化学镀法制备超细Ag-SnO2粉末的烧结

采用在1μm粒径的超细SnO2粉末化学镀银的方法,制备了超细Ag-SnO2复合粉末.通过压制成形、烧结等粉末冶金工艺,对粉末进行烧结试验,结果发现试样表面存在鼓泡现象.文章分析了鼓泡的成因,并采用降低成形压力及粉末煅烧处理等手段消除鼓泡现象.热重分析结果及烧结后的金相组织分析结果表明较低的成形压力可以改善鼓泡现象,但要从根本上消除鼓泡现象则必须对粉末进行高于450℃的煅烧处理.所得Ag-SnO2材料中SnO2颗粒分布均匀,电阻率、密度、硬度分别为2.25μΩcm、9.85 gcm-3和98 HB.     

车轮钢中的白点(一)

研究了车轮钢中白点形成的机理以及白点对断口形貌的影响.结果表明,氢和空位聚集导致鼓泡形核和长大,随着鼓泡内氢气压力的升高,裂纹从鼓泡核壁形核、扩展导致白点形成.白点的断口为准解理,和氢致滞后开裂断口相同,含白点试样的断口形貌依赖于断裂方式和试样厚度.钢中的白点除了产生二次裂纹和局部准解理断面外,对各种断口形貌均没有明显的影响.     

冷轧基料起鼓原因分析与改进

针对德龙钢铁有限公司1250生产线冷轧基料在下游客户冷轧后＂起鼓＂现象,分析其形成原因。在生产实际中通过优化辊型、改善冷却条件、优化生产计划编排等一系列措施的落实,带钢的横断面形状得到有效控制,冷轧基料在冷轧过程中＂起鼓＂的比例大为下降,产品的实物质量得到明显改善。     

钼合金表面MoSi2涂层氧化行为和氧化机理的研究

采用包埋渗硅法在钼合金表面制备了MoSi2涂层,研究了涂层的氧化行为和抗氧化机理.结果表明,钼合金基体经历30 min高温氧化后,样品表面鼓泡严重,质量失重率在11%左右;在钼合金基体表面形成MoSi2涂层后,抗氧化能力大幅度提高,经过60min的高温氧化后,样品表面完好,质量增重率为0.58%;在高温氧化过程中,Mo...     

管线管氢致开裂试样检测及分析

对管线管氢致开裂(HIC)试验后试样进行超声波探伤和金相分析。结果表明:HIC试验后未发现氢致裂纹缺陷,但超声波探伤可检测到大型B类夹杂物及表面氢鼓泡。本试验所取试样较大B类夹杂物出现在管体壁厚中心与外壁之间,可以大致推断较大B类夹杂位于原始铸坯1/2半径到表层细晶区之间,其成因与铸坯芯部成分偏析无关。氢鼓泡中有大颗粒状氧化镁及硫化钙夹杂,其余区域为铝酸钙夹杂,故夹杂物是形成氢鼓泡的诱因之一。     

鼓泡流化床流动特性的数值模拟

在双流体模型的基础上利用计算流体力学软件(Fluent)对气固鼓泡流化床的流动特性进行了模拟,得到了鼓泡流化床的一种流动形式.计算结果与流态化原理以及文献结果的吻合性好.     

新型鼓泡管通道换热性能的数值分析

针对热回收领域由于积灰、阻力损失大等造成换热器换热性能差的缺点,提出了新型鼓泡换热管结构。建立周期性单元流道数值计算模型,对其换热性能进行研究,结果表明:顺排分布鼓泡时,鼓泡间距为16mm的鼓泡管换热性能最好,换热通道的阻力损失随鼓泡间距的增大而减小;鼓泡间距为16mm的换热通道,鼓泡叉排分布时的换能因子j较顺排分布时的换能因子提高30.61%,阻力特性因子f较顺排时降低了32.46%。     

冷轧薄板表面缺陷研究

介绍了冷轧薄板表面主要缺陷的形貌、形成原因及预防措施。研究表明：冷轧薄板表面缺陷主要分为常规缺陷和非常规缺陷两大类。常规缺陷的产生与冷轧工艺质量密切相关,而非常规缺陷的形成机理则比较复杂,可能在炼钢工序也可能在轧钢工序形成,需具体情况具体分析。     

