Aluminum alloy hull solidification die forging method

Abstract

The present invention relates to a method for forming an aluminum alloy hull by die forging, and the steps are as follows: heating the metal ingot: heating the aluminum alloy ingot that meets the requirements of the hull after inspection to 660-760°C to make a molten metal and put it into an automatic pouring system; pouring: pouring the treated molten metal at a temperature of 700-760°C into the lower mold cavity of the mold in a quantitative manner; mold closing and filling: the hydraulic system drives the movable beam of the hydraulic press at a speed of 30-40mm / s to drive the upper mold of the mold connected thereto to perform pressure filling, and the filling tonnage is 1 / 10 of the tonnage of the hydraulic press; cooling and upsetting: when the workpiece is cooled to a semi-solid state, the hydraulic press upsetting cylinder drives the hydraulic press force amplification mechanism to drive the upper mold of the mold to perform full tonnage upsetting pressing; and opening the mold to take the material. The aluminum alloy hull die forging forming method of the present invention adopts the integrated forming of the hull and the internal rib plate, the welding quality is easy to control, the process is simplified, the cost is low, and the product qualification rate is high.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum alloy hull manufacturing, in particular to an aluminum alloy hull press-forging method for integrally forming a hull with complex curved surfaces and internal ribs by press-forging. Background Art

[0002] In recent years, orders for yachts, fishing boats, etc. have hit new highs as consumer demand has surged. Coupled with favorable factors such as policy support from various countries and economic growth in recent years, the development of the yacht market industry has shown a favorable prospect.

[0003] The hull is an important structural part of the ship and is the key to ensuring the safe navigation of the ship. During the navigation process, the hull is mainly subjected to the total longitudinal bending force, transverse load and other local forces. Therefore, the hull needs to be able to resist various external forces without causing serious deformation or damage, and it also needs to be watertight.

[0004] Currently, yacht hulls are mostly made of fiberglass or aluminum alloy. FRP has high hardness and wear resistance, good corrosion resistance, but poor rigidity, shear resistance, and weak aging resistance. Its strength will drop greatly under long-term high temperature conditions. Yachts need to be exposed to the sea for a long time, and their strength performance and the service life of the hull will be affected; aluminum alloy boats are lighter, 25% lighter than fiberglass boats of the same style, and save more than 20% fuel consumption; they are not afraid of minor bumps, and dents will occur after bumps, but there will be no water leakage because aluminum alloy is more resistant; its corrosion resistance is better, and its strength is higher than steel. Its service life can be more than 20 years, and it can be recycled and reused.

[0005] Due to the complex curved surface of the hull, there are a lot of reinforcing ribs inside (see Figure 1 ), conventional methods cannot be integrated into one, and currently the main method used is assembly welding: the aluminum plates are cut according to the requirements and assembled and welded. In order to reduce welding deformation, a large number of extruded materials in various forms and large-size integral wall panels are used; MIG welding with small line energy is used and corrected after welding. However, aluminum alloy has a large linear expansion coefficient and strong thermal conductivity, which is prone to welding deformation, easily produces defective products, and the quality of the weld is not easy to guarantee. Therefore, there are extremely strong requirements for welding methods and processes, as well as the control of welding deformation. During the hull's navigation, the assembled and welded hull is prone to cracking under complex forces and seawater corrosion, causing water leakage, and cannot guarantee the hull's watertightness and navigation safety. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide an integrated forming method for aluminum alloy hull press forging, thereby ensuring the strength, linearity, watertightness and integrated forming of the aluminum alloy hull with complex curved surfaces and internal ribs, improving the product qualification rate and simplifying the process.

