Wax pattern for shell butt joint, investment casting method and its application

Abstract

The present invention relates to the field of precision casting technology, and in particular, to a butt-jointed wax mold for mold shell butt-jointed, a method for precision casting with investment wax, and its application. The butt-jointed wax mold for mold shell butt-jointed comprises a first wax mold and a second wax mold; the first wax mold comprises a fixedly connected annular structure and a connecting portion that closes one end of the annular structure, the first wax mold also comprises a cylindrical core connected to the connecting portion, the core portion is partially accommodated in the annular structure and forms an annular groove with the annular structure; the second wax mold comprises a first truncated cone, a first cylinder, and a second cylinder that are fixedly connected in sequence; the outer diameter of the first cylinder is Rmm, and the inner diameter of the annular structure is R‑1mm~Rmm. The butt-jointed wax mold can connect several small module groups, which is safe and reliable, and can effectively ensure the metallurgical quality of the casting, while eliminating the paste baking process, with low cost and improved production efficiency.

Description

Technical Field

[0001] The present invention relates to the field of precision casting technology, and in particular, to a butt-jointed wax pattern for mold-shell butt-jointing, a method for investment casting and applications thereof; more particularly, to a butt-jointed wax pattern for mold-shell butt-jointing, a wax pattern assembly, a method for investment casting and a method for preparing titanium alloy castings. Background Art

[0002] Titanium alloys are widely used in the aerospace field due to their comprehensive properties such as low density, high specific strength, strong corrosion resistance, and good mechanical properties at room and high temperatures. The casting processes of titanium alloys include graphite molds, sand molds, and investment casting. Among them, investment casting is widely used due to its near-net-shape process characteristics. The entire process is relatively complicated, and the production sections include: wax mold preparation—shell preparation—melting and pouring—post-finishing, and the four major sections include several processes. One of the key core technologies in the near-net-shape process is the shell preparation process, because the quality of the shell directly affects the metallurgical quality of the casting.

[0003] There are two methods used in the prior art to prepare medium and large mold shells: first, by designing corresponding coating tools and tools to perform the operation; second, by splitting the large module and then hard-connecting it or connecting and sealing it with graphite rings and graphite plugs. The above-mentioned mold shell preparation method can realize the shell making of large modules, but it cannot guarantee the quality of the mold shell, because in the process of making the shell of the large module, as the number of layers increases, the weight also increases, and the mold shell is very easy to crack and cannot be detected. In addition, the huge pouring system structure design is not good at drying during the shell making process, all of which means that the quality of the mold shell is directly affected, and the metallurgical quality of the titanium alloy casting cannot be guaranteed.

[0004] In addition, after the preparation of the shell of medium and small modules is completed, the following two processes are generally used during melting and pouring: 1) The graphite runner and the graphite ring are connected. Although this process is simple and convenient to operate, the price of high-purity graphite is relatively expensive, and it needs to be vacuum-degassed at high temperature before use, which is not economical and has low production efficiency. 2) After cutting the shell joint interface, paint is applied to make a hard connection, and then the paste is baked. This method is more difficult to ensure the quality of the shell, because the molten titanium metal liquid is easy to come into contact with the reinforcement layer material of the shell to react strongly, which seriously affects the quality of the casting.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The first purpose of the present invention is to provide a wax mold for shell butt joint, which can connect several small modules safely and reliably, effectively ensure the metallurgical quality of castings, avoid the contact between molten metal and reinforcement layer materials caused by the traditional shell rigid connection, and save the paste baking process, thereby improving production efficiency. In addition, the wax mold for shell butt joint provided by the present invention is used to replace high-purity graphite products, without the need to purchase expensive graphite accessories or perform high-temperature degassing operations, which effectively reduces costs and significantly improves efficiency.

[0007] The second object of the present invention is to provide a wax model module.

[0008] The third object of the present invention is to provide a method for investment casting.

[0009] A fourth object of the present invention is to provide a method for preparing a titanium alloy casting.

[0010] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0011] In a first aspect, the present invention provides a wax mold for butt jointing of mold shells, comprising a first wax mold and a second wax mold;

[0012] The first wax model comprises a fixedly connected annular structure and a connecting portion that closes one end of the annular structure, and the first wax model also comprises a cylindrical core connected to the connecting portion, wherein the core is partially accommodated in the annular structure and forms an annular groove with the annular structure; the axis of the annular structure coincides with the axis of the core; and the annular structure is further provided with an annular sharp corner at one end away from the connecting portion;

[0013] The second wax model comprises a first truncated cone, a first cylinder and a second cylinder which are fixedly connected in sequence; the axes of the first truncated cone, the first cylinder and the second cylinder coincide with each other; the outer diameter of the first cylinder is greater than the outer diameter of the second cylinder; the surface of the first truncated cone connected to the first cylinder is the first bottom surface, and the surface not connected to the first cylinder is the second bottom surface, the diameter of the second bottom surface is smaller than the diameter of the first bottom surface, and the diameter of the first bottom surface is greater than the outer diameter of the first cylinder;

[0014] The outer diameter of the first cylinder is Rmm, and the inner diameter of the annular structure is R-1mm~Rmm.

