Motors are essential components in electric vehicles and there are at present worldwide efforts to improve their efficiency and reduce their weight. One of these areas concerns improving the quality of steel laminations that are used for their magnetic properties in rotors and stators. These are ‘soft’ magnetically, meaning that they can be easily magnetised and demagnetised. Improvements in magnetic quality, i.e. reductions in power loss during magnetisation, have been pursued for many years but the high-speed motors in vehicles are also subject to greater mechanical loading, in particular in the rotors of IPM-machines (Internal Permanent Magnet rotor machines). These are the dominating type of electric motor for electrified vehicles due to their high efficiency and high power/torque density. As a result, there are increasing requirements for new steel products that combine low power losses with high strength. This is difficult because most ways of raising the strength result in the magnetic characteristics becoming also undesirably harder. The present paper starts with a consideration of how magnetic power losses are defined and the factors that influence these. Then, different strengthening methods are considered together with their effects on magnetisation. Strengthening can be achieved by (i) solid solution alloying, (ii) grain refinement, (iii) work hardening, (iv) precipitation and (v) texture control. Most commonly, the requirements are in conflict. Only solid solution strengthening can confer benefits to both strength and power loss although extremely fine nanoprecipitation can raise the strength with little or no magnetic detriment. Based on this analysis, results from research publications and patents are summarised and reviewed.

电机是电动汽车的重要部件，目前全世界都在努力提高其效率并减轻其重量。这些领域之一涉及提高用于转子和定子磁性能的钢叠片的质量。它们在磁性上是“软的”，这意味着它们可以很容易地磁化和消磁。多年来一直致力于改善磁质量，即减少磁化过程中的功率损耗，但车辆中的高速电机也承受更大的机械负载，特别是在 IPM 电机（内部永磁转子电机）的转子中）。由于其高效率和高功率/扭矩密度，这些是电动汽车的主要电动机类型。因此，对兼具低功率损耗和高强度的新型钢铁产品的要求越来越高。这是困难的，因为提高强度的大多数方法导致磁特性也变得不合需要地更硬。本文首先考虑如何定义磁功率损耗以及影响这些的因素。然后，考虑不同的强化方法及其对磁化的影响。强化可以通过 (i) 固溶合金化、(ii) 晶粒细化、(iii) 加工硬化、(iv) 沉淀和 (v) 织构控制来实现。最常见的是，这些要求是相互冲突的。尽管极细的纳米沉淀可以在几乎没有或没有磁性损害的情况下提高强度，但只有固溶强化才能同时提高强度和功率损失。