Li Shuangjiang, Wang Yongfei, Li Zeyuan, Liu Xiaoming, Zhao Shengdun
School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an 710049, China.
State Key Laboratory of Compressor Technology (Anhui Laboratory of Compressor Technology), Hefei 230031, China.
Materials (Basel). 2023 Jul 3;16(13):4790. doi: 10.3390/ma16134790.
Low-carbon steel has been popularly applied in numerous applications because of its unique features, such as good plasticity, high strength, great hardness, and excellent toughness. Additionally, the semi-solid thixotropic forging forming method has been widely used in light alloys, due to its advantages of low forming force and high forming quality, whereas its application in ferrous materials is still limited. In this study, the semi-solid thixotropic forging forming process is proposed for producing the low-carbon steel claw pole, with the main stages being radial forging deformation, isothermal treatment, and forging forming. The effect of the area reduction rate on the effective strain from the cross sections of the radial-forged metal bar was studied using numerical simulations. The effect of the isothermal holding process on the microstructures of radial-forged billets was investigated, to obtain the ideal semi-solid microstructures. The microstructure and mechanical properties of low-carbon steel claw poles from the thixotropic forging experiment are presented and discussed. It was found that when the area reduction rate was 67%, the effective strain at the edge of the metal bar exceeded 5.0, while the effective strain at the center was above 1.2, indicating an excellent quality of forging for the bar. The optimization of the process parameters for preparing low-carbon steel semi-solid billets with fine and globular microstructures was achieved with an area reduction rate of 67%, an isothermal temperature of 1500 °C, and a duration time of 15 min. Moreover, the low-carbon steel claw pole fabricated with the optimized operating parameters was found fully filled, with a sharp profile and a flat surface, where the yield strength and tensile strength increased by 88.5% and 79.8%, respectively, compared to the starting materials.
低碳钢因其具有良好的塑性、高强度、高硬度和优异的韧性等独特特性，已广泛应用于众多领域。此外，半固态触变锻造成形方法因其成形力低、成形质量高的优点，已在轻合金中得到广泛应用，而其在黑色金属材料中的应用仍较为有限。在本研究中，提出了采用半固态触变锻造成形工艺来生产低碳钢爪极，主要阶段包括径向锻造变形、等温处理和锻造成形。通过数值模拟研究了面积缩减率对径向锻造金属棒材横截面有效应变的影响。研究了等温保温过程对径向锻造坯料微观组织的影响，以获得理想的半固态微观组织。展示并讨论了触变锻造实验中低碳钢爪极的微观组织和力学性能。结果发现，当面积缩减率为67%时，金属棒材边缘的有效应变超过5.0，而中心的有效应变高于1.2，表明该棒材锻造质量优异。通过67%的面积缩减率、1500℃的等温温度和15分钟的保温时间，实现了制备具有细小等轴球状微观组织的低碳钢半固态坯料工艺参数的优化。此外，采用优化操作参数制造的低碳钢爪极填充完整，轮廓清晰，表面平整，与原材料相比，其屈服强度和抗拉强度分别提高了88.5%和79.8%。
