What are the heat treatment processes and surface treatment methods of free forging?
The heat treatment process of free forgings usually includes annealing, normalizing, quenching and tempering. The main surface treatment methods are coating, nitriding, carburizing, hydrogen treatment, shot peening and so on. Annealing: The free forging is heated to a certain temperature, and after holding for a period of time, it is slowly cooled to reduce the stress and hardness inside the forging, and improve the toughness and processing performance. Normalizing: the forging is heated to the transition temperature or higher than the transition temperature, and after holding for a period of time, it is rapidly cooled by air cooling or water cooling to obtain a certain hardness and strength. quenching: The forgings are heated above the transition temperature, and after holding for a period of time, rapid quenching (usually water-cooled or oil-cooled) causes the surface of the forgings to harden rapidly, resulting in residual stress inside and increasing hardness and strength. Tempering: after quenching, the forging is reheated to the appropriate temperature, maintained for a period of time after cooling, in order to reduce the stress and brittleness caused by quenching, improve toughness and plasticity. For surface treatment methods: coating: The use of electroplating, hot dip plating and other methods to form a layer of metal or alloy coating with certain functions on the surface of the forging, such as electrogalvanizing, chrome plating, etc., to improve corrosion resistance, wear resistance and aesthetics. Nitriding: By heating the forging to a certain temperature, it reacts with nitrogen on the surface to form a nitriding layer with higher hardness to improve the surface hardness and friction performance. Carburizing: The forgings are placed in the carburizing medium containing carbon sources and carburized at high temperatures to increase the carbon content on the surface of the forgings and form a carburizing layer with higher hardness to improve the surface hardness and wear resistance. Hydrogen treatment: the forging is treated in a hydrogen environment, so that the surface of the hydrogen embrittlement phenomenon, change the surface properties. Shot blasting: Using sandblasting and other methods, spray particles on the surface of the forging, remove the surface oxide layer, remove stains, and improve the surface finish and adhesion. It is necessary to select the appropriate heat treatment process and surface treatment method according to the specific material and requirements.
