EP0897018A1 - Duplex stainless steel with high tensile strength and good corrosion properties - Google Patents
Duplex stainless steel with high tensile strength and good corrosion properties Download PDFInfo
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- EP0897018A1 EP0897018A1 EP98890210A EP98890210A EP0897018A1 EP 0897018 A1 EP0897018 A1 EP 0897018A1 EP 98890210 A EP98890210 A EP 98890210A EP 98890210 A EP98890210 A EP 98890210A EP 0897018 A1 EP0897018 A1 EP 0897018A1
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
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- the invention relates to a duplex alloy for components subject to complex stress high corrosion resistance and high strength containing the Alloy components Si, Mn, Cr, Mo. Ni, W, N, Al and V, balance Fe and Accompanying elements, which in the heat-treated state are essentially Sigma-phase and nitride-free microstructure and a material strength RM of greater than 800 MPa, a 0.2 proof stress of at least 600 MPa and one Charpy V toughness greater than 125 joules.
- Duplex alloys are materials for complex components, which high mechanical values regarding the strength and toughness of the material have and a toughness transition temperature of below - 20 ° C if possible should have. Furthermore, the corrosion resistance of the duplex alloys of great importance because these, abbreviated to DSS (duplex stainless steel), in corrosive media in the chemical industry and especially in the OFFSHORE TECHNOLOGY can be used for system components. A good Weldability while avoiding any cracks and maintaining the Corrosion resistance in the zone affected by welding are further requirements for such materials.
- the invention is based on this prior art (EP-455 625-B) the task of creating a generic duplex alloy, which both in the corrosion and welding property is improved as well as higher mechanical material values and a material strength RM of greater than 800 MPa, a 0.2 proof stress of at least 600 MPa and one Charpy V toughness greater than 125 joules.
- the advantages of the duplex alloy according to the invention are in particular that this improved corrosion resistance and increased mechanical Has properties of the material at the same time. Furthermore, the Temperature range for solution annealing before the cooling of the raw or components expanded so that the heat treatment to adjust the desired austenite-ferrite structure in the structure less accuracy Execution demands or the generation security is significantly improved. It lies namely with this new alloy through the total effect of the intended Elements in a wide solution annealing temperature range essentially constant and in this form desired ratio of ferrite to austenite in Material before, which is an advantageous latitude regarding the temperature control in the heat treatment. This gives another advantage to one Use of the alloy according to the invention that also with thick-walled parts a microstructure which is substantially uniform over the cross section are.
- the composition of the duplex material according to the invention in each case within narrow limits.
- Chromium, molybdenum, tungsten and nitrogen generally improve with increasing contents the corrosion resistance of the material, however indicate in their effect and mutual influence of the structural morphology pronounced limits. If the requirements are exceeded Limits of 26.0, 5.0, 1.0 and 0.39 in% by weight for the above Elements have been found to promote the formation of the sigma phase and Nitrides excreted. As a result or exacerbate these excretions not only the mechanical properties and the weldability of the Material leaps and bounds, the corrosion resistance of it is also affected by a so-called phase limit depletion adversely affected. At Concentrations below 24 wt% Cr, 4 wt% Mo, 0.51 wt% W and The corrosion resistance is reduced in particular below 0.351% by weight of N. and especially the strength of the alloy.
- a comparatively high nitrogen content within narrow limits from 0.351 to 0.39 % By weight is important in the material according to the invention, because thereby how Surprisingly, it was found to be an advantageously homogeneous Distribution of elements between austenite and ferrite in the structure is achieved with In other words, chrome, tungsten and molybdenum are made by the high Compensating nitrogen contents from the usually alloyed ferrite in the alloyed austenite, which is a significant increase in Corrosion resistance and the tendency to excrete the SIGMA phase largely suppressed.
- manganese in one Concentration range of 2.5 to 3.5 wt .-% is present because manganese on the one hand Nitrogen solubility increased and on the other hand has an austenite-forming function. Contents of more than 3.5% by weight of Mn increase the austenite content in the structure, however, reduce the corrosion resistance, and may also have an effect disadvantageous in terms of the achievable material strength and in particular secure setting of a desired ratio of ferrite to austenite at the Heat treatment of the parts. Increase manganese contents lower than 2.5% by weight however, the activity of nitrogen in the steel and therefore the risk of Nitride deposits and also change the phase distribution of the structure in disadvantageously.
- the content of austenite in the structure is greater than that of the ferrite at a high nitrogen content according to the invention due to the corresponding contents of Mn, Cr, Mo, W, Ni, as the results of the investigation showed, the tendency to form nitrides, in particular chromium nitride ( Cr 2 N), largely suppressed, whereby the best corrosion resistance of the material can be achieved.
- Ni contents higher than 7.5% by weight have an extraordinary effect in the alloy stabilizing, resulting in long thermal treatment times and unevenly high
- austenite levels depending on the temperature with lower ones Concentrations than 6.5% by weight of nickel have higher ferrite contents with the resultant cause excretions.
