Aluminum / magnesium / aluminum composite plate rolling method based on interface nitriding treatment

Abstract

The invention belongs to the technical field of layered metal composite plate rolling processes, and discloses a rolling method of an aluminum / magnesium / aluminum composite plate based on interface nitriding treatment. The rolling method comprises the following steps: sequentially carrying out pretreatment and nitriding treatment on a to-be-compounded metal sheet; the nitrided metal sheets to be compounded are stacked to form a composite plate blank, and then the composite plate blank is heated; after the upper roller and the lower roller are subjected to preheating treatment, one-pass ultrasonic auxiliary rolling is conducted on the composite plate blank subjected to heating treatment under the condition that ultrasonic vibration is applied, and the rolled-state aluminum / magnesium / aluminum composite plate is obtained; and the rolled aluminum / magnesium / aluminum composite plate is subjected to diffusion annealing treatment and finishing treatment, and the aluminum / magnesium / aluminum composite plate is obtained. The method is easy to operate, the interface bonding strength and the interface bonding quality are effectively improved, and the overall mechanical property, the corrosion resistance and the high temperature resistance of the aluminum / magnesium / aluminum composite board are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of rolling processes for laminated metal composite plates, and particularly to a rolling method for aluminum / magnesium / aluminum composite plates based on interfacial nitriding treatment. Background Art

[0002] As a green functional material in the 21st century, magnesium alloys have particularly broad application prospects due to their low density, high specific strength, good damping performance, and good processing performance. Magnesium alloy thin plates and strips are widely used in fields such as aerospace, national defense, automotive manufacturing, and electronic technology. However, due to the poor plastic deformation ability of magnesium alloys at room temperature and their poor corrosion resistance, their wide application is restricted. To meet specific performance requirements, aluminum alloys with better corrosion resistance are usually used as the clad metal and combined by mechanical or metallurgical means. On the one hand, it can prevent the direct contact between magnesium alloys and corrosive media in the environment, providing effective corrosion protection for magnesium alloys; on the other hand, it forms tensile stress on the surface of magnesium alloys, reducing the generation of surface cracks during the forming process of magnesium alloys and significantly improving the forming and manufacturing ability of magnesium alloys. Aluminum / magnesium / aluminum laminated metal composite plates suitable for industrial applications prepared by this method combine the excellent properties of magnesium and aluminum alloys and have the advantages of simple preparation method, high bonding strength, and low cost.

[0003] At present, there are many methods for preparing aluminum / magnesium / aluminum laminated metal composite plates, such as rolling composite method, explosive welding method, diffusion welding method, ultrasonic consolidation method, etc. Since the explosive welding method requires the use of explosives as power, there are safety hazards, and the surface quality of thin plates is poor; the ultrasonic consolidation method can improve the interfacial bonding strength, but has high requirements for equipment; the diffusion welding method needs to be carried out under vacuum conditions, has high requirements for equipment, complex processes, long time consumption, and low production efficiency. The rolling composite method is simple in operation, high in production efficiency, low in cost, good in surface quality, and easy to achieve large-scale industrial production, and has received extensive attention from many scholars; however, the metal composite plates prepared by the rolling composite method have problems of unstable bonding quality and low bonding strength. Summary of the Invention

[0004] To solve the above technical problems, the present invention explores and analyzes the reasons for the problems of unstable bonding quality and low bonding strength in metal composite plates prepared by the rolling composite method, and finds that the main reasons can be attributed to the following two points: First, the billets before rolling are prone to oxidation in the air, forming an oxide layer. Second, a large reduction ratio is required during the rolling process to obtain a composite plate with a tightly bonded interface, and the high rolling force is likely to damage the rolling mill and reduce the service life of the rolling mill. Therefore, the present invention provides a rolling method for an aluminum / magnesium / aluminum composite plate based on interface nitriding treatment. By nitriding the surfaces to be bonded, a nitride layer with an appropriate thickness is formed on the metal surface. The formed nitride layer can prevent the metal slab from oxidizing during the heating process. In addition, a nitride layer with a certain thickness will expose more fresh metal during the rolling process of the composite plate, increasing the surface roughness of the interface, thereby enhancing the mechanical meshing degree between the magnesium thin plate and the aluminum thin plate and improving the interface bonding strength.

[0005] A rolling method for an aluminum / magnesium / aluminum composite plate based on interface nitriding treatment of the present invention is realized through the following technical solutions:

[0006] The present invention provides a rolling method for an aluminum / magnesium / aluminum composite plate based on interface nitriding treatment, including the following steps:

[0007] Step 1, surface cleaning treatment:

[0008] Prepare two aluminum alloy thin plates and one magnesium alloy thin plate, and perform pre-treatment on the two aluminum alloy thin plates and one magnesium alloy thin plate respectively to remove impurities and oxide films on the surfaces of the two aluminum alloy thin plates and one magnesium alloy thin plate, and obtain two clean aluminum alloy thin plates and one clean magnesium alloy thin plate.

[0009] Step 2, nitriding treatment:

[0010] Perform nitriding treatment on the two clean aluminum alloy thin plates and one clean magnesium alloy thin plate respectively to form a nitride layer on the surfaces of the two clean aluminum alloy thin plates and one clean magnesium alloy thin plate respectively.

[0011] Step 3, heating treatment:

[0012] Stack the nitrided aluminum alloy thin plates, the nitrided magnesium alloy thin plate, and the nitrided aluminum alloy thin plate in the order of aluminum / magnesium / aluminum to form a composite slab, and perform heating treatment on the composite slab.

