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Forging process of large forgings

Large forgings are generally used in the key parts of large machinery. Due to the poor working environment and complex and variable forces, the quality of large forgings in the production process is very demanding. Large forgings are forged directly from ingots. In the production of large forgings, even with advanced metallurgical technology, there are inevitably micro-cracks, looseness, shrinkage, segregation, and other defects inside the ingot, seriously affecting the quality of forgings. To eliminate these defects and improve the quality of forgings, the forging process must be improved, and reasonable forging process parameters must be selected.

Forging process of large forgings

forging process of large forgings - Forging process of large forgings

Large forgings are forged not only to meet the shape and size of the required parts but also to break the casting organization, refine the particles, uniform organization, forging shrinkage holes, holes, looseness, and other defects, and improve the internal quality of forgings. The larger the size of the ingot, the more serious the defects in the ingot, and the more difficult it is to forge to improve the defects, thus increasing the difficulty of forging. In the forging process, rolling and stretching are basic and indispensable processes. Tire dies forging is also more commonly used for forgings with special shapes.

20230426020833 60807 - Forging process of large forgings

1. Upsetting process

In the production of large forgings, the upsetting process, also known as rolled head deformation, plays a crucial role in determining the overall quality of the finished product. Employing the correct process parameters for the upsetting process ensures a higher forging ratio for billets and the proper distribution of carbides in alloy steel. Moreover, it enhances horizontal mechanical properties and reduces anisotropy in large forgings.

Section 1: Challenges in Large Cake and Wide Plate Forgings

Large pie and wide plate forgings primarily involve substantial head deformation in the upsetting process. A major concern in this area is the high rate of ultrasonic flaw detection due to internal horizontal cracks and layer defects. Unfortunately, current process theories cannot adequately explain these issues. Since the 1990s, Chinese scholars have extensively researched head theory, analyzing the main and passive deformation zones in depth.

Section 2: Theoretical Advances in the Upsetting Process

These research efforts have led to the development of the tensile stress theory based on the rigid plastic mechanical model and the shear stress theory based on the hydrostatic stress mechanical model. Additionally, numerous qualitative physical simulation experiments have been conducted, providing valuable insights into the internal stress state of workpieces. Analytical tools such as the generalized slip line and mechanical chunking methods have been employed to validate the theories.

Section 3: Enhancements in Internal Stress Distribution and Tapered Plate Rolling

The research findings have elucidated the distribution laws governing the internal stress of ordinary flat cylinders. This paved the way for introducing a new process: tapered plate rolling. Establishing a rigid plastic machinery model has significantly improved the upsetting process, resulting in fewer defects and higher quality large forgings.

Section 4: Factors to Consider in Selecting Upsetting Process Parameters

When choosing the appropriate parameters for the upsetting process, it is essential to consider several factors to ensure optimal results. These factors include the material properties of the billet, the desired forging ratio, and the overall dimensions of the finished forging. Moreover, the temperature, deformation rate, and friction conditions should be carefully managed to prevent the formation of internal defects.

Section 5: Implementing Advanced Techniques to Improve the Upsetting Process

Several advanced techniques can be implemented in large forging production to enhance the upsetting process further. These methods include computer-aided simulations for predicting and optimizing process parameters, advanced tooling design for improved deformation control, and monitoring technologies for real-time assessment of internal stress distribution.

Section 6: The Future of Large Forging Production and the Upsetting Process

As the demand for large forgings continues to grow, staying up-to-date with the latest developments in the upsetting process is crucial. Advancements in material science, computer simulation, and manufacturing technologies will enable even more precise control over the process, ultimately leading to higher quality and more reliable large forgings.

2. The drawing process

The drawing process is an essential aspect of large shaft forging production, significantly influencing the quality of the final product. The drawing process ensures homogeneous and dense forgings by reducing the billet’s cross-sectional area, increasing its length, and refining the ingot’s structure. This article will explore the various advanced drawing techniques currently available, including WHF, KD, FM, JTS, FML, TER, SUF, and new FM forging methods. It will provide a detailed overview of their unique principles and applications.

