针对316LN不锈钢动态再结晶模型的DEFORM二次开发

根据已知的316LN不锈钢的动态再结晶模型,对DEFORM数值模拟软件的微观组织部分进行了二次开发,预测316LN热塑性变形过程中动态再结晶组织的体积分数和晶粒平均尺寸的变化过程,使热塑性变形过程的有限元变形一传热一组织演化耦合分析功能得到了增强。最后得出的模拟结果和实验结果能够很好的吻合,这说明二次开发是成功的,为以后对锻件的组织优化和控制奠定了理论依据。     

316LN不锈钢动态再结晶研究

利用Gleeble-1500D热力模拟试验机在850～1250℃,应变速率0.01～10 s-1,变形程度0.91条件下对316LN奥氏体不锈钢进行热压缩变形试验。在真应力应变曲线上没有出现明显应力峰值,金相观察表明,316LN不锈钢在热变形过程中发生了动态再结晶。对实验数据进行拟合,得到316LN不锈钢的热激活能和热变形方程,并给出了发生动态再结晶的临界应变和临界应力以及Zener-Hollomon参数。     

不同热变形条件下310S奥氏体不锈钢动态再结晶行为研究

利用显微组织观察和显微硬度测试两种方法研究了热压缩试验后的310S奥氏体不锈钢动态再结晶行为,热压缩试验在Gleeble-3800热模拟试验机上进行,应变速率采用0.1s-1和1s-1、变形温度在900~1150℃之间。研究结果表明,随着变形温度的升高,310S奥氏体不锈钢的变形抗力降低。在应变速率为0.1s-1时,其完全动态再结晶的变形温度为1000℃;应变速率升高至1s-1时,其完全动态再结晶的变形温度升高至1100℃,高的应变速率可以细化再结晶晶粒。     

316LN奥氏体不锈钢的高温流变行为与本构模型

利用Gleeble-3500热模拟试验机对锻造态316LN不锈钢进行了等温热压缩试验,研究了应变速率为0.001～1 s^-1、变形温度为1223～1523 K、压缩变形量为65%条件下材料的高温流变行为,建立了流变应力本构模型,并将其应用于Deform-3D软件平台,通过导入新材料数据,考虑界面摩擦等尺寸仿真了热模拟试验结果。结果表明:相同应变速率下,随着变形温度升高,316LN奥氏体不锈钢的压缩应力逐渐减小;相同变形温度下,随着应变速率增加,材料的压缩应力逐渐增大;且在真应力-真应变曲线中,随应变量增大,压应力在后期逐渐达到一个稳定值;考虑界面摩擦因数,并利用Arrhenius本构模型进行变形模拟仿真说明了本构方程和仿真模型的有效性和可靠性,可为316LN不锈钢材料的工程应用提供研究基础和理论依据。     

J4节镍奥氏体不锈钢动态再结晶行为的研究

通过在Gleeble- 1500D热模拟试验机上进行等温压缩试验,研究了变形工艺参数对节镍奥氏体不锈钢J4动态再结晶行为的影响.结果表明,应变率越小、变形温度越高、应变量越大,J4钢越易发生动态再结晶.J4钢在(ε)＜0.1s-1、T≥950℃和(ε)=0.1s-1、T＞ 1200℃时,将发生动态再结晶.在(ε)=0....     

316LN奥氏体不锈钢在预蠕变条件下位错的变化

在320℃(核电主管道AP1000近似运行温度)和600℃(液态用核电材料近似运行温度)条件下,分别在20和120 MPa的应力下老化500和2000 h进行316LN不锈钢预蠕变试验。通过光学显微镜(OM)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)观测预蠕变后试样的微观组织。结果表明:在预蠕变阶段受到温度和应力作用,晶面滑移产生位错以及原有位错发生分解,被激活的位错在同一个平面内沿不同方向滑移移动,相遇时发生反应生成四边形或六边形的位错网络,随着温度以及应力增大位错网络消失。对于硬度变化而言随着温度从320℃升高到600℃时,显微硬度逐渐升高。     

316LN钢多道次变形条件下的动态再结晶行为

通过高温热力学模拟实验,研究了大型核电主管道用钢316LN在应变速率0.01s-1,温度1200℃～1150℃、1100℃～1050℃、1000℃～950℃双道次变形条件下的高温变形行为,得到了该钢种在多道次变形条件下的流动应力曲线。通过对热模拟试样高温淬火后显微组织的研究分析,得到了多道次变形条件下的动态再结晶规律和组织控制规律。     

316LN钢高温流动应力与动态再结晶模型

利用Gleeble热模拟压缩实验,研究316LN奥氏体不锈钢在温度950℃¹250℃、应变速率0.001s-11250℃、应变速率0.001s-1¹.0s-1下的高温变形特征,并测得相应的流动应力曲线。对实验数据进行计算拟合,建立加工硬化-动态回复和动态再结晶"两阶段"高温流动应力模型、动态再结晶百分数及晶粒尺寸模型。将所建模型写入有限元软件进行数值模拟,其结果与实验吻合,说明该模型准确可靠,可用于316LN热变形过程的数值模拟。     

用于ITER的316LN不锈钢热变形行为

通过在Gleeble-1500热模拟试验机进行高温压缩试验,以实验得到316LN奥氏体不锈钢真应力-真应变曲线为基础,并结合高温变形显微组织,对其动态再结晶行为进行研究,从而得到热激活能Q、热变形方程以及动态再结晶的基本规律,初步建议在生产轧制过程中,将轧制温度控制在1050℃左右,应变速率小于0.01 s-1为宜,为该产品生产提供了重要依据。     

Effects of Different Forging Processes on Microstructure Evolution for 316LN Austenitic Stainless Steel

