Through the in-depth research on the forming method of 7075 aluminum alloy large long cylinder forgings forging and reaming link, the finite element analysis and optimization of the staged reaming of the long cylinder by using DEFORM-3D software solves the problem of shortening the length of the horse bar reaming during the forming of large long cylindrical forgings. The adoption of this key technology can produce high-quality large long cylindrical forgings.
Aluminum alloy large long cylindrical forgings are the main parts of seamless cylinder joint devices for large pressure vessels, which are widely used in aerospace, petrochemical, nuclear power and other fields. With the progress of science and technology and the development of the manufacturing industry, the application of large long cylinder is increasing, the size is getting bigger and bigger, and the technical requirements are improving. The forging is finally formed by reaming, but warpage, flare, length shortening and other problems will occur in the reaming stage, which seriously affects the size processing of the forging.
Using DEFORM molding simulation, we adjusted the molding scheme and finally solved the problems smoothly to ensure the smooth batch production of forgings.
1. Molding program
This study uses a large 7075 aluminum alloy long cylinder forgings. Processing size of forgings: outer diameter ϕ550-1150mm, wall thickness 50mm, length 2550mm. 7075 aluminum alloy long cylinder forgings feature: thin wall thickness, long length, large size changes, forging and forming is more difficult.
1.2 Process route
The molding program of this large-scale long cylinder forgings: sawing machine discharging → ingot heating → free forging billet → counter-extrusion → sawing cylinder bottom → mandrel elongation → horse bar reaming.
1.3 Horse bar reaming
Horse bar reaming is a key link in the production of large cylinder forgings, and its deformation will directly affect the final quality of the product. In the final actual horse bar reaming process, there is a large number of axial length contractions of the cylinder after reaming, which is inconsistent with previous production experience. Generally, the height of the cylindrical part will increase slightly after reaming rather than shortening. In order to explore the impact of the length of cylindrical parts reaming in stages, to reduce the consumption of workforce and material resources, the use of DEFORM-3D simulation of large forged cylindrical parts molding, 7075 aluminum alloy cylindrical parts reaming molding process as the object of the study, the study of three different molding programs.
2. Simulation analysis of segmented reaming length shortening
This time, the main simulation of a 7075 aluminum alloy large long cylinder forming when the reaming shrinkage problem, through the simulation of the length of the horse bar reaming after the change of the length of the situation, combined with practice, to optimize the large aluminum alloy long cylinder forming to provide theoretical and practical support.
The billet information of this simulation is shown in Table 1, and the mold information is shown in Table 2.
Table.1 Blank information
|Internal Diameter||External Diameter||External Diameter|
Table.2 Mold information
|Upper flat anvil||Saddle|
2.1 Simulation process
2.1.1 Two-stage reaming
(1) 1st lap reaming: upper anvil pressing length 1475mm; upper anvil pressing down speed 20mm/s; upper anvil pressing down amount 20mm, billet rotating speed 18°/pressing down. Fig.1 shows the effect diagram before and after the 1st lap reaming.
Fig.1 The effect diagram before and after the 1st circle reaming
(2) The 2nd circle reaming: upper anvil pressing material length ≈1793mm; upper anvil pressing down speed 20mm/s; upper anvil pressing down amount 20mm; workpiece rotating speed 18°/pressing down. Fig.2 shows the effect diagram after the 2nd circle reaming.
Figure.2 The effect diagram after the 2nd circle reaming
(3) The 3rd circle reaming: upper anvil pressing length ≈1818mm; upper anvil pressing speed 20mm/s; upper anvil pressing down amount 10mm; workpiece rotating speed 16°/pressing down. Fig.3 illustrates the effect after reaming of Fig.3.
Fig.3 The effect diagram after reaming of the 3rd figure
(4) Hole reaming of the 4th circle: upper anvil pressing length ≈1428mm; upper anvil pressing speed 20mm/s; upper anvil pressing down amount 10mm; workpiece rotating speed 16°/pressing down. Fig.4 illustrates the effect after reaming of the 4th figure.
Fig.4 The effect diagram after reaming in the 4th circle
(5) The 5th circle reaming: upper anvil pressing material length ≈1378mm; upper anvil pressing down speed 20mm/s; upper anvil pressing down amount 2.5mm; workpiece rotating speed 15°/pressing down. Fig.5 shows the effect diagram after the 5th circle reaming.
Fig.5 The effect diagram after the 5th circle reaming
(6) The 6th circle reaming: upper anvil pressing length ≈1982mm; upper anvil pressing speed 20mm/s; upper anvil pressing down amount 2.5mm; workpiece rotating speed 15°/pressing down. Fig.6 shows the effect diagram after the 6th circle reaming.
