TW202022126A - Nickel-based austenitic alloy and method of forming the same - Google Patents

Abstract

The present invention is related to nickel-based austenitic alloy and a method of forming the same. In the method, an alloy billet having a specific composition is processed to achieve specific compression ratio, so as to form the nickel-based austenitic alloy having sufficient strength and elongation under a high temperature.

Description

Nickel base water field iron series alloy and manufacturing method thereof

The present invention relates to a nickel-baseworthy iron-based alloy and a manufacturing method thereof, and particularly relates to a nickel-baseworthy iron-based alloy with a specific composition, which is processed by a deformation process with a specific compression ratio Made.

Common austenitic iron alloys include nickel-based superalloys (such as Alloy 800H, 825 and Nimonic 80) and 300 series stainless steels (such as 310 and 316 stainless steel). Due to the addition of sufficient nickel, the main structure of the above alloy is a face-centered cubic austenitic iron phase. In addition, in order to make the alloy have sufficient strength at high temperatures to be used in high temperature bearing environments, titanium is often added to the alloy. For example: Alloy 800H generally adds 0.15 weight percent (wt.%) to 0.6wt.% of titanium to form a precipitated phase with strengthening effect. The above-mentioned alloys are often used in applications requiring high-temperature mechanical properties, such as engine components, turbine engine fasteners, high-temperature bearings, heating furnace covers, and so on.

However, when the strength of the alloy increases, the ductility will decrease. Therefore, the performance of the strength and ductility of the alloy can be regarded as a typical trade-off property. That is, alloys with higher strength generally have lower extension Malleability, this property limits the processing and application range of the alloy at high temperatures. For example, when performing processing processes such as forging, rolling, or extrusion of austenitic alloys at high temperatures, the decrease in ductility often results in cracking of the alloy. Generally speaking, the elongation of metal materials does not exceed 90%, and the elongation of high-strength alloys is usually only 50% to 80%. Therefore, if an alloy with low ductility is applied at high temperature, it is prone to sudden fracture or reduced service life, which affects its applicability and application range.

In view of the above-mentioned various problems, there is an urgent need to propose a nickel-baseworth field iron-based alloy, which can have both good strength and ductility, so as to expand the applicable range.

Therefore, one aspect of the present invention is to provide a method for manufacturing a nickel-baseworth iron-based alloy. In some embodiments, this manufacturing method first provides an alloy blank comprising the following composition: 2 weight percent (wt.%) to 4.5wt.% molybdenum, 0.5wt.% to 1.5wt.% titanium, 0.02wt. % To 0.08wt.% carbon, 30wt.% to 54wt.% nickel, 15wt.% to 25wt.% chromium, 1.0wt.% to 3.5wt.% copper, less than or equal to 1.0wt.% silicon , Other elements less than 3wt.%, and the balance of iron. Next, a forging step is performed on the alloy blank to form a forged material. Then, the forged material is deformed and processed to form a processed material. Next, a heat treatment step is performed on the processed material to obtain a nickel-based Wust iron-based alloy.

According to some embodiments of the present invention, after the forging step and the deformation processing process, the processed material has a compression ratio of at least 9 relative to the alloy blank.

According to some embodiments of the present invention, the deformation processing process includes Hot rolling step, cold rolling step, wire drawing step and/or pipe threading step.

According to some embodiments of the present invention, the hot rolling step is performed at 950°C to 1250°C.

According to some embodiments of the present invention, the heat treatment step is performed at 920°C to 1100°C.

According to some embodiments of the present invention, the heat treatment step is performed for 3 minutes to 120 minutes.

According to some embodiments of the present invention, after the heat treatment step, the manufacturing method further includes a cooling step.

According to some embodiments of the present invention, the other elements include one or more of manganese, aluminum, niobium, and tungsten.

According to some embodiments of the present invention, the step of providing the alloy blank includes performing a fuel heating furnace smelting step or a non-vacuum electric furnace smelting step to form an ingot; and performing an argon oxygen blowing and denitrification step on the ingot to obtain an alloy Embryo.

According to some embodiments of the present invention, the step of providing alloy blanks includes performing a vacuum induction melting furnace smelting step or a vacuum arc melting furnace smelting step to obtain an ingot; and performing a vacuum oxygen blowing and decarburization step on the ingot and electroslag Remelting step or vacuum arc remelting step to obtain alloy blanks.

