铌基超高温合金熔体与陶瓷类坩埚的高温反应

分别在陶瓷类ZrO2、Y2O3、BN和Al2O3坩埚内于2053K（或2153K）保温30min（或10min）重熔铌基超高温合金（主要组分为Nb、Si、Ti、Hf等），以研究该合金的高温熔体与不同材料坩埚的反应情况。实验发现Y2O3、BN和Ai2O3坩埚对熔体都发生了不同程度的沾污反应；在ZrO2坩埚壁上出现了50～60μm厚且具有微小裂纹或熔蚀坑的反应层，其内含有HfO2和TiO2，但ZrO2坩埚对熔体内部基本没有污染。在石墨坩埚上进行制备YSZ涂层的实验发现，ZrO2同石墨基体发生反应生成了ZrC0因此，据有关实验结果，可以先在石墨坩埚基体上用CVD法制备一层SiC内层，再在SiC内层上用浸涂法制备ZrO2涂层，以用于铌基超高温合金熔炼。     

针对高温电解铝液熔铸净化工艺的探讨

首先介绍了铝熔体净化的原理及主要的方法,然后以某实例项目进行了实际净化工艺对电解铝液生产铝合金熔体的工艺进行了佐证,确认了该工艺选择的适用及合理性,为铝熔铸类似工程提供了理论及实例的帮助。     

The growth of Cu-Sn intermetallics at a pretinned copper-solder interface

This article reports a comparative study of the formation and growth of intermetallic phases at the interface of Cu wetted with a thick solder joint or a thin, pretinned solder layer. The η phase (Cu₆Sn₅) forms when Cu is wet with eutectic solder at temperatures below 400 °C. The intermetallic layer is essentially unaffected by aging at 70 °C for as long as 13 weeks. On aging a eutectic joint at 170 °C, the η-phase intermetallic layer thickens and ε phase (Cu₃Sn) nucleates at the Cu/intermetallic interface and grows to a thickness comparable to that of the η phase, while a Pb-rich boundary layer forms in the solder. The aging behavior of a thin, pretinned eutectic layer is qualitatively different. At 170 °C, the Sn in the eutectic is rapidly consumed to form η-phase intermetallic, which converts to ε phase. The residual Pb withdraws into isolated islands, and the solderability of the surface deteriorates. When the pretinned layer is Pb-rich (95Pb-5Sn), the Sn in the layer is also rapidly converted into η phase, in the form of dendrites penetrating from the intermetallic at the Cu interface and discrete precipitates in the bulk. How ever, the development of the intermetallic largely ceases when the Sn is consumed; ε phase does not form, and the residual Pb remains as an essentially continuous layer, preserving the solderability of the sample. These observations are interpreted in light of the Cu-Sn and Pb-Sn phase diagrams, the temperature of initial wetting, and the relative diffusivities of Cu and Sn in the solder and intermetallic phases. A.J. SUNWOO, Formerly with the Lawrence Berkeley Laboratory, Berkeley, CA,     

Nb-Ti-Al高温铌合金氧化行为研究

研究了Nb-35Ti-6Al、Nb-15Ti—llAl以及Nb-30Ti-15Al三组合金于900℃和1000℃在空气中的氧化行为，建立了Nb-Ti—A1合金高温氧化动力学模型。研究表明，元素Ti和Al的加入能有效改善合金的抗氧化性能，合金中占相的存在降低了氧的溶解度。同时抑制氧的扩散，因而两相合金Nb-15Ti-llAl和Nb-30Ti-15Al（β＋δ相）抗氧化性能优于单相合金Nb-35Ti-6Al（β相）。     

钼镧合金板材高温抗下垂性能的研究

以粉末冶金法生产的180 mm×20 mm×1.5 mm钼镧合金板材为试验原料,通过对比轧制和高温定型处理制备的钼镧合金板材在1 750℃高温和500 g重物荷载条件的下垂值,并研究了这两种板材的组织形态。结果表明:采用常规工艺轧制的钼镧合金板材组织纤维发达,而采用了高温定型处理后的钼镧合金板材形成了一种粗大、组织相互搭接的再结晶组织;在1 750℃高温及500 g重物的载荷条件下,高温定型后的钼镧合金板材的下垂值较小,其下垂值从常规工艺轧制的钼镧板的4.2 mm减小到1.8 mm,表现出良好的高温抗下垂性能。     

Very High Cycle Fatigue of Ni-Based Single-Crystal Superalloys at High Temperature

