超纯铁素体不锈钢的组织、织构及深拉伸性能

重点研究了冷轧压下率对冷轧、再结晶织构的影响.结果表明:当终轧温度为750℃时,热轧带退火后以{111}再结晶织构为主.随着冷轧压下量的增加,γ织构减弱,α织构增强,{111}再结晶织构明显增强.当冷轧压下率为84%时,{111}再结晶组分的体积分数达到64.5%,退火板的平均塑性应变比(-R)高达1.69,平面各向异性(ΔR)仅为-0.17,深拉伸性能优良.     

异步热轧对低合金钢显微组织及力学性能的影响

分别采用同步热轧及异速比为1.2的异步热轧对低合金钢进行热轧,研究异步热轧对低合金钢显微组织及力学性能的影响机制.结果表明,与同步热轧相比,异步热轧可显著促进低合金钢奥氏体/铁素体相变,提高热轧钢板厚度方向的组织均匀性.同步热轧工艺下,钢板表层为细晶铁素体层,厚度1/4或1/2处组织为粗大的贝氏体.异步热轧工艺下,钢板板厚方向主要为均匀的铁素体组织.两种热轧条件下,实验钢的抗拉强度和延伸率相当,分别为710~718 MPa和20%.采用异步热轧代替同步热轧后,实验钢的屈服强度由526MPa提高至561 MPa.这主要是由于同步热轧的钢板相变强化占主导,而异步热轧的钢板细晶强化相对较强.     

半工艺无取向硅钢加临界变形的织构演变

测定了半工艺无取向电工钢热轧(终轧温度在Ar1以下)到成品各工序的织构,以取向分布函数(ODF)的形式对加临界变形的半工艺无取向硅钢的织构演变作了分析.发现其热轧板表层织构基本是典型的铁素体再结晶{111}组分,心部和1/4厚度处以铁素体剪切织构和轧制变形织构为主.冷轧变形后,心部和表层织构组分比较接近,{111}、{112}和{100}面织构都增加,但{111}组分增加最明显.软化退火后,{001}<110>与{112}<110>组分迅速降低,织构组分以γ纤维织构为主.通过增加临界变形,在最终去应力退火后,{111}不利面织构大量减少,高斯组分增加明显.Taylor因子可以表征不同取向晶粒对变形能的储存能力,从轧制变形时Taylor因子的分布可以解释该实验结果.     

高纯Cr17铁素体不锈钢的热变形行为

采用MMS200热/力模拟机及Thermo-Calc热力学计算方法,研究了高纯Cr17铁素体不锈钢在变形温度为600～1 100℃、应变速率为1～10 s-1条件下的热变形规律.结果表明,在热变形过程中,高纯Cr17铁素体不锈钢的组织均以铁素体为主,不存在γ/α相变且仅仅发生较快的动态回复软化;高纯Cr17铁素体不锈钢热的变形激活能为384.985 kJ/mol.在此基础上,确定了Z参数,并得到了高纯Cr17铁素体不锈钢的峰值应力σp与Z参数间的关系.     

Ti微合金化Q390高强钢热变形行为研究

通过单道次压缩实验,研究了屈服强度390 MPa级Ti微合金化高强钢的热变形行为,并建立了实验钢的变形抗力模型和动态再结晶数学模型.结果表明:随着变形温度的降低,变形抗力逐渐增大;随着应变速率的增大,应力-应变曲线由动态再结晶型转变为动态回复型.Q390钢的动态再结晶激活能为257.142 k J/mol.建立的高精度的数学模型可表征Ti微合金化Q390钢的高温变形行为.与常规成分体系相比,Ti微合金化成分设计的实验钢轧制时所需的轧制力较小,更容易发生动态再结晶,有利于奥氏体晶粒的细化,可有效地提高钢材强韧性.     

