WO2005014872A1 - Acier non oxydable duplex et procede de production correspondant - Google Patents

Acier non oxydable duplex et procede de production correspondant Download PDF

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Publication number
WO2005014872A1
WO2005014872A1 PCT/JP2004/011070 JP2004011070W WO2005014872A1 WO 2005014872 A1 WO2005014872 A1 WO 2005014872A1 JP 2004011070 W JP2004011070 W JP 2004011070W WO 2005014872 A1 WO2005014872 A1 WO 2005014872A1
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Prior art keywords
stainless steel
less
mass
oxide
duplex stainless
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PCT/JP2004/011070
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English (en)
Japanese (ja)
Inventor
Tomohiko Omura
Satoshi Matsumoto
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Sumitomo Metal Industries, Ltd.
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Application filed by Sumitomo Metal Industries, Ltd. filed Critical Sumitomo Metal Industries, Ltd.
Priority to AU2004262702A priority Critical patent/AU2004262702B2/en
Priority to BRPI0406423-2A priority patent/BRPI0406423B1/pt
Priority to EP04748203A priority patent/EP1561834B1/fr
Priority to KR1020057004913A priority patent/KR100661328B1/ko
Priority to CNB2004800009689A priority patent/CN100427627C/zh
Priority to JP2005512929A priority patent/JP4155300B2/ja
Publication of WO2005014872A1 publication Critical patent/WO2005014872A1/fr
Priority to NO20052266A priority patent/NO336117B1/no
Priority to US11/135,448 priority patent/US7396421B2/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/064—Dephosphorising; Desulfurising
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0087—Treatment of slags covering the steel bath, e.g. for separating slag from the molten metal
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/06—Deoxidising, e.g. killing
    • 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
    • C22C38/42—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
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten

Definitions

  • the present invention relates to a duplex stainless steel having excellent corrosion resistance in seawater.
  • This steel may be steel pipes or steel plates, such as heat exchange piping, piping or structures for chemical plants, line pipes, casings or tubing for oil or gas wells, or umbilical tubes (piping for controlling offshore oil wells). Used for etc.
  • Patent Document 1 discloses that in general, the content of Cr, Mo and N (nitrogen) effective for improving the pitting corrosion resistance of a duplex stainless steel is adjusted, and that W is contained to improve the pitting corrosion resistance.
  • An enhanced, so-called super duplex stainless steel is disclosed.
  • the pitting corrosion resistance index PRE Pitting Resistance Equivalent
  • the pitting resistance index PRE or PREW is adjusted to be 35 or more, and further, in a super duplex stainless steel, it is adjusted to be 40 or more.
  • Conventional techniques for improving pitting resistance have been based on the ability to increase the pitting resistance index PRE or PREW.
  • Oxide-based inclusions contained in stainless steel are generally A1 oxide (Al ⁇ ), Si
  • a composite oxide composed of oxides such as 23 oxide (SiO 2) and Cr oxide (Cr 2 O 3). They are also possible.
  • Patent Document 1 JP-A-5-132741
  • Non-patent document 1 J.E.Castle, et al., "Studies by Auger Spectroscopy of Pitlnitiation at the site of Inclusions in Stainless Steel ,,, Corrosion Science ⁇ Volume 30, No. 4/5, p. 409
  • the present invention has been made to solve these problems, and an object of the present invention is to provide a duplex stainless steel capable of stably obtaining good pitting corrosion resistance and a method for producing the same. Means to solve
  • the present inventors have investigated metallurgical factors affecting pitting resistance of a duplex stainless steel in detail. As a result, even if the oxide inclusions formed during the melting process only by the conventional causes of pitting corrosion described above, those containing Ca and Mg and those containing S, Has a significant effect on The findings obtained by the study of the present inventors are as follows.
  • oxide-based inclusions formed in the steel mainly contain insoluble Al 2 O 3.
  • the oxide-based inclusions formed in the steel include Al O and (Ca, Mg) 0 and coexistence
  • pitting corrosion may or may not occur depending on the size and number of oxide-based inclusions formed in the steel I found that.
  • S is an element inevitably present in steel, and its content cannot be made completely zero by current steelmaking technology.
  • S is contained in a large amount in oxide-based inclusions formed in steel, S deteriorates pitting corrosion resistance. It has been found that the occurrence of pitting can be suppressed by adjusting the size and the number.
  • the present invention provides a chemical composition of a steel material capable of securing performance as a duplex stainless steel, It was completed based on the state of oxide inclusions that greatly improve pitting corrosion resistance and the manufacturing conditions for achieving high cleanliness.
  • the gist of the present invention is a method for producing a duplex stainless steel shown in the following (a) and (b) and a duplex stainless steel shown in the following (c).
  • oxide inclusions having a total content of Ca and Mg of 2040% by mass and a major axis of not less than 7 ⁇ m have a cross section lmm 2 perpendicular to the processing direction.
  • a duplex stainless steel characterized in that there are no more than 10 per steel.
  • Oxide inclusions that are stainless steel and have a total content of Ca and Mg of 20-40% by mass and a major axis of 7 ⁇ m or more in the inclusions contained therein Vertical cross section Not more than 10 pieces per lmm 2 , and oxide inclusions with an S content of 15% by mass or more and a major axis of 1 ⁇ m or more are perpendicular to the processing direction.
  • Duplex stainless steel characterized in that there are no more than 10 per 2 .
  • the steel described in (a) or (b) above has a Cu, B and W content of 0.2-2%, 0.001 0.01% and 0.1-4% in mass%, respectively. Desired Les ,. Further, it is desirable that the pitting resistance index PREW represented by the following formula (1) is 40 or more. However, each element symbol in the formula (1) means the content (% by mass) of each element.
  • Equation (3) AO denotes the cross-section ⁇ ⁇ before deformation in the plastic deformation process, and A denotes the cross-sectional area after deformation in the plastic deformation process, and each subscript n (l, 2, ⁇ ) means the order of each stand in the plastic deformation process.
  • a duplex stainless steel having good porosity resistance can be stably obtained.
  • the chemical composition of the steel material must be in the following range to ensure sufficient pitting resistance as duplex stainless steel.
  • “% of the content” means I ”mass 0 / oj.
  • C is inevitably present in steel. If the content exceeds 0.03%, carbides are liable to precipitate and pitting corrosion resistance is reduced. Therefore, the content of C is set to 0.03% or less.
