Aluminum and aluminum alloys are the most widely used non-ferrous metals, and their output is second only to steel. In terms of the amount of crustal deposits, it accounts for about 8.13 of the crustal mass, which is more than double the amount of iron, and more than the sum of other nonferrous metals.
Aluminum alloy characteristics
The density of aluminum alloy is only one third of that of steel (the density of aluminum alloy is 2.7g / cm3, and the density of steel is 7.85g / cm3).Custom Aluminum parts is an ideal lightweight material. It has large specific strength, large specific rigidity and high fatigue strength, so it is suitable for key load-bearing parts with high weight. Aluminum alloy has good plasticity and can be processed into various high-precision forgings with complex shapes. Aluminum forgings have good corrosion resistance, thermal conductivity and non-magnetic, which is unmatched by steel forgings.
Aluminium and aluminum Tailan are all available
Because aluminum and aluminum alloys have excellent properties, aluminum and aluminum alloys have been widely used in machinery, aviation, automobiles, railway vehicles, ships and ships, construction, bridges, chemicals, power, electronics, instruments, hardware, and household goods. field.
The replacement of some steels with aluminum alloys can greatly reduce the weight of mechanical products and increase structural stability. Therefore, aluminum and aluminum alloys are even more essential materials in aviation, aerospace and many defense industry sectors. For example, there are many aluminum alloy forgings on aircraft, and the amount of aluminum alloy used in aircraft is 15% -50%. Aluminum is widely used in construction, automobiles and packaging, and has become the three major uses of industrial developed countries today.
Aluminum alloy gong pieces develop rapidly
(1) Sichuan aluminum alloy forgings are a development trend internationally.
Because the weight reduction of automobiles is of great significance (reducing fuel consumption and reducing environmental pollution), automobile giants in Europe, America and Japan have invested a lot of manpower and financial resources to reduce the weight of cars and use aluminum alloy instead of steel to make some parts. For example, Japan invested huge manpower and material resources in the research and development of an aluminum alloy. In 2009, Japan ’s aluminum alloy forging services output was 30459t, accounting for 2.7% of the total die forgings. According to a strategy report released by Honda Motors in October 2004, each car is used 200kg aluminum alloy parts (about 20% of the total weight of the car), of which 40kg are aluminum forgings.
Aluminum alloy forgings are a development trend internationally. Most forgings are used in automobile axles and chassis components, such as aluminum alloy wheels and aluminum control arms. According to statistics, the proportion of aluminum forgings in the world’s total forgings increased from 0.5% in 1985 to 15% in 2002. With the development of energy saving and environmental protection, aluminum alloy forgings will certainly have greater development in the future.
(2) Aluminum alloy forgings have developed rapidly.
In recent years, aluminum alloy forgings for automobiles have developed rapidly. Due to global warming and energy shortages; in addition, consumers demand comfortable rides and flexible handling, which pose severe challenges to the automotive industry and accelerate the lightweight development of the automotive industry The weight of the car is reduced by 10%, and the fuel consumption is reduced by 8% to 10%. According to the conference materials, the United States
The use of aluminum alloys (forgings, stampings) in a car reached 36.3%. The use of aluminum alloys per car in Europe and Japan exceeded 15% of its own weight, while the use of aluminum alloys in domestic cars was less. Automotive experts predict that more and more aluminum alloy forgings will replace steel forgings in the future.
In addition, the lightweight of high-speed trains has also prompted chess to use aluminum alloy parts. For example, a forging company produces 7075 high-strength aluminum alloy forgings for high-speed trains.
Forgeability analysis of wrought aluminum alloy
Segmentability definitions and metrics
(1) Definition of forgeability of aluminum alloy.
Forgeability (flowability) of aluminum alloy refers to the ability of aluminum alloy to fill the mold groove under the action of external force. High forgeability, that is, the ability of the blank to fill the mold groove is strong.
(2) Forgeability index.
