Extrusion casting blank preheating device and method for cooperatively preparing thermoplastic deformation blank

Abstract

The invention belongs to the technical field of thermoplastic deformation blank processing, and discloses an extrusion casting blank preheating device and a method for synergistically preparing a thermoplastic deformation blank, the extrusion casting blank preheating device comprises a pit furnace, a sample placing assembly and a gas guide assembly, a heating unit is arranged in the side wall of the pit furnace, a furnace cover is arranged on an opening of the pit furnace, and a hearth of the pit furnace is used for filling a heat-conducting medium; a temperature measuring unit is also arranged in the shell; the sample placing assembly comprises a sample placing barrel and a supporting frame, the sample placing barrel and the hearth are coaxially arranged, the sample placing barrel can be inserted into a heat-conducting medium in the hearth, the supporting frame is arranged in the hearth and located below the sample placing barrel, and a sample placing cavity for placing extrusion casting blanks is formed between the supporting frame and the sample placing barrel; the sample placing barrel can also be moved out of the hearth, so that the heat-conducting medium buries the extrusion casting blank; the gas guide assembly is located below the supporting frame and used for introducing shielding gas into the hearth. The extrusion casting blank can be rapidly heated to the thermoplastic deformation temperature, and low-cost, high-efficiency and high-quality production of thermoplastic deformation workpieces is achieved.

Description

Technical Field

[0001] The present application belongs to the technical field of thermoplastic deformation billet processing, and more specifically, relates to an extrusion casting billet preheating device and a method for collaboratively preparing thermoplastic deformation billets. Background Art

[0002] Thermoplastic deformation processing technology is a commonly used technology in metal processing. It uses the plastic properties of metal at high temperatures to deform the solid blank by applying external force, thereby obtaining a product of the desired shape and size. The main feature of thermoplastic deformation processing technology is that the metal temperature is higher than the recrystallization temperature. This usually requires heating the metal to a certain temperature to make it reach the conditions for plastic deformation. Within this temperature range, the bonding force between metal atoms is weakened, and the metal's thermal deformation ability is enhanced. It can be deformed by applying pressure or impact force. According to the force and deformation mode of the workpiece during processing, common thermoplastic processing methods include forging, rolling, extrusion, drawing, etc.

[0003] Traditional solid billets are usually prepared by continuous or semi-continuous casting. In order to eliminate the component segregation inside the billet, make its organizational structure and performance more uniform, improve the plasticity of the billet, reduce deformation resistance, and facilitate subsequent plastic deformation processing, the solid billet often needs to undergo a long period of homogenization heat treatment before deformation, and then remove the surface oxide scale through machining, and process it to the desired shape and size, and finally heat it again to the deformation temperature before thermoplastic processing can be carried out.

[0004] Although the above process is dominant in current production practice, there are still many shortcomings that need to be improved. First, the homogenization heat treatment process is time-consuming and energy-consuming. This step requires the metal material to be kept at a high temperature for a long time to achieve homogenization of the structure. This process usually consumes a lot of time and energy. Due to the need for long-term heating and insulation, as well as the special equipment and process control that may be required, homogenization heat treatment may increase the preparation cost of metal billets. Secondly, due to the poor surface finish and poor dimensional accuracy of traditional casting billets, solid billets often need additional machining after heat treatment to remove the surface oxide layer and process the billets to the desired shape and size. Finally, although homogenization heat treatment can improve the thermal deformation ability of billets to a certain extent, it may also lead to a decrease in other properties. For example, excessively high temperatures may cause the grain growth of the billet, thereby reducing its mechanical properties, and also lead to the disappearance of low-melting second phase particles, inhibiting their promotion of dynamic recrystallization behavior during subsequent deformation. Summary of the invention

[0005] In response to the defects of the prior art or the need for improvement, the present application provides an extrusion casting billet preheating device and a method for collaboratively preparing thermoplastic deformation billets using the same, aiming to solve the problems of the existing homogenization heat treatment process being time-consuming and energy-consuming, the billet having many defects, and the coarse microstructure.

[0006] The present application provides an extrusion casting billet preheating device, comprising a pit-type furnace, a sample placement component and an air guide component, wherein a heating unit is provided in the side wall of the pit-type furnace, and a furnace cover is provided on the opening thereof, the furnace chamber of the pit-type furnace is used to load a heat-conducting medium, and a temperature measuring unit is also provided therein; the sample placement component comprises a sample placement tube and a support frame, the sample placement tube is coaxially arranged with the furnace chamber, and can be inserted into the heat-conducting medium in the furnace chamber, the support frame is arranged in the furnace chamber and located below the sample placement tube, so as to form a sample placement cavity for placing the extrusion casting billet between the sample placement tube and the sample placement tube; the sample placement tube can also be moved out of the furnace chamber so that the heat-conducting medium buries the extrusion casting billet; the air guide component is located below the support frame, and is used to pass protective gas into the furnace chamber.