中低碳钢氢鼓泡形成机理分析

对中低碳钢氢致开裂(HIC)试验氢鼓泡进行了解剖分析。结果表明:氢鼓泡中均发现有夹杂物,包括A类硫化锰类夹杂、B类氧化铝类夹杂和大型的D类球形夹杂,所以氢鼓泡成因与A、B、D类夹杂均有关系。普通碳钢氢鼓泡中有片状硫化锰夹杂,而低硫钢氢鼓泡中主要是氧化铝类夹杂。氢鼓泡的大小与夹杂的大小和聚集程度有关。     

冷轧边损问题解析及改善对策

采用金相显微镜及扫描电镜,观察典型冷轧边损样表面组织形貌特征,解析典型冷轧边损形成原因.并采集酸轧表检仪数据及热轧过程数据分析比对炼钢、热轧及冷轧工序对冷轧边损的影响.依据冷轧边损宏观形貌及微观特征判断缺陷成因,将边损成因进行分类,针对性提出改善对策.     

冷轧镀锌板典型表面质量缺陷成因及控制措施

采用SEM、EDS等试验手段,研究了冷轧镀锌板典型的表面质量缺陷形貌及缺陷部位元素分布特征。结果表明:油脂类物质残留可导致冷轧镀锌板表面漏镀缺陷,氧化铁颗粒压入引起表面黑点缺陷,机械划伤可造成表面线状缺陷,保护渣卷入致使镀锌板表面出现孔洞缺陷。阐述了镀锌板各类表面缺陷的形成机理,并提出了相应缺陷的控制处理措施。     

Noise of Acoustic Doppler Velocimeter Data in Bubbly Flows

Acoustic Doppler velocimeter (ADV) measurements are useful and powerful for measurements of mean and turbulent components of fluids in both hydraulic experimental facilities and fields. However, it is difficult to use the ADV in bubbly flows because air bubbles generate spike noise in the ADV velocity data. This study describes the validity of the ADV measurements in bubbly flows. The true three-dimensional phase space method originally developed by Goring and Nikora in 2002 is significantly useful to eliminate spike noise of ADV recorded data in bubbly flow in comparison with the classical low correlation method.     

Numerical Simulations of Inclusion Behavior in Gas-Stirred Ladles

A computation fluid dynamics–population balance model (CFD–PBM) coupled model has been proposed to investigate the bubbly plume flow and inclusion behavior including growth, size distribution, and removal in gas-stirred ladles, and some new and important phenomena and mechanisms were presented. For the bubbly plume flow, a modified k-ε model with extra source terms to account for the bubble-induced turbulence was adopted to model the turbulence, and the bubble turbulent dispersion force was taken into account to predict gas volume fraction distribution in the turbulent gas-stirred system. For inclusion behavior, the phenomena of inclusions turbulent random motion, bubbles wake, and slag eye forming on the molten steel surface were considered. In addition, the multiple mechanisms both that promote inclusion growth due to inclusion–inclusion collision caused by turbulent random motion, shear rate in turbulent eddy, and difference inclusion Stokes velocities, and the mechanisms that promote inclusion removal due to bubble-inclusion turbulence random collision, bubble-inclusion turbulent shear collision, bubble-inclusion buoyancy collision, inclusion own floatation near slag–metal interface, bubble wake capture, and wall adhesion were investigated. The importance of different mechanisms and total inclusion removal ratio under different conditions, and the distribution of inclusion number densities in ladle, were discussed and clarified. The results show that at a low gas flow rate, the inclusion growth is mainly attributed to both turbulent shear collision and Stokes collision, which is notably affected by the Stokes collision efficiency, and the inclusion removal is mainly attributed to the bubble-inclusion buoyancy collision and inclusion own floatation near slag–metal interface. At a higher gas flow rate, the inclusions appear as turbulence random motion in bubbly plume zone, and both the inclusion–inclusion and inclusion-bubble turbulent random collisions become important for inclusion growth and removal. With the increase of the gas flow rate, the total removal ratio increases, but when the gas flow rate exceeds 200 NL/min in 150-ton ladle, the total removal ration almost does not change. For the larger size inclusions, the number density in bubbly plume zone is less than that in the sidewall recirculation zones, but for the small size inclusions, the distribution of number density shows the opposite trend.     