Very high cycle fatigue (VHCF) properties at high temperature of Ni-based single-crystal (SX) superalloys and of a directionally solidified (DS) superalloy have been investigated at 20 kHz and a temperature of 1000 °C. Under fully reversed conditions (R = ? 1), no noticeable difference in VHCF lifetimes between all investigated alloys has been observed. Internal casting pores size is the main VHCF lifetime-controlling factor whatever the chemical composition of the alloys. Other types of microstructural defects (eutectics, carbides), if present, may act as stress concentration sites when the number of cycles exceed 10⁹ cycles or when porosity is absent by applying a prior hot isostatic pressing treatment. For longer tests (> 30 hours), oxidation also controls the main crack initiation sites leading to a mode I crack initiation from oxidized layer. Under such conditions, alloy’s resistance to oxidation has a prominent role in controlling the VHCF. When creep damage is present at high ratios (R ≥ 0.8), creep resistance of SX/DS alloys governs VHCF lifetime. Under such high mean stress conditions, SX alloys developed to retard the initiation and creep propagation of mode I micro-cracks from pores have better VHCF lifetimes.     

高速电气化铁道用铜锡合金接触线的开发

介绍了采用连铸连轧工艺生产φ20mm铜锡合金线坯的过程,分析了线坯氧含量、锡含量对生产稳定性的影响。阐述了拉拔机冷拉成型接触线的工艺过程,对产品的抗拉强度、延伸率等性能指标进行了研究及对比。     

熔体形核与二维稳态温度起伏数学模型

用数学方法证明了二维稳态温度起伏数学模型的Fourier级数形式解是收敛的,该温度起伏的数学模型的解是惟一的而且是稳定的.这个模型的温度解呈现出指数振荡衰减,验证了熔液对流促使温度产生大的起伏,导致大量晶核形成这一熔体形核机制的正确性.     

高速电气化铁道用铜锡合金接触线的开发

介绍了采用连铸连轧工艺生产φ20mm铜锡合金线坯的过程,分析了线坯氧含量、锡含量对生产稳定性的影响.阐述了拉拔机冷拉成型接触线的工艺过程,对产品的抗拉强度、延伸率等性能指标进行了研究及对比.     

非碳冶金高温熔炼的研究

通过与碳冶金的对比分析,提出将太阳能、风能的利用与冶金技术结合的非碳冶金的概念,阐述了风光互补非碳冶金的理念。非碳冶金技术包括4项单元技术-光电转换、蓄电、配控电和冶金反应器,通过技术集成创新的1 kg非碳冶金实验炉系统进行了非碳冶金试验,并通过初步的系统能量分析,验证了系统参数。实验结果表明,直接使用风光互补技术可以获得1 600℃以上的熔炼高温,可进行各种金属的冶炼。     

高温合金表面激光熔铸镍基合金涂层的组织与耐磨性能

研究了高温合金ＧＨ３３表面激光熔铸镍基合金涂层的组织和耐磨性能。结果表明,基材对涂层合金的稀释作用较小;涂层与基材之间形成良好的冶金接合;涂层基体组织为γ－Ｎｉ枝晶,枝晶间为γ－Ｎｉ、Ｍ２３（ＣＢ）６、Ｎｉ３Ｂ、Ｃｒ２Ｂ、ＣｒＢ、ＷＣ等;涂层耐磨性能的平均值较基材提高４倍以上。     

Thermodynamic Calculations of Melt in Melt Pool During Laser Cladding High Silicon Coatings

Based on the Miedema＇s formation heat model for binary alloys and the Toop＇s asymmetric model for ternary alloys, the formation heat, excess entropy, and activity coefficients of silicon ranging from 1 900 K to 4 100 K in the Fe-Si-C melt formed during the laser cladding high silicon coatings process were calculated. The results indicated that all values of lnγ^0Si, ε^CSi,ρ^SiSi and ρ^CSi are negative in the temperature range and these values increase as the temperature increases. And all values of ε^SiSi and ρ^Si-CSi are positive and these values decrease with increasing temperature. The iso-activity lines of silicon are distributed axisymmetrically to the incident laser beam in the melt pool vertical to the laser scanning direction. And the iso-activity lines of silicon in the front of the melt pool along the laser scanning direction are more intensive than those in the back of the melt pool. The activity of silicon on the bottom of the melt pool is lower than that in the effecting center of laser beam on the top surface of the melt pool and it may be the important reason for the formation of the silicides and excellent metallurgical bonding between the laser cladding coating and the substrate.     

