High chromium cast iron alloy and its manufacturing method

Abstract

A method for manufacturing a high-chromium cast iron alloy is provided, comprising the steps of: manufacturing a pre-alloy by performing a first heat treatment on an alloy raw material containing chromium; and manufacturing a high-chromium cast iron alloy by performing a second heat treatment on the pre-alloy at a temperature higher than the first heat treatment, wherein, depending on the chromium content contained in the alloy raw material, an additional third heat treatment is performed or omitted for the high-chromium cast iron alloy, and wherein the third heat treatment is performed at a temperature lower than the second heat treatment.

Description

Technology Field

[0001] The present application relates to a high-chromium cast iron alloy and a method for manufacturing the same, and more specifically, to a high-chromium cast iron alloy in which a heat treatment step is controlled according to the chromium content contained in the alloy raw material, and a method for manufacturing the same. Background Technology

[0003] In flue gas desulfurization (FGD) systems of thermal power plants, impellers can be used in various components such as slurry circulation pumps and oxidation air blowers. For example, Korean Published Patent Application No. 10-2023-0173466 describes a slurry pump for a flue gas desulfurization facility of a thermal power plant, comprising: a slurry pump body that is cylindrical, open on both sides, and equipped with an impeller inside, and discharges slurry flowing in from one side through an outlet formed on the side; a first cover that is fastened to one side of the slurry pump body, wherein the inner surface facing the slurry pump body contacts the impeller, has an intake port formed in the center for slurry inflow, and has a ceramic liner groove formed radially on the inner surface relative to the intake port, into which a ceramic liner is fitted; and a second cover that is fastened to the other side of the slurry pump body, wherein the inner surface facing the slurry pump body contacts the impeller, has an impeller hole formed in the center into which a rotating shaft connected to the impeller is inserted, and has a ceramic liner groove formed radially on the inner surface relative to the rotating shaft, into which a ceramic liner is fitted, wherein the ceramic liner is connected to the first cover and by the impeller A slurry pump for a thermal power plant is disclosed that can prevent the inner surface of the second cover above from wearing out.

[0004] The desulfurization solution in thermal power plants can be highly abrasive because it contains lime (CaCO3) and gypsum (CaSO4·2H2O) in a slurry state. In addition, the desulfurization solution in thermal power plants contains fluoride ions (F₂) dissolved as coal impurities. -), chloride ion (Cl - ), and sulfate ions (SO4 2- Because it contains ), it can be highly corrosive.

[0005] Accordingly, impellers used in desulfurization facilities within thermal power plants may be required to have high wear resistance and high corrosion resistance.

[0006] Accordingly, high-chromium cast iron alloys with excellent wear resistance and corrosion resistance were previously used for impellers used in desulfurization facilities within thermal power plants.

[0007] However, impellers manufactured from conventional high-chromium cast iron alloys had a limitation in that they frequently failed before reaching their designed lifespan.

[0008] This may be due to the occurrence of a potential difference between the matrix structure and metal carbides within the existing high-chromium cast iron alloy. When a potential difference occurs between the matrix structure and metal carbides of a high-chromium cast iron alloy, microgalvanic corrosion may occur.

[0009] As a result, corrosion of the matrix structure in high-chromium cast iron alloys can be accelerated, and due to the continuous acceleration of matrix structure corrosion, substantially only carbides may remain inside the high-chromium cast iron alloy.

[0010] Accordingly, there was a limitation in that impellers manufactured from high-chromium cast iron alloys failed before their designed lifespan due to increased brittleness of the alloy.

[0011] Accordingly, there is a need for high-chromium cast iron alloys with improved wear resistance and corrosion resistance. The problem to be solved

[0013] The technical problem that this application aims to solve is to provide a high-chromium cast iron alloy and a method for manufacturing the same, in which the process is simplified while wear resistance and corrosion resistance are maximized.

[0014] Another technical problem that this application aims to solve is to provide a high-chromium cast iron alloy and a method for manufacturing the same, wherein the heat treatment step is controlled to maximize wear resistance and corrosion resistance according to the chromium content included in the alloy raw material.

[0015] The technical problems that this application aims to solve are not limited to those described above. means of solving the problem

[0017] To solve the above technical problem, the present application provides a method for manufacturing a high-chromium cast iron alloy.

[0018] According to one embodiment, the method for manufacturing a high-chromium cast iron alloy comprises the steps of: producing a pre-alloy by performing a first heat treatment on an alloy raw material containing chromium; and producing a high-chromium cast iron alloy by performing a second heat treatment on the pre-alloy at a temperature higher than the first heat treatment, wherein, depending on the chromium content contained in the alloy raw material, an additional third heat treatment may be performed or omitted on the high-chromium cast iron alloy, and the third heat treatment may be performed at a temperature lower than the second heat treatment.

[0019] According to one embodiment, the chromium content included in the alloy raw material is 27 wt% or more to less than 29 wt%, and the third heat treatment can be performed.

[0020] According to one embodiment, the chromium content included in the alloy raw material is 29 wt% or more to less than 33 wt%, and the third heat treatment may be omitted.

[0021] According to one embodiment, the chromium content included in the alloy raw material is 29 wt% or more to less than 33 wt%, and the high-chromium cast iron alloy in which the third heat treatment is omitted may have a corrosion current density in a lower range compared to a reference alloy defined as having undergone the third heat treatment.

[0022] According to one embodiment, the third heat treatment may be performed at a temperature greater than 250 ℃ and less than 350 ℃.

[0023] According to one embodiment, at the temperature at which the third heat treatment is performed, the shock absorption energy may be maximum.

[0024] According to one embodiment, the chromium content included in the alloy raw material is 27 wt% or more to less than 29 wt%, and the high-chromium cast iron alloy in which the third heat treatment is performed may have a corrosion current density within a reference range with respect to the high-chromium cast iron alloy, which is defined as having the third heat treatment omitted.

[0025] According to one embodiment, the method for manufacturing the high-chromium cast iron alloy can be used for an impeller of a desulfurization facility in a thermal power plant.

[0027] To solve the above technical problem, the present application provides a high-chromium cast iron alloy.

[0028] According to one embodiment, the high-chromium cast iron alloy may contain an austenite phase of more than 3.5 vol% and less than 23.1 vol%, and may have a hardness of more than 50 HRC and less than 57 HRC and an impact absorption energy of more than 2.5 J and less than 3 J.

[0029] According to one embodiment, the high-chromium cast iron alloy may contain 29 wt% or more and less than 31 wt% chromium.

[0031] To solve the above technical problem, the present application provides a high-chromium cast iron alloy.

