6.5wt%高硅钢薄板复合技术制备研究

发布时间：2018-03-02 12:01

本文选题：6.5wt%高硅钢复合板　切入点：轧制　出处：《北京科技大学》2015年博士论文　论文类型：学位论文

【摘要】：6.5wt%高硅钢具有磁致伸缩系数接近零、磁导率大、矫顽力低和铁损低等优异的软磁性能,在降低高频电器的能源损耗、噪音污染等方面优势明显；但是合金自身显著的低温脆性严重影响了该材料的广泛应用。明确6.5wt%高硅钢的脆性本质和塑性变形机制,并在制备和成形加工过程中对该合金的不足施加积极的避免和有效的控制,所以研究开发一种流程短、效率高的制备加工方法,是实现6.5、wt%高硅钢工业化生产的关键问题。本论文针对6.5wt%高硅钢合金室温脆性显著、常规方法难以成形的特点,依据层状复合材料的对称结构,利用塑性变形过程中覆层材料对芯层材料的保护以及应力场的变化,实现了6.5wt%高硅钢薄板的复合制备成形工艺,并对该合金复合板的铸坯制备、成形过程、热处理工艺、合金元素分布、内部界面演化、微观组织结构、磁学性能特征等方面进行了研究,得出的主要结论如下： (1)对复合板铸坯进行结构和成分的设计,采用包覆浇铸制备出了芯层为高硅合金(10-12wt%Si)、覆层为普通硅钢(3wt%Si)的三块高硅钢复合板坯,通过锻造后,复合板各层比例发生变化,芯层和覆层的Si元素含量有些下降,说明在高温下Si元素氧化损失严重； (2)对高硅钢复合板的热轧变形进行理论研究,制定热轧工艺,通过热轧后复合板板厚约为2.5mm左右、覆层和芯层的厚度比例在1：l左右；对热轧后复合板进行XRD相分析,发现芯层除D03相外,还存在Fe2SiO4、FeSiO3、 Fe1.6SiO4以及SiQ等相,证实Si元素以氧化物形式丢失； (3)对热轧复合板进行热处理工艺研究,发现复合板在850℃退火保温60min后,盐水(15wt%NaCl水溶液)冷却后复合板不开裂,芯层硬度从556HV下降到482HV,通过显微组织及XRD相分析,芯层的D03相向B2相转变使得复合板有序度降低得到软化,同时出现B20相； (4)经过热处理有序度得到降低的复合板在温轧中变形更容易,在690℃进行恒温轧制,复合板表面质量较好、各层厚度比例趋于合理,且芯层组织呈现细小的纤维状；说明复合板的有序度降低是保证温轧可持续进行的前提,温轧后复合板的厚度约为0.5mm；对温轧过程中的复合板进行Si元素跟踪扫描,发现在750℃下不存在Si元素丢失现象,这说明加热温度在高硅钢合金的再结晶温度以下时,可以消除复合板的加工硬化,同时不降低Si元素含量； (5)温轧后的复合板不能直接冷轧成薄带,必须通过热处理改变温轧后的组织,否则在冷轧过程中,复合板将出现开裂；后续变形中对复合板进行中温回火处理可持续轧制到0.2mm；通过热处理降低有序度后的0.2mm复合板,在冷轧机上可以持续变形为厚度约0.05mm的薄带； (6)通过对冷轧变形的复合板显微组织变化观察和Si元素含量测试,复合板在冷轧变形的初期三层结构清晰可见,即可以观察到过渡层,随着变形程度的增大,过渡层变得模糊,覆层在冷轧的开始阶段主要承担复合板的变形,随着加工硬化的增大,芯层变形量也变大,冷轧后的复合板各层组织呈现拉长的纤维状态、晶界平直； (7)对0.8mm复合板进行扩散退火处理,发现1100。C保温时间较短的复合板芯层Si元素难以发生扩散,1150-C短时保温后Si元素开始发生扩散,但扩散速率较慢,1200。C短时保温后,Si元素扩散明显,经过一定时间后,复合板整体Si元素含量几乎达到均匀,约为6.41wt%；对0.5mm复合板在1200℃保温75min,复合板Si元素已经扩散均匀,整体Si元素含量约为6.43wt%； (8)高硅钢复合板在1200℃下扩散效果最好,对扩散后的复合板进行磁性能检测,0.8mm复合板的铁损P15/50为3.906W/Kg,B8为1.297T,B5o为1.584T；对于0.5mm的3号复合板,铁损P15/50为2.833W/kg,B8为1.371T,B50为1.628T；对于0.5mm的1号复合板铁损P15/50为3.327W/kg,B8为1.332T,B5o为1.609T。
[Abstract]:6.5wt% steel has high magnetostrictive coefficient is close to zero, high permeability, low coercivity and low loss of excellent soft magnetic properties, reduce the energy loss in high frequency equipment, noise pollution and other advantages; but the alloy itself significantly low temperature brittleness has seriously affected the extensive application of the material. The inherent brittleness of 6.5wt% steel is clear and the plastic deformation mechanism, and actively prevent and effectively control applied in the preparation of the alloy and insufficient forming process, so the research and development of a short process, preparation and processing method of high efficiency, is to realize the 6.5 key problems of wt% steel in industrial production.
In this paper 6.5wt% high silicon steel alloy brittleness at room temperature significantly, conventional methods are difficult to form, based on the symmetrical structure of laminated composite materials, the use of plastic deformation changes of cladding material in the process of core material protection and stress field, to achieve the 6.5wt% high silicon steel sheet composite preparation and casting forming process. For the alloy composite plate preparation, forming process, heat treatment process, the distribution of alloying elements, internal interface evolution, microstructure, magnetism properties were studied, the main conclusions are as follows:
(1) design of the structure and composition of the composite plate billet, the coating was prepared by casting the core layer is high silicon alloy (10-12wt%Si) coatings, ordinary silicon steel (3wt%Si) of the three pieces of high silicon steel by forging composite slab, composite plate, each layer ratio changes, the content of Si layer the core and the cladding layers decreases, in high temperature oxidation loss of Si element;