Section 1: WHF (Warm-Hot Forging) – A Revolutionary Technique

Warm-Hot Forging (WHF) is a drawing technique combining the advantages of warm and hot forging, reducing the negative effects of oxidation and decarburization. By controlling the forging temperature and deformation rate, WHF allows for a more refined grain structure, improving the overall mechanical properties of the forged material.

Section 2: KD (Kocks-Draw) – Enhancing Structural Integrity

The Kocks-Draw (KD) method is an advanced drawing technique utilizing grooved rolls to shape and refine the billet. This method significantly enhances the material’s structural integrity by redistributing internal stresses and reducing surface defects. As a result, KD-forged products exhibit superior strength, ductility, and fatigue resistance.

Section 3: FM (Flow Manipulation) – Guiding Material Flow for Optimal Results

Flow Manipulation (FM) is an innovative forging technique that employs customized die designs to guide material flow during the drawing process. This method allows for better control over grain flow and microstructure development, resulting in improved mechanical properties and a more homogeneous material distribution.

Section 4: JTS (Joint Tapered Shear) – Combining Efficiency and Precision

Joint Tapered Shear (JTS) is a drawing technique that combines two or more tapered rolls to create a shear action, allowing for precise control over the material flow. This method promotes uniform grain structure and reduces the likelihood of defects, making it an efficient and precise option for large shaft forgings.

Section 5: FML (Forging Mandrel Length) – Streamlining the Drawing Process

Forging Mandrel Length (FML) is a method that uses a mandrel to support and shape the billet during the drawing process. This technique enables a more streamlined process, improving dimensional accuracy, reducing material waste, and increasing production efficiency.

Section 6: TER (Tapered End Rolling) – Enhancing Surface Quality

Tapered End Rolling (TER) is an advanced drawing technique that focuses on improving the surface quality of forged products. TER minimizes surface defects and promotes a more uniform grain structure by using tapered rolls to shape the billet, leading to enhanced strength and fatigue resistance.

Section 7: SUF (Surface Upsetting Forging) – Optimizing Surface Properties

Surface Upsetting Forging (SUF) is a drawing method that concentrates deformation on the metal material‘s surface layers, leading to optimized surface properties and improved overall performance. This technique is particularly effective when crucial wear resistance and fatigue strength are enhanced.

Section 8: New FM Forging Methods – Exploring Cutting-Edge Techniques

New FM forging methods continue to emerge, pushing the boundaries of conventional drawing techniques. By incorporating innovative technologies, such as advanced materials and computer-aided design, these cutting-edge methods offer new possibilities for improved performance and efficiency in large shaft forging production.

3. The Tire Die Forging Technique

Tire die forging is an innovative method that involves pre-forging a billet or free forging into the desired shape and dimensions for tire production. The final forging is carried out on free forging equipment utilizing tire dies. This process does not require the die to be permanently affixed to the forging equipment, allowing for easy placement on the lower anvil of the device when needed. This eliminates the necessity for installation and significantly reduces die testing time, making the process more versatile and adaptable.

Since metal deformation occurs entirely within the die chamber, the tire die primarily determines the forging’s shape and size. This enables the creation of intricate shapes with precise dimensional accuracy while minimizing heating and deformation processes. As a result, metal material utilization is enhanced, processing time is reduced, and labor productivity is significantly increased.

In terms of forging quality, the die’s role in constraining metal deformation results in a denser forging structure and improved overall quality. This process also yields excellent surface quality, minimal machining allowances, and greater material utilization rates. Additionally, tire die forging allows for high production efficiency, complex forgings creation, and large forgings production using smaller equipment through localized molding.

Due to these numerous benefits, tire dies forging has garnered considerable interest and appreciation from various manufacturers.

Source: China Large Forgings Manufacturer – Yaang Pipe Industry (



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