EP0301228A1 - Process for producing hot-rolled strip - Google Patents
Process for producing hot-rolled strip Download PDFInfo
- Publication number
- EP0301228A1 EP0301228A1 EP88109771A EP88109771A EP0301228A1 EP 0301228 A1 EP0301228 A1 EP 0301228A1 EP 88109771 A EP88109771 A EP 88109771A EP 88109771 A EP88109771 A EP 88109771A EP 0301228 A1 EP0301228 A1 EP 0301228A1
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- EP
- European Patent Office
- Prior art keywords
- hot
- rolling
- hot strip
- coil
- strip
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- 238000000034 method Methods 0.000 title claims abstract description 30
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 39
- 239000010959 steel Substances 0.000 claims abstract description 39
- 238000001816 cooling Methods 0.000 claims abstract description 26
- 238000006243 chemical reaction Methods 0.000 claims abstract description 23
- 238000005098 hot rolling Methods 0.000 claims abstract description 12
- 229910052799 carbon Inorganic materials 0.000 claims description 22
- 238000005096 rolling process Methods 0.000 claims description 15
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 14
- 238000004519 manufacturing process Methods 0.000 claims description 11
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 5
- 229910052757 nitrogen Inorganic materials 0.000 claims description 4
- 229910052726 zirconium Inorganic materials 0.000 claims description 4
- 229910000851 Alloy steel Inorganic materials 0.000 claims description 3
- 229910052796 boron Inorganic materials 0.000 claims description 3
- 229910052804 chromium Inorganic materials 0.000 claims description 3
- 229910052742 iron Inorganic materials 0.000 claims description 3
- 229910052748 manganese Inorganic materials 0.000 claims description 3
- 229910052750 molybdenum Inorganic materials 0.000 claims description 3
- 229910052759 nickel Inorganic materials 0.000 claims description 3
- 229910052717 sulfur Inorganic materials 0.000 claims description 3
- 229910052714 tellurium Inorganic materials 0.000 claims description 3
- 229910052720 vanadium Inorganic materials 0.000 claims description 3
- 239000012535 impurity Substances 0.000 claims description 2
- 229910052698 phosphorus Inorganic materials 0.000 claims description 2
- 239000000956 alloy Substances 0.000 abstract 1
- 229910045601 alloy Inorganic materials 0.000 abstract 1
- 229910001562 pearlite Inorganic materials 0.000 description 19
- 230000015572 biosynthetic process Effects 0.000 description 9
- 229910000859 α-Fe Inorganic materials 0.000 description 6
- 241000446313 Lamella Species 0.000 description 5
- 238000004804 winding Methods 0.000 description 5
- 230000009466 transformation Effects 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 238000005452 bending Methods 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 238000005496 tempering Methods 0.000 description 2
- 238000005275 alloying Methods 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 239000000498 cooling water Substances 0.000 description 1
- 238000011033 desalting Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 229910052740 iodine Inorganic materials 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 125000000101 thioether group Chemical group 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
- C21D8/0221—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
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
- C21D9/54—Furnaces for treating strips or wire
- C21D9/68—Furnace coilers; Hot coilers
Definitions
- the invention relates to a method for producing hot strip from unalloyed or low-alloy steel with carbon contents in the range from 0.3-0.9% with the steps - austenitizing a slab, - hot rolling the heated slab, Cooling the belt and -Coiling the tape into a coil.
- Hot strip from these steels is used for direct further processing by forming or for the production of cold-rolled strip. Finished parts made from these steels are usually heat-treated by hardening and tempering to set the required strength and hardness values.
- the tensile strength of hot strip made from these steels is high due to the carbon content. It depends on the pearlite content in the structure and on the formation of pearlite. In the case of steels with carbon contents between 0.4 and 0.7%, an increase in the pearlite content in the structure of 50-100% causes an increase in the tensile strength of 600 to 1100 N / mm2 (Journal of the Iron and Steel Institute, 205, 1967, page 653/664). An increase in the pearlite content in the structure with a reduction in the amount of ferrite results if the cooling rate of the strip is high in the region of the ⁇ / ⁇ conversion.
- Cooling rate in the area of the ⁇ / ⁇ conversion is the lamellar spacing of the pearlitic structure and thus also the strength.
- increasing the cooling rate from 5 to 30 K / s reduces the lamellar spacing of the pearlite and thereby increases the tensile strength from 950 to 1300 N / mm2 (Atlas for heat treatment of Staele, Verlag Stahl-Eisen, Duesseldorf, 1961, Plate II - 101 E and Mem.Sci.Revue de Metallurgie 75, 1978, pages 149/159).
- the high strength means that the resulting high forming forces place a high load on the systems. This entails both increased energy consumption and a reduction in the lifespan of the systems.
- the primary goal in the method according to the invention is the lamellar spacing of the pearlite, i.e. of the structural component, which accounts for more than half of the microstructure formation in the pearlitic-ferritic steels in question, and thereby lower the tensile strength.
- the invention has for its object to lower the tensile strength of hot strip from unalloyed or low-alloy steel with 0.3 to 0.9% C, without affecting the uniformity of the properties and structure over the length and width of the hot strip.
- This object is achieved according to the invention by a method which is characterized in that the hot rolling and the cooling of the hot strip on the run-out roller table are controlled in such a way that the ⁇ / ⁇ conversion in the hot strip only begins in the coiled coil and is ended in the coil.
- the process according to the invention makes use of the fact that pearlitic-ferritic steels have a low temperature at the start of the ⁇ / ⁇ conversion on cooling and that a temperature increase occurs during the conversion into the pearlite stage.
- the process according to the invention is carried out in such a way that the ⁇ / ⁇ conversion in the hot strip, which previously took place on the exit roller table of the hot strip mill, is shifted into the coil.
- this solution means a coarsening of the pearlitic structure.
- the lamellar spacing of pearlite is about twice as high as that of the structure with fine-lamellar pearlite.
- the ferrite content in the structure is increased and thus the pearlite content is lowered. Both structural changes contribute to a reduction in the strength of the hot strip.
- the already mentioned phenomenon contributes to a good uniformity of the properties and the microstructure formation according to the invention, according to which steels with a higher carbon content show a strong heat development during the transformation in the pearlite stage.
