EP0030309A2 - Hot rolled strip or plate of denitrided steel and process for its production - Google Patents
Hot rolled strip or plate of denitrided steel and process for its production Download PDFInfo
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- EP0030309A2 EP0030309A2 EP80107296A EP80107296A EP0030309A2 EP 0030309 A2 EP0030309 A2 EP 0030309A2 EP 80107296 A EP80107296 A EP 80107296A EP 80107296 A EP80107296 A EP 80107296A EP 0030309 A2 EP0030309 A2 EP 0030309A2
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- Prior art keywords
- temperature
- steel
- hot strip
- heavy plate
- intermediate temperature
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 54
- 239000010959 steel Substances 0.000 title claims abstract description 54
- 238000000034 method Methods 0.000 title claims description 19
- 238000004519 manufacturing process Methods 0.000 title description 9
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 10
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims abstract description 10
- 238000005098 hot rolling Methods 0.000 claims abstract description 9
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims abstract description 8
- 239000011651 chromium Substances 0.000 claims abstract description 8
- 238000001816 cooling Methods 0.000 claims abstract description 8
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims abstract description 7
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 7
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 7
- 239000011572 manganese Substances 0.000 claims abstract description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 6
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 6
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 6
- 239000010955 niobium Substances 0.000 claims abstract description 6
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 claims abstract description 6
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims abstract description 5
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 5
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims abstract description 5
- 239000000654 additive Substances 0.000 claims abstract description 5
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 5
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 5
- 229910052742 iron Inorganic materials 0.000 claims abstract description 5
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 5
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 5
- 239000011574 phosphorus Substances 0.000 claims abstract description 5
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 5
- 239000010703 silicon Substances 0.000 claims abstract description 5
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 5
- 239000011593 sulfur Substances 0.000 claims abstract description 5
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims abstract description 4
- 239000012535 impurity Substances 0.000 claims abstract description 4
- 239000011733 molybdenum Substances 0.000 claims abstract description 4
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 3
- 238000007792 addition Methods 0.000 claims description 9
- 238000012360 testing method Methods 0.000 claims description 7
- 229910052720 vanadium Inorganic materials 0.000 claims description 5
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 claims description 5
- 229910052684 Cerium Inorganic materials 0.000 claims description 2
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 claims description 2
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims description 2
- 229910052726 zirconium Inorganic materials 0.000 claims description 2
- 238000000926 separation method Methods 0.000 description 14
- 238000009863 impact test Methods 0.000 description 5
- 230000007704 transition Effects 0.000 description 5
- 239000000463 material Substances 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 238000005096 rolling process Methods 0.000 description 4
- 229910045601 alloy Inorganic materials 0.000 description 3
- 239000000956 alloy Substances 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- 229910000599 Cr alloy Inorganic materials 0.000 description 1
- 229910001182 Mo alloy Inorganic materials 0.000 description 1
- 229910000990 Ni alloy Inorganic materials 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 229910001563 bainite Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- ABLLXXOPOBEPIU-UHFFFAOYSA-N niobium vanadium Chemical compound [V].[Nb] ABLLXXOPOBEPIU-UHFFFAOYSA-N 0.000 description 1
- 238000005121 nitriding Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000000930 thermomechanical effect Effects 0.000 description 1
- 229910000859 α-Fe Inorganic materials 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
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- 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
Definitions
- the invention relates to a method for producing hot strip or heavy plate from a denitrified steel.
- the invention further relates to hot strip or heavy plate made from denitrated steel.
- thermo-mechanical treatment of steels means a controlled reshaping of the steel in a temperature range around the transformation point Ar 3 with a controlled precipitation and / or transformation of the structure at the same time.
- thermo-mechanically treated steels In the mechanical-technological testing of these steels, especially in the presence of notches in a wide temperature range above the complete brittle fracture (Charpy impact test), tears are often observed perpendicular to the fracture surface (referred to as “separation”, “splitting” or “splitting”).
- This tendency to split the fracture surfaces of thermo-mechanically treated steels is important, for example, for the operation of long-distance pipelines because it reduces the ability of these steels to stop the propagation of tough fractures.
- Proposals have already been made for the production of high-strength steels for long-distance pipelines, in which fracture splitting no longer occurs in the impact strength test, but all of which are associated with high alloy costs and high production costs.
- the object of the invention is to achieve an increased notched impact strength even at low temperatures (i.e. CVN transition temperature T050 of at least minus 30 ° C.) by controlling the occurrence of the separation in a hot-rolled hot strip or heavy plate.
- the steel with the composition carbon 0.04 to 0.16%, manganese 1.25 to 1.90%, silicon 0.02 to 0.55%, phosphorus 0.004 to 0.020%, sulfur 0.002 to 0.015%, aluminum 0.02 to 0.08%, niobium 0.02 to 0.08%, remainder iron and any impurities is subjected to a hot rolling process in which the hot strip or sheet metal is the last finishing stand with a temperature of 750 Leaves ° to 820 ° C and cooled at a cooling rate of 2 ° to 10 ° C / s to an intermediate temperature of 450 ° C to 570 ° C and is coiled at this temperature or cooled in a stack.
