Microstructure analysis of AISI 304 stainless steel produced by twin-roll thin strip casting process

The microstructure of AISI 304 austenlte stainless steel fabricated by the thin strip casting process were investigated using optical microscope, scanning electron microscope （SEM）, transmission electron microscope （TEM）, and X-ray diffraction （XRD）. The microstructures of the casting strips show a duplex structure consisting of delta ferrite and austenite. The volume fraction of the delta ferrite is about 9.74vo1% at the center and 6.77vo1% at the surface of the casting thin strip, in vermicular and hand shapes. On account of rapid cooling and solidification in the continuous casting process, many kinds of inclusions and precipitates have been found. Most of the inclusions and precipitates are spherical complex compounds consisting of oxides, such as, SiO2, MnO, Al2O3, Cr2O3, and FeO or their multiplicity oxides of MnO.Al2O3, 2FeO.SiO2, and 2MnO.SiO2. Many defects including dislocations and stacking faults have also formed during the rapid cooling and solidification process, which is helpful to improve the mechanical properties of the casting strips.

Effects of Al and Ca on microstructure and surface defect of magnesium alloy thin strip

Mg-Al-Zn alloy thin strips were prepared by vertical twin-roll casting.Effects of Al and Ca on the microstructure and the surface defects of the thin strips were investigated.The results show that with the increase of Al content,the quantity of surface cracks of the thin strips increases rapidly and their locations are moved to the center of the thin strips.The alloy melts with more than 0.10%Ca(mass fraction)stick on the roller and a poor surface quality of the thin strips appears.With the increase of Al content,the microstructure of the thin strips evolves from singleα-Mg phase,characterized by the uniform and equiaxed recrystallization grains, to the combination of dendriticα-Mg with Al supersaturatedα-Mg.The minor addition of Ca can obviously refine the grains of Mg-3Al-1Zn thin strip because the formation of Al2Ca and the finest grains are obtained by adding 0.08%Ca.

Elastic-plastic solution to stamping thin strip on elastic foundation

An analytical method was proposed to solve the mechanical problems of stamping a thin strip on an elastic foundation. The thin strip was divided into four parts according to its deformation and contact with the punch and the elastic foundation, especially an elastic-plastic part was considered in the deflection of the thin strip. Analytical solutions were derived individually for each part and two models were established with the help of elastic and plastic large deflection theories. Compatibility conditions between the neighboring parts of the thin strip constructed the non-linear equation group. Solutions were carried out by programming with a software. The deformation shape, the membrane force, and the moment and shear force of the deformed thin strip were obtained. The results of the two models were compared. The study shows that the method is effective.

Wearing Property and Friction Mechanism of Ceramic Side Dams Used in Thin Strip Continuous Casting

In this paper,based on three different kinds of ceramic side dams for thin strip antinuous casting,the friction and wearing property were studied.The effects of friction pressure,temperature and friction time on the friction and wearing property of the ceramic side dam were researched.What’s more,the friction mechanism and wearing mechanism of the ceramic side dam were researched as well.Results show that the ceramic side dam of BN-SiA lO N has the best wearing resistance property.while at room temperature,16 min of friction time and0.35 MPa of friction pressure,the test friction coefficient is 0.60 and wearing capacity is 272.358 mm-3.In addition,when at 400℃,16 min of friction time and 0.18MPa of friction pressure,the test friction coefficient is0.70.The friction mechanism of ceramic side dam with the opposite wearing material is mainly the composite wear of adhesion,abrasive and fatigue.

Analysis of strip edge cracks during cold rolling of thin strip

In this paper,the mechanics of strip edge cracks and its propagation has been studied,and the effects of strip edge drop and stress intensity factor(SIF) on edge crack defections during cold rolling of thin strip have been discussed.An experimental investigation was presented into the effect of strip edge drop on edge cracks during cold rolling of thin strip.The edge crack increases significantly due to more inhomogeneous deformation and work hardening at the strip edge.The effective stress intensity factor range is important as it represents the major physical cause of the crack propagation.The efficiency and reliability of the SIF analytical model has been demonstrated in the study.The proposed method for predicting strip edge crack is helpful in producing defect-free products and providing an understanding of the mechanics of edge crack propagation in cold rolling of thin strip.