- the heating for a steel with approximately 0.35% C is 20 to 30 K and for a steel with approximately 0.8% C 40 to 60 K.
- the production steps are carried out in such a way that the ⁇ / ⁇ conversion in the hot strip only begins in the coiled coil and ends in the coil.
- the heat development in the coil leads to an equalization of the temperature of the wound strip into the outer and inner turns of the coil and at the same time to a decrease in the cooling rate in the area of the ⁇ / ⁇ conversion with the described consequences for the reduced strength of the hot strip.
- the heat generated during the ⁇ / ⁇ conversion was dissipated by connecting additional water cooling systems on the run-out roller table.
- the control loop of the cooling reacts to the measured reel temperature with a time delay.
- the heat generated during the conversion causes fluctuations in the cooling speed of the hot strip, which, depending on the speed of the cooling water control, lead to local fluctuations in the microstructure formation and the properties over the strip length.
- the production of hot strip with low strength by the method according to the invention rules out such fluctuations due to the fact that the conversion only takes place in the wound coil. It is therefore essential for the process according to the invention that a complete course of the conversion in the coil is ensured.
- the uniformity of the properties and the structure formation impaired. Furthermore, the winding state of the tape is negatively influenced by an undefined course of the conversion over the length of the tape.
- a low tensile strength of 500 to 780 N / mm2 and a coarse-lamellar pearlite formation (average lamellar spacing of the pearlite greater than 0.3 ⁇ m) of the hot strip is achieved according to the invention when the cooling rate in the range of ⁇ / ⁇ conversion of around 4 to 40 so far K / s is reduced to 0.05 K / s or less.
- the final rolling temperature during hot rolling is 860 ° C or higher
- a rolling speed in the last finishing stand of at least 7 m / s is set and the reel temperature is kept at 640 ° C or higher by low water cooling
- -that with a carbon content of the hot strip in the range of 0.33 to 0.49% for setting a tensile strength of at most 650 N / mm2 the final rolling temperature during hot rolling is 860 ° C or higher
- a rolling speed in the last finishing stand is set at least 8 m / s and the reel temperature is kept at 680 ° C or higher
- -that with a carbon content of the hot strip in the range of 0.50 to 0.65% for setting a tensile strength of at most 730 N / mm2 the final rolling temperature during hot rolling is 860 ° C or higher
- one The rolling speed in the last finishing stand is set to at least 7.5 m
- the specified parameters are particularly suitable for hot strip thicknesses of 2 - 3 mm and outlet roller table lengths between 100 and 150 m in order to ensure that the ⁇ / ⁇ conversion in the coiled coil is completed.
- the method is applicable to steels made from 0.32-0.9% C 0.20 - 1.5% Mn up to 2.0% Si up to 0.05% P up to 0.05% S up to 0.02% N up to 0.15% Al Rest of iron and unavoidable impurities are produced.
- the steel can also be alloyed with up to 3.5% Cr up to 3.5% Ni up to 0.5% Mo up to 0.20% V up to 0.03% Ti up to 0.15% Zr up to 0.005% Te up to 0.01% B.
- alloying elements serve to increase the hardenability (Cr, Ni, Mo, V, B) or the nitrogen setting (Ti, Zr) or to influence the sulfide form (Zr, Te).
- Steels A, B, D, E, J, M, Q, R, X, Y fall under the invention.
- Another important criterion of the method according to the invention is the lamella spacing of the pearlitic structure.
- the steels produced by the process according to the invention have an average lamella spacing greater than 0.3 ⁇ m, while the steels with fine-lamellar pearlite have an average lamella spacing less than 0.2 ⁇ m.
- the example of steels R and S makes it particularly clear that the complete ⁇ / ⁇ conversion in the wound coil is important.
- the reel temperature of the steel S which does not fall under the invention, is 680 ° C higher than that of the steel R according to the invention at 665 ° C, the tensile strength of the steel S is significantly higher than that of the steel R.
- the ⁇ / ⁇ conversion partially took place on the run-out roller table, the heat generated during the conversion leading to an increase in the reel temperature.
- the ⁇ / ⁇ conversion took place completely in the coiled coil.
- the increase in temperature during pearlite conversion led to an equalization of the temperature into the outer and inner turns of the coil and at the same time to a reduction in the cooling rate to 0.01 K / s, which led to a reduction in the strength of the strip.
- the hot strips produced by the method according to the invention can be directly processed further at a lower cost by forming, such as bending, straightening, wrapping, etc., or rolled into cold strips. At the same time, the hot strips are characterized by uniformity of properties and structure over the length and width.
- Plate 1 Chemical composition of the steels stolen In% by weight Ref. Type C.
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Mechanical Engineering (AREA)
- Physics & Mathematics (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Sheet Steel (AREA)
- Heat Treatment Of Steel (AREA)
- Heat Treatment Of Strip Materials And Filament Materials (AREA)
- Yarns And Mechanical Finishing Of Yarns Or Ropes (AREA)
- Iron Core Of Rotating Electric Machines (AREA)
- Nonmetallic Welding Materials (AREA)
Abstract
Description
Die Erfindung betrifft ein Verfahren zur Herstellung von Warmband aus unlegiertem oder niedriglegiertem Stahl mit Kohlenstoffgehalten im Bereich von 0,3 - 0,9 % mit den Schritten
- Austenitisieren einer Bramme,
- Warmwalzen der erwärmten Bramme,
- Abkühlen des Bandes und
-Aufhaspeln des Bandes zu einem Coil.The invention relates to a method for producing hot strip from unalloyed or low-alloy steel with carbon contents in the range from 0.3-0.9% with the steps
- austenitizing a slab,
- hot rolling the heated slab,
Cooling the belt and
-Coiling the tape into a coil.
Warmband aus diesen Stählen wird zur direkten Weiterverarbeitung durch Umformen oder zur Herstellung von kaltgewalztem Band eingesetzt. An Fertigteilen aus diesen Stählen wird üblicherweise eine Wärmebehandlung durch Härten und Anlassen zur Einstellung der geforderten Festigkeits- und Härtewerte vorgenommen.Hot strip from these steels is used for direct further processing by forming or for the production of cold-rolled strip. Finished parts made from these steels are usually heat-treated by hardening and tempering to set the required strength and hardness values.