  • Si is an element effective for deoxidizing steel and must be contained at 0.01% or more. However, if its content exceeds 2%, it promotes the formation of intermetallic compounds and lowers pitting resistance. Therefore, the content of Si 0.01 ⁇ 2 ⁇ / ⁇ .
  • ⁇ is effective in stabilizing the austenite phase like Ni, and contains 0.1% or more. Need to be done. On the other hand, if Mn exceeds 2%, pitting corrosion resistance is reduced. Therefore, the content of Mn was set to 0.1-2%.
  • P is inevitably present in steel as an impurity, and dissolves actively to lower pitting corrosion resistance. If the content exceeds 0.05%, this effect becomes remarkable, so it is necessary to reduce the content to 0.05% or less. It is desirable that the content of P be as low as possible.
  • A1 is an element necessary for deoxidation of steel and must be contained at 0.003% or more. On the other hand, when contained excessively, A1 nitride precipitates and absorbs N (nitrogen), which is an element effective in improving pitting corrosion resistance, and lowers pitting corrosion resistance. Therefore, the content of A1 was set to 0.003-0.05%.
  • A1 means "sol.Al (acid soluble A1)".
  • M is an element that stabilizes the austenitic phase, and its effect is insufficient if less than 4%. On the other hand, if it exceeds 12%, the austenite phase becomes excessive and the mechanical properties of the duplex stainless steel deteriorate. Therefore, the content of M was set to 412%.
  • Cr is effective in improving pitting corrosion resistance, and if its content is less than 18%, pitting corrosion resistance becomes insufficient. On the other hand, if the content exceeds 32%, the ferrite phase becomes excessive and the mechanical properties of the duplex stainless steel are impaired. Therefore, the content of Cr was set to 1832%.
  • Mo is also an element that enhances pitting corrosion resistance like Cr, and its effect is not sufficient if it is less than 0.2%. On the other hand, if it exceeds 5%, an intermetallic compound is precipitated, and on the contrary, pitting corrosion resistance is reduced. Therefore, the content of Mo is set to 0.25%.
  • N (nitrogen), like Ni, is an element that has the effect of stabilizing the austenite phase.
  • N (nitrogen) is also an element having an effect of improving pitting corrosion resistance, like Cr and Mo.
  • the content is less than 0.05%, these effects are insufficient.
  • the content exceeds 0.4%, the hot workability decreases. Therefore, the content of N (nitrogen) was set to 0.05 0.4%.
  • o Oxygen
  • Oxygen is inevitably present in steel, as in S, and exists as oxide inclusions. As described later, depending on the composition, the oxide becomes a starting point of pitting corrosion and lowers pitting resistance. In particular, when the content exceeds 0.01%, coarse oxides increase and this tendency becomes remarkable. Therefore, o (oxygen) must be limited to 0.01% or less. It is desirable that the content of ⁇ (oxygen) be as low as possible.
  • Ca and Mg are elements that have the effect of improving the hot workability of steel by fixing S as sulfide. As described above, in a duplex stainless steel containing Ca: 0.0005-0.005% and Mg: 0.0001-0.005%, A1 ⁇ and (Ca, Mg) 0
  • the contents of Ca and Mg are specified as 0.0005-0.005% and 0.0001-0.005%, respectively, in which the pitting corrosion resistance tends to deteriorate.
  • the pitting corrosion resistance of the duplex stainless steel of the present invention is improved by regulating the state of the oxide inclusions, as described later.
  • the duplex stainless steel of the present invention is a steel having the above chemical composition, with the balance being Fe and impurities. Further, the duplex stainless steel of the present invention may contain one or more of Cu, B and W as optional additional elements.
  • Cu like Ni, stabilizes the austenitic phase. It also stabilizes the sulfide film in a hydrogen sulfide environment and improves pitting resistance. Therefore, Cu may be included if necessary. To obtain the above effects, it is desirable to contain 0.2% or more, but if it exceeds 2%, the hot workability decreases. Therefore, when Cu is contained, the content is desirably 0.2 to 2%. [0040] B: 0-0.01%
  • B is an element effective for improving hot workability, it may be contained as necessary. In order to obtain this effect, it is desirable that the content is 0.001% or more, but if the content exceeds 0.01%, the effect is saturated. Therefore, when B is contained, its content is preferably set to 0.001 to 0.01%.
  • W is an element that is effective in improving pitting corrosion resistance, like Cr and Mo, and therefore may be included as necessary. These effects become remarkable when the content is 0.1% or more. However, if the content exceeds 4%, an intermetallic compound is precipitated and the pitting corrosion resistance is rather lowered. Therefore, when W is contained, its content is desirably 0.1-4%.
  • the duplex stainless steel of the present invention is desirably a super duplex stainless steel having the above chemical composition and having a pitting resistance index of 40 or more as defined below.
  • each element symbol in the formula (1) means the content (% by mass) of each element.
