Directional solidification method for improving secondary shrinkage cavity of high-temperature alloy master alloy ingot

Abstract

The invention relates to a directional solidification method for improving a secondary shrinkage cavity of a high-temperature alloy master alloy ingot, which comprises the following steps of: providing a sand box, controlling the depth of the sand box to be (2 / 3 * mold pipe length + / -10) mm, filling steel sand in the sand box, controlling the filling depth of the steel sand to be (2 / 9 * mold pipe length + / -10) mm, filling quartz sand on the steel sand, and controlling the filling depth of the quartz sand to be (2 / 9 * mold pipe length + / -10) mm. The filling depth of the quartz sand is controlled to be (2 / 9 * mold pipe length + / -10) mm; the module is subjected to heat preservation after being baked, the baking temperature is controlled to be 300-600 DEG C, and the heat preservation time is controlled to be 10-60 min; and transferring the module subjected to heat preservation into a steel sand box through a module frame, and pushing the steel sand box and the module into a mold car chamber together, so that subsequent smelting can be carried out. The method can effectively improve and even completely solve the secondary shrinkage problem of the vacuum induction melting high-temperature alloy master alloy ingot, and the implementation cost of the method is relatively low.

Description

Technical Field

[0001] The invention belongs to the technical field of casting high-temperature alloy master alloy smelting, and specifically discloses a directional solidification method for improving secondary shrinkage cavities of high-temperature alloy master alloy ingots. Background Art

[0002] Thanks to its excellent comprehensive properties, high-temperature alloys can work for a long time under high-temperature stress and extreme conditions, and have a wide range of applications. With the expansion of the application range of high-temperature alloys, the quality requirements are becoming more and more stringent. Therefore, the production process of the master alloy is particularly important. The vacuum induction melting of high-temperature alloy master alloys usually adopts the mold casting method. The mold tube material is 45 steel or cast iron. During the pouring process of the master alloy, since the final solidification position is in the middle of the master alloy ingot, the metal liquid cannot be used to compensate for shrinkage, and closed shrinkage cavities will be formed, that is, secondary shrinkage cavities. These shrinkage cavities are usually distributed continuously or discontinuously and are difficult to remove, thus affecting the quality of the master alloy. Ordinary casting methods are difficult to eliminate secondary shrinkage cavities located inside the alloy ingot, which will increase the risk of bringing in impurities when casting castings, resulting in poor fluorescence.

[0003] Directional solidification technology was first established and perfected in the research of high-temperature alloys and has been widely used in industry and high-tech fields. The technology was originally used to eliminate the transverse grain boundaries produced during the crystallization process, thereby improving the unidirectional mechanical properties of the material. The most representative contribution of directional solidification technology is its use in the production of gas turbine engine blades. Almost all advanced military engines use directional solidification single-crystal turbines and guide blades. Directional solidification is a forced solidification process. Its principle is to separate the upper heating zone and the lower cooling zone of the device by an insulation layer, forming a one-dimensional temperature gradient along the axial direction of the casting. The casting is melted and overheated at the top, and forced to cool at the bottom. The solidification interface is located near the insulation baffle, and a unidirectionally arranged solidification structure is obtained by pulling downward.

[0004] Two conditions must be met to achieve directional solidification: (1) the heat flow is in a single direction and perpendicular to the solid-liquid interface during solidification; (2) there is no stable crystallization core in the molten metal in front of the crystal growth. Therefore, the process must avoid lateral heat dissipation of the alloy ingot and form a large temperature gradient in the molten metal near the solid-liquid interface. During the solidification of liquid metal in the mold tube, due to poor shrinkage compensation, holes will form in the last solidified part. The use of directional solidification method can make the solidification shrinkage of each part of the alloy ingot be compensated by liquid metal, thereby transferring the shrinkage hole to the riser above the mold tube. The riser is the redundant part of the alloy ingot, which is convenient for cutting. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a directional solidification method for improving secondary shrinkage cavities of a high-temperature alloy master alloy ingot.

