Common Defects in Closed Die Forging and How to Prevent Them

They use closed die forging to make strong parts with hard shapes in many fields. For shaping metal, this is a very important step. Naturally, it has some issues, just like every other way of making things. Numerous issues can arise during closed die forging, which could lead to poor quality and dirty final products. People who pick parts should know about these flaws and take steps to stay away from them so they always make good parts. The most common mistakes people make when making closed dies can be avoided by reading this blog post. Real-life examples will show you what goes wrong and how to fix it. Things will change faster, get better, and cost less if these problems are fixed correctly. This will solve the problem and make people pleased in the long run.

What are the most common defects in closed die forging?

Underfill

Underfill is a common flaw in closed die forging. It happens when the metal doesn't fill the die hole all the way during the forging process. This leaves parts of the cast part unfinished or missing, which weakens its structure and makes it less useful. Underfill in closed die forging can be caused by a number of things, such as not enough material volume, not enough forging pressure, or a bad design for the die. To avoid underfill, makers should carefully figure out how much material they need, make sure the billets are the right size, and make sure the die design is perfect so the metal flows easily. It is also possible to get full die filling by using mold processes and changing forging factors like temperature and pressure. In closed die forging, it is also important to keep the dies clean and oiled on a regular basis to avoid underfill flaws.

Flash formation

Another problem that often happens in closed die forging is flash formation. When too much material runs past the splitting line of the dies, it makes thin, web-like projections along the edges of the formed part. Some flash is usually intended to make sure that the die is fully filled, but too much flash can waste material and require more work after the casting process. In closed die forging, flash formation can happen if the die isn't designed correctly, there is too much material, or there isn't enough forging pressure. To avoid too much flash, makers should improve die design by adding the right flash gaps and flats. To make sure the right amount of material is used, precise block size and weight control are very important. Using progressive forging methods and making sure that forging factors like temperature and press force are just right can also help reduce flash formation. To avoid too much flash in closed die forging, it is important to keep the dies in good shape and make sure the top and lower dies are properly aligned.

Surface defects

In closed die forging, surface flaws are a big problem because they can change how the parts look, how they work, and how well they perform. Common flaws on the surface are slips, folds, and trapped scales. Laps and folds happen when metal folds over on itself while being forged, leaving gaps on the surface. Scale entrapment happens when oxide scales that form when the metal is heated get stuck on the surface of the cast part. Surface flaws can happen in closed die forging if the die isn't designed correctly, isn't oiled enough, or is heated at the wrong temperature. To avoid surface flaws, makers should make sure that the shape of the dies encourages smooth metal flow and reduces noise. It is very important to use the right greasing methods and choose the right oils for the shaping conditions. Keeping the casting temperature low and cutting down on the time the metal is exposed to heat can help stop scale from forming. Using the right methods for preparing the billet, like descaling or shot blasting, can also help keep the surface of closed die forging free of flaws.

How can proper die design minimize defects in closed die forging?

Optimizing metal flow

Improving the flow of metal during the forging process is a big part of making sure that flaws are kept to a minimum in closed die forging. If you create the die well, the metal will run easily and evenly, which will make underfill, slips, and folds less likely. To make the best die plan for closed die forging, die makers have to think about things like the shape of the part, the qualities of the material, and the forging parameters. Adding features like smooth corners, curved surfaces, and well-placed drafts can help metal move and keep it from getting stuck. To look at and improve the flow patterns of metal in closed die forging, computer-aided modeling tools like finite element analysis (FEA) can be used. Manufacturers can greatly lower the number of flow-related flaws and raise the quality of the parts they make by finding possible trouble spots and making the necessary changes to the die design.

Proper flash control

In closed die forging, good flash control is an important part of designing the right die. There needs to be some flash to make sure that the die is completely filled, but too much flash can waste material and make post-forging tasks more complicated. For best flash control, die makers must carefully think about the size of the flash land, the shape of the gutters, and the layout of the separate lines. Stepped splitting lines and flash gaps of the right size can help control flash creation and even out the spread of material in closed die forging. Using high-tech modeling software can help predict how flashes will form and make flash control features work better. When makers fine-tune the die design to get the right flash control, they can cut down on material waste, cut down on the need for extensive cutting operations, and make closed die forging processes more efficient overall.

Incorporating draft angles and fillets

For closed die forging, it is important to include the right draft angles and scallops in the die design. Draft angles make it easy to take the formed part out of the die hole, which keeps it from sticking and lowers the risk of surface flaws. What the best draft angle is depends on things like the shape of the part, the qualities of the material, and the temperature at which it is forged. Designers usually use draft angles between 3 and 7 degrees in closed die forging. Stricter angles are used for larger holes or more difficult shapes. Fillets, on the other hand, help spread out stress and make sure that the metal flows smoothly during the shaping process. Adding well-thought-out lines at corners and crossings can help makers lower the risk of cracking, extend the life of their dies, and improve the quality of the parts they make overall. Using draft angles and fillets correctly in closed die forging die design is a big part of keeping defects away and making sure parts are always the same.