  • the present inventors investigated the effect of oxide-based inclusions on pitting corrosion resistance by the following method.
  • Molten steel having the chemical composition shown in Tables 3 and 4 described below was processed under various conditions to produce a duplex stainless steel pipe having a wall thickness of 1.4 to 16 (mm). After flattening these steel pipes, test pieces having a pipe wall thickness of X10 mm X 10 mm were cut out. After the resin was loaded in a cross section perpendicular to the processing direction of the test piece (the “observation surface” shown in FIG. 1), the cross section was mirror-polished. The polished surface was observed using a scanning electron microscope (SEM), and the major diameter and chemical composition of the oxide-based inclusions were measured.
  • SEM scanning electron microscope
  • the major axis of the oxide-based inclusion is, as shown in Fig. 2, the length of the longest straight line (al or al) among two straight lines connecting two different points on the interface between the base material and the inclusion. means a2).
  • the composition of the oxide-based inclusions is EDX (energy dispersive X-ray analysis) near the center of the inclusion (bl or b2 in the example shown in Fig. 2), ie, near the center of gravity of the cross-sectional shape of the inclusion.
  • EDX energy dispersive X-ray analysis
  • oxide-based inclusions After observing the oxide-based inclusions, they were immersed in a 6% ferric chloride aqueous solution at 80 ° C. for 6 hours, and the corrosion state around the oxide-based inclusions was observed. Pitting corrosion originating from oxide inclusions was observed.
  • the oxide inclusions that have caused pitting are Al O and (Ca,
  • FIG. 3 is a diagram showing the relationship between the major axis of the oxide-based inclusions and the total content of Ca and Mg. Note that “X” in FIG. 3 indicates an oxide-based inclusion that started pitting, and “ ⁇ ” indicates an oxide-based inclusion that did not start pitting.
  • Oxides of not less than / im were the starting point of pitting corrosion. However, oxides having a total content of Ca and Mg of less than 20% were mainly composed of A1 oxides, and eluted as a starting point of pitting corrosion. Oxides with a total content of Ca and Mg exceeding 40% were completely eluted, but did not progress to pitting, where the effect of forming gaps with the base material was small. Furthermore, even for oxide-based inclusions with a total Ca and Mg content of 20-40%, if the major axis is less than 7 ⁇ m, the gaps will not be sufficiently large and oxide will elute. Did not progress to pitting
  • the pitting corrosion temperature was investigated by focusing on oxide-based inclusions having a total content of Ca and Mg of 20 to 40% and a major axis of 7 ⁇ m or more.
  • the critical pitting temperature is the maximum temperature at which pitting did not occur, after immersing for 24 hours in a 6% ferric salt aqueous solution of 35 ° C-80 ° C with the temperature changed every 5 ° C for 24 hours. Means As a result, the number of oxide-based inclusions with a total Ca and Mg content of 20-40% and a major axis of 7 ⁇ m or more was reduced to 10 per lmm 2 in a cross section perpendicular to the processing direction. If it exceeds, the critical pitting temperature is remarkably lowered, and it has been found that the corrosion resistance in the above severe corrosive environment becomes insufficient.
  • the content of Ca and Mg is 2040% in total, and the number of oxide-based inclusions having a major axis of 7 ⁇ m or more is 10 or less per lmm 2 in a cross section perpendicular to the processing direction.
  • the tendency of pitting to occur for various oxide-based inclusions was arranged in the same way as for Ca and Mg.
  • FIG. 4 is a diagram showing the relationship between the major axis of the oxide-based inclusions and the S content.
  • oxide inclusions having an S content of 15% or more and a major axis of 1 ⁇ m or more became pitting initiation points.
  • the oxide-based inclusions containing S are minute and completely eluted after the pitting test, but the hydrogen sulfide generated after the elution accelerated the corrosion and progressed to pitting.
  • oxide inclusions having a major axis of less than 1 zm and oxide inclusions having an S content of less than 15% did not become pitting corrosion starting points.
  • the same critical pitting temperature was investigated by focusing on oxide-based inclusions having an S content of 15% or more and a major axis of 1 ⁇ m or more. It was found that the pitting corrosion resistance was improved when the number of the inclusions was 10 or less per 0.1 mm 2 in a cross section perpendicular to the processing direction.
  • each compound in the formula (2) means the concentration of each compound in slag (% by mass).
  • the slag basicity represented by the above formula (2) needs to be 0.5 or more.
  • the slag basicity in order to minimize the S content in the oxide-based inclusions, it is desirable that the slag basicity be 1.0 or more.
  • the slag basicity if the slag basicity is too high, the fluidity becomes poor as the melting point rises, and oxide inclusions with a total content of Ca and Mg of 2040% tend to remain in the steel. As a result, the pitting corrosion resistance of the steel decreases. From this viewpoint, the upper limit must be 3.0.