[0015] Preferably, the inner diameter of the annular structure gradually decreases in a direction approaching the connecting portion.

[0016] Preferably, the second wax mold is hollow.

[0017] Preferably, the butt joint wax mold for butt joint of the mold shell further comprises a third wax mold and a fourth wax mold, and the third wax mold and the fourth wax mold are used to seal the mold shell;

[0018] The third wax model is a hollow truncated cone with a trapezoidal cross section, one end of the hollow truncated cone is closed and the other end is open, and a disc body extends outward from the closed end; a first annular cavity and a second annular cavity with successively increasing diameters are formed inside the hollow truncated cone, and the first annular cavity and the second annular cavity form a first step and a second step connected in sequence;

[0019] The fourth wax mold is a hollow structure with one end closed and the other end open, and the hollow structure includes a second truncated cone, a first circular ring, and a second circular ring which are fixedly connected in sequence and whose axes coincide with each other, and the outer diameter of the first circular ring is larger than the outer diameter of the second circular ring; the outer surfaces of the first circular ring and the second circular ring form a third step and a fourth step which are connected in sequence; the surface of the second truncated cone connected to the first circular ring is the third bottom surface, and the surface not connected to the first circular ring is the fourth bottom surface, the diameter of the fourth bottom surface is smaller than the diameter of the third bottom surface, and the diameter of the third bottom surface is larger than the outer diameter of the first circular ring;

[0020] Wherein, the difference between the outer diameter of the second circular ring and the diameter of the first annular cavity is less than or equal to 1 mm;

[0021] The difference between the outer diameter of the first circular ring and the diameter of the second annular cavity is less than or equal to 1 mm.

[0022] In a second aspect, the present invention provides a wax mold set, including the wax mold for butt jointing of mold shells as described above.

[0023] In a third aspect, the present invention provides an investment casting method, using the butt wax pattern for butt jointing of mold shells as described above, the investment casting method comprising the following steps:

[0024] (a) connecting the first wax mold to a monomer mold to obtain a first mold; connecting the second wax mold to a main casting system wax mold to obtain a second mold;

[0025] (b) coating the surfaces of the first mold group and the second mold group respectively, and obtaining a first shell and a second shell after drying; wherein the coating fills the annular groove;

[0026] (c) peeling off the shell on the surface of the connecting portion and the shell on the surface of the annular structure in the first shell, and peeling off the shell on the second bottom surface of the first truncated cone and the shell on the side surface of the first truncated cone in the second shell;

[0027] (d) After the first shell and the second shell are dewaxed and fired in sequence, the first shell forms a first protrusion and the second shell forms a first groove. The first protrusion and the first groove are spliced, and then melted and poured to obtain a casting.

[0028] Preferably, in step (d), after the sintering and before the splicing, the following step is further included: removing excess mold shell that affects the splicing of the protrusion and the groove.

[0029] Preferably, in step (a), after the second wax mold is connected to the main pouring system wax mold, the following steps are further included: connecting the fourth wax mold to the bottom of the main pouring system wax mold to obtain the second mold assembly;

[0030] Preferably, step (b) further comprises the following steps: coating the surface of the third wax mold with a coating, and obtaining a third shell after drying; wherein the coating fills the first annular cavity and the second annular cavity;

[0031] Preferably, step (c) further comprises the following steps: peeling off the fourth bottom surface and the side surface of the second truncated cone in the second shell; and peeling off the shell of the side surface of the disk body and the hollow truncated cone in the third shell;

[0032] Preferably, in step (d), after the roasting and before the smelting and pouring, a second groove is formed at the bottom of the second shell, and a second protrusion is formed at the third shell, and the second protrusion and the second groove are spliced.

[0033] Preferably, in step (c), the stripping method comprises: drilling holes at the locations to be stripped, and then introducing air into the holes to increase the pressure in the shell to be stripped, causing fractures at the sharp corners.

[0034] In a fourth aspect, the present invention provides a method for preparing a titanium alloy casting, comprising the investment casting method as described above.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) The wax mold for mold shell docking provided by the present invention can connect several small mold groups safely and reliably, and can effectively ensure the metallurgical quality of the casting. It avoids the problem of contact between molten metal and reinforcement layer materials caused by traditional mold shell rigid connection, thereby affecting the quality of the casting. At the same time, it saves the paste baking process and improves production efficiency.

[0037] (2) The wax mold for shell butt joint provided by the present invention is used to replace high-purity graphite products, which eliminates the need to purchase expensive graphite accessories and high-temperature degassing operations, thereby effectively reducing costs and significantly improving efficiency.

[0038] (3) The butt-jointed wax mold shell for mold shell butt joint provided by the present invention realizes a stable connection between a plurality of single small modules, and the operation of the single small module shell coating is easier, and the controllability and drying performance are better, and the quality of the mold shell can be effectively guaranteed.

