Weldable low-rare earth magnesium alloy seamless profile and method for producing the same

Abstract

The present application relates to alloy material and metallurgical technology field, specifically relates to a kind of weldable low rare earth magnesium alloy seamless section bar and its preparation method.Weldable low rare earth magnesium alloy seamless section bar alloy composition is:Al7~9%, Zn 0.8~1.0%, Mn 0.3~0.5%, Gd 0.3~0.8%, Ce 0.3~0.8%, Y 0.3~0.8%, the balance is Mg;Including the following steps: alloy component is smelted, and refining agent is added to refine, then casting is formed into ingot;The ingot is kept at 330~350 ℃, and kept warm after heating to 400~410 ℃, and extrusion is formed into section bar, welding is carried out under protective gas, and heat treatment is obtained after it.Just the section bar prepared by the present application shows the characteristics of high-temperature resistance and low-temperature resistance weldable, and can be applied in building materials, rail transit vehicles, sports equipment, arctic research vessels, aerospace and other fields at room temperature and extreme temperature.

Description

Technical Field

[0001] This invention relates to the fields of alloy materials and metallurgical technology, specifically to a weldable low-rare-earth magnesium alloy seamless profile and its preparation method. Background Technology

[0002] Magnesium alloys, as the lightest metallic structural materials currently available, have excellent application prospects in building materials, rail vehicles, sports equipment, Arctic research vessels, aerospace, and other fields. Commonly used magnesium alloys have a density of only 1.8 g / cm³. 3 Magnesium alloys weigh approximately 65% ​​of aluminum alloys and 22% of steel. Under the major trend of energy conservation and emission reduction, the enormous weight reduction potential of magnesium alloys has attracted widespread attention from materials scientists. Furthermore, magnesium alloys possess many excellent properties such as high specific strength and specific stiffness, good electromagnetic shielding, and easy recyclability.

[0003] However, traditional magnesium alloy extruded tubing is typically welded; for example, AZ31 magnesium alloy tubing produced using a split-flow die has welded seams and often exists in a simple, single-tube form. Some complex-shaped magnesium alloy structural components usually require welding different tubing or sheet metal before use, but the room temperature mechanical properties after welding are significantly reduced, failing to meet usage requirements, let alone applications in high and low temperature environments. This is a pressing problem facing magnesium alloy tubing and sheet metal production, resulting in actual application volumes far below expectations, which is extremely detrimental to the market promotion of magnesium alloy tubing and sheet metal.

[0004] To address these challenges, it is necessary to ensure that magnesium alloy pipes or sheets retain excellent mechanical properties after welding, while also improving their mechanical properties under high and low temperature environments to meet service requirements in complex conditions. Currently, the main approach is to improve the mechanical properties of seamless magnesium alloy pipes and sheets by rationally controlling the composition and altering the multi-level microstructure.

[0005] Currently, the mechanical properties of Mg-Zn magnesium alloys have been improved by adding appropriate rare earth elements, such as Er, Y, Nd, Gd, and Ce. This is because rare earth elements can refine grains and form strengthening phases, thereby enhancing the mechanical properties of magnesium alloys. For example, the tensile strength of the Mg-3.8Zn-2.2Ca-1.0Gd alloy in the as-cast state is 131 MPa; the tensile strength of the Mg-2Zn-0.46Y-0.5Nd alloy in the extruded state is 269 MPa; and the tensile strength of the Mg-3.5Zn-0.6Gd alloy in the extruded state is 308 MPa. However, when these magnesium alloy materials are made into pipes or plates, their mechanical strength decreases significantly after welding, failing to meet the strength requirements of the alloy. This is especially true under extreme temperature conditions, where the mechanical properties deteriorate significantly after welding, making it unsuitable for service in complex environments. Summary of the Invention

[0006] To address the problem of reduced mechanical properties of existing magnesium alloys after welding, especially under extreme temperature conditions, the present invention aims to provide a high-temperature resistant and low-temperature resistant weldable low-rare-earth magnesium alloy seamless profile and its preparation method.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows.

[0008] The first aspect of the present invention provides a method for preparing a weldable low-rare-earth magnesium alloy seamless profile, wherein the alloy composition of the weldable low-rare-earth magnesium alloy seamless profile, by weight percentage, is: Al 7-9%, Zn 0.8-1.0%, Mn 0.3-0.5%, Gd 0.3-0.8%, Ce 0.3-0.8%, Y 0.3-0.8%, with the balance being Mg;

[0009] The method for preparing the weldable low-rare-earth magnesium alloy seamless profile includes the following steps:

[0010] The alloy components are melted at 730–750°C to obtain a liquid alloy;

[0011] The alloy liquid is mixed with a refining agent for refining, and then cast to form a magnesium alloy ingot.

[0012] Magnesium alloy ingots are held at 330–350°C, then heated to 400–410°C in the furnace and held thereafter. Finally, they are extruded at 330–350°C to obtain profiles.

[0013] The profiles are welded under a protective gas to obtain weldable profiles; after heat treatment, weldable low rare earth magnesium alloy seamless profiles are obtained.

[0014] In a preferred embodiment, the refining agent is a mixture of potassium chloride, calcium chloride, sodium chloride, barium chloride, calcium fluoride, sodium hexafluoroaluminate, and gadolinium chloride; wherein the mass ratio of potassium chloride, calcium chloride, sodium chloride, barium chloride, calcium fluoride, sodium hexafluoroaluminate, and gadolinium chloride in the refining agent is 49:18:3:16:5:3:6.

[0015] In a preferred embodiment, the mass ratio of the molten alloy to the refining agent is 49:1.

[0016] In a preferred embodiment, the refining process further includes a standing period of 20–25 minutes.

[0017] In a preferred embodiment, the casting is performed by casting the molten alloy into a bar shape using a semi-continuous casting process.

[0018] In a preferred embodiment, the heat treatment at 330–350°C is carried out for 420–480 min; the heat treatment at 400–410°C is carried out for 420–480 min.

[0019] In a preferred embodiment, the specific method for preparing the profile is as follows:

[0020] Magnesium alloy ingots are held at 340℃ for 420–480 min, then heated to 400℃ in the furnace and held for 420–480 min. The ingots are then transferred to an extrusion cylinder and extruded at 330–350℃ to obtain profiles.

[0021] In a preferred embodiment, the extrusion speed of the extrusion molding is 0.4 to 0.6 m / min.

[0022] In a preferred embodiment, the profile is a sheet or a tube;

[0023] The extrusion molding process of the tube is as follows: the heated magnesium alloy ingot is reverse-extruded into a tube.

[0024] The extrusion molding process of the sheet is as follows: the heated magnesium alloy ingot is forward extruded into a sheet.

[0025] In a preferred embodiment, the extrusion ratio in the extrusion molding process of the sheet material is 40-50:1; and the extrusion ratio in the extrusion molding process of the pipe material is 100-110:1.

