Anca Denisa-Elena, Stan Iuliana, Riposan Iulian, Stan Stelian
Materials Science and Engineering Faculty, Politehnica University of Bucharest, 060042 Bucharest, Romania.
Materials (Basel). 2022 Apr 7;15(8):2712. doi: 10.3390/ma15082712.
In recent years, high-Si ductile cast irons (3-6% Si) have begun to be used more and more in the automotive and maritime industries, but also in wind energy technology and mechanical engineering. Si-alloyed ferrite has high strength, hardness and oxidation and corrosion resistance, but it has low ductility, toughness and thermal conductivity, with graphite as an important influencing factor. In this study, 4.5% Si uninoculated ductile iron solidified in thin wall castings (up to 15 mm section size) via a permanent (metal) mold versus a sand mold, was evaluated. Solidification in a metal mold led to small size, higher graphite particles (less dependent on the section size). The graphite particles' real perimeter was 3-5% higher than the convex perimeter, while the values of these parameters were 41-43% higher in the sand mold. Increasing the casting section size led to an increased graphite perimeter, with it being much higher for sand mold. The graphite particles' shape factors, involving the maximum and minimum size, were at a lower level for metal mold solidification, while by involving the difference between P and P, is higher for the metal mold. The shape factor, including the graphite area and maximum size, had higher values in the metal mold, sustaining a higher compactness degree of graphite particles and a higher nodularity regarding metal mold solidification (75.5% versus 67.4%). The higher was due to the graphite compactness degree level (shape factor increasing from 0.50 up to 0.80), while the lower was due to the graphite nodularity for both the metal mold (39.1% versus 88.5%) and the sand mold (32.3% versus 83.1%). The difference between the metal mold and sand mold as the average graphite nodularity increased favored the metal mold.
近年来，高硅球墨铸铁（硅含量为3%-6%）在汽车和船舶工业中开始越来越多地得到应用，在风能技术和机械工程领域也有应用。硅合金铁素体具有高强度、硬度以及抗氧化和耐腐蚀性能，但它的延展性、韧性和热导率较低，其中石墨是一个重要的影响因素。在本研究中，对通过金属型（永久模）与砂型凝固在薄壁铸件（截面尺寸达15毫米）中的4.5%硅未孕育球墨铸铁进行了评估。在金属型中凝固导致石墨颗粒尺寸小、数量多（对截面尺寸的依赖性较小）。石墨颗粒的真实周长比凸周长高3%-5%，而在砂型中这些参数的值高41%-43%。增加铸件截面尺寸会导致石墨周长增加，砂型中的增加幅度更大。涉及最大和最小尺寸的石墨颗粒形状因子在金属型凝固时处于较低水平，而涉及P与P差值的形状因子在金属型中更高。包括石墨面积和最大尺寸的形状因子在金属型中有更高的值，表明金属型凝固时石墨颗粒的致密程度更高、球化率更高（分别为75.5%和67.4%）。较高的值归因于石墨致密程度水平（形状因子从0.50增至0.80），而较低的值归因于金属型（分别为39.1%和88.5%）和砂型（分别为32.3%和83.1%）的石墨球化率。随着平均石墨球化率增加，金属型和砂型之间的差异对金属型有利。
