EP3960881A1 - Acier inoxydable austénitique - Google Patents

Acier inoxydable austénitique Download PDF

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EP3960881A1
EP3960881A1 EP20193794.3A EP20193794A EP3960881A1 EP 3960881 A1 EP3960881 A1 EP 3960881A1 EP 20193794 A EP20193794 A EP 20193794A EP 3960881 A1 EP3960881 A1 EP 3960881A1
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Prior art keywords
weight
stainless steel
austenitic stainless
steel according
content
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German (de)
English (en)
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James Oliver
Jan Y. Jonsson
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Outokumpu Oyj
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Outokumpu Oyj
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Priority to EP20193794.3A priority Critical patent/EP3960881A1/fr
Priority to US18/042,891 priority patent/US20230357909A1/en
Priority to BR112023003604A priority patent/BR112023003604A2/pt
Priority to MX2023002487A priority patent/MX2023002487A/es
Priority to TW110132317A priority patent/TW202214879A/zh
Priority to PCT/EP2021/073959 priority patent/WO2022049051A1/fr
Priority to KR1020237010596A priority patent/KR20230060512A/ko
Priority to JP2023512449A priority patent/JP2023540461A/ja
Priority to CN202180053606.XA priority patent/CN115997042A/zh
Publication of EP3960881A1 publication Critical patent/EP3960881A1/fr
Pending legal-status Critical Current

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    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
    • 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
    • C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
    • 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
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • 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
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • 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
    • 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
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/001—Austenite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • 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
    • 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
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese

Definitions

  • This invention relates to an austenitic stainless steel which has high formability with the TRIP (Transformation Induced Plasticity) effect and high corrosion resistance and optimized pitting resistance equivalent (PRE).
  • TRIP Transformation Induced Plasticity
  • PRE pitting resistance equivalent
  • the transformation induced plasticity (TRIP) effect refers to the transformation of metastable retained austenite to martensite during plastic deformation as a result of imposed stress or strain. This property allows stainless steels having the TRIP effect to have a high formability, while retaining excellent strength.
  • Sulphur is limited to less than 0,010 weight % and preferably less than 0,005 weight %
  • the phosphorus content is less than 0,040 weight % and the sum of sulphur and phosphorus (S+P) is less than 0,04 weight %
  • the total oxygen content is below 100 ppm.
  • the aluminium content is maximized to less than 0,04 weight % and preferably the maximum is less than 0,03 weight %.
  • boron, calcium and cerium are optionally added in small quantities; the preferred contents for boron and calcium are less than 0,004 weight % and for cerium less than 0,1 weight %.
  • cobalt can be added up to 1 weight % for partial replacement of nickel.
  • one or more of the group containing niobium, titanium and vanadium can be optionally added in the stainless steel of the invention, the contents of niobium and titanium being limited up to 0,1 weight % and the vanadium content being limited up to 0,2 weight %.
  • the pitting resistance equivalent has been optimized to give good corrosion resistance, being in the range of 30-36.
  • the critical pitting temperature (CPT) is in the range of 34-45°C.
  • Heat treatment is performed so that the microstructure of the stainless steel contains 45 - 80 % austenite in the heat treated condition, the remaining microstructure being ferrite.
  • the measured M d30 temperature of the stainless steel is adjusted between -30 and 90°C, preferably in the range 10-60°C in order to utilize the TRIP effect for improving the formability of the stainless steel.
  • WO patent application 2011/135170 a method for manufacturing a ferritic-austenitic stainless steel having good formability and high elongation, which steel contains in weight % less than 0,05 % C, 0,2-0,7 % Si, 2-5 % Mn, 19-20,5 % Cr, 0,8-1,35 % Ni, less than 0,6 % Mo, less than 1 % Cu, 0,16-0,24 % N, the balance being iron and inevitable impurities.
  • the stainless steel of the WO patent application 2011/135170 is heat treated so that the microstructure of the stainless steel contains 45 - 75 % austenite in the heat treated condition, the remaining microstructure being ferrite. Further, the measured M d30 temperature of the stainless steel is adjusted between 0 and 50 °C in order to utilize the TRIP effect for improving the formability of the stainless steel.