- the method according to the invention can thus significantly improve the usability of the steel, for example for large pipe pipelines, without the need for excessive alloy additives.
- vanadium 0.02 to 0.10% has a particularly favorable effect on the increase in the strength properties of a steel according to the invention, since the vanadium precipitates mainly in the ferrite grain and not on Grain boundaries takes place.
- the steel has a ferritic-pearlitic structure and the ratio of Cvmax to C v 100 is between 1.0 and 1.3.
- C v 100 denotes the high notch impact value (highest values) at which the samples are still showing a 100% deformation fracture.
- C V max is the temperature-dependent value that has the highest impact value of the entire test.
- the steel produced according to the invention has a complete absence of fracture splits in the CVN impact test (CVN-Charpy-V-Notch) while at the same time ensuring CVN transition temperatures of at least -30 ° C.
- the steel of the composition mentioned has a reduced number of separations. Nevertheless, it still has a significantly higher notched impact strength.
- the notched impact strength test of hot strip and / or sheet metal with separations it was found that the notched impact strength in J / cm 2 decreases with increasing number of "separations" in the fracture surfaces of the CVN samples.
- the reason for this decrease in impact strength lies in the fact that the separations that run perpendicular to the main fracture surface and parallel to the sample surface mainly occur before they pass through the main crack, as can be seen in Figure 1, so that when the samples are bent during the Impact test requires less energy to initiate the necking start.
- Such a material is obtained by maintaining an intermediate temperature of 500 to 570 ° C.
- the intermediate temperature is 550 ° to 620 ° C
- the temperature on the last finishing stand from 750 ° C to 850 ° C can be.
- FIGS. 2 and 3 clearly show the advantages of reducing the number of "separations" in the impact test.
- the notched impact strength increases on average from 150 J / cm 2 to 230 J / cm 2 for those with molybdenum, chromium or nickel alloys alloyed steels of grade X 70 (Fig. 3) and from 160 J / cm 2 to 280 J / cm 2 for niobium-vanadium steels of grade X 70 (Fig. 2), which increased the impact strength by 53 and 75 respectively % corresponds.
- the temperature at which the hot strip or sheet leaves the last finishing stand during hot rolling need not be quite as narrow for a low-separation steel according to the invention as for the production of a separation-free steel.
- a temperature range from 750 ° to 850 ° C is possible.
- additions of 0.002 to 0.08 zirconium and / or 0.004 to 0.051 cerium can also be used when carrying out the new process with an intermediate temperature of 550 ° to 620 ° C.
- the composition of the steels is shown in Table 6, in which the proportions of the constituents contained in the steel in Percent. Are given. The numbers of the melts are only used to identify the steel.
- the steels were manufactured according to the parameters given in Table 7. It shows the initial thickness, the thickness of the rolled steel sheet, the blast furnace temperature, the end temperature of the roll and the temperature after cooling (coiling temperature). In all cases with the exception of sheet A, the steel was wound up. The last column shows the cooling rate from the final roll temperature to the reel temperature in ° C / s. The steel then cools slowly in the reel, for example at a rate of about 0.5 ° C / h.
- the mechanical-technological properties of the investigated and inventive steels are summarized in Table 8.
- the letters “L” and “Q” characterize the sample position in relation to the rolling direction, namely "L” a longitudinal sample and “Q” a transverse sample on which the impact test was carried out.
- the other three columns contain the usual information on the yield strength and tensile strength.
- the a k value indicates the energy consumption of the steel at various points on the a k curve as a function of the temperature.
- C V 100 characterizes the lowest temperature at which there is still a complete deformation fracture.
- C v max characterizes the area of maximum energy absorption
- TÜ 50 indicates the temperature at which the Charpy-V notch impact specimens according to DIN 50.115 show 50% deformation fracture in the fracture areas in the transition area between brittle fracture and deformation fracture.
- Tables 1 to 5 relate to low-separation steels according to the invention with a higher notched impact strength
- Tables 6 to 8 characterize separation-free steels which naturally have a very high notched impact strength.
