Vacuum melting furnace

Abstract

The utility model discloses a vacuum smelting furnace, and relates to the technical field of metal smelting. The device structurally comprises a high-frequency induction heater, a supporting base, a quartz glass tube, a crucible, a crucible supporting seat, a water-cooling upper pressing seat, a pull rod, a vacuumizing upper end cover and a stirring rod, the crucible supporting seat is fixedly arranged on the supporting base through four first nuts; the crucible is placed on the crucible supporting seat; the quartz glass tube is inserted and mounted on the crucible supporting seat; and the crucible is arranged in the quartz glass tube. According to the utility model, the high-frequency induction heater is combined with the quartz glass tube, so that the heating is more uniform, the problem of local overheating is avoided, and a plurality of sealing rubber rings and an accurate mechanical structure design ensure the high sealing property of the heating cavity, which is crucial for high-temperature smelting in a vacuum environment. And the good sealing performance is beneficial to maintaining the stable vacuum degree, external gas is prevented from entering, and therefore the purity and high quality of the nickel-based single crystal high-temperature alloy in the smelting process are guaranteed.

Description

Technical Field

[0001] The utility model belongs to the technical field of metal smelting, in particular to a vacuum smelting furnace. Background Art

[0002] In modern materials science, nickel-based single-crystal superalloys are widely used in high-tech fields such as aviation, aerospace, and energy due to their exceptional high-temperature performance and superior mechanical strength. The preparation of these alloys typically involves a sophisticated melting process, with vacuum melting being the preferred method due to its ability to provide a pure, impurity-free melting environment. However, conventional vacuum melting equipment suffers from numerous deficiencies in sealing, heating uniformity, cooling efficiency, and ease of operation, limiting the production efficiency and consistency of high-quality nickel-based single-crystal superalloys.

[0003] Specifically, the vacuum melting furnaces in the prior art are often difficult to achieve efficient sealing, resulting in susceptibility to interference from external gases during the high-temperature melting process, affecting the purity and performance of the alloy. In addition, uneven heating may lead to local overheating or incomplete melting, affecting the microstructure and mechanical properties of the material. At the same time, a fast and effective cooling mechanism is crucial for controlling the solidification process of the alloy, but the design of existing equipment in this regard is often not perfect, resulting in slow cooling speed, affecting production efficiency and product quality. Furthermore, complex operation and inconvenient maintenance are also common problems of existing vacuum melting equipment, which to a certain extent limit its application in scientific research and small-batch production.

[0004] Therefore, developing a new type of vacuum melting furnace to solve the above problems and improve the melting quality and efficiency of nickel-based single crystal high-temperature alloys has become a technical problem that needs to be solved urgently by technical personnel in this field. Utility Model Content

[0005] The purpose of the utility model is to provide a vacuum melting furnace, which ensures the vacuum degree during the overall melting process through the combination of multiple components, and uses a high-frequency induction heater in combination with a quartz glass tube to make heating more uniform.

[0006] In order to solve the above technical problems, the present invention is achieved through the following technical solutions:

[0007] The utility model discloses a vacuum melting furnace, comprising a high-frequency induction heater, a support base, a quartz glass tube, a crucible, a crucible support base, a water-cooled upper pressure base, a pull rod, a vacuum upper end cover and a stirring rod; the crucible support base is fixed on the support base by four first nuts; the crucible is placed on the crucible support base; the quartz glass tube is plugged and installed on the crucible support base; the crucible is placed inside the quartz glass tube, and the spiral induction coil on the high-frequency induction heater is sleeved on the outside of the quartz glass tube and at the same height as the crucible; the quartz At least two first sealing rubber rings are arranged between the outer wall of the glass tube and the crucible support seat; the water-cooled upper pressure seat is plugged and installed on the upper end of the quartz glass tube; at least two second sealing rubber rings are arranged between the outer wall of the quartz glass tube and the water-cooled upper pressure seat; the water-cooled upper pressure seat and the support base are clamped by two pull rods and two second nuts; the vacuum upper end cover is installed on the water-cooled upper pressure seat by bolts, and a first sealing ring is arranged between the vacuum upper end cover and the water-cooled upper pressure seat; the stirring rod is sealed and slidably connected to the vacuum upper end cover.

