Study On Forging Process Of Avoiding Tensile Stress In Heavy Forgings

During ingot casting, it would raise so many kinds of inner metallurgy defects, such as cavity, porosity, and so on. If these defects couldn’t get controlled in forging process, the heavy forging wouldn’t be qualified.30Cr2Ni4MoV rotor steel is a general material which is used to produce heavy axial forgings of nuclear power. In stretching process, tensile stress should be avoided, if not, detects may be expanded. So, It must be ensured that the central point in a ingot is always in a state of three-direction compressive stress during forging process, and this is also one of main research goal to forging technology. So far, LZ method, NFM method and JTS method have been invented to reach this goal, but they just provide a vague scope of process parameters, meanwhile, some critical influences should be reconsidered.This paper will take30Cr2Ni4MoV rotor steel as the material, and then, do a lot of simulation on different kinds of forging process by DEFORM-3D. Besides, the whole simulation would take thermomechanical coupling into account.To start this study, analyze the effect of parameters on the stress state of the central point successively. Then, search for the new rules between these parameters. And then, try to take main parameters as variable and describe the stress state by f (x, y), among this, x means the ration of billet width to billet height (BWR), y means the ration of anvil width to billet height (AWR). When f (x, y)>0, it means that the central point in the ingot is always in a state of three-direction compressive stress during forging process; When f (x, y)<0, it means that the central point in the ingot get some tensile stress (transversal tensile stress or axial tensile stress) during forging process.Moreover, some actual production condition should be considered so that my research could be applied to practice, for example, flip the entire forging90degrees and then start the second stretching. The requirement of second stretching on the initial process parameters can be described byg(x, y), among this, x means the ration of billet width to billet height (BWR), y means the ration of anvil width to billet height (AWR). For the same reason, wheng(x, y)>0, it means that the central point in the ingot is always in a state of three-direction compressive stress during forging process; When g(x, y)<0, it means that the central point in the ingot get some tensile stress (transversal tensile stress or axial tensile stress) during forging process.Finally, improve the LZ method and NFM method, and perfect the functions as well.