The process of aluminum alloy forging generally includes the following steps:
1. Raw material preparation
a. Selection of suitable aluminum alloy forging materials:
According to the use requirements and performance characteristics of the product, select the appropriate grade of aluminum alloy, such as 6061, 7075, 6063 and so on. Different grades of aluminum alloys have differences in strength, hardness, corrosion resistance and so on.
b. Inspection of material quality:
Strict inspection of the purchased aluminum alloy raw materials, including chemical composition analysis, mechanical properties testing, appearance inspection, etc., to ensure that the material meets the requirements of the forging process.
c. Calculate the size of the material to be discharged:
According to the size and shape of the aluminum alloy forging products, calculate the weight and size specifications of the required aluminum alloy materials and discharging. The size of the material to be discharged should take into account the machining allowance in the forging process and the forging ratio and other factors.
2.Heating billet
a. Preheating:
Put the aluminum alloy forging billet into the heating furnace for preheating after discharging, the preheating temperature is generally around 200 – 300°C, the purpose is to reduce the thermal stress of the billet in the process of heating, to prevent cracking.
b. Heating to aluminum forging temperature:
According to the type of aluminum alloy and the requirements of forging process, the billet will be heated to a suitable range of forging temperature. Generally speaking, most aluminum alloys are forged at temperatures between 400 – 500°C. For example, 6061 aluminum alloy is forged at temperatures between 400 and 500°C. For example, the forging temperature of 6061 aluminum alloy is usually 450 – 470°C. During the heating process, the heating speed and heating time should be strictly controlled to ensure that the billet is heated evenly.
3. Forging molding
a. Adopt suitable aluminum alloy forging equipment:
According to the size, shape and batch of forging parts and other factors, choose the appropriate aluminum alloy forging equipment, such as hydraulic presses, mechanical presses, friction presses and so on. For precision forging of small parts, small and medium-sized forgings, usually use mechanical presses or friction presses, etc., because it is conducive to the forming of aluminum alloys and ensure the quality of forgings;.b. Perform aluminum forging operation: the heated billet is placed in the die of aluminum alloy forging equipment, and the billet is plastically deformed by applying pressure to gradually form the desired shape of the forging part. In the process of aluminum forging, it may be necessary to carry out several upsetting, drawing and other processes to improve the internal organization of aluminum alloy and improve the mechanical properties of forgings. At the same time, to control the forging ratio, general forging ratio between 3 – 5 is appropriate.
4.Cooling treatment
a. Air cooling:
For some common requirements of aluminum alloy forgings, can be used in the way of air cooling for cooling. The forged forgings will be removed from the mold and placed in the air for natural cooling. Air cooling speed is relatively slow, to avoid excessive internal stress and deformation of the forging.
b. Water or oil cooling: For some aluminum alloy forgings with high strength and hardness requirements, such as 7075 aluminum alloy, in order to obtain better mechanical properties, it may be necessary to use water or oil cooling and other rapid cooling methods. However, rapid cooling is likely to produce large internal stresses in the forging, so it is necessary to carry out stress relief treatment in time after cooling.
5. Subsequent processing
a. Trimming and punching:
After forging aluminum forgings are usually with flying edges and burrs, which need to be removed through the trimming process, so that the size and shape of the forgings in line with the design requirements. For some forgings with holes, punching operation is also needed to form the required holes.
b. Machining: According to the end-use requirements of the product, aluminum forgings are subjected to various machining processes, such as turning, milling, drilling, grinding, etc., in order to obtain accurate dimensional accuracy and surface quality. For example, for the aluminum alloy forgings used in the aerospace field, its dimensional accuracy and surface roughness requirements are very high, which need to be ensured by precision machining.
c. Heat treatment:
In order to further improve the mechanical properties of aluminum alloy forgings, heat treatment is usually required, such as solid solution treatment, aging treatment and so on. Solid solution treatment can make the alloy elements in the aluminum alloy fully dissolved in the matrix, improve the strength and hardness of the alloy; aging treatment is after solid solution treatment, by holding at a certain temperature for a certain period of time, so that the solute atoms in the alloy precipitation precipitation, so as to further improve the strength and hardness of the alloy.
d. Surface treatment:
In order to improve the corrosion resistance, wear resistance and decorative properties of aluminum alloy forgings, it is necessary to carry out surface treatment, such as anodic oxidation, chemical nickel plating, electroplating hard chrome and so on. Anodic oxidation is a common surface treatment method, which can form a hard, wear-resistant and corrosion-resistant oxide film on the surface of aluminum alloy, and at the same time, it can be dyed and other processes to obtain different colors.
6.Quality Inspection
a. Appearance inspection:
Mainly check the surface of aluminum alloy forgings for cracks, folding, pores, sand holes and other defects, as well as whether the surface roughness meets the requirements. For forgings with high surface quality requirements, it may be necessary to use optical microscope or electron microscope and other equipment for microscopic inspection.
b. Dimensional accuracy measurements:
Use gauges such as calipers, micrometers, coordinate measuring machines, etc. to measure the key dimensions of the forgings to ensure that the dimensional deviation is within the tolerance of the design requirements.
c. Mechanical properties test:
Through tensile test, hardness test, impact test and other methods, test the mechanical properties of forgings, such as tensile strength, yield strength, elongation, hardness, etc., to ensure that it meets the relevant standards and product use requirements.
d. Internal quality testing:
Ultrasonic testing, ray testing, magnetic particle testing and other non-destructive testing methods, the internal quality of the forging test, check whether there are internal cracks, loose, inclusions and other defects.
The above is the general process of aluminum alloy forging, in the actual production process, may be based on different product requirements and production conditions, the process of appropriate adjustment and optimization.
