Preparation of medium manganese steel high strength plastic with composition gradient by solid state decarbonization
HONG Lu-kuo1, AI Li-qun1, SUN Cai-jiao1, LI Ya-qiang2, ZHOU Mei-jie1, MENG Fan-jun1
1. College of Metallurgy and Energy, North China University of Science and Technology, Tangshan 063210, Hebei, China; 2. Hebei University of Science and Technology, Xingtai 054099, Hebei, China
Abstract:The strength-ductility trade-off has been a long-standing dilemma in materials science. Many organisms have evolved over millions of years through natural selection and optimization. In many biological systems,structures such as bones and plant stems change gradually from the surface to the interior. This gradient structure can make biological systems strong and tough to survive severe natural forces. A process strategy of solid state decarbonization for preparing composition gradient steel was proposed,breaking the trade-off relationship between strength and ductility. In order to verify the feasibility of this technological concept,solid state decarburization research was carried out with alloy thickness of 1 mm and composition of 2.7%C-12%Mn-Fe(mass percent)as the research object. Excellent strength and ductility of manganese steels prepared in this experiment have been obtained. The experimental results show that the solid state decarbonization method has achieved surprising success in the preparation of medium manganese steels. The carbon mass percent of medium manganese steel can be removed from 2.7% to 0.23% in H2O-H2 atmosphere for 50 min. The component gradient was measured by glow discharge spectrometer and optical microscope. The decarbonized and hot rolled medium manganese steel plates have obvious composition gradient and holistic gradient structure in the thickness direction. This holistic gradient structure is a key factor to guarantee the deformability of the medium manganese steel. The cross section hardness distribution of medium manganese steel was measured by Vickers hardness tester. Solid state decarbonization inevitably creates a thick transition layer in the interior and directly resulting in a gradually increased hardness from the surface of the centre layer (668HV) to the interior (747HV). This unique hardness gradient is inherent to the compositional gradient material and lays the foundation for continuous strain hardening. When the homogeneous steel is deformed to increase strength,its ductility usually drops dramatically. In contrast,the strength of compositional gradient steel increased from 1 339.1 MPa to 1 513.5 MPa and the ductility increased from 26.3% to 29.8%. This indicates that the strategy of solid state decarbonization to prepare compositional gradient steels has obtained good comprehensive mechanical properties. More importantly,the proposed strategy is a general conception,and other metal material such as DP,QP,HSLA and PHS,can also be selected. This is also the future focus.
洪陆阔, 艾立群, 孙彩娇, 李亚强, 周美洁, 孟凡峻. 固态脱碳法制备高强塑性成分梯度中锰钢[J]. 钢铁, 2023, 58(5): 131-136.
HONG Lu-kuo, AI Li-qun, SUN Cai-jiao, LI Ya-qiang, ZHOU Mei-jie, MENG Fan-jun. Preparation of medium manganese steel high strength plastic with composition gradient by solid state decarbonization[J]. Iron and Steel, 2023, 58(5): 131-136.
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