[0007] Furthermore, the air guide assembly includes an air inlet pipe and an air guide pipe, the air inlet end of the air inlet pipe is located outside the pit furnace, and the air outlet end thereof is connected to the air inlet end of the air guide pipe; a plurality of air outlet holes are opened on the air guide pipe, and foam ceramics are provided in each of the air outlet holes.

[0008] Furthermore, the air inlet pipe is perpendicular to the bottom surface of the furnace, the air guide pipe is parallel to the bottom surface of the furnace, and the air outlet faces the support frame.

[0009] Furthermore, the extrusion casting blank is wrapped with a sampling net bag, and the material of the sampling net bag is stainless steel wire, ceramic fiber or glass fiber.

[0010] Furthermore, the temperature measuring unit is a thermocouple or a thermal resistor, one end of the temperature measuring unit is located outside the pit furnace, and the other end thereof is in contact with the support frame.

[0011] Furthermore, the diameter of the sample placing tube is not less than 110% of the maximum transverse dimension of the extrusion casting billet, and the height of the sample placing tube is not less than 200% of the maximum vertical dimension of the extrusion casting billet.

[0012] Furthermore, the heat-conducting medium is cylindrical coarse-grained graphite with a diameter and a height between 1 mm and 20 mm, or spherical or flaky coarse-grained graphite with a particle size between 2 meshes and 1000 meshes.

[0013] According to another aspect of the present application, a method for preparing a thermoplastic deformation billet using the extrusion casting billet preheating device as described in any one of the above items comprises the following steps:

[0014] S1: filling the furnace of the pit furnace with a heat-conducting medium and preheating it. When the preheating temperature exceeds a set threshold, the gas guide component simultaneously introduces protective gas into the furnace;

[0015] S2: insert the sample placement tube into the heat-conducting medium and place it above the support frame, and take out the heat-conducting medium inside the sample placement tube;

[0016] S3: forming the alloy melt by extrusion casting, and obtaining an extrusion casting billet after holding the pressure for a preset time; cooling the extrusion casting billet in air for a preset time;

[0017] S4: placing the cooled extrusion casting blank on a support frame, and taking out the sample placing tube, so that the heat conducting medium whose temperature has reached the preheating temperature buries and preheats the extrusion casting blank;

[0018] S5 takes out the preheated extrusion casting billet and performs thermoplastic deformation;

[0019] S6 repeats steps S2-S5 to achieve thermoplastic deformation of large quantities of extrusion casting billets.

[0020] The present application adopts extrusion casting technology to replace the traditional continuous or semi-continuous casting technology to prepare thermoplastic deformation billets, and quickly heats the extrusion casting billets to the thermoplastic deformation temperature through an extrusion casting billet preheating device, in order to obtain a better solid billet.

[0021] Furthermore, in step S3, the height of the heat-conducting medium at the top of the extrusion casting billet is not less than 10 cm.

[0022] Furthermore, if the material of the extrusion casting billet is magnesium alloy, copper alloy, aluminum-lithium alloy or aluminum-magnesium alloy with a magnesium content exceeding 2%, then in step S1, when the preheating temperature is lower than the set threshold, the air guide component is also opened to introduce protective gas.

[0023] Furthermore, the overflow rate of the protective gas at the top of the heat-conducting medium is 10 -5 L / (min·dm 2 )~10L / (min·dm 2 ).

[0024] Furthermore, the inlet flow rate of the protective gas is the product of the overflow rate and the bottom area of ​​the furnace.

[0025] Furthermore, the shape and size of the mold cavity of the extrusion casting mold are the same as the shape and size of the blank required by the thermoplastic deformation process.

[0026] In general, the above technical solutions conceived by this application have the following technical advantages compared with the prior art:

[0027] 1. The present application provides an extrusion casting billet preheating device for extrusion casting billets, which can quickly adjust the temperature of the extrusion casting billet to the temperature required by the thermoplastic deformation process. Since the sample placement tube can be repeatedly inserted and removed from the furnace, it is possible to simultaneously preheat a large number of extrusion casting billets after the preheating device is started. The extrusion casting billet preheating device is filled with a heat-conducting medium, which has good thermal conductivity, fast heating speed and a wide heating temperature range. The heat-conducting medium can adapt to extrusion casting billets of different shapes and sizes, and can also tightly fill the gap between the billet and the furnace body, saving the amount of protective gas.

