Method for preparing and forming large-size homogeneous magnesium alloy thick plate

Abstract

The invention provides a large-size homogeneous magnesium alloy thick plate preparing and forming method, and relates to the technical field of magnesium alloy machining. The method comprises the following steps: firstly, preparing a magnesium alloy ingot with low rare earth content, and then carrying out multidirectional forging forming on the magnesium alloy ingot; forming by an array type screw-in forging method; and finally rolling and forming. According to the Mg-5Zn-1Gd-1Y-1Mn magnesium alloy plate prepared through the method, the thickness is 45 mm, the long axis is 1500 mm, the short axis length is 1050 mm, and the hardness ranges from 63 HV to 66 HV. Compared with the addition of high-rare-earth alloy elements, low-content rare earth alloy components are used, and the cost is saved; by means of the array type precession forging method, the formability and uniformity of materials are greatly improved, operation is easy, and safety and reliability are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of magnesium alloy processing, and in particular to a method for preparing and forming a large-size homogeneous magnesium alloy thick plate. Background Art

[0002] Magnesium is highly favored in modern industry for its light weight, high specific strength and high specific stiffness. It has low density and is one of the lightest metals in structural materials. In the fields of electronic products, there is an important demand for uniform thick magnesium alloy plates. Therefore, the development of large-scale uniform magnesium alloy thick plates is of great significance to the current development. However, due to the close-packed hexagonal crystal structure of magnesium, its plastic deformation ability is relatively poor, which limits the size and specifications of the plates.

[0003] Rolling forming is the main method of producing magnesium alloy plates, and plays an important role in improving the mechanical properties of plates and regulating the uniformity of their organization. However, the forming of thick plates usually requires reducing the amount of rolling deformation, which makes it difficult to ensure uniformity and the mechanical properties are not high. Therefore, how to adjust the deformation process to develop large-scale homogeneous magnesium alloy thick plates while achieving uniform organization and improving mechanical properties is a technical problem that needs to be solved urgently. Summary of the invention

[0004] Based on this, the main purpose of the present invention is to overcome the deficiencies in the prior art, solve the problems of poor plasticity of existing magnesium alloys, difficulty in forming large-sized billets, and high production costs caused by adding high rare earth elements, and the present invention designs and develops a forming method for large-sized magnesium alloy sheets with low rare earth content. The present invention performs an array-type screw-forging method on magnesium alloy materials to achieve local deformation, thereby achieving the purpose of improving the microstructure and macroscopic morphology of magnesium alloy billets in different directions, and prepares uniform large-sized uniform thick plates of magnesium alloys with a long axis and a short axis length of more than 1000 mm and a hardness of 63 to 66 HV.

[0005] The present invention is achieved through the following technical solutions:

[0006] A large-size homogeneous magnesium alloy thick plate preparation and forming process comprises the following steps:

[0007] S1. Preparation of low rare earth magnesium alloy ingots

[0008] Prepare raw materials according to the following mass percentages of each element: Zn: 4.5-5.3wt.%, Gd: 0.9-1.3wt.%, Y: 1-1.5wt.%, Mn: 0.8-1.1wt.%, and the rest is Mg; heat and melt metal magnesium under a protective atmosphere to obtain a liquid pure magnesium melt; then add pure Zn, MgGd master alloy, MgY master alloy, and MgMn master alloy in sequence for mixed melting to obtain a melt, pour the melt into a mold for casting and molding, and obtain a low rare earth content magnesium alloy ingot after cooling;

[0009] S2, multi-directional forging the low rare earth magnesium alloy ingot

[0010] S2-1, subjecting the low rare earth magnesium alloy ingot to a solid solution treatment to obtain a homogenized magnesium alloy ingot;

[0011] S2-2, polishing the homogenized magnesium alloy ingot to make it smooth, placing it in a multi-directional forging die, and preheating it for standby use;

[0012] S2-3, the ingot is subjected to multi-directional forging along the vertical direction for multiple passes, with a rate of 3 KN / s and a loading rate of 280 KN, and the pressure is maintained for 180 to 240 seconds, the initial forging temperature is 400 to 420° C., and then the temperature is reduced by 10 to 20° C. in each pass, and the forging temperature of the last pass is 300 to 350° C. to obtain a magnesium alloy forging billet;