Numerical simulation of the temperature field of twin-roll thin strip continuous casting

In this study, the temperature field model of twin-roll thin strip continuous casting was developed, and the interface heat transfer coefficient between the air and the strip surface was computed by using the inverse method. The effects of the process parameters including the casting speed, liquid level height, pouring temperature and thickness of the thin strip on the outlet temperature of the rotating rolls and the surface temperature of the thin strip were analyzed.

Determination of Hypoxanthine in the Presence of Copper by Adsorptive Stripping Voltammetry

A stripping method for the determination of hypoxanthine in the presence of copper at the submicromolar concentration levels is described. The method is based on controlled adsorptive accumulation of hypoxanthine-copper at the thin-film mercury electrode followed by a fast linear scan voltammetric measurement of the surface species. Optimum experimental conditions were found to be the use of 1.0 × 10﹣3 mol·L﹣1 NaOH solution as electrolyte supporting, an accumulation potential of ﹣0.50 V and a linear scan rate of 200 mV·s﹣1. The response of hypoxanthine-copper is linear over the concentration ranges of 10 - 60 ppb. For an accumulation time of 30 minutes, the detection limit was found to be 250 ppt (1.8 × 10﹣9 mol·L﹣1). Adequate conditions for measuring the hypoxanthine in the presence of metal ions, xanthine, uric acid and other nitrogenated bases were also investigated. The utility of the method is demonstrated by the presence of hypoxanthine associated in ATP or ssDNA.

松软薄煤层条带消突下斜定向钻孔成孔护孔技术研究与应用

针对松软薄煤层煤巷条带消突长距离下斜钻孔,存在成孔难、易钻遇煤层顶底板、积水堵塞瓦斯抽采通道的难题,提出了氮气排渣下斜定向钻进成孔与护孔技术,采用高压氮气排渣、大功率气动螺杆钻具定向、“波浪式”轨迹控制和三层管护孔排水技术,在河南省平煤股份一矿开展现场试验,完成8个孔深超300 m下斜定向长钻孔,煤层钻遇率90%以上,全孔段下三层护排水管,平均下入深度302 m,支管平均抽采纯量1.66 m^(3)/min,平均瓦斯浓度17.5%。试验结果表明:该技术可有效解决松软薄煤层下斜钻孔长距离定向成孔、全孔段筛管护孔和排水的技术难题,提高了钻孔成孔深度和煤层钻遇率,实现了下斜孔全孔段护孔和排水,保障了瓦斯抽采效果,为松软薄煤层煤巷条带长距离消突提供技术保障,在类似地层条件具有广泛的应用推广价值。

薄壁杆件屈曲模态分析的力特征约束有限条法

整体、畸变、局部等基本变形模式的划分是条理化开展薄壁杆件工程计算的必要手段。薄壁杆件的基本变形模式传统上基于简化应力-应变关系,采用变形、应变等几何特征进行定义,不利于因应复杂化应力-应变关系。提出一套完全基于力特征和正交完备性原则的基本模式定义。与广义梁理论和约束有限条法相比,提出的整体、畸变、局部3种基本变形模式关于刚度严格正交,且完整覆盖薄壁杆件全变形域。基于该定义实现了针对薄壁杆件有限条模型的屈曲模态分解和识别。算例表明,提出的基本模式定义和屈曲模态分析方法具有开、闭口和折、曲线形截面的一致适应能力,剪应变和横向伸缩的影响在基本屈曲模式中得到合理表达,曲线形截面薄壁构件具有与多边形截面薄壁构件一致的整体、畸变和局部屈曲机理。