- Tungsten fractions of 0.5 to 1.0% by weight increase the corrosion resistance and reduce the tendency to form intermetallic phases in the Heat treatment of the material. At W contents below 0.5% by weight they are mechanical material properties deteriorated, whereas the limit of W values exceeding 1.0% by weight can cause production disadvantages.
- the alloy component vanadium as a strong nitride former is in the intended Limits in terms of fine microstructure and high homogeneity meaningful of the material. Vanadium contents higher than 0.2% by weight mask nitrogen and form harmful, especially row-shaped Nitrides, whereas lower levels of vanadium are no longer effective are, so that coarse grain can arise disadvantageously. This also applies to the in this regard partially substitutable elements Ti and Nb / Ta.
- Silicon contents in the range between 0.2 and 0.8 wt .-% are with regard to the Material quality is important. Lower concentrations of Si can increase Oxygen levels and a poor degree of purity of the material cause. High values above 0.8% by weight influence the due to the ferrite-forming and nitride-forming effects of Si Phase formation disadvantageous. Another disadvantage of higher Si contents is that these favor the formation of intermetallic phases or precipitations
- Aluminum contents of 0.003 to 0.006% by weight are provided in the alloy. Higher Al contents again promote nitride formation and thereby Reduction of the proportion of dissolved nitrogen with all of the above Disadvantages and smaller aluminum values increase the tendency to form coarse grains.
- the austenite is compared to the ferrite Phase with the lower hardness and strength, it is for components from the alloy according to the invention important that the volume fraction of austenite is greater than that of the ferrite is present in the structure. On the one hand, this increases the tendency formation of chromium nitride, which worsens the Usage properties of the part causes, reduced, on the other hand, the Austenite phase due to the dissolved nitrogen with regard to the mechanical Properties improved.
- the new duplex steel according to the invention in specialist circles HDSS (Hyper-Duplex-Stainless- Steel) connects the lowest differences in corrosion potential between alpha and gamma or maximum corrosion resistance and optimal Phase formation kinetics with largely homogeneous distribution of elements between Ferrite and austenite and is therefore concerning the chemical attack that Weldability and the strength properties of the generic Superior materials according to the state of the art.
- HDSS Hydro-Duplex-Stainless- Steel
- the PREN factor calculated from the current alloy composition a value between 44.6 and 49.5, preferably between 45.5 and 48.0, exhibits the highest corrosion resistance of the duplex material become.
- the heat treatment uses a ratio of ferrite to austenite in the structure between 0 , 42 and 0.8, preferably between 0.60 and 0.69, is set, the proportion of the sigma phase and the nitride proportion and the proportion of carbides being less than 5% by weight, preferably less than 0.5% by weight is.
- the good weldability of the material is further improved, with practically none in particular in the zones of the base material which are influenced by the welding Impairment of the properties are caused.
- the homogeneity of the material properties especially with regard to a mechanical stress, but also the local corrosion behavior be brought to a higher level if one is made of duplex alloy formed part has a degree of deformation of at least 2.5 times, in particular of at least 3.8 times, the degree of deformation being the sum of the Reduction of the cross-sectional area is to be understood.
- Tab. 1 shows the chemical composition and the PREN factor achieved of examined melts or samples.
- Tab. 2 shows the heat treatment and the test results compiled.
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Abstract
Description
Die Erfindung betrifft eine Duplexlegierung für komplex beanspruchte Bauteile mit hoher Korrosionsbeständigkeit und hoher Festigkeit enthaltend die Legierungsbestandteile Si, Mn, Cr, Mo. Ni, W, N, Al und V, Rest Fe und Begleitelemente, welche im wärmebehandeltem Zustand ein im wesentlichen sigmaphasen- und nitridfreies Mikrogefüge und eine Materialfestigkeit RM von größer als 800 MPa, eine 0,2 Dehngrenze von mindestens 600 MPa und eine Charpy-V-Zähigkeit von höher als 125 Joule aufweist.The invention relates to a duplex alloy for components subject to complex stress high corrosion resistance and high strength containing the Alloy components Si, Mn, Cr, Mo. Ni, W, N, Al and V, balance Fe and Accompanying elements, which in the heat-treated state are essentially Sigma-phase and nitride-free microstructure and a material strength RM of greater than 800 MPa, a 0.2 proof stress of at least 600 MPa and one Charpy V toughness greater than 125 joules.
Duplexlegierungen sind Werkstoffe für komplex beanspruchte Bauteile, welche hohe mechanische Werte betreffend die Festigkeit und die Zähigkeit des Materials besitzen und eine Zähigkeitsübergangstemperatur vom möglichst unter - 20 °C aufweisen sollen. Weiters ist die Korrosionsbeständigkeit der Duplexlegierungen von großer Bedeutung, weil diese, abgekürzt DSS ( Duplex- Stainless-Steels), in korrosiven Medien in der chemischen Industrie und insbesondere in der OFFSHORE-TECHNIK für Anlagenkomponenten Verwendung finden. Eine gute Schweißbarkeit und dabei eine Vermeidung jeglicher Risse sowie ein Erhalt der Korrosionsbeständigkeit in der durch eine Schweißung wärmebeeinflußten Zone sind weitere Forderungen an derartige Werkstoffe.Duplex alloys are materials for complex components, which high mechanical values regarding the strength and toughness of the material have and a toughness transition temperature of below - 20 ° C if possible should have. Furthermore, the corrosion resistance of the duplex alloys of great importance because these, abbreviated to DSS (duplex stainless steel), in corrosive media in the chemical industry and especially in the OFFSHORE TECHNOLOGY can be used for system components. A good Weldability while avoiding any cracks and maintaining the Corrosion resistance in the zone affected by welding are further requirements for such materials.
