Device and method for preparing magnesium alloy wire

Abstract

The invention discloses a device and method for preparing a magnesium alloy wire. The device comprises a heating cabin, an extrusion unit and a wire mold. The extrusion unit is arranged in the heating cabin, a blank to be extruded is arranged in the extrusion unit, an outlet is formed below the extrusion unit, and the wire mold is mounted at the outlet below the extrusion unit. The device and the method in the technical scheme both reflect innovation and practicability. The device is reasonable in design and complete in function, and powerful support is provided for preparation of the magnesium alloy wires; according to the method part, high quality and stability of the wire are ensured through a scientific technological process and strict management and control measures. The preparation process is expected to have good economic benefits and application prospects in the market.

Description

Technical Field

[0001] The invention belongs to the technical field of magnesium alloy wire preparation, and in particular relates to a device and a method for preparing a magnesium alloy wire. Background Art

[0002] As one of the most important raw materials for high-end applications such as magnesium alloy welding and 3D printing, magnesium alloy wires on the market still generally have problems such as low quality, no clear design standards and poor versatility. From the initial raw materials to downstream processes such as extrusion and drawing, impurities are easily introduced, and the existence of tissue genetic effects will lead to a series of problems such as uneven composition of the final wire, oxide inclusions and poor controllability. Therefore, the development and research of high-quality magnesium alloy wires will become a crucial link restricting the development of the magnesium alloy industry.

[0003] In the traditional preparation process of magnesium alloy wire, it usually goes through complicated processes such as raw material melting, casting, homogenization, extrusion, drawing and intermediate annealing. These processes require repeated heating, which will greatly increase the production cost. If magnesium alloy filaments are obtained directly by extrusion, a considerable extrusion ratio is required, which puts higher requirements on the equipment tonnage of the extruder. Such problems are more obvious in high-strength magnesium alloys containing rare earth or high alloy elements; on the other hand, filaments can also be prepared by extrusion + drawing process, but the magnesium matrix of the hcp crystal structure has fewer slip systems and weak plastic deformation ability. It is easy to break when drawing at room temperature. High-temperature drawing is easy to cause the wire grains to grow again or oxidize, and may also cause a decrease in dimensional stability. In addition, conventional magnesium alloys need to be preheated or homogenized before extrusion. Oxides will be generated on the end face of the ingot under high temperature environment, which is easy to introduce oxidation inclusions during the extrusion process, and will also cause the wire overlap between adjacent ingots to deteriorate, affecting its use function.

[0004] At present, the measures to improve the composition and performance stability of magnesium alloy wire are: (1) Alloy composition optimization design: While the strength and plasticity are improved by introducing Gd and Y elements, Zr element is also added to purify the matrix to reduce the content of impurity elements.

[0005] The above alloying design increases the complexity of the alloy system, and the large amount of rare earth elements added also greatly increases the economic cost. At the same time, the presence of Zr element is not conducive to obtaining wire with good composition uniformity.

[0006] (2) Improvement and innovation of forming process: By continuously hot-drawing the magnesium alloy thick wire obtained by the previous extrusion for multiple times, a fine wire with a wire diameter as low as 0.5 mm can be finally obtained. In addition, benefiting from the electroplastic characteristics of the metal, a pulsed magnetic field is introduced into the wire drawing device. The pulsed current generated can activate cross-slip and produce a wavy dislocation morphology, thus assisting the wire drawing at a lower temperature.

[0007] However, the first method mentioned above often requires multiple rounds of hot drawing, and even 19 rounds of hot drawing are required. Usually the extrusion and drawing processes are carried out in an atmospheric environment. Such repeated heating processes are bound to cause severe oxidation, affecting the performance of subsequent welding and additive manufacturing products. In addition, the introduction of electrolyte and pulse current also causes the complexity and instability of the process itself, and this method is currently more common in scientific research and is difficult to guide the industrial production of magnesium alloy wire. Summary of the invention

[0008] The object of the present invention is to provide a device and a method for preparing magnesium alloy wire to solve the above problems.