[0039] (4) The wax mold for mold shell docking provided by the present invention is configured such that the inner surface of the annular structure of the first wax mold has a certain slope, that is, the inner diameter of the annular structure gradually decreases in the direction approaching the connecting portion, which can improve the docking effect of the mold shell.

[0040] (5) The wax mold for shell butt joint provided by the present invention can achieve tight sealing of the bottom of the entire large mold assembly after assembly by setting the third wax mold and the fourth wax mold.

[0041] (6) The investment casting method provided by the present invention is to split the overall large mold group into multiple small mold groups, and respectively connect the multiple small mold groups with the first wax mold and the second wax mold of the specific structure, and then form a concave and convex mortise and tenon structure (i.e., the first protrusion and the first groove) through coating shell making, peeling off part of the mold shell, dewaxing, and baking. After docking and assembly, melting and pouring are carried out to produce high-quality castings with the advantages of simple process, low labor intensity, high production efficiency, and low cost.

[0042] (7) The investment casting method provided by the present invention solves the problems existing in the prior art, such as long drying time of large molds during shell making, easy cracking, inability to ensure the metallurgical quality of titanium alloy castings, high labor intensity, low production efficiency, high cost of using graphite, high-temperature vacuum degassing before use, coating after cutting the shell joints to make hard connections and then baking the paste, and the molten metal liquid easily reacting with the reinforcement layer material of the shell to affect the quality of the casting. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0044] Figure 1 A schematic diagram of the three-dimensional structure of the first wax model provided by the present invention;

[0045] Figure 2 A partial cross-sectional schematic diagram of the first wax model provided by the present invention; wherein, Figure 2 (a) is a schematic diagram showing that the inner diameter of the annular structure remains unchanged along the A direction, Figure 2 (b) A schematic diagram showing that the inner diameter of the annular structure gradually increases along the direction A;

[0046] Figure 3 A side view of a first wax model provided by the present invention;

[0047] Figure 4 A schematic diagram of the three-dimensional structure of the second wax model provided by the present invention;

[0048] Figure 5 A side view of a second wax model provided by the present invention;

[0049] Figure 6 A cross-sectional view of a first wax model provided by the present invention;

[0050] Figure 7 A schematic diagram of the three-dimensional structure of a third wax model provided by the present invention;

[0051] Figure 8 A schematic diagram of the three-dimensional structure of a fourth wax model provided by the present invention;

[0052] Fig. 9 A schematic diagram of the structure after the first wax model provided by the present invention is connected to the monomer module;

[0053] Fig.10 A schematic diagram of the structure after the second wax model provided by the present invention is connected to the wax model of the main casting system;

[0054] Fig.11 A cross-sectional view of a first shell provided by the present invention;

[0055] Fig.12 A cross-sectional view of a second shell provided by the present invention;

[0056] Fig.13 A cross-sectional view of a first protrusion and a first groove provided by the present invention;

[0057] Fig.14 A partial structural physical diagram of a first mold shell having a first protrusion and a second mold shell having a first groove provided by the present invention;

[0058] Fig.15 A schematic diagram of the three-dimensional structure of the second groove and the second protrusion provided by the present invention;

[0059] Fig.16 A schematic cross-sectional view of the second protrusion and the second groove provided by the present invention. DETAILED DESCRIPTION

[0060] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0061] In a first aspect, the present invention provides a wax mold for mold shell docking, comprising a first wax mold and a second wax mold.

[0062] The first wax mold forms a protruding structure after shell making, peeling and dewaxing, and the second wax mold forms a groove structure corresponding to the above-mentioned protruding structure after shell making, peeling and dewaxing. The connection between the shells can be achieved by docking (splicing) the protruding structure and the groove structure.

[0063] Among them, Figure 1 and Figure 3 As shown, the first wax model includes a fixedly connected annular structure and a connecting portion that closes one end of the annular structure, and the first wax model also includes a cylindrical core connected to the connecting portion, the core portion is partially accommodated in the annular structure and forms an annular groove between the core and the annular structure; the axis of the annular structure (also called the central axis, center line, symmetry center line) coincides with the axis of the core; the annular structure is also provided with an annular sharp corner at the end away from the connecting portion.

[0064] See also Figure 1 The shape formed by the annular structure and the connecting portion is an inverted C shape. The cross-sectional shape of the connecting portion is circular (the connecting portion has a certain thickness), the outer diameter of the connecting portion is equal to the outer diameter of the annular structure, and the axes of the annular structure and the connecting portion coincide with each other, so that one end of the annular structure is closed.

[0065] The shape formed by the annular structure and the connecting part can also be regarded as a hollow cylinder with a bottom surface cut off. One end of the core is in the cavity of the hollow cylinder and connected to the connecting part; the other end of the core is exposed outside the hollow cylinder.

[0066] The core is in the shape of a cylinder, the diameter of the bottom surface of the core is smaller than the inner diameter of the annular structure, and an annular groove is formed between the core and the annular structure.