[0008] As a preferred technical solution of the present invention, a second sealing ring is provided between the upper end of the quartz glass tube and the water-cooled upper pressure seat; and a third sealing ring is provided between the lower end of the quartz glass tube and the crucible support seat.

[0009] As an optimal technical solution of the present utility model, the support base includes a bottom plate; four cylindrical rods for supporting the crucible support seat are fixed on the upper surface of the bottom plate; a coaxially arranged threaded column head is fixed on the upper end of the cylindrical rod; two inverted U-shaped plates are fixed on the upper surface of the bottom plate; a U-shaped notch with an open side is provided on the top of the U-shaped plate; the pull rod includes a single-head stud; a round cake is fixed at the lower end of the single-head stud; the round cake is placed inside the U-shaped plate, and the single-head stud passes through the U-shaped notch.

[0010] As an optimal technical solution of the present invention, the crucible support seat includes a rectangular base with an inner cavity; a circular groove for inserting the quartz glass tube is provided at the upper end of the rectangular base; a first ring groove cooperating with the first sealing rubber ring is provided on the inner wall of the circular groove; a plurality of copper pillars are fixed in a ring-shaped arrangement on the bottom of the circular groove; a horizontal support part for supporting the crucible is fixed on the copper pillar; a lower water inlet joint communicating with its inner cavity is fixed through the bottom of the rectangular base; a lower water outlet joint communicating with its inner cavity is fixed through the side wall of the rectangular base; a first circular through hole cooperating with the threaded column head is provided at each corner of the rectangular base.

[0011] As an optimal technical solution of the present utility model, the water-cooled upper pressure seat includes an inner circle outer square base with an inner cavity; the inner ring surface of the inner circle outer square base is provided with a second ring groove that cooperates with the second sealing rubber ring; an upper water inlet joint connected to its inner cavity is fixed through one side wall of the inner circle outer square base; an upper water outlet joint connected to its inner cavity is fixed through the other side wall of the inner circle outer square base; horizontal ear plates are symmetrically fixed on the other two opposite side walls of the inner circle outer square base; a C-shaped notch that cooperates with the single-head stud is provided at the end of the horizontal ear plate; a radial flange that is connected and cooperates with the vacuum upper end cover is fixed on the upper end of the inner ring surface of the inner circle outer square base.

[0012] As an optimal technical solution of the present utility model, the vacuum upper end cover includes a round cover with a lower opening; a sliding sleeve that slides with the axis of the stirring rod is fixed through the inner wall of the top of the round cover; a coaxially arranged cylinder is fixed on the upper surface of the round cover; at least two third sealing rubber rings are arranged between the inner wall of the cylinder and the stirring rod; the inner wall of the upper end of the cylinder is threadedly connected to a limiting ring cover; a flange ring is fixed to the bottom of the round cover; an air guide tube is fixed through the side wall of the round cover; a pressure gauge and a gas tank are installed on the air guide tube; and a ball valve is installed at the end of the air guide tube.

[0013] As a preferred technical solution of the present invention, the stirring rod includes a cylindrical guide rod; a stirring head is fixed to the lower end of the cylindrical guide rod; and a handle is fixed to the upper end of the cylindrical guide rod.

[0014] The utility model has the following beneficial effects:

[0015] 1. This utility model ensures a high degree of sealing of the heating chamber through multiple sealing rubber rings and precise mechanical structure design, which is crucial for high-temperature melting in a vacuum environment. Good sealing performance helps maintain a stable vacuum level and prevents the ingress of external gases, thereby ensuring the purity and high quality of the nickel-based single crystal high-temperature alloy melting process.

[0016] 2. This invention utilizes a high-frequency induction heater combined with a quartz glass tube, resulting in more uniform heating and avoiding local overheating. Furthermore, the stirring rod design effectively stirs the alloy material in its molten state, promoting homogenization of its components, which is particularly important for preparing single crystal alloys with consistent performance.

