WO2024084877A1 - Alliage à base de ni-cr-fe-mo ayant d'excellentes propriétés de surface, et son procédé de production - Google Patents

Alliage à base de ni-cr-fe-mo ayant d'excellentes propriétés de surface, et son procédé de production Download PDF

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WO2024084877A1
WO2024084877A1 PCT/JP2023/033908 JP2023033908W WO2024084877A1 WO 2024084877 A1 WO2024084877 A1 WO 2024084877A1 JP 2023033908 W JP2023033908 W JP 2023033908W WO 2024084877 A1 WO2024084877 A1 WO 2024084877A1
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mgo
alloy
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建次 水野
大樹 小笠原
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日本冶金工業株式会社
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D1/00—Treatment of fused masses in the ladle or the supply runners before casting
    • 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
    • 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
    • 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
    • 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
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/068—Decarburising
    • 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
    • C21C7/076—Use of slags or fluxes as treating agents
    • 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
    • C21C7/10—Handling in a vacuum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C19/00—Alloys based on nickel or cobalt
    • C22C19/03—Alloys based on nickel or cobalt based on nickel
    • C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C30/00—Alloys containing less than 50% by weight of each constituent
    • C22C30/02—Alloys containing less than 50% by weight of each constituent containing copper

Definitions

  • the present invention relates to a Ni-Cr-Fe-Mo alloy with excellent surface properties and a method for producing the same, and in particular to a Ni-Cr-Fe-Mo alloy with excellent surface properties in which the nonmetallic inclusions in the molten metal are controlled to a harmless composition by controlling the slag composition and the Si, Al, Mg, Ca, and O in the molten metal, and the number of inclusions on the surface is reduced, and to a method for producing the same.
  • the present invention relates to a Ni-Cr-Fe-Mo alloy with high creep properties that can withstand harsh environments and is used in gas turbine combustion tower parts through which high-temperature gases exceeding 1000°C flow.
  • Gas turbine combustors are components that burn fuel to generate high-temperature, high-pressure combustion gases to drive the turbine, and guide the combustion gases to the turbine inlet.
  • the temperature of the combustion gases used in gas turbines is generally 1100°C to 1300°C, and the temperature of the combustor at this time is about 550°C to 650°C.
  • the temperature of the combustion gas has been rising year by year to improve power generation efficiency, and combustors with temperatures exceeding 1500°C have been developed.
  • gas turbines with combustion gas temperatures of about 1600°C are expected to be realized, and the temperature of the combustor is expected to rise to about 1000°C. For this reason, there is a demand for the development of Ni-based alloys that exhibit creep properties at higher temperatures than the Ni-based alloys that have been used traditionally as combustor materials.
  • Ni-based alloys which have excellent high-temperature strength and corrosion resistance, contain Cr, Mo, Nb, and Ti in addition to the main component Ni. Since these metals are extremely expensive compared to iron, it is extremely important to improve yield and reduce manufacturing costs. Here, if surface defects such as linear scratches occur on the surface of Ni-Cr-Fe-Mo alloys, they must be removed by grinding or cutting, which significantly reduces yield, so there is a demand for Ni-Cr-Fe-Mo alloys with excellent surface properties.
  • Patent Document 1 discloses a technology that realizes a Ni-based alloy material with excellent strength, workability, and creep properties at room temperature by precipitating carbides and nitrides through heat treatment.
  • carbides and nitrides do not cause defects on the surface of the product, and the invention of Patent Document 1 cannot be applied to the problem of surface properties caused by oxide-based non-metallic inclusions generated during the refining process that is the subject of the present invention, and the problem of surface defects caused by oxide-based non-metallic inclusions remains.
  • Patent Document 2 discloses a technique for a high-Ni alloy containing Al and Ti for high temperatures and a method for producing the high-Ni alloy, in which the composition of the oxide-based inclusions is controlled to a CaO-Al 2 O 3 system having a low melting point by setting the Ca/Al mass ratio in the oxide-based inclusions in the range of 1.0 to 1.5, thereby preventing clogging of the immersion nozzle of a continuous casting machine and preventing surface defects in the product.
  • Patent Document 2 targets high Ni alloys containing 5% or less Mo
  • the present application is an invention related to Ni-Cr-Fe-Mo alloys containing 6.0 to 15.0% Mo.
  • Mo is a component that significantly increases the activity of Si, which is a deoxidizer, and even if trace components such as Ca, Mg, Al, Si, and O are the same, the composition of oxide-based nonmetallic inclusions varies greatly, and different techniques are required to control the inclusion composition of alloys with different Mo concentrations.
  • Patent Document 2 controls the inclusion composition by adding a Ca alloy to molten steel.
  • Ca is a stronger deoxidizer than Al, Si, Ti, etc., and has the ability to change the composition of inclusions that have already been formed to CaO-Al 2 O 3 -based, but at the same time, a large number of inclusions are formed.
  • adding a strong deoxidizer such as Ca at the end of refining will deteriorate the cleanliness and the surface quality of the product.
  • Patent Document 2 sufficiently improves the surface properties of the Ni--Cr--Fe--Mo alloy of the present invention.
  • Patent Document 3 discloses a technique for reducing surface defects in high Ni alloys by controlling the composition of nonmetallic inclusions in the alloy and forming low-melting-point inclusions with good stretchability and separability during hot or cold rolling.