[0028] 2. In the extrusion casting billet preheating device provided by the present application, when the preheating temperature reaches a preset threshold, a protective gas is introduced to allow the heat-conducting medium, such as residual air between coarse-grained graphite particles, to overflow from the gap between the furnace cover and the furnace, and the complex pore structure between the graphite particles is used to inhibit the free flow of external air, thereby preventing the extrusion casting billet and the graphite particles from contacting the air and avoiding oxidation at high temperatures. In the thermoplastic billet preparation method provided by the present application, within the preset overflow rate range, the utilization rate of the protective gas is the highest. If the overflow rate is exceeded, the excessive gas flow may cause temperature fluctuations in the extrusion casting billet preheating device, affecting preheating and wasting protective gas.

[0029] 3. In this application, the extrusion casting technology is used to solidify the alloy melt under pressure. The high cooling rate can promote heterogeneous nucleation of grains and inhibit their growth, so the alloy solidification structure is significantly refined. The effect of pressure can increase the liquidus temperature in the alloy phase diagram, which is conducive to the precipitation of second phase particles. In addition, solidification under pressure can also eliminate defects such as pores and shrinkage by forced shrinkage compensation, thereby improving the quality of the billet. Rapid solidification in a closed mold cavity also reduces oxidation on the surface of the ingot.

[0030] 4. The extrusion casting billet prepared in the present application has high dimensional accuracy and good surface quality, and can be directly used for thermoplastic deformation without further machining. The extrusion casting billet preheating device used in the preparation process can effectively prevent the extrusion casting billet from grain coarsening, second phase particle dissolution or surface oxidation during the long homogenization heat treatment process, and retain the excellent original state of the extrusion casting billet. Thanks to the retention of fine grains and high content of second phase particles in the extrusion casting billet, more nucleation sites can be provided in the subsequent thermoplastic deformation process to enhance the kinetic process of dynamic recrystallization, thereby increasing the degree of dynamic recrystallization and making the thermoplastic deformation alloy have a more uniform microstructure.

[0031] 5. The method for preparing thermoplastic blanks provided in the present application eliminates the tedious processes such as homogenization treatment of the ingot before hot extrusion and surface oxide skin turning, reduces production energy consumption, shortens the production process, improves production efficiency, and reduces oxidation loss, ultimately achieving short-process, high-efficiency, low-energy consumption and low-cost production of thermoplastic deformation workpieces. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a schematic diagram of the structure of the preheating device provided in Example 1 of the present application;

[0033] Figure 2 It is a schematic diagram of the structure of a preheating device for placing an extrusion casting blank provided in Example 1 of the present application;

[0034] Figure 3 is a schematic diagram of the structure of the preheating device during preheating provided in Example 1 of the present application;

[0035] Figure 4 It is a schematic structural diagram of a preheating device for removing an extrusion casting billet provided in Example 1 of the present application;

[0036] Figure 5 This is a schematic diagram of the top view of the structure of the air guide assembly and the support frame provided in Example 1 of the present application;

[0037] Figure 6 This is a microstructure picture of an AZ31 magnesium alloy extrusion casting billet prepared by a rapid preheating process provided in Example 3 of the present application;

[0038] Figure 7 This is a picture of the structure of the AZ31 magnesium alloy extrusion casting billet after hot extrusion processing, which is prepared by the rapid preheating process in Example 3 of the present application.

[0039] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0040] 1-well furnace, 11-furnace, 12-heating unit, 13-furnace cover, 14-temperature measuring unit, 21-air inlet pipe, 22-air guide pipe, 23-foam ceramic, 31-sample tube, 32-support frame, 33-sampling net bag, 4-graphite particles. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0042] Example 1

[0043] This embodiment provides a device for preheating a billet for extrusion casting, such as Figure 1-5As shown, it includes a pit furnace 1, a sample placement component and a gas guide component.

[0044] like Figure 1 As shown, a heating unit 12 is provided in the side wall of the pit furnace 1. The heating unit is any unit that can realize a controllable heating function, such as an electric furnace wire, a silicon carbon rod, a heating rod, a heating tube, etc. A furnace cover 13 is also provided on the opening of the pit furnace 1. The furnace cover 13 cooperates with the pit furnace 1 to make the pit furnace in a closed but not sealed state. A temperature measuring unit 14 is provided in the furnace 11. The temperature measuring unit 14 is used to measure the temperature of the graphite particles 4. The temperature measuring unit 14 in this embodiment is a thermocouple, and it is penetrated in the bottom surface of the furnace, one end of which is located in the furnace 11 and in contact with the support frame, and the other end is located outside the furnace 11.

