Composite die pipe and die assembling method for reducing scorch rate and inclusion content of high-temperature alloy

Abstract

The application provides a composite die pipe for reducing the hot face rate and inclusion content of a high-temperature alloy and a die assembling method. The composite die pipe comprises an outer die pipe and an inner die pipe, and the outer die pipe and the inner die pipe are integrally formed. The outer wall of the inner die pipe is tightly combined with the inner wall of the outer die pipe. The top end of the inner die pipe is flush with the top end of the outer die pipe. The height of the outer die pipe is greater than the height of the inner die pipe. During die assembling, the inner die pipe is sleeved outside a heat preservation riser, and then a nickel foil paper is tightly placed around the inner die pipe by being wound into a circle. Then, a graphite bottom pad is embedded into the lower end of the outer die pipe. Finally, the inner wall of the outer die pipe is tightly combined with the outer wall of the inner die pipe to complete the die assembling, and the riser is covered by an aluminum foil paper. The application is simple and convenient to operate, can reduce the hot face rate and inclusion content of the master alloy, and effectively improves the yield rate and purification level of the high-temperature alloy master alloy.

Description

Technical Field

[0001] This invention belongs to the field of casting high-temperature alloy smelting technology, specifically relating to a composite mold tube and a method for reducing the hot wall rate and inclusion content of high-temperature alloys. Background Technology

[0002] Cast high-temperature alloys are alloys designed for long-term service at temperatures above 600℃ and under certain stress conditions. They possess excellent high-temperature strength, superior creep resistance, corrosion resistance, and oxidation resistance, and are primarily used in the manufacture of hot-end components for aero engines and gas turbines. Currently, a problem exists during the casting process of high-temperature alloys: wall scorching. This phenomenon severely affects the yield of the alloy. Because the molten alloy melts the 45 steel mold tube during wall scorching, the iron content at the scorched area is high. Even with grinding treatment, the adverse effects of excessive iron content cannot be completely eliminated.

[0003] In existing mold assembly methods, the mold tube is a hollow cylinder made of 45 steel, with an inner diameter of 50-140mm, a height of 700-1400mm, and a wall thickness of 15-20mm. During mold assembly, a graphite base is first placed at the lower end of the mold tube, and then the insulating riser is placed at the upper end to complete the assembly. During alloy pouring, the following two situations can cause scalding of the alloy ingot to varying degrees: First, the alloy liquid column is tilted due to the inclination of the spout in the chute; second, the alloy liquid column is dispersed due to an excessively long pouring distance. A tilted liquid column causes the alloy liquid to continuously scour a portion of the mold tube, resulting in partial melting of that part and scalding. Dispersion of the alloy liquid column causes the alloy liquid to contact the mold tube prematurely, resulting in partial melting of the mold tube and scalding.

[0004] Hot-wall defects reduce the yield of finished alloys, significantly increasing smelting costs. Therefore, developing a novel mold tube and assembly method to reduce the hot-wall defect rate of high-temperature alloys is of great engineering significance. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a composite mold tube and assembly method for reducing the wall scorching rate and inclusion content of high-temperature alloys. Using the assembly method and composite mold tube of this invention, the inclined liquid column first contacts the nickel foil, preventing melting of the mold tube wall. Even if partial melting occurs, the inner mold tube is made of pure nickel, and the cast high-temperature alloy is a nickel-based high-temperature alloy with a high nickel content; therefore, partial melting of the tube wall will not significantly affect the alloy's chemical composition. Thus, using this composite mold tube and assembly method not only reduces wall scorching but also avoids the introduction of iron impurities into the alloy.

[0006] To achieve the above technical objectives, the technical solution adopted in the embodiments of the present invention is as follows:

[0007] On one hand, embodiments of the present invention provide a composite mold tube for reducing the hot wall rate and inclusion content of high-temperature alloys, comprising an outer mold tube and an inner mold tube, both of which are integrally formed, the outer wall of the inner mold tube being tightly fitted to the inner wall of the outer mold tube, the top end of the inner mold tube being flush with the top end of the outer mold tube, and the height of the outer mold tube being greater than the height of the inner mold tube.

