Method for manufacturing aluminum alloy and composite material thereof through additional ultrasonic vibration assisted pulse current arc wire feeding

Abstract

The invention discloses a method for manufacturing an aluminum alloy and a composite material thereof through additional ultrasonic vibration assisted pulse current electric arc wire feeding, and belongs to the technical field of electric arc additive preparation of aluminum alloys and aluminum alloy composite materials. The technical problems that an existing aluminum alloy electric arc additive structure is thick and large, air holes are many, and the deposition quality is poor are solved. The method comprises the following steps: pre-treating a substrate and a welding wire; an ultrasonic vibration head is arranged on a base plate, ultrasonic equipment vibrates in the z-axis direction under protective gas, and meanwhile welding wires are stacked layer by layer in a certain direction on the x-y plane through electric arc wire feeding; and then solid solution treatment, water quenching and aging treatment are sequentially carried out, and the process is completed. In the printing process, the current pulse and the ultrasonic vibration are applied at the same time, the stirring effect on the molten pool is formed, dendritic crystal breaking is promoted, the solidified grain structure is obviously refined, meanwhile, the defects such as air holes are reduced, and the mechanical property of the product is improved. The machining method is used for machining the large-size thin-wall cylinder part.

Description

Technical Field

[0001] The present invention belongs to the technical field of arc additive manufacturing of aluminum alloys and aluminum alloy composite materials, and specifically relates to a method for manufacturing aluminum alloys and their composite materials by pulse current arc wire feeding assisted by external ultrasonic vibration, which is particularly suitable for the processing of large-sized thin-walled cylinders. Background Art

[0002] Aluminum alloys and aluminum alloy composites have excellent properties such as low density, high strength, good corrosion resistance and good weldability, and are widely used in aviation, aerospace, electronics, machinery and other fields. Large-sized thin-walled cylindrical products have always been a manufacturing difficulty in this field. Traditional methods such as precision casting, plastic forming, welding and connection have problems such as low manufacturing efficiency, long cycle and high cost. High-efficiency and low-cost additive manufacturing technology has become a research hotspot today.

[0003] Arc wire feeding additive manufacturing technology uses an electric arc as a heat source and aluminum alloy or aluminum alloy composite millimeter diameter wire (generally 1.2-1.5mm in diameter) as an electrode. The robot arm moves precisely to manufacture complex shaped products according to the product shape requirements. Due to the large heat input of the arc, the liquid aluminum alloy stays for a long time under high temperature conditions and the solidification rate of the molten pool is slow, which can easily lead to problems such as coarse metal grains and poor product precision after solidification, thereby reducing the mechanical properties and forming accuracy of the product. How to optimize the arc additive technology of aluminum alloys has become a key issue restricting the application of this technology. Summary of the invention

[0004] The present invention aims at the technical problems of the existing aluminum alloy arc additives such as coarse structure, many pores, and poor deposition quality; a method for manufacturing aluminum alloy and its composite material by adding ultrasonic vibration-assisted pulse current arc wire feeding is proposed; the method of the present invention adopts ultrasonic vibration-assisted current pulse arc additive method to improve the microstructure and performance of the additive aluminum alloy, refine the aluminum alloy structure, reduce defects, and finally obtain arc additive aluminum alloy materials and composite materials with better performance through heat treatment, and large-sized thin-walled cylinders can be obtained. Taking 4-series aluminum silicon alloy as an example, a dense aluminum silicon alloy with few defects and fine structure is prepared to improve its mechanical properties. At the same time, this method is also applicable to other grades such as 2-series and 5-series aluminum alloy materials and aluminum-based composite materials with added ceramic phases such as TiB2 and SiC.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] The object of the present invention is to provide a method for welding aluminum alloy and its composite materials by arc wire feeding assisted by external ultrasonic vibration, characterized in that it comprises the following steps:

[0007] Step 1: remove the oxide film on the surface of the substrate, then clean the substrate and welding wire with acetone, and vacuum dry;

[0008] Step 2: The ultrasonic vibration head is set on the substrate. Under the protective gas, the ultrasonic device vibrates in the z-axis direction, and the arc wire is fed to stack the welding wire layer by layer in a certain direction on the xy plane;

[0009] Step 3: Then carry out solution treatment, water quenching and aging treatment in sequence to complete the process.