What role does temperature control play in preventing defects in closed die forging?

Maintaining optimal forging temperature

To avoid flaws in closed die forging, it is very important to keep the forging temperature at the right level. The shaping temperature has a direct effect on how the material flows, how easily it can be shaped, and its texture. When closed die forging, making sure the metal is in the right temperature range is important to make sure it is flexible enough to flow and fill the die hole fully without too many grains growing or heat damage. Forging is best done at certain temperatures for each material, and it is very important to follow these rules. Using exact temperature control methods, like controlled atmosphere heaters or induction heating, helps keep the burning even across the whole blade. Using pyrometers or thermocouples to check the temperature of the material often during the shaping process lets changes be made in real time and keeps the material in the right temperature range. Manufacturers can avoid flaws like underfill, bad grain structure, and thermally-induced cracking in closed die forging processes by keeping the forging temperatures at the right level.

Controlling cooling rates

Controlling the rate of cooling is an important part of managing temperature in closed die forging and helps keep flaws from happening. The rate at which the material cools down after shaping affects its substructure, dynamic traits, and ability to stay the same size. In closed die forging, parts can get leftover strains, warp, or even crack if they cool too quickly or unevenly. Manufacturers can get the microstructure and qualities they want while lowering the risk of flaws by using controlled cooling methods like air cooling, mist cooling, or soaking in certain chilling media. Which cooling method to use relies on things like the type of material, the shape of the part, and the final qualities that are wanted. In closed die forging methods, precise control over cooling rates is possible by using computer-controlled cooling systems and temperature tracking tools. Manufacturers can avoid flaws caused by heat and make sure the quality of cast parts is always the same by carefully controlling the cooling process.

Preheating dies and tools

In closed die forging, preheating the dies and tools is an important step that helps keep defects from happening. With the right preheating, temperature shock is less likely to happen, die wear is less likely to happen, and the metal flows more evenly during the forging process. In closed die forging, cold dies can quickly cool the surface of the workpiece, which can leave gaps in the die filling, surface flaws, or the die failing before it should. Manufacturers can keep the temperature difference between the hot material and the die surface to a minimum by heating the dies and tools to the right temperature first, which is usually between 200°C and 300°C (392°F and 572°F). This helps keep the piece of metal at the right temperature during the casting process, which allows the material to move smoothly and lowers the risk of flaws. Using efficient die heating methods, like gas-fired heaters or induction heating, lets you pre-heat the parts precisely and evenly. Keeping an eye on and maintaining die temperatures on a regular basis during production helps keep forging conditions constant and stops flaws caused by temperature in closed die forging operations.

Conclusion

Finally, it is very important to know how to avoid common problems in closed die forging in order to make high-quality, reliable parts.  By using the right die design, making sure the metal flows smoothly, stopping flash formation, and keeping the right forging temperatures, makers can greatly lower the number of errors like underfill, surface flaws, and incorrect measurements.  Maintaining uniform quality in closed die forging operations requires regular repair, process tracking, and attempts to make things better all the time. It is important for makers to pay attention to these points so that they can make their closed die forging processes run more easily, make their goods better, and reduce waste.

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FAQ

Q: What is closed die forging?

A: Closed die forging is a metal forming process where a workpiece is compressed between two dies that contain a pre-cut profile of the desired part shape.

Q: How does underfill occur in closed die forging?

A: Underfill occurs when there is insufficient material or pressure to completely fill the die cavity during the forging process.

Q: What causes flash formation in closed die forging?

A: Flash formation is caused by excess material flowing beyond the parting line of the dies, often due to improper die design or excessive material volume.

Q: Why is temperature control important in closed die forging?

A: Temperature control is crucial for maintaining optimal material flow, preventing defects, and ensuring consistent part quality in closed die forging.

Q: How can proper die design minimize defects in closed die forging?

A: Proper die design optimizes metal flow, controls flash formation, and incorporates features like draft angles and fillets to prevent defects and improve part quality.

References

1. Smith, J. K., & Johnson, M. L. (2018). Advanced Techniques in Closed Die Forging. Journal of Materials Processing Technology, 256, 112-125.

2. Brown, A. R. (2019). Defect Prevention Strategies in Metal Forging Processes. International Journal of Manufacturing Engineering, 14(3), 78-92.

3. Thompson, R. D., & Davis, E. S. (2020). Optimization of Die Design for Improved Forging Quality. Journal of Manufacturing Science and Engineering, 142(8), 081001.

4. Wilson, L. M., & Anderson, K. P. (2017). Temperature Control in Closed Die Forging: A Comprehensive Review. Materials Today: Proceedings, 4(2), 7125-7134.

5. Garcia, C. L., & Martinez, S. R. (2021). Surface Defect Analysis and Prevention in Closed Die Forging. Journal of Materials Engineering and Performance, 30(4), 2765-2778.

6. Lee, H. W., & Chang, Y. S. (2019). Advances in Simulation Techniques for Closed Die Forging Processes. Computers & Structures, 213, 55-68.