The use of self-smelting materials to replace the pressing material processing car tanning construction skills
1 Technical Background Analysis The development of the automobile industry has brought people comfort and convenience to the automotive civilization. At the same time, it has also brought with it increasingly serious environmental problems. The World Organization for Environmental Health Cooperation and Development has pointed out that transportation tools have become one of the important sources of atmospheric pollution. According to statistics, carbon dioxide emitted by automobile exhaust gas currently accounts for 20%-30% of global carbon dioxide emissions; in some developed countries, automobile emissions have accounted for 30%-60% of atmospheric pollution. At the end of the 20th century, the energy crisis became more and more serious, which made the requirements for modern vehicles to reduce weight and save energy. The reduction in weight has become the main development direction of automobile selection. Studies abroad show that for every 100kg of vehicle mass reduction, fuel consumption per 100km can be reduced by 0.27L, and for every 10% reduction in vehicle weight, fuel efficiency can be increased by 5.5%. The developed countries continuously strengthen restrictions on vehicle energy consumption and exhaust pollution (). The automobile manufacturers are urged to pay attention to the development of lightweight vehicles. At present, European automakers have proposed an environmental protection goal to achieve a 30% reduction in the average CO2 emissions of passenger vehicles, which is equivalent to reducing the vehicle weight by half based on the current average vehicle weight. Lightweighting has become one of the major pursuits for the development of automotive technology in the future. At present, aluminum vehicles have emerged in Europe. From the aspect of driving, the acceleration of the vehicle after lightening is improved, and the stability, noise and vibration are also improved. From the safety point of view, the inertia at the time of collision is small and the braking distance is reduced. In addition, when the collision occurs, the impact of the plastic material on the person is much smaller, so it is safer. Lightweighting of automobiles, especially the use of lightweight plastic materials, has become the direction of future automotive technology development. Under this background, the number of aluminum alloy materials used in the automotive industry has increased dramatically. The application of aluminum alloy materials in the automotive industry was limited to the power system and some simple parts, such as cylinders, instrument panels, doors, and seat frames. Nowadays, the application of aluminum alloy materials in the automotive industry is almost everywhere in the car body. Parts of aluminum alloys such as Mercedes-Benz cars, BMW cars, Jaguar cars, etc. are widely used, and the Audi A2 has even achieved a full range of car body and peripheral components. Aluminum body. Aluminum alloy material applied to the automotive industry can not only achieve light weight, but also has anti-rust function; at the same time, aluminum alloy material is different from composite high-molecular organic material. The most important feature is that it can be fully recovered and reused, which is important for environmental protection and resource recycling and utilization. significance. It is precisely because of its advantages of low density, high recycling rate, good processing performance, better vibration absorption than steel, and so on. It is widely used in the automotive industry. However, the competition in the modern automobile industry is very fierce, and it will inevitably require the control of various factors such as costs. This project adopts advanced equipment and rationally utilizes the advantage of regional specific resources to develop a new process method that can provide auto parts manufacturers with high quality and low cost, effectively reducing product costs and providing automotive manufacturers with a competitive advantage. condition. 2 Technical Line Introduction 2.1 Overview of the traditional forging process for producing aluminum alloy car control arms Aluminum alloy automotive control arm traditional forging process uses extruded aluminum bar as raw material, its production process is as follows: Extrusion of aluminum alloy bar sawing, blanking, forging, machining heat treatment, the specific process is as follows: (1) Extruded extruded aluminum alloy bar saws are inspected for peeled and qualified round ingots. The main production line equipment configuration: sawing machine (with sawing, flaw detection, peeling and other functions), face milling machine and chamfering machine. (2) Homogenizing annealing of qualified round ingots; pre-forging blanks; forging billet bending; heating of blanks before forging; die forging (pre-forging and final forging); flashing, and peeling. The main equipment configuration of the production line: horizontal wedge mill, 5000 tons forging hydraulic press, 500 tons crank press, pusher type uniform annealing furnace, push rod type forging heating furnace and so on. (3) Heat treatment, machining and assembly of forgings. The main equipment configuration of the production line: heat treatment aging furnace, solid furnace, flaw detection and cleaning machine, surface treatment ultrasonic cleaning machine, and other mechanical processing equipment. 2. 