轴承钢GCr15低温轧制组织研究

利用Gleeble2000热模拟机研究了轴承钢GCr15在不同形变温度条件下的形变奥氏体组织状态,分析了950℃的高温轧制和750℃低温轧制的室温组织区别,结果表明,高温轧制时奥氏体发生动态再结晶,室温组织珠光体晶粒较大,珠光体组织内的渗碳体片层清晰,生长有规则;低温轧制时轴承钢GCr15为奥氏体＋渗碳体双相区形变,奥氏体不发生动态再结晶,同时渗碳体沿晶界发生动态析出,呈断续和球状,室温组织网状和珠光体晶粒尺寸降低,渗碳体片层生长不规则。     

冷连轧机动态变规格轧制失稳原因分析及控制措施

介绍了冷连轧动态变规格的概念及作用，分析了动态变规格期间钢种及规格等轧制参数切换对稳定轧制的影响，提出了动态变规格稳定轧制控制措施实施，通过措施实施有效的减少了动态变规格过程中出现的各类事故，提高了轧制稳定性，取得了良好的效果。     

GCr15控制轧制新工艺的模拟研究

用热扭转试验机，实现了热变形模拟轴承钢控制轧制工艺。研究了形变过程中所发生的静态和动态软化过程，观察了形变后的组织，证实在生产过程中实现的可能性，为在生产中推广使用提供了科学依据。     

热变形奥氏体动态再结晶晶粒直径与形变参数间的关系

本文采用高温轧制变形方式,研究了低碳低合金钢的热变形奥氏体动态再结晶行为以及动态再结晶晶粒直径与形变参数间的关系,并着重讨论了形变量对动态再结晶晶粒直径的影响,结果表明:热变形奥氏体动态再结晶晶粒直径不仅与Z参数有关(随Z增大而减小),而且还与形变量有关。在一定形变量范围内,随形变量增加,动态再结晶晶粒直径减小。     

00Cr25Ni7Mo4N双相不锈钢的热轧组织与织构

观察了00cr25Ni7M04N双相不锈钢在不同轧制温度和不同压下率下的组织形貌和晶粒取向,结果表明,在相同压下量下,奥氏体相形变程度随轧制温度上升而减弱;铁素体相织构复杂,织构强度远大于奥氏体相.轧制过程中的相变、形变和动态再结晶是产生上述这些现象的原因.     

采用显式动态弹塑性有限元法模拟板材轧制

采用显式动态弹塑性有限元法对平板轧制过程进行了模拟计算，得出了整个轧制过程的应力应变场。轧制压力的计算结果与实测值基本相符。     

动态设定型板形厚自动控制系统

应用最近建立的解析板形方程推出板形最佳轧制规程和板形厚协调控制新方法。该方法特征是静、动态负荷分配，动态设定ＡＧＣ完成了板形板厚的闭环控制，其计算方法是贝尔曼动态规划。新方法可以应用于刚度较低的轧机来提高产品精度。从经济效益角度看，现行宣传的自由轧制应该被否定，提倡传统的调度计划、配轧辊凸度和轧制规程优化，从而由高投入高消耗的板形控制方法转向无投入、无消耗的利用信息流的闭环最优板形控制方法。     

热轧带钢半无头轧制动态变规格过程张力设定

在常规连轧张力公式和冷连轧动态变规格张力公式的基础上，分析了热轧带钢半无头轧制工艺动态变规格过程张力设定值变化规律的要求，合理确定了张力设定变更点，并给出热轧带钢半无头轧制工艺动态变规格过程楔形区张应力的设定计算公式。     

中厚板轧制过程中轧制力参数的动态修正

分析了一种中厚板的轧制力在线动态修正算法,该算法以实测轧制力为基础,通过道次实测轧制力和模型计算轧制力的值决定轧制力模型参数修正量的大小,真正做到以实测轧制力数据动态校正中厚板轧制力模型,大大提高了轧制力模型的预报精度并使其具有良好的自学习功能.该算法已经在现场获得应用,并具有良好的应用效果.     

形变Z因子与动态再结晶晶粒尺寸间的理论模型

以晶界迁移机制进行再结晶的材料，其稳定动态昌粒尺寸Ｄ取决于形变Ｚｅｎｅｒ－ｈｏｌｌｏｍｏｎ参数（Ｚ因子）。作建立了反映Ｄ－Ｚ间关系的理论模型，进行了Ｓｔ４１钢平面应变热变形动态再结晶实验，探讨了动态再结晶晶粒细化的机理。该理论模型为Ｓｅｌｌａｒｓ的经验公式提供了物理基础。研究结果表明，提高形变储存能是动态再结晶晶粒的重要途径。     

Effects of Temperature and Strain Rate on Flow Behavior and Microstructural Evolution of Super Duplex Stainless Steel under Hot Deformation

Hot compression tests were carried out in the temperature range of 1 223-1 473 Kand strain rate range of0.01-30s-1 to investigate the flow behavior and microstructural evolution of super duplex stainless steel 2507(SDSS2507).It is found that most of the flow curves exhibit a characteristic of dynamic recrystallization(DRX)and the flow stress increases with the decrease of temperature and the increase of strain rate.The apparent activation energy Qof SDSS2507 with varying true strain and strain rate is determined.As the strain increases,the value of Qdeclines in different ways with varying strain rate.The microstructural evolution characteristics and the strain partition between the two constituent phases are significantly affected by the Zener-Hollomon parameter(Z).At a lower lnZ,dynamic recovery(DRV)and continuous dynamic recrystallization(CDRX)of the ferrite dominate the softening mechanism during the compression.At this time,steady state deformation takes place at the last stage of deformation.In contrast,a higher lnZ will facilitate the plastic deformation of the austenite and then activate the discontinuous dynamic recrystallization(DDRX)of the austenite,which leads to a continuous decline of the flow stress even at the last deformation stage together with CDRX of the ferrite.     

