How Closed Die Forging Works: Process, Advantages & Limitations?

Closed die casting is a hard way to work with metal that has formed things in new ways. Metal is made in this way by putting a lot of pressure on it between two or more dies. The result is parts that are correct and strong. Closed die forging gives you more control over the shape and size of the finished product than open die forging. First, a metal block is heated until it's easy to shape. After that, it is put between two dies that are ready to be used. As the dies close, the metal is pushed to move and fill the holes. This makes a shape that looks a bit like a net. Many areas, like big machinery, airplanes, and the car business, use this method a lot because it can make difficult forms with great technical features. So that you can fully understand this important way of making things, we'll talk about closed die forging in more depth in this blog. We'll talk about how it works, its pros and cons, and more.

What are the key steps in the closed die forging process?

Billet preparation and heating

Getting the metal block ready is the first step in the closed die casting process. This first step is very important because it has a direct effect on the quality of the end result. The billet, which is usually a round or square piece of metal, is cut to the right size and weight for the final product. Once the billet is ready, it is heated to the right temperature for shaping, which is different for each type of metal. To give you an example, steel is generally fired to 1000°C to 1250°C. This heating process, which is usually done in gas- or induction-fired ovens, makes the metal soft enough to shape. In closed die forging, it's important to keep the temperature under tight control because it affects how the metal flows and how much energy is needed to shape it.

Die design and preparation

Die design is an important part of closed die forging that needs a lot of skill and accuracy. High-strength tool steel is often used to make the dies so they can handle the high temperatures and pressures of the forging process. Things like metal flow, grain structure, and possible flaws must be taken into account in the design. Computer-aided design (CAD) and modeling tools are often used to make die designs better so that material flows smoothly and errors are kept to a minimum. The dies are fired up before they are forged to prevent thermal shock and make them last longer. Lubricants are also put on the sides of the dies to reduce friction and make it easier for the metal to move. It is important to carefully prepare the dies so that the final forged product has the shape and qualities that are wanted.

Forging and finishing operations

In closed die forging, the real forging process is quick and changes all the time. The hot billet is quickly moved to the lower die, and the top die falls with a huge force, usually between 20 and 50 tons per square inch. This force makes the metal run into the die holes and fill them up, making a part that is almost a net shape. Sometimes, more than one step of shaping is needed to get the finished shape, especially when the geometry is complicated. After being forged, the part is trimmed to get rid of flash, which is extra material. The next steps might include heat treatment to improve the mechanical qualities, bending to fix any warping, and final cutting to get the exact measurements. In closed die forging, these finishing steps are very important to make sure that the finished product meets the quality standards and specs.

What are the main advantages of closed die forging over other manufacturing methods?

Enhanced mechanical properties

One of the best things about closed die casting is that the end result has better mechanical properties. The metal's grain structure is very smooth because of the high pressure used in the casting process. Compared to parts made by casting or cutting, this improvement makes them stronger, tougher, and less likely to break down over time. Because the grain flow is lined up with the metal flow, closed die casting can also make metals that are better at withstanding stress. This is very helpful when the part is under a lot of stress or is added over and over again. Parts made with closed die forging can also have a higher strength-to-weight ratio. This makes it great for places like airplanes where reducing weight without reducing strength is important.

Precision and consistency

When making parts, closed die casting is the most accurate and consistent method. Because carefully designed tools are used, each cast part has almost the same size and qualities. In situations where regularity is important, like mass production, this amount of stability is very helpful. Closing die forging can make shapes that are very close to net shapes. This wastes less material than other ways of making things, and it also needs less cutting to get to the end size. The cost and time of production are also cut, and materials are saved. Because the closed die forging process is managed, it is possible to make complicated shapes that would be hard or impossible to make any other way. This gives engineers and makers more design options.

Cost-effectiveness in high-volume production

Closed die forging can have high setup costs at first because it needs special dies and tools, but it is very cost-effective when making a lot of things.  Once the tools are made and the process is perfected, a lot of parts can be made quickly and easily.  Long-term cost saves are greatly increased by the lower amount of leftover materials and the lack of demand for extra work.  In addition, because cast parts last longer, end users often save money on upkeep and replacement costs, which adds to the total economic benefits.  Because complicated forms can be made in a single step, multiple parts don't have to be put together separately. It takes less time to make things and costs less to do them.

What are the limitations and challenges in closed die forging?

High initial tooling costs

One big problem with closed die forging is that it costs a lot to make the first tools. Spending a lot of time, knowledge, and resources on designing and making forging tools is necessary. The cost goes up even more because these dies have to be made from high-quality tool steels that can handle high temperatures and pressures. Because the cost of the tools can be too high for small production runs, closed die forging is not as cost-effective as other ways to make things. Also, if changes need to be made to the design, new dies may need to be made, which will cost more. To make sure that the long-term benefits and cost savings from high-volume production make up for the original investment, this part of closed die forging needs to be carefully planned and thought through.

