EP0337846B1 - Austeno-ferritic stainless steel - Google Patents
Austeno-ferritic stainless steel Download PDFInfo
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- EP0337846B1 EP0337846B1 EP89400888A EP89400888A EP0337846B1 EP 0337846 B1 EP0337846 B1 EP 0337846B1 EP 89400888 A EP89400888 A EP 89400888A EP 89400888 A EP89400888 A EP 89400888A EP 0337846 B1 EP0337846 B1 EP 0337846B1
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- Prior art keywords
- alloy
- stainless steel
- heat treatment
- copper
- austeno
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- 229910001220 stainless steel Inorganic materials 0.000 title claims abstract description 10
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 55
- 239000000956 alloy Substances 0.000 claims abstract description 55
- 239000010949 copper Substances 0.000 claims abstract description 25
- 229910052802 copper Inorganic materials 0.000 claims abstract description 20
- 230000007797 corrosion Effects 0.000 claims abstract description 19
- 238000005260 corrosion Methods 0.000 claims abstract description 19
- 238000010438 heat treatment Methods 0.000 claims abstract description 14
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims abstract description 13
- 239000000203 mixture Substances 0.000 claims abstract description 11
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 11
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 10
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims abstract description 9
- 239000011733 molybdenum Substances 0.000 claims abstract description 8
- 229910052742 iron Inorganic materials 0.000 claims abstract description 3
- 238000001816 cooling Methods 0.000 claims description 4
- 229910000831 Steel Inorganic materials 0.000 claims description 2
- 230000008018 melting Effects 0.000 claims description 2
- 238000002844 melting Methods 0.000 claims description 2
- 238000007711 solidification Methods 0.000 claims description 2
- 230000008023 solidification Effects 0.000 claims description 2
- 239000010959 steel Substances 0.000 claims description 2
- 239000010935 stainless steel Substances 0.000 claims 5
- 229910000859 α-Fe Inorganic materials 0.000 abstract description 12
- 229910001566 austenite Inorganic materials 0.000 abstract description 4
- 229910052757 nitrogen Inorganic materials 0.000 description 12
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 11
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 11
- 229910052804 chromium Inorganic materials 0.000 description 11
- 239000011651 chromium Substances 0.000 description 11
- 238000007792 addition Methods 0.000 description 7
- 229910052748 manganese Inorganic materials 0.000 description 7
- 239000011572 manganese Substances 0.000 description 7
- 229910052759 nickel Inorganic materials 0.000 description 6
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 5
- 230000015572 biosynthetic process Effects 0.000 description 5
- 238000001556 precipitation Methods 0.000 description 4
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 3
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 230000001627 detrimental effect Effects 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 230000002378 acidificating effect Effects 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 235000011149 sulphuric acid Nutrition 0.000 description 2
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 229910052797 bismuth Inorganic materials 0.000 description 1
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000001186 cumulative effect Effects 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- ZOMNIUBKTOKEHS-UHFFFAOYSA-L dimercury dichloride Chemical class Cl[Hg][Hg]Cl ZOMNIUBKTOKEHS-UHFFFAOYSA-L 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000005553 drilling Methods 0.000 description 1
- 229910000765 intermetallic Inorganic materials 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229910000734 martensite Inorganic materials 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000002161 passivation Methods 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 230000007928 solubilization Effects 0.000 description 1
- 238000005063 solubilization Methods 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 238000011282 treatment Methods 0.000 description 1
- 230000004580 weight loss Effects 0.000 description 1
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
Definitions
- the present invention relates to an austenitic-ferritic stainless steel.
- Austeno-ferritic stainless steels are known having good mechanical properties, good corrosion resistance and good weldability.
- Patent application EP 0.156.778 thus describes an austenitic-ferritic stainless steel alloy whose austenitic phase remains stable allowing cold deformation between 10 and 30%, good weldability and good corrosion resistance.
- Patent application GB-A-1 456 634 discloses an austeno-ferritic steel with the composition in percentage by weight: 0.01-0.1% C, 0.2-2% Si, 0.2-4% Mn, 23-30% Cr, 4 -7% Ni, 0.06-0.4% N, 1-5% Mo, 1.3-4% Cu, the balance being Fe.
