Multi-physics modelling of semi-solid deformation and hot tearing in advanced high strength steels

先进的高强度钢(AHSS)是减轻车辆重量、从而减少与温室气体排放相关的燃油消耗的关键部件。与传统的高强度钢相比，AHSS在保持成形性的同时获得了显著的强度。更高的成形性使部件更复杂，从而减少了单个部件的数量，提高了制造灵活性。然而，由于AHSS板坯的合金含量很高--锰含量高达5%，硅含量高达2%，铝含量高达2%，因此通常会出现由凝固壳热撕裂引起的表面横向裂纹和中心裂纹。这些裂缝导致钢铁生产商的运营延迟和产品质量低劣。在这项与安大略省汽车行业主要钢铁生产商和供应商安赛乐米塔尔·多法斯科的合作研究中，我们打算研究AHSS中热裂的形成和传播。拟开展的研究分为两个方面的研究。第一个是开发一种新的多物理模型，该模型同时模拟连铸过程中柱状晶和柱状晶/等轴晶网络的凝固、渗流、补缩和变形，用于模拟热撕裂。第二种是直接测量半固态AHSS的本构行为，以确定该合金家族对热撕裂的敏感程度。提出的研究计划的共同目标是确定减少AHSS合金热撕裂形成的最佳工艺路线。

Advanced high strength steels (AHSS) represent a key component in reducing vehicle weight and hence reducing fuel consumption related greenhouse gas emissions. In comparison to traditional high strength steels, AHSS achieve significant strength while retaining formability. The increased formability enables greater component complexity, which leads to fewer individual parts and more manufacturing flexibility. However, due to their high alloy contents - manganese up to 5%, silicon up to 2% and aluminum up to 2% - AHSS slabs routinely exhibit transverse surface cracks and centreline cracks caused by hot tearing of the solidifying shell. These cracks result in operational delays and poor product quality for steel producers. In this collaborative study with ArcelorMittal Dofasco, a major producer and supplier of steels to the automotive industry in Ontario, we intend to examine the formation and propagation of hot tears in AHSS. The proposed research is divided into two areas of study. The first is the development of a new multi-physics model that concurrently simulates the solidification, percolation, feeding, and deformation of a network of columnar and columnar/equiaxed grains during continuous casting, for modelling of hot tearing. The second is the direct measurement of the constitutive behaviour of semi-solid AHSS to determine the degree to which this alloy family is susceptible to hot tearing. The joint goal of the proposed research program is to identify the optimal processing routes for reducing hot tearing formation in AHSS alloys.