[0006] According to the technical solution provided by the present invention, the directional solidification method for improving the secondary shrinkage cavity of the high-temperature alloy master alloy ingot comprises the following steps:

[0007] S1. Provide a sand box. The bottom size of the sand box is consistent with the bottom size of the module frame. The depth of the sand box is controlled at (2 / 3×mold tube length ± 10) mm. First, fill the sand box with steel sand. The steel sand particle size is 1-8 mm. The filling depth of the steel sand is controlled at (2 / 9×mold tube length ± 10) mm. Then fill the steel sand with quartz sand. The quartz sand particle size is 9-15 mm. The filling depth of the quartz sand is controlled at (2 / 9×mold tube length ± 10) mm.

[0008] S2, assembling the mold tube and the diverter plate to form a module, so that the mold tubes do not contact each other, baking the module and then keeping it warm, the baking temperature is controlled at 300-600°C, and the insulation time is controlled at 10-60min;

[0009] S3. Transfer the mold after insulation to the sand box through the mold frame. The transfer time is controlled within 10 minutes. Insert the mold tube vertically into the steel sand and quartz sand. The bottom end of the mold tube contacts the bottom surface of the sand box. Push the sand box together with the mold into the mold car room for subsequent smelting.

[0010] Preferably, in step S1, the depth of the sand box is 2 / 3 of the length of the mold tube.

[0011] Preferably, in step S1, the filling depth of the steel sand is 2 / 9 of the length of the mold tube.

[0012] Preferably, in step S1, the filling depth of the quartz sand is 2 / 9 of the length of the mold tube.

[0013] Preferably, in step S1, the minimum length of the mold tube is 830 mm.

[0014] Preferably, in step S1, the sand box is a steel sand box.

[0015] The present invention can effectively improve or even completely solve the secondary shrinkage problem of vacuum induction melting high-temperature alloy master alloy ingots, and the implementation cost of the present invention is relatively low. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the shrinkage cavity image on the surface of the alloy ingot obtained in Example 1.

[0017] Figure 2 This is the shrinkage image of the alloy ingot surface obtained in Comparative Example 1.

[0018] Figure 3 This is the shrinkage cavity image on the surface of the alloy ingot obtained in Example 2.

[0019] Figure 4 This is the shrinkage image of the alloy ingot surface obtained in Comparative Example 2.

[0020] Figure 5 This is the shrinkage cavity image on the surface of the alloy ingot obtained in Example 3.

[0021] Figure 6 This is the shrinkage cavity image on the surface of the alloy ingot obtained in Comparative Example 3. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0023] Example 1

[0024] A directional solidification method for improving secondary shrinkage of INCO713C nickel-based superalloy master alloy ingot. The pouring temperature of INCO713C alloy is 1510-1530°C. The specific alloy composition range and measured values ​​of INCO713C nickel-based superalloy are shown in Table 1.

[0025] Table 1

[0026] element C Cr Mo Al Ti B Zr Nb content 0.08～0.20 12.0～14.0 3.8～5.2 5.5～6.5 0.5～1.0 0.005～0.015 0.05～0.15 1.8～2.8 Measured value 0.14 12.77 4.52 6.09 0.74 0.013 0.10 2.36

[0027] A mold tube with an inner diameter of 52.2 mm and a length of 950 mm was selected, and the number of mold tubes was 160.

[0028] The above method specifically comprises the following steps:

[0029] S1. Provide a sand box. The bottom size of the sand box is consistent with the bottom size of the module frame. The depth of the sand box is controlled at 623-643mm. First, fill the sand box with steel sand. The steel sand particle size is 1-8mm. The filling depth of the steel sand is controlled at 201-211mm. Then fill the steel sand with quartz sand. The quartz sand particle size is 9-15mm. The filling depth of the quartz sand is controlled at 201-211mm.

[0030] S2, assembling the mold tube and the diverter plate to form a module, so that the mold tubes do not contact each other, baking the module and then keeping it warm, the baking temperature is controlled at 300-600°C, and the insulation time is controlled at 10-60min;

[0031] S3, the mold group after heat preservation is transferred to the sand box through the mold group frame, the transfer time is controlled within 10 minutes, the mold tube is vertically inserted into the steel sand and quartz sand, the bottom end of the mold tube is in contact with the bottom surface of the sand box, and the sand box and the mold group are pushed into the mold car room, and subsequent smelting can be carried out to obtain INCO713C nickel-based high-temperature alloy master alloy ingot. The surface shrinkage image of the INCO713C nickel-based high-temperature alloy master alloy ingot obtained in Example 1 is shown in FIG. Figure 1 The shrinkage data of the INCO713C nickel-based high-temperature alloy master alloy ingot obtained in Example 1 is shown in Table 2.