Ti_(3)C_(2)T_(x)超薄纳米片高效率去除废水中重金属的研究

通过刻蚀剥离法制备了Ti_(3)C_(2)T_(x)超薄纳米片,探究了其对废水中重金属离子的吸附特性。通过SEM、XRD、AFM、FT-IR、Raman对Ti_(3)C_(2)T_(x)超薄纳米片的形貌和结构进行了表征,通过ICP-MS对处理前后水体中重金属离子的含量进行了测试。结果表明剥离的Ti_(3)C_(2)T_(x)超薄纳米片表面含有结构缺陷和羟基,当水体中Cu(Ⅱ)、Pb(Ⅱ)、Cr(Ⅵ)初始浓度为50 mg/L时,47.5 mg Ti_(3)C_(2)T_(x)超薄纳米片对其的去除效率高达90%以上,尤其是对Pb(Ⅱ)的去除效率达到了98.81%,吸附性能远高于大孔树脂、硅藻土和活性炭等常见吸附试剂。在Na(Ⅰ)、Cu(Ⅱ)、Pb(Ⅱ)、Cr(Ⅵ)4种离子共存溶液中,Ti_(3)C_(2)T_(x)超薄纳米片对于Pb(Ⅱ)和Cr(Ⅵ)的去除依然可以达到92%以上。通过动力学和吸附等温拟合,Ti_(3)C_(2)T_(x)纳米片对Pb(Ⅱ)的吸附符合拟二级动力学模型和Langmuir等温模型,对Pb(Ⅱ)的最大吸附量和最低检出限分别为81.7 mg/g和0.0094 mg/L。Ti_(3)C_(2)T_(x)超薄纳米片对重金属离子的吸附特性在化学工业、食品加工的废水处理中具有良好的应用前景。

高性能Cu-Fe合金薄带材及其短流程制备技术

为了解决Cu-Fe合金常规制备流程中重力分层的问题,利用铸轧工艺的亚快速凝固特点抑制其液相分离,并结合Marangoni效应及热泳力的耦合作用合理调控铸轧参数,获得厚度为2.2~2.4 mm、铁磁相尺寸和分布可控的Cu-20%Fe和Cu-30%Fe带材。通过金相与EBSD分析确定铸带形成了Cu相-富Fe相-Cu相的“三明治”层状复合结构,其中Cu-20%Fe铸带中的Fe相分布更为均匀,且EBSD分析结果表明凝固层中形成了大量的低能晶界,如Σ1和Σ3等。将Cu-20%Fe合金从2.4 mm冷轧至0.4 mm,在不同温度下进行热处理后继续冷轧至0.12 mm。结果表明:450℃热处理对轧板性能更好,导电率超过50%IACS,抗拉强度超过600 MPa,均匀伸长率达到7.5%,饱和磁化强度超过4.24×10^(5)A/m。

轧制速度对二十辊轧机轧制硅钢薄带的影响分析

重点讨论了轧制速度在二十辊可逆冷轧机轧制生产硅钢薄带时对带钢表面质量和生产效率的影响:改变轧制速度可以在不改变预设压下率的情况下对带钢产品进行厚度微调,适宜的轧制速度可以使产品的厚度精度更高;适宜的轧制速度可以减少带材表面缺陷和不均匀性,提高硅钢带材的表面质量。在大量生产实验中,通过改变轧制速度,研究了轧后带材的厚度精度和表面质量。结果表明,通过选择合适的轧制速度可以在不影响成品带材质量的情况下有效提高硅钢薄带的生产效率。该研究针对森吉米尔二十辊可逆冷轧机的设备特点和轧制速度对硅钢生产的影响进行了深入探讨,为优化冷轧硅钢带材生产工艺提供了重要参考价值。