Ausgehend von einer Standard-Duplexlegierung, enthaltend im wesentlichen in Gew.-% 1,2 Mn, 23,0 Cr, 3,2 Mo, 6,0 Ni und 0,18 N, wurde einerseits erfolgreich versucht, die Festigkeit des Materials durch eine Erhöhung des Stickstoffgehaltes auf 0,35 Gew.-% sowie der Cr- und Mn-Konzentration auf 26,0 und 5,7 Gew.-% bei einer Verminderung des Ni- und Mo-Anteiles auf 4,0 und 2,0 Gew.-% anzuheben. Andererseits erfolge eine metallurgische Weiterentwicklung in der Richtung einer verbesserten Korrosionsbeständigkeit, was durch ein Anheben in geringerem Ausmaß des Ni- Gehaltes bei einer Vergrößerung der N- und insbesondere der Mo-Konzentration in der Legierung erreicht wurde.Starting from a standard duplex alloy, essentially containing in On the one hand, 1.2% by weight of 1.2 Mn, 23.0 Cr, 3.2 Mo, 6.0 Ni and 0.18 N was successful tries to increase the strength of the material by increasing the nitrogen content to 0.35% by weight and the Cr and Mn concentration to 26.0 and 5.7% by weight a decrease in the Ni and Mo content to 4.0 and 2.0 wt .-%. On the other hand, there is a metallurgical development in the direction of one improved corrosion resistance, which is due to lifting in less Extent of the Ni content with an increase in the N and in particular the Mo concentration in the alloy was reached.
Eine sowohl hinsichtlich des Korrosionsverhaltens verbesserte als auch in den mechanischen und Schweißeigenschaften erhöhte Duplexlegierung, ein sogenannter SDSS ( Super-Duplex-Stainless-Steel), offenbart die EP-455625-B. Bei einer Legierungszusammensetzung von im wesentlichen in Gew.-% 2,4 Mn, 25,0 Cr, 4,0 Mo, 6,8 Ni 0,75 W, 0,25 N und 0,1 V, Rest Fe und Begleitelemente und einem Einstellen eines in Grenzen bestimmten Ni- zu Mn- Verhältniswertes sowie eines Gefügephasenfaktors sind die Eigenschaften insgesamt verbessert.An improved both in terms of corrosion behavior and in the mechanical and welding properties increased duplex alloy, a So-called SDSS (Super-Duplex-Stainless-Steel) is disclosed in EP-455625-B. At an alloy composition of essentially in% by weight 2.4 Mn, 25.0 Cr, 4.0 Mo, 6.8 Ni 0.75 W, 0.25 N and 0.1 V, balance Fe and accompanying elements and setting a Ni to Mn ratio value determined within limits and of a structure phase factor, the properties are improved overall.
Ausgehend von diesem Stand der Technik ( EP-455 625-B) stellt sich die Erfindung die Aufgabe, eine gattungsgemäße Duplexlegierung zu schaffen, welche sowohl in der Korrosions- und Schweißeigenschaft verbessert ist, als auch höhere mechanische Werkstoffwerte und zwar eine Materialfestigkeit RM von größer als 800 MPa, eine 0,2 Dehngrenze von mindestens 600 MPa und eine Charpy-V-Zähigkeit von höher als 125 Joule aufweist.The invention is based on this prior art (EP-455 625-B) the task of creating a generic duplex alloy, which both in the corrosion and welding property is improved as well as higher mechanical material values and a material strength RM of greater than 800 MPa, a 0.2 proof stress of at least 600 MPa and one Charpy V toughness greater than 125 joules.