[0032] According to one embodiment, the high-chromium cast iron alloy can have a higher range of shock absorption energy compared to the reference alloy, in a high-chromium cast iron alloy manufactured by omitting the third heat treatment step compared to a reference alloy manufactured by a method comprising a first heat treatment step of an alloy raw material containing chromium, a second heat treatment step of being performed at a temperature higher than the first heat treatment step, and a third heat treatment step of being performed at a temperature lower than the second heat treatment step.

[0033] According to one embodiment, the high-chromium cast iron alloy may have a low range of corrosion current density compared to the reference alloy.

[0034] According to one embodiment, the high-chromium cast iron alloy may contain 29 wt% or more and less than 33 wt% chromium.

[0035] According to one embodiment, the high-chromium cast iron alloy can be used in the impeller of a desulfurization facility in a thermal power plant. Effects of the invention

[0037] According to an embodiment of the present application, a method for manufacturing a high-chromium cast iron alloy may be provided, comprising the steps of: manufacturing a pre-alloy by performing a first heat treatment on an alloy raw material containing chromium; and manufacturing a high-chromium cast iron alloy by performing a second heat treatment on the pre-alloy at a temperature higher than the first heat treatment, wherein, depending on the chromium content contained in the alloy raw material, an additional third heat treatment may be performed or omitted on the high-chromium cast iron alloy, and wherein the third heat treatment is performed at a temperature lower than the second heat treatment.

[0038] According to one embodiment, through the first heat treatment, residual stress in the pre-alloy produced from the alloy raw material can be minimized, and the formation of carbides in the pre-alloy can be stabilized.

[0039] According to one embodiment, through the second heat treatment, the hardness and wear resistance of the high-chromium cast iron alloy produced from the pre-alloy can be improved.

[0040] According to an embodiment of the present application, the third heat treatment may be controlled to be performed or omitted depending on the chromium content included in the alloy raw material.

[0041] As a result, the wear resistance and corrosion resistance of the high-chromium cast iron alloy manufactured according to the embodiment of the present application can be maximized. Brief explanation of the drawing

[0043] FIG. 1 is a drawing for explaining a method for manufacturing a high-chromium cast iron alloy according to an embodiment of the present application. FIG. 2 is a drawing for explaining a method for manufacturing a high-chromium cast iron alloy in which a third heat treatment is performed according to the chromium content according to an embodiment of the present application. FIG. 3 is a drawing for explaining a method for manufacturing a high-chromium cast iron alloy in which a third heat treatment is omitted depending on the chromium content according to an embodiment of the present application. FIG. 4 is a drawing for explaining a high-chromium cast iron alloy according to an embodiment of the present application. Figure 5 is a micrograph of the microstructure analysis of a high-chromium cast iron alloy according to Experimental Example 1-1 of the present application. Figure 6 is a micrograph of the microstructure analysis of a high-chromium cast iron alloy according to Experimental Example 2-1 of the present application. Figure 7 is a micrograph of the microstructure analysis of a high-chromium cast iron alloy according to Experimental Example 3-1 of the present application. FIG. 8 is a graph showing the fraction of carbides of high-chromium cast iron alloys according to Experimental Example 1-1, Experimental Example 2-1, and Experimental Example 3-1 of the present application. Figure 9 is a scanning electron microscopy-electron probe microanalysis (SEM-EPMA) of a high-chromium cast iron alloy according to Experimental Example 1-1 of the present application. FIG. 10 is a scanning electron microscope-electron probe microanalysis (SEM-EPMA) of a high-chromium cast iron alloy according to Experimental Example 2-1 of the present application. FIG. 11 is a scanning electron microscope-electron probe microanalysis (SEM-EPMA) of a high-chromium cast iron alloy according to Experimental Example 3-1 of the present application. Figure 12 is a phase analysis photograph of a high-chromium cast iron alloy according to Experimental Example 1-1 of the present application. Figure 13 is a phase analysis photograph of a high-chromium cast iron alloy according to Experimental Example 2-1 of the present application. Figure 14 is a phase analysis photograph of a high-chromium cast iron alloy according to Experimental Example 3-1 of the present application. FIG. 15 is a micrograph of the microstructure analysis of a high-chromium cast iron alloy according to Experimental Example 3-1 of the present application. Figure 16 is a micrograph of the microstructure analysis of a high-chromium cast iron alloy according to Experimental Example 3-2 of the present application. FIG. 17 is a micrograph of the microstructure analysis of a high-chromium cast iron alloy according to Experimental Example 3-3 of the present application. FIG. 18 is a micrograph of a high-chromium cast iron alloy according to Experimental Example 3-4 of the present application. FIG. 19 is a graph showing the fraction of carbides in high-chromium cast iron alloys according to Experimental Examples 3-1 to 3-4 of the present application. FIG. 20 is a scanning electron microscope-electron probe microanalysis (SEM-EPMA) of a high-chromium cast iron alloy according to Experimental Example 3-1 of the present application. FIG. 21 is a scanning electron microscope-electron probe microanalysis (SEM-EPMA) of a high-chromium cast iron alloy according to Experimental Example 3-4 of the present application. FIG. 22 is the result of a potentiodynamic polarization test of a high-chromium cast iron alloy according to Experimental Examples 1-1 to 1-4 of the present application. FIG. 23 is the result of the potentiodynamic polarization test of high-chromium cast iron alloys according to Experimental Examples 3-1 to 3-4 of the present application. FIG. 24 shows the surface potential between the microstructures of a high-chromium cast iron alloy according to Experimental Example 3-4 of the present application. FIG. 25 is a line profile according to surface dislocations between microstructures of a high-chromium cast iron alloy according to Experimental Example 3-4 of the present application. Specific details for implementing the invention

[0044] Hereinafter, preferred embodiments of the present application will be described in detail with reference to the attached drawings. However, the technical concept of the present application is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed content is thorough and complete and to ensure that the concept of the present application is sufficiently conveyed to those skilled in the art.

[0045] In this specification, when a component is described as being on another component, it means that it may be formed directly on the other component or that a third component may be interposed between them. Additionally, in the drawings, the thicknesses of the films and regions are exaggerated for the effective illustration of the technical content.

[0046] Additionally, although terms such as first, second, third, etc., have been used to describe various components in the various embodiments of this specification, these components should not be limited by such terms. These terms are used merely to distinguish one component from another. Accordingly, what is referred to as the first component in one embodiment may be referred to as the second component in another embodiment. Each embodiment described and illustrated herein also includes its complementary embodiment. Furthermore, in this specification, "and / or" is used to mean including at least one of the components listed before and after it.

