C-Mn钢窄带热轧时的再结晶软化规律

针对唐山钢铁有限责任公司带钢厂的生产实际,借助理论与实验结果,研究了C-Mn钢热轧过程中各道次奥氏体的再结晶规律,计算结果与实测结果吻合较好,说明给出的组合模型用于窄带热轧的生产是可行的,它为在生产中控制与预报带钢的组织性能提供了奥氏体再结晶的定量化基础,并为再结晶软化不充分时的力能计算提供了修正依据.     

CSP工艺冷轧薄板盐浴退火再结晶实验

 研究了以CSP工艺热轧板卷为原料的冷轧薄板在盐浴退火过程中的再结晶行为,通过显微组织、显微硬度及电子背散射衍射技术观察、分析揭示了再结晶的规律,结果表明,CSP工艺冷轧薄板经盐浴退火后的再结晶组织为等轴状晶粒;在相同温度下盐浴退火,冷轧压下率较大时,完成再结晶所需的保温时间较短,再结晶晶粒细小。     

Numerical Simulation of Austenite Recrystallization in CSP Hot Rolled CMn Steel Strip

An integrated mathematical model is developed to predict the microstructure evolution of CMn steel during multipass hot rolling on the CSP production line, and the thermal evolution, the temperature distribution, the deformation, and the austenite recrystallization are simulated. The characteristics of austenite recrystallization of hot rolled CMn steel in the CSP process are also discussed. The simulation of the microstructure evolution of CMn steel ZJ510L during CSP multipass hot rolling indicates that dynamic recrystallization and metadynamic recrystallization may easily occur in the first few passes, where nonuniform recrystallization and inhomogeneous grain size microstructure may readily occur; during the last few passes, static recrystallization may occur dominantly, and the microstructure will become more homogeneous and partial recrystallization may occur at relatively low temperature.     

C-Mn钢热轧带奥氏体再结晶晶粒尺寸的预测

在研究板带控轧控冷过程中钢中显微组织演变过程奥氏体再结晶、碳氮化合物析出、奥氏体相变和组织性能对应关系的物理冶金模型的基础上，通过Gleeble-1500热模拟机和计算机模拟计算得出成分(％)0．16C，0．06Si，1．30Mn钢在1173～1081K经7道次热变形后奥氏体晶粒尺寸为43μm，同时实测7道次变形后轧钢组织中奥氏体尺寸为38μm，相对误差13％。计算机模拟计算的奥氏体再结晶晶粒尺寸与实测结果吻合较好。     

含钛钢的奥氏体晶粒粗化与再结晶参数

研究了3种不同含Ti量(0.04%-0.16%Ti)钢奥氏体晶粒粗化温度及热轧后奥体再结晶的行为。在950-1200℃加热,含0.04%Ti钢奥氏体晶粒最小,其晶粒开始粗化温度在1 150℃以上。得出含Ti钢开始再结晶的临界形变率(ε_c)与原始奥氏体晶粒直径(D₀)、轧制温度(T)间定量关系。     

碳锰钢热变形行为及动态再结晶模型

 采用单道次热模拟实验分析了各变形参数(初始晶粒尺寸、变形速率、变形温度和变形量)对碳锰钢动态再结晶的影响。结果表明,当初始晶粒越细小、变形温度越高、变形速率越小时,越易发生动态再结晶,同时在能够发生动态再结晶的条件下,变形量越大,动态再结晶越充分。得到了发生动态再结晶时的形变激活能Qdef、临界变形量模型、动态再结晶百分数模型及动态再结晶晶粒尺寸模型。计算得出ε05模型的平均误差为395%,模型预测值与实验数据计算值符合较好。     

Recrystallization Behavior of Deformed Austenite in High Strength Microalloyed Pipeline Steel

 Using methods of single hit hot compression and stress relaxation after deformation on a Gleeble 1500D thermomechanical simulator, the curves of flow stress and stress relaxation, the microstructure and the recrystallization behavior of Nb V Ti high strength microalloyed low carbon pipeline steel were studied, and the influence of the thermomechanical treatment parameters on dynamic and static recrystallization of the steel was investigated. It was found that microalloying elements improved the deformation activation energy and produced a retardation of the recrystallization due to the solid solution and precipitation pinning. The deformation conditions such as deformation temperature, strain, and strain rate influenced the recrystallization kinetics and the microstructure respectively. Equations obtained can be used to valuate and predict the dynamic and static recrystallizations.     