Determination of the Critical Strains for the Initiation of Dynamic Transformation and Dynamic Recrystallization in Four Steels of Increasing Carbon Contents

Hot torsion tests are carried on three plain carbon steels and a Nb microalloyed steel of increasing C concentrations. The tests are performed at strain rates up to 4 s^?1 and over the temperature range 743–917°C. The onsets of dynamic transformation (DT) and dynamic recrystallization (DRX) are detected using the double‐differentiation method. Both mechanisms are initiated under all testing conditions but one. The critical strain for DT increases with temperature while the reverse dependency is exhibited by the critical strain for DRX.     

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。     

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The effect of deformation parameters on hot deformation of superalloy 800H was studied by means of single-pass compression test. It was found that smaller initial grain size, higher deformation temperature and lower strain rate are more easily to cause dynamic recrystallization. And when dynamic recrystallization can take place during deformation, the fraction of dynamic recrystallization increases with increasing of strain. The models of dynamic recrystallization activation energy, critical strain, dynamic recrystallization kinetics, dynamic recrystallization kinematics and grain size of dynamic recrystallization for 800H were obtained through the analysis of data obtained by single-pass compression. The variation tendency for grain size simulated by Deform-2D is consistent with metallographic statistics, and the average error is 4. 5??m. Very small average error shows that the model is consistent with practical situation and can be used to predict recrystallized grain size for 800H during thermal deformation.     

2Cr11Mo1VNbN钢再结晶动力学方程及本构方程的建立

采用Gleeble-3800热模拟试验机,在温度为1 000~1 200℃、应变速率为0.01~1 s-1和变形量为70%的条件下研究了2Cr11Mo1VNbN钢的热变形行为,建立了动态再结晶型本构模型以及动态再结晶体积分数模型。结果表明:2Cr11Mo1VNbN钢在高温小应变速率的变形条件下易发生动态再结晶,计算得出2Cr11Mo1VNbN钢发生动态再结晶时的临界应变以及变形激活能并得到了动态再结晶体积分数模型,最终构建出的动态再结晶型本构方程能良好地描述2Cr11Mo1VNbN钢的高温流变行为。     

CSP生产Q235B钢的动态再结晶规律的研究

为研究CSP工艺条件下钢的动态再结晶规律,利用Gleeble-1500热模拟实验机对CSP工艺生产的Q235B钢连铸坯进行了热模拟研究。研究结果表明,在较高变形温度和较低应变速率下Q235B钢容易发生动态再结晶,试验中Q235B钢发生动态再结晶的适宜条件为:变形温度970℃以上、应变速率在5/s以下。再结晶组织为铁素体和少量珠光体。通过热模拟数据的拟合分析,得出了其动态再结晶模型为Z=εexp(289.58/RT)。     

热变形动态软化本构模型

动态回复、动态再结晶是奥氏体热变形过程中动态软化的主要机制。建立了动态回复、动态再结晶型流变曲线模型,５０％再结晶应变等特征应变与形变参数Ｚ间的关系模型以及基于Ｅｎｇｌｅ／Ｂｒｅｗｅｒ理论的形变激活能模型。提出了一种应用最优化技术求解 线性本构模型的新方法。用Ｇｌｅｅｂｌｅ－２０００型热／力模拟试验机对Ｓｔ４１钢进行了平面应变热压缩试验。实验结果及有关文献报导印证了模型的正确性。     

Effect of Carbon on Dynamic Recrystallization Behavior of Vanadium Microalloy Steels

The hot working behavior especially dynamic recrystallization of low-carbon and medium-carbon vanadium microalloy steels has been studied by performing isothermally compression tests and Avrami analysis.The Avrami plots of the two experiment steels have been constructed based on flow stress curves following a new approach (Jonas,et al.Acta Mater.,2009,57(2):2748-2756;Wu et al,Acta Metall.Sin.,2010,46(7):838-843).It is experimentally found that the carbon effect on dynamic recrystallization is opposite to each other in lower and higher strain ranges:Carbon causes a softening effect at low strain rates (0.01,0.1,and 1.0 s-1),and a hardening effect at high strain rates (10.0 and 30.0 s-1).Correspondingly,carbon promotes the dynamic recrystallization at low strain rates and retards the dynamic recrystallization at high strain rates in the experimental steels.The phenomenon is then tentatively explained based on the possible mechanisms of dynamic process at different strain rates.     

F45MnVS钢热变形本构方程

 为了建立可以满足计算精度的F45MnVS钢高温塑性变形本构关系模型,利用Gleeble-3500试验机完成了热模拟等温压缩试验,获得了变形温度为800~1 000 ℃、应变速率为0.01~10 s-1、变形量为0~70%时的金属流变行为。结果表明,应力随应变的变化具有明显动态再结晶特征,应力随变形温度的降低、应变速率的增加而增大;基于对Arrhenius方程和Zener-Hollomon参数的解析,获得了热变形激活能Q,建立了峰值应力本构模型;基于应力-位错关系和动态再结晶动力学,建立了加工硬化-动态回复和动态再结晶两个阶段的机理型本构模型,用于描述不同变形温度和应变速率时应力与应变之间的关系;采用所建模型完成了不同变形条件的应力应变预测,与试验结果的对比分析表明,相关系数为0.997,吻合度高。