[0009] To achieve the above object, the present invention adopts the following technical solutions: A device for preparing magnesium alloy wire comprises a heating chamber, an extrusion unit and a wire die; the extrusion unit is arranged in the heating chamber, a blank to be extruded is arranged in the extrusion unit, an outlet is located below the extrusion unit, and the wire die is installed at the outlet below the extrusion unit.

[0010] Furthermore, the top and bottom of the heating chamber are both provided with openings, a bottom plate is provided on the bottom opening, and a guide wire inclined surface is provided on the bottom plate.

[0011] Furthermore, the extrusion unit includes an extrusion rod, an extrusion cylinder and a punch. The extrusion rod is arranged in the top opening of the heating chamber and can move up and down in the top opening. The punch is installed on the extrusion rod; the extrusion cylinder is arranged inside the heating chamber, and the billet to be extruded is arranged in the extrusion cylinder. When the extrusion rod moves up and down, the billet to be extruded can be extruded.

[0012] Furthermore, the extrusion cylinder is a cylindrical structure with openings at both ends, the wire mold is installed at the bottom of the extrusion cylinder, and the extrusion rod can extend into the extrusion cylinder.

[0013] Furthermore, an outer protective sleeve is arranged outside the extrusion cylinder.

[0014] Furthermore, a water cooling pipeline is arranged on the upper side of the wire die, and the water cooling pipeline is externally connected to cooling water.

[0015] Furthermore, a side wall inclined hole is arranged on the upper part of the extrusion barrel, and the side wall inclined hole is used for introducing protective gas and arranging an external heating couple to measure the temperature of the extrusion barrel.

[0016] Furthermore, the position of the side wall oblique hole is higher than that of the outer protective cover.

[0017] A method for preparing a magnesium alloy wire comprises the following steps: In a protective gas atmosphere, the cast billet to be extruded is homogenized, and after the homogenization is completed, the billet is further subjected to hot extrusion pre-deformation treatment to obtain a pre-deformed billet; An external heating couple is used to measure the temperature of the pre-deformed blank, and the pre-deformed blank is heated to a semi-solid temperature range to obtain a semi-solid blank; The extrusion rod is pushed to extrude the semi-solid billet, and the wire is extruded through a wire die provided with a water-cooling sleeve and led out from the wire guide slope.

[0018] . A method for preparing a magnesium alloy wire according to claim, characterized in that the flow rate of the protective gas is 5 L / min.

[0019] Compared with the prior art, the present invention has the following technical effects: The heating chamber of the present invention provides a controllable temperature environment for the entire extrusion process, ensuring that the magnesium alloy blank can be extruded at a suitable temperature, which is crucial for semi-solid extrusion forming. The top and bottom openings are designed to facilitate the loading of blanks and the export of wires. At the same time, the bottom plate and wire guide slope design on the bottom opening facilitate the smooth export of wires, reducing friction and resistance.

[0020] The extrusion unit of the present invention comprises an extrusion rod, an extrusion barrel and a punch, and this design makes the extrusion process more stable and controllable. The extrusion rod can move up and down in the top opening, and the blank is extruded by the punch, thereby realizing precise control of the blank. The extrusion barrel is a cylindrical structure with openings at both ends, which is convenient for placing the blank and leading out the wire after extrusion.

[0021] The wire die of the present invention is installed at the bottom of the extrusion barrel, ensuring that the extruded wire has the required shape and size. The circumferentially arranged water cooling pipeline can quickly cool the extruded wire to prevent it from being deformed or defective due to high temperature. The design of the side wall oblique hole is convenient for the introduction of protective gas and the installation of external heating couples, which not only protects the blank from oxidation, but also can monitor the temperature in the extrusion barrel in real time.

[0022] The present invention performs homogenization treatment under a protective gas atmosphere, thereby preventing the blank from being oxidized during the heating process and ensuring the purity of the blank.

