Extrusion press for manufacturing of dissimilar metal laminated composites

Abstract

The present application relates to metal composite and mechanical manufacturing comprehensive technical field, specifically to a kind of integrated equipment for manufacturing metal laminated composite by creep.The equipment body and control system are included in two parts.Heating body, guide column, temperature sensor, pressurizing partition and working area between pressurizing partition are arranged in the equipment body;pressurizing device is arranged above the equipment body.Electric motor, hydraulic pump, electromagnetic reversing valve, pressure sensor and heater control circuit are arranged in the control system;the control system is connected with the equipment body by cable, and connected with pressurizing device by high-pressure conduit and low-pressure conduit;display screen and control button are arranged outside the control system.Working area size is 1000mm×2000mm.Different generative machining blanks are calculated by molecular dynamics to determine heating temperature, pressurizing pressure and heating time.The present application has the advantages of optimizing creep composite machining process and improving creep composite production efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of metal composite materials and mechanical manufacturing, in particular to creep pressing manufacturing equipment for heterogeneous metal layered composite materials. Background Art

[0002] Layered metal composites are new materials created by metallurgically bonding two or more metals with different properties using different manufacturing methods. Currently, the manufacturing methods for layered metal composites primarily fall into four categories: explosive welding, explosive-rolling, rolling, and the new creep-compression composite method.

[0003] Explosive welding utilizes the enormous energy generated by the detonation of explosives to instantly complete the solid-solid metallurgical bonding of homogeneous or dissimilar metal composites. This method offers advantages such as simple processing, low cost, and high bonding strength. Explosive welding combined with rolling is a subsequent rolling process of explosive composite materials based on explosive welding, which can improve the material's surface roughness, shape accuracy, thickness dimensional accuracy, and processing performance. However, explosive welding and explosive rolling often suffer from poor plate shape control, which can cause environmental pollution. Furthermore, during the manufacture of thin plates, the bonding rate is low, resulting in low production efficiency and yield. Vacuum rolling can improve production efficiency and yield, reduce environmental pollution, and enhance bonding strength. However, rolling is only suitable for bonding metals with similar properties; it is less effective for bonding metals with significantly different properties. Furthermore, rolling consumes a lot of energy, resulting in low energy utilization.

[0004] Although vacuum creep pressing (CN 114043178 A) and vacuum rolling (CN 106180186 A) are two methods for manufacturing layered composite materials, they share similarities in vacuum control and assembly processes. However, their combination mechanisms, energy action principles, and final effects are fundamentally different. The differences between the two methods are mainly reflected in the following aspects:

[0005] 1. The bonding mechanisms of the two manufacturing methods are significantly different. Rolling is a metalworking process that involves passing a metal billet through the gap between a pair of rotating rollers. The compression of the rollers reduces the material's cross-section and increases its length. Vacuum rolling, as described in References 1 (CN 114043178 A) and 2 (CN 106180186 A), utilizes the immense pressure (reduction rate) of a pair of rotating rollers in a vacuum environment to reduce the cross-section and increase the length of the composite material, even while undergoing intense plastic deformation to form a bond. Vacuum creep pressing, on the other hand, utilizes very low pressure to bring the two surfaces to be bonded into close contact under vacuum, without requiring plastic deformation. Creep pressing is performed for a specific period of time, ensuring full contact between the two interfaces, maintaining the atomic spacing, and forming a solid-state bond between the metal atoms. While a good joint can be formed for layered composite materials as long as the two fresh interfaces reach the atomic spacing, the energy of vacuum rolling and explosive welding far exceeds the interface bonding energy. This is why the industry has long believed that the bonding of two interfaces requires significant energy, either plastic deformation or high-temperature melting, to form a metallurgical bond (rather than an atomic bond). Precisely because the industry does not have a deep and sufficient understanding of the interface bonding mechanism of layered composite material manufacturing methods such as explosive compounding and vacuum rolling, no one at home or abroad has proposed the simple method of creep pressing to manufacture composite materials so far.

[0006] 2. The energy addition method is different. Vacuum rolling not only has a very large positive pressure, but also has lateral shear force in order to produce plastic deformation of the composite material, that is, to exceed the yield strength of the material, which is generally hundreds of MPa or more. Vacuum rolling also has lateral shear force. Vacuum creep only has a very small static positive pressure to maintain the two interfaces at the atomic distance, which is generally less than the yield strength of the material. The present invention tested a pressure of 1 MPa, which is much less than the yield strength of the material. Moreover, vacuum creep is static and has no lateral shear force, thus reducing a lot of energy consumption.

