Toughening and its Application of Austempered Ductile Cast Iron by Thermomechanically Treatment

在1998财政年度，研究了变形量、等温淬火温度和形变热处理时间对奥贝球铁韧性的影响。在1999财政年度，为了优化和效率的热机械处理条件，石墨直径和等温淬火温度对韧性的影响进行了研究。在2000年的财政年度中，评估了轧制压下量和奥氏体稳定性对强度和韧性的影响，已经证实石墨尺寸对ADI断裂韧性的影响几乎可以忽略。另一方面，通过对γ池与韧性关系的分析，发现γ池对ADI断裂韧性的影响占主导地位，石墨球间形成的剪切带虽然有效地作为贝氏体铁素体的形核位置，但有时也会导致断裂。结论是， 关于我们 大的石墨球对于热机械处理的实际应用是优选的。在压下量为40%、等温淬火时间为14.4ks时，合金的吸收能量最大，而断裂韧性在压下量为60%时最大。当压下量为0 ~ 40%时，抗拉强度超过1000 MPa，伸长率在40%时达到最大值。在此范围内，残余奥氏体减少，稳定性提高，形变诱发马氏体相变消失，综合考虑，从强韧性平衡的角度考虑，40%的压下量为最佳压下量。强度在较低的轧制压下率侧变得较高，而韧性在较高的侧变得上级。通过利用以上获得的知识，各个部分的特性的优化与近净成形一起成为可能。通过在上述概念的基础上进行球墨铸铁的显微组织和成分设计，可以认识到相对于传统钢的优势，这使得能够替代钢。少

In the fiscal year 1998, effects of rolling reduction, austempering temperature and its time during thermo-mechanical treatments on toughness of the ADI were investigated. In the fiscal year 1999, in order for the optimization and efficiency of the thermo-mechanical treatment conditions, effects of graphite diameter and austempering temperature on toughness were investigated. In the fiscal year 2000, effects of rolling reduction and stability of Austenite on strength and toughness were evaluated.It has been certified that the effects of the graphite size on the fracture toughness of the ADI is almost negligible.. On the other hand, according to the analysis of the relationship between the gamma pool and toughness, the gamma pool is predominant over the fracture toughness properties of the ADI.Although shear bands which are formed in-between the graphite nodules act as a nucleation site for the beinitic ferrite effectively, it sometimes causes fracture there. It has been concluded that … More large graphite nodules are preferable for the practical application of the thermo-mechanical treatment. As for the absorbed energy, the maximum value was obtained for the rolling reduction of 40% and austempering time of 14.4ks, while the fracture toughness reached maximum for the rolling reduction of 60%. The tensile strength exceeds 1000MPa when the rolling reduction ranges 0 to 4O%, and the elongation reached the maximum for the 4O% reduction. The residual Austenite decreased and its stability increased within the range and deformation-induced Martensite transformation disappeared in the high rolling reduction range.Comprehensively speaking, the rolling reduction of 40% is concluded as the best condition from a viewpoint of the balance between strength and toughness. Strength becomes higher in the lower rolling reduction side, while toughness becomes superior in the higher side. The optimization of characteristics of respective portion becomes possible together with near-net-shape forming by utilizing the knowledge obtained above. By performing microstructural and component designs of the ductile cast irons on the basis of the above-mentioned concepts, predominance over the traditional steel can be recognized which enables substitution from the steels. Less