[0067] In some specific embodiments of the present invention, the annular structure has a certain length along its axial direction, that is, the annular structure extends outward in a direction away from the connecting portion. Assuming that the outward extending direction is direction A (i.e., the direction away from the connecting portion), see Figure 2 , the outer diameter of the annular structure remains unchanged along the A direction, and the inner diameter of the annular structure remains unchanged along the A direction (such as Figure 2 (a)) or gradually increase (as shown Figure 2 (as shown in (b)).

[0068] The annular structure extends outwardly in the direction away from the connecting portion (i.e., direction A) with the annular sharp corner, and the shape of the annular sharp corner is a hollow truncated cone, whose bottom surface with a smaller diameter is connected to the annular structure, and there is a certain angle between the side of the truncated cone and the bottom surface with a larger diameter, forming a sharp angle structure. Such a sharp angle structure is convenient for later stripping of the shell. Among them, the angle formed between the side of the truncated cone and the bottom surface with a larger diameter can adopt any conventional angle, such as 5° to 85°, including but not limited to any point value of 8°, 10°, 12°, 15°, 18°, 20°, 23°, 25°, 28°, 30°, 35°, 40°, 42°, 45°, 48°, 50°, 55°, 60°, 65°, 70°, 75°, 80° or any range value between two thereof; preferably 10° to 40°.

[0069] like Figure 4 and Figure 5 As shown, the second wax mold includes a first truncated cone, a first cylinder and a second cylinder which are fixedly connected in sequence; the axes of the first truncated cone, the first cylinder and the second cylinder coincide with each other; the outer diameter of the first cylinder is greater than the outer diameter of the second cylinder; the surface of the first truncated cone connected to the first cylinder is the first bottom surface, and the surface not connected to the first cylinder is the second bottom surface, the diameter of the second bottom surface is smaller than the diameter of the first bottom surface, and the diameter of the first bottom surface is greater than the outer diameter of the first cylinder;

[0070] from Figure 4 It can be seen that the first cylinder is arranged between the first truncated cone and the second cylinder, and the bottom diameter of the first cylinder is greater than the bottom diameter of the second cylinder.

[0071] An acute angle structure is formed between the side surface and the first bottom surface of the first truncated cone, and the acute angle structure facilitates the later peeling of the shell. The angle formed between the side surface and the first bottom surface of the first truncated cone can be any conventional angle, such as 5° to 85°, including but not limited to any point value of 8°, 10°, 12°, 15°, 18°, 20°, 23°, 25°, 28°, 30°, 35°, 40°, 42°, 45°, 48°, 50°, 55°, 60°, 65°, 70°, 75°, 80° or any range value between two thereof; preferably 10° to 40°.

[0072] The outer diameter of the first cylinder is Rmm, and the inner diameter of the annular structure is R-1mm~Rmm (including but not limited to any point value of R-0.9mm, R-0.8mm, R-0.7mm, R-0.6mm, R-0.5mm, R-0.4mm, R-0.3mm, R-0.2mm, R-0.1mm or the range value between any two of them).

[0073] The outer diameter of the first cylinder and the inner diameter of the annular structure may be equal to or different from each other.

[0074] The method and principle of use of the wax mold for shell docking provided by the present invention are as follows: first, the casting to be made is made of wax material into a number of small monomer mold groups, the small monomer mold groups include a first model and a second model, and then one end of the first wax mold (the connecting end is the bottom surface outside the annular structure where the core extends) is connected to the first model, and one end of the second wax mold (the connecting end is the bottom surface of the second cylinder away from the first cylinder) is connected to the second model, and then shell making, peeling (peeling off the shell near the sharp corner), and dewaxing are carried out in sequence. In the process of shell making of the first wax mold, the coating is applied to the annular groove, and after peeling off the sharp corner structure and dewaxing, the shell at the annular groove will form a convex structure. After shell making, peeling off the sharp corner structure, and dewaxing, the shell at the connection between the bottom surface of the first cylinder (the bottom surface connected to the second cylinder) and its side surface of the second wax mold will form a groove structure. Finally, the protrusion structure and the groove structure are butt-jointed (spliced). This mortise and tenon-type butt-joint structure can achieve a firm connection between the shell of the first model and the shell of the second model, increase the strength and sealing of the butt joint (connection), and prevent the molten metal from flowing out easily.

[0075] The butt-jointing wax pattern for mold shell butt-jointing provided by the present invention can connect a number of small mold groups safely and reliably, can effectively ensure the metallurgical quality of the casting, avoids the problem of contact between molten metal and reinforcement layer material caused by traditional mold shell rigid connection, thereby affecting the quality of the casting, and at the same time saves the paste baking process, thereby improving production efficiency.

[0076] In addition, the use of the butt wax mold to replace high-purity graphite products eliminates the need to purchase expensive graphite accessories or perform high-temperature degassing operations, which effectively reduces costs and significantly improves efficiency.