  • a ferritic austenitic stainless steel utilizing the TRIP effect which contains less than 0,04 weight % C, less than 0,7 weight % Si, less than 2,5 weight % Mn, 18,5-22,5 weight % Cr, 0,8-4,5 weight % Ni, 0,6-1,4 weight % Mo, less than 1 weight % Cu, 0,10-0,24 weight % N, the rest being iron and inevitable impurities occurring in stainless steels.
  • Sulphur is limited to less than 0,010 weight % and preferably less than 0,005 weight %
  • the phosphorus content is less than 0,040 weight % and the sum of sulphur and phosphorus (S+P) is less than 0,04 weight %
  • the total oxygen content is below 100 ppm.
  • the stainless steel optionally contains one or more added elements in the following: the aluminium content is maximized to less than 0,04 weight % and preferably the maximum is less than 0,03 weight %.
  • boron, calcium and cerium are optionally added in small quantities; the preferred contents for boron and calcium are less than 0,003 weight % and for cerium less than 0,1 weight %.
  • cobalt can be added up to 1 weight % for partial replacement of nickel, and tungsten can be added up to 0,5 weight % as partial replacement of molybdenum.
  • one or more of the group containing niobium, titanium and vanadium can be optionally added in the stainless steel of the invention, the contents of niobium and titanium being limited up to 0,1 weight % and the vanadium content being limited up to 0,2 weight %.
  • the pitting resistance equivalent has been optimized to give good corrosion resistance, being in the range of 27-29,5.
  • the critical pitting temperature (CPT) is in the range of 20-33 °C, preferably 23-31 °C.
  • the TRIP (Transformation Induced Plasticity) effect in the austenite phase is maintained in accordance with the measured M d30 temperature at the range of 0-90°C, preferably in the range of 10-70°C, in order to ensure the good formability.
  • the proportion of the austenite phase in the microstructure of the stainless steel of the invention is in the heat treated condition 45-75 volume %, advantageously 55-65 volume %, the rest being ferrite, in order to create favourable conditions for the TRIP effect.
  • the heat treatment can be carried out using different heat treatment methods, such as solution annealing, high-frequency induction annealing or local annealing, at the temperature range from 900 to 1200 °C, preferably from 950 to 1150°C.
  • Japanese patent application 2014001422A shows an austenitic stainless steel with composition in mass%, C: 0.02 to 0.30%, Cr: 10.0 to 25.0%, Ni: 3.5 to 10.0%, Si: 0.1 to 3.0%, Mn: 0.5% to 5.0%, N: 0.10 to 0.40%, Mo: 0 to 3.0%, Cu: 0 to 3.0%, Ti: 0 to 0.10%, Nb: 0 to 0.50%, V: 0 to 1.0%, with a calculated M d30 of 0-40 based on a formula very similar to Nohara.
  • the chemical range is very wide but the examples given in the invention show predominantly low levels of Mo and N which give a low PRE and corrosion resistance.
  • the invention shows that austenitic alloys with a balanced Ni and N content can have a low stabililty but this is done only with a low PRE and corrosion resistance due to low Mo and in reality the real M d30 is likely to be much higher than the claimed region.
  • the present invention describes a new austenitic stainless steel utilizing the TRIP effect described in the prior art with an addition of a high pitting resistance equivalent (PRE) and giving therefore superior corrosion resistance combined with a TRIP effect with improved formability.
  • PRE pitting resistance equivalent
  • the new invention has a PRE and corrosion resistance that is far superior.
  • the TRIP effect and PRE is substantially higher.
  • the PRE and corrosion resistance of the invention is up to a similar level, but with a far superior TRIP effect that is not otherwise observed in any other high alloyed austenitic stainless steel.
  • the new invention has a much leaner composition in particular considering the Ni-content. This gives the invention a unique combination of high corrosion, TRIP and a cost effective alternative.
  • the essential features of the invention are enlisted in the appended claims.