[0013] Step 4, one-pass ultrasonic-assisted rolling treatment:

[0014] The upper roll and the lower roll are preheated, and then ultrasonic vibration is applied to the preheated upper roll and lower roll through an ultrasonic vibration system, and a one-pass ultrasonic-assisted rolling treatment is performed on the heat-treated composite slab to obtain a rolled aluminum / magnesium / aluminum composite plate.

[0015] In Step 1 above, it should be noted that the present invention prepares two aluminum alloy thin plates and one magnesium alloy thin plate to be compounded. First, the aluminum alloy thin plate and the magnesium alloy thin plate to be compounded are respectively pretreated, and the impurities and oxide films on the bonding surfaces of the aluminum alloy thin plate and the magnesium alloy thin plate are removed through the pretreatment, so as to improve the bonding effect of the magnesium alloy thin plate and the aluminum alloy thin plate in the subsequent treatment process and improve the interfacial bonding strength.

[0016] In some preferred embodiments of the present invention, the pretreatment includes the following steps: the surfaces of the aluminum alloy thin plate and the magnesium alloy thin plate are respectively mechanically polished, surface cleaned and dried in sequence to obtain the aluminum alloy thin plate and the magnesium alloy thin plate after removing the surface impurities and oxide layers.

[0017] In some more preferred embodiments of the present invention, a grinding machine equipped with a T-shaped wire brush with a diameter of 0.3 mm is used to respectively grind the bonding surfaces of the aluminum alloy thin plate and the magnesium alloy thin plate, and the grinding direction is parallel to the rolling direction until the natural oxide layer on the bonding surface of the metal thin plate to be compounded disappears and the surface presents a rough "frosted" shape.

[0018] In some more preferred embodiments of the present invention, an anhydrous ethanol solution is used to clean the bonding surfaces of the ground metal thin plates to remove the impurities on the surfaces after grinding and obtain clean bonding surfaces.

[0019] In some more preferred embodiments of the present invention, a blower is used to dry the bonding surfaces of the metal thin plates.

[0020] In Step 2 above, it should be noted that in order to prevent the aluminum alloy thin plate and the magnesium alloy thin plate from oxidizing in the air before rolling, the present invention forms a dense nitride layer on the surfaces of the clean aluminum alloy thin plate and the magnesium alloy thin plate through nitriding treatment.

[0021] In some preferred embodiments of the present invention, the thickness of the nitride layer on the surface of the magnesium alloy thin sheet and the nitride layer on the surface of the aluminum alloy thin sheet is both 3 μm to 6 μm, so as to ensure that the formed dense nitride layer can isolate oxygen, thereby avoiding the surface oxidation of the magnesium alloy thin sheet and the aluminum alloy thin sheet during the heating process, further improving the interfacial bonding strength, and enhancing the overall mechanical properties of the material. Moreover, the dense nitride layer formed on the surface of the magnesium alloy thin sheet and the aluminum alloy thin sheet has high corrosion resistance, enabling the surfaces of the aluminum alloy thin sheet and the magnesium alloy thin sheet to resist the erosion of various corrosive media, and thus improving the corrosion resistance of the overall composite plate. In addition, the nitride has a high melting point and hardness, and can maintain good mechanical properties at high temperatures, thereby improving the high-temperature resistance of the overall composite plate.

[0022] In some preferred embodiments of the present invention, the nitriding treatment is carried out by means of glow ion nitriding. The present invention uses the method of glow ion nitriding for nitriding treatment, which can not only simplify the preparation process, reduce the preparation time and cost, improve the production efficiency, but also does not use harmful substances during the interfacial nitriding treatment, will not cause environmental pollution, and realizes green production. And it is realized through the following steps:

[0023] Vacuum is pumped to a vacuum degree of <1 Pa, and then ammonia gas is introduced until the working pressure is 200 Pa to 300 Pa; after the pulsed power supply is turned on to form glow discharge, the cathode voltage is adjusted to 500 V to 800 V, and the temperature is kept at 350 °C to 450 °C for 1 h to 2 h.

[0024] It should also be noted that during the glow ion nitriding treatment, ammonia gas is partially decomposed under the action of glow discharge to generate nitrogen ions, and the nitrogen ions then react with the surfaces of the aluminum alloy thin sheet and the magnesium alloy thin sheet, so as to form a dense nitride layer on the surfaces of the aluminum alloy thin sheet and the magnesium alloy thin sheet, thereby isolating oxygen and avoiding the generation of an oxide layer.

[0025] The present invention can realize the control of the nitride layer thickness by regulating the process parameters of glow ion nitriding, and further realize the effective control of the interfacial bonding strength of the rolled composite of billets with different thicknesses.

[0026] In the above step 3, it should be noted that in the present invention, the nitrided aluminum alloy thin sheet and the nitrided magnesium alloy thin sheet are stacked in the order of aluminum / magnesium / aluminum to form a composite slab. And, the head and tail of the composite slab are fixed with rivets to ensure that the slab does not move relatively during the rolling process. Then, the composite slab is subjected to heat treatment to achieve the purpose of reducing the deformation resistance of the material and promoting the effective bonding of the interface during the rolling process.

[0027] In some preferred embodiments of the present invention, the temperature of the heat treatment is 350°C to 450°C, and the heat preservation time is 10 min to 20 min, so that the inside of the composite slab can reach the specified temperature and the internal structure will not show the phenomenon of coarse grains.

[0028] In step 4 above, it should be noted that considering the factor that the surface of the composite slab may crack due to too large a temperature difference when it is in direct contact with the rolling rolls, the present invention first preheats the upper rolling roll and the lower rolling roll, and then uses the preheated upper rolling roll and lower rolling roll to roll the heat-treated composite plate to achieve the hot rolling combination of the aluminum / magnesium / aluminum pre-composite plate. It should also be emphasized that ultrasonic vibration is introduced during the rolling process in the present invention to assist rolling, so as to cause micro-area plastic deformation and shallow diffusion of atoms at the contact interface between the magnesium alloy thin plate and the aluminum alloy thin plate by means of ultrasonic waves, improve the interfacial bonding force of the magnesium / aluminum metal composite plate, and enhance the overall mechanical properties of the material.