[0077] In addition, the butt-jointed wax mold shell for mold shell butt-jointing provided by the present invention realizes a stable connection between several single small modules, the operation of the single small module shell making coating is easier, the controllability and drying performance are better, and the quality of the mold shell can be effectively guaranteed.

[0078] Preferably, if Figure 6 As shown, the inner diameter of the annular structure gradually decreases in the direction approaching the connecting portion.

[0079] That is, the inner diameter of the annular structure gradually increases along the A direction, see Figure 3 .

[0080] Since the shrinkage during the wax model and shell making stages is unstable, the present application sets a certain slope on the inner surface of the annular structure of the first wax model, which can improve the docking effect of the shell.

[0081] Preferably, the second wax mold is hollow.

[0082] That is, the interior of the second wax model is a hollow structure, which is not easy to expand during dewaxing and is convenient for subsequent stripping.

[0083] Preferably, the butt joint wax mold for butt joint of the mold shell further includes a third wax mold and a fourth wax mold, and the third wax mold and the fourth wax mold are used to seal the mold shell.

[0084] After several small modules are connected to form a large module, the smelting and pouring process is started. During the smelting and pouring process, the bottom of the large module needs to be sealed (to prevent the molten metal from flowing out), and the third wax mold and the fourth wax mold can be used to achieve a tight sealing of the bottom of the entire assembled large module.

[0085] Among them, Figure 7 As shown, the third wax model is a hollow cone with a trapezoidal cross-section, one end of the hollow cone is closed and the other end is open, and a disc body extends outward from the closed end; the interior of the hollow cone is formed with a first annular cavity and a second annular cavity with successively increasing diameters, and the first annular cavity and the second annular cavity form a first step and a second step connected in sequence.

[0086] That is, the third wax model includes a hollow truncated cone and a disc body which are integrally connected and whose axes overlap with each other. One bottom surface of the hollow truncated cone (hereinafter referred to as the "first bottom surface") is connected to the disc body to form a closed structure, and the other bottom surface (hereinafter referred to as the "second bottom surface") is open.

[0087] The cross section of the disc body is circular, and the diameter of the cross section is the same as the diameter of the first bottom surface of the hollow truncated cone. The disc body has a certain thickness along its axial direction.

[0088] The interior of the hollow truncated cone includes a first annular cavity and a second annular cavity, the diameter of the second annular cavity is larger than the diameter of the first annular cavity, and the axes of the first annular cavity and the second annular cavity coincide with each other. Due to the different diameters of the first annular cavity and the second annular cavity, a first step and a second step are formed.

[0089] like Figure 8 As shown, the fourth wax model is a hollow structure with one end closed and the other end open, and the hollow structure includes a second frustum, a first ring and a second ring which are fixedly connected in sequence and whose axes coincide with each other, the outer diameter of the first ring is larger than the outer diameter of the second ring; the outer surfaces of the first ring and the second ring form a third step and a fourth step which are connected in sequence; the surface of the second frustum connected to the first ring is the third bottom surface, and the other surface which is not connected to the first ring is the fourth bottom surface, the diameter of the fourth bottom surface is smaller than the diameter of the third bottom surface, and the diameter of the third bottom surface is larger than the outer diameter of the first ring.

[0090] That is, the fourth wax model includes a second truncated cone body, a first circular ring, and a second circular ring, which are integrally connected and have their axes overlapped with each other. One end of the second truncated cone body is closed and the other end is open; the first circular ring and the second circular ring are both hollow. Due to the different diameters of the first circular ring and the second circular ring, the third step and the fourth step are formed.

[0091] Wherein, the difference between the outer diameter of the second circular ring of the fourth wax model and the diameter of the first annular cavity of the third wax model is less than or equal to 1 mm. That is, the outer diameter of the second circular ring is equal to the diameter of the first annular cavity, or the difference between the outer diameter of the second circular ring and the diameter of the first annular cavity is less than 1 mm, including but not limited to any point value of 0.9 mm, 0.8 mm, 0.7 mm, 0.6 mm, 0.5 mm, 0.4 mm, 0.3 mm, 0.2 mm, 0.1 mm, 0.05 mm or any range value between two of them.

[0092] Preferably, the difference between the outer diameter of the second ring and the diameter of the first annular cavity is less than 1 mm, so that the outer diameter of the second ring is equal along its axis, while the first annular cavity gradually decreases along its axis and in the direction close to the disc body (i.e., from the open end to the closed end). In this way, the obtained shell has a certain inclination, which is conducive to improving the docking effect of the shell.

[0093] The difference between the outer diameter of the first annular ring and the diameter of the second annular cavity is less than or equal to 1 mm. That is, the outer diameter of the first annular ring is equal to the diameter of the second annular cavity, or the difference between the outer diameter of the first annular ring and the diameter of the second annular cavity is less than 1 mm, including but not limited to any point value of 0.9 mm, 0.8 mm, 0.7 mm, 0.6 mm, 0.5 mm, 0.4 mm, 0.3 mm, 0.2 mm, 0.1 mm, 0.05 mm or any range value between two of them.