[0047] In the specification, singular expressions include plural expressions unless the context clearly indicates otherwise. Furthermore, terms such as "include" or "have" are intended to specify the existence of the features, numbers, steps, components, or combinations thereof described in the specification, and should not be understood as excluding the existence or addition of one or more other features, numbers, steps, components, or combinations thereof. Additionally, in this specification, "connection" is used to include both indirectly connecting multiple components and directly connecting them.

[0048] Furthermore, in describing the present application below, if it is determined that a detailed description of related known functions or configurations could unnecessarily obscure the essence of the application, such detailed description will be omitted.

[0050] FIG. 1 is a drawing for explaining a method for manufacturing a high-chromium cast iron alloy according to an embodiment of the present application, FIG. 2 is a drawing for explaining a method for manufacturing a high-chromium cast iron alloy in which a third heat treatment is performed according to the chromium content according to an embodiment of the present application, FIG. 3 is a drawing for explaining a method for manufacturing a high-chromium cast iron alloy in which the third heat treatment is omitted according to the chromium content according to an embodiment of the present application, and FIG. 4 is a drawing for explaining a high-chromium cast iron alloy according to an embodiment of the present application.

[0051] Referring to FIGS. 1 to 3, an alloy raw material containing chromium may be subjected to a first heat treatment to produce a pre-alloy (S110). The first heat treatment may be performed, for example, at 850°C or higher and less than 950°C for 3 hours. However, it is not limited thereto.

[0052] According to one embodiment, depending on the chromium content contained in the alloy raw material, a subsequent third heat treatment may be performed or omitted. Specifically, for example, if the alloy raw material contains less than 29 wt% chromium, a subsequent third heat treatment may be additionally performed. More specifically, for example, if the alloy raw material contains 27 wt% or more and less than 29 wt% chromium, a subsequent third heat treatment may be additionally performed. On the other hand, if the alloy raw material contains 29 wt% or more chromium, the third heat treatment may be omitted. More specifically, for example, if the alloy raw material contains 29 wt% or more and less than 33 wt% chromium, the third heat treatment may be omitted.

[0053] Accordingly, according to the embodiment of the present application, the wear resistance and corrosion resistance of the high-chromium cast iron alloy (100, see FIG. 4) produced can be maximized because, depending on the chromium content included in the alloy raw material, additional heat treatment, i.e., the third heat treatment, is performed or omitted. In other words, in the embodiment of the present application, the heat treatment step can be controlled so that the wear resistance and corrosion resistance of the high-chromium cast iron alloy (100) produced can be maximized depending on the chromium content included in the alloy raw material.

[0054] According to one embodiment, through the first heat treatment, residual stress in the pre-alloy produced from the alloy raw material can be minimized, and the formation of carbides in the pre-alloy can be stabilized. Meanwhile, through the first heat treatment, the hardness of the pre-alloy produced from the alloy raw material can be lowered.

[0055] According to an embodiment of the present application, a subsequent heat treatment step (S120) may be performed to improve the hardness of the pre-alloy that has been lowered through the first heat treatment.

[0056] According to one embodiment, after the first heat treatment is performed, slow cooling may be performed before a subsequent heat treatment, i.e., a second heat treatment, is performed. The slow cooling after the first heat treatment may be performed, for example, at 25°C / hour. However, it is not limited thereto.

[0057] According to one embodiment, the fraction of phases contained in the high-chromium cast iron alloy (100) manufactured may vary depending on the chromium content contained in the alloy raw material. More specifically, the higher the chromium content contained in the alloy raw material, the more the high-chromium cast iron alloy (100) may contain less austenite phase and more ferrite phase.

[0058] Referring further to FIGS. 1 to 3, the pre-alloy may be subjected to a second heat treatment at a temperature higher than the first heat treatment to produce a high-chromium cast iron alloy (100) (S120). The second heat treatment may be performed, for example, at a temperature of 950°C or higher and 1100°C or lower for 3 hours. However, it is not limited thereto.

[0059] According to an embodiment of the present application, depending on the chromium content included in the alloy raw material, a subsequent third heat treatment may be performed or omitted. Specifically, for example, if the alloy raw material contains less than 29 wt% chromium, more specifically, for example, if the alloy raw material contains 27 wt% or more and less than 29 wt% chromium, an additional third heat treatment may be performed on the high-chromium cast iron alloy (100) manufactured in this step (S120), as shown in FIGS. 1 and 2. On the other hand, if the alloy raw material contains 29 wt% or more chromium, more specifically, for example, if the alloy raw material contains 29 wt% or more and less than 33 wt% chromium, the third heat treatment may be omitted, as shown in FIGS. 1 and 3, and the manufacturing process of the high-chromium cast iron alloy (100) may be terminated in this step (S120).

[0060] Accordingly, according to an embodiment of the present application, depending on the chromium content included in the alloy raw material, additional heat treatment, i.e., the third heat treatment, is performed or omitted, so the wear resistance and corrosion resistance of the high-chromium cast iron alloy (100) being manufactured can be maximized.

[0061] According to one embodiment, through the second heat treatment, the hardness and wear resistance of the high-chromium cast iron alloy (100) produced from the pre-alloy can be improved.

[0062] According to one embodiment, rapid cooling may be performed after the second heat treatment is performed. The rapid cooling after the second heat treatment may be performed, for example, at 150°C / hour. However, it is not limited thereto.

[0063] Thus, when the alloy raw material contains 29 wt% or more of chromium, more specifically, for example, when the alloy raw material contains 29 wt% or more to less than 33 wt% of chromium, as shown in FIG. 1 and FIG. 3, the third heat treatment is omitted, the manufacturing process is terminated in this step (S120), and the high-chromium cast iron alloy (100) can be manufactured.

[0064] According to one embodiment, the chromium content included in the alloy raw material is 29 wt% or more, more specifically, for example, 29 wt% or more to less than 33 wt%, and the high-chromium cast iron alloy (100) manufactured by omitting the third heat treatment may have a corrosion current density in a lower range compared to a reference alloy defined as having undergone the third heat treatment for the high-chromium cast iron alloy (100).

[0065] In other words, the high-chromium cast iron alloy (100) manufactured with a chromium content of 29 wt% or more and with the third heat treatment omitted has a slower corrosion rate than the reference alloy manufactured with the third heat treatment, and thus may have higher corrosion resistance.