Diese Aufgabe wird durch eine Duplexlegierung der eingangs genannten Art
dadurch erreicht, daß die Legierung eine chemische Zusammensetzung in Gew.-%
von
Die Vorteile der erfindungsgemäßen Duplexlegierung bestehen insbesondere darin, daß diese verbesserte Korrosionsbeständigkeit und erhöhte mechanische Eigenschaften des Werkstoffes gleichzeitig aufweist. Dabei wird weiters der Temperaturbereich für das Lösungsglühen vor dem verstärkten Abkühlen der Roh- oder Bauteile erweitert, so daß die Wärmebehandlung zur Einstellung der gewünschten Austenit-Ferrit-Struktur im Gefüge weniger Genauigkeit bei deren Ausführung fordert bzw. die Erzeugungssicherheit wesentlich verbessert ist. Es liegt nämlich bei dieser neuen Legierung durch die Summenwirkung der vorgesehenen Elemente in einem weiten Lösungsglüh- Temperaturbereich ein im wesentlichen gleichbleibendes und in dieser Form gewünschtes Verhältnis Ferrit zu Austenit im Werkstoff vor, was einen vorteilhaften Spielraum betreffend die Temperaturführung bei der Wärmebehandlung erbringt. Daraus ergibt sich ein weiterer Vorteil bei einer Verwendung der erfindungsgemäßen Legierung, daß auch dickwandige Teile mit einer über den Querschnitt im wesentlichen gleichmäßiger Mikrostruktur herstellbar sind.The advantages of the duplex alloy according to the invention are in particular that this improved corrosion resistance and increased mechanical Has properties of the material at the same time. Furthermore, the Temperature range for solution annealing before the cooling of the raw or components expanded so that the heat treatment to adjust the desired austenite-ferrite structure in the structure less accuracy Execution demands or the generation security is significantly improved. It lies namely with this new alloy through the total effect of the intended Elements in a wide solution annealing temperature range essentially constant and in this form desired ratio of ferrite to austenite in Material before, which is an advantageous latitude regarding the temperature control in the heat treatment. This gives another advantage to one Use of the alloy according to the invention that also with thick-walled parts a microstructure which is substantially uniform over the cross section are.
Weil nun einerseits eine starke Wechselwirkung der Legierungselemente miteinander gegeben ist und andererseits höchste korrosionschemische und mechanische Eigenschaften erreicht werden, liegt die Zusammensetzung des erfindungsgemäßen Duplexmaterials jeweils in engen Grenzen vor.Because on the one hand there is a strong interaction of the alloying elements is given to each other and on the other hand the highest corrosion chemical and mechanical properties are achieved, the composition of the duplex material according to the invention in each case within narrow limits.
Chrom, Molybdän, Wolfram sowie Stickstoff verbessem im allgemeinen mit steigenden Gehalten die Korrosionsbeständigkeit des Werkstoffes, weisen jedoch in ihrer Wirkung und gegenseitigen Beeinflussung der Gefügemorphologie ausgeprägte Grenzwerte auf. Bei einem Überschreiten der anspruchsgemäßen Grenzen von 26,0, 5,0, 1,0 und 0,39 in Gew.-% für diese oben angeführten Elemente werden, wie gefunden wurde, eine Bildung der Sigmaphase gefördert und Nitride ausgeschieden. Dadurch bzw. durch diese Ausscheidungen verschlechtern sich nicht nur die mechanischen Eigenschaften und die Schweißbarkeit des Materiales sprunghaft, auch die Korrosionsbeständigkeit desselben wird durch eine sogenannte Phasengrenzbereichsverarmung nachteilig beeinflußt. Bei Konzentrationen unter 24 Gew.-% Cr, 4 Gew.-% Mo, 0,51 Gew.-% W und insbesondere unter 0,351 Gew.-% N vermindem sich die Korrosionsbeständigkeit und insbesondere die Festigkeit der Legierung.Chromium, molybdenum, tungsten and nitrogen generally improve with increasing contents the corrosion resistance of the material, however indicate in their effect and mutual influence of the structural morphology pronounced limits. If the requirements are exceeded Limits of 26.0, 5.0, 1.0 and 0.39 in% by weight for the above Elements have been found to promote the formation of the sigma phase and Nitrides excreted. As a result or exacerbate these excretions not only the mechanical properties and the weldability of the Material leaps and bounds, the corrosion resistance of it is also affected by a so-called phase limit depletion adversely affected. At Concentrations below 24 wt% Cr, 4 wt% Mo, 0.51 wt% W and The corrosion resistance is reduced in particular below 0.351% by weight of N. and especially the strength of the alloy.
Ein vergleichsweise hoher Stickstoffgehalt in engen Grenzen von 0,351 bis 0,39 Gew.-% ist beim erfindungsgemäßen Werkstoff wichtig, weil dadurch , wie überraschend festgestellt werden konnte, eine vorteilhaft homogene Elementeverteilung zwischen Austenit und Ferrit im Gefüge erreicht wird, mit anderen Worten, Chrom, Wolfram und Molybdän werden durch die hohen Stickstoffgehalte ausgleichend vom üblicherweise überlegierten Ferrit in den unterlegierten Austenit verbracht, was eine wesentliche Steigerung der Korrosionsbeständigkeit bewirkt und die Neigung zur Ausscheidung der SIGMA-Phase weitgehend unterdrückt. Dabei ist es wichtig, daß Mangan in einem Konzentrationsbereich von 2,5 bis 3,5 Gew.-% vorliegt, weil Mangan einerseits die Stickstofflöslichkeit erhöht und andererseits eine Austenitbildnerfunktion ausübt. Gehalte über 3,5 Gew.-% Mn vergrößem zwar den Austenitanteil im Gefüge, vermindern jedoch die Korrosionsbeständigkeit, wirken auch gegebenenfalls nachteilig hinsichtlich der erreichbaren Materialfestigkeit und insbesondere der sicheren Einstellung eines gewünschten Verhältnisses von Ferrit zu Austenit bei der Wärmebehandlung der Teile. Niedrigere Mangangehalte als 2,5 Gew.-% vergrößern jedoch die Aktivität von Stickstoff im Stahl und damit die Gefahr von Nitridausscheidungen und ändern auch die Phasenverteilung der Gefügestuktur in nachteiliger Weise.A comparatively high nitrogen content within narrow limits from 0.351 to 0.39 % By weight is important in the material according to the invention, because thereby how Surprisingly, it was found to be an advantageously homogeneous Distribution of elements between austenite and ferrite in the structure is achieved with In other words, chrome, tungsten and molybdenum are made by the high Compensating nitrogen contents from the usually alloyed ferrite in the alloyed austenite, which is a significant increase in Corrosion resistance and the tendency to excrete the SIGMA phase largely suppressed. It is important that manganese in one Concentration range of 2.5 to 3.5 wt .-% is present because manganese on the one hand Nitrogen solubility increased and on the other hand has an austenite-forming function. Contents of more than 3.5% by weight of Mn increase the austenite content in the structure, however, reduce the corrosion resistance, and may also have an effect disadvantageous in terms of the achievable material strength and in particular secure setting of a desired ratio of ferrite to austenite at the Heat treatment of the parts. Increase manganese contents lower than 2.5% by weight however, the activity of nitrogen in the steel and therefore the risk of Nitride deposits and also change the phase distribution of the structure in disadvantageously.