[0007] The present invention solves the technical problem by the following technical solutions:

[0008] A method for forming an aluminum alloy hull by press die forging, comprising the following steps:

[0009] 1) Heating of metal ingots: Heat the 5083 aluminum alloy ingots that have been tested and meet the requirements of the hull to 660-760℃ to make molten metal, add 0.15% of a modifier containing metallic rhenium, and place the treated molten metal into the automatic pouring system;

[0010] 2) Pouring: The automatic pouring system pours the processed molten metal at a temperature of 700-760°C into the mold cavity below the mold in a quantitative manner;

[0011] 3) Mold closing and filling: The hydraulic system drives the movable beam of the hydraulic press at a speed of 30-40mm / s, driving the upper mold of the mold connected to it for pressure filling. The filling tonnage is 1 / 10 of the tonnage of the hydraulic press;

[0012] 4) Cooling upsetting: When the workpiece is cooled to a semi-solid state, the hydraulic press upsetting cylinder drives the hydraulic press force-enhancing mechanism to drive the upper die of the die to perform full-tonnage upsetting pressing. The upsetting speed is 0.5-1mm / s, the upsetting time is 8-16S, and the pressure is maintained for about 8-10S;

[0013] 5) Mold opening and material collection: The mold is opened, the hydraulic press material receiving trolley moves into the equipment, and the ejector cylinder in the hydraulic press ejector cylinder mounting plate knocks the workpiece hanging on the upper mold of the mold onto the material receiving trolley. The material receiving trolley moves out of the equipment, and the sling takes the workpiece away;

[0014] 6) Post-forging processing: Perform other finishing processes on the workpiece as required to produce the aluminum alloy hull.

[0015] Moreover, during the mold closing and filling process of step 3), the molten metal in the lower mold cavity of the mold is filled with the upper mold of the mold for 20-25 seconds. The mold closing and filling is stopped at a position 1.01 times the height of the workpiece to wait for the molten metal to solidify. In the cooling and upsetting step of step 4), the upsetting pressing stroke is 1% of the final height of the forged workpiece until the mold is completely closed.

[0016] Moreover, during the mold closing and filling process of step 3), direct compression solidification is used for mold closing and filling. The metal melt flow rate of the cavity of the lower mold of the mold needs to be maintained below 0.1m / s according to the wall thickness and length of the aluminum alloy hull, and the speed of the movable beam of the hydraulic press needs to be maintained at 30-40mm / s.

[0017] Furthermore, in the step 5), the friction force of the upper die of the mold on the workpiece is greater than the friction force of the lower die of the mold on the workpiece, so that after the mold is opened, the workpiece rises with the upper die of the mold.

[0018] The advantages and beneficial effects of the present invention are:

[0019] 1. In the aluminum alloy hull press die forging forming method of the present invention, a modifier containing 0.15% metallic rhenium is added to the molten metal to remove alloy impurities and refine the alloy structure.

[0020] 2. The aluminum alloy hull press die forging forming method of the present invention controls the liquid filling pressure and speed to ensure that no pores are formed in the product and the internal quality of the product is guaranteed.

[0021] 3. The aluminum alloy hull pressure forging forming method of the present invention adopts direct pressure forging, and the pressure directly acts on the entire liquid surface to improve the quality of the product.

[0022] 4. The aluminum alloy hull press-forming method of the present invention semi-solidifies and upsets the workpiece under high specific pressure to ensure that the workpiece does not produce shrinkage and shrinkage cavities.

[0023] 5. In the aluminum alloy hull press-forging forming method of the present invention, the friction forces of the upper and lower dies on the workpiece are different, so that the workpiece remains in the upper die, solving the problem of difficulty in sealing liquid in the reserved punching holes in the lower die.

[0024] 6. The aluminum alloy hull press-forging forming method of the present invention adopts the integrated forming of the hull and the internal rib plate, which does not cause the problems of difficult welding and poor control of welding quality caused by welding methods, simplifies the process, reduces costs, and improves the product qualification rate.

[0025] 7. The aluminum alloy hull die forging forming method of the present invention enables the complex curved surfaces and internal ribs of the hull to be formed in an integrated manner. A modifier containing metallic rhenium is added to the molten metal to remove alloy impurities and refine the alloy structure; the liquid filling pressure and speed are controlled to ensure that no pores are formed in the product and the internal quality of the product is guaranteed; direct die forging is adopted, and the pressure directly acts on the entire liquid surface to improve the quality of the product; semi-solidified upset forging of the product under high specific pressure ensures that the product does not produce shrinkage and shrinkage cavities; the upper and lower dies have different friction forces on the product, so that the product remains in the upper die, solving the problem of difficulty in sealing the punching holes reserved in the lower die. The above method ensures the strength, linearity, water tightness and integrated forming of the hull, does not cause problems caused by welding methods, simplifies the process, reduces costs, and improves the product qualification rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a structural diagram of the aluminum alloy yacht hull of the present invention;

[0027] Figure 2 It is a schematic diagram of the upper mold of the mold of the present invention;

[0028] Figure 3 It is a schematic diagram of the lower mold of the mold of the present invention;

[0029] Figure 4It is a schematic diagram of the structure of the hydraulic press of the present invention.

