yield strength) evaluated by tensile test (JIS Z-2241) in relation to the total content of C, N, O, P and S for a series of annealed cold rolled Fe-18% Cr alloy plates.
  • JIS Z-2241 tensile test
  • the Fe-Cr alloy of the present invention contains C, N, O, P and S in a total content of 100 ppm or less.
  • the alloy plate has a significantly improved ductility, and hence, workability when the total content of C, N, O, P and S is 100 ppm or less.
  • the alloy plate will have a reduced ductility, and hence, a reduced workability as the total content of C, N, O, P and S exceeds 100 ppm.
  • the Fe-Cr alloy of the present invention has a Cr content of from 3 to 60% by weight, and preferably, from 5 to 30% by weight.
  • the Cr content of less than 3% by weight will result in a poor corrosion resistance, while the Cr content in excess of 60% by weight will result in an insufficient workability even when the content of C, N, O, P and S is reduced.
  • an Fe-Cr alloy having a total content of C, N, O, P and S of up to 100 ppm and a Cr content of from 3 to 60% by weight would have a significantly improved workability as well as a sufficient corrosion resistance.
  • the alloy of the present invention may also have such an additional element as Al, Mo, Nb, B, Si, Mn, Cu, Ni, Co, or Ca added thereto.
  • a high-purity electrolytic iron and a high-purity electrolytic chromium may be employed as the starting materials.
  • the optionally added element is also added in its high purity form.
  • the primary impurity is oxygen regardless of the type of the starting material, and therefore, in the production of the Fe-Cr alloy of the present invention, melting and casting are carried out under an ultra-high vacuum of 10- 7 torr or less.
  • the alloy of the present invention will exert its merits whether the product is an annealed hot rolled plate or an annealed cold rolled plate, and in addition, whether the surface finishing of the annealed cold rolled plate is BA, 2B, 2D, HL or ground finish.
  • FIG. 2 diagrammatically shows corrosion rate in relation to the total content of C, N, O, P and S for a series of alloy plates comprising Fe - 36% Cr - 3.2% Co. As apparent from FIG. 2, the alloy plate would exhibit a significantly low degree of corrosion when the total content of C, N, O, P and S is 100 ppm or less.
  • FIG. 3 diagrammatically shows corrosion rate in relation to Cr content for two series of alloy plates comprising Fe - Cr - 1.6% Ni - 1.4% Co respectively having a total content of C, N, O, P and S of 100 ppm or less and in excess of 100 ppm.
  • the corrosion rate is significantly low in the alloys having the total content of C, N, O, P and S of 100 ppm or less compared to the alloys having the total content of C, N, O, P and S in excess of 100 ppm, and such difference in the corrosion resistance is even more significant when the Cr content is 5% by weight or more.
  • FIG. 4 diagrammatically shows corrosion rate in relation to (Ni + Co + 2Cu) for a series of alloy plates comprising Fe - 38% Cr having the total content of C, N, O, P and S of 62 ppm. As apparent from FIG. 4, the corrosion rate would rapidly decrease when the (Ni + Co + 2Cu) value reaches 0.01 % by weight.
  • Cr content is limited to the range of from 5 to 60% by weight, and preferably, from 10 to 40% by weight. As described above, the alloy having the Cr content within such a range would exhibit a sufficient acid resistance. Addition of an excessive amount of the Cr would result in poor workability. In addition, such an excessive addition of the Cr would not contribute to further improvement in the acid resistance.
  • C, N, O, P and S These elements are contained in total content of 100 ppm or less, and preferably in the total content of 85 ppm or less. As described above, the alloy plate would exhibit an improved acid resistance as well as an excellent workability when the total content of C, N, O, P and S is 100 ppm or less and other conditions are also satisfied.
  • the alloy of the present invention contains at least one member selected from these elements in an amount that meets the following relation: and preferably, in an amount that meets the following relation:
  • a content of Ni, Co and Cu less than the above-defined range would result in an insufficient corrosion resistance, and a content in excess of the above-defined range would result in a reduced production efficiency of the alloy.
  • the Fe-Cr alloys satisfying the above-described conditions would have a significantly improved corrosion resistance in addition to an excellent workability.
  • an ultra high-purity electrolytic iron, an electrolytic Cr, an electrolytic Ni, an electrolytic Cu, an electrolytic Co, an iodide-processed Ti, an electrolytically reduced Nb, a molten salt electrolytic Zr, a reduced V, an electrolytic Ta, an electrolytically reduced W, and a high purity ferroboron may be employed for the starting materials.
  • the primary impurity is oxygen regardless of the type of the component, and therefore, melting and casting may be carried out under an ultra-high vacuum of 10- 5 torr or less, and preferably, 10- 7 torr or less for the production of the Fe-Cr alloy of the present invention.
  • FIG. 5 diagrammatically shows abnormally oxidized area in a continuous oxidation test in relation to the total content of C, N, O, P and S for a series of alloys comprising Fe - 24% Cr - 0.01 % REM (Y: 0.05%; La: 0.03%; Ce: 0.02%).
  • the abnormally oxidized area would be very small when the total content of C, N, O, P and S is 100 ppm or less.
  • FIG. 6 diagrammatically shows weight increase in an oxidation test in relation to Cr content for a series of Fe-Cr-AI alloys. As apparent from FIG. 6, the weight increase in the oxidation would significantly decrease when the Cr content is 3.0% by weight or more when the total content of C, N, O, P and S is 100 ppm or less.
  • FIG. 7 diagrammatically shows abnormally oxidized area in a continuous oxidation test in relation to the value of (3AI + 2Si + Mn) for a series of Fe - 28% Cr alloys having the total content of C, N, O, P and S of 51 ppm.
  • the abnormally oxidized area would significantly decrease when the (3AI + 2Si + Mn) value is 0.1 % by weight or more.
  • FIG. 8 diagrammatically shows percentage of the area of the oxide film that was peeled in a repeated- heating test in relation to the value of (4Ca + 4Mg + REM) for a series of Fe - 26% Cr alloys having the total content of C, N, O, P and S of 72 ppm.
  • the oxide film-peeled area would significantly decrease when the (4Ca + 4Mg + REM) value is 0.001 % by weight or less.
  • the composition of the alloy according to this invention and aspects of the invention are described below.
  • the Fe-Cr alloy of the present invention having an improved workability as well as an excellent oxidation resistance has three aspects as described below.
  • Cr content is limited to the range of from 3 to 60% by weight, and preferably, from 10 to 40% by weight. When the Cr content is within such a range and other conditions are also satisfied, the resulting alloy would have a sufficient oxidation resistance. Addition of the Cr in excess of such an amount is likely to induce a decrease in workability, and would not contribute to further improvement in the oxidation resistance.
  • C, N, O, P and S are contained in total content of 100 ppm or less, and preferably, 85 ppm or less. Abnormal oxidation is avoided when such conditions are satisfied. Such conditions in association with other conditions would result in an alloy having an improved oxidation resistance as well as an excellent ductility, and hence, high workability.
  • the alloy of the first aspect of the invention contains at least one such metal in an amount that meets the following relation (2): and preferably, in an amount that meets the following relation (2a): When the content is within such a range and other conditions are also satisfied, the resulting alloy would have a significantly improved oxidation resistance. These elements should not be contained in an excess amount since the elements contained such that the (3AI + 2Si + Mn) value is in excess of the range of relation (2) would render the alloy production difficult.
  • the elements are respectively contained in the amounts as described below for the reasons as noted below.
  • An Fe-Cr alloy which meets the above-described conditions would have an improved oxidation resistance as well as excellent workability, and therefore, such an alloy may be adequately used for producing various components in automobile exhaust gas system or various pipes used under the conditions of repeated high temperature oxidation.
  • the alloy according to the second aspect of the invention comprises at least one member selected from Ca, Mg and rare earth metals (REM) in an amount that meets the following relation (3): and preferably, in an amount that meets the following relation (3a):
  • REM rare earth metals
  • the resulting alloy would have a sufficient oxidation resistance as well as an excellent workability.
  • These elements are significantly effective in improving the protectability of the oxide film formed on the surface of the alloy according to the second aspect of the invention, and hence, in suppressing the abnormal oxidation which is likely to take place in an extremely thin material.
  • the elements also improve adhesion of the oxide film to the underlying material.
  • Ca, Mg and the rare earth metal are respectively contained in the amounts as described below for the reasons as noted below.
  • Rare earth metal 0.005 to 0.1 % by weight
  • the alloy according to the second aspect of the invention may be used for applications similar to those of the alloy according to the first aspect of the invention.
  • the alloy according to the third aspect of the invention comprises an alloy which meets the conditions for both the alloys according to the first and the second aspects of the invention, namely, an alloy having a Cr content of from 3 to 60% by weight; a total content of C, N, O, P and S of up to 100 ppm; a content of at least one member selected from Si, Mn and AI in the range that meets the above-mentioned relation (2); and a content of at least one member selected from Ca, Mg, and rare earth metals (REM) in the range that meets the above-mentioned relation (3).
  • Such an alloy has an excellent workability as well as an oxidation resistance even superior to that of the alloy according to the first or the second aspect of the invention, and therefore, may be appropriately used for any of the above-mentioned applications.
  • an ultra high-purity electrolytic iron, an electrolytic chromium, a zone melting-processed silicon, a molten salt-electrolytic manganese, a molten salt-electrolytic aluminum, a molten salt-electrolytic calcium, an electrolytically reduced magnesium, and an electrolytically reduced rare earth metal may be employed as the starting materials.
  • the primary impurity is oxygen regardless of the type of the starting material, and therefore, melting and casting are carried out under an ultra-high vacuum of 10- 5 torr or less for the production of the Fe-Cr alloy of the present invention.
