Effect of Cold Drawing Strain on Morphology and Distribution of Primary Carbides in High Nb Austenitic Stainless Steel

The hot forged high Nb austenitic stainless steel was treated by cold drawing with different strains (0,0.45, 0.71, 1.02) and solution treatment. The effect of cold drawing strain on the morphology and distribution of primary carbides were studied, and the influence mechanism was analyzed. The results show that the microstructure of the test steel consisted of anstenite and coarse NbC, and cold drawing could refine NbC effectively. Increasing the cold drawing strain was beneficial to refine NbC, enhance its dispersion, but the range of change was reduced. Under the same cold drawing strain, the NbC at the test steel edge was smaller and more dispersive than that at the core. The large difference between the ductility of NbC and the austenitic matrix, resulting in the incoordinate of the deformation. Under the combination of stress concentration and dislocation slip, mechanical breaking of NbC occured along the cold drawing direction. That was the refining mechanism of NbC during cold drawing.