[0023] The pre-deformation treatment of the present invention can eliminate the internal stress in the blank and improve the extrudability of the blank. Through the pre-deformation treatment, the structure of the blank becomes more uniform, which is conducive to the subsequent extrusion forming. Semi-solid extrusion forming utilizes the characteristics of magnesium alloy with low deformation resistance in semi-solid state, reducing the force and energy consumption required for extrusion. Semi-solid extrusion forming can maintain the uniformity of the blank's structure and improve the performance and stability of the wire.

[0024] The full inert atmosphere environment control of the present invention prevents oxidation of the blank and the wire during processing, ensuring the purity and performance of the wire. This control method also reduces the generation of oxidative inclusions and improves the uniformity of the organization and mechanical properties of the wire.

[0025] Compared with the traditional extrusion-drawing process, this method has been greatly simplified, significantly reducing energy consumption and production costs. The short process and good continuity have improved production efficiency and met the market demand for high-quality magnesium alloy wire.

[0026] In summary, both the device and method in this technical solution are innovative and practical. The device is reasonably designed and fully functional, providing strong support for the preparation of magnesium alloy wires; the method ensures the high quality and stability of the wires through scientific process flow and strict control measures. This preparation process is expected to have good economic benefits and application prospects in the market. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the structure of the present invention.

[0028] Figure 2 Technology roadmap for semi-solid extruded wire of magnesium alloy.

[0029] Figure 3 Heat treatment roadmap for magnesium alloy billets.

[0030] Figure 4 Comparison of extruded wire morphology of AZ80A case 1 (a) and comparative example 1 (b).

[0031] Figure 5 Diameter statistics of wire obtained from AZ80A case 1 Figure 6 (a) Surface and (b) core microstructure of the wire obtained in AZ80A Case 1.

[0032] 1-extrusion rod; 2-heating chamber; 3-extrusion cylinder; 4-water cooling pipeline; 5-wire guide slope; 6-wire die; 7-outer protective cover; 8-side wall inclined hole; 9-punch. DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with the accompanying drawings: Example 1, please refer to Figure 1 The present invention provides a device for preparing magnesium alloy wire, comprising a heating chamber 2, an extrusion unit and a wire die 6; the extrusion unit is arranged in the heating chamber 2, a blank to be extruded is arranged in the extrusion unit, the lower part of the extrusion unit is an outlet, and the wire die 6 is installed at the lower outlet of the extrusion unit.

[0034] The device integrates the heating chamber, extrusion unit and wire die into a compact production system. This integrated design not only saves space, but also reduces the transfer time of materials between different equipment and improves production efficiency. Due to the high degree of integration of the device, operators can more easily monitor and adjust the production process, reducing the difficulty and complexity of operation.

[0035] The heating chamber provides a stable temperature environment for the extrusion process. By accurately controlling the temperature of the heating chamber, it is possible to ensure that the blank reaches the required semi-solid temperature range before extrusion, thereby improving the quality and stability of extrusion. The integrated design reduces the temperature fluctuation of the blank during the transfer process, avoids the organizational changes caused by temperature changes, and further ensures the performance consistency of the wire.

[0036] The design of the extrusion unit makes the extrusion process more controllable. By adjusting the moving speed and pressure of the extrusion rod, the deformation degree and extrusion speed of the blank can be accurately controlled to obtain the wire of the required shape and size. The wire die is installed at the lower outlet of the extrusion unit to ensure that the extruded wire can directly enter the die for forming. This precise positioning design improves the forming accuracy and surface quality of the wire.

[0037] The device improves production efficiency through integrated and precisely controlled design, and further shortens production cycle by reducing material transfer and waiting time.

[0038] The device simplifies the post-drawing processing process in the traditional wire preparation process and reduces production costs. In addition, since the continuity and dimensional stability of the wire are improved, the scrap rate and subsequent processing costs are also reduced.

[0039] In summary, the device for preparing magnesium alloy wire provided by the present invention has multiple technical effects such as integration and compactness, temperature control accuracy, controllability of the extrusion process, production efficiency and cost-effectiveness, and stability and reliability of product quality. These technical effects together constitute the innovation and competitive advantage of the device, and provide an efficient, stable and economical solution for the preparation of magnesium alloy wire.