[0029] In some preferred embodiments of the present invention, the reduction ratio of the first-pass ultrasonic-assisted rolling treatment is 40% to 55%. The selection of this reduction ratio can avoid the defect of cracking of the magnesium alloy intermediate layer of the composite slab and enable interfacial combination. A more preferred reduction ratio is 45% to 50% to effectively avoid the defect of cracking of the magnesium alloy intermediate layer of the composite slab and enable effective interfacial combination.

[0030] In some preferred embodiments of the present invention, the rolling speed of the first-pass ultrasonic-assisted rolling treatment is 0.5 m / min to 2 m / min. The selection of this rolling speed can avoid the defect of wrinkles in the magnesium alloy intermediate layer of the composite slab, and can also avoid the stress concentration phenomenon caused by the aggravation of work hardening, which is beneficial to the subsequent heat treatment to eliminate residual stress.

[0031] In some preferred embodiments of the present invention, the vibration frequency of the ultrasonic vibration is 10 kHz to 30 kHz, and the amplitude is 5 μm to 200 μm, so as to break the hard nitride layer through ultrasonic waves during the rolling process, make the hard nitride fragments insert into the composite interface, increase the effective contact area of the composite interface, provide a channel for element diffusion, and further improve the bonding performance of the composite interface.

[0032] In some preferred embodiments of the present invention, the preheating treatment is realized by applying an induction heating power supply to the upper rolling roll and the lower rolling roll respectively. The frequency of the induction heating power supply is 500 Hz to 2000 Hz, and the current density is 50 A / mm 2 ~100 A / mm 2, the selection of the process parameters can ensure that the upper roll and the lower roll are preheated to 50°C - 60°C within 1 minute to 2 minutes, thereby avoiding the defect of surface cracking of the composite slab caused by too large a temperature difference when the composite slab is in direct contact with the roll.

[0033] In some more preferred embodiments of the present invention, the ultrasonic vibration system includes an upper roll, a lower roll, two drive modules, two induction heating power supply modules, two ultrasonic generating modules, and an upper roll adjusting device.

[0034] In some preferred embodiments of the present invention, the upper roll and the lower roll are placed in parallel, and there is a gap between the upper roll and the lower roll, and the gap is for the composite slab to be compounded to pass through, so as to roll the composite slab through the upper roll and the lower roll.

[0035] In some preferred embodiments of the present invention, the two drive modules are respectively signal-connected to the upper roll and the lower roll to respectively drive the upper roll and the lower roll to rotate around their own axes. In some more preferred embodiments of the present invention, each drive module includes a drive shaft and a drive motor, one end of the drive shaft is connected to the output shaft of the drive motor, and the other end of the drive shaft is drivingly connected to the corresponding upper roll or lower roll.

[0036] In some preferred embodiments of the present invention, the two induction heating power supply modules are respectively located at the upper frame of the upper roll and the lower frame of the lower roll, and the two induction heating power supply modules are respectively signal-connected to the upper roll and the lower roll to respectively heat the upper roll and the lower roll.

[0037] In some preferred embodiments of the present invention, the two ultrasonic generating modules are respectively signal-connected to the upper roll and the lower roll to respectively apply ultrasonic vibration to the upper roll and the lower roll.

[0038] In some preferred embodiments of the present invention, the upper roll adjusting device is drivingly connected to the upper roll and is used to adjust the position of the upper roll relative to the lower roll.

[0039] It should be emphasized that the ultrasonic vibration system of the present invention can realize driving the upper roll and the lower roll to rotate respectively by starting two induction heating power supply modules and two driving modules simultaneously, and heating the upper roll and the lower roll respectively by the two induction heating power supply modules, so that the upper roll and the lower roll can be uniformly heated in the circumferential direction by means of rotational heating, thus facilitating the uniformly preheated upper roll and lower roll to uniformly perform a one-pass ultrasonic-assisted rolling process on the composite slab. During the one-pass ultrasonic-assisted rolling process, the two induction heating power supply modules are turned off, and the ultrasonic generating module is turned on. The ultrasonic generating module applies ultrasonic vibration to the upper roll and the lower roll, so that the upper roll and the lower roll perform a one-pass ultrasonic-assisted rolling process on the composite slab under ultrasonic assistance.

[0040] In some more preferred embodiments of the present invention, the rotation rates of the two driving modules for driving the upper roll and the lower roll to rotate are 2 r / s respectively. The selection of this roll rotation speed can ensure that the induction heating device can fully preheat the roll surface to reach the specified 50°C to 60°C.

[0041] Step 5, post-treatment:

[0042] The rolled aluminum / magnesium / aluminum composite plate is subjected to diffusion annealing treatment, and then trimming treatment is carried out to obtain the aluminum / magnesium / aluminum composite plate.

[0043] It should be noted that considering the factor that residual stress will be generated during the rolling process, the present invention eliminates the residual stress at the composite interface of the rolled aluminum / magnesium / aluminum composite plate by performing diffusion annealing treatment on it. Also considering that edge cracking will occur during the rolling process of the aluminum / magnesium / aluminum composite plate, the present invention also performs trimming treatment on the annealed aluminum / magnesium / aluminum composite plate after diffusion annealing treatment to meet the actual production needs.