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
- Heat Treatment Of Sheet Steel (AREA)
Abstract
Zur Herstellung von Warmband oder Grobblech mit einer hohen Kerbschlagzähigkeit auch bei niedrigen Temperaturen wird ein denitrierter Stahl bestehend aus Kohlenstoff 0,04 bis 0,16%, Mangan 1,25 bis 1,90%, Silizium 0,02 bis 0,55%, Phosphor 0,004 bis 0,020%, Schwefel 0,002 bis 0,015%, Aluminium 0,02 bis 0,08%, Niob 0,02 bis 0,08%, Rest Eisen und etwaige Verunreinigungen verwendet, wobei das Warmband oder Blech beim Warmwalzen das letzte Fertiggerüst mit einer Temperatur von 750° C bis 820° C verläßt, bis auf eine Zwischentemperatur von 450° C bis 570° C mit einer Abkühlgeschwindigkeit von 2 bis 10° C/s abgekühlt wird und danach im Haspel oder im Stapel an Luft langsam auf Raumtemperatur abkühlt. Sind dem Stahl Zusätze von Molybdän 0,15 bis 0,35%, von Chrom 0,10 bis 0,30% und/oder Nickel 0,30 bis 0,90% allein oder in Kombination zugesetzt, kann die Temperatur am letzten Fertiggerüst 750° C bis 850° C und die Zwischentemperatur 450° C bis 620° C sein.To produce hot strip or heavy plate with high impact strength even at low temperatures, a denitrified steel consisting of carbon 0.04 to 0.16%, manganese 1.25 to 1.90%, silicon 0.02 to 0.55%, Phosphorus 0.004 to 0.020%, sulfur 0.002 to 0.015%, aluminum 0.02 to 0.08%, niobium 0.02 to 0.08%, remainder iron and any impurities used, the hot strip or sheet being used during the hot rolling with the last finishing stand a temperature of 750 ° C to 820 ° C, is cooled to an intermediate temperature of 450 ° C to 570 ° C with a cooling rate of 2 to 10 ° C / s and then slowly cools to room temperature in the reel or in a stack of air . If the steel contains additives of 0.15 to 0.35% molybdenum, 0.10 to 0.30% chromium and / or 0.30 to 0.90% nickel alone or in combination, the temperature on the last finishing stand can be 750 ° C to 850 ° C and the intermediate temperature 450 ° C to 620 ° C.
Description
Die Erfindung betrifft ein Verfahren zur Herstellung von Warmband oder Grobblech aus einem denitrierten Stahl. Die Erfindung betrifft weiterhin aus denitriertem Stahl hergestelltes Warmband oder Grobblech.The invention relates to a method for producing hot strip or heavy plate from a denitrified steel. The invention further relates to hot strip or heavy plate made from denitrated steel.
Seit längerer Zeit besteht die Forderung nach der Entwicklung von höherfesten Stählen mit guten Zähigkeitswerten, die in Form von Warmbändern oder Grobblechen beispielsweise für Großrohr-fernleitungen Verwendung finden können. Zur Herstellung hat sich das kontrollierte und gesteuerte Warmwalzen als wirtschaftliches Verfahren für die Herstellung von thermo-mechanisch behandelten Warmbändern oder Grobblechen immer mehr durchgesetzt. Unter einer thermo-mechanischen Behandlung von Stählen versteht man eine kontrollierte Umformung des Stahles in einem Temperaturbereich um den Umwandlungspunkt Ar3 mit einer gleichzeitig gesteuerten Ausscheidung und/oder Umwandlung des Gefüges.For a long time there has been a demand for the development of high-strength steels with good toughness values, which can be used in the form of hot strips or heavy plates, for example for long-distance pipelines. Controlled and controlled hot rolling has become more and more established as an economical process for the production of thermo-mechanically treated hot strips or heavy plates. A thermo-mechanical treatment of steels means a controlled reshaping of the steel in a temperature range around the transformation point Ar 3 with a controlled precipitation and / or transformation of the structure at the same time.
Es ist bekannt, denitrierten Stahl mit einer Zusammensetzung Kohlenstoff 0,04 bis 0,16 %, Mangan 1,25 bis 1,90 %, Silizium 0,02 bis 0,55 %, Phosphor 0,004 bis0,020 %, Schwefel 0,002 bis 0,015 %, Aluminium 0,02 bis 0,08 %, Niob 0,02 bis 0,08 %, Rest Eisen und etwaige Verunreinigungen zu benutzen. Ggf. können diesem Stahl Zusätze von Molybdän 0,015 bis 0,35 %, Chrom 0,10 bis 0,30 % und/oder Nickel 0,30 bis 0,90 % allein oder in Kombination zulegiert werden.It is known to denitrified steel with a composition of carbon 0.04 to 0.16%, manganese 1.25 to 1.90%, silicon 0.02 to 0.55%, phosphorus 0.004 to 0.020%, sulfur 0.002 to 0.015 %, Aluminum 0.02 to 0.08%, niobium 0.02 to 0.08%, balance Use iron and any contaminants. Possibly. Additions of molybdenum 0.015 to 0.35%, chromium 0.10 to 0.30% and / or nickel 0.30 to 0.90% can be added to this steel alone or in combination.