2 Overview of the New Process for Producing Automotive Control Arms by Using Aluminum Alloy Continuous Cast Slabs Instead of Extruded Aluminium Alloy Bars Extruded aluminum bars are produced by hot extrusion of aluminum alloy ingots. For enterprises that have the advantages of electrolytic aluminum liquid resources, if aluminum alloy ingots are directly blended with liquid aluminum to produce extruded aluminum alloy rods, the hot extrusion process of aluminum alloy ingots will be eliminated, thereby reducing the raw material production costs. However, the aluminum alloy ingot has poorer metallographic density than the extruded aluminum alloy bar. How to produce an aluminum alloy ingot satisfying the density requirement of the metal phase becomes the core of the technical development of the project. In this project, aluminum alloy continuous casting blanks are used instead of extruded aluminum alloy bars. The scientific and rational design of the smelting casting process is first to make the difference between the aluminum alloy continuous casting blank and the extruded aluminum alloy bar as small as possible; secondly, the subsequent processing technology It is moderately strengthened to further compensate for the differences in raw materials and finally achieve the homogeneity of the products produced by the two raw materials. 2. 2. 1 Melting process The smelting process uses smelting and stirring analysis, on-line degassing refining, and filter semi-continuous casting cooling bed sawing to inspect the advanced production process of the peeled milling surface and the chamfered qualified round ingots. The production process is briefly described as follows: (1) Furnace installation : According to the grade of the alloy produced and the amount of furnace installed, the calculation of the ingredients shall be carried out according to the ingredients specifications and process requirements. Firstly put small pieces or scraps of scraps, and at the same time, put the intermediate alloy and aluminum shavings with low melting point and easy to oxidize on the bottom of the furnace. Use a 20/5t crane to hang the aluminum troughs to the furnace door of the resistance furnace, and then use a 20/5t crane. The vacuum bag is hoisted to the aluminum slot, manual manual tilting of the vacuum bag to the resistance furnace against the aluminum liquid against the aluminum slot, after the completion of the aluminum liquid, the vacuum bag and the aluminum slot are respectively lifted from the resistance furnace. After the charge is melted, the high-melting intermediate alloy and valuable metals (such as copper plates, zinc ingots, etc.) are loaded into the furnace. All the solid charge is loaded from the furnace door and the furnace door is closed. (2) Smelting: The furnace can be smelted after its completion, and the smelting process is carried out according to the technological operation procedures. During the melting process, as the temperature of the charge rises, in order to reduce the burning loss of the liquid metal in the smelting process and at the same time prevent the metal suction in the melting process, a layer of powdery coating agent should be appropriately sprinkled on the surface of the liquid metal. In the smelting process, local overheating of the melt is prevented, and the temperature in the molten pool is uniform throughout. The melt should be properly agitated to accelerate melting. (3) slag slag, stirring, sampling analysis, composition adjustment, standing: When the molten aluminum melts in the bath, when the melt temperature reaches the smelting temperature, the powder is uniformly dispersed into the melt to make the slag and the liquid metal. Separation, which is not only conducive to slag slag but also can reduce metal slag carry away the metal, then eliminate the large amount of slag floating on the surface of the melt. The slag should be stable to prevent slag from getting into the melt. The slag must be thoroughly removed. The presence of scum will increase the gas content of the melt and contaminate the metal. After the slag is removed, the magnesium ingot can be added to the melt and the powdered agent is covered to prevent magnesium from burning. Furnace melting furnace is equipped with a permanent magnet stirring device. When the furnace charging is completed, the permanent magnet stirrer is turned on to stir the furnace smelt, which is beneficial to the uniformity of temperature and composition, and is beneficial to improving the operating conditions and shortening the smelting time. After all the intermediate alloys are added, the melt is fully stirred to achieve a uniform temperature. Stirring should be carried out smoothly, with no waves of excessive stress to prevent the oxidized slag from getting into the melt. After a quick sampling analysis, the sample should be taken at one-half of the deepest part of the middle of the bath. According to the results of the composition analysis, the chemical composition of the molten aluminum is adjusted. When the rapid analysis results do not meet the alloy composition requirements, the melt should be diluted or fed. After adjustment, the melt should be stirred again. After the qualified aluminum melt in the resistance furnace settles out, the scum is pulled out, and the temperature of the aluminum solution is adjusted to the temperature required for the semi-continuous casting process to prepare for casting. (4) On-line processing: When the aluminum solution is transferred, Al-Ti-B round rods are continuously added on-line in the aluminum melt through a wire feeder to refine the grains, and further degassing and refining are further performed by the on-line degassing refining device. And filter. High purity nitrogen is used for the refining gas. The on-line refining device itself has a heating system, blowing nitrogen and filtering will not cause the temperature drop of the aluminum liquid. (5) Semi-continuous casting: According to the alloy grade and specification of the ingot produced, casting process parameters are selected. The in-line processed aluminum melt enters the mold through a diverter plate for casting; when the ingot reaches the desired length, casting is automatically stopped. Open the tilting platform of the casting platform, raise the round ingot to a proper position, and use a crane to lift the round ingot from the casting well to the ingot storage area for cooling. Then place the casting platform and prepare for the next casting. (6) Sawing: The round ingots are finished on the sawing machine, followed by round ingot cutting, tail cutting, length cutting and end printing. (7) Inspection, peeling, end milling and chamfering: inspect according to the relevant regulations or requirements of the forging workshop. The quality of the ingots in line with the technical requirements shall be removed by the on-line peeling machine to remove the oxide scales on the surface, through the face milling machine and the chamfering machine. The combined machine tool performs face milling and chamfering. The main equipments of the casting process are selected according to the principle of mature technology, reliability, guaranteeing excellent product quality, and saving engineering construction investment. Casting production equipment is equipped with: 15t rectangular resistance type aluminum liquid mixing furnace, permanent magnetic stirring device, on-line refinement and filtration device, 15t hydraulic externally guided round ingot semi-continuous casting machine, sawing machine, 1. 