凝固、冷却及热处理一体化柔性调控无取向硅钢夹杂物与析出物的基础研究

Steels for high efficiency compact motors have been obtained by mainly decreasing （Si+Al）content, improving product texture and controlling inclusions and precipitates in recent years. In spite of eliminating hot rolling and normalizing in traditional processes, the twin roll strip casting can obtain large and uniform microstructures, poorer γ texture and minor ultra-fine or coarse precipitates by controlling solidfication and secondary cooling parameters , and then show a distinct advantage in producing non-oriented silicon steels with high magnetic induction and low iron loss. The project combines "twin roll strip casting" with "ultra-rapid heat treatment " characterized by high-speed heating and cooling. Based on thermodynamics and kinetics theories of second-phase precipitation, under the sub-rapid solidafication, complex-path control during secondary cooling (holding at high temperature, ultra-rapid cooling, etc.) and ultra-rapid annealing conditions, the behaviors of inclusions and precipitates of non-oriented Fe-Si alloy such as nucleation, growth and coarsening, will be studied systematically, to achieve the precise control over the whole process. The relationship between microstructure, texture, magnetic properties and precipitation of non-oriented Fe-Si material in an ultra-short technologic route will be revealed. The aim of this investigation is to solve the key scientific problems about controlling inclusions and precipitates by strip-casting and ultra-rapid annealing technology, which has important scientific significance and practical value.

降低Si+Al含量、优化成品织构、夹杂物与析出物控制已经成为近年来高效率高性能电机用钢研究的主要方向。双辊薄带连铸可以通过取消热轧和常化，并合理控制凝固及二次冷却工艺，获得均匀粗大的组织、较弱的γ织构和少量的超细或粗大析出，在开发高磁感低铁损无取向硅钢方面具有独特的优势。本项目将“双辊薄带连铸”与可实现高速加热和冷却的“超快速热处理”相结合，以第二相析出热力学和动力学理论为基础，系统研究在亚快速凝固、二冷段复杂路径（高温保温、超快速冷却等）和超快速退火条件下，无取向Fe-Si合金夹杂物与析出物形核、长大和聚集粗化行为的基础理论、影响因素和控制方法，实现全过程第二相析出行为的精确设计与调控，提出超短流程无取向Fe-Si材料制备过程的析出物与组织、织构、磁性能一体化控制理论与技术。本研究旨在突破薄带连铸和新一代热处理技术在夹杂物和析出物控制中的关键问题，具有重要的科学意义和应用价值。

双辊薄带连铸技术是连铸领域最具潜力的一项新技术，引领着钢铁工业的发展方向。本项目研究了薄带连铸Fe-Si合金在凝固、冷却及热处理过程中析出物和夹杂物演变的基础理论，阐明了铸轧无取向硅钢第二相粒子与组织、织构演变之间的交互作用关系，提出了以“三次析出调控”为特征的第二相粒子“两极化”控制理论，开发了以发达Cube再结晶织构为特征的高磁感、低铁损无取向硅钢一体化调控技术。研究获得以下重要结果：(1)薄带连铸Fe-Si合金凝固组织及织构形成机制，铜铸辊及大温度梯度有利于获得以发达{001}织构为主的柱状晶组织。(2)亚快速凝固过程Σ3等特殊晶界演变机制及影响因素。(3)亚快速凝固条件下第二相粒子的析出机理，浇注温度、凝固速率、布流水口及钢液Ca处理将会影响第二相粒子尺寸分布。(4)高温固溶过程中析出物热稳定性及粗化机制。(5)冷却区间与速率对第二相粒子形貌及尺寸的影响。(6)铸带热变形对组织、织构及析出物的作用机理。(7)铸带热处理对组织、析出物的影响机制。(8)不同冷轧工艺下组织、织构及析出物演变规律，合适的两阶段冷轧能增加η再结晶织构、减弱γ织构。(9)超快速退火对组织、织构及析出物的影响机制，升温速率的提高可增加退火板中50nm以下析出物数量。(10)无取向硅钢极薄带制备方法及组织、织构演变特征。(11)薄带连铸无取向Fe-6.5%Si钢凝固组织控制及有序相演变规律。(12)与常规流程相比，铸轧无取向硅钢拥有更强的Cube织构、更弱的γ织构，磁感值普遍高0.03~0.12T，磁各向异性降低。(13)薄带连铸硅钢Cube再结晶织构形成机制，铸带特有的强Cube、{110}<110>织构以及粗大晶粒强化了Cube再结晶晶粒的形核和长大。(14)以“三次析出控制”及λ织构强化为特征的薄带连铸无取向硅钢磁性能优化技术。Fe-1.3%Si钢磁感达到1.77T，铁损4.07W/kg；Fe-3.0%Si钢磁感达到1.75T，铁损2.92W/kg，磁性能特别是磁感值远高于同牌号商业化产品典型值。上述研究结果突破了薄带连铸硅钢在析出物、组织和织构调控方面的关键科学问题，为生产超低铁损、超高磁感无取向电工钢开辟了新的理论基础和技术途径。