消失模铸造金属液流动前沿气隙中气体压力的研究

利用基础理论计算出消失模铸造正常浇注时金属液流动前沿气隙中压力P膜随直浇道的面积S直与液态金属在其内部的流速ν直的乘积、浇注温度T膜、模型的密度ρ模、涂层厚度H的增大而增大;随真空度P真、铸件的水平周长S、透气性K的增加而减小,并通过生产实践加以验证.     

消失模负压铸造液流前沿气膜厚度与其放热系数的关系

为寻求更通用简洁的消失模负压铸造液态金属流动前沿气膜厚度“δ”,运用传热学原理及函数的线性化方法,找到了适用于平衡充型状态及非平衡充型状态“δ”的计算方法：δ与气膜面积A、液态金属的浇注温度T金呈正比,与在直浇道的横截面积S直、在其中的液态金属的流速V直、气化单位质量消失模的吸热量WQ和消失模的密度ρ模呈反比。     

可控气压下镁合金消失模铸造工艺参数的研究

研究了模样密度、涂层厚度、浇注温度、真空度等工艺参数对可控气压下镁合金消失模铸造时液态金属的充填形态和充型速度的影响,以及充型速度与充型形态之间的关系.结果表明:在可控气压下镁合金消失模铸造过程中,液态镁合金呈拱形平稳向前推进,并随着泡沫模样密度的降低、涂层厚度的减小、浇注温度和真空度的提高,充型速度提高.各因素对充型速度的影响效果由大到小的顺序是:泡沫模样密度→涂层厚度→浇注温度→真空度.通过分析实验数据,建立了可控气压下镁合金消失模铸造的充型速度的非线性数学模型.     

消失模充型过程中液态金属前沿与消失模的放热系数研究

应用基础理论推导出消失模铸造液态金属流动前沿有关参数的变化关系。结果表明:液态金属流动前沿放热系数与进入铸型的流量、气化消失模单位体积所耗的热量成正比,与铸型的水平截面积和浇注温度成反比,而且是变化的,但进入直浇道液态金属的流量是常数,而这恰好验证了达朗贝尔的热量传递的类比关系,并对消失模铸造一些习惯作法予以解释。     

消失模铸造的合理浇注速度研究

利用基础理论计算出消失模铸造的速度流量随着静压头、气隙的厚度、气隙的周长、透气性的增大而增大,随涂料层厚度、消失模密度、液态金属的浇注温度的增大而减小,并在生产实践中验证.     

消失模铸造充型速度和流动前沿温度的数值模拟研究

采用数值模拟方法,通过模拟板形灰铸铁件的消失模铸造充型过程,分析了各种工艺因素对充型过程中金属液前沿的流动速度和温度的影响规律.结果表明,液态金属充型速度随浇注温度、负压度和涂层透气性的增大而增大,随模样密度和涂层厚度的增大而减小;金属液流动前沿温度随模样密度和涂层厚度的增大而下降,而随负压度的增大而提高.     

镁合金真空低压消失模铸造的技术特征与实践

详细介绍了镁合金在真空低压消失模铸造下的技术特征.试验研究表明真空低压消失模铸造的流动性受充型气体的流量与压力、浇注温度、涂层厚度、泡沫密度、真空度等多方面的因素影响;在低充型速度和低真空度的条件下,液态镁合金在真空低压消失模铸造过程中的充型形貌均呈现以内浇道为中心的拱形层状推进流动,如充型速度加快,金属液流动前沿拱形形貌更加突出,而真空度增加会出现明显的"附壁效应";与重力消失模铸造比较,真空低压消失模铸造镁合金铸件凝固更呈现"同时凝固"特征;由于快速充型、压力下凝固,镁合金真空低压消失模铸造零件的铸态抗拉强度(σb=180.8MPa)、屈服强度(σ0.2=113.2 MPa)、伸长率(δ=4.4%),高于重力消失模铸造、树脂砂真空型铸造的铸态性能,达到了金属型铸造的铸态性能,经热处理达到了压力铸造镁合金的性能范围.浇注实践表明,真空低压消失模铸造对液态镁合金,具有良好的抗氧化保护能力、优良的浇注充型性能和力学性能,可铸造出高精度的、薄壁复杂的镁合金消失模铸件.     

