The Forgeability Of Metal Materials
The factor that has a greater influence on the forgeability of the metal is the shaping of the metal itself. The better the plasticity, the less likely it is to crack during forging. The plasticity of a metal is closely related to the structure of the metal. The finer the crystal grains, the more uniform the structure and the better the plasticity. Therefore, the forgeability of the metal can be improved by refining the crystal grains and the uniform structure. The metal material can change its shape without cracking during pressure machining. It includes machining such as hammer forging, rolling, stretching, and extrusion in the hot or cold state. The forgeability is mainly related to the chemical composition of metal materials.
The Essence Of Metal
1.1 Influence of chemical composition
Metals with different chemical compositions have different forgeability. Generally, pure metals have better forgeability than alloys; the lower the carbon mass fraction of carbon steel, the better the forgeability; when the steel contains more carbide-forming elements (chromium, tungsten, molybdenum, vanadium, etc.) , The forgeability is significantly reduced.
1.2 Influence of metal structure
The metal structure is different, and its forgeability is also very different. When the alloy is in a single-phase solid solution structure (such as austenite), the forgeability is good; when the metal has a metal compound structure (such as cementite), the forgeability is poor. The cast columnar structure and coarse grains are not as malleable as the uniform and fine structure after pressure machining.
2.1 Deformation temperature
Increasing the temperature when the metal is deformed is an effective measure to improve the forgeability of the metal. During the heating process of the metal, as the heating temperature increases, the mobility of metal atoms increases, the attraction between the atoms decreases, and slippage is easy to occur. Therefore, the plasticity is improved, the deformation resistance is reduced, and the forgeability is significantly improved. All are carried out at high temperatures.
2.2 Deformation speed
Deformation speed is the degree of deformation per unit time. The effect of deformation speed on metal forgeability is shown in Figure 2. It can be seen from the figure that its influence on malleability is contradictory. On the one hand, as the deformation speed increases, recovery and recrystallization are too late to overcome the work hardening phenomenon in time, so that the plasticity of the metal decreases, deformation resistance increases, and the forgeability deteriorates (point a in the figure to the left). On the other hand, in the process of metal deformation, part of the energy consumed in plastic deformation is converted into heat energy, which is equivalent to heating the metal, so that the plasticity of the metal is increased, the deformation resistance is reduced, and the forgeability is improved (point a in the figure to the right ). The greater the deformation speed, the more obvious the thermal effect.
Figure 2 Effect of deformation speed on plasticity and deformation resistance
2.3 Deformation method (stress state)
The deformation mode is different, and the internal stress state of the deformed metal is different. For example, in the case of extrusion deformation, it is in a three-way compression state; in the case of drawing, it is in a two-way compression state and a one-way compression state; when upsetting, the stress state of the central part of the blank is a three-way compression stress, and the peripheral part is up and down and radial It is compressive stress, and tangential is tensile stress, as shown in Figure 3.
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