[0013] S2-4, quenching the magnesium alloy forging blank, and after the forging blank is cooled to room temperature, polishing the surface clean for standby use;

[0014] S3, performing array-type rotary forging on the magnesium alloy forging blank:

[0015] S3-1, heating the magnesium alloy forging billet to 320-350°C, keeping the temperature for 1 hour, then turning it over 90° for upsetting, with a pressing deformation of 30-40%, a speed of 1 mm / s, and holding the pressure for 120-150 seconds to obtain a round forging billet; then heating it to 320-350°C again, keeping the temperature for 1 hour, turning it over 180°, and performing secondary upsetting, with a pressing deformation of 40-50%, a speed of 1 mm / s, and holding the pressure for 120-150 seconds to obtain a short round forging billet;

[0016] S3-2, heating the short round forging billet to 300-320°C, keeping the temperature for 0.5h, and then placing it on the turntable, and forging along the outer edge of the short round forging billet with an array-type ram, with a first pass of 40-45mm and a deformation of 30-33%, and then raising the ram, rotating the forging billet, rotating it 20mm along the circumference, and then immediately lowering the ram, forging the second pass, and repeating the cycle until one circle is completed;

[0017] S3-3, the forging blank obtained in step 3-2 is turned 180 degrees, and the array-type ram is also forged along the outer edge of the circular forging blank. The first pass has a reduction of 45 to 50 mm and a deformation of 50 to 55%. Then the ram is raised, the forging blank is rotated, and the forging blank is rotated 20 mm along the circumference direction. Then the ram is immediately lowered for the second pass, and the reduction is kept unchanged, and the cycle is repeated until one circle is rotated.

[0018] S3-4, putting the forging blank obtained in step 3-3 into a heat treatment furnace to supplement heat, the heating temperature is 300-320°C, and after heating, the heat is kept for 0.5h, and then quickly put it on the turntable, aligning the undeformed core of the forging blank with the ram, and forging along the core of the circular forging blank with the array ram. The first pass is pressed down by 40-45mm, and the deformation is 30-33%. Then, the ram is raised, the forging blank is rotated, and the ram is translated 20mm along the core direction, and then the ram is immediately lowered for a second forging, and the cycle is repeated until the core is completely deformed;

[0019] S3-5, the forging blank obtained in step 3-4 is turned 180 degrees, and the array-type ram is also forged along the core. The first pass is pressed down by 45-50 mm, and the deformation is 50-55%. Then the ram is raised, and the forging blank is translated by 20 mm along the core direction. Then the ram is immediately lowered for the second pass, and the cycle is repeated until the core is completely deformed; the elliptical slab is flattened to the finished product size, and the major axis of the elliptical slab is 1400-1500 mm, the minor axis is 1000-1050 mm, and the thickness is 45-50 mm;

[0020] S4, rolling the oval slab into shape

[0021] S4-1, grinding the surface of the elliptical slab, and grinding a 45° chamfer on the edge of one end ready to enter the rolling mill for subsequent use;

[0022] S4-2. The magnesium alloy sheet pretreated in step S4-1 is placed in a heat treatment furnace for heating. The first heating temperature is 250°C, the heating time is 30 minutes, and the thickness between the rolling rollers is maintained at 45 mm. After rolling, it is then inverted 180° and quickly returned to the heat treatment furnace for annealing. The second heating temperature is 250°C, the heating time is 15 minutes, and the distance between the two rollers is still maintained at 45 mm. After rolling, it is turned to obtain a magnesium alloy sheet with a thickness of 45 mm, a major axis of 1500 mm, and a minor axis of 1050 mm. The surface is smooth and the size is regular.

[0023] Preferably, the temperature of the solution treatment in step S2-1 is 480-500°C, and the temperature is kept for 12-14 hours.

[0024] Preferably, step S2-3 performs multi-directional forging for a total of 6 times.

