Rotary reciprocating extrusion device for superfine crystal magnesium alloy and processing method

[0036] Example

[0037] In the present invention, the components of the reciprocating extrusion die are all made of chromium tungsten manganese steel, and the left and right extrusion die cavities and the inner cavity of the rotating wheel have smooth surfaces, and the roughness is Ra0.16-0.32 μm.

[0038] Materials and chemical reagents used: magnesium alloy profile: AZ31 magnesium alloy block blank; sandpaper: SiC, 600 mesh, 2 sheets; 1000 mesh, 2 sheets; 1200 mesh, 2 sheets; 2500 mesh, 2 sheets; high temperature graphite oil solution: C, 30ml; absolute ethanol: CH 3 CH 2 OH, 1200ml; Acetone: C 3 H 6 O, 800ml.

[0039] A processing technology and method for variable-channel rotary reciprocating extrusion of magnesium alloy adopts the following steps:

[0040] (1) Install the rotary reciprocating extrusion device on the horizontal hydraulic extruder, the installation is firm, the position of each part, the connection relationship should be correct, and the operation should be performed in order;

[0041] (2) Grind the outer surface of the AZ31 magnesium alloy block blank with 600 grit sandpaper to remove oil stains, and then sand with 1000, 1200, and 2500 grit sandpaper in turn to ensure that the surface is clean and smooth; the polished magnesium alloy block blank Place it in a mixture of acetone and absolute ethanol at a volume ratio of 3:2 for ultrasonic cleaning for 30 minutes, then clean with alcohol and blow dry with a hair dryer;

[0042] (3) Turn on the vacuum atmosphere heating furnace to preheat the magnesium alloy bulk material. The preset temperature is 250-450℃. When the predetermined temperature is reached, continue to place the magnesium alloy bulk material in the heating furnace for 0.5-4h;

[0043] (4) Turn on the external heating device of the extrusion die cavity to heat the rotary reciprocating extrusion device. The heating temperature is preset to 250°C-450°C. After reaching the preset temperature, it will continue to keep for 0.5h-4h;

[0044] (5) Apply high-temperature graphite oil solution to the surface of the magnesium alloy block blank for lubrication, exit the extrusion rod I5, the size of the extrusion rod I5 is the same as that of the extrusion rod II6, and place the preheated magnesium alloy block blank in the die In the cavity I3, the extrusion rod I5 is extended into the mold cavity I3 and contacts the magnesium alloy block material blank. In the present invention, the components of the reciprocating extrusion die are made of chromium tungsten-manganese steel. The surface of the cavity Ⅰ3, cavity Ⅱ4 and the inner cavity of the rotating wheel 7 are smooth, and the roughness is Ra0.16-0.32μm;

[0045] (6) Turn on the motor, the rotating wheel 7 rotates through the roller bearing 8, which promotes the rotation of the cavity III11. The cavity III11 forms a constantly changing extrusion channel with the cavity I3 and the cavity II4, and at the same time introduces torsional deformation. Pressurizing extrusion rod I5, set the pressure to 400MPa~700MPa, to squeeze the magnesium alloy billet placed in the cavity I3, when the billet passes through the cavity III11, due to the rotation of the cavity III11, the wall of the cavity III11 is against the billet The torsion force is generated, and the magnesium alloy blank in the straight section of the cavity I3 will not rotate. The magnesium alloy blank in the deformed section of the cavity I3 is continuously twisted due to the rotation of the rotating wheel. At the same time, the extrusion rod I5 Continuously apply pressure to squeeze the billet. When the billet enters the die cavity Ⅱ4 and contacts the extrusion rod Ⅱ6, the extrusion pressure of the extrusion rod Ⅰ5 is increased, and the pressure is 800MPa~1000MPa, and the extrusion rod Ⅱ6 applies the opposite direction to the billet. Back pressure, the pressure is 200MPa~300MPa, stop advancing when the magnesium alloy billet completely enters the cavity Ⅱ4, and complete one processing;

[0046] (7) Reverse drive extrusion rod Ⅰ5 and extrusion rod Ⅱ6, the main pressure is 800MPa~1000MPa, the back pressure is 200MPa~300MPa, the blank is at the main pressure of extrusion rod Ⅱ6, and the extrusion rod Ⅰ5 is back pressure. Under the action, enter the cavity Ⅲ11 from the cavity Ⅱ4 and then into the cavity Ⅰ3 to complete the second pass processing;

[0047] (8) Repeat the above steps (6) and (7) at least twice to realize the variable-channel rotary reciprocating extrusion process of magnesium alloy profiles;

[0048] (9) Take out the magnesium alloy bar, polish its surface with sandpaper, then place it in a mixture of acetone and absolute ethanol at a volume ratio of 3:2 for ultrasonic cleaning, and finally clean it with alcohol and dry it with a hair dryer.