[0045] like Figure 1 and 2 As shown, the sample placement assembly includes a sample placement tube 31 and a support frame 32. The sample placement tube 31 is coaxially and movably arranged in the furnace 11, that is, it can be inserted into the heat-conducting medium in the furnace 11; the support frame 32 is located in the furnace 11 and below the sample placement tube 31.

[0046] Specifically, the support frame 32 is located in the opening of the sample placing tube 31 at one end away from the furnace cover 13 to cooperate with the side wall of the sample placing tube to form a sample placing cavity.

[0047] More specifically, the support frame 32 includes a support column vertically fixed on the bottom plate of the furnace 11, and a plurality of support rods arranged radially and horizontally are connected to the upper end of the support column. The support frame 32 is used to support the extrusion casting billet to prevent the extrusion casting billet from compacting the gaps between the graphite particles 4 or crushing the graphite particles, while avoiding hindering the direct contact between the graphite particles 4 and the extrusion casting billet.

[0048] Before the extrusion casting blank is placed, the graphite particles 4 are first filled into the furnace 11 for preheating, and then the sample placing tube 31 is inserted into the graphite particles and is sleeved on the outside of the support frame 32, and then the graphite particles between the sample placing tube and the support frame 32 are taken out to form a sample placing cavity, and then the extrusion casting blank is placed in the sample placing cavity, and finally the sample placing tube 31 is taken out so that the graphite particles 4 bury the extrusion casting blank.

[0049] In this embodiment, the gas guide component is located below the support frame 32, and is used to introduce protective gas into the furnace 11; specifically, the gas guide component includes an air inlet pipe 21 and an air guide pipe 22, the air inlet end of the air inlet pipe 21 is located outside the pit furnace 1, and its air outlet end is rigidly connected and communicated with the air inlet end of the air guide pipe 22 to form a protective gas pipeline, and the protective gas is such as N2, Ar, He, CO2 and other gases or their mixed gases; a plurality of air outlet holes are opened on the air guide pipe 22, and the plurality of air outlet holes are evenly arranged in a row, and a foam ceramic 23 is inserted in each air outlet hole, and the foam ceramic 23 can prevent graphite particles from entering the air outlet hole to block the protective gas channel.

[0050] When in use, graphite particles are buried in the preheating device in advance, and after the temperature is raised to a preset temperature, the sample placement tube 31 is inserted into the graphite particles and placed above the support frame 32, and the graphite particles 4 inside the sample placement tube are taken out to form a sample placement cavity; then the extruded casting blank wrapped with a sampling net bag 33 is placed on the support frame 32, as shown in FIG. Figure 3 As shown, the sample placing tube 31 is taken out to bury the graphite particles 4 in the extrusion casting billet, and the furnace cover is closed to start preheating. After the preheating is completed, Figure 4 As shown, the sampling net bag 33 is taken out to obtain the preheated extrusion casting blank. The graphite particles directly bury the extrusion casting blank and tightly wrap it, which can play a good heat conduction and heat equalization effect. The protective gas flows into the air guide pipe 22 along the air inlet pipe 21 and is discharged from the foam ceramic 23. The protective gas discharged from the foam ceramic 23 flows upward from the gaps between the graphite particles, so that the air in the gaps between the graphite particles is discharged, avoiding oxidation and burning of the graphite particles 4, and realizing effective protection of the extrusion casting blank.

[0051] In this embodiment, Figure 1 and 5 As shown, the air inlet pipe 21 is vertically penetrated through the bottom surface of the furnace, the air guide pipe 22 is parallel to the bottom surface of the furnace, and the air outlet thereon faces the support frame 32.

[0052] In this embodiment, the extrusion casting blank is wrapped with a sampling net bag 33, which is made of stainless steel wire, ceramic fiber or glass fiber and is used to quickly take out the extrusion casting blank while avoiding direct contact between graphite particles and the extrusion casting blank.

[0053] In this embodiment, the temperature measuring unit 14 is a thermocouple or a thermal resistor. The temperature measuring unit 14 passes through the bottom of the furnace 11 , and one end of the temperature measuring unit 14 is located outside the pit furnace 1 , and the other end is located inside the pit furnace 1 and contacts the support frame 32 .

[0054] In this embodiment, a plurality of heating units 12 are evenly arranged in an array on the side wall of the pit furnace 1, and the heating is controlled by an external controller.

