WO2017169056A1 - Cr-BASED TWO-PHASE ALLOY AND PRODUCT THEREOF - Google Patents

Abstract

The purpose of the present invention is to provide a two-phase alloy having Cr, which is inexpensive, as the main component thereof and having excellent corrosion resistance, strength characteristics including toughness, and abrasion resistance that exceed those of conventional alloys, even in highly corrosive environments such as oil wells, etc. This Cr-based two-phase alloy has two phases, i.e. a ferrite phase and an austenite phase, mixed therein and is characterized by: the chemical composition of the Cr-based two-phase alloy comprising a main component, an auxiliary component, impurities, a first optional auxiliary component, and a second optional auxiliary component; and the main component comprising 33%-65% by mass Cr, 18%-40% by mass Ni; and 10%-33% by mass Fe.

Description

Cr-based two-phase alloy and product thereof

The present invention relates to a two-phase alloy containing a Cr group.

Equipment materials for oil and natural gas wells are often exposed to acidified and extremely harsh corrosive environments containing chloride ions and also containing the corrosive gases carbon dioxide (CO ₂ ) and hydrogen sulfide (H ₂ S). The Materials exposed to such harsh corrosive environments can also be found in materials for components such as waste plants, chemical plants, nuclear power plants and nuclear reprocessing facilities. The properties required for these equipment materials generally have good corrosion resistance and strength. Further, wear resistance is additionally required in the sliding part material of the product.

Conventionally, low alloy steels, stainless steels, Ni-based alloys, etc. have been used as equipment materials with such performance depending on the severity of the corrosive environment. In material selection, stainless steel is more dominant when higher strength properties (high yield strength, toughness ensured) and cost advantages are required in addition to higher corrosion resistance. The Ni-based alloy is mainly composed of expensive Ni, so that the cost advantage is inferior. When wear resistance is required, alloys in which a hard phase is precipitated in a corrosion-resistant matrix, such as Co-base alloy stellite, are widely used as cladding materials.

In stainless steel, duplex stainless steel is superior in balance of corrosion resistance and strength characteristics. In general, duplex stainless steels contain Cr, Ni, Mo, and N to ensure corrosion resistance. However, duplex stainless steels containing Cu to further improve the corrosion resistance (see, for example, Patent Documents 1 and 2). Is disclosed. However, when considering the application in terms of further extending the life of structural materials and ensuring reliability in more severe corrosive environments, it is necessary to further improve and improve the corrosion resistance and strength of duplex stainless steels. . Further, duplex stainless steel as a sliding member used in a corrosive environment cannot be expected to have sufficient wear resistance.

On the other hand, in order to improve corrosion resistance and heat resistance, a Cr-based alloy containing Cr exceeding 60% by mass and having a body-centered cubic structure and a ferrite single phase is disclosed (see Patent Documents 3, 4 and 5). However, these Cr-based alloys can be expected to have corrosion resistance and wear resistance, but are not ductile in strength and very brittle.

JP-A-4-72013 WO2013 / 058274A1 Japanese Patent Laid-Open No. 04-301048 JP 04-301049 A Japanese Patent Application Laid-Open No. 08-291355

Conventional Fe-based duplex stainless steels (see, for example, Patent Documents 1 and 2) and ferrite single-phase Cr-based alloys (see, for example, Patent Documents 3 to 5) are suitable for use in severe corrosive environments. There are needs and challenges to improve the corrosion resistance, strength, and wear resistance of the steel. Moreover, there is no alloy that has Cr as the main component that satisfies these characteristics and is cheaper than Ni-based alloys.

Therefore, the present invention is mainly composed of inexpensive Cr, and by adding an element such as Cu that effectively improves the high corrosion resistance due to the high Cr content, duplex stainless steel and Cr are also used in severe corrosive environments. It is an object of the present invention to provide a two-phase alloy of a ferrite phase and an austenite phase, which is superior in strength properties such as corrosion resistance, proof strength, toughness, and wear resistance as compared with conventional materials of a base single phase alloy.

The present inventors produced Cr-based two-phase alloys containing Cu or the like in the main Cr—Ni—Fe composition containing 33 mass% or more of Cr using different manufacturing processes. That is, the ingot produced in the melting-casting process is used as a master ingot, 1) a hot forging process of the master ingot, a heat treatment process including solution treatment, 2) a remelting of the master ingot, a casting process, and 3) Re-dissolving the master ingot-In the gas atomization process, a ferrite and austenite alloy containing Cu is produced and its corrosion resistance, mechanical properties and wear resistance are evaluated, and the present invention is achieved. did.

The present invention is a Cr-based two-phase alloy in which two phases of a ferrite phase and an austenite phase are mixed, and the chemical composition of the Cr-based two-phase alloy has a main component, subcomponent, impurity, first optional subcomponent, and second Consisting of optional subcomponents, the main component consisting of 33 mass% or more and 65 mass% or less of Cr, 18 mass% or more and 40 mass% or less of Ni, and 10 mass% or more and 33 mass% or less of Fe, The subcomponent is 0.1% by mass or more and 2% by mass or less of Mn, 0.1% by mass or more and 1.0% by mass or less of Si, 0.005% by mass or more and 0.05% by mass or less of Al, 0.1 mass% or more and 5.0 mass% or less of Cu, and the impurities are more than 0 mass% and 0.04 mass% or less of P, and more than 0 mass% of 0.01 mass% or less of S and , More than 0 mass% and 0.03 mass% or less C and more than 0 mass% and 0.02 mass% or less When, characterized in that it comprises a O below 0 mass percent 0.03% by weight.

According to the present invention, it is possible to provide a two-phase alloy having inexpensive Cr as a main component and excellent in strength characteristics such as corrosion resistance and toughness and wear resistance even in a highly corrosive environment.

It is process drawing for demonstrating hot processing among the manufacturing methods of the two-phase alloy which concerns on embodiment of this invention. It is process drawing for demonstrating casting among the manufacturing methods of the two-phase alloy which concerns on embodiment of this invention. It is process drawing for demonstrating pulverization among the manufacturing methods of the two-phase alloy which concerns on embodiment of this invention. 2 is an optical micrograph of a two-phase alloy produced by hot working. 2 is an optical micrograph of a two-phase alloy produced by casting. It is an optical microscope photograph of the two-phase alloy which carried out powder overlay welding.

Next, the two-phase alloy according to the embodiment of the present invention will be described in detail.

