Optimize Forging Plasticity with Temperature Control

In metal plastic processing, temperature is one of the key factors that determine the material's deformation characteristics and final quality. Proper control of the processing temperature not only improves the material's plasticity and reduces deformation resistance but also effectively prevents defects, ensuring the stability and reliability of the forged parts during high-temperature processing. This is especially crucial in high-temperature processes such as forging, where avoiding the brittle temperature zone and precisely controlling deformation conditions become core elements in improving product quality and production efficiency. By understanding how temperature affects material plasticity and microstructure, we can adopt suitable processes to maximize the plasticity of forged parts, optimize the deformation process, and achieve efficient and precise production goals.

Effects of the Brittle Zone and How to Avoid It

In plastic processing, it is crucial to avoid entering the brittle temperature zone. For example, during the forging of wheel hubs, if deformation occurs in the blue brittle temperature zone, the forged part is prone to brittle fracture, which negatively affects its mechanical properties and service life. During the hot processing of steel, it is important to avoid the high-temperature brittle zone to prevent coarse microstructure or cracking defects after forging. While the plasticity is high and deformation resistance is low in the hot brittle zone, under certain processing conditions, the characteristics of this zone can be used to simplify operations, but temperature and deformation speed must be carefully controlled.

Effects of Temperature Increase on Forged Part Plasticity

As temperature increases, the plasticity of forged parts typically improves due to several factors.
 

1. Recrystallization and Recovery

Increasing temperature promotes recovery and recrystallization in materials. Recovery softens the alloy, reducing internal stress, while recrystallization eliminates work hardening, restoring material plasticity. For example, at high temperatures, the material's internal lattice structure reorders, eliminating dislocations accumulated during processing, thereby reducing deformation resistance and enhancing plasticity.

2. Atomic Energy and Dislocation Activity

As the temperature rises, atomic energy increases, making dislocations more active. Increased dislocation activity allows more slip systems to operate, improving deformation coordination between grains. This phenomenon positively impacts the material's plasticity at high temperatures. In particular, temperature increases significantly facilitate grain boundary slip and planar slip, which enhances the material's plastic flow.

3. Microstructure Changes and Grain Refinement

As temperature increases, the material's microstructure undergoes significant changes. For carbon steel, within the temperature range of 950°C to 1250°C, the material typically remains in a single-phase austenite state, where plasticity is optimal. This process is closely related to microstructure over-heating and the cessation of slip. In this temperature range, the material's grains are usually finer, enhancing its thermal plasticity.

4. Thermoplastic Effects

At high temperatures, thermoplastic effects become more pronounced, especially at grain boundaries. Fine grains contribute to enhancing thermoplasticity, as slip at grain boundaries becomes easier. The material's resistance to slip between grains is significantly reduced, and the stress concentration caused by uneven deformation at neighboring grain boundaries is eliminated, improving high-temperature plasticity.

Process Measures to Improve Forged Part Plasticity

To optimize the plasticity of forged parts and reduce deformation resistance, several process measures can be adopted. These measures aim to improve the flowability of the metal billet, optimize the deformation process, reduce energy consumption, and improve production efficiency.

1. Reasonable Selection of Deformation Temperature and Speed

First, understanding the characteristics of the forging material and reasonably selecting deformation temperature, speed, and extent of deformation are fundamental to improving the plasticity of forged parts. In practical production, the best deformation conditions should be determined based on the material's chemical composition and microstructure, ensuring material uniformity and reducing internal stress.

2. Homogenization Treatment

Homogenization treatment of large forged parts, such as high-alloy steel ingots, at high temperatures can effectively enhance material plasticity. This treatment makes the material's microstructure more uniform, improving the overall plasticity of the forged parts and preventing processing defects caused by poor local plasticity.

3. Use of Appropriate Deformation Processes

Different materials have different levels of deformation difficulty, so choosing the right deformation process is crucial to improving forged part plasticity. For example, when forging high-alloy steel parts with low plasticity, adopting a sleeve upsetting process can effectively avoid surface tangential tensile stress-induced cracking, improving the forming quality of the forged parts.

4. Optimizing Tool Use and Operation

The choice and operation of tools during the forging process have an important impact on forged part plasticity. For example, when forging elongated shaft-type parts, using a V-shaped or round anvil can apply greater pressure to the surface of the part, improving plasticity and preventing cracking in both the surface and the core. Additionally, proper tool usage can reduce unevenness during the deformation process.

5. Improving Operation Methods and Lubrication

Reducing friction and improving lubrication are essential for enhancing forged part plasticity and minimizing defects. Proper lubrication measures can significantly improve the friction between the forged part and the mold, ensuring uniformity in the deformation process. For example, when processing low-plasticity materials for thin-disk type forgings, a two-step upsetting process, where the parts are stacked and upset once, then flipped 180° and upset again, can effectively solve the problem of upsetting cracks.

Conclusion

The effects of temperature on the plasticity and deformation resistance of forged parts are complex. Correctly understanding and controlling temperature changes are crucial for improving the quality of forged parts. By selecting appropriate deformation temperatures, optimizing deformation processes, homogenizing materials, using the right tools, and improving operational methods, the plasticity of forged parts can be effectively enhanced, and deformation resistance reduced, ensuring an efficient and stable production process. Additionally, proper lubrication measures and detailed process control also play an important role in improving forging quality. By applying these comprehensive measures, forging efficiency can be significantly increased, production costs reduced, and the final product quality guaranteed.