- the copper content allows an improvement in resistance to rupture and corrosion.
- the object of the present invention is to produce an austeno-ferritic alloy whose corrosion resistance is improved compared to existing alloys and which has a high machinability index.
- Such an alloy has a low percentage of molybdenum but a high copper content, the latter being dissolved by heat treatment above 900 ° C. and followed by rapid cooling to ambient, the composition of this alloy being the next, expressed as a percentage by weight. the balance being Fe.
- the composition is balanced to obtain between 38 and 70% of ferrite at 300 K (27 ° C).
- compositions have been summarized as elements of addition to Fe for the alloys A and B according to the invention and the known alloys.
- the alloys of the invention are produced by melting to a minimum of 1600 ° C. and reheated to approximately 1180 ° C. after solidification. They undergo sheet metal rolling. Samples are taken in order to determine the structural stability as a function of the heat treatments and more particularly the hardening, the mechanical and physical characteristics, the corrosion resistance as well as the aptitude for machinability.
- Carbon is reduced to lower lower contents to 0.06% in order to reduce the risks of carbide formation during heat treatments which would be detrimental to the resistance to certain forms of corrosion.
- the silicon is reduced to low contents lower than 1.2% in order to reduce the risks of formation of intermetallic compounds which weaken the alloy.
- Manganese makes it possible to increase the solid dissolution of nitrogen in the alloy but its content must be limited to 3% so as not to become detrimental to the resistance to generalized and localized corrosion in certain cases.
- the chromium is controlled so that the volume fractions of the ferritic and austenitic phases are close. Too low a content does not allow a sufficient volume fraction of ferrite to be obtained.
- Too high a content may require significant additions of nickel and nitrogen, which, given the price of nickel, should be avoided.
- the alloy has an increased tendency to precipitate embrittling intermetallic phases during heat treatments.
- chromium contents between 21 and 25% are used, more precisely a content of 23.5%. At such a percentage, the alloy has excellent corrosion resistance.
- Such a chromium content associated with a low nickel and molybdenum content makes it possible to avoid, even for heat treatments of a few hours, the formation of an ⁇ 'phase, by demixing of the ⁇ phase, hardening and embrittling.
- Nickel is an element which stabilizes the austenitic phase so as to optimize the austenite / ferrite balance. Given its price, its addition is limited to 3 to 6%, in particular 4.2%. Nitrogen is involved in maintaining the austenite / ferrite balance and, moreover, such an addition makes it possible to increase the mechanical characteristics and the resistance to pitting corrosion. The addition of nitrogen is limited to 0.30 and often close to 0.13%.
- Molybdenum is limited to a percentage of 1% maximum so as to reduce the manufacturing costs of the alloy and limit the formation of intermetallic phases. Molybdenum improves the corrosion resistance of the alloy.
- Copper unlike known alloys, is present in relatively large percentages between 1 and 3.5%. This element is generally present in small quantities in known alloys because its solubility in austeno-ferritic alloys during cooling is limited.
- This hardening is proportional for a heat treatment given to the copper content.
- hardened alloy B it is alloy B which has been subjected to a heat treatment of 5 h at 400 ° C.
- the alloys according to the invention have improved mechanical properties, in particular the values of the conventional elastic limit (Re 0.2%) and the elastic limit at 1% (Re 1%) while retaining a resilience value on a V-notch test piece (KCV) and sufficient ductility (Elongation A).
- the machinability index of the alloys according to the invention is significantly improved compared to known alloys and in particular to the alloy of patent application EP 0.156.778.
- the three parameters studied are Brinnel hardness (HB), the machinability index for a cutting speed of 0.5 m / min and a drilling test in number of holes corresponding to a cumulative length of 500mm (0.5 m).
- the known alloys have hardness values which frame the hardness value of sample A of the alloy according to the invention and all of the two machinability tests clearly show performance. of alloy A.
- the starting potential is -600 mV relative to a saturated calomel electrode (DHW) and for a scanning speed of 0.25 mV / sec.
