CA2625564A1 - Method for producing hot strip with a multiphase structure - Google Patents
Method for producing hot strip with a multiphase structure Download PDFInfo
- Publication number
- CA2625564A1 CA2625564A1 CA002625564A CA2625564A CA2625564A1 CA 2625564 A1 CA2625564 A1 CA 2625564A1 CA 002625564 A CA002625564 A CA 002625564A CA 2625564 A CA2625564 A CA 2625564A CA 2625564 A1 CA2625564 A1 CA 2625564A1
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- Prior art keywords
- cooling
- hot
- austenite
- rolled strip
- ferrite
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- Abandoned
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- 238000004519 manufacturing process Methods 0.000 title claims abstract description 17
- 238000001816 cooling Methods 0.000 claims abstract description 93
- 229910001566 austenite Inorganic materials 0.000 claims abstract description 29
- 238000005096 rolling process Methods 0.000 claims abstract description 23
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 21
- 239000010959 steel Substances 0.000 claims abstract description 21
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 21
- 230000009466 transformation Effects 0.000 claims abstract description 18
- 229910001563 bainite Inorganic materials 0.000 claims abstract description 14
- 238000000034 method Methods 0.000 claims abstract description 12
- 229910000794 TRIP steel Inorganic materials 0.000 claims abstract description 10
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 9
- 239000000203 mixture Substances 0.000 claims abstract description 9
- 239000000126 substance Substances 0.000 claims abstract description 8
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 7
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 26
- 230000000717 retained effect Effects 0.000 claims description 8
- 239000007921 spray Substances 0.000 claims description 7
- 238000009749 continuous casting Methods 0.000 claims description 5
- 229910000734 martensite Inorganic materials 0.000 description 10
- 229910000885 Dual-phase steel Inorganic materials 0.000 description 6
- 238000000137 annealing Methods 0.000 description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000005275 alloying Methods 0.000 description 2
- 238000005266 casting Methods 0.000 description 2
- 238000009776 industrial production Methods 0.000 description 2
- 238000009434 installation Methods 0.000 description 2
- 229910001562 pearlite Inorganic materials 0.000 description 2
- 238000002791 soaking Methods 0.000 description 2
- 230000006978 adaptation Effects 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000009529 body temperature measurement Methods 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 239000000161 steel melt Substances 0.000 description 1
- 238000005482 strain hardening Methods 0.000 description 1
Classifications
-
- 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
- C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
-
- 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
- C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
- C21D8/041—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing involving a particular fabrication or treatment of ingot or slab
- C21D8/0415—Rapid solidification; Thin strip casting
-
- 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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
- C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
- C21D1/20—Isothermal quenching, e.g. bainitic hardening
-
- 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
- C21D8/021—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular fabrication or treatment of ingot or slab
- C21D8/0215—Rapid solidification; Thin strip casting
-
- 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
- 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
- C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
- C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
- C21D8/0426—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
- C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
- C21D8/0447—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment
- C21D8/0463—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment following hot rolling
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/001—Austenite
-
- 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
- C21D2211/002—Bainite
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Sheet Steel (AREA)
- Metal Rolling (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
For the production of hot strip referred to as TRIP steel (transformation induced plasticity), with a multiphase structure and with outstandingly good deformation properties along with high strengths, from the hot-rolled state, the invention proposes a method which is carried out with a predetermined chemical composition of the steel grade used within the limits 0.12 - 0.25% C;
0.05 - 1.8% Si; 1.0 -2.0% Mn; the remainder Fe and customary accompanying elements and with a combined rolling and cooling strategy in such a way that a structure comprising 40 - 70% ferrite, 15 - 45% bainite and 5 - 20% residual austenite is obtained, wherein the finish rolling of the hot strip (7) is performed to set a very fine austenite grain (d < 8 ~m) in the final forming operation (6') at temperatures between 770 and 830~C just above Ar3 in the region of the metastable austenite, and a controlled two-stage cooling (10, 11, 12) is carried out after the last rolling stand (6') of the hot strip (7) to a strip temperature in the range of bainite formation of 320 - 480~C, with a holding time of about 650 - 730~C, the beginning of which is determined by the entry of the cooling curve into the ferrite region and the duration of which is determined by the transformation of the austenite into at least 40%
ferrite.
0.05 - 1.8% Si; 1.0 -2.0% Mn; the remainder Fe and customary accompanying elements and with a combined rolling and cooling strategy in such a way that a structure comprising 40 - 70% ferrite, 15 - 45% bainite and 5 - 20% residual austenite is obtained, wherein the finish rolling of the hot strip (7) is performed to set a very fine austenite grain (d < 8 ~m) in the final forming operation (6') at temperatures between 770 and 830~C just above Ar3 in the region of the metastable austenite, and a controlled two-stage cooling (10, 11, 12) is carried out after the last rolling stand (6') of the hot strip (7) to a strip temperature in the range of bainite formation of 320 - 480~C, with a holding time of about 650 - 730~C, the beginning of which is determined by the entry of the cooling curve into the ferrite region and the duration of which is determined by the transformation of the austenite into at least 40%
ferrite.
Description
METHOD FOR PRODUCING HOT STRIP WITH A
MULTIPHASE STRUCTURE
The invention concerns a method for producing hot-rolled strip that consists of TRIP (transformation-induced plasticity) steel with a multiphase microstructure and with both high strength values and outstanding deformation properties, where the TRIP steel strip is produced from the hot-rolled state by controlled cooling after the last rolling stand.
The adjustment of the microstructure is a complex matter in TRIP steels, since, besides ferrite and bainite, a third phase is present in the form of retained austenite or, after a subsequent deformation, in the form of martensite. TRIP
steels are now usually produced in a two-stage heat cycle.