[0030] Description of Figure Numbers

[0031] 1. Aluminum alloy hull; 2. Upper mold; 3. Lower mold; 4. Crossbeam; 5. Hydraulic press support; 6. Hydraulic press force amplification mechanism; 7. Hydraulic press movable beam; 8. Hydraulic press material receiving trolley; 9. Hydraulic press ejector cylinder mounting plate; 10. Hydraulic press lower crossbeam; 11. Hydraulic press movable workbench; 12. Hydraulic press tie rod and lock nut; 13. Hydraulic press upsetting cylinder. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below through specific examples. The following examples are only illustrative and not restrictive, and the protection scope of the present invention cannot be limited thereto.

[0033] A method for forming an aluminum alloy hull by press die forging, the method comprising the following steps:

[0034] (1) Heating of metal ingots: Heat the 5083 aluminum alloy ingots that have been tested and meet the requirements of the hull to 660-760℃ to make a molten metal, add 0.15% of metal rhenium modifier, and put the treated molten metal into the pouring system. 5083 aluminum alloy is a high-magnesium alloy with good strength and corrosion resistance; good machinability and good arc welding performance. Adding 0.15% of metal rhenium modifier can remove harmful impurities in the molten metal. Rhenium forms binary compounds with low melting point harmful impurities. These compounds have the characteristics of high melting point, low density and stable chemical properties. They can float to slag and be removed, thereby purifying the molten metal; they can produce a metamorphic effect. The atomic radius of rhenium is larger than that of aluminum atoms, and its properties are relatively active. When melted in aluminum liquid, it can fill the surface defects of the alloy phase, reduce the surface tension at the interface between the new and old phases, increase the growth rate of the crystal nucleus, and at the same time form a surface active film between the grains and the molten liquid to prevent the generated grains from growing and refine the alloy structure.

[0035] (2) Pouring: The automatic pouring system pours the processed molten metal at a temperature of 700-760℃ into the cavity of the lower mold 3 of the mold in a quantitative manner. The upper mold 2 and the lower mold 3 of the mold are equipped with electric heating tubes, water cooling plates and heat insulation plates. The electric heating tubes heat evenly to keep the temperature of the upper mold and the lower mold at 350℃-370℃. The preheating temperature of the molten metal and the upper mold 2 and the lower mold 3 of the mold should be kept at the set temperature. Due to the large filling area of ​​the aluminum alloy hull and the many internal ribs, the temperature of the molten metal drops too quickly, which will cause cold shut defects during the filling process. The function of the water cooling plate is to ensure that the heat of the upper mold 2 and the lower mold 3 of the mold is not transferred to the hydraulic press, so as to prevent the hydraulic press drive cylinder seal from overheating and damage. The function of the heat insulation plate is to add a layer of mica plate between the upper mold 2, the lower mold 3 of the mold and the water cooling plate, so that the electric heating and water circulation cooling of the upper mold 2 and the lower mold 3 of the mold do not affect each other and cause energy waste. The upper mold 2 and the lower mold 3 are made of H13 hot working mold steel, which has excellent thermal crack resistance, high temperature softening resistance, and wear resistance.