  • the alloy of this invention comprises the alloy of particularly excellent acid resistance described in the above (II) having added thereto the components of the alloy of particularly improved oxidation resistance described in the above (III).
  • the alloy of this invention is hereinafter described merely for its composition, and detailed description for each alloy component is omitted since it is the same as the one given in (II) and (III).
  • this invention comprises three aspects.
  • the content of C + N + 0 + S + P is up to 100 ppm, and the Cr content is from 5 to 60% by weight in all three aspects of the invention.
  • the components which may vary are described below for each aspect.
  • the alloy contains at least one member selected from Ni, Co and Cu in an amount that meets the following relation (1): and preferably, in an amount that meets the following relation:
  • the alloy also contains at least one member selected from Si, Mn and AI in an amount that meets the following relation (2): and preferably, in an amount that meets the following relation:
  • the alloy contains at least one member selected from Ni, Co and Cu in an amount that meets the following relation (1): and preferably, in an amount that meets the following relation:
  • the alloy also contains at least one member selected from Ca, Mg and rare earth metals (REM) in an amount that meets the following relation (3): and preferably, in an amount that meets the following relation:
  • REM rare earth metals
  • the alloy contains at least one member selected from Ni, Co and Cu in an amount that meets the following relation (1): and preferably, in an amount that meets the following relation:
  • the alloy also contains at least one member selected from Si, Mn and AI in an amount that meets the following relation (2): and preferably, in an amount that meets the following relation:
  • the alloy also contains at least one member selected from Ca, Mg and rare earth metals (REM) in an amount that meets the following relation (3): and preferably, in an amount that meets the following relation:
  • REM rare earth metals
  • the process for producing the alloy of this invention is the same as the above-described processes, and therefore, detailed description of the production process is omitted.
  • FIG. 9 diagrammatically shows results of tensile test at room temperature in relation to the total content of C, N, O, P and S for a series of Fe-18% Cr alloy plates by using the results for a conventional alloy plate having a total content of C, N, O, P and S of about 500 ppm as a reference.
  • the alloy plate would exhibit a significantly increased elongation as well as a significantly decreased yield strength to indicate a markedly improved ductility when the total content of C, N, O, P and S is 100 ppm or less, as compared to the conventional alloy.
  • increase in elongation (%) and decrease in proof stress (yield strength) indicate difference in respective tensile properties from the alloy having the
  • the tensile properties used for such calculation are:
  • FIG. 10 diagrammatically shows increase in high temperature proof stress (at 900 °C) in relation to the value of (Ti + Nb + Zr + V + Ta + W + 50B).
  • the high temperature strength would increase by 0.1 N/mm 2 and the alloy material would have a significantly improved high temperature strength when the above-defined value reaches 0.01 % by weight.
  • composition of the alloy according to this invention is hereinafter described in detail.
  • Cr content is limited to the range of from 3 to 60% by weight, and preferably, from 5 to 45% by weight. When the Cr content is within such a range and other conditions are satisfied, the resulting alloy plate would have a sufficient oxidation resistance. Addition of the Cr in excess of 60% by weight is undesirable in view of an increased cost.
  • C, N, O, P and S are contained in a total content of 100 ppm or less, and preferably, 85 ppm or less.
  • the resulting alloy would have an improved ductility, and hence, workability, and the resulting alloy would also have an improved oxidation resistance when the Cr content is within the above-defined range.
  • the content is in excess of 100 ppm, the resulting alloy would not have such improved properties.
  • the alloy of the present invention contains at least one element selected from Ti, Nb, Zr, V, Ta, W and B in an amount that meets the following relation (1): and preferably, in an amount that meets the following relation (1 a):
  • the alloy of the present invention containing such elements in an amount within the above-defined range has a significantly improved high temperature strength.
  • an addition of such elements in excess of the range defined by (1) may lead to an increased brittleness although the high temperature strength would be maintained at the sufficient level.
  • the Ti, Nb, Zr, V, Ta, W and B may respectively have the following contents:
  • An alloy which meets the above-described conditions would have an improved workability as well as a sufficient high temperature strength, and therefore, would be adequate for such applications as an automobile exhaust gas pipe, wherein the alloy material made into a pipe should be subsequently bent.
  • the primary impurity is oxygen regardless of the type of the starting material, and therefore, melting and casting may be carried out under such an ultra-high vacuum as 10- 5 torr or less for the production of the Fe-Cr alloy of the present invention.
  • FIG. 9 diagrammatically shows results of tensile test at room temperature in relation to the total content of C, N, O, P and S for a series of Fe-18% Cr alloy plates by using the results for a conventional alloy plate having a total content of C, N, O, P and S of about 500 ppm as a reference.
  • the alloy plate would exhibit a significantly increased elongation as well as a significantly decreased yield strength to indicate a markedly improved ductility when the total content of C, N, O, P and S is 100 ppm or less, as compared to the conventional alloy.
  • FIG. 10 diagrammatically shows increase in high temperature proof stress (at 900 °C) in relation to the value of (Ti + Nb + Zr + V + Ta + W + 50B).
  • the high temperature proof stress would increase by 0.1 N/mm 2 and the alloy material would have a significantly improved high temperature strength when the above-defined value reaches 0.01 % by weight.
  • FIG. 11 diagrammatically shows corrosion rate in relation to the total content of C, N, O, P and S for a series of alloy plates comprising Fe - 36% Cr - 3.2% Co. As apparent from FIG. 11, the alloy plate would exhibit a significantly low degree of corrosion when the total content of C, N, O, P and S is 100 ppm or less.
  • FIG. 12 diagrammatically shows corrosion rate in relation to Cr content for two series of alloy plates comprising Fe - Cr - 1.6% Ni - 1.4% Co respectively having a total content of C, N, O, P and S of 100 ppm or less and in excess of 100 ppm.
  • the corrosion rate is significantly low in the alloys having the total content of C, N, O, P and S of 100 ppm or less compared to the alloys having the total content of C, N, O, P and S in excess of 100 ppm, and such difference in the corrosion resistance is even more significant when the Cr content is 5% by weight or more.
  • FIG. 13 diagrammatically shows corrosion rate in relation to (Ni + Co + 2Cu) for a series of alloy plates comprising Fe - 38% Cr having the total content of C, N, O, P and S of 62 ppm. As apparent from FIG. 13, the corrosion rate would rapidly decrease when the (Ni + Co + 2Cu) value reaches 0.01% by weight.
  • FIG. 14 diagrammatically shows corrosion rate in relation to the value of (Ti + Nb + Zr + Ta + V + W + 20B) (in % by weight) for a series of alloy plates comprising Fe - 46% Cr - 3.0% Co - 1.2% Cu having a total content of C, N, O, P and S of 64 ppm or less. As apparent from FIG. 14, corrosion rate would be significantly reduced when the above-defined value reaches 0.01%.
  • composition of the alloy according to this invention is hereinafter described in detail.
  • Cr content is limited to the range of from 5 to 60% by weight, and preferably, from 10 to 40% by weight. As described above, the alloy having the Cr content within such a range would exhibit a sufficient acid resistance. Addition of an excessive amount of the Cr would result in poor workability. In addition, such an excessive addition of the Cr would not contribute to further improvement in the acid resistance.
  • C, N, O, P and S These elements are contained in total content of 100 ppm or less, and preferably in the total content of 85 ppm or less. As described above, the alloy plate would exhibit an improved acid resistance as well as an excellent workability when the total content of C, N, O, P and S is 100 ppm or less and other conditions are also satisfied.
  • the alloy of the present invention contains at least one element selected from Ti, Nb, Zr, V, Ta, W and B in an amount that meets the following relation (1): and preferably, in an amount that meets the following relation (1 a):
  • the alloy of the present invention containing such elements in an amount within the above-defined range has a significantly improved high temperature strength.
  • an addition of such elements in excess of the range defined by (1) may lead to an increased brittleness although the high temperature strength would be maintained at the sufficient level.
  • the Ti, Nb, Zr, V, Ta, W and B may respectively have the following contents:
  • the alloy of the present invention contain at least one member selected from these elements in an amount that meets the following relation: and preferably, in an amount that meets the following relation:
  • a content of Ni, Co and Cu less than the above-defined range would result in an insufficient corrosion resistance, and a content in excess of the above-defined range would result in a reduced production efficiency of the alloy.
  • the Fe-Cr alloys satisfying the above-described conditions would have a significantly improved corrosion resistance in addition to an excellent workability.
  • an ultra high-purity electrolytic iron, an electrolytic Cr, an electrolytic Ni, an electrolytic Cu, an electrolytic Co, an iodide-processed Ti, an electrolytically reduced Nb, a molten salt electrolytic Zr, a reduced V, an electrolytic Ta, an electrolytically reduced W, and a high purity ferroboron may be employed for the starting materials.
  • the primary impurity is oxygen regardless of the type of the component, and therefore, melting and casting may be carried out under an ultra-high vacuum of 10- 5 torr or less, and preferably, 10- 7 torr or less for the production of the Fe-Cr alloy of the present invention.
  • FIG. 9 diagrammatically shows results of tensile test at room temperature in relation to the total content of C, N, O, P and S for a series of Fe-18% Cr alloy plates by using the results for a conventional alloy plate having a total content of C, N, O, P and S of about 500 ppm as a reference.
  • the alloy plate would exhibit a significantly increased elongation as well as a significantly decreased yield strength to indicate a markedly improved ductility when the total content of C, N, O, P and S is 100 ppm or less, as compared to the conventional alloy.
  • FIG. 10 diagrammatically shows increase in high temperature proof stress (at 900 °C) in relation to the value of (Ti + Nb + Zr + V + Ta + W + 50B).
