Thermo-mechanisch hergestelltes, mehrphasiges Kugelgraphitgusseisen

在本项目中，提出了一种新的加工方法，研究在两相铁素体+奥氏体区域缓慢冷却到不同淬火温度（TQ）之前，通过多道次变形对母奥氏体进行晶粒细化来提高球墨铸铁（DI）强度和伸长率的可能性。目的是获得不同的铁素体与奥氏体的比率。随后将材料从两相区淬火至室温，得到马氏体+铁素体基体，或淬火至等温，得到铁素体+奥铁素体+残余奥氏体基体。在一个工艺链中，建议的加工方法结合了两种方法，即热机械加工和双基体结构（DMS）的生产，以改善球墨铸铁的优良组合和力学性能范围。这种采用控制轧制和冷却技术的加工方法将在热轧带钢的广泛领域得到应用。该技术的应用有助于管理各种冶金过程的动力学，如奥氏体形成、再结晶和奥氏体分解行为。多相钢，如热轧双相钢（dp钢），trip钢和复杂相钢（cp钢）是此类轧机产品的例子。计划将上述已用于钢铁的技术转移到生产多相扁钢球墨铸铁，用于要求高韧性的应用，特别是汽车工业。

In this project, a new processing method is proposed to investigate the possibility to improve the strength and elongation of ductile iron (DI) by grain refinement of parent austenite using multipass deformation before slow cooling in the two phase ferrite+austenite region to various quenching temperatures (TQ). The aim is to obtain different ferrite to austenite ratios. The material is subsequently to be quenched from the two phase region either to room temperature, to obtain a martensite + ferrite matrix, or to austempering temperature to obtain a ferrite + ausferrite + retained austenite matrix. In one process-chain, the suggested processing method combines two processes reported to improve the excellent combination and range of mechanical properties of ductile irons namely, thermomechanical processing and production of dual matrix structure (DMS). Such a processing-method would find its application in the wide-spread field of hot strip rolling mills, using controlled rolling and cooling technologies. Application of this technology helps to manage the kinetics of various metallurgical processes, like austenite formation, recrystallization and austenite decomposition behaviours. Multiphase steels such as hot rolled dual phase steel (DP-steel), TRIPsteel and complex phase steel (CP-steel) are examples of products from such rolling mills. It is planned to transfer the preceding technology, already used for steel, to produce multi-phase flat rolled ductile-iron for the use in applications requiring high toughness, particularly for automotive industry.