Apparatus and method for semi-solid extrusion of thin-walled components

Abstract

The application discloses a kind of semi-solid extrusion forming thin-walled component device and method, it is related to metal processing technical field, the device of semi-solid extrusion forming thin-walled component disclosed in the application includes preprocessing unit, extrusion unit and heat treatment unit, preprocessing unit includes first gradient heating temperature control device and preprocessing mould, extrusion unit includes second gradient heating temperature control device and extrusion mould, heat treatment unit includes third gradient heating temperature control device and heat treatment carrier, the method of semi-solid extrusion forming thin-walled component disclosed in the application includes obtaining cylindrical semi-solid blank, preheating, spraying lubricant, remelting heating, extruding thin-walled component and heat treatment;Semi-solid extrusion forming thin-walled component device and method disclosed in the application reduce the extrusion force requirement, with good forming effect.

Description

Technical Field

[0001] This invention relates to the field of metal processing technology, and in particular to an apparatus and method for semi-solid extrusion molding of thin-walled components. Background Technology

[0002] High-strength aluminum alloys possess significant advantages such as high strength, corrosion resistance, high temperature resistance, and high designability. They also have an extremely wide application temperature range and are poised to become key materials for components in high-end equipment such as aerospace, shipbuilding, and weaponry. Thin-walled tubing, due to its closed geometry, is an ideal blank structure for forming integral, complex curved, thin-walled parts.

[0003] Large, thin-walled aluminum alloy cylindrical parts are typical workpieces in the aerospace industry. "Large" refers to their overall large dimensions, typically exceeding 500mm; "thin-walled" refers to their small average wall thickness, generally less than 10mm. Furthermore, the inner walls of these parts often feature crisscrossing reinforcing ribs and bosses, further complicating their structure and increasing manufacturing difficulty. Large, thin-walled cylindrical parts are usually produced using casting processes, followed by heat treatment and machining to ensure the final mechanical properties and dimensional accuracy. Traditional casting processes, such as ordinary sand casting and gravity casting, are prone to defects like undercasting, cold shuts, shrinkage cavities, porosity, deformation, and dimensional deviations due to the complex structure of the castings, resulting in a low yield rate.

[0004] Compared to traditional casting processes, aluminum alloy plastic extrusion molding offers advantages such as high production efficiency, the ability to extrude complex cross-section profiles in a single step, high forming precision, and high stability. It has been increasingly applied in the manufacturing of large, high-performance aluminum alloy components for aerospace applications. However, manufacturing wide-width integral wall panels using extrusion places high demands on both press tonnage and tooling equipment. Extruding 800mm wide sheets requires a 125MN extrusion press; extruding 1000mm wide sheets requires an extrusion pressure of 225MN, and the process is more difficult, prone to instability, and costly. Summary of the Invention

[0005] The purpose of this invention is to provide an apparatus and method for semi-solid extrusion molding of thin-walled components, so as to solve the problems existing in the prior art, reduce the extrusion pressure requirement, and achieve better molding effect.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] The present invention provides an apparatus for semi-solid extrusion molding of thin-walled components, comprising a pretreatment unit, an extrusion unit, and a heat treatment unit;

[0008] The pretreatment unit includes a first gradient heating and temperature control device and a pretreatment mold. The pretreatment mold includes an extrusion cylinder, an extrusion punch, a connecting rod, and a mold frame. The extrusion cylinder has openings at both ends and its interior is used to accommodate semi-solid billets. One end of the extrusion punch is fixedly connected to the mold frame via the connecting rod. The extrusion punch can extend into the extrusion cylinder from the opening at the end of the extrusion cylinder closest to the mold frame. A gap is left between the outer side wall of the extrusion punch and the inner side wall of the extrusion cylinder. The extrusion punch can reciprocate in the axial direction of the extrusion cylinder. The end of the mold frame away from the extrusion punch is used to connect to the pressure shaft of the extruder. The first gradient heating and temperature control device is fixedly disposed outside the extrusion cylinder and can heat the extrusion cylinder.

[0009] The extrusion unit includes a second gradient heating and temperature control device and an extrusion die. The extrusion die includes a punch and a die. The die is fixedly disposed at the end of the extrusion cylinder away from the die frame. The punch is fixedly disposed between the die and the extrusion cylinder. The punch can seal the opening at the end of the extrusion cylinder away from the die frame. The punch and the die together form an annular welding chamber and an annular working belt. One end of the annular working belt communicates with the welding chamber. The punch has several portholes that allow the welding chamber to communicate with the interior of the extrusion cylinder, so that semi-solid billets can enter the welding chamber through the portholes. The second gradient heating and temperature control device is fixedly disposed outside the extrusion die and can heat the extrusion die.

[0010] The heat treatment unit includes a third gradient heating and temperature control device and a heat treatment carrier. The heat treatment carrier has an annular channel, one end of which is connected to the end of the annular working belt away from the welding chamber. The third gradient heating and temperature control device is fixedly installed outside the heat treatment carrier and heats the heat treatment carrier.

[0011] Preferably, the first gradient heating and temperature control device is fixedly sleeved on the outer wall of the extrusion cylinder, the second gradient heating and temperature control device is fixedly sleeved on the outer wall of the extrusion die, and the third gradient heating and temperature control device is fixedly sleeved on the outer wall of the heat treatment support; a heat insulation layer is fixedly sleeved on the outer walls of the first gradient heating and temperature control device, the second gradient heating and temperature control device, and the third gradient heating and temperature control device; a heat insulation connecting plate is fixedly provided between the die frame and the pressure shaft of the extruder, between the extrusion cylinder and the punch, and between the die and the heat treatment support.