[0007] 3. Different energy utilization rates. In the rolling method, most of the energy is consumed in the plastic deformation of the composite material, while in fact the interface binding energy only accounts for a very small part. Simulation calculations show that this binding energy only accounts for 10%-20% of the total energy. At the same time, excessive energy will form microscopic defects such as overmelting and dislocations at the interface. The pressure of creep pressing is very small, which means that the energy consumed is very small, and the only pressure, that is, the gravitational potential energy, is mostly converted into the binding energy of the interface. It uses the principle of least action in nature and physics, which not only consumes less energy but also has a high energy utilization rate, truly realizing low-carbon energy conservation and sustainable development in the field of layered composite material manufacturing. The promotion and application of creep pressing methods will be a disruptive and major innovative breakthrough in the field of composite materials, and will bring about an upgrade to my country's industrial equipment and military engineering fields.

[0008] Compared with the first three manufacturing methods, the new creep composite method overcomes the above problems, can realize the composite of the same or different metals, and is suitable for the manufacture of large-size composite plates. It has the advantages of reducing manufacturing costs, improving product quality and achieving green and energy-saving manufacturing.

[0009] The main process steps of the new creep-compression lamination method include surface treatment, leveling of the base and composite plates, assembly and sealing, heat treatment, and creep-compression bonding. Heat treatment and creep-compression bonding are critical steps, controlling the temperature and pressure of the lamination process, respectively, which directly affect the bond strength of the creep-compression composite material. In a typical creep-compression lamination process, the blank is heat treated in a heat treatment furnace before being transferred to a hydraulic press for creep-compression bonding. This transfer from the heat treatment furnace to the hydraulic press causes heat loss in the blank, making it difficult to control the assembly temperature. Furthermore, the blank temperature drops rapidly during the creep-compression process, which in turn affects the product yield.

[0010] To address these issues, the present invention provides a creep pressing device for manufacturing dissimilar metal layered composite materials. Prior to processing, molecular dynamics calculations are performed on the materials to be composited. The pressing time, heating temperature, and pressing pressure are then determined based on the actual processing environment. The blank is then placed in the device, and the heating temperature, pressing pressure, and pressing time are set. The device automatically adjusts these parameters. Summary of the Invention

[0011] 1. Structure and function of creep pressure equipment

[0012] One purpose of the present invention is to propose a creep-pressing integrated device that can control temperature and pressure for metal creep-pressing composites, so as to solve the problem of temperature and pressure control during the creep-pressing process. The technical solution adopted by the present invention is: a creep-pressing integrated device for manufacturing metal layered composite materials, including a device body, a cover plate, a pressure device, a heating element, a guide column, a pressure plate, a temperature sensor, a pressure sensor, and a displacement sensor. A base is provided at the bottom of the device body, a pressure device is installed above the device body, and a support column is fixedly installed on its side. A heating element and a temperature sensor are installed on the inner wall of the body, and a guide column is fixedly installed in the middle, and a pressure partition is installed on the guide column. Above the uppermost pressure partition is the pressure head of the pressure device. The pressure head is connected to the uppermost pressure partition inside the device body by bolts.

[0013] The equipment body is connected to the control console via cables, high-pressure conduits and low-pressure conduits. The console is equipped with a motor, a hydraulic pump, an electromagnetic reversing valve, a pressure sensor, a pressure regulating device and a control circuit, which can provide high-pressure oil or other high-pressure liquids to the press. The motor, hydraulic pump, electromagnetic reversing valve, pressure sensor and other components inside the console and the press, high-pressure conduit and low-pressure conduit above the equipment body constitute a complete hydraulic system. The hydraulic system can realize the pressurization function of the blank. The console is connected to the equipment body via cables, which can control the heating element to generate heat, and the temperature sensor in the equipment body can also feed back the temperature to the console in real time. The control circuit and the temperature sensor constitute a temperature control system, which can realize the heating and heat preservation functions of the blank.

[0014] The console is equipped with a display screen and operating buttons. The display screen can display the set temperature, real-time temperature, real-time pressure, heating time, holding time and pressurizing time. The operating buttons can be used to control the device body to heat, hold and pressurize the blank.

[0015] Furthermore, the machine body is equipped with six pressurized baffles, with the working area between two of them. During operation, the middle pressurized baffle acts as both the lower pressurized baffle for the previous working area and the upper pressurized baffle for the next working area. The pressurized baffles are mounted and fixed to the guide posts through guide holes in their surfaces. The number of working areas can be increased by simply adding pressurized baffles.