Bei der mechanisch-technologischen Prüfung dieser Stähle, besonders in Anwesenheit von Kerben in einem breiten Temperaturbereich oberhalb des vollständigen Sprödbruchs (Charpy-Kerbschlagprobe) beobachtet man oft Aufreißungen senkrecht zur Bruchfläche (als "Separation", "Spaltung" oder "Splitting" bezeichnet). Diese Neigung zur Aufspaltung der Bruchflächen von thermo-mechanisch behandelten Stählen ist beispielsweise für die Betreibung von Großrohr-Fernleitungen von Bedeutung, weil die Fähigkeit dieser Stähle, eine Zähbruchfortpflanzung zu stoppen, dadurch vermindert wird. Für die Herstellung von höherfesten Stählen für Großrohr-Fernleitungen, bei denen keine Bruchaufspaltungen bei der Kerbschlagzähigkeitsprüfung mehr auftreten, wurden schon Vorschläge gemacht, die jedoch alle mit hohen Legierungskosten und hohen Herstellungskosten verbunden sind. So wird beispielsweise in der DE-OS 26 53847 empfohlen, dem Stahl Chrom- und Manganzusätze von bis zu 3,5 % bzw. zu 2,5 % zuzulegieren, nachdem der Stahl einer Aufstickung (Stickstoffanreicherung) auf Gehalte von 0,012 % unterworfen wurde. Bei diesem Stahl wird das Warmwalzen kompliziert gestaltet. Das Walzgut wird bei Temperaturen zwischen 950° C und 1100° C einer Verformung von 30 bis 60 %, einer anschließenden Unterbrechung des Walz-vorganges und bei Temperaturen zwischen 700 und 900° C einer Verformung von 75 bis 95 % der ursprünglichen Dicke unterworfen. Das verformte Gefüge wird schließlich in der unteren Bainitstufe umgewandelt. Das Zulegieren der Chrom- und Manganzusätze verteuert bekanntlich Stähle erheblich. Durch den komplizierten und aufwendigen Walzvorgang entstehen weiter erhöhte Herstellungskosten.In the mechanical-technological testing of these steels, especially in the presence of notches in a wide temperature range above the complete brittle fracture (Charpy impact test), tears are often observed perpendicular to the fracture surface (referred to as "separation", "splitting" or "splitting"). This tendency to split the fracture surfaces of thermo-mechanically treated steels is important, for example, for the operation of long-distance pipelines because it reduces the ability of these steels to stop the propagation of tough fractures. Proposals have already been made for the production of high-strength steels for long-distance pipelines, in which fracture splitting no longer occurs in the impact strength test, but all of which are associated with high alloy costs and high production costs. For example, in DE-OS 26 53847 it is recommended to add chromium and manganese additions of up to 3.5% and 2.5% to the steel after the steel has been subjected to nitriding (nitrogen enrichment) to contents of 0.012%. Hot rolling is complicated with this steel. The rolling stock is subjected to a deformation of 30 to 60% at temperatures between 950 ° C and 1100 ° C, a subsequent interruption of the rolling process and a deformation of 75 to 95% of the original thickness at temperatures between 700 and 900 ° C. The deformed structure is finally transformed in the lower bainite stage. Alloying the addition of chromium and manganese is known to make steel considerably more expensive. The complicated and time-consuming rolling process further increases manufacturing costs.
Der Erfindung liegt die Aufgabe zugrunde, durch eine Steuerung des Auftreten der Separation bei einem warmgewalzten Warmband oder Grobblech eine erhöhte Kerbschlagzähigkeit auch bei niedrigen Temperaturen (d.h. CVN-übergangstemperatur T050 von mindestens minus 30° C) zu erreichen.The object of the invention is to achieve an increased notched impact strength even at low temperatures (i.e. CVN transition temperature T050 of at least minus 30 ° C.) by controlling the occurrence of the separation in a hot-rolled hot strip or heavy plate.
Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daß der Stahl mit der Zusammensetzung Kohlenstoff 0,04 bis 0,16 %, Mangan 1,25 bis 1,90 %, Silizium 0,02 bis 0,55 %, Phosphor 0,004 bis 0,020 %, Schwefel 0,002 bis 0,015 %, Aluminium 0,02 bis 0,08 %, Niob 0,02 bis 0,08 %, Rest Eisen und etwaige Verunreinigungen, einem Warmwalzvorgang unterworfen wird, bei dem Warmband oder das Blech das letzte Fertiggerüst mit einer Temperatur von 750° bis 820° C verläßt und mit einer Abkühlungsgeschwindigkeit von 2° bis 10° C/s bis auf eine Zwischentemperatur von 450° C bis 570° C abgekühlt und bei dieser Temperatur gehaspelt bzw. im Stapel abgekühlt wird.This object is achieved in that the steel with the composition carbon 0.04 to 0.16%, manganese 1.25 to 1.90%, silicon 0.02 to 0.55%, phosphorus 0.004 to 0.020%, sulfur 0.002 to 0.015%, aluminum 0.02 to 0.08%, niobium 0.02 to 0.08%, remainder iron and any impurities, is subjected to a hot rolling process in which the hot strip or sheet metal is the last finishing stand with a temperature of 750 Leaves ° to 820 ° C and cooled at a cooling rate of 2 ° to 10 ° C / s to an intermediate temperature of 450 ° C to 570 ° C and is coiled at this temperature or cooled in a stack.
