EP3677700B1 - Stahl mit hohem mn-gehalt und herstellungsverfahren dafür - Google Patents

Stahl mit hohem mn-gehalt und herstellungsverfahren dafür Download PDF

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EP3677700B1
EP3677700B1 EP18851150.5A EP18851150A EP3677700B1 EP 3677700 B1 EP3677700 B1 EP 3677700B1 EP 18851150 A EP18851150 A EP 18851150A EP 3677700 B1 EP3677700 B1 EP 3677700B1
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steel
temperature
comparative example
rolling
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French (fr)
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EP3677700A1 (de
EP3677700A4 (de
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Daichi Izumi
Keiji Ueda
Kazukuni Hase
Koichi Nakashima
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JFE Steel Corp
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JFE 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
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/001—Austenite

Definitions

  • This invention relates to high-Mn steel that is suitable for structural steel used in an extremely low-temperature environment such as a storage tank of liquefied gas, in particular, high-Mn steel excellent in toughness at low temperature, and a production method therefor.
  • JP 2016 196 703 A relates to a high Mn steel material for cryogenic use, wherein the volume fraction of austenite is 95% or more, the austenite has a crystal grain size of 20 to 200 ⁇ m, and the carbide coverage ratio at the crystal grain boundary of the austenite is 50% or less.
  • the steel plate needs to have high strength and excellent toughness at low temperature because the structure is used at extremely low temperature.
  • excellent toughness needs to be guaranteed at the boiling point of the liquefied natural gas, that is, -164 °C or lower.
  • a steel material has poor low-temperature toughness, the safety as a structure for an extremely low temperature storage tank may not be maintained.
  • an extremely low temperature range including -164 °C is referred to as "low temperature”.
  • austenitic stainless steel which has austenite as a microstructure of a steel plate, the austenite having no brittleness at low temperature, 9 % Ni steel, or five thousand series aluminum alloys have been conventionally used.
  • the alloy cost and production cost are high, and thus there is a demand for steel materials which are inexpensive and excellent in low-temperature toughness.
  • JP 2017-71817 A proposes using, as structural steel used in a low temperature environment, high-Mn steel added with a large amount of Mn which is a relatively inexpensive austenite-stabilizing element.
  • PTL 1 proposes a technique of controlling the Mn segregation ratio to prevent carbides generated in crystal grain boundaries from becoming an origin of fracture.
  • the phrase "excellent in low-temperature toughness" means that the absorbed energy vE -196 in a Charpy impact test at -196 °C is 100 J or more.
  • the KAM (Kernel Average Misorientation) value represents an average of orientation difference between each pixel (having a pitch of 0.3 ⁇ m) and the adjacent pixel in a crystal grain.
  • EBSD Electro Backscatter Diffraction
  • the C is an inexpensive austenite-stabilizing element, and an important element to obtain austenite. To obtain this effect, the C content needs to be 0.100 % or more. On the other hand, a C content beyond 0.700 % generates excessive Cr carbides, deteriorating low-temperature toughness. Therefore, the C content is set to be 0.100 % or more and 0.700 % or less. The C content is preferably 0.200 % or more and 0.600 % or less.
  • Si 0.05 % or more and 1.00 % or less
  • Si acts as a deoxidizer, is necessary for steelmaking, and is effective at increasing the strength of a steel plate by solid solution strengthening when dissolved in steel. To obtain such an effect, the Si content needs to be 0.05 % or more. On the other hand, a Si content beyond 1.00 % deteriorates weldability. Therefore, the Si content is set to 0.05 % or more and 1.00 % or less, and preferably 0.07 % or more and 0.50 % or less.
  • Mn 20.0 % or more and 35.0 % or less
  • Mn is a relatively inexpensive austenite-stabilizing element.
  • Mn is an important element for achieving both strength and low-temperature toughness.
  • the Mn content needs to be 20.0 % or more.
  • a Mn content beyond 35.0 % deteriorates low-temperature toughness.