[0026] In a preferred embodiment, the protective gas is argon, and the flow rate of the protective gas is 10 L / min; the welding speed is 100 mm / min; the welding method is AC TIG welding; and the diameter of the welding wire is 2.4 mm. The composition of the welding wire is the same as that of the profile.

[0027] In a preferred embodiment, the heat treatment temperature is 150–170°C, and the heat treatment time is 1–48 h.

[0028] A second aspect of the present invention provides a weldable low-rare-earth magnesium alloy seamless profile, which is prepared by the preparation method described in the first aspect.

[0029] The plates or pipes prepared by the method of the present invention have the characteristics of high temperature resistance, low temperature resistance and weldability, and can be used in building materials, rail transit vehicles, sports equipment, Arctic scientific research vessels, aerospace and other fields at room temperature and extreme temperatures.

[0030] The beneficial effects of this invention are:

[0031] 1. This invention, by adding small amounts of Mn, Ce, and Y elements, achieves a refining effect through the synergistic effect of these elements, promoting grain refinement and improving welding performance. On the other hand, the micron-scale crystalline phase formed can effectively prevent grain boundary slip and also strengthen the material through the refinement of dendrites and the dispersion of precipitate products. As a result, the magnesium alloy profile has excellent high and low temperature mechanical properties, solving the problem of reduced mechanical properties of existing magnesium alloys after welding, especially the problem of reduced mechanical properties under extreme temperature environments.

[0032] 2. The weldable low-rare-earth magnesium alloy seamless profiles prepared by this invention exhibit higher mechanical strength in the welded pipes and plates at 150℃, 200℃ and 250℃ than before welding. At -196℃, the mechanical properties after welding are slightly lower than before welding, demonstrating the characteristics of high temperature resistance, low temperature resistance and weldability. It can be applied in building materials, rail transit vehicles, sports equipment, Arctic research vessels, aerospace and other fields at room temperature and extreme temperatures. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0034] 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.

[0035] The first aspect of the present invention provides a method for preparing a weldable seamless profile of low rare earth magnesium alloy.

[0036] This invention adds a small amount of manganese (Mn) to magnesium alloys. Mn forms compounds with Fe or other heavy metals in the alloy, causing some harmful intermetallic compounds to separate during the smelting process and be removed as slag. Simultaneously, Mn inhibits the rate of hydrogen evolution at the cathode, preventing the formation of harmful intermetallic compounds and thus improving the corrosion resistance of the magnesium alloy. During the alloy solution treatment process, Mn surrounds the Fe, reducing the effect of localized cathode formation. Furthermore, the low Mn content prevents the precipitation of coarse, polygonal Al8Mn5 phases, achieving grain refinement and improved weldability. This solves the problem that the mechanical properties of traditional magnesium alloys after welding cannot meet practical application requirements.

[0037] This invention utilizes the rare earth element Ce to enhance the Mg content in magnesium alloys. 17 Al 12The phases are significantly refined; moreover, the new phases formed by Ce and Al, as well as Ce itself, can inhibit grain growth; in addition, Ce can also form rare earth compound phases with Mg, producing a good precipitation hardening effect. These rare earth phases have high melting points and thermal stability, which can effectively prevent grain boundary slip, and these dispersed rare earth phases are not easily decomposed at high temperatures.

[0038] This invention also adds rare earth element Y, which plays a solid solution strengthening role in magnesium alloys. The strengthening effect is achieved through the refinement of dendrite structure and the dispersion of precipitated products, thereby giving the magnesium alloy profiles, such as magnesium alloy pipes or magnesium alloy plates, good high and low temperature mechanical properties.

[0039] The weldable low-rare-earth magnesium alloy seamless profile, by weight percentage, has the following alloy composition: Al 7-9%, Zn 0.8-1.0%, Mn 0.3-0.5%, Gd 0.3-0.8%, Ce 0.3-0.8%, Y 0.3-0.8%, with the balance being Mg; the preparation method of the weldable low-rare-earth magnesium alloy seamless profile includes the following steps:

[0040] 1) The alloy composition is melted at 730-750°C to obtain an alloy liquid;

[0041] 2) The alloy liquid is mixed with a refining agent for refining, and then cast to form a magnesium alloy ingot;

[0042] 3) The magnesium alloy ingot is held at 330-350℃, then heated to 400-410℃ in the furnace and held thereafter, and then extruded at 330-350℃ to obtain the profile.

[0043] 4) The profiles are welded under a protective gas to obtain weldable profiles; after heat treatment, weldable low rare earth magnesium alloy seamless profiles are obtained.

[0044] For step 1), the preparation of the alloy liquid, the present invention mainly utilizes the prepared alloy components to melt at a set temperature, so that the alloy components are mixed evenly to form an alloy liquid.

[0045] In a preferred embodiment, the melting temperature is 730–750°C, for example, 730°C, 735°C, 740°C, 745°C, 750°C, etc.

[0046] For step 2) in the preparation of magnesium alloy ingots, this invention mainly involves refining the alloy liquid with added refining agents. These agents remove hydrogen and floating oxide inclusions from the alloy liquid, making it purer. Some components of the refining agent decompose at high temperatures, generating gases that readily react with hydrogen to remove it from the alloy liquid. Furthermore, the refining agent has a strong adsorption capacity for oxide inclusions, allowing them to escape rapidly from the alloy liquid.

[0047] In a preferred embodiment, the refining agent is a mixture of potassium chloride, calcium chloride, sodium chloride, barium chloride, calcium fluoride, sodium hexafluoroaluminate, and gadolinium chloride;

[0048] The refining agent contains potassium chloride, calcium chloride, sodium chloride, barium chloride, calcium fluoride, sodium hexafluoroaluminate, and gadolinium chloride in a mass ratio of 49:18:3:16:5:3:6.

[0049] In a preferred embodiment, the mass ratio of the molten alloy to the refining agent is 49:1.

[0050] In a preferred embodiment, the refining process further includes a standing period of 20–25 minutes. Examples include 20 minutes, 21 minutes, 22 minutes, 23 minutes, 24 minutes, and 25 minutes.

[0051] In a preferred embodiment, the casting is performed by casting the molten alloy into bars using a semi-continuous casting process.

[0052] For the preparation in step 3):

[0053] In a preferred embodiment, the heat treatment at 330–350°C is carried out for 420–480 min; the heat treatment at 400–410°C is carried out for 420–480 min.