[0055] In this embodiment, the diameter of the sample placing tube 31 is not less than 110% of the maximum transverse dimension of the extrusion casting billet, and the height of the sample placing tube 31 is not less than 200% of the maximum vertical dimension of the extrusion casting billet, providing sufficient accommodating space for the extrusion casting billet.

[0056] Example 2

[0057] A method for preparing a thermoplastic deformation billet using any one of the extrusion casting billet preheating devices in Example 1 comprises the following steps:

[0058] S1: filling the extrusion casting billet preheating device with graphite particles 4 and preheating the device. When the preheating temperature exceeds a set threshold, the gas guide component simultaneously introduces protective gas into the preheating device.

[0059] Specifically, the extrusion casting billet preheating device is turned on, and a sufficient amount of graphite particles 4 is added into the extrusion casting billet preheating device for preheating.

[0060] More specifically, the added graphite particles are cylindrical graphite particles with a diameter and height between 1 mm and 20 mm, or spherical or flaky graphite particles with a particle size between 2 mesh and 100 mesh. The amount of graphite particles added should ensure that the subsequently placed extrusion casting billet can be completely covered, and the height of the graphite particles on the top of the extrusion casting billet is not less than 10 cm.

[0061] More specifically, if the preheating temperature does not exceed the set threshold, in this embodiment the set threshold is selected as 450°C, and when the material of the extrusion casting billet itself is not easily oxidized, there is no need to introduce protective gas; if the preheating temperature exceeds 450°C, or when the material of the extrusion casting billet itself is easily oxidized, protective gas is introduced; that is, if the material of the extrusion casting billet is an easily oxidized material such as magnesium alloy, copper alloy, aluminum-lithium alloy or aluminum-magnesium alloy with a magnesium content exceeding 2%, then when the preheating temperature is lower than 450°C, open the gas guide assembly to introduce protective gas.

[0062] The overflow rate of the shielding gas on the top of the graphite particles is 10 -5 L / (min·dm 2 )~10L / (min·dm 2 ), the inlet flow rate of the protective gas is the product of the overflow rate and the bottom area of ​​the pit furnace.

[0063] S2: insert the sample placement tube 31 into the graphite particles and place it above the support frame 32, and take out the graphite particles inside the sample placement tube 31 to form a sample placement cavity;

[0064] S3 injects the alloy melt into the extrusion casting mold and holds the pressure for 1s to 600s to obtain the extrusion casting billet. Specifically, the required material mass is calculated according to the theoretical component ratio, the raw materials prepared in proportion are mixed and smelted to obtain the alloy melt, and the alloy melt is poured into the extrusion casting mold for extrusion casting, and the pressure is held for 1 to 600s, such as 50s, 100s, 200s, 300s, 400s, 500s, 600s, etc., or any holding time between any two of the above times.

[0065] The extrusion casting billet after pressure maintenance is then placed in the air to cool for a period of time, the air cooling time is 1s to 600s, such as 100s, 200s, 300s, 400s, 500s, 600s, or a cooling time between any two of the aforementioned times.

[0066] The shape and size of the cavity of the aforementioned extrusion casting mold are consistent with the shape and size of the blank required by the thermoplastic deformation process.

[0067] S4: The cooled extrusion casting billet is placed in the extrusion casting billet preheating device after the temperature is increased, and the sample placing tube 31 is taken out to bury the graphite particles in the preheated extrusion casting billet.

[0068] S5 takes the preheated extrusion casting billet out of the extrusion casting billet preheating device for hot plastic deformation.

[0069] Specifically, the extrusion casting billet is wrapped with a high temperature resistant sampling net bag 33 and placed in a heated extrusion casting billet preheating device for preheating. The preheating time is 1 minute to 60 minutes. After the preheating is completed, the sampling net bag 33 is lifted and the extrusion casting billet is taken out of the extrusion casting billet preheating device for thermoplastic deformation.

[0070] S6 repeats steps S2-S5 to achieve thermoplastic deformation of large quantities of extrusion casting billets.

[0071] Example 3

[0072] AZ31 is a typical deformable magnesium alloy, which can be used to prepare various magnesium alloy tubes, bars or profiles by hot extrusion. However, magnesium alloys have poor thermoplastic deformation ability and often require long-term homogenization treatment, which leads to a more serious degree of surface oxidation. Traditional hot extrusion forming of AZ31 magnesium alloy profiles usually requires the semi-continuous ingot to be homogenized at 420°C for 10 hours, and the surface oxide scale is turned off after cooling. After processing to the shape and size required for hot extrusion, it is again kept warm for at least 1 hour and preheated to 380°C for hot extrusion.