Hot Deformation and Dynamic Recrystallization Behaviour of Medium Carbon Steel in Austenite Region

The hot deformation behaviour of a 0.47%C (JIS‐S45C) steel in the stable austenite region was systematically investigated under various deformation conditions to collect fundamental data on its high‐temperature deformation and microstructure evolution. The medium carbon steel showed dynamic recrystallization in a wide range of temperatures (850°C～1150°C) and strain rates (10^‐3 s^‐1～100 s^‐1) in the stable austenite region. The dynamically recrystallized grain size was monotonically decreasing with increasing steady state stress. The minimum grain size obtained through dynamic recrystallization was 8.3 μm when the S45C specimen was deformed at 850°C and 1 s^‐1. The stress‐strain relationships were formularized based on a phenomenological model. The stress‐strain curves estimated by the obtained equation were in good agreement with the experimental results.     

低碳钢热变形奥氏体的再结晶行为

对热变形奥氏体的再结晶动力学和微观组织演变进行了模拟计算,对晶粒尺寸的模拟值和实测值作了比较,分析了化学成分对动态再结晶率的影响以及残余应变与变形温度的关系.结果表明:在温度较高、应变速率较低的条件下容易发生动态再结晶,随着变形温度的降低,发生动态再结晶的几率减小,而静态再结晶在前几道次进行得比较充分,随后进行得不充分,增加碳和锰的含量可以促进动态再结晶的发生,残余应变随变形温度的降低而增大,晶粒尺寸的模拟值和实测值吻合较好,表明所选用的模型有一定的参考价值.     

Recrystallization Behavior of Deformed Austenite in High Strength Microailoyed Pipeline Steel

Using methods of single-hit hot compression and stress relaxation after deformation on a Gleeble 1500D thermomechanical simulator, the curves of flow stress and stress relaxation, the microstructure and the recrystallization behavior of Nb-V-Ti high strength microalloyed low carbon pipeline steel were studied, and the influence of the thermomechanical treatment parameters on dynamic and static recrystallization of the steel was investigated. It was found that microalloying elements improved the deformation activation energy and produced a retardation of the recrystallization due to the solid solution and precipitation pinning. The deformation conditions such as deformation temperature, strain, and strain rate influenced the recrystallization kinetics and the microstructure respectively. Equations obtained can be used to valuate and predict the dynamic and static recrystallizations.     

X46级管线钢热连轧过程中温度场及平均流变应力的预测

采用有限元计算模型和实测轧件温度以及精轧各道次的轧制压力值，对不同边界条件下的传热系数和塑性功转热率进行了优化计算，得到了轧件断面温度场。在此基础上考虑了再结晶等因素，建立了计算精轧过程中应力一应变曲线的流变应力模型，并利用该模型对X46级管线钢精轧各道次的流变应力进行了预测。结果表明：该模型的计算结果与用Sims法计算的结果吻合较好，能真实反映工业生产的实际情况。     

精轧区热轧带钢温度场的数值模拟

通过对带钢热连轧过程传热关系的分折，利用有限差分法建立了带钢三维温度场的数值计算模型。结合攀枝花钢铁集团公司热轧生产线的实际条件，利用该模型模拟了精轧区带钢的温度场，并与实泅结果进行了比较，验证了模型的可靠性。在此基础上，讨论了终轧厚度和轧制速度对带钢温度场的影响，为改进和优化轧制工艺提供了理论依据。     

Numerical Simulation of Coupled Molten Steel Flow and Temperature Fields in Compact Strip Production Casting

  Based on the casting manufacture practice of steel slabs by CSP technology, the flow and the temperature fields of the funnel mould and the secondary cooling segment were simulated using the commercial code, CFX4. Compared with other physical investigations, the correlative data of the present simulation results are in good agreement with them. Therefore, a more comprehensive survey for metallurgy characteristic of the flow and the temperature fields in CSP continuous casting process can be achieved.     