[0017] 3. The utility model utilizes a cooling system design consisting of a crucible support and a water-cooled upper pressure seat to rapidly dissipate heat generated during the smelting process, preventing equipment damage or seal failure caused by excessive temperatures. This rapid cooling mechanism not only protects the equipment but also facilitates rapid solidification of the alloy material, maintaining its microstructural integrity.

[0018] 4. This utility model has a compact overall structure and is quick and easy to install, making it particularly suitable for the research and production of small quantities of nickel-based single crystal high-temperature alloy materials. The modular design makes maintenance and component replacement easier, improving the efficiency and flexibility of the equipment.

[0019] 5. The vacuum upper end cover of the utility model is equipped with a gas tank, which can expand the capacity of the vacuum melting space, reduce the impact of trace gas release on the melting process, further optimize the vacuum environment, and provide a strong guarantee for the high-quality melting of nickel-based single crystal high-temperature alloys.

[0020] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0022] Figure 1 This is a schematic structural diagram of the vacuum melting furnace of the utility model.

[0023] Figure 2 for Figure 1 Cross-sectional view at AA in the middle.

[0024] Figure 3 for Figure 2 A partial enlarged view of point A in the middle.

[0025] Figure 4 for Figure 2 A partial enlarged view of point B in the middle.

[0026] Figure 5 Schematic diagram of the structure of the support base.

[0027] Figure 6 It is a structural schematic diagram of the crucible support seat.

[0028] Figure 7 This is a structural diagram of the water-cooled upper pressure seat.

[0029] Figure 8 It is a structural diagram of the vacuum upper end cover.

[0030] Figure 9 Schematic diagram of the structure of the pull rod.

[0031] In the accompanying drawings, the components represented by the reference numerals are as follows:

[0032] 1-high frequency induction heater, 2-support base, 3-quartz glass tube, 4-crucible, 5-crucible support base, 6-water cooling upper pressure base, 7-pull rod, 8-vacuum upper end cover, 9-stirring rod, 10-first sealing rubber ring, 11-second sealing rubber ring, 12-first sealing ring, 13-second sealing ring, 14-third sealing ring, 15-third sealing rubber ring, 21-bottom plate, 22-cylindrical rod, 23-threaded column head, 24-U-shaped plate, 25-U-shaped notch, 51-rectangular base, 52-circular groove, 53-first ring groove, 54-copper column, 55- Horizontal support part, 56-lower water inlet joint, 57-lower water outlet joint, 58-first circular through hole, 61-inner circle and outer square base, 62-second ring groove, 63-upper water inlet joint, 64-upper water outlet joint, 65-horizontal ear plate, 66-C-shaped notch, 67-diameter flange, 71-single-head stud, 72-round cake, 81-round cover, 82-sliding sleeve, 83-cylinder, 84-limiting ring cover, 85-flange ring, 86-air guide tube, 87-pressure gauge, 88-gas tank, 89-ball valve, 91-cylindrical guide rod, 92-stirring head, 93-handle. DETAILED DESCRIPTION

[0033] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only 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 ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention. Specific embodiment one:

[0035] See also Figure 1-8As shown, the utility model is a vacuum melting furnace, comprising a high-frequency induction heater 1, a support base 2, a quartz glass tube 3, a crucible 4, a crucible support seat 5, a water-cooled upper pressure seat 6, a pull rod 7, a vacuum upper end cover 8 and a stirring rod 9. The support base 2 is used to support the installation position of the crucible 4 at a height corresponding to the spiral induction coil of the high-frequency induction heater 1. The support base 2, the quartz glass tube 3, the crucible support seat 5, the water-cooled upper pressure seat 6, the pull rod 7, the vacuum upper end cover 8 and the stirring rod 9 are connected to form a sealed heating chamber structure. The crucible 4 is placed on the crucible support seat 5 in the quartz glass tube 3. Nickel-based single crystal high-temperature alloy raw material is placed in the crucible 4. The vacuum upper end cover 8 is connected to a vacuum pump to extract air to evacuate the inside of the heating chamber into a vacuum. The high-frequency induction heater 1 heats the raw nickel-based single crystal superalloy material, and the stirring rod 9 moves downward into the crucible 4 to evenly stir the molten single crystal alloy material. After the heating reaction of the nickel-based single crystal superalloy is completed, the high-frequency induction heater 1 is turned off, and the pressure in the crucible 4 is released after the crucible 4 solidifies and forms. The vacuum upper end cap 8 is removed by removing the combination of the vacuum upper end cap 8 and the stirring rod 9, and the new nickel-based single crystal superalloy material can be removed from the crucible 4 within the quartz glass tube 3. The vacuum melting furnace of the present invention is suitable for the rapid melting and production of small amounts of nickel-based single crystal superalloy material. The integrated melting furnace is quick and easy to install, making it suitable for the production and research of small amounts of nickel-based single crystal superalloy material.