[0036] (3) Mold closing and filling: The lower mold 3 and the upper mold 2 are connected to the hydraulic press movable worktable 11 and the hydraulic press movable beam 7 respectively by T-bolts. The hydraulic system drives the hydraulic press movable beam 7 at a speed of 30-40 mm / s, driving the upper mold 2 connected to it for pressure filling. The filling tonnage is 1 / 10 of the hydraulic press tonnage (the product of the liquid specific pressure 15 MPa and the projected area of ​​the workpiece). The molten metal in the mold cavity of the lower mold 3 is filled under the action of the upper mold 2, and the filling time is 20-25 seconds. The mold closing and filling is stopped at a position 1.01 times the height of the workpiece to wait for the molten metal to solidify. The flow rate of the molten metal in the mold cavity under the direct pressing method needs to be kept below 0.1 m / s according to the wall thickness and length of the hull, so the speed of the hydraulic press movable beam 7 should be kept at 30-40 mm / s. The filling speed should not be too fast or too slow. If the filling speed is too fast, it is easy to cause turbulence and form air entrapment; if the filling speed is too slow, it is easy to cause incomplete filling. Direct die forging is to apply pressure directly to the entire surface of the liquid metal, which can obtain an internal quality close to that of the forging; indirect die forging, the pressure acts indirectly on the liquid metal through the runner, and the internal quality is lower than that of the direct die forging. The parts currently using die forging technology are basically made by indirect die forging;

[0037] (4) Cooling upset forging: After the workpiece is cooled to a semi-solid state, the hydraulic press upset cylinder 13 drives the hydraulic press force-enhancing mechanism 6 to perform full tonnage (the product of the liquid specific pressure of 150 MPa and the projected area of ​​the workpiece) upset forging, with an upset speed of 0.5-1 mm / s, and a stroke of 1% of the final height of the forged workpiece until the die is fully closed. The upset time is 8-16 seconds, and the pressure is maintained for about 8-10 seconds. The hydraulic press upper beam 4, the hydraulic press support 5, the hydraulic press tie rod and lock nut 12, and the hydraulic press lower beam 10 form a closed force frame to withstand full tonnage die closing. The hydraulic press force-enhancing mechanism 6 adopts multi-link fulcrum force-enhancing technology. Compared with the traditional hydraulic cylinder directly driving the hydraulic press, the hydraulic press can reduce the cylinder tonnage and the size of the hydraulic press frame through the connecting rod force-enhancing, thereby reducing the equipment investment of the hydraulic press. 1% of the height of the upset forged part in the semi-solid state is to ensure the plasticizing effect at a high liquid specific pressure (150MPa). The microstructure of the semi-solid melt is a mixture of a solid phase with greater rigidity and a liquid phase with better rheology. The pressure die forging is always under pressure. When the liquid solidifies, the existence form of the liquid phase in the semi-solid melt gradually changes from a continuous phase to an isolated phase as the solidification process proceeds. When the liquid phase is a continuous phase, under the action of pressure, the shrinkage site will be supplemented by the flow of the liquid phase of the adjacent site with a relatively high temperature, and no shrinkage cavity will appear. When the liquid phase enclosed by the solid phase is not connected, the use of a high liquid specific pressure (150MPa) can cause the solid phases in contact with each other to undergo overall rheology. The shrinkage of this dispersed liquid can be supplemented by the rheology of the adjacent solid phase, thereby solving the problem of shrinkage cavity. After the upsetting is completed, the pressure is maintained for 8-10 seconds to ensure the plasticizing effect. If the pressure holding time is too short, the pressure will be released when the core of the workpiece is not completely solidified, and the core will not be able to obtain pressure compensation, resulting in defects such as residual shrinkage or shrinkage holes, and uneven metal structure; if the pressure holding time is too long, the temperature of the workpiece is low, the linear shrinkage increases, and the internal stress of the workpiece itself is bound to increase, making it difficult to demold the workpiece. The calculation of the solidification time of the metal solution is equal to the square of the quotient of the equivalent thickness of the workpiece divided by the metal solidification coefficient. The solidification coefficient of aluminum alloy is 2.8-3.0cm / min1 / 2;

[0038] (5) Mold opening and material removal: The mold is opened, and the hydraulic press material receiving trolley 8 is moved into the equipment. The ejector cylinder in the hydraulic press ejector cylinder mounting plate 9 knocks the workpiece hanging on the upper mold 2 onto the material receiving trolley. The material receiving trolley is moved out of the equipment, and the workpiece is manually removed using a sling. The hydraulic press mobile workbench 11 is used to remove the mold when replacing the mold and repairing the mold. The mold design makes the friction force of the upper mold on the workpiece greater than the friction force of the lower mold on the workpiece. After the pressing is completed, the workpiece remains in the upper mold, solving the problem of difficulty in sealing the liquid caused by the reserved punching hole in the lower mold;

[0039] (6) Post-forging processing: Aluminum alloy hull 1 is processed as required, such as Figure 1 As shown, perform other finishing.