Another aspect of the present invention is to provide a nickel-based austenitic iron-based alloy, which is produced by using the above-mentioned nickel-based austenitic iron-based alloy manufacturing method. At a temperature of 600° C. to 900° C., the Ni-based Wust iron alloy has a tensile strength of at least 115 MPa, a yield strength of at least 65 MPa, and an elongation of at least 45%.

100‧‧‧Method

110‧‧‧Provide alloy blanks

120‧‧‧Forging the alloy blank to form a forged material

130‧‧‧Deformation process for forging materials to form processed materials

140‧‧‧Heat treatment of the processed material to obtain a nickel-based Wust iron alloy

601, 602‧‧‧ circle

In order to make the above and other objectives, features, advantages and embodiments of the present invention more comprehensible, the detailed description of the accompanying drawings is as follows: [FIG. 1] is a nickel baseworth according to some embodiments of the present invention Schematic flow chart of the manufacturing method of Tiantie alloy.

[Figure 2] is the tensile strength of Examples 1 to 3 and Comparative Example 1 between 600°C and 900°C.

[Figure 3] shows the yield strength of Examples 1 to 3 and Comparative Example 1 between 600°C and 900°C.

[Figure 4] is the elongation of Examples 1 to 3 and Comparative Example 1 between 600°C and 900°C.

[Fig. 5A] and [Fig. 5B] are the scanning electron micrographs of the Ni-based Wust-based iron alloy of Example 1 at different magnifications.

[Fig. 6A] and [Fig. 6B] are the scanning electron microscope images of the Ni-based Wust-based iron alloy of Comparative Example 1 with different magnifications.

The titanium added to the alloy can form precipitation strengthening phases such as Ti(C, N) and Ni ₃ Ti. Among them, Ti(C,N) can be divided into those produced during the smelting stage and those produced during thermal processing/heat treatment or high-temperature applications. The Ti(C,N) produced in the smelting stage is usually titanium nitride particles with a relatively high nitrogen content, and their size is generally 3.0 μm to 50 μm. Titanium carbide precipitates are usually produced during hot working/heat treatment or high-temperature applications, and their size is generally 0.01 μm to 5.0 μm, and such titanium carbide precipitates contribute a lot to the improvement of creep resistance.

Generally speaking, increasing the amount of titanium added can enhance the precipitation effect of titanium carbide, thereby increasing the high temperature strength and high temperature creep resistance of the alloy. In addition, molybdenum with a larger atomic radius can also be added, which can be dissolved in the austenitic iron phase base, and can improve the corrosion resistance of the alloy in the reducing environment, and has the effect of solid solution strengthening to increase the high temperature of the alloy strength. Furthermore, addition of carbon in the alloy increases the M ₂₃ C ₆ phase precipitation strengthening tendency was precipitated M ₂₃ C ₆ and this strengthening phase precipitation occurred was also hinder precipitation strengthening effect of slip dislocations, it may increase the alloy High temperature strength. However, the M ₂₃ C ₆ strengthening phase precipitates can cause corrosion-resistant elements such as chromium or molybdenum to accumulate, especially on the grain boundaries, causing a depleted zone in a local area of the alloy, resulting in sensitization, For example, poor corrosion resistance) occurs.

Therefore, one aspect of the present invention is to provide a nickel-baseworthy steel alloy having both high-temperature strength and ductility and a manufacturing method thereof. In some embodiments, by adjusting the composition of the alloy blank, the amount of deformation (or compression ratio), and the process parameters of the heat treatment step, the Ni-based Wust iron-based alloy has an appropriate grain size, and the grains have Sufficient differential displacement and dispersed strengthening phase precipitates enable this Ni-based Wust-based iron alloy to have both high temperature strength and ductility.

The compression ratio referred to here is the ratio of the size of the alloy blank to the size of the processed material after processing, where the size referred to can be, for example, diameter or thickness.

The high-temperature strength referred to here can be expressed by tensile strength (TS) and yield strength (YS).

The high temperature ductility referred to here can be expressed by elongation (EL).