Forging experiments were designed and carried out on a 3150 kN hydraulic press to investigate the effects of different processes on the microstructure evolution for 316LN steel. The forging processes included single-pass (upsetting) and multipass (stretching) deformations, and the experimental results indicated that the average grain size varied with forging processes. Moreover, the size had distinct differences at different positions in the workpiece. Meanwhile, numerical simulations were implemented to study the influence of temperature, strain, and strain rate on microstructure evolution. The results of experiments and simulations comprehensively demonstrated that dynamic, static, and meta-dynamic recrystallization could coexist in the hot forging process and that the recrystallization process could easily occur under the conditions of higher temperature, larger strain, and higher strain rate. Moreover, the temperature had more significant influence on both recrystallization and grain growth. A higher temperature could not only promote the recrystallization but also speed up the grain growth. Therefore, a lower temperature is beneficial to obtain refinement grains on the premise that the recrystallization can occur completely.     

Research on Flow Stress During Hot Deformation Process and Processing Map for 316LN Austenitic Stainless Steel

In this study, the hot deformation behavior of austenitic stainless steel was investigated using Gleeble-3500 thermomechanical simulator at deformation temperatures in the range of 900-1200?°C and strain rates in the range of 0.001-10?s^?1. The effects of initial austenitic grain size and deformation conditions on hot deformation behavior of 316LN were analyzed through true stress-strain curves under different deformation conditions. Both the constitutive equation and processing map for 316LN were obtained. The results show that, with the increase of the deformation temperature and the decrease of the strain rate, the peak stress decreases, and the initial austenitic grain size has a little influence on the peak stress. The relative error between the peak stress values calculated using the constitutive equation and the values measured is less than 10%. Using the processing map, the best hot-working condition for 316LN in the range of experimental deformation parameters appears when T?=?1200?°C and $\dot{\upvarepsilon } = 0.001\,{\text{s}}^{-1}.$      

加热规范对316LN铸态奥氏体不锈钢组织和性能的影响

研究了316LN奥氏体不锈钢在不同温度和不同保温时间下,铁素体的含量、形貌的变化规律以及对力学性能的影响.结果表明:随同溶温度的升高、固溶时间的延长,铁素体的含量逐渐减少,形貌由原来的骨骼状逐渐向比较光滑的圆点状演变,硬度有整体下降的趋势.     

Impression Creep Behavior of 316LN Stainless Steel

Impression creep tests have been carried out at 923 K on 316LN SS containing 0.07, 0.14, and 0.22 wt.% nitrogen, under different applied stress levels. It was observed that the impression creep depth versus time curves were similar to the creep curves obtained from conventional uniaxial creep tests. The impression creep curves were characterized by a loading strain and primary and secondary creep stages similar to uniaxial creep curves. The tertiary stage observed in uniaxial creep curves was absent. The steady-state impression velocity was found to increase with increasing applied stress. The equivalent steady-state creep rates calculated from impression velocities were found to be in good agreement with the steady-state creep rates obtained from conventional uniaxial creep tests. Equivalence between applied stress and steady-state impression velocity with uniaxial creep stress and steady-state creep rate, respectively, has been established based on the laws of mechanics for time-dependent plasticity. It was found that impression velocity was sensitive to the variation in nitrogen content in the steel; impression velocity decreased with increasing nitrogen content, and the results obtained in this study were in agreement with those obtained from uniaxial creep tests.     

Enhancement Mechanism of Cerium in 316LN Austenitic Stainless Steel During Creep at 700 °C

Effect of cerium (Ce) on creep strength and microstructure of 316LN austenitic stainless steel (316LN steel) at 700 °C/150 MPa was investigated by scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM) and thermodynamic calculations. Addition of 0.032 wt% Ce to 316LN steel results in a prominent increase in creep life from 313 to 556 h. Ce enriches in titanium nitride nanoparticles, increases slightly the activity and diffusion coefficient of Mo, and facilitates the formation of fine and dense intragranular Laves phase precipitates. Thus the creep strength is remarkably enhanced by Ce addition in 316LN steel through the intragranular Laves phase precipitation strengthening. It reveals a new insight into the improvement effect of rare earth (RE) elements such as Ce on creep strength of austenitic stainless steels, which inspired the design of RE-microalloying heat-resistant steels.     

316L奥氏体不锈钢的腐蚀行为

综述了316L奥氏体不锈钢应用过程中的腐蚀行为,包括晶间腐蚀、应力腐蚀开裂、缝隙腐蚀、环烷酸腐蚀、大气腐蚀和海水腐蚀。同时介绍了合金元素Mo、N和Al,以及电解质类型、温度、浓度等因素对其腐蚀行为的影响。最后讨论了应用中存在的问题,并对未来的发展做了一些展望。     

316LN奥氏体不锈钢波动管超声检测无底波原因分析及改善

对316LN奥氏体不锈钢波动管超声检测无底波的原因进行了分析,确定晶粒状态后对锻件进行了均质热处理来改善组织性能,从而有效实施产品超声检测。     

316L不锈钢板坯金相组织和夹杂物分析

不锈钢铸坯内部质量直接影响着最终产品的表面质量和力学性能.对316L奥氏体不锈钢板坯中金相组织和夹杂物进行了检测分析.结果表明:316L不锈钢铸坯的表层残留铁素体呈骨骼状分布,角部晶粒细小;铸坯中心残留铁素体相比较分散,呈条状或不连续骨架形式分布;铸坯三角区铁素体含量最高为15.17％,明显高于其他部位;铸坯中夹杂物都呈现为球状,类型为Al2O3-MgO-CaO-SiO2;三角区5～10 μm的夹杂物数量多,心部试样以0～5 μm的夹杂物为主.