[0044] In some preferred embodiments of the present invention, the temperature of the diffusion annealing treatment is 150°C to 200°C, the holding time is 1 h, and air cooling is performed. The selection of these process parameters can avoid the problem that hard and brittle intermetallic compounds are generated at the composite interface after too high temperature, resulting in a decrease in mechanical properties, and can also avoid the problem that the grain size becomes coarse due to too long holding time, and then the strength of the composite plate decreases.

[0045] In some preferred embodiments of the present invention, the trimming treatment can be carried out according to the actual finished product requirements, such as cutting, leveling, grinding, and cleaning.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] Compared with the existing rolling composite technology, in the present invention, the aluminum alloy thin sheet and the magnesium alloy thin sheet to be compounded are respectively pretreated to remove impurities and oxide films on the surfaces of the aluminum alloy thin sheet and the magnesium alloy thin sheet through the pretreatment, so as to improve the bonding effect of the aluminum alloy thin sheet and the magnesium alloy thin sheet in the subsequent treatment process and enhance the interfacial bonding strength. Then, through nitriding treatment, a dense nitride layer is formed on the surfaces of the cleaned aluminum alloy thin sheet and the magnesium alloy thin sheet respectively, thereby isolating oxygen to avoid oxidation of the aluminum alloy thin sheet and the magnesium alloy thin sheet in the air before rolling, and further enhancing the interfacial bonding strength. Then, the metal thin sheets to be compounded after nitriding treatment, that is, the aluminum alloy thin sheet after nitriding treatment and the magnesium alloy thin sheet after nitriding treatment, are stacked in sequence according to the required structure. For example, the aluminum alloy thin sheet after nitriding treatment and the magnesium alloy thin sheet after nitriding treatment are stacked in sequence in the manner of aluminum alloy thin sheet, magnesium alloy thin sheet, and aluminum alloy thin sheet to form a composite slab. Then, the composite slab is subjected to heat treatment to achieve the purpose of reducing the deformation resistance of the material and promoting effective interfacial bonding during rolling. The upper roll and the lower roll are preheated, and then the preheated upper roll and lower roll are used to roll the heat-treated composite plate to achieve the hot rolling bonding of the aluminum / magnesium / aluminum composite plate. Then, a single-pass ultrasonic-assisted rolling treatment is carried out, so that ultrasonic vibration is introduced during rolling to assist rolling, and the contact interface between the magnesium alloy thin sheet and the aluminum alloy thin sheet undergoes micro-area plastic deformation and shallow diffusion of atoms by means of ultrasonic waves, thereby improving the interfacial bonding force of the aluminum / magnesium / aluminum composite plate and enhancing the overall mechanical properties of the material.

[0048] The method of the present invention is simple to operate. Through the synergistic effect of nitriding treatment and single-pass ultrasonic-assisted rolling treatment, it not only effectively improves the interfacial bonding strength and interfacial bonding quality, solves the problems of unstable interfacial bonding quality and low bonding strength of the composite plate, but also improves the overall mechanical properties, corrosion resistance and high-temperature resistance of the aluminum / magnesium / aluminum composite plate. Brief Description of the Drawings

[0049] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required to be used in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0050] Figure 1 It is a process schematic diagram of grinding treatment in the pretreatment process of the present invention.

[0051] Figure 2 It is a process schematic diagram of surface cleaning treatment in the pretreatment process of the present invention.

[0052] Figure 3Schematic diagram of the drying process in the pretreatment of the present invention.

[0053] Figure 4 Schematic diagram of the nitriding process of the present invention.

[0054] Figure 5 Schematic diagram of the process for assembling blanks of dissimilar alloy thin plates of the present invention.

[0055] Figure 6 Schematic diagram of the heat treatment process of the present invention.

[0056] Figure 7 Schematic diagram of the process for preparing an aluminum / magnesium / aluminum composite plate by ultrasonic vibration-assisted rolling of the present invention.

[0057] Figure 8 Schematic diagram of the annealing process in the post-treatment of the present invention.

[0058] Figure 9 Schematic diagram of the aluminum / magnesium / aluminum composite plate obtained after cutting in the post-treatment of the present invention.

[0059] The reference numerals in the figure are:

[0060] 1 - upper rolling roll; 2 - lower rolling roll; 3 - driving module; 31 - driving shaft, 32 - driving motor; 4 - induction heating power supply module; 5 - ultrasonic generating module; 6 - upper rolling roll adjusting device; 7 - upper aluminum alloy thin plate; 8 - magnesium alloy thin plate; 9 - lower aluminum alloy thin plate; 10 - T-shaped wire brush; 11 - absolute ethanol solution; 12 - cleaning cloth; 13 - blower; 14 - glow ion nitriding furnace; 15 - rivet; 16 - composite plate blank; 17 - box-type resistance furnace; 18 - as-rolled aluminum / magnesium / aluminum composite plate; 19 - annealing furnace; 20 - aluminum / magnesium / aluminum composite plate. Detailed implementation manners

[0061] The technical solutions in the embodiments of the present invention will be clearly and completely described below.

[0062] Embodiment 1

[0063] This embodiment provides a rolling method for an aluminum / magnesium / aluminum composite plate based on interfacial nitriding treatment, including the following steps:

[0064] Step 1, surface cleaning treatment:

[0065] 1.1) Prepare the metal thin plates to be compounded:

[0066] In this embodiment, two aluminum alloy thin plates and one magnesium alloy thin plate are prepared. The magnesium alloy thin plate used in this embodiment is AZ31B, and the aluminum alloy thin plate used is 5052. The size of the AZ31B magnesium alloy thin plate used is 100 mm × 60 mm × 5 mm, and the size of the above-mentioned 5052 aluminum alloy thin plate is 100 mm × 60 mm × 0.1 mm.