  • the high Ni alloys in Patent Document 3 are intended for alloys containing 0.5% or less Cr or 3-10%, and are different from the Ni-Cr-Fe-Mo alloys of the present invention, which contain 18.0-28.0% Cr.
  • the Cr content has a large effect on inclusion composition control, and even if the trace elements such as Ca, Mg, Al, Si, and O are the same, the composition of oxide-based nonmetallic inclusions is significantly different.
  • the method for controlling the composition of nonmetallic inclusions described in Patent Document 3 cannot be said to sufficiently improve the surface properties of the Ni-Cr-Fe-Mo alloys of the present invention.
  • Patent Document 4 reports a technique for reducing surface defects by controlling inclusions in stainless steel sheets to harmless MgO and CaO-Al 2 O 3 -MgO oxides.
  • Nb which is contained in the Ni-Cr-Fe-Mo alloy of the present invention at 0.02 to 0.60%, has the same oxidation ability as Si and Mn.
  • the stainless steel sheet described in Patent Document 4 does not contain Nb.
  • the stainless steel sheet of Patent Document 4 does not contain Ti, which is contained in the Ni-Cr-Fe-Mo alloy of the present invention at 0.01 to 0.40%.
  • Ti is also a component that greatly affects the composition of nonmetallic inclusions, and the technique disclosed in Patent Document 4 cannot improve the surface properties of the Ni-Cr-Fe-Mo alloy of the present invention.
  • Patent Document 5 reports a technique for adding Nb to Fe-Ni-Cr alloys with a high yield.
  • the target Fe-Ni-Cr alloy has a Mo content of 1-5%
  • the present application is an invention related to Ni-Cr-Fe-Mo alloys with Mo of 6.0-15.0%.
  • Mo is a component that significantly increases the activity of Si, which is a deoxidizing agent, and even if trace components such as Ca, Mg, Al, Si, and O are the same, the composition of oxide-based nonmetallic inclusions varies greatly, and a different technique is required to control the inclusion composition of alloys with different Mo concentrations.
  • Patent Document 6 does not contain Ti.
  • Ti is a component that greatly affects the nonmetallic inclusion composition, and the control of nonmetallic inclusions is significantly different from that of the Ni-Cr-Fe-Mo alloys containing Ti: 0.01-0.40% of the present application.
  • the technology in Patent Document 5 cannot be used for surface defects in the Fe-Ni-Cr alloys that are the subject of this application.
  • Patent Document 6 discloses a technology that suppresses large clusters by controlling nonmetallic inclusions in Ni-Cr-Mo-Nb alloys to simple MgO and complex oxynitrides of MgO and (Ti, Nb)N, thereby obtaining good quality without surface defects in thin plate products.
  • the Ni-Cr-Mo-Nb alloys covered by Patent Document 6 are technologies that target Ni-Cr-Mo-Nb alloys containing 2.5-5% Nb, and are significantly different from the Ni-Cr-Fe-Mo alloys of the present patent that contain 0.02-0.60% Nb.
  • Nb is a component that greatly affects the composition of nonmetallic inclusions, and is significantly different from the control of nonmetallic inclusions that is required.
  • the technology of Patent Document 6 cannot be used for surface defects in Fe-Ni-Cr alloys that are the subject of the present patent.
  • the present invention aims to provide a Ni-Cr-Fe-Mo alloy with excellent surface properties by controlling the composition of nonmetallic inclusions that affect the surface properties. Furthermore, the invention also provides a manufacturing method for the Ni-Cr-Fe-Mo alloy to achieve this.
  • Figures 1 and 2 show the mechanism by which the surface defects occur in continuous casting.
  • reference numeral 1 denotes a ladle that holds molten metal 2.
  • the molten metal 2 is transferred to a tundish 3 and poured into a mold 5 through a submerged nozzle 4.
  • the molten metal 2 in the mold 5 is pulled downward, solidifies to form a solidified shell 6, and is cooled in a spray cooling zone 7, obtaining a slab downstream.
  • nonmetallic inclusions 8a contained in the molten metal 2 flow, and a part of them adheres to the inner wall of the submerged nozzle 4 to form a lump like 8b.
  • This type of nonmetallic inclusion is likely to adhere to the inner wall of the submerged nozzle for pouring molten metal from the tundish into the mold in a continuous casting machine and to grow in size, and those that fall off, as shown in 8c, flow into the mold 5 and are captured by the solidified shell 6 and are likely to become the starting point of surface defects, which have been the starting point of surface defects in Ni-Cr-Fe-Mo alloy sheets.
  • a tundish and a submerged nozzle are not used in normal ingot making (ingot making)
  • a similar refractory flow path is used to guide the molten metal to the mold, and therefore there is a problem similar to that of continuous casting, in that nonmetallic inclusions adhere to the inner wall of the flow path.
  • the inventors further conducted intensive research into the relationship between the inclusion composition and metal components in Ni-Cr-Fe-Mo alloys. Specifically, during the manufacturing process of Ni-Cr-Fe-Mo alloys, metal samples of Ni-Cr-Fe-Mo alloys were taken from the tundish of a continuous casting machine, and 20 inclusions larger than 5 ⁇ m were randomly selected from the samples, and the inclusion composition was measured using SEM/EDS. In addition, a submerged nozzle for supplying molten metal from the tundish of the continuous casting machine to the mold was taken, and the composition of the deposits on the inner wall of the nozzle, as shown in Figure 2, was analyzed using SEM/EDS. Based on the above, intensive research was conducted into the relationship between the inclusion composition, metal components, and the deposits on the inner wall of the submerged nozzle.