  • such a high Mn content deteriorates weldability and cuttability, and further promotes segregation as well as the occurrence of stress corrosion cracking. Therefore, the Mn content is set to 20.0 % or more and 35.0 % or less, preferably 23.0 % or more and 30.0 % or less, and more preferably 28.0 % or less.
  • the upper limit of the P content is 0.030 %, and desirably, the P content is kept as small as possible. Therefore, the P content is set to 0.030 % or less. Excessively reducing P involves high refining cost and is economically disadvantageous. Therefore, the P content is desirably set to 0.002 % or more, preferably 0.005 % or more and 0.028 % or less, and more preferably 0.024 % or less.
  • the upper limit of the S content is 0.0070 %, and desirably, the S content is kept as small as possible. Therefore, the S content is set to 0.0070 % or less. Excessively reducing S involves high refining cost and is economically disadvantageous. Therefore, the lower limit of the S content is desirably set to 0.001 % or more.
  • the S content is preferably set to 0.0020 % or more and 0.0060 % or less.
  • Al 0.01 % or more and 0.07 % or less
  • Al acts as a deoxidizer and is used most commonly in molten steel deoxidizing processes to obtain a steel plate. To obtain such an effect, the Al content needs to be 0.01 % or more. On the other hand, when the Al content is beyond 0.07 %, Al is mixed into a weld metal portion during welding, deteriorating the toughness of the weld metal. Therefore, the Al content is set to 0.07 % or less. Therefore, the Al content is set to 0.01 % or more and 0.07 % or less, and preferably 0.02 % or more and 0.06 % or less.
  • the Cr content is an element which stabilizes austenite with an appropriate amount of addition and is effective for improving low-temperature toughness and base metal strength. To obtain such effects, the Cr content needs to be 0.5 % or more. On the other hand, a Cr content beyond 7.0 % generates Cr carbides, deteriorating low-temperature toughness and stress corrosion cracking resistance. Therefore, the Cr content is set to 0.5 % or more and 7.0 % or less, preferably 1.0 % or more and 6.7 % or less, and more preferably 1.2 % or more and 6.5 % or less. To further improve stress corrosion cracking resistance, the Cr content is further preferably 2.0 % or more and 6.0 % or less.
  • N 0.0050 % or more and 0.0500 % or less
  • N is an austenite-stabilizing element and an element which is effective for improving low-temperature toughness. To obtain such an effect, the N content needs to be 0.0050 % or more. On the other hand, the N content beyond 0.0500 % coarsens nitrides or carbonitrides, deteriorating toughness. Therefore, the N content is set to 0.0050 % or more and 0.0500 % or less, and preferably 0.0060 % or more and 0.0400 % or less.
  • the O content is set to 0.0050 % or less, and preferably 0.0045 % or less. Excessively reducing O involves high refining cost and is economically disadvantageous. Therefore, the O content is desirably set to 0.0010 % or more.
  • Ti and Nb form carbonitrides with a high melting point in steel to prevent coarsening of crystal grains, then becoming an origin of fracture and a propagation path of cracks.
  • Ti and Nb hinder microstructure control for enhancing low-temperature toughness and improving ductility, and thus, need to be intentionally limited.
  • Ti and Nb are components which are inevitably mixed from raw materials and the like into steel, and Ti of more than 0.005 % and 0.010 % or less and Nb of more than 0.005 % and 0.010 % or less are typically mixed.
  • each Ti and Nb By limiting the content of each Ti and Nb to 0.005 % or less, it is possible to eliminate the adverse effect of carbonitrides and guarantee excellent low-temperature toughness and ductility.
  • the content of each Ti and Nb is preferably set to 0.003 % or less.
  • the contents of each Ti and Nb may be 0 %.
  • the balance other than the aforementioned components is Fe and inevitable impurities.
  • the inevitable impurities include H, and a total content of 0.01 % or less is allowable.
  • the steel material When a steel material has a body centered cubic (bcc) crystal structure, the steel material may cause brittle fracture in a low temperature environment, and thus, is not suitable for use in a low temperature environment.