The starting material is hot-rolled or cold-rolled strip, in which an approximately 50% a- 50% y initial microstructure is adjusted. Due to the higher solubility of carbon in austenite, austenite has a higher carbon concentration. After the annealing treatment, rapid cooling is carried out past the ferrite and pearlite range into the bainite range, in which isothermal conditions are maintained for some time. The austenite is partially transformed to bainite, and at the same time the remainder of the austenite becomes further enriched with carbon. In this way, the martensite start temperature Ms is reduced to values below ambient temperature, and consequently the retained austenite also continues to exist at ambient temperature. The final microstructure consists of 40-70% ferrite, 15-40% bainite, and 5-20% retained austenite.
The special effect of TRIP steels is the transformation of the metastable retained austenite to martensite when external plastic deformation occurs. The transformation of the austenite to martensite is accompanied by an increase in volume, which is supported not just by the austenite alone but rather by the surrounding microstructural components as well.
The ferritic matrix is plasticized, which in turn results in greater strain hardening and leads overall to higher plastic elongations. Steels produced in this way have an extraordinary combination of high strength and high ductility, which makes them suitable especially for use in the automobile industry.
The process management described above which is presently used mostly for the industrial production of TRIP steels, is complicated and expensive due to the additional annealing and cooling treatment after the rolling operation, which is the reason that attempts have been made to produce these TRIP
steels directly as hot-rolled strip in industrial production plants for hot strip production. For example, EP 1 396 549 Al discloses a method for producing pearlite-free hot-rolled steel strip with TRIP properties in a continuously running operational process, in which a steel melt, which contains, in addition to iron and unavoidable impurities, 0.06-0.3% C; 0.1-3.0% Si; 0.3-1.1% Mn (with the total amount of Si and Mn being 1.5-3.5%); 0.005-0.15% of at least one of the elements Ti or Nb as an essential component; and optionally one or more of the following elements: max. 0.8% Cr; max. 0.8% Cu; and max.
1.0% Ni, is cast into thin slabs, which are annealed at 1,000-1,200 C for an annealing time of 10-60 minutes in an annealing furnace, starting from a run-in temperature of 850-1,050 C.
After descaling, the thin slabs are finish hot rolled in the range of 750-1,000 C and then cooled to a coiling temperature of 300-530 C. The controlled cooling is carried out in two stages at a cooling rate of the first stage of at least 150 K/s with a cooling interruption of 4-8 seconds.
Alternatively, it is proposed that the controlled cooling be carried out continuously at a cooling rate of 10-70 K/s without a holding interruption. Finally, a third possibility is proposed, in which the cooling is controlled in such a way that the hot rolled strip is cooled in a first phase to a temperature of about 80 C above coiling temperature within 1-7 seconds and is then cooled to coiling temperature by air cooling. Besides the prescribed process management, the presence of Ti and/or Nb is important, since these elements remain in solution until the start of the hot rolling and, upon their subsequent precipitation, improve, among other properties, the grain fineness of the hot-rolled strip and increase the retained austenite content and its stability.
Using this prior art as a point of departure, the objective of the invention is to specify a method which allows simpler and more economical production of TRIP steels in existing plants and in which an annealing treatment and the addition of alloying elements that are otherwise not absolutely necessary can be eliminated.
This objective is achieved by the characterizing features of Claim 1, according to which the production of the hot-rolled strip in a thin-slab continuous casting and rolling plant (CSP plant) with a predetermined chemical composition of the steel grade that is used within the following limits:
0.12-0.25% C; 0.05-1.8% Si; 1.0-2.0% Mn; the remainder Fe and customary accompanying elements is carried out with a combined rolling and cooling strategy in such a way that a microstructure is obtained which consists of 40-70% ferrite, 15-45% bainite, and 5-20% retained austenite, such that = the finish rolling of the hot-rolled strip for adjusting a very fine austenite grain (d < 8 pm) during the last deformation is carried out at temperatures of 770-830 C, just above Ar3 in the range of metastable austenite, and = immediately after the last rolling stand, a controlled two-stage cooling of the hot-rolled strip to a strip temperature in the range of bainite formation of 320-480 C is carried out with a holding time at about 650-730 C, whose start is determined by the entry of the cooling curve into the ferrite range and whose duration is determined by the transformation of the austenite to at least 40% ferrite.
In contrast to the usual procedure that was described earlier, in accordance with the invention, in an austenitically finish rolled hot strip, the typical microstructure for a TRIP steel is adjusted immediately after the last rolling stand by a two-stage cooling operation in the cooling line. In this connection, the adjustment of the appropriate microstructure requires extensive process know-how as well as very exact maintenance of the necessary process parameters. Due to the narrow tolerance range for the production of TRIP steels on hot wide strip mills, since the introduction of thin-slab continuous casting and rolling technology, a plant configuration has been available which provides much better conditions for the direct production of TRIP steels than hot-rolled strip, compared to conventional hot-rolled strip mills. Due to the high degree of uniformity of temperature over the thickness, width, and length of the strip, TRIP steels with constant mechanical properties can be reproducibly produced in this way. Due to the short length of the conventional cooling lines used in this process in existing continuous casting and rolling mills, the production of hot-rolled strip with TRIP microstructure is possible only with a special rolling and cooling strategy.
The rolling strategy of the invention is used for adjusting a very fine austenite grain (d < 8 pm) during the last deformation, which has an accelerating effect on the ferrite transformation in the subsequent cooling line.
Therefore, the finish rolling of the strip takes place at temperatures of 770-830 C, just above Ar3 in the range of metastable austenite.