  • the non-metallic inclusions contain one or more types of MgO, CaO, MgO-CaO-based oxides, and MgO-CaO-NbO- TiO2 -based oxides, and that if the MgO-CaO-NbO- TiO2 -based oxide contains, in mass %, 0.1 to 5.0% NbO and 20% or less TiO2 , the non-metallic inclusions are less likely to adhere to and accumulate on the inner wall of the submerged nozzle, i.e., are less likely to increase in size, and are less likely to cause surface defects.
  • MgO, CaO, and MgO-CaO oxide inclusions are fine nonmetallic inclusions that do not adhere to the inner wall of the submerged nozzle of the tundish of a continuous casting machine, do not affect the surface quality of the Ni-Cr-Fe-Mo alloy plate of the present invention, and are one of the preferred nonmetallic inclusion compositions that should be controlled to MgO, CaO, and MgO-CaO oxide inclusions.
  • the Ni-Cr-Fe-Mo alloy of the present invention has been made based on the above findings, and contains the following components, in mass%, C: 0.03-0.30%, Si: 0.05-1.50%, Mn: 0.05-2.00%, P: 0.05% or less, S: 0.005% or less, Cr: 18.0-28.0%, Mo: 6.0-15.0%, Cu: 1.0% or less, Al: 0.01-0.50%, Ti: 0.01-0.40%, Nb: 0.02-0.60%, Fe: 15.
  • a Ni-Cr-Fe-Mo alloy having the following composition: 0-22.0%, Co: 0.5-4.0%, W: 0.10-2.00%, B: 0.0001-0.0100%, N: 0.005-0.100%, O: 0.0001-0.0060%, Mg: 0.0001-0.0300%, Ca: 0.0001-0.0080%, and the balance being Ni and unavoidable impurities, and the nonmetallic inclusions are MgO, CaO, MgO-CaO-based oxides, MgO-CaO-NbO-TiO
  • the composition contains one or more of the MgO-CaO-NbO-TiO2-based oxides, and in the case where the composition contains an MgO-CaO-NbO- TiO2 -based oxide, the MgO-CaO-NbO-TiO2 - based oxide is characterized by containing, in mass%, 0.1 to 5.0% NbO and 20% or less TiO2 .
  • the ratio of MgO-CaO-NbO- TiO2- based oxides to the nonmetallic inclusions is 50% or less.
  • the present invention also provides a manufacturing method, which is to say, by melting the raw materials in an electric furnace, then decarburizing them with AOD and/or VOD, adding lime and fluorite, then adding one or two of a ferrosilicon alloy and pure silicon, and Al for primary deoxidization, and adding Nb when the O concentration reaches 0.0070-0.0120%, and then producing a CaO-SiO 2 -MgO-Al 2 O 3 alloy consisting of CaO: 50-70%, SiO 2 : 1-8%, Al 2 O 3 : 10-30%, MgO: 5-15 %, and F: 2-8 %.
  • This method for producing a Ni-Cr-Fe-Mo alloy having excellent surface properties is characterized in that, using -F-based slag, one or both of a ferrosilicon alloy and pure silicon, and Al are added to carry out Cr reduction, secondary deoxidization, and desulfurization, and then, when the O concentration becomes 0.0060% or less, Ti is added, and a slab or ingot is produced by a continuous casting machine or ordinary ingot making, and in the case of an ingot, hot forging is performed, followed by hot rolling or hot rolling and cold rolling.
  • FIG. 2 is a schematic cross-sectional view of a continuous casting machine during casting.
  • FIG. 2 is a schematic cross-sectional view of a submerged nozzle.
  • FIG. 2 is a schematic diagram of a nonmetallic inclusion.
  • FIG. 2 is a schematic diagram of nonmetallic inclusions with a low melting point.
  • FIG. 2 is a schematic diagram of nonmetallic inclusions having a high melting point.
  • FIG. 2 is a schematic diagram of nonmetallic inclusions having a high melting point.
  • % means “mass% (mass %)”.
  • C 0.03 to 0.30%) C forms M6C type carbides. It is also an element that forms new M6C type carbides and M23C type carbides during use at high temperatures, strengthening the grain boundaries and inside the grains and improving creep properties. To obtain this effect, at least 0.03% must be added. However, if it is added in excess of 0.30%, coarse undissolved carbides are generated and remain, deteriorating workability and creep properties. For this reason, the C content is set to the range of 0.03 to 0.30%, preferably 0.04 to 0.20%, and more preferably 0.05 to 0.10%.
  • Si 0.05 to 1.50% Since Si is an element effective in improving oxidation resistance and is also effective in deoxidization, it is an important element in the present invention. 0.05% is necessary to control the oxygen concentration to 0.0001-0.0060%. Furthermore, it also plays a role in reducing CaO and MgO in CaO-SiO 2 -MgO-Al 2 O 3 -F slag and adjusting Mg and Ca in the molten metal to 0.0001-0.0300% and 0.0001-0.0080%, respectively. This has the effect of controlling the composition of nonmetallic inclusions. From this viewpoint, 0.05% is also necessary.
  • the Si content is specified to be 0.05 to 1.50%, preferably 0.10 to 1.00%, and more preferably 0.20 to 0.60%.