[0012] Preferably, the extrusion cylinder has a first temperature measuring channel, in which a first temperature measuring element is fixedly installed; the extrusion die has a second temperature measuring channel, in which a second temperature measuring element is fixedly installed; and the heat treatment support has a third temperature measuring channel, in which a third temperature measuring element is fixedly installed. The first gradient heating and temperature control device and the first temperature measuring element are both connected to the heating and temperature control system; the second gradient heating and temperature control device and the second temperature measuring element are both connected to the heating and temperature control system; and the third gradient heating and temperature control device and the third temperature measuring element are both connected to the heating and temperature control system.

[0013] Preferably, a prestressed ring is fixedly fitted on the outer wall of the first gradient heating and temperature control device.

[0014] Preferably, the annular channel includes a front channel and a rear channel connected in sequence. The front channel is located between the annular working belt and the rear channel. The length of the front channel is greater than 500 mm, the length of the rear channel is greater than 100 mm, the radius of the front channel is 5-10 mm larger than the radius of the annular working belt, and the radius of the rear channel is 20-30 mm larger than the radius of the front channel.

[0015] The present invention also provides a method for semi-solid extrusion molding of thin-walled components, using the apparatus for semi-solid extrusion molding of thin-walled components as described in any one of the above claims, comprising the following steps:

[0016] S1. Prepare a semi-solid billet, turn the semi-solid billet to remove the oxide scale, and then process and cut it to obtain a cylindrical semi-solid billet;

[0017] S2. Preheat the extrusion cylinder using the first gradient heating and temperature control device; preheat the extrusion die using the second gradient heating and temperature control device; preheat the heat treatment carrier using the third gradient heating and temperature control device;

[0018] S3. Apply lubricant evenly to the working surfaces of the extrusion cylinder, punch, die, and annular channel;

[0019] S4. The semi-solid billet is remelted and heated in a resistance furnace. The cylindrical semi-solid billet obtained in S1 is placed in the resistance furnace, heated and kept at the temperature.

[0020] S5. The heated and kept-warm semi-solid billet is taken out from the resistance furnace and clamped into the extrusion cylinder. The extruder drives the extrusion punch to extrude the semi-solid billet in the extrusion cylinder into the extrusion die, and extrudes the thin-walled component from the annular working belt.

[0021] S6. The thin-walled component extruded from the annular working belt enters the annular channel and moves slowly along the annular channel for heat treatment to adjust its properties;

[0022] S7. After the semi-solid billet in the extrusion cylinder has been extruded, the extruder drives the extrusion punch to exit the extrusion cylinder.

[0023] S8. Repeat S1 to S7 to continuously extrude and form thin-walled components in a semi-solid state.

[0024] Preferably, in S4, the remelting heating temperature is 300-700℃, and the remelting heating holding time is 5-40min.

[0025] Preferably, in S2, after the extrusion cylinder is preheated by the first gradient heating and temperature control device, the temperature of the semi-solid billet near the punch is 400-700℃, that is, the semi-solid billet near the punch has 10-60% liquid billet, and the temperature of the semi-solid billet near the extrusion punch is 200-450℃, that is, the semi-solid billet near the extrusion punch is completely solid.

[0026] Preferably, in S2, the extrusion die is preheated using a second gradient heating and temperature control device to make the temperature of the punch and die 200-650°C and the temperature of the annular working belt 200-450°C; the heat treatment carrier is preheated using a third gradient heating and temperature control device to make the temperature in the annular channel 250-550°C.

[0027] Preferably, in S5, the extrusion speed of the extrusion punch is 1-20 mm / s.

[0028] The present invention achieves the following technical effects compared to the prior art:

[0029] The apparatus and method for semi-solid extrusion molding of thin-walled components provided by this invention achieve the integral molding of large thin-walled components through extrusion, realizing the goal of producing large thin-walled components with relatively small molding force. Compared with the traditional casting molding of large thin-walled components, this invention utilizes the high strain rate hardening effect of the material under large strain extrusion to further accumulate dislocation substructures and improve wall thickness uniformity. The extruded large thin-walled components enter an annular channel for heat treatment, thereby obtaining large thin-walled components with good microstructure and improving the molding quality of large thin-walled components. At the same time, it can solve the problems of large machining volume, high manufacturing cost, poor molding accuracy, and damage to rheological structure in traditional processing methods. The performance of the large thin-walled components extruded from the self-extrusion die is controlled by the annular channel structure. Compared with the heat treatment of large thin-walled components, the step of transferring from the extrusion equipment to the holding furnace can be eliminated, saving time and improving production efficiency. The apparatus and method for semi-solid extrusion molding of thin-walled components have the advantages of high efficiency, greenness, and energy saving, and reduce costs and extrusion force requirements, while achieving better molding results. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the apparatus for semi-solid extrusion molding of thin-walled components provided by the present invention;

[0032] Figure 2 This is a schematic flowchart of the method for semi-solid extrusion molding of thin-walled components provided by the present invention;

[0033] Figure 3 yes Figure 1 Half-section view of the die cavity and punch.

[0034] Figure 4 This is a flowchart of the preparation of semi-solid billets using the strain-induced melting activation method in Example 1.

[0035] Figure 5 This is a flowchart of the process for preparing semi-solid billets using the recrystallization partial remelting method in Example 2.

[0036] Figure 6 This is a schematic diagram of the punch structure in Embodiment 2.

[0037] Figure 7 This is the rear view of the punch in Embodiment 2.

[0038] Figure 8 This is a structural schematic diagram of the thin-walled reinforced member in Embodiment 2.