Weil nun bei erfindungsgemäß hohem Stickstoffgehalt durch ehtsprechende Gehalte an Mn, Cr, Mo, W, Ni legierungstechnisch der Austenitanteil im Gefüge größer als derjenige des Ferrites eingestellt ist, ist, wie die Untersuchungsergebnisse zeigten, die Neigung zur Bildung von Nitriden, insbesondere von Chromnitrid ( Cr2N ), weitgehend unterdrückt, wodurch beste Korrosionsbeständigkeit des Werkstoffes erreichbar ist.. Because the content of austenite in the structure is greater than that of the ferrite at a high nitrogen content according to the invention due to the corresponding contents of Mn, Cr, Mo, W, Ni, as the results of the investigation showed, the tendency to form nitrides, in particular chromium nitride ( Cr 2 N), largely suppressed, whereby the best corrosion resistance of the material can be achieved.
Von besonderer Wichtigkeit für eine Gefügestabilität und einen hohen, in engen Grenzen einzustellenden Austenitanteil sind Gehalte von 6,5 bis 7,5 Gew.-% Ni. Höhere Ni-Gehalte als 7,5 Gew.-% wirken in der Legierung außerordentlich stabilisierend, was hohe thermische Behandlungszeiten und ungleich hohe Austenitgehalte in Abhängigkeit von der Temperatur erbringen, wobei niedrigere Konzentrationen als 6,5 Gew.-% an Nickel höhere Ferritgehalte mit den dadurch bewirkten Ausscheidungen nach sich ziehen.Of particular importance for a structural stability and a high, in narrow Limits of austenite to be set are contents of 6.5 to 7.5% by weight of Ni. Ni contents higher than 7.5% by weight have an extraordinary effect in the alloy stabilizing, resulting in long thermal treatment times and unevenly high Provide austenite levels depending on the temperature, with lower ones Concentrations than 6.5% by weight of nickel have higher ferrite contents with the resultant cause excretions.
Wolframanteile von 0,5 bis 1,0 Gew.-% erhöhen die Korrosionsbeständigkeit und vermindern die Neigung zur Ausbildung intermetallischer Phasen bei der Wärmebehandlung des Materials. Bei W-Gehalten unter 0,5 Gew.-% sind die mechanischen Materialeigenschaften verschlechtert, wohingegen die Grenze von 1,0 Gew.-% überschreitende W-Werte Produktionsnachteile verursachen können.Tungsten fractions of 0.5 to 1.0% by weight increase the corrosion resistance and reduce the tendency to form intermetallic phases in the Heat treatment of the material. At W contents below 0.5% by weight they are mechanical material properties deteriorated, whereas the limit of W values exceeding 1.0% by weight can cause production disadvantages.
Der Legierungsbestandteil Vanadin als starker Nitridbildner ist in den vorgesehenen Grenzen im Hinblick auf eine feine Gefügeausbildung und eine hohe Homogenität des Werkstoffes bedeutungsvoll. Höhere Vanadingehalte als 0,2 Gew.-% maskieren Stickstoff und bilden schädliche, insbesondere reihenförmig ausgebildete Nitride, wohingegen niedrigere Vanadinanteile nicht mehr komfeinend wirksam sind, so daß in nachteiliger Weise Grobkorn entstehen kann. Dies gilt auch für die diesbezüglich teilweise substituierbaren Elemente Ti und Nb/Ta.The alloy component vanadium as a strong nitride former is in the intended Limits in terms of fine microstructure and high homogeneity meaningful of the material. Vanadium contents higher than 0.2% by weight mask nitrogen and form harmful, especially row-shaped Nitrides, whereas lower levels of vanadium are no longer effective are, so that coarse grain can arise disadvantageously. This also applies to the in this regard partially substitutable elements Ti and Nb / Ta.