  • the high temperature proof stress would increase by 0.1 N/mm 2 and the alloy material would have a significantly improved high temperature strength when the above-defined value reaches 0.01 % by weight.
  • FIG. 15 diagrammatically shows results of oxidation resistance test (weight loss upon scale removal after exposure to air at 1,350 K for 12 hours) for two series of Fe-Cr alloy plates respectively having a total content of C, N, O, P and S of 100 ppm or less and 100 ppm or more.
  • the alloy containing 3% or more of Cr would have an oxidation resistance equivalent to that of the the conventional steel having a Cr content of 12% or more to reveal effectiveness of the increased purity on the decrease in the Cr content, and hence, resources saving.
  • FIG. 16 diagrammatically shows results of oxidation resistance test (weight loss upon scale removal after exposure to air at 1,350 K for 12 hours) for a series of Fe-(15-30)% Cr alloy plates. As apparent from FIG. 16, the alloy containing 0.1% or more of (3AI + 2Si + Mn) would have an improved oxidation resistance.
  • FIG. 17 diagrammatically shows results of oxidation resistance test (weight loss upon scale removal after exposure to air at 1,350 K for 12 hours) for a series of Fe-(15-30)% Cr alloy plates. As apparent from FIG. 17, the alloy containing 0.001% or more of (4Ca + 4Mg + REM) would have an improved oxidation resistance.
  • the composition of the alloy according to this invention and aspects of the invention are described below.
  • the Fe-Cr alloy of the present invention having an improved workability as well as excellent high temperature strength and oxidation resistance has three aspects as described below.
  • Cr content is limited to the range of from 3 to 60% by weight, and preferably, from 5 to 45% by weight. When the Cr content is within such a range and other conditions are satisfied, the resulting alloy plate would have a sufficient oxidation resistance. Addition of the Cr in excess of 60% by weight is undesirable in view of an increased cost.
  • C, N, O, P and S These elements are contained in a total content of 100 ppm or less, and preferably, 85 ppm or less.
  • the resulting alloy would have an improved ductility, and hence, workability, and the resulting alloy would also have an improved oxidation resistance when the Cr content is within the above-defined range.
  • the content is in excess of 100 ppm, the resulting alloy would not have such improved properties.
  • the alloy of the present invention contains at least one element selected from Ti, Nb, Zr, V, Ta, W and B in an amount that meets the following relation (1): and preferably, in an amount that meets the following relation (1 a):
  • the alloy containing such elements in an amount within the above-defined range has a significantly improved high temperature strength.
  • an addition of such elements in excess of the range defined by (1) may lead to an increased brittleness although the high temperature strength would be maintained at the sufficient level.
  • the Ti, Nb, Zr, V, Ta, W and B may respectively have the following contents:
  • the alloy of the present invention contains at least one element selected from Al, Si and Mn in an amount that meets the following relation (3): and preferably, in an amount that meets the following relation (3a): Inclusion in the alloy of such elements at a content within the above-defined range would result in an improved oxidation resistance of the resulting alloy. However, when these elements are added to such a content that (3AI + 2Si + Mn) exceeds 50% by weight, the resulting alloy would have an insufficient workability, and therefore, such an excessive inclusion is not preferred.
  • Al, Si and Mn are respectively contained in the amounts as described below.
  • the Cr content the content of C, N, O, P and S, and the preferable content of Ti, Nb, Zr, V, Ta, W and B, what has been described for the first aspect of the invention is applicable for the second aspect of the invention.
  • the alloy according to the second aspect of the invention comprises at least one member selected from Ca, Mg and rare earth metals (REM) as described below.
  • REM rare earth metals
  • Ca, Mg, and REM These elements are not critical for the alloy of the present invention. However, oxidation resistance of the alloy may be improved by including these elements in an amount that meets the following relation (4): An excessive inclusion of these elements to an amount such that the (4Ca + 4Mg + REM) value is in excess of 0.2% by weight is undesirable since such an addition is likely to result in surface defects of the resulting alloy.
  • Ca, Mg and the rare earth metal are respectively contained in the amounts as described below.
  • An alloy which meets the above-described conditions would have an improved workability as well as sufficient high temperature strength and oxidation resistance, and therefore, would be adequate for such applications as an automobile exhaust gas pipe, wherein the alloy material made into a pipe should be subsequently bent.
  • an ultra high-purity electrolytic iron and an electrolytic Cr are employed for the starting materials.
  • the primary impurity is oxygen regardless of the type of the starting material, and therefore, melting and casting may be carried out under such an ultra-high vacuum as 10- 7 torr or less for the production of the Fe-Cr alloy of the present invention.
  • the alloy according to the third aspect of the invention comprises an alloy which meets the conditions for both the alloys according to the first and the second aspects of the invention, namely, an alloy having a Cr content of from 3 to 60% by weight; a total content of C, N, O, P and S of up to 100 ppm; a content of at least one member selected from Ti, Nb, Zr, V, Ta, W and B in in the range that meets the above-mentioned relation (1); a content of at least one member selected from Si, Mn and AI in the range that meets the above-mentioned relation (3); and a content of at least one member selected from Ca, Mg, and rare earth metals (REM) in the range that meets the above-mentioned relation (4).
  • Such an alloy has an excellent workability as well as an oxidation resistance even superior to those of the alloy according to the first or the second aspect of the invention, and therefore, may be appropriately used for any of the above-mentioned applications.
  • an ultra high-purity electrolytic iron, an electrolytic chromium, a zone melting-processed silicon, a molten salt-electrolytic manganese, a molten salt-electrolytic aluminum, a molten salt-electrolytic calcium, an electrolytically reduced magnesium, and an electrolytically reduced rare earth metal may be employed as the starting materials.
  • the primary impurity is oxygen regardless of the type of the starting material, and therefore, melting and casting are carried out under an ultra-high vacuum of 10- 5 torr or less for the production of the Fe-Cr alloy of the present invention.
  • the alloy of this invention comprises the alloy of particularly excellent acid resistance described in the above (II) having added thereto the components of the alloy of particularly improved oxidation resistance described in the above (III).
  • the alloy of this invention is hereinafter described merely for its composition, and detailed description for each alloy component is omitted since it is the same as the one given in (II) and (III).
  • this invention comprises three aspects.
  • the content of C + N + 0 + P is up to 100 ppm; the Cr content is from 5 to 60% by weight; and the content of Ti + Nb + Zr + V + Ta + W + 50B is 0.01 % to 6 % in all three aspects of the invention.
  • the components which may vary are described below for each aspect.
  • the alloy contains at least one member selected from Ni, Co and Cu in an amount that meets the following relation (2):
  • the alloy also contains at least one member selected from Si, Mn and AI in an amount that meets the following relation (3):
  • the alloy contains at least one member selected from Ni, Co and Cu in an amount that meets the following relation (2):
  • the alloy also contains at least one member selected from Ca, Mg and rare earth metals (REM) in an amount that meets the following relation (4):
  • the alloy contains at least one member selected from Ni, Co and Cu in an amount that meets the following relation (2):
  • the alloy also contains at least one member selected from Si, Mn and AI in an amount that meets the following relation (3):
  • the alloy also contains at least one member selected from Ca, Mg and rare earth metals (REM) in an amount that meets the following relation (4):
  • the process for producing the alloy of this invention is the same as the above-described processes, and therefore, detailed description of the production process is omitted.
  • FIG. 18 diagrammatically shows increase in elongation and decrease in yield strength evaluated by tensile tests in accordance with JIS Z-2241 in relation to the total content of C, N, O, P and S for a series of annealed cold rolled Fe-18% Cr alloy plates.
  • the alloy would become soft when the total content of C, N, O, P and S is 100 ppm or less as evidenced by a significantly superior ductility and a significantly lower yield strength.
  • FIG. 19 diagrammatically shows pitting potential (measured in accordance with JIS G 0577) in relation to Mo content for a series of annealed cold rolled Fe - 16% Cr alloy plates having the total content of C, N, O, P and S of 100 ppm or less.
  • the pitting potential would significantly increase when the Mo content is 0.5% by weight or more to result in an improved pitting resistance.
  • composition of the alloy according to the present invention is hereinafter described.
  • Cr content is limited to the range of from 5 to 60% by weight, and preferably, from 10 to 40% by weight. When the Cr content is within such a range, the resulting alloy plate would have a sufficient corrosion resistance. Addition of the Cr in excess of such an amount lacks economic rationality since such an excessive addition would not contribute to further improvement in the corrosion resistance. Furthermore, addition of an excessive amount of Cr is undesirable since a decrease in workability is likely to be induced by solid-solution strengthening of the Cr itself even when (C + N + 0 + P + S) is limited to up to 100 ppm.
  • C, N, O, P and S These elements are contained in total content of 100 ppm or less. As described above, the alloy plate would have a significantly improved ductility, and hence, improved workability when the total content of C, N, O, P and S is 100 ppm or less.
  • Mo content is limited to the range of from 0.5 to 20% by weight, and preferably, from 0.5 to 5% by weight. Mo added to an amount of 0.5% by weight or more will result in an improved pitting resistance. An excessive addition of Mo is undesirable from economic point of view.
  • FIG. 20 diagrammatically shows corrosion rate in 0.3 % by weight aqueous HCI solution in relation to (Ni + Co + 2Cu) in % by weight for a series of annealed cold rolled Fe - 16% Cr alloy plates having a total content of C, N, O, P and S of 100 ppm or less.
  • the corrosion rate would significantly decrease when the (Ni + Co + 2Cu) value is 0.01% by weight or more to result in an improved acid resistance.