[0054] In this invention, the as-cast magnesium alloy ingot is placed in a furnace and heated in two steps to improve the uniformity of the microstructure and the yield. The first step of the stepped heating involves holding the ingot at 330–350°C for 420–480 minutes; the heating temperature is 330–350°C, for example, 330°C, 335°C, 340°C, 345°C, 350°C, etc.; the heating time is 420–480 minutes, for example, 420 minutes, 430 minutes, 440 minutes, 450 minutes, 460 minutes, 470 minutes, 480 minutes, etc. The second step involves a stepped heating process, where the temperature is raised to 400–410℃ and then held for 420–480 minutes. The heating temperature is 400–410℃, for example, 400℃, 405℃, or 410℃; the heating time is 420–480 minutes, for example, 420 minutes, 430 minutes, 440 minutes, 450 minutes, 460 minutes, 470 minutes, or 480 minutes.

[0055] In a preferred embodiment, the specific method for preparing the profile is as follows:

[0056] Magnesium alloy ingots are held at 340℃ for 420–480 min, then heated in a furnace to 400℃ and held therefore for another 420–480 min. The ingots are then transferred to an extrusion cylinder and extruded at 330–350℃ to obtain profiles. The temperature inside the extrusion cylinder is 330–350℃, for example, 330℃, 335℃, 340℃, 345℃, or 350℃.

[0057] In a preferred embodiment, the extrusion speed is 0.4–0.6 m / min. Examples include 0.4 m / min, 0.5 m / min, and 0.6 m / min.

[0058] In a preferred embodiment, the profile is a sheet or a tube;

[0059] The extrusion molding process of the tube is as follows: the heated magnesium alloy ingot is reverse-extruded into a tube.

[0060] The extrusion molding process of the sheet is as follows: the heated magnesium alloy ingot is forward extruded into a sheet.

[0061] In a preferred embodiment, the extrusion ratio in the sheet metal extrusion process is 40–50:1; for example, 40:1, 41:1, 42:1, 43:1, 44:1, 45:1, 46:1, 47:1, 48:1, 49:1, 50:1, etc. In the pipe extrusion process, the extrusion ratio is 100–110:1; for example, 100:1, 101:1, 102:1, 103:1, 104:1, 105:1, 106:1, 107:1, 108:1, 109:1, 110:1, etc.

[0062] For the preparation in step 4):

[0063] In a preferred embodiment, the protective gas is argon, and the flow rate of the protective gas is 10 L / min; the welding speed is 100 mm / min; the welding method is AC TIG welding; and the diameter of the welding wire is 2.4 mm. The composition of the welding wire is the same as that of the profile.

[0064] In a preferred embodiment, the heat treatment temperature is 150–170°C, for example, 150°C, 160°C, 170°C, etc. The heat treatment time is 1–48 hours, for example, 1 hour, 4 hours, 6 hours, 8 hours, 12 hours, 16 hours, 18 hours, 20 hours, 24 hours, 26 hours, 28 hours, 30 hours, 32 hours, 34 hours, 38 hours, 40 hours, 42 hours, 44 hours, 48 ​​hours, etc.

[0065] A second aspect of the present invention provides a weldable low-rare-earth magnesium alloy seamless profile, which is prepared by the preparation method described in the first aspect.

[0066] The room temperature tensile strength of the seamless magnesium alloy pipes and plates of this invention after welding heat treatment can reach up to ~348MPa and ~337MPa, respectively. The room temperature tensile strength loss rate of the magnesium alloy pipes relative to the pre-welding strength is less than 2%, and the room temperature tensile strength loss rate of the magnesium alloy plates relative to the pre-welding strength is less than 9%. The magnesium alloy pipes and plates exhibit excellent high and low temperature resistance. During tensile testing at -196℃, the tensile strength of the pipes and plates after welding heat treatment reaches a maximum of ~395MPa and ~384MPa, respectively; during tensile testing at 150℃, the tensile strength reaches a maximum of ~233MPa and ~229MPa, respectively; during tensile testing at 200℃, the tensile strength reaches a maximum of ~163MPa and ~154MPa, respectively; and during tensile testing at 250℃, the tensile strength reaches a maximum of ~106MPa and ~105MPa, respectively. At tensile temperatures of 150℃, 200℃, and 250℃, the mechanical strength of the pipes and plates after welding is higher than that before welding. The plates or pipes prepared by the method of this invention possess high-temperature resistance, low-temperature resistance, and weldability, and can be applied in building materials, rail vehicles, sports equipment, Arctic research vessels, aerospace, and other fields at room temperature and extreme temperatures. Specific Implementation

[0068] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0069] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0070] Unless otherwise specified, the methods described in the following embodiments are conventional methods; the reagents and materials mentioned are commercially available unless otherwise specified.

[0071] The refining agent is a mixture of potassium chloride, calcium chloride, sodium chloride, barium chloride, calcium fluoride, sodium hexafluoroaluminate, and gadolinium chloride in a mass ratio of 49:18:3:16:5:3:6.

[0072] Example 1

[0073] A method for preparing a weldable low-rare-earth magnesium alloy seamless profile includes the following steps:

[0074] 1) Weigh the alloy components: By weight percentage, the alloy composition of the weldable low rare earth magnesium alloy seamless profile is: Al 8.8%, Zn 1.0%, Mn 0.3%, Gd 0.5%, Ce 0.3%, Y 0.7%, with the balance being Mg. Place the above alloy components in a crucible, heat to 730-750℃, melt the above alloy components into a liquid state, and stir to mix them evenly to obtain an alloy liquid;

[0075] 2) Semi-continuous melting and casting: A refining agent is added to the alloy liquid to refine it. After refining, the liquid is allowed to stand for 25 minutes. Then, the refined alloy liquid is cast into magnesium alloy rods through a semi-continuous casting process.

[0076] 3) Heating and extrusion: The cast magnesium alloy bar is placed in a furnace and heated in two steps. First, it is held at 340℃ for 460 min, and then heated to 410℃ at a rate of 1℃ / min and held for 460 min. Then, the heated magnesium alloy bar is reverse-extruded into seamless magnesium alloy tubes at an extrusion speed of 0.6 m / min. The extrusion cylinder temperature is 350℃ and the extrusion ratio is 100:1.

[0077] 4) Welding: The extruded magnesium alloy seamless tube is subjected to AC TIG welding at a speed of 100 mm / min under argon protection at a flow rate of 10 L / min to obtain welded magnesium alloy tube; the diameter of the magnesium alloy welding wire is 2.4 mm, and the composition of the welding wire is the same as that of the base material; the welded magnesium alloy tube is subjected to heat treatment at a temperature of 160℃ for 1 hour to obtain weldable low rare earth magnesium alloy seamless tube.

[0078] Example 2

[0079] A method for preparing weldable low-rare-earth magnesium alloy seamless profiles differs from the method in Example 1 in that the heat treatment time for the welded pipe is different. The specific method includes the following steps:

[0080] 1) Weigh the alloy components: By weight percentage, the alloy composition of the weldable low rare earth magnesium alloy seamless profile is: Al 8.8%, Zn 1.0%, Mn 0.3%, Gd 0.5%, Ce 0.3%, Y 0.7%, with the balance being Mg. Place the above alloy components in a crucible, heat to 730-750℃, melt the above alloy components into a liquid state, and stir to mix them evenly to obtain an alloy liquid;

[0081] 2) Semi-continuous melting and casting: A refining agent is added to the alloy liquid to refine it. After refining, the liquid is allowed to stand for 25 minutes. Then, the refined alloy liquid is cast into magnesium alloy rods through a semi-continuous casting process.