纯钛极薄带微流道刚柔复合模成形工艺

纯钛因存在延展性和各向异性导致成形性能差,难以成形高深宽比微流道。针对上述问题,提出了纯钛极薄带微流道刚柔复合模成形工艺,以提高纯钛极薄带成形性能,成形更大深宽比、壁厚更均匀的纯钛双极板微流道。通过单向拉伸实验测试了纯钛极薄带力学性能参数,采用刚柔复合模成形工艺研究了纯钛极薄带微流道成形极限,采用光学显微镜对微流道深度、深宽比和壁厚进行了测量分析。结果表明,纯钛极薄带存在显著的各向异性,TD方向r值最大为2.56,选择该方向垂直于微流道进行成形实验;在柔性垫厚度为0.35 mm时,微流道具有最大深宽比为0.53,较传统刚模微流道成形极限提高了26.7%,并显著提高了微流道壁厚分布均匀性。

超高强钢薄带温轧变形区温度场的模拟研究

超高强钢薄带温轧过程中变形区出口温度的精确预测是轧制工艺制定及过程温度控制的关键。本文利用Deform-3D数值模拟软件对超高强钢薄带的温轧过程进行模拟,分析了轧件入口温度、轧辊表面温度、轧制速度、压下率以及摩擦系数对变形区出口温度的影响,通过回归分析建立了变形区温度场的数学模型。结果表明,该温度场数学模型计算结果与模拟结果的误差在±11.5℃内,能够反映各温轧工艺参数对变形区出口温度的影响规律。

冲击力下薄壁内衬复合管界面黏结强度效应分析

【目的】研究薄壁内衬复合管在受冲击力作用下的界面黏结强度对层间剥离屈曲的影响。【方法】建立薄壁内衬复合管在弹性阶段的非线性分析模型,对薄壁内衬复合管材模态试验与分析模型的分析结果进行对比,验证有限元分析模型可靠性。通过改变衬层与原基层管壁间的界面黏结强度,研究复合管在冲击力下的动态特征。【结果】研究结果表明,当冲击荷载较小、管道变形处于弹性阶段时,薄壁内衬复合管的损伤大都集中在层间界面处。界面黏结强度对层间剥离屈曲有较大的影响,随着层间界面黏结强度的增加,外基层管与内衬层的最大等效应力差值减少。此外,外基层管和内衬层的变形协调性能力随着黏结强度增加而增大,径向层间位移减小,增加了复合管的整体性和连续性。【结论】研究结果可为薄壁内衬修复管道设计方法及层间界面效应分析提供参考。

柔性条式疏花执行装置试验研究

疏花可以调整果树负载量,是影响果树产量和质量的重要因素。为研究机械疏花效果及其影响因素,采用自主研发的柔性条式疏花机执行装置对桃花进行试验,选取橡胶和尼龙两种材料的疏花条,以疏花条轴向间距、疏花条列数、主轴转速、工作模式为试验因素,以疏花指数来评价疏花效果,并优化了装置的工作参数。结果表明:若采用尼龙疏花,疏花轴转速为400 r/min、疏花条列数为4、工作模式为冠内垂直、疏花条轴向间距为5 cm时效果最优;若采用胶条疏花,疏花轴转速为450 r/min、疏花条列数为4、工作模式为冠外平行、疏花条轴向间距为4 cm时效果最优。经试验验证,设计满足疏花的工作要求,为柔性条式疏花机的研发提供了理论依据。

基于模板剥离法制备高性能钙钛矿单晶薄膜光电探测器

近年来,杂化钙钛矿半导体材料由于其带隙可调、吸收系数高、载流子迁移率高、成本低廉等诸多优点,在光电器件领域备受青睐,如太阳能电池、电致发光器件、光电探测器等。其中,钙钛矿单晶薄膜因其无晶界、杂质和缺陷含量低等特点,展现出更为优异的光学、电学特性,成为制备高性能光电器件的理想材料体系。然而,钙钛矿单晶薄膜常采用空间限域法直接生长在空穴传输层上,不可避免地将导致界面缺陷和载流子层间输运等问题,严重制约了钙钛矿单晶薄膜光电探测器的性能。为此,本文通过引入模板剥离法工艺技术,在钙钛矿单晶薄膜两侧分别蒸镀功能层材料,制备了结构为Cu/BCP/C_(60)/MAPbBr_(3)/MoO_(3)/Ag的钙钛矿单晶薄膜光电探测器。基于模板剥离法,两侧蒸镀的功能层与钙钛矿单晶薄膜接触紧密,将有效改善载流子的注入和传输;同时,优化的器件结构以及考虑能带匹配等因素可实现高灵敏、响应快速的钙钛矿单晶薄膜光电探测器。改进后器件的开关比高达3.1×10^(3),响应度可达7.15 A/W,探测率为5.39×10^(12)Jones,外量子效率达到1794%。该工作为进一步改善和提升钙钛矿单晶薄膜光电探测器的探测性能提供了一种可行性技术方案。