  • Mn 0.05 to 2.00%
  • Mn is an austenite phase stabilizing element and also contributes to deoxidation, so it is necessary to add 0.05% or more. However, adding a large amount impairs oxidation resistance, so the upper limit is set at 2.00%.
  • the preferred range is 0.10 to 1.50%, and the more preferred range is 0.30 to 1.00%.
  • P 0.05% or less Since P is a harmful element that segregates at grain boundaries and causes cracks during hot working, it is desirable to reduce the P content as much as possible and limit it to 0.05% or less, preferably 0.04% or less, and more preferably 0.03% or less.
  • S is a harmful element that segregates at grain boundaries to form low melting point compounds and impair hot workability, so it is desirable to reduce it as much as possible and limit it to 0.005% or less.
  • the lower limit of the Al content is set to 0.01%, and deoxidation is promoted by controlling the O concentration to the range of 0.0001 to 0.0060%, thereby promoting desulfurization. It is preferably 0.003% or less. More preferably, it is 0.001% or less.
  • Cr is one of the main elements of the Ni-Cr-Fe-Mo alloy of the present invention, and the Cr component forms a good protective film to improve the oxidation resistance of the alloy.
  • M23C6 type carbides acts to increase the strength of the grain boundaries. It is a heavy element.
  • the Cr content is specified to be 18.0 to 28.0%. Preferably, it is 19.0 to 26.0%. More preferably, it is 20.0 to 24.0%.
  • Mo is one of the main elements constituting the Ni-based alloy material of the present invention. It has the effect of improving creep properties by dissolving in the matrix and strengthening it by forming M6C-type carbides with C. Furthermore, it has the effect of improving creep properties by forming M6C-type carbides and precipitating them in crystal grains during use at high temperatures. If the Mo content is less than 6.0%, sufficient creep properties cannot be obtained. On the other hand, if the Mo content exceeds 15.0%, oxidation resistance deteriorates. Therefore, the Mo content range is specified to be 6.0 to 15.0%. It is preferably 7.0 to 12.5%. More preferably, it is 8.0 to 10.0%.
  • Mo also has the effect of increasing the activity coefficient of Si, the main deoxidizing component, and strengthening the deoxidizing power. Therefore, in order to control the inclusion composition, it is necessary to consider the amount and timing of addition of the deoxidizing materials Al and Si, taking into account the Mo content range of this application.
  • Cu 1.0% or less
  • the Cu content is set to 1.0% or less, preferably 0.5% or less, and more preferably 0.3% or less.
  • the figures in parentheses indicate the components in the slag, and the underlines indicate the components in the molten metal.
  • the Al concentration is less than 0.01%, deoxidation will not proceed sufficiently, and the oxygen concentration will exceed 0.0060%, resulting in a high oxygen concentration. Furthermore, because deoxidation does not proceed, desulfurization will be inhibited, and the S concentration will exceed 0.005%, resulting in a high S concentration.
  • the Al concentration is higher than 0.50%, the Mg concentration will exceed 0.0300% due to the reaction in formula (1) above, and the Ca concentration will also exceed 0.0080% due to the reaction in formula (2) above. Therefore, the range of Al content is specified as 0.01 to 0.50%. Preferably, it is 0.03 to 0.40%. More preferably, it is 0.05 to 0.30%.
  • Ti 0.01 to 0.40%
  • Ti forms TiN nitrides that remain even after annealing, suppressing the growth of crystal grains during annealing, and improving strength at room temperature by making the crystal grains finer.
  • Ti precipitates extremely fine TiN nitrides in crystal grains during use at high temperatures, and these precipitate M6C type carbides uniformly and finely, improving creep properties. 0.01% or more is necessary to improve strength and creep properties.
  • the Ti content is specified to be 0.01 to 0.40%.
  • it is 0.02 to 0.30%. More preferably, it is 0.03 to 0.20%.
  • Nb is an important element in the present invention, and forms NbN nitrides that remain even after annealing, suppressing the growth of crystal grains during annealing, and improving strength at room temperature by making the crystal grains finer. In addition, it has the effect of improving creep properties by precipitating extremely fine NbN nitrides in crystal grains during use at high temperatures, and using these as nuclei to precipitate M6C type carbides uniformly and finely. In order to improve strength and creep properties, 0.02% or more is necessary. However, if Nb is added in excess of 0.60%, the thermal expansion coefficient increases and the weld cracking sensitivity increases. Therefore, the Nb content is specified to be 0.02 to 0.60%. Preferably, it is 0.05 to 0.50%. More preferably, it is 0.10 to 0.30%.
  • Fe 15.0 to 22.0%
  • Fe is one of the main elements contained due to scrap, which is the raw material, and if the Fe content exceeds 22.0%, the Ni content decreases relatively and the oxidation resistance decreases. On the other hand, if the Fe content is reduced to less than 15.0%, the Ni content increases relatively, which not only increases the raw material cost but also reduces the hot workability. Therefore, the Fe content is set to 15.0 to 22.0%, preferably 16.0 to 21.0%, and more preferably 17.0 to 20.0%.
  • Co 0.5 to 4.0%
  • Co is an element that improves creep properties by its solid solution strengthening effect.
  • Co is an expensive element, and the above effect saturates when the content exceeds 4.0%, and the effect commensurate with the amount added is no longer obtained. Therefore, the Co content is specified to be 0.5 to 4.0%, preferably 0.6 to 3.0%, and more preferably 0.7 to 2.0%.