[0082] 3) Heating and extrusion: The cast magnesium alloy bar is placed in a furnace and heated in two steps. First, it is held at 340℃ for 460 min, and then heated to 410℃ at a rate of 1℃ / min and held for 460 min. Then, the heated magnesium alloy bar is reverse-extruded into seamless magnesium alloy tubes at an extrusion speed of 0.6 m / min. The extrusion cylinder temperature is 350℃ and the extrusion ratio is 100:1.

[0083] 4) Welding: The extruded magnesium alloy seamless tube is subjected to AC TIG welding at a speed of 100 mm / min under argon protection at a flow rate of 10 L / min to obtain welded magnesium alloy tube; the diameter of the magnesium alloy welding wire is 2.4 mm, and the composition of the welding wire is the same as that of the base material; the welded magnesium alloy tube is subjected to heat treatment at a temperature of 160℃ for 12 hours to obtain weldable low rare earth magnesium alloy seamless tube.

[0084] Example 3

[0085] A method for preparing weldable low-rare-earth magnesium alloy seamless profiles differs from the method in Example 1 in that the heat treatment time for the welded pipe is different. The specific method includes the following steps:

[0086] 1) Weigh the alloy components: By weight percentage, the alloy composition of the weldable low rare earth magnesium alloy seamless profile is: Al 8.8%, Zn 1.0%, Mn 0.3%, Gd 0.5%, Ce 0.3%, Y 0.7%, with the balance being Mg. Place the above alloy components in a crucible, heat to 730-750℃, melt the above alloy components into a liquid state, and stir to mix them evenly to obtain an alloy liquid;

[0087] 2) Semi-continuous melting and casting: A refining agent is added to the alloy liquid to refine it. After refining, the liquid is allowed to stand for 25 minutes. Then, the refined alloy liquid is cast into magnesium alloy rods through a semi-continuous casting process.

[0088] 3) Heating and extrusion: The cast magnesium alloy bar is placed in a furnace and heated in two steps. First, it is held at 340℃ for 460 min, and then heated to 410℃ at a rate of 1℃ / min and held for 460 min. Then, the heated magnesium alloy bar is reverse-extruded into seamless magnesium alloy tubes at an extrusion speed of 0.6 m / min. The extrusion cylinder temperature is 350℃ and the extrusion ratio is 100:1.

[0089] 4) Welding: The extruded magnesium alloy seamless tube is subjected to AC TIG welding at a speed of 100 mm / min under argon protection at a flow rate of 10 L / min to obtain welded magnesium alloy tube; the diameter of the magnesium alloy welding wire is 2.4 mm, and the composition of the welding wire is the same as that of the base material; the welded magnesium alloy tube is subjected to heat treatment at a temperature of 160℃ for 24 h to obtain weldable low rare earth magnesium alloy seamless tube.

[0090] Example 4

[0091] A method for preparing weldable low-rare-earth magnesium alloy seamless profiles differs from the method in Example 1 in that the heat treatment time for the welded pipe is different. The specific method includes the following steps:

[0092] 1) Weigh the alloy components: By weight percentage, the alloy composition of the weldable low rare earth magnesium alloy seamless profile is: Al 8.8%, Zn 1.0%, Mn 0.3%, Gd 0.5%, Ce 0.3%, Y 0.7%, with the balance being Mg. Place the above alloy components in a crucible, heat to 730-750℃, melt the above alloy components into a liquid state, and stir to mix them evenly to obtain an alloy liquid;

[0093] 2) Semi-continuous melting and casting: A refining agent is added to the alloy liquid to refine it. After refining, the liquid is allowed to stand for 25 minutes. Then, the refined alloy liquid is cast into magnesium alloy rods through a semi-continuous casting process.

[0094] 3) Heating and extrusion: The cast magnesium alloy bar is placed in a furnace and heated in two steps. First, it is held at 340℃ for 460 min, and then heated to 410℃ at a rate of 1℃ / min and held for 460 min. Then, the heated magnesium alloy bar is reverse-extruded into seamless magnesium alloy tubes at an extrusion speed of 0.6 m / min. The extrusion cylinder temperature is 350℃ and the extrusion ratio is 100:1.

[0095] 4) Welding: The extruded magnesium alloy seamless tube is subjected to AC TIG welding at a speed of 100 mm / min under argon protection at a flow rate of 10 L / min to obtain welded magnesium alloy tube; the diameter of the magnesium alloy welding wire is 2.4 mm, and the composition of the welding wire is the same as that of the base material; the welded magnesium alloy tube is subjected to heat treatment at a temperature of 160℃ for 48 h to obtain weldable low rare earth magnesium alloy seamless tube.

[0096] Example 5

[0097] A method for preparing weldable low-rare-earth magnesium alloy seamless profiles differs from the method in Example 4 in that the heat treatment temperature of the welded pipe is different. The specific method includes the following steps:

[0098] 1) Weigh the alloy components: By weight percentage, the alloy composition of the weldable low rare earth magnesium alloy seamless profile is: Al 8.8%, Zn 1.0%, Mn 0.3%, Gd 0.5%, Ce 0.3%, Y 0.7%, with the balance being Mg. Place the above alloy components in a crucible, heat to 730-750℃, melt the above alloy components into a liquid state, and stir to mix them evenly to obtain an alloy liquid;

[0099] 2) Semi-continuous melting and casting: A refining agent is added to the alloy liquid to refine it. After refining, the liquid is allowed to stand for 25 minutes. Then, the refined alloy liquid is cast into magnesium alloy rods through a semi-continuous casting process.

[0100] 3) Heating and extrusion: The cast magnesium alloy bar is placed in a furnace and heated in two steps. First, it is held at 340℃ for 460 min, and then heated to 410℃ at a rate of 1℃ / min and held for 460 min. Then, the heated magnesium alloy bar is reverse-extruded into seamless magnesium alloy tubes at an extrusion speed of 0.6 m / min. The extrusion cylinder temperature is 350℃ and the extrusion ratio is 100:1.

[0101] 4) Welding: The extruded magnesium alloy seamless tube is subjected to AC TIG welding at a speed of 100 mm / min under argon protection at a flow rate of 10 L / min to obtain welded magnesium alloy tube; the diameter of the magnesium alloy welding wire is 2.4 mm, and the composition of the welding wire is the same as that of the base material; the welded magnesium alloy tube is subjected to heat treatment at a temperature of 150℃ for 48 h to obtain weldable low rare earth magnesium alloy seamless tube.