  • the slag basicity is desirably 2.5 or less.
  • the above-mentioned reduction treatment with slag basicity is usually performed only once, but in order to further reduce oxygen and sulfur, it is desirable to repeat this reduction period two or more times.
  • the slag generated in the first reduction treatment is discharged out of the furnace before performing the second reduction by tilting the secondary refining furnace body and extracting it with an appropriate jig. This is important for removing desulfurized slag generated in the first reduction phase, thereby increasing the desulfurization capacity in the second reduction phase.
  • Killing after the reduction treatment is performed at a temperature of 1500 ° C or more for 5 minutes or more.
  • the molten steel that has been subjected to secondary refining by fine adjustment to a predetermined component is tapped into a ladle and manufactured. Until the molten steel is tapped, the molten steel is floated on the molten steel, moved to a place where it is mixed with the slag again, or moved to a place where it is filled. This treatment is called killing, and during the killing, a part of the oxide suspended in the molten steel floats due to the difference in specific gravity and is absorbed and separated in the slag. In order to give the desired state of oxide-based inclusions to the duplex stainless steel, it is necessary to separate large oxides by flotation.
  • the killing temperature is set to 1500 ° C or higher, and the killing time is reduced. You need to wait at least 5 minutes. To further promote the floating removal of these oxides, it is desirable to set the killing temperature to 1550 ° C or more and the killing time to 10 minutes or more.
  • Equation (3) Processing after fabrication is performed under the condition that the total working ratio R expressed by the following equation (3) is 10 or more.
  • AO in equation (3) is the cross-sectional area before deformation in the plastic deformation process, and A is the change in the plastic deformation process.
  • the produced piece is made by hot rolling and 1 / ⁇ hot rolling or cold rolling! After being processed, it is molded to the specified product dimensions. At this time, as the material is deformed in the processing direction by the processing, the oxide-based inclusion is crushed and miniaturized. In order to give the desired state of oxide inclusions to the duplex stainless steel, it is necessary to make the total processing ratio R from the single strength to the final product 10 or more.
  • the plastic deformation step does not include a cutting step or any other processing step that does not involve elongation. Therefore, even when a cutting step is included between the plastic deformation steps, the calculation of the above equation (3) is performed without considering the change in the cross section ⁇ ⁇ ⁇ due to the cutting step.
  • Duplex stainless steel having the composition shown in Table 1 (super duplex stainless steel with a pitting resistance index PREW of 40 or more) was melted in a 500 kg induction melting furnace, then transferred to an AOD furnace, and subjected to secondary » I got it. At this time, the slag basicity in the reduction phase was set to 2.0. Slag and molten steel were sampled after the end of the reduction period, respectively. Further, after was allowed measured immediately mono- Mokappuru molten steel is tapped into a ladle, to measure the time until ⁇ inclusive initiation D
  • the ladle was allowed to stand still at a certain position and the vibration was not applied to perform the killing until the ladle was lifted with a ladle crane to start the loading.
  • the killing conditions at this time are as shown in Table 2.
  • the molten steel was formed into a steel ingot having an average size of 160 mm on one side by a lower casting method or into a round piece having an outer diameter of 180 mm by a continuous forming method. ⁇
  • the forged steel slab is subjected to forging, hot extrusion, and cold rolling to various degrees of processing to form a seamless steel pipe with an outer diameter of 16-280 mm and a wall thickness of 1.4--16 mm. After holding at C for 3 minutes, a water-cooled solution heat treatment was performed.
  • the major axis of the oxide-based inclusion was measured according to the definition in Fig. 2, and the composition analysis of the vicinity of the center of the oxide-based inclusion (bl or b2 in Fig. 2) by EDX (energy dispersive X-ray analysis) was performed. did.
  • EDX energy dispersive X-ray analysis
  • the measured value of ⁇ (oxygen) had low reliability in accuracy, so the mass ratio of Al, Ca, Mg, S, and Mn excluding O (oxygen) was measured.
  • the tube was cut into 10 mm lengths, and the cut end face was polished with No. 600 emery paper and subjected to a pitting corrosion test. It was immersed for 24 hours in a 6% ferric chloride aqueous solution of 35 ° C. to 80 ° C., the temperature of which was changed every 5 ° C., and the maximum temperature at which no pitting occurred was measured. The measurement was performed using five test pieces per test tube, and the lowest value was defined as the critical pitting temperature, which was used as a measure of pitting resistance.