The successful implementation of the cooling strategy makes it absolutely necessary to maintain certain limits of chemical composition in order to realize the desired degree of transformation within the short total cooling time that is available. Therefore, the chemical analysis proposed for the production of TRIP steels varies within the following limits:
0.12-0.25% C, 0.05-1.8% Si, 1.0-2.0% Mn, the remainder Fe and customary accompanying elements.
The cooling strategy involves two-stage cooling with the option of using different cooling rates in each stage. The start of the holding time at temperatures of 650-730 C is determined by the entry of the cooling curve into the ferrite range. The desired transformation of the austenite to at least 40% ferrite then takes place during the following brief cooling interruption. The holding time is then immediately followed by the second cooling stage, in which the hot-rolled strip is cooled to a temperature of 320-480 C. The transformation of austenite to at least 15% bainite takes place at this temperature.
In addition to the use of a short holding time, the cooling strategy is determined by an exactly defined, predetermined cooling rate for the two cooling stages. This cooling rate is V = 30-150 K/s and preferably V = 50-90 K/s, depending on the geometry of the hot-rolled strip and the chemical composition of the steel grade that is used. In regard to these cooling rates, it should be noted that a cooling rate less than 30 K/s is not possible due to the small amount of time that is available in the conventional cooling line of a continuous casting and rolling plant, and that cooling rates greater than 150 K/s likewise cannot be realized in cooling lines of this type, which consist of a succession of water cooling zones spaced a certain distance apart.
The hot-rolled strip produced with the method of the invention with TRIP steel properties for different strength levels with an elastic limit tensile strength ratio Rpo.2 / Rm in the range of 0.45-0.75 has the following combinations of tensile strength Rm and percentage elongation after fracture A:
Rm = 600-700 MPa => A > 25%
Rm = 700-800 MPa => A > 23%
Rm = 800-900 MPa ~ A > 21%
Rn, = 900-1,000 MPa ~ A > 18%
Rm > 1,000 MPa ~ A > 15%
Further details and advantages of the invention are explained in greater detail below with reference to the specific embodiment of the invention illustrated in the accompanying drawings.
-- Figure 1 shows a CSP plant.
- Figure 2 shows a modified cooling line of the CSP
plant.
-- Figure 3 shows cooling curves for a dual-phase steel and a TRIP steel in a TTT diagram.
Figure 1 shows the layout of a conventional CSP plant 1 schematically. In the illustrated example, it comprises the following main components in the direction of conveyance (from left to right in the drawing): the casting installation with two strands 2, the strand guides 3, the soaking furnaces 4 with a furnace transverse conveyor 5, a multiple-stand rolling mill 6, the cooling line 10, and coilers 8.
Figure 2 shows a modified cooling line 10 of a CSP plant 1, which is necessary for carrying out cooling in accordance with the invention and is already known from EP 1 108 072 Bl, which describes a method for producing dual-phase steel. This modified cooling line 10 of the CSP plant 1 is installed downstream of the last finish rolling stand 61. The cooling line 10 has several successive water cooling zones 111_7, 12 that are spaced a certain distance apart and can be automatically controlled. The water cooling zones 111_7, 12 are equipped with water spray heads 13, which evenly spray the upper and lower surfaces of the hot-rolled strip 7 with a specific amount of water. The positioning of the water cooling zones 111_7, 12 within the cooling line 10, their number, their spacing, and the number of water spray heads 13 per water cooling zone 111_7, 12 are chosen in such a way that the desired cooling rate of the two cooling stages can be variably adjusted in advance in order to achieve optimum adaptation of the water cooling zones 111_7, 12 to the cooling conditions that are to be adjusted. Automatic control of the amount of water sprayed thus makes it possible, even during the cooling operation, to make any necessary change in the cooling rate.
An additional water cooling zone 12 is installed a greater distance from the last water cooling zone 117 of the first cooling stage than the distance between the individual zones of water cooling zones 111_7. The second cooling stage is carried out in this additional water cooling zone 12. In this water cooling zone 12, in contrast to the water cooling zones 111_7 of the first cooling stage, there is a significantly larger number of water spray heads 13 in order to carry out forced intensive cooling over a shorter distance.
The distance between the last water cooling zone 117 of the first cooling stage and the water cooling zone 12 of the second cooling stage is chosen sufficiently large to obtain the holding time necessary to achieve transformation of the austenite to at least 40% ferrite, as prescribed by the invention, at the predetermined strip speed.
Figure 3 shows a TTT diagram with the transformation lines for ferrite, pearlite, and bainite and with the temperature lines (20, 21, 22, 24) for Ac3, Acl, and Ms.
Horizontal shift arrows 27 for the transformation lines and vertical shift arrows 28 for the temperature lines show the effect of existing or added alloying elements on the position of these transformation and temperature lines in the TTT
diagram. The cooling curve 25 for the production of a dual-phase steel and the cooling curve 26 for the production of a TRIP steel in accordance with the invention are plotted in this TTT diagram as examples. At approximately the same start temperature (above Ac3) at the start of cooling and approximately the same holding time temperature (above Acl), a significantly different microstructural composition is obtained due to the different courses of the cooling and the different compositions of the initial steels. According to the plotted cooling curve 25 for the dual-phase steel, the cooling curve 25 passes only into the ferrite range and ends below the martensite start temperature line 22, which is well above room temperature 23, so that, as desired, a dual microstructure that consists only of ferrite and martensite is obtained. On the other hand, the cooling curve 26 for the production of a TRIP steel in accordance with the invention passes first through the ferrite range and then through the bainite range and ends above the martensite start temperature line 24, which is now below room temperature 23, so that transformation to martensite during cooling does not take place, and, in accordance with the invention, a microstructure is obtained that consists of ferrite, bainite, and some retained austenite.