[0102] Example 6

[0103] A method for preparing weldable low-rare-earth magnesium alloy seamless profiles differs from the method in Example 4 in that the heat treatment temperature of the welded pipe is different. The specific method includes the following steps:

[0104] 1) Weigh the alloy components: By weight percentage, the alloy composition of the weldable low rare earth magnesium alloy seamless profile is: Al 8.8%, Zn 1.0%, Mn 0.3%, Gd 0.5%, Ce 0.3%, Y 0.7%, with the balance being Mg. Place the above alloy components in a crucible, heat to 730-750℃, melt the above alloy components into a liquid state, and stir to mix them evenly to obtain an alloy liquid;

[0105] 2) Semi-continuous melting and casting: A refining agent is added to the alloy liquid to refine it. After refining, the liquid is allowed to stand for 25 minutes. Then, the refined alloy liquid is cast into magnesium alloy rods through a semi-continuous casting process.

[0106] 3) Heating and extrusion: The cast magnesium alloy bar is placed in a furnace and heated in two steps. First, it is held at 340℃ for 460 min, and then heated to 410℃ at a rate of 1℃ / min and held for 460 min. Then, the heated magnesium alloy bar is reverse-extruded into seamless magnesium alloy tubes at an extrusion speed of 0.6 m / min. The extrusion cylinder temperature is 350℃ and the extrusion ratio is 100:1.

[0107] 4) Welding: The extruded magnesium alloy seamless tube is subjected to AC TIG welding at a speed of 100 mm / min under argon protection at a flow rate of 10 L / min to obtain welded magnesium alloy tube; the diameter of the magnesium alloy welding wire is 2.4 mm, and the composition of the welding wire is the same as that of the base material; the welded magnesium alloy tube is subjected to heat treatment at a temperature of 170℃ for 48 h to obtain weldable low rare earth magnesium alloy seamless tube.

[0108] Example 7

[0109] A method for preparing a weldable low-rare-earth magnesium alloy seamless profile differs from the method in Example 1 in that the profile prepared is different. The specific method includes the following steps:

[0110] 1) Weigh the alloy components: By weight percentage, the alloy composition of the weldable low rare earth magnesium alloy seamless profile is: Al 8.8%, Zn 1.0%, Mn 0.3%, Gd 0.5%, Ce 0.3%, Y 0.7%, with the balance being Mg. Place the above alloy components in a crucible, heat to 730-750℃, melt the above alloy components into a liquid state, and stir to mix them evenly to obtain an alloy liquid;

[0111] 2) Semi-continuous melting and casting: A refining agent is added to the alloy liquid to refine it. After refining, the liquid is allowed to stand for 25 minutes. Then, the refined alloy liquid is cast into magnesium alloy rods through a semi-continuous casting process.

[0112] 3) Heating and extrusion: The cast magnesium alloy rod is placed in a furnace and heated in two steps. First, it is held at 340℃ for 460 min, and then heated to 410℃ at a rate of 1℃ / min and held for 460 min. Then, the heated magnesium alloy rod is forward extruded into magnesium alloy sheet at an extrusion speed of 0.6 m / min. The extrusion cylinder temperature is 350℃ and the extrusion ratio is 40:1.

[0113] 4) Welding: The extruded magnesium alloy sheet is subjected to AC TIG welding at a welding speed of 100 mm / min under argon protection at a flow rate of 10 L / min to obtain a welded magnesium alloy sheet; the diameter of the magnesium alloy welding wire is 2.4 mm, and the composition of the welding wire is the same as that of the base material; the welded magnesium alloy sheet is subjected to heat treatment at a temperature of 160℃ for 1 hour to obtain a weldable low rare earth magnesium alloy sheet.

[0114] Example 8

[0115] A method for preparing weldable low-rare-earth magnesium alloy seamless profiles differs from the method in Example 7 in that the heat treatment time for the welded sheet is different. The specific method includes the following steps:

[0116] 1) Weigh the alloy components: By weight percentage, the alloy composition of the weldable low rare earth magnesium alloy seamless profile is: Al 8.8%, Zn 1.0%, Mn 0.3%, Gd 0.5%, Ce 0.3%, Y 0.7%, with the balance being Mg. Place the above alloy components in a crucible, heat to 730-750℃, melt the above alloy components into a liquid state, and stir to mix them evenly to obtain an alloy liquid;

[0117] 2) Semi-continuous melting and casting: A refining agent is added to the alloy liquid to refine it. After refining, the liquid is allowed to stand for 25 minutes. Then, the refined alloy liquid is cast into magnesium alloy rods through a semi-continuous casting process.

[0118] 3) Heating and extrusion: The cast magnesium alloy rod is placed in a furnace and heated in two steps. First, it is held at 340℃ for 460 min, and then heated to 410℃ at a rate of 1℃ / min and held for 460 min. Then, the heated magnesium alloy rod is forward extruded into magnesium alloy sheet at an extrusion speed of 0.6 m / min. The extrusion cylinder temperature is 350℃ and the extrusion ratio is 40:1.

[0119] 4) Welding: The extruded magnesium alloy sheet is subjected to AC TIG welding at a welding speed of 100 mm / min under argon protection at a flow rate of 10 L / min to obtain a welded magnesium alloy sheet; the diameter of the magnesium alloy welding wire is 2.4 mm, and the composition of the welding wire is the same as that of the base material; the welded magnesium alloy sheet is subjected to heat treatment at a temperature of 160℃ for 48 h to obtain a weldable low rare earth magnesium alloy sheet.

[0120] Example 9

[0121] A method for preparing a weldable low rare earth magnesium alloy seamless profile differs from the method in Example 1 in that the alloy composition is different. By changing the alloy composition, the effect of the change on the pipe is investigated. The specific alloy composition is shown in Table 1.

[0122] Table 1 Alloy composition of weldable low rare earth magnesium alloy seamless profiles

[0123]

[0124]

[0125] Note: % represents mass percentage.

[0126] Example 10

[0127] A method for preparing a weldable low-rare-earth magnesium alloy seamless profile includes the following steps:

[0128] 1) Weigh the alloy components: By weight percentage, the alloy composition of the weldable low rare earth magnesium alloy seamless profile is: Al 8.8%, Zn 1.0%, Mn 0.3%, Gd 0.5%, Ce 0.3%, Y 0.7%, with the balance being Mg. Place the above alloy components in a crucible, heat to 730-750℃, melt the above alloy components into a liquid state, and stir to mix them evenly to obtain an alloy liquid;

[0129] 2) Semi-continuous melting and casting: A refining agent is added to the alloy liquid to refine it. After refining, the liquid is allowed to stand for 20 minutes. Then, the refined alloy liquid is cast into magnesium alloy rods through a semi-continuous casting process.