[0039] Figure 9 This is a schematic diagram of the grain size at each stage in the semi-solid extrusion molding method for thin-walled components provided by the present invention;

[0040] In the diagram: 101, mold frame; 102, connecting rod; 103, extrusion punch; 104, extrusion cylinder; 105, semi-solid billet; 106, first gradient heating and temperature control device; 107, prestressed ring; 201, punch; 202, die; 203, annular working belt; 204, welding chamber; 205, porthole; 206, second gradient heating and temperature control device; 207, punch mandrel; 208, punch body; 301, annular channel; 302, front channel; 303, rear channel; 304, third gradient heating and temperature control device; 401, heat insulation connecting plate; 402, first temperature measuring channel; 403, second temperature measuring channel; 404, third temperature measuring channel; 405, first temperature measuring element; 406, second temperature measuring element; 407, third temperature measuring element; 408, thermal insulation layer. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] The purpose of this invention is to provide an apparatus and method for semi-solid extrusion molding of thin-walled components, so as to solve the problems existing in the prior art, reduce the extrusion pressure requirement, and achieve better molding effect.

[0043] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] like Figure 1-9 As shown, the present invention provides an apparatus for semi-solid extrusion molding of thin-walled components, including a pretreatment unit, an extrusion unit, and a heat treatment unit.

[0045] The pretreatment unit includes a first gradient heating and temperature control device 106 and a pretreatment mold. The pretreatment mold includes an extrusion cylinder 104, an extrusion punch 103, a connecting rod 102, and a mold frame 101. The extrusion cylinder 104 has openings at both ends. The interior of the extrusion cylinder 104 is used to accommodate a semi-solid billet 105. One end of the extrusion punch 103 is fixedly connected to the mold frame 101 via the connecting rod 102. The extrusion punch 103 can extend into the extrusion cylinder 104 from the opening at the end of the extrusion cylinder 104 closest to the mold frame 101. A gap is left between the outer side wall of the extrusion punch 103 and the inner side wall of the extrusion cylinder 104. The extrusion punch 103 can reciprocate in the axial direction of the extrusion cylinder 104. The end of the mold frame 101 away from the extrusion punch 103 is used to connect to the pressure shaft of the extruder. The first gradient heating and temperature control device 106 is fixedly installed outside the extrusion cylinder 104. The first gradient heating and temperature control device 106 can heat the extrusion cylinder 104.

[0046] The extrusion unit includes a second gradient heating and temperature control device 206 and an extrusion die. The extrusion die includes a punch 201 and a die 202. The die 202 is fixedly disposed at one end of the extrusion cylinder 104 away from the die frame 101. The punch 201 is fixedly disposed between the die 202 and the extrusion cylinder 104. The punch 201 can block the opening at one end of the extrusion cylinder 104 away from the die frame 101. The punch 201 and the die 202 are combined to form an annular welding chamber 204 and an annular working belt 203. One end of the annular working belt 203 is connected to the welding chamber 204. The punch 201 is provided with several portholes 205. The portholes 205 can connect the welding chamber 204 with the interior of the extrusion cylinder 104 so that the semi-solid billet 105 can enter the welding chamber 204 through the portholes 205. The second gradient heating and temperature control device 206 is fixedly disposed outside the extrusion die. The second gradient heating and temperature control device 206 can heat the extrusion die.

[0047] The heat treatment unit includes a third gradient heating and temperature control device 304 and a heat treatment carrier. An annular channel 301 is provided on the heat treatment carrier. One end of the annular channel 301 is connected to the end of the annular working belt 203 away from the welding chamber 204. The third gradient heating and temperature control device 304 is fixedly installed outside the heat treatment carrier and heats the heat treatment carrier.

[0048] The apparatus for semi-solid extrusion molding of thin-walled components provided by the present invention is suitable for the production of thin-walled components, especially for the production of large thin-walled components. The first gradient heating and temperature control device 106 in the pretreatment unit can heat and keep the extrusion cylinder 104 and the semi-solid blank 105 at a certain temperature. After the temperature is kept at a certain temperature, the extrusion punch 103 extrudes and molds the semi-solid blank 105. After molding, the heat treatment unit is used for heat treatment to obtain thin-walled components with good microstructure and good structural performance and high dimensional accuracy.

[0049] In a preferred embodiment, the semi-solid billet 105 is processed into a cylindrical structure. Both the semi-solid billet 105 and the extrusion punch 103 are fitted with the extrusion cylinder 104 with a clearance to achieve an extrusion ratio in the range of 10-50. The wall thickness of the extruded tube is 0.5-5 mm, enabling the extrusion forming of large thin-walled components. The high strain rate hardening effect under large strain extrusion further accumulates dislocation substructures, improving wall thickness uniformity. In practical applications, a specific heating method can be selected according to the specific working conditions, allowing the semi-solid billet 105 to undergo extrusion processing in a suitable environment. The cylindrical semi-solid billet 105 is preferably, but not limited to, aluminum alloy or magnesium alloy, and its microstructure exhibits fine equiaxed crystals.

[0050] In this embodiment, the punch 201 includes a punch mandrel 207 and a punch body 208, which are connected as one unit.