[0032] Comparative Example 1

[0033] The conventional mold assembly method and the same process parameters as in Example 1 were used for smelting to obtain an INCO713C nickel-based high-temperature alloy master alloy ingot. The surface shrinkage image of the INCO713C nickel-based high-temperature alloy master alloy ingot obtained in Comparative Example 1 is shown in FIG. Figure 2 The shrinkage data of the INCO713C nickel-based high-temperature alloy master alloy ingot obtained in Comparative Example 1 is shown in Table 2.

[0034] Table 2

[0035] Serial number Maximum shrinkage hole size / mm Shrinkage ratio of the whole alloy ingot Shrinkage distribution Example 1 4.42 34.5％ 29% concentrated in the upper part of the alloy ingot Comparative Example 1 11.27 56.4％ Discontinuously distributed throughout the alloy ingot

[0036] It can be seen from Table 2 that the internal shrinkage cavities of the INCO713C nickel-based high-temperature alloy master alloy ingot are improved from the continuous distribution state of Comparative Example 1 to the point state of Example 1, and the maximum size is improved from the secondary shrinkage cavity of 11.27 mm in Comparative Example 1 to the central secondary shrinkage cavity of no more than 5 mm in Example 1.

[0037] From Table 2 and combined Figure 1 and Figure 2 It can be seen that the smelting test of the master alloy by the process of Example 1 can effectively reduce the secondary shrinkage cavity inside the master alloy ingot, and the position of the secondary shrinkage cavity in the alloy ingot can be moved up or even transferred to the riser under the action of the directional solidification method.

[0038] Example 2

[0039] A directional solidification method for improving secondary shrinkage of K418 nickel-based high-temperature alloy master alloy ingot. The pouring temperature of K418 alloy is 1490-1520°C. The specific alloy composition range and measured values ​​of K418 nickel-based high-temperature alloy are shown in Table 3.

[0040] Table 3

[0041] element C Cr Mo Al Ti B Zr Nb+Ta content 0.08～0.16 12.0～13.5 3.8～4.8 5.5～6.4 0.5～1.0 0.008～0.015 0.06～0.15 1.8～2.8 Measured value 0.14 12.96 4.55 6.05 0.76 0.013 0.1 2.32

[0042] A mold tube with an inner diameter of 52.2 mm and a length of 830 mm was selected, and the number of mold tubes was 160.

[0043] The above method specifically comprises the following steps:

[0044] S1. Provide a sand box. The bottom size of the sand box is consistent with the bottom size of the module frame. The depth of the sand box is controlled at 623-643mm. First, fill the sand box with steel sand. The steel sand particle size is 1-8mm. The filling depth of the steel sand is controlled at 201-211mm. Then fill the steel sand with quartz sand. The quartz sand particle size is 9-15mm. The filling depth of the quartz sand is controlled at 201-211mm.

[0045] S2, assembling the mold tube and the diverter plate to form a module, so that the mold tubes do not contact each other, baking the module and then keeping it warm, the baking temperature is controlled at 300-600°C, and the insulation time is controlled at 10-60min;

[0046] S3, the mold group after the insulation is transferred to the sand box through the mold group frame, the transfer time is controlled within 10 minutes, the mold tube is vertically inserted into the steel sand and quartz sand, the bottom end of the mold tube is in contact with the bottom surface of the sand box, and the sand box and the mold group are pushed into the mold car room, and subsequent smelting can be carried out to obtain K418 nickel-based high-temperature alloy master alloy ingots. The surface shrinkage image of the K418 nickel-based high-temperature alloy master alloy ingot obtained in Example 1 is shown in FIG. Figure 3 The shrinkage data of the K418 nickel-based high-temperature alloy master alloy ingot obtained in Example 1 is shown in Table 4.

[0047] Comparative Example 2

[0048] The conventional die assembly method and the same process parameters as in Example 2 were used for smelting to obtain a K418 nickel-based high-temperature alloy master alloy ingot. The surface shrinkage image of the K418 nickel-based high-temperature alloy master alloy ingot obtained in Comparative Example 2 is shown in FIG. Figure 4 The shrinkage data of the K418 nickel-based high-temperature alloy master alloy ingot obtained in Comparative Example 2 is shown in Table 4.