[0067] 1.2) Pretreatment:

[0068] 1.2.1) Please refer to Figure 1 , select a grinding machine equipped with a T-shaped wire brush 10 with a diameter of 0.3 mm to grind the bonding surfaces of the upper aluminum alloy thin plate 7, the magnesium alloy thin plate 8, and the lower aluminum alloy thin plate 9 respectively. The grinding direction is parallel to the rolling direction until the natural oxide layer on the bonding surface of the composite metal thin plates to be bonded disappears and the interface surface presents a rough "frosted" shape.

[0069] 1.2.2) Please refer to Figure 2 , use anhydrous ethanol solution 11 and cleaning cloth 12 to clean the bonding surfaces of the ground magnesium alloy thin plate and aluminum alloy thin plate to remove impurities on the bonding surfaces after grinding and obtain clean bonding surfaces.

[0070] 1.2.3) Please refer to Figure 3 , use a blower 13 to dry the bonding surfaces to obtain clean magnesium alloy thin plate and aluminum alloy thin plate after pretreatment.

[0071] Step 2, nitriding treatment:

[0072] 2.1) Place the clean magnesium alloy thin plate and aluminum alloy thin plate into a glow ion nitriding furnace 14 respectively. Then evacuate to a vacuum degree of <1 Pa and fill with ammonia gas until the working pressure is 250 Pa. For example, as Figure 4 shown, place the clean aluminum alloy thin plate into the glow ion nitriding furnace 14.

[0073] 2.2) After turning on the pulse power supply to form glow discharge, adjust the cathode voltage to 600 V and keep it at 400 °C for 2 h.

[0074] 2.3) Air-cool to room temperature to obtain the magnesium alloy thin plate and aluminum alloy thin plate after nitriding treatment.

[0075] Step 3, heat treatment:

[0076] 3.1) Please refer to Figure 5 , stack the nitrided magnesium alloy thin plate and aluminum alloy thin plate in the order of aluminum / magnesium / aluminum. At the four corners of the stacked three-layer alloy thin plate, use a drilling machine to drill holes with a diameter of 1.5 mm, and use rivets 15 to pass through the drilled holes to fix the four corners of the thin plate to prevent the three thin plates from separating during the rolling process and obtain a composite slab 16.

[0077] 3.2) Refer to Figure 6 , and feed the obtained composite slab 16 into the box-type resistance furnace 17, and heat-treat the composite slab at 400 °C for 15 min.

[0078] Step 4, one-pass ultrasonic-assisted rolling treatment:

[0079] Refer to Figure 7 , the present invention adopts an ultrasonic vibration system for one-pass ultrasonic-assisted rolling treatment, and the adopted ultrasonic vibration system includes an upper roll 1, a lower roll 2, two drive modules 3, two induction heating power supply modules 4, two ultrasonic generating modules 5 and an upper roll adjusting device 6.

[0080] Among them, the upper roll 1 and the lower roll 2 are placed in parallel, and the upper roll 1 is drivingly connected to the upper roll adjusting device to adjust the position of the upper roll 1 relative to the lower roll 2 through the upper roll adjusting device according to actual needs, so that the gap between the upper roll 1 and the lower roll 2 can allow the composite slab to be compounded to pass through, so as to roll the composite slab through the upper roll 1 and the lower roll 2.

[0081] Each drive module 3 includes a drive shaft 31 and a drive motor 32. One end of the drive shaft 31 of one drive module 3 is connected to the output shaft of the corresponding drive motor 32, and the other end of the drive shaft 31 is drivingly connected to the upper roll 1 to drive the upper roll 1 to rotate around its own axis. One end of the drive shaft 31 of the other drive module 3 is connected to the output shaft of the corresponding drive motor 32, and the other end of the drive shaft 31 is drivingly connected to the lower roll 2 to drive the lower roll 2 to rotate around its own axis.

[0082] The two induction heating power supply modules 4 are respectively signal-connected to the upper roll 1 and the lower roll 2 to heat the upper roll 1 and the lower roll 2 respectively. The ultrasonic generating module 5 is respectively signal-connected to the upper roll 1 and the lower roll 2 to apply ultrasonic vibration to the upper roll 1 and the lower roll 2 respectively.

[0083] 4.1) First, start the two induction heating power supply modules 4 and the two drive modules 3 simultaneously, so as to drive the upper roll 1 and the lower roll 2 to rotate at a rate of 2 r / s through the two drive modules 3 respectively. At the same time, adjust the frequencies of the two induction heating power supply modules 4 to 500 Hz and the current density to 50 A / mm 2 , to heat the upper roll 1 and the lower roll 2 respectively, so that the upper roll 1 and the lower roll 2 can be uniformly heated in the circumferential direction by means of rotational heating, so that both the upper roll 1 and the lower roll 2 are preheated to 60 °C.

[0084] 4.2) Turn on the ultrasonic generating module 5, and apply ultrasonic vibration to the upper roll 1 and the lower roll 2 through the ultrasonic generating module 5. The vibration frequency is 20 kHz and the amplitude is 15 μm. Then, the upper roll 1 and the lower roll 2 perform a one-pass ultrasonic-assisted rolling process on the composite slab under ultrasonic assistance. The reduction rate of the one-pass ultrasonic-assisted rolling process is 50%, and the rolling speed is 0.01 m / s, obtaining the rolled aluminum / magnesium / aluminum composite plate 18.

[0085] Step 5, post-treatment:

[0086] 5.1) Please refer to Figure 8 , place the rolled aluminum / magnesium / aluminum composite plate 18 in the annealing furnace 19 and keep it at 200 °C for 1 h, and then air-cool it to room temperature to obtain the annealed aluminum / magnesium / aluminum composite plate after diffusion annealing treatment.

