Effect of copper element on hot behavior of 304L stainless steel

Abstract

Hot-deformation behavior of the 304L stainless steel containing copper was investigated with compression experiments at temperatures ranging from 1173 K to 1423 K under strain rates of 0.01-20 s-1 up to the true strain of 0.69. The adiabatic heating analysis indicated that the addition of copper to 304L resulted in a temperature rise, which was found to be sensitive to the strain rate. By calculating the constitutive equation, the hot-deformation activation energy of the non-Cu-containing steel was found to be 409 kJ/mol, but it reduced to 376 kJ/mol when 2.42 % copper was added to the steel, which implied that the addition of copper to stainless steel was not conducive to the occurrence of dynamic recrystallization. Furthermore, the true stress-strain curves indicated that the dynamic-recrystallization temperature and strain rate of the 2.42 % Cu-304L steel decreased. The processing maps showed that the unstable region increased and the hot-working area became narrower. The instability region was dominated by the adiabatic-shear zone and local-flow instability. Moreover, the morphological changes of d-ferrite into coarse columnar crystals made the steel more prone to cracking.

Modelling of the Steel High-Temperature Deformation Behaviour Using Artificial Neural Network

“…Increasing the Ni and Cr concentrations from low to high limit leads to a rise of the flow stress on 20-30 MPa dependently on the deformation temperature. Copper influences more intensively on the stress and may change its value on 90 MPa at a deformation temperature of 1150 • C. A similar result was previously obtained experimentally by Li et al [65]: adding copper to 304L stainless steel significantly decreased the true stress due to increasing the stacking fault energy and, consequently, inhibiting the dynamic recrystallisation. Previously, the significant influence of the minor variations of the 25CrMo steel chemical composition on the hot fracture behaviour was shown by Zheng et al [66].…”

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“…Li and Sun calculated the constitutive equation and hot working diagram for copper-containing austenitic stainless steel and ferritic stainless steel, respectively, and determined the machinable range of the material. [6][7][8] In the process of slab processing, an appropriate amount of copper can improve the properties of steel; however, excessive copper will segregate at dislocations and crystallization, and the addition of copper also hinders the recrystallization process of the rolled sheet and affects the recrystallization texture. [9] Moreover, during the heating process, liquid copper is enriched at the interface of oxide scale/matrix to form copper spinel (Fe 2 CuO 4 )-containing mixed oxides.…”