- the return was made for a current of 100 ⁇ A up to -1100 mV / DHW.
- the passivation current Ip is reduced while the breaking potential is increased, which makes it possible to extend the field of use of the alloy according to the invention in terms of redox potential.
- the alloy according to the invention solves the problem posed, by improving the mechanical characteristics, the machinability without these improvements being detrimental to the qualities of corrosion resistance.
- the Cu content must be limited to 3.5% in order to avoid the major risks of tearing of products during processing.
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
- Catalysts (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Glass Compositions (AREA)
Abstract
Description
La présente invention a pour objet un acier inoxydable austéno-ferritique.The present invention relates to an austenitic-ferritic stainless steel.
On connaît des aciers inoxydables austéno-ferritiques ayant de bonnes propriétés mécaniques, une bonne résistance à la corrosion et une bonne soudabilité.Austeno-ferritic stainless steels are known having good mechanical properties, good corrosion resistance and good weldability.
De tels alliages comprennent, outre le fer qui constitue le solde, du
- chrome et du molybdène de façon à améliorer les propriétés résistance à la corrosion ;
- nickel et azote de façon à améliorer la stabilité de la phase austénitique ;
- carbone en faible pourcentage car il affecte la résistance à la corrosion compte tenu de sa faible solubilité dans la ferrite ;
- silicium ;
- manganèse.
- chromium and molybdenum so as to improve the corrosion resistance properties;
- nickel and nitrogen so as to improve the stability of the austenitic phase;
- carbon in low percentage because it affects corrosion resistance due to its low solubility in ferrite;
- silicon;
- manganese.
La demande de brevet EP 0.156.778 décrit ainsi un alliage d'acier inoxydable austéno-ferritique dont la phase austénitique reste stable autorisant des déformations à froid entre 10 et 30 %, une bonne soudabilité et une bonne résistance à la corrosion.Patent application EP 0.156.778 thus describes an austenitic-ferritic stainless steel alloy whose austenitic phase remains stable allowing cold deformation between 10 and 30%, good weldability and good corrosion resistance.
La composition d'un tel alliage est la suivante :
le solde étant du Fe, les composés ci-dessus devant répondre par ailleurs aux conditions suivantes :
- pourcentage de ferrite α entre 35 et 65
- pourcentage de ferrite α < 0,20 (% Cr/% N) + 23
- (% Cr + % Mn)/% N > 120.
- 22,4 x % Cr + 30 x % Mn + 22 x Mo + 26 % Cu + 110 x % N > 540.
- % Mo + % Cu > 0,15 avec % Cu d'au moins 0,005 %.
the balance being Fe, the above compounds must also meet the following conditions:
- percentage of α ferrite between 35 and 65
- percentage of ferrite α <0.20 (% Cr /% N) + 23
- (% Cr +% Mn) /% N> 120.
- 22.4 x% Cr + 30 x% Mn + 22 x Mo + 26% Cu + 110 x% N> 540.
- % Mo +% Cu> 0.15 with% Cu of at least 0.005%.
De tels alliages ont une phase austénitique stable qui n'a pas tendance à se transformer en martensite mais ils sont difficilement usinables et leurs propriétés mécaniques restent faibles. La demande de brevet GB-A-1 456 634 divulgue un acier austéno-ferritique à la composition en pourcentage en poids : 0.01-0.1 % C, 0.2-2 % Si, 0.2-4 % Mn, 23-30 % Cr, 4-7 % Ni, 0.06-0.4 % N, 1-5 % Mo, 1.3-4 % Cu, le solde étant du Fe. La teneur en cuivre permet une amélioration de la résistance à la rupture et à la corrosion.Such alloys have a stable austenitic phase which does not tend to transform into martensite but they are difficult to machine and their mechanical properties remain weak. Patent application GB-A-1 456 634 discloses an austeno-ferritic steel with the composition in percentage by weight: 0.01-0.1% C, 0.2-2% Si, 0.2-4% Mn, 23-30% Cr, 4 -7% Ni, 0.06-0.4% N, 1-5% Mo, 1.3-4% Cu, the balance being Fe. The copper content allows an improvement in resistance to rupture and corrosion.
