Publish Time: 2023-04-13 Origin: Site
Heat treatment is one of the important processes in mechanical manufacturing. It generally does not change the shape and overall chemical composition of the workpiece, and is characterized by improving the internal quality of the workpiece. The heat treatment of large forgings is due to the large section size and complicated production process. Jiahangaero said that the following characteristics should be considered in the heat treatment: the structure and properties are uneven; there is a large residual stress; the grain size is uneven; some forgings are prone to white spot defects.
When quenching large forging workpieces, the heating rate is very important. When the workpiece enters the furnace to 350°C, due to the poor thermal conductivity of the material at low temperature, a large temperature difference occurs on the surface, generally above 100°C. It should be kept at about 350°C to reduce the temperature difference and avoid thermal stress on the workpiece.
Large forgings should be added anti-white point annealing treatment for gas removal
Cooling after tempering: Slow cooling rate after tempering is mainly to consider reducing residual stress.
There is a low temperature residence time between quenching and tempering of large forgings. During this residence period, the temperature of the core must be reached and continued to decrease. The surface layer is tempered by itself while maintaining the final cooling temperature or slightly increasing it. The surface temperature rises too high, so that the temperature at different sections is uniform, and part of the residual stress is eliminated.