LIST OF REFERENCE NUMBERS
1 CSP plant 2 casting installation with two strands 3 strand guide 4 soaking furnace furnace transverse conveyor 6 multiple-stand rolling mill 6 6' last rolling stand 7 hot-rolled strip 8 coiler 9 temperature measurement cooling line 111_7 water cooling zones 12 water cooling zone 13 water spray heads Ac3 temperature line 21 Acl temperature line 22 martensite start temperature line for a dual-phase steel 23 room temperature line 24 martensite start temperature line for a TRIP steel cooling curve for a dual-phase steel 26 cooling curve for a TRIP steel 27 horizontal shift arrows of the transformation lines 28 vertical shift of the temperature lines
MULTIPHASE STRUCTURE
The invention concerns a method for producing hot-rolled strip that consists of TRIP (transformation-induced plasticity) steel with a multiphase microstructure and with both high strength values and outstanding deformation properties, where the TRIP steel strip is produced from the hot-rolled state by controlled cooling after the last rolling stand.
The adjustment of the microstructure is a complex matter in TRIP steels, since, besides ferrite and bainite, a third phase is present in the form of retained austenite or, after a subsequent deformation, in the form of martensite. TRIP
steels are now usually produced in a two-stage heat cycle.
The starting material is hot-rolled or cold-rolled strip, in which an approximately 50% a- 50% y initial microstructure is adjusted. Due to the higher solubility of carbon in austenite, austenite has a higher carbon concentration. After the annealing treatment, rapid cooling is carried out past the ferrite and pearlite range into the bainite range, in which isothermal conditions are maintained for some time. The austenite is partially transformed to bainite, and at the same time the remainder of the austenite becomes further enriched with carbon. In this way, the martensite start temperature Ms is reduced to values below ambient temperature, and consequently the retained austenite also continues to exist at ambient temperature. The final microstructure consists of 40-70% ferrite, 15-40% bainite, and 5-20% retained austenite.
The special effect of TRIP steels is the transformation of the metastable retained austenite to martensite when external plastic deformation occurs. The transformation of the austenite to martensite is accompanied by an increase in volume, which is supported not just by the austenite alone but rather by the surrounding microstructural components as well.
The ferritic matrix is plasticized, which in turn results in greater strain hardening and leads overall to higher plastic elongations. Steels produced in this way have an extraordinary combination of high strength and high ductility, which makes them suitable especially for use in the automobile industry.
The process management described above which is presently used mostly for the industrial production of TRIP steels, is complicated and expensive due to the additional annealing and cooling treatment after the rolling operation, which is the reason that attempts have been made to produce these TRIP
steels directly as hot-rolled strip in industrial production plants for hot strip production. For example, EP 1 396 549 Al discloses a method for producing pearlite-free hot-rolled steel strip with TRIP properties in a continuously running operational process, in which a steel melt, which contains, in addition to iron and unavoidable impurities, 0.06-0.3% C; 0.1-3.0% Si; 0.3-1.1% Mn (with the total amount of Si and Mn being 1.5-3.5%); 0.005-0.15% of at least one of the elements Ti or Nb as an essential component; and optionally one or more of the following elements: max. 0.8% Cr; max. 0.8% Cu; and max.
1.0% Ni, is cast into thin slabs, which are annealed at 1,000-1,200 C for an annealing time of 10-60 minutes in an annealing furnace, starting from a run-in temperature of 850-1,050 C.
After descaling, the thin slabs are finish hot rolled in the range of 750-1,000 C and then cooled to a coiling temperature of 300-530 C. The controlled cooling is carried out in two stages at a cooling rate of the first stage of at least 150 K/s with a cooling interruption of 4-8 seconds.
Alternatively, it is proposed that the controlled cooling be carried out continuously at a cooling rate of 10-70 K/s without a holding interruption. Finally, a third possibility is proposed, in which the cooling is controlled in such a way that the hot rolled strip is cooled in a first phase to a temperature of about 80 C above coiling temperature within 1-7 seconds and is then cooled to coiling temperature by air cooling. Besides the prescribed process management, the presence of Ti and/or Nb is important, since these elements remain in solution until the start of the hot rolling and, upon their subsequent precipitation, improve, among other properties, the grain fineness of the hot-rolled strip and increase the retained austenite content and its stability.
Using this prior art as a point of departure, the objective of the invention is to specify a method which allows simpler and more economical production of TRIP steels in existing plants and in which an annealing treatment and the addition of alloying elements that are otherwise not absolutely necessary can be eliminated.
This objective is achieved by the characterizing features of Claim 1, according to which the production of the hot-rolled strip in a thin-slab continuous casting and rolling plant (CSP plant) with a predetermined chemical composition of the steel grade that is used within the following limits:
0.12-0.25% C; 0.05-1.8% Si; 1.0-2.0% Mn; the remainder Fe and customary accompanying elements is carried out with a combined rolling and cooling strategy in such a way that a microstructure is obtained which consists of 40-70% ferrite, 15-45% bainite, and 5-20% retained austenite, such that = the finish rolling of the hot-rolled strip for adjusting a very fine austenite grain (d < 8 pm) during the last deformation is carried out at temperatures of 770-830 C, just above Ar3 in the range of metastable austenite, and = immediately after the last rolling stand, a controlled two-stage cooling of the hot-rolled strip to a strip temperature in the range of bainite formation of 320-480 C is carried out with a holding time at about 650-730 C, whose start is determined by the entry of the cooling curve into the ferrite range and whose duration is determined by the transformation of the austenite to at least 40% ferrite.