[0008] Furthermore, both the outer mold tube and the inner mold tube are hollow cylinders, wherein the wall thickness of the outer mold tube is 15-20mm and the wall thickness of the inner mold tube is 5-10mm.

[0009] Furthermore, the length of the outer mold tube is 700-1400mm;

[0010] The height difference H1-H2 between the outer mold tube and the inner mold tube is 15-50mm, wherein the height of the outer mold tube is H1 and the height of the inner mold tube is H2.

[0011] Furthermore, the outer mold tube is made of 45 steel, and the inner mold tube is made of pure nickel.

[0012] On the other hand, embodiments of the present invention provide a method for assembling a composite mold tube to reduce the hot-wall rate and inclusion content of high-temperature alloys, comprising the following steps:

[0013] Step S1: Place the inner mold tube over the outside of the insulation riser and blow it clean;

[0014] Step S2: Roll the nickel foil into a circle and place it tightly against the inner wall of the inner mold tube, then blow it clean.

[0015] Step S3: Place the graphite base pad at the bottom of the outer mold tube and blow it clean;

[0016] Step S4: Fit the inner wall of the outer mold tube with the outer wall of the inner mold tube, ensuring that the top of the inner mold tube is flush with the top of the outer mold tube, and then blow it clean.

[0017] Step S5: Cover the riser with aluminum foil.

[0018] Furthermore, the thickness of the graphite base pad is 15-50mm, and the thickness of the graphite base pad is equal to the height difference H1-H2 between the outer mold tube and the inner mold tube.

[0019] Furthermore, the high-temperature alloy is a nickel-based high-temperature alloy.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] In traditional mold assembly methods, during alloy casting, tilting of the liquid column can cause the molten alloy to continuously scour a portion of the 45 steel mold tube, or dispersion of the molten alloy column can cause the molten alloy to come into premature contact with the mold tube, resulting in partial melting of the mold tube and the phenomenon of hot-wall melting. This results in an excessively high iron content in the alloy chemical composition at the hot-walled area.

[0022] Using the molding method and composite mold tube of this invention, the liquid column, when tilted or dispersed, first contacts the nickel foil, preventing melting of the mold tube wall. Even if partial melting occurs, the inner mold tube is made of pure nickel, and the cast high-temperature alloy is a nickel-based high-temperature alloy with a high nickel content. Therefore, partial melting of the tube wall will not significantly affect the alloy's chemical composition. Thus, using this composite mold tube and molding method not only reduces wall scalding but also avoids the introduction of iron impurities into the alloy.

[0023] During alloy casting, splashing of liquid droplets in the chute and dust in the air can introduce inclusions into the alloy. The mold assembly method of this invention avoids the detachment of refractory material during the matching of riser and mold tube, reduces the content of inclusions in the alloy, and the aluminum foil on the riser can effectively block the introduction of alloy liquid splashes and dust in the air, effectively reducing the inclusion content of high-temperature alloy ingots and improving the purity level of cast high-temperature alloys. Attached Figure Description

[0024] Figure 1 This is a cross-sectional structural diagram of the composite mold tube of the present invention.

[0025] Explanation of reference numerals in the attached diagram: 1-Aluminum foil; 2-Insulating riser; 3-Outer mold tube; 4-Inner mold tube; 5-Nickel foil; 6-Graphite base. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0027] Example 1

[0028] like Figure 1 As shown, a composite mold tube for reducing the hot wall rate and inclusion content of high-temperature alloys includes an outer mold tube 3 and an inner mold tube 4, wherein the outer mold tube 3 and the inner mold tube 4 are integrally formed, the outer wall of the inner mold tube 4 is tightly fitted with the inner wall of the outer mold tube 3, the top end of the inner mold tube 4 is flush with the top end of the outer mold tube 3, and the height of the outer mold tube 3 is greater than the height of the inner mold tube 4.