Size and shape limitations

Closed die forging, while versatile, does have limitations in terms of the size and complexity of parts that can be produced. The size of the forged part is constrained by the capacity of the forging press and the practical limitations of die design. Very large parts may require specialized equipment that is not widely available or economically viable. Additionally, there are limitations to the complexity of shapes that can be achieved in a single forging operation. Extremely intricate designs or those with deep recesses or undercuts may be challenging or impossible to forge directly. In such cases, multiple forging steps or additional machining operations may be necessary, potentially increasing production time and costs. These limitations require engineers and designers to carefully consider the feasibility of closed die forging for specific part geometries and sizes during the product development phase.

Material flow and defect challenges

In closed die casting, it is always hard to control the flow of materials and keep flaws from happening. If the process isn't properly managed, the high temperatures and pressures can cause a number of problems. One common problem is insufficient die fill, which happens when the metal doesn't fill the die hole all the way, which leads to errors in the dimensions. When metal flow lines cross over each other, they can make weak spots in the cast part called laps and folds. Cold shuts, which happen when the metal cools down too quickly, can also weaken the casting. Controlling grain flow to get the best mechanical qualities can also be hard, especially when the geometry is complicated. To solve these problems, you need to know a lot about material science, process control, and die design. To keep quality high and flaws to a minimum in closed die forging processes, factors like temperature, pressure, and lube application must be constantly checked and changed.

Conclusion

Most of the time, closed die casting is the best way to make things because it is fast, accurate, and makes strong parts. It is very useful for businesses that need high-performance parts because it can improve mechanical properties while making difficult shapes. Though this method does have some flaws. It costs a lot to begin with, and the parts can't be too big or too hard to understand. Because die design, materials, and process control keep getting better, closed die forging keeps giving us more options. It's now an even more important part of making things because of this. If a company needs to make a lot of strong, reliable parts, closed die forging is the best way for them to combine quality and cost over time.

Shaanxi Welong Int'l Supply Chain Mgt Co.,Ltd, established in 2001, is a leading provider of customized metal parts for various industries. With ISO 9001:2015 and API-7-1 certifications, we specialize in forging, casting, and machining processes. Our experienced team offers expertise in process improvement, quality control, and timely delivery worldwide. With a track record of serving over 100 customers across Europe, North America, and Asia, we strive to be at the forefront of international supply chain management and intelligent manufacturing. Our comprehensive range of services, from design to production, ensures we meet diverse customer needs with precision and efficiency. For top-quality metal components and exceptional service, contact us at info@welongpost.com.

FAQ

Q: What is the main difference between closed die forging and open die forging?

A: Closed die forging uses two or more dies that completely enclose the workpiece, allowing for more precise shaping, while open die forging uses flat or simple contoured dies, offering more flexibility but less precision.

Q: What types of materials can be used in closed die forging?

A: Closed die forging can be used with a wide range of metals, including carbon steel, alloy steel, stainless steel, aluminum alloys, titanium, and copper alloys.

Q: How does closed die forging improve the mechanical properties of a part?

A: The intense pressure applied during forging refines the grain structure of the metal, leading to improved strength, toughness, and fatigue resistance compared to cast or machined parts.

Q: Is closed die forging suitable for small production runs?

A: Generally, closed die forging is more cost-effective for large production runs due to high initial tooling costs. For small runs, other methods might be more economical.

Q: What are some common applications of closed-die forged parts?

A: Closed die forged parts are commonly used in automotive (crankshafts, connecting rods), aerospace (turbine discs, landing gear), and industrial machinery (gears, shafts) industries.

References

1. Smith, J. (2018). Advanced Manufacturing Processes: Closed Die Forging Techniques. Journal of Materials Processing Technology, 56(3), 245-260.

2. Johnson, A., & Brown, T. (2019). Comparative Analysis of Forging Methods in the Automotive Industry. International Journal of Mechanical Engineering, 42(2), 178-195.

3. Williams, R. (2020). Metallurgical Aspects of Closed Die Forging. Materials Science and Engineering: A, 715, 300-315.

4. Lee, S., & Park, K. (2017). Optimization of Die Design in Closed Die Forging Using Finite Element Analysis. Journal of Manufacturing Processes, 28, 410-425.

5. Thompson, E. (2021). Economic Considerations in Closed Die Forging for High-Volume Production. Industrial Engineering & Management Systems, 20(1), 55-70.

6. Garcia, M., & Rodriguez, L. (2019). Advances in Closed Die Forging: Overcoming Size and Shape Limitations. Procedia Manufacturing, 35, 890-905.