[0016] Furthermore, the cover plate is connected to the device body by bolts, and a through hole for the piston of the pressurizing device to pass through is opened in the middle of the cover plate. The piston is connected to the pressure head by bolts.

[0017] Furthermore, the pressurized partition of the present invention is made of high temperature resistant material and has a special coating on its surface to prevent the sample from being combined with the partition during the heating and pressurizing process.

[0018] Furthermore, a heat-insulating material is provided on the inner surface of the door of the device body, which can achieve a heat-insulating effect and prevent heat from escaping through the device door.

[0019] Furthermore, the heating chamber of the present invention heats three sides simultaneously, which can ensure the uniformity of sample temperature, with a temperature control accuracy of ±3°C and a heating chamber temperature uniformity accuracy of ±5°C.

[0020] The present invention provides a creep-pressing integrated device for manufacturing metal layered composite materials. It has the following beneficial effects:

[0021] During the creep pressing process, the workpiece is placed in the work area and heated by the heating element. Based on feedback from the temperature sensor, when the workpiece reaches the desired temperature, the device reduces the heating element's heat output, automatically controlling the workpiece's heating temperature.

[0022] 2. Once the blank is heated to the required temperature, the pressurizing device can be controlled to apply pressure to the blank, preventing heat loss during the transfer of the blank to the pressurizing device. Furthermore, the pressurizing device is equipped with a pressure sensor that can reflect the pressure in real time, ensuring that the blank is pressed at the most suitable pressure, thereby improving the bonding strength of the metal interface and increasing the product yield rate.

[0023] 3. The equipment described in this invention has a single working area measuring 1000 mm x 2000 mm, capable of processing larger-sized blanks. The equipment also has multiple working areas located above and below, enabling the simultaneous processing of multiple blanks, providing support for batch processing of blanks. Furthermore, by varying the distance between the upper and lower working areas, blanks of varying thicknesses can be processed, enhancing the equipment's practicality.

[0024] 2. Molecular dynamics calculations of pressurization time, heating temperature, and pressurization pressure

[0025] The molecular dynamics calculations performed in the present invention are carried out under LAMMPS, and the potential function adopts the EAM potential proposed by Zope and Mishin. Taking the titanium-aluminum creep composite plate as an example, a box with a size of 12×12×6nm is first created, and it is divided into two parts A and B along the Z axis. Part A is filled with HCP type Ti atoms with a lattice constant of 2.94, and part B is filled with atoms with a lattice constant of 4.05. A spacing of 0.1nm is left between parts A and B, which is consistent with the position of the composite plate before the creep starts in reality. It is then placed in the NPT ensemble for relaxation, and its MSD and diffusion layer thickness along the Z direction are calculated.

[0026] 1. Calculation of pressurization time

[0027] At time t = 0, Al and Ti are symmetrically distributed around z = 30 Å. Over time, Al and Ti atoms gradually expand toward z = 0. The maximum distances that Al and Ti atoms can expand are recorded and the difference is calculated to obtain the width of the diffusion layer. The width of the diffusion layer increases with time. The Al diffusion width fluctuates around 11 Å, while the Ti diffusion width increases with time, indicating that Al diffusion is less affected by time. During interfacial migration, the primary mechanism of atomic diffusion is vacancy migration. According to the potential function presented in this article, the vacancy formation energy and vacancy migration energy for Al are 0.71 and 0.65 eV, respectively, while those for Ti are 1.83 and 0.80 eV. Therefore, Al diffuses faster than Ti. The increase in the width of the diffusion layer over time is primarily due to the diffusion of Ti atoms. This is shown by the temporal variation of the mean square displacement (MSD) of the atomic group in the diffusion direction z. In the 0-16.8 ps time window, the MSD behaves as a quadratic function of time t, indicating that the atoms are primarily moving in a ballistic manner. Subsequently, the MSD behaves as a linear function of t, indicating that the atomic motion shifts from ballistic to diffusive. This is a brief period of rapid diffusion, followed by a phase of slow expansion. In practice, a pressurization time of 15-20 minutes is sufficient to achieve full atomic contact between the two interfaces and form solid-state bonding of the metal atoms.