[0051] Furthermore, the first gradient heating and temperature control device 106 is fixedly sleeved on the outer wall of the extrusion cylinder 104, the second gradient heating and temperature control device 206 is fixedly sleeved on the outer wall of the extrusion die, and the third gradient heating and temperature control device 304 is fixedly sleeved on the outer wall of the heat treatment support; a heat insulation layer 408 is fixedly sleeved on the outer walls of the first gradient heating and temperature control device 106, the second gradient heating and temperature control device 206, and the third gradient heating and temperature control device 304; a heat insulation connecting plate 4 is fixedly installed between the die frame 101 and the pressure shaft of the extruder, between the extrusion cylinder 104 and the punch 201, and between the die 202 and the heat treatment support. 01; The thermal insulation layer 408 and the thermal insulation connecting plate 401 are both made of thermal insulation material to reduce the heat exchange between the device for semi-solid extrusion molding of thin-walled components provided by the present invention and the external environment, ensuring different temperature conditions in the pretreatment unit, extrusion unit and heat treatment unit, and providing a guarantee for improving the molding quality of large thin-walled components; As a preferred embodiment, the first gradient heating and temperature control device 106, the second gradient heating and temperature control device 206 and the third gradient heating and temperature control device 304 are all annular. The first gradient heating and temperature control device 106 is located on the outer wall of the extrusion cylinder 104 and can heat the extrusion cylinder 104. 04 and the semi-solid billet 105 inside the extrusion cylinder 104; the second gradient heating and temperature control device 206 is located on the outer wall of the punch 201 and the die 202, and can heat the punch 201 and the die 202 and the semi-solid billet 105 extruded into the punch 201 and the die 202; the third gradient heating and temperature control device 304 is located on the outer wall of the heat treatment carrier where the annular channel 301 is located, and can heat the annular channel 301 and the large thin-walled component extruded from the extrusion die; as a preferred embodiment, the first gradient heating and temperature control device 106, the second gradient heating and temperature control device 206 and the third gradient heating and temperature control device All 304 components are made using induction heating coils. The induction heating coils are connected to induction heaters, which output power current. The output power of the induction heating coils is controlled by the induction heaters. Temperature gradient control is achieved by changing the density of the coils, which is also known as the pitch. This results in different heating powers for different parts of the semi-solid billet 105. The denser the coils, the higher the heating efficiency, and the sparser the coils, the lower the heating efficiency, thus creating a temperature gradient. This gradient heats the semi-solid billet 105 and the extrusion die, allowing them to be heated to the required temperature and held at that temperature.

[0052] Furthermore, the extrusion cylinder 104 has a first temperature measuring channel 402, in which a first temperature measuring element 405 is fixedly installed; the extrusion die has a second temperature measuring channel 403, in which a second temperature measuring element 406 is fixedly installed; and the heat treatment carrier has a third temperature measuring channel 404, in which a third temperature measuring element 407 is fixedly installed. The first gradient heating and temperature control device 106 and the first temperature measuring element 405 are both connected to the heating and temperature control system; the second gradient heating and temperature control device 206 and the second temperature measuring element 406 are both connected to the heating and temperature control system; and the third gradient heating and temperature control device 304 and the third temperature measuring element 407 are both connected to the heating and temperature control system. The first temperature measuring element 405 can monitor the pretreatment die and the pretreatment mold. The temperature of the semi-solid billet 105 inside the die is monitored by the second temperature sensing element 406, which can monitor the temperature of the extrusion die and the semi-solid billet 105 inside the extrusion die, and the temperature of the annular channel 301 and the semi-solid billet 105 inside the annular channel 301. In a preferred embodiment, the first temperature sensing element 405, the second temperature sensing element 406, and the third temperature sensing element 407 can be thermocouples with a temperature measurement range of 0℃ to 1200℃. The first temperature sensing element 405 is in contact with the extrusion cylinder 104, the second temperature sensing element 406 is in contact with the punch 201, and the third temperature sensing element 407 is in contact with the side wall of the annular channel 301. The entire device is temperature-controlled using a heating and temperature control system to provide a suitable high-temperature environment for the semi-solid billet 105.

[0053] Furthermore, a prestressed ring 107 is fixedly sleeved on the outer wall of the first gradient heating and temperature control device 106; the inner wall of the prestressed ring 107 is interference-fitted with the outer wall of the first gradient heating and temperature control device 106 to ensure that the extrusion cylinder 104 is in a circumferential compressive stress state. The load-bearing capacity and durability of the extrusion cylinder 104 are improved by applying a predefined amount of circumferential compressive stress. The prestressed ring 107 is preferably, but not limited to, made of a high-toughness mold material without cold brittleness. The extrusion punch 103 and the extrusion cylinder 104 are preferably, but not limited to, made of a hard alloy mold material without cold brittleness. Specifically, they can be made of tungsten steel, high-speed tool steel or cold work die steel.

[0054] Furthermore, the annular channel 301 includes a front channel 302 and a rear channel 303 connected in sequence. The front channel 302 is located between the annular working belt 203 and the rear channel 303. The length of the front channel 302 is greater than 500 mm, and the length of the rear channel 303 is greater than 100 mm. The radius of the front channel 302 is 5-10 mm larger than the radius of the annular working belt 203, and the radius of the rear channel 303 is 20-30 mm larger than the radius of the front channel 302. It should be noted that the inner wall of the annular channel 301 needs to be lubricated with a lubricant such as graphite powder in advance to prevent scratches or even mold blockage on the surface of the extruded large thin-walled component.

[0055] The present invention also provides a method for semi-solid extrusion molding of thin-walled components, using the apparatus for semi-solid extrusion molding of thin-walled components according to any one of the above methods, comprising the following steps:

[0056] S1. Prepare a semi-solid blank 105, turn the semi-solid blank 105 to remove the oxide scale, and then process and cut it to obtain a cylindrical semi-solid blank 105;

[0057] S2. The extrusion cylinder 104 is preheated using the first gradient heating and temperature control device 106; the extrusion die is preheated using the second gradient heating and temperature control device 206; and the heat treatment carrier is preheated using the third gradient heating and temperature control device 304.

[0058] S3. Spray the lubricant evenly onto the working surfaces of the extrusion cylinder 104, punch 201, die 202 and annular channel 301;

[0059] S4. The semi-solid billet 105 is remelted and heated in a resistance furnace. The cylindrical semi-solid billet 105 obtained in S1 is placed in the resistance furnace, heated and kept at a certain temperature.

[0060] S5. The heated and kept-warm semi-solid billet 105 is taken out from the resistance furnace and clamped into the extrusion cylinder 104. The extruder drives the extrusion punch 103 to extrude the semi-solid billet 105 in the extrusion cylinder 104 into the extrusion die, and extrudes the thin-walled component from the annular working belt 203.