<Dual phase alloy>
The two-phase alloy according to the embodiment of the present invention is a two-phase alloy containing an element such as Cu that further enhances corrosion resistance in the composition of Cr—Ni—Fe containing Cr as a main component. This two-phase alloy is formed of two phases of a ferrite phase and an austenite phase as a main phase structure, contains a predetermined amount of Ni, Fe, Mn, Si, Al, Cu, Mo, etc., with the balance being Cr and inevitable impurities Consists of. Further, at least one of V, Nb, Ta, and Ti is added to control C, N, and O that affect strength and corrosion resistance. Hereinafter, each structure of this two-phase alloy will be described.

<Material structure>
The material structure in the two-phase alloy of this embodiment is a two-phase structure of a ferrite phase and an austenite phase. The two-phase structure is formed through different manufacturing methods described later, that is, through a process of thermal processing, casting or gas atomization of a master ingot. By the way, the material structure of the hot-worked product is different from the material structure of the build-up material using a cast or gas atomized powder. The former basically promotes sufficient elimination of component segregation and refinement of the structure, while the latter is based on a solidified structure that allows component segregation.

Generally, a ferrite single-phase Cr-based alloy having a body-centered cubic structure in terms of crystal structure has higher strength and superior wear resistance, but is inferior in toughness. In particular, when the content of C, N and O is increased, the plastic deformability is sensitively lowered. An austenite single-phase Ni-based alloy having a face-centered cubic structure is ductile and excellent in toughness, but is expensive.

On the other hand, the two-phase alloy of the present embodiment comprises Cr as a main component and is composed of a ferrite phase and an austenite phase, has high corrosion resistance due to high Cr concentration and addition of Cu, and strength and resistance including toughness. Excellent wear and economical efficiency.

The ferrite phase occupancy (hereinafter simply referred to as “ferrite ratio”) in the two-phase alloy of this embodiment is 10% or more and 95% or less, and the corresponding austenite phase occupancy is 5% or more and 90%. Each can be set within the following ranges. The reason why the ferrite ratio is 95% or less in order to retain the austenite phase is to ensure toughness. A structure having a higher ferrite ratio has a higher Cr concentration as a composition, and is observed in a rapidly solidified structure as in, for example, overlay welding.

The chemical composition range of the two-phase alloy of this embodiment is determined so as to realize the set phase fraction range. This chemical composition range is adjusted in particular between the contents of Cr and Ni, which are the main components. Here, when the solution temperature is 1100 ° C. or higher and the ferrite ratio exceeds 95% in the two-phase alloy manufactured in the heat processing step, a heat treatment for adjusting the phase ratio is performed in the range of 800 to 1000 ° C. Further, it is possible to maintain a ferrite ratio of 95% or less.

On the other hand, since the structure of the two-phase alloy produced by the casting or gas atomizing process becomes a solidified structure affected by the structure formed at a higher temperature of 1100 ° C. or higher, a two-phase alloy having a high Cr content Then, the ferrite rate increases more. Therefore, in order to maintain the predetermined ferrite ratio at 95% or less, it is necessary to generally decrease the Cr content and increase the Ni content as shown in <Chemical composition> below. However, in a cast that can be heat-treated, by adjusting the ratio between the ferrite and austenite phases in the range of 800 to 1000 ° C. (phase ratio adjustment), it is possible to ensure a ferrite ratio of 95% or less.

In addition, the “ferrite ratio” in the present embodiment is the ferrite occupation amount [%] obtained from EBSP (Electron BackScattering Pattern) analysis.

Incidentally, the ferrite ratio in the two-phase alloy of the present embodiment is more preferably 20% or more and 70% or less from the viewpoint of ensuring both corrosion resistance and strength characteristics including good toughness.

In addition, the duplex alloy in the present embodiment is preferably, for example, a duplex stainless steel that does not include a hard heterogeneous phase such as a sigma (σ) phase that precipitates due to a phase transformation from a ferrite phase. It is permissible if it contains the above characteristics to the extent that they do not significantly harm.

<Chemical composition>
Next, the reason for limiting the numerical range of the chemical composition in the two-phase alloy of this embodiment will be described. In addition, content of each component is shown by the mass%.
Cr is the remaining component and has the highest concentration among the components of the two-phase alloy. However, in the Cr—Ni—Fe-based two-phase alloy of this embodiment, the high strength Cr-based ferrite is structurally related. It is a phase forming element, and as a solid solution element, it enhances corrosion resistance.

The Cr content is set so as to form a two-phase structure of a ferrite phase and an austenite phase as a thermal equilibrium state structure of these main ternary systems at a solution temperature of 1050 to 1250 ° C., which will be described later.

The content of Cr is the amount of main components of Ni, Fe, the amount of minor components such as active elements such as Mn, Si, Al, Cu, Mo, P, S, C, N, O, V, and inevitable impurities. Considering the amount, 33% or more is desirable. By setting the Cr content to 33% or more, it is possible to increase the concentration of Cr and further improve the corrosion resistance of the two-phase alloy.

In addition, the Cr content is desirably 65% or less in the case of a two-phase alloy manufactured by a hot working process. By setting the Cr content to 65% or less, excellent toughness can be imparted to the two-phase alloy while maintaining high yield strength and high hardness. On the other hand, in a two-phase alloy manufactured by a casting or gas atomizing process, a structure with a high ferrite ratio is formed particularly in a high Cr concentration composition. Therefore, the Cr content is decreased in order to maintain a ferrite ratio of 95% or less. 60% or less is preferable.

In this example, the chemical composition of the Cr-based two-phase alloy was composed of a main component, subcomponents, impurities, a first optional subcomponent, and a second optional subcomponent. The main component is composed of Cr, Ni and Fe, the subcomponent is composed of Mn, Si, Al and Cu, the impurity is composed of P, S, C, N and O, and the first optional subcomponent is composed of Mo. The second optional subcomponent is composed of V, Nb, Ta, and Ti.

Ni stabilizes the austenite phase and maintains a two-phase state with the ferrite phase by solution treatment. Further, Ni imparts ductility and toughness as well as corrosion resistance to the two-phase alloy.

The content of Ni is set to 18% or more in the two-phase alloy manufactured in the hot working process. As a result, the occupation ratio of the austenite phase at the solution temperature described later becomes 10% or more, which contributes to further enhancing the toughness of the structure. On the other hand, in the two-phase alloy produced by the casting or gas atomizing process, since the structure has a high ferrite ratio as described above, the Ni content is increased to maintain a ferrite ratio of 95% or less, and 23% The above is preferable. Further, the Ni content is set to 40% or less. Thereby, the ferrite rate at the solution temperature described later is 10% or more.

The content of Fe is set to 10% or more. This reduces the content of Ni and Cr, which are more expensive than Fe, and suppresses the formation of intermetallic compounds that may have an adverse effect on strength properties during the melting and quenching process of the two-phase alloy.