überraschenderweise hat sich herausgestellt, daß nur bei der Einhaltung des beschriebenen, relativ einfachen Warmwalzvorganges der genannte Stahl eine bedeutende Verminderung der Bruchaufspaltungen in den CVN-Kerbschlagproben (CVN-Charpy-V-Notch) bei CVN-Übergangstemperaturen von mindestens -30° C und damit eine erheblich erhöhte Kerbschlagzähigkeit zeigt.Surprisingly, it has been found that only if the described, relatively simple hot rolling process is followed does the steel mentioned significantly reduce the fracture splitting in the CVN notch impact specimens (CVN-Charpy-V-Notch) at CVN transition temperatures of at least -30 ° C. and thus shows a significantly increased impact strength.
Durch das erfindungsgemäße Verfahren kann also ohne die Notwendigkeit von überhöhten Legierungszusätzen die Brauchbarkeit des Stahls, beispielsweise für Großrohr-Fernleitungen, erheblich verbessert werden.The method according to the invention can thus significantly improve the usability of the steel, for example for large pipe pipelines, without the need for excessive alloy additives.
Es hat sich herausgestellt, daß eine Zugabe von Vanadin 0,02 bis 0,10 % sich besonders günstig auf die Erhöhung der Festigkeitseigenschaften eines erfindungsgemäßen Stahls auswirkt, da die Vanadin-Ausscheidungen hauptsächlich im Ferritkorn und nicht an Korngrenzen stattfindet.It has been found that the addition of vanadium 0.02 to 0.10% has a particularly favorable effect on the increase in the strength properties of a steel according to the invention, since the vanadium precipitates mainly in the ferrite grain and not on Grain boundaries takes place.
Wenn eine Zwischentemperatur von 450° C bis 500° C eingehalten wird, läßt sich die Entstehung von Separationen vollständig vermeiden. Der Stahl weist ein ferritisch-perlitisches Gefüge auf und das Verhältnis von Cvmax zu Cv 100 liegt zwischen 1,0 und 1,3. Dabei bezeichnet Cv100 die Kerbschlaghochlage (höchste Werte), bei der die Probennoch gerade einen 100 %igen Verformungsbruch aufweisen.If an intermediate temperature of 450 ° C to 500 ° C is maintained, the formation of separations can be completely avoided. The steel has a ferritic-pearlitic structure and the ratio of Cvmax to C v 100 is between 1.0 and 1.3. C v 100 denotes the high notch impact value (highest values) at which the samples are still showing a 100% deformation fracture.
CV max ist der Wert in Abhängigkeit von der Temperatur, der den höchsten Kerbschlagzähigkeitswert der gesamten Prüfung aufweist. Der erfindungsgemäß hergestellte Stahl weist ein völliges Fehlen von Bruchaufspaltungen in den CVN-Kerbschlagproben (CVN-Charpy-V-Notch) bei gleichzeitiger Gewährleistung von CVN-Obergangstemperaturen von mindestens -30° C auf.C V max is the temperature-dependent value that has the highest impact value of the entire test. The steel produced according to the invention has a complete absence of fracture splits in the CVN impact test (CVN-Charpy-V-Notch) while at the same time ensuring CVN transition temperatures of at least -30 ° C.
Bei der Einhaltung einer Zwischentemperatur von 500° C bis 570° C weist der Stahl der genannten Zusammensetzung eine verringerte Anzahl von Separationen auf. Trotzdem weist er noch eine wesentlich erhöhte Kerbschlagzähigkeit auf. Bei der Kerbschlagzähigkeitsprüfung von mit Separationen behaftetem Warmband und/oder Blech hat sich gezeigt, daß mit zunehmender Anzahl von "Separations" in den Bruchflächen der CVN-Proben die Kerbschlagzähigkeit in J/cm2 abnimmt. Der Grund für diese Abnahme der Kerbschlagzähigkeit liegt in der Tatsache, daß die Separationen,die senkrecht zur Hauptbruchfläche und parallel zur Probenoberfläche verlaufen, hauptsächlich vor dem Durchlaufen des Hauptrisses entstehen, wie dies aus Bild 1 ersichtlich ist, so daß beim Biegen der Proben während der Kerbschlagprüfung eine geringere Energie für die Einleitung des Einschnürbeginns benötigt wird. Dies ist insofern von Bedeutung, als bei der Erzeugung von Warmbändern bzw. Blechen nicht immer "separationsfreies" Material mit höchsten Kerbschlagzähigkeitswerten gefordert wird, so daß auch Material mit etwas geringerer Anzahl von "Separationen", jedoch mit erhöhter Kerbschlagzähigkeit Anwendung findet.If an intermediate temperature of 500 ° C to 570 ° C is maintained, the steel of the composition mentioned has a reduced number of separations. Nevertheless, it still has a significantly higher notched impact strength. In the notched impact strength test of hot strip and / or sheet metal with separations, it was found that the notched impact strength in J / cm 2 decreases with increasing number of "separations" in the fracture surfaces of the CVN samples. The reason for this decrease in impact strength lies in the fact that the separations that run perpendicular to the main fracture surface and parallel to the sample surface mainly occur before they pass through the main crack, as can be seen in Figure 1, so that when the samples are bent during the Impact test requires less energy to initiate the necking start. This is important in that in the production of warm Strips or sheets are not always required to have "separation-free" material with the highest notched impact strength values, so that material with a somewhat smaller number of "separations" but with increased notched impact strength is also used.