消失模铸造充型过程中的气膜压力及其厚度的数值模拟

采用数值模拟方法,通过模拟板形灰铸铁件的消失模铸造充型过程,分析了各种工艺因素对充型过程中的气膜压力和气膜厚度的影响.结果表明,液态金属充型的驱动力并非重力而是消失模的退让速度,而这一速度是由气膜压力和气膜厚度的相互自动变化来调节,使充型达到稳态.结合理论计算,得到底注式浇注时充型可达到稳态,且气膜厚度和气膜压力随浇注温度、模样密度、涂料层厚度的增大而增大,随负压度和涂层透气性的增大而减小.     

镁合金真空低压消失模铸造的技术特征与实践

介绍了镁合金在真空低压消失模铸造下的技术特征。研究表明：真空低压消失模铸造的流动性受充型气体的流量与压力、浇注温度、涂层厚度、泡沫密度、真空度等多方面的因素影响；在低充型速度和低真空度的条件下，液态镁合金在真空低压消失模铸造过程中的充型形貌均呈现以内浇道为中心的拱形层状推进流动，如充型速度加快金属液流动前沿拱形形貌更加突出。而真空度增加会出现明显的“附壁效应”；与重力消失模铸造比较，真空低压消失模铸造镁合金铸件凝固更呈现“同时凝固”特征；由于快速充型、压力下凝固，镁合金真空低压消失模铸造零件的铸态抗拉强度（σh=180．8MPa）、屈服强度（σ0.2=113．2MPa）、伸长率（δ=4．4％），高于重力消失模铸造、树脂砂空型铸造的铸态性能，达到了金属型铸造的铸态性能，经热处理达到了压铸镁合金的性能范围。浇注实践表明，真空低压消失模铸造对液态镁合金，具有良好的抗氧化保护能力、优良的浇注充型性能和力学性能，可铸造出高精度的、薄壁复杂的镁合金消失模铸件，是一种极有潜力和优势的镁（铝）合金精密铸造技术。     

空心直浇道消失模铸造充型模式的数值模拟及分析

通过将空心直浇道消失模铸造完型过程处理为液态金属在普通砂型中的流动和置换消失模样的流动，实现了带有空心直浇道消失模铸造充型过程的数值计算，模拟对比分析了空心、实心直说道消失模铸造及其与普通砂型铸造充型模式的差异．     

Progress in application of rare metals in superalloys

Rare metals play an important role in development of superalloys. Over the last two decades, the application of the rare metals in superalloys has achieved progress significantly. They present multi-beneficial effects for strengthening the matrix and the c0phase, increasing the lattice misfit, cleaning the grain boundary, improving the carbides and eutectics, refining the grain, stabilizing the oxidation film, etc., so that the elevated temperature rupture life and elevated temperature oxidation resistance are improved significantly, leading to a broad application in the superalloys. In order to meet the higher demand for better superalloys in the future, more intensive research is necessary on the effects of the rare metals on the superalloy, and especially on the combination effect of various rare metals and mutual influence among them. Utilization of the computational materials science and combinatorial high throughput experiment will be of importance in application of rare metals in superalloys.     

Ag—Cu—Ti钎料中Ti元素在金刚石界面的特征

研究了金刚石钎焊接头中碳化物形成元素Ti与金刚石（或石墨）之间的相互作用行为。通过对接头界面处的成分分布和断口形貌观察,分析了Ti的作用机理、新生儿合物TiC的断口形及生长规律,结果表明：在一定的条件下,Ti元素与组成金刚石（或石墨）的碳元素发生反应形成TiC层;碳化物层使钎料与金刚石之间产生冶金结合;TiC与金刚石之间存在有明显的界面,TiC断口的微观表面形态呈韧窝状;在金刚石表面初始形成的TiC的生长方向与金刚石的晶向指数有关。     