  • the austenitic stainless steel contains less than 0,04 weight % C, 0,2-0,8 weight % Si, 0-2,0 weight % Mn, 16,0-19,0 weight % Cr, 4,0-6,5 weight % Ni, 1,0-4,0 weight % Mo, 0-4,0 weight % W, 0-2,0 weight % Cu, 0,20-0,30 weight % N, the rest being iron and inevitable impurities occurring in stainless steels.
  • Sulphur is limited to less than 0,010 weight % and preferably less than 0,005 weight %
  • the phosphorus content is less than 0,040 weight % and the sum of sulphur and phosphorus (S+P) is less than 0,04 weight %
  • the total oxygen content is below 100 ppm.
  • the austenitic stainless steel of the invention optionally contains one or more added elements in the following: the aluminium content is maximized to less than 0,04 weight % and preferably the maximum is less than 0,03 weight %. Further, boron, calcium and cerium are optionally added in small quantities; the preferred contents for boron and calcium are less than 0,004 weight % and for cerium less than 0,1 weight %. Optionally cobalt can be added up to 1 weight % for partial replacement of nickel. Also one or more of the group containing niobium, titanium and vanadium can be optionally added in the austenitic stainless steel of the invention, the contents of niobium and titanium being limited up to 0,1 weight % and the vanadium content being limited up to 0,2 weight %.
  • the pitting resistance equivalent has been optimized to give good corrosion resistance, being at the range of 27-35.
  • the critical pitting temperature (CPT) is in the range of 30-50°C
  • the TRIP (Transformation Induced Plasticity) effect in the austenite phase is maintained in accordance with the calculated M d30 temperature at the range of - 70°C to +60°C.
  • the M d30 -temperature which is a measure for the austenite stability to the TRIP effect, is defined as the temperature at which 0,3 true strain yields 50% transformation of the austenite to martensite.
  • the stacking fault energy of the invented stainless steels is much lower than commercially available stainless steels and is between 10-16mJ/m 2 according to formula (3).
  • the proportion of the ferrite phase in the microstructure of the austenitic stainless steel of the invention is in the heat treated condition ⁇ 10 volume %.
  • the heat treatment can be carried out using different heat treatment methods, such as solution annealing, high-frequency induction annealing, local annealing or any other type of heat treatment at the temperature range from 900 to 1200 °C, preferably from 950 to 1150°C.
  • Carbon (C) partitions to the austenite phase and has a strong effect on austenite stability. Carbon can be added up to 0,04 % but higher levels have detrimental influence on corrosion resistance.
  • Nitrogen (N) is an important austenite stabilizer in stainless steels and like carbon it increases the stability against martensite. Nitrogen also increases strength, strain hardening and corrosion resistance. The general empirical expressions on the M d30 temperature indicate that nitrogen and carbon have the same strong influence on austenite stability, but this is lower than previously reported in other M d30 expressions. Because nitrogen can be added to stainless steels in larger extent than carbon without adverse effects on corrosion resistance the nitrogen contents from 0,20 up 0,30 % are effective in present stainless steels.
  • Silicon (Si) is normally added to stainless steels for deoxidizing purposes in the melt shop and should not be below 0,2 %. Silicon has a stronger stabilizing effect on austenite stability against martensite formation than shown in current expressions. For this reason silicon is maximized to 0,8 %, preferably to 0,5 %.
  • Manganese (Mn) is an important addition to stabilize the austenite phase and to increase the solubility of nitrogen in the stainless steel. Manganese can partly replace the expensive nickel and bring the stainless steel to the right phase balance. Too high level in the content will reduce the corrosion resistance. Manganese has a stronger effect on austenite stability against deformation martensite and, therefore, the manganese content must be carefully addressed.
  • the range of manganese shall be 0-2,0 %, preferably 0-1,5 %.