  • the steel material When the steel material is assumed to be used in a low temperature environment, the steel material is required to have, as a matrix phase, an austenite microstructure which has a face centered cubic (fcc) crystal structure.
  • the phrase "having austenite as a matrix phase” and similar phrases mean that the area ratio of an austenite phase is 90 % or more.
  • the balance other than the austenite phase is a ferrite or martensite phase.
  • the area ratio of the austenite phase is preferably 95 % or more.
  • a segregation portion having a low Mn concentration and a segregation portion having a high Mn concentration, compared with the Mn content in the chemical composition are formed.
  • the Mn concentration of a Mn segregation portion and an absorbed energy in a Charpy impact test at -196 °C were measured on a steel plate obtained by hot rolling a steel material having the aforementioned chemical composition under various conditions.
  • the Mn segregation portion which is a region having a low or high Mn concentration within a Mn segregation band, is specifically represented by a region having a lowest or highest Mn concentration which is measured by EBSD (Electron Backscatter Diffraction) analysis on a polished surface in a cross section along a rolling direction of a steel plate after hot rolling.
  • EBSD Electro Backscatter Diffraction
  • FIG. 1 illustrates the result of measuring the Mn concentration and the absorbed energy in the Charpy impact test at -196 °C, it is found that when the Mn concentration in the Mn segregation portion is 16 % or more, an absorbed energy of 100 J or more is achieved.
  • the Mn concentration in the Mn segregation portion is preferably 17 % or more.
  • FIG. 2 illustrates a result obtained by measuring the Mn concentration and the absorbed energy in the Charpy impact test at -196 °C, it is found that when the Mn concentration in the Mn segregation portion is 38 % or less, an absorbed energy of 100 J or more is achieved.
  • the Mn concentration in the Mn segregation portion is preferably 37 % or less.
  • KAM Kernel Average Misorientation
  • the KAM value is determined by performing EBSD (Electron Backscatter Diffraction) analysis in a field of 500 ⁇ m ⁇ 200 ⁇ m in an arbitrary two fields of a steel plate after hot rolling and calculating from the analysis results an average of orientation difference between each pixel (having a pitch of 0.3 ⁇ m) and the adjacent pixel in a crystal grain.
  • the KAM value reflects the local crystal orientation change caused by dislocation in the microstructure.
  • a higher KAM value represents a larger orientation difference between a measurement point and the adjacent portion.
  • a higher KAM value means a higher local deformation degree in a grain. Therefore, a higher KAM value in a steel plate after rolling means a higher dislocation density.
  • the average KAM value when the average KAM value is 0.3 or more, it means accumulation of a large amount of dislocation, and thus, yield stress increases.
  • the average KAM value is preferably 0.5 or more.
  • the average KAM value when the average KAM value is beyond 1.3, toughness may be deteriorated.
  • the average KAM value is preferably 1.3 or less.
  • a Mn segregation portion having a Mn concentration of 16 % or more and 38 % or less and an average KAM value of 0.3 or more as stated above can be obtained by adjusting the chemical composition as described above and performing hot rolling according to the following conditions.
  • the following elements can be contained as necessary.
  • Mo At least one of Mo: 2.0 % or less, V: 2.0 % or less, W: 2.0 % or less, Ca: 0.0005 % or more and 0.0050 % or less, Mg: 0.0005 % or more and 0.0050 % or less, and REM: 0.0010 % or more and 0.0200 % or less.
  • Mo, V, and W 2.0 % or less
  • Mo, V, and W contribute to stabilizing austenite and improving base metal strength.
  • Mo, V, and/or W is preferably contained in an amount of 0.001 % or more.
  • the content of Mo, V, and/or W is beyond 2.0 %, coarse carbonitrides are generated, which may become an origin of fracture, and additionally increase production cost. Therefore, when Mo, V, and/or W is contained, the content of each added alloying element is 2.0 %, preferably 0.003 % or more and 1.7 % or less, and more preferably 1.5 % or less.
  • Ca, Mg, and REM are elements useful for morphological control of inclusions and can be contained as necessary.