La présente invention a pour but la réalisation d'un alliage austéno-ferritique dont la tenue à la corrosion est améliorée par rapport aux alliages existants et qui présente un indice élevé d'usinabilité.The object of the present invention is to produce an austeno-ferritic alloy whose corrosion resistance is improved compared to existing alloys and which has a high machinability index.
Un tel alliage possède un faible pourcentage de molybdène mais une forte teneur en cuivre, ce dernier étant mis en solution par traitement thermique au-dessus de 900°C et suivi d'un refroidissement rapide à l'ambiante, la composition de cet alliage étant la suivante, exprimée en pourcentage en poids.
le solde étant du Fe. La composition est équilibrée pour obtenir entre 38 et 70 % de ferrite à 300 K (27°C).Such an alloy has a low percentage of molybdenum but a high copper content, the latter being dissolved by heat treatment above 900 ° C. and followed by rapid cooling to ambient, the composition of this alloy being the next, expressed as a percentage by weight.
the balance being Fe. The composition is balanced to obtain between 38 and 70% of ferrite at 300 K (27 ° C).
D'autres avantages et caractéristiques apparaîtront à la lecture de la description qui va suivre de modes de réalisation particuliers de l'alliage selon l'invention, la figure unique annexée représentant les domaines de durcissement de l'alliage dans un diagramme temps, température.Other advantages and characteristics will appear on reading the following description of particular embodiments of the alloy according to the invention, the single appended figure representing the areas of hardening of the alloy in a time, temperature diagram.
Deux alliages particuliers A et B sont analysés comparativement à des alliages de composition connue, notamment l'UNS 32304 correspondant à l'alliage décrit dans la demande de brevet EP 0.156.778.
Dans le tableau ci-dessus, on a récapitulé les compositions en éléments d'addition au Fe pour les alliages A et B selon l'invention et les alliages connus.In the table above, the compositions have been summarized as elements of addition to Fe for the alloys A and B according to the invention and the known alloys.
Les alliages de l'invention sont réalisés par fusion jusqu'à 1600°C minimum et réchauffés à 1180°C environ après solidification. Ils subissent un laminage en tôles. Des prélèvements sont effectués afin de déterminer la stabilité structurale en fonction des traitements thermiques et plus particulièrement le durcissement, les caractéristiques mécaniques et physiques, la résistance à la corrosion ainsi que l'aptitude à l'usinabilité.The alloys of the invention are produced by melting to a minimum of 1600 ° C. and reheated to approximately 1180 ° C. after solidification. They undergo sheet metal rolling. Samples are taken in order to determine the structural stability as a function of the heat treatments and more particularly the hardening, the mechanical and physical characteristics, the corrosion resistance as well as the aptitude for machinability.
Au préalable, il est nécessaire d'étudier l'influence des différents éléments d'addition.
Le carbone est réduit à de faibles teneurs inférieures à 0,06 % afin de réduire les risques de formation de carbures au cours des traitements thermiques ce qui serait préjudiciable à la résistance à certaines formes de corrosion.
Le silicium est réduit à de faibles teneurs inférieures à 1,2 % afin de réduire les risques de formation de composés intermétalliques qui fragilisent l'alliage.
Le manganèse permet d'augmenter la mise en solution solide de l'azote dans l'alliage mais sa teneur doit être limitée à 3 % pour ne pas devenir préjudiciable à la tenue à la corrosion généralisée et localisée dans certains cas.
Le chrome est contrôlé de façon à ce que les fractions volumiques des phases ferritiques et austénitiques soient voisines. Une teneur trop faible ne permet pas d'obtenir une fraction volumique de ferrite suffisante.Beforehand, it is necessary to study the influence of the different elements of addition.
Carbon is reduced to lower lower contents to 0.06% in order to reduce the risks of carbide formation during heat treatments which would be detrimental to the resistance to certain forms of corrosion.
The silicon is reduced to low contents lower than 1.2% in order to reduce the risks of formation of intermetallic compounds which weaken the alloy.
