Temperature Drop of Molten Metals in Open Channels

The temperature drop of molten metal flowing in open channels is numerically determined. Rectangular, trapezoidal and triangular geometries are considered. The overall heat transfer coefficients for the bottom, side walls and free surface of the channel have been taken from the literature. For each geometry, the volumetric flow rate, mean residence time and temperature drop as a function of the channel inclination angle were determined. The rectangular and trapezoidal geometries present the smallest temperature drops, while the triangular geometry presents the greatest temperature drop. The factors that most affect this drop are the value of the free surface area of the channel, and the average residence time of the molten metal in the channel.

Impact response and energy absorption of metallic buffer with entangled wire mesh damper

An innovative metallic buffer consisting of series-connected hat-shaped entangled wire mesh damper(EWMD)and parallel springs are proposed in this work to enhance the reliability of engineering equipment.The impact response and the energy dissipation mechanism of hat-shaped EWMD under different quasi-static compression deformations(2-7 mm)and impact heights(100-200 mm)are investigated using experimental and numerical methods.The results demonstrate distinct stages in the quasi-static mechanical characteristics of hat-shaped EWMD,including stiffness softening,negative stiffness,and stiffness hardening.The loss factor gradually increases with increasing compression deformation before entering the stiffness hardening stage.Under impact loads,the hat-shaped EWMD exhibits optimal impact energy absorption when it enters the negative stiffness stage(150 mm),resulting in the best impact isolation effect of metallic buffer.However,the impact energy absorption significantly decreases when hat-shaped EWMD enters the stiffness hardening stage.Interestingly,quasi-static compression analysis after experiencing different impact loads reveals the disappearance of the negative stiffness phenomenon.Moreover,with increasing impact loads,the stiffness hardening point progressively shifts to an earlier stage.

Numerical simulation of copper based filler metal droplets spreading under arc brazing

The spreading behavior of copper filler metal droplets under arc brazing was studied by numerical simulation method using Surface Evolver software. The mathematical model in which arc pressure force acceleration was added to the droplet microelement as the form of gravity acceleration was used in numerical simulation. Then the 3D filler metal droplet profile for different welding currents was simulated. The results show that the simulation results and the experimental results are in good accordance. And it can be seen that the spreading height decreases and diameter increases with the increasing welding current in an approximate linear relation.

Preliminary Analysis of Liquid Metal MHD Pressure Drop in the Blanket for the FDS

Preliminary analysis and calculation of liquid metal Li17Pb83 magnetohydrodynamic (MHD) pressure drop in the blanket for the FDS have been presented to evaluate the significance of MHD effects on the thermal-hydraulic design of the blanket. To decrease the liquid metal MHD pressure drop, Al2O3 is applied as an electronically insulated coating onto the inner surface of the ducts. The requirement for the insulated coating to reduce the additional leakage pressure drop caused by coating imperfections has been analyzed. Finally, the total liquid metal MHD pressure drop and magnetic pump power in the FDS blanket have been given.

金属粉末床粘结剂喷射3D打印关键问题的研究现状与展望

针对金属粉末床粘结剂喷射3D打印技术存在薄层铺粉难、粘结剂不匹配、初坯及烧结件密度低等问题,首先从原材料特征、铺粉机构及数值模拟等方面总结当前粉末铺展研究现状;接着阐述了粘结剂与粉床作用、粘结剂类型和性能以及残留问题的研究进展,指出优化粘结剂体系、限制残留物,有利于提升粘结剂喷射成形金属零件性能;然后介绍了烧结和浸渗等当前常见致密化方法,指出致密化过程中需考虑变形和精度控制,并通过热等静压、固溶和时效等后处理方法对零件孔隙及相组成进行调控;最后指出高精度、高性能和难成形材料打印是未来发展趋势。

