Effects of cooling rates on microstructures and mechanical properties of Nb-Ti microalloyed steel

The mechanical properties and microstructure of as-cast Nb-Ti microalloyed steel at different temperatures and cooling rates are investigated in this paper. The III brittle zone (700?C900°C) is revealed. The reduction of the hot ductility is due to the film-like proeutectoid ferrite or the Nb(C, N) precipitates along the austenitic grain boundaries. In the temperature range of 850?C1 000°C, with the increase of the cooling rate, the hot ductility decreases. However, in the range of 650?C850°C, the appearance of large volume fractions of ferrite on austenite grain boundaries minimizes the effect of cooling rate on hot ductility. When the cooling rate is 10°C/s, austenite transforms more quickly to ferrite and at a lower temperature a larger amount of ferrite nucleates and precipitates in the grain, which leads to a sharper improvement in the hot ductility at 650°C.     

耐候钢09CuPCrNi拉伸变形行为与组织变化的研究

本文采用标准拉伸试验、光学金相和透射电镜研究了09CuPCrNi 热轧耐候钢的室温拉伸变形行为和组织变化结果表明,由于应力诱发马氏体相变发生及铁素体的加工硬化,引起材料出现锯齿状不连续屈服,应力诱发马氏体岛沿晶界呈连续网状分布及晶界珠光体组织导致塑性降低,马氏体岛由位错板条马氏体组成,变形后铁素体内位错密度升高.     

Influence of soaking temperature on microstructure of multi-pass compression deformation for low carbon steels

The influence of soaking temperature on microstructure of high temperature multi-pass compression deformation for two low carbon steels (steel A: w _C = 0.032% and w _Mn = 0.25%; steel B: w _C = 0.165% and w _Mn = 0.38%) is studied on the thermal-mechanical simulator in order to rationalize the hot-rolling schedule of low-carbon steel and to promote the low-temperature heating technology. The results show that the microstructures of steel A are almost not affected by reducing soaking temperature, but the acicular ferrite forms in steel B when the soaking temperature is reduced from 1 200 to 1 170°C, due to its smaller initial austenite grain size according to recrystallization kinetics theory.     

典型冷作模具钢经强韧化奥氏体化后的过冷奥氏体中温转变研究

研究了典型冷作横具钢65Cr4W3Mo2VNb,Cr7Mo3V2Si 和 Cr12MoV 经强韧化奥氏体化后的过冷奥氏体中温转变,测定了其中温转变 TTT 曲线,求出强韧化奥氏体化后钢中基体含碳量,得出了奥氏体化温度和中温转变等温温度对下贝氏体组织的影响以及中温转变等温时间对下贝氏体量的影响规律,还得出了部分低温转变对随后中温转变下贝氏体形成孕育和和下贝氏体组织的影响特点,包括连续冷却和等温马氏体转变的影响规律.     

Dynamic recrystallization behavior and microstructural evolution in SPHC steel

The dynamic recrystallization(DRX) behaviors in SPHC steel were investigated with hot compression tests at deformation temperatures of 950-1 150,strain rates of 0.1-15 s-1,and initial austenite grain sizes of 86-232 μm.The effects of deformation temperature,strain,strain rate and the initial austenite grain size on the microstructural evolution during DRX were studied in detail.The results show that DRX is observed under the condition of the Zener-Hollomon parameter being less than 1.07×10 13 s-1.The deformation activation energy for SPHC steel is calculated to be 299.4 kJ/mol by regression analysis.Austenite grain size of DRX is refined with decreasing temperature and increasing strain rate under steady state conditions,but it is not influenced by the initial grain size.The mathematical equation of DRX grain size of SPHC steel is obtained.     

焊接修复对铁素体不锈钢焊接接头组织和性能的影响

通过拉伸、弯曲、冲击、硬度、金相组织分析等试验,对不同焊修次数T4003铁素体不锈钢焊接接头的组织和性能进行研究.试验结果表明:焊修一、二次对T4003铁素体不锈钢焊接接头的抗拉、弯曲和冲击性能均影响不大;不同焊修次数T4003铁素体不锈钢焊缝的显微组织为奥氏体+δ铁素体;熔合区的显微组织为铁素体+马氏体,晶粒粗大;母材的显微组织为块状铁素体,沿轧制方向成条状分布.焊接修复对T4003铁素体不锈钢焊接接头的粗晶区宽度、晶粒度与马氏体含量的影响不大.不同焊修次数T4003铁素体不锈钢焊接接头焊缝的显微硬度相近,母材显微硬度大致相同,热影响区显微硬度的变化不大.     