5t holding furnace, pouring hand, Gravity casting machine, face milling machine and chamfering machine. 2. 2. 2 after processing Forging and subsequent processing of the main process, including the workpiece forging, heat treatment, machining and assembly. The continuous casting billet in the casting workshop is flawed, peeled, sawed for the specified length of forging, and then entered the forging shop. The main processes for forging and subsequent processing are as follows: (1) Homogenization annealing. The first step in forging is to homogenize the forged billet after casting to eliminate internal segregation and casting stress of the cast billet, refine the grain, improve the forging processing state and the performance of the final product, and improve the plasticity. Follow-up forging processing. As this project is a medium-small-diameter round bar with large output and stable annealing process, the annealing furnace equipment is selected as the pusher type uniform annealing furnace. The ingot is continuously fed into the homogenization annealing furnace by the transport mechanism, and after completing the temperature increase and the heat preservation process in different sections of the furnace, it enters the cooling chamber and is cooled to room temperature at the set speed, and then the ingot is continuously cooled by the transport mechanism. Room shipped out. (2) Pre-forging blanks. The second step of forging is to forge the pre-forging billet after homogenization and annealing. Through the billet making process, the ingot is made into the required initial size and shape of the workpiece for forging to reduce the subsequent forging process. The degree of complexity and produce the least burr waste; Second, through the process of radial compression and axial extension deformation, to further improve the internal structure of the blank. The blanking equipment was selected as a horizontal wedge mill. Compared with traditional forging and blanking equipment, cross wedge rolling mill has the characteristics of high productivity, energy saving, and high product precision. It is widely used in the production of blanks for axles such as automobiles, tractors, motorcycles, and internal combustion engines, as well as precision blanking for die forgings. (3) Bend. The third step of forging is to bend the forged billet from the horizontal wedge mill according to the characteristics of the parts of the project so that the billet shape is closer to the shape of the forging and further preparations are made for the next step of die forging. . The equipment used was a 500-ton crank press. (4) Heating before forging. The fourth step of forging is forging pre-heating. Due to the narrow forging temperature range of the aluminum alloy in this project, the heating temperature is close to the overheating and over-firing temperature. Therefore, it is required that the heating furnace must maintain accurate temperature and must be forced. Recirculating air and automatic adjustment function. The equipment used is a push rod type forging furnace. (5) Pre-forging and final forging. The fifth step in forging is a key core process that places the heated blank on a hydraulic press for pre-forging and final forging. Because the part shape of this project is not complicated, the pre-forging and final forging die are set on a pair of dies, and the pre-forging and final forging are performed only once, and the pressure forming of the parts can be completed. Aluminum alloys are most suitable for forging on hydraulic presses because of the small deformation speed of the hydraulic press, smooth metal flow, uniform deformation, continuous metal fibers, less surface defects on the forgings, and relatively uniform internal structures. Therefore, the die forging equipment selected for this project is a 5,000 ton die forging hydraulic press. In order to ensure the deformation within the specified forging temperature range, to improve the uniformity of deformation, and to increase the metal's fluidity in order to fill the mold cavity with metal, we set up a mold warm-up program to preheat the mold temperature to 250 420. This project is equipped with a special die induction heating device for preheating the die forging die. When the aluminum alloy is swaged, the mold groove must be lubricated. Because of the high temperature and external force, aluminum alloy has obvious adhesion tendency to the steel mold. In order to avoid sticking and make the workpiece release smoothly, the groove of the mold must be lubricated, lubrication of the groove of the mold can also reduce the forgings. Surface defects reduce the pressure during die forging. The traditional aluminum alloy forging release agent often uses engine oil and graphite or other graphite products. In the process of use, it not only has black dust and oil fume pollution, but also has bad smell, bad operating environment, and residual lubricant is difficult to remove. Particles embedded on the surface will form stains, pitting and corrosion. The project's die forging hydraulic press is selected for environmentally friendly forging release agent. The release agent overcomes the above shortcomings. It is a water-soluble translucent liquid, it is made of special high-temperature ultra-fine lubrication transparent particles and non-ferrous metal