  • the morphological control of inclusions means granulating elongated sulfide-based inclusions.
  • the morphological control of inclusions improves ductility, toughness, and sulfide stress corrosion cracking resistance.
  • Ca and/or Mg is preferably contained in an amount of 0.0005 % or more and REM is preferably contained in an amount of 0.0010 % or more.
  • these elements are contained in a large amount, not only the amount of nonmetallic inclusions may be increased, ending up deteriorating ductility, toughness, and sulfide stress corrosion cracking resistance, but also an economic disadvantage may be entailed.
  • the content of each element is set to 0.0005 % or more and 0.0050 % or less.
  • the content is set to 0.0010 % or more and 0.0200 % or less.
  • the Ca content is set to 0.0010 % or more and 0.0040 % or less
  • the Mg content is set to 0.0010 % or more and 0.0040 % or less
  • the REM content is set to 0.0020 % or more and 0.0150 % or less.
  • Our high-Mn steel can be obtained from molten steel having the aforementioned chemical composition which is prepared by steelmaking using a publicly-known method such as using a converter and an electric heating furnace.
  • the high-Mn steel may also be subjected to secondary refinement in a vacuum degassing furnace.
  • secondary refinement to limit the contents of Ti and Nb which hinder suitable microstructure control within the aforementioned range, it is necessary to prevent Ti and Nb from being inevitably mixed from raw materials or the like into steel and decrease the contents of Ti and Nb. For example, by decreasing the basicity of slag in the refining stage such that these alloy elements are concentrated in the slag to be discharged, it is possible to reduce the Ti and Nb concentrations in a final slab product.
  • the following provides a further definition of production conditions to make the aforementioned steel material into a steel material exhibiting excellent low-temperature toughness.
  • Heating temperature of steel material 1100 °C or higher and 1300 °C or lower
  • the heating temperature before the rolling is set to 1100 °C or higher.
  • a heating temperature beyond 1300 °C may trigger steel melting, and thus, the upper limit of the heating temperature is set to 1300 °C.
  • the heating temperature is preferably 1150 °C or higher and 1250 °C or lower.
  • the rolling finish temperature is set to 800 °C or higher. This is because Mn is not sufficiently diffused at a temperature of lower than 800 °C, which is well below two thirds of the melting point of Mn.
  • the rolling finish temperature is preferably 950 °C or higher and more preferably 1000 °C or higher and 1050 °C or lower.
  • the total rolling reduction is preferably 30 % or more. No upper limit is placed on the total rolling reduction, but from the viewpoint of improving rolling efficiency, the upper limit is preferably 98 %.
  • the second hot rolling may be continued as it is, whereas when the finish temperature is lower than 1100 °C, re-heating to 1100 °C or higher is performed.
  • a heating temperature beyond 1300 °C may trigger steel melting.
  • the upper limit of the heating temperature is set to 1300 °C.
  • the temperature is controlled based on the surface temperature of the steel material.
  • the heating temperature is preferably 1150 °C or higher and 1250 °C or lower.
  • the second hot rolling requires at least one pass of final finish rolling at 700 °C or higher and lower than 950 °C. Specifically, by performing at least one pass of rolling preferably with a rolling reduction of 10 % or more at lower than 950 °C, dislocations having being introduced during the first rolling are less likely to be recovered and easily remain, and thus, the KAM value can be increased. Further, crystal grains become excessively coarse in a finish temperature range of 950 °C or higher, and thus desired yield stress cannot be obtained. Therefore, it is preferable to perform at least one pass of final finish rolling at lower than 950 °C.
  • the finish temperature is preferably 900 °C or lower and more preferably 850 °C or lower.
  • a finish temperature of lower than 700 °C deteriorates toughness, and thus, the finish temperature is set to 700 °C or higher, and preferably 750 °C or higher.
  • the rolling reduction at lower than 950 °C is preferably 20 % or more and more preferably 50 % or more. However, rolling with a rolling reduction of beyond 95 % deteriorates toughness, and thus, a rolling reduction of 95 % or less is preferable.
  • cooling is immediately performed.