附载体极薄铜箔的剥离机制

目的研究一种极薄铜箔制备过程中所需要的新型剥离层结构,以此来实现极薄铜箔的顺利剥离。方法利用两步电沉积法制备了可剥离的极薄铜箔,利用EBSD分析了“载体铜箔-剥离层-极薄铜箔”结构的附载体铜箔截面晶粒分布规律,利用聚焦离子束技术(FIB)制备了TEM样品,通过HRTEM对“载体铜箔-剥离层-极薄铜箔”结构中剥离层/极薄铜箔、剥离层/载体铜箔的界面微观结构进行了研究。结果与单一Ni剥离层相比,通过两步电沉积法制备的复合剥离层(Ni,Cr-O)具有更好的可剥离性,复合剥离层由有序Ni层和无序Cr-O层组成。复合剥离层中的Ni层与载体铜箔相结合,界面完全共格,形成较强的界面结合;复合剥离层中的无序Cr-O层与极薄铜箔相结合,Cr-O层与极薄铜箔界面原子紊乱,形成较弱的界面结合。对制备的极薄铜箔剥离强度进行测试可知,极薄铜箔与载体铜箔能够剥离,极薄铜箔与剥离层之间的剥离强度约为0.01N/mm。结论利用载体铜箔-剥离层、极薄铜箔-剥离层结合界面的差异化实现了界面结合的差异化,复合剥离层内有序和无序的结构分布调控了载体铜箔与剥离层、极薄铜箔与剥离层之间的界面结合,使剥离层与极薄铜箔之间的结合弱于剥离层与载体铜箔之间的结合,有助于极薄铜箔与剥离层分离,同时剥离层与载体铜箔之间不会分离,进而获得可洁净剥离的极薄铜箔。

T2紫铜复杂异形零件渐进微冲裁工艺研究

为探究厚度为0.2 mm的介观尺度T2紫铜复杂异形成形件的渐进微冲裁工艺,通过金相腐蚀和拉伸试验获得T2紫铜薄带的微观组织及力学性能,分别利用传统微冲裁工艺与渐进微冲裁工艺制备复杂异形零件,并通过三维激光电镜和扫描电镜对成形件的整体形貌和冲裁断口形貌进行了观测分析。结果表明,渐进微冲裁成形技术与传统微冲裁工艺相比,成形件的尺寸精度和形状精度较高,该工艺可显著降低传统微冲裁工艺中的冲裁件断面圆角带面积,改善撕裂带形貌与光亮带的表面光洁度,获得更好的冲裁断面质量。

热轧薄规格带钢板凸度纵向分布特征的研究

为了控制某1780 mm热轧生产线薄带钢板凸度的纵向分布,通过分析现场轧制过程工艺及板凸度数据,对影响因素进行了定量分析。结果表明:随着带钢厚度的减小,带钢板凸度纵向差值越大,其带钢长度方向上F7机架出口温度、速度和F1机架轧制压力和弯辊力差值越大。随着带钢宽度的减小,板凸度纵向衰减量逐渐增大,带钢中后部的板凸度逐渐低于目标值的下限。随精轧F7机架出口速度、温度的升高以及F1机架轧制压力和弯辊力的降低,板凸度发生衰减,且上述轧制参数波动值越大衰减特征越明显、衰减量越大。