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利用现代铸造技术以及等温球化处理,使球状石墨铸钢的力学性能达到最佳组合,这是一项既经济又有发展前景的成果。这些钢的最大使用潜力与其制造技术和特征技术参数有关,其中最重要的一项是冷却曲线图(TTT曲线)。在本试验中,冶炼了3炉不同铌含量(0.0%、0.5%和1.0%)及其它元素名义成分(质量分数)为1.0%C、2.3%Si、0.4%Mn的石墨铸钢。用热膨胀试验测定了TTT曲线,各组试验用钢的试样都进行了等温淬火。将试样进行了硬度测试及用光镜和扫描电镜进行了组织观察,并进行了拉伸、无缺口试样冲击及磨损试验。结果表明,铌的加入明显改变了TTT曲线,随着铌含量的增加,使得珠光体转变鼻尖右移,贝氏体转变鼻尖左移。这些合金的抗拉强度都很高,在1700 MPa左右,含1%铌的合金的冲击值为45 J,含0.5%铌合金的为49 J,不含铌的无缺口试样没有被冲断。
The use of modern casting technology and isothermal ball treatment, the mechanical properties of spherical graphite cast steel to achieve the best combination, which is both economic and development prospects of the results. The maximum potential of these steels is related to their manufacturing technology and characteristic specifications, the most important of which is the cooling curve (TTT curve). In this test, three castings of graphite with different contents of niobium (0.0%, 0.5% and 1.0%) and other nominal compositions (mass fraction) of 1.0% C, 2.3% Si and 0.4% Mn were smelted. The TTT curve was measured by the thermal expansion test, and the specimens for each test steel were isothermal quenched. The specimens were tested for hardness and microstructures were observed with light and scanning electron microscopy. Tensile, notched specimen impact and wear tests were performed. The results show that the addition of niobium significantly changes the TTT curve. With the increase of niobium content, the tip of pearlite changes to the right and the bainite changes to the left. The tensile strength of these alloys is very high. At about 1700 MPa, the impact value of the alloy containing 1% niobium is 45 J, that of the alloy containing 0.5% niobium is 49 J, and the unvulcanized niobium-free sample is not punched .