Abstract：High-strength and high-plasticity metal materials have broad application prospects. In order to obtain high-strength and high-plasticity metal materials at the same time,a process strategy of solid state decarburization to produce steel materials with gradient structure is proposed and 2.7%C-medium ferromanganese alloy plate with thickness of 1 mm was selected as the research object. Solid state decarbonization was carried out in H2O-H2 atmosphere,the average carbon content of medium manganese steel after decarburization was determined by carbon-sulfur meter,the microstructure and surface oxidation of decarburized medium manganese steel were observed by optical microscope. The simple hot rolling-tempering treatment of decarburized medium manganese steel was carried out,then the mechanical properties of medium manganese steel were measured by universal tensile testing machine. The results show that the amount of decarbonization increases gradually with the increase of decarbonization temperature and the thickness of oxide layer on the surface of medium manganese steel increases gradually with the extension of decarbonization time. The increase of temperature will increase the migration rate of solid solution carbon,so the growth of oxide layer thickness does not increase with the increase of temperature. Therefore,the control of oxidation layer in the process of decarbonization should reasonably adjust the decarbonization temperature,atmosphere conditions and decarbonization time according to the target carbon content. The carbon mass percent of medium manganese steel can be removed from 2.7% to less than 0.5% and the thickness of oxide layer can be controlled below 15 μm at 1 383 K temperature for 50 min. After solid state decarbonization,the structure of the medium manganese steel change gradually from the surface to the interior. The gradient layer gradually migrates to the center with the extension of decarbonization time. The evolution of gradient layer is caused by the migration of solid carbon to the surface of manganese steel during solid decarburization. This mechanism of using solid state decarbonization to create gradual changes in the internal structure of the steel material from surface to interior is conducive to additional strain hardening and high ductility. The strain-hardening ability of solid decarburized medium manganese steel was enhanced significantly after simple hot-rolling and tempering treatment,and the strength and plasticity matching were obtained,with the highest product of strength and ductility of 45.1 GPa·%. Solid state decarbonization method does not destroy the integrity of the material and creates a gradient structure with strong strain hardening effect,which does not exist in homogeneous materials under the same treatment conditions.
洪陆阔, 艾立群, 孙彩娇, 孟凡峻, 王旭锋, 佟帅. 固态脱碳过程中锰钢微观组织演变及力学性能[J]. 钢铁, 2023, 58(6): 118-125.
HONG Lukuo, AI Liqun, SUN Caijiao, MENG Fanjun, WANG Xufeng, TONG Shuai. Microstructure evolution and mechanical properties of manganese steel during solid state decarburization[J]. Iron and Steel, 2023, 58(6): 118-125.
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