  • Chromium is the main addition to make the steel resistant to corrosion. Further, chromium strongly increases the resistance to martensite formation and, therefore, reduces the TRIP effect. Also being a strong ferrite stabilizer the level of Cr needs to be limited in the austenitic stainless steel. To bring about these functions the chromium level should be at least 16.0% and the maximum level 19.0%. Preferably the chromium content is 16,5-18,7%
  • Nickel (Ni) is an essential alloying element for stabilizing the austenite phase and for good ductility and at least 4,5 % must be added to the stainless steel of the invention. Having a large influence on austenite stability against martensite formation nickel has to be present in a narrow range. Ni also has a significant influence on increasing the stacking fault energy of stainless steels. Further, because of nickel's high cost and price fluctuation nickel should be maximized in the stainless steel of the invention to 6,5 %, preferably to 6,2%
  • Copper (Cu) is normally present as a residual of 0,1-0,5 % in most stainless steels, when the raw materials to a great deal are in the form of stainless scrap containing this element. Copper is a weak stabilizer of the austenite phase but has a strong effect on the resistance to martensite formation and must be considered in evaluation of formability of the present stainless steels. An intentional addition up to 2,0 % can be made, but preferably the copper content is up to 1,6 %.
  • Molybdenum (Mo) be added to significantly increase the PRE and corrosion resistance and, therefore, molybdenum shall have a content at least 1,0 %, preferably at least 1,5 %. Further it has been found that, molybdenum, like chromium, strongly increases the resistance to martensite formation and reduces the TRIP effect significantly more than previous expected. Therefore, molybdenum cannot be added to more than 4,0.
  • Tungsten (W) has similar properties as molybdenum and can sometimes replace molybdenum.
  • tungsten and molybdenum promote sigma phase precipitation and the sum of the molybdenum and tungsten contents according to the formula (Mo + 0,5W) should be 0-4,0 %, preferably 2,0 - 4,0 %, where the promotion of sigma and chi phases are possible to handle in technically relevant processes.
  • the most important influence of tungsten is the surprisingly positive impact on the TRIP effect which in turn could be related to the effect on the stacking fault energy of the alloy since the stacking fault energy controls the deformation response in terms of dislocation glide, twinning or martensite formation.
  • tungsten should be limited up to 3,8 %, but preferably at least 1,0 % when tungsten is used to replace molybdenum.
  • Boron (B), calcium (Ca) and cerium (Ce) are added in small quantities in austenitic steels to improve hot workability and not at too high contents as this can deteriorate other properties.
  • the preferred contents for boron and calcium in the stainless steel of the invention are less than 0,004 % and for cerium less than 0,1 %.
  • Sulphur (S) in austenitic steels deteriorates hot workability and can form sulphide inclusions that influence pitting corrosion resistance negatively.
  • the content of sulphur should therefore be limited to less than 0,010 % and preferably less than 0,005 %.
  • Phosphorus (P) deteriorates hot workability and can form phosphide particles or films that influence corrosion resistance negatively.
  • the content of phosphorus should therefore be limited to less than 0,040 %, and so that the sum of sulphur and phosphorus (S+P) contents is less than 0,04 %.
  • Oxygen (O) together with other residual elements has an adverse effect on hot ductility.
  • the presence of oxide inclusions may reduce corrosion resistance (pitting corrosion) depending on type of inclusion.
  • High oxygen content also reduces impact toughness.
  • sulphur oxygen improves weld penetration by changing the surface energy of the weld pool.
  • the advisable maximum oxygen level is below 100 ppm. In a case of a metallic powder the maximum oxygen content can be up to 250 ppm.
  • Aluminium (Al) should be kept at a low level in the austenitic stainless steel of the invention with high nitrogen content as these two elements can combine and form aluminium nitrides that will deteriorate the impact toughness.
  • the aluminium content is limited to less than 0,04 % and preferably to less than 0,03 %.
  • Co has similar metallurgical behaviour as its sister element, nickel, and cobalt may be treated in much the same way in steel and alloy production. Cobalt inhibits grain growth at elevated temperatures and considerably improves the retention of hardness and hot strength. Cobalt increases the cavitation erosion resistance and the strain hardening. Cobalt reduces the risk of sigma phase formation in stainless steels. The cobalt content is limited up to 1,0 %.
