控制轧制工艺参数对15MnV钢奥氏体状态和铁素体组织的影响

本文研究了热轧工艺参数对15MnV钢奥氏体再结晶行为,奥氏体状态和铁素体组织的影响。实验结果表明,由于奥氏体的形变和再结晶细化,铜坯的加热温度对轧后奥氏体晶粒大小影响不大。在奥氏体的完全再结晶温度范围内,形变量对再结晶百分数有显著的影响。低于完全再结晶温度范围,则热轧温度的影响将会变得更为重要。随着形变温度的下降或形变量增大,奥氏体晶粒内的形变带密度将增大,铁素体晶粒将细化。     

成果鉴定简讯

(一) “普低钢热形变过程中动态再结晶细化和静态再结晶细化的相关性”研究课题于1991年6月通过了冶金工业部鉴定。鉴定委员会专家们认为:该课题组在均匀奥氏体晶粒热轧形变再结晶细化规律的研究上,首次提出了晶粒细化极限值的新见解,揭示了在不同形变速率条件下细化晶粒所需要控制的工艺参数,为建立控轧的数理模型提供了重要依     

X80管线钢热变形过程中再结晶行为及组织细化

利用Gleeble-1500D热模拟试验机研究了X80管线钢热轧过程中的再结晶行为及精轧过程中后四道次变形的再结晶特点与室温组织的关系.揭示了X80管线钢动态再结晶临界钢应变量与变形温度的关系,确定了奥氏体再结晶温度区和非再结晶温度区,所得到的技术要点对精轧过程轧制工艺制定细化奥氏体晶粒具有指导性,有助于X80管线钢获得细小均匀的室温组织.     

热模拟技术优化X80管线钢热轧工艺

用Gleeble 1500D热模拟实验机,对X80管线钢进行单道次双道次以及多道次压缩实验,找出动态再结晶的临界应变量和未再结晶区,在未再结晶区内优化精轧道次轧制工艺,通过抑制道次间的静态再结晶累积应变,在多道次轧制过程中使其在最后一道次超过临界应变量发生动态再结晶,从而避免晶粒大小不均并实现晶粒细化.     

细化母相奥氏体组织的研究

在Gleeble 1500热模拟机上以SS400钢为研究对象，采用冷加工＋α→γ逆相变等实验工艺，研究了此变形工艺对奥氏体再结晶行煌 影响以及细化母相奥氏体晶粒的方法，结果表明，由于低温大变形及快速升温同时有铁素体基体的回复，再结晶或奥氏体相变这三个相互竞争的过程发生，可得到晶粒尺寸为10－12um的奥氏体晶粒。     

初始组织对电脉冲处理逆变奥氏体晶粒细化效果的影响

通过金相组织观察、显微硬度测试,研究了电脉冲处理条件下,不同初始组织对逆变奥氏体晶粒细化效果的影响。结果表明:回火马氏体初始组织电脉冲奥氏体化过程为α+Fe_3C→γ扩散型逆相变,逆变奥氏体晶粒获得超细化(d_γ5μm),这证实了脉冲电流促进奥氏体形核率提高的理论分析;马氏体初始组织电脉冲奥氏体化过程为α′→γ位移型逆相变;初始马氏体的原奥氏体晶界在逆相变过程中未发生变化,形成晶粒粗大的位移型逆变奥氏体;从位移型逆变奥氏体淬火得到的马氏体获得再次强化;升高电脉冲处理峰值温度,位移型逆变奥氏体发生再结晶;再结晶形核始于位移型逆变奥氏体晶界这唯一具有大角度位相差的区域;再结晶完成后,奥氏体平均晶粒直径为11μm。     

ZrC粒子对低碳钢晶粒细化及力学性能的影响

在低碳低合金钢熔炼过程中加入平均径为0．5μm，体积分散为0．8％的ZrC粒子，研究了不同轧制变形量条件下的晶粒细化行为及力学性能，轧制变形过程中在ZrC粒子周围形成高位错密度和高晶格畸区，成为形为核心和再结晶核心，促进了高温奥氏体非自发再结晶细化奥氏体晶粒；由于奥氏体晶粒尺寸细化，奥氏体晶界面积增大，随着后进行的铁体相变的铁素体形核位置增多，从而大大细化了铁素体晶粒尺寸：轧制变形量与ZrC粒子体积分数存在一定的最佳配合才能对晶粒细有作用，本实验中轧制变形量为62％，ZrC粒子体积分数0．8％以及轧后水冷条件下，铁素体晶粒尺寸细化到9．8μm，屈服强度和抗拉强度明显提高，分别达到386．4MPa和522．1MPa；同时冲击吸收功（AKV＝118．5J）不降低且延伸率（δ5＝34．5％）有所提高，说明添加ZrC粒子粒子可促进晶粒细化。     

