Forming process and mold design of aluminum alloy flange
The mold design of the isothermal plastic forming process of aluminum alloy flange and its forming process are introduced. By using an isothermal plastic forming process, the products can be formed with good plasticity, stable quality, good organizational properties, no obvious defects on the surface, and less machining allowance, which can greatly reduce the equipment energy; the die structure is reasonable and easy to operate, which not only improves the production efficiency but also reduces the production cost.
As one of the advanced methods of forging and forming in metal pressure processing, the isothermal plastic forming process is increasingly used in many industries, such as equipment manufacturing, military, aviation, aerospace, and shipping. As the main feature of the isothermal plastic forming process is that the die and forming products have basically the same temperature, they need to be equipped with die heating and temperature control devices; the quality of die forgings is stable, the organization is fine, the performance is high, the consistency of forgings is good, the scrap rate is low, especially suitable for forgings with high dimensional accuracy and uniform internal organization, which not only saves raw materials but also reduces the time of post-process mechanical processing.
1. Forming process of aluminum alloy flange
Aluminum alloy flange is a kind of electrical fittings, forgings as shown in Figure 1; the material is forged aluminum alloy bar 6A02H112, its performance requirements are hardness ≥ 85HBW, and parts forgings require high precision and good surface quality.
Forged aluminum alloy 6A02H112 material in the temperature of more than 500 ℃ grain growth, below 380 ℃ when the deformation resistance increases sharply, is not conducive to its material forming. In order to reduce the deformation resistance of the metal material, the forging temperature should be controllable, so the die should have a small temperature error with the forming forgings and need to have a die heating and temperature control device; and because the forging temperature range of the forming material is narrow, the forging product forming process is more complex, so the flange product forming process decided to use the more ideal isothermal plastic forming process.
In order to reduce the deformation resistance in the forming process, the forging temperature of forging aluminum alloy 6A02H112 material forming is determined as follows: the initial forging temperature ≤ 490℃, the final forging temperature ≥ 380℃, and the aluminum alloy material are heated by 60kW box type resistance furnace. The die heating temperature is set at (480±5)℃, and an isothermal resistance furnace heats the die.
6A02H112 aluminum alloy has good plasticity, and it is easy to stick to the die at high temperatures, so good lubrication can ensure the surface quality of the parts. Therefore, to effectively reduce mold wear, reduce the deformation resistance in the plastic forming process, and improve production efficiency, mold lubrication uses graphite and gun oil in a certain proportion of the lubricant. When lubricating the mold, the lubricant is evenly brushed on the effective working surface of the mold, and the effect is more ideal.
The energy required for the isothermal plastic forming process is 40%-50% of the energy required for ordinary die forging. After calculation, the plastic forming force required by the isothermal plastic forming process of aluminum alloy flange is <500×104N, so the plastic forming equipment selected a 500×104N universal hydraulic press for the process of aluminum alloy flange forming.
After several times of process debugging, the plastic forming process test program was prepared, and the forming process flow was determined as follows: material feeding → raw material heating → mold heating → mold lubrication → forming → trimming → inspection.
2. Die design of aluminum alloy flange
The overall design process of the die follows the requirements of forging die design; the specific design steps are as follows:
- (1) According to the part diagram and the thermal expansion coefficient of aluminum alloy in the plastic forming heating process, the size of the part is put, and the hot forging part diagram of the flange is determined (Figure 1) design plan;
- (2) According to the forging drawing, determine the die-forming method;
- (3) Determine the die assembly drawing;
- (4) Determine the isothermal resistance furnace of the die;
- (5) Design the convex and concave die parts drawing, and other die parts drawing.
Figure.1 Flange forging diagram
According to the above steps, the die is designed reasonably, and the schematic diagram of the die structure is shown in Figure 2.
Figure.2 Schematic diagram of die assembly of flanges
In order to achieve the accuracy requirement of ±0.5mm for the forging uninjection tolerance, the heat shrinkage of 6A02H112 material used in the die and forging must be considered, and the heat shrinkage is one of the keys to designing the die. In actual production, it is difficult to determine the heat shrinkage of 6A02H112 material, so in the design of the mold, the mold cavity uses the maximum volume principle in the tolerance and fit, that is, the mold hole to take the smallest size, in other parts to take the larger size. After the completion of die mechanical processing, test the forging flange, measuring its size to determine whether the die needs to modify the processing size until it reaches the dimensional accuracy required by the forging diagram. Flange forgings are symmetrical parts. The die is self-guided to ensure the accuracy and concentricity of the forgings. Because the upper plane of the forging requires a flatness of 0.2, so the processed die parts have the same strict requirements for flatness.
- (1) Isothermal plastic forming process realizes the precise control of isothermal furnace temperature. Using the isothermal plastic forming process to form the products, the metal plastic forming is good and stable.
- (2) After isothermal plastic forming and heat treatment, the aluminum alloy flanges meet the technical requirements of the process, and the heat treatment process is stable.
- (3) The process mold structure is reasonable, easy to operate, has high production efficiency, reduces production costs, realizes the mass production of products, and achieves good economic benefits.
Source: China Flange Manufacturer – Yaang Pipe Industry (www.steeljrv.com)