Die Zugfestigkeit von Warmband aus diesen Stählen ist aufgrund der Kohlenstoffgehalte hoch. Sie hängt von dem Perlitanteil im Gefüge und von der Ausbildung des Perlits ab. Bei Stählen mit Kohlenstoffgehalten zwischen 0,4 und 0,7 % bewirkt eine Erhöhung des Perlitanteils im Gefüge von 50 - 100 % einen Anstieg der Zugfestigkeit von 600 bis 1100 N/mm² (Journal of the Iron and Steel Institute, 205, 1967, Seite 653/664). Eine Erhöhung des Perlitanteils im Gefüge bei einer Verringerung der Ferritmenge ergibt sich, wenn die Abkühlgeschwindigkeit des Bandes im Bereich der γ/α-Umwandlung hoch ist. Ferner beeinflußt die Abkühlungsgeschwindigkeit im Bereich der γ/α-Umwandlung den Lamellenabstand des perlitischen Gefüges und dadurch ebenfalls die Festigkeit. Bei einem Stahl mit 0,72 % C und 0,73 % Mn wird durch eine Erhöhung der Abkühlungsgeschwindigkeit von 5 auf 30 K/s der Lamellenabstand des Perlits verringert und dadurch die Zugfestigkeit von 950 auf 1300 N/mm² angehoben (Atlas zur Wärmebehandlung der Stähle, Verlag Stahl-Eisen, Düsseldorf, 1961, Tafel II - 101 E und Mem. Sci. Revue de Metallurgie 75, 1978, Seiten 149/159).The tensile strength of hot strip made from these steels is high due to the carbon content. It depends on the pearlite content in the structure and on the formation of pearlite. In the case of steels with carbon contents between 0.4 and 0.7%, an increase in the pearlite content in the structure of 50-100% causes an increase in the tensile strength of 600 to 1100 N / mm² (Journal of the Iron and Steel Institute, 205, 1967, page 653/664). An increase in the pearlite content in the structure with a reduction in the amount of ferrite results if the cooling rate of the strip is high in the region of the γ / α conversion. It also affects Cooling rate in the area of the γ / α conversion is the lamellar spacing of the pearlitic structure and thus also the strength. In the case of a steel with 0.72% C and 0.73% Mn, increasing the cooling rate from 5 to 30 K / s reduces the lamellar spacing of the pearlite and thereby increases the tensile strength from 950 to 1300 N / mm² (Atlas for heat treatment of Staele, Verlag Stahl-Eisen, Duesseldorf, 1961, Plate II - 101 E and Mem.Sci.Revue de Metallurgie 75, 1978, pages 149/159).
Bei der Herstellung von Warmband aus Stählen mit höheren Kohlenstoffgehalten wird in der Praxis eine starke Wasserkühlung des Warmbandes auf dem Auslaufrollgang der Warmbandstraße vorgenommen. Durch diese Verfahrensweise soll eine Vergleichmäßigung der mechanischen Eigenschaften und der Gefügeausbildung über die Länge des Warmbandes sichergestellt werden (Stahl und Eisen, 89, 1969, Seite 815/824). Die hohe Abkühlgeschwindigkeit aufgrund der starken Wasserkühlung führt, wie bereits beschrieben, zu einer Erhöhung des Perlitanteiles bzw. zu einer Verringerung des Ferritanteils und zu einer Verringerung des Lamellenabstandes des Perlits. Beide Veränderungen bewirken, wie erläutert, eine Erhöhung der Festigkeit des Warmbandes.In the production of hot strip from steels with higher carbon contents, in practice a strong water cooling of the hot strip is carried out on the exit roller table of the hot strip mill. This procedure is intended to ensure that the mechanical properties and microstructure are made uniform over the length of the hot strip (Stahl und Eisen, 89, 1969, page 815/824). The high cooling rate due to the strong water cooling leads, as already described, to an increase in the pearlite content or to a reduction in the ferrite content and to a reduction in the lamella spacing of the pearlite. As explained, both changes increase the strength of the hot strip.
Bei diesem Erzeugungsweg ergeben sich für zwei Stähle nach DIN 17200 und DIN 17220 folgende typische Eigenschaften des Warmbandes:
Für die Direktweiterverarbeitung von so hergestelltem Warmband durch Biegen, Richten, Wickeln, Stanzen oder zur Herstellung von kaltgewalztem Band bedeuten die hohen Festigkeiten aufgrund der daraus resultierenden hohen Umformkräfte eine hohe Belastung der Anlagen. Damit verbunden ist sowohl ein erhöhter Energieaufwand als auch eine Verkürzung der Lebensdauer der Anlagen.For the direct further processing of hot strip produced in this way by bending, straightening, winding, punching or for the production of cold-rolled strip, the high strength means that the resulting high forming forces place a high load on the systems. This entails both increased energy consumption and a reduction in the lifespan of the systems.
Es sind Verfahren bekannt (EP-PSen 0 019 193 und 0 099 520), bei denen durch den Einbau einer zusätzlichen Einrichtung auf dem Auslaufrollgang der Warmbandstraße eine partielle Verringerung der Abkühlgeschwindigkeit im γ/α-Gebiet erreicht wird, und zwar durch Aufwickeln des Bandes in einem Inkubator. Bei beiden bekannten Verfahren ist die Verweilzeit des aufgewickelten Bandes im Inkubator kleiner als 2 min. Dann erfolgt das Abwickeln und die Kühlung sowie das Aufwickeln des Bandes in einer üblichen Haspelanlage. Ziel der Verringerung der Abkühlgeschwindigkeit durch das Aufwickeln im Inkubator ist es, die Ferritbildung zu fördern und dadurch den Ferritanteil im Gefüge anzuheben. Die in beiden Schriften genannten Stähle weisen jedoch niedrige Kohlenstoffgehalte auf, und das Gefüge dieser Stähle besteht überwiegend aus Ferrit. Im Gegensatz dazu ist beim erfindungsgemäßen Verfahren das vorrangige Ziel, den Lamellenabstand des Perlits, d.h. des Gefügebestandteiles, der bei den in Frage stehenden perlitisch-ferritischen Stählen mehr als die Hälfte der Gefügeausbildung ausmacht, zu erhöhen und dadurch die Zugfestigkeit abzusenken.Methods are known (EP-PS 0 019 193 and 0 099 520) in which the installation of an additional device on the exit roller table of the hot strip mill results in a partial reduction in the cooling rate in the γ / α region, namely by winding the strip in an incubator. In both known methods, the residence time of the wound tape in the incubator is less than 2 minutes. Then the unwinding and cooling as well as the winding of the strip takes place in a conventional coiler. The aim of reducing the cooling rate by winding in the incubator is to promote the formation of ferrite and thereby to increase the ferrite content in the structure. However, the steels mentioned in both documents have low carbon contents, and the structure of these steels consists predominantly of ferrite. In contrast to this, the primary goal in the method according to the invention is the lamellar spacing of the pearlite, i.e. of the structural component, which accounts for more than half of the microstructure formation in the pearlitic-ferritic steels in question, and thereby lower the tensile strength.
