本文選題：珠光體鋼絲 + 拉拔形變　； 參考：《東南大學(xué)》2015年碩士論文

【摘要】：為研究適合拉拔形變的珠光體組織,以珠光體鋼絲為原材料,經(jīng)退火處理得到球狀珠光體組織,經(jīng)淬火+高溫回火處理得到不同尺寸的球狀滲碳體+基體鐵素體組織,以這四種組織的拉拔形變過程為研究對(duì)象,采用掃描電鏡(SEM)、透射電鏡(TEM)和電子背散射衍射(EBSD)等手段,研究了滲碳體的形貌、分布、尺寸對(duì)鋼絲冷拉拔形變的影響,并探討了其形變強(qiáng)化機(jī)制,得出以下結(jié)論：比較研究了片狀珠光體鋼絲(片狀滲碳體+鐵素體)與球狀珠光體鋼絲(球狀滲碳體+鐵素體)的冷拉形變過程,結(jié)果表明：1)片狀滲碳體在形變中表現(xiàn)出一定的變形能力,處于有利取向的層片細(xì)化、間距減少,不利取向的層片則發(fā)生了彎曲、扭轉(zhuǎn),甚至斷裂、碎化；硬的球狀滲碳體在鋼絲形變時(shí)不發(fā)生塑性變形,而會(huì)隨著鐵素體的塑性變形逐漸轉(zhuǎn)向于平行拉拔的方向,應(yīng)變量為1.6左右時(shí)已基本平行于拉拔方向,同時(shí)形變組織中的碳化物周圍出現(xiàn)了較多的微觀缺陷。2)片狀珠光體鋼絲強(qiáng)度遠(yuǎn)高于球狀珠光體鋼絲,且片狀珠光體鋼絲在應(yīng)變量ε1.6左右時(shí),加工硬化率明顯增加。3)片狀珠光體組織的110織構(gòu)強(qiáng)度隨應(yīng)變量的增加不斷增強(qiáng),與球狀珠光體組織相比,片狀珠光體組織的織構(gòu)強(qiáng)度更高。對(duì)球狀珠光體鋼絲和淬火+高溫回火態(tài)鋼絲(球狀滲碳體+鐵素體)的冷拉形變過程進(jìn)行對(duì)比研究,結(jié)果表明：1)當(dāng)組織中存在較多的大尺寸碳化物,且碳化物彌散分布時(shí),容易在形變時(shí)產(chǎn)生缺陷。2)滲碳體粒子平均粒徑越小,粒子分布越彌散,強(qiáng)度越高,因此淬火+高溫回火態(tài)(小尺寸Fe3C球)鋼絲強(qiáng)度高于淬火+高溫回火態(tài)(大尺寸Fe3C球)鋼絲,球狀珠光體鋼絲強(qiáng)度最低。3)根據(jù)加工硬化率可將形變過程分為三階段：較小形變(ε0.4)時(shí)球狀珠光體組織的加工硬化率較大：中等形變階段(0.4ε1.6)三種組織的加工硬化率相當(dāng)；較大形變階段(ε1.6),碳化物彌散分布的組織加工硬化作用更明顯。球狀滲碳體+鐵素體雙相材料的形變強(qiáng)化研究結(jié)果表明：1)材料形變后,在晶粒內(nèi)形成了多處高密度位錯(cuò)纏結(jié)區(qū),在碳化物周圍形成了位錯(cuò)環(huán)、位錯(cuò)纏結(jié),以此阻礙后續(xù)位錯(cuò)的運(yùn)動(dòng),使材料加工硬化。2)位錯(cuò)在大顆碳化物周圍更容易形成位錯(cuò)纏結(jié),周圍應(yīng)力更集中,因此更易形成缺陷。3)滲碳體為球狀時(shí),形變過程中碳化物不變形,其周圍形成了嚴(yán)重的位錯(cuò)塞積和應(yīng)力集中,因此組織中易出現(xiàn)缺陷；滲碳體為片狀時(shí),滲碳體在鋼絲拉拔過程中能與基體協(xié)調(diào)變形,組織中不易產(chǎn)生缺陷,因此片狀珠光體的可拉拔性能更佳。
[Abstract]:In order to study the pearlite microstructure suitable for drawing deformation, the spherical pearlite structure was obtained by annealing with pearlite wire as raw material, and the ferrite structure of spherical cementite matrix was obtained by quenching and tempering at high temperature. The effects of morphology, distribution and size of cementite on cold drawing deformation of steel wire were studied by means of scanning electron microscope (SEM), transmission electron microscope (TEM) and electron backscatter diffraction (EBSD). The mechanism of deformation strengthening is also discussed. The following conclusions are drawn: the cold tensile deformation process of sheet pearlite steel wire (lamellar cementite ferrite) and spherical pearlite steel wire (spherical cementite ferrite) is studied. The results show that the plate-like cementite shows a certain deformation ability during deformation. The layers in favorable orientation are thinned and the spacing is reduced, while the unfavorable orientation of the lamellae is bending, torsion, even fracture and fragmentation. The hard spherical cementite does not produce plastic deformation when the steel wire is deformed, but gradually turns to the direction of parallel drawing with the plastic deformation of the ferrite. When the strain is about 1.6, it is basically parallel to the drawing direction. At the same time, there are many microdefects around carbide in deformed microstructure. 2) the strength of lamellar pearlite steel wire is much higher than that of spherical pearlite steel wire, and the lamellar pearlite steel wire is about 1.6 when the strain is about 1.6. The strength of 110 texture of lamellar pearlite increases with the increase of strain, and the texture strength of lamellar pearlite is higher than that of spherical pearlite. The cold tensile deformation process of spherical pearlite steel wire and quenched high temperature tempered steel wire (spherical cementite ferrite) is studied. The results show that: 1) when there are more large size carbides in the microstructure and the carbides are dispersed, The smaller the average particle size of cementite particle is, the more dispersed the particle distribution is and the higher the strength is. Therefore, the strength of quenched high-temperature tempered steel wire (small size Fe3C ball) is higher than that of quenched high-temperature tempered steel wire (large size Fe3C ball). According to the work hardening rate, the deformation process can be divided into three stages: when the deformation is smaller (蔚 0.4), the working hardening rate of the spherical pearlite is higher than that in the middle deformation stage (0.4 蔚 1.6). In the larger deformation stage (蔚 1.6), the effect of microstructure hardening on the distribution of carbide dispersion is more obvious. The results of deformation strengthening of spherical cementite ferrite biphasic materials show that after deformation, there are many high density dislocation entanglement regions in the grains, dislocation rings and dislocation entanglement around the carbides. In this way, the movement of subsequent dislocations is obstructed, and the working-hardening. 2) dislocations of materials are easier to form dislocation entanglement around large carbides, and the stress around them is more concentrated, so it is easier to form defects. 3) when the cementite is spherical, the carbides do not deform during deformation. Because of the serious dislocation accumulation and stress concentration around the cementite, defects are easy to occur in the microstructure. When the cementite is flake, the cementite can deform harmoniously with the matrix during the drawing process of the steel wire, but it is not easy to produce the defect in the microstructure. Therefore, the pullability of lamellar pearlite is better.
【學(xué)位授予單位】：東南大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TG356.46;TG162.85

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