Sensitivity to Stress Concentration of Steel at High Temperature

Thesurfacetransversalcrackonacontinuouscastingslabisthoughttoberelatedtothedefectsontheslabsurfacesuchasthelardandthevibrationtraceontheinnerarcsideofslab ,anditgeneratesinthesecondarycoolingzoneofcontinuouscastingpro cess .Inordertodeterminethedeformationtemper atureofslabinthesecondarycoolingzoneofthecontinuouscastingprocess ,thethermalplasticityofsteelismeasuredinthermalmechanicalsimulatorus ingcontinuoussampleontheassumptionthatthecontinuouscastingslabisauniformandcontinuousonewithoutanydef…     

高温膨胀节衬里结构的研制与应用

衬里是许多石油化工设备通常采用的一种内部结构,对设备的安全运行起着举足轻重的作用。文章分析和探讨了高温膨胀节衬里脱落的原因,研究设计出了以耐火砖、耐火浇注料和耐火浇泥为主的衬里材料,对衬里结构重新设计,不仅满足了生产需要,同时也在这方面开闢出了一条新思路。     

几何结构影响高温空气燃烧特性的数值分析

通过改变燃料喷口周围空气喷口分布夹角,采用数值计算的方法研究了高温空气燃烧特性的变化,包括燃烧温度场、速度场和NOx的生成和出口排放情况。模拟结果说明,减小空气分布夹角可以降低燃烧区最高温度和平均温度,扩大燃烧室内低氧范围,有效抑制热力型NOx的生成和排放。所采用的计算模型和计算方法可以较好地模拟高温空气燃烧过程,计算结果可信。     

钢水真空脱气处理的成本结构

 在很宽的钢水质量范围内对包括钢包炉和多种真空处理在内的二次冶金工艺的成本进行了分析,并对两种常用的真空泵系统进行了比较。干式机械真空泵在最多360t的整个钢水质量范围内都具有明显的成本优势,节约的幅度随工艺而变化,具体同能源(无论何种形式)的供应和设备的产能有关。通过快速抽真空缩短处理的周期时间,降低了钢水的过热需要,从而降低了生产成本,提高了产能,改善了质量。     

中碳钢的高温力学行为

借助Gleeble1500热模拟试验机,测试了45钢自凝固点至600℃温温度范围内的强度和塑性变化规律,并就加热方式、应变速率、冷却速度等因素对凝固温度区、奥氏体区和γ→α相变区的强度和塑性的影响进行了研究,还对3个区形成裂纹的机理进行了初步探讨。     

高风温长寿热风炉的设计

介绍了不同形式热风炉的特点和结构稳定性,针对鞍钢4号高炉增建4号热风炉采用的新技术－近似悬链线拱顶、烟气分配、冷风分配、圆形火井、板块结构、滑动缝、膨胀缝、不锈钢隔板、七孔格子砖以及组合砖等进行了介绍,同时对在有预热技术的情况下,有效地提高风温问题进行了探讨。     

Combustion Characteristics of Polyethylene and Coal Powder at High Temperature

To study the combustion characteristics of the polyethylene（PE）particle and coal powder at blast temperature of the blast furnace,the contents of CO and CO2 of off-gas during the combustion of PE particle and coal powder at the 1 200 ℃ and 1 250 ℃ were measured using carbon monoxide and carbon dioxide infrared analyzer,and then the corresponding combustion ratio was calculated.The results showed that when the temperature is high,the combustion speed of PE and coal powder is high and the corresponding combustion ratio is high.Whereas,the combustion speed and ratio of PE are much higher than those of coal powder.     

NM360耐磨钢的高温变形行为

试验用NM360钢（/%:0.17C,0.38Si,1.28Mn,0.014P,0.005S,0.23Cr,0.14Mo,0.02Ti,0.04Al）30mm厚板的生产工艺流程为90t EAF-LF-VD-180mm×1330mm坯连铸-轧制30mm板-950℃淬火,350℃回火。利用Gleeble-3500热模拟试验机研究了耐磨钢NM360在900~1200℃,应变速率为0.1、1、10s^-1下的变形行为,确定了NM360耐磨钢的热变形方程,建立了热加工图。结果表明,利用Zener-Hollomon参数可很好描述NM360钢热压缩变形时的流变特性,计算的动态再结晶激活能为305kJ/mol。随着温度升高以及应变速率降低,能量耗散效率逐渐升高;在1100℃,应变速率为0.1s^-1时,变形能量耗散效率达到最大值0.34。该耐磨钢在1070~1170℃,应变速率0.1~0.5s^-1时,具有较好的变形能力。通过优化工艺的生产结果表明,180mm铸坯（1200±20）℃加热,（1050±10）℃开轧,（950±10℃终轧成30mm板、水冷,350~550℃回火1h,NM360钢HB硬度值为368~385,屈服强度830~920MPa,抗拉强度1030~1120MPa,延伸率10%~15%,具有良好的力学性能。