Sn和Ce元素复合添加对BAg5CuZn钎料钎缝组织与性能影响

研究了Sn和Ce元素复合添加对低银BAg5CuZn钎料熔化特性、铺展性能、钎缝组织及钎焊接头力学性能的影响.结果表明,随着低银钎料中Sn和Ce元素的复合添加,钎料的固、液相线温度显著降低,钎料在母材上的铺展面积增大,但当添加的Ce元素含量高于0.15%(质量分数)时,Ce元素会恶化钎料的铺展性能.适量的Sn和Ce元素的添加可以显著改善BAg5CuZn钎料钎缝的显微组织,当添加Sn和Ce元素含量分别达到2%和0.15%时,钎缝组织明显细化且分布最为均匀.然而,钎料中Ce元素添加量过多时,会倾向于Ag和Sn元素形成复杂的金属间化合物,并在组织晶界处析出,而使得钎缝组织的均匀性显著恶化.当钎料中的Sn和Ce元素含量分别为2%和0.15%时,其钎焊接头抗剪强度达到最大值495 MPa,相比于BAg5CuZn钎料钎焊的接头抗剪强度提高了23.1%.

Ag10CuZnSn-xIn-yCe低银钎料组织及性能

通过向Ag10CuZnSn低银钎料中添加微量的In元素和Ce元素,研究了In元素和Ce元素的复合添加对低银钎料的固相线温度液相线温度和铺展性能的影响,同时分析了两种合金元素对Ag10CuZnSn钎料的显微组织及钎焊接头力学性能的影响规律.结果表明,微量In元素和Ce元素的添加可以显著地降低Ag10CuZnSn低银钎料的固相线和液相线温度,同时可以提高Ag10CuZnSn钎料在T2紫铜和304不锈钢基板上的铺展面积,当In元素和Ce元素的质量分数分别为1.5%和0.15%时,钎料在T2紫铜和304不锈钢上的铺展面积分别提升了21.1%和35.7%. In元素和Ce元素可以改善低银钎料的显微组织,当In元素和Ce元素的质量分数分别为1.5%和0.15%时,Ag10CuZnSn低银钎料显微组织的细化作用最为明显,此时304不锈钢钎焊接头的抗剪强度也达到最大值,为375 MPa.然而,质量分数3%的In元素和质量分数0.5%的Ce元素会在Ag10CuZnSn钎料的显微组织中形成脆性的Ag-In-Sn金属间化合物相和Sn-Ce稀土相,钎焊接头的抗剪强度也有所降低.

喷印金属双液滴撞击固体形成气泡的模拟研究

喷墨打印镓金属液滴撞击固体表面时会产生空气夹带,造成气泡沉积出现喷墨打印导线不互联现象,深入理解气泡形成的影响因素是解决此问题的关键。为消除气泡,提高打印导线互联性,本研究使用Ansys Fluent软件,采用VOF耦合水平集方法,建立了二维镓金属双液滴撞击固体铜基板过程的仿真模型,研究了水平壁面温度、双液滴间距、倾斜壁面角度、倾斜壁面温度等参数对金属双液滴撞击固体壁面形成气泡过程的影响规律。研究结果表明,对于水平基板,在不同基板温度下气泡的大小呈现双向变化,金属双液滴间距的增加更有利于液滴铺展。当金属双液滴间距S=D_(0)-2.38D_(0)时,有气泡形成;当S=2.38D_(0)-2.5 D_(0)时,液滴铺展出现断裂,且气泡随温度的增加没有明显变化;当金属双液滴间距S=2.6 D_(0)时,随着温度的增加不再产生气泡,此时喷墨打印液滴表现出最佳精度,提高了打印导线的互联性。对于倾斜基板,使用参数韦伯数(We⊥)和参数(K⊥)表征金属双液滴形成的气泡,当撞击倾斜壁面韦伯数We⊥>15、K⊥>0.035时,液滴会在固体表面上形成气泡;当We⊥>16、K⊥>0.04时,形成的气泡直径随壁面温度的增加而减小;当15<We⊥<16、0.035<K⊥<0.04时,液滴出现铺展断裂,并且气泡直径随着壁面温度的增加而减小;当5<We⊥<15、0.015<K⊥<0.035时,液滴铺展断裂且气泡直径变大;当We⊥<5、K⊥<0.01时,液滴在基板形成的气泡消失,此时为喷墨打印液滴的最佳精度,可提高打印导线的互联性。该研究为优化喷墨打印金属液滴的工艺提供了重要理论依据,有望在实际应用中消除气泡,进一步提高喷墨打印导线的互联性。