  • Gentle cooling of the steel plate after the hot rolling promotes formation of precipitates, thus deteriorating low-temperature toughness. Cooling the steel plate at a cooling rate of 1.0 °C/s or more can prevent formation of these precipitates. Further, excessive cooling distorts the steel plate, deteriorating productivity.
  • the upper limit of the cooling start temperature is set to 900 °C.
  • the average cooling rate within a range of a temperature at or above (a rolling finish temperature - 100 °C) to a temperature ranging from 300 °C to 650 °C is set to 1.0 °C/s or more. Note that the subsequent heating treatment is unnecessary because the Mn segregation portions in the as-rolled state are maintained within a narrow Mn concentration range.
  • Steel slabs having the chemical compositions listed in Table 1 were made by a converter-ladle refining-continuous casting process. Next, the obtained steel slabs were subjected to blooming (the first hot rolling) and hot rolling (the second hot rolling) under conditions listed in Table 2 to obtain steel plates having a thickness of 10 mm to 30 mm. Tensile properties, toughness, and microstructure of the obtained steel plates were evaluated as described below.
  • JIS NO. 5 tensile test pieces were collected from each steel plate. Then, the test pieces were subjected to a tensile test in conformity with JIS Z 2241 (1998) to investigate tensile properties.
  • a test piece had a yield stress of 400 MPa or more and a tensile strength of 800 MPa or more, the corresponding steel plate was determined to have excellent tensile properties. Further, when a test piece had an elongation of 40 % or more, the corresponding steel plate was determined to have excellent ductility.
  • Charpy V-notch test pieces were collected from each steel plate having a plate thickness of more than 20 mm at a 1/4 position of the plate thickness or from each steel plate having a plate thickness of 20 mm or less at a 1/2 position of the plate thickness, in a direction parallel to the rolling direction in conformity with JIS Z 2242 (2005). Then, the test pieces were subjected to Charpy impact test in conformity with JIS Z 2242 (2005), where three test pieces were used for each steel plate, to determine absorbed energy at -196 °C and evaluate base metal toughness. In this invention, when the three test pieces had an average absorbed energy (vE -196 ) of 100 J or more, the corresponding steel plate was determined to have excellent base steel toughness.
  • Charpy V-notch test pieces having a sub-size of 5 mm were collected from each steel plate at a 1/2 position of the plate thickness, in a direction parallel to the rolling direction in conformity with JIS Z 2242 (2005). Then, the test pieces were subjected to Charpy impact test at -196 °C in conformity with JIS Z 2242 (2005), where three test pieces were used for each steel plate. When the three test pieces had an average absorbed energy (vE -196 ) of 67 J or more, the corresponding steel plate was determined to have excellent base steel toughness.
  • EBSD Electro Backscatter Diffraction
  • test piece was polished stepwise for convenience of observation to its notch bottom.
  • five fields with a size of 100 ⁇ m ⁇ 100 ⁇ m were observed by EBSD analysis (measurement step: 0.08 ⁇ m) to determine the presence/absence of deformation-induced martensite.