Der Erfindung liegt die Aufgabe zugrunde, die Zugfestigkeit von Warmband aus unlegiertem oder niedriglegiertem Stahl mit 0,3 bis 0,9 % C abzusenken, ohne die Gleichmäßigkeit der Eigenschaften und der Gefügeausbildung über die Länge und Breite des Warmbandes zu beeinträchtigen.The invention has for its object to lower the tensile strength of hot strip from unalloyed or low-alloy steel with 0.3 to 0.9% C, without affecting the uniformity of the properties and structure over the length and width of the hot strip.
Diese Aufgabe wird erfindungsgemäß durch ein Verfahren gelöst, das dadurch gekennzeichnet ist, daß das Warmwalzen und das Abkühlen des Warmbandes auf dem Auslaufrollgang so gesteuert werden, daß die γ/α- Umwandlung im Warmband erst im gehaspelten Coil beginnt und im Coil beendet wird.This object is achieved according to the invention by a method which is characterized in that the hot rolling and the cooling of the hot strip on the run-out roller table are controlled in such a way that the γ / α conversion in the hot strip only begins in the coiled coil and is ended in the coil.
Beim erfindungsgemäßen Verfahren wird davon Gebrauch gemacht, daß perlitisch-ferritische Stähle eine niedrige Temperatur des Beginns der γ/α-Umwandlung bei der Abkühlung aufweisen und daß während der Umwandlung in die Perlitstufe eine Temperaturerhöhung eintritt. Das erfindungsgemäße Verfahren wird so geführt, daß die γ/α-Umwandlung im Warmband die bisher auf dem Auslaufrollgang der Warmbandstraße stattfand, in das Coil verlagert wird. Im Hinblick auf die Gefügeausbildung bedeutet diese Lösung eine Vergröberung des perlitischen Gefüges. Der Lamellenabstand des Perlits liegt mit 0,3 µm und höher etwa doppelt so hoch, wie beim Gefüge mit feinlamellarem Perlit. Gleichzeitig wird der Ferritanteil im Gefüge erhöht und damit der Perlitanteil abgesenkt. Beide Gefügeänderungen tragen zu einer Absenkung der Festigkeit des Warmbandes bei.The process according to the invention makes use of the fact that pearlitic-ferritic steels have a low temperature at the start of the γ / α conversion on cooling and that a temperature increase occurs during the conversion into the pearlite stage. The process according to the invention is carried out in such a way that the γ / α conversion in the hot strip, which previously took place on the exit roller table of the hot strip mill, is shifted into the coil. In terms of microstructure formation, this solution means a coarsening of the pearlitic structure. At 0.3 µm and higher, the lamellar spacing of pearlite is about twice as high as that of the structure with fine-lamellar pearlite. At the same time, the ferrite content in the structure is increased and thus the pearlite content is lowered. Both structural changes contribute to a reduction in the strength of the hot strip.
So werden beispielsweise die Zugfestigkeitswerte von Warmband aus den eingangs beschriebenen Stählen C 45 und C 75 bei Anwendung des erfindungsgemäßen Verfahrens auf maximal Rm = 650 bzw. Rm = 750 N/mm² herabgesetzt. Dies ergibt eine Festigkeitserniedrigung gegenüber Stählen, die nach bisherigen Verfahren hergestellt wurden, von 150 bzw. 250 N/mm² oder mehr.For example, the tensile strength values of hot strip made of the steels C 45 and C 75 described at the outset are reduced to a maximum of Rm = 650 and Rm = 750 N / mm² when using the method according to the invention. This results in a reduction in strength compared to steels which have been produced by previous processes of 150 or 250 N / mm² or more.
Zu einer guten Gleichmäßigkeit der Eigenschaften und der Gefügeausbildung nach dem erfindungsgemäßen Verfahren trägt die bereits genannte Erscheinung bei, nach welcher Stähle mit höherem Kohlenstoffgehalt eine starke Wärmeentwicklung im Verlauf der Umwandlung in der Perlitstufe aufweisen. So beträgt die Erwärmung bei einem Stahl mit etwa 0,35 % C 20 bis 30 K und bei einem Stahl mit etwa 0,8 % C 40 bis 60 K. Beim erfindungsgemäßen Verfahren werden die Erzeugungsschritte so geführt, daß die γ/α-Umwandlung im Warmband erst im gehaspelten Coil beginnt und im Coil beendet wird. Die Wärmeentwicklung im Coil führt zu einer Vergleichmäßigung der Temperatur des aufgewickelten Bandes bis in die Außen- und Innenwindungen des Coils und gleichzeitig zu einer Absenkung der Abkühlungsgeschwindigkeit im Bereich der γ/α-Umwandlung mit den beschriebenen Folgen für die herabgesetzte Festigkeit des Warmbandes.The already mentioned phenomenon contributes to a good uniformity of the properties and the microstructure formation according to the invention, according to which steels with a higher carbon content show a strong heat development during the transformation in the pearlite stage. For example, the heating for a steel with approximately 0.35% C is 20 to 30 K and for a steel with approximately 0.8% C 40 to 60 K. In the method according to the invention, the production steps are carried out in such a way that the γ / α conversion in the hot strip only begins in the coiled coil and ends in the coil. The heat development in the coil leads to an equalization of the temperature of the wound strip into the outer and inner turns of the coil and at the same time to a decrease in the cooling rate in the area of the γ / α conversion with the described consequences for the reduced strength of the hot strip.