[0094] Preferably, the difference between the outer diameter of the first annular ring and the diameter of the second annular cavity is less than 1 mm, so that the outer diameter of the first annular ring is equal along its axis, while the second annular cavity gradually decreases along its axis and in the direction close to the disc body (i.e., from the open end to the closed end). In this way, the obtained shell can have a certain inclination, which is conducive to improving the docking effect of the shell.

[0095] The use method and principle of the third wax mold and the fourth wax mold are as follows: After connecting one end of the fourth wax mold (the connecting end is the end of the second circular ring) to the wax mold module, apply paint to it so that the paint fills the first annular cavity and the second annular cavity to prepare a mold shell. At the same time, apply paint to the outer surface of the third wax mold to prepare a mold shell. Then peel off the mold shell at the second truncated cone body on the surface of the fourth wax mold (the second truncated cone body has a sharp angle structure and is easy to peel off) to obtain a mold shell with two stepped groove structures. And peel off the disk body on the surface of the third wax mold and the mold shell on the side surface of the hollow truncated cone to obtain a mold shell with two stepped convex structures. This two-step mortise and tenon joint structure can achieve a tight sealing of the bottom of the mold shell.

[0096] In some specific embodiments of the present invention, the sizes of the first wax model and the second wax model can be any conventional size, and can be set and adjusted according to the size of the casting or the wax model module to be connected. For example, R = 10 to 100 mm, including but not limited to any point value of 20 mm, 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm or any range value between two of them.

[0097] In some specific embodiments of the present invention, the sizes of the third wax mold and the fourth wax mold can be of any conventional size, and can be set and adjusted according to the size of the casting or the wax mold module to be connected. For example, the diameter of the first annular cavity and the outer diameter of the second circular ring can be selected from 10 to 100 mm, including but not limited to any point value of 20 mm, 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm or any range value between the two. The diameter of the second annular cavity and the outer diameter of the first circular ring can be selected from 20 to 110 mm, including but not limited to any point value of 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm or any range value between the two.

[0098] In a second aspect, the present invention provides a wax mold set, including the wax mold for butt jointing of mold shells as described above.

[0099] Using the wax mold assembly as described above for investment casting can improve production efficiency, greatly reduce costs, and ensure the quality of the mold shell.

[0100] In some specific embodiments of the present invention, the first wax mold and the second wax mold can be used for any two monomer small module groups to be connected. It is only necessary to connect one of the monomer small module groups to the first wax mold, and the other monomer small module group to the second wax mold. Among them, the connection end of the first wax mold is the bottom surface of the core that is not connected to the connecting part. The connection end of the second wax mold is the bottom surface of the second cylinder that is not connected to the first cylinder. Preferably, the first wax mold is connected to the monomer small module group with a smaller volume, and the second wax mold is connected to the monomer small module group with a larger volume, which is convenient for operation and observation of the docking effect.

[0101] In a third aspect, the present invention provides an investment casting method, using the butt wax pattern for butt jointing of mold shells as described above, the investment casting method comprising the following steps:

[0102] First, according to the shape and structure of the casting to be produced, a plurality of single modules and at least one main pouring system are made of wax material, and the first wax model and the second wax model are produced by mold pressing (making a wax mold, using a wax press to press the wax model), laser rapid prototyping (PSB powder laser rapid prototyping to make a wax model) or 3D printing photosensitive resin (printing photosensitive resin as a wax model for shell preparation). The wax material includes precision casting wax.

[0103] (a) Fig. 9 As shown, the first wax model is connected (welded) to the monomer module to obtain the first module; Fig.10As shown, the second wax mold is connected (welded) to the main casting system wax mold to obtain a second mold set.

[0104] Wherein, the number of the monomer modules is at least one, including but not limited to any one of 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 15, 17, 18, 20, 22, 24, 25, 28, 30, 40, 50 or any range between two thereof. The number of the first wax molds is the same as the number of the monomer modules. The number of the second wax molds is the same as the number of the first wax molds.

[0105] (b), coating the surfaces of the first mold group and the second mold group respectively, and obtaining a first shell and a second shell after drying; wherein the coating fills the annular groove; Fig.11 and Fig.12 shown.

[0106] In some specific embodiments of the present invention, the coating specifically includes the following steps: sequentially coating 2 layers of surface coating, 1 layer of transition layer coating, 6 to 10 layers of reinforcement layer coating and 1 layer of sealing coating. Preferably, the surface coating includes yttrium oxide and / or zirconium oxide. The chemical properties of titanium alloy are extremely active. It reacts with most metals or non-metals in a high-temperature molten state. Yttrium oxide and zirconium oxide have good inertness and do not react with molten titanium. Preferably, the transition layer coating includes sand and silica sol slurry, and the combination of the two can better connect the surface coating and the reinforcement layer coating. Preferably, the number of layers of the reinforcement layer coating can be specifically set and adjusted according to the structural size of the casting; the reinforcement layer coating includes bauxite sand and silica sol, and the combination of the two can increase the strength of the shell and meet the requirements of smelting, pouring and process. Finally, the sealing coating is applied to prevent sand from falling off the shell surface and ensure the quality of the shell. The sealing coating can use any conventional sealing coating.