[0061] S6. The thin-walled component extruded from the annular working belt 203 enters the annular channel 301 and moves slowly along the annular channel 301 for heat treatment to adjust its performance.

[0062] S7. After the semi-solid billet 105 in the extrusion cylinder 104 has been extruded, the extruder drives the extrusion punch 103 to exit the extrusion cylinder 104.

[0063] S8. Repeat S1 to S7 to continuously extrude and form thin-walled components in a semi-solid state.

[0064] In S1, the semi-solid billet 105 can be prepared using methods such as mechanical stirring, electromagnetic stirring, strain-induced melting activation, or recrystallization partial remelting. Taking strain-induced melting activation as an example, ... Figure 4 As shown, the strain-induced melting activation method uses continuous casting to produce metal ingots with fine grains. The metal ingots are heated to the range of the metal's recovery recrystallization temperature, and hot extrusion processing is applied to the metal ingots. Through large deformation, the as-cast dendritic structure of the ingots is fully broken. Subsequently, a small amount of cold deformation is performed on the deformed metal ingots to store some deformation energy in the billet. Finally, according to the shape of the part, the semi-solid billet 105 is cut into appropriate sizes and shapes.

[0065] In S3, the lubricant can be grease-graphite, which can be uniformly sprayed onto the working surfaces of the extrusion cylinder 104, punch 201, die 202 and annular channel 301 using a high-pressure air pump. This not only prevents the semi-solid blank 105 from sticking to the mold and scratching the mold surface, but also ensures the surface quality of the molded parts. The semi-solid blank 105 has a certain liquid phase at the semi-solid temperature, which makes it easy for the semi-solid blank 105 to stick to the mold during thixotropic extrusion molding. Therefore, lubrication of the device is crucial.

[0066] In S4, a resistance furnace is used to remelt and heat the semi-solid billet 105. When the furnace temperature reaches the set remelting temperature, the processed cylindrical alloy billet is placed into the resistance furnace, and timing begins when the furnace temperature reaches the set temperature again. After the billet's remelting holding time reaches the predetermined value, it is held for a certain period of time to obtain a semi-solid billet 105 with spherical microstructure and thixotropic properties. The remelting temperature of the semi-solid billet 105 determines its liquid phase fraction and fluidity. If the remelting temperature of the semi-solid billet 105 is too low, the liquid phase volume fraction of the semi-solid billet 105 during forming is small, and the liquid phase cannot continuously wet the grain boundaries. Since some solid particles cannot be continuously wrapped by the liquid phase, it is difficult for the solid phase to flow with the liquid phase to complete the filling process. The liquid phase in the forming process does not play the necessary lubricating role between solid particles, resulting in poor material fluidity. Moreover, for some difficult-to-deform aluminum alloys, when there is less liquid phase inside the metal, its recrystallization and spheroidization processes are insufficient, further... The flowability of the billet is reduced. When the remelting temperature of the semi-solid billet 105 is too high, the liquid phase volume fraction of the semi-solid billet 105 is large during molding. Although this can reduce the flow stress of the semi-solid billet 105 and allow for extrusion molding under lower pressure, the clamping strength of the semi-solid billet 105 is low at high temperatures, making it difficult to be clamped and transported smoothly into the extrusion cylinder 104, and the coarsening of solid particles is relatively severe. In addition, an excessively high liquid phase ratio can easily cause solid-liquid segregation in the semi-solid billet 105 during molding, resulting in parts with uneven structure. When the remelting temperature is appropriate, the liquid phase volume fraction in the semi-solid billet 105 is more suitable for thixotropic molding. During molding, the liquid phase encapsulates the solid particles and flows together to complete the filling process. At this temperature, the semi-solid billet 105 has good thixotropy, which allows it to be smoothly clamped into the extrusion cylinder 104 and has good flowability. The microstructure of the semi-solid billet 105 is relatively fine, thus obtaining extruded parts with good structure and performance.

[0067] In S2, the extrusion cylinder 104 is preheated using the first gradient heating and temperature control device 106; the extrusion die is preheated using the second gradient heating and temperature control device 206; and the heat treatment carrier is preheated using the third gradient heating and temperature control device 304. The extrusion cylinder 104, punch 201, die 202, and annular channel 301 are preheated to a suitable temperature, which has an important impact on the extrusion of the semi-solid billet 105. When the preheating temperature is low, the heat of the semi-solid billet 105 dissipates quickly. After being placed in the extrusion die, the part of the billet in contact with the extrusion die will cool down rapidly first, forming a shell with a very low liquid phase content, which affects the uniformity of the extruded part's structure and causes surface cracks. When the preheating temperature is high, die sticking and large flash will occur. In addition, because the part cools down slowly, the solidification time is prolonged, and the part is prone to defects such as micro-shrinkage porosity and thermal cracking, and the grain size is relatively coarse.

[0068] In S5, the extruder drives the extrusion punch 103 to extrude the semi-solid billet 105 inside the extrusion cylinder 104 into the extrusion die. The extrusion punch 103 performs upsetting extrusion on the semi-solid billet 105, eliminating shrinkage porosity and shrinkage defects in the semi-solid billet 105 through dislocation pile-up. The high strain rate hardening effect under large strain extrusion further accumulates dislocation substructures, improving wall thickness uniformity. The semi-solid billet 105 is a solid-liquid mixture; the extrusion speed affects the synergistic application of the solid and liquid phases during the forming process of the semi-solid billet 105. The distribution has a significant impact. When the extrusion speed is too high, the solid and liquid phases in the semi-solid billet 105 cannot move synchronously in time, which can easily lead to the separation of the solid and liquid phases and uneven microstructure distribution of the part. A lower extrusion speed is beneficial for the good filling of the semi-solid billet 105, but it should not be too low. If it is too low, the liquid phase inside the part may solidify prematurely due to the slow pressure transmission, and the extrusion molding pressure may not be able to be transmitted to the micro-region inside the part, resulting in uneven microstructure. Therefore, it is necessary to select the extrusion speed reasonably based on the actual needs and the specific properties of the semi-solid billet 105.