[0040] Embodiment 2, the present invention provides a device for preparing magnesium alloy wire, specifically comprising: Figure 1The cross-sectional view of the device for semi-solid extrusion of magnesium alloy is shown, which is assembled from a total of 9 parts. Among them, the lower end of the extrusion rod 1 is bolted with a punch 9 for direct contact extrusion of magnesium alloy. A heating chamber 2 with a resistance wire is provided inside. The extrusion cylinder 3 is the location for placing the pre-compressed billet, which is divided into an upper and a lower part, which is connected by bolts in the middle, and there is space for placing the wire mold 6. In addition, a circle of water-cooling pipeline 4 for placing circular copper tubes is processed on the outer periphery of the mold; the setting of the wire guide slope 5 is to facilitate the smooth horizontal output of the wire extruded vertically downward; the outer protective sleeve 7 is a cylindrical protective sleeve made of 45 steel, but a side wall inclined hole 8 is processed for the thermocouple and protective gas pipeline to extend into. Except for the outer protective sleeve 7, all devices are made of H13 mold steel.

[0041] The working principle of the device is as follows: first, the whole device is heated up to the preset temperature under the action of the heating chamber 2. Then, the protective gas is introduced for a period of time to remove the internal air as much as possible, and then the billet after homogenization and pre-compression is transferred to the extrusion barrel 3. After the billet temperature reaches the preset temperature after being kept warm for a period of time, extrusion can begin. Under the push of the extrusion rod 1, the punch 9 continuously acts on the billet, and the semi-solid magnesium alloy begins to be extruded downward through the small hole of the wire die 6. After contacting the guide wire slope 5, it is manually pulled to change its output direction to horizontal, and is wound into a disk or cut into strips at the end to complete the extrusion. When extruding at low temperature or solidifying magnesium alloy wires that are fast, the water cooling pipe 4 may not be used to accelerate cooling.

[0042] Example 3, a method for preparing a magnesium alloy wire, the present invention takes Mg-Al series AZ80A magnesium alloy as an example (GB / T5153-2016, Mg-(7.8-9.2)Al-(0.2-0.8)Zn-(0.15-0.50)Mn (wt.%)), by Figure 2 Technical solution to achieve the whole process of wire preparation under atmosphere protection: (1) Pre-deformation treatment of semi-solid billet Before semi-solid hot extrusion, the as-cast billet is homogenized (410℃, 10~12h) to eliminate the component segregation and internal stress inside the billet. After the homogenization treatment is completed, the billet is further subjected to hot extrusion pre-deformation treatment.

[0043] This step is carried out using an extrusion process, which is an efficient and controllable way to induce strain. The deformation energy accumulated by plastic deformation can improve the microstructure of the semi-solid billet during the subsequent semi-solid heating process. On the one hand, the growth rate of the billet grains is limited to avoid the rapid growth of the material grains; on the other hand, it can promote the generation of more liquid phases, further improve the roundness and distribution uniformity of the solid phase particles, and facilitate the thixoforming process.

[0044] During the above process, high-purity argon gas was continuously introduced into the entire system, and the flow rate was set to 5 L / min.

[0045] (2) Semi-solid hot extrusion An external heating couple is used to measure the ingot temperature. The pre-deformed billet is first heated to a semi-solid temperature range (taking AZ80 magnesium alloy as an example, its semi-solid temperature range is about 480~580℃, and the liquid phase ratio of the tissue can reach 30%-50%vol.%).

[0046] The semi-solid AZ80A is extruded by the extrusion rod pushing method. The inner diameter of the extrusion chamber is Φ65, the number of wire outlets is set to 8, the wire diameter is Φ3.5, the extrusion ratio is about 43, the extrusion speed is 8 mm / min, and the extrusion wire is equipped with a water-cooling sleeve for accelerated cooling and assisted by a wire guide device.

