xiehe model

Forging is a common forging processing method. It refers to a workpiece or blank obtained by forging a metal blank and deforming it. The metal blank is plastically deformed under compression and changes its mechanical properties. So what is the heat treatment process of forgings? Next, Xiehe will introduce the following methods to you.

1. Reasonable selection of deformation temperature and deformation speed

It is very important for plastic forming to reasonably select the deformation temperature and deformation speed during deformation to ensure that the metal has good plasticity during forming. If the deformation temperature is too high, the deformed metal is easily overheated, resulting in coarse grains. If the temperature is too low, work hardening will occur when the metal is deformed, which will increase the deformation resistance, reduce the plasticity of the forging metal, and cause deformation and cracking in severe cases. For materials with high deformation velocity sensitivity, the deformation velocity should be selected reasonably. Generally speaking, the deformation speed of the hammer equipment is the highest, the deformation speed of the hydraulic machine is the lowest, and the deformation speed of the press machine is between the two. For example, magnesium alloy forgings are suitable for forging on a press. If forging with a hammer, it is best to tap lightly at the beginning, and gradually increase the degree of deformation as the groove is filled with each hammer forging.

2. Deformation method

The choice of deformation method directly affects the plastic flow and stress state of the deformed body in the cavity. For example, the more compressive stress a blank bears during deformation, the better its plasticity. Therefore, for materials with low plasticity during plastic deformation, some measures can be taken to increase the three-dimensional compressive stress state and prevent the blank from cracking. For example, when upsetting, the movable collar or sheath can be used to facilitate forming, and the use of anvil for drawing is conducive to forming and improving drawing efficiency.

3. Improve the uniformity of material composition and organization

The chemical composition and structural properties of alloy ingots are very uneven. High-temperature diffusion annealing can be carried out before plastic processing to make the structure and composition of the ingot uniform and improve the plasticity of the material. For example, magnesium alloy MA3 undergoes high-temperature homogenization treatment at 400°C for 10 hours, and its compression deformation on the press can reach more than 75%, but without high-temperature homogenization treatment, its allowable deformation is only about 45%. .

For high-alloy steel ingots, depending on the composition of the forgings, it can be maintained at a temperature range of 1050-1150 °C or even higher for a long time, and good results can also be obtained. Due to the long production cycle and high cost of high-temperature homogenization treatment, the holding time can be appropriately extended during forging heating instead. The disadvantage is that the productivity is reduced, and care should be taken to avoid coarse grains.

4. Reduce the degree of uneven deformation

Uneven deformation will generate additional stress, which will reduce the plasticity of the billet and promote the generation of cracks. Commonly used measures to reduce uneven deformation are: reasonable operating specifications, good lubrication, and suitable tool and mold shapes can reduce uneven deformation. For example, when drawing lengths, choose an appropriate feed. If the feed rate is too small, the center of the billet cannot be forged through, and additional stress will be generated. In severe cases, core cracks will be formed; the upsetting of the metal gasket is conducive to reducing the drum shape of the billet and preventing cracks on the surface.