[0107] (c) peeling off the shell on the surface of the connecting portion and the shell on the surface of the annular structure in the first shell. Fig.11 As shown, the mold shell on the B side is peeled off, but the mold shell in the annular groove is not peeled off. The mold shell on the second bottom surface of the first truncated cone and the mold shell on the side surface of the second mold shell are peeled off; as shown Fig.12 As shown, the shell on the C side is peeled off.

[0108] (d) After the first shell and the second shell are dewaxed and fired in sequence, the first shell forms a first protrusion and the second shell forms a first groove. Fig.13The first protrusion and the first groove are spliced ​​together, and then melted and poured to obtain a casting.

[0109] The investment casting method provided by the present invention is also a process for butt jointing investment casting mold shells, which involves splitting the overall large mold group into multiple small mold groups, and connecting the multiple small mold groups to the first wax mold and the second wax mold of a specific structure, respectively, and then making a shell with paint, peeling off part of the mold shell, dewaxing, and roasting to form a concave and convex mortise and tenon structure (i.e., a first protrusion and a first groove), and then butt jointing and assembly, and then melting and pouring are performed to produce high-quality castings, and the castings have the advantages of simple process, low labor intensity, high production efficiency, and low cost.

[0110] The invention solves the problems existing in the prior art, such as long drying time of large molds during shell making, easy cracking, inability to ensure the metallurgical quality of titanium alloy castings, high labor intensity, low production efficiency, high cost of using graphite, high-temperature vacuum degassing before use, coating after cutting the shell joints for hard connection and then baking the paste, and molten metal easily coming into contact with the reinforcement layer material of the shell to react and affect the forming quality of the casting.

[0111] In a specific embodiment of the present invention, the partial structure of the first shell having the first protrusion and the second shell having the first groove is shown in the figure. Fig.14 shown.

[0112] Preferably, in step (d), after the sintering and before the splicing, the following step is further included: removing excess mold shell that affects the splicing of the protrusion and the groove.

[0113] like Fig.14 As shown, if the outermost shell has a protrusion when the first protrusion and the first groove are connected, it will affect the connection between the two. Therefore, it is necessary to remove the redundant shell that affects the connection between the protrusion and the groove.

[0114] Preferably, in step (a), after the second wax mold is connected to the main pouring system wax mold, the following step is further included: connecting the fourth wax mold to the bottom of the main pouring system wax mold to obtain the second mold assembly. The fourth wax mold is used to seal the bottom of the mold shell.

[0115] Furthermore, after obtaining the second mold set, coating is applied on the surface of the second mold set including the second wax mold and the fourth wax mold, and a second mold shell is obtained after drying.

[0116] Preferably, step (b) further includes the following steps: coating a coating on the surface of the third wax mold, and obtaining a third shell after drying; wherein the coating fills the first annular cavity and the second annular cavity.

[0117] Preferably, step (c) further includes the following steps: peeling off the fourth bottom surface and the side surface of the second truncated cone in the second mold shell; and peeling off the mold shell of the side surface of the disk body and the hollow truncated cone in the third mold shell.

[0118] Preferably, in step (d), after the roasting and before the smelting and pouring, the bottom of the second shell is further formed with a second groove, and the third shell is formed with a second protrusion, such as Fig.15 and Fig.16 As shown, the second protrusion and the second groove are spliced ​​together.

[0119] The second protrusion refers to a protrusion structure with two stepped distributions, and the second groove refers to a groove structure with two stepped distributions. Such a double-step mortise and tenon joint structure can achieve a tight sealing of the bottom of the shell.

[0120] Preferably, in step (c), the stripping method comprises: drilling holes at the locations to be stripped, and then introducing air into the holes to increase the pressure in the shell to be stripped, causing fractures at the sharp corners.

[0121] The first wax model, the second wax model, the third wax model and the fourth wax model provided by the present application have sharp corner structures, the coating property at the sharp corners is poor, and the mold shell strength at the sharp corners is low, so an electric drill is used to drill a small hole, and then compressed air is introduced into the hole, so that the mold shell at the sharp corners can be easily broken. This method is easy to operate and quick.

[0122] In a fourth aspect, the present invention provides a method for preparing a titanium alloy casting, comprising the investment casting method as described above.

[0123] The titanium alloy castings produced by the method have good quality, high production efficiency and low production cost.