[0049] Conclusion: Through the bidirectional variable channel rotary reciprocating extrusion processing method of the present invention, the average grain size of magnesium alloy blanks is greatly reduced compared with conventional magnesium alloys. Picture 11 As shown, the grain size of the magnesium alloy is reduced from the original 33 μm to 1.52 μm, and the tensile strength is significantly increased, and its value can reach 500 MPa, which can meet the current market demand for high-strength bars.

[0050] The step angles in cavity Ⅰ and cavity Ⅱ and cavity Ⅲ are respectively θ 1 , Θ 2 , Θ 3 , Θ 4 , Θ 5 , Θ 6 Etc., where θ 1 Can=θ 2 =θ 3 =θ 4 =θ 5 =θ 6 =θ 7 ……Or θ 1 ≠θ 2 ≠θ 3 ≠θ 4 ≠θ 5 ≠θ 6 ≠θ 7 ……, the size of θ is not specific; the length of the steps in the left and right extrusion die cavity are l 5 , l 6 , l 7 , l 8 , l 9 Etc., where l 5 Can = l 6 = L 7 = L 8 = L 9...Or l 5 ≠l 6 ≠l 7 ≠l 8 ≠l 9..., the size of l is not specific to a certain value. As attached image 3 , 4 As shown, when the values ​​of θ and l change, the shape of the left and right extrusion die cavities will change. Due to the uneven flow rate of the die cavity material during the extrusion process, the shear deformation will be further introduced, and the rotating wheel and the rotating channel will be further introduced into the shear The shear deformation refines the grains.

[0051] In the present invention, a rotating wheel is added during the deformation process to promote the rotation of the extrusion die cavity to change the extrusion path, thereby realizing the introduction of torsion deformation during the extrusion process, and further multi-pass reciprocating rotary extrusion, so that the metal blank undergoes severe plastic deformation , Prepared ultra-fine-grained magnesium alloy material.

[0052] In the present invention, the speed and direction of the rotating wheel can be adjusted as required, and the ratio of the extrusion speed to the rotation speed of the rotating wheel can be 6:1; 8:1; 10:1;...

[0053] Such as image 3 As shown, the deformed section is a ladder-shaped channel, such as Figure 4 As shown, the deformed section is an inclined ladder-shaped channel.

[0054] The principle of the present invention for preparing ultra-fine-grained magnesium alloy rods through variable-channel rotary reciprocating extrusion is: under the premise of applying pressure to the extrusion rod I5, the magnesium alloy blank starts to be extruded, and the rotating wheel 7 passes through the roller bearing 8. The rotation promotes the rotation of the cavity III11, and the cavity III11 forms a constantly changing extrusion channel with the cavity I3 and the cavity II4, and at the same time introduces torsional deformation. When the blank passes through the cavity III11, due to the rotation of the cavity III11, the cavity wall produces a torsion force on the blank. The magnesium alloy blank in the straight section of the cavity I3 will not rotate, and the magnesium in the deformed section of the cavity I3 The alloy billet continuously produces torsional deformation due to the rotation of the rotating wheel. At the same time, the extrusion rod I5 continuously exerts pressure to extrude the magnesium alloy billet. When the magnesium alloy billet enters the die cavity II4 and contacts the extrusion rod II6, the extrusion is increased. The extrusion pressure of the pressing rod Ⅰ5, while the extrusion rod Ⅱ6 exerts reverse pressure on the magnesium alloy billet, and stops advancing when the magnesium alloy billet completely enters the mold cavity Ⅱ4, completing one processing, and the entire reciprocating rotation extrusion shear deformation During the process, the magnesium alloy billet continuously accumulates deformation through multiple passes of deformation, introduces large strains, and refines the metal grains to obtain ultra-fine crystalline metal, which improves the mechanical properties of the metal bar.