[0025] Preferably, step S2-4 is to place the forging blank of step 2-3 into warm water at 50-80° C. for quenching.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention not only effectively controls the cost of materials through low rare earth microalloying and array-type screw forging deformation, but also effectively solves the shortcomings of low plasticity, poor deformation ability and difficulty in producing large-sized plates of magnesium alloys. By adding alloying elements, the grain size of the alloy is refined, and the amount of the second phase is increased. Subsequently, the organization is further controlled through a deformation method combining multi-directional forging with array-type screw forging. While the grains are further refined, the size and distribution of the second phase are also regulated. A uniform large-sized uniform thick plate of magnesium alloy with a thickness of 45 mm, a major axis of 1500 mm, a minor axis of 1050 mm, and a hardness of 63-66 HV is successfully prepared. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of a press workbench during array-type screw forging process;

[0029] Figure 2 It is a schematic diagram of the indenter of the array type screw forging method;

[0030] Figure 3 Microstructure morphology of Mg-5Zn-1Gd-1Y magnesium alloy at different positions after rolling.

[0031] Figure 4 The hardness curve and value of Mg-5Zn-1Gd-1Y magnesium alloy at different positions after rolling; DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the present invention clearer, the preferred embodiments of the present invention are further described in detail in conjunction with the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Example 1

[0034] A large-size homogeneous magnesium alloy thick plate preparation and forming process, the specific steps are as follows:

[0035] S1. Preparation of low rare earth magnesium alloy ingots

[0036] The polished pure magnesium is heated to 750°C under a protective atmosphere to obtain a liquid pure magnesium melt, and then the heating temperature is adjusted to 720°C, pure zinc is added, and the mixture is allowed to stand for 15 minutes, and the temperature is raised to 780°C, and Gd, Y, and Mn are added in sequence, and the mixture is kept warm for 50 minutes, and the mixture is poured into a preheated mold for casting, and after cooling, a Mg-5Zn-1Gd-1Y-1Mn low rare earth content magnesium alloy ingot is obtained;

[0037] S2, multi-directional forging the low rare earth magnesium alloy ingot

[0038] S2-1. First, the low rare earth magnesium alloy ingot is placed in a heat treatment furnace for solution treatment at a heating temperature of 500°C and a holding time of 13 hours;

[0039] S2-2, process the magnesium alloy ingot after homogenization treatment in step S2-1 into a standard sample size, and grind the surface of the ingot until it is smooth. Then put the ingot into a multi-directional forging die, and preheat the ingot and the forging die for subsequent use;

[0040] S2-3, multi-directional forging is performed on the ingot in step 2-2 along the vertical direction, for a total of 6 passes, with a rate of 3KN / s and a load of 280KN, and a pressure holding time of 180s. The initial forging temperature is 420°C, and then the temperature is reduced by 15°C in each pass, and the forging temperature of the last pass is 330°C. A magnesium alloy forging billet with a length and width of 400m and a height of 450m is obtained;

[0041] S2-4, putting the forging blank in step 2-3 into 70°C warm water for quenching treatment, taking out the forging blank after it cools to room temperature, and polishing the surface for subsequent use;

[0042] S3, performing array-type rotary forging on the magnesium alloy forging blank:

[0043] S3-1, heating the forging blank obtained in step 2 at a heating temperature of 350°C, keeping the temperature for 1h after the heating is completed, then turning it 90° for upsetting, with a pressing deformation of 40%, a speed of 1mm / s, and holding the pressure for 120s to obtain a round forging blank with a height of 270mm, then heating it again at a heating temperature of 350°C, keeping the temperature for 1h after the heating is completed, turning it 180°, performing secondary upsetting, with a pressing deformation of 50%, a speed of 1mm / s, and holding the pressure for 120s to obtain a round forging blank with a height of 135mm;

[0044] S3-2, the forging blank obtained in step 3-1 is placed in a heat treatment furnace to supplement heat, the heating temperature is 320°C, and the heating is maintained for 0.5h after the heating is completed, and then the forging blank is placed on a turntable, and the array-type ram is forged along the outer edge of the circular forging blank, the first pass is pressed down by 45mm, and the deformation is 33%, and then the ram is raised, the forging blank is rotated, and the forging blank is rotated 20mm along the circumference direction, and then the ram is immediately lowered for the second forging, and the cycle is repeated until one circle is rotated;