[0049] Table 4

[0050] Serial number Maximum shrinkage hole size / mm Shrinkage ratio of the whole alloy ingot Shrinkage distribution Example 2 3.63 40.2％ 36% concentrated in the upper part of the alloy ingot Comparative Example 2 11.91 56.7％ Discontinuously distributed throughout the alloy ingot

[0051] It can be seen from Table 4 that the internal shrinkage cavities of the K418 nickel-based high-temperature alloy master alloy ingot are improved from the continuous distribution state of Comparative Example 2 to the point state of Example 2, and the maximum size is improved from the secondary shrinkage cavity of 11.91 mm in Comparative Example 2 to the central secondary shrinkage cavity with a maximum size not exceeding 4 mm in Example 2.

[0052] From Table 4 and combined Figure 3 and Figure 4 It can be seen that the smelting test of the master alloy through the process of Example 2 can effectively alleviate the secondary shrinkage cavity inside the master alloy ingot, and the position of the secondary shrinkage cavity in the alloy ingot can be moved up or even transferred to the riser under the action of the directional solidification method.

[0053] Example 3

[0054] A directional solidification method for improving secondary shrinkage of K4222 nickel-based high-temperature alloy master alloy ingot. The pouring temperature of K4222 alloy is 1480-1510°C. The specific alloy composition range and measured values ​​of K4222 nickel-based high-temperature alloy are shown in Table 5.

[0055] Table 5

[0056] element C Cr Co W Nb content 0.08～0.12 22.2～22.8 18.5～19.5 1.8～2.2 0.70～0.90 Measured value 0.10 22.50 18.96 2.01 0.84 element Zr B Al Ti Ta content 0.005～0.020 0.002～0.007 1.10～1.30 2.20～2.40 0.90～1.10 Measured value 0.012 0.0052 1.22 2.34 1.07

[0057] A mold tube with an inner diameter of 82 mm and a length of 1200 mm was selected, and the number of mold tubes was 48.

[0058] The above method specifically comprises the following steps:

[0059] S1. Provide a sand box. The bottom size of the sand box is consistent with the bottom size of the module frame. The depth of the sand box is controlled at 790-810mm. First, fill the sand box with steel sand. The steel sand particle size is 1-8mm. The filling depth of the steel sand is controlled at 257-277mm. Then fill the steel sand with quartz sand. The quartz sand particle size is 9-15mm. The filling depth of the quartz sand is controlled at 257-277mm.

[0060] S2, assembling the mold tube and the diverter plate to form a module, so that the mold tubes do not contact each other, baking the module and then keeping it warm, the baking temperature is controlled at 300-600°C, and the insulation time is controlled at 10-60min;

[0061] S3, the mold group after the insulation is transferred to the sand box through the mold group frame, the transfer time is controlled within 10 minutes, the mold tube is vertically inserted into the steel sand and quartz sand, the bottom end of the mold tube is in contact with the bottom surface of the sand box, and the sand box and the mold group are pushed into the mold car room, and subsequent smelting can be carried out to obtain K4222 nickel-based high-temperature alloy master alloy ingots. The surface shrinkage image of the K4222 nickel-based high-temperature alloy master alloy ingot obtained in Example 3 is shown in FIG. Figure 5 The shrinkage data of the K4222 nickel-based high-temperature alloy master alloy ingot obtained in Example 3 is shown in Table 6.

[0062] Comparative Example 3

[0063] The conventional die assembly method and the same process parameters as those in Example 3 were used for smelting to obtain a K4222 nickel-based high-temperature alloy master alloy ingot. The surface shrinkage image of the K4222 nickel-based high-temperature alloy master alloy ingot obtained in Comparative Example 3 is shown in FIG. Figure 6 The shrinkage data of the K4222 nickel-based high-temperature alloy master alloy ingot obtained in Comparative Example 3 is shown in Table 6.