[0036] Specifically, the crucible support seat 5 is fixed to the support base 2 by four first nuts. The crucible 4 is placed on the crucible support seat 5. The quartz glass tube 3 is plugged into and installed on the crucible support seat 5. The crucible 4 is placed inside the quartz glass tube 3, and the spiral induction coil on the high-frequency induction heater 1 is sleeved on the outside of the quartz glass tube 3 and at the same height as the crucible 4. At least two first sealing rubber rings 10 are provided between the outer wall of the quartz glass tube 3 and the crucible support seat 5. The water-cooled upper pressure seat 6 is plugged into and installed on the upper end of the quartz glass tube 3. At least two second sealing rubber rings 11 are provided between the outer wall of the quartz glass tube 3 and the water-cooled upper pressure seat 6. The water-cooled upper pressure seat 6 and the support base 2 are clamped by two pull rods 7 and two second nuts. The vacuum upper end cover 8 is installed on the water-cooled upper pressure seat 6 by bolts, and a first sealing ring 12 is provided between the vacuum upper end cover 8 and the water-cooled upper pressure seat 6. The stirring rod 9 is sealed and slidably connected to the vacuum upper end cover 8. A second sealing ring 13 is provided between the upper end of the quartz glass tube 3 and the water-cooled upper pressure seat 6. A third sealing ring 14 is provided between the lower end of the quartz glass tube 3 and the crucible support seat 5. The support base 2 includes a bottom plate 21. Four cylindrical rods 22 for supporting the crucible support seat 5 are fixed to the upper surface of the bottom plate 21. A coaxially arranged threaded column head 23 is fixed to the upper end of the cylindrical rod 22. Two inverted U-shaped plates 24 are fixed to the upper surface of the bottom plate 21. A U-shaped notch 25 with one side open is provided at the top of the U-shaped plate 24. The pull rod 7 includes a single-head stud 71. A round cake 72 is fixed to the lower end of the single-head stud 71. The round cake 72 is placed inside the U-shaped plate 24, and the single-head stud 71 passes through the U-shaped notch 25.

[0037] The crucible support 5 specifically includes a rectangular base 51 with an inner cavity. A circular groove 52 is provided at the upper end of the rectangular base 51 for inserting the quartz glass tube 3. A first annular groove 53 is provided on the inner wall of the circular groove 52, which cooperates with the first sealing rubber ring 10. A plurality of copper pillars 54 are fixed in a circular arrangement at the bottom of the circular groove 52. A horizontal support portion 55 for supporting the crucible 4 is fixed to the copper pillars 54. A lower water inlet connector 56 is fixed through the bottom of the rectangular base 51, communicating with its inner cavity. A lower water outlet connector 57 is fixed through the side wall of the rectangular base 51, communicating with its inner cavity. A first circular through-hole 58 is provided at each corner of the rectangular base 51, which cooperates with the threaded stud 23. The lower water inlet connector 56 and the lower water outlet connector 57 of the crucible support 5 are connected to a circulating water chiller via water pipes to continuously cool the crucible support 5 and reduce sealing problems caused by the increase in temperature of the crucible support 5.

