Study On The Bonding Behavior Of Void Casting Defects During Forging And Rolling Process

Round bloom with its obvious advantages have played important roles in the industry,such as chemical industry,railway ingreat heavy mining machinery,electric power and soon.In recent years,with the requirements of increasing round bloom’s size,it is necessary tomake appropriate changes for production conditions of the continuous casting and toimprove the quality of round bloom.However,heavy continuous casting blooms have manyinternal metallurgy defects,such as void.Its presence affects the quality of products and thepassing rate of detection,however, the continuous casting technology is difficult to avoidthe defects,it could only be repaired by a special hot deformation.So it is very necessary topay more attention to modification of inner defects,improvement of material tissue,so thatthe mechanical performance,inner quality and carrying ability of materials will beimproved greatly.This paper selected the heavy round bloom of HSLA steel Q345D and pure nickelslab of N6as the research object,the experiment were discussed and the theoretical wasanalysised of the bonding behavior of two kinds of materials for void defects by means ofnumerical simulation and physical simulation.1. Thermal deformation test of Q345D on Gleeble-3500machine,achieve the processconditions of this material to obtain a fine and uniform grains:with deformationtemperature ranging from950℃to1100℃,pass deformation is greater than20%,theincrease of deformation amount of the lower temperature region,the large deformationoccurs at between950℃-1000℃.2. A FEM model of void closure in forging process of Q345D was estabilishedthrough Deform-3D.The results showed that the void closure is not sensitive to thedeformation temperature,the void closing critical reduction ratio around30%;simulatedthe pure nickle plate of N6in rolling process,1/2Ho location void was the most difficult toclose,and obtain the process parameters to close the center void.3. Microstructure observation and mechanical property orthogonal experiment wasexamined to investigate the bonding rules of the inner void,The influence on the bondingeffect from large to small:deformation temperature,engineering strain,holdingtemperature,holding time.Ferrite healing belt was appeared near he stage after bonding process.The inner void can be well bonded when the temperature is1050℃-1150℃,theengineering strain is0.4.4. By observing the microscopic shape of bonding-surface,proposed the repair ofrecrystallization mechanism during defects bonding of pure nickel in hotdeformation.And find that inner defect of pure nickel slab could bonding throughappropriate rolling process.