多道次轧制过程中超细晶粒控制

在高强度水平的基础上获得较高的韧性,控制热加工工艺实现晶粒尺寸超细化是最佳的途径之一。低碳管线钢的超细铁索体晶粒可以从相变前的超细奥氏体晶粒获得。通过优化轧制工艺使得奥氏体的动态再结晶发生在Z（Zeller-Hollomon）参数较大的工艺条件下,获得超细的奥氏体动态再结晶晶粒尺寸。然而,大的Z参数往往具有较大的动态再结晶临界应变。为了获得足够的应变积累来克服动态再结晶的临界应变,低温大变形量的变形是基本条件。提出了在多道次轧制过程中积累应变的条件以及避免混晶的技术路线,利用提出的模型对工业轧制工艺进行优化,模拟实验的结果得到了最终产品晶粒尺寸为1.5μm。     

控制轧制及控制冷却技术在16MnR钢的应用

16MnR钢中加入0．01％钒、钛,1100℃开轧、850℃终轧、分别在奥氏体再结晶区及奥氏体未再结晶区控孔、轧后给以3－4℃／s冷速控冷,获得的组织细小、带状珠光体减少,钢的各项性能指标均得到了较大的提高。     

控制轧制及控制冷却技术在1 6MnR钢的应用

16MnR钢中加入0.01%钒、钛,1100℃开轧、850℃终轧、分别在奥氏体再结晶区及奥氏体未再结晶区控轧、轧后给以3～4℃/s冷速控冷,获得的组织细小、带状珠光体减少,钢的各项性能指标均得到了较大的提高.     

Austenite formation during intercritical annealing in C-Mn cold-rolled dual phase steel

Two different kinds of experimental techniques were used to in-situ study the austenite formation during intercritical annealing in C-Mn dual phase steel. The microstructure evolution was observed by confocal laser scanning microscope, and the austenite isothermal and non-isothermal transformation kinetics were studied by dilatometry. The results indicate that banded structure is produced for the reason of composition segregation and the competition between recrystallization and phase transformation. Austenite prefers to nucleate not only at ferrite/ferrite grain boundaries, but also inside the grains of ferrite.Furthermore, the austenitizing process is accomplished mainly via migration of the existing austenite/ferrite interface rather than nucleation of new grains. The incubation process can be divided into two stages which are controlled by carbon and manganese diffusion, respectively. During the incubation process, the nucleation rate of austenite decreases, and austenite growth changes from two-dimensional to one-dimensional. The partitioning coefficient, defined as the ratio of manganese content in the austenite to that in the adjacent ferrite, increases with increasing soaking time.     

Effect of deformation and cooling rate on the transformation behavior and microstructure of X70 steels

The effects of the deformation in the non-recrystallization region of austenite and the cooling rate on the transformation behavior and microstructure of low-carbon low-alloy steel for pipeline application were studied on the thermal-mechanical simulator Gleeble-1500. It was shown that an increase in deformation amount can greatly increase the nucleation site of ferrite when deformed in the non-recrystallization region of austenite, and an increase in nucleation ratio can greatly refine grains. When the cooling rate is accelerated, the driving force of nucleation is increased and the nucleation rate also improves. Ultra-refine grains can be obtained by controlled rolling. The high density of ferrite nucleus, which forms along the austenite grain boundary, twin interface, and deforma- tion band are introduced in the matrix of austenite by the control of hot rolling, after which the microstructure can be refined. It was found that the acicular ferrite has a very fine sub-structure, high dislocation density, and a thin slab with ultra-fine grains. Small M/A islands and cementite are precipitated on the matrix of the slabs by the analysis technique of TEM and SEM.     