  • titanium (Ti), vanadium (V) and niobium (Nb) belong to a group of additions so named because they significantly change the steels properties at low concentrations, often with beneficial effects in carbon steel but in the case of austenitic stainless steels they also contribute to undesired property changes, such as reduced impact properties, higher surface defects levels and reduced ductility during casting and hot rolling. Many of these effects depend on their strong affinity for carbon and in particular nitrogen in the case of modern austenitic stainless steels.
  • niobium and titanium should be limited to maximum level of 0,1% whereas vanadium is less detrimental and should be less than 0,2%.
  • the M d30 limiting values given are the preferred limiting values of the invention calculated in accordance with a mathematical constraint of optimization used in this invention. These calculated M d30 values are given in table 2 for all the alloys. In addition, the limiting Nohara M d30 values are also given in the figures for reference and comparison.
  • Figures 5-7 show the microstructures of some of the alloys after annealing at 1100°C followed by water quenching.
  • Figure 5 and Figure7 shows the microstructure of two of the invented alloys, showing how the observed level of martensite is related to the calculated M d30 value of the invention. Also shown is the low ferrite content illustrating that the invented alloys are considered to be fully austenitic.
  • Figure 6 is from reference alloy UNS S30403 for comparison purposes.
  • Table 1 contains also the typical chemical composition for the reference commercially available austenitic stainless steels named as T to X, all the contents of the table 1 in weight %.
  • the alloys A - S were manufactured in an induction furnace in 1 kg laboratory scale to small slabs.
  • the referred alloys T and X were produced in 100 ton production scale followed by hot rolling and cold rolling to coil form with varying final dimensions.
  • CPT critical pitting temperature
  • the sums of the element contents for C+N, Cr+Si, Cu+Mo+0,5W and Mn+Ni in weight % are also calculated for the alloys of the table 1 in the table 2.
  • the sums C+N and Mn+Ni represent austenite stabilizers, while the sum Si+Cr represents ferrite stabilizers and the sum Cu+Mo+0,5W elements having resistance to martensite formation.
  • the PRE value of for alloys A-S having the range of 27-35 is higher than the PRE value in the referred stainless steels T-V which means that the corrosion resistance of the alloys A - S is higher.
  • the critical pitting temperature CPT is in the range of 31 - 48 °C, which is a high level of corrosion resistance and much higher than the CPT for the referred austenitic stainless steels T to V.
  • the predicted M d30 temperatures using the Nohara expression (1) agree well with the known M d30 for the reference alloys T-V, but are not considered to be accurate for the inventive alloys A to S.
  • the inventive alloys A-S have a chemical composition unique from the austenitic steels that the Nohara expression was originally derived.
  • the effect of N on the austenite stability and M d30 although still high has been found to be considerably lower in these inventive steels.
  • the Nohara expression was originally derived for austenitic steels with low N and therefore the total effect of nitrogen in those steels was little.
  • to increase the austenitic content given that the Ni is low, and to have a high corrosion resistant stainless steel, i.e.
  • FIG. 6 shows the as-quenched microstructure of reference Alloy T (UNS S30403), remelted to give an equivalent cast microstructure and Alloy E.
  • This microstructure shows no, or at least very little martensite, which is expected for this commercially available grade with an M d30 of 0-10 predicted by both Nohara and the calculated M d30 of this invention.
  • Figure 7 shows the microstructure of alloy P which has a calculated M d30 of -35 and as seen no evidence of martensite in the as-quenched condition. Additionally, when observing the microstructures of Figure 5 and Figure 7 , in is noted that the austenite content is high and that the remaining ferrite content is less than 10%. Fully austenitic stainless steels typically have a ferrite content of up to 10% as illustrated by the microstructure of Figure 6 for Alloy T. These examples show that the alloys with higher and lower calculated M d30 (-70°C to +60°C) have an austenitic microstructure equivalent to the reference alloy T.