In contrast to the usual procedure that was described earlier, in accordance with the invention, in an austenitically finish rolled hot strip, the typical microstructure for a TRIP steel is adjusted immediately after the last rolling stand by a two-stage cooling operation in the cooling line. In this connection, the adjustment of the appropriate microstructure requires extensive process know-how as well as very exact maintenance of the necessary process parameters. Due to the narrow tolerance range for the production of TRIP steels on hot wide strip mills, since the introduction of thin-slab continuous casting and rolling technology, a plant configuration has been available which provides much better conditions for the direct production of TRIP steels than hot-rolled strip, compared to conventional hot-rolled strip mills. Due to the high degree of uniformity of temperature over the thickness, width, and length of the strip, TRIP steels with constant mechanical properties can be reproducibly produced in this way. Due to the short length of the conventional cooling lines used in this process in existing continuous casting and rolling mills, the production of hot-rolled strip with TRIP microstructure is possible only with a special rolling and cooling strategy.
The rolling strategy of the invention is used for adjusting a very fine austenite grain (d < 8 pm) during the last deformation, which has an accelerating effect on the ferrite transformation in the subsequent cooling line.
Therefore, the finish rolling of the strip takes place at temperatures of 770-830 C, just above Ar3 in the range of metastable austenite.
The successful implementation of the cooling strategy makes it absolutely necessary to maintain certain limits of chemical composition in order to realize the desired degree of transformation within the short total cooling time that is available. Therefore, the chemical analysis proposed for the production of TRIP steels varies within the following limits:
0.12-0.25% C, 0.05-1.8% Si, 1.0-2.0% Mn, the remainder Fe and customary accompanying elements.
The cooling strategy involves two-stage cooling with the option of using different cooling rates in each stage. The start of the holding time at temperatures of 650-730 C is determined by the entry of the cooling curve into the ferrite range. The desired transformation of the austenite to at least 40% ferrite then takes place during the following brief cooling interruption. The holding time is then immediately followed by the second cooling stage, in which the hot-rolled strip is cooled to a temperature of 320-480 C. The transformation of austenite to at least 15% bainite takes place at this temperature.
In addition to the use of a short holding time, the cooling strategy is determined by an exactly defined, predetermined cooling rate for the two cooling stages. This cooling rate is V = 30-150 K/s and preferably V = 50-90 K/s, depending on the geometry of the hot-rolled strip and the chemical composition of the steel grade that is used. In regard to these cooling rates, it should be noted that a cooling rate less than 30 K/s is not possible due to the small amount of time that is available in the conventional cooling line of a continuous casting and rolling plant, and that cooling rates greater than 150 K/s likewise cannot be realized in cooling lines of this type, which consist of a succession of water cooling zones spaced a certain distance apart.
The hot-rolled strip produced with the method of the invention with TRIP steel properties for different strength levels with an elastic limit tensile strength ratio Rpo.2 / Rm in the range of 0.45-0.75 has the following combinations of tensile strength Rm and percentage elongation after fracture A:
Rm = 600-700 MPa => A > 25%
Rm = 700-800 MPa => A > 23%
Rm = 800-900 MPa ~ A > 21%
Rn, = 900-1,000 MPa ~ A > 18%
Rm > 1,000 MPa ~ A > 15%
Further details and advantages of the invention are explained in greater detail below with reference to the specific embodiment of the invention illustrated in the accompanying drawings.
-- Figure 1 shows a CSP plant.
- Figure 2 shows a modified cooling line of the CSP
plant.
-- Figure 3 shows cooling curves for a dual-phase steel and a TRIP steel in a TTT diagram.
Figure 1 shows the layout of a conventional CSP plant 1 schematically. In the illustrated example, it comprises the following main components in the direction of conveyance (from left to right in the drawing): the casting installation with two strands 2, the strand guides 3, the soaking furnaces 4 with a furnace transverse conveyor 5, a multiple-stand rolling mill 6, the cooling line 10, and coilers 8.
Figure 2 shows a modified cooling line 10 of a CSP plant 1, which is necessary for carrying out cooling in accordance with the invention and is already known from EP 1 108 072 Bl, which describes a method for producing dual-phase steel. This modified cooling line 10 of the CSP plant 1 is installed downstream of the last finish rolling stand 61. The cooling line 10 has several successive water cooling zones 111_7, 12 that are spaced a certain distance apart and can be automatically controlled. The water cooling zones 111_7, 12 are equipped with water spray heads 13, which evenly spray the upper and lower surfaces of the hot-rolled strip 7 with a specific amount of water. The positioning of the water cooling zones 111_7, 12 within the cooling line 10, their number, their spacing, and the number of water spray heads 13 per water cooling zone 111_7, 12 are chosen in such a way that the desired cooling rate of the two cooling stages can be variably adjusted in advance in order to achieve optimum adaptation of the water cooling zones 111_7, 12 to the cooling conditions that are to be adjusted. Automatic control of the amount of water sprayed thus makes it possible, even during the cooling operation, to make any necessary change in the cooling rate.
An additional water cooling zone 12 is installed a greater distance from the last water cooling zone 117 of the first cooling stage than the distance between the individual zones of water cooling zones 111_7. The second cooling stage is carried out in this additional water cooling zone 12. In this water cooling zone 12, in contrast to the water cooling zones 111_7 of the first cooling stage, there is a significantly larger number of water spray heads 13 in order to carry out forced intensive cooling over a shorter distance.
The distance between the last water cooling zone 117 of the first cooling stage and the water cooling zone 12 of the second cooling stage is chosen sufficiently large to obtain the holding time necessary to achieve transformation of the austenite to at least 40% ferrite, as prescribed by the invention, at the predetermined strip speed.
Figure 3 shows a TTT diagram with the transformation lines for ferrite, pearlite, and bainite and with the temperature lines (20, 21, 22, 24) for Ac3, Acl, and Ms.