[0010] It is further defined that the material of the welding wire is 4-series aluminum-silicon alloy, 2-series aluminum alloy, 5-series aluminum alloy, or aluminum-based composite material with added ceramic phase, wherein the ceramic phase is one or more of TiB2, SiC, and TiC.

[0011] It is further defined that in step 1, vacuum drying is performed at 100° C.-150° C. for 6 h-10 h.

[0012] It is further defined that in step one, the diameter of the welding wire is 1.2 mm.

[0013] It is further defined that in step 2, the diameter of the ultrasonic vibration head is 55 mm.

[0014] It is further defined that in step 2, the protective gas is Ar+20 vol% CO2 (ie, CO2 accounts for 20% of the total volume of Ar and CO2 gases), and the gas flow rate is 10 L / min-20 L / min.

[0015] Further defined, the process parameters of step 2 are: welding gun speed is 30mm / min-50mm / min, pulse voltage is up to 21V-22V, pulse time is 2.0ms-3.2ms, pulse current is up to 235A-238A, SKS base current is 26A-32A, base current time is 3.0ms-3.2ms; arc starting current is 80A-90A, arc ending current is 60A-70A, welding current is 110A-135A, welding speed is 350mm / min-500mm / min, wire feeding speed is 5m / min-9m / min, substrate temperature is 100℃-200℃, and the welding interval time between layers is 45s-90s. Within this range, the optimal heat input of the welding process is 240-350J / mm, and the deposition morphology is the best.

[0016] It is further defined that in step three, solution treatment is performed at 500°C-520°C for 4h-6h.

[0017] It is further defined that in step three, the aging treatment is performed at 180°C-200°C for 4h-8h.

[0018] It is further defined that the welding wire of the present invention is a 4047 aluminum alloy wire, which can be prepared by the following operations: subjecting the 4047 aluminum alloy ingot to homogenization treatment at a temperature of 450-480°C for a homogenization treatment time of 6-8h, then extruding the ingot into a rod with a diameter of 10mm, and subjecting the ingot to multiple cold drawing. For each 0.4mm reduction in diameter, an intermediate annealing is performed at a temperature of 400°C-460°C for an annealing time of 2-8h, and finally drawing the wire into an aluminum-silicon alloy welding wire with a diameter of 1.2mm; wherein the Si content in the 4047 aluminum alloy ingot is 11.0%-13.0%, the Fe content is 0.8%-1.0%, the Cu content is 0.2-0.3%, the Mg content is 0.05%-0.1%, the Mn content is 0.05%-0.1%, the Zn content is 0.1%-0.2%, and the balance is Al element.

[0019] Any of the above methods is used to process large-sized thin-walled cylindrical parts.

[0020] The present application simultaneously applies current pulses and ultrasonic vibrations during the printing process to form a stirring effect on the molten pool, thereby promoting dendrite breakage, significantly refining the grain structure after solidification, reducing defects such as pores, and improving the mechanical properties of the product.

[0021] In the arc wire printing process, from the current-voltage waveform, it is mainly divided into pulse mode and constant current mode, which form pulse arc and non-pulse arc respectively. The pulse mode can achieve three types of droplets: one droplet transmitted per pulse, one droplet transmitted by multiple pulses, or multiple drops transmitted by one pulse. It is necessary to adjust the current-voltage waveform to achieve one droplet transmitted per pulse (i.e. one drop per pulse), so as to reduce droplet splashing, ensure the stability of the manufacturing process and improve the forming quality of the product. Under the same arc power, the manufacturing efficiency of the pulse mode is higher than that of the constant current mode. At the same time, it has a stirring effect on the molten pool, which can achieve the purpose of refining the structure and reducing pores.