多晶Ni2.1Mn0.9Ga0.9C0.1合金的马氏体相变特征

采用电阻、热膨胀、磁致伸缩及光学金等试验方法研究了多晶Ni2.1Mn0.9Ga0.9C0.1合金的马氏体相变特征。结果表明：Ni2.1Mn0.9Ga0.9C0.1合金在400～100K之间发生两次相变,第一次为马氏体相变,它的热滞后比较小,马氏体相的电阻率高于母相的电阻率;而第二次相变的结构变化尚未澄清,它的热滞后比较大,新相的电阻率低于母相的电阻率。马氏体相变时,合金结晶方向长度收缩,磁致伸缩急剧减小。合金中马氏体基本为相互平行的片状组织。     

临界区奥氏体化过程的研究

以铁素体+珠光体为原始组织,研究了20号钢、16Mn钢和11CuP0.5Si2.0Mn钢在临界区加热时奥氏体的形成。测定了临界加热奥氏体转变的动力学曲线,并用电子探针分析了合金元素的分配。     

氮对奥氏体不锈钢氢脆敏感性的影响

本文研究了气相充氢条件下,氮对２１—６—９奥氏体不锈钢力学性能的影响,以及不同牌号的Ｃｒ─Ｎｉ—Ｍｎ系奥氏体不锈钢充氢后力学性能的变化。结果表明,不同牌号奥氏体不锈钢的抗氢脆能力随其层错能的增加而提高,氮含量的增加则使２１—６—９钢的抗氢脆能力下降。由此推论氮可能具有降低奥氏体钢层错能的作用。     

一种连铸连轧低碳低合金钢板的组织特征

利用光学显微镜、直读光谱仪和电子探针研究了一种用连铸连轧工艺生产的低碳低合金钢板的组织特征及成分偏析.结果表明：该钢板的显微组织以珠光体/铁素体带状组织为主要特征,并且随距钢板表面距离增加,带状组织中珠光体比例增加,铁素体平均晶粒尺寸增大.锰含量沿垂直带状组织方向波动,在珠光体条带内含量较高,而在铁素体条带内含量相对较低.钢板中心偏析明显,形成较多长条状硫化物夹杂.     

Computer simulation of the continuous annealing recrystallization for cold-rolled strip in galvanizing line

The continuous heating transformation program is developed to investigate the influence of continuous annealing technological parameters on recrystalization for cold-rolled strip in galvanizing line. This program can be used for the calculation of the continuous annealing temperature field of strip steel, determination of the start and end time of recrystallization in continuous heating process, and procurement of the continuous heating transformation diagram. The temperature field for continuous annealing is simulated by means of finite difference method. Based on the Scheil superposition principle, the continuous heating transformation curve is obtained by using time temperature transformation (TTT) curve which is measured experimentally. The developed program has been used in practice, and the strip speed on production line increases by more than 10%.     

Calculation Method Study on Steel Plate Deformation Under Impulse Loading of Thin Explosive

Basis of explosion's responsive analysis and anti-explosion's structure design is the relation among thin explosive mass, impulse and plate deformation. In this paper, the limitations of theoretical calculation and experimental methods are analyzed according to the relation between impulse loading and deformation of steel plate in thin explosive experiment. The time histories of deformation for the square steel plate under the impulse of thin explosive are calculated by the fluid-solid coupling method and the pressure loading method. The advantages of the pressure loading method and the fluid-solid coupling method are compared. The results show that the steel plate deformation can be estimated accurately using the fluid-solid coupling method when the explosive impulse is unknown, while the theoretical calculation and the pressure loading method provide quick and accurate prediction on the steel plate deformation when the explosive impulse is known.     

波形钢腹板组合箱梁自振特性与试验研究

为了精确计算波形钢腹板组合箱梁的振动频率,根据能量变分原理,推导了振动频率公式,得到了考虑剪切变形及剪力滞效应的各阶自振频率的解析解。对一试验波形钢腹板组合箱梁进行了动力测试,得到了实际自振频率,并与简单梁理论、本文理论公式与三维有限元模型的计算频率进行对比。结果表明:剪力滞效应及剪切变形对波形钢腹板组合箱梁的振动频率影响较大,考虑剪力滞及剪切变形影响后的波形钢腹板组合箱梁的振动频率有所降低,且降低程度随着计算频率阶次的增加而迅速增加,因而在波形钢腹板组合箱梁振动频率的计算中须计其影响。     

高填方钢波纹管涵垂直土压力计算

引入表征钢波纹管波形特性的惯性矩计算方法, 通过Spangler管-土相互作用模型, 得到了钢波纹管涵竖向收敛变形计算公式; 假设管涵顶部填土为半无限直线变形体, 将条形基础沉降倒置后比拟上埋式管涵的受力模型; 基于弹性力学推导的基础沉降计算公式, 着重考虑管涵侧向土体压缩变形与管涵自身的竖向收敛变形之差, 推导了管涵垂直土压力的计算公式; 以广巴广陕高速公路连接线吴家浩-张家湾段高填方钢波纹管涵工程为例, 对涵顶垂直土压力进行了现场测试, 将采用公式计算所得涵顶垂直土压力与现场试验结果和应用实测沉降差反算的垂直土压力进行了对比。研究结果表明: 涵顶垂直土压力随填方高度的增加而增大, 填土至设计标高后涵顶垂直土压力计算值、实测值和反算值分别为224.14、221.98、211.33kPa, 计算值与实测值的相对误差约为0.9%, 反算值分别比计算值和实测值小6.1%、5.0%, 且计算结果、反算结果均与实测涵顶垂直土压力变化规律一致, 填方越高, 误差越小。可见, 提出的高填方钢波纹管涵垂直土压力计算公式可行, 不仅考虑了涵侧土体的抗力系数和基床系数, 而且体现了钢波纹管的变形与受力特征。      