CSP热卷生产冷轧镀锌产品表面质量控制

 CSP工艺生产的热轧卷作为冷轧原料生产冷轧镀锌产品的表面质量较难控制。冷轧镀锌产品表面缺陷多种、共生,消除缺陷需要确定缺陷类别,产生工序和相应的控制点。讨论了一种由薄板坯纵裂纹衍生而产生的冷轧镀锌产品表面缺陷控制方法。通过对钢水精炼工艺和CSP铸机工艺参数的调整,此种表面缺陷控制取得明显效果。     

热冲125榴弹弹体毛坯表面缺陷产生原因的分析

鞍山钢铁（集团）公司生产的８２３钢１１５ｍｍ方坯热冲弹性毛坯存在明显的表面缺陷（裂缝和孔洞），造成毛坯件失效。对有缺陷的弹性毛坯件的定心桩和弹体壁部位取样进行金相检验，查明此缺陷是由于热冲方坯料在加热过程中局部过热和过烧所致。     

激光诱导击穿光谱法判断汽车板表面划痕缺陷

采用激光诱导击穿光谱法对汽车板表面划痕类缺陷进行了分析和判断。通过使用激光诱导击穿光谱深度分析的方法对比了汽车板表面划痕缺陷部位与非缺陷部位的深度分布特点,并在选取的积分段内,对样品表面进行线扫描,得到表面元素的分布情况。依据缺陷部位某些元素的缺失现象,推断了该部位缺陷类型为表面划痕缺陷。判断结果与扫描电镜的检测结果相符。本文建立的方法具有分析时间短（< 30 s）、分析准确度高、无需样品前处理等特点,适用于汽车板表面划痕类缺陷的快速判别。     

Surface Defects of Cold-Rolled Ti-IF Steel Sheets due to Non-Metallic Inclusions

Surface defects of the cold-rolled sheets of Ti-IF steel were studied and analyzed. After analyzing surface defects of cold-rolled sheets, such as shelling defects, holes and sliver defects by SEM/EDS, a variety of inclusions were found. In addition, the distribution of macro-inclusions in slabs was analyzed by MIDAS method. The results show the macroscopic inclusion bands of head slabs and normal slabs are in 1/8 slab thickness regions of both inner arc side and outer arc side. The formation process of the defects in the cold-rolled sheets was simulated with an experimental cold-rolling machine for comparison. The results show that there were three kinds of inclusions underneath the surface defects: Al2O3, SiO2 and particles from slag entrainment, which were the main reason for defect formation during cold rolling.     

Q345B热轧板板面结疤缺陷产生原因分析

采用微观组织分析法, 对某钢铁公司生产的Q345B热轧板板面结疤缺陷的成因进行了分析。结果表明,该类热轧板的结疤缺陷是由于连铸工艺出现异常,造成板面或近表层卷渣、微裂纹和气泡等板坯缺陷,并在连铸过程中裂纹出现了高温氧化行为,在加热炉中裂纹发生二次氧化、脱碳、晶界弱氧化等行为,在后续轧制过程中进一步恶化板面,从而造成了板面大面积结疤产生。     

中厚板边部折叠模拟实验及机理研究

通过对中厚板边部折叠试样的检测分析,对其产生机理和影响因素进行研究.结果显示,中厚板边部折叠现象是板材横轧宽展过程中侧面材料在轧制中受轧辊作用而翻转到板材表面的结果.折叠缺陷处所观察到的微观组织结构,是轧制前板材表面在高温下形成的氧化铁及脱碳层形成的.建立了轧制有限元数值模型,证实折叠缺陷是在轧制过程中由侧面的折叠翻转所造成的.通过实验室实验,得到铸坯边部质量、轧制制度、宽展道次及轧制压下量对中厚板折叠缺陷的影响.实验结果表明横轧宽展导致折叠缺陷的出现,铸坯边部质量对其没有影响,轧制过程中铸坯侧边的折叠经翻平形成表面折叠缺陷,随着横轧展宽的道次及压下量增加,折叠缺陷距边部距离变大.      

Surface inclusions and their evolution on strip rolled on CSP line and in following cold rolling process

Abstract

Hot and cold rolled strip samples with surface defects such as black pockmark, sliver and central cracking were collected from a compact strip production line followed by cold rolling. Microstructures and chemical compositions of the strip with defects were studied by scanning electronic microscopy and energy dispersive X-ray spectroscopy. Four typical types of defects on strip including surface spherical mould powder entrapment, centre spherical mould powder entrapment, surface linear mould powder entrapment and centre linear mould powder entrapment were studied by hot and cold rolling experiment in laboratory. It was observed that spherical mould powder entrapment was transformed into the surface black pockmark after the hot rolling and cold rolling process. Centre spherical mould powder entrapment led to central fracture in the hot and cold rolling process. Surface linear mould powder entrapment resulted in sliver and centre linear mould powder entrapment led to severe sliver.