Bei der bisherigen Herstellungsweise wurde die bei der γ/α-Umwandlung entstehende Wärme durch eine Zuschaltung weiterer Wasserkühlsysteme auf dem Auslaufrollgang abgeführt. Der Regelkreis der Kühlung reagiert jedoch mit einer zeitlichen Verzögerung auf die jeweils gemessene Haspeltemperatur. Dies bedeutet, daß die Wärmeentwicklung bei der Umwandlung Schwankungen in der Abkühlgeschwindikeit des Warmbandes verursacht, die je nach der Geschwindigkeit der Kühlwasserregelung zu lokalen Schwankungen der Gefügeausbildung und der Eigenschaften über die Bandlänge führten. Die Herstellung von Warmband mit niedriger Festigkeit nach dem erfindungsgemäßen Verfahren schließt aufgrund der Tatsache, daß die Umwandlung erst im aufgewickelten Coil abläuft, solche Schwankungen aus. Daher ist es für das erfindungsgemäße Verfahren wesentlich, daß ein vollständiger Ablauf der Umwandlung im Coil sichergestellt wird. Läuft hingegen die Umwandlung zum Teil auf dem Auslaufrollgang und zum Teil im Coil ab, so wird die Gleichmäßigkeit der Eigenschaften und der Gefügeausbildung beeinträchtigt. Weiterhin wird durch einen über die Länge des Bandes undefinierten Ablauf der Umwandlung der Wickelzustand des Bandes negativ beeinflußt.In the previous production method, the heat generated during the γ / α conversion was dissipated by connecting additional water cooling systems on the run-out roller table. However, the control loop of the cooling reacts to the measured reel temperature with a time delay. This means that the heat generated during the conversion causes fluctuations in the cooling speed of the hot strip, which, depending on the speed of the cooling water control, lead to local fluctuations in the microstructure formation and the properties over the strip length. The production of hot strip with low strength by the method according to the invention rules out such fluctuations due to the fact that the conversion only takes place in the wound coil. It is therefore essential for the process according to the invention that a complete course of the conversion in the coil is ensured. If, on the other hand, the conversion takes place partly on the runout roller table and partly in the coil, then the uniformity of the properties and the structure formation impaired. Furthermore, the winding state of the tape is negatively influenced by an undefined course of the conversion over the length of the tape.
Eine niedrige Zugfestigkeit von 500 bis 780 N/mm² und eine groblamellare Perlitausbildung (mittlerer Lamellenabstand des Perlits größer als 0,3 µm) des Warmbandes wird erfindungsgemäß dann erreicht, wenn die Abkühlungsgeschwindigkeit im Bereich der γ/α-Umwandlung von bisher rund 4 - 40 K/s auf 0,05 K/s oder geringer herabgesetzt wird.A low tensile strength of 500 to 780 N / mm² and a coarse-lamellar pearlite formation (average lamellar spacing of the pearlite greater than 0.3 μm) of the hot strip is achieved according to the invention when the cooling rate in the range of γ / α conversion of around 4 to 40 so far K / s is reduced to 0.05 K / s or less.
Zur Einstellung einer derart niedrigen Abkühlungsgeschwindigkeit wird erfindungsgemäß vorgeschlagen, in Abhängigkeit vom Kohlenstoffgehalt folgende Bedingungen einzuhalten:
- daß die Endwalztemperatur beim Warmwalzen bei 860 °C oder höher liegt, eine Walzgeschwindigkeit im letzten Fertiggerüst von mindestens 7 m/s eingestellt wird und die Haspeltemperatur durch eine geringe Wasserkühlung auf 640 °C oder höher gehalten wird,
-daß bei einem Kohlenstoffgehalt des Warmbandes im Bereich von 0,33 bis 0,49 % zur Einstellung einer Zugfestigkeit von höchstens 650 N/mm² die Endwalztemperatur beim Warmwalzen 860 °C oder höher liegt, eine Walzgeschwindigkeit im letzten Fertiggerüst mindestens 8 m/s eingestellt und die Haspeltemperatur bei 680 °C oder höher gehalten wird,
-daß bei einem Kohlenstoffgehalt des Warmbandes im Bereich von 0,50 bis 0,65 % zur Einstellung einer Zugfestigkeit von höchstens 730 N/mm² die Endwalztemperatur beim Warmwalzen 860 °C oder höher liegt, eine Walzgeschwindigkeit im letzten Fertiggerüst mindestens 7,5 m/s eingestellt und die Haspeltemperatur bei 660 °C oder höher gehalten wird,
-daß bei einem Kohlenstoffgehalt des Warmbandes im Bereich von 0,66 bis 0,90 % zur Einstellung einer Zugfestigkeit von höchstens 780 N/mm² die Entwalztemperatur beim Warmwalzen 860 °C oder höher liegt, eine Walzgeschwindigkeit im letzten Fertiggerüst von mindestens 7 m/s eingestellt und die Haspeltemperatur bei 640 °C oder höher gehalten wird.To set such a low cooling rate, it is proposed according to the invention to comply with the following conditions depending on the carbon content:
- that the final rolling temperature during hot rolling is 860 ° C or higher, a rolling speed in the last finishing stand of at least 7 m / s is set and the reel temperature is kept at 640 ° C or higher by low water cooling,
-that with a carbon content of the hot strip in the range of 0.33 to 0.49% for setting a tensile strength of at most 650 N / mm² the final rolling temperature during hot rolling is 860 ° C or higher, a rolling speed in the last finishing stand is set at least 8 m / s and the reel temperature is kept at 680 ° C or higher,
-that with a carbon content of the hot strip in the range of 0.50 to 0.65% for setting a tensile strength of at most 730 N / mm² the final rolling temperature during hot rolling is 860 ° C or higher, one The rolling speed in the last finishing stand is set to at least 7.5 m / s and the reel temperature is kept at 660 ° C or higher,
-that with a carbon content of the hot strip in the range of 0.66 to 0.90% to set a tensile strength of at most 780 N / mm² the desalting temperature during hot rolling is 860 ° C or higher, a rolling speed in the last finishing stand of at least 7 m / s set and the reel temperature is kept at 640 ° C or higher.