[0073] In this embodiment, the extrusion casting and the extrusion casting billet preheating device are used to prepare the size of The cylindrical AZ31 hot extrusion billet is hot extruded into Rod.

[0074] The method comprises the following steps:

[0075] 1. Add sufficient spherical graphite particles with a particle size of 20-40 mesh to the extrusion casting billet preheating device to ensure that the thickness of the graphite particles on the top of the extrusion casting billet reaches 15 cm; The sample tube 31 is inserted and placed outside the support frame 31, and the graphite particles inside the sample tube 31 are dug out; the preheating temperature is set to 380°C, and the sample is heated for 10 -4 ~10 -2 L / (min·dm 2 )’s overflow rate and Ar protective gas was introduced.

[0076] 2. Mix 99.95% pure magnesium ingot (mass fraction, the same below), 99.95% pure aluminum, 99.99% pure zinc and Al 10wt.% Mn master alloy according to the alloy composition of 3wt.% Al, 1wt.% Zn, 0.5wt.% Mn, and the balance is Mg. Put the prepared raw materials into a crucible and heat them up to melt, and use 1vol.% SF6+99vol.% N2 mixed gas for protection. After all the alloys are melted, adjust the temperature of the alloy liquid to 700℃ and remove the surface scum.

[0077] 3. Pour the AZ31 alloy melt into the mold cavity with a size of The extrusion casting blank is then wrapped with a sampling net bag 33 and placed in an extrusion casting blank preheating device for 10 minutes. After the rapid preheating is completed, the sampling net bag 33 is lifted, the extrusion casting blank is taken out, placed in a hot extrusion die, and hot extrusion deformation is performed to obtain The hot extruded rod has an average grain size of 5.1 μm, and the room temperature mechanical properties can reach an ultimate tensile strength of 300 MPa and an elongation of 15.6%. Figure 6 This is a schematic diagram of the organizational structure of the AZ31 magnesium alloy extrusion casting billet prepared in this embodiment. It can be seen that Figure 6 The medium billet has fine structure, fewer defects and high dimensional accuracy. Figure 7 This is a schematic diagram of the organizational structure of AZ31 magnesium alloy extrusion casting billet after hot extrusion. It can be seen from the figure that the microstructure in the hot plastic deformation alloy is more uniform.

[0078] Example 4

[0079] 7075 aluminum alloy is a typical aluminum alloy for aviation, with multiple characteristics such as high strength and light weight, and high requirements for organization and performance. In recent years, 7075 aluminum alloy has been continuously used for civilian purposes and has been used to manufacture automotive parts. It has great potential in replacing some high-strength steel for automobiles. The traditional hot rolling process is casting → homogenization → sawing → milling → preheating → hot rolling, which is a cumbersome process and time-consuming and energy-consuming.

[0080] This embodiment provides a method for preparing a plate-shaped 7075 hot-rolling billet with a size of 300×100×20 mm by cooperating with an extrusion casting billet preheating device, and hot-rolling the billet into a plate with a thickness of only 1 mm.

[0081] The method comprises the following steps:

[0082] 1. Add sufficient flake graphite particles with a particle size of 40 to 80 meshes into the extrusion casting billet preheating device to ensure that the thickness of the graphite particles on the top of the extrusion casting billet reaches 10 cm; insert and place the sample placement tube 31 with a size of φ350×100 mm outside the support frame 31, and dig out the graphite particles inside the sample placement tube 31; set the preheating temperature to 430°C, and do not introduce protective gas.

[0083] 2. Mix 99.95% pure aluminum ingot, 99.95% pure magnesium, 99.99% pure zinc, Al 20wt.% Si, Al10wt.% Mn master alloy and other raw materials according to the alloy composition ratio, and then put the prepared raw materials into the crucible to heat and melt. After the temperature of the molten alloy is adjusted to 720℃, remove the surface scum.

[0084] 3. Pour the 7075 aluminum alloy melt into an extrusion casting mold with a cavity size of 300×100×20mm for extrusion casting, take it out after holding the pressure for 3s to 5s, and air cool it for 60s to 120s. Then wrap the extrusion casting billet with a sampling net bag 33 and put it into the extrusion casting billet preheating device for 10 to 15 minutes. After the rapid preheating is completed, lift the sampling net bag 33, take out the extrusion casting billet, put it into the hot rolling mill, and perform multiple hot rolling until a hot-rolled plate with a thickness of 1mm is finally obtained. The peak hardness of the hot-rolled plate can reach 180HV after subsequent solid solution and aging heat treatment.