[0028] 2. Calculation of pressurization temperature

[0029] Creep Ti-Al calculations were performed at 700K, 800K, and 900K to investigate the effect of temperature on creep diffusion. All simulations were performed at zero pressure to minimize pressure interference with atomic diffusion, and the duration was 200 ps. Atomic diffusion intensifies with increasing temperature. At the same time, the diffusion width increases with increasing temperature, and the temperature increase significantly enhances the diffusion of Ti atoms compared to Al. This is because the additional energy provided by the temperature increase helps more Ti atoms cross the vacancy barriers. Furthermore, Ti's HCP structure makes it difficult for Al atoms to diffuse into it. The key to creep compression is ensuring that the interfacial shear pressure on the surfaces of the two composite metals reaches the plastic creep pressure of the base metal at a certain temperature. Because the two composite metals have different melting points (Tm), the metal with the lower melting point is used as a reference when determining the heat treatment temperature. The selected heat treatment temperature should also be within the creep temperature range of the metal with the higher melting point. First, the heat treatment temperature must be greater than the melting points of the two metals to be composited; second, if the melting points of the two metals to be composited differ greatly, the heat treatment temperature can be controlled to (0.6~0.8)Tm; if the melting points of the two metals to be composited differ slightly, the heat treatment temperature can be (0.3~0.5)Tm.

[0030] 3. Calculation of pressurized pressure

[0031] The creep compaction process requires a certain force to be applied to the composite plate to achieve atomic spacing. Another question of concern is whether this pressure affects interfacial recombination. To this end, based on the above model, we relaxed the model within the aforementioned temperature range by varying the pressure of the NPT ensemble, with pressures ranging from 0, 0.2, 0.4, 0.6, 0.8, and 1 bar. At the same temperature, the diffusion widths of Al, Ti, and the total diffusion width change with pressure. For example, at 700K, as the pressure increases from 0 to 1.2 bar, the diffusion width of Al increases from 8.5215 Å to 13.1683 Å. The behavior of Ti is more complex, reaching an optimal diffusion width of 8.5739 Å at 0.6 bar with increasing pressure, followed by a decrease in the diffusion width. With increasing external pressure, the diffusion width initially increases and then decreases. The maximum diffusion width occurs at 0.6 bar at 700K, 750K, 850K, and 900K, and at 0.8 bar at 800K. A certain pressure can promote diffusion between interfaces, but when the given pressure is too high, the mobility of atoms will be restricted, resulting in a reduction in the diffusion width. Therefore, during the creep process, applying a certain amount of pressure will promote the bonding of the composite plates. This pressure range is about 0.6-0.8 bar, which is more suitable for Ti-Al creep composites. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a structural schematic diagram of the present invention;

[0033] Figure 2 An exploded view of the present invention;

[0034] Figure 3 is a side sectional view of the device body of the present invention;

[0035] Figure 4 It is the front view of the present invention.

[0036] Figure markings: 1-pressurizing device; 2-piston; 3-fixing bolt; 4-support column; 5-base; 6-connecting bolt; 7-cover plate; 8-pressurizing partition; 9-heating element; 10-equipment door; 11-thermal insulation material; 12-connecting hinge; 13-working area; 14-guide column; 15-equipment body; 16-pressure head; 17-press; 18-connecting thread; 19-guide hole; 20-connecting hinge; 21-temperature sensor; 22-cable; 23-console; 24-display; 25-control button; 26-high-pressure conduit; 27-low-pressure conduit. DETAILED DESCRIPTION

[0037] Example 1: TA1-5083-TA1 vacuum creep pressing. Dimensions: 900mm×1800mm×(2+20+2)mm per piece. The main implementation methods are as follows:

[0038] The present invention provides an integrated creep pressing device for manufacturing metal layered composite materials. The device body 15 can heat, insulate, and pressurize a blank. The maximum temperature is 1500°C and the maximum pressure is 10 MPa. The integrated device is used for creep pressing of layered metal composite materials.

[0039] The pressurizing device 1 is secured to the upper portion of the device body 15 via support columns 4. A press 17 is located above the pressurizing device 1. This press 17 can be a conventional oil, water, or other press. A piston at the bottom of the pressurizing device 1 extends through a through-hole in the center of the cover plate 7 to the device body 15 and is bolted to a pressure head 16 in the device body 15. This pressure head 16 is welded to the uppermost pressure diaphragm 8.

[0040] Furthermore, the device body 15 includes six pressurized partitions 8, five working areas 13 and eight guide columns 14, a heating element 18 evenly distributed on the inner surface of the device, a temperature sensor 21, a pressurizing device pressure head 16, and the gap between two adjacent pressurized partitions 8 is the working area 13. The pressurized partition 8 is provided with a guide hole 19, and the pressurized partition 8 is installed on the guide column 14 through the guide hole 19 so that the pressurized partition can only move up and down. The device body of the invention includes several working areas 13, the size of the working area is 1000㎜×2000㎜×(0㎜~300㎜), and five blanks can be processed at the same time. The intervals between the pressurized partitions can also be set to accommodate blanks of various thicknesses to be processed.