[0066] On the other hand, if the chromium content is 29 wt% or more and the third heat treatment is performed, the corrosion current density of the high-chromium cast iron alloy produced, i.e., the reference alloy, may increase. More specifically, if the chromium content included in the alloy raw material is 29 wt% or more, the concentration of carbides inside the high-chromium cast iron alloy (100) produced through the first and second heat treatments may be higher than if the chromium content is less than 29 wt%.

[0067] Accordingly, the reference alloy that has been additionally heat-treated with the high-chromium cast iron alloy (100) having a high concentration of carbides may have additional carbides formed inside and galvanic corrosion may be accelerated.

[0068] Accordingly, the above reference alloy may have a rapid corrosion rate and reduced corrosion resistance.

[0069] However, according to an embodiment of the present application, if the alloy raw material contains 29 wt% or more of chromium, the third heat treatment may be omitted, and accordingly, the corrosion resistance of the high-chromium cast iron alloy (100) produced may be high.

[0070] That is, according to an embodiment of the present application, when the chromium content included in the alloy raw material is within the standard range, i.e., 29 wt% or more, the third heat treatment is omitted, so the process steps can be simplified. Furthermore, since the corrosion resistance of the high-chromium cast iron alloy (100) produced through the simplified process is excellent, a combined synergistic effect of process step simplification and physical property improvement can be provided.

[0071] According to one embodiment, the chromium content included in the alloy raw material is 29 wt% or more, more specifically, for example, 29 wt% or more to less than 33 wt%, and the high-chromium cast iron alloy (100) manufactured by omitting the third heat treatment can have a high range of shock absorption energy compared to a reference alloy defined as having undergone the third heat treatment with respect to the high-chromium cast iron alloy (100).

[0072] In other words, the high-chromium cast iron alloy (100) manufactured with a chromium content of 29 wt% or more and with the third heat treatment omitted has higher toughness than the reference alloy manufactured with the third heat treatment, and thus may have higher wear resistance.

[0073] On the other hand, if the chromium content is 29 wt% or more and the third heat treatment is performed, the impact absorption energy of the high-chromium cast iron alloy produced, i.e., the reference alloy, may be reduced. More specifically, if the chromium content included in the alloy raw material is 29 wt% or more, the concentration of carbides inside the high-chromium cast iron alloy (100) produced through the first and second heat treatments may be higher than when the chromium content is less than 29 wt%.

[0074] Accordingly, the reference alloy that has been additionally heat-treated with the high-chromium cast iron alloy (100) having a high concentration of carbides may have additional carbides formed inside, and the shock absorption energy may be reduced by precipitation hardening.

[0075] Accordingly, the above reference alloy may have low toughness and reduced wear resistance.

[0076] However, according to an embodiment of the present application, if the alloy raw material contains 29 wt% or more of chromium, the third heat treatment may be omitted, and accordingly, the wear resistance of the high-chromium cast iron alloy (100) produced may be high.

[0077] That is, according to an embodiment of the present application, when the chromium content included in the alloy raw material is within the standard range, i.e., 29 wt% or more, the third heat treatment is omitted, so the process steps can be simplified. Furthermore, since the high-chromium cast iron alloy (100) produced through the simplified process has excellent corrosion resistance as well as wear resistance, it can provide a combined synergistic effect of process step simplification and physical property improvement.

[0078] Referring further to FIGS. 1 and 2, the high-chromium cast iron alloy (100) may be additionally heat-treated a third time at a temperature lower than the second heat treatment (S130). The third heat treatment may be performed, for example, at a temperature of 200°C or higher and 400°C or lower for 1 hour. However, it is not limited thereto.

[0079] According to an embodiment of the present application, the third heat treatment may be performed or omitted depending on the chromium content included in the alloy raw material. For example, if the alloy raw material contains less than 29 wt% chromium, more specifically, for example, if the alloy raw material contains 27 wt% or more and less than 29 wt% chromium, the additional third heat treatment may be performed on the high-chromium cast iron alloy (100) as shown in FIGS. 1 and 2.

[0080] According to one embodiment, the chromium content included in the alloy raw material is less than 29 wt%, more specifically, for example, 27 wt% or more to less than 29 wt%, and the high-chromium cast iron alloy (100) manufactured by performing the third heat treatment may have a high range of shock absorption energy compared to a reference alloy defined as having the third heat treatment omitted for the high-chromium cast iron alloy (100). More specifically, for example, the third heat treatment may be performed at a temperature greater than 250 ℃ to less than 350 ℃, and accordingly, the shock absorption energy of the high-chromium cast iron alloy (100) manufactured through the third heat treatment may be maximum. When the chromium content included in the alloy raw material is less than 29 wt%, the concentration of carbides inside the high-chromium cast iron alloy (100) manufactured through the first and second heat treatments may be lower than when the chromium content is 29 wt% or more.

[0081] Accordingly, when the high-chromium cast iron alloy (100) with a low concentration of carbides is additionally subjected to the third heat treatment, the concentration of carbides within the high-chromium cast iron alloy (100) is improved to an appropriate amount, and the shock absorption energy of the high-chromium cast iron alloy (100) can be increased compared to the reference alloy.

[0082] Accordingly, the wear resistance of the above high-chromium cast iron alloy (100) can be high.

[0083] That is, according to an embodiment of the present application, when the chromium content included in the alloy raw material is within the standard range, i.e., less than 29 wt%, the carbide concentration inside the high-chromium cast iron alloy (100) is taken into account and the third heat treatment is performed, thereby providing the effect of improving the physical properties of the high-chromium cast iron alloy (100) being manufactured.

[0084] On the other hand, if the chromium content is less than 29 wt% and the third heat treatment is performed at a temperature of 350°C or higher, outside the temperature range described above, i.e., greater than 250°C and less than 350°C, the impact absorption energy of the high-chromium cast iron alloy being manufactured may be reduced. This may be because the high-chromium cast iron alloy is additionally subjected to a third heat treatment at an excessively high temperature, resulting in an excessive concentration of carbides being formed inside the high-chromium cast iron alloy.

[0085] However, according to an embodiment of the present application, the third heat treatment can be performed at a temperature greater than 250°C and less than 350°C, and thereby the carbide concentration inside the high-chromium cast iron alloy (100) can be improved to an appropriate amount.

[0086] Accordingly, the shock absorption energy of the high-chromium cast iron alloy (100) produced through the third heat treatment can be maximized.

[0087] According to one embodiment, the chromium content included in the alloy raw material is less than 29 wt%, more specifically, for example, 27 wt% or more to less than 29 wt%, and the high-chromium cast iron alloy (100) manufactured by performing the third heat treatment may have a corrosion current density within a reference range with respect to the high-chromium cast iron alloy (100), which is defined as having the third heat treatment omitted. More specifically, for example, the third heat treatment may be performed at a temperature greater than 250 ℃ to less than 350 ℃, and accordingly, the corrosion current density of the high-chromium cast iron alloy (100) manufactured through the third heat treatment may be maintained similarly to that before the third heat treatment.

