In order to improve the comprehensive properties of metal parts, it is necessary to process them by Hardening heat treatment furnace, and the metal parts with high hardness, strength and wear resistance can be obtained after processing.
The heat treatment quenching of the parts is from the austenitizing temperature and should be cooled rapidly at a rate greater than the critical cooling rate in order to obtain the required microstructure and properties. In the area of Austenite, the surface layer is compressed by thermal stress, which can not only avoid the decomposition of the part, but also prevent the cracking of the parts. when the temperature drops below the Ms point, the Austenite is transformed into martensite to produce transformation stress. At this time, the higher the cooling rate is, the greater the phase transition stress is and the higher the tensile stress on the surface of the part is. Therefore, when the difference between the transformation stress and the thermal stress exceeds the fracture strength of the material, it will lead to quenching and cracking. In the actual production process, we should cool slowly in this area as much as possible, that is, in order to harden and not crack, that is, the nose of C curve is cooled quickly and the martensite transformation zone is slow cold.
In order to get the required hardness and performance of the workpiece and meet the actual needs, the appropriate quenching method should be selected after heating, that is, the quenching and hardening of the workpiece should be realized without cracking, and the workpiece should be quenched in the critical zone at a critical cooling rate greater than its critical cooling rate. At the same time, the cooling method should be slow and cold in the dangerous area (low temperature area). This kind of cooling method can ensure that the technical requirements of the workpiece and the deformation of the parts are small and there is no cracking phenomenon, so the material, shape and requirements of the workpiece are different. There are great differences in cooling methods, which should be treated concretely, but the purpose is to ensure the quality of the workpiece after heat treatment.
Overseas manager: Tom Wang
Phone: 0086-13303078975(whatsapp, wechat,line)
Specialist of bar heat treatment furnace in China; Glad to be your business partner in induction heating field.
Post time: 06-11-2019