A single-pass thermal compression deformation experiment with the true strain of 0.7 was conducted on niobium microalloyed Q345qD steel using MMS-300 thermal simulation tester machine under deformation temperature of 850‒1 150℃ and strain rate of 0.01‒5.00 s-1.The thermal deformation behaviors were analyzed by the thermal compression rheology curves and the intrinsic equations and the thermal processing diagrams were established.The results showed that when the strain rate ranges from 0.01‒5.00 s-1 and the deformation temperature was higher than 1 050℃,the true stress-strain curve of the experimental steel exhibited dynamic recrystallization characteristics.Based on the true stress-true strain data,the thermal deformation constitutive equations for the experimental steel were constructed.When the true strain was 0.2,the thermal deformation activation energy(Q)of the experimental steel was 379.558 9 kJ/mol.Based on the on the dynamic material modeling theory,thermal processing diagram of experimental steel at different true strains were drawn.When the true strain was 0.4,the reasonable thermal deformation parameters for the experimental steel were deformation temperature of 940‒1 150℃,strain rate of 0.01‒0.07 s‒1,and deformation temperature of 1 080‒1 150℃,strain rate of 1.70‒5.00 s‒1,respectively.
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