  • the stacking fault energies were calculated using the formula (3) of G. Meric de Bellefon, J. C. van Duysen, and K. Sridharan, "Composition-dependence of stacking fault energy in austenitic stainless steels through linear regression with random intercepts," J. Nucl. Mater., vol. 492 , for austenitic stainless steels.
  • SFE mJ / m 2 2.2 + 1.9 Ni ⁇ 2.9 Si + 0.77 Mo + 0.5 Mn + 40 C ⁇ 0.016 Cr ⁇ 3.6 N
  • the stacking fault energies (SFE) of the austenitic stainless steels of the invention are lower than the commercially available austenitic stainless steel.
  • the SFE of the reference alloys , T and X, that are relatively low alloyed with a low PRE ( ⁇ 27) and consequently a higher M d30 , >0 is greater than 16 mJ/m 2 .
  • the SFE for the higher alloyed and high PRE (>35) with low M d30 ( ⁇ -70) grade 904L is also greater than 16 mJ/m 2 .
  • Alloys A to S of the invention are unique in the sense that all have SFE lower than 16 mJ/m 2 whilst having a PRE between 27-35 and an M d30 between -70 to +60.
  • Fig. 1 a chemical composition window for Si+Cr and Cu+Mo+0,5W is established with the preferred ranges of 0,21-0,33 for C+N and 4,0-7,7for Mn+Ni It is also noticed in Fig. 1 that the sum Si+Cr is limited to 16,2 ⁇ Si+Cr ⁇ 19,8 and the sum of Cu+Mo+0,5W is limited to 1,0 ⁇ Cu+Mo+0,5W ⁇ 6,0 in accordance with the stainless steel of the invention.
  • the chemical composition window which lies within the frame of the area a', b', c', d', e', f' and g' in Fig. 1 , is defined with the following labelled positions of the coordination in the table 3.
  • Table 3 Si+Cr % Cu+Mo+0,5W % C+N% Mn+Ni % a' 19,8 1,0 0,24 8,5 b' 19,8 4,4 0,21 4,0 c' 18,8 5,6 0,21 4,0 d' 17,4 6,0 0,21 5,5 e' 16,2 6,0 0,30 4,0 f' 16,2 2,1 0,33 6,2 g 19,6 1,0 0,28 6,2
  • Fig 1 shows that that the composition ranges of the invention for Si+C and Cu+Mo+0,5W are further limited by the constraint of the 27 ⁇ PRE>35 and a calculated M d30 >-30 (alternatively Nohara M d30 ⁇ -70) when the composition limits for C+N and Ni+Mn are within the preferred limits of the invention.
  • Fig. 2 illustrates one chemical composition example window of Fig. 1 when constant values of 0,295 for C+N and 6,0 for Mn+Ni are used at all points instead of the preferred ranges for C+N and Mn+Ni in Fig. 1 .
  • the same limitations of the invention are given to the sum of Si+Cr and Cu+Mo+0.5W in Fig. 2 as in Fig. 1 .
  • the chemical composition window which lies within the frame of the area a, b, c, d, e, f and g in Fig. 2 , is defined with the following labelled positions of the coordination in the table 4.
  • Fig 2 shows that that the composition ranges of the invention for Si+C and Cu+Mo+0,5W are limited even more when specific constant levels of C+N and Mn+Ni are given.
  • the composition window is also limited by the line of the calculated M d30 ⁇ 60 (alternatively Nohara ⁇ 10)
  • Fig. 3 illustrates a chemical composition window for C+N and Mn+Ni with the preferred composition ranges 16,5-19,5 for Cr+Si and 2,2-5,7 for Cu+Mo+0,5W, when the austenitic stainless steel was annealed at the temperature of 1050 °C. Further, in accordance with invention the sum C+N is limited to 0,20 ⁇ C+N ⁇ 0,34 and the sum Mn+Ni is limited to 4,0 ⁇ Mn+Ni ⁇ 8,5. In FIG 3 the possible constraints of the SFE are also added.
  • the chemical composition window which lies within the frame of the area p', q' r' and s' in Fig. 3 , is defined with the following labelled positions of the coordination in the table 5.