[0038] The water-cooled upper press seat 6 includes an inner-circle-outer-square base 61 with an inner cavity. The inner annular surface of the inner-circle-outer-square base 61 defines a second annular groove 62 that mates with the second sealing rubber ring 11. An upper water inlet connector 63, communicating with the inner cavity, is fixedly secured through one sidewall of the inner-circle-outer-square base 61. An upper water outlet connector 64, communicating with the inner cavity, is fixedly secured through the other opposite sidewall of the inner-circle-outer-square base 61. Horizontal lugs 65 are symmetrically secured to the other two opposing sidewalls of the inner-circle-outer-square base 61. The ends of the horizontal lugs 65 define C-shaped notches 66 that mate with single-head studs 71. A flange 67 with a diameter is fixedly secured to the upper end of the inner annular surface of the inner-circle-outer-square base 61, which mates with the vacuum upper end cover 8. The upper water inlet connector 63 and the upper water outlet connector 64 of the water-cooled upper press seat 6 are connected to a circulating water chiller via water pipes to continuously cool the water-cooled upper press seat 6 and mitigate sealing issues caused by warming of the water-cooled upper press seat 6. The continuous cooling of the crucible support seat 5 and the continuous cooling of the water-cooled upper pressure seat 6 effectively ensure the stability of the vacuum sealing environment during the entire vacuum heating and melting process, ensuring that the nickel-based single crystal high-temperature alloy is melted in a stable vacuum environment.

[0039] The vacuum upper end cover 8 includes a circular cover 81 with a lower opening. A sliding sleeve 82 is fixed through the inner wall of the top of the circular cover 81, which slides with the axis of the stirring rod 9. A coaxially arranged cylinder 83 is fixed to the upper surface of the circular cover 81. At least two third sealing rubber rings 15 are provided between the inner wall of the cylinder 83 and the stirring rod 9. A limit ring cover 84 is threadedly connected to the inner wall of the upper end of the cylinder 83. A flange ring 85 is fixed to the bottom of the circular cover 81. An air guide tube 86 is fixed through the side wall of the circular cover 81. A pressure gauge 87 and a gas tank 88 are installed on the air guide tube 86. A ball valve 89 is installed at the end of the air guide tube 86. The stirring rod 9 includes a cylindrical guide rod 91. A stirring head 92 is fixed to the lower end of the cylindrical guide rod 91. The stirring rod 9 moves downward in the vacuum upper end cover 8 to stir the alloy material solution in the crucible 4. After stirring is completed, it is pulled upward to separate from the crucible 4. A handle 93 is fixed to the upper end of the cylindrical guide rod 91. The vacuum upper end cover 8 is provided with a gas tank 88 to expand the capacity of the entire vacuum melting space and reduce the influence of trace gas release during the melting process of nickel-based single crystal high-temperature alloy on the melting process.

[0040] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0041] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. The preferred embodiments do not describe all details in detail, nor do they limit the present invention to the specific embodiments described. Obviously, many modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A vacuum melting furnace, characterized in that: It includes a high-frequency induction heater (1), a support base (2), a quartz glass tube (3), a crucible (4), a crucible support base (5), a water-cooled upper pressure base (6), a pull rod (7), a vacuum upper end cover (8) and a stirring rod (9); The crucible support seat (5) is fixed on the support base (2) via four first nuts; the crucible (4) is placed on the crucible support seat (5); The quartz glass tube (3) is plugged and installed on the crucible support seat (5); the crucible (4) is placed inside the quartz glass tube (3), and the spiral induction coil on the high-frequency induction heater (1) is sleeved on the outside of the quartz glass tube (3) and at the same height as the crucible (4); at least two first sealing rubber rings (10) are provided between the outer wall of the quartz glass tube (3) and the crucible support seat (5); The water-cooled upper press seat (6) is plugged and installed on the upper end of the quartz glass tube (3); at least two second sealing rubber rings (11) are provided between the outer wall of the quartz glass tube (3) and the water-cooled upper press seat (6); the water-cooled upper press seat (6) and the support base (2) are clamped by two pull rods (7) and two second nuts; The vacuum upper end cover (8) is mounted on the water-cooled upper pressure seat (6) by means of bolts, and a first sealing ring (12) is provided between the vacuum upper end cover (8) and the water-cooled upper pressure seat (6); The stirring rod (9) is in sealing and sliding connection with the vacuum upper end cover (8).

