本文選題：6.5wt%高硅鋼復合板　切入點：軋制　出處：《北京科技大學》2015年博士論文　論文類型：學位論文

【摘要】：6.5wt%高硅鋼具有磁致伸縮系數(shù)接近零、磁導率大、矯頑力低和鐵損低等優(yōu)異的軟磁性能,在降低高頻電器的能源損耗、噪音污染等方面優(yōu)勢明顯；但是合金自身顯著的低溫脆性嚴重影響了該材料的廣泛應用。明確6.5wt%高硅鋼的脆性本質和塑性變形機制,并在制備和成形加工過程中對該合金的不足施加積極的避免和有效的控制,所以研究開發(fā)一種流程短、效率高的制備加工方法,是實現(xiàn)6.5、wt%高硅鋼工業(yè)化生產(chǎn)的關鍵問題。 本論文針對6.5wt%高硅鋼合金室溫脆性顯著、常規(guī)方法難以成形的特點,依據(jù)層狀復合材料的對稱結構,利用塑性變形過程中覆層材料對芯層材料的保護以及應力場的變化,實現(xiàn)了6.5wt%高硅鋼薄板的復合制備成形工藝,并對該合金復合板的鑄坯制備、成形過程、熱處理工藝、合金元素分布、內(nèi)部界面演化、微觀組織結構、磁學性能特征等方面進行了研究,得出的主要結論如下： (1)對復合板鑄坯進行結構和成分的設計,采用包覆澆鑄制備出了芯層為高硅合金(10-12wt%Si)、覆層為普通硅鋼(3wt%Si)的三塊高硅鋼復合板坯,通過鍛造后,復合板各層比例發(fā)生變化,芯層和覆層的Si元素含量有些下降,說明在高溫下Si元素氧化損失嚴重； (2)對高硅鋼復合板的熱軋變形進行理論研究,制定熱軋工藝,通過熱軋后復合板板厚約為2.5mm左右、覆層和芯層的厚度比例在1：l左右；對熱軋后復合板進行XRD相分析,發(fā)現(xiàn)芯層除D03相外,還存在Fe2SiO4、FeSiO3、 Fe1.6SiO4以及SiQ等相,證實Si元素以氧化物形式丟失； (3)對熱軋復合板進行熱處理工藝研究,發(fā)現(xiàn)復合板在850℃退火保溫60min后,鹽水(15wt%NaCl水溶液)冷卻后復合板不開裂,芯層硬度從556HV下降到482HV,通過顯微組織及XRD相分析,芯層的D03相向B2相轉變使得復合板有序度降低得到軟化,同時出現(xiàn)B20相； (4)經(jīng)過熱處理有序度得到降低的復合板在溫軋中變形更容易,在690℃進行恒溫軋制,復合板表面質量較好、各層厚度比例趨于合理,且芯層組織呈現(xiàn)細小的纖維狀；說明復合板的有序度降低是保證溫軋可持續(xù)進行的前提,溫軋后復合板的厚度約為0.5mm；對溫軋過程中的復合板進行Si元素跟蹤掃描,發(fā)現(xiàn)在750℃下不存在Si元素丟失現(xiàn)象,這說明加熱溫度在高硅鋼合金的再結晶溫度以下時,可以消除復合板的加工硬化,同時不降低Si元素含量； (5)溫軋后的復合板不能直接冷軋成薄帶,必須通過熱處理改變溫軋后的組織,否則在冷軋過程中,復合板將出現(xiàn)開裂；后續(xù)變形中對復合板進行中溫回火處理可持續(xù)軋制到0.2mm；通過熱處理降低有序度后的0.2mm復合板,在冷軋機上可以持續(xù)變形為厚度約0.05mm的薄帶； (6)通過對冷軋變形的復合板顯微組織變化觀察和Si元素含量測試,復合板在冷軋變形的初期三層結構清晰可見,即可以觀察到過渡層,隨著變形程度的增大,過渡層變得模糊,覆層在冷軋的開始階段主要承擔復合板的變形,隨著加工硬化的增大,芯層變形量也變大,冷軋后的復合板各層組織呈現(xiàn)拉長的纖維狀態(tài)、晶界平直； (7)對0.8mm復合板進行擴散退火處理,發(fā)現(xiàn)1100。C保溫時間較短的復合板芯層Si元素難以發(fā)生擴散,1150-C短時保溫后Si元素開始發(fā)生擴散,但擴散速率較慢,1200。C短時保溫后,Si元素擴散明顯,經(jīng)過一定時間后,復合板整體Si元素含量幾乎達到均勻,約為6.41wt%；對0.5mm復合板在1200℃保溫75min,復合板Si元素已經(jīng)擴散均勻,整體Si元素含量約為6.43wt%； (8)高硅鋼復合板在1200℃下擴散效果最好,對擴散后的復合板進行磁性能檢測,0.8mm復合板的鐵損P15/50為3.906W/Kg,B8為1.297T,B5o為1.584T；對于0.5mm的3號復合板,鐵損P15/50為2.833W/kg,B8為1.371T,B50為1.628T；對于0.5mm的1號復合板鐵損P15/50為3.327W/kg,B8為1.332T,B5o為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.

【學位授予單位】：北京科技大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TG335;TG260;TG161

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