TWIP钢高温变形行为的研究

通过单道次压缩试验,对Fe-Mn-C系孪生诱导塑性钢(TWIP钢),在800~1 000℃,应变速率0.01~10.0 s-1条件下的热变形行为及组织演变规律进行了研究.实验结果表明,升高温度和降低应变速率均可促进奥氏体发生动态再结晶.根据实验所得流变应力曲线,由热变形方程计算得到了TWIP钢热变形激活能Q=421.37 kJ/mol.并在此基础上得到了TWIP钢高温变形的热加工方程.采用Z参数预测了动态再结晶的临界条件,当Z≤9.94×1018时TWIP钢易发生动态再结晶,具有较好的热加工性能.     

Microstructure evolution and mechanical properties of a hot-rolled Ti alloy

The microstructure evolution and mechanical properties of a hot-rolled Ti-5.1 Al-2.5 Cr-0.5 Fe-4.5 Mo-1.1 Sn-1.8 Zr-2.9 Zn titanium alloy sheet along the thickness direction were investigated.The results indicated that the hotrolled titanium alloy sheet presented different microstructures along the thickness direction owing to the uneven distribution of stress and temperature during the hot rolling.The grains in central region underwent a larger deformation,leading to relative complete grain fragmentation and the formation of fine grains.During the air cooling process followed by hot rolling,the fraction of a phase precipitated in the central region was lower than that in the regions near the surface of the sheet.During hot rolling process,more deformation energy transformed to thermal energy and lower cooling rate in the central region promoted the α→β phase transformation,resulting in the increasing of the dynamic recrystallization in the β phase.By contrast,the dynamic recrystallization for a phase decreased.Distinct {0001}_α and {001}_β textures were observed,and these textures were markedly strengthened with the increasing distance from the central region.Due to the softening induced by dynamic recrystallization and the strengthening by concentrated dislocations,the surface of the sheet exhibits highest yield strength and lowest elongation.     

热轧工艺中加热温度对IF钢组织性能的影响

选取Ti-Nb-IF钢热轧工艺中的加热温度为影响因素,采用显微观察、TEM二相粒子分析、织构分析等实验分析手段,研究了1 140℃和1 214℃两种热轧加热温度制备的Ti-Nb-IF钢样品在随后的冷轧、退火和平整过程中显微组织演变和织构演变特征的影响及最终产品的力学性能.结果表明,低温加热有利于IF钢屈强比的降低及深冲性能的提高,加热温度为1 140℃比1 214℃,其屈服强度可降低30 MPa,塑性应变比可提高0.16.其主要原因为低温加热工艺保障IF钢热轧后产生粗大的二相粒子和细小铁素体晶粒,在随后的冷轧和退火处理过程中产生分布均匀和强的γ再结晶织构.     

高强钢300M静态再结晶动力学研究

为研究高强钢300M静态再结晶行为,采用Gleeble-3800型热模拟试验机对300M钢进行单/双道次热压缩试验.通过双道次热压缩试验分析了变形温度、应变速率、变形量和初始晶粒尺寸对静态再结晶体积分数的影响.变形温度越高,应变速率越大,变形量越大,初始晶粒尺寸越小,则静态再结晶体积分数越大.其中变形温度、变形量和应变速率对静态再结晶体积分数影响较大,初始晶粒尺寸的影响相比较小.基于双道次热压缩试验结果建立了300M钢的静态再结晶体积分数模型,基于单道次热压缩试验结果建立了300M钢完全静态再结晶晶粒尺寸模型,并验证了静态再结晶体积分数模型的正确性.     

Experimental study on Ti+Nb bearing ultra-low carbon bake hardening sheet steel hot-rolled in the ferrite region

A Ti+Nb bearing ultra-low carbon bake hardening sheet steel hot-rolled in the conventional austenite region and in the ferrite region with lubrication was experimentally studied. Subsequent cold rolling and continuous annealing processes were also conducted. The results show that microstructures of ultra-low carbon bake hardening hot strips at room temperature are basically irregular polygonal ferrites. The yield strength, ultimate tensile strength, n value, and r value of the No.2 specimen hot-rolled in the ferrite region with lubrication are 243 MPa, 364 MPa, 0.29, and 1.74, respectively, which are similar to those of the No.1 specimen hot-roiled in the conventional austenite region. The elongation rate and bake hardening value of No.2 specimen are 51% and 49.4 MPa, respectively, which are greater than those of No. 1 specimen. The No.2 specimen hot-rolled in the ferrite region with lubrication exhibits good mechanical properties and relatively excellent baking hardening performance. Therefore, the hot rolling experiment of Ti+Nb bearing ultra-low carbon bake hardening steel in the ferrite region with lubrication is feasible and can be considered in the future industrial trial production.     

