Control of anisotropic properties of ring forgings

By utilizing the properties of forging blanks reasonably, a method for controlling the anisotropy of ring forgings was studied, and the feasibility of this method was verified through experiments on aluminum alloy forgings.

When producing the free forging ring forging shown in Figure 1, sometimes different requirements are required not only for the overall performance of the forging but also for the anisotropic (radial, tangential, and high) performance. In addition to placing reasonable requirements on the forging blank and post-forging heat treatment to ensure the overall performance, appropriate forging methods should also be adopted to adjust the anisotropic properties. This article proposes a forging method that enables the radial performance of forgings to be higher than the other two directions through experimental research on the forging method of aluminum alloy ring parts.

Figure.1 Free forging ring forgings

1. Experimental plan

1.1 Rough and forged parts

The blank is a 7175-T74 extruded bar, with a size of Φ175mm × 450mm, subjected to high-temperature treatment (500 ℃/6h) before forging. They were forging size Φ360mm/Φ190mm × 95mm, solid solution treatment, and two-stage aging after forging.

1.2 Forging process parameters

The heating temperature is 430-450 ℃/2h, the initial forging temperature is 380-420 ℃, the final forging temperature is 350-400 ℃, and the flat anvil temperature is 350-450 ℃.

1.3 Forging equipment

3000t hydraulic forging machine.

1.4 Forging method

In the experiment, two forging methods were used: forging five (Figure 2) and forging three (Figure 3), both of which used Φ175mm × Forge 450mm blank into Φ360mm × 95mm round cake, then punch and bore Φ190mm holes. The performance test results of forgings after heat treatment are shown in Table 1.

Figure.2 Forging Method of Forging Five

Figure.3 Forging Method of Forging Three
Table.1 Effect of Forging Methods on the Properties of 7175-T74 Alloy Forgings

2. Analysis of experimental results

From Table 1, it can be seen that for forgings produced by the forging five methods, in addition to the plasticity index (δ) higher than radial and tangential, the strength index (σ) three directions are similar, which is due to the large degree of forging deformation, which weakens the influence of the anisotropic microstructure of the forging blank (extruded blank), resulting in sufficient and uniform deformation of the forging. The forgings produced by the three forging methods have higher radial performance, tangential performance, and lower high performance. This is because the forgings fully utilize the fiber structure of the blank (extruded bar); that is, the axial direction of the forgings remains unchanged throughout the entire forging process and is consistent with the axial direction of the blank. From this, it can be seen that different forging methods can be used to adjust and control the anisotropic properties of the forging based on the original structure of the blank.

3. Examples of main production processes for forgings

Dimensions of aluminum alloy 7175-T74 circular forgings (in mm, the same as below): Φ360/Φ190 × 95. Φ465/Φ225 × 185.
Production process: (1) Batch casting → (2) Homogenization treatment → (3) Extrusion of blank (Φ175) × 500, Φ260 × 750) → (4) High temperature treatment → (5) Forging: Blank Φ175 × 500 → Upsetting Φ275 × 200 → elongation Φ225 × 300 → pier thickness Φ360 × 95 → Punching and boring Φ360/Φ90 × 95; Blank Φ260 × 750 → Upsetting Φ410 × 300 → elongation Φ340 × 440 → Upsetting Φ465 × 185 → Punching and boring Φ465/Φ190 × 95 → (6) Solid solution treatment → (7) Double stage aging → (8) Performance testing → (9) Flaw detection → (10) Packaging acceptance. Table 2 shows the sampling inspection results of the performance of the forging.

4. Conclusion

• (1) The comprehensive performance of forgings must be ensured from three aspects: forging blank, forging process, and post-forging heat treatment.
• (2) The isotropic properties of forgings can be controlled and adjusted through forging methods (fully utilizing the properties and microstructure of the blank).
• (3) When the ring forging is produced using the three forging methods, the deformation at the center of the forging is small, and the performance is low. Still, it can be naturally avoided through subsequent punching and boring, which has no impact on the service performance of the forging.
• (4) The inspection and comparison of the performance of forgings (see Table 2) shows that this control method is feasible and has certain reference significance for similar forgings.

Table.2 Comparison of Mechanical Properties of 7175-T74 Forgings

Author: Ning Ailin, Shen Qizhi