Fig.6 The result after reaming in the 6th circle
The results of two-stage reaming are shown in Fig.7; the wall thickness of the long tube is 102.5mm before reaming, and 70mm after reaming. The change of axial dimensions of the long tube forging in the process of reaming is shown in Fig.8.The deformation of the forging is irregular after the simulation is completed. The whole is in the shape of a flared mouth: the outer diameter of the largemouth end is about 1272.8mm, the inner diameter is about 1134.35mm; the outer diameter of the small mouth end is about 1071.69mm, and the inner diameter is about 932.833mm; the maximum value of axial bus length is about 2558.98mm, the minimum value is about 2528mm, the effective axial length of the forging is shortened by 22mm compared with that before drawing.
Fig.7 Dimensions of the workpiece after completion of two-stage hole reaming
Fig.8 Axial dimension of long cylinder forging in the process of reaming
2.1.2 Three-stage reaming
Expand based on the above simulation to explore the effect of three-stage horse bar reaming: whether it is favorable to long cylinder reaming uniform deformation axial length change.
According to the three-stage reaming sequence, it is divided into “123 program” and “132 program,” two small programs, see Figure 9, respectively, to explore the simulation.
Fig.9 Three-stage distribution of the long pipe
Adopting the same simulation variables as the two-stage under-pressing speed, rotation angle, etc., through different pressing order and segments, the results of the three-stage reaming-“123” and “132” are shown in Fig. 10 and Fig. 11, respectively, and the wall thickness of the long tube is 102.5mm before reaming. Thickness before reaming is 102.5mm after reaming is 70mm. The overall workpiece after completion in the simulation is straight, but the diameter of different parts has some differences, specifically:
- (1) Program “123” final molding long tube axial dimensions of about 2587.78-2593.17mm, compared with the pre-reaming (2550mm) elongation of about 37mm.
- (2) The final shape of the long tube of plan “132” is more irregular, and the axial dimension after reaming is about 2588.28-2597.6mm, and the elongation is about 38mm compared with that before reaming (2550mm).
Figure.10 Schematic diagram of simulation results of “123” horse bar reaming
Figure.11 Schematic diagram of simulation results of reaming of horse bar in scheme “132”
2.2 Simulation results
- (1) With The use of the two-stage reaming method simulation, the axial length of the reaming will be shortened by about 22mm, the deformation of the forging after reaming is irregular, and the whole is more serious flare shape.
- (2) The use of “Program 123” or “Program 132” horse bar reaming, the axial length of its growth, the degree of elongation of the two is not much different, the former elongation of about 37mm, the latter elongation of 38mm.
- (3) 2550mm long pipe using “Program 123” and the use of “Program 132” horse bar reaming compared to the former shape change is more regular.
- (4) In the simulation process of both schemes, the workpiece along the axis of the horse bar is expected to limit the axial movement will be conducive to its uniform deformation.
3. Analysis and discussion
Because the length of the flat anvil cannot cover the full length of the billet, it is necessary to use segmented reaming.
Reaming in two sections: in order to ensure the uniformity of reaming, for each reaming, the middle part of the billet will contact the anvil and deformation, the corresponding middle part of the reaming deformation is larger, the metal flow is larger, the cylinder presents an arch, which ultimately leads to the shortening of the length. The practice has shown that the outer diameter of 1200mm billet, wall thickness from 105mm reaming to 70mm, and axial contraction of about 22mm. And easy to get a large diameter at one end; the other end of the diameter of the trumpet-shaped forging pipe is small.
Divided into three reaming is relatively uniform force, the size is easy to control, the two ends and the middle section of the diameter is similar, the axial length will grow 35-45mm, three-part reaming whether it is using the “123” or “132” way of deformation, the results are not very different! The result will not be much different whether the “123” or “132” method is used. To control the amount of pressure and rotation angle of each pass, the amount of pressure is too large; the axial movement is large. The recommended amount of each press is down 10-20mm, rotation angle of 10 ° -15 °. Note that the measurement of the two ends of the inner diameter, as long as the three segments of the outer circular surface of the bus are basically straight, the inner circular surface is also basically straight. Due to the influence of mandrel bending deflection, the wall thickness of the middle section is 3-5mm more than the two ends.
For long cylinder reaming, when the length of the cylinder exceeds the length of the upper flat anvil, two-stage reaming is easy to form a long flared cylinder with a large diameter at one end and a small diameter at the other end and the length will be shortened.
Three-stage reaming is easy to control. The axial length will grow. Accordingly, the diameters of the two ends and the middle section are similar, and the results are not much different whether the three sections are deformed from one end to the other or the two ends are deformed first and the middle section is deformed last.
Author: Cong Zhenyu