[0047] Example 4, taking AZ80A magnesium alloy as an example (GB / T 5153-2016, Mg-(7.8-9.2)Al-(0.2-0.8)Zn-(0.15-0.50)Mn (wt.%)): (1) Pre-deformation treatment of semi-solid extrusion billet Before the semi-solid hot extrusion, the as-cast billet was homogenized (410℃, 10~12 h) to eliminate the component segregation and internal stress inside the billet. After the homogenization treatment, the billet was transferred to the extruder for hot extrusion pre-deformation treatment, with an extrusion temperature of 300~350℃ and an extrusion ratio of 10:1~20:1. This step is carried out by extrusion process, which is an efficient and controllable strain-induced method. The deformation energy storage accumulated by plastic deformation can improve the microstructure of the semi-solid billet in the subsequent semi-solid heating process. On the one hand, the growth rate of the billet grains is limited to avoid the rapid growth of the material grains; on the other hand, it can promote the generation of more liquid phases, further improve the roundness and distribution uniformity of the solid phase particles, and facilitate the thixoforming process.

[0048] High-purity argon gas was continuously introduced during the pretreatment and extrusion processes, and the flow rate was set to 5 L / min.

[0049] (2) Semi-solid hot extrusion Before placing the pre-deformed billet, the die of the extrusion chamber was raised to 500℃ and kept warm for 2 h. The pre-deformed billet was placed in the extrusion chamber for heating. When the thermocouple detected that the billet had heated to the target semi-solid range (480~500℃), extrusion began. The semi-solid AZ80A was extruded by the extrusion rod pushing method. The inner diameter of the extrusion chamber was Φ65, the number of wire outlets was set to 8, the wire diameter was Φ3.5, the extrusion ratio was about 43, and the extrusion speed was 8 mm / min. The extruded wire was cooled by a water-cooling sleeve, and a wire guide slope was set at the lower end of the die outlet to ensure that the wire was pushed out smoothly from the lateral direction.

[0050] (3) Thermal processing history diagram Figure 3 Taking AZ80A magnesium alloy as an example, the heat treatment roadmap of the billet from homogenization, pre-deformation to final extrusion wire is summarized. Tm and Tα are the melting point of magnesium alloy and the temperature at which α-Mg begins to melt, respectively. After the homogenization and pre-extrusion deformation are completed, the treated billet is further heated to a semi-solid extrusion temperature zone with a certain liquid phase volume fraction to carry out the final extrusion wire process.

[0051] (4) Wire material comparison The morphology of the extruded wire in this case is compared with that of the wire in comparative example 1 (conventionally processed by extrusion-drawing). Figure 4 As shown. It is easy to see that the morphology of the AZ80A wire obtained by the semi-solid extrusion molding proposed in the present invention is basically consistent with that of the traditional extrusion-drawing. The wire has good continuity, no major bending, twisting or breaking occurs, and the surface has good finish, and no defects such as thermal cracking and oxidation are found.

[0052] Since 3 of the wires are shorter, Figure 5 The diameters of five wires with relatively uniform lengths were plotted. It can be seen that the wire diameters are relatively uniform, all concentrated in the range of 3.3-3.4 mm, and the diameter fluctuation of a single wire does not exceed ±70 μm, indicating that the wire diameter obtained by this method has good uniformity.

[0053] Figure 6 The microstructure of the obtained wire is shown: when extruding in the semi-solid temperature zone, due to the pre-compression process, the original liquid phase mostly appears at the grain boundary position, and the roundness of the grain is relatively high. During the extrusion process, the surface deformation of the wire and the friction of the inner wall of the mold are the largest, and it is in direct contact with the air, with good cooling conditions, so the grains show typical deformed grain structure characteristics (a), and the second phase content is also less; while the core deformation is small, the heat dissipation conditions are poor, and the second phase precipitation is relatively complete, showing a developed and dense solidified dendrite (b).