Horizontal shift arrows 27 for the transformation lines and vertical shift arrows 28 for the temperature lines show the effect of existing or added alloying elements on the position of these transformation and temperature lines in the TTT
diagram. The cooling curve 25 for the production of a dual-phase steel and the cooling curve 26 for the production of a TRIP steel in accordance with the invention are plotted in this TTT diagram as examples. At approximately the same start temperature (above Ac3) at the start of cooling and approximately the same holding time temperature (above Acl), a significantly different microstructural composition is obtained due to the different courses of the cooling and the different compositions of the initial steels. According to the plotted cooling curve 25 for the dual-phase steel, the cooling curve 25 passes only into the ferrite range and ends below the martensite start temperature line 22, which is well above room temperature 23, so that, as desired, a dual microstructure that consists only of ferrite and martensite is obtained. On the other hand, the cooling curve 26 for the production of a TRIP steel in accordance with the invention passes first through the ferrite range and then through the bainite range and ends above the martensite start temperature line 24, which is now below room temperature 23, so that transformation to martensite during cooling does not take place, and, in accordance with the invention, a microstructure is obtained that consists of ferrite, bainite, and some retained austenite.
LIST OF REFERENCE NUMBERS
1 CSP plant 2 casting installation with two strands 3 strand guide 4 soaking furnace furnace transverse conveyor 6 multiple-stand rolling mill 6 6' last rolling stand 7 hot-rolled strip 8 coiler 9 temperature measurement cooling line 111_7 water cooling zones 12 water cooling zone 13 water spray heads Ac3 temperature line 21 Acl temperature line 22 martensite start temperature line for a dual-phase steel 23 room temperature line 24 martensite start temperature line for a TRIP steel cooling curve for a dual-phase steel 26 cooling curve for a TRIP steel 27 horizontal shift arrows of the transformation lines 28 vertical shift of the temperature lines
Claims (4)
1. A method for producing hot-rolled strip that consists of TRIP (transformation-induced plasticity) steel with both high strength values and outstanding deformation properties, a refinement of dual-phase steels with a predetermined chemical composition of the steel grade that is used within the following limits: 0.12-0.25% C; 0.05-1.8% Si; 1.0-2.0% Mn;
the remainder Fe and customary accompanying elements, and a multiphase microstructure which consists of 40-70% ferrite, 15-45% bainite, and 5-20% retained austenite, from the hot-rolled state in a thin-slab continuous casting and rolling plant (CSP plant) (1), wherein the finish rolling of the hot-rolled strip (7) for adjusting a very fine austenite grain (d < 8 µm) during the last deformation is carried out at temperatures of 770-830°C, just above Ar3 in the range of metastable austenite, and wherein immediately after the last rolling stand (6'), a controlled two-stage cooling of the hot-rolled strip (7) to a strip temperature in the range of bainite formation of 320-480°C is carried out with a holding time at about 650-730°C, whose start is determined by the entry of the cooling curve (26) into the ferrite range and whose duration is determined by the transformation of the austenite to at least 40% ferrite, wherein the controlled two-stage cooling of the hot-rolled strip (7) is carried out in a cooling line (10) that consists of a succession of water cooling zones (11 1-7, 12) that are spaced a certain distance apart, can be automatically controlled, and are equipped with water spray heads (13), which evenly spray the upper and lower surfaces of the hot-rolled strip 7 with a specific amount of water.
the remainder Fe and customary accompanying elements, and a multiphase microstructure which consists of 40-70% ferrite, 15-45% bainite, and 5-20% retained austenite, from the hot-rolled state in a thin-slab continuous casting and rolling plant (CSP plant) (1), wherein the finish rolling of the hot-rolled strip (7) for adjusting a very fine austenite grain (d < 8 µm) during the last deformation is carried out at temperatures of 770-830°C, just above Ar3 in the range of metastable austenite, and wherein immediately after the last rolling stand (6'), a controlled two-stage cooling of the hot-rolled strip (7) to a strip temperature in the range of bainite formation of 320-480°C is carried out with a holding time at about 650-730°C, whose start is determined by the entry of the cooling curve (26) into the ferrite range and whose duration is determined by the transformation of the austenite to at least 40% ferrite, wherein the controlled two-stage cooling of the hot-rolled strip (7) is carried out in a cooling line (10) that consists of a succession of water cooling zones (11 1-7, 12) that are spaced a certain distance apart, can be automatically controlled, and are equipped with water spray heads (13), which evenly spray the upper and lower surfaces of the hot-rolled strip 7 with a specific amount of water.
2. A method in accordance with Claim 1, wherein the cooling rate is V = 30-150 K/s, and preferably V = 50-90 K/s, depending on the chemical composition of the steel grade that is used and on the geometry of the hot-rolled strip (7).
3. A method in accordance with Claim 1, wherein the controlled two-stage cooling of the hot-rolled strip (7) is carried out in a cooling line (10) that consists of a succession of water cooling zones (11 1-7, 12) spaced a certain distance apart.
4. A hot-rolled strip (7) with TRIP steel properties, characterized by a chemical composition within the following limits: 0.12-0.25% C; 0.05-1.8% Si; 1.0-2.0% Mn; the remainder Fe and customary accompanying elements; an elastic limit tensile strength ratio R p0.2 / R m in the range of 0.45-0.75; and a possible level of strength with respect to combinations of tensile strength R m and elongation after fracture A:
R m = 600-700 MPa .fwdarw. A > 25%
R m = 700-800 MPa .fwdarw. A > 23%
R m = 800-900 MPa ~.fwdarw. A > 21%
R m = 900-1,000 MPa .fwdarw. A > 18%
R m > 1,000 MPa ~.fwdarw. A > 15%.