Manganese makes it possible to increase the solid dissolution of nitrogen in the alloy but its content must be limited to 3% so as not to become detrimental to the resistance to generalized and localized corrosion in certain cases.
The chromium is controlled so that the volume fractions of the ferritic and austenitic phases are close. Too low a content does not allow a sufficient volume fraction of ferrite to be obtained.
Une teneur trop élevée peut nécessiter des additions importantes de nickel et d'azote, ce qui, compte tenu du prix du nickel, doit être évité. De plus, l'alliage a une tendance accrue à la précipitation de phases intermétalliques fragilisantes lors des traitements thermiques.Too high a content may require significant additions of nickel and nitrogen, which, given the price of nickel, should be avoided. In addition, the alloy has an increased tendency to precipitate embrittling intermetallic phases during heat treatments.
Aussi de façon classique on utilise on utilise des teneurs en chrome comprises entre 21 et 25 %, plus exactement une teneur de 23,5 %. A un tel pourcentage, l'alliage a une excellente résistance à la corrosion.Also in a conventional manner, chromium contents between 21 and 25% are used, more precisely a content of 23.5%. At such a percentage, the alloy has excellent corrosion resistance.
Une telle teneur en chrome associée à une faible teneur en nickel et molybdène permet d'éviter, même pour des traitements thermiques de quelques heures, la formation d'une phase α', par démixtion de la phase α, durcissante et fragilisante. La formation d'une telle phase α' intervient lors de traitements thermiques entre 300 et 500°C.
Le nickel est un élément qui stabilise la phase austénitique de façon à optimiser l'équilibre austénite/ferrite. Compte tenu de son prix on limite son addition entre 3 et 6 % plus particulièrement 4,2 %.
L'azote intervient pour maintenir l'équilibre austénite/ferrite et de plus une telle addition permet d'accroître les caractéristiques mécaniques et la tenue à la corrosion par piqûres. L'addition de l'azote est limitée à 0,30 et souvent voisine de 0,13 %.Such a chromium content associated with a low nickel and molybdenum content makes it possible to avoid, even for heat treatments of a few hours, the formation of an α 'phase, by demixing of the α phase, hardening and embrittling. The formation of such a phase α 'occurs during treatments thermal between 300 and 500 ° C.
Nickel is an element which stabilizes the austenitic phase so as to optimize the austenite / ferrite balance. Given its price, its addition is limited to 3 to 6%, in particular 4.2%.
Nitrogen is involved in maintaining the austenite / ferrite balance and, moreover, such an addition makes it possible to increase the mechanical characteristics and the resistance to pitting corrosion. The addition of nitrogen is limited to 0.30 and often close to 0.13%.
Le molybdène est limité à un pourcentage de 1 % maximum de façon à réduire les coûts de fabrication de l'alliage et à limiter la formation de phases intermétalliques. Le molybdène améliore la tenue à la corrosion de l'alliage.Molybdenum is limited to a percentage of 1% maximum so as to reduce the manufacturing costs of the alloy and limit the formation of intermetallic phases. Molybdenum improves the corrosion resistance of the alloy.
Le cuivre, contrairement aux alliages connus, est présent dans des pourcentages relativement importants entre 1 et 3,5 %. Cet élément est généralement présent en faible quantité dans les alliages connus car sa solubilité dans les alliages austéno-ferritiques lors du refroidssement est limitée.Copper, unlike known alloys, is present in relatively large percentages between 1 and 3.5%. This element is generally present in small quantities in known alloys because its solubility in austeno-ferritic alloys during cooling is limited.
Par contre, selon l'invention, une mise en solution par traitement thermique à haute température à des températures supérieures à 900°C est possible. Cette étape doit être suivie d'un refroidissement rapide à l'ambiante de façon à ce que la structure austénite/ferrite soit exempte de précipitation et reste sursaturée en cuivre. Le cuivre : - augmente la tenue de l'alliage vis-à-vis de certains milieux acides notamment les milieux sulfuriques.