邯钢新区铁钢界面汽车“一罐到底”运行实践

河钢集团邯钢新区系邯钢东区退城整合搬迁项目,受山区地形及土地面积限制,该项目采用紧凑式布局,高炉到转炉最近距离450 m,吨钢占地面积仅0.3 m^(2),铁钢界面采用汽车“一罐到底”模式进行铁水驳运,铁水罐受铁完毕后10 min即可拉到炼钢生产,并运用了数字、物联网等新技术加以辅助,经过投产以来的改进优化,新区铁水罐周转率达到7.0次/日、进炼钢铁水温度1440℃、“一罐到底”比例99%,较搬迁前分别提高4.0次/日、98℃、39百分点;铁水温降降低到82℃,较搬迁前减少81℃,界面热量损耗大幅降低,为炼钢工序增钢降耗创造了有利条件,符合国家节能减排的理念,对行业“双碳”战略具有一定借鉴意义。

基于物联网的铁水调度系统的应用与实践

随着市场行情的持续低迷,降本增效是钢企转型的重中之重。提高炼钢入炉铁水温度可以为生产创造有利条件,是铁水调度工作的重要目的。本文介绍了新开发出的符合三钢特色的铁水调度平台,建立铁钢匹配生产模式,并基于新的调度系统采取了一系列针对性的管理措施。通过控制在线周转铁罐的个数,降低铁罐空、重载时长,提高铁水罐的周转效率,有效降低高炉至转炉的铁水过程温降。通过控制在线铁水量,提高铁水消耗速率,为高效生产创造良好条件。

Droplet impact on regular micro-grooved surfaces

We have investigated experimentally the process of a droplet impact on a regular micro-grooved surface. The target surfaces are patterned such that micro-scale spokes radiate from the center, concentric circles, and parallel lines on the polishing copper plate, using Quasi-LIGA molding technology. The dynamic behavior of water droplets impacting on these structured surfaces is examined using a high-speed camera, including the drop impact processes, the maximum spreading diameters, and the lengths and numbers of fingers at different values of Weber number. Experimental results validate that the spreading processes are arrested on all target surfaces at low velocity. Also, the experimental results at higher impact velocity demonstrate that the spreading process is conducted on the surface parallel to the micro-grooves, but is arrested in the direction perpendicular to the micro-grooves. Besides, the lengths of fingers increase observably, even when they are ejected out as tiny droplets along the groove direction, at the same time the drop recoil velocity is reduced by micro-grooves which are parallel to the spreading direction, but not by micro-grooves which are vertical to the spreading direction.

Analysis of MHD Pressure Drop in Liquid LiPb Flow in Chinese ITER DFLL-TBM with Insulating Coating

Magnetohydrodynamic （MHD） pressure drop in the Chinese Dual Functional Liquid Lithium-lead Test Blanket Module （DFLL-TBM） proposed for ITER is discussed in this paper. Electrical insulation between the coolant channel surfaces and the liquid metal is required to reduce the MHD pressure drop to a manageable level. Insulation can be provided by a thin insulating coating, such as Al2O3, which can also serve as a tritium barrier layer, at the channel surfaces in contact with LiPb. The coating＇s effectiveness for reducing the MHD pressure drop is analysed through three-dimensional numerical simulation. A MHD-based commercial computational fluid dynamic （CFD） software FLUENT is used to simulate the LiPb flow. The effect on the MHD pressure drop due to cracks or faults in the coating layer is also considered. The insulating performance requirement for the coating material in DFLL-TBM design is proposed according to the analysis.