[0045] S3-3, the forging blank obtained in step 3-2 is turned 180°, and the array-type ram is forged along the outer edge of the circular forging blank in the same manner, with a first pass of 45 mm and a deformation of 50%, and then the ram is raised, the forging blank is rotated, and the forging blank is rotated 20 mm along the circumference direction, and then the ram is immediately lowered for a second pass, and the pressing amount is kept unchanged, and the cycle is repeated until one circle is rotated;

[0046] S3-4, putting the forging blank obtained in step 3-3 into a heat treatment furnace to supplement heat, the heating temperature is 320°C, and after heating, the blank is kept warm for 0.5h, and then quickly put on the turntable, and the deformed core of the forging blank is aligned with the ram, and the array ram is forged along the core of the circular forging blank. The first pass is pressed down by 45mm, and the deformation is 33%. Then the ram is raised, the forging blank is rotated, and the ram is translated 20mm along the core direction, and then the ram is immediately lowered for the second forging, and the cycle is repeated until the core is completely deformed;

[0047] S3-5, the forging blank obtained in step 3-4 is turned 180°, and the array-type ram is also forged along the core. The first pass is pressed down by 45 mm and the deformation is 50%. Then the ram is raised, the forging blank is translated by 20 mm along the core direction, and then the ram is immediately lowered for the second pass. The cycle is repeated until the core is completely deformed; the elliptical slab is flattened to the finished product size. The major axis of the elliptical slab is 1500 mm, the minor axis is 1050 mm, and the thickness is 45 mm.

[0048] S4, rolling the oval slab into shape

[0049] S4-1, grinding the cut surface of the elliptical slab obtained in step S3, and grinding a 45° chamfer on the edge of one end ready to enter the rolling mill for subsequent use;

[0050] S4-2, placing the magnesium alloy sheet pretreated in step S4-1 into a heat treatment furnace for heating, the first heating temperature is 250°C, the heating time is 30 min, the thickness between the rolling rollers is maintained at 45 mm, then inverted 180° and quickly placed back into the heat treatment furnace for annealing, the second heating temperature is 250°C, the heating time is 15 min, the distance between the two rollers is still maintained at 45 mm, and after rolling, a magnesium alloy sheet with a smooth surface and regular size is obtained with a thickness of 45 mm, a major axis of 1500 mm, and a minor axis of 1050 mm;

[0051] By comparing the microstructures of the magnesium alloy slab at different positions, it can be seen that by adding alloying elements, the grain size of the alloy is refined, the amount of the second phase is increased, and the subsequent multi-directional forging further controls the organization. While the grains are further refined, the organizational uniformity of the forging block is increased. The organizations at different positions are deformed grains, recrystallized grains, and banded phases. Finally, after rolling and forming, the surface of the plate is leveled, and a uniform large-size thick plate of magnesium alloy with a thickness of 45 mm, a major axis of 1500 mm, a minor axis of 1050 mm, and an average hardness of 66 HV is successfully obtained.

[0052] Example 2

[0053] A large-size homogeneous magnesium alloy thick plate preparation and forming process, the specific steps are as follows:

[0054] S1. Preparation of low rare earth magnesium alloy ingots

[0055] The polished pure magnesium is heated to 750°C under a protective atmosphere to obtain a liquid pure magnesium melt, and then the heating temperature is adjusted to 720°C, pure zinc is added, and the mixture is allowed to stand for 15 minutes, and the temperature is raised to 780°C, and Gd, Y, and Mn are added in sequence, and the mixture is kept warm for 50 minutes, and the mixture is poured into a preheated mold for casting, and after cooling, a Mg-5Zn-1Gd-1Y-1Mn low rare earth content magnesium alloy ingot is obtained;