  • W 0.10 to 2.00%
  • W is an element that improves creep properties by its solid solution strengthening action. It also strengthens by forming M6C type carbides with C. Furthermore, even during use at high temperatures, it forms M6C type carbides and precipitates within crystal grains, improving creep properties.
  • W is an expensive element, and the above effects saturate when the content exceeds 2.00%, and the effect commensurate with the amount added is no longer obtained. Therefore, the W content is set to 0.10 to 2.00%, preferably 0.18 to 1.80%, and more preferably 0.20 to 1.50%.
  • B is an element that increases the strength of grain boundaries and improves creep properties. However, if B is added in an amount exceeding 0.0100%, low-melting point compounds precipitate, reducing hot workability. Therefore, the B content is set to 0.0001 to 0.0100%, preferably 0.0005 to 0.0080%, and more preferably 0.0010 to 0.0050%.
  • N has the effect of increasing the strength at room temperature and high temperature by dissolving in the parent phase, and is considered to be a useful element that should be actively added. Moreover, it forms fine MN-type nitrides with Ti and Nb, suppresses the growth of crystal grains during annealing, and refines the crystal grains, thereby improving the strength at room temperature. Furthermore, during use at high temperatures, it has the effect of precipitating extremely fine MN-type nitrides within the crystal grains, which become nuclei to precipitate M6C-type carbides uniformly and finely, thereby improving creep properties. Such effects are manifested by the addition of 0.005% or more.
  • the content of N is 0.005 to 0.100%. It is preferably 0.010 to 0.080%, and more preferably 0.015 to 0.060%.
  • N also affects the properties of non-metallic inclusions produced during the refining process, making it an element that must be precisely controlled.
  • N is added by blowing nitrogen gas into the molten metal with AOD or VOD, and when it is necessary to lower the N content, the N concentration can be lowered by blowing Ar gas with AOD, VOD or LF, allowing precise control of the N content in the molten metal.
  • the oxygen concentration is very important in the present invention because it is closely related to inclusions. If the O content in the alloy exceeds 0.0060%, the number of inclusions increases, which leads to the generation of surface defects, and desulfurization is hindered, resulting in a high S concentration. However, if the O content is less than 0.0001%, the Al's ability to reduce CaO and MgO in the slag increases too much, causing the Mg concentration to exceed the upper limit of 0.0300% and the Ca concentration to exceed the upper limit of 0.0080%. Therefore, the O content is specified to be 0.0001 to 0.0060%. Preferably, it is 0.0003 to 0.0050%. More preferably, it is 0.0005 to 0.0040%.
  • Mg is an element effective in controlling the composition of nonmetallic inclusions in the molten metal to MgO and MgO-CaO oxides that do not adversely affect the surface properties. This effect cannot be obtained if the content is less than 0.0001%, and conversely, if the content exceeds 0.0300%, the hot workability decreases, making it easier for cracks to occur in the hot rolling process, resulting in surface defects in the final product. For this reason, the Mg content is specified to be 0.0001 to 0.0300%, preferably 0.0005 to 0.0200%, and more preferably 0.0010 to 0.0100%.
  • the slag composition should be controlled to CaO: 50-70%, SiO2 : 1-8%, Al2O3 : 10-30%, MgO: 5-15%, and F: 2-8%.
  • Ca 0.0001 to 0.0080%
  • Ca is an element effective in controlling the composition of nonmetallic inclusions in the molten metal to CaO and MgO-CaO oxides that do not form clusters and have no adverse effect on surface quality. This effect cannot be obtained if the Ca content is less than 0.0001%, and conversely, if the Ca content exceeds 0.0080%, the hot workability decreases, making the material more susceptible to cracking during the hot rolling process and causing surface defects in the final product. For this reason, the Ca content is specified to be 0.0001 to 0.0080%. Preferably, it is 0.0002 to 0.0050%. More preferably, it is 0.0003 to 0.0030%.
  • the slag composition should be controlled to CaO: 50-70%, SiO 2 : 1-8%, Al 2 O 3 : 10-30%, MgO: 5-15%, and F: 2-8%.
  • the subject alloy of the present invention contains the components described above, with the balance being Ni.
  • the nonmetallic inclusions include one or more of MgO, CaO, MgO-CaO-based oxides, and MgO-CaO-NbO- TiO2 -based oxides, and in a preferred embodiment, the MgO-CaO-NbO- TiO2 -based oxide contains, in mass%, 0.1 to 5.0% NbO and 20% or less TiO2 .
  • the ratio of the number of MgO-CaO-NbO- TiO2 -based oxides is 50% or less.
  • the reasons for limiting the composition and number ratio of nonmetallic inclusions are shown below. (Contains one or more of MgO, CaO, MgO-CaO-based oxides, and MgO-CaO-NbO- TiO2- based oxides)
  • the Ni-Cr-Fe-Mo alloy according to the present invention contains one or more of MgO, CaO, MgO-CaO-based oxides, and MgO-CaO-NbO-TiO2- based oxides, depending on the contents of Si, Al, Mg, Ca, and O in the Ni-Cr-Fe-Mo alloy and the amounts and timing of addition of Nb and Ti.
  • MgO, CaO, and MgO-CaO oxides are non-metallic inclusions with a high melting point and solid phase, so they do not adhere to the inner wall of the submerged nozzle of the tundish of the continuous casting machine and are fine non-metallic inclusions, and do not affect the surface quality of the Ni-Cr-Fe-Mo alloy sheet of the present invention.