应用铁素体区热轧工艺开发超低碳热轧深冲板

研究了铁素体轧制工艺条件对一种Ti-IF钢的性能,特别是深冲性能的影响.采用铁素体区润滑轧制和高温卷取,r值最高为1.38,延伸率达到50%以上.而奥氏体轧制条件下r值低于1.0.织构分析证实在润滑轧制条件下,强的{111}再结晶织构沿厚度方向较均匀分布,剪切织构较弱,而在无润滑轧制条件下,{111}再结晶织构很弱,并且形成了较强的{110}剪切织构.为获得具有良好深冲性能的热轧板,要求加热温度在1 100-1 150℃之间,终轧温度在750-800℃之间, 卷取温度大于650℃.     

S32750超级双相不锈钢的热变形及组织分析

利用MMS-200热模拟实验机,对S32750超级双相不锈钢在温度为1 000～1 150℃,应变速率为0.01～10 s-1的条件下进行了单道次压缩实验,测定了真应力-真应变曲线,对热变形组织进行了分析.实验结果表明:当变形温度一定时,峰值应力随着应变速率的增加而增加.提高热变形温度,降低应变速率,可以促进奥氏体动态再结晶的发生.根据热变形方程计算得到压缩变形时的热变形激活能Q=460 kJ/mol.在相应的变形条件下,获得了S32750超级双相不锈钢热变形过程中峰值应力与Z参数的关系式.     

Microstructure homogenization control of Nb-bearing X65 pipeline steel by the CSP process

In order to get the controlled methods of microstructure homogenization and high strengthening-toughening combination by compact strip production (CSP) rolling, the dynamic recrystallization characteristics of each pass were obtained during CSP rolling using a Gleeble-1500 thermal mechanical simulator. Then, the CSP process was simulated by laboratory rolling experiment. Through thermal mechanical simulation experiment and laboratory rolling experiment, a design idea of Nb-bearing pipeline steel by CSP can be obtained as the following: the level of dynamic recrystallization behavior should be increased through the reasonable balance of high deformation temperature and deformation amount in F1 and F2 passes, and F3-F7 passes should be controlled in the austenite non-recrystallization zone. Finally, X65 pipeline steel with microstructure uniformity and good properties was produced by CSP. The yield strength is up to 497 MPa, the tensile strength is up to 563 MPa, the elongation is 30% on average, and the toughness is very good whose Charpy impact value is 110 J on average and drop-weight tear test shearing areas are all 100% at -60, -40, -20, 0, and 20℃.     

Q550D超低碳贝氏体钢的微观组织模拟

摘要： 利用Q550D超低碳贝氏体钢的热压缩试验数据建立了动态再结晶模型及元胞自动机模型,通过有限元软件DEFORM 3D对试样热变形过程的微观组织演变过程进行了模拟.结果表明：在变形温度为1 150 °C条件下,当应变速率为0.05 s-1时,热变形过程中的试样微观组织发生了动态再结晶现象,晶粒尺寸得到细化;在变形温度为1 050 °C条件下,当应变速率不断增大时,奥氏体动态再结晶的晶粒尺寸减小;模拟结果与试验结果较吻合.     