Experimental Base of an Innovation S-Channel to Reduce MHD Pressure Drop

Consequent on MHD geometry sensibility phenomena was measured in an accident case;the more detail experiments have been conducted at the liquid metal experimental loop upgrade facility (LMEL-U). The experimental results indicate that MHD pressure drop can be greatly reduced in the special designed ducts. Base on the experimental data, an innovation channel concept (tentatively called as the secondary flow channel, short in “S-channel”) is addressed as a reducing MHD pressure drop channel for the application of a liquid metal blanket system in fusion reactor. It may be a dawn for solving MHD pressure drop key issue of liquid metal blanket system.

Analysis on Width Spread of Cold Rolled Strip

Width spread is usually considered in hot rolling, nevertheless, it can be ignore in cold rolling. In order to control the crown and flatness better simultaneously and realize the decoupling of crown and flatness, the transverse displacement function of strip is defined and deduced. The factors that affects the width spread are analyzing with the function. According to the unchanged principle of volume before and after rolling, the flatness model which considers the width spread is deduced. Through the model, the transverse metal flowing of different stands and different thickness is analyzing, it is found that the width spread is biggest in cold rolling at the No. 1 stand because of the maximum thickness and reduction and the minimum deformation resistance. It gives a good foundation for the decoupling of crown and flatness.

高碱金属燃料灰结渣特性表征方法

由于准东煤和生物质等碱金属含量高,其燃烧用于发电供热易造成锅炉受热面沾污结渣,成为锅炉安全稳定长周期运行的技术瓶颈。灰的熔融特征参数是指导锅炉设计和运行的重要依据,实际工程应用中,普遍采用GB/T 219—2008《煤灰熔融性的测定方法》测定4个特征温度来描述灰熔融过程的变化,从而判断灰的沾污结渣特性。然而该方法制灰过程中碱金属挥发,导致测量结果明显高于实际值,对锅炉设计运行无指导意义。总结不同灰化终温下碱/碱土金属的释放规律:准东煤550℃时,Na析出约20%~50%,815℃时,析出在30%~80%;生物质中K在400℃时开始析出,到800℃时,K几乎全部析出。在此基础上,进一步分析了国标法制灰后熔点的测量方法,尽管采用低温灰样,在制灰过程中抑制了碱金属的挥发,但在后续加热测量熔点的过程中仍会引起碱金属的释放,进而明确了国标法不适用于高碱金属燃料灰熔融特性的测定。为此,针对高碱金属燃料,提出一种低温灰化后,用压差法测定灰初试烧结温度的测量方法,并在压差法试验装置上进行测量,达初始烧结温度前,样品室压降随温度升高而增大,满足达西定律,一旦出现烧结时,样品体积收缩,样品室两端压降迅速降低,则压降变化的拐点为燃料的初始烧结温度,也是灰熔融团聚的最低温度。采用低温灰化仪制得稻壳灰,并在试验台上开展初步试验,测得其初始烧结温度为695℃,与工业上实际结渣温度吻合较好,而国标法测得软化温度高达1500℃以上,远高于稻壳实际结渣温度,初步表明,该试验方法可准确表征高碱金属燃料结渣特性,为工业应用提供参考。

金属夹造袋牵引法辅助内镜黏膜下剥离术治疗结直肠肿瘤的临床效果

目的分析金属夹造袋牵引法辅助内镜黏膜下剥离术(ESD)治疗结直肠肿瘤的临床效果。方法选取2019年1月~2022年12月该院进行结直肠ESD治疗的结直肠肿瘤244例患者作为研究对象。根据ESD术中是否实施金属夹造袋牵引法,将患者分为金属夹牵引组(M-ESD,n=75)和无牵引组(N-ESD,n=169)。采用倾向性评分匹配法筛选患者,以一般临床资料为协变量进行匹配。比较匹配后两组患者的手术时间、手术切除结果指标、不良事件发生率和病理组织学诊断指标。结果M-ESD组的手术时间短于N-ESD组(分别为20.0[15.0,30.0]min和30[20.0,45.0]min,P=0.008)。M-ESD组与N-ESD组的整块切除率(100%vs98.6%)、完全切除率(97.3%vs96%)以及根治切除率(97.3%vs96%)均无统计学差异(P>0.05)。M-ESD和N-ESD组的不良事件发生率较低且无统计学差异(P>0.05)。结论尽管与无牵引组相比,金属夹牵引组在手术切除率和不良事件发生率无明显差异,但是使用金属夹造袋牵引法可能具有缩短ESD手术时间的临床作用。