[0085] Example 5

[0086] Copper-tin alloy has the properties of wear resistance, high thermal conductivity and corrosion resistance. It is often used to prepare rotating components such as connecting rod bushings through spin forming. The blank is usually cylindrical and has high requirements for defect control.

[0087] This embodiment relates to a method for preparing a material having a size of The method is to prepare a cylindrical AZ31 hot extrusion billet with a wall thickness of 10 mm, and process the billet into a thin-walled cylindrical part with a wall thickness of 2 mm by hot spinning.

[0088] The method comprises the following steps:

[0089] 1. Add enough cylindrical graphite particles with a size of φ2×10mm to the extrusion casting billet preheating device to ensure that the thickness of the graphite particles on the top of the extrusion casting billet reaches 20cm; insert and place the sample placement tube 31 with a size of φ150×300mm outside the support frame 31, and dig out the graphite particles inside the sample placement tube 31; set the preheating temperature to 520℃ and heat it at 1L / (min·dm 2 ) with an overflow rate of N2 gas protection gas;

[0090] 2. Mix 99.95% pure copper, 99.95% pure tin, 99.99% pure zinc and other raw materials according to the alloy composition. Put the prepared raw materials into the crucible and heat them up to melt. After all the raw materials are melted, adjust the temperature of the alloy liquid to 1200℃ and remove the scum on the surface;

[0091] 3. Pour the alloy melt into an extrusion casting mold with a cavity size of φ100 (inner) - φ120 (outer) × 150 mm for extrusion casting, take it out after holding the pressure for 10 to 15 seconds, and air cool it for 120 to 150 seconds. Then wrap the extrusion casting billet with a sampling net bag 33 and put it into the extrusion casting billet preheating device for 20 minutes to 40 minutes. After the rapid preheating is completed, lift the sampling net bag 33, take out the extrusion casting billet, put it into the hot spinning forming mold, and perform multiple hot spinning deformations to finally obtain a thin-walled cylindrical part with a wall thickness of 2 mm. The average grain size of the material is 3.7μm.

[0092] Example 6

[0093] 6A02 aluminum alloy is a medium-strength aluminum alloy that is corrosion-resistant and weldable. It is widely used in ships. Various special-shaped connectors can be processed by free forging.

[0094] This embodiment provides a method for preparing a columnar 6A02 free forging blank with a size of φ235×280 mm by cooperating with an extrusion casting and a preheating device, and processing the blank into a special-shaped connecting piece by free forging.

[0095] The method comprises the following steps:

[0096] 1. Add sufficient spherical graphite particles with a particle size of 50-100 meshes to the extrusion casting billet preheating device to ensure that the thickness of the graphite particles on the top of the extrusion casting billet reaches 20 cm; insert and place the sample placement tube 31 with a size of φ280×600 mm outside the support frame 31, and dig out the graphite particles 4 inside the sample placement tube 31; set the preheating temperature to 480°C and heat at 0.5L / (min·dm 2 ) with an overflow rate of N2 protective gas;

[0097] 2. Prepare 99.95% pure aluminum ingot, 99.95% pure magnesium, 99.99% pure zinc, Al 20wt.% Si, Al 10wt.% Mn master alloy and other raw materials according to the alloy composition ratio. Put the prepared raw materials into the crucible and heat them up to melt. Then adjust the temperature of the molten alloy liquid to 730℃ and remove the surface scum.

[0098] 3. Pour 6A02 aluminum alloy melt into the mold cavity with a size of The extrusion casting is performed in an extrusion casting mold, and the extrusion casting is taken out after holding the pressure for 15s to 20s, and air-cooled for 120s to 180s. The extrusion casting billet is then wrapped with a sampling net bag 33 and placed in an extrusion casting billet preheating device for 20 to 30 minutes. After the rapid preheating is completed, the sampling net bag 33 is lifted, the extrusion casting billet is taken out, placed in a free forging machine, and a special-shaped connector is obtained by free forging. The surface peak hardness of the special-shaped connector can reach 120HB after subsequent solid solution and aging heat treatment.

[0099] It should be understood that expressions such as "include" and "may include" used in this application indicate the existence of the disclosed functions, operations or constituent elements, and do not limit one or more additional functions, operations and constituent elements. In this application, terms such as "include" and / or "have" may be interpreted as indicating specific characteristics, numbers, operations, constituent elements, components or combinations thereof, but may not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components or combinations thereof.