Dynamic Recrystallization of Hot Deformed 3Cr2NiMnMo Steel: Modeling and Numerical Simulation

Hot compression tests of 3Cr2NiMnMo steel were performed at temperatures in the range of 850 to 1100 °C and with strain rates of 10^?2s^?1 to 1s^?1. Both the constitutive equations and the hot deformation activation energy were derived from the correlativity of flow stress, strain rate and temperature. The mathematical models of the dynamic recrystallization of 3Cr2NiMnMo steel, which include the dynamic recrystallization kinetics model and the crystallization grain size model, are based on Avrami's law and the results of thermosimulation experiments. By integrating derived dynamic recrystallization models with the thermal-mechanical coupled finite element method, the microstructure evolution in hot compressive deformation was simulated. The distribution of dynamic recrystallization grains and grain sizes were determined through a comparison of the simulation results with the experimental results. The distribution of strain and dynamic recrystallization grain is also discussed. The similarity between the experimental results and the simulated results indicates that the derived dynamic recrystallization models can be applied effectively to predict and analyze the microstructure evolution in hot deformed 3Cr2NiMnMo steel.     

Three-dimensional Numerical Simulation and Experimental Analysis of Austenite Grain Growth Behavior in Hot Forging Processes of 300M Steel Large Components

The microstructure models were integrated into finite element (FE)code,and a three-dimensional (3D) FE analysis on the entire hot forging processes of 300M steel large components was performed to predict the distri-butions of effective strain,temperature field and austenite grain size.The simulated results show that the finest grains distribute in the maximum effective strain region because large strain induces the occurrence of dynamic re-crystallization.However,coarse macro-grains appear in the minimum effective strain region.Then,300M steel forg-ing test was performed to validate the results of FE simulation,and microstructure observations and quantitative analysis were implemented.The average relative difference between the calculated and experimental austenite grain size is 7.5 6%,implying that the present microstructure models are reasonable and can be used to analyze the hot forging processes of 300M steel.     

Prediction of Rolling Load, Recrystallization Kinetics, and Microstructure During Hot Strip Rolling

 The recrystallization kinetics and grain size models were developed for the C Mn and niobium containing steels to describe the metallurgical phenomenon such as softening, grain growth, and strain accumulation. Based on the recrystallization kinetics equations, the mean flow stress and the rolling load of each pass were predicted and the optimum rolling schedule was proposed for hot strip rolling. The austenite grain refinement is associated with the addition of niobium, the decrease of starting temperature of finish rolling, and the reduction of finished thickness. The mean flow stress curve with a continuous rising characteristic can be usually observed in the finish rolling of niobium containing steel, which is formed as a result of the heavy incomplete softening and strain accumulation. The predicted rolling loads are in good agreement with the measured ones.     

Ti对低碳Mn-V钢奥氏体动态再结晶的影响

采用Gleeble热模拟试验机和透射电镜、扫描电镜及定量金相等分析技术,就钛对低碳Mn-V钢奥氏体晶粒长大行为、奥氏体动态再结晶行为等进行了研究.结果表明,含钛钢中形成稳定的碳氮化钛,对阻止再加热奥氏体晶粒长大有利.含钛钢变形抗力比不含钛钢要高,其动态再结晶开始的临界变形量比不加钛钢的小,易于发生再结晶,且含钛钢的再结晶晶粒尺寸相对较细,再结晶晶粒长大速度也更慢.     

热轧相变诱发塑性钢的热模拟实验

 利用Gleeble 1500热应力 应变模拟机研究了铌含量、热变形参数(终轧温度和卷取温度)对相变诱发塑性(TRIP)钢组织和性能的影响。实验结果表明：不含铌实验钢的残余奥氏体量、残余奥氏体相中的碳含量、宏观维氏硬度和抗拉强度与常规低碳硅锰系TRIP钢的水平相当;增加铌含量,残余奥氏体量和残余奥氏体相中的碳含量有所下降,而宏观维氏硬度和抗拉强度提高;铌含量为0014%、终轧温度为780 ℃、卷取温度为400 ℃时,残余奥氏体量、残余奥氏体相中的碳含量与宏观维氏硬度和抗拉强度具有最佳组合。     

低碳钢Q235形变奥氏体的静态再结晶

在Thermecmastor-Z热模拟试验机上进行了低碳钢Q235的双道次压缩试验,确定了该钢静态再结晶的动力学方程.结果表明,在大变形量下,即使变形温度较低(850～800℃),应变速率较高时,静态再结晶的速度仍然很快.通过静态再结晶可以将奥氏体晶粒尺寸细化至10～20μm.