金属氧化物对镁粉尘层火蔓延的增强机制

易分解的固体惰化剂会增加镁粉尘层的燃烧强度,为探究不易分解的金属氧化物对镁粉尘层燃烧是否具有抑制效应,选用TiO_(2),MgO,CaO进行实验研究.结果表明:TiO_(2),MgO,CaO在质量分数小于75%时均大幅增强镁粉尘层火蔓延的燃烧强度,火焰相态由纯镁粉尘层燃烧时的表面非均相燃烧转变为气相燃烧;TiO_(2)通过与镁粉发生化学反应增强火蔓延行为,在TiO_(2)和Mg恰好完全反应(TiO_(2)质量分数为63%)的工况下粉尘层火蔓延速率增加了50余倍;MgO,CaO通过增大镁粉颗粒间距,减缓了镁粉燃烧产物形成致密氧化层,从而增强镁粉尘层火蔓延行为.实际生产过程应高度关注镁粉尘与金属氧化物的接触工况,研究结果能够为镁粉尘防护提供理论基础.

减压塔内件材料表面改性工业应用实践

华中地区某炼化公司8000 kt/a常减压装置减压塔在投产后第2个运行周期的中后期全塔压降明显升高,严重影响装置平稳操作和总拔出率。经分析,主要是由于减压塔的洗涤段结焦造成气相通道减小、压降攀升,导致进料段的闪蒸量减小、减压塔拔出率降低。2017年大检修时,对洗涤段填料进行了床层高度改造和耐蚀抗焦表面处理。改造后1个周期内,减压塔的压降和装置拔出率平稳。2021年再次检修时发现,填料结焦情况得到明显改善。上述改造成果说明,应用表面改性技术并配合操作的调整,能有效减缓洗涤段填料表面的结焦趋势,避免因为减压塔压降升高造成的拔出率降低,经济效益显著。

水成膜泡沫剂对液滴冷却高温金属表面的影响

向细水雾中添加水成膜泡沫灭火剂成分能明显提升针对B类火灾的灭火效果,但添加剂能否提升水雾对火灾区域内固体表面的冷却效果尚不清楚。分别从金属表面温度、We数和是否添加泡沫灭火剂3个方面设置了试验条件,开展了单液滴撞击高温金属表面模拟试验并对冷却效果进行了定量计算。结果表明,液滴的最大铺展因子与撞击动量正相关,含添加剂液滴表面张力降低且流变特性呈现剪切变稀特征。当Leidenfrost现象发生时,碰撞试验表明泡沫溶液液滴相较于纯水液滴的最大铺展系数更小且回弹速率更大,因此泡沫灭火剂的添加不利于提升吸热效率。研究结果可为泡沫细水雾技术的灭火实践提供理论指导。

低泡沫无水印金属表面清洗剂配方的优化

为避免金属清洗过程中产生泡沫以及在表面残留水印的困扰,选用具有超级润湿与铺展作用的低泡沫表面活性剂脂肪酸甲酯乙氧基化物FMEE作为清洗剂的主体成分,并将柠檬酸钠与无磷螯合剂乙二胺二邻苯基乙酸钠按照质量比1:1复配替代磷酸盐三聚磷酸钠作为助洗剂。最终确定了低泡沫无水印金属清洗剂的配方为:喜赫EO/PO无规嵌段FMEE10%,柠檬酸钠5%,乙二胺二邻苯基乙酸钠EDDHA-Na5%,耦合剂M4005%,杀菌剂0.1%,纯水74.9%。