[0087] 5.2) The annealed aluminum / magnesium / aluminum composite plate after diffusion annealing treatment is successively cut, leveled, polished and cleaned to obtain the aluminum / magnesium / aluminum composite plate 20 as Figure 9 shown.

[0088] Example 2

[0089] This example provides a rolling method for an aluminum / magnesium / aluminum composite plate based on interfacial nitriding treatment, including the following steps:

[0090] Step 1, surface cleaning treatment:

[0091] 1.1) Prepare the metal thin plates to be compounded:

[0092] In this example, two aluminum alloy thin plates and one magnesium alloy thin plate are prepared. The magnesium alloy thin plate used in this example is AZ31B, and the aluminum alloy thin plate used is 5052. The size of the AZ31B magnesium alloy thin plate used is 90 mm × 40 mm × 8 mm, and the size of the above-mentioned 5052 aluminum alloy thin plate is 90 mm × 40 mm × 0.15 mm.

[0093] 1.2) Pretreatment:

[0094] 1.2.1) Please refer to Figure 1 , select a grinding machine equipped with a T-shaped wire brush 10 with a diameter of 0.3 mm to respectively grind the bonding surfaces of the upper aluminum alloy thin plate 7, the magnesium alloy thin plate 8 and the lower aluminum alloy thin plate 9. The grinding direction is parallel to the rolling direction, and grind until the natural oxide layer on the bonding surfaces of the metal thin plates to be compounded disappears, and the interface surface presents a rough "frosted" shape.

[0095] 1.2.2) Please refer to Figure 2, use an anhydrous ethanol solution 11 and a cleaning cloth 12 to clean the surfaces to be joined of the polished magnesium alloy sheet and the aluminum alloy sheet, so as to remove impurities on the surfaces to be joined after polishing and obtain clean surfaces to be joined.

[0096] 1.2.3) Please refer to Figure 3 , use a blower 13 to blow dry the surfaces to be joined, and obtain the polished magnesium alloy sheet and aluminum alloy sheet that are clean after pretreatment.

[0097] Step 2, nitriding treatment:

[0098] 2.1) Please refer to Figure 4 , place the clean magnesium alloy sheet and aluminum alloy sheet into a glow ion nitriding furnace 14 respectively, then evacuate to a vacuum degree of <1 Pa, and then fill with ammonia gas until the working pressure is 250 Pa.

[0099] 2.2) After turning on the pulse power supply to form glow discharge, adjust the cathode voltage to 600 V and keep it at 400 °C for 2 h.

[0100] 2.3) Air-cool to room temperature to obtain the magnesium alloy sheet and aluminum alloy sheet after nitriding treatment.

[0101] Step 3, heat treatment:

[0102] 3.1) Please refer to Figure 5 , stack the nitrided magnesium alloy sheet and aluminum alloy sheet in the order of aluminum / magnesium / aluminum, and at the four corners of the stacked three-layer alloy sheet, use a drilling machine to drill holes with a diameter of 1.5 mm, and use rivets 15 to pass through the drilled holes to fix the four corners of the sheet, preventing the three-layer sheet from separating during the rolling process, and obtain a composite slab 16.

[0103] 3.2) Please refer to Figure 6 , send the obtained composite slab 16 into a box-type resistance furnace 17 and perform heat treatment on the composite slab at 400 °C for 20 min.

[0104] Step 4, one-pass ultrasonic-assisted rolling treatment:

[0105] Please refer to Figure 7 , the present invention adopts an ultrasonic vibration system for one-pass ultrasonic-assisted rolling treatment, and the adopted ultrasonic vibration system includes an upper rolling roll 1, a lower rolling roll 2, two driving modules 3, two induction heating power supply modules 4, two ultrasonic generating modules 5 and an upper rolling roll adjusting device 6.

[0106] Among them, the upper roll 1 and the lower roll 2 are placed in parallel, and there is a gap between the upper roll 1 and the lower roll 2. The gap is for the composite slab to be compounded to pass through, so as to roll the composite slab through the upper roll 1 and the lower roll 2. The two driving modules 3 are respectively signal-connected to the upper roll 1 and the lower roll 2 to respectively drive the upper roll 1 and the lower roll 2 to rotate around their own axes. The two induction heating power supply modules 4 are respectively signal-connected to the upper roll 1 and the lower roll 2 to respectively heat the upper roll 1 and the lower roll 2. The ultrasonic generating module 5 is respectively signal-connected to the upper roll 1 and the lower roll 2 to respectively apply ultrasonic vibration to the upper roll 1 and the lower roll 2.

[0107] 4.1) First, start the two induction heating power supply modules 4 and the two driving modules 3 simultaneously, so as to respectively drive the upper roll 1 and the lower roll 2 to rotate at a rate of 2 r / s through the two driving modules 3. At the same time, adjust the frequencies of the two induction heating power supply modules 4 to 500 Hz and the current density to 50 A / mm 2 , so as to respectively heat the upper roll 1 and the lower roll 2, enabling the upper roll 1 and the lower roll 2 to be uniformly heated in the circumferential direction by means of rotational heating, and preheating the upper roll 1 and the lower roll to 60 °C.

[0108] 4.2) Turn on the ultrasonic generating module 5, and apply ultrasonic vibration to the upper roll 1 and the lower roll 2 through the ultrasonic generating module 5. The vibration frequency is 20 kHz and the amplitude is 15 μm. Furthermore, enable the upper roll 1 and the lower roll 2 to perform a single-pass ultrasonic-assisted rolling treatment on the composite slab under ultrasonic assistance. The reduction rate of the single-pass ultrasonic-assisted rolling treatment is 50%, and the rolling speed is 0.01 m / s, obtaining the rolled aluminum / magnesium / aluminum composite plate 18.