  • the alloy according to the aspect (II) of the invention further comprises at least one member selected from Ni, Cu and Co in an amount that meets the following relation (1): and preferably, in an amount that meets the following relation (1 a): Such an alloy would have an excellent acid resistance in addition to the above-described properties.
  • Ni, Co and Cu in excess of the amount represented by the relation (1) is undesirable since such an excessive addition of the Ni, Co and Cu, which are austenite stabilization elements, is inconvenient for formation of single-phase ferritic structure.
  • An alloy according to the aspect (II) of the invention which meets the above-described conditions would have an improved workability as well as sufficient pitting resistance and acid resistance.
  • a high-purity electrolytic iron, an electrolytic Cr, a metallic Mo, an electrolytic Ni, an electrolytic Cu, and a metallic Co may be employed as the starting materials.
  • the primary impurity is oxygen regardless of the type of the starting material, and therefore, melting and casting are carried out under an ultra-high vacuum of 10- 7 torr or less for the production of the Fe-Cr alloy of the present invention.
  • the alloy of the present invention will fully exert its merits whether the product is an annealed hot rolled plate or an annealed cold rolled plate, and in addition, whether the final surface finishing is BA, 2B, 2D, HL or ground finish.
  • FIG. 21 diagrammatically shows results of oxidation resistance test (weight loss upon scale removal after exposure to air at 1,350 K for 12 hours) for a series of Fe-(15-30)% Cr alloy plates. As apparent from FIG. 21, the alloy containing 0.1% or more of (3AI + 2Si + Mn) would have an improved oxidation resistance.
  • FIG. 22 diagrammatically shows results of oxidation resistance test (weight loss upon scale removal after exposure to air at 1,350 K for 12 hours) for a series of Fe-(15-30)% Cr alloy plates. As apparent from FIG. 22, the alloy containing 0.001% or more of (4Ca + 4Mg + REM) would have an improved oxidation resistance.
  • the composition of the alloy according to this invention and aspects of the invention are described below.
  • the Fe-Cr alloy of the present invention having an improved workability as well as excellent pitting resistance and oxidation resistance has three aspects as described below.
  • Cr content is limited to the range of from 5 to 60% by weight, and preferably, from 5 to 45% by weight. When the Cr content is within such a range and other conditions are satisfied, the resulting alloy plate would have a sufficient oxidation resistance. Addition of the Cr in excess of 60% by weight is undesirable in view of an increased cost.
  • C, N, O, P and S These elements are contained in a total content of 100 ppm or less, and preferably, 85 ppm or less.
  • the resulting alloy would have an improved ductility, and hence, workability, and the resulting alloy would also have an improved oxidation resistance when the Cr content is within the above-defined range.
  • the total content is in excess of 100 ppm, the resulting alloy would not have such improved properties.
  • the alloy of the present invention contains Mo in an amount of from 0.5 to 20% by weight, and preferably, in an amount of from 0.5 to 5% by weight.
  • the alloy of the present invention containing Mo in an amount within such a range has a significantly improved pitting resistance.
  • inclusion of the Mo in excess of 20% by weight may lead to an increased cost, and therefore, such an excessive inclusion is not preferable.
  • the alloy of the present invention contains at least one element selected from Al, Si and Mn in an amount that meets the following relation (2): and preferably, in an amount that meets the following relation (2a): Inclusion in the alloy of such elements at a content within the above-defined range would result in an improved oxidation resistance of the resulting alloy. However, when these elements are added to such a content that (3AI + 2Si + Mn) exceeds 50% by weight, the resulting alloy would have an insufficient workability, and therefore, such an excessive inclusion is not preferred.
  • Al, Si and/or Mn are respectively contained in the amounts as described below.
  • the alloy according to this aspect of the invention contains at least one member selected from Ca, Mg and REM.
  • Oxidation resistance of the alloy may be improved by including these elements in an amount that meets the following relation (3):
  • Ca, Mg and the rare earth metal are respectively contained in the amounts as described below.
  • an ultra high-purity electrolytic iron and an electrolytic Cr are employed as the starting materials.
  • the primary impurity is oxygen regardless of the type of the starting material, and therefore, melting and casting may be carried out under such an ultra-high vacuum as 10- 7 torr or less for the production of the Fe-Cr alloy of the present invention.
  • the alloy according to the third aspect of the invention comprises an alloy which meets the conditions for both the alloys according to the first and the second aspects of the invention, namely, an alloy having a Cr content of from 5 to 60% by weight; a total content of C, N, O, P and S of up to 100 ppm; a Mo content of from 0.5 to 20% by weight; a content of at least one member selected from Si, Mn and AI in the range that meets the above-mentioned relation (2); and a content of at least one member selected from Ca, Mg, and rare earth metals (REM) in the range that meets the above-mentioned relation (3).
  • Such an alloy has an excellent workability as well as an oxidation resistance even superior to those of the alloy according to the first or the second aspect of the invention, and therefore, may be appropriately used for any of the above-mentioned applications.
  • an ultra high-purity electrolytic iron, an electrolytic chromium, a zone melting-processed silicon, a molten salt-electrolytic manganese, a molten salt-electrolytic aluminum, a molten salt-electrolytic calcium, an electrolytically reduced magnesium, and an electrolytically reduced rare earth metal may be employed as the starting materials.
  • the primary impurity is oxygen regardless of the type of the starting material, and therefore, melting and casting are carried out under an ultra-high vacuum of 10- 5 torr or less for the production of the Fe-Cr alloy of the present invention.
  • the alloy of this invention comprises the alloy of particularly excellent acid resistance described in the above (II) having added thereto the components of the alloy of particularly improved oxidation resistance described in the above (III).
  • the alloy of this invention is hereinafter described merely for its composition, and detailed description for each alloy component is omitted since it is the same as the one given in (II) and (III).
  • this invention comprises three aspects.
  • the content of C + N + 0 + P is up to 100 ppm; the Cr content is from 5 to 60% by weight; the Mo content is from 0.5 to 20% by weight; and the content of Ni + Co + 2Cu is from 0.01% to 6% in all three aspects of the invention.
  • the components which may vary are described below for each aspect.
  • the alloy contains at least one member selected from Ni, Co and Cu in an amount that meets the following relation (1):
  • the alloy also contains at least one member selected from Si, Mn and AI in an amount that meets the following relation (2):
  • the alloy contains at least one member selected from Ni, Co and Cu in an amount that meets the following relation (1):
  • the alloy also contains at least one member selected from Ca, Mg and rare earth metals (REM) in an amount that meets the following relation (3):
  • the alloy contains at least one member selected from Ni, Co and Cu in an amount that meets the following relation (1
  • the alloy also contains at least one member selected from Si, Mn and AI in an amount that meets the following relation (2):
  • the alloy also contains at least one member selected from Ca, Mg and rare earth metals (REM) in an amount that meets the following relation (3):
  • the process for producing the alloy of this invention is the same as the above-described processes, and therefore, detailed description of the production process is omitted.
  • FIG. 23 diagrammatically shows results of tensile test at room temperature in relation to the total content of C, N, O, P and S for a series of Fe-18% Cr alloy plates by using the results for a conventional alloy plate having a total content of C, N, O, P and S of about 500 ppm as a reference.
  • the alloy plate would exhibit a significantly increased elongation as well as a significantly decreased yield strength to indicate a markedly improved ductility when the total content of C, N, O, P and S is 100 ppm or less, as compared to the conventional alloy.
  • test samples had been prepared and evaluated as described below.
  • Test sample The test plate was prepared by melting and casting the starting materials in a 10 kg vacuum melting furnace, hot rolling the molten material into a plate of 4 mm thick, recrystallization-annealing and descaling the hot-rolled plate, cold rolling the plate to a thickness of 0.8 mm, and subjecting the cold rolled plate to recrystallization-annealing.
  • test samples were evaluated by a tensile test according to JIS Z-2241.
  • the test samples of L, X and C directions were prepared, and the elongation was calculated by (L + C + 2 x X) / 4.
  • the tensile properties used for such calculation are:
  • FIG. 24 diagrammatically shows pitting potential in relation to Mo content for a series of annealed cold rolled Fe-16% Cr alloy plates having a total content of C, N, O, P and S of 100 ppm or less. As apparent from FIG. 24, the pitting potential would rapidly increase when the Mo content reaches 0.5% by weight to result in an improved pitting resistance.
  • test samples had been prepared and evaluated as described below.
  • Test sample The test plate was prepared by melting and casting the starting materials in a 10 kg vacuum melting furnace, hot rolling the molten material into a plate of 4 mm thick, recrystallization-annealing and descaling the hot-rolled plate, cold rolling the plate to a thickness of 0.8 mm, subjecting the cold rolled plate to recrystallization-annealing, and grinding the surface with Emery #800.
  • FIG. 25 diagrammatically shows the results of a test for intergranular corrosion of TIG weld zone in relation to the value of (Ti + Nb + Zr + V + Ta + W + 50 x B) (in % by weight) for a series of annealed cold rolled Fe-20% Cr alloy plates having a total content of C, N, O, P and S of 100 ppm or less.
  • weld zone-corrosion resistance (intergranular corrosion resistance) would be significantly improved when the above-defined value reaches 0.01%.
  • test samples had been prepared and evaluated as described below.
  • Test sample The test plate was prepared by melting and casting the starting materials in a 10 kg vacuum melting furnace, hot rolling the molten material into a plate of 4 mm thick, recrystallization-annealing and descaling the hot-rolled plate, cold rolling the plate to a thickness of 0.8 mm, subjecting the cold rolled plate to recrystallization-annealing, and grinding the surface with Emery #500.
  • the thus prepared plate was subjected to TIG welding (bead on) to prepare the test sample.