  • Example 13 of the present invention since the starting temperature of the killing was 1500 ° C. or more and the temperature was maintained for 5 minutes or more, the total content of Ca and Mg among the inclusions was 20 to 40% and the major axis was long. Good pitting corrosion resistance was obtained when the number of oxide-based inclusions having a diameter of 7 ⁇ m or more was 10 or less per lmm 2 of the cross section perpendicular to the processing direction. In particular, in Examples 1 and 2 of the present invention, the content of S was 15% or more, and the oxide-based inclusions having a long diameter of 1 ⁇ m or more were 10 pieces or less per 0.1 mm 2 in a cross section perpendicular to the processing direction. As a result, the critical pitting temperature was 80 ° C, showing extremely good pitting resistance.
  • Duplex stainless steels having the compositions shown in Tables 3 and 4 were melted in a 500 kg induction melting furnace, transferred to an AOD furnace, and subjected to secondary refining. At this time, the slag basicity in the reduction phase was varied. Slag and molten steel were sampled after the completion of the reduction phase and immediately after the fine adjustment of the components, respectively, and their composition was analyzed by chemical analysis. Also, go out to the ladle Immediately after the temperature of the steel melted was measured with a thermo cup, the time until the start of filling was measured.
  • the ladle was placed blue at a fixed position so as not to vibrate until the ladle was lifted by a ladle crane to start loading.
  • the molten steel was formed into a steel ingot with an average size of 160 mm on one side by the sub-casting method or a round piece with an outer diameter of 180 mm by the continuous manufacturing method.
  • the forged, hot extruded, and cold-rolled steel slabs are added to various degrees of work to obtain an outer diameter of 16
  • the solution was kept at 1100 ° C. for 3 minutes, and then subjected to a water-cooled solution heat treatment. Tables 5 and 6 show the slag basicity during the reduction phase, the killing conditions and the total processing ratio.
  • the tube was cut into 10 mm lengths, and the cut end faces were polished with No. 600 emery paper and subjected to a pitting corrosion test.
  • the specimens were immersed in a 6% ferric salt aqueous solution of 35 ° C-80 ° C for 24 hours with the temperature changed every 5 ° C for 24 hours, and the maximum temperature at which no pitting occurred was measured. The measurement was performed using five test pieces per test tube, and the lowest value was defined as the critical pitting temperature, which was used as a measure of pitting resistance.
  • the target value of pitting corrosion resistance is a normal duplex stainless steel having a pitting resistance index PRE (or PREW) of less than 40 (steel Nos. 1-8, 10, and 21 shown in Tables 3 and 4).
  • a super duplex stainless steel with a critical pitting temperature of 35 ° C and a pitting resistance index PRE (or PREW) of 40 or more (Steel No. 9 in Tables 3 and 4) , 11-12, 28-41, 44, 45, 47 and 48), the critical pitting temperature was 70 ° C.
  • the results are shown in Tables 5 and 6.
  • the total content of Ga and Mg is meant a 20-40% der Li, and the cross section perpendicular 1 mm 2 number per the working direction of the oxide inclusions is major axis 7 U m or more .
  • Oxide-based inclusions whose S content is 15% or more and whose major axis is 1 m or more
  • the chemical composition and the total number of oxide-based inclusions having a total content of Ca and Mg of 20 to 40% and a major axis of 7 ⁇ m or more are defined by the present invention. It was within the specified range. For this reason, excellent pitting corrosion resistance exceeding the above-mentioned target values was obtained for both ordinary stainless steel and super stainless steel.
  • Comparative Example 2031 in which the chemical composition was out of the range specified in the present invention could not secure sufficient corrosion resistance as a two-phase stainless steel. Further, the chemical group defined in the present invention In Comparative Example 419, in which the production conditions are not suitable, the pitting corrosion resistance was poor because a large amount of oxide inclusions harmful to pitting remained.
  • a duplex stainless steel having good pitting corrosion resistance can be stably obtained.
  • pipes or structures for heat exchange for example, pipes or structures for chemical plants, line pipes, casings or tubing for oil wells or gas wells, or steel pipes or steel plates such as umbilical tubes (pipes for controlling submarine oil wells)
  • umbilical tubes pipes for controlling submarine oil wells
  • FIG. 1 is a view showing an observation surface of an oxide-based inclusion.
  • FIG. 2 is a diagram that defines the measurement points of the major axis and the composition of oxide-based inclusions.
  • FIG. 3 is a graph showing the relationship between the major axis of oxide-based inclusions and the total content of Ca and Mg.
  • FIG. 4 is a graph showing the relationship between the major axis of oxide-based inclusions and the S content.