[0130] 3) Heating and extrusion: The cast magnesium alloy bar is placed in a furnace and heated in two steps. First, it is held at 340℃ for 420 min, and then heated to 410℃ at a rate of 1℃ / min and held for 420 min. Then, the heated magnesium alloy bar is reverse extruded into seamless magnesium alloy tubes at an extrusion speed of 0.4 m / min. The extrusion cylinder temperature is 330℃ and the extrusion ratio is 100:1.

[0131] 4) Welding: The extruded magnesium alloy seamless tube is subjected to AC TIG welding at a speed of 100 mm / min under argon protection at a flow rate of 10 L / min to obtain welded magnesium alloy tube; the diameter of the magnesium alloy welding wire is 2.4 mm, and the composition of the welding wire is the same as that of the base material; the welded magnesium alloy tube is subjected to heat treatment at a temperature of 160℃ for 48 h to obtain weldable low rare earth magnesium alloy seamless tube.

[0132] Example 11

[0133] A method for preparing a weldable low-rare-earth magnesium alloy seamless profile includes the following steps:

[0134] 1) Weigh the alloy components: By weight percentage, the alloy composition of the weldable low rare earth magnesium alloy seamless profile is: Al 8.8%, Zn 1.0%, Mn 0.3%, Gd 0.5%, Ce 0.3%, Y 0.7%, with the balance being Mg. Place the above alloy components in a crucible, heat to 730-750℃, melt the above alloy components into a liquid state, and stir to mix them evenly to obtain an alloy liquid;

[0135] 2) Semi-continuous melting and casting: A refining agent is added to the alloy liquid to refine it. After refining, the liquid is allowed to stand for 20 minutes. Then, the refined alloy liquid is cast into magnesium alloy rods through a semi-continuous casting process.

[0136] 3) Heating and extrusion: The cast magnesium alloy bar is placed in a furnace and heated in two steps. First, it is held at 350℃ for 420 min, and then heated to 410℃ at a rate of 1℃ / min and held for 420 min. Then, the heated magnesium alloy bar is reverse-extruded into seamless magnesium alloy tubes at an extrusion speed of 0.4 m / min. The extrusion cylinder temperature is 340℃ and the extrusion ratio is 100:1.

[0137] 4) Welding: The extruded magnesium alloy seamless tube is subjected to AC TIG welding at a speed of 100 mm / min under argon protection at a flow rate of 10 L / min to obtain welded magnesium alloy tube; the diameter of the magnesium alloy welding wire is 2.4 mm, and the composition of the welding wire is the same as that of the base material; the welded magnesium alloy tube is subjected to heat treatment at a temperature of 160℃ for 48 h to obtain weldable low rare earth magnesium alloy seamless tube.

[0138] Example 12

[0139] A method for preparing a weldable low-rare-earth magnesium alloy seamless profile includes the following steps:

[0140] 1) Weigh the alloy components: By weight percentage, the alloy composition of the weldable low rare earth magnesium alloy seamless profile is: Al 8.8%, Zn 1.0%, Mn 0.3%, Gd 0.5%, Ce 0.3%, Y 0.7%, with the balance being Mg. Place the above alloy components in a crucible, heat to 730-750℃, melt the above alloy components into a liquid state, and stir to mix them evenly to obtain an alloy liquid;

[0141] 2) Semi-continuous melting and casting: A refining agent is added to the alloy liquid to refine it. After refining, the liquid is allowed to stand for 25 minutes. Then, the refined alloy liquid is cast into magnesium alloy rods through a semi-continuous casting process.

[0142] 3) Heating and extrusion: The cast magnesium alloy bar is placed in a furnace and heated in two steps. First, it is held at 330℃ for 480 min, and then heated to 400℃ at a rate of 1℃ / min and held for 480 min. Then, the heated magnesium alloy bar is reverse-extruded into seamless magnesium alloy tubes at an extrusion speed of 0.4 m / min. The extrusion cylinder temperature is 350℃ and the extrusion ratio is 100:1.

[0143] 4) Welding: The extruded magnesium alloy seamless tube is subjected to AC TIG welding at a speed of 100 mm / min under argon protection at a flow rate of 10 L / min to obtain welded magnesium alloy tube; the diameter of the magnesium alloy welding wire is 2.4 mm, and the composition of the welding wire is the same as that of the base material; the welded magnesium alloy tube is subjected to heat treatment at a temperature of 160℃ for 48 h to obtain weldable low rare earth magnesium alloy seamless tube.

[0144] Comparative Example 1

[0145] A method for preparing a weldable low-rare-earth magnesium alloy seamless profile, differing from Example 1 in that no welding is performed, and the specific method includes the following steps:

[0146] 1) Weigh the alloy components: By weight percentage, the alloy composition of the weldable low rare earth magnesium alloy seamless profile is: Al 8.8%, Zn 1.0%, Mn 0.3%, Gd 0.5%, Ce 0.3%, Y 0.7%, with the balance being Mg. Place the above alloy components in a crucible, heat to 730-750℃, melt the above alloy components into a liquid state, and stir to mix them evenly to obtain an alloy liquid;

[0147] 2) Semi-continuous melting and casting: A refining agent is added to the alloy liquid to refine it. After refining, the liquid is allowed to stand for 25 minutes. Then, the refined alloy liquid is cast into magnesium alloy rods through a semi-continuous casting process.

[0148] 3) Heating and extrusion: The cast magnesium alloy bar is placed in a furnace and heated in two steps. First, it is held at 340℃ for 460 min, and then heated to 410℃ at a rate of 1℃ / min and held for 460 min. Then, the heated magnesium alloy bar is reverse-extruded into seamless magnesium alloy tubes at an extrusion speed of 0.6 m / min. The extrusion cylinder temperature is 350℃ and the extrusion ratio is 100:1.

[0149] 4) Heat treatment: The extruded magnesium alloy seamless tubes are heat treated at a temperature of 160℃ for 1 hour.

[0150] Comparative Example 2

[0151] A method for preparing a weldable low-rare-earth magnesium alloy seamless profile, differing from Example 4 in that no welding is performed, and the specific method includes the following steps:

[0152] 1) Weigh the alloy components: By weight percentage, the alloy composition of the weldable low rare earth magnesium alloy seamless profile is: Al 8.8%, Zn 1.0%, Mn 0.3%, Gd 0.5%, Ce 0.3%, Y 0.7%, with the balance being Mg. Place the above alloy components in a crucible, heat to 730-750℃, melt the above alloy components into a liquid state, and stir to mix them evenly to obtain an alloy liquid;

[0153] 2) Semi-continuous melting and casting: A refining agent is added to the alloy liquid to refine it. After refining, the liquid is allowed to stand for 25 minutes. Then, the refined alloy liquid is cast into magnesium alloy rods through a semi-continuous casting process.