2. The vacuum melting furnace according to claim 1, characterized in that A second sealing ring (13) is provided between the upper end of the quartz glass tube (3) and the water-cooled upper pressure seat (6); and a third sealing ring (14) is provided between the lower end of the quartz glass tube (3) and the crucible support seat (5).

3. The vacuum melting furnace according to claim 2, characterized in that: The support base (2) includes a bottom plate (21); four cylindrical rods (22) for supporting the crucible support seat (5) are fixed on the upper surface of the bottom plate (21); a coaxially arranged threaded column head (23) is fixed on the upper end of the cylindrical rod (22); two inverted U-shaped plates (24) are fixed on the upper surface of the bottom plate (21); a U-shaped notch (25) with one side open is provided on the top of the U-shaped plate (24); the pull rod (7) includes a single-head stud (71); a round cake (72) is fixed on the lower end of the single-head stud (71); the round cake (72) is placed inside the U-shaped plate (24), and the single-head stud (71) passes through the U-shaped notch (25).

4. The vacuum melting furnace according to claim 3, characterized in that The crucible support seat (5) comprises a rectangular base (51) with an inner cavity; a circular groove (52) for inserting the quartz glass tube (3) is provided at the upper end of the rectangular base (51); a first annular groove (53) cooperating with the first sealing rubber ring (10) is provided on the inner wall of the circular groove (52); a plurality of copper pillars (54) are fixed in an annular arrangement on the bottom of the circular groove (52); a horizontal support portion (55) for supporting the crucible (4) is fixed on the copper pillars (54); a lower water inlet joint (56) communicating with the inner cavity of the rectangular base (51) is fixed through the bottom; a lower water outlet joint (57) communicating with the inner cavity of the rectangular base (51) is fixed through the side wall; and a first round through hole (58) cooperating with the threaded column head (23) is provided at each of the four corners of the rectangular base (51).

5. The vacuum melting furnace according to claim 4, characterized in that: The water-cooled upper pressure seat (6) includes an inner circle outer square base (61) with an inner cavity; the inner ring surface of the inner circle outer square base (61) is provided with a second ring groove (62) that cooperates with the second sealing rubber ring (11); an upper water inlet joint (63) communicating with its inner cavity is fixed through one side wall of the inner circle outer square base (61); an upper water outlet joint (64) communicating with its inner cavity is fixed through the other side wall of the inner circle outer square base (61); horizontal ear plates (65) are symmetrically fixed to the other two opposite side walls of the inner circle outer square base (61); a C-shaped notch (66) that cooperates with the single-head stud (71) is provided at the end of the horizontal ear plate (65); a radial flange (67) that is connected and cooperates with the vacuum upper end cover (8) is fixed on the upper end of the inner ring surface of the inner circle outer square base (61).

6. The vacuum melting furnace according to claim 5, characterized in that: The vacuum upper end cover (8) comprises a circular cover (81) with a lower opening; a sliding sleeve (82) that is slidably matched with the axis of the stirring rod (9) is fixed through the inner wall of the top of the circular cover (81); a coaxially arranged cylinder (83) is fixed on the upper surface of the circular cover (81); at least two third sealing rubber rings (15) are provided between the inner wall of the cylinder (83) and the stirring rod (9); the inner wall of the upper end of the cylinder (83) is threadedly connected to a limit ring cover (84); a flange ring (85) is fixed to the bottom of the circular cover (81); an air guide tube (86) is fixed through the side wall of the circular cover (81); a pressure gauge (87) and a gas tank (88) are installed on the air guide tube (86); and a ball valve (89) is installed at the end of the air guide tube (86).

7. The vacuum melting furnace according to claim 6, characterized in that: The stirring rod (9) comprises a cylindrical guide rod (91); a stirring head (92) is fixed to the lower end of the cylindrical guide rod (91); and a handle (93) is fixed to the upper end of the cylindrical guide rod (91).

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