[0064] Table 6

[0065] Serial number Maximum shrinkage hole size / mm Shrinkage ratio of the whole alloy ingot Shrinkage distribution Example 3 4.35 30.2％ 20% concentrated on the upper part of the alloy ingot Comparative Example 3 16.08 45.6％ Discontinuously distributed throughout the alloy ingot

[0066] It can be seen from Table 6 that the internal shrinkage cavities of the K4222 nickel-based high-temperature alloy master alloy ingot are improved from the continuous distribution state of Comparative Example 3 to the point state of Example 3, and the maximum size is improved from the secondary shrinkage cavities of 16.08 mm in Comparative Example 3 to the central secondary shrinkage cavities with a maximum size of no more than 5 mm in Example 3.

[0067] From Table 6 and combined Figure 5 and Figure 6 It can be seen that the smelting test of the master alloy by the process of Example 3 can effectively reduce the secondary shrinkage cavity inside the master alloy ingot, and the position of the secondary shrinkage cavity in the alloy ingot can be moved up or even transferred to the riser under the action of the directional solidification method.

[0068] The design principle of the present invention is to add a sand box device on the basis of an ordinary mold group, and the sand box is filled with two materials with different thermal conductivities; the lower layer in the sand box is steel sand with a larger thermal conductivity to improve the cooling speed and uniformity of the master alloy; the upper layer in the sand box is quartz sand with a smaller thermal conductivity to reduce the heat dissipation during the solidification process of the master alloy; therefore, by filling two materials with different thermal conductivities around the mold tube, a temperature gradient along the longitudinal direction of the mold tube can be formed, so that the alloy can achieve an effect similar to directional solidification, thereby transferring the secondary shrinkage cavity to the riser position, and improving the secondary shrinkage cavity in the master alloy.

[0069] The advantages of the present invention are:

[0070] 1. The present invention utilizes a sand box device and, through the difference in thermal conductivity between steel sand and quartz sand, effectively combines the two processes of smelting process of high-temperature alloy master alloy and directional solidification technology to improve shrinkage cavities, establishes a temperature gradient in the solidification process, thereby achieving sequential solidification and transferring secondary shrinkage cavities to the riser position, thereby improving or even eliminating secondary shrinkage cavities in the master alloy.

[0071] 2. The steel sand and quartz sand used in the present invention are easy to obtain and can be recycled, the implementation cost is low, and the assembly device is simple and convenient, and the operability is strong.

[0072] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A directional solidification method for improving secondary shrinkage of high-temperature alloy master alloy ingots, characterized in that The method comprises the following steps: S1. Provide a sand box. The bottom size of the sand box is consistent with the bottom size of the module frame. The depth of the sand box is controlled at (2 / 3×mold tube length ± 10) mm. First, fill the sand box with steel sand. The steel sand particle size is 1~8 mm. The filling depth of the steel sand is controlled at (2 / 9×mold tube length ± 10) mm. Then fill the steel sand with quartz sand. The quartz sand particle size is 9~15 mm. The filling depth of the quartz sand is controlled at (2 / 9×mold tube length ± 10) mm. S2, assembling the mold tube and the diverter plate to form a module, so that the mold tubes do not contact each other, baking the module and then keeping it warm, the baking temperature is controlled at 300-600°C, and the insulation time is controlled at 10-60min; S3. Transfer the mold after insulation to the sand box through the mold frame. The transfer time is controlled within 10 minutes. Insert the mold tube vertically into the steel sand and quartz sand. The bottom end of the mold tube contacts the bottom surface of the sand box. Push the sand box together with the mold into the mold car room for subsequent smelting.

2. The directional solidification method for improving secondary shrinkage of high temperature alloy master alloy ingot according to claim 1, characterized in that: In step S1, the depth of the sand box is 2 / 3 of the length of the mold tube.

3. The directional solidification method for improving secondary shrinkage cavity of high temperature alloy master alloy ingot according to claim 1, characterized in that: In step S1, the filling depth of the steel sand is 2 / 9 of the length of the mold tube.

4. The directional solidification method for improving secondary shrinkage cavity of high temperature alloy master alloy ingot according to claim 1, characterized in that: In step S1, the filling depth of the quartz sand is 2 / 9 of the length of the mold tube.

5. The directional solidification method for improving secondary shrinkage cavity of high temperature alloy master alloy ingot according to claim 1, characterized in that: In step S1, the minimum length of the mold tube is 830 mm.

6. The directional solidification method for improving secondary shrinkage cavity of high temperature alloy master alloy ingot according to claim 1, characterized in that: In step S1, the sand box is a steel sand box.

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