Also, the Fe content is set to 33% or less. Generally, in the ternary alloy of Cr—Ni—Fe, when the Fe concentration increases, a σ phase is generated in a temperature range centered on 800 ° C., but in the two-phase alloy of this embodiment, the Fe content Is set to 33% or less, the generation of the σ phase is suppressed.

The total content of the Ni component and the Fe component is preferably 37% by mass or more and 65% by mass or less. When the total content is less than 37% by mass, the ductility / toughness of the two-phase alloy becomes insufficient. On the other hand, when the total content exceeds 65% by mass, the mechanical strength is greatly reduced.

The Mn content is set to 0.1% or more. Thereby, desulfurization and deoxidation of the two-phase alloy are performed, and the strength and toughness of the two-phase alloy are improved. A preferred lower limit is 0.3%.

Also, the Mn content is set to 2.0% or less. Thereby, deterioration of corrosion resistance and strength caused by forming coarse MnS is suppressed, and the carbon dioxide corrosion resistance of the two-phase alloy is maintained well.

The Si content is set to 0.1% or more. Thereby, deoxidation of the two-phase alloy is performed, and the strength and toughness of the two-phase alloy are improved. A preferred lower limit is 0.3%.

Also, the Si content is set to 1.0% or less. Thereby, the effect of the hot forging process described later is sufficiently exhibited, and the toughness of the two-phase alloy is maintained well.

The Al content is set to 0.005% or more. Thereby, the deoxidation action is improved together with Mn and Si. A more preferred lower limit is 0.008%.
The Al content is set to 0.05% or less. In the Cr-based two-phase alloy of the present invention, the reduction of the oxygen content is essential in terms of hot forgeability and ensuring the toughness of the alloy of the present invention. While reducing the oxygen content as much as possible during production, Al ₂ O ₃ and AlN formed by the inclusion of a large amount of Al inhibit the toughness of the alloy, so their production amount should be suppressed as much as possible, preferably 0.05% or less.

Cu content, like Mo, is an element that improves the corrosion resistance of the Cr-based two-phase alloy of the present invention, and can be contained at the same time as necessary to enhance the effect cooperatively. When contained, it is set to 0.1% or more for improving corrosion resistance. The content of Cu stabilizes the austenite phase, but the excessive content is desirably 5.0% or less, preferably in order to reduce the workability by forming Cu precipitates in the ferrite phase especially during hot working. Is 3.0% or less.

The content of Mo is an element that enhances the corrosion resistance of the Cr-based two-phase alloy, and is particularly effective for stabilizing the passive film, and is expected to have more pitting corrosion resistance. , Can enhance the effect cooperatively. When contained, it is set to 0.1% or more for improving corrosion resistance. On the other hand, the inclusion of Mo stabilizes the ferrite phase, but the inclusion of a higher concentration includes the possibility of the formation of a sigma phase and the formation of intermetallic compounds during thermal processing, which further reduces workability and corrosion resistance. In addition, 3% or less is desirable, and preferably 2% or less.

The content of P is set to 0.04% or less in the two-phase alloy. P is an element that deteriorates corrosion resistance, weldability, and workability, and should be limited as much as possible in production. By setting the P content to 0.04% or less, the segregation of P at the grain boundaries is prevented, and the toughness of the two-phase alloy and the corrosion resistance of the grain boundaries are favorably maintained.
Moreover, P content can be reduced more by utilizing a more refined refinement | purification and manufacturing process. Accordingly, the lower limit value of P is not more than the detection limit of analysis and may not be contained in the two-phase alloy, that is, 0%.

The S content is set to 0.01% or less. S is an element that generates sulfides such as MnS and degrades the corrosion resistance and workability, and should be limited as much as possible in production. By setting the S content to 0.01% or less, the amount of sulfide is reduced, and pitting corrosion resistance and toughness are favorably maintained.

In addition, the S content can be further reduced by utilizing a more sophisticated refining and manufacturing process. Accordingly, the lower limit value of S is not more than the detection limit of analysis and may not be contained in the two-phase alloy, that is, 0%.

C has a solid solution hardening at a low concentration as its concentration increases, and greatly inhibits plastic deformation of the ferrite phase. At a high concentration, especially, Cr carbide is formed, and corrosion resistance is lowered by causing a Cr concentration decrease locally in the vicinity thereof. Moreover, if the carbides increase, the toughness decreases. In addition, in the case of addition of active elements of V, Nb, Ta, and Ti, it is desirable to reduce the C content in order to suppress the formation amount of those carbides as much as possible, and 0.03% or less is preferable. .

In addition, the C content can be further reduced by utilizing a more sophisticated refining and manufacturing process. Accordingly, the lower limit value of C is not more than the detection limit of analysis and may not be contained in the two-phase alloy, that is, 0%.

N increases the solid solution hardening and corrosion resistance of N as its concentration increases, but at higher concentrations, there is a concern that toughness may decrease due to the formation of nitrides such as Cr. In the two-phase alloy of the present invention produced by the following hot working manufacturing process, the N content is preferably 0.02% or less in order to ensure workability. In addition, the content of N can be further reduced by utilizing a more sophisticated refining and manufacturing process. Accordingly, the lower limit value of N is equal to or lower than the detection limit of analysis and may not be contained in the two-phase alloy, that is, 0%.

On the other hand, in the casting or powder of the two-phase alloy of the present invention manufactured by the casting process or the gas atomizing process, even if the above manufacturing atmosphere is an inert gas atmosphere, inevitable mixing of N must be considered. However, the content is increased, the upper limit is set to 0.04%, and the lower limit is set to 0.005%.

O tends to form an oxide with a metal element in the two-phase alloy, and there is a concern that the toughness is lowered due to an increase in oxide accompanying an increase in the O content. In the two-phase alloy of the present invention produced by the following hot working manufacturing process, the O content is preferably 0.03% or less in order to ensure workability. Moreover, the content of O can be further reduced by utilizing a more sophisticated refining and manufacturing process. Accordingly, the lower limit value of O is equal to or lower than the detection limit of analysis and may not be contained in the two-phase alloy, that is, 0%.

On the other hand, in the casting or powder of the two-phase alloy of the present invention produced by the casting process or the gas atomizing process, even if the above production atmosphere is an inert gas atmosphere, the inevitable mixing of O must be fully considered. The content is increased, the upper limit is set to 0.05%, and the lower limit is set to 0.005%.