Die angegebenen Parameter eignen sich besonders für Warmbanddicken von 2 - 3 mm und Auslaufrollgangslängen zwischen 100 und 150 m, um den vollständigen Ablauf der γ/α-Umwandlung im gehaspelten Coil sicherzustellen.The specified parameters are particularly suitable for hot strip thicknesses of 2 - 3 mm and outlet roller table lengths between 100 and 150 m in order to ensure that the γ / α conversion in the coiled coil is completed.
Das Verfahren ist für Stähle anwendbar, die aus
0,32 - 0,9 % C
0,20 - 1,5 % Mn
bis 2,0 % Si
bis 0,05 % P
bis 0,05 % S
bis 0,02 % N
bis 0,15 % Al
Rest Eisen und unvermeidbare Verunreinigungen hergestellt werden. Der Stahl kann zusätzlich legiert sein mit
bis 3,5 % Cr
bis 3,5 % Ni
bis 0,5 % Mo
bis 0,20 % V
bis 0,03 % Ti
bis 0,15 % Zr
bis 0,005 % Te
bis 0,01 % B .The method is applicable to steels made from
0.32-0.9% C
0.20 - 1.5% Mn
up to 2.0% Si
up to 0.05% P
up to 0.05% S
up to 0.02% N
up to 0.15% Al
Rest of iron and unavoidable impurities are produced. The steel can also be alloyed with
up to 3.5% Cr
up to 3.5% Ni
up to 0.5% Mo
up to 0.20% V
up to 0.03% Ti
up to 0.15% Zr
up to 0.005% Te
up to 0.01% B.
Diese Legierungselemente dienen der Erhöhung der Härtbarkeit (Cr, Ni, Mo, V, B) bzw. der Stickstoffabbindung (Ti, Zr) oder Sulfidformbeeinflußung (Zr, Te).These alloying elements serve to increase the hardenability (Cr, Ni, Mo, V, B) or the nitrogen setting (Ti, Zr) or to influence the sulfide form (Zr, Te).
Die Erfindung wird nachstehend anhand von Ausführungsbeispielen näher erläutert. Ferner wird das erfindungsgemäße Verfahren mit nicht unter die Erfindung fallenden Herstellungsbedingungen verglichen.The invention is explained in more detail below on the basis of exemplary embodiments. Furthermore, the method according to the invention is compared with manufacturing conditions not falling under the invention.
Die in Tafel 1 aufgeführten Stähle A bis Z wurden nach dem Sauerstoffaufblasverfahren erschmolzen. Es handelt sich dabei um unlegierte und niedriglegierte Vergütungsstähle nach DIN 17200 und 17222. In Tafel 2 sind die Herstellungsparameter, die Werte der mechanischen Eigenschaften und der Perlitausbildung aufgeführt.Steels A to Z listed in Table 1 were melted using the oxygen inflation process. These are unalloyed and low-alloyed tempering steels according to DIN 17200 and 17222. Table 2 lists the manufacturing parameters, the values of the mechanical properties and the pearlite formation.
Die Stähle A, B, D, E, J, M, Q, R, X, Y fallen unter die Erfindung. Die Stähle C, H, I, O, P, T, U, V und Z, die eine Umwandlung auf dem Auslaufrollgang erfahren haben, sowie die Stähle F, G, K, L, N, und S, bei denen die Umwandlung teils auf dem Auslaufrollgang und teils im aufgewickelten Coil erfolgte, fallen nicht unter die Erfindung.Steels A, B, D, E, J, M, Q, R, X, Y fall under the invention. The steels C, H, I, O, P, T, U, V and Z, which have undergone a transformation on the run-out roller table, as well as the steels F, G, K, L, N, and S, in which the transformation partly on the outfeed roller table and partly in the wound coil are not covered by the invention.
Aus den Werten von Tafel 2 wird deutlich, daß die unter die Erfindung fallenden Stähle wesentlich niedrigere Werte der Zugfestigkeit und der Härte aufweisen. Die Festigkeitsunterschiede zwischen Stählen, die nach dem bisherigen und dem erfindungsgemäßen Verfahren hergestellt wurden, werden mit steigendem Kohlenstoffgehalt größer.From the values in Table 2 it is clear that the steels covered by the invention have significantly lower values of tensile strength and hardness. The differences in strength between steels which were produced by the previous method and the method according to the invention increase with increasing carbon content.
Ein weiteres wichtiges Kriterium des erfindungsgemäßen Verfahrens ist der Lamellenabstand des perlitischen Gefüges. Die nach dem erfindungsgemäßen Verfahren hergestellten Stähle weisen einen mittleren Lamellenabstand größer als 0,3 µm auf, während die Stähle mit feinlamellarem Perlit einen mittleren Lamellanabstand kleiner als 0,2 µm haben.Another important criterion of the method according to the invention is the lamella spacing of the pearlitic structure. The steels produced by the process according to the invention have an average lamella spacing greater than 0.3 μm, while the steels with fine-lamellar pearlite have an average lamella spacing less than 0.2 μm.
Am Beispiel der Stähle R und S wird besonders deutlich, daß die vollständige γ/α-Umwandlung im aufgewickelten Coil wichtig ist. Obwohl die Haspeltemperatur des Stahles S, der nicht unter die Erfindung fällt, mit 680 °C höher ist, als die des erfindungsgemäßen Stahles R mit 665 °C, liegt die Zugfestigkeit des Stahles S deutlich höher als die des Stahles R. Bei dem Stahl S lief die γ/α-Umwandlung infolge der höheren Abkühlungsgeschwindigkeit von 15 K/s zum Teil schon auf dem Auslaufrollgang ab, wobei die bei der Umwandlung entstandene Wärme zur Erhöhung der Haspeltemperatur führte. Hingegen erfolgte beim erfindungsgemäßen Stahl R die γ/α-Umwandlung vollständig im gehaspelten Coil. Die bei der Perlitumwandlung auftretende Temperaturerhöhung führte zu einer Vergleichmäßigung der Temperatur bis in die Außen- und Innenwindungen des Coils und gleichzeitig zu einer Absenkung der Abkühlungsgeschwindigkeit auf 0,01 K/s, was zu einer Herabsetzung der Festigkeit des Bandes führte.The example of steels R and S makes it particularly clear that the complete γ / α conversion in the wound coil is important. Although the reel temperature of the steel S, which does not fall under the invention, is 680 ° C higher than that of the steel R according to the invention at 665 ° C, the tensile strength of the steel S is significantly higher than that of the steel R. With the steel S As a result of the higher cooling rate of 15 K / s, the γ / α conversion partially took place on the run-out roller table, the heat generated during the conversion leading to an increase in the reel temperature. In contrast, in the steel R according to the invention the γ / α conversion took place completely in the coiled coil. The increase in temperature during pearlite conversion led to an equalization of the temperature into the outer and inner turns of the coil and at the same time to a reduction in the cooling rate to 0.01 K / s, which led to a reduction in the strength of the strip.
