1200MPa级冷轧超高强钢板的相变和纳米析出复合强化机制及工艺控制

The cold-rolled ultra-high strength steel plays an important role in ultra-lightweight steel automotive body manufacturing and automobile lightweighting. By precise controlling the phase transformation structural refinement and nano-particles precipitation, it is very likely to get the high-performance cold-rolled ultra-high strength steel sheets with low cost. Finding out the mechanism of phase transformation and nano-precipitation composite strengthening and controlling the process efficiently is the key..In this project, the simple and low-cost composition design of Ti and Ti-Nb micro alloyed is proposed and based on a composition of C-Si-Mn, and we formed a design of composition and multiphase microstructure of 1200MPa grade new type cold-rolled ultra-high strength steel which is ultrafine multiphase microstructure with nano-precipitation composite strengthen. By hot rolling, cold rolling, continuous annealing and rapid cooling(water quenching and rapid spray cooling) process, the phase transformation and structural refinement of cold-rolled ultra-high strength steel is precise controlled and effectively controlling the precipitation of nano-particles in steel, revealing the mechanism of phase transformation and nano-precipitation composite strengthening of cold-rolled ultra-high strength steel and establishing relevant process control methods, thus significantly improving the strength and keeping the good formability of steel, which all of the above provides a scientific basis for saving the alloy resources, reducing the costs and at the same time, the research, development and application of the high-performance, ultra high strength and toughness steel..

冷轧超高强钢在超轻型钢制车体制造、实现汽车轻量化中占有重要地位，通过相变组织细化及纳米粒子析出精细控制，极有希望获得具有较低成本的高性能冷轧超高强钢板，搞清相变及纳米析出复合强化机制并进行有效工艺控制是其关键。. 本项目提出并建立在C-Si-Mn成分基础上进行钛及钛铌微合金化的低成本简约化成分设计，形成超细化复相组织加纳米粒子析出复合强化的1200MPa级新型冷轧超高强钢的成分与复相组织设计方法；通过先进的热轧、冷轧及连续退火快速冷却工艺（水淬及快速气雾冷却）精确控制冷轧超高强钢的相变与组织细化，并有效控制钢中纳米粒子析出，揭示冷轧超高强钢的相变与纳米粒子复合强化机制，建立相关工艺控制方法，由此显著提高钢的强度并保持良好的成形性能，为节约合金资源、降低成本并同时获得高性能、超高强韧钢材的研究开发及应用提供科学依据。

首先在C-Si-Mn成分基础上进行了DP1200级冷轧超高强双相钢的开发研制，并对比实验及理论分析了添加微合金Nb,Ti元素对组织及性能的影响规律，形成了超细化复相组织加纳米粒子析出复合强化的1200MPa新型冷轧超高强钢的成分与复相组织设计方法。研究了实验钢的基础性能以及在热轧、冷轧、连退、卷曲、热处理工艺等过程中的不同参数对纳米析出的影响及其与组织性能的关系。.同时还在C-Si-Mn成分基础上进行了1200MPa级冷轧超高强Q&P钢的开发研制，形成了超细化复相组织加纳米粒子析出复合强化的Q&P1200MPa新型冷轧超高强钢的成分与复相组织设计方法。研究了两种钢的基础性能以及在热轧、冷轧、连退、卷曲、热处理工艺等过程中的不同参数对纳米析出的影响及其与组织性能的关系。.在实验及理论分析基础上提出并建立了在C-Si-Mn成分基础上进行钛及钛铌微合金化的低成本简约化成分设计，形成超细化复相组织加纳米粒子析出复合强化的1200MPa级新型冷轧超高强钢的成分与复相组织设计方法。通过科学合理的热轧、冷轧及连续退火快速冷却工艺，精确控制冷轧超高强钢的相变与组织细化及钢中纳米粒子析出，揭示了冷轧超高强钢的相变与纳米粒子复合强化机制，建立了相关工艺控制方法，显著提高了钢的强度并保持良好的成形性能，为节约合金资源、降低成本并同时获得高性能、超高强韧钢材的研究开发及应用提供了科学依据。项目共发表11篇（SCI收录7篇,EI收录3篇,国际会议1篇）；培养博士生4名，硕士生3名。