[0088] Accordingly, the corrosion resistance of the high-chromium cast iron alloy (100) manufactured can be excellent.

[0089] That is, according to an embodiment of the present application, when the chromium content included in the alloy raw material is less than the standard range, i.e., 29 wt%, the carbide concentration is taken into account and the third heat treatment is performed in the temperature range described above, so that the high-chromium cast iron alloy (100) being manufactured can provide a combined synergistic effect of excellent wear resistance as well as corrosion resistance.

[0091] According to the embodiments of the present application described above, a high-chromium cast iron alloy (100) manufactured by performing or omitting the additional third heat treatment depending on the chromium content included in the alloy raw material may be provided.

[0092] Referring to FIG. 4, the high-chromium cast iron alloy (100) may contain an appropriate amount of carbide (110) because the third heat treatment is additionally performed or omitted depending on the chromium content included in the alloy raw material.

[0093] Accordingly, the high-chromium cast iron alloy (100) may have a low corrosion current density and high shock absorption energy. As a result, the high-chromium cast iron alloy (100) may have excellent wear resistance and corrosion resistance.

[0094] Accordingly, the above high-chromium cast iron alloy (100) can be suitably used for an impeller of a desulfurization facility in a thermal power plant.

[0096] Specific experimental examples and characteristic evaluation results according to the embodiments of the present application are described below.

[0098] Preparation of high-chromium cast iron alloy (ex1-1) according to Experimental Example 1-1

[0099] The above alloy raw material was prepared containing 1.70 wt% carbon (C), 27.54 wt% chromium (Cr), 2.55 wt% nickel (Ni), 1.46 wt% copper (Cu), 1.17 wt% molybdenum (Mo), 1.17 wt% manganese (Mn), and the remainder being iron (Fe) to make the total 100 wt%.

[0100] After the above alloy raw material was subjected to the above first heat treatment at 850 ℃ or higher and less than 950 ℃ for 3 hours, it was slow-cooled at 25 ℃ / hour to produce the above pre-alloy.

[0101] After the above pre-alloy was subjected to the above second heat treatment at 950°C or higher and 1100°C or lower for 3 hours, it was rapidly cooled at 150°C / hour to produce a high-chromium cast iron alloy (ex1-1) according to Experimental Example 1-1.

[0103] Preparation of high-chromium cast iron alloy (ex1-2) according to Experimental Example 1-2

[0104] In the above-described Experimental Example 1-1, the third heat treatment was additionally performed at 250°C for 1 hour to produce a high-chromium cast iron alloy (ex1-2) according to Experimental Example 1-2.

[0106] Preparation of high-chromium cast iron alloy (ex1-3) according to Experimental Example 1-3

[0107] In the above-described Experimental Example 1-1, the third heat treatment was additionally performed at 300°C for 1 hour to produce a high-chromium cast iron alloy (ex1-3) according to Experimental Example 1-3.

[0109] Preparation of high-chromium cast iron alloy (ex1-4) according to Experimental Example 1-4

[0110] In the above-described Experimental Example 1-1, the third heat treatment was additionally performed at 350°C for 1 hour to produce a high-chromium cast iron alloy (ex1-4) according to Experimental Example 1-4.

[0112] Preparation of high-chromium cast iron alloy (ex2-1) according to Experimental Example 2-1

[0113] The above alloy raw material was prepared containing 2.21 wt% carbon (C), 30.03 wt% chromium (Cr), 1.78 wt% nickel (Ni), 1.71 wt% copper (Cu), 0.81 wt% molybdenum (Mo), 1.01 wt% manganese (Mn), and the remainder being iron (Fe) to make the total 100 wt%.

[0114] After the above alloy raw material was subjected to the above first heat treatment at 850 ℃ or higher and less than 950 ℃ for 3 hours, it was slow-cooled at 25 ℃ / hour to produce the above pre-alloy.

[0115] After the above pre-alloy was subjected to the above second heat treatment at 950°C or higher and 1100°C or lower for 3 hours, it was rapidly cooled at 150°C / hour to produce a high-chromium cast iron alloy (ex2-1) according to Experimental Example 2-1.

[0117] Preparation of high-chromium cast iron alloy (ex2-2) according to Experimental Example 2-2

[0118] In the above-described Experimental Example 2-1, the third heat treatment was additionally performed at 250°C for 1 hour to produce a high-chromium cast iron alloy (ex2-2) according to Experimental Example 2-2.

[0120] Preparation of high-chromium cast iron alloy (ex2-3) according to Experimental Example 2-3

[0121] In the above-described Experimental Example 2-1, the third heat treatment was additionally performed at 300°C for 1 hour to produce a high-chromium cast iron alloy (ex2-3) according to Experimental Example 2-3.

[0123] Preparation of high-chromium cast iron alloy (ex2-4) according to Experimental Example 2-4

[0124] In the above-described Experimental Example 2-1, the third heat treatment was additionally performed at 350°C for 1 hour to produce a high-chromium cast iron alloy (ex2-4) according to Experimental Example 2-4.

[0126] Preparation of high-chromium cast iron alloy (ex3-1) according to Experimental Example 3-1

[0127] The above alloy raw material was prepared containing 2.08 wt% carbon (C), 32.08 wt% chromium (Cr), 1.75 wt% nickel (Ni), 1.59 wt% copper (Cu), 0.65 wt% molybdenum (Mo), 0.79 wt% manganese (Mn), and the remainder being iron (Fe) to make the total 100 wt%.

[0128] After the above alloy raw material was subjected to the above first heat treatment at 850 ℃ or higher and less than 950 ℃ for 3 hours, it was slow-cooled at 25 ℃ / hour to produce the above pre-alloy.

[0129] After the above pre-alloy was subjected to the above second heat treatment at 950°C or higher and 1100°C or lower for 3 hours, it was rapidly cooled at 150°C / hour to produce a high-chromium cast iron alloy (ex3-1) according to Experimental Example 3-1.

[0131] Preparation of high-chromium cast iron alloy (ex3-2) according to Experimental Example 3-2

[0132] In the above-described Experimental Example 3-1, the third heat treatment was additionally performed at 250°C for 1 hour to produce a high-chromium cast iron alloy (ex3-2) according to Experimental Example 3-2.