  • EPMA Electro Probe Micro Analyzer
  • Second rolling conditions Remarks Plate No. thickness Slab heating temperature Rolling finish temperature Total rolling reduction Re-heating temperature Rolling finish temperature Cooling start temperature Cooling rate within a range of 300 °C to 650 °C (mm) (°C) (°C) (%) (°C) (°C) (°C) (°C/s) 1 1 22 1130 921 32 1130 810 774 8 Example 2 2 25 1130 918 29 1130 823 787 9 Example 3 3 18 1100 887 36 1100 765 702 9 Example 4 4 20 1100 892 35 1100 796 734 8 Example 5 5 25 1150 939 43 1150 838 805 8 Example 6 6 15 1150 937 46 1150 811 741 12 Example 7 7 10 1180 946 51 1180 805 728 16 Example 8 10 1200 953 53 1200 763 671 10 Example 9 9 13 1160 941 30 1160 813 762 7 Example 10 10 28 1250 1034 26 1250 946 915 16 Example 11 1 30 1300 1102 20

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  • Engineering & Computer Science (AREA)
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Claims (3)

  1. Stahl mit hohem Mn-Gehalt, umfassend:,
    eine chemische Zusammensetzung, die in Masse-% umfasst:
    C: 0,100 % oder mehr und 0,700 % oder weniger,
    Si: 0,05 % oder mehr und 1,00 % oder weniger,
    Mn: 20,0 % oder mehr und 35,0 % oder weniger,
    P: 0,030 % oder weniger,
    S: 0,0070 % oder weniger,
    AI: 0,01 % oder mehr und 0,07 % oder weniger,
    Cr: 0,5 % oder mehr und 7,0 % oder weniger,
    N: 0,0050 % oder mehr und 0,0500 % oder weniger,
    O: 0,0050 % oder weniger,
    Ti: 0,005 % oder weniger und
    Nb: 0,005 % oder weniger,
    gegebenenfalls mindestens ein Element, ausgewählt aus der Gruppe bestehend aus:
    Mo: 2,0 % oder weniger,
    V: 2,0 % oder weniger,
    W: 2,0 % oder weniger,
    Ca: 0,0005 % oder mehr und 0,0050 % oder weniger,
    Mg: 0,0005 % oder mehr und 0,0050 % oder weniger, und
    REM: 0,0010 % oder mehr und 0,0200 % oder weniger,
    wobei der Rest Fe und unvermeidbare Verunreinigungen sind, und
    eine Mikrostruktur mit Austenit als Matrixphase, wobei das Flächenverhältnis einer Austenitphase 90 % oder mehr beträgt, wobei
    die Mikrostruktur einen Mn-Segregationsanteil mit einer Mn-Konzentration von 16 % oder mehr und 38 % oder weniger aufweist, und
    der Stahl mit hohem Mn-Gehalt einen durchschnittlichen Wert der durchschnittlichen kernbasierten Missorientierung von 0,3 oder mehr aufweist,
    eine absorbierte Energie in einem Charpy-Kerbschlagbiegeversuch bei -196 °C von 100 J oder mehr und eine Streckspannung von 400 MPa oder mehr, die nach den in der Beschreibung angegebenen Verfahren gemessen werden.
  2. Verfahren zur Herstellung von Stahl mit hohem Mn-Gehalt, umfassend:
    Erhitzen eines Stahlmaterials mit der chemischen Zusammensetzung gemäß Anspruch 1 auf einen Temperaturbereich von 1100 °C oder höher und 1300 °C oder niedriger und
    einen Warmwalzschritt, bei dem das Warmwalzen des Stahlmaterials mit einer Fertigwalztemperatur von 800 °C oder höher und einer Gesamtwalzreduktion von 20 % oder mehr durchgeführt wird.
  3. Verfahren zur Herstellung von Stahl mit hohem Mn-Gehalt gemäß Anspruch 2, das ferner umfasst:
    einen zweiten Warmwalzschritt, bei dem das Warmwalzen des Stahlmaterials mit einer Fertigwalztemperatur von 700 °C oder mehr und weniger als 950 °C durchgeführt wird,
    wobei nach dem zweiten Warmwalzschritt das Stahlmaterial einer Abkühlungsbehandlung mit einer durchschnittlichen Abkühlungsrate von 1,0 °C/s oder mehr in einem Bereich von einer Temperatur bei oder über der Walzendtemperatur -100 °C bis zu einer Temperatur im Bereich von 300 °C bis 650 °C unterzogen wird.
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WO2020027211A1 (ja) * 2018-08-03 2020-02-06 Ｊｆｅスチール株式会社 高Ｍｎ鋼およびその製造方法
KR20220030292A (ko) * 2019-08-21 2022-03-10 제이에프이 스틸 가부시키가이샤 강 및 그 제조 방법
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EP4239097A1 (de) * 2020-12-17 2023-09-06 JFE Steel Corporation Untergetauchter lichtbogenschweissdraht und verfahren zur herstellung einer schweissverbindung damit
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