Ein derartiges Material wird mit der Einhaltung einer Zwischentemperatur von 500 bis 570° C erhalten.Such a material is obtained by maintaining an intermediate temperature of 500 to 570 ° C.
Bei der Verwendung eines Stahls mit Zusätzen von Molydän von 0,15 bis 0,35 %, von Chrom von 0,10 bis 0,35 % und/oder von Nickel von 0,30 bis 0,90 % allein oder in Kombination reichen zur Erzeugung eines "separationsfreien" Materials unter Beibehaltung derselben Abkühlbedingungen von 2° bis 10° C/s auch Zwischentemperaturen von 550° C aus, so daß die Abkühlung nur auf diese Temperatur erfolgen muß.When using a steel with additions of molydane from 0.15 to 0.35%, chromium from 0.10 to 0.35% and / or nickel from 0.30 to 0.90% alone or in combination are sufficient Generation of a "separation-free" material while maintaining the same cooling conditions of 2 ° to 10 ° C / s and intermediate temperatures of 550 ° C, so that the cooling only has to take place at this temperature.
Zur Herstellung eines Stahls mit den Zulegierungen, der eine verringerte Anzahl von Separationen aber eine erhöhte Kerbschlagzähigkeit aufweist, ist es ausreichend, wenn die Zwischentemperatur 550° bis 620° C beträgt, wobei die Temperatur am letzten Fertiggerüst von 750° C bis zu 850° C betragen kann.To produce a steel with the alloys, which has a reduced number of separations but an increased impact strength, it is sufficient if the intermediate temperature is 550 ° to 620 ° C, the temperature on the last finishing stand from 750 ° C to 850 ° C can be.
Welche Vorteile eine Reduzierung der Anzahl von "Separationen" bei der Kerbschlagprüfung mit sich bringt, geht aus den Bildern 2 und 3 eindeutig hervor.Figures 2 and 3 clearly show the advantages of reducing the number of "separations" in the impact test.
Nimmt z.B. das Verhältnis CVmax zu Cv100 von rund 2,0 auf Werte von 1,3 ab, dann steigt die Kerbschlagzähigkeit im Durchschnitt von 150 J/cm2 auf 230 J/cm2 bei den mit Molybdän-, Chrom- oder Nickelzusätzen legierten Stählen der Güte X 70 (Bild 3) und von 160 J/cm2 auf 280 J/cm2 bei den niob-vanadinhaltigen Stählen der Güte X 70 an (Bild 2) was einer Steigerung der Kerbschlagzähigkeit von 53 bzw. 75 % entspricht.For example, if the ratio C V max to C v 100 decreases from around 2.0 to values of 1.3, the notched impact strength increases on average from 150 J / cm 2 to 230 J / cm 2 for those with molybdenum, chromium or nickel alloys alloyed steels of grade X 70 (Fig. 3) and from 160 J / cm 2 to 280 J / cm 2 for niobium-vanadium steels of grade X 70 (Fig. 2), which increased the impact strength by 53 and 75 respectively % corresponds.
Die Darstellung der Kerbschlagzähigkeit als Funktion des Verhältnisses Cvmax zu Cv100 wurde deshalb für die Bilder 2 und 3 gewählt, weil das Verhältnis von Cvmax zu Cv100 empfindlicher auf die Anzahl der Separationen reagiert als alle anderen Parameter.The representation of the notched impact strength as a function of the ratio C v max to C v 100 was chosen for Figures 2 and 3 because the ratio of C v max to C v 100 is more sensitive to the number of separations than all other parameters.
Im Sauerstoffaufblaskonverter wurden die Stähle der Tabelle 1 und 2 erschmolzen und gemäß den Bedingungen der Tabellen 3, 4 und 5 zu Warmbändern bzw. Grobblechen gewalzt und geprüft.The steels in Tables 1 and 2 were melted in the oxygen inflation converter and rolled and tested to hot strips or heavy plates in accordance with the conditions in Tables 3, 4 and 5.
Die ermittelten Ergebnisse, die zusätzlich in den Bildern 4 und 5 bzw. 6 und 7 dargestellt sind, zeigen, daß ein deutlicher Kerbschlagzähigkeitsanstieg gegenüber den herkömmlich gefertigten mikrolegierten Vergleichsstählen erzielt wurde.The results obtained, which are additionally shown in Figures 4 and 5 or 6 and 7, show that a significant increase in notched impact strength was achieved compared to the conventionally produced microalloyed comparison steels.