[0134] Preparation of high-chromium cast iron alloy (ex3-3) according to Experimental Example 3-3

[0135] In the above-described Experimental Example 3-1, the third heat treatment was additionally performed at 300°C for 1 hour to produce a high-chromium cast iron alloy (ex3-3) according to Experimental Example 3-3.

[0137] Preparation of high-chromium cast iron alloy (ex3-4) according to Experimental Example 3-4

[0138] In the above-described Experimental Example 3-1, the third heat treatment was additionally performed at 350°C for 1 hour to produce a high-chromium cast iron alloy (ex3-4) according to Experimental Example 3-4.

[0140] The composition of the alloy raw materials in the above-described experimental examples 1-1 to 3-2 can be summarized as shown in Table 1 below.

[0141] Classification (wt%) C Cr Ni Cu Mo Mn Fe Experimental Examples 1-1~1-4 (ex1-1~1-4) 1.70 27.54 2.55 1.46 1.17 1.17 Bal. Experimental Examples 2-1, 2-2 (ex2-1, 2-2) 2.21 30.03 1.78 1.71 0.81 1.01 Bal. Experimental Examples 3-1, 3-2 (ex3-1, 3-2) 2.08 32.08 1.75 1.59 0.65 0.79 Bal.

[0143] In addition, the third heat treatment in the above-described experimental examples 1-1 to 3-2 can be summarized as shown in Tables 2 to 4 below.

[0144] division 3rd heat treatment Experiment Example 1-1 (ex1-1) omission Experiment Example 1-2 (ex1-2) 250 ℃ Experimental Example 1-3 (ex1-3) 300 ℃ Experimental Example 1-4 (ex1-4) 350 ℃

[0146] division 3rd heat treatment Experiment Example 2-1 (ex2-1) omission Experiment Example 2-2 (ex2-2) 250 ℃ Experiment Example 2-3 (ex2-3) 300 ℃ Experiment Example 2-4 (ex2-4) 350 ℃

[0148] division 3rd heat treatment Experiment Example 3-1 (ex3-1) omission Experiment Example 3-2 (ex3-2) 250 ℃ Experiment Example 3-3 (ex3-3) 300 ℃ Experiment Example 3-4 (ex3-4) 350 ℃

[0150] FIG. 5 is a micrograph of the microstructure analysis of a high-chromium cast iron alloy according to Experimental Example 1-1 of the present application, FIG. 6 is a micrograph of the microstructure analysis of a high-chromium cast iron alloy according to Experimental Example 2-1 of the present application, FIG. 7 is a micrograph of the microstructure analysis of a high-chromium cast iron alloy according to Experimental Example 3-1 of the present application, FIG. 8 is a graph showing the fraction of carbides of high-chromium cast iron alloys according to Experimental Examples 1-1, 2-1, and 3-1 of the present application, FIG. 9 is a scanning electron microscopy-electron probe microanalysis (SEM-EPMA) of the high-chromium cast iron alloy according to Experimental Example 1-1 of the present application, FIG. 10 is a scanning electron microscopy-electron probe microanalysis (SEM-EPMA) of the high-chromium cast iron alloy according to Experimental Example 2-1 of the present application, and FIG. 11 is an experimental example of the present application This is a scanning electron microscope-electron probe microanalysis (SEM-EPMA) of a high-chromium cast iron alloy according to 3-1.

[0151] Referring to FIGS. 5 to 11, it can be seen that the higher the chromium content in the alloy raw material, the higher the fraction of carbides in the high-chromium cast iron alloy (100).

[0152] Thus, it can be proven that the higher the chromium content included in the alloy raw material, the higher the concentration of carbides inside the high-chromium cast iron alloy (100).

[0154] FIG. 12 is a phase analysis photograph of a high-chromium cast iron alloy according to Experimental Example 1-1 of the present application, FIG. 13 is a phase analysis photograph of a high-chromium cast iron alloy according to Experimental Example 2-1 of the present application, and FIG. 14 is a phase analysis photograph of a high-chromium cast iron alloy according to Experimental Example 3-1 of the present application.

[0155] Figures 12 to 14 can be summarized as shown in Table 5 below.

[0156] division Chromium (Cr) composition (vol%) Ferrite phase (vol%) Austenite phase (vol%) Experiment Example 1-1 (ex1-1) 27.54 76.9 23.1 Experiment Example 2-1 (ex2-1) 30.03 88.6 11.4 Experiment Example 3-1 (ex3-1) 32.08 96.5 3.5

[0158] Referring to FIGS. 12 to 14 and Table 5, it can be seen that the higher the chromium content in the alloy raw material, the more the high-chromium cast iron alloy (100) contains less austenite phase and more ferrite phase.

[0159] Thus, it can be proven that the higher the chromium content in the alloy raw material, the more the high-chromium cast iron alloy (100) contains less austenite phase and more ferrite phase.

[0161] FIG. 15 is a micrograph of the microstructure analysis of a high-chromium cast iron alloy according to Experimental Example 3-1 of the present application, FIG. 16 is a micrograph of the microstructure analysis of a high-chromium cast iron alloy according to Experimental Example 3-2 of the present application, FIG. 17 is a micrograph of the microstructure analysis of a high-chromium cast iron alloy according to Experimental Example 3-3 of the present application, FIG. 18 is a micrograph of the microstructure analysis of a high-chromium cast iron alloy according to Experimental Example 3-4 of the present application, FIG. 19 is a graph showing the fraction of carbides of the high-chromium cast iron alloy according to Experimental Examples 3-1 to 3-4 of the present application, FIG. 20 is a scanning electron microscope-electron probe microanalysis (SEM-EPMA) of the high-chromium cast iron alloy according to Experimental Example 3-1 of the present application, and FIG. 21 is a scanning electron microscope-electron probe microanalysis (SEM-EPMA) of the high-chromium cast iron alloy according to Experimental Example 3-4 of the present application.

[0162] Figures 15 to 19 can be summarized as shown in Table 6 below.

[0163] division 3rd heat treatment Carbide fraction (vol%) Experiment Example 3-1 (ex3-1) omission 41.1 Experiment Example 3-2 (ex3-2) 250 ℃ 51.1 Experiment Example 3-3 (ex3-3) 300 ℃ 51.5 Experiment Example 3-4 (ex3-4) 350 ℃ 52.1

[0165] Referring to FIGS. 5 to 19 and Table 6, it can be seen that the higher the temperature at which the high-chromium cast iron alloy (100) is subjected to the third heat treatment, the higher the fraction of carbides formed inside the high-chromium cast iron alloy (100).

[0166] Thus, it can be proven that if the temperature at which the high-chromium cast iron alloy (100) is additionally heat-treated in the third step is excessively high, the carbide concentration of the high-chromium cast iron alloy (100) may become excessively high.