[0154] 3) Heating and extrusion: The cast magnesium alloy bar is placed in a furnace and heated in two steps. First, it is held at 340℃ for 460 min, and then heated to 410℃ at a rate of 1℃ / min and held for 460 min. Then, the heated magnesium alloy bar is reverse-extruded into seamless magnesium alloy tubes at an extrusion speed of 0.6 m / min. The extrusion cylinder temperature is 350℃ and the extrusion ratio is 100:1.

[0155] 4) Heat treatment: The extruded magnesium alloy seamless tubes are heat treated at a temperature of 160℃ for 48 hours.

[0156] Comparative Example 3

[0157] A method for preparing a weldable low-rare-earth magnesium alloy seamless profile, differing from Example 7 in that it is not welded, and the specific method includes the following steps:

[0158] 1) Weigh the alloy components: By weight percentage, the alloy composition of the weldable low rare earth magnesium alloy seamless profile is: Al 8.8%, Zn 1.0%, Mn 0.3%, Gd 0.5%, Ce 0.3%, Y 0.7%, with the balance being Mg. Place the above alloy components in a crucible, heat to 730-750℃, melt the above alloy components into a liquid state, and stir to mix them evenly to obtain an alloy liquid;

[0159] 2) Semi-continuous melting and casting: A refining agent is added to the alloy liquid to refine it. After refining, the liquid is allowed to stand for 25 minutes. Then, the refined alloy liquid is cast into magnesium alloy rods through a semi-continuous casting process.

[0160] 3) Heating and extrusion: The cast magnesium alloy rod is placed in a furnace and heated in two steps. First, it is held at 340℃ for 460 min, and then heated to 410℃ at a rate of 1℃ / min and held for 460 min. Then, the heated magnesium alloy rod is forward extruded into magnesium alloy sheet at an extrusion speed of 0.6 m / min. The extrusion cylinder temperature is 350℃ and the extrusion ratio is 40:1.

[0161] 4) Heat treatment: The extruded magnesium alloy sheet is heat treated at a temperature of 160℃ for 1 hour.

[0162] Comparative Example 4

[0163] A method for preparing a weldable low-rare-earth magnesium alloy seamless profile, differing from Example 8 in that it is not welded, and the specific method includes the following steps:

[0164] 1) Weigh the alloy components: By weight percentage, the alloy composition of the weldable low rare earth magnesium alloy seamless profile is: Al 8.8%, Zn 1.0%, Mn 0.3%, Gd 0.5%, Ce 0.3%, Y 0.7%, with the balance being Mg. Place the above alloy components in a crucible, heat to 730-750℃, melt the above alloy components into a liquid state, and stir to mix them evenly to obtain an alloy liquid;

[0165] 2) Semi-continuous melting and casting: A refining agent is added to the alloy liquid to refine it. After refining, the liquid is allowed to stand for 25 minutes. Then, the refined alloy liquid is cast into magnesium alloy rods through a semi-continuous casting process.

[0166] 3) Heating and extrusion: The cast magnesium alloy rod is placed in a furnace and heated in two steps. First, it is held at 340℃ for 460 min, and then heated to 410℃ at a rate of 1℃ / min and held for 460 min. Then, the heated magnesium alloy rod is forward extruded into magnesium alloy sheet at an extrusion speed of 0.6 m / min. The extrusion cylinder temperature is 350℃ and the extrusion ratio is 40:1.

[0167] 4) Heat treatment: The extruded magnesium alloy sheet is heat treated at a temperature of 160℃ for 48 hours.

[0168] The profiles prepared in the above embodiments were subjected to performance tests.

[0169] Test 1: The effect of different heat treatment conditions on welded magnesium alloy pipes.

[0170] The room temperature tensile strength of the welded magnesium alloy pipes prepared in Examples 1 to 6 was tested, and the results are shown in Table 2.

[0171] Table 2. Effects of different heat treatment conditions on the welded magnesium alloy pipes in Examples 1-6.

[0172]

[0173]

[0174] As shown in Table 2, under constant temperature, the room temperature tensile strength of the welded magnesium alloy pipe gradually increases with increasing heat treatment time, reaching its maximum at 48 hours. Under constant heat treatment time, the room temperature tensile strength of the welded magnesium alloy pipe decreases with increasing heat treatment temperature. Based on this, the preferred heat treatment conditions are: heat treatment temperature 150–160℃, and heat treatment time 24–48 hours.

[0175] When the inventors conducted room temperature mechanical property tests on the profiles of subsequent Examples 10-12, they found that the test results were comparable to those of Example 4, so no relevant data were recorded.

[0176] Test 2: Comparison of mechanical properties of magnesium alloy profiles before and after welding, see Table 3-4.

[0177] Table 3. Conditions of magnesium alloy profiles before and after welding.

[0178]

[0179] Table 4 Comparison of mechanical properties of magnesium alloy profiles before and after welding

[0180]

[0181]

[0182] As can be seen from Tables 3-4, compared with traditional magnesium alloy pipes and plates, the weldable magnesium alloy pipes and plates obtained by the preparation method provided in this embodiment of the invention have significantly improved room temperature and high and low temperature mechanical properties before and after welding.

[0183] Comparing the room temperature mechanical properties of the embodiments and corresponding comparative examples, the maximum room temperature (25°C) tensile strength of the magnesium alloy pipe before welding can reach ~353 MPa, and the maximum room temperature (25°C) tensile strength of the magnesium alloy plate before welding can reach ~367 MPa; the maximum room temperature (25°C) tensile strength of the magnesium alloy pipe after welding can reach ~348 MPa, and the maximum room temperature (25°C) tensile strength of the magnesium alloy plate after welding can reach ~337 MPa; and the room temperature (25°C) tensile strength loss rate of the magnesium alloy pipe obtained by the preparation method provided in the embodiments of the present invention is less than 2% compared with that before welding, and the room temperature (25°C) tensile strength loss rate of the obtained magnesium alloy plate is less than 9% compared with that before welding; this greatly improves the applicability of the welded magnesium alloy pipe and plate.

[0184] Comparing the high-temperature mechanical properties (150°C) of the comparative examples and corresponding comparative examples, the highest tensile strengths of the magnesium alloy pipes and magnesium alloy plates at 150°C before welding reached ~208 MPa and [missing data], respectively.

[0185] ~220MPa; the maximum tensile strength of the welded magnesium alloy pipes and sheets at 150℃ can reach ~233MPa and ~229MPa respectively; this shows that the mechanical strength of the welded magnesium alloy pipes and sheets at 150℃ is higher than that before welding.

[0186] Comparing the high-temperature mechanical properties (200°C) of the comparative examples and corresponding comparative examples, the highest tensile strengths of the magnesium alloy tubing and magnesium alloy sheet at 200°C before welding reached ~140 MPa and respectively.

[0187] The tensile strength of the welded magnesium alloy pipes and sheets at 200℃ can reach ~136MPa, and the maximum tensile strength can reach ~163MPa and ~154MPa respectively; this shows that the mechanical strength of the welded magnesium alloy pipes and sheets at 200℃ is higher than that before welding.