[0056] S2, multi-directional forging the low rare earth magnesium alloy ingot

[0057] S2-1. First, the low rare earth magnesium alloy ingot is placed in a heat treatment furnace for solution treatment at a heating temperature of 480°C and a holding time of 12 hours;

[0058] S2-2, process the magnesium alloy ingot after homogenization treatment in step S2-1 into a standard sample size, and grind the surface of the ingot until it is smooth. Then put the ingot into a multi-directional forging die, and preheat the ingot and the forging die for subsequent use;

[0059] S2-3, multi-directional forging is performed on the ingot in step 2-2 along the vertical direction, for a total of 6 passes, with a rate of 3KN / s and a load of 280KN, and a pressure holding time of 180s. The initial forging temperature is 420°C, and then the temperature is reduced by 20°C in each pass, and the forging temperature of the last pass is 300°C. A magnesium alloy forging billet with a length and width of 400m and a height of 450m is obtained;

[0060] S2-4, putting the forging blank in step 2-3 into -80°C warm water for quenching treatment, taking out the forging blank after it cools to room temperature, and polishing the surface for subsequent use;

[0061] S3, performing array-type rotary forging on the magnesium alloy forging blank:

[0062] S3-1, heating the forging blank obtained in step 2 at a heating temperature of 320°C, keeping the temperature for 1h after the heating is completed, then turning it 90° for upsetting, with a pressing deformation of 40%, a speed of 1mm / s, and holding the pressure for 120s to obtain a round forging blank with a height of 270mm, then heating it again at a heating temperature of 350°C, keeping the temperature for 1h after the heating is completed, turning it 180°, performing secondary upsetting, with a pressing deformation of 50%, a speed of 1mm / s, and holding the pressure for 120s to obtain a round forging blank with a height of 135mm;

[0063] S3-2, the forging blank obtained in step 3-1 is placed in a heat treatment furnace to supplement heat, the heating temperature is 300°C, and after heating, it is kept warm for 0.5h, and then placed on a turntable, and the array-type ram is forged along the outer edge of the circular forging blank, the first pass is pressed down by 45mm, the deformation is 33%, and then the ram is raised, the forging blank is rotated, and the circumference direction is rotated by 20mm, and then the ram is immediately lowered for the second forging, and the cycle is repeated until one circle is rotated;

[0064] S3-3, the forging blank obtained in step 3-2 is turned 180°, and the array-type ram is forged along the outer edge of the circular forging blank in the same manner, with a first pass of 45 mm and a deformation of 50%, and then the ram is raised, the forging blank is rotated, and the forging blank is rotated 20 mm along the circumference direction, and then the ram is immediately lowered for a second pass, and the pressing amount is kept unchanged, and the cycle is repeated until one circle is rotated;

[0065] S3-4, putting the forging blank obtained in step 3-3 into a heat treatment furnace to supplement heat, the heating temperature is 300°C, and after heating is completed, the heat is kept for 0.5h, and then quickly put on the turntable, aligning the deformed core of the forging blank with the ram, and forging along the core of the circular forging blank with the array ram. The first pass is pressed down by 45mm, and the deformation is 33%. Then, the ram is raised, the forging blank is rotated, and the ram is translated 20mm along the core direction, and then the ram is immediately lowered for the second forging, and the cycle is repeated until the core is completely deformed;

[0066] S3-5, the forging blank obtained in step 3-4 is turned 180°, and the array-type ram is also forged along the core. The first pass is pressed down by 45 mm and the deformation is 50%. Then the ram is raised, the forging blank is translated by 20 mm along the core direction, and then the ram is immediately lowered for the second pass. The cycle is repeated until the core is completely deformed; the elliptical slab is flattened to the finished product size. The major axis of the elliptical slab is 1500 mm, the minor axis is 1050 mm, and the thickness is 45 mm.