Fig. 1 is a schematic flow chart of a method for manufacturing a nickel-baseworth iron-based alloy according to some embodiments of the present invention. In the method 100 of FIG. 1, first, in step 110, an alloy blank having the following composition is provided: 2 weight percent (wt.%) to 4.5wt.% molybdenum, 0.5wt.% to 1.5wt.% titanium, 0.02wt.% to 0.08wt.% carbon, 30wt.% to 54wt.% nickel, 15wt.% to 25wt.% chromium, 1.0wt.% to 3.5wt.% copper, less than or equal to 1.0wt.%. % Silicon, less than 3wt.% other elements, and the balance iron.

The molybdenum and titanium in the above-mentioned alloy blanks can form MC (M is mainly molybdenum or titanium) or M ₂₃ C ₆ (M is mainly chromium, iron, molybdenum) strengthening phase precipitates with carbon, which helps to improve the nickel baseworth The strength of Tian iron alloy. However, too much molybdenum and titanium will reduce the ductility of the Ni-based Watts iron-based alloy, resulting in the Ni-based Watts iron-based alloy is easy to crack or reduce service life.

The carbon in the above-mentioned alloy blank can strengthen the strength of the nickel-based alloy. Therefore, if the carbon content is less than 0.02wt.%, the strength of the nickel-based austenitic alloy is not good. However, if the carbon content is greater than 0.08 wt.%, the brittleness of the Ni-based Wust iron alloy increases and the ductility deteriorates. In addition, too high carbon content can also easily aggregate solid-solution metals, forming solute-deficient areas and causing alloy sensitization (that is, insufficient corrosion resistance).

The chromium in the alloy blank can increase the corrosion resistance of the Ni-based Wust iron-based alloy. If the above-mentioned chromium content is less than 15wt.%, the obtained Ni-based Wust iron-based alloy will be resistant to corrosion. Poor corrosiveness.

The copper in the alloy blank can be used to replace nickel as an element for stabilizing the austenitic iron phase, and the cost of copper is lower than that of nickel. However, if the copper content in the alloy blank is too high, the processability of the alloy blank will be poor.

The silicon in the alloy blank can improve the oxidation resistance of the alloy blank. However, if too much silicon is contained in the alloy blank, coarse inclusions will be formed, which will not only lead to poor workability, but also make the austenitic iron phase unstable.

The above-mentioned other elements may, for example, include one or more of manganese, aluminum, niobium and tungsten, which are also precipitation strengthening elements, which can further improve the strength of the Ni-based Wust iron alloy. Too much of these elements also has the problem of insufficient ductility of Ni-based Wust iron alloys.

In some embodiments, the alloy blank can be prepared by, for example, a vacuum or non-vacuum melting process, optionally with a refining process, and casting. The vacuum melting process can be performed by, for example, a vacuum inducting melting (VIM) or a vacuum arc melting (VAM). The non-vacuum melting process may be, for example, fuel heating furnace melting or non-vacuum electric arc furnace (EAF) melting. The refining process may include argon oxygen decarburization (AOD), vacuum oxygen decarburization (VOD), electroslag remelting (ESR), or vacuum arc remelting (vacuum arc remelting). ; VAR). In the above refining process, argon gas can be introduced to protect the alloy material to avoid excessive oxidation or nitridation, so as to improve the quality of the alloy blank. In some embodiments, the alloy blank may be surface treated after casting. For example: depending on the surface condition of the alloy blank, it can be cut, ground, peeled and other surface finishing To ensure the surface quality of the alloy blank.

In some examples, the alloy material may be first subjected to a fuel heating furnace smelting step or a non-vacuum electric furnace smelting step to form an ingot. And then the argon blowing oxygen denitrification step is obtained.

In some examples, the alloy material can be first subjected to a vacuum induction melting furnace melting step or a vacuum arc melting furnace melting step to form an ingot. And then it is obtained by vacuum oxygen blowing decarburization step, electroslag remelting step or vacuum arc remelting step.

Next, as shown in step 120, a forging step is performed on the alloy blank to form a forged material. In some embodiments, relative to the alloy blank, the forged material may have a compression ratio of about 3, but the present invention is not limited thereto. The compression ratio in the forging step can be adjusted according to factors such as the specifications of the finished product and the specifications of the forging machinery. In some examples, the forged material may be, for example, a small square blank. In other examples, the forged material may be, for example, a flat blank.