  • MgO, CaO, and MgO-CaO oxide inclusions are a preferred non-metallic inclusion composition that should be controlled.
  • CaO and MgO-CaO oxide inclusions are generated when part of CaO reacts with S in the molten metal during the solidification process of the Ni-Cr-Fe-Mo alloy in the continuous casting machine to generate CaS.
  • CaO and MgO-CaO oxide inclusions have the effect of maintaining clean surface quality by fixing S in the molten metal, which deteriorates hot workability, as CaS.
  • Ni-Cr-Fe-Mo alloys of the present application are used in gas turbine combustion tower parts through which high-temperature gases exceeding 1000°C flow, and therefore there is no problem of deterioration of corrosion resistance in a humid environment due to CaO inclusions.
  • MgO-CaO-NbO- TiO2 oxide contains, by mass%, 0.1 to 5.0% NbO and 20% or less TiO2 )
  • 1600°C which is the refining temperature of Ni-Cr-Fe-Mo alloy
  • MgO-CaO-TiO 2 oxides are in the form of liquid phase MgO-CaO-TiO 2 oxides around MgO, CaO, and MgO-CaO oxide inclusions, as shown in Figure 3.
  • liquid phase MgO-CaO-TiO 2 oxides are formed around MgO, CaO, and MgO-CaO oxide inclusions
  • the liquid phase inclusions play a role like an adhesive
  • the solid phase MgO, CaO, and MgO-CaO oxides play a role as aggregates, which promotes the adhesion of nonmetallic inclusions to the refractory on the inner wall of the submerged nozzle, as shown in Figure 2, and the nonmetallic inclusions fall off after coarsening, are carried into the mold together with the molten metal, and are captured by the solidified shell, which may cause surface defects.
  • the inventors conducted extensive research into the deposits on the inner wall of the submerged nozzle and the nonmetallic inclusions inside the surface defects of Ni-Cr-Fe-Mo alloys and plates, and discovered that by adding 0.1 to 5.0% NbO by mass to the MgO-CaO- TiO2 oxide, it is possible to prevent adhesion to the inner wall of the submerged nozzle and prevent deterioration of the surface properties.
  • NbO will be explained.
  • NbO in the MgO-CaO- TiO2 system oxide is present in the liquid phase, and NbO has the effect of lowering the melting point of the liquid phase MgO-CaO- TiO2 system oxide.
  • NbO reduces the adhesive effect of the liquid phase MgO-CaO- TiO2 system oxide, and has the effect of preventing the MgO-CaO- TiO2 system oxide from adhering to the inner wall of the submerged nozzle.
  • NbN is a nitride with a melting point of 2573°C, and as shown in Figure 5, a liquid phase MgO-CaO- TiO2 oxide +NbO (-NbN) with a high melting point is generated again around the MgO, CaO, and MgO-CaO oxide inclusions.
  • the high melting point liquid phase inclusions again act as an adhesive, promoting the adhesion of non-metallic inclusions to the inner wall of the submerged nozzle, and the non-metallic inclusions adhere to and accumulate on the inner wall, coarsen, and then fall off, resulting in a deterioration in cleanliness.
  • the MgO-CaO-NbO- TiO2 oxide contains 0.1 to 5.0% NbO by mass%.
  • TiN is a nitride with a melting point of 2950°C, and generates a liquid phase MgO-CaO-NbO-TiO 2 (-TiN) oxide with a high melting point around MgO, CaO, and MgO-CaO oxide inclusions as shown in Figure 6. Even if 0.1 to 5.0% by mass of NbO is added to an MgO-CaO-NbO-TiO 2 oxide containing more than 20% by mass of TiO 2 , the effect of lowering the melting point of the liquid phase inclusions is lost, resulting in a deterioration in cleanliness. For the above reasons, the MgO-CaO-NbO-TiO 2 oxide is specified to contain 0.1 to 5.0% by mass of NbO and 20% or less of TiO 2 .
  • the timing of adding Nb during smelting of the molten metal is important.
  • the timing of adding Nb during smelting of the molten metal is important.
  • the NbO concentration in the nonmetallic inclusions can be precisely controlled.
  • the timing of adding Ti during molten metal refining is important. After the primary deoxidation, Nb is added, and then CaO- SiO2 -MgO- Al2O3-F system slag consisting of CaO: 50-70%, SiO2 : 1-8%, Al2O3 : 10-30 %, MgO: 5-15%, F: 2-8% is used, and one or two of ferrosilicon alloy and pure silicon, and Al are added to perform Cr reduction, secondary deoxidation, and desulfurization, and then when the O concentration becomes 0.0060% or less, it is important to add Ti, and the TiO2 concentration in the nonmetallic inclusions can be controlled to 20% or less.
  • N is added by blowing nitrogen gas into the molten metal with AOD or VOD, and when it is necessary to lower the N content, the N concentration can be lowered by blowing Ar gas with AOD, VOD or LF, allowing for precise control of the N content of the molten metal.
  • the composition of the nonmetallic inclusions consisting of oxides of two or more phases as shown in Figures 3 to 6 is the overall average composition, and represents the concentration (mass %) of each component of the nonmetallic inclusions.
  • the ratio of MgO-CaO-NbO- TiO2 oxides is 50% or less
  • MgO-CaO-NbO-TiO 2 -based oxides are one of the non-metallic inclusions that adhere to the inner wall of the submerged nozzle, coarsen, and then fall off, causing a deterioration in cleanliness.