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  • Heat Treatment Of Steel (AREA)

Abstract

L'invention concerne un acier non oxdydable duplex possédant une composition chimique, en masse % ainsi répartie : C: 0,03 % ou moins, Si: 0,01 à 2 %, Mn: 0,1 à 2 %, P: 0,05 % ou moins, S: 0,001 % ou moins, Al: 0,003 à 0,05 %, Ni: 4 à 12 %, Cr: 18 à 32 %, Mo: 0,2 à 5 %, N (azote): 0,05 à 0,4 %, O(oxygène): 0,01 % ou moins, Ca: 0,0005 à 0,005 %, Mg: 0,0001 à 0,005 %, Cu: 0 à 2 %, B: 0 à 0,01 %, W: 0 à 4 %, et le reste: Fe et des impuretés. Cet acier est caractérisé en ce qu'il contient des inclusions de type oxyde à teneur totale de Ca et Mg comprise entre 20 et 40 masse % et qu'il possède un diamètre plus long compris entre 7 νm ou plus dans une quantité de 10 pièces ou moins pour 1 mm2 de la perpendiculaire transversale au sens de travail, ou en ce qu'il contient des inclusions de type oxyde et qu'il possède une teneur en S de 15 masse % ou plus et un diamètre plus long compris entre 1 νm ou plus dans une quantité de 10 pièces ou moins pour 0,1 mm2 de la perpendiculaire transversale au sens de travail. Plus particulièrement, il est souhaitable que les teneurs en Cu, B et W soient, respectivement, de 0,2 à 2 %, 0,001 à 0,01 % et 0,1 à 4 %.
PCT/JP2004/011070 2003-08-07 2004-08-03 Acier non oxydable duplex et procede de production correspondant WO2005014872A1 (fr)

Priority Applications (8)

Application Number Priority Date Filing Date Title
AU2004262702A AU2004262702B2 (en) 2003-08-07 2004-08-03 Duplex stainless steel and method for production thereof
BRPI0406423-2A BRPI0406423B1 (pt) 2003-08-07 2004-08-03 aço inoxidável duplex e seu método de produção.
EP04748203A EP1561834B1 (fr) 2003-08-07 2004-08-03 Acier non oxydable duplex et procede de production correspondant
KR1020057004913A KR100661328B1 (ko) 2003-08-07 2004-08-03 2상 스테인레스강 및 그 제조 방법
CNB2004800009689A CN100427627C (zh) 2003-08-07 2004-08-03 二相不锈钢及其制造方法
JP2005512929A JP4155300B2 (ja) 2003-08-07 2004-08-03 二相ステンレス鋼およびその製造方法
NO20052266A NO336117B1 (no) 2003-08-07 2005-05-10 Dupleks rustfritt stål og fremstillingsmetode derav
US11/135,448 US7396421B2 (en) 2003-08-07 2005-05-24 Duplex stainless steel and manufacturing method thereof

Applications Claiming Priority (2)

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JP2003289418 2003-08-07
JP2003-289418 2003-08-07

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US11/135,448 Continuation US7396421B2 (en) 2003-08-07 2005-05-24 Duplex stainless steel and manufacturing method thereof

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WO2005014872A1 true WO2005014872A1 (fr) 2005-02-17

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EP (1) EP1561834B1 (fr)
JP (1) JP4155300B2 (fr)
KR (1) KR100661328B1 (fr)
CN (1) CN100427627C (fr)
AU (1) AU2004262702B2 (fr)
BR (1) BRPI0406423B1 (fr)
NO (1) NO336117B1 (fr)
WO (1) WO2005014872A1 (fr)

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US8192813B2 (en) 2003-08-12 2012-06-05 Exxonmobil Chemical Patents, Inc. Crosslinked polyethylene articles and processes to produce same
WO2012121232A1 (fr) * 2011-03-10 2012-09-13 住友金属工業株式会社 Tôle d'acier inoxydable duplex
WO2014112445A1 (fr) 2013-01-15 2014-07-24 株式会社神戸製鋼所 Matière d'acier inoxydable duplex et tuyau d'acier inoxydable duplex
JP2015078429A (ja) * 2013-09-11 2015-04-23 株式会社神戸製鋼所 二相ステンレス鋼材および二相ステンレス鋼管
JP2015110828A (ja) * 2013-11-05 2015-06-18 株式会社神戸製鋼所 二相ステンレス鋼材および二相ステンレス鋼管
JP2016003377A (ja) * 2014-06-18 2016-01-12 新日鐵住金株式会社 二相ステンレス鋼管
JP2017509790A (ja) * 2014-02-03 2017-04-06 オウトクンプ オサケイティオ ユルキネンＯｕｔｏｋｕｍｐｕ Ｏｙｊ 二相ステンレス鋼
KR20190092493A (ko) * 2016-12-07 2019-08-07 회가내스 아베 (피유비엘) 듀플렉스 소결된 스테인리스 강을 제조하기 위한 스테인리스 강 분말