- améliore l'aptitude à l'usinabilité.By cons, according to the invention, a solution by heat treatment at high temperature at temperatures above 900 ° C is possible. This step should be followed by rapid ambient cooling so that the austenite / ferrite structure is free of precipitation and remains supersaturated with copper. Copper: - increases the resistance of the alloy to certain acidic media, in particular sulfuric media.
- improves the ability to be machined.
On a étudié la stabilité structurale de l'alliage B en fonction du temps et de la température ainsi que représenté à la figure en annexe.We studied the structural stability of alloy B as a function of time and temperature as shown in the attached figure.
Dans l'intervalle 300-600°C, un durcissement important de l'alliage se produit par précipitation de particules enrichies en cuivre dans la phase ferritique de l'alliage.In the range 300-600 ° C, significant hardening of the alloy occurs by precipitation of copper-enriched particles in the ferritic phase of the alloy.
Ce durcissement est proportionnel pour un traitement thermique donné à la teneur en cuivre.This hardening is proportional for a heat treatment given to the copper content.
Par contre il y a un retard à la précipitation pour les maintiens à 700°-900°C dû à la stabilité de la phase ferritique vis-à-vis de la phase intermétallique, conférée par la très faible teneur en molybdène.On the other hand, there is a delay in precipitation for maintaining at 700 ° -900 ° C due to the stability of the ferritic phase with respect to the intermetallic phase, conferred by the very low molybdenum content.
Les propriétés mécaniques sont récapitulées dans le tableau ci-dessous
Quant à l'alliage B durci, il s'agit de l'alliage B auquel on a fait subir un traitement thermique de 5 h à 400°C.As for hardened alloy B, it is alloy B which has been subjected to a heat treatment of 5 h at 400 ° C.
Les alliages selon l'invention possèdent des propriétés mécaniques améliorées notamment les valeurs de la limite d'élasticité conventionnelle (Re 0,2 %) et de la limite d'élasticité à 1 % (Re 1 %) tout en conservant une valeur de la résilience sur éprouvette à entaille en V (KCV) et une ductilité (Allongement A) suffisantes.The alloys according to the invention have improved mechanical properties, in particular the values of the conventional elastic limit (Re 0.2%) and the elastic limit at 1% (Re 1%) while retaining a resilience value on a V-notch test piece (KCV) and sufficient ductility (Elongation A).
Quant à la dureté, elle augmente sensiblement notamment après traitement thermique.As for hardness, it increases significantly, especially after heat treatment.
L'indice d'usinabilité des alliages selon l'invention est amélioré de façon notable comparé aux alliages connus et notamment à l'alliage de la demande de brevet EP 0.156.778.The machinability index of the alloys according to the invention is significantly improved compared to known alloys and in particular to the alloy of patent application EP 0.156.778.
Les résultats sont récapitulés dans le tableau suivant :
Les trois paramètres étudiés sont la dureté Brinnel (HB), l'indice d'usinabilité pour une vitesse de coupe de 0,5 m/mn et un essai de perçage en nombre de trous correspondant à une longueur cumulée de 500mm (0,5 m).The three parameters studied are Brinnel hardness (HB), the machinability index for a cutting speed of 0.5 m / min and a drilling test in number of holes corresponding to a cumulative length of 500mm (0.5 m).
Les alliages connus ont des valeurs de dureté qui encadrent la valeur de dureté de l'échantillon A de l'alliage selon l'invention et l'ensemble des deux tests d'usinabilité montre des performances netement supérieures de l'alliage A.The known alloys have hardness values which frame the hardness value of sample A of the alloy according to the invention and all of the two machinability tests clearly show performance. of alloy A.
Les essais de corrosion montrent que les avantages acquis ne le sont pas au détriment de la résistance à la corrosion.Corrosion tests show that the advantages gained are not at the expense of corrosion resistance.
Les mesures récapitulées dans le tableau ci-dessous ont été obtenues en milieux acides (H₂SO₄ à 50°C).
Pour l'obtention des courbes de polarisation qui ont conduit à ces résultats, le potentiel de départ est de -600 mV par rapport à une électrode au calomel saturé (ecs) et pour une vitesse de balayage de 0,25 mV/sec. Le retour a été réalisé pour un courant de 100 µA jusqu'à -1100 mV/ecs.To obtain the polarization curves which led to these results, the starting potential is -600 mV relative to a saturated calomel electrode (DHW) and for a scanning speed of 0.25 mV / sec. The return was made for a current of 100 µA up to -1100 mV / DHW.