[0067] S4, rolling the oval slab into shape

[0068] S4-1, grinding the cut surface of the elliptical slab obtained in step S3, and grinding a 45° chamfer on the edge of one end ready to enter the rolling mill for subsequent use;

[0069] S4-2, placing the magnesium alloy sheet pretreated in step S4-1 into a heat treatment furnace for heating, the first heating temperature is 250°C, the heating time is 30 min, the thickness between the rolling rollers is maintained at 45 mm, then inverted 180° and quickly placed back into the heat treatment furnace for annealing, the second heating temperature is 250°C, the heating time is 15 min, the distance between the two rollers is still maintained at 45 mm, and after rolling, a magnesium alloy sheet with a smooth surface and regular size is obtained with a thickness of 45 mm, a major axis of 1500 mm, and a minor axis of 1050 mm;

[0070] By comparing the microstructures of the magnesium alloy slab at different positions, it can be seen that by adding alloying elements, the grain size of the alloy is refined, the amount of the second phase is increased, and the subsequent multi-directional forging further controls the organization. While the grains are further refined, the organizational uniformity of the forging block is increased. The organizations at different positions are deformed grains, recrystallized grains, and banded phases. Finally, after rolling and forming, the surface of the plate is leveled, and a uniform large-size thick plate of magnesium alloy with a thickness of 45 mm, a major axis of 1500 mm, a minor axis of 1050 mm, and an average hardness of 65 HV is successfully obtained.

[0071] Example 3

[0072] A large-size homogeneous magnesium alloy thick plate preparation and forming process, the specific steps are as follows:

[0073] S1. Preparation of low rare earth magnesium alloy ingots

[0074] The polished pure magnesium is heated to 750°C under a protective atmosphere to obtain a liquid pure magnesium melt, and then the heating temperature is adjusted to 720°C, pure zinc is added, and the mixture is allowed to stand for 15 minutes, and the temperature is raised to 780°C, and Gd, Y, and Mn are added in sequence, and the mixture is kept warm for 50 minutes, and the mixture is poured into a preheated mold for casting, and after cooling, a Mg-5Zn-1Gd-1Y-1Mn low rare earth content magnesium alloy ingot is obtained;

[0075] S2, multi-directional forging the low rare earth magnesium alloy ingot

[0076] S2-1. First, the low rare earth magnesium alloy ingot is placed in a heat treatment furnace for solution treatment at a heating temperature of 480°C and a holding time of 14 hours;

[0077] S2-2, process the magnesium alloy ingot after homogenization treatment in step S2-1 into a standard sample size, and grind the surface of the ingot until it is smooth. Then put the ingot into a multi-directional forging die, and preheat the ingot and the forging die for subsequent use;

[0078] S2-3, multi-directional forging is performed on the ingot in step 2-2 along the vertical direction, for a total of 6 passes, with a rate of 3KN / s and a load of 280KN, and a pressure holding time of 180s. The initial forging temperature is 420°C, and then the temperature is reduced by 20°C in each pass, and the forging temperature of the last pass is 300°C. A magnesium alloy forging billet with a length and width of 400m and a height of 450m is obtained;

[0079] S2-4, putting the forging blank in step 2-3 into warm water at 50-80°C for quenching treatment, taking out the forging blank after it cools to room temperature, and polishing the surface for subsequent use;

[0080] S3, performing array-type rotary forging on the magnesium alloy forging blank:

[0081] S3-1, heating the forging blank obtained in step 2 at a heating temperature of 340°C, keeping the temperature for 1h after the heating is completed, then turning it 90° for upsetting, pressing down a deformation amount of 40%, a speed of 1mm / s, and holding the pressure for 120s to obtain a round forging blank with a height of 270mm, then heating it again at a heating temperature of 350°C, keeping the temperature for 1h after the heating is completed, turning it 180°, performing secondary upsetting, pressing down a deformation amount of 50%, a speed of 1mm / s, and holding the pressure for 120s to obtain a round forging blank with a height of 135mm;

[0082] S3-2, the forging blank obtained in step 3-1 is placed in a heat treatment furnace to supplement heat, the heating temperature is 320°C, and the heating is maintained for 0.5h after the heating is completed, and then the forging blank is placed on a turntable, and the array-type ram is forged along the outer edge of the circular forging blank, the first pass is pressed down by 45mm, and the deformation is 33%, and then the ram is raised, the forging blank is rotated, and the forging blank is rotated 20mm along the circumference direction, and then the ram is immediately lowered for the second forging, and the cycle is repeated until one circle is rotated;