Siliziumgehalte im Bereich zwischen 0,2 und 0,8 Gew.-% sind im Hinblick auf die Materialgüte wichtig. Geringere Konzentrationen von Si können erhöhte Sauerstoffgehalte und einen schlechten Reinheitsgrad des Werkstoffes verursachen. Hohe, über einem Gehalt von 0,8 Gew.-% liegende Werte beeinflussen auf Grund der ferritbildenden und nitridbildenden Wirkung von Si die Phasenbildung nachteilig. Ein weiterer Nachteil höherer Si-Gehalte liegt darin, daß diese eine Bildung von intermetallischen Phasen bzw. Ausscheidungen begünstigenSilicon contents in the range between 0.2 and 0.8 wt .-% are with regard to the Material quality is important. Lower concentrations of Si can increase Oxygen levels and a poor degree of purity of the material cause. High values above 0.8% by weight influence the due to the ferrite-forming and nitride-forming effects of Si Phase formation disadvantageous. Another disadvantage of higher Si contents is that these favor the formation of intermetallic phases or precipitations
Zur Erreichung einer besonderen Kornfeinheit sind erfindungsgemäß auch Aluminiumgehalte von 0,003 bis 0,006 Gew.-% in der Legierung vorgesehen. Höhere Al-Gehalte wirken wieder fördernd für eine Nitridbildung und dadurch Herabsetzung des Anteiles an gelöstem Stickstoff mit all den vorab dargelegten Nachteilen und kleinere Aluminiumwerte steigem die Tendenz zur Grobkornbildung.To achieve a particular grain size are also according to the invention Aluminum contents of 0.003 to 0.006% by weight are provided in the alloy. Higher Al contents again promote nitride formation and thereby Reduction of the proportion of dissolved nitrogen with all of the above Disadvantages and smaller aluminum values increase the tendency to form coarse grains.
Obwohl in Standard-Duplexlegierungen der Austenit im Vergleich mit dem Ferrit die Phase mit der geringeren Härte und Festigkeit ist, ist es für Bauteile aus der erfindungsgemäßen Legierung wichtig, daß der Volumsanteil von Austenit größer als derjenige des Ferrits im Gefüge vorliegt. Einerseits wird dadurch die Neigung zu einer Bildung von Chromnitrid, was eine Verschlechterung der Gebrauchseigenschaften des Teiles bewirkt, verringert, andererseits wird die Austenitphase durch den gelösten Stickstoff hinsichtlich der mechanischen Eigenschaften verbessert.Although in standard duplex alloys the austenite is compared to the ferrite Phase with the lower hardness and strength, it is for components from the alloy according to the invention important that the volume fraction of austenite is greater than that of the ferrite is present in the structure. On the one hand, this increases the tendency formation of chromium nitride, which worsens the Usage properties of the part causes, reduced, on the other hand, the Austenite phase due to the dissolved nitrogen with regard to the mechanical Properties improved.
Der neue erfindungsgemäße Duplexstahl, in Fachkreisen HDSS ( Hyper-Duplex-Stainless- Steel) genannt, verbindet niedrigste Korrosionspotentialdifferenzen zwischen Alpha und Gamma bzw. höchste Korrosionsbeständigkeit und optimale Phasenbildungskinetik bei weitgehend homogener Elementenverteilung zwischen Ferrit und Austenit und ist deshalb betreffend den chemischen Angriff, die Schweißbarkeit und die Festigkeitseigenschaften den gattungsgemäßen Werkstoffen gemäß dem Stand der Technik überlegen.The new duplex steel according to the invention, in specialist circles HDSS (Hyper-Duplex-Stainless- Steel) connects the lowest differences in corrosion potential between alpha and gamma or maximum corrosion resistance and optimal Phase formation kinetics with largely homogeneous distribution of elements between Ferrite and austenite and is therefore concerning the chemical attack that Weldability and the strength properties of the generic Superior materials according to the state of the art.
Die vorteilhaften Eigenschaften der Duplexlegierung können optimiert werden, wenn
diese eine chemische Zusammensetzung in Gew.-% von
Besonders wichtig ist, wie auch oben erwähnt, eine Einhaltung von Konzentrationswerten für Cr, Mo, W, Si und Al einerseits und für Mn, Ni und N andererseits in den gekennzeichneten Bereichen der Legierung. Erfindungsgemäß werden nach einer Wärmebehandlung durch ein Lösungsglühen zwischen 1180°C und 850°C, vorzugsweise zwischen 1150 °C und 1000°C, mit nachfolgendem Abschrecken des gemäß der Kennzeichnung zusammengesetzten Teiles eine wesentliche verbesserte Korrosionsbeständigkeit, eine erhöhte Festigkeit bei guter Zähigkeit und niedriger FATT, eine geringe Neigung zur Ausscheidung von intermetallischen Phasen, insbesondere von SIGMA- und EPSILON-Phasen, und eine geringere Tendenz zur Bildung von sekundären Austenit beim Abkühlen des Materials erreicht.As mentioned above, compliance with is particularly important Concentration values for Cr, Mo, W, Si and Al on the one hand and for Mn, Ni and N on the other hand in the marked areas of the alloy. According to the invention after heat treatment by solution annealing between 1180 ° C and 850 ° C, preferably between 1150 ° C and 1000 ° C, with the following Quenching the part assembled according to the marking significantly improved corrosion resistance, increased strength with good Toughness and low FATT, a low tendency to excrete intermetallic phases, in particular SIGMA and EPSILON phases, and a lower tendency to form secondary austenite when cooling the Material reached.