[0069] In S6, the thin-walled component extruded from the annular working belt 203 enters the annular channel 301 and moves slowly along the annular channel 301 for heat treatment to adjust its properties, thereby obtaining a large thin-walled component with good microstructure and improving the molding quality of the large thin-walled component.

[0070] The apparatus and method for semi-solid extrusion molding of thin-walled components provided by this invention achieves integral molding of large thin-walled components through extrusion, achieving the goal of producing large thin-walled components with relatively small molding force. Compared with the traditional casting molding of large thin-walled components, this invention utilizes the high strain rate hardening effect of the material under large strain extrusion to further accumulate dislocation substructures and improve wall thickness uniformity. The extruded large thin-walled components enter the annular channel 301 for heat treatment, thereby obtaining large thin-walled components with good microstructure and improving the molding quality of large thin-walled components. At the same time, it can solve the problems of large machining volume, high manufacturing cost, poor molding accuracy, and damage to rheological structure in traditional processing methods. The annular channel 301 structure controls the performance of the large thin-walled components extruded from the extrusion die. Compared with the heat treatment of traditional large thin-walled components, the step of transferring from the extrusion equipment to the holding furnace can be eliminated, saving time and improving production efficiency. The apparatus and method for semi-solid extrusion molding of thin-walled components have the advantages of high efficiency, greenness, and energy saving, and reduce costs and extrusion force requirements, while achieving better molding results.

[0071] In a preferred embodiment, in S4, the remelting heating temperature is 300-700℃, and the remelting heating holding time is 5-40 minutes.

[0072] In a preferred embodiment, in S2, after the extrusion cylinder 104 is preheated by the first gradient heating and temperature control device 106, the temperature of the semi-solid blank 105 near the punch 201 is 400-700°C, that is, the semi-solid blank 105 near the punch 201 has 10-60% liquid blank, and the temperature of the semi-solid blank 105 near the extrusion punch 103 is 200-450°C, that is, the semi-solid blank 105 near the extrusion punch 103 is completely solid. The extrusion punch 103 and the extrusion cylinder 104 are fitted with a clearance to prevent the semi-solid blank 105 from being squeezed out from the joint between the extrusion punch 103 and the extrusion cylinder 104 during the extrusion process.

[0073] Furthermore, the semi-solid billet 105 needs to be heated in the extrusion cylinder 104 for a period of time so that both the surface and the interior of the semi-solid billet 105 reach the set temperature before extrusion. In practical applications, the heating temperature and holding time of the billet and the extrusion die can be determined according to the specific material of the semi-solid billet 105.

[0074] In a preferred embodiment, in S2, the extrusion die is preheated using the second gradient heating and temperature control device 206, so that the temperature of the punch 201 and die 202 is 200-650°C, keeping the billet in a semi-solid state to facilitate billet flow and reduce extrusion pressure, and the temperature at the annular working belt 203 is 200-450°C, so that the extruded large thin-walled component cools and solidifies; the heat treatment carrier is preheated using the third gradient heating and temperature control device 304, so that the temperature inside the annular channel 301 is 250-550°C. In practical applications, the heat treatment temperature and holding time can be determined according to the specific material of the semi-solid billet 105, and the speed of the extrusion punch 103 can be determined according to the holding time and the length of the front channel 302.

[0075] Furthermore, if the material strength still does not meet the requirements after heat treatment in the front channel 302, solution aging treatment can be performed on the large thin-walled components. The solution temperature is 300-550℃ and the solution time is 1-8h; the aging temperature is 100-300℃ and the aging time is 4-48h.

[0076] In a preferred embodiment, in S5, the extrusion speed of the extrusion punch 103 is 1-20 mm / s.

[0077] Example 1

[0078] The semi-solid billet 105 is made of 7075 aluminum alloy, which is difficult to deform; the extrusion punch 103 and the extrusion cylinder 104 are both made of D2 cold work die steel, with nitriding treatment and grinding and polishing; the prestressed ring 107 is made of 316L stainless steel. The specific steps are as follows:

[0079] S1. As Figure 4As shown, a 7075 aluminum alloy semi-solid billet 105 was prepared using the strain-induced melting activation method. After removing the oxide scale by turning, the semi-solid billet 105 was machined and cut to prepare a cylindrical 7075 aluminum alloy semi-solid billet 105 with a radius of 50 mm and a length of 200 mm. After machining, the outer diameter of the semi-solid billet 105 is the same as the outer diameter of the extrusion cylinder 104, with a clearance fit. The length of the semi-solid billet 105 is less than the length of the extrusion cylinder 104.

[0080] S2. The extrusion cylinder 104 and the semi-solid billet 105 are subjected to gradient heating treatment using the first gradient heating and temperature control device 106, so that the temperature of the extrusion cylinder 104 near the punch 201 is 540°C and the temperature of the extrusion cylinder 104 near the extrusion punch 103 is 400°C; the punch 201 and the die 202 are subjected to gradient heating treatment using the second gradient heating and temperature control device 206, so that the temperature of the main body of the punch 201 and the die 202 is 450°C and the temperature of the annular working belt 203 is 400°C; the annular channel 301 is heated using the third gradient heating and temperature control device 304, so that the heating temperature of the annular channel 301 is 400°C.

