37Mn5钢热变形行为与流变应力模型研究

利用Gleeble-1500热模拟实验机研究37Mn5钢在变形温度为800～1150℃、变形速率为0．1～10s^-1条件下的热压缩变形行为。采用应变硬化率-应力曲线图较精确地获得峰值应力,并用双曲正弦方程描述37Mn5钢热压缩变形过程中的峰值应力与Zener—Hollomon参数的关系。回归分析得到方程中变形激活能及各材料常数的值,获得37Mn5钢在高温条件下的流变应力本构方程。结果表明,采用该本构方程计算出的流变应力值与实验所得应力值非常接近。     

动态再结晶动力学模型的研究

本文提出了依据热变形σ－ε信息确定动态再结晶分数的方法，建立了ε０．５同变形工艺参数间的关系模型，构造了一种新的动力学表象模型。本文还提出了求解模型待定参数的数值方法。作为应用，考察了Ｓｔ４１钢热压缩条件下动态再结晶动力学行为。结果表明，动力学方程中的α值及ε０．５指数同关于Ｃ－Ｍｎ钢报道值一致。     

动态再结晶动力学模型的研究

本文提出了依据热变形σ－ε信息确定动态再结晶分数的方法，建立了ε_（０．５）同变形工艺参数间的关系模型，构造了一种新的动力学表象模型。本文还提出了求解模型待定参数的数值方法。作为应用，考察了Ｓｔ４１钢热压缩条件下动态再结晶动力学行为。结果表明、动力学方程中的α值及ε_（０．５）指教同关于Ｃ－Ｍｎ钢报道值一致。     

高强钢变形抗力实验研究

利用MMS-200热模拟试验机测定不同变形温度、变形速率下高强钢的变形抗力,分析各工艺参数对变形抗力的影响,通过回归分析得出该钢的变形抗力数学模型.     

37Mn5钢高温形变再结晶规律的研究

本文采用定量金相的方法研究了37Mn5钢(N80石油套管)在再加热前的不同组织状态、加热温度、形变温度、形变量以及形变后在空气中的停留时间等诸参数对奥氏体高温形变再结晶规律的影响。为钢管在淬火前获得最佳奥氏体状态确定比较合理的工艺参数。     

Q345B钢动态再结晶动力学模型研究

在Gleeble1500热模拟机上进行Q345B钢单道次压缩变形实验,得到其真应力-真应变曲线,结合加工硬化率曲线,确定了Q345B钢动态再结晶临界应变εc、峰值应变εP和稳态应变εs。根据实验结果得到Zener-Hollomon方程和动态再结晶状态图,利用Johnson-Mehl-Avrami（JMA）方程法得到再结晶体积分数实际值,采用3种不同的再结晶体积分数预报模型对实验数据进行回归,并对再结晶体积分数实测值和预报值进行对比。结果表明,Epsilon-S／Epsilon-C模型精度最高,Epsilon-S模型精度次之,Epsilon-P模型精度最差。     

Modeling of metadynamic recrystallization kinetics after hot deformation of low-alloy steel Q345B

Based on the steady-state strain measured by single-pass hot compression tests, the method by a double-pass hot compression testing was developed to measure the metadynamic-recrystallization kinetics. The metadynamic recrystallization behavior of low-alloy steel Q345B during hot compression deformation was investigated in the temperature range of 1 000–1 100 °C, the strain rate range of 0.01–0.10 s⁻¹ and the interpass time range of 0.5–50 s on a Gleeble-3500 thermo-simulation machine. The results show that metadynamic recrystallization during the interpass time can be observed. As the deformation temperature and strain rate increase, softening caused by metadynamic recrystallization is obvious. According to the data of thermo-simulation, the metadynamic recrystallization activation energy is obtained to be Q _md=100.674 kJ/mol and metadynamic recrystallization kinetics model is set up. Finally, the error analysis of metadynamic recrystallization kinetics model proves that the model has high accuracy (correlation coefficient R=0.988 6).     

X100管线钢的高温变形力学行为

采用Gleeble-3500热模拟试验机对X100管线钢进行单道次压缩试验,研究其变形抗力与应变量、应变速率和变形温度的关系,利用回归分析确立合适的变形抗力数学模型,并将模型预测值与试验值进行比较。结果表明,变形温度对X100管线钢变形抗力影响显著;高温低应变速率更有利于X100管线钢回复和再结晶的发生;应变速率过高会引起非稳态变形,不利于X100管线钢轧制过程的控制;利用回归分析确定的变形抗力模型能够准确预测X100管线钢的变形抗力,相关系数为0.986。     