[0167] In addition, referring to FIGS. 20 and 21, unlike the case where the third heat treatment is omitted according to Experimental Example 3-1 (ex3-1), when the third heat treatment is performed at 350 ℃ according to Experimental Example 3-4 (ex3-4), it can be confirmed that carbides are precipitated within the matrix structure of the high-chromium cast iron alloy (100).

[0168] Thus, it can be proven that when the chromium content in the alloy raw material is 29 wt% or more and the third heat treatment is additionally performed, carbides are additionally formed in the high-chromium cast iron alloy (100) being manufactured.

[0170] Classification (HRC) 3rd heat treatment hardness Experiment Example 1-1 (ex1-1) omission 51.3 Experiment Example 1-2 (ex1-2) 250 ℃ 51.4 Experimental Example 1-3 (ex1-3) 300 ℃ 51.6 Experimental Example 1-4 (ex1-4) 350 ℃ 52.6

[0172] Classification (HRC) 3rd heat treatment hardness Experiment Example 2-1 (ex2-1) omission 55.5 Experiment Example 2-2 (ex2-2) 250 ℃ 55.8 Experiment Example 2-3 (ex2-3) 300 ℃ 56 Experiment Example 2-4 (ex2-4) 350 ℃ 56.4

[0174] Classification (HRC) 3rd heat treatment hardness Experiment Example 3-1 (ex3-1) omission 52.5 Experiment Example 3-2 (ex3-2) 250 ℃ 54.1 Experiment Example 3-3 (ex3-3) 300 ℃ 53.9 Experiment Example 3-4 (ex3-4) 350 ℃ 54.7

[0176] Referring to Tables 7 through 9, it can be seen that the hardness of the high-chromium cast iron alloy (100) produced is similar when the third heat treatment is additionally performed or omitted. More specifically, when the third heat treatment is additionally performed or omitted, it can be seen that the hardness of the high-chromium cast iron alloy (100) produced is within a standard range of 51.3 HRC or higher to 56.4 HRC or lower.

[0177] Thus, it can be proven that the third heat treatment has a weak effect on the hardness of the high-chromium cast iron alloy (100) being manufactured.

[0179] Classification (J) 3rd heat treatment Shock absorption energy Experiment Example 1-1 (ex1-1) omission 1.53 Experiment Example 1-2 (ex1-2) 250 ℃ 2.14 Experimental Example 1-3 (ex1-3) 300 ℃ 2.64 Experimental Example 1-4 (ex1-4) 350 ℃ 2.05

[0181] Classification (J) 3rd heat treatment Shock absorption energy Experiment Example 2-1 (ex2-1) omission 2.61 Experiment Example 2-4 (ex2-4) 350 ℃ 1.83

[0183] Classification (J) 3rd heat treatment Shock absorption energy Experiment Example 3-1 (ex3-1) omission 1.91 Experiment Example 3-4 (ex3-4) 350 ℃ 1.65

[0185] Referring to Table 10, it can be seen that the impact absorption energy of the high-chromium cast iron alloy (ex1-3) according to Experimental Example 1-3, which was performed at a temperature greater than 250 ℃ and less than 350 ℃, i.e., 300 ℃, is the greatest for the third heat treatment.

[0186] On the other hand, if the third heat treatment is performed outside the temperature range described above, namely 250°C to 350°C, at temperatures below 250°C and above 350°C, it can be observed that the impact absorption energy of the manufactured high-chromium cast iron alloy (ex1-2, ex1-4) is actually reduced. This may be because the high-chromium cast iron alloy is additionally subjected to the third heat treatment at a low temperature or is not subjected to the third heat treatment, resulting in a low concentration of carbides within the high-chromium cast iron alloy. Alternatively, it may be because the high-chromium cast iron alloy is additionally subjected to the third heat treatment at an excessively high temperature, resulting in an excessive concentration of carbides within the high-chromium cast iron alloy.

[0187] Thus, it can be proven that when the chromium content included in the alloy raw material is less than 29 wt%, more specifically, for example, 27 wt% or more to less than 29 wt%, and the third heat treatment is performed at a temperature greater than 250 ℃ to less than 350 ℃, the carbide concentration inside the high-chromium cast iron alloy (100) is improved to an appropriate amount, and the impact absorption energy of the high-chromium cast iron alloy (100) being manufactured is maximized.

[0188] Referring to Tables 11 and 12, it can be seen that the high-chromium cast iron alloys (ex2-1, ex3-1) according to Experimental Example 2-1 and Experimental Example 3-1, which were manufactured with the third heat treatment omitted, have higher shock absorption energy than the high-chromium cast iron alloys (ex2-4, ex3-4) according to Experimental Example 2-4 and Experimental Example 3-4, which had the third heat treatment performed.

[0189] Thus, it can be proven that the shock absorption energy of the high-chromium cast iron alloy (100) produced is maximized when the chromium content included in the alloy raw material is 29 wt% or more, more specifically, for example, 29 wt% or more to less than 33 wt%, and the third heat treatment is omitted.

[0191] FIG. 22 is the result of a potentiodynamic polarization test of a high-chromium cast iron alloy according to Experimental Examples 1-1 to 1-4 of the present application, FIG. 23 is the result of a potentiodynamic polarization test of a high-chromium cast iron alloy according to Experimental Examples 3-1 to 3-4 of the present application, FIG. 24 is the surface potential between microstructures of a high-chromium cast iron alloy according to Experimental Example 3-4 of the present application, and FIG. 25 is a line profile according to the surface potential between microstructures of a high-chromium cast iron alloy according to Experimental Example 3-4 of the present application.

[0192] Figures 22 and 23 can be summarized as shown in Tables 13 and 14 below.