V combines with gas impurities C, N and O to form respective compounds, and collects and immobilizes gas impurities. This action of cleaning the base material is effective in improving toughness. However, in the case of excessive addition of V, V reacts with other component elements, and the intermetallic compound is easily formed, which raises the concern of a decrease in toughness. A suitable V addition amount in the production in which surplus V exceeding immobilization is suppressed as much as possible is preferably in the range of 0.8 to 2 times the atomic% total of C, N and O in atomic%. When at least one of Nb, Ta and Ti is added simultaneously with V, the total range including V is preferably 0.8 times or more and 2 times or less.

Nb combines with gas impurities C, N and O to form respective compounds, and collects and immobilizes gas impurities. This action of cleaning the base material is effective in improving toughness. However, when Nb is excessively added, Nb reacts with other component elements, so that the intermetallic compound is easily formed, and there is a concern about a decrease in toughness.
A suitable amount of Nb added in production in which excess Nb exceeding immobilization is suppressed as much as possible is preferably in the range of 0.8 to 2 times the atomic% total of C, N and O in atomic%. Also when adding at least one of V, Ta and Ti simultaneously with Nb, the total range including Nb is preferably 0.8 times or more and 2 times or less.

Ta combines with gas impurities C, N and O to form respective compounds, and collects and stabilizes gas impurities. This action of cleaning the base material is effective in improving toughness. However, when Ta is excessively added, Ta reacts with other component elements to easily form an intermetallic compound, thereby causing a concern about a decrease in toughness. A suitable amount of Ta added in production in which excess Ta exceeding the immobilization is suppressed as much as possible is preferably in the range of 0.8 to 2 times the atomic% total of C, N and O in atomic%. When adding at least one of V, Nb, and Ti simultaneously with Ta, a total range including Ta of 0.8 times or more and 2 times or less is desirable.

Ti combines with gas impurities C, N and O to form respective compounds, and collects and stabilizes gas impurities. This action of cleaning the base material is effective in improving toughness. However, when Ti is excessively added, Ti reacts with other component elements, so that the intermetallic compound is easily formed, and there is a concern about a decrease in toughness.
The preferable amount of Ti added in the production in which surplus Ti exceeding the immobilization is suppressed as much as possible is preferably in the range of 0.8 to 2 times the atomic% total of C, N and O in atomic%. When at least one of V, Nb and Ta is added simultaneously with Ti, the total range including Ti is preferably 0.8 times or more and 2 times or less.

<Manufacturing method of two-phase alloy>
Next, the manufacturing method of the two-phase alloy of this embodiment is demonstrated. As a final material form, the two-phase alloy of the present invention is obtained by remelting a hot-worked product manufactured by a series of manufacturing processes such as melting-ingot formation-hot forging-solution treatment process, and the master ingot. Provided as a powder by casting and atomizing process.

<Hot processing>
FIG. 1 is a process diagram for explaining a method for producing a two-phase alloy according to the present embodiment.

As shown in FIG. 1, in this manufacturing method, at least one of the above-described Cr, Ni, Fe, Mn, Si, Al, Cu, Mo, and V, Nb, Ta, and Ti as necessary. One or more predetermined amounts are melted and alloyed in a high-frequency vacuum melting furnace (step F1). In addition, the melting furnace used at this process is not limited to a high frequency vacuum melting furnace, In this invention, another melting furnace can also be used.

Next, an ingot is formed by casting using a predetermined mold (step F2). The obtained ingot can be used as a master ingot for casting and powder production of the following two-phase alloys. Subsequently, a hot forging process is performed on the ingot (step F3). In this step, hot forging using a press forging machine or a hammer forging machine is performed on the ingot, and the required product shape can be obtained. The temperature of hot forging is set to about 1050 to 1250 ° C. Hot forging can promote the elimination of component segregation in the ingot and refinement of the structure. Further, as the subsequent heat processing, for example, if a plate-like two-phase alloy is desired, hot rolling is performed at a temperature range of 1050 ° C. or higher, and if a tubular two-phase alloy is desired, the above temperature range is used. Hot extrusion may be performed.

Next, a solution heat treatment process is performed on the hot forging (step F4). This solution heat treatment basically determines the structure of the two-phase alloy. The temperature of the solution heat treatment is desirably in the range of 1050 to 1250 ° C. and is preferably 1100 to 1200 ° C. for the purpose of sufficient solid solution of constituent atoms and disappearance of lattice defects such as dislocations remaining after hot working. . By setting the solution temperature range, the ferrite ratio of the two-phase alloy can be sufficiently set to 10 to 95%.

Further, in order to improve the strength, a so-called aging heat treatment is performed as an additional heat treatment after the solution heat treatment (step F5) to promote the phase transformation from the ferrite phase to the austenite phase and from the austenite phase to the ferrite phase on the high Ni side. . Thereby, the phase ratio can be adjusted to a desired value in the range of 10 to 95%. The conditions for this aging heat treatment are desirably set at a solution temperature of 1050 to 1250 ° C., an aging temperature of 800 to 1000 ° C., and an aging time of 0.5 to 6 hours depending on the degree of phase ratio adjustment. In the case of a two-phase alloy having a higher Cr concentration, the ferrite ratio is expected to exceed 90% at a solution temperature of 1150 ° C. or higher, but it can be adjusted to the prescribed phase ratio by aging heat treatment.

This makes it possible to improve the elongation and toughness of the two-phase alloy by reducing the ferrite phase quantitatively and increasing the austenite phase in the two-phase alloy having a ferrite ratio of approximately 30% or more in the solution-treated alloy. In an alloy in which the ferrite ratio is approximately 30% or less and the austenite phase is more dominant, when the austenite phase decreases due to aging and the ferrite phase increases, the improvement in yield strength and tensile strength can be improved.

On the other hand, after the solution heat treatment is performed on the active element-added two-phase alloy, an aging heat treatment step similar to the above is performed (step F5), and a series of the two-phase alloy manufacturing method is completed. This aging heat treatment can cause an appropriate aging reaction between the active element and C, N and O, that is, precipitation of these compounds. At the same time, the phase ratio can be adjusted. The conditions of this aging heat treatment are desirably a solution temperature of 1050 to 1250 ° C., an aging temperature of 800 to 1000 ° C., and an aging time of 0.5 to 6 hours.

The final heat treatment step in such a method for producing a two-phase alloy may be a solution heat treatment step depending on the desired corrosion resistance and strength characteristics, and may be performed up to the aging heat treatment step after the solution heat treatment. Also good.

In addition, according to such a method for producing a two-phase alloy, a hot forging step of an ingot and a subsequent heat treatment step are performed, thereby causing a high occupation rate of the ferrite phase including casting defects and segregation of alloy elements. The coarse two-phase cast solidified structure is destroyed. Thus, the two-phase alloy of the present embodiment having a two-phase structure which is homogeneous in chemical composition and structure and thermodynamically stable can be obtained.