  • FIG. 26 diagrammatically shows corrosion rate in 5 % by weight aqueous HCI solution in relation to (Ni + Co + 2Cu) in % by weight for a series of Fe-(24-25)% Cr alloy plates having the total content of C, N, O, P and S of 100 ppm or less.
  • the corrosion rate would rapidly decrease when the (Ni + Co + 2Cu) value reaches 0.01 % by weight to result in an improved acid resistance.
  • test samples had been prepared and evaluated as described below.
  • Test sample The test plate was prepared by melting and casting the starting materials in a 10 kg vacuum melting furnace, hot rolling the molten material into a plate of 4 mm thick, recrystallization-annealing and descaling the hot-rolled plate, cold rolling the plate to a thickness of 0.8 mm, subjecting the cold rolled plate to recrystallization-annealing, and grinding the surface with Emery #500.
  • composition of the alloy according to this invention is hereinafter described in detail.
  • Cr content is limited to the range of from 5 to 60% by weight, and preferably, from 10 to 35% by weight. When the Cr content is within such a range, the resulting alloy plate would have a sufficient corrosion resistance. Addition of the Cr in excess of such an amount lacks economic rationality since such an excessive addition would not contribute to further improvement in the corrosion resistance. Furthermore, addition of an excessive amount of Cr is undesirable since a decrease in workability is likely to be induced.
  • C, N, O, P and S These elements are contained in total content of 100 ppm or less. As described above, the alloy plate would have a significantly improved ductility, and hence, improved workability when the total content of C, N, O, P and S is 100 ppm or less.
  • Mo content is limited to the range of from 0.5 to 20% by weight, and preferably, from 1 to 10% by weight. Mo added to an amount of 0.5% by weight or more will result in an improved pitting resistance, while an excessive addition of Mo is undesirable from economic point of view.
  • the alloy of the present invention contains at least one element selected from Ti, Nb, Zr, V, Ta, W and B in an amount that meets the following relation (1): and preferably, in an amount that meets the following relation (1 a):
  • the alloy of the present invention containing such elements in an amount within the range defined by such a relation has a significantly improved weld zone-corrosion resistance (intergranular corrosion resistance).
  • an excessive addition of such elements is undesirable since a decrease in workability is likely to be induced by solid-solution strengthening of such elements themselves.
  • the Ti, Nb, Zr, V, Ta, W and B may respectively have the following contents:
  • An Fe-Cr alloy which meets the above-described conditions would have a significantly improved workability as well as sufficient pitting resistance and weld zone-corrosion resistance (intergranular corrosion resistance), and therefore, would be adequate for a variety of applications including can body of a water heater and automobile muffler.
  • An alloy comprising at least one member selected from Ni, Cu and Co in an amount that meets the following relation (2): and preferably, in an amount that meets the following relation (2a): in additions to the alloy components described in the above (I) would have an excellent acid resistance in addition to the above-described properties.
  • Ni, Co and Cu in excess of the amount represented by the relation (2) is undesirable since such an excessive addition of the Ni, Co and Cu, which are austenite stabilization elements, would necessitate an addition of Cr and Mo in an increased amount for formation of a single-phase ferritic structure as required in the present invention.
  • An alloy which meets the conditions described in (I) or (II) would have an improved workability as well as sufficient pitting resistance, weld zone-corrosion resistance (intergranular corrosion resistance) and acid resistance, and therefore, would be adequate for a variety of applications including automobile muffler, can body of a water heater, and chemical plant materials.
  • a high-purity electrolytic iron, an electrolytic Cr, a metallic Mo, a metallic Ti, a metallic Nb, a metallic Zr, a metallic V, a metallic Ta, a metallic W, a high purity (Fe-B), an electrolytic Ni, an electrolytic Cu, and a metallic Co may be employed for the starting materials.
  • the primary impurity is oxygen regardless of the type of the starting material, and therefore, melting and casting are carried out under an ultra-high vacuum of 10- 7 torr or less for the production of the Fe-Cr alloy of the present invention.
  • FIG. 27 diagrammatically shows results of oxidation resistance test (weight loss upon scale removal after exposure to air at 1,350 K for 12 hours) for a series of Fe-(15-30)% Cr alloy plates having a total content of C, N, O, P and S of up to 100 ppm.
  • the alloy containing 0.1 % or more of (3AI + 2Si + Mn) would have an improved oxidation resistance.
  • FIG. 28 diagrammatically shows results of oxidation resistance test (weight loss upon scale removal after exposure to air at 1,350 K for 12 hours) for a series of Fe-(15-30)% Cr alloy plates having a total content of C, N, O, P and S of up to 100 ppm.
  • the alloy containing 0.001% or more of (4Ca + 4Mg + REM) would have an improved oxidation resistance.
  • the composition of the alloy according to this invention and aspects of the invention are described below.
  • the Fe-Cr alloy of the present invention having an improved workability as well as an excellent oxidation resistance has three aspects as described below.
  • Cr content is limited to the range of from 5 to 60% by weight, and preferably, from 10 to 40% by weight. When the Cr content is within such a range and other conditions are also satisfied, the resulting alloy would have a sufficient oxidation resistance. Addition of the Cr in excess of such an amount is likely to induce a decrease in workability, and would not contribute to further improvement in the oxidation resistance.
  • C, N, O, P and S are contained in total content of 100 ppm or less, and preferably, 85 ppm or less. Abnormal oxidation is avoided when such conditions are satisfied. Such conditions in association with other conditions would result in an alloy having an improved oxidation resistance as well as an excellent ductility, and hence, high workability.
  • Mo content is limited to the range of from 0.5 to 20% by weight, and preferably, from 1 to 10% by weight. Mo added to an amount of 0.5% by weight or more will result in an improved pitting resistance, while an excessive addition of Mo is undesirable from economic point of view.
  • the alloy of the present invention contains at least one element selected from Ti, Nb, Zr, V, Ta, W and B in an amount that meets the following relation (1): and preferably, in an amount that meets the following relation (1 a):
  • the alloy of the present invention containing such elements in an amount within the range defined by such a relation has a significantly improved weld zone-corrosion resistance (intergranular corrosion resistance).
  • an excessive addition of such elements is undesirable since a decrease in workability is likely to be induced by solid-solution strengthening of such elements themselves.
  • An Fe-Cr alloy which meets the above-described conditions would have a significantly improved workability as well as sufficient pitting resistance and weld zone-corrosion resistance (intergranular corrosion resistance), and therefore, would be adequate for a variety of applications including can body of a water heater and automobile muffler.
  • the alloy of the first aspect of the invention contains at least one such metal in an amount that meets the following relation (3): and preferably, in an amount that meets the following relation (3a): When the content is within such a range and other conditions are also satisfied, the resulting alloy would have a significantly improved oxidation resistance. These elements should not be contained in an excess amount since the elements contained such that the (3AI + 2Si + Mn) value is in excess of the range of relation (3) would render the alloy production difficult.
  • the elements are respectively contained in the amounts as described below for the reasons as noted below.
  • An Fe-Cr alloy which meets the above-described conditions would have an improved oxidation resistance as well as excellent workability, and therefore, such an alloy may be adequately used for producing various components in automobile exhaust gas system or various pipes used under the conditions of repeated high-temperature oxidation.
  • the alloy according to the second aspect of the invention comprises at least one member selected from Ca, Mg and rare earth metals (REM) in an amount that meets the following relation (4): and preferably, in an amount that meets the following relation (4a):
  • REM rare earth metals
  • the resulting alloy would have a sufficient oxidation resistance as well as an excellent workability.
  • These elements are significantly effective in improving the protectability of the oxide film formed on the surface of the alloy according to the second aspect of the invention, and hence, in suppressing the abnormal oxidation which is likely to take place in an extremely thin material.
  • the elements also improve adhesion of the oxide film to the underlying material.
  • Ca, Mg and the rare earth metal are respectively contained in the amounts as described below for the reasons as noted below.
  • the alloy according to the second aspect of the invention may be used for applications similar to those of the alloy according to the first aspect of the invention.
  • the alloy according to the third aspect of the invention comprises an alloy which meets the conditions for both the alloys according to the first and the second aspects of the invention, namely, an alloy having a Cr content of from 3 to 60% by weight; a total content of C, N, O, P and S of up to 100 ppm; a Mn content of from 0.5 to 20% by weight; a content of at least one member selected from Ti, Nb, Zr, V, Ta, W and B in the range that meets the above-mentioned relation (1); a content of at least one member selected from Si, Mn and AI in the range that meets the above-mentioned relation (2); and a content of at least one member selected from Ca, Mg, and rare earth metals (REM) in the range that meets the above-mentioned relation (3).
  • Such an alloy has an excellent workability as well as an oxidation resistance even superior to that of the alloy according to the first or the second aspect of the invention, and therefore, may be appropriately used for any of the above-mentioned applications.
  • an ultra high-purity electrolytic iron, an electrolytic chromium, a zone melting-processed silicon, a molten salt-electrolytic manganese, a molten salt-electrolytic aluminum, a molten salt-electrolytic calcium, an electrolytically reduced magnesium, and an electrolytically reduced rare earth metal may be employed as the starting materials.
  • the primary impurity is oxygen regardless of the type of the starting material, and therefore, melting and casting are carried out under an ultra-high vacuum of 10- 5 torr or less for the production of the Fe-Cr alloy of the present invention.
  • the alloy of this invention comprises the alloy of particularly excellent acid resistance described in the above (II) having added thereto the components of the alloy of particularly improved oxidation resistance described in the above (III).
  • the alloy of this invention is hereinafter described merely for its composition, and detailed description for each alloy component is omitted since it is the same as the one given in (II) and (III).