15MnV钢热变形中组织变化的数学模型

采用热压模拟机研究了15MnV钢热形变中及其以后的冷却后的组织变化，得到计算组织变化的数学模型，该模型中包括有：单道次形变，多道次形变，等温形变，连续冷却形变等条件的奥氏体再结晶动力学，再结晶晶粒尺寸，再结晶后的晶粒粗化，以及热变形奥氏体转变的铁素体等，用模型计算的结果与实测值吻合较好。     

Static Recrystallization Behavior of SCM435 Steel

The static recrystallization behaviors in SCM435 steel were investigated by two-pass hot compression tests on MMS-200 thermosimulation machine. Effects of deformation temperature, strain rate,deformation degree and the initial austenite grain size on static softening were analyzed. The stress compensation method was used to calculate the static recrystallization. The kinetics model of the static recrystallization of SCM435 steel was established and the obtained activation energy for static recrystallization was 182. 8 kJ /mol. Results showed that within a certain time interval( 1-100 s),the static recrystallization fraction X of SCM435 steel increased as the deformation temperature,the deformation rate and the amount of deformation increased,and it decreased as the initial grain size increased and increased as the time interval increased.     

TSCR工艺参数对Fe-3%Si钢带显微组织的影响

在实验室模拟薄板坯连铸连轧(TSCR)生产Fe-3%Si钢带,研究薄板坯连铸连轧不同工艺参数对Fe-3%Si钢带热轧和常化显微组织的影响.结果表明,TSCR工艺生产的Fe-3%Si钢带热轧显微组织沿板厚方向呈现组织不均匀性,1 200℃保温20 min,前两道压下量较大、道次递减的显微组织过渡层再结晶晶粒数较多且相对均匀细小,没有中心层拉长的条带组织,有利于二次再结晶的完善.显微组织平均晶粒尺寸与传统流程热轧平均晶粒尺寸相差1.5μm,具有几乎相同的位错形貌,头部和中部显微组织差别都很小.热轧显微组织质量决定了常化后显微组织的质量.     

铁素体不锈钢热轧板材的拉伸行为和断裂特征

用金相显微镜、X射线衍射仪、SEM手段研究2种铁素体不锈钢热轧板材0.04C-16Cr、0.02C-12Cr在室温下的拉伸行为和断裂特征.结果表明,这2种铁素体不锈钢的强度高,但塑性较差;C、Cr含量较低的0.02C-12Cr钢的强度、硬度均较0.04C-16Cr的高,这是由于0.02C-12Cr在空冷过程中产生了大量的马氏体;2种钢室温下都为韧性断裂,其断口微观形貌主要为细小韧窝聚集,沿轧制方向分布的条带组织中存在细小的碳化物颗粒,成为韧窝的发源地;部分断口出现了分层和侧向开裂现象.分析其断口形貌、断裂过程和组织特征,可知沿着轧制方向分布的条带组织致使材料表现出上述力学行为和断裂特征.     

Hot deformation mechanism and microstructure evolution of an ultra-high nitrogen austenitic steel containing Nb and V

The flow curves of an ultra-high nitrogen austenitic steel containing niobium (Nb) and vanadium (V) were obtained by hot compression deformation at temperatures ranging from 1000℃ to 1200℃ and strain rates ranging from 0.001 s-1 to 10 s-1. The mechanical behavior during hot deformation was discussed on the basis of flow curves and hot processing maps. The microstructures were analyzed via scanning electron microscopy and electron backscatter diffraction. The relationship between deformation conditions and grain size after dynamic recrystallization was obtained. The results show that the flow stress and peak strain both increase with decreasing temperature and increasing strain rate. The hot deformation activation energy is approximately 631 kJ/mol, and a hot deformation equation is proposed. (Nb,V)N precipitates with either round, square, or irregular shapes are observed at the grain boundaries and in the matrix after deformation. According to the discussion, the hot working should be processed in the temperature range of 1050℃ to 1150℃ and in the strain rate range of 0.01 to 1 s-1.     

新一代热轧TRIP钢的研究

对热轧后等温淬火的热轧Si-Mn TRIP钢进行了研究,通过对该钢的组织性能检测,讨论了其相变诱发塑性(TRIP)机制.结果表明:热轧Si-Mn TRIP钢中发生了残余奥氏体的应变诱导马氏体相变,表现出抗拉强度和总延伸率的良好配合.残余奥氏体的稳定性随等温保温时间的增加而增加,进一步增加等温时间则又使残余奥氏体稳定性降低.等温25 min时力学性能最佳,抗拉强度、总延伸率和强韧性平衡分别达到了774 MPa,33%和25 542 MPa%的最高值.