[0054] The present invention realizes low-cost and short-process preparation of difficult-to-extrude magnesium alloy wires through thixoforming, and the obtained wires have good continuity. Theoretically, if the extruded blanks are sufficient and the device is large enough, the wires can be produced without breakpoints, ensuring the stability of the welding and additive manufacturing processes. This method is applicable to magnesium alloys such as AZ, WE and VW series. The present invention is aimed at thixoforming of semi-solid magnesium alloys, and its thermoplastic deformation resistance will be reduced by an order of magnitude compared with traditional extrusion, which greatly improves production efficiency and reduces the heavy pressure of equipment upgrades; The proposed wire preparation process is fully simplified, significantly reducing energy consumption and production costs, and is in line with the industry's needs to solve multiple processes and high processing costs in existing industrial production; The wire preparation process of the present invention adopts a fully inert atmosphere protection, which avoids air oxidation caused by direct contact with the external environment in the traditional drawing process and avoids the formation of oxidized inclusions in the wire. The good formability of the semi-solid raw material also helps to improve the accuracy of the wire diameter. The magnesium alloy wire described in the present invention is extruded in the solid-liquid two-phase temperature range. At this temperature, the ingot undergoes a composition homogenization process, which can eliminate the adverse effects of the segregation of alloy elements inside the original ingot on the wire composition and performance, and is conducive to obtaining high-quality magnesium alloy wire with excellent and stable performance.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A device for preparing magnesium alloy wire, characterized in that: It comprises a heating chamber (2), an extrusion unit and a wire die (6); the extrusion unit is arranged in the heating chamber (2), a blank to be extruded is arranged in the extrusion unit, the bottom of the extrusion unit is an outlet, and the wire die (6) is installed at the bottom outlet of the extrusion unit.

2. The device for preparing magnesium alloy wire according to claim 1, characterized in that: The top and bottom of the heating chamber (2) are both provided with openings, a bottom plate is provided on the bottom opening, and a guide wire inclined surface (5) is provided on the bottom plate.

3. The device for preparing magnesium alloy wire according to claim 2, characterized in that: The extrusion unit comprises an extrusion rod (1), an extrusion cylinder (3) and a punch (9); the extrusion rod (1) is arranged in a top opening of a heating chamber (2) and is capable of moving up and down in the top opening; the punch (9) is mounted on the extrusion rod (1); the extrusion cylinder (3) is arranged inside the heating chamber (2); a blank to be extruded is arranged in the extrusion cylinder (3); and when the extrusion rod (1) moves up and down, the blank to be extruded can be extruded.

4. The device for preparing magnesium alloy wire according to claim 3, characterized in that: The extrusion cylinder (3) is a cylindrical structure with openings at both ends; the wire die (6) is mounted at the bottom of the extrusion cylinder (3); and the extrusion rod (1) can extend into the extrusion cylinder (3).

5. The device for preparing magnesium alloy wire according to claim 3, characterized in that: An outer protective sleeve (7) is arranged outside the extrusion cylinder (3).

6. The device for preparing magnesium alloy wire according to claim 1, characterized in that: A water cooling pipeline (4) is disposed on the upper side of the wire die (6), and the water cooling pipeline (4) is externally connected to cooling water.

7. The device for preparing magnesium alloy wire according to claim 5, characterized in that: The upper portion of the extrusion barrel (3) is provided with a side wall oblique hole (8), and the side wall oblique hole (8) is used to introduce protective gas and to set an external heating couple to measure the temperature of the extrusion barrel (3).

8. The device for preparing magnesium alloy wire according to claim 7, characterized in that: The position of the side wall oblique hole (8) is higher than the position of the outer protective sleeve (7).

9. A method for preparing a magnesium alloy wire, characterized in that: A device for preparing a magnesium alloy wire according to any one of claims 1 to 8, comprising the following steps: In a protective gas atmosphere, the cast billet to be extruded is homogenized, and after the homogenization is completed, the billet is further subjected to hot extrusion pre-deformation treatment to obtain a pre-deformed billet; An external heating couple is used to measure the temperature of the pre-deformed blank, and the pre-deformed blank is heated to a semi-solid temperature range to obtain a semi-solid blank; The extrusion rod is pushed to extrude the semi-solid billet, and the wire is extruded through a wire die provided with a water-cooling sleeve and led out from the wire guide slope.

10. The method for preparing a magnesium alloy wire according to claim 9, characterized in that: The protective gas flow rate is 5 L / min.

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