Microstructural Features During Strain Induced Ferrite Transformation in 08 and 20Mn Steels

The microstructure evolution during strain induced ferrite transformation was followed in thermal-simulation tests of clean 08 and 20Mn steels. The influences of carbon equivalence and initial austenite grain size on ferrite grain refinement and the volume frac- tion of ferrite during straining were inspected. The results revealed that the accelerating effect of ferrite transformation by strain was increased as the carbon equivalence decreased. However, finer ferrite grains were obtained at higher carbon content. At strain of -1 .5 ferrite grains less than 3 μm and 2 μm can be obtained in 08 and 20Mn steels respectively. Whereas the ferrite grain refinement in 08 steel was due to both effects of strain induced transformation and ferrite dynamic recrystallization, that in 20Mn was mainly due to st fain induced transformation. Heavy strain can produce fine ferrite grains in coarse austenite grained 08 steel, but it would lead to band microstructure in coarse austenite grained 20Mn.     

无取向硅钢晶粒与晶界特征的EBSD分析

借助电子背散射衍射（EBSD）技术测量和计算了无取向硅钢再结晶退火后再结晶百分比、晶粒尺寸、取向差分布等参数,分析了再结晶退火温度对无取向硅钢晶粒大小、微观取向和耐蚀性的影响。结果表明,3个温度（810、840、880℃）下退火3 min后,再结晶均充分完成。随着退火温度的升高,再结晶晶粒尺寸长大。拥有{100}面织构的晶粒比其他取向晶粒具有更好的耐蚀性,侵蚀后晶粒凸出于试样表面。880℃退火后的小尺寸晶粒周围多为小角度晶界,不易迁移,不易被侵蚀。     

微合金化钢的动态再结晶及其显微组织的研究

应用Ｇｌｅｅｂｌｅ－１５００热模拟试验机测定了微合金化钢在不同终轧温度下的真应力－－真应变曲线，研究了终轧温度及微合金元素含量对动态再结晶的影响，研究结果表明，Ｖ，Ｎｂ可显著抑制微合金化钢轧制过程中形变奥氏体的动态再结晶，因此，在较高的终轧温度下，仍能得到细小而均匀的显微组织。     

脉冲电流对7475铝合金再结晶的影响

通过在不同条件下对7475铝合金进行再结晶退火处理,研究了脉冲电流对7475铝合金再结晶的影响.结果表明,脉冲电流使合金的硬度在再结晶完成之前低于无脉冲电流合金的硬度,而在再结晶完成之后高于无脉冲电流时合金的硬度;加快了再结晶进程,使晶粒细化.     

结构钢奥氏体晶粒度的控制及检验方法的探讨

本文简介了航空结构钢奥氏体晶粒度的攻关成果,即提高奥氏体晶粒度粗化温度的重要途径是0.02～0.05％的残余铝含量和合理的热工艺。文中探讨了粗晶拉沿棒材外圆周规律性分布的成因(低温大变形和负偏析),粗晶的危害及改善措施,并对传统奥氏体本质晶粒度检验方法提出了更改意见。仅就晶粒度而言,最直接影响钢的机械性能的是实际晶粒度而不是本质晶位度,对于结构钢,应以实际晶粒度为验收标准。     

Recrystallization of High Carbon Steel during High Strain Rate

The recrystallization of high carbon steel during high temperature and high speed rolling has been studied by analyzing the Stress-strain curves and the austenite grain size. Isothermal multi-pass hot compression at high strain rate was carried out by Gleeble-2000. The austenite grain size was measured by IBAS image analysis system. The results show that static recrystallization occurred at interpass time Under pre-finish rolling, and at the finish rolling stage, due to the brief interpass time, static recrystallization can not be found.     

Grain refinement in the coarse-grained region of the heat-affected zone in low-carbon high-strength microalloyed steels

The microstrueturai features and grain refinement in the coarse-grained region of the heat-affected zone in low-carbon high-strength micro,alloyed steels were investigated using optical microscopy,scanning electron microscopy,and electron back,scattering diffraction.The coarse-grained region of the heat-affected zone consists of predominantly bainite and a small proportion of acieular ferrite.Bainite packets are separated by high angle boundaries.Acicular ferrite laths or plates in the coarse-grained region of the heat-affected zone formed prior to bainite packets partition austenite grains into many smaller and separate areas,resulting in fine-grained mixed microstructures.Electron baekseattering diffraction analysis indicates that the average crystallographic grain size of the coarse-grained region of the heat-affected zone reaches 6-9 μm,much smaller than that of austenite grains.