In the two-phase alloy containing at least one of V, Nb, Ta, and Ti, the heat treatment process is performed to achieve more efficient stabilization of the C, N, and O. can do.

The two-phase alloy according to the present embodiment obtained by subjecting the ingot having the predetermined chemical composition to hot forging and heat treatment under the predetermined conditions is a two-phase of a ferrite phase containing Cr as a main component and an austenite phase. Formed with. Such a two-phase alloy of this embodiment is mainly composed of inexpensive Cr, and is superior in strength properties such as corrosion resistance and toughness even in a highly corrosive environment such as an oil well.

<Casting>
FIG. 2 is a process diagram for explaining a method for producing a two-phase alloy casting according to the present embodiment.

The master ingot casted in step F2 in the process of FIG. 1 is used as a raw material and is remelted in a melting furnace such as a high frequency or induction furnace (step C1), and then cast into a mold (step C2) to produce a casting. To do. The melting and casting atmosphere can be air, inert gas or vacuum depending on the application, but in order to prevent contamination such as oxidation as much as possible, inert gas or vacuum clean casting is preferred.

The casting is a solidified structure, and additional heat treatment can be performed after casting in order to improve segregation of component elements. Thereby, desirable corrosion resistance and strength characteristics can be obtained. Specifically, the casting can be subjected to solution treatment for homogenization of constituent components, or subsequent heat treatment including aging (step C3). The temperature of the solution heat treatment is desirably about 1050 to 1250 ° C., and preferably 1100 to 1200 ° C. In addition, when an aging heat treatment for promoting an appropriate aging reaction between an active element and C, N, and O is performed on a phase-adjusted and active element-added two-phase alloy, the solution temperature is set to 1050 to 1250. It is desirable that the aging treatment temperature is 800 to 1000 ° C. and the aging time is 0.5 to 6 hours.

FIG. 5 is an optical micrograph of a two-phase alloy produced by casting.

<Powdering>
FIG. 3 is a process diagram for explaining the method for producing a two-phase alloy powder according to the present embodiment.

In the process of FIG. 1, the master ingot cast in step F2 is used as a raw material and re-melted in a melting furnace such as a high-frequency or induction furnace (step A1), and a low oxygen amount is obtained by a gas atomizing method using an inert gas Ar or He. A two-phase alloy powder can be obtained (step A2). Thereafter, these powders are classified to a range of about 50 to 200 μm (step A3) and used as the two-phase alloy powder of the present invention. The range of the two-phase alloy powder size can be changed by adjusting the classification according to the application. Since the structure of the two-phase alloy powder is a rapidly solidified structure from a temperature near the liquid phase, particularly in some alloy powders having a composition of high Cr (55% or more) and low Ni (25% or less), The ferrite phase is more likely to be rich, and the specified range of the ferrite ratio of 95% or less is not necessarily satisfied. However, when these alloy powders become a two-phase alloy product that is subsequently heat-processed depending on the application and have a structure that satisfies the specified range, alloy powders with a ferrite ratio of 95% or more are allowed. As an application destination, for example, it can be provided as a two-phase alloy powder for overlaying, 3D printer, or sintering.

FIG. 6 is an optical micrograph of a two-phase alloy powder overlay welded.

Such a two-phase alloy can be suitably used as, for example, a sliding part as a constituent material of equipment such as a compressor and a pump used in a highly corrosive environment of an oil well. In addition to being used for such equipment materials, the two-phase alloys can also be used as structural materials for seawater environments such as umbilicals, seawater desalination plants, LNG vaporizers, and various chemical plants. .

Next, an example in which the effect of the two-phase alloy of the present invention is verified will be described.

<Hot-working alloy>
(Examples 1 to 22)
Here, the hot-worked two-phase alloy containing no active element such as V of the present invention was verified. Table 1 shows the chemical compositions of the alloys having the alloy numbers A1 to A16 used in Examples 1 to 22. The production details of these alloys are shown below. These were melted in a high-frequency vacuum melting furnace (Ar atmosphere under reduced pressure, melting temperature 1500 ° C. or higher) to produce master ingots of these alloys.

The hot forging was performed on the obtained ingot. Hot forging was performed at 1250 to 1050 ° C. in the temperature range where the drawing was 60% or more in the tensile test. Forging cracks did not occur. This forging condition was similarly applied to the alloys of all Examples and Comparative Examples related to hot forging described later. Next, the solution treatment was carried out under the condition of water cooling after holding at 1100 ° C. for 60 minutes in most of the two-phase alloys, but A6 (Examples 7 to 9), A11 (Examples 15 to 17), A15 For the alloy of (Example 21), it is carried out at 1100, 1200 or 1250 ° C., and after that it is kept at 900 to 1000 ° C. for 60 minutes for adjusting the phase ratio, and then subjected to additional aging heat treatment under water cooling conditions. Carried out. Alloys of alloy numbers A1 to A16 having the chemical composition shown in Table 1 were manufactured by such steps.

Alloys with alloy numbers A1 to A16 are Cr-based alloys containing Cr as a main component and Cu in a mass% of 0.11 to 4.65, and are two-phase alloys composed of a ferrite phase and an austenite phase. It was. Further, alloys of alloy numbers A14 to A16 further contained Mo. Table 2 shows the ferrite ratios of the alloys of Examples 1 to 22 (alloy numbers A1 to A16). In addition, the ferrite rate in this embodiment is shown by the ferrite rate [%] obtained from the EBSP analysis. The ferrite ratio tended to increase with increasing Cr concentration. In Examples 7 to 9, 15 to 17, and 21 subjected to the aging treatment, the ferrite ratio decreased due to aging, and a structure in which the secondary austenite phase was finely precipitated in the ferrite phase due to phase transformation was obtained.

FIG. 4 is an optical micrograph of the two-phase alloy of Alloy No. A10 manufactured in Example 13. This optical micrograph was observed after the surface of the two-phase alloy of Example 13 was mirror-polished and subjected to electric field etching in an oxalic acid aqueous solution.