rust inhibitor composition. Good demoulding effect, forging the surface of the workpiece is bright, easy to use, can be sprayed directly, can also be added after the appropriate amount of water spray, can replace similar imported products, and the price is low, economical and practical. (6) Finishing. The final step in forging is to remove the flash and the skin from the blank after forging to complete the entire forging process of the part. For aluminum alloys, it is not suitable to cut the burrs for a long time after forging because it may cause aging strengthening, and tears occur at the shearing edges during cutting to produce waste products. For this reason, after the forging is forged from the hydraulic press, it immediately enters the quenching tank for water cooling, so that the flash and the skin can be removed in time. In this project, a 500-ton crank press was selected for the removal of flash and skin equipment. In order to increase the productivity and reduce the labor intensity of the operator, all the processes from the casting raw materials to cutting off the flash of the forgings and the entire forging process are program control, and three robots are connected to each process equipment and process. 3 process characteristics The salient features of this project's process are: direct use of liquid metal aluminum melting and casting provided by the electrolysis workshop to produce aluminum alloy ingots instead of extruded aluminum alloy bars, eliminating the hot extrusion process of aluminum alloy ingots, thereby achieving energy saving and reducing raw material production The purpose of the cost. In the original process, the raw material was an extruded bar. In the processing process, after many times of heat deformation, the extruded structure has undergone a fundamental change, basically losing the characteristics of the extruded structure: The repeated repeated thermal deformation of as-cast microstructures breaks the large columnar grains and repeatedly deforms the microstructure of the material into uniform and fine equiaxed grains. It also enables some tiny cracks to heal. The effect of hydrostatic pressure in the stress state can promote the bubble welding, shrinkage pore compaction, loosening and densification in the as-cast microstructure, and turn into a denser structure; due to the strengthening of the high-temperature atomic heat movement ability, under stress, With the aid of free diffusion and different diffusion of atoms, the inhomogeneity of the chemical composition of the ingot is relatively reduced; through thermal deformation, the ingot structure changes into a deformed structure or a processed structure, and has a high density, uniform and fine equiaxed grains. And relatively uniform chemical composition, so the plasticity and strength indicators have significantly improved. Aluminum alloy continuous casting blanks are used instead of extruded aluminum alloy bars. In the subsequent processing, after several times of moderately intensified heating and pressure processing processes, the advantages of extruded aluminum alloy bars can be moderately strengthened. The processing, especially the heating of the last fire, has a decisive effect on the organization of the material. Therefore, it is feasible to use an aluminum alloy continuous casting blank instead of an extruded aluminum alloy bar. Based on the above factors and economic analysis, it is reasonable to make some necessary improvements to the original process. It is believed that the raw material used in the original process is not very significant for the extruded bar, and the raw material is changed to aluminum rod cast into aluminum rods. Instead of outsourcing extruded bar, it can fully meet the requirements of raw materials for products, and also meet the requirements of end users for product quality at home and abroad. 4 Technical and Innovation Points This project consists of a casting process and a follow-up process. For the smelting process, the quality difference between the aluminum alloy billet and the extruded aluminum bar should be reduced as much as possible. What is the quality of the aluminum alloy bar cast by the semi-continuous casting machine? , directly related to the success of the entire process, so we must ensure the smooth progress of the casting process, cast a qualified aluminum bar; for the subsequent processing process to moderately strengthen the process conditions, and further make up for the differences in raw material defects, the final realization of two The homogenization of products produced from various kinds of raw materials meets the requirements of various physical and mechanical properties of products and meets market demands. 5 Innovative Analysis of Melt Casting Process In order to homogenize the quality of aluminum alloy slabs, the following measures are taken: During the smelting, the furnace melt is stirred by a permanent magnet stirrer to homogenize the components and to shorten the smelting time; the wire is passed through the aluminum melt in a wire feeder. The Al-Ti-B round bars were continuously added to refine the grains and further degassed, refined and filtered by an on-line degassing refining device. 6 analysis of subsequent processing In order to further reduce the difference in defects between the extruded aluminum alloy bar and the cast aluminum alloy bar, the follow-up processing technology should be moderately strengthened, mainly reflected in the inspection of the aluminum alloy continuous casting on-line inspection, and the radial and axis of the blank. Inspect the shrinkage hole, air hole and crack less than 0.8mm, and display and alarm. At the same time, detect and alarm the layering to prevent the casting defect blank from going down; strengthen the uniform annealing to eliminate the internal organizational segregation of the cast blank. And casting stress, grain refinement; strengthen pre-forging billet, increase radial compression force and axial extension deformation force, and further improve the internal structure of the billet.
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