铌对弹簧钢60Si2MnA动态再结晶的影响

在Gleeble-1500热模拟实验机上研究含铌弹簧钢的动态再结晶行为,用透射电镜对铌的析出物进行观察,并分析铌对弹簧钢动态再结晶的影响。结果表明,含铌弹簧钢易发生动态再结晶,在温度为850-1050℃、变形速率为0.1-20 s^-1条件下均发生动态再结晶;在变形速率为5 s^-1的条件下,60Si2MnA动态再结晶的发生推迟50℃左右;在低温情况下,铌推迟60Si2MnA动态再结晶的主要原因是Nb（C,N）的析出及其钉扎作用。     

T8Mn钢株光体连续冷却转变动力学研究

利用定量金相法测得T8Mn钢以 1℃ /min冷速连续冷却转变的动力学曲线 应用Formastor Digital膨胀仪测得T8Mn钢在不同冷速下连续冷却转变的动力学曲线 并利用BASIC软件对曲线进行线性回归分析 ,得到动力学转变的数学模型     

82B高碳钢热变形行为研究

采用单道次热压缩实验方法,在Thermomaster-Z型热模拟试验机上模拟高碳钢高速线材热轧变形过程动态再结晶行为,测定82B高碳钢在变形温度为800～1 100℃、变形速率为0.1～50 s-1、变形程度为0～0.60条件下的真应力-应变曲线,利用曲线特征值确定高应变速率下的变形激活能,根据实验结果分析动态再结晶变形条件,建立动态再结晶状态图。     

High temperature plastic deformation behavior of non-oriented electrical steel

High temperature plastic deformation behavior of non-orientated electrical steel was investigated by Gleeble 1500 thermo-mechanical simulator at strain rate of 0.01−10 s⁻¹ and high temperature of 500–1 200 °C. The stress level factor (a), stress exponent (n), structural factor (A) and activation energy (Q) of high temperature plastic deformation process of non-orientated electrical steel in different temperature ranges were calculated by the Arrhenius model. The results show that, with dynamic elevation of deformation temperature, phase transformation from α-Fe to γ-Fe takes place simultaneously during plastic deformation, dynamic recovery and dynamic recrystallization process, leading to an irregular change of the steady flow stress. For high temperature plastic deformation between 500 and 800°C, the calculated values of a, n, A, and Q are 0.039 0 MPa⁻¹, 7.93, 1.9×10¹⁸ s⁻¹, and 334.8 kJ/mol, respectively, and for high temperature plastic deformation between 1 050 and 1 200 °C, the calculated values of a, n, A, and Q are 0.125 8 MPa⁻¹, 5.29, 1.0×10²⁸ s⁻¹, and 769.9 kJ/mol, respectively. Foundation item: Project(2005038560) supported by the Postdoctoral Foundation of China; Project(05GK1002-2) supported by Key Program of Hunan Province     

Hot deformation behavior of low carbon steel during compression at elevated temperature

Hot compression tests of low carbon steel were carried out on Gleeble-3500 system in the temperature range from 750 to 900 ℃ and in the strain rate range from 0.001 to 1.0 s-1, and the associated microstructural evolution was studied by observations with a metallographic microscope. The results show that the stress-strain curves exhibit a peak stress at critical strain, after which the fl ow stresses decrease monotonically until reaching high strains, showing a dynamic fl ow softening. The peak stress level decreases with increasing deformation temperature and decreasing strain rate, which can be represented by the Zener-Hollomon parameter Z in the hyperbolic sine equation. The fl ow stress increases with increasing strain rate and decreasing deforming temperature. The fl ow stress can be described by constitutive equation in hyperbolic sine function and can also be described by a Zener–Hollomon parameter Z. With increasing deformation temperature and decreasing strain rate, the grain size as well as the volume fraction of the recrystallized grains increase. The safe region for hot working of the alloy has been determined according to the processing map and microstructure at the true strain of 0.5, which is the deformation temperature of 840-940 ℃ and the strain rate of 0.001-1.0 s-1.     

Research on microstructural evolution and dynamic recrystallization behavior of JB800 bainitic steel by FEM

Single pass compression tests were conducted on Gleeble1500 thermal simulator. The effect of different deformation parameters on the grain size of dynamically recrystallized austenite was analyzed. A mathematical model of dynamic recrystallization and a material database of JB800 steel, whose tensile strength is above 800 Mpa, were set up. A subprogram was compiled using Fortran language and called by Marc finite element software. A thermal coupled elastoplastic finite element model was established to simulate the compression process. The grain size of recrystallized austenite obtained by different recrystailization models was simulated. The results show that the optimized dynamic recrystallization model of JBS00 bainitic steel has a higher precision and yields good agreement with metallographic observations.     

高温空气介质下U71Mn钢氧化动力学实验研究

为了研究重轨钢(U71Mn)在空气介质下高温氧化动力学规律,对其在900～1 300℃之间进行了5组恒温50min的氧化实验,分别绘制了在这些温度下的氧化增重曲线,并计算出了不同实验温度下该钢种的氧化动力学速率.结果表明,重轨钢在900～1300℃时氧化动力学曲线遵守直线规律.