熔模铸造400系列不锈钢铸件表面麻点缺陷探索

400系列不锈钢材质在熔模铸造生产中易发生氧化,导致铸件产生麻点及麻坑缺陷。在制壳过程中加一层石墨砂,使浇注后钢液与型壳接触面形成还原性气氛,可防止麻点麻坑的产生,保证成品率,提高生产效