Es wurde festgestellt, daß die Temperatur, mit der das Warmband oder Blech beim Warmwalzen das letzte Fertiggerüst verläßt, bei einem separationsarmen Stahl gemäß der Erfindung nicht ganz so eng zu sein braucht wie bei der Herstellung eines separationsfreien Stahls. Ein Temperaturbereich von 750° bis 850° C ist möglich.It has been found that the temperature at which the hot strip or sheet leaves the last finishing stand during hot rolling need not be quite as narrow for a low-separation steel according to the invention as for the production of a separation-free steel. A temperature range from 750 ° to 850 ° C is possible.
Erfindungsgemäß können bei Durchführung des neuen Verfahrens mit einer Zwischentemperatur von 550° bis 620° C auch noch Zusätze von 0,002 bis 0,08 Zirkon und/oder 0,004 bis 0,051 Cer verwendet werden.According to the invention, additions of 0.002 to 0.08 zirconium and / or 0.004 to 0.051 cerium can also be used when carrying out the new process with an intermediate temperature of 550 ° to 620 ° C.
Zur Herstellung von separationsfreien Stählen gemäß Anspruch 3 oder Anspruch 7 wurden Versuche an elf Stahlsorten mit verschiedenen Kohlenstoffgehalten und Kombinationen von Mikrolegierungszusätzen an Niob, Vanadin, Nickel und Chrom durchgeführt.For the production of separation-free steels according to claim 3 or claim 7, tests were carried out on eleven types of steel with different carbon contents and combinations of microalloying additives on niobium, vanadium, nickel and chromium.
Die Zusammensetzung der Stähle ist der Tabelle 6 zu entnehmen, in der die Anteile der im Stahl enthaltenen Bestandteile in Prozent.angegeben sind. Die Nummern der Schmelzen dienen lediglich zur Identifizierung des Stahls.The composition of the steels is shown in Table 6, in which the proportions of the constituents contained in the steel in Percent. Are given. The numbers of the melts are only used to identify the steel.
Die Stähle wurden gemäß der in Tabelle 7 angegebenen Parameter hergestellt. Darin sind die Ausgangsdicke, die Dicke des gewalzten Stahlbleches, die Stoßofentemperatur, die Walzendtemperatur und die Temperatur nach der Abkühlung (Haspeltemperatur) angegeben. In allen Fällen mit Ausnahme des Bleches A wurde der Stahl aufgehaspelt. Die letzte Spalte gibt die Abkühlgeschwindigkeit von der Walzendtemperatur zur Haspeltemperatur in °C/s an. Im Haspel kühlt der Stahl dann langsam ab, beispielsweise mit einer Rate von etwa 0,5° C/h.The steels were manufactured according to the parameters given in Table 7. It shows the initial thickness, the thickness of the rolled steel sheet, the blast furnace temperature, the end temperature of the roll and the temperature after cooling (coiling temperature). In all cases with the exception of sheet A, the steel was wound up. The last column shows the cooling rate from the final roll temperature to the reel temperature in ° C / s. The steel then cools slowly in the reel, for example at a rate of about 0.5 ° C / h.
Die mechanisch-technologischen Eigenschaften der untersuchten und erfindungsgemäßen Stähle sind in der Tabelle 8 zusammengefaßt. Die Buchstaben "L" und "Q" charakterisieren die Probenlage in Bezug auf die Walzrichtung, nämlich "L" eine Längsprobe und "Q" eine Querprobe, an der die Kerbschlagprobe vorgenommen worden ist. Die weiteren drei Spalten enthalten die üblichen Angaben zur Streckgrenze und zur Zugfestigkeit. Der ak-Wert gibt die Energieaufnahme des Stahls bei verschiedenen Punkten der ak-Kurve in Abhängigkeit von der Temperatur an. CV 100 charakteri- siert die tiefste Temperatur, bei der noch ein vollständiger Verformungsbruch einsetzt. Cvmax charakterisiert den Bereich der maximalen Energieaufnahme, während TÜ50 die Temperatur angibt, in der im übergangsbereich zwischen Sprödbruch und Verformungsbruch die Charpy-V-Kerbschlagproben nach DIN 50.115 50 % Verformungsbruch in den Bruchflächen zeigen.The mechanical-technological properties of the investigated and inventive steels are summarized in Table 8. The letters "L" and "Q" characterize the sample position in relation to the rolling direction, namely "L" a longitudinal sample and "Q" a transverse sample on which the impact test was carried out. The other three columns contain the usual information on the yield strength and tensile strength. The a k value indicates the energy consumption of the steel at various points on the a k curve as a function of the temperature. C V 100 characterizes the lowest temperature at which there is still a complete deformation fracture. C v max characterizes the area of maximum energy absorption, while TÜ 50 indicates the temperature at which the Charpy-V notch impact specimens according to DIN 50.115 show 50% deformation fracture in the fracture areas in the transition area between brittle fracture and deformation fracture.