[0188] Comparing the high-temperature mechanical properties (250°C) of the comparative examples and corresponding comparative examples, the highest tensile strengths (250°C) of the magnesium alloy pipes and magnesium alloy plates before welding at 250°C reached ~91 MPa and ~98 MPa, respectively. The highest tensile strengths (250°C) of the magnesium alloy pipes and magnesium alloy plates after welding reached [missing values].

[0189] ~106MPa and ~105MPa; this indicates that the mechanical strength of the welded magnesium alloy pipes and sheets at 250℃ is higher than that before welding.

[0190] Comparing the low-temperature mechanical properties (-196°C) of the comparative examples and the corresponding comparative examples, the highest tensile strengths of the magnesium alloy tubing and magnesium alloy sheet at -196°C before welding reached ~408 MPa and ~408 MPa, respectively.

[0191] The maximum tensile strength of the welded magnesium alloy pipes and sheets at -196℃ is ~421MPa, reaching ~395MPa and ~384MPa respectively. This indicates that the mechanical strength of the welded magnesium alloy pipes and sheets at -196℃ is lower than that before welding.

[0192] The results show that the mechanical strength of the welded magnesium alloy pipes and sheets is higher than that before welding at 150℃, 200℃ and 250℃; the mechanical properties after welding at -196℃ are slightly lower than those before welding. It can be seen that the weldable low rare earth magnesium alloy sheets or weldable low rare earth magnesium alloy seamless pipes prepared in the embodiments of the present invention exhibit good high and low temperature mechanical properties, and can be used in building materials, rail transit vehicles, sports equipment, Arctic research vessels, aerospace and other fields at room temperature and extreme temperatures.

[0193] Test 3: The effect of alloy composition on the performance of weldable low rare earth magnesium alloy seamless profiles.

[0194] Table 5. Effects of Alloy Composition on Pipe Performance

[0195]

[0196] As can be seen from the results in Table 5, when the alloy composition of the weldable low rare earth magnesium alloy seamless profile is: Al 7-9%, Zn 0.8-1.0%, Mn 0.3-0.5%, Gd 0.3-0.8%, Ce 0.3-0.8%, Y 0.3-0.8%, with the balance being Mg, the room temperature tensile strength of the prepared weldable low rare earth magnesium alloy seamless profile is in the range of 306-318 MPa.

[0197] Comparing the results of Group A9 with those of Example 1, it can be seen that the lack of Mn element will reduce the room temperature tensile strength of the prepared weldable low rare earth magnesium alloy seamless profile from 312 MPa to 306 MPa.

[0198] Comparing the results of group A10 with those of Example 1, it can be seen that the absence of Ce element will reduce the room temperature tensile strength of the prepared weldable low rare earth magnesium alloy seamless profile from 312 MPa to 298 MPa.

[0199] Comparing the results of group A11 with those of Example 1, it can be seen that the absence of Y element will reduce the room temperature tensile strength of the prepared weldable low rare earth magnesium alloy seamless profile from 312 MPa to 293 MPa.

[0200] This also demonstrates that by adding small amounts of Mn, Ce, and Y elements, the room temperature tensile strength of weldable low-rare-earth magnesium alloy seamless profiles can be improved through the synergistic effect of these elements. This is mainly because the addition of these elements serves two purposes: firstly, it refines the grains, promoting grain refinement and improving weldability; secondly, the resulting micron-scale crystalline phases effectively prevent grain boundary slip and strengthen the profile through dendrite refinement and dispersion of precipitate products, thus giving the magnesium alloy profile excellent high and low temperature mechanical properties.

[0201] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a weldable low-rare-earth magnesium alloy seamless profile, characterized in that, The alloy composition of the weldable low rare earth magnesium alloy seamless profile, by weight percentage, is: Al 7%~9%, Zn 0.8%~1.0%, Mn 0.3%~0.5%, Gd 0.3%~0.8%, Ce 0.3%~0.8%, Y 0.3%~0.8%, with the balance being Mg; The method for preparing the weldable low-rare-earth magnesium alloy seamless profile includes the following steps: The alloy composition is melted at 730℃~750℃ to obtain an alloy liquid; The alloy liquid is mixed with a refining agent for refining, and then cast to form a magnesium alloy ingot. Magnesium alloy ingots are held at 330℃~350℃, then heated to 400~410℃ in the furnace and held thereafter, and then extruded at 330℃~350℃ to obtain profiles. The profiles are welded under a protective gas to obtain weldable profiles; after heat treatment, weldable low rare earth magnesium alloy seamless profiles are obtained; the heat treatment temperature is 150℃~170℃ and the heat treatment time is 1h~48h.

2. The method for preparing weldable low-rare-earth magnesium alloy seamless profiles according to claim 1, characterized in that, The refining agent is a mixture of potassium chloride, calcium chloride, sodium chloride, barium chloride, calcium fluoride, sodium hexafluoroaluminate, and gadolinium chloride; The refining agent contains potassium chloride, calcium chloride, sodium chloride, barium chloride, calcium fluoride, sodium hexafluoroaluminate, and gadolinium chloride in a mass ratio of 49:18:3:16:5:3:

6.

3. The method for preparing weldable low-rare-earth magnesium alloy seamless profiles according to claim 1, characterized in that, The mass ratio of molten alloy to refining agent is 49:

1.

4. The method for preparing weldable low-rare-earth magnesium alloy seamless profiles according to claim 1, characterized in that, The heat treatment time at 330℃~350℃ is 420min~480min; The heat treatment time after 400℃~410℃ is 420min~480min.

5. The method for preparing weldable low-rare-earth magnesium alloy seamless profiles according to claim 1, characterized in that, The extrusion speed of the extrusion molding is 0.4 m / min to 0.6 m / min.

6. The method for preparing weldable low-rare-earth magnesium alloy seamless profiles according to claim 1, characterized in that, The profile is a sheet or a pipe; The extrusion molding process of the tube is as follows: the heated magnesium alloy ingot is reverse-extruded into a tube. The extrusion molding process of the sheet is as follows: the heated magnesium alloy ingot is forward extruded into a sheet.

7. The method for preparing weldable low-rare-earth magnesium alloy seamless profiles according to claim 6, characterized in that, In the extrusion molding process of the sheet material, the extrusion ratio is 40~50:1; in the extrusion molding process of the pipe material, the extrusion ratio is 100~110:

1.

8. The method for preparing weldable low-rare-earth magnesium alloy seamless profiles according to claim 1, characterized in that, The protective gas is argon, and the flow rate of the protective gas is 10 L / min; The welding speed is 100 mm / min; the welding method is AC TIG welding; the diameter of the welding wire is 2.4 mm; the composition of the welding wire is the same as that of the profile.

9. A weldable low-rare-earth magnesium alloy seamless profile, characterized in that, It was prepared using the preparation method described in claim 1.

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