[0022] In the process of arc additive manufacturing, ultrasonic vibration is applied to the substrate, and the ultrasonic vibration is transmitted to the molten pool through the substrate, which can also play a stirring role on the molten pool. Ultrasonic vibration can accelerate the molten pool metal to form convection movement from the solid-liquid interface to the center of the molten pool, which is beneficial to increase the cooling rate of the melt. The liquid phase maintains convection movement, and the melt solidifies rapidly along the temperature gradient direction, which is not only beneficial to refine the grains and reduce defects, but also plays a role in improving the microstructure and improving the material properties. Therefore, combining ultrasonic vibration with pulsed arc mode can further refine the aluminum alloy structure, reduce defects, and improve performance.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention adopts an ultrasonic vibration assisted current pulse arc additive method to prepare aluminum alloy materials and composite materials thereof, thereby refining the aluminum alloy structure and reducing defects, and finally obtaining arc additive aluminum alloy materials and composite materials thereof with better performance through heat treatment.

[0025] In order to further understand the features and technical contents of the present invention, please refer to the following detailed description and drawings of the present invention. However, the attached drawings are only provided for reference and illustration and are not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the ultrasonic vibration-assisted current pulse device in Example 1;

[0027] Figure 2 This is a picture of the aluminum alloy structure of ultrasonic vibration assisted current pulse arc additive in Example 1;

[0028] Figure 3 is the tensile stress-strain curve of the aluminum alloy material in Example 1;

[0029] Figure 4 This is the XRD curve of the aluminum alloy in Example 1. DETAILED DESCRIPTION

[0030] The present invention will be described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, and do not limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0031] Embodiment 1: The preparation method of ultrasonic vibration assisted current pulse arc additive aluminum alloy and its composite material in this embodiment is carried out according to the following steps:

[0032] Step 1. Pretreatment of substrate and 4047 aluminum alloy welding wire: Select 350×350mm 1060 pure aluminum as the arc additive substrate to prevent the introduction of other elements by high temperature. The aluminum alloy welding wire is ER4047 with a diameter of 1.2mm. Use an angle grinder with shutter blades to grind the aluminum alloy substrate to remove the oxide film on the surface. Then use acetone to clean the surface of the substrate and welding wire to remove the oil stains remaining on the surface of the substrate and welding wire. Finally, place the welding wire and substrate in a vacuum drying oven at 120℃ for 8h, and then take them out for subsequent arc additive manufacturing.

[0033] Step 2: The ultrasonic vibration head is set on the substrate. Under the protective gas, the ultrasonic device vibrates in the z-axis direction, and the arc wire is fed to stack the welding wire layer by layer in a certain direction on the xy plane;

[0034] Step 3: Then carry out solution treatment, water quenching and aging treatment in sequence to complete the process.

[0035] In this embodiment, the ultrasonic system is composed of an ultrasonic transducer, an horn and an ultrasonic vibration head. The ultrasonic transducer converts the input electrical power into ultrasonic waves and transmits them out. The horn is mainly used to change the resonant frequency of the vibration system. Finally, the ultrasonic waves are transmitted to the substrate through the ultrasonic vibration head. The diameter of the ultrasonic vibration head is 55mm. The power of the ultrasonic vibration device is 1000W, the output frequency is 30kHz, and the amplitude is 100μm. The ultrasonic device is fixed to the surface of the substrate with a clamp, and the ultrasonic vibration is transmitted to the molten pool through the substrate. The ultrasonic vibration is applied while the melting electrode gas shielded welding is performed to accelerate the convective movement of the molten pool metal from the solid-liquid interface to the center of the molten pool, which is beneficial to increase the cooling rate of the melt, which is not only beneficial to refine the grains and reduce defects, but also can interrupt the growing dendrites and large grains, and block the growth of columnar crystals.