Then, as shown in step 130, a deformation processing process is performed on the forged material to form a processed material. In some embodiments, the total deformation (or compression ratio) performed in the two stages of the forging step and the deformation processing process is at least 9. Preferably, the compression ratio may be greater than 50. When the compression ratio is less than 9, the material is prone to void defects or solute segregation, which reduces the mechanical properties of the material. A sufficient reduction ratio can refine the grains and make the strengthening phase precipitates uniformly distributed in the grains instead of aggregation On the grain boundary, the effect of increasing strength is achieved.

Specifically, the method of the present invention uses the aforementioned specific alloy blank composition and a specific compression ratio to generate sufficient displacement in the grains of the Ni-based Wust iron alloy to make the fine MC or M ₂₃ C ₆ Such strengthening phase precipitates are easy to generate inside the grains, rather than forming large precipitates on the grain boundaries. These strengthening phase precipitates can effectively contain the difference and provide a strengthening effect. Titanium in the solid solution state can also reduce the cross slip of the stacking fault energy by reducing the stacking fault energy, so as to inhibit the occurrence of recovery, thereby enhancing the driving force for dynamic recrystallization. . Furthermore, because molybdenum has a large atomic radius, a low diffusion coefficient and a significant solid solution strengthening effect, it is easy to cause the differential row to be affected by the solute drag effect, and it can also suppress the occurrence of recovery.

In summary, the addition of titanium and molybdenum allows the alloy blank to accumulate sufficient displacement density and strain energy during high temperature deformation (such as forging steps) to drive dynamic recrystallization. The strain-free grains produced by dynamic recrystallization can survive the extension and deformation (such as deformation processing process), and avoid rapid accumulation on the grain boundaries, so it can improve the Ni-based Wust iron alloy Malleability. Furthermore, a sufficient compression ratio can produce precipitation strengthening phases dispersed in the crystal grains to increase the strength of the alloy and maintain the ductility of the alloy.

In some embodiments, the deformation processing process may include a hot rolling step, a cold rolling step, a wire drawing step, and/or a pipe threading step. In some examples, the hot rolling step may be performed at 950°C to 1250°C, for example. Alternatively, the cold rolling step may be performed after the hot rolling step. In some examples, the total compression ratio of the hot rolling step and the cold rolling step may be, for example, about 75, but the present invention is not limited to this value.

In some embodiments, when the aforementioned forged material is a flat blank, the aforementioned hot rolling step and cold rolling step may be performed to form a processed plate. In other embodiments, when the aforementioned forged material is a small square blank, hot rolling can be selectively performed Step and cold rolling step, followed by a wire drawing step to form a processed wire. In still other embodiments, when the aforementioned forged material is a small square blank, the hot rolling step and the cold rolling step may be selectively performed, and then the pipe threading step may be performed to form a processed pipe. Therefore, the manufacturing method of the present invention is suitable for the process of forming various alloy plates, coils, rods, wires, tubes and other products to facilitate various types of industrial applications.

Next, as shown in step 140, a heat treatment step is performed on the processed material to obtain a nickel-based Wust iron-based alloy. This heat treatment step can be performed, for example, at 920°C to 1100°C. In some embodiments, this heat treatment step can be performed for 3 minutes to 120 minutes. When the temperature of this heat treatment step is lower than 920°C or the time is less than 3 minutes, the internal stress of the nickel-based austenitic alloy cannot be properly eliminated, resulting in insufficient ductility of the nickel-based austenitic alloy. However, when the temperature of this heat treatment step is higher than 1100°C or the time is longer than 120 minutes, the grains of the Ni-based Wust iron alloy grow excessively, resulting in a substantial increase in ductility but insufficient strength. In fact, the temperature and holding time of this heat treatment step can prevent a large amount of solid solution of the aforementioned strengthening phase precipitates, so that the Ni-based Wust iron alloy can have both strength and ductility. In other words, the manufacturing method of the present invention excludes high-temperature solution treatment.

In some embodiments, a cooling step may be performed after the heat treatment step. In some examples, this cooling step can be water cooling or air cooling.

In some embodiments, at a temperature of 600° C. to 900° C., the Ni-based Wust steel alloy has a tensile strength of at least 115 MPa, a yield strength of at least 65 MPa, and an elongation of at least 45%. In some examples, the nickel-baseworthy iron-based alloy may have an average grain size of 20 μm to 55 μm.