Wenn dabei der aus der aktuellen Legierungszusammensetzung errechnete PREN-Faktor einen Wert zwischen 44,6 und 49,5, vorzugsweise zwischen 45,5 und 48,0, aufweist, kann höchste Korrosionsbeständigkeit des Duplexmaterials erstellt werden.If the PREN factor calculated from the current alloy composition a value between 44.6 and 49.5, preferably between 45.5 and 48.0, exhibits the highest corrosion resistance of the duplex material become.
Um weiters verbesserte Korrosionsbeständigkeit hinsichtlich Loch,- Spalt- und
Spannungsrißkorrosion bei erhöhter Festigkeit des Duplexwerkstoffes sowie
verminderte Ausscheidungsneigung und geringere Tendenz zur Bildung von
sekundärem Ferrit zu erwirken, ist es von Vorteil, wenn mittels der
Wärmebehandlung ein Verhältniswert von Ferrit zu Austenit inm Gefüge zwischen
0,42 und 0,8, vorzugsweise zwischen 0,60 und 0,69, eingestellt wird, wobei der
Anteil der Sigmaphase und der Nitridanteil und der Anteil an Karbiden unter 5
Gew.-%, vorzugsweise unter 0,5 Gew.-% ausgebildet ist. Die gute Schweißbarkeit
des Werkstoffes wird dabei weiter verbessert, wobei auch insbesondere in den
durch die Schweißung wärmebeeinflußten Zonen des Grundmaterials praktisch
keinerlei
Beeinträchtigung der Eigenschaften bewirkt sind.In order to further improve corrosion resistance with regard to pitting, crevice and stress corrosion cracking with increased strength of the duplex material as well as reduced tendency to precipitate and less tendency to form secondary ferrite, it is advantageous if the heat treatment uses a ratio of ferrite to austenite in the structure between 0 , 42 and 0.8, preferably between 0.60 and 0.69, is set, the proportion of the sigma phase and the nitride proportion and the proportion of carbides being less than 5% by weight, preferably less than 0.5% by weight is. The good weldability of the material is further improved, with practically none in particular in the zones of the base material which are influenced by the welding
Impairment of the properties are caused.
Die Homogenität der Materialeigenschaften insbesondere hinsichtlich einer mechanischen Beanspruchung, aber auch das örtliche Korrosionsverhalten können auf ein höheres Niveau gebracht werden, wenn ein aus der Duplexlegierung gebildeter Formteil einen Verformungsgrad von mindestens 2,5fach, insbesondere von mindestens 3,8fach, aufweist, wobei der Verformungsgrad als Summe der Reduktion der Querschnittsfläche zu verstehen ist.The homogeneity of the material properties, especially with regard to a mechanical stress, but also the local corrosion behavior be brought to a higher level if one is made of duplex alloy formed part has a degree of deformation of at least 2.5 times, in particular of at least 3.8 times, the degree of deformation being the sum of the Reduction of the cross-sectional area is to be understood.
Anhand von Tabellen wird die Erfindung weiter erläutert.
Es zeigen
Show it
In der Tab. 1 sind die chemische Zusammensetzung und der erreichnete PREN-Faktor von untersuchten Schmelzen bzw. Proben angegeben.Tab. 1 shows the chemical composition and the PREN factor achieved of examined melts or samples.
In der Tab. 2 sind die Wärmebehandlung und die Erprobungsergebnisse zusammengestellt.Tab. 2 shows the heat treatment and the test results compiled.