[0124] Although the present invention has been illustrated and described with specific embodiments, it should be appreciated that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents without departing from the spirit and scope of the present invention. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A wax pattern for shell butt joint, characterized in that: comprising a first wax model and a second wax model; The first wax model comprises a fixedly connected annular structure and a connecting portion that closes one end of the annular structure, and the first wax model also comprises a cylindrical core connected to the connecting portion, wherein the core is partially accommodated in the annular structure and forms an annular groove with the annular structure; the axis of the annular structure coincides with the axis of the core; and the annular structure is further provided with an annular sharp corner at one end away from the connecting portion; The second wax model comprises a first truncated cone, a first cylinder and a second cylinder which are fixedly connected in sequence; the axes of the first truncated cone, the first cylinder and the second cylinder coincide with each other; the outer diameter of the first cylinder is greater than the outer diameter of the second cylinder; the surface of the first truncated cone connected to the first cylinder is the first bottom surface, and the surface not connected to the first cylinder is the second bottom surface, the diameter of the second bottom surface is smaller than the diameter of the first bottom surface, and the diameter of the first bottom surface is greater than the outer diameter of the first cylinder; The outer diameter of the first cylinder is Rmm, and the inner diameter of the annular structure is R-1mm~Rmm.

2. The wax pattern for shell butt joint according to claim 1, characterized in that: The inner diameter of the annular structure gradually decreases in a direction approaching the connecting portion.

3. The wax pattern for shell butt joint according to claim 1, characterized in that: The second wax mold is hollow.

4. The wax pattern for shell butt joint according to claim 1, characterized in that: The butt joint wax mold for butt joint of the mold shell further comprises a third wax mold and a fourth wax mold, and the third wax mold and the fourth wax mold are used to seal the mold shell; The third wax model is a hollow truncated cone with a trapezoidal cross section, one end of the hollow truncated cone is closed and the other end is open, and a disc body extends outward from the closed end; a first annular cavity and a second annular cavity with successively increasing diameters are formed inside the hollow truncated cone, and the first annular cavity and the second annular cavity form a first step and a second step connected in sequence; The fourth wax mold is a hollow structure with one end closed and the other end open, and the hollow structure includes a second truncated cone, a first circular ring, and a second circular ring which are fixedly connected in sequence and whose axes coincide with each other, and the outer diameter of the first circular ring is larger than the outer diameter of the second circular ring; the outer surfaces of the first circular ring and the second circular ring form a third step and a fourth step which are connected in sequence; the surface of the second truncated cone connected to the first circular ring is the third bottom surface, and the surface not connected to the first circular ring is the fourth bottom surface, the diameter of the fourth bottom surface is smaller than the diameter of the third bottom surface, and the diameter of the third bottom surface is larger than the outer diameter of the first circular ring; Wherein, the difference between the outer diameter of the second circular ring and the diameter of the first annular cavity is less than or equal to 1 mm; The difference between the outer diameter of the first circular ring and the diameter of the second annular cavity is less than or equal to 1 mm.

5. Wax model module, characterized in that: It comprises a wax pattern for shell butt joint as described in any one of claims 1 to 4.

6. Investment casting method, characterized in that: Using the butt-jointing wax pattern for shell butt-jointing as claimed in any one of claims 1 to 4, the investment casting method comprises the following steps: (a) The first wax mold is connected to a monomer mold to obtain a first mold; the second wax mold is connected to a main casting system wax mold to obtain a second mold; (b) coating the surfaces of the first mold group and the second mold group respectively, and obtaining a first shell and a second shell after drying; wherein the coating fills the annular groove; (c) peeling off the shell on the surface of the connecting portion and the shell on the surface of the annular structure in the first shell, and peeling off the shell on the second bottom surface of the first truncated cone and the shell on the side surface of the first truncated cone in the second shell; (d) After the first shell and the second shell are dewaxed and fired in sequence, the first shell forms a first protrusion and the second shell forms a first groove. The first protrusion and the first groove are spliced, and then melted and poured to obtain a casting.

7. The investment casting method according to claim 6, characterized in that: In step (d), after the sintering and before the splicing, the following step is further included: removing the redundant mold shell that affects the splicing of the first protrusion and the first groove.

8. The investment casting method according to claim 6, characterized in that: In step (a), after the second wax mold is connected to the main pouring system wax mold, the following step is further included: connecting the fourth wax mold to the bottom of the main pouring system wax mold to obtain the second mold assembly.

9. The investment casting method according to claim 6, characterized in that: Step (b) further includes the following steps: coating the surface of the third wax mold with a coating, and obtaining a third shell after drying; wherein the coating fills the first annular cavity and the second annular cavity.

10. The investment casting method according to claim 9, characterized in that: Step (c) also includes the following steps: peeling off the fourth bottom surface and the side surface of the second truncated cone in the second shell; and peeling off the shell of the side surface of the disk body and the hollow truncated cone in the third shell.

11. The investment casting method according to claim 9, characterized in that: In step (d), after the sintering and before the smelting and pouring, a second groove is formed on the bottom of the second shell, a second protrusion is formed on the third shell, and the second protrusion and the second groove are spliced.

12. The investment casting method according to claim 10, characterized in that: In step (c), the stripping method includes: drilling holes at the locations to be stripped, and then introducing air into the holes to increase the pressure in the shell to be stripped, causing fractures at the sharp corners.

13. A method for preparing a titanium alloy casting, characterized in that: Including the investment casting method as described in any one of claims 6 to 12.

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