[0036] In this embodiment, the current pulse mode arc additive parameters: the welding power supply can be mainly divided into pulse mode and constant current mode according to the current waveform of the process. In this process, the microMIG pulse mode is mainly used for welding tests. First, the welding gun movement speed is set to 48mm / min, and then the pulse parameters are set: the pulse voltage is up to 22V, the pulse time is 2.4ms, the pulse current is up to 238A, the SKS base current is 26A, and the base current time is 3.0ms. The pulse mode is divided into two stages. The first stage is the pulse stage, in which the welding wire is quickly melted by the pulse current. The second stage is the short-circuit stage, in which the current is reduced to the SKS base current, and the temperature of the molten pool spreads rapidly without heat input. In the pulse process, attention should be paid to the coordination of pulse voltage, current and welding speed. The increase of pulse voltage and current will lead to an increase in heat input, resulting in too fast melting of the welding wire, which has a greater impact on the welding morphology. Compared with the ordinary pulse process, this process appropriately optimizes and reduces the pulse current and voltage and adjusts the pulse time, which can better complete the transition of one pulse and one drop. The basic parameters are arc starting current 80A, arc ending current 60A, welding current 122A, welding speed 390mm / min, and wire feeding speed 9.0m / min. Finally, in order to avoid a large temperature gradient between the molten pool and the substrate and reduce the porosity, the substrate temperature is selected to be 100℃. At the same time, the welding interval time between layers is 60s, which is conducive to the cooling of the single layer. During the welding process, protective gas Ar+20vol%CO2 is introduced with a gas flow rate of 20L / min. According to this process parameter, 4047 aluminum alloy material is prepared.

[0037] 5. Heat treatment of 4047 aluminum alloy: The obtained 4047 aluminum alloy material was solution treated at 500°C in a muffle furnace for 5 hours, taken out and water quenched, and then placed in a constant temperature drying oven for aging treatment at 200°C for 6 hours.

[0038] This embodiment adopts ultrasonic vibration assisted current pulse arc additive technology to prepare 4047 aluminum alloy material. From the perspectives of process parameters, arc, weld bead control, based on the comprehensive control of welding heat input control, weld morphology control, and deposition size, the problems of coarse structure and poor deposition quality in the aluminum alloy printing process are solved, and relatively excellent mechanical properties are obtained.

[0039] Schematic diagram of ultrasonic vibration assisted current pulse arc additive device Figure 1 As shown. The arc additive remanufacturing power supply system is: SKS LSQ5 welding power supply and Power Feeder PF5 wire feeder of Sake Welding Equipment (Shanghai) Co., Ltd. In this process, the microMIG pulse mode is mainly used for welding test. The Power Feeder PF5 wire feeder has a mechanical pulling function. When matched with the welding power supply, the wire feeding speed can be quickly adjusted according to the welding current in real time, realizing the digital control of wire feeding speed and droplet transition. The instrument consists of Yaskawa MOTOMAN-AR2010 industrial robot, teaching programmer, YRC1000 control cabinet, positioner and ultrasonic system. The robot has six degrees of freedom, each axis has a servo motor, and the repeat positioning accuracy error is within ±0.08mm, which ensures the accuracy of path planning in the arc additive remanufacturing process. The ultrasonic equipment vibrates in the z-axis direction and is transmitted to the molten pool through the substrate. The welding gun accumulates layer by layer in a certain direction on the xy plane, and finally obtains the arc additive 4047 aluminum alloy material.

[0040] Ultrasonic vibration assisted pulsed current arc additive manufacturing of 4047 aluminum alloy microstructure Figure 2 As shown in the figure, in ordinary casting and arc additive aluminum-silicon alloys, due to the thermal field effect at the junction of the molten pool and the molten pool layer, the organization grows, and most of them are coarse columnar crystals. In the alloy organization prepared by ultrasonic vibration assisted current pulse technology, most of the grains are small, a small number of columnar crystals, the average grain size is 10.8μm, the organization is uniform, and there are fewer defects. In the literature "Effect of Ultrasonic Vibration on the Organization and Properties of Aluminum Alloys Made by CMT Arc Additive Manufacturing", the average grain size of ultrasonic vibration alone at an amplitude of 25μm is 15.4μm, and in the literature "Organization and Tensile Properties of 4043 Aluminum Alloy Thin-walled Parts Made by Cold Metal Transition and Pulsed Arc Additive Manufacturing", the average grain size is 20-30μm, and there are a large number of coarse columnar crystals in the organization.