铝土矿酸介质中铁的行为

研究了高温高压条件下铝土矿中铁在硫酸介质中的溶解行为，结果表明：在一定的温度条件下，铝土矿的赤褐铁矿能较好地溶于硫酸溶液中，而铝土矿中含铝矿物的性质不发生变化，从而为铝土矿的进一步加工利用提供了条件。详细讨论了反应温度、反应时间、硫酸浓度、液固比等因素对铁的溶解行为的影响，得出了在最佳工艺条件，即在反应温度160℃、反应时间3h、硫酸浓度0．7mo1/L和液固比6：1时除铁效率最高。     

我院区2016年利奈唑胺临床应用合理性评价

目的: 评价湖南省人民医院院区2016年利奈唑胺临床应用的合理性及有效安全性,为其临床应用提供参考。方法: 采用回顾性研究,利用医院信息管理系统调取2016年使用利奈唑胺患者病例资料,设计调查表,统计用药合理率,分析不合理原因;计算临床治愈率,病原菌清除率及综合治愈率;监测用药前后红细胞、血红蛋白、血小板下降程度。结果: 利奈唑胺临床应用合理率为48.1%,不合理原因主要是适应症把握不准确及疗程不合理;临床有效率为40.4%,病原菌清除率为42.3%,综合治愈率为56.4%;骨髓抑制发生率为21.2%,发生的平均年龄为（81.4±8.7）岁,平均用药时间为（13.6±5.6） d。结论: 我院区利奈唑胺临床应用合理性有待提高,正确把握适应症和疗程将很大程度提高合理率;综合疗效尚可,老年患者需特别注意骨髓抑制的发生。     

柔性制造技术在冷柜内胆绕管成形中的应用

针对冷柜内胆人工绕管成形生产中存在的问题,提出将柔性制造技术应用于全自动冷柜内胆的绕管成形并研制开发了生产线。介绍了绕管成形柔性制造系统的模具结构设计和功能,从生产结果来看,采用柔性技术得到的产品性能比原产品有较大幅度的提高,达到了预期目的。采用改进的生产工艺和技术不仅使生产顺利,且节省了能源。     

Development of a protective coating in induction brazing of joints in pipelines in air

Abstract

Flash welding, through conferring a number of important advantages, such as high productivity, good-quality welds, and suitability for welding of components with large cross-sections, is extensively used for shop welding of rails, plating of hot coils, welding of wheel rims, etc.^1–3 More compact welding facilities are also being sought through further exploitation of mechanical control technology for practical applications in job-site welding of rails, H-steel sections, etc.⁴     

Behaviour of Zinc in Sea Water in the Presence of Sulphides

Abstract

The effect of sulphides on the corrosion of zinc in artificial sea water has been studied over the pH range 6·5 to 8·6. A comparison of the weight loss and potential values of specimens in aerated and deaerated sea water, with or without the addition of sulphide, has shown that at pH values > 7·2 the presence of sulphides increases the corrosion, while at lower pH values it is partially inhibited. This is related to changes in the concentration of S^2- ions in the solution. The corrosion products formed in the more corrosive solutions were shown to consist mainly of ZnS, which is believed to cause loss of adhesion of the corrosion products on the zinc surface, and thus to accelerate the corrosion.     

Examination of negative factors of radiation in arc welding in shipbuilding

The effect of anomalies detected in x-ray diffraction and metallographic examination of welded joints on the properties of resistance butt welded joints in 1201 aluminium alloy is determined and recommendations are given for the standards for permissible defects.     

The measurement of forces in grinding in the presence of vibration

Most investigations of chatter have made the assumption that torsional vibration is not a significant factor. Some recent work has shown that chatter in grinding is affected by a change in the torsional stiffness of the workpiece drive. Also, a theoretical model of grinding chatter has been developed that confirmed the significance of torsional effects. However, the model for the grinding force was assumed to be a dynamic equivalent of a published steady-state model. This paper describes tests conducted to measure the variation in force caused by an oscillation in workpiece speed. The oscillating test results indicate that the torsional vibration of the workpiece may well be a significant effect on chatter in grinding. Moreover, as the grinding force changes with workpiece speed, it may be possible to use variation of workpiece speed at high frequency to reduce chatter.