As shown in FIG. 4, the structure of the alloy of Example 13 which was solution-treated at 1100 ° C. after hot forging was composed of a bright austenite phase P1 and a dark ferrite phase P2, and each phase had a fine structure. New ferrite and austenite phases. Similar structures were observed in other two-phase alloys of the present invention that were heat processed. Furthermore, alloys Nos. A9 and A11 having a large amount of Fe component and the possibility of σ phase formation were further heat-treated at 800 ° C. for 60 minutes in order to investigate the presence or absence of σ phase formation. These alloys after the heat treatment were analyzed by X-ray diffraction, and it was confirmed that no σ phase was formed. This means that it is difficult for the σ phase to be generated in the intermediate temperature range around 800 ° C. even in the alloys of other examples including addition of activating elements such as Cu and V except for the case of Mo-containing below. Indicates. In the alloy No. 16 having a high Fe content and containing a large amount of Mo, the σ phase was not confirmed by the solution treatment, but the formation of the σ phase was confirmed in the subsequent aging at 800 ° C.

Further, as shown in Table 2, the alloys of Examples 1 to 22 (alloy numbers A1 to A16) were subjected to a strength test, a corrosion test, and a wear test.

(Strength test)
Vickers hardness and tensile tests were performed to determine 0.2% yield strength, tensile strength and plastic elongation. The Vickers hardness was measured by a Vickers hardness tester under the conditions of a load of 1 kg and a load application time of 15 seconds, and was obtained as an average value of 5 measurements.

The tensile test was performed at room temperature of 23 ° C. using a test piece having a diameter of 4.0 mm and a parallel part length of 20 mm. The strain rate was 3 × 10 ⁻⁴ / s. Three samples were provided for each alloy in the tensile test, and the average of the measured values was obtained. In the stress-strain curve, when the test piece broke brittlely before the yield point or in the middle of the flow stress with positive work hardening, the breaking stress was defined instead of the proof stress or tensile strength. These measurement results are shown in Table 2. However, the “*” mark in Table 2 represents the value of the breaking stress obtained in place of the proof stress or tensile strength. The plastic elongation was evaluated as A: 15% or more, B: 5 to less than 15%, C: 0.2 to less than 5.0%, and D: less than 0.2%, and the measurement results are shown in Table 2.

(Corrosion test)
The corrosion test was conducted for pitting corrosion resistance and oxidation resistance. First, the pitting corrosion resistance was evaluated in accordance with JIS G0577 (2005). Specifically, two polarization test pieces each having an area of 10 mm × 10 mm were collected from each of the alloys of Examples 1 to 22, and the following test was performed to evaluate pitting corrosion resistance. A polarization test piece was attached to a crevice corrosion prevention electrode. An anodic polarization curve was measured using a crevice corrosion prevention electrode, and an average potential corresponding to a corrosion current density of 100 μA / cm ² was measured. A saturated candy electrode was used as a reference electrode. After the measurement, the presence or absence of pitting corrosion was confirmed with an optical microscope.

Next, the oxidation resistance was evaluated based on the corrosion rate in sulfuric acid according to JISG0591 (2000). Two test pieces each having a thickness of 3 mm, a width of 1.30 mm and a length of 40 mm were sampled from the alloys of Examples 1 to 22, and subjected to a 6-hour immersion test in boiling 5% sulfuric acid. Evaluated. The weight of each test piece before and after the test was measured, and the average weight reduction rate m [g / (m ² · h)] due to corrosion was measured. The weight reduction rate in sulfuric acid for each alloy of Examples 1 to 22 was classified into the following categories A to D to evaluate sulfuric acid resistance. A: m <0.1, B: 0.1 ≦ m <0.3, C: 0.3 ≦ m <0.5, and D: 0.5 ≦ m. The evaluation results are shown in Table 2.

(Abrasion test)
Wear resistance was evaluated by an abrasive wear test. Two cylindrical pin-shaped test pieces each having a diameter of 10 mm and a length of 20 mm were collected from the alloys of Examples 1 to 22 and subjected to wear tests. For the wear test, a Pin-on-Disk type friction and wear tester was used. The test method is as follows. Attach a water-resistant abrasive paper (fixed piece) with a particle size of 240 to the disc, rotate the disc at a rotation speed of 200 rpm, and press the pin (movable piece) of the test piece against the water-resistant abrasive paper with a load of 4 kgf. The wear test was carried out by moving toward the center. A similar test was continuously performed using three water-resistant abrasive papers. The outermost sliding diameter was 156 mm, and the total moving distance of the pins was about 6 m. From the above, under the conditions of room temperature 22 ± 2 ° C. and air atmosphere, the average decrease in pin length due to wear in two samples was measured as the amount of wear.

As shown in Table 6 below, Stellite No. The amount of dimensional reduction corresponding to 6 (alloy number C19) powder overlay (Comparative Example 11) was 0.088 mm. Taking this value as 100, the relative values of the respective dimensional reduction amounts in the two-phase alloys of Examples 1 to 22 were determined, and these are shown in Table 2 as evaluation of abrasive wear resistance.

The same strength tests, corrosion tests, and wear tests were performed on the alloys of the following other examples and comparative examples.

(Comparative Examples 1 to 5)
Table 1 shows the chemical compositions of alloys Nos. A17 to A21 used in Comparative Examples 1 to 5 with respect to Examples 1 to 22. The same processes as those of the alloys having the alloy numbers A1 to A16 were performed to manufacture alloys having the alloy numbers A17 to A21.

Alloys with alloy numbers A17 and A18 are Cr-based two-phase alloys that do not contain Cu. The alloys of Alloy Nos. A19 and 20 are ferrite single-phase Cr-based alloys that do not contain Cu and each contain Cr as a main component, and are austenite single-phase Ni-base alloys that contain Ni as a main component. Alloy No. A21 is a Cu-containing duplex stainless steel. For these alloys, the ferrite ratio was measured in the same manner as the two-phase alloys of Alloy Nos. 1 to 16 in the Examples. The measurement results are shown in Table 2.

As shown in Table 2, the ferrite ratio of the alloy of Comparative Example 3 (Alloy No. A19) is 100% and is a ferrite single phase, and the ferrite ratio of the alloy of Comparative Example 4 (Alloy No. A20) is 0%. The austenite single phase was confirmed. Further, Comparative Example 5 (Alloy No. A21) was a duplex stainless steel having a ferrite rate of 43%.

Further, the strength test was performed on the alloys of Comparative Examples 1 to 4, the corrosion test was performed on the alloys of Comparative Examples 1 to 5, and the wear test was performed on the alloys of Comparative Examples 1 to 4. The results are shown in Table 2.

(Examples 23 to 38)

Here, a hot-worked alloy containing an active element such as V of the present invention was verified. Table 3 shows the chemical compositions of alloys Nos. B1 to B14 used in Examples 23 to 38. The master ingots of alloys having alloy numbers B1 to B14 were produced by melting in a high-frequency vacuum melting furnace. The numbers in parentheses in Table 3 are multiples of V, Nb, Ta and Ti with respect to the total atomic% of C, N and O, respectively. In the B8 alloy, Nb and Ti were added simultaneously, but the magnifications were 0.51 and 0.49, respectively, for a total addition of 1.00 times.

