Plastic processing is mostly made from simple-shaped blanks, which are directly made into the required products through large plastic deformation. The deformation resistance is generally large, and the life of the tool and mold is not long. By controlling deformation factors, improving the plasticity of metal and reducing deformation resistance are of great significance for forging.

1) Homogenize the material composition and structure

Perform high-temperature diffusion annealing on the alloy ingot or appropriately extend the holding time at the forging temperature to make the chemical composition and structure uniform , can improve the plasticity, and this treatment of certain steels that are sensitive to white spots can also eliminate white spots and prevent internal cracks.

After ultra-fine treatment of steel and alloys, stable and uniform ultra-fine grains with a diameter of less than 5 μm can be obtained, and superplasticity with an elongation of 200%-2000% can be obtained, while also greatly reducing deformation. Resistance.

2) Reasonable selection of deformation temperature, deformation speed and deformation degree

The forging temperature range of alloy steel is only 100-200℃. When selecting the forging temperature, work hardening should be avoided to ensure that the deformed metal Fully recrystallized. If the heating temperature is too high, overheating or overburning will easily occur. For some austenitic steels, a phase will be formed, and for ferrite, the grains will grow too much. If the deformation temperature is too low, it is not conducive to the elimination of work hardening. When selecting the heating method, it is necessary to ensure that the temperature of the blank is evenly distributed. When considering the forging temperature, the temperature array during the contact between the blank and the tool and die must be taken into consideration, and the tool and die must be preheated.

For alloys with a high degree of difficulty in deforming, such as high-temperature alloys, slow deformation should be used as much as possible, and the deformation amount of each hammer blow or each stroke of the press should be controlled, generally controlled at around 20% , for speed-sensitive materials, the temperature effect must also be considered when selecting the deformation speed.

When determining the degree of deformation, avoid its critical value. When the total deformation degree of cold extrusion exceeds the allowable value of the material and the deformation resistance exceeds the bearing capacity of the mold, the extrusion must be divided into several processes. conduct.

3) Choose a favorable deformation method

The plasticity of closed die forging is better than open die forging, and open die forging is better than free forging. In the free forging process, the long-drawn anvil and upsetting with a ring can exert the plasticity of the metal better than the long-drawn anvil and upsetting without a ring. In short, the deformation method of hydrostatic pressure is beneficial to improving the plasticity of metals.

4) Improve the operating method to improve the uneven deformation

When drawing elongation with low plasticity, attention should be paid to selecting the appropriate feed ratio. When the feed ratio is too small, the deformation is concentrated in the upper and lower parts, and the center is not forged through, and tensile stress is generated along the axial direction, resulting in internal transverse cracks. When upsetting, soft pad upsetting or stacking upsetting (used for forging pancake-shaped parts) is often used to improve the unevenness of deformation and prevent surface cracks.

5) Use good lubrication to improve surface conditions

When metal is plastically deformed, lubrication plays a role in reducing friction, improving metal flow, and reducing wear of tools and molds, especially in cold conditions. , It is indispensable in temperature deformation. The surface of the tool and mold is smooth and the surface quality of the blank is good, which has the same effect.

6) Reduce the contact surface between the tool die and the deformed metal

When using an arc-shaped anvil to forge thin workpieces, the total deformation is reduced, and due to the reduction of external friction, Flow resistance can also be reduced. Replacing the global deformation with continuous local deformation (such as rolling, radial forging, etc.) also has the same effect.