Forgeability is commonly measured by the plasticity and deformation resistance of metals. The higher the plasticity, the smaller the deformation resistance, and the better the forgeability. Forgeability depends on the nature of the aluminum alloy (plasticity and strength limits) and machining conditions. Forgeability is a process performance index that measures how easy it is for a metal to obtain good parts through plastic working.
Aluminum alloy when full cosiro characteristics
The forgeability characteristics of aluminum alloy are compared with the forgeability of carbon steel and low alloy structural steel.
(1) Characteristics of high temperature deformation resistance of aluminum alloy.
① The resistance to high temperature deformation of various aluminum alloys varies widely. The deformation resistance (also called flow stress) of aluminum alloys varies significantly with different compositions. Some low-strength aluminum alloys and medium-strength aluminum alloys, such as 6000 series aluminum alloys, have lower high-temperature deformation resistance. -Mg-Cu aluminum alloy, such as 7000 series aluminum alloy, has higher resistance to high temperature deformation.
For example, the strength limit of forged aluminum 2A50 aluminum alloy at 500 degrees Celsius is 20 MPa, and the strength limit of hard aluminum 2A12 aluminum alloy at 500 degrees Celsius is 40 MPa. The difference between the two is twice, that is, the required forging deformation load is about two times different.
②Most commonly used deformed aluminum alloys have lower deformation resistance at room temperature than carbon steel, but there are three types of deformation resistance at high temperature: lower than carbon steel, equivalent to carbon steel, and higher than carbon steel.
③Aluminum alloy deformation resistance is very sensitive to temperature (changes rapidly with increasing or decreasing temperature): as temperature decreases, its resistance to high temperature deformation increases rapidly, faster than carbon steel. It can be seen from the comparison that the high-temperature strength limit increase rate is faster than that of carbon steel when dry, and the temperature of carbon steel and low-alloy structural steel decreases by 100 degrees Celsius, and the strength limit increases by about 50%. The temperature of aluminum alloys decreases by 50 degrees Celsius, and the strength limit increases by 50% to 300%. Therefore, aluminum alloys, especially aluminum alloys with a high degree of alloying, cannot be forged at low temperatures. Therefore, the forging temperature range of aluminum alloys is narrow, and the operation should be rapid. . The deformation resistance of aluminum alloy die forging determines its material strength limit, machining conditions and the complexity of the forging.
(2) Plastic characteristics of aluminum alloy.
Plasticity refers to the ability of a metal material to deform without damaging its integrity under external forces. The plasticity of aluminum alloy during die forging determines its plasticity and machining conditions. The friction coefficient between the aluminum alloy and the surface of the mold is three times that of steel, and the flow rate is only half of that of the steel. It has strong seasonal adhesion, poor fluidity, and poor plasticity.
In summary, due to the different types and contents of alloying elements in various aluminum alloys; the nature, number, and distribution characteristics of strengthening phases are different, which seriously affects the plasticity and deformation resistance of aluminum alloys. In addition, machining conditions also greatly affect the plasticity and deformation resistance of aluminum alloys. Therefore, the forgeability (flowability) of aluminum alloys is worse than that of carbon steels and low-alloy structural steels, but better than that of superalloys and chitin alloys.
Effect of machining conditions on forgeability of aluminum alloy
Machining conditions affect the forgeability of aluminum alloys more sensitively than carbon steels and low-alloy structural steels, that is, machining conditions seriously affect the forgeability of deformed aluminum alloys.
(1) Deformation temperature of billet
The forgeability (fluidity) of various aluminum alloys increases with increasing temperature, but the degree of influence of temperature on various aluminum alloys is different, and their temperature effects are quite different. For example, the forgeability of 4032 aluminum alloys with high silicon content basins is very sensitive to temperature changes, while the forgeability of high-strength AI-Zn-Mg-Cu series 7075 aluminum alloys is less affected by temperature.