[0029] Specifically, the height of the outer mold tube 3 is 1200 mm, and the height of the inner mold tube 4 is 1180 mm.

[0030] The outer mold tube 3 has a wall thickness of 15mm, and the inner mold tube 4 has a wall thickness of 10mm.

[0031] The outer mold tube 3 is made of 45 steel, and the inner mold tube 4 is made of pure nickel.

[0032] The above-mentioned method for assembling composite mold tubes to reduce the hot wall rate and inclusion content of high-temperature alloys includes the following steps:

[0033] Step S1: Place the inner mold tube 4 over the outside of the insulation riser 2 and blow it clean;

[0034] Step S2: Roll the nickel foil paper 5 into a circle and place it tightly against the inner wall of the inner mold tube 4, then blow it clean.

[0035] Step S3: Place the graphite base pad 6 at the bottom of the outer mold tube 3 and blow it clean. The diameter of the graphite base pad 6 is equal to the inner diameter of the outer mold tube 3.

[0036] Step S4: Fit the inner wall of the outer mold tube 3 with the outer wall of the inner mold tube 4, ensuring that the top of the inner mold tube 4 is flush with the top of the outer mold tube 3, and then blow it clean.

[0037] Step S5: Cover the riser with aluminum foil 1.

[0038] When assembling the mold, the lower end of the insulation riser 2 is 100mm long, and direct pouring is used during casting.

[0039] The thickness of the graphite base 6 is 20mm, and the thickness of the graphite base 6 is equal to the height difference H1-H2 between the outer mold tube 3 and the inner mold tube 4.

[0040] The mold is baked at 500±100℃ for more than 2 hours, and then cooled to 200±100℃ before being placed in the ingot mold chamber of the melting furnace for casting.

[0041] Comparative Example 1

[0042] The mold tube used in the traditional mold assembly method is a hollow cylinder with an inner diameter of 80mm, a height of 1200mm, a wall thickness of 25mm, and is made of 45 steel.

[0043] When assembling the mold, first place the graphite base pad at the bottom of the mold tube, and then place the insulating riser at the top of the mold tube.

[0044] When assembling the mold, the lower end of the insulating riser is 100mm long. Direct pouring is used during casting, and the molten alloy comes into direct contact with the mold tube.

[0045] The thickness of the graphite base 4 is 20 mm.

[0046] The mold is baked at 500±100℃ for more than 2 hours, and then cooled to 200±100℃ before being placed in the ingot mold chamber of the melting furnace for casting.

[0047] The inclusion levels of the alloys prepared using the above method are shown in the table below:

[0048] Table 1. Comparison of alloy inclusion grades obtained after molding of the mold tube assembly in Comparative Example 1 and Example 1

[0049]

[0050] As shown in Table 1, the hot wall ratio and inclusion content of the high-temperature alloy master alloy cast using the composite mold tube and mold assembly method in Example 1 of the present invention are both lower than those in Comparative Example 1, indicating that the present invention can effectively reduce the hot wall ratio and inclusion content of high-temperature alloys and improve the alloy yield and purity level.

[0051] In Comparative Example 1, the mold tube is a hollow cylinder made of 45 steel. During the alloy pouring process, the alloy liquid column is deflected, causing the alloy liquid to continuously wash over a part of the 45 steel mold tube. This results in partial melting of that part of the mold tube, causing a scalding phenomenon, and resulting in an excessively high iron content in the alloy chemical composition at the scalded area. In addition, the traditional mold assembly method disperses the alloy liquid column, causing the alloy liquid to come into contact with the mold tube prematurely, leading to partial melting of the mold tube and the scalding phenomenon.

[0052] The composite mold tube in this embodiment of the invention includes an outer mold tube and an inner mold tube, both integrally formed. The outer wall of the inner mold tube is tightly fitted to the inner wall of the outer mold tube. The outer mold tube is made of 45 steel, and the inner mold tube is made of pure nickel. Compared to traditional mold tubes, because the inner mold tube is made of pure nickel, and the cast high-temperature alloy is a nickel-based high-temperature alloy with a high nickel content, the melting of the tube wall will not have a significant impact on the chemical composition of the alloy.