R m = 600-700 MPa .fwdarw. A > 25%
R m = 700-800 MPa .fwdarw. A > 23%
R m = 800-900 MPa ~.fwdarw. A > 21%
R m = 900-1,000 MPa .fwdarw. A > 18%
R m > 1,000 MPa ~.fwdarw. A > 15%.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE102005051052A DE102005051052A1 (en) | 2005-10-25 | 2005-10-25 | Process for the production of hot strip with multiphase structure |
| DE102005051052.3 | 2005-10-25 | ||
| PCT/EP2006/009755 WO2007048497A1 (en) | 2005-10-25 | 2006-10-10 | Method for producing hot strip with a multiphase structure |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2625564A1 true CA2625564A1 (en) | 2007-05-03 |
Family
ID=37459318
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002625564A Abandoned CA2625564A1 (en) | 2005-10-25 | 2006-10-10 | Method for producing hot strip with a multiphase structure |
Country Status (14)
| Country | Link |
|---|---|
| US (1) | US20090214377A1 (en) |
| EP (1) | EP1954842A1 (en) |
| JP (1) | JP5130221B2 (en) |
| KR (1) | KR20080063307A (en) |
| CN (1) | CN101297049B (en) |
| AU (1) | AU2006308245B2 (en) |
| BR (1) | BRPI0617753A2 (en) |
| CA (1) | CA2625564A1 (en) |
| DE (1) | DE102005051052A1 (en) |
| RU (1) | RU2398028C2 (en) |
| TW (1) | TW200724690A (en) |
| UA (1) | UA90436C2 (en) |
| WO (1) | WO2007048497A1 (en) |
| ZA (1) | ZA200802524B (en) |
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| KR101181028B1 (en) * | 2007-08-01 | 2012-09-07 | 가부시키가이샤 고베 세이코쇼 | High-strength steel sheet excellent in bendability and fatigue strength |
| DE102010050647A1 (en) * | 2009-11-21 | 2011-05-26 | Sms Siemag Aktiengesellschaft | Plant and method for casting and rolling metal |
| CN102133579B (en) * | 2010-01-27 | 2013-05-01 | 中国钢铁股份有限公司 | Steel blank hot rolling process reducing generation of etch pit |
| US9896736B2 (en) | 2010-10-22 | 2018-02-20 | Nippon Steel & Sumitomo Metal Corporation | Method for manufacturing hot stamped body having vertical wall and hot stamped body having vertical wall |
| WO2012053642A1 (en) | 2010-10-22 | 2012-04-26 | 新日本製鐵株式会社 | Method for manufacturing hot stamped body having vertical wall, and hot stamped body having vertical wall |
| CN103314120B (en) | 2010-10-22 | 2014-11-05 | 新日铁住金株式会社 | Process for producing hot stamp molded article, and hot stamp molded article |
| WO2012064129A2 (en) * | 2010-11-10 | 2012-05-18 | (주)포스코 | Method for manufacturing high-strength cold-rolled/hot-rolled trip steel having a tensile strength of 590 mpa grade, superior workability, and low mechanical-property deviation |
| MX363038B (en) * | 2011-07-06 | 2019-03-01 | Nippon Steel & Sumitomo Metal Corp | Method for producing cold-rolled steel sheet. |
| MX2014002922A (en) * | 2011-09-13 | 2014-05-21 | Tata Steel Ijmuiden Bv | High strength hot dip galvanised steel strip. |
| CZ2011612A3 (en) * | 2011-09-30 | 2013-07-10 | Západoceská Univerzita V Plzni | Method of achieving TRIP microstructure in steels by deformation heat |
| CN104169444B (en) * | 2012-03-30 | 2017-03-29 | 奥钢联钢铁有限责任公司 | The method of high strength cold rolled steel plate and this steel plate of production |
| CN102586562B (en) * | 2012-03-30 | 2013-08-21 | 河北钢铁集团有限公司 | Production process for shock-proof disaster-relieving hot rolled transformation-induced plasticity (TRIP) steel plates |
| CZ304832B6 (en) * | 2013-04-13 | 2014-11-26 | Západočeská Univerzita V Plzni | Heat treatment process of TRIP steel half-finished products |
| CN103898404B (en) * | 2014-04-28 | 2015-12-09 | 莱芜钢铁集团有限公司 | A kind of vanadium micro-alloying hot-rolled transformation induction plasticity steel and preparation method |
| CN104233092B (en) * | 2014-09-15 | 2016-12-07 | 首钢总公司 | A kind of analysis of producing hot rolled TRIP and preparation method thereof |
| WO2016132542A1 (en) * | 2015-02-20 | 2016-08-25 | 新日鐵住金株式会社 | Hot-rolled steel sheet |
| CN105063309B (en) * | 2015-07-31 | 2017-11-17 | 首钢总公司 | A kind of method for improving low-carbon microalloy hardness of steel |
| WO2017109538A1 (en) | 2015-12-21 | 2017-06-29 | Arcelormittal | Method for producing a steel sheet having improved strength, ductility and formability |
| WO2017109540A1 (en) * | 2015-12-21 | 2017-06-29 | Arcelormittal | Method for producing a high strength steel sheet having improved ductility and formability, and obtained steel sheet |
| CN106048176B (en) * | 2016-06-06 | 2019-01-08 | 日照宝华新材料有限公司 | Method based on ESP bar strip continuous casting and rolling flow path production low-carbon hot-rolling TRIP steel |
| CN105821190B (en) * | 2016-06-06 | 2019-01-08 | 日照宝华新材料有限公司 | Method based on carbon analysis of producing hot rolled TRIP in the production of ESP bar strip continuous casting and rolling flow path |