Die nach dem erfindungsgemäßen Verfahren hergestellten Warmbänder können aufgrund der herabgesetzten Festigkeit und gleichmäßigen Eigenschaften mit geringeren Kosten durch Umformen, wie Biegen, Richten, Umwickeln usw. direkt weiterverarbeitet oder zu Kaltbändern ausgewalzt werden. Gleichzeitig zeichnen sich die Warmbänder durch Gleichmäßigkeit der Eigenschaften und der Gefügeausbildung über die Länge und Breite aus.
Claims (8)
dadurch gekennzeichnet , (wherein) daß das Warmwalzen und das Abkühlen des Warmbandes auf dem Auslaufrollgang so gesteuert werden, daß die γ/α-Umwandlung im Warmband erst im gehaspelten Coil beginnt und im Coil beendet wird.1. Process for the production of hot strip with tensile strength values of Rm = 500 to 780 N / mm² from unalloyed or low-alloy steel with 0.3 to 0.9% C, in which a steel slab is austenitized and hot-rolled into a hot strip after cooling the Hot strip on an outfeed roller table, it is coiled into a coil,
characterized in (wherein) that the hot rolling and the cooling of the hot strip on the outfeed roller table are controlled so that the γ / α conversion in the hot strip only begins in the coiled coil and ends in the coil.
dadurch gekennzeichnet , daß die Endwalztemperatur beim Warmwalzen bei 860 °C oder höher liegt, eine Walzgeschwindigkeit im letzten Fertiggerüst von mindestens 7 m/s eingestellt wird und die Haspeltemperatur durch eine geringe Wasserkühlung auf 640 °C oder höher gehalten wird.2. The method according to claim 1,
characterized in that the final rolling temperature during hot rolling is 860 ° C or higher, a rolling speed in the last finishing stand of at least 7 m / s is set and the reel temperature is kept at 640 ° C or higher by a low water cooling.
dadurch gekennzeichnet , daß bei einem Kohlenstoffgehalt des Warmbandes im Bereich von 0,33 bis 0,49 % zur Einstellung einer Zugfestigkeit von höchstens 650 N/mm² die Endwalztemperatur beim Warmwalzen 860 °C oder höher liegt, eine Walzgeschwindigkeit im letzten Fertiggerüst mindestens 8 m/s eingestellt und die Haspeltemperatur bei 680 °C oder höher gehalten wird.3. The method according to claim 1,
characterized in that with a carbon content of the hot strip in the range from 0.33 to 0.49% for setting a tensile strength of at most 650 N / mm² the final rolling temperature during hot rolling is 860 ° C or higher, a rolling speed in the last finishing stand of at least 8 m / s set and the reel temperature is kept at 680 ° C or higher.
dadurch gekennzeichnet , daß bei einem Kohlenstoffgehalt des Warmbandes im Bereich von 0,50 bis 0,65 % zur Einstellung einer Zugfestigkeit von höchstens 730 N/mm² die Endwalztemperatur beim Warmwalzen 860 °C oder höher liegt, eine Walzgeschwindigkeit im letzten Fertiggerüst mindestens 7,5 m/s eingestellt und die Haspeltemperatur bei 660 °C oder höher gehalten wird.4. The method according to claim 1,
characterized in that with a carbon content of the hot strip in the range from 0.50 to 0.65% for setting a tensile strength of at most 730 N / mm² the final rolling temperature during hot rolling is 860 ° C or higher, a rolling speed in the last finishing stand of at least 7.5 m / s and the reel temperature is kept at 660 ° C or higher.
dadurch gekennzeichnet , daß bei einem Kohlenstoffgehalt des Warmbandes im Bereich von 0,66 bis 0,90 % zur Einstellung einer Zugfestigkeit von höchstens 780 N/mm² die Entwalztemperatur beim Warmwalzen 860 °C oder höher liegt, eine Walzgeschwindigkeit im letzten Fertiggerüst von mindestens 7 m/s eingestellt und die Haspeltemperatur bei 640 °C oder höher gehalten wird.5. The method according to claim 1,
characterized in that with a carbon content of the hot strip in the range of 0.66 to 0.90% for setting a tensile strength of at most 780 N / mm² the rolling temperature during hot rolling is 860 ° C or higher, a rolling speed in the last finishing stand of at least 7 m / s and the reel temperature is kept at 640 ° C or higher.
dadurch gekennzeichnet , daß die Abkühlungsgeschwindigkeit im Coil auf 0,05 K/s oder kleiner eingestellt wird.6. The method according to claim 1,
characterized in that the cooling rate in the coil is set to 0.05 K / s or less.
dadurch gekennzeichnet , daß das Warmband aus einem Stahl bestehend aus
0,32 - 0,9 % C
0,20 - 1,5 % Mn
bis 2,0 % Si
bis 0,05 % P
bis 0,05 % S
bis 0,02 % N
bis 0,15 % Al
Rest Eisen und unvermeidbare Verunreinigungen hergestellt wird.7. The method according to claim 1,
characterized in that the hot strip is made of a steel
0.32-0.9% C
0.20 - 1.5% Mn
up to 2.0% Si
up to 0.05% P
up to 0.05% S
up to 0.02% N
up to 0.15% Al
Rest of iron and unavoidable impurities is produced.