[0109] Step 5, post-treatment:

[0110] 5.1) Please refer to Figure 8 , place the rolled aluminum / magnesium / aluminum composite plate 18 in the annealing furnace 19, keep it at 200 °C for 1 h, and then air-cool it to room temperature to obtain the annealed aluminum / magnesium / aluminum composite plate after diffusion annealing treatment.

[0111] 5.2) Cut, level, polish, and clean the annealed aluminum / magnesium / aluminum composite plate after diffusion annealing treatment in sequence to obtain the aluminum / magnesium / aluminum composite plate 20 as Figure 9 shown.

[0112] Example 3

[0113] This example provides a rolling method for an aluminum / magnesium / aluminum composite plate based on interfacial nitriding treatment. The difference between this example and Example 1 is only that:

[0114] In this embodiment, the process parameters of the nitriding treatment are as follows: ammonia gas is introduced until the working pressure is 200 Pa; after the pulsed power supply is turned on to form glow discharge, the cathode voltage is adjusted to 500 V, and the treatment is carried out at 350 °C for 1 h.

[0115] Moreover, the process parameters of the one-pass ultrasonic-assisted rolling treatment are as follows: the reduction rate is 40%, and the rolling speed is 0.5 m / min; the vibration frequency of the ultrasonic vibration is 10 kHz, and the amplitude is 5 μm.

[0116] The frequency of the induction heating power supply is 500 Hz, and the current density is 50 A / mm 2 。

[0117] Example 4

[0118] This embodiment provides a rolling method for an aluminum / magnesium / aluminum composite plate based on interfacial nitriding treatment. The difference between this embodiment and Embodiment 1 is only that:

[0119] In this embodiment, the process parameters of the nitriding treatment are as follows: ammonia gas is introduced until the working pressure is 300 Pa; after the pulsed power supply is turned on to form glow discharge, the cathode voltage is adjusted to 800 V, and the treatment is carried out at 450 °C for 1 h.

[0120] Moreover, the process parameters of the one-pass ultrasonic-assisted rolling treatment are as follows: the reduction rate is 55%, and the rolling speed is 2 m / min; the vibration frequency of the ultrasonic vibration is 10 kHz, and the amplitude is 5 μm.

[0121] The frequency of the induction heating power supply is 2000 Hz, and the current density is 100 A / mm 2 。

[0122] Comparative Example 1

[0123] This comparative example provides a rolling method for an aluminum / magnesium / aluminum composite plate based on interfacial nitriding treatment, including the following steps:

[0124] Step 1, surface cleaning treatment:

[0125] 1.1) Prepare the metal thin plates to be compounded:

[0126] In this embodiment, two aluminum alloy thin plates and one magnesium alloy thin plate are prepared. The magnesium alloy thin plate used in this embodiment is AZ31B, and the aluminum alloy thin plate used is 5052. The size of the AZ31B magnesium alloy thin plate used is 90 mm × 40 mm × 8 mm, and the size of the above 5052 aluminum alloy thin plate is 90 mm × 40 mm × 0.15 mm.

[0127] 1.2) Pretreatment:

[0128] 1.2.1) Use a grinding machine equipped with a T-shaped wire brush with a diameter of 0.3 mm to grind the bonding surfaces of the aluminum alloy thin sheet and the magnesium alloy thin sheet respectively. The grinding direction is parallel to the rolling direction until the natural oxide layer on the bonding surface of the composite metal thin sheet to be bonded disappears and the interface surface presents a rough "frosted" shape.

[0129] 1.2.2) Use anhydrous ethanol solution to clean the bonding surfaces of the ground magnesium alloy thin sheet and aluminum alloy thin sheet to remove the impurities on the surface after grinding, and obtain clean bonding surfaces.

[0130] 1.2.3) Use a blower to dry the bonding surfaces to obtain the pre-treated clean magnesium alloy thin sheet and aluminum alloy thin sheet.

[0131] Step 2, heat treatment:

[0132] 2.1) Stack the nitrided magnesium alloy thin sheet and aluminum alloy thin sheet in the order of aluminum / magnesium / aluminum. At the four corners of the stacked three-layer alloy thin sheet, use a drilling machine to drill holes with a diameter of 1.5 mm, and use rivets to pass through the drilled holes to fix the four corners of the thin sheet to prevent the three-layer thin sheet from separating during the rolling process, and obtain a composite slab.

[0133] 2.2) Feed the obtained composite slab into a box-type resistance furnace and heat-treat the composite slab at 400 °C for 20 min.

[0134] Step 3, one-pass rolling treatment:

[0135] Use traditional two-high rolling and perform one-pass rolling under the conditions of a reduction ratio of 50% and a rolling speed of 0.01 m / s to obtain the rolled aluminum / magnesium / aluminum composite plate in the as-rolled state.

[0136] Step 4, post-treatment:

[0137] 4.1) Keep the as-rolled aluminum / magnesium / aluminum pre-composite plate at 200 °C for 1 h, and then air-cool it to room temperature to obtain the annealed aluminum / magnesium / aluminum composite plate after diffusion annealing treatment.

[0138] 4.2) Cut, level, grind and clean the annealed aluminum / magnesium / aluminum composite plate after diffusion annealing treatment in sequence to obtain the aluminum / magnesium / aluminum composite plate.

[0139] That is, the difference between this comparative example and Example 1 is only:

[0140] This comparative example does not perform nitriding treatment and uses traditional two-high rolling to replace the one-pass ultrasonic-assisted rolling treatment in Example 1.

[0141] Moreover, the mechanical properties of the aluminum / magnesium / aluminum composite plates prepared in Examples 1 to 4 and Comparative Example 1 were tested. The results showed that the strength of the aluminum / magnesium / aluminum composite plates in Examples 1 to 4 increased by 5% to 20% compared to that of Comparative Example 1. This indicates that, compared with the traditional two-roll rolling method in the prior art, the rolling method of the present invention can effectively improve the interfacial bonding strength and the bonding quality stability between the magnesium thin plate and the aluminum thin plate.