The obtained ingot was subjected to hot forging treatment and solution heat treatment under the same conditions as the alloys of alloy numbers A1 to A21. Thereafter, aging heat treatment was further performed on all alloy types.

As shown in Table 4, the aging heat treatment was performed at a temperature of 800, 900 and 1000 ° C. for the alloy number B6, and for all other alloys at 900 ° C. for 60 minutes, and then under water cooling conditions. As a result, C, N, and O are stabilized by the reaction with the active elements of V, Nb, Ta, and Ti, and at the same time, the phase ratio is adjusted, and Examples 23 to 38 of the alloys of Alloy Nos. B1 to B14 are performed. was gotten.

Alloys of alloy numbers B1 to B14 stabilized with active elements as described above are Cr-based alloys containing Cr as a main component and Cu in a mass percentage of 0.11 to 4.53, and include ferrite phases and austenite. It was a two-phase alloy consisting of phases. Further, the alloy of alloy number B14 further contained Mo. Table 4 shows the ferrite ratios of alloys Nos. B1 to B14. The ferrite ratio in this embodiment was obtained by EBSP analysis as in Examples 1 to 22. Further, in order to investigate the presence or absence of the generation of σ phase, alloys of alloy numbers B12 and B13 with a large amount of Fe component and the possibility of σ phase generation were heat-treated at 800 ° C. for 60 minutes. These heat-treated alloys were analyzed by X-ray diffraction, and it was confirmed that no σ phase was generated as in the case of the A series alloys. This indicates that in the B series alloy of the example, the σ phase is hardly generated in an intermediate temperature range around 800 ° C.

Also, the strength test, corrosion resistance test and wear test were performed on the alloys of Examples 23 to 38 (alloy numbers B1 to B14). The results are shown in Table 4.

<Casting alloy, powder alloy>
(Examples 39 to 51)
Here, the two-phase alloy casting and the powder alloy of the present invention were verified. First, Table 5 shows the chemical compositions of alloys Nos. C1 to C8 used in Examples 39 to 46, which are castings of the two-phase alloy of the present invention.

First, a master ingot of alloy Nos. A4, 5 and 8 was added in a small amount of Cu and Al and Mo prepared as needed in an Ar atmosphere, and remelted. Castings of alloys with alloy numbers C1 to C4 were produced by casting into water-cooled copper molds having parts. The dimensions of the cast ingot were 40 mm in outer diameter and 100 mm in length. Next, when re-melting the master ingot of the alloys of alloy numbers A4, 5, 8, and 10, at least one or more of V, Nb, Ta, and Ti mixed with a trace amount of Cu and Al are added simultaneously, An alloy casting of alloy numbers C5 to C8, which was melted and then cast to the above dimensions in the same manner, was produced. Example 43 and alloy No. C5 were subjected to solution treatment at 1100 ° C. for 1 hour, and alloy No. C8 was subjected to solution treatment at 1200 ° C. for 1 hour followed by aging treatment at 900 ° C. for 1 hour. 46.

Specimens were collected from the lower part and the central part of the produced ingot and subjected to a structure investigation, a Vickers hardness measurement, a strength test, a corrosion test, and a wear test. Table 6 shows the results of the ferrite ratio, Vickers hardness, strength characteristics, corrosion test, and wear test of the alloys of Examples 39 to 46 (alloy numbers C1 to 8).

Next, Table 5 shows the chemical compositions of alloys Nos. C9 to C13 used in Examples 47 to 51, which are powder alloys of the two-phase alloy of the present invention. First, the master ingots of alloys Nos. A4 and 5 were re-dissolved by adding a small amount of Cu and Al in an Ar atmosphere, and pulverized by a gas atomization method to obtain powder alloys of Alloy Nos. C9 and C10. Furthermore, in a master ingot of alloy Nos. A4, 5 and 10, a small amount of Cu and Al, Mo prepared as needed, and at least one of V, Nb, Ta and Ti are simultaneously added and dissolved. Then, it was pulverized by a gas atomizing method to obtain powder alloys having alloy numbers C11 to C13. Each gold powder having a particle size in the range of 50 to 200 μm was obtained by classification. These powder alloys were built up to a thickness of about 5 mm on the surface of commercially available SUS304 steel by a powder plasma build-up welding method. The build-up welding conditions were an arc current of 120 A, a voltage of 25 V, and a welding speed of 9 cm / min.

Specimens for the structure investigation, Vickers hardness measurement, corrosion test, and wear test were collected from the surface of the built-up portion of the two-phase alloy of the present invention, and their characteristics were evaluated. Table 6 shows the results of the above characteristics of the alloys of Examples 47 to 51 (alloy numbers C9 to C13).

(Comparative Examples 6 to 11)
Table 5 shows the chemical compositions of alloys Nos. C14 to C19 provided as Comparative Examples 6 to 11 with respect to Examples 39 to 51. Alloys C14 to C16 are produced by the same casting process as described above using a Cr-based dual-phase alloy of alloy number A17 containing no Cu, a Cr-based ferrite single-phase alloy of A19 and a duplex-phase steel of A21 containing Cu as a master ingot. Was manufactured. Also, the master ingots of the alloys of the same alloy numbers A17 and A19 and the commercially available stellite No. 6 were redissolved, and the powder alloys of the alloy numbers C17 to C19 were manufactured by the same gas atomizing process as described above.

The casting two-phase alloy of Examples 39 to 46 and the cladding material of Examples 47 to 51 are compared using test pieces collected from the alloy of the casting and the cladding material produced from the powder alloy. Measurements and tests similar to those described above were performed. The results are shown in Table 6 as Comparative Examples 6 to 11.

Next, the evaluation results of the strength, corrosion resistance and wear resistance of the two-phase alloy of the present invention will be described.

[Evaluation of strength]
Vickers hardness increased linearly with increasing ferrite rate. Further, the Vickers hardness was 400 or more when the ferrite ratio was approximately 40% or more.

Yield increased with increasing ferrite rate. As shown in Table 2 or 4, it was possible to reduce the proof stress too high by reducing the ferrite rate by aging treatment. This contributes to the following improvement in ductility.

When the ferrite percentage exceeds 60%, the plastic elongation becomes 5.0% or less so as to be inversely proportional to the increase in yield strength (C evaluation), and in a ferrite single-phase alloy with a ferrite percentage of 100%, it broke before the yield point ( D evaluation).

The two-phase alloy in which the amount of Cr was reduced or the ferrite phase was reduced by aging heat treatment at 800 to 1000 ° C. showed an elongation exceeding 20%.