(2) of hot rolled high silicon steel composite plate deformation theory, developed by hot rolling process, rolling composite plate thickness is about 2.5mm, the cladding layer and core layer thickness ratio is about 1:l; phase analysis of hot-rolled composite plate XRD, found that the core layer in D03 phase, there are Fe2SiO4, FeSiO3, Fe1.6SiO4 and SiQ, Si confirmed that the missing element in the form of oxide;
(3) study of heat treatment process on hot rolled composite plate and composite plate found at 850 DEG C 60min after annealing, brine (15wt%NaCl solution) composite plate does not crack after cooling, the core hardness decreased from 556HV to 482HV, the microstructure and phase analysis by XRD, the core layer D03 phase to B2 phase transition of the composite in order to get lower softening, appear at the same time B20;
(4) after heat treatment in order of composite plate decreased in warm rolling deformation more easily, the temperature of rolling at 690 degrees, the surface quality of composite plate is good, the thickness of each layer and core layer more reasonable proportion, fine fibrous tissue showed that the degree of order; composite plate is the premise to ensure sustainable warm rolling reduction the temperature after rolling composite plate thickness is about 0.5mm; Si tracking scan of the composite plate rolling process, it is found that Si lost phenomenon does not exist under 750 degrees, the heating temperature in high silicon alloy below recrystallization temperature, can eliminate the work hardening of the composite plate, at the same time do not reduce the content of Si;
(5) direct cold rolling composite plate can temperature after rolling into thin strips, must change temperature after rolling by heat treatment, or in the cold rolling process of composite plate will appear crack; subsequent deformation of composite plate temperature tempering treatment to sustainable rolling 0.2mm; through heat treatment reduced 0.2mm composite plate of low order after, in the cold rolling mill for thin strip continuous deformation can be the thickness of about 0.05mm;
(6) by testing the microstructure of composite plate and to observe the change of Si content on cold rolling deformation of the composite plate is visible in the early cold rolling deformation of three layer structure is clear, which can be observed in the transition layer, with the increase of deformation degree, transition layer becomes blurred, clad in cold start stage is mainly responsible for the deformation of composite plate with the increase of work hardening, the core layer deformation, fiber state after cold rolling composite plate of each layer of tissue showed elongated, flat boundaries;
(7) diffusion annealing treatment on 0.8mm composite board, found the composite plate core layer Si element 1100.C holding time shorter to spread, 1150-C short holding time Si elements began to spread, but the slow diffusion rate of 1200.C, short holding time, the diffusion of Si obviously, after a certain period of time, the overall content of Si composite in almost uniform, about 6.41wt%; the 0.5mm composite board insulation 75min at 1200 DEG C, Si composite plate elements have been spread evenly, the whole content of Si is about 6.43wt%;
(8) high silicon steel composite plate under the temperature of 1200 DEG C diffusion effect is the best, the composite plate diffusion after the magnetic detection, 0.8mm composite board for 3.906W/Kg B8 as the core loss P15/50, 1.297T, B5o for 1.584T; 0.5mm for the No. 3 composite board, 2.833W/kg B8 as the core loss P15/50, 1.371T, B50 for 1.628T; for the 0.5mm 1 composite plate core loss P15/50 3.327W/kg, B8 1.332T, B5o 1.609T.

【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TG335;TG260;TG161

【参考文献】