[0100] It should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0101] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0102] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0103] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A device for preheating billets for extrusion casting, characterized in that: The invention comprises a pit furnace (1), a sample placement component and an air guide component. A heating unit (12) is provided in the side wall of the pit furnace (1), and a furnace cover (13) is provided on the opening thereof. The furnace chamber (11) of the pit furnace (1) is used to load a heat-conducting medium, and a temperature measuring unit (14) is also provided therein. The sample placement component comprises a sample placement cylinder (31) and a support frame (32). The sample placement cylinder (31) is coaxially arranged with the furnace chamber (11) and can be inserted into the heat-conducting medium in the furnace chamber (11). The support frame (32) is arranged in the furnace chamber (11) and is located below the sample placement cylinder (31) so as to form a sample placement cavity for placing extrusion casting blanks between the sample placement cylinder (31) and the support frame (32). The sample placement tube (31) can also be moved out of the furnace (11) so that the heat-conducting medium buries the extrusion casting blank; the gas guide component is located below the support frame (32) and is used to pass protective gas into the furnace (11).

2. The extrusion casting billet preheating device according to claim 1, characterized in that: The air guide assembly comprises an air inlet pipe (21) and an air guide pipe (22); the air inlet end of the air inlet pipe (21) is located outside the pit furnace (1), and the air outlet end thereof is connected to the air inlet end of the air guide pipe (22); a plurality of air outlet holes are provided on the air guide pipe (22), and foam ceramics (23) are provided in each of the air outlet holes.

3. The extrusion casting billet preheating device according to claim 1, characterized in that: The air inlet pipe (21) is perpendicular to the bottom surface of the furnace, the air guide pipe (22) is parallel to the bottom surface of the furnace, and the air outlet faces the support frame (32).

4. The extrusion casting billet preheating device according to claim 1, characterized in that: The extrusion casting blank is wrapped with a sampling net bag (33), and the material of the sampling net bag (33) is stainless steel wire, ceramic fiber or glass fiber.

5. The extrusion casting billet preheating device according to claim 1, characterized in that: The temperature measuring unit (14) is a thermocouple or a thermal resistor; one end of the temperature measuring unit (14) is located outside the pit furnace (1), and the other end is in contact with the support frame (32).

6. The extrusion casting billet preheating device according to claim 1, characterized in that: The diameter of the sample placing tube (31) is not less than 110% of the maximum transverse dimension of the extrusion casting blank, and the height of the sample placing tube (31) is not less than 200% of the maximum vertical dimension of the extrusion casting blank.

7. The extrusion casting billet preheating device according to claim 1, characterized in that: The heat-conducting medium is cylindrical coarse-grained graphite with a diameter and a height of 1 mm to 20 mm, or spherical or flaky coarse-grained graphite with a particle size of 2 meshes to 1000 meshes.

8. A method for preparing a thermoplastic deformation billet using the extrusion casting billet preheating device according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1: filling a heat-conducting medium into the furnace (11) of the pit-type furnace (1) and preheating the medium; when the preheating temperature exceeds a set threshold, a gas guide component simultaneously introduces protective gas into the furnace (11); S2: inserting the sample placement tube (31) into the heat-conducting medium and positioning it above the support frame (32), and taking out the heat-conducting medium inside the sample placement tube (31); S3: forming the alloy melt by extrusion casting, and obtaining an extrusion casting billet after holding the pressure for a preset time; cooling the extrusion casting billet in air for a preset time; S4: placing the cooled extrusion casting blank on a support frame (32), taking out the sample placing tube (31), and burying and preheating the extrusion casting blank with a heat conducting medium having a temperature reaching the preheating temperature; S5 takes out the preheated extrusion casting billet and performs thermoplastic deformation; S6 repeats steps S2-S5 to achieve thermoplastic deformation of large quantities of extrusion casting billets.

9. The method according to claim 8, characterized in that In step S3, the height of the heat-conducting medium at the top of the extrusion casting billet is not less than 10 cm.

10. The method according to claim 8, characterized in that If the material of the extrusion casting billet is magnesium alloy, copper alloy, aluminum-lithium alloy or aluminum-magnesium alloy with a magnesium content exceeding 2%, then in step S1, when the preheating temperature is lower than the set threshold, the air guide component is also opened to introduce protective gas; preferably, the overflow rate of the protective gas at the top of the heat conducting medium is 10 -5 L / (min·dm 2 )~10L / (min·dm 2 ); preferably, the air intake flow rate of the protective gas is the product of the overflow rate and the bottom area of ​​the furnace; preferably, the shape and size of the mold cavity of the extrusion casting mold are the same as the shape and size of the billet required by the thermoplastic deformation process.

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