[0040] The aluminum alloy hull pressure forging forming method of this project enables the complex curved surfaces and internal ribs of the hull to be formed in one piece. Adding a modifier containing metallic rhenium to the molten metal can remove alloy impurities and refine the alloy structure; controlling the liquid filling pressure and speed to ensure that the parts do not form pores and ensure the internal quality of the parts; using direct pressure forging, the pressure directly acts on the entire liquid surface to improve the quality of the parts; semi-solidified upsetting of the parts under high specific pressure to ensure that the parts do not produce shrinkage and shrinkage holes; the friction between the upper and lower dies on the parts is different, so that the parts remain in the upper die, solving the problem of difficulty in sealing the reserved punching holes in the lower die. The above methods ensure the strength, linearity, watertightness and integrated forming of the hull. There will be no problems caused by welding methods, which simplifies the process, reduces costs and improves the product qualification rate.

[0041] Although the embodiments and drawings of the present invention are disclosed for illustrative purposes, those skilled in the art will appreciate that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments and drawings.

Claims

1. A method for forming an aluminum alloy hull by solidifying die forging, characterized in that: The steps include: 1) Heating of metal ingots: Heat the 5083 aluminum alloy ingots that have been tested and meet the requirements of the hull to 660-760℃ to make molten metal, add 0.15% of a modifier containing metallic rhenium, and place the treated molten metal into the automatic pouring system; 2) Pouring: The automatic pouring system pours the processed molten metal at a temperature of 700-760°C into the cavity of the lower mold (3). 3) Mold closing and filling: The hydraulic system drives the movable beam (7) of the hydraulic press at a speed of 30-40 mm / s, driving the upper mold (2) connected to it to perform pressure filling. The filling tonnage is 1 / 10 of the tonnage of the hydraulic press; 4) Cooling upsetting: After the workpiece is cooled to a semi-solid state, the hydraulic press upsetting cylinder (13) drives the hydraulic press force amplification mechanism (6) to drive the upper die (2) to perform full-tonnage upsetting pressing, the upsetting speed is 0.5-1 mm / s, the upsetting time is 8-16 seconds, and the pressure is maintained for 8-10 seconds; 5) Mold opening and material collection: The mold is opened, the hydraulic press material receiving trolley (8) is moved into the equipment, and the ejector cylinder in the hydraulic press ejector cylinder mounting plate (9) knocks the workpiece hanging on the mold upper mold (2) onto the material receiving trolley, and the material receiving trolley is moved out of the equipment, and the lifting device takes the workpiece away; 6) Post-forging processing: Perform other finishing processes on the workpiece as required to produce the aluminum alloy hull; During the mold closing and filling process of step 3), the metal liquid in the mold cavity of the lower mold (3) is filled by the upper mold (2) for 20-25 seconds. The mold closing and filling is stopped at a position 1.01 times the height of the workpiece to wait for the metal liquid to solidify. In the cooling and upsetting step of step 4), the upsetting pressing stroke is 1% of the final height of the forged workpiece until the mold is completely closed. During the mold closing and filling process of step 3), the mold closing and filling is carried out by direct pressing and solidification. The metal melt flow rate of the cavity of the lower mold of the mold needs to be kept below 0.1m / s according to the wall thickness and length of the aluminum alloy hull, and the speed of the hydraulic press movable beam (7) needs to be kept at 30-40mm / s.

2. The aluminum alloy hull press die forging method according to claim 1, characterized in that: In the step 5), the friction force of the upper die (2) on the workpiece is greater than the friction force of the lower die (3) on the workpiece, so that after the mold is opened, the workpiece rises with the upper die.

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