  • this invention comprises three aspects.
  • the content of C + N + 0 + P is up to 100 ppm; the Cr content is from 5 to 60% by weight; the Mo content is from 0.5 to 20% by weight; and the content of Ti + Nb + Zr + V + W + 50B is from 0.01 to 1% in all three aspects of the invention.
  • the components which may vary are described below for each aspect.
  • the alloy contains at least one member selected from Ni, Co and Cu in an amount that meets the following relation (2):
  • the alloy also contains at least one member selected from Si, Mn and AI in an amount that meets the following relation (3): and preferably, in an amount that meets the following relation:
  • the alloy contains at least one member selected from Ni, Co and Cu in an amount that meets the following relation (2):
  • the alloy also contains at least one member selected from Ca, Mg and rare earth metals (REM) in an amount that meets the following relation (4): and preferably, in an amount that meets the following relation:
  • REM rare earth metals
  • the alloy contains at least one member selected from Ni, Co and Cu in an amount that meets the following relation (2):
  • the alloy also contains at least one member selected from Si, Mn and AI in an amount that meets the following relation (3): and preferably, in an amount that meets the following relation:
  • the alloy also contains at least one member selected from Ca, Mg and rare earth metals (REM) in an amount that meets the following relation (4): and preferably, in an amount that meets the following relation:
  • REM rare earth metals
  • the process for producing the alloy of this invention is the same as the above-described processes, and therefore, detailed description of the production process is omitted.
  • Alloys having the chemical compositions shown in Table 1 were prepared by melting and casting the materials in a 10 kg vacuum melting furnace, and the alloys were hot rolled into hot rolled plates of 4 mm thick. The plates were further subjected to recrystallization annealing, descaling, and cold rolling to produce cold rolled plates of 0.7 mm thick. Finally, the plates were subjected to a recrystallization annealing to produce annealed cold rolled plates.
  • the thus obtained annealed cold rolled plates were subjected to a tensile test according to JIS Z-2241 to evaluate for their elongation.
  • the elongation is shown in Table 2.
  • the plates were also subjected to a bend test by tightly folding to 180* in C direction after cold rolling to 50%. After the bend test, the plates were examined for cracks, and the thus examined conditions are shown in Table 2.
  • test samples obtained in all examples were evaluated for their increase in elongation and decrease in proof stress (yield strength).
  • the increase in elongation (%) and the decrease in proof stress (yield strength) (N/mm 2 ) indicate difference in respective tensile properties from the alloy having the (C + N + 0 + S + P) of 500 ppm.
  • the tensile properties used for such calculation are:
  • the alloy plate By reducing the C, N, O, P and S, which have been well known impurities, to a total content of 100 ppm or less, the alloy plate would have an excellent workability irrespective of its Cr content as evidenced by the absence of cracks after 50% cold rolling and complete folding in C direction.
  • a series of alloys having the composition: Fe - 11% Cr- 0.003% Si - 0.005% Mn - 0.007% AI and varying total contents of C, N, O, P and S were prepared in the same manner as the alloy plates of Table 1, and ground finished with Emery #600.
  • the alloy plates were then subjected to a salt spray test using 5% NaCl at 50 ° C (24 hr), and examined for rust development. The results are shown in Table 2 (Criteria: A: no rust; B: little rust; C: considerable rust; and D: severe rust).
  • Test materials having the chemical compositions shown in Table 1 were prepared in a 100 kg highfrequency induction heating ultra high-vacuum melting furnace. The test materials were forged, cut, hot rolled, annealed, and cold rolled to produce a steel plate of 1.0 mm thick.
  • Test samples of 1 mm (thickness) x 50 mm x 50 mm were prepared from the thus produced test materials. The test samples were then subjected to
  • the Fe-Cr based alloy (5 ⁇ Cr 60) having a total content of C, N, O, P and S of up to 100 ppm and a content of at least one member selected from Cu, Ni and Co in the range of 0.01 wt % Ni + Co + 2Cu 6 6 wt% has an improved acid resistance.
  • Test materials having the chemical compositions shown in Table 1 were prepared in a 100 kg highfrequency induction heating ultra-vacuum melting furnace. The thus prepared test materials were repeatedly forged, cut, hot rolled, annealed, and cold rolled to produce a foil strip having a thickness of 50 ⁇ m and a width of 200 mm.
  • Test samples 50 ⁇ m (thickness) x 50 mm x 50 mm were prepared from the above-described foil strips, and the test samples were subjected to a continuous oxidation test and a repeated heating test as described below. The results are shown in Table 2.
  • test strips were heated to 1,150°C for 300 hours in the air, and then measured for their abnormally oxidized area.
  • the results were evaluated in accordance with the following criteria:
  • test strips were subjected to 50 cycles of heating at 1,150°C for 30 minutes and cooling for 30 minutes, and then measured for their area of the oxide film that had been peeled. The results were evaluated in accordance with the following criteria:
  • the improvements were significant when the (3AI + 2Si + Mn) was 0.1% or more.
  • a highly oxidation-resistant Fe-Cr alloy may be obtained by reducing the total content of S, P, O, N and C to 100 ppm or less, and adding at least one or two members selected from Si, AI and Mn to a content of 0.1% by weight ⁇ 3Al + 2Si + Mn 50% by weight in the Fe-Cr based alloy (3 ⁇ Cr 60).
  • the oxidation resistance of the Fe-Cr alloy may be further improved by adding at least one member selected from Ca, Mg, and rare earth metals to a content of 0.001 % by weight ⁇ 4Ca + 4Mg + REM 0.2% by weight in addition to the above-mentioned elements.
  • Test materials having the chemical compositions shown in Table 1 were prepared in a 100 kg highfrequency induction heating ultra-vacuum melting furnace. The thus prepared test materials were repeatedly forged, cut, hot rolled, annealed, and cold rolled to produce a foil strip having a thickness of 50 ⁇ m and a width of 200 mm.
  • Foil strip test samples 50 ⁇ m (thickness) x 50 mm x 50 mm
  • Example 3-1 the heating temperature is 1100°C.
  • the results are shown in Table 2.
  • the oxide films of the test samples of the invention were free from defects and highly adhesive to the underlying material while those of the comparative examples were less adhesive to the underlying material and susceptible to abnormal oxidation.
  • a highly oxidation-resistant Fe-Cr alloy may be obtained by reducing the total content of the S, P, O, N and C to 100 ppm or less, and adding at least one member selected from Ca, Mg, and rare earth metals to the content of 0.001 4Ca + 4Mg + REM 0.2 in the Fe-Cr based alloy (3 ⁇ Cr 60).
  • Test materials having the chemical compositions shown in Table 1 were prepared in a 100 kg highfrequency induction heating ultra-vacuum melting furnace. The thus prepared test materials were repeatedly forged, cut, hot rolled, annealed, and cold rolled to produce a foil strip having a thickness of 50 ⁇ m and a width of 200 mm.
  • test samples were then subjected to (1) a corrosion test wherein the samples are immersed in 5% HCI at 40°C; (2) a corrosion test wherein the samples are immersed in 40% H2SO4 at 50 ° C; (3) a continuous oxidation test; and (4) a repeated heating test by repeating the procedure of the above-described examples.
  • the results were also evaluated in a similar manner. The results are shown in Table 2. The results clearly reveal that the test samples having the alloy composition within the scope of the present invention have excellent properties.
  • Fe-Cr alloys of improved workability having excellent acid resistance and/or oxidation resistance are provided. Such Fe-Cr alloys may be utilized in a wide variety of fields.
  • Alloys having the chemical compositions shown in Table 1 were prepared in an ultra high-vacuum melting furnace of 10- 5 Torr or less from an ultra high-purity electrolytic iron and other high-purity metal materials produced, for example, by an electrolytic process.
  • the alloy materials were heated to about 1,200 ° C and hot rolled into plates of about 5 mm thick, and finally, cold rolled to a thickness of 1.0 to 2.0 mm.
  • the plates were further annealed at 500 to 1,100 ° C for recrystallization and particle size adjustment.
  • Test samples were cut out of the thus prepared alloy materials for tensile tests at room temperature and at an elevated temperature in accordance with Japanese Industrial Standard (The tensile test at room temperature was carried out in accordance with JIS 5, and the tensile test at an elevated temperature was carried out in accordance with JIS G 0567).
  • the alloy materials of the Table 1 prepared in an ultra high-vacuum furnace from high-purity metals were also subjected to an oxidation test wherein the alloy materials were heated in an electric furnace open to atmosphere to 1,350 K for 12 hours, and cooled by air to room temperature, and measured for their weight loss after scale removal. The thus evaluated weight loss was used as an index for their oxidation resistance.
  • Table 2 The results are shown in Table 2.
  • the results in Table 2 reveal that both the workability and the high-temperature strength are markedly improved in the samples having the alloy composition within the scope of the present invention compared to those of the comparative examples.
  • Test materials having the chemical compositions shown in Table 1 were prepared in a 100 kg highfrequency induction heating ultra high-vacuum melting furnace. The test materials were forged, cut, hot rolled, annealed, and cold rolled to produce a steel plate of 1.0 mm thick.
  • Test samples of 1 mm (thickness) x 50 mm x 50 mm were prepared from the thus produced test materials. The test samples were then subjected to
  • the Fe-Cr based alloy (5 ⁇ Cr 60) having a total content of C, N, O, P and S of up to 100 ppm and a content of at least one member selected from Cu, Ni and Co in the range of 0.01 wt% Ni + Co + 2Cu ⁇ 6 wt% has an improved acid resistance.
  • the alloy further comprising at least one member selected from Ti, Nb, Zr, V, Ta, W and B in a content in the range of of 0.01 wt% Ti + Nb + Zr + V + Ta + W + 50B 6.0 wt% has a further improved acid resistance.