Le courant de passivation Ip est réduit tandis que le potentiel de rupture est augmenté ce qui permet d'étendre le domaine d'emploi de l'alliage selon l'invention en matière de potentiel d'oxydo réduction.The passivation current Ip is reduced while the breaking potential is increased, which makes it possible to extend the field of use of the alloy according to the invention in terms of redox potential.
Ceci est également dû au cuivre ce qui est confirmé par la résistance de l'alliage B après traitement thermique dans un milieu acide en présence de particules abrasives de diamètre 0,5 ; 1,19 et 2,38 mm (cf tableau ci-dessous) :This is also due to copper, which is confirmed by the resistance of alloy B after heat treatment in an acid medium in the presence of abrasive particles with a diameter of 0.5; 1.19 and 2.38 mm (see table below):
Résultat de perte de poids (mg) 8 h H₂SO₄ (2N)
L'alliage selon l'invention résoud le problème posé, en améliorant les caractéristiques mécaniques, l'usinabilité sans que ces améliorations soient préjudiciables aux qualités de résistance à la corrosion.The alloy according to the invention solves the problem posed, by improving the mechanical characteristics, the machinability without these improvements being detrimental to the qualities of corrosion resistance.
Les améliorations des qualités de cet alliage lui sont conférées par l'augmentation du pourcentage en cuivre et la solubilisation ou la précipitation partielle de ce dernier.Improvements in the qualities of this alloy are given to it by the increase in the percentage of copper and the solubilization or partial precipitation of the latter.
Ces résultats sont remarquables compte-tenu du fait que les alliages connus notamment UNS 32304 préconisent des pourcentages Cu + Mo = 1 % dans un mode de réalisation préféré.These results are remarkable in view of the fact that the known alloys in particular UNS 32304 recommend percentages Cu + Mo = 1% in a preferred embodiment.
Néanmoins, dans l'alliage selon l'invention, la teneur en Cu doit être limitée à 3,5 % afin d'éviter les risques majeurs de déchirures de produits lors de la mise en oeuvre.However, in the alloy according to the invention, the Cu content must be limited to 3.5% in order to avoid the major risks of tearing of products during processing.
Dans cette fourchette de 1 à 3,5 %, l'homme de l'art adaptera le pourcentage en fonction de l'utilisation de l'alliage.Within this range of 1 to 3.5%, a person skilled in the art will adapt the percentage according to the use of the alloy.
De même des additions complémentaires connues permettent d'augmenter l'usinabilité telles que soufre, bismuth.Similarly, known additional additions make it possible to increase the machinability such as sulfur, bismuth.
Claims (6)
- An austeno-ferritic alloy of stainless steel having a very good corrosion stability and a high machinability index, comprising a low content of molybdenum and a high content of copper dissolved by heat treatment of the alloy above 900°C followed by rapid cooling at the ambient temperature, the composition ding the following:the remainder being iron.
- An alloy of stainless steel according to Claim 1, characterised in that it has the following composition:
C = 0.02% by weight
Si = 0.6
Mn = 1.9
Ni = 4.1
Cr = 23.5
Mo = 0.13
N = 0.1
Cu = 1.6. - An alloy of stainless steel according to Claim 1, characterised in that it has the following composition:
C = 0.02
Si = 0.5
Mn = 2
Ni = 3.9
Cr = 24.3
Mo = 0.14
N = 0.09
Cu = 2.8. - An alloy of stainless steel according to any one of Claims 1 to 3, characterised in that the copper is solubilised by melting at a minimum of 1600°C and then treating again at 1180°C after solidification.
- An alloy of steel according to Claim 4, characterised in that the alloy undergoes heat treatment between 300 and 500°C so as to precipitate the solubilised copper partially.