[0053] Using the molding method and composite mold tube of this invention, the liquid column first contacts the nickel foil, preventing the mold tube wall from melting. Even if the wall partially melts, it will not significantly affect the chemical composition of the alloy. Therefore, using this composite mold tube and molding method can not only reduce wall scalding but also avoid the introduction of iron impurities into the alloy.

[0054] Using pure nickel mold tubes would greatly increase costs, while the composite mold tubes used in this invention can not only reduce costs, but also reduce the hot wall rate and inclusion content of nickel-based high-temperature alloys when combined with the mold assembly method.

[0055] It should be noted that the composite mold tube and the mold assembly method of this application can also be applied to other metal-based high-temperature alloys. When the main metal elements of the high-temperature alloy are the same as the metal elements of the inner mold tube in the composite mold tube, and foil with the same composition as the inner mold tube is used during mold assembly, similar technical effects can be achieved.

[0056] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A composite mold tube for reducing the hot-wall rate and inclusion content of high-temperature alloys, characterized in that, It includes an outer mold tube (3) and an inner mold tube (4), both of which are integrally formed. The outer wall of the inner mold tube (4) is closely fitted with the inner wall of the outer mold tube (3). The top end of the inner mold tube (4) is flush with the top end of the outer mold tube (3). The height H1 of the outer mold tube (3) is greater than the height H2 of the inner mold tube (4). The height H1 of the outer mold tube (3) is 700-1400mm; the height difference H1-H2 between the outer mold tube (3) and the inner mold tube (4) is 15-50mm; The height difference H1-H2 between the outer mold tube (3) and the inner mold tube (4) is equal to the thickness of the graphite base pad (6). The graphite base pad (6) is placed at the bottom of the outer mold tube (3). The diameter of the graphite base pad (6) is equal to the inner diameter of the outer mold tube (3). The main metal elements of the high-temperature alloy are the same as those of the inner mold tube in the composite mold tube, and the foil with the same composition as the inner mold tube (4) is used when assembling the mold.

2. The composite mold tube for reducing the hot-wall rate and inclusion content of high-temperature alloys according to claim 1, characterized in that, Both the outer mold tube (3) and the inner mold tube (4) are hollow cylinders, wherein the wall thickness of the outer mold tube (3) is 15-20mm and the wall thickness of the inner mold tube (4) is 5-10mm.

3. The composite mold tube for reducing the hot-wall ratio and inclusion content of high-temperature alloys according to claim 1, characterized in that, The outer mold tube (3) is made of 45 steel, and the inner mold tube (4) is made of pure nickel.

4. The method for assembling a composite mold tube to reduce the hot-wall ratio and inclusion content of high-temperature alloys according to any one of claims 1-3, characterized in that, Includes the following steps: Step S1: Place the inner mold tube (4) over the outside of the insulation riser (2) and blow it clean; Step S2: Roll the nickel foil (5) into a circle and place it tightly against the inner wall of the inner mold tube (4), and blow it clean. Step S3: Place the graphite base pad (6) at the bottom of the outer mold tube (3) and blow it clean; Step S4: Fit the inner wall of the outer mold tube (3) with the outer wall of the inner mold tube (4) to ensure that the top end of the inner mold tube (4) is flush with the top end of the outer mold tube (3), and blow it clean. Step S5: Cover the riser with aluminum foil (1).

5. The method for assembling a composite mold tube to reduce the hot-wall rate and inclusion content of high-temperature alloys according to claim 4, characterized in that, The thickness of the graphite base (6) is 15-50 mm.

6. The method for assembling a composite mold tube to reduce the hot-wall rate and inclusion content of high-temperature alloys according to claim 4, characterized in that, The high-temperature alloy is a nickel-based high-temperature alloy.

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