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CN102031461A (zh) * 2010-10-22 2011-04-27 重庆仪表材料研究所 一种高屈强比高韧性长期弹性稳定性耐热合金
EP3685952B1 (fr) * 2011-01-27 2021-10-13 NIPPON STEEL Stainless Steel Corporation Matériau d'acier inoxydable duplex laminé à chaud permettant d'économiser un élément d'alliage et son procédé de production
FI126574B (fi) * 2011-09-07 2017-02-28 Outokumpu Oy Dupleksinen ruostumaton teräs
FI126577B (en) 2014-06-17 2017-02-28 Outokumpu Oy DUPLEX STAINLESS STEEL
KR101668534B1 (ko) * 2014-12-26 2016-10-24 주식회사 포스코 수퍼 듀플렉스 스테인레스강 및 그 제조 방법
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CN115210387B (zh) * 2020-02-27 2023-06-27 日铁不锈钢株式会社 镜面研磨性优异的不锈钢及其制造方法
WO2021172378A1 (fr) * 2020-02-27 2021-09-02 日鉄ステンレス株式会社 Acier inoxydable, matériau d'acier inoxydable et procédé de production d'acier inoxydable

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Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7759415B2 (en) 2002-08-12 2010-07-20 Exxonmobil Chemical Patents Inc. Method to make an article comprising polymer concentrate
US7662885B2 (en) 2002-08-12 2010-02-16 Exxonmobil Chemical Patents Inc. Method to make an article comprising polymer concentrate
US8192813B2 (en) 2003-08-12 2012-06-05 Exxonmobil Chemical Patents, Inc. Crosslinked polyethylene articles and processes to produce same
US8703030B2 (en) 2003-08-12 2014-04-22 Exxonmobil Chemical Patents Inc. Crosslinked polyethylene process
US9512509B2 (en) 2011-03-10 2016-12-06 Nippon Steel & Sumitomo Metal Corportion Duplex stainless steel
WO2012121232A1 (fr) * 2011-03-10 2012-09-13 住友金属工業株式会社 Tôle d'acier inoxydable duplex
JP5088455B2 (ja) * 2011-03-10 2012-12-05 住友金属工業株式会社 二相ステンレス鋼
WO2014112445A1 (fr) 2013-01-15 2014-07-24 株式会社神戸製鋼所 Matière d'acier inoxydable duplex et tuyau d'acier inoxydable duplex
KR20150087430A (ko) 2013-01-15 2015-07-29 가부시키가이샤 고베 세이코쇼 2상 스테인리스강재 및 2상 스테인리스강관
JP2015078429A (ja) * 2013-09-11 2015-04-23 株式会社神戸製鋼所 二相ステンレス鋼材および二相ステンレス鋼管
JP2015110828A (ja) * 2013-11-05 2015-06-18 株式会社神戸製鋼所 二相ステンレス鋼材および二相ステンレス鋼管
JP2017509790A (ja) * 2014-02-03 2017-04-06 オウトクンプ オサケイティオ ユルキネンＯｕｔｏｋｕｍｐｕ Ｏｙｊ 二相ステンレス鋼
JP2016003377A (ja) * 2014-06-18 2016-01-12 新日鐵住金株式会社 二相ステンレス鋼管
KR20190092493A (ko) * 2016-12-07 2019-08-07 회가내스 아베 (피유비엘) 듀플렉스 소결된 스테인리스 강을 제조하기 위한 스테인리스 강 분말
KR102408835B1 (ko) 2016-12-07 2022-06-13 회가내스 아베 (피유비엘) 듀플렉스 소결된 스테인리스 강을 제조하기 위한 스테인리스 강 분말

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NO20052266D0 (no) 2005-05-10
JP4155300B2 (ja) 2008-09-24
KR100661328B1 (ko) 2006-12-27
AU2004262702B2 (en) 2007-05-03
BRPI0406423B1 (pt) 2012-12-11
KR20060024316A (ko) 2006-03-16
NO336117B1 (no) 2015-05-18
JPWO2005014872A1 (ja) 2006-10-05
BRPI0406423A (pt) 2005-10-04
NO20052266L (no) 2005-07-06
CN100427627C (zh) 2008-10-22
EP1561834A1 (fr) 2005-08-10
EP1561834B1 (fr) 2011-04-20
CN1701126A (zh) 2005-11-23
EP1561834A4 (fr) 2007-07-11

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