[0142] Obviously, the above embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

Claims

1. A rolling method for aluminum / magnesium / aluminum composite plates based on interface nitridation treatment, characterized in that: The following steps are involved: Preparing two aluminum alloy thin plates and one magnesium alloy thin plate, and performing pretreatment on the two aluminum alloy thin plates and one magnesium alloy thin plate respectively to remove impurities and oxide films on the surfaces of the two aluminum alloy thin plates and one magnesium alloy thin plate, thereby obtaining two clean aluminum alloy thin plates and one clean magnesium alloy thin plate; Performing nitriding treatment on two clean aluminum alloy thin plates and one clean magnesium alloy thin plate respectively, so as to form a nitride layer on the surface of the two clean aluminum alloy thin plates and one clean magnesium alloy thin plate respectively; In the manner of aluminum / magnesium / aluminum, a nitrided aluminum alloy sheet, a nitrided magnesium alloy sheet, and a nitrided aluminum alloy sheet are stacked in sequence to form a composite slab, and the composite slab is subjected to a heating treatment; The upper roller and the lower roller are preheated, and then ultrasonic vibration is applied to the upper roller and the lower roller after the preheating treatment through an ultrasonic vibration system, and the composite slab after the heating treatment is subjected to one-pass ultrasonic assisted rolling treatment to obtain a rolled aluminum / magnesium / aluminum composite plate; The rolled aluminum / magnesium / aluminum composite plate is subjected to diffusion annealing treatment and then subjected to trimming treatment to obtain the aluminum / magnesium / aluminum composite plate.

2. The rolling method of aluminum / magnesium / aluminum composite plate based on interface nitriding treatment according to claim 1, characterized in that: The thickness of the nitride layer on the surface of the magnesium alloy thin plate and the nitride layer on the surface of the aluminum alloy thin plate are both 3 μm to 6 μm.

3. The rolling method of aluminum / magnesium / aluminum composite plate based on interface nitriding treatment according to claim 1, characterized in that: The nitriding treatment is carried out by glow ion nitriding and is achieved by the following steps: Evacuate to a vacuum degree of <1Pa, then introduce ammonia until the working pressure is 200Pa~300Pa; turn on the pulse power supply to form a glow discharge, adjust the cathode voltage to 500V~800V, and treat at 350℃~450℃ for 1h~2h.

4. The rolling method of aluminum / magnesium / aluminum composite plate based on interface nitriding treatment according to claim 1, characterized in that: The reduction rate of the ultrasonic assisted rolling process is 40% to 55%, and the rolling speed is 0.5 m / min to 2 m / min; The ultrasonic vibration has a vibration frequency of 10 kHz to 30 kHz and an amplitude of 5 μm to 200 μm.

5. The rolling method of aluminum / magnesium / aluminum composite plate based on interface nitriding treatment according to claim 1, characterized in that: The temperature of the heating treatment is 350° C. to 450° C., and the insulation time is 10 min to 20 min.

6. The rolling method of aluminum / magnesium / aluminum composite plate based on interface nitriding treatment according to claim 1, characterized in that: The preheating treatment is achieved by applying an induction heating power supply to the upper roller and the lower roller respectively; the frequency of the induction heating power supply is 500Hz to 2000Hz, and the current density is 50A / mm 2 ~100A / mm 2 , to preheat the upper and lower rolls to 50℃~60℃ and maintain them until the end of the rolling process.

7. The rolling method of aluminum / magnesium / aluminum composite plate based on interface nitriding treatment according to claim 1, characterized in that: The thickness of the magnesium alloy thin plate is 5 mm to 10 mm, and the thickness of the aluminum alloy thin plate is 0.1 mm to 0.2 mm.

8. The rolling method of aluminum / magnesium / aluminum composite plate based on interface nitriding treatment according to claim 1, characterized in that: The ultrasonic vibration system comprises an upper roller (1), a lower roller (2), two drive modules (3), two induction heating power modules (4), two ultrasonic generating modules (5) and an upper roller adjustment device (6); The upper roller (1) and the lower roller (2) are placed in parallel, and there is a gap between the upper roller (1) and the lower roller (2), and the gap is used for the composite slab to be composited to pass through; The two driving modules (3) are respectively connected to the upper roller (1) and the lower roller (2) by signals so as to respectively drive the upper roller (1) and the lower roller (2) to rotate around their own axes; The two induction heating power supply modules (4) are respectively connected to the upper roller (1) and the lower roller (2) by signals so as to heat the upper roller (1) and the lower roller (2) respectively; The two ultrasonic generating modules (5) are respectively connected to the upper roller (1) and the lower roller (2) by signals so as to respectively apply ultrasonic vibration to the upper roller (1) and the lower roller (2); The upper roller adjustment device (6) is drivingly connected to the upper roller (1) and is used to adjust the position of the upper roller (1) relative to the lower roller (2).

9. The rolling method of aluminum / magnesium / aluminum composite plate based on interface nitriding treatment according to claim 1, characterized in that: The diffusion annealing treatment is performed at a temperature of 150° C. to 200° C., with a heat preservation time of 0.8 h to 1.2 h, and air cooling.

10. The rolling method of aluminum / magnesium / aluminum composite plate based on interface nitriding treatment according to claim 1, characterized in that: The pre-treatment comprises the following steps: The surfaces of the aluminum alloy sheet and the magnesium alloy sheet to be bonded are respectively subjected to mechanical grinding, surface cleaning treatment and drying treatment in sequence.

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