  • the number ratio of MgO-CaO-NbO-TiO 2 -based oxides is 50% or less, the tendency for them to adhere is mild and the number of surface defects is reduced. Therefore, the number ratio of MgO-CaO-NbO-TiO 2 -based oxides is specified to be 50% or less.
  • the present invention also proposes a method for producing a Ni--Cr--Fe--Mo alloy.
  • the raw materials are melted in an electric furnace to produce a Ni-Cr-Fe-Mo molten metal having a specified composition.
  • the molten metal is decarburized using AOD (Argon Oxygen Decarburization) or AOD followed by VOD (Vacuum Oxygen Decarburization).
  • AOD Aron Oxygen Decarburization
  • VOD Vauum Oxygen Decarburization
  • ferrosilicon alloy and pure silicon, and Al are added to perform Cr reduction, secondary deoxidization, and desulfurization, and then when the O concentration becomes 0.0060% or less, Ti is added, and then the molten metal is tapped into a ladle, and the temperature and composition are adjusted in an LF (Ladle Furnace), and a slab or ingot is produced by a continuous casting machine or a normal ingot casting machine. The ingot is hot forged to produce a slab.
  • LF Ladle Furnace
  • the nonmetallic inclusions include one or more of MgO, CaO, MgO-CaO-based oxides, and MgO-CaO-NbO-TiO 2 -based oxides, and if the MgO-CaO-NbO-TiO 2- based oxide contains 0.1 to 5.0% NbO by mass and TiO 2 is 20% or less, a Ni-Cr-Fe-Mo-based alloy with excellent surface properties can be obtained.
  • the produced slabs have their surfaces ground, are heated, and then are hot-rolled or hot-rolled and then cold-rolled, annealed, pickled, and the surface scale is removed, to finally produce plates.
  • the slag composition is characterized as described above.
  • the basis for the slag composition specified in the present invention will be explained below.
  • the CaO concentration and SiO2 concentration in the slag are elements for efficiently performing deoxidation and desulfurization and controlling inclusions. If the CaO concentration exceeds 70%, the activity of CaO in the slag becomes high, and the reaction of formula (2) proceeds too much. Therefore, if the Ca concentration reduced in the molten metal exceeds 0.0080%, the hot workability decreases, making it easier for cracks to occur in the hot rolling process, resulting in surface defects in the final product. Therefore, the upper limit is specified as 70%.
  • the lower limit is specified as 50%. Preferably, it is 53 to 67%. More preferably, it is 55 to 65%.
  • SiO2 in the slag is an element necessary to ensure the proper fluidity of the slag, so at least 1% is necessary. However, if it exceeds 8%, the Al concentration, Mg concentration, and Ca concentration in the molten metal will fall below the specified range, so the upper limit is set to 8%. It is preferably 2 to 7%. More preferably, it is 3 to 6%.
  • Al2O3 10-30 % If the Al 2 O 3 content in the slag is higher than 30%, deoxidation does not proceed sufficiently, the O concentration is not controlled within the specified range, and MgO-CaO-NbO-TiO 2 oxides are generated as non-metallic inclusions at a number ratio of more than 50%. On the other hand, if the Al 2 O 3 content in the slag is lower than 10%, the fluidity of the slag cannot be ensured, desulfurization does not proceed, and the S concentration exceeds the specified range.
  • the preferred content is 12-28%. More preferably, the preferred content is 15-25%.
  • MgO in the slag is an important element for controlling the Mg concentration in the molten metal to the concentration range described in the claims, and is also an important element for controlling nonmetallic inclusions to a composition preferable for the present invention. Therefore, the MgO content in the slag must be at least 5%. On the other hand, if the MgO content exceeds 15%, the reaction of formula (1) proceeds too much, the Mg content in the molten metal becomes high, and the hot workability decreases, resulting in surface defects in the final product. Therefore, the upper limit of the MgO content is set to 15%.
  • the MgO content in the slag is within a predetermined range when the dolomite bricks or magnesia-chrome bricks used in AOD refining or VOD refining dissolve in the slag.
  • a predetermined range when the dolomite bricks or magnesia-chrome bricks used in AOD refining or VOD refining dissolve in the slag.
  • one or both of the waste dolomite bricks and magnesia-chrome bricks may be added. It is preferably 7 to 14%. More preferably, it is 9 to 13%.
  • F 2-8%
  • fluorite which is added during slag refining, and plays a role in precisely adjusting the molten state of the slag, so it is necessary to add at least 2%. If the F concentration falls below 2%, the slag will not melt and will have low fluidity. On the other hand, if the F concentration exceeds 8%, the fluidity of the slag will increase significantly, causing significant damage to the bricks. Therefore, the F concentration is specified as 2-8%.
  • the surface of the produced slab was ground, heated to 1200°C and hot rolled to produce a hot coil. It was then annealed and pickled to remove surface scale, and cold rolled to the specified thickness to produce a cold rolled coil.
  • the chemical composition of the obtained Ni-Cr-Fe-Mo alloy, as well as the slag composition at the end of AOD or VOD refining, the production process, the composition of nonmetallic inclusions, the morphology of inclusions and the quality evaluation are shown in Tables 1 and 2.
  • values in parentheses indicate that they are outside the scope of the claims. Note that there are some invention examples in parentheses, but although they do not meet the scope of the dependent claims, they do meet the scope of the independent claims.