[0081] S3. A high-pressure air pump is used to uniformly spray grease and graphite onto the working surfaces of the extrusion cylinder 104, punch 201, die 202 and annular channel 301;

[0082] S4. The semi-solid billet 105 is remelted and heated in a resistance furnace. When the furnace temperature reaches 540℃, the processed cylindrical alloy billet is placed into the resistance furnace. Timing starts when the furnace temperature reaches the set temperature again. After the remelting holding time of the billet reaches the predetermined value, it is held for 5 minutes.

[0083] S5. The semi-solid billet 105 is then quickly removed from the furnace and clamped into the extrusion cylinder 104. The extrusion punch 103 extrudes the semi-solid billet 105 into the punch 201 and the die 202, and then extrudes a large thin-walled component from the annular working belt 203. Its wall thickness is only 1 mm and its radius is 200 mm. The moving speed of the extrusion punch 103 is 2 mm / s.

[0084] S6. The extruded large thin-walled component enters the annular channel 301 and moves slowly along the annular channel 301 for heat treatment to adjust its properties.

[0085] S7. After the semi-solid billet 105 is extruded, the extrusion punch 103 retracts;

[0086] S8. Repeat S1 to S7 to continuously extrude and form thin-walled components in a semi-solid state.

[0087] It should be explained that during the extrusion molding process, the extruder drives the connecting rod 102 and the extrusion punch 103 to move. The extrusion pressure of the extruder is greater than 6000 tons. The connecting rod 102 is fixed on the mold frame 101, and the mold frame 101 is fixed on the upper table of the extruder. The extruder's mold closing speed is greater than 100 mm / s to ensure that the rapid extrusion molding under non-isothermal conditions can proceed smoothly. In addition, the extrusion punch 103 has a hardness greater than 50 HRC.

[0088] The front channel 302 is 720mm long and the rear channel 303 is 100mm long. The radius of the front channel 302 is 10mm larger than the radius of the annular working belt 203, and the radius of the rear channel 303 is 30mm larger than the radius of the front channel 302. The annular channel 301 needs to be lubricated with graphite powder in advance to prevent the surface of the extruded large thin-walled component from being scratched or even blocked.

[0089] Example 2

[0090] The semi-solid extrusion molding method for thin-walled components provided in this embodiment is used to mold components such as... Figure 8 The large ribbed thin-walled component shown has a wall thickness of 1.5 mm and a rib height of 15 mm. The die 202 and punch 201 required for the large ribbed thin-walled component are as follows: Figure 7 As shown, the specific steps are as follows:

[0091] S1. As Figure 4 As shown, a 7075 aluminum alloy semi-solid billet 105 was prepared using the strain-induced melting activation method. After removing the oxide scale by turning, the semi-solid billet 105 was further processed and cut to prepare a cylindrical 7075 aluminum alloy semi-solid billet 105 with a radius of 50 mm and a length of 200 mm. After machining, the outer diameter of the semi-solid billet 105 is the same as the outer diameter of the extrusion cylinder 104, with a clearance fit. The length of the semi-solid billet 105 is less than the length of the extrusion cylinder 104.

[0092] S2. The extrusion cylinder 104 and the semi-solid billet 105 are subjected to gradient heating treatment using the first gradient heating and temperature control device 106, so that the temperature of the extrusion cylinder 104 near the punch 201 is 560°C and the temperature of the extrusion cylinder 104 near the extrusion punch 103 is 420°C; the punch 201 and the die 202 are subjected to gradient heating treatment using the second gradient heating and temperature control device 206, so that the temperature of the main body of the punch 201 and the die 202 is 500°C and the temperature of the annular working belt 203 is 420°C; the annular channel 301 is heated using the third gradient heating and temperature control device 304, so that the heating temperature of the annular channel 301 is 420°C.

[0093] S3. A high-pressure air pump is used to uniformly spray grease and graphite onto the working surfaces of the extrusion cylinder 104, punch 201, die 202 and annular channel 301;

[0094] S4, the semi-solid billet 105 is remelted and heated in a resistance furnace. When the furnace temperature reaches 540℃, the processed cylindrical alloy billet is placed in the resistance furnace. Timing starts when the furnace temperature reaches the set temperature again. After the remelting holding time of the billet reaches the predetermined value, it is held for 5 minutes.

[0095] S5. The semi-solid billet 105 is then quickly removed from the furnace and clamped into the extrusion cylinder 104. The extrusion punch 103 squeezes the semi-solid billet 105 into the punch 201 and die 202, and then extrudes a large thin-walled component from the annular working belt 203. The component has a wall thickness of 1.5 mm, a rib height of 15 mm, and a radius of 200 mm.

[0096] The speed of the extrusion bar is 1 mm / s;

[0097] S6. The extruded large thin-walled component enters the annular channel 301 and moves slowly along the annular channel 301 for heat treatment to adjust its properties.

[0098] S7. After the semi-solid billet 105 is extruded, the extrusion punch 103 retracts;

[0099] S8. Repeat S1 to S7 to continuously extrude and form thin-walled components in a semi-solid state.