[0193] division E corr (V SCE ) i corr (A / cm 2 ) Experiment Example 1-1 (ex1-1) -0.325 2.16X10 -6 Experiment Example 1-2 (ex1-2) -0.306 3.38X10 -6 Experimental Example 1-3 (ex1-3) -0.414 3.32X10 -6 Experimental Example 1-4 (ex1-4) -0.275 3.64X10 -6

[0195] division E corr (V SCE ) i corr (A / cm 2 ) Experiment Example 3-1 (ex3-1) -0.357 8.89X10 -7 Experiment Example 3-2 (ex3-2) -0.343 2.07X10 -6 Experiment Example 3-3 (ex3-3) -0.335 4.12X10 -6 Experiment Example 3-4 (ex3-4) -0.272 5.74X10 -6

[0197] Referring to FIG. 22 and Table 13, it can be confirmed that the high-chromium cast iron alloys (ex1-1 to ex1-4) according to Experimental Examples 1-1 to 1-4, which are manufactured in which the chromium content in the alloy raw material is less than 29 wt%, more specifically, for example, 27 wt% or more to less than 29 wt%, and the third heat treatment is omitted or performed, have a similar level of corrosion current density. More specifically, when the chromium content in the alloy raw material is less than 29 wt%, more specifically, for example, 27 wt% or more to less than 29 wt%, and the third heat treatment is additionally performed or omitted, the corrosion current density of the high-chromium cast iron alloy (100) manufactured is 2.16X10 -6 A / cm 2 3.6X10 or more -6 A / cm 2 It can be confirmed that it is within the following standard range. However, within the above standard range, it can be confirmed that as the third heat treatment temperature increases, it has a relatively lower corrosion current density.

[0198] Thus, it can be seen that when the chromium content included in the alloy raw material is less than 29 wt%, the third heat treatment has a weak effect on the corrosion resistance of the high-chromium cast iron alloy (100) being manufactured.

[0199] Referring to FIG. 23 and Table 14, it can be seen that the high-chromium cast iron alloy (ex3-1) according to Experimental Example 3-1, which is manufactured with a chromium content of 29 wt% or more, more specifically, 29 wt% or more to less than 33 wt%, and with the third heat treatment omitted, has a lower range of corrosion current density compared to the high-chromium cast iron alloys (ex3-2 to 3-4) according to other experimental examples. Additionally, it can be seen that the corrosion current density is relatively lower as the temperature of the third heat treatment increases.

[0200] Accordingly, the high-chromium cast iron alloy (100) manufactured with a chromium content of 29 wt% or more and with the third heat treatment omitted can be proven to have a slower corrosion rate than the reference alloy manufactured with the third heat treatment, and thus have higher corrosion resistance.

[0201] Referring to FIGS. 24 and 25, through the surface potential analysis results of the high-chromium cast iron alloy (ex3-4) according to Experimental Example 3-4, a potential difference of about 50 mV can be confirmed between the matrix structure and the carbides of the high-chromium cast iron alloy (100) according to Experimental Example 3-4. This is a sufficient potential difference to cause galvanic corrosion, and it can be determined that as the concentration of carbides formed inside the high-chromium cast iron alloy (100) increases, micro-galvanic corrosion around the carbides is accelerated.

[0202] Accordingly, according to the above experimental example 3-4 (ex3-4), it can be proven that the corrosion resistance of the manufactured high-chromium cast iron alloy (100) is reduced when the chromium content is 29 wt% or more and the third heat treatment is performed, and it can be predicted that if the micro-galvanic corrosion continues to occur, the brittleness increases due to corrosion of the matrix structure and the retention of carbides, and the high-chromium cast iron alloy may fail prematurely.

[0204] Although the present application has been described in detail using preferred embodiments, the scope of the present application is not limited to specific embodiments and should be interpreted by the appended claims. Furthermore, those skilled in the art will understand that many modifications and variations are possible without departing from the scope of the present application. Explanation of the symbols

[0206] 100: High-chromium cast iron alloy 110: Carbide

Claims

Claim 1 A method for manufacturing a high-chromium cast iron alloy, comprising: a step of manufacturing a pre-alloy by performing a first heat treatment on an alloy raw material containing chromium; and a step of manufacturing a high-chromium cast iron alloy by performing a second heat treatment on the pre-alloy at a temperature higher than the first heat treatment, wherein, depending on the chromium content contained in the alloy raw material, an additional third heat treatment is performed or omitted for the high-chromium cast iron alloy, and wherein the third heat treatment is performed at a temperature lower than the second heat treatment. Claim 2 A method for manufacturing a high-chromium cast iron alloy according to claim 1, wherein the chromium content included in the alloy raw material is 27 wt% or more to less than 29 wt%, and the third heat treatment is performed. Claim 3 A method for manufacturing a high-chromium cast iron alloy according to claim 1, wherein the chromium content included in the alloy raw material is 29 wt% or more to less than 33 wt%, and the third heat treatment is omitted. Claim 4 A method for manufacturing a high-chromium cast iron alloy according to claim 3, wherein the chromium content included in the alloy raw material is 29 wt% or more to less than 33 wt%, and the high-chromium cast iron alloy in which the third heat treatment is omitted has a corrosion current density in a lower range compared to a reference alloy defined as having undergone the third heat treatment. Claim 5 A method for manufacturing a high-chromium cast iron alloy according to claim 2, wherein the third heat treatment is performed at a temperature greater than 250 ℃ and less than 350 ℃. Claim 6 A method for manufacturing a high-chromium cast iron alloy according to claim 5, wherein the shock absorption energy is maximum at the temperature at which the third heat treatment is performed. Claim 7 A method for manufacturing a high-chromium cast iron alloy according to claim 2, wherein the chromium content included in the alloy raw material is 27 wt% or more to less than 29 wt%, and the high-chromium cast iron alloy subjected to the third heat treatment has a corrosion current density within a reference range with respect to the high-chromium cast iron alloy, which is defined as having the third heat treatment omitted. Claim 8 A method for manufacturing a high-chromium cast iron alloy according to claim 1, including one used in an impeller of a desulfurization facility in a thermal power plant. Claim 9 A high-chromium cast iron alloy comprising more than 3.5 vol% and less than 23.1 vol% of an austenite phase, having a hardness of more than 50 HRC and less than 57 HRC, and having an impact absorption energy of more than 2.5 J and less than 3 J. Claim 10 In claim 9, a high-chromium cast iron alloy containing 29 wt% or more and less than 31 wt% chromium. Claim 11 A high-chromium cast iron alloy, wherein the third heat treatment step is omitted in comparison to a reference alloy manufactured by a method for manufacturing a high-chromium cast iron alloy comprising a first heat treatment step of an alloy raw material containing chromium, a second heat treatment step of being performed at a temperature higher than the first heat treatment step, and a third heat treatment step of being performed at a temperature lower than the second heat treatment step, and wherein the high-chromium cast iron alloy comprises having a higher range of shock absorption energy compared to the reference alloy. Claim 12 A high-chromium cast iron alloy according to claim 11, comprising having a corrosion current density in a lower range compared to the reference alloy. Claim 13 A high-chromium cast iron alloy according to claim 11, comprising 29 wt% or more and less than 33 wt% chromium. Claim 14 A high-chromium cast iron alloy according to claim 11, including one used in the impeller of a desulfurization facility in a thermal power plant.

Images