[0083] S3-3, the forging blank obtained in step 3-2 is turned 180°, and the array-type ram is forged along the outer edge of the circular forging blank in the same manner, with a first pass of 45 mm and a deformation of 50%, and then the ram is raised, the forging blank is rotated, and the forging blank is rotated 20 mm along the circumference direction, and then the ram is immediately lowered for a second pass, and the pressing amount is kept unchanged, and the cycle is repeated until one circle is rotated;

[0084] S3-4, putting the forging blank obtained in step 3-3 into a heat treatment furnace to supplement heat, the heating temperature is 320°C, and after heating, the blank is kept warm for 0.5h, and then quickly put on the turntable, and the deformed core of the forging blank is aligned with the ram, and the array ram is forged along the core of the circular forging blank. The first pass is pressed down by 45mm, and the deformation is 33%. Then the ram is raised, the forging blank is rotated, and the ram is translated 20mm along the core direction, and then the ram is immediately lowered for the second forging, and the cycle is repeated until the core is completely deformed;

[0085] S3-5, the forging blank obtained in step 3-4 is turned 180°, and the array-type ram is also forged along the core. The first pass is pressed down by 45 mm and the deformation is 50%. Then the ram is raised, the forging blank is translated by 20 mm along the core direction, and then the ram is immediately lowered for the second pass. The cycle is repeated until the core is completely deformed; the elliptical slab is flattened to the finished product size. The major axis of the elliptical slab is 1500 mm, the minor axis is 1050 mm, and the thickness is 45 mm.

[0086] S4, rolling the oval slab into shape

[0087] S4-1, grinding the cut surface of the elliptical slab obtained in step S3, and grinding a 45° chamfer on the edge of one end ready to enter the rolling mill for subsequent use;

[0088] S4-2, placing the magnesium alloy sheet pretreated in step S4-1 into a heat treatment furnace for heating, the first heating temperature is 250°C, the heating time is 30 min, the thickness between the rolling rollers is maintained at 45 mm, then inverted 180° and quickly placed back into the heat treatment furnace for annealing, the second heating temperature is 250°C, the heating time is 15 min, the distance between the two rollers is still maintained at 45 mm, and after rolling, a magnesium alloy sheet with a smooth surface and regular size is obtained with a thickness of 45 mm, a major axis of 1500 mm, and a minor axis of 1050 mm;

[0089] By comparing the microstructures of the magnesium alloy slab at different positions, it can be seen that by adding alloying elements, the grain size of the alloy is refined, the amount of the second phase is increased, and the subsequent multi-directional forging further controls the structure. While the grains are further refined, the uniformity of the structure of the forging block is increased. The structures at different positions are deformed grains, recrystallized grains, and banded phases. Finally, after rolling and forming, the surface of the plate is leveled, and a uniform large-size thick plate of magnesium alloy with a thickness of 45 mm, a major axis of 1500 mm, a minor axis of 1050 mm, and an average hardness of 63 HV is successfully obtained.