dadurch gekennzeichnet , daß der Stahl zusätzlich noch mit
bis 3,5 % Cr
bis 3,5 % Ni
bis 0,5 % Mo
bis 0,20 % V
bis 0,03 % Ti
bis 0,15 % Zr
bis 0,005 % Te
bis 0,01 % B
einzeln oder zu mehreren legiert wird.8. The method according to claim 7,
characterized in that the steel additionally with
up to 3.5% Cr
up to 3.5% Ni
up to 0.5% Mo
up to 0.20% V
up to 0.03% Ti
up to 0.15% Zr
up to 0.005% Te
up to 0.01% B
alloyed individually or in groups.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AT88109771T ATE67792T1 (en) | 1987-07-01 | 1988-06-20 | PROCESS FOR MANUFACTURING HOT STRIP. |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE3721641A DE3721641C1 (en) | 1987-07-01 | 1987-07-01 | Process for the production of hot strip |
DE3721641 | 1987-07-01 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0301228A1 true EP0301228A1 (en) | 1989-02-01 |
EP0301228B1 EP0301228B1 (en) | 1991-09-25 |
Family
ID=6330614
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP88109771A Expired - Lifetime EP0301228B1 (en) | 1987-07-01 | 1988-06-20 | Process for producing hot-rolled strip |
Country Status (6)
Country | Link |
---|---|
US (1) | US4898629A (en) |
EP (1) | EP0301228B1 (en) |
AT (1) | ATE67792T1 (en) |
CA (1) | CA1305023C (en) |
DE (2) | DE3721641C1 (en) |
ES (1) | ES2025246B3 (en) |
Cited By (6)
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EP0593000A1 (en) * | 1992-10-15 | 1994-04-20 | NMH STAHLWERKE GmbH | Steels for rails |
FR2704238A1 (en) * | 1993-04-19 | 1994-10-28 | Lorraine Laminage | Process for the manufacture of a hot-rolled steel strip in reel form |
EP0632138A1 (en) * | 1993-06-30 | 1995-01-04 | Samsung Heavy Industry Co., Ltd | High toughness and high strength untempered steel and processing method thereof |
GB2294270A (en) * | 1994-10-14 | 1996-04-24 | Nsk Ltd | Bearing steel and bearing |
GB2306506A (en) * | 1995-11-01 | 1997-05-07 | Sanyo Special Steel Co Ltd | Bearing steel |
US6077287A (en) * | 1997-06-11 | 2000-06-20 | Endius Incorporated | Surgical instrument |
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DE3934037C1 (en) * | 1989-10-12 | 1991-02-14 | Thyssen Stahl Ag, 4100 Duisburg, De | |
US5279688A (en) * | 1989-12-06 | 1994-01-18 | Daido Tokushuko Kabushiki Kaisha | Steel shaft material which is capable of being directly cut and induction hardened and a method for manufacturing the same |
US5863361A (en) * | 1997-05-01 | 1999-01-26 | Pennock Corporation | Method for steckel mill operation |
JP4119516B2 (en) * | 1998-03-04 | 2008-07-16 | 新日本製鐵株式会社 | Steel for cold forging |
DE19821299A1 (en) * | 1998-05-13 | 1999-11-18 | Abb Patent Gmbh | Arrangement and method for producing hot-rolled steel strip |
FR2841370B1 (en) * | 2002-06-19 | 2004-08-06 | Technip France | METHOD FOR IMMOBILIZING METAL SODIUM IN THE FORM OF GLASS |
WO2007064172A1 (en) * | 2005-12-01 | 2007-06-07 | Posco | Steel sheet for hot press forming having excellent heat treatment and impact property, hot press parts made of it and the method for manufacturing thereof |
JP4609585B2 (en) * | 2008-06-06 | 2011-01-12 | 住友金属工業株式会社 | Soft nitriding steel, soft nitriding steel and crankshaft |
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JPS5828329B2 (en) * | 1977-04-18 | 1983-06-15 | 日本鋼管株式会社 | Manufacturing method of thick-walled high-toughness steel plate |
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STAHL UND EISEN, Band 89, Nr. 15, 24. Juli 1969, Seiten 815-824; H.W. GRASSHOFF: "Erfahrungen bei der Herstellung von Warm- und Kaltband aus kohlenstoffreichen Stählen mit sorbitischen Gefügeanteilen" * |
STAHL UND EISEN, vol. 89, 1969, pages 815 |
Cited By (10)
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EP0593000A1 (en) * | 1992-10-15 | 1994-04-20 | NMH STAHLWERKE GmbH | Steels for rails |
FR2704238A1 (en) * | 1993-04-19 | 1994-10-28 | Lorraine Laminage | Process for the manufacture of a hot-rolled steel strip in reel form |
EP0632138A1 (en) * | 1993-06-30 | 1995-01-04 | Samsung Heavy Industry Co., Ltd | High toughness and high strength untempered steel and processing method thereof |
GB2294270A (en) * | 1994-10-14 | 1996-04-24 | Nsk Ltd | Bearing steel and bearing |
GB2294270B (en) * | 1994-10-14 | 1998-03-18 | Nsk Ltd | Rolling Bearing. |
US5853660A (en) * | 1994-10-14 | 1998-12-29 | Nsk Ltd. | Rolling bearing made of improved bearing steel |
GB2306506A (en) * | 1995-11-01 | 1997-05-07 | Sanyo Special Steel Co Ltd | Bearing steel |
US5788923A (en) * | 1995-11-01 | 1998-08-04 | Sanyo Special Steel Co., Ltd. | Bearing steel |
GB2306506B (en) * | 1995-11-01 | 1999-07-28 | Sanyo Special Steel Co Ltd | Bearing steel |
US6077287A (en) * | 1997-06-11 | 2000-06-20 | Endius Incorporated | Surgical instrument |
Also Published As
Publication number | Publication date |
---|---|
DE3865139D1 (en) | 1991-10-31 |
ES2025246B3 (en) | 1992-03-16 |
EP0301228B1 (en) | 1991-09-25 |
ATE67792T1 (en) | 1991-10-15 |
DE3721641C1 (en) | 1989-01-12 |
US4898629A (en) | 1990-02-06 |
CA1305023C (en) | 1992-07-14 |
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