  • Alloys having the chemical compositions shown in Table 1 were prepared in an ultra high-vacuum melting furnace of 10- 7 Torr or less from an ultra high-purity electrolytic iron, an electrolytic Cr and other high-purity metal materials.
  • the alloy materials were heated to about 1,200 ° C and hot rolled into plates of about 5 mm thick, and finally, cold rolled to a thickness of 1.0 to 2.0 mm.
  • the plates were further annealed at 500 to 1,100 ° C for recrystallization and particle size adjustment.
  • Test samples were cut out of the thus prepared alloy materials for tensile tests at room temperature and at an elevated temperature in accordance with Japanese Industrial Standard (The tensile test at room temperature was carried out in accordance with JIS 5, and the tensile test at an elevated temperature was carried out in accordance with JIS G 0567 at 900 ° C).
  • the samples were also subjected to an oxidation test wherein the samples were heated in an electric furnace open to atmosphere to 1,350 K for 12 hours, and cooled by air to room temperature, and measured for their weight loss after scale removal. The thus evaluated weight loss was used as an index for their oxidation resistance.
  • the test results are shown in Table 2. The results in Table 2 reveal that the oxidation resistance is markedly improved in the samples having the alloy composition within the scope of the present invention compared to those of the comparative examples.
  • Alloys having the chemical compositions shown in Table 1 were prepared in an ultra high-vacuum melting furnace of 10- 7 Torr or less from an ultra high-purity electrolytic iron, an electrolytic Cr and other high-purity metal materials.
  • the alloy materials were heated to about 1,200 ° C and hot rolled into plates of about 5 mm thick, and finally, cold rolled to a thickness of 1.0 to 2.0 mm.
  • the plates were further annealed at 500 to 1,100 ° C for recrystallization and particle size adjustment.
  • test samples were then subjected to (1) a corrosion test wherein the samples are immersed in 5% HCI at 40 °C; (2) a corrosion test wherein the samples are immersed in 40% H 2 S0 4 at 50 ° C; and (3) a high-temperature tensile test at 900 ° C by repeating the procedure of the above-described examples.
  • test samples obtained in all of the above-described examples were evaluated for their increase in elongation and decrease in proof stress (yield strength).
  • the increase in elongation (%) and the decrease in proof stress (yield strength) (N/mm 2 ) indicate difference in respective tensile properties from the alloy having the (C + N + O + S + P) of 500 ppm.
  • the tensile properties used for such calculation are:
  • Fe-Cr alloys of improved workability and high-temperature strength having excellent acid resistance and/or oxidation resistance are provided. Such Fe-Cr alloys may be suitably utilized in such applications as automobile exhaust pipes.
  • Alloys having the chemical compositions shown in Table 1 were prepared by melting and casting the materials in a 10 kg vacuum melting furnace, and the alloys were hot rolled into hot rolled plates of 4 mm thick. The plates were further subjected to recrystallization annealing, descaling, and cold rolling to produce cold rolled plates of 0.7 mm thick. Finally, the plates were subjected to a recrystallization annealing to produce annealed cold rolled plates.
  • the resulting alloy plates were subjected to the tests as described below.
  • Alloys 1 and 6 of the invention and Comparative alloys 1 and 6 were subjected to a tensile test according to JIS Z-2241 to evaluate for their elongation.
  • the plates were also subjected to a bend test by tightly folding to 180 ° in C direction after cold rolling to 50%. After the bend test, the plates were examined for cracks, and evaluated in accordance with the following criteria:
  • Test pieces of Comparative alloy 2, and Alloys 1 and 7 of the invention were ground finished with Emery #500.
  • the test pieces were then evaluated for their pitting resistance by immersing in an aqueous solution of (2% FeC1 3 + 1/20 HCI) at 30 °C for 4 hours, and measuring their weight loss caused by the corrosion to thereby calculate their corrosion rate.
  • the test pieces were also evaluated for their acid resistance by immersing in a 0.1 % by weight aqueous solution of HCI for 4 hours and measuring their weight loss caused by the corrosion to thereby calculate their corrosion rate.
  • the results are shown in Table 2.
  • test samples of Comparative alloy 5, and Alloys 10 and 6 of the invention were then evaluated for their pitting resistance by immersing in an aqueous solution of (5% FeC1 3 + 1/20 N HCI) at 30°C for 4 hours, and measuring their weight loss caused by the corrosion to thereby calculate their corrosion rate.
  • the test samples were also evaluated for their acid resistance by immersing in a 0.3 % by weight aqueous solution of HCI for 4 hours and measuring their weight loss caused by the corrosion to thereby calculate their corrosion rate. The results are shown in Table 2.
  • test samples of Comparative alloy 4, and Alloys 4 and 5 of the invention were then evaluated for their pitting resistance by immersing in an aqueous solution of (5% FeC1 3 + 1/20 N HCI) at 30°C for 4 hours, and measuring their weight loss caused by the corrosion to thereby calculate their corrosion rate.
  • the test samples were also evaluated for their acid resistance by immersing in a 0.3 % by weight aqueous solution of HCI for 4 hours and measuring their weight loss caused by the corrosion to thereby calculate their corrosion rate. The results are shown in Table 2.
  • test samples of Comparative alloy 3, and Alloys 2 and 8 of the invention were then evaluated for their pitting resistance by immersing in an aqueous solution of (5% FeC1 3 + 1/20 N HCI) at 80°C for 4 hours, and measuring their weight loss caused by the corrosion to thereby calculate their corrosion rate.
  • the test samples were also evaluated for their acid resistance by immersing in a 5 % by weight aqueous solution of HCI for 4 hours and measuring their weight loss caused by the corrosion to thereby calculate their corrosion rate. The results are shown in Table 2.
  • test samples of Comparative alloy 7, and Alloys 3 and 9 of the invention were then evaluated for their pitting resistance by immersing in an aqueous solution of (10% FeC1 3 + 1/20 N HCI) at 80 ° C for 4 hours, and measuring their weight loss caused by the corrosion to thereby calculate their corrosion rate.
  • the test samples were also evaluated for their acid resistance by immersing in a 5 % by weight aqueous solution of HCI for 4 hours and measuring their weight loss caused by the corrosion to thereby calculate their corrosion rate. The results are shown in Table 2.
  • the pitting resistance may be markedly improved by the inclusion of Mo in an amount within the range of the present invention, and that the acid resistance may be additionally improved by the inclusion of the Ni, Co and Cu in an amount within the range of the present invention.
  • Alloys having the chemical compositions shown in Table 1 were prepared in an ultra high-vacuum melting furnace of 10- 7 Torr or less from an ultra high-purity electrolytic iron, an electrolytic Cr and other high-purity metal materials.
  • the alloy materials were heated to about 1,200 ° C and hot rolled into plates of about 5 mm thick, and finally, cold rolled to a thickness of 1.0 to 2.0 mm.
  • the plates were further annealed at 500 to 1,100 ° C for recrystallization and particle size adjustment.
  • Test samples were cut out of the thus prepared alloy materials for tensile tests at room temperature and at an elevated temperature in accordance with Japanese Industrial Standard (The tensile test at room temperature was carried out in accordance with JIS 5, and the tensile test at an elevated temperature was carried out in accordance with JIS G 0567).
  • the alloy materials of the Table 1 prepared in an ultra high-vacuum furnace from high-purity metals were also subjected to an oxidation test wherein the alloy materials were heated in an electric furnace open to atmosphere to 1,350 K for 12 hours, and cooled by air to room temperature, and measured for their weight loss after scale removal. The thus evaluated weight loss was used as an index for their oxidation resistance. The results are shown in Table 2.
  • Alloys having the chemical compositions shown in Table 1 were prepared in an ultra high-vacuum melting furnace of 10- 7 Torr or less from an ultra high-purity electrolytic iron, an electrolytic Cr and other high-purity metal materials.
  • the alloy materials were heated to about 1,200 ° C and hot rolled into plates of about 5 mm thick, and finally, cold rolled to a thickness of 1.0 to 2.0 mm.
  • the plates were further annealed at 500 to 1,100 ° C for recrystallization and particle size adjustment.
  • test samples were then evaluated for their acid resistance and oxidation resistance. The results clearly reveal that the test samples of the present invention have excellent properties.
  • test samples obtained in all of the above-described examples were evaluated for their increase in elongation and decrease in proof stress (yield strength).
  • the increase in elongation (%) and the decrease in proof stress (yield strength) (N/mm 2 ) indicate difference in respective tensile properties from the alloy having the (C + N + 0 + S + P) of 500 ppm.
  • the tensile properties used for such calculation are:
  • the alloys according to the present invention have excellent acid resistance and/or oxidation resistance in addition to improved workability and pitting resistance, and therefore, may be suitably utilized in such applications as automobile exhaust pipes.
  • Alloys having the chemical compositions shown in Table 1 were prepared by melting and casting the materials in a 10 kg vacuum melting furnace, and the alloys were hot rolled into hot rolled plates of 4 mm thick. The plates were further subjected to recrystallization annealing, descaling, and cold rolling to produce cold rolled plates of 0.7 mm thick. Finally, the plates were subjected to a recrystallization annealing to produce annealed cold rolled plates.
  • the resulting alloy plates were subjected to the tests as described below.
  • Alloys 1 and 2 of the invention and Comparative alloys 1 and 2 were subjected to a tensile test according to JIS Z-2241 to evaluate for their elongation.
