Study On Healing Of Interior Crack-type Fault In Heavy Forging By Modeling

Heavy forgings, as the primary components of large-sized equipment, play a pivotal role in the national economy construction, military accoutering, and advanced scientific device manufacturing. The level of heavy forging production represents a country's level of industrialization. Discarding a heavy forging of poor quality in production means extremely costly loss of money and time. The healing mechanism and process of interior cavity-type fault in heavy forging were systematically studied against the common problems in heavy forging manufacturing.The healing mechanism of interior cavity-type fault in heavy forging was studied experimentally. According to the characteristics of heavy forging, three crack models were established to simulate the interior cavity-type faults, simulating experiments were carefully designed, and healing method based on transient temperature was proposed. The influence of temperature, heating time, variance ratio of temperature, and load on the change of crack size, microscopic structure, crystal grain, composition, hardness, and strength were studied.By analyzing the microstructure variation behavior during the healing in heavy forging, it is discovered that healing-crystal is the primary source for interior cavity-type crack healing. During the healing process, there are several types of healing-crystal at the free surface of crack. The materials needed are supplied by diffusion of matrix. This process results in the appearance of abnormal structure, small grain, inconsistent composition, and variation of crystal lattice.The healing process was theoretically analyzed according to energy balance by G criterion of crack extension. The process was divided into three stages based on experimental results. Three crack healing levels and healing criterion were established. The phenomenon of crack healing in heavy forging manufacturing was explained.It was found that there is mimic-biology phenomenon in the healing process of interior cavity-type fault in metal. The scar is formed during crack healing, which is similar to the scar formed in healing of trauma of body. There are two types of growth factors during crack healing: the negative growth factor and positive one. Future ofmimic-biology study in material crack healing was also discussed.Innovative studies were conducted on: influence of thermal parameters on crack healing, mechanism of healing, method of mimic-biology, and process of healing. The phenomena of successful or unsuccessful healing were explained based on the discoveries. The results may be applied to the healing of interior cavity-type crack in heavy forging production and help improve the quality.