斜支撑钢箱梁变形分析

介绍箱形梁变形的特点,分析在不同斜率下斜支撑连续钢箱梁的变形。根据具体的试验规划,建立支撑线与梁横向交角为0°、15°、30°、45°的三跨连续钢箱梁的试验模型。利用ABAQUS通用有限元程序建立与试验相对应的计算模型。其有限元计算结果与试验数据吻合较好。通过试验数据采集和有限元计算,主要考虑钢箱梁在弹性工作状态下的节点竖向位移、纵向位移以及不同斜率下的挠度,对比分析斜率对钢箱梁变形的影响。     

60Si2Mn和5160H弹簧钢的脱碳行为

用显微组织法比较了60Si2Mn和5160H弹风在不同加热条件下的脱碳行为。结果表明，两种弹簧钢的脱碳深度随提高加热温度和增加加热时间增大，Si增加奥氏体中碳的活度使60SiMn销钢表面脱碳较5160H严重。     

ER8C和ER8材质高速动车组车轮的服役性能

为全面掌握高速动车组用ER8C和ER8车轮服役性能,使用OBLFQSN750型电火花直读光谱仪等设备分别实测了新旧车轮材料的化学成分、常规力学性能、疲劳特性、冲击性能及韧脆转变温度、断裂韧性、疲劳裂纹扩展门槛值和疲劳裂纹扩展速率等,并进行了金相组织观测,综合评价分析了两种材质车轮服役性能. 结果表明:1） ER8C材质车轮比ER8材质车轮中Si含量高2.74倍,Mn含量高1.29倍,Cr+Mo+Ni总含量低45%,C含量略低,其抗拉强度和屈服强度提高5%,疲劳强度提高15%. 2） 车轮显微组织为珠光体+少量铁素体,踏面下相同深度,ER8C材质车轮中铁素体更均匀细小,晶粒度大于8.5级,ER8材质车轮铁素体粗大,晶粒度为8级. 3） ER8C材质车轮韧脆转变温度为84.30 ℃,ER8材质车轮韧脆转变温度为71.97 ℃,车轮运用工况处于两种材质的脆性区. 4） ER8C材质车轮断裂韧性比ER8材质车轮高约6%,其阻止裂纹产生的能力优于ER8材质车轮;ER8材质车轮裂纹扩展门槛值比ER8C材质高17%,其阻止裂纹扩展的能力优于ER8C材质车轮;两种材质车轮的裂纹扩展速率相当. 5） 服役过程中ER8C材质车轮踏面垂直磨耗速率略大于ER8材质车轮.      

一种高强度钢的低周疲劳特性及其微观机理的研究

研究了６０Ｓｉ２ＣｒＶＡ高强度钢在低周疲劳条件下循环变形的宏观特性,结合材料在低周疲劳过程中位错组态的电镜观察,分该高强度钢中的铁素体和回火马氏体内的位错组态的微观行为。     

30Mn23Al4Cr5超低温无磁钢的冷加工强化

本文研究了冷加工对30Mn23Al4Cr5超低温无磁钢硬度、强度、塑性和冲击韧性的影响,试验结果表明,随着冷轧比的增加,硬度和屈服强度按抛物线规律增加,塑性和韧性按抛物线规律降低,而抗拉强度近似线性增加,冷轧引起的位错塞积和形变孪晶结构导致强度增加及塑性与韧性降低。     

装配式圆钢管约束混凝土柱的轴压性能

为了研究钢套管及套筒连接装配式圆钢管约束混凝土柱轴压性能,基于试验研究结果,对钢套管及套筒连接装配式圆钢管约束混凝土柱轴压性能进行了有限元分析. 首先通过有限元建立了现浇式和装配式圆钢管约束混凝土柱模型;然后从承载力-平均纵向应变关系曲线、钢管应力、钢筋应力和混凝土应力方面对比了现浇式与装配式柱的轴压性能;其次分析了装配式柱变形形态及受力机理;最后提出了装配式柱轴压承载力计算方法. 研究结果表明:与现浇式柱相比,装配式柱也具有良好的轴压性能和延性性能,钢管及钢套管对核心混凝土的约束作用更强,轴压承载力提高幅度为1.94%～6.17%;增加钢管厚度对提高装配式圆钢管约束混凝土柱轴压承载力最有效,提高幅度达59.15%,增加箍筋间距对其轴压承载力影响较小,减小幅度为2.91%;钢管纵向应力在靠近钢套管与钢管连接处较大,钢管环向应力在钢管通缝上、下附近区域较大,在钢套管装配处也较大;所提装配式柱轴压承载力公式计算值（N_uc）与有限元值（N_uf）、试验值（N_ut）的比值均值分别为0.964、1.014,方差分别为0.003 5、0.002 9.