Further, as shown in Table 4, in the two-phase alloy to which an active element such as V was added, the plastic elongation tended to increase clearly as compared with the two-phase alloy not containing the active element in Table 2. From Tables 2 and 4, the A rating increased in the latter. On the other hand, in the two-phase alloys (alloy numbers C1 to C8) manufactured in the casting process, the ferrite ratio was higher due to the rapidly solidified structure from high temperature, and the elongation was reduced.

[Evaluation of corrosion resistance]
As for pitting corrosion resistance, good results were obtained with the two-phase alloys containing Cu and the alloys of Comparative Examples 1 to 10. That is, all the potentials corresponding to the corrosion current density of 100 μA / cm ² were 1000 mV (vs. SHE) or higher, and oxygen was generated in the hyperpassive region at potentials higher than this. Also, no pitting corrosion was observed in all tested alloys. On the other hand, in the stellite of Comparative Example 11, the corrosion current density exceeded 100 μA / cm ² at a potential of 400 mV (vs. SHE).

As shown in Tables 2, 4 and 6, the sulfuric acid resistance is a two-phase alloy containing 0.1 to 4.65 Cu by mass%, and the m value of the average weight reduction rate due to corrosion is 0.1 g. It was the evaluation of the best A section smaller than / (m ² · h). Comparative Examples 1 and 2, which are two-phase alloys without Cu addition, were evaluated as B, and the effect of Cu addition on corrosion resistance was confirmed. In addition, in the alloy in which Cu and Mo coexist, evaluation of the best A section smaller than 0.1 g / (m ² · h) was obtained.

On the other hand, in Comparative Examples 5 and 8 of the Cu-added duplex stainless steel, the evaluations were B and C, respectively. The stellite no. In No. 6, the weight reduction rate is 152 g / (m ² · h), and the sulfuric acid resistance is poor.

From the results of the above corrosion tests on pitting corrosion resistance and sulfuric acid resistance, it is evaluated that the corrosion resistance of the two-phase alloy containing Cr as a main component is good, but the sulfuric acid resistance of the two-phase alloy is further increased by addition of Cu, Overall, it can be said that higher corrosion resistance was achieved.

[Evaluation of wear resistance]
The abrasion resistance is Stellite No. 6 is shown as a relative value when the amount of wear is set to 100, and generally decreases in inverse proportion to the increase in hardness, that is, the increase in ferrite phase, except for Comparative Example 4 (alloy number A20) of an austenite single phase alloy. , Both of them Excellent wear resistance than 6.

Thus, the two-phase alloy of the build-up material formed of the hot-worked product, cast product and powder of the present invention can effectively improve the abrasive wear resistance by having a hard ferrite phase.

As described above, by increasing the Cr content and making it a two-phase alloy consisting of the ferrite and austenite phases of the example instead of the ferrite single phase, it is possible to ensure strength and elongation as material characteristics, and Cu as a constituent element. By including, it can have high corrosion resistance, and also can improve abrasion resistance by including a hard ferrite phase.

Such a two-phase alloy having comprehensive and multifaceted good characteristics is used as a build-up material formed from hot-worked products, castings and powders, and is particularly suitable as a device material subjected to a severe corrosive environment. It is.

The two-phase alloys of the examples of the present invention as described above have inexpensive Cr as the main component, and are superior in strength, corrosion resistance and wear resistance compared to conventional ones even in highly corrosive environments such as oil wells. Was verified.

P1 Austenitic phase P2 Ferrite phase

Claims (13)

A Cr-based two-phase alloy in which two phases of a ferrite phase and an austenite phase are mixed,
The chemical composition of the Cr-based two-phase alloy consists of a main component, subcomponents, impurities, a first optional subcomponent, and a second optional subcomponent,
The main component consists of 33 mass% or more and 65 mass% or less of Cr, 18 mass% or more and 40 mass% or less of Ni, and 10 mass% or more and 33 mass% or less of Fe,
The subcomponent is 0.1% by mass or more and 2% by mass or less of Mn, 0.1% by mass or more and 1.0% by mass or less of Si, 0.005% by mass or more and 0.05% by mass or less of Al, , 0.1 wt% or more and 5.0 wt% or less of Cu,
The impurities are more than 0% by mass 0.04% by mass P, more than 0% by mass 0.01% by mass S, more than 0% by mass 0.03% by mass C, and more than 0% by mass. A Cr-based two-phase alloy comprising N of 0.02% by mass or less and O of more than 0% by mass and 0.03% by mass or less. In the Cr-based two-phase alloy according to claim 1,
The Cr-based two-phase alloy, wherein the first optional subcomponent is 0.1 mass% or more and 3.0 mass% or less of Mo. In the Cr-based two-phase alloy according to claim 1 or 2,
The second optional subcomponent consists of at least one of V, Nb, Ta and Ti,
A Cr-based two-phase alloy characterized in that the total atomic content of V, Nb, Ta and Ti is in the range of 0.8 to 2 times the total atomic content of C, N and O. In the Cr-based two-phase alloy according to any one of claims 1 to 3,
A Cr-based two-phase alloy characterized in that the ferrite phase occupancy is 10% or more and 95% or less. In the Cr-based two-phase alloy according to claim 1,
A Cr-based two-phase alloy characterized in that the Ni component range is 23 mass% or more and 40 mass% or less. In the Cr-based two-phase alloy according to claim 5,
The Cr-based two-phase alloy, wherein the first optional subcomponent is 0.1 mass% or more and 3.0 mass% or less of Mo. In the Cr-based two-phase alloy according to claim 5 or 6,
The second optional subcomponent consists of at least one of V, Nb, Ta and Ti,
A Cr-based two-phase alloy characterized in that the total atomic content of V, Nb, Ta and Ti is in the range of 0.8 to 2 times the total atomic content of C, N and O. In the Cr-based two-phase alloy according to any one of claims 5 to 7,
A Cr-based two-phase alloy characterized in that the ferrite phase occupancy is 10% or more and 95% or less. A product using a two-phase alloy,
The two-phase alloy product is a Cr-based two-phase alloy according to any one of claims 1 to 4. A product using a two-phase alloy,
The two-phase alloy product is a Cr-based two-phase alloy according to any one of claims 5 to 8. The two-phase alloy product according to claim 9,
A two-phase alloy product, wherein the product is a compact having a forged structure. The two-phase alloy product according to claim 10,
A two-phase alloy product characterized in that the product is a compact having a cast structure. The two-phase alloy product according to claim 10,
A two-phase alloy product, wherein the product is a powder.

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