If the forging temperature of the aluminum alloy billet is reasonable, the deformation resistance is small and the plasticity is good. However, if the temperature of the billet is too high, coarse crystals and even over-burning are easily caused. If the forging temperature of the billet is low, the deformation resistance is increased, the forgeability is poor, and coarse crystals are easily generated. Therefore, adopting a reasonable forging temperature is the key to the success or failure of the aluminum alloy forging process.
(2) Deformation speed of billet.
The deformation speed refers to the amount of deformation per unit time. The fast deformation speed has two effects on the forgeability: First, the deformation heat generated during the deformation process increases the metal temperature (called the thermal effect phenomenon). The larger the deformation speed and the more significant the thermal effect, the higher the plasticity of the metal and the reduced resistance to deformation. Increase forgeability. Second, the deformation speed is too fast, the recovery and recrystallization cannot overcome the work hardening phenomenon in time, the plasticity of the metal decreases, the deformation resistance increases, and the forgeability decreases.
Aluminum alloy is more sensitive to deformation speed, and the thermal effect of aluminum alloy deformation is also stronger. Rapid heating caused by rapid deformation will cause a series of defects in aluminum forgings (coarse grains and grains are not uniform). In addition, high-speed forging also increases deformation resistance (although thermal effects reduce deformation Resistance, but the deformation resistance increased by the increase of the deformation speed), in principle, no forging hammer is used. Slow deformation speed is beneficial for aluminum alloy die forging, but too low deformation speed (hydraulic machine) will lead to low productivity.
(3) The mold is preheated.
The preheating of the mold is very important. The mold temperature not only affects the forgeability of the aluminum alloy billet, but also affects the fixture and jig life (improper preheating and premature failure of the mold), which is one of the key factors for the failure of aluminum alloy forging. Aluminum alloy has high thermal conductivity. In order to prevent the heat of the billet from being dissipated too quickly, the mold and the tool in contact with the workpiece must be preheated to a higher temperature. The preheating time of small molds is more than 2h, and the preheating temperature is 2000 ° C or higher (determined by the type of aluminum alloy and mold steel). Large molds take longer. The mold is preheated correctly. First, it is beneficial to aluminum alloy forging (good forgeability, avoiding defects such as surface peeling and coarse grains), and also improves the service life of the mold.
(4) Mold lubrication.
At the forging temperature, aluminum alloys have poor forging fluidity (friction coefficient is 3 times that of steel and flow speed is 1/2 of steel), and the tendency of die sticking is serious. Therefore, when forging aluminum alloys, mold lubrication becomes particularly important. Mold lubrication can improve metal flow, prevent mold sticking, reduce surface defects in forgings, and reduce die forging resistance by 9% to 15%.
(5) Mold roughness.
The roughness of the mold directly affects the fluidity of the metal, so the surface of the mold should be polished, and the mold groove. The surface treatment should be smooth and bright, and the roughness should be less than or equal to Ra0.4 μm. If the mold groove has high roughness, it will not only affect the forgeability of aluminum alloys, but also easily fold the complex aluminum alloy forgings.
(6) Deformation stress state.
Practice has proved that when the metal deforms, the more the number of compressive stresses in the three directions, the better the plasticity of the metal. The greater the number of tensile stresses, the worse the plasticity of the metal.
The deformation resistance caused by the stress of the same sign is larger than that under the stress of the different sign. Therefore, closed die forging (three-dimensional compressive stress deformation) should be used for aluminum alloy die forging to improve the degree of plastic deformation and primary deformation of aluminum alloy.
In summary, the commonly used deformed aluminum alloy has a large coefficient of friction with the die at forging temperature, strong adhesion, and poor fluidity, so the aluminum alloy has poor forgeability (compared with carbon steel and low-alloy structural steel). However, as long as the working conditions of the deformed aluminum alloy are forged and optimized, that is, reasonable deformation temperature and speed, good lubrication, mold roughness less than or equal to Ra0.4 μm and preheating, and closed die forging, etc. Alloys, like carbon steels and low-alloy structural steels, have low deformation resistance, good plasticity, and good forgeability, and can be used to produce various shapes and types of forgings.