Die nächsten beiden Spalten geben die übergangstemperatur für die Punkte CV 100 und TÜ50 an. Es zeigt sich, daß die TO 50 immer beträchtlich unter -30° C liegt, so daß eine hohe Zähigkeit auch bei tiefen Temperaturen gewährleistet ist. Die Stähle zeichnen sich durch eine hohe Energieaufnahme aus. Bei den erfindungsgemäßen separationsfreien Stählen liegt der Quotient CVmax zu Cv100 bei nahe 1, nämlich zwischen 1 und 1,3. Alle diese Stähle sind frei von Aufreißungen senkrecht zur Bruchfläche (separations).The next two columns indicate the transition temperature for points C V 100 and TÜ 50 . It turns out that the TO 50 always is considerably below -30 ° C, so that high toughness is guaranteed even at low temperatures. The steels are characterized by a high energy consumption. In the separation-free steels according to the invention, the quotient C V max to C v 100 is close to 1, namely between 1 and 1.3. All of these steels are free of tears perpendicular to the fracture surface (separations).
Während also die Tabellen 1 bis 5 erfindungsgemäße separationsarme Stähle mit einer höheren Kerbschlagzähigkeit betreffen, charakterisieren die Tabellen 6 bis 8 separationsfreie Stähle, die naturgemäß eine sehr hohe Kerbschlagzähigkeit aufweisen.Thus, while Tables 1 to 5 relate to low-separation steels according to the invention with a higher notched impact strength, Tables 6 to 8 characterize separation-free steels which naturally have a very high notched impact strength.
Claims (15)
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
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DE19792949124 DE2949124C2 (en) | 1979-12-06 | 1979-12-06 | Denitrided steel hot rolled strip or heavy plate and process for its manufacture |
DE2949124 | 1979-12-06 | ||
DE19803030060 DE3030060A1 (en) | 1980-08-08 | 1980-08-08 | Hot rolled low alloy steel strip or plate prodn. - using controlled rolling finish temp. and cooling to improve notch ductility |
DE3030060 | 1980-08-08 |
Publications (3)
Publication Number | Publication Date |
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EP0030309A2 true EP0030309A2 (en) | 1981-06-17 |
EP0030309A3 EP0030309A3 (en) | 1982-05-12 |
EP0030309B1 EP0030309B1 (en) | 1985-02-13 |
Family
ID=25782269
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Application Number | Title | Priority Date | Filing Date |
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EP80107296A Expired EP0030309B1 (en) | 1979-12-06 | 1980-11-22 | Hot rolled strip or plate of denitrided steel and process for its production |
Country Status (4)
Country | Link |
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US (1) | US4397697A (en) |
EP (1) | EP0030309B1 (en) |
CA (1) | CA1149711A (en) |
DE (1) | DE3070180D1 (en) |
Cited By (4)
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EP0345206A1 (en) * | 1988-06-01 | 1989-12-06 | MANNESMANN Aktiengesellschaft | Method of producing thick plate |
FR2633208A1 (en) * | 1988-06-22 | 1989-12-29 | Vizi Gyorgy | ANGLE ELEMENT FOR CONTAINERS |
EP0481575A2 (en) * | 1990-10-19 | 1992-04-22 | Preussag Stahl Aktiengesellschaft | Process for manufacturing weldable high-tensile steel sheets and use of these sheets |
EP3913105A1 (en) * | 2020-05-19 | 2021-11-24 | ThyssenKrupp Steel Europe AG | Flat steel product and method of manufacturing the same |
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JPS59100214A (en) * | 1982-11-29 | 1984-06-09 | Nippon Kokan Kk <Nkk> | Production of thick walled high tension steel |
US4662950A (en) * | 1985-11-05 | 1987-05-05 | Bethlehem Steel Corporation | Method of making a steel plate for construction applications |
DE3721641C1 (en) * | 1987-07-01 | 1989-01-12 | Thyssen Stahl Ag | Process for the production of hot strip |
US5833667A (en) * | 1993-03-19 | 1998-11-10 | Venetec International, Inc. | Catheter anchoring system |
JP3509603B2 (en) * | 1998-03-05 | 2004-03-22 | Jfeスチール株式会社 | Extra-thick H-section steel with excellent toughness and yield strength of 325 MPa or more |
EP1205570A4 (en) * | 2000-03-02 | 2004-11-10 | Matsushita Electric Ind Co Ltd | Color crt mask frame, steel plate for use therein, process for producing the steel plate, and color crt having the frame |
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EP0345206A1 (en) * | 1988-06-01 | 1989-12-06 | MANNESMANN Aktiengesellschaft | Method of producing thick plate |
FR2633208A1 (en) * | 1988-06-22 | 1989-12-29 | Vizi Gyorgy | ANGLE ELEMENT FOR CONTAINERS |
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EP3913105A1 (en) * | 2020-05-19 | 2021-11-24 | ThyssenKrupp Steel Europe AG | Flat steel product and method of manufacturing the same |
Also Published As
Publication number | Publication date |
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DE3070180D1 (en) | 1985-03-28 |
EP0030309B1 (en) | 1985-02-13 |
EP0030309A3 (en) | 1982-05-12 |
CA1149711A (en) | 1983-07-12 |
US4397697A (en) | 1983-08-09 |
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