Forging Process: Free Forging Process Of Titanium Alloy Forging
Forging process: free forging process of titanium alloy forging
Free forging ingot is mainly used for early processing, manufacturing round bars wear surface, square section or rectangular cross section of semi-finished products. Single piece or small batch production in free forging forging economically more reasonable than often use free forging to manufacture large size blank.
From the ingot to the finished bar, the forging process is usually divided into three stages.
Its initial forging (opening) temperature in the beta transition point above 150 ~ 250 degrees C, then, the best casting microstructure. At the beginning, a fast strike should make ingot deformation, until broken primary coarse grain organization so far. Deformation degree must be kept in the range of 20% ~ 30%. The ingot is forged into the desired cross section, and then cut into the size of the blank.
The plastic increase of casting microstructure. Collective recrystallization temperature rise, heat preservation time is longer and the grain refinement and intensified, in order to prevent aggregation and crystallization must be with the grain refinement and gradually reduce the forging temperature and heat preservation time to be strictly controlled.
2. more repeated upsetting and stretching
It is in the beta transition temperature above 80 to 120 DEG initial forging, alternately for 2 ~ 3 times upsetting and drawing, and alternate change axis and the edge. In this way, the whole blank cross section can be obtained very uniform recrystallization microstructure with the deformation characteristics of the beta region. If the blank in rolling, may not have such multi-directional upsetting.
3. second times more repeated upsetting and stretching
It with the first multi repeated upsetting and stretching in the same way, but the forging temperature depending on forging of half finished product after is under the process of the blank or delivery of the products. If the blank of the next process, the initial forging temperature is higher than the beta transition temperature of 30 to 50 degrees Celsius; if the delivery of the product, the beginning of the transition temperature is 20 ~ 40 C
Due to the low thermal conductivity of titanium, in free forging equipment upsetting or drawing a blank, if tool preheating temperature is too low, the hit rate of the device is low, deformation degree and larger, often in the longitudinal section and cross section form X-shaped shear band. The hydraulic press on non isothermal upsetting especially. This is because low temperature instruments, the blank and tools contact caused by chilling the surface of the metal blank, the deformation process, metal to produce thermal deformation and to less than to the surrounding heat conduction, from the surface to the center of the formation of large temperature gradient and the metal forming with a strong flow of strain. The greater the degree of deformation, the more obvious shear bands, and finally the formation of cracks under the effect of tensile stress on the opposite sign. Therefore, in free forging of titanium alloys, blow speed should be faster, try to shorten the blank and tools of the contact time and preheating tools to higher temperature as soon as possible, at the same time, we should properly control the deformation degree of a trip.
Forging, edges and corners of the fastest cooling. Therefore, when stretching must repeatedly flip blank, and adjust the hammering force, so as to avoid sharp. Hammer forging, beginning to tap, the deformation degree of not more than 5% ~ 8%, then gradually increase the amount of deformation.