- An alloy of stainless steel according to Claim 5, characterised in that the heat treatment is carried out for 5 hours at 400°C.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT89400888T ATE89874T1 (en) | 1988-04-15 | 1989-03-30 | AUSTENITIC-FERRITIC STAINLESS STEEL. |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR8805045A FR2630132B1 (en) | 1988-04-15 | 1988-04-15 | AUSTENO-FERRITIC STAINLESS STEEL |
| FR8805045 | 1988-04-15 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0337846A1 EP0337846A1 (en) | 1989-10-18 |
| EP0337846B1 true EP0337846B1 (en) | 1993-05-26 |
Family
ID=9365363
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP89400888A Expired - Lifetime EP0337846B1 (en) | 1988-04-15 | 1989-03-30 | Austeno-ferritic stainless steel |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0337846B1 (en) |
| AT (1) | ATE89874T1 (en) |
| CA (1) | CA1340030C (en) |
| DE (1) | DE68906708T2 (en) |
| FI (1) | FI93126C (en) |
| FR (1) | FR2630132B1 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0750053B1 (en) * | 1994-12-16 | 2001-10-10 | Sumitomo Metal Industries, Ltd. | Duplex stainless steel excellent in corrosion resistance |
| JP3508095B2 (en) * | 1999-06-15 | 2004-03-22 | 株式会社クボタ | Ferrite-austenite duplex stainless steel with excellent heat fatigue resistance, corrosion fatigue resistance, drillability, etc. and suction roll body for papermaking |
| KR20090005252A (en) * | 2004-01-29 | 2009-01-12 | 제이에프이 스틸 가부시키가이샤 | Austenitic-ferritic stainless steel |
| TWI394848B (en) | 2007-10-10 | 2013-05-01 | Nippon Steel & Sumikin Sst | Two-phase stainless steel wire rod, steel wire, bolt and manufacturing method thereof |
| SE533635C2 (en) | 2009-01-30 | 2010-11-16 | Sandvik Intellectual Property | Austenitic stainless steel alloy with low nickel content, and article thereof |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1158614A (en) * | 1967-03-16 | 1969-07-16 | Langley Alloys Ltd | Improvement in Stainless Steels |
| GB1456634A (en) * | 1972-09-13 | 1976-11-24 | Langley Alloys Ltd | High strength stainless steel having a high resistance to corro sive and abrasive wear in corrosive environments particularly chloride environments |
| CA1242095A (en) * | 1984-02-07 | 1988-09-20 | Akira Yoshitake | Ferritic-austenitic duplex stainless steel |
| SE451465B (en) * | 1984-03-30 | 1987-10-12 | Sandvik Steel Ab | FERRIT-AUSTENITIC STAINLESS STEEL MICROLEGATED WITH MOLYBID AND COPPER AND APPLICATION OF THE STEEL |
| US4612069A (en) * | 1984-08-06 | 1986-09-16 | Sandusky Foundry & Machine Company | Pitting resistant duplex stainless steel alloy |
-
1988
- 1988-04-15 FR FR8805045A patent/FR2630132B1/en not_active Expired - Lifetime
-
1989
- 1989-03-30 DE DE8989400888T patent/DE68906708T2/en not_active Expired - Fee Related
- 1989-03-30 AT AT89400888T patent/ATE89874T1/en not_active IP Right Cessation
- 1989-03-30 EP EP89400888A patent/EP0337846B1/en not_active Expired - Lifetime
- 1989-04-14 FI FI891783A patent/FI93126C/en not_active IP Right Cessation
- 1989-04-14 CA CA000596675A patent/CA1340030C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| FI891783A0 (en) | 1989-04-14 |
| FI93126B (en) | 1994-11-15 |
| DE68906708D1 (en) | 1993-07-01 |
| EP0337846A1 (en) | 1989-10-18 |
| FI891783A (en) | 1989-10-16 |
| FR2630132B1 (en) | 1990-08-24 |
| CA1340030C (en) | 1998-09-08 |
| ATE89874T1 (en) | 1993-06-15 |
| FI93126C (en) | 1995-02-27 |
| FR2630132A1 (en) | 1989-10-20 |
| DE68906708T2 (en) | 1993-09-16 |
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