Research on the Forging Process of Large Shaft Forgings with Intermediate Flange

Research on the Forging Process of Large Shaft Forgings with Intermediate Flange

Introduced the forging process of large shaft forgings with intermediate flanges. A new forging process was determined by designing different forging processes and using the finite element method for numerical simulation analysis and comparison, and good results were achieved.

1. Question raising

Large shaft forgings with intermediate flanges are one of the main forgings of certain equipment. Figure 1 shows the rough machined shape of the movable trunnion, which is mainly characterized by a flange in the middle. This article uses the forging shown in Figure 1 as an example to study the process.
In the previous production, the forging shaft used the traditional free-forging process. A large shoulder allowance must be added to ensure a sufficient forging ratio for the middle flange and smooth forging of the two small ends. As shown in Figure 1, the design weight of the forging is 8604kg. After increasing the shoulder allowance, the forging design uses an ingot shape of 23t, and the utilization rate of the steel ingot is only 37.4%. The process design is three heat forging.
The specific shortcomings of the original process are as follows:

• ① Low utilization rate of raw materials;
• ② The increase in forging weight leads to longer heating time and higher energy consumption;
• ③ Increase a load of mechanical equipment during the forging process;
• ④ Large cutting amount of surplus material after forging;
• ⑤ Added post-forging processing, resulting in longer forging cycles and higher overall costs.

Figure.1 Rough machining diagram of movable trunnion
It has been decided to adopt the tire die forging process to meet the requirements of energy conservation and consumption reduction and improve material utilization. The tire dies forging process has high production efficiency, saves materials, and is more suitable for mass production.
The main idea of the new process is to use a simple mold to upset the middle step part, which can reduce the shoulder allowance of the forging and improve the utilization rate of the steel ingot.

2. Determination of process plan

Use a mold to suppress deformation at both shafts ends and upset the middle flange part into shape. In this process design, there is no need to increase the shoulder allowance, and the forging allowance in the axial direction is also less than the free forging allowance. There are two options for process design:

Option 1 directly forges the raw materials into equal diameter billets (Figure 2), then upsets the middle flange part through a mold.

Figure.2 Schematic diagram of equal diameter billets

Option 2: Forging a smaller diameter intermediate flange (as shown in Figure 3) without or with less shoulder allowance and then upsetting the middle part to form it.

Figure.3 Schematic diagram of the blank with intermediate steps

3. Numerical simulation effect

Two processes were simulated and analyzed using the finite element method. A symmetrical model was used to simplify the calculation, and the mold’s nonmain parameters were simplified. The upper mold was set with a uniform compression speed, while the lower mold remained stationary. The initial conditions for calculation are shown in Table 1. The final deformation results of the simulation are shown in Figures 4 and 5.

The simulated deformation shows that Scheme 1 has a relatively large amount of deformation compared to the middle part of Scheme 2, and both schemes have good flange vertical surface forming effects. However, Scheme 1 has a larger bulge rate and a larger transition fillet between the flange axis surface and the vertical edge of the step compared to Scheme 2, which is not conducive to the later trimming of the middle flange part. From the perspective of deformation, Scheme 2 has a better effect than Scheme 1.

Figure.4 Numerical Simulation Results of Option 1

Figure.5 Numerical Simulation Results of Option 2

Table.1 Calculation of Initial Conditions

Boundary		Parameter settings
		Option 1	Option 2
Upper mold	Movement speed	200mm/s	60mm/s
	Exercise time	2.5s	3s
Lower die		Regular	Regular
Frictional coefficient		0.3	0.3

Figures 6 and 7, respectively, show the required forming forces during the forming process of the two schemes. From the figure, it can be seen that the required forming force during the forming process of the two schemes is similar. As the diameter of the middle part of the billet in Scheme 2 is larger than that in Scheme 1, the forming force is higher.

After a comprehensive analysis, it was determined that the forming effect of Scheme 2 is better than Scheme 1. Therefore, in actual production, it was decided to follow the new process of Scheme 2.

Figure.6 Required Forming Force for Option 1

Figure.7 Required Forming Force for Option 2

4. Process design and production

The difficulty in forming large shaft forgings with intermediate flanges lies in controlling the deformation uniformity of the middle part of the billet. The main influencing process parameters include step height, upper and lower mold fillet, initial flange height, initial flange diameter, and two small end diameters.
After optimizing each parameter, the new process was developed as follows:

• First heat: press the clamp handle, chamfer, and crush the ingot tail.
• Second heat: upsetting; WHF method for elongation; Trim the blank to the size shown in Figure 8.
• Third heat: Die upsetting; Forging each part to size; Finishing, straightening, and producing finished products.

Figure.8 Schematic diagram of blank size

Figure 9 shows a shaft forging with a flange in the middle forged using a new process. In actual production, to ensure that the size of the middle flange can meet the requirements, the diameter of the flange after upsetting is designed to be 1.1 times the required value, and then it is repaired. The finishing of the flange section should take priority over the finishing of the two small ends.

Figure.9 Schematic diagram of finished forgings

5. Conclusion

The large shaft forgings with intermediate flanges adopt a new process of upsetting the intermediate flange. Compared with the original process, the weight of the forgings is reduced to 7636kg; The design uses a steel ingot shape of 10.5t, reducing raw materials by 54.3%, increasing the allowable charging temperature, reducing the heating and insulation time from the original 26h to 16h, saving 4861.25m³ of natural gas, shortening the production cycle, saving energy, and achieving good economic benefits.

Author: Su Yuejuan

Source: China Forged Flanges Manufacturer – Yaang Pipe Industry Co., Limited (www.pipelinedubai.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

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