Several methods for prevent the common defects of large forgings

The causes of the defects of forging a lot, also is varied, have caused by poor forging process, the cause of the raw material, have caused by mold design is not reasonable, and so on. Especially no less machining precision forgings, it is difficult to fully control. 1. Big grain grain is usually caused by a lack of forging temperature and deformation degree, or finish forging temperature is too high, or caused by the deformation degree fell into critical deformation zone. Aluminum alloy deformation degree is too big, form texture; High temperature alloys deformation temperature is too low, the formation of deformation mixed can also cause bulky grain, coarse grains will reduce the plasticity and toughness of forgings, fatigue performance significantly decreased. 2. Uneven uneven grain of grain is refers to the special thick grain of forging parts, some parts are smaller. Produce uneven grain is the main reason of the billet throughout the deformation uneven grain crushing degree is differ, or local deformation degree fell into the critical deformation zone, or high temperature alloy local work hardening, or quenching heating local coarse grains. Heat resistant steel and high temperature alloy particularly sensitive to uneven grain. Uneven grain will make the forgings durable performance, fatigue performance significantly decreased. 3. Cold hard phenomenon when the deformation due to the low temperature or deformation speed too fast, and too fast cooling after forging, both may be caused by recrystallization softening of reinforcement (caused by deformation of can't keep up with Hardening) After, so that the hot forging forgings interior is still keeping the cold deformation. The existence of this organization to improve the strength and hardness of the forgings, but reduces the plasticity and toughness. Serious hard phenomenon may cause cold forging cracking. 4. Crack crack usually existed during forging large tensile stress, shear stress or stress caused by William gallas. Crack parts is often happened in billet the thinnest part of the largest stress and thickness. If the billet surface and internal micro cracks, or blank within tissue defect, improper or hot working temperature to lower material plastic, too much too fast or deformation, deformation degree, more than material allows the plastic handle, etc. , are upsetting, long pull, punching, reaming, bending and extrusion process can produce crack. 5. Cracking cracking is present shallow tortoise in forging surface shape crack. The surface of the tensile stress in the forging forming ( For example, is not full of extruding part or the curved part) The easiest way to produce this kind of defect. Cause the cause of cracks may be various: (1) raw materials of fusible element such as Cu, Sn and too much. (2) when heated to high temperature for a long time, steel material surface of copper precipitation and surface coarse grains, decarburization, or after a lot of heating surface. (3) fuel sulfur content is exorbitant, sulfur impregnation steel material surface. 6. Flash flash of crack crack is die forging and the trimming cracking at the parting surface. Flash crack reasons may be: (1) in die forging operations due to blow strongly metal flow in steel. (2) magnesium alloy die forgings cutting temperature is too low; Copper alloy die forgings cutting temperature is too high. 7. Parting surface crack parting surface crack is produced along the forging die surface crack. Raw materials, non-metallic inclusions to die forging surface flow and concentration or shrinkage residual crowded when die forging flash tube often form after parting surface crack. 8. Folding folding is already oxidation surface in the process of metal deformation of metal joined together to form. It can be formed by two shares ( or