Forging production is an intermediate process between metallurgy (raw materials) and final heat treatment. The quality of heat treatment calendar and the service performance of parts are greatly affected.
The normal forging structure can obtain the required structure and energy after reasonable final heat treatment FJ. However, some structural defects caused by improper forging process or some defects left over from raw materials have a great impact on the quality of forgings after heat treatment. Here are some examples:
1. the structure defects of some forgings can be improved during post forging heat treatment, but the forging is still: satisfactory structure and properties can still be obtained after final heat treatment. For example, in general overheated structural steel forgings, small coarse products and widmanstatten structure, slight network carbides caused by improper cooling of eutectoid shed support steel, etc.
2. the structural defects of some forgings are difficult to be eliminated by normal heat treatment, and can only be improved by high-temperature normalizing, repeated normalizing, low-temperature decomposition, and same temperature expansion. For example, the twin carbides of 9C R18 stone rust steel.
3. the structure defects of some forgings can not be eliminated by the general heat treatment process. As a result, the properties of the forgings after the final heat treatment are still reduced by F, or even 4; Qualified. For example, there are severe corundum like fracture gate and edge fracture, Dao alkane, ferrite band in stainless sodium, carbide mesh and band in ledeburite high platform metalworking tool steel, etc.
4. save some structural defects of forgings, which will be further developed during final heat treatment to cause cracking. For example, if the coarse structure of alloy structural steel forgings is not improved during the silver post heat treatment, after the carbon and nitrogen are mixed and quenched, the coarse martensite pin and the high-speed zero inverted 'R.I banded carbide of the performance team are often caused, and the cracking is caused by the quenching UJ.