[0090] The embodiments described above are part of the embodiments of the present invention, rather than all of the embodiments. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. A method for preparing and forming a large-sized homogeneous magnesium alloy thick plate, characterized in that: The following steps are involved: S1. Preparation of low rare earth magnesium alloy ingots The metal magnesium is heated and melted in a protective atmosphere to obtain a liquid pure magnesium melt; then Zn, Gd, Y, and Mn are added in sequence for mixed melting to obtain a melt, the melt is poured into a mold for casting and molding, and after cooling, a low rare earth content magnesium alloy ingot is obtained; S2, multi-directional forging the low rare earth magnesium alloy ingot S2-1, subjecting the low rare earth magnesium alloy ingot to a solid solution treatment to obtain a homogenized magnesium alloy ingot; S2-2, polishing the homogenized magnesium alloy ingot to make it smooth, placing it in a multi-directional forging die, and preheating it for standby use; S2-3, the ingot is subjected to multi-directional forging along the vertical direction for multiple passes, with a rate of 3 KN / s and a loading rate of 280 KN, and the pressure is maintained for 180 s. The initial forging temperature is 400-420° C., and then the temperature is reduced by 10-20° C. in each pass, and the forging temperature of the last pass is 300-350° C. to obtain a magnesium alloy forging billet; S2-4, quenching the magnesium alloy forging blank, and after the forging blank is cooled to room temperature, polishing the surface clean for standby use; S3, performing array-type rotary forging on the magnesium alloy forging blank: S3-1, heating the magnesium alloy forging blank to 320-350°C, keeping the temperature for 1 hour, then turning it 90° for upsetting, pressing down the deformation amount of 40%, the speed of 1 mm / s, and holding the pressure for 120 seconds to obtain a round forging blank; then heating it to 320-350°C, keeping the temperature for 1 hour, turning it 180°, performing secondary upsetting, pressing down the deformation amount of 50%, the speed of 1 mm / s, and holding the pressure for 120 seconds to obtain a short round forging blank; S3-2, heating the short round forging billet to 300-320°C, keeping the temperature for 0.5h, and then placing it on the turntable, and forging along the outer edge of the short round forging billet with an array-type ram, with a first pass of 45mm and a deformation of 33%, and then raising the ram, rotating the forging billet, rotating it 20mm along the circumference, and then immediately lowering the ram, forging the second pass, and repeating the cycle until one circle is completed; S3-3, the forging blank obtained in step 3-2 is turned 180°, and the array-type ram is forged along the outer edge of the circular forging blank in the same manner, with a first pass of 45 mm and a deformation of 50%, and then the ram is raised, the forging blank is rotated, and the forging blank is rotated 20 mm along the circumference direction, and then the ram is immediately lowered for a second pass, and the pressing amount is kept unchanged, and the cycle is repeated until one circle is rotated; S3-4, putting the forging blank obtained in step 3-3 into a heat treatment furnace to supplement heat, the heating temperature is 300-320°C, and after heating, it is kept warm for 0.5h, and then quickly put on the turntable, aligning the deformed core of the forging blank with the ram, and forging along the core of the circular forging blank with the array ram. The first pass is pressed down by 45mm, and the deformation is 33%. Then, the ram is raised, the forging blank is rotated, and the ram is translated 20mm along the core direction, and then the ram is immediately lowered for the second forging, and the cycle is repeated until the core is completely deformed; S3-5, the forging blank obtained in step 3-4 is turned 180°, and the array-type ram is also forged along the core. The first pass is pressed down by 45 mm and the deformation is 50%. Then the ram is raised, the forging blank is translated by 20 mm along the core direction, and then the ram is immediately lowered for the second pass. The cycle is repeated until the core is completely deformed; the elliptical slab is flattened to the finished product size. The major axis of the elliptical slab is 1500 mm, the minor axis is 1050 mm, and the thickness is 45 mm. S4, rolling the oval slab into shape S4-1, grinding the surface of the elliptical slab, and grinding a 45° chamfer on the edge of one end ready to enter the rolling mill for subsequent use; S4-2. The magnesium alloy sheet pretreated in step S4-1 is placed in a heat treatment furnace for heating. The first heating temperature is 250°C, the heating time is 30 min, and the thickness between the rolling rollers is maintained at 45 mm. Then, it is inverted 180° and quickly returned to the heat treatment furnace for annealing. The second heating temperature is 250°C, the heating time is 15 min, and the thickness between the two rollers is still maintained at 45 mm. After rolling, a magnesium alloy sheet with a smooth surface and regular size is obtained with a thickness of 45 mm, a major axis of 1500 mm, and a minor axis of 1050 mm.

2. The preparation method according to claim 1, characterized in that: The temperature of the solution treatment in step S2-1 is 480-500°C, and the temperature is kept for 12-14 hours.

3. The preparation method according to claim 1, characterized in that: Step S2-3 performs a total of 6 multi-directional forging passes.

4. The preparation method according to claim 1, characterized in that: Step S2-4 is to place the forging blank of step 2-3 into warm water at 50-80°C for quenching.

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