The following examples and comparative examples are used to illustrate the implementation and efficacy of the manufacturing method of the nickel-baseworth iron-based alloy of the present invention.

Example 1

First, a non-vacuum electric furnace smelting and argon blowing and oxygen decarburization steps are used to obtain alloy blanks with the composition shown in Table 1. The diameter of this alloy blank is 450mm. Next, a forging step is performed to forge this alloy blank into a flat blank with a thickness of 150 mm. Then, at 920°C, the flat blank was hot rolled to a thickness of 6 mm. After that, the hot rolled flat blank was cold rolled to a thickness of 2 mm. The compression ratio of this alloy billet is 225 (calculated from the original diameter (or thickness) of the alloy billet 450mm/the thickness of the cold rolled flat billet 2mm). Then, a heat treatment step was performed at 980° C. for 7 minutes and water-cooled to obtain the nickel-based Wust iron-based alloy of Example 1. Please refer to Table 2, Table 3, Figs. 2 to 4, Fig. 5A and Fig. 5B for the evaluation results of the nickel-baseworth iron-based alloy of Example 1.

Examples 2 to 3 and Comparative Example 1

Examples 2 to 3 and Comparative Example 1 were performed in the same manner as Example 1. The difference is that Examples 2 to 3 and Comparative Example 1 change the composition of the alloy blanks. Table 1 shows the composition of the alloy blanks of the respective examples and comparative examples. Please refer to Table 2, Table 3, Figs. 2 to 4, Fig. 6A and Fig. 6B for the evaluation results of the nickel-baseworth iron-based alloys of Examples 2 to 3 and Comparative Example 1.

Please refer to Figures 2 and 3, which show the tensile strength and yield strength of Examples 1 to 3 and Comparative Example 1 between 600°C and 900°C, respectively. It can be seen from Fig. 2 and Fig. 3 that when the alloy blank contains a certain amount of molybdenum and titanium, the obtained Ni-based Wust iron alloy can have good high temperature strength. Furthermore, as shown in Fig. 4, at 600°C to 900°C, the Ni-based Wust iron-based alloy of Examples 1 to 3 has sufficient elongation. On the other hand, the tensile strength, blessing strength, and elongation of Comparative Example 1 did not perform well in the above-mentioned temperature range.

Please refer to Table 2 again. At a lower fixed temperature, the Ni-based Wust iron-based alloys of Examples 1 to 3 clearly have better strength and elongation than Comparative Example 1. Specifically, at 650°C, the nickel baseworth of Examples 1 to 3 The iron-based alloy can reach a tensile strength of at least 445MPa, a yield strength of at least 185MPa, and an elongation of at least 45%.

Please refer to Table 3 again. Even at a higher fixed temperature, the strength of Examples 1 to 3 is still comparable to that of Comparative Example 1, but the elongation of Examples 1 to 3 is much better than that of Comparative Example 1, especially Example 1 at 900°C The elongation rate of the product exceeds 170%, which is 2.2 times that of Comparative Example 1. Specifically, at 900° C., the Ni-based Wust iron-based alloys of Examples 1 to 3 may have a tensile strength of at least 110 MPa, a yield strength of at least 65 MPa, and an elongation of at least 95%.

Obviously, through a specific alloy blank composition and a specific compression ratio, it is enough to make the Ni-based Wust iron alloy have smaller grains and higher differential density, so it can have both strength and ductility.

Please refer to FIG. 5A and FIG. 5B, which are scanning electron microscope images of the Ni-based Wust iron alloy of Example 1 at different magnifications. As shown in FIG. 5A and FIG. 5B, the grain size of the nickel-baseworth iron-based alloy of Example 1 is about 42 μm. In addition, the austenitic iron phase base of this nickel base austenitic alloy has a fine strengthening phase MC (M mainly Ti or Mo) and M ₂₃ C ₆ (M mainly chromium, iron, molybdenum) distribution, Therefore, the Ni-based Wust iron-based alloy of Example 1 can have both strength and ductility. Examples 2 to 3 have similar situations.