  • Inventive Examples 1 to 13 satisfied the range of the present invention, and therefore had few surface defects on the plate and achieved good surface properties.
  • Inventive Example 12 the Si concentration was 0.11% and the Al concentration was 0.03%, both of which were within the prescribed range but low, resulting in slightly weak deoxidation and a high O concentration of 0.0045%.
  • the supply of Mg and Ca from the slag was also low, with Mg being 0.0008% and Ca being 0.0002%.
  • the number ratio of MgO-CaO-NbO- TiO2- based oxides was high at 65%, several coarse inclusions were generated, and the number of surface defects was 7, resulting in a ⁇ rating.
  • the Si concentration was 0.09% and the Al concentration was 0.02%, both of which were within the prescribed range but low, resulting in slightly weak deoxidation and a high O concentration of 0.0048%.
  • the supply of Mg and Ca from the slag was also low, with Mg being 0.0007% and Ca being 0.0002%.
  • the nonmetallic inclusions were only MgO-CaO-NbO- TiO2 oxides, several coarse inclusions occurred, and the number of surface defects was 9, resulting in a ⁇ rating.
  • Comparative Examples 14 to 20 were outside the scope of the present invention, and thus many surface defects occurred, resulting in poor surface properties.
  • Each example will be described below.
  • the O concentration after primary deoxidation and before adding Nb was high at 0.0142%, and the NbO in the MgO-CaO-NbO- TiO2 oxide was high at 5.5%.
  • Some NbN was also generated in the liquid phase of the MgO-CaO-NbO- TiO2 oxide, resulting in a high melting point.
  • MgO.Al2O3 and Al2O3 - SiO2 - MnO - Cr2O3 - based oxides were detected.
  • MgO.Al2O3 is one of the nonmetallic inclusions that should be avoided as it easily adheres to the inside of the submerged nozzle, and Al2O3 - SiO2 - MnO - Cr2O3 -based oxides are low -grade oxides that form in molten metal that has not been sufficiently deoxidized. Due to insufficient deoxidization, many nonmetallic inclusions remain in the molten metal and flow into the mold, so they are also one of the nonmetallic inclusions that should be avoided. A large number of surface defects (27) occurred. The evaluation was poor.
  • the technology of the present invention controls the morphology of nonmetallic inclusions, making it possible to supply Ni-Cr-Fe-Mo alloys with excellent surface properties and high creep resistance suitable for use in gas turbine combustion tower components.

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Abstract

L'invention concerne un alliage à base de Ni-Cr-Fe-Mo dans lequel la composition d'inclusions non métalliques est contrôlée et qui comprend, en termes de % en masse, 0,03 à 0,30 % de C, 0,05 à 1,50 % de Si, 0,05 à 2,00 % de Mn, 0,05 % ou moins de P, 0,005 % ou moins de S, 18,0 à 28,0 % de Cr, 6,0 à 15,0% de Mo, 1.0% ou moins de Cu, 0,01 à 0,50% de Al, 0,01 à 0,40% de Ti, 0,02 à 0,60% de Nb, 15,0 à 22,0% de Fe, 0,5 à 4,0% de Co, 0,10 à 2,00% de W, 0,0001 à 0,0100% de B, 0,005 à 0,100% de N, 0,0001 à 0,0060% de O, 0,0001 à 0,0300% de Mg, et 0,0001 à 0,0080% de Ca, le reste étant du Ni et les impuretés inévitables.
PCT/JP2023/033908 2022-10-21 2023-09-19 Alliage à base de ni-cr-fe-mo ayant d'excellentes propriétés de surface, et son procédé de production WO2024084877A1 (fr)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2012229463A (ja) * 2011-04-25 2012-11-22 Nippon Yakin Kogyo Co Ltd Ｆｅ−Ｎｉ−Ｃｒ−Ｍｏ合金およびその製造方法
JP2017043826A (ja) * 2015-08-28 2017-03-02 日本冶金工業株式会社 Ｆｅ−Ｃｒ−Ｎｉ−Ｍｏ合金とその製造方法
WO2018151222A1 (fr) * 2017-02-15 2018-08-23 新日鐵住金株式会社 ALLIAGE RÉSISTANT À LA CHALEUR À BASE DE Ni ET SON PROCÉDÉ DE FABRICATION
JP6990337B1 (ja) * 2021-10-11 2022-02-15 日本冶金工業株式会社 表面性状に優れたＮｉ基合金およびその製造方法

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WO2022220242A1 (fr) 2021-04-14 2022-10-20 日鉄ステンレス株式会社 Alliage à haute teneur en nickel présentant une excellente résistance à la fissuration à haute température de soudage

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2012229463A (ja) * 2011-04-25 2012-11-22 Nippon Yakin Kogyo Co Ltd Ｆｅ−Ｎｉ−Ｃｒ−Ｍｏ合金およびその製造方法
JP2017043826A (ja) * 2015-08-28 2017-03-02 日本冶金工業株式会社 Ｆｅ−Ｃｒ−Ｎｉ−Ｍｏ合金とその製造方法
WO2018151222A1 (fr) * 2017-02-15 2018-08-23 新日鐵住金株式会社 ALLIAGE RÉSISTANT À LA CHALEUR À BASE DE Ni ET SON PROCÉDÉ DE FABRICATION
JP6990337B1 (ja) * 2021-10-11 2022-02-15 日本冶金工業株式会社 表面性状に優れたＮｉ基合金およびその製造方法

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