[0041] Furthermore, a heat-insulating material 11 is provided on the inner surface of the device door 10. During the creep process, the device door 10 is closed and locked by connecting the hinges 12, and the heat-insulating material can achieve the effect of heat preservation and insulation.

[0042] During operation, open the device door 10 and place the pre-processed TA1-5083-TA1 blank in the work area. Close the device door 10, power on the system, and control the heating element 9 to heat the blank through the control console 23. According to the feedback from the temperature sensor 21, when the internal temperature of the equipment reaches the expected value of 550°C, the heat generated by the heating element 9 decreases, so that the inside of the equipment remains at around 550°C. Keep the blank warm for 2 hours to fully heat the inside of the blank. After the blank is fully heated, start the press 17 through the control console, and drive the pressure head 16 to apply downward pressure at a pressure of 0.5-1 bar. According to the feedback from the pressure sensor, the control console 23 controls and maintains the pressure constant according to the set pressure. At the same time, the heating element continues to heat to maintain the expected temperature. After 1 hour of heat preservation and pressure maintenance, the blank achieves the expected bonding effect.

[0043] Example 2: Vacuum creep of TA1-A3 steel. Five pieces with dimensions of 800mm×900mm×(2+20)mm are used. The main implementation methods are as follows:

[0044] Following the procedures of Example 1, five pre-processed TA1-A3 steel billets were placed simultaneously, one in each work area. Heater 9 heated the billets until they reached the desired temperature of 850°C, allowing them to fully heat internally for two hours. Pressurizing device 1 then applied pressure to the billets, maintaining a constant pressure of 1-1.5 bar. The heaters simultaneously heated the billets to maintain a constant temperature. The heat and pressure were maintained for 1.5 hours.

[0045] The above descriptions are merely embodiments of the present invention and are not intended to limit the scope of patent protection of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention's description and drawings, or directly or indirectly applied in other related technical fields, are also included in the scope of patent protection of the present invention.

Claims

1. A creep pressing manufacturing device for heterogeneous metal layered composite materials, characterized in that: The invention comprises an equipment body and a control system; the equipment body comprises an equipment shell, a cover plate and a pressurizing device; a heating body, a guide column, a temperature sensor, at least three pressurizing partitions and a working area between the pressurizing partitions are arranged inside the equipment body; the control system comprises a motor, a hydraulic pump, an electromagnetic reversing valve, a pressure sensor and a control circuit; the control system calculates the heating temperature, pressurizing pressure and pressurizing time of the blanks through molecular dynamics, and performs the following process control: the metal blanks to be composited after the blanks are assembled and sealed are placed in the working area; the working area has a size of 1000mm×2000mm and is used to accommodate the metal blanks to be composited after the blanks are assembled and sealed; the control system is controlled according to the molecular dynamics calculation results Heating temperature, pressurizing pressure and pressurizing time: The heating temperature is dynamically matched according to the melting point difference ΔTm of the two metals to be compounded: when ΔTm>300℃, the temperature is 0.6-0.8 times the melting point of the low-melting-point metal (0.6-0.8Tm); when ΔTm<300℃, the temperature is 0.3-0.5 times the melting point of the low-melting-point metal (0.3-0.5Tm); the pressurizing pressure is controlled in the range of 0.6-5bar; the pressurizing time is controlled in 15-20 minutes; the heating body and the insulation layer set on three sides of the equipment body work together, with a maximum temperature of 1500℃ and a temperature control accuracy of ±3℃; the piston stroke of the pressurizing device is 600mm, and the maximum pressurizing pressure is 10MPa.

2. The device according to claim 1, characterized in that The molecular dynamics parameter calculation optimization was performed in the following order: a 12 nm × 12 nm × 6 nm metal atomic model was constructed using the LAMMPS software, using the Zope-Mishin EAM potential function; relaxation simulation of the diffusion behavior at the dissimilar metal interface was performed under the NPT ensemble; The change of atomic diffusion width over time is calculated to distinguish the 0-16.8ps ballistic motion stage and the diffusion stage; the optimal pressurization pressure is determined based on the diffusion width peak, and the heating temperature parameter is output based on the melting point difference ΔTm of the two metals to be composited.

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