On the other hand, please refer to FIG. 6A and FIG. 6B, which are scanning electron microscope images of the Ni-based Wust iron alloy of Comparative Example 1 with different magnifications. Since the addition amount of molybdenum and titanium in Comparative Example 1 is relatively low, the number of precipitates shown in circle 601 in FIG. 6A and circle 602 in FIG. 6B can be found less. In addition, the crystal grain size of Comparative Example 1 is also relatively large (about 62 μm). Therefore, the Ni-based Wust iron-based alloy of Comparative Example 1 cannot have both strength and ductility.

By applying the nickel-based Wostfield iron-based alloy and its manufacturing method of the present invention, a nickel-based alloy with high-temperature strength and ductility can be prepared by being composed of specific alloy blanks and having a large processing deformation (or compression ratio). Austenitic iron alloy.

Although the present invention has been disclosed as above in the embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the technical field to which the present invention belongs can make various changes without departing from the spirit and scope of the present invention. Retouching, therefore, the protection scope of the present invention shall be subject to the scope defined in the appended patent application.

100‧‧‧Method

110‧‧‧Provide alloy blanks

120‧‧‧Forging the alloy blank to form a forged material

130‧‧‧Deformation process for forging materials to form processed materials

140‧‧‧Heat treatment of the processed material to obtain a nickel-based Wust iron alloy

Claims (11)

A method for manufacturing a nickel-based Wust-based iron-based alloy, comprising: providing an alloy blank, comprising: 2 weight percent (wt.%) to 4.5wt.% of molybdenum; 0.5wt.% to 1.5wt.% of titanium; 0.02wt.% to 0.08wt.% carbon; 30wt.% to 54wt.% nickel; 15wt.% to 25wt.% chromium; 1.0wt.% to 3.5wt.% copper; less than or equal to 1.0wt. % Of silicon; less than 3wt.% of other elements; and the balance of iron, perform a forging step on the alloy blank to form a forged material; perform a deformation processing process on the forged material to form a processed material; and The processed material undergoes a heat treatment step to obtain a nickel-based Wust-based iron alloy. As described in the first item of the scope of patent application, the method for manufacturing the nickel-based waterfield iron-based alloy, wherein after the forging step and the deforming process, the processed material has a compression ratio of at least 9 relative to the alloy blank . The manufacturing method of the Ni-based Wust iron-based alloy described in item 1 of the scope of the patent application, wherein the deformation processing process includes a hot rolling step Step, a cold rolling step, a wire drawing step and/or a pipe threading step. As described in the first item of the scope of patent application, the method for manufacturing a nickel-based Wust iron-based alloy, wherein the hot rolling step is performed at 950°C to 1250°C. As described in the first item of the scope of the patent application, the method for manufacturing a nickel-based austenitic iron-based alloy, wherein the heat treatment step is performed at 920°C to 1100°C. According to the method for manufacturing a nickel-based Wust-based iron-based alloy described in item 1 of the scope of patent application, the heat treatment step is performed for 3 minutes to 120 minutes. According to the method for manufacturing a nickel-based austenitic iron-based alloy described in item 1 of the scope of patent application, after the heat treatment step, the manufacturing method further includes a cooling step. According to the method for manufacturing a nickel-based Wattland iron-based alloy described in the first item of the scope of the patent application, the other elements include one or more of manganese, aluminum, niobium and tungsten. As described in the first item of the scope of patent application, the manufacturing method of nickel-based water field iron-based alloy, wherein the step of providing the alloy blank includes: performing a fuel heating furnace smelting step or a non-vacuum electric furnace smelting step Step to form an ingot; and perform an argon blowing and oxygen denitrification step on the ingot to obtain the alloy blank. As described in the first item of the scope of patent application, the manufacturing method of nickel-based water field iron-based alloy, wherein the step of providing the alloy blank includes: performing a melting step in a vacuum induction melting furnace or a melting step in a vacuum arc melting furnace to obtain An ingot; and performing a vacuum oxygen blowing decarburization step, an electroslag remelting step or a vacuum arc remelting step on the ingot to obtain the alloy embryo. A nickel-based water-based iron-based alloy, which is prepared by a method for manufacturing a nickel-based water-based iron-based alloy according to any one of items 1 to 10 in the scope of patent application, wherein the temperature is between 600°C and 900°C , The Ni-based Wust-based iron alloy has a tensile strength of at least 115 MPa, a yield strength of at least 65 MPa, and an elongation of at least 45%.

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