1. The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, Hubei, China; 2. Collaborative Innovation Center for Advanced Steels, Wuhan University of Science and Technology, Wuhan 430081, Hubei, China; 3. Metals Valley-Band (Foshan) Metallic Composite Co., Ltd., Foshan 528000, Guangdong, China
Abstract:Low density steel has become a research hotspot in the development of materials that meet the requirements of safety and energy saving. In order to achieve lightweight materials and promote green development, an appropriate amount of light elements medium Mn (mass fraction is 5%) and medium Al (mass fraction is 5%) were added to the alloy design of ultra-high strength pearlite cable steel to reduce the density of the steel. The theoretical density was reduced from 7.85 g/cm3to 6.81 g/cm3, and a decrease of 13.2%. At the same pearlite isothermal temperature (600 ℃-0.5 h and 500 ℃-2.0 h), compared with the traditional pearlite steel, the tensile strengthand yield strength of low density pearlite steel significantly increased (from (1 237±24) MPa to (1 247±37) MPa, (923±12) MPa to(1 171 ±34) MPa, respectively),while the elongation slightly decreased(from 6.46%±0.20% to 5.18%±0.06%), and the microstructure changed from traditional θ-pearlite (ferrite+ cementite) to θ-pearlite and κ-pearlite (ferrite + cementite + κ-carbide). The results show that the addition of appropriate amount of Al and Mn can restrain the diffusion of C, increase the transformation free energy of pearlite, significantly delay the eutectoid transformation process of pearlite, refine the lamellar spacing of ultra-fine pearlite and obviously reduce the cluster size. It also promotes the formation of κ-carbide in low density pearlite steel, the interaction between κ-carbide and dislocation improves the strain hardening of the material, and comprehensively realizes the goal of low density and ultra-high strength of ultra-fine pearlite bridge cable steel.
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