[0100] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. An apparatus for semi-solid extrusion molding of thin-walled components, characterized in that: It includes a pretreatment unit, an extrusion unit, and a heat treatment unit; The pretreatment unit includes a first gradient heating and temperature control device and a pretreatment mold. The pretreatment mold includes an extrusion cylinder, an extrusion punch, a connecting rod, and a mold frame. The extrusion cylinder has openings at both ends and its interior is used to accommodate semi-solid billets. One end of the extrusion punch is fixedly connected to the mold frame via the connecting rod. The extrusion punch can extend into the extrusion cylinder from the opening at the end of the extrusion cylinder closest to the mold frame. A gap is left between the outer side wall of the extrusion punch and the inner side wall of the extrusion cylinder. The extrusion punch can reciprocate in the axial direction of the extrusion cylinder. The end of the mold frame away from the extrusion punch is used to connect to the pressure shaft of the extruder. The first gradient heating and temperature control device is fixedly disposed outside the extrusion cylinder and can heat the extrusion cylinder. The extrusion unit includes a second gradient heating and temperature control device and an extrusion die. The extrusion die includes a punch and a die. The die is fixedly disposed at the end of the extrusion cylinder away from the die frame. The punch is fixedly disposed between the die and the extrusion cylinder. The punch can seal the opening at the end of the extrusion cylinder away from the die frame. The punch and the die together form an annular welding chamber and an annular working belt. One end of the annular working belt communicates with the welding chamber. The punch has several portholes that allow the welding chamber to communicate with the interior of the extrusion cylinder, so that semi-solid billets can enter the welding chamber through the portholes. The second gradient heating and temperature control device is fixedly disposed outside the extrusion die and can heat the extrusion die. The heat treatment unit includes a third gradient heating and temperature control device and a heat treatment carrier. The heat treatment carrier has an annular channel, one end of which is connected to the end of the annular working belt away from the welding chamber. The third gradient heating and temperature control device is fixedly installed outside the heat treatment carrier and heats the heat treatment carrier.

2. The apparatus for semi-solid extrusion molding of thin-walled components according to claim 1, characterized in that: The first gradient heating and temperature control device is fixedly sleeved on the outer wall of the extrusion cylinder, the second gradient heating and temperature control device is fixedly sleeved on the outer wall of the extrusion die, and the third gradient heating and temperature control device is fixedly sleeved on the outer wall of the heat treatment support. A heat insulation layer is fixedly sleeved on the outer walls of the first, second, and third gradient heating and temperature control devices. Heat-insulating connecting plates are fixedly installed between the die frame and the pressure shaft of the extruder, between the extrusion cylinder and the punch, and between the die and the heat treatment support.

3. The apparatus for semi-solid extrusion molding of thin-walled components according to claim 2, characterized in that: The extrusion cylinder has a first temperature measuring channel, in which a first temperature measuring element is fixedly installed. The extrusion die has a second temperature measuring channel, in which a second temperature measuring element is fixedly installed. The heat treatment support has a third temperature measuring channel, in which a third temperature measuring element is fixedly installed. The first gradient heating and temperature control device and the first temperature measuring element are both connected to the heating and temperature control system. The second gradient heating and temperature control device and the second temperature measuring element are both connected to the heating and temperature control system. The third gradient heating and temperature control device and the third temperature measuring element are both connected to the heating and temperature control system.

4. The apparatus for semi-solid extrusion molding of thin-walled components according to claim 3, characterized in that: A prestressed ring is fixedly fitted on the outer wall of the first gradient heating and temperature control device.

5. The apparatus for semi-solid extrusion molding of thin-walled components according to claim 1, characterized in that: The annular channel includes a front channel and a rear channel connected in sequence. The front channel is located between the annular working belt and the rear channel. The length of the front channel is greater than 500 mm, the length of the rear channel is greater than 100 mm, the radius of the front channel is 5-10 mm larger than the radius of the annular working belt, and the radius of the rear channel is 20-30 mm larger than the radius of the front channel.

6. A method for semi-solid extrusion molding of thin-walled components, using the apparatus for semi-solid extrusion molding of thin-walled components as described in any one of claims 1-5, characterized in that: Includes the following steps: S1. Prepare a semi-solid billet, turn the semi-solid billet to remove the oxide scale, and then process and cut it to obtain a cylindrical semi-solid billet; S2. Preheat the extrusion cylinder using the first gradient heating and temperature control device; preheat the extrusion die using the second gradient heating and temperature control device; preheat the heat treatment carrier using the third gradient heating and temperature control device; S3. Apply lubricant evenly to the working surfaces of the extrusion cylinder, punch, die, and annular channel; S4. The semi-solid billet is remelted and heated in a resistance furnace. The cylindrical semi-solid billet obtained in S1 is placed in the resistance furnace, heated and kept at the temperature. S5. The heated and kept-warm semi-solid billet is taken out from the resistance furnace and clamped into the extrusion cylinder. The extruder drives the extrusion punch to extrude the semi-solid billet in the extrusion cylinder into the extrusion die, and extrudes the thin-walled component from the annular working belt. S6. The thin-walled component extruded from the annular working belt enters the annular channel and moves slowly along the annular channel for heat treatment to adjust its properties; S7. After the semi-solid billet in the extrusion cylinder has been extruded, the extruder drives the extrusion punch to exit the extrusion cylinder. S8. Repeat S1 to S7 to continuously extrude and form thin-walled components in a semi-solid state.

7. The method for semi-solid extrusion molding of thin-walled components according to claim 6, characterized in that: In S4, the remelting heating temperature is 300-700℃, and the remelting heating holding time is 5-40 minutes.

8. The method for semi-solid extrusion molding of thin-walled components according to claim 6, characterized in that: In S2, after the extrusion cylinder is preheated by the first gradient heating and temperature control device, the temperature of the semi-solid billet near the punch is 400-700℃, that is, the semi-solid billet near the punch has 10-60% liquid billet, and the temperature of the semi-solid billet near the extrusion punch is 200-450℃, that is, the semi-solid billet near the extrusion punch is completely solid.

9. The method for semi-solid extrusion molding of thin-walled components according to claim 6, characterized in that: In S2, the extrusion die is preheated using a second gradient heating and temperature control device, so that the temperature of the punch and die is 200-650℃ and the temperature of the annular working belt is 200-450℃; the heat treatment carrier is preheated using a third gradient heating and temperature control device, so that the temperature in the annular channel is 250-550℃.

10. The method for semi-solid extrusion molding of thin-walled components according to claim 6, characterized in that: In S5, the extrusion speed of the extrusion punch is 1-20 mm / s.

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