| BR112019000766B8 (en) | 2016-08-05 | 2023-03-14 | Nippon Steel & Sumitomo Metal Corp | STEEL SHEET |
| KR101917448B1 (en) * | 2016-12-20 | 2018-11-09 | 주식회사 포스코 | High strength hot-rolled steel sheet having excellent weldability and ductility, and mathod for manufacturing same |
| CN108531811B (en) * | 2018-05-16 | 2020-05-01 | 东北大学 | Preparation method of cast-rolled TRIP steel thin strip |
| RU2689348C1 (en) * | 2018-06-26 | 2019-05-27 | Публичное акционерное общество "Северсталь" (ПАО "Северсталь") | Method for production of hot-rolled high-strength rolled metal |
| AT525283B1 (en) * | 2021-10-29 | 2023-02-15 | Primetals Technologies Austria GmbH | Method for producing a dual-phase steel strip in a combined casting and rolling plant, a dual-phase steel strip produced using the method and a combined casting and rolling facility |
| CN114645187A (en) * | 2022-01-29 | 2022-06-21 | 安阳钢铁股份有限公司 | Non-quenched and tempered 950 MPa-grade high-strength strapping steel and production method thereof |
| CN115976396B (en) * | 2022-12-30 | 2024-04-30 | 包头钢铁（集团）有限责任公司 | High-strength corrosion-resistant hot rolled steel strip Q550NQR1 for container and production method thereof |
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| EP0295500B2 (en) * | 1987-06-03 | 2003-09-10 | Nippon Steel Corporation | Hot rolled steel sheet with a high strength and a distinguished formability |
| US6190469B1 (en) * | 1996-11-05 | 2001-02-20 | Pohang Iron & Steel Co., Ltd. | Method for manufacturing high strength and high formability hot-rolled transformation induced plasticity steel containing copper |
| BE1011149A3 (en) * | 1997-05-12 | 1999-05-04 | Cockerill Rech & Dev | Steel ductile high elastic limit and method for manufacturing steel. |
| JP2000087141A (en) * | 1998-09-10 | 2000-03-28 | Nkk Corp | Production of thin high tensile hot rolled steel strip containing residual austenite |
| JP3081197B1 (en) * | 1999-02-17 | 2000-08-28 | 株式会社神戸製鋼所 | High strength steel sheet with excellent workability and fatigue properties |
| DE19911287C1 (en) * | 1999-03-13 | 2000-08-31 | Thyssenkrupp Stahl Ag | Process for producing a hot strip |
| FR2796966B1 (en) * | 1999-07-30 | 2001-09-21 | Ugine Sa | PROCESS FOR THE MANUFACTURE OF THIN STRIP OF TRIP-TYPE STEEL AND THIN STRIP THUS OBTAINED |
| FR2801061B1 (en) * | 1999-11-12 | 2001-12-14 | Lorraine Laminage | PROCESS FOR PRODUCING A VERY HIGH STRENGTH HOT LAMINATED SHEET METAL FOR USE IN FORMING AND IN PARTICULAR FOR STAMPING |
| CA2387322C (en) * | 2001-06-06 | 2008-09-30 | Kawasaki Steel Corporation | High-ductility steel sheet excellent in press formability and strain age hardenability, and method for manufacturing the same |
| JP3764411B2 (en) * | 2002-08-20 | 2006-04-05 | 株式会社神戸製鋼所 | Composite steel sheet with excellent bake hardenability |
-
2005
- 2005-10-25 DE DE102005051052A patent/DE102005051052A1/en not_active Withdrawn
-
2006
- 2006-10-10 WO PCT/EP2006/009755 patent/WO2007048497A1/en active Application Filing
- 2006-10-10 UA UAA200807183A patent/UA90436C2/en unknown
- 2006-10-10 US US12/083,822 patent/US20090214377A1/en not_active Abandoned
- 2006-10-10 CA CA002625564A patent/CA2625564A1/en not_active Abandoned
- 2006-10-10 KR KR1020087008724A patent/KR20080063307A/en not_active Application Discontinuation
- 2006-10-10 JP JP2008536963A patent/JP5130221B2/en not_active Expired - Fee Related
- 2006-10-10 BR BRPI0617753-0A patent/BRPI0617753A2/en not_active IP Right Cessation
- 2006-10-10 RU RU2008120667/02A patent/RU2398028C2/en not_active IP Right Cessation
- 2006-10-10 EP EP06806132A patent/EP1954842A1/en not_active Withdrawn
- 2006-10-10 AU AU2006308245A patent/AU2006308245B2/en not_active Ceased
- 2006-10-10 CN CN2006800397062A patent/CN101297049B/en not_active Expired - Fee Related
- 2006-10-11 TW TW095137306A patent/TW200724690A/en unknown
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Also Published As
| Publication number | Publication date |
|---|---|
| AU2006308245B2 (en) | 2010-09-30 |
| CN101297049B (en) | 2012-01-11 |
| EP1954842A1 (en) | 2008-08-13 |
| AU2006308245A1 (en) | 2007-05-03 |
| TW200724690A (en) | 2007-07-01 |
| DE102005051052A1 (en) | 2007-04-26 |
| JP5130221B2 (en) | 2013-01-30 |
| JP2009512783A (en) | 2009-03-26 |
| UA90436C2 (en) | 2010-04-26 |
| US20090214377A1 (en) | 2009-08-27 |
| KR20080063307A (en) | 2008-07-03 |
| AU2006308245A2 (en) | 2008-06-19 |
| RU2398028C2 (en) | 2010-08-27 |
| ZA200802524B (en) | 2009-06-24 |
| WO2007048497A1 (en) | 2007-05-03 |
| CN101297049A (en) | 2008-10-29 |
| RU2008120667A (en) | 2009-12-10 |
| BRPI0617753A2 (en) | 2011-08-02 |
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