[0041] 4047 aluminum alloy tensile properties Figure 3As shown, its tensile strength is between 180-210MPa, yield strength is between 100-110MPa, and elongation is 3.6%-3.8%. Reference "Effect of Additional Water Cooling on the Microstructure and Mechanical Properties of 4047 Aluminum Alloy Components Made by Arc Additive Manufacturing" has a strength higher than that of the material by 30-50MPa, and an aluminum-silicon alloy with better mechanical properties is obtained.

[0042] XRD phase analysis of 4047 aluminum alloy Figure 4 As shown, the phases in the figure are mainly Al phase and Si phase, the content of precipitated phase is very small, there is almost no peak of precipitated phase, and no impurities are introduced into the material during the welding process.

[0043] The statistics of density and porosity of printed 4047 aluminum alloy in this embodiment are shown in Table 1.

[0044] Table 1 Statistics of density and porosity of printed 4047 aluminum alloy

[0045] Number of trials M1 / g M2 / g Density / % Porosity / % 1 1.6117 0.9799 95.9 4.1 2 1.6102 0.9805 96.1 3.8 3 1.6111 0.9774 95.6 4.4

[0046] Table 1 shows the density and porosity of the samples tested using the Archimedes drainage method. The calculation formula is: where ρ s is the actual density of the sample, ρ w is the density of water, M1 is the mass of the dry sample, and M2 is the mass of the sample when it is completely immersed and there are no bubbles on the surface. The actual density is divided by the standard density to get the sample density. The porosity calculation formula is: where ρ st The standard density of aluminum alloy. (The standard density of 4047 aluminum alloy is 2.66g / cm 3 ) obtained a density of 95-96% and a porosity of 3.8-4.4%, with a lower porosity and a higher density.

[0047] The above describes the specific embodiments of the present invention. It should be noted that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various modifications or variations within the scope of the claims, which does not affect the essential content of the present invention.

Claims

1. A method for manufacturing aluminum alloy and its composite materials by applying ultrasonic vibration-assisted pulse current arc wire feeding, characterized in that: The following steps are involved: Step 1: remove the oxide film on the surface of the substrate, then clean the substrate and welding wire with acetone, and vacuum dry; Step 2: The ultrasonic vibration head is set on the substrate. Under the protective gas, the ultrasonic device vibrates in the z-axis direction, and the arc wire is fed to stack the welding wire layer by layer in a certain direction on the xy plane; Step 3: Then carry out solution treatment, water quenching and aging treatment in sequence to complete the process.

2. The method according to claim 1, characterized in that: The material of the welding wire is 4-series aluminum silicon alloy, 2-series aluminum alloy, 5-series aluminum alloy, and aluminum-based composite material with added ceramic phase, wherein the ceramic phase is one or more of TiB2, SiC, and TiC.

3. The method according to claim 1, characterized in that: Vacuum dry at 100℃-150℃ for 6h-10h.

4. The method according to claim 1, characterized in that: The wire diameter is 1.2mm.

5. The method according to claim 1, characterized in that: The diameter of the ultrasonic vibration head is 55mm.

6. The method according to claim 1, characterized in that: The method according to claim 1 is characterized in that the protective gas is Ar+20vol% (volume) CO2, and the gas flow rate is 10L / min-20L / min.

7. The method according to claim 1, characterized in that: Step 2 process parameters: welding gun movement speed is 30mm / min-50mm / min, pulse voltage is up to 21V-22V, pulse time is 2.0ms-3.2ms, pulse current is up to 235A-238A, SKS base current is 26A-32A, base current time is 3.0ms-3.2ms; arc starting current is 80A-90A, arc ending current is 60A-70A, welding current is 110A-135A, welding speed is 350mm / min-500mm / min, wire feeding speed is 5m / min-9m / min, substrate temperature is selected at 100℃-200℃, and the welding interval time between layers is 45s-90s.

8. The method according to claim 1, characterized in that: Solution treatment at 500℃-520℃ for 4h-6h.

9. The method according to claim 1, characterized in that: Aging treatment at 180℃-200℃ for 4h-8h.

10. A method as claimed in any one of claims 1 to 9 for processing large-sized thin-walled cylinders.

Images