  • Fig. 4 illustrates one chemical composition example window of Fig. 3 with the constant values of 17,6 for Cr+Si and 3,5 for Cu+Mo+0.5W and further, with the limitations of 0,20 ⁇ C+N ⁇ 0.34 and 4.0 ⁇ Mn+Ni.
  • the chemical composition window which lies within the frame of the area p, q, r and s in Fig. 4 , is defined with the following labelled positions of the coordination in the table 6.
  • Table 6 Si+Cr % Cu+Mo+0,5W % C+N % Mn+Ni % P 17,6 3,5 0,34 4,0 q 17,6 3,5 0,34 7,6 r 17,6 3,5 0,20 8,2 s 17,6 3,5 0,20 4,4
  • Fig 4 shows that that the composition ranges of the invention for the sums of C+N and Mn+Ni are now limited by the constraint of the calculated M d30 >-30 (alternatively Nohara M d30 ⁇ -70) and SFE > 10 when the composition limits for Si+Cr and Cu+Mo+0.5W have the constant values as given in Table 6.
  • the austenitic ferritic austenitic stainless steel of the invention can be produced as ingots, slabs, blooms, billets and flat products such as plates, sheets, strips, coils, and long products such as bars, rods, wires, profiles and shapes, seamless and welded tubes and/or pipes. Further, additional products such as metallic powder, formed shapes and profiles can be produced.

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  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
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  • Organic Chemistry (AREA)
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EP20193794.3A 2020-09-01 2020-09-01 Acier inoxydable austénitique Pending EP3960881A1 (fr)

Priority Applications (9)

Application Number Priority Date Filing Date Title
EP20193794.3A EP3960881A1 (fr) 2020-09-01 2020-09-01 Acier inoxydable austénitique
US18/042,891 US20230357909A1 (en) 2020-09-01 2021-08-31 Austenitic stainless steel
BR112023003604A BR112023003604A2 (pt) 2020-09-01 2021-08-31 Aço inoxidável austenítico utilizando o efeito trip
MX2023002487A MX2023002487A (es) 2020-09-01 2021-08-31 Acero inoxidable austenitico.
TW110132317A TW202214879A (zh) 2020-09-01 2021-08-31 沃斯田鐵系不鏽鋼
PCT/EP2021/073959 WO2022049051A1 (fr) 2020-09-01 2021-08-31 Acier inoxydable austénitique
KR1020237010596A KR20230060512A (ko) 2020-09-01 2021-08-31 오스테나이트계 스테인리스 강
JP2023512449A JP2023540461A (ja) 2020-09-01 2021-08-31 オーステナイト系ステンレス鋼
CN202180053606.XA CN115997042A (zh) 2020-09-01 2021-08-31 沃斯田铁系不锈钢

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CN117845128A (zh) * 2023-11-22 2024-04-09 重庆材料研究院有限公司 深海机器人用长期弹性稳定性不锈钢材料
CN117737579A (zh) * 2023-11-22 2024-03-22 重庆材料研究院有限公司 深海机器人紧固件用不锈钢材料

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EP0659896A1 (fr) * 1993-12-20 1995-06-28 Shinko Kosen Kogyo Kabushiki Kaisha Produit filiforme en acier inoxydable
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WO2013034804A1 (fr) 2011-09-07 2013-03-14 Outokumpu Oyj Acier inoxydable duplex
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EP2832886A1 (fr) * 2012-03-30 2015-02-04 Nippon Steel & Sumikin Stainless Steel Corporation Tôle en acier inoxydable austénitique qui résiste à la chaleur
WO2015063374A1 (fr) * 2013-11-04 2015-05-07 Outokumpu Oyj Acier inoxydable austénitique résistant à la corrosion intergranulaire et procédé pour sa production
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KR20230060512A (ko) 2023-05-04
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CN115997042A (zh) 2023-04-21
BR112023003604A2 (pt) 2023-05-09
US20230357909A1 (en) 2023-11-09
MX2023002487A (es) 2023-03-08

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