Claims (5)
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AT136597 | 1997-08-13 | ||
AT1365/97 | 1997-08-13 | ||
AT136597A AT405297B (en) | 1997-08-13 | 1997-08-13 | DUPLEX ALLOY FOR COMPLEXLY STRESSED COMPONENTS |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0897018A1 true EP0897018A1 (en) | 1999-02-17 |
EP0897018B1 EP0897018B1 (en) | 2003-09-03 |
Family
ID=3512308
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19980890210 Expired - Lifetime EP0897018B1 (en) | 1997-08-13 | 1998-07-17 | Duplex stainless steel with high tensile strength and good corrosion properties |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0897018B1 (en) |
AT (1) | AT405297B (en) |
DE (1) | DE59809467D1 (en) |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6187045B1 (en) * | 1999-02-10 | 2001-02-13 | Thomas K. Fehring | Enhanced biocompatible implants and alloys |
WO2003020995A1 (en) * | 2001-09-02 | 2003-03-13 | Sandvik Ab | Use of a duplex stainless steel alloy |
WO2003020994A1 (en) * | 2001-09-02 | 2003-03-13 | Sandvik Ab | Duplex steel alloy |
WO2004079028A1 (en) * | 2003-03-02 | 2004-09-16 | Sandvik Intellectual Property Ab | Duplex stainless steel alloy and use thereof |
WO2004079027A1 (en) * | 2003-03-02 | 2004-09-16 | Sandvik Intellectual Property Ab | Duplex stainless steel alloy for use in seawater applications |
WO2016118358A1 (en) * | 2015-01-20 | 2016-07-28 | General Electric Company | Corrosion resistant article and methods of making |
EP2947169A4 (en) * | 2013-01-15 | 2016-12-21 | Kobe Steel Ltd | Duplex stainless steel material and duplex stainless steel pipe |
CN113584377A (en) * | 2021-06-22 | 2021-11-02 | 济源市瑞麦特金属材料有限公司 | Nitrogen-containing stainless steel and preparation method thereof |
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EP0455625A1 (en) * | 1990-05-03 | 1991-11-06 | BÖHLER Edelstahl GmbH | High strength corrosion-resistant duplex alloy |
EP0545753A1 (en) * | 1991-11-11 | 1993-06-09 | Sumitomo Metal Industries, Ltd. | Duplex stainless steel having improved strength and corrosion resistance |
WO1995000674A1 (en) * | 1993-06-21 | 1995-01-05 | Sandvik Ab | Ferritic-austenitic stainless steel and use of the steel |
EP0683241A2 (en) * | 1994-05-21 | 1995-11-22 | Yong Soo Park | Duplex stainless steel with high corrosion resistance |
-
1997
- 1997-08-13 AT AT136597A patent/AT405297B/en not_active IP Right Cessation
-
1998
- 1998-07-17 DE DE59809467T patent/DE59809467D1/en not_active Expired - Lifetime
- 1998-07-17 EP EP19980890210 patent/EP0897018B1/en not_active Expired - Lifetime
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
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EP0455625A1 (en) * | 1990-05-03 | 1991-11-06 | BÖHLER Edelstahl GmbH | High strength corrosion-resistant duplex alloy |
EP0545753A1 (en) * | 1991-11-11 | 1993-06-09 | Sumitomo Metal Industries, Ltd. | Duplex stainless steel having improved strength and corrosion resistance |
WO1995000674A1 (en) * | 1993-06-21 | 1995-01-05 | Sandvik Ab | Ferritic-austenitic stainless steel and use of the steel |
EP0683241A2 (en) * | 1994-05-21 | 1995-11-22 | Yong Soo Park | Duplex stainless steel with high corrosion resistance |
Non-Patent Citations (1)
Title |
---|
HORVATH, W. ET AL.: "Microstructures and yield strength of nitrogen alloyed super duplex steels", ACTA MATERIALA, vol. 45, no. 4, 1997, United States, pages 1645 - 1654, XP002086990 * |
Cited By (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6187045B1 (en) * | 1999-02-10 | 2001-02-13 | Thomas K. Fehring | Enhanced biocompatible implants and alloys |
US6773520B1 (en) | 1999-02-10 | 2004-08-10 | University Of North Carolina At Charlotte | Enhanced biocompatible implants and alloys |
WO2003020995A1 (en) * | 2001-09-02 | 2003-03-13 | Sandvik Ab | Use of a duplex stainless steel alloy |
WO2003020994A1 (en) * | 2001-09-02 | 2003-03-13 | Sandvik Ab | Duplex steel alloy |
EA009108B1 (en) * | 2003-03-02 | 2007-10-26 | Сандвик Интеллекчуал Проперти Аб | Duplex stainless steel alloy for use in seawater applications |
WO2004079027A1 (en) * | 2003-03-02 | 2004-09-16 | Sandvik Intellectual Property Ab | Duplex stainless steel alloy for use in seawater applications |
WO2004079028A1 (en) * | 2003-03-02 | 2004-09-16 | Sandvik Intellectual Property Ab | Duplex stainless steel alloy and use thereof |
EA009438B1 (en) * | 2003-03-02 | 2007-12-28 | Сандвик Интеллекчуал Проперти Аб | Duplex stainless steel alloy and use thereof |
US7892366B2 (en) | 2003-03-02 | 2011-02-22 | Sandvik Intellectual Property Ab | Duplex stainless steel alloy and use thereof |
EP2947169A4 (en) * | 2013-01-15 | 2016-12-21 | Kobe Steel Ltd | Duplex stainless steel material and duplex stainless steel pipe |
WO2016118358A1 (en) * | 2015-01-20 | 2016-07-28 | General Electric Company | Corrosion resistant article and methods of making |
CN107429368A (en) * | 2015-01-20 | 2017-12-01 | 诺沃皮尼奥内技术股份有限公司 | Corrosion resistant article and its manufacture method |
CN113584377A (en) * | 2021-06-22 | 2021-11-02 | 济源市瑞麦特金属材料有限公司 | Nitrogen-containing stainless steel and preparation method thereof |
Also Published As
Publication number | Publication date |
---|---|
ATA136597A (en) | 1998-11-15 |
DE59809467D1 (en) | 2003-10-09 |
AT405297B (en) | 1999-06-25 |
EP0897018B1 (en) | 2003-09-03 |
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