  • the plates were also subjected to a bend test by tightly folding to 180 ° in C direction after cold rolling to 50%. After the bend test, the plates were examined for cracks, and evaluated in accordance with the following criteria:
  • TIG welding bead on
  • sulfuric acid-copper sulfate test according to JIS G-0572
  • Test samples were prepared by repeating the above-described procedure, and the test samples were evaluated for their intergranular corrosion resistance by the same procedure as described above.
  • the test samples were also evaluated for their acid resistance by immersing in aqueous HCI solutions shown in Table 2 for 24 hours and measuring their weight loss caused by the corrosion to thereby calculate their corrosion rate. The results are shown in Table 2.
  • the oxidation test was carried out by heat treating the test samples in air at 1350°K for 12 hours, and descaling the heat treated samples. The samples were then weighed to determine their weight loss.
  • the resulting test samples were evaluated for their increase in elongation and decrease in proof stress (yield strength).
  • the increase in elongation (%) and the decrease in proof stress (yield strength) (N/mm 2 ) indicate difference in respective tensile properties from the alloy having the (C + N + 0 + S + P) of 500 ppm.
  • the tensile properties used for such calculation are:
  • the pitting resistance may be markedly improved by the inclusion of Mo in an amount within the range of the present invention, and that the intergranular corrosion resistance in the weld zone may be improved by the inclusion of Ti, Nb, V, Ta, W, Zr, and/or B in an adequate amount.
  • the above results reveal that the acid resistance may be significantly improved by the inclusion of the Ni, Co and/or Cu in an adequate amount.
  • the above results reveal that the oxidation resistance may be significantly improved by the inclusion in an adequate amount of at least one member selected from Si, Mn and Al; and/or at least one member selected from Ca, Mg and REM.
  • the Fe-Cr alloys according to the present invention containing C, N, O, P and S in a total amount of 100 ppm or less and a predetermined amount of Mo and at least one member selected from Ti, Nb, Zr, V, Ta, W and B have excellent workability as well as significantly improved pitting resistance and weld zone corrosion resistance (intergranular corrosion resistance).
  • the Fe-Cr alloys further comprising a predetermined amount of at least one member selected from Ni, Cu and Co has a significantly improved acid resistance in addition to the above-mentioned properties.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)
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EP19930911960 1992-04-30 1993-04-30 Fe-cr alloy excellent in workability. Ceased EP0597129A4 (en)

Applications Claiming Priority (17)

Application Number Priority Date Filing Date Title
JP111014/92 1992-04-30
JP111430/92 1992-04-30
JP11101492 1992-04-30
JP11143092 1992-04-30
JP112522/92 1992-05-01
JP11252292 1992-05-01
JP117358/92 1992-05-11
JP11735892 1992-05-11
JP128751/92 1992-05-21
JP12875192 1992-05-21
JP14165692 1992-06-02
JP141655/92 1992-06-02
JP141653/92 1992-06-02
JP14165592 1992-06-02
JP141656/92 1992-06-02
JP14165392 1992-06-02
PCT/JP1993/000580 WO1993022471A1 (en) 1992-04-30 1993-04-30 Fe-Cr ALLOY EXCELLENT IN WORKABILITY

Publications (2)

Publication Number Publication Date
EP0597129A1 true EP0597129A1 (de) 1994-05-18
EP0597129A4 EP0597129A4 (en) 1994-08-10

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EP19930911960 Ceased EP0597129A4 (en) 1992-04-30 1993-04-30 Fe-cr alloy excellent in workability.

Country Status (3)

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EP (1) EP0597129A4 (de)
KR (1) KR100253543B1 (de)
WO (1) WO1993022471A1 (de)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0894874A1 (de) * 1997-08-01 1999-02-03 Kawasaki Steel Corporation Fe-Cr-Si Stahl mit guten Korrosionseigenschaften und Verfahren zu seiner Herstellung
WO1999025890A1 (en) * 1997-11-17 1999-05-27 Ceramic Fuel Cells Limited A heat resistant steel
DE19803084A1 (de) * 1998-01-28 1999-07-29 Max Planck Inst Eisenforschung Verwendung von Stahlpulver auf der Basis Fe-Cr-Si für korrosionsbeständige Beschichtungen
DE19820806A1 (de) * 1998-05-09 1999-11-18 Max Planck Inst Eisenforschung Leichtbaustahl und seine Verwendung
WO2000073523A1 (fr) * 1999-05-27 2000-12-07 Japan Science And Technology Corporation Alliage a base de chrome dote d'un excellent equilibre resistance-ductilite a haute temperature
AU737814B2 (en) * 1997-11-17 2001-08-30 Ceramic Fuel Cells Limited A heat resistant steel
EP1160347A1 (de) * 2000-05-31 2001-12-05 Kawasaki Steel Corporation Fe-Cr-Legierung mit ausgezeichnetem Korrosionswiderstand, ausgezeichneter Verarbeitbarkeit und ausgezeichneter Schweissbarkeit
US6884869B2 (en) 2001-04-30 2005-04-26 Seattle Genetics, Inc. Pentapeptide compounds and uses related thereto
DE102007056144A1 (de) * 2007-11-16 2009-05-20 Volkswagen Ag Abgaskrümmer oder Turboladergehäuse aus einer FeAl-Stahllegierung
EP2933349A1 (de) * 2012-12-17 2015-10-21 JFE Steel Corporation Edelstahlblech und edelstahlfolie
US10196721B2 (en) 2011-06-21 2019-02-05 Vdm Metals International Gmbh Heat-resistant iron-chromium-aluminum alloy with low chromium vaporization rate and elevated thermal stability

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See also references of WO9322471A1 *

Cited By (24)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6207103B1 (en) 1997-08-01 2001-03-27 Kawasaki Steel Corporation Fe-Cr-Si steel sheets having excellent corrosion resistance and method for manufacturing the same
EP0894874A1 (de) * 1997-08-01 1999-02-03 Kawasaki Steel Corporation Fe-Cr-Si Stahl mit guten Korrosionseigenschaften und Verfahren zu seiner Herstellung
DE19882827B4 (de) * 1997-11-17 2010-09-23 Ceramic Fuel Cells Ltd. Hitzebeständiger Stahl
GB2346894A (en) * 1997-11-17 2000-08-23 Ceramic Fuel Cells Ltd A heat resistant steel
WO1999025890A1 (en) * 1997-11-17 1999-05-27 Ceramic Fuel Cells Limited A heat resistant steel
GB2346894B (en) * 1997-11-17 2001-12-12 Ceramic Fuel Cells Ltd A heat resistant steel
US6294131B1 (en) 1997-11-17 2001-09-25 Ceramic Fuel Cells Limited Heat resistant steel
AU737814B2 (en) * 1997-11-17 2001-08-30 Ceramic Fuel Cells Limited A heat resistant steel
DE19803084B4 (de) * 1998-01-28 2005-07-28 Max-Planck-Institut Für Eisenforschung GmbH Verwendung von Stahlpulver auf der Basis Fe-Cr-Si für korrosionsbeständige Beschichtungen
DE19803084A1 (de) * 1998-01-28 1999-07-29 Max Planck Inst Eisenforschung Verwendung von Stahlpulver auf der Basis Fe-Cr-Si für korrosionsbeständige Beschichtungen
DE19820806B4 (de) * 1998-05-09 2004-03-04 Max-Planck-Institut Für Eisenforschung GmbH Verwendungen eines Leichtbaustahls
DE19820806A1 (de) * 1998-05-09 1999-11-18 Max Planck Inst Eisenforschung Leichtbaustahl und seine Verwendung
US7037467B1 (en) 1999-05-27 2006-05-02 Japan Science And Technology Agency Cr-based alloy excellent in balance between strength and ductility at high temperature
WO2000073523A1 (fr) * 1999-05-27 2000-12-07 Japan Science And Technology Corporation Alliage a base de chrome dote d'un excellent equilibre resistance-ductilite a haute temperature
US8685315B2 (en) 1999-05-27 2014-04-01 Japan Science And Technology Agency Cr-based alloy having an excellent strength-ductility balance at high temperature
KR100503548B1 (ko) * 2000-05-31 2005-07-25 제이에프이 스틸 가부시키가이샤 초기 녹발생 방지성, 가공성 및 용접성이 우수한 철-크롬합금
EP1160347A1 (de) * 2000-05-31 2001-12-05 Kawasaki Steel Corporation Fe-Cr-Legierung mit ausgezeichnetem Korrosionswiderstand, ausgezeichneter Verarbeitbarkeit und ausgezeichneter Schweissbarkeit
US6419878B2 (en) 2000-05-31 2002-07-16 Kawasaki Steel Corporation Fe-Cr alloy having excellent initial rust resistance, workability and weldability
US6884869B2 (en) 2001-04-30 2005-04-26 Seattle Genetics, Inc. Pentapeptide compounds and uses related thereto
DE102007056144A1 (de) * 2007-11-16 2009-05-20 Volkswagen Ag Abgaskrümmer oder Turboladergehäuse aus einer FeAl-Stahllegierung
US10196721B2 (en) 2011-06-21 2019-02-05 Vdm Metals International Gmbh Heat-resistant iron-chromium-aluminum alloy with low chromium vaporization rate and elevated thermal stability
EP2933349A4 (de) * 2012-12-17 2016-04-06 Jfe Steel Corp Edelstahlblech und edelstahlfolie
US9777357B2 (en) 2012-12-17 2017-10-03 Jfe Steel Corporation Stainless steel foil
EP2933349A1 (de) * 2012-12-17 2015-10-21 JFE Steel Corporation Edelstahlblech und edelstahlfolie

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Publication number Publication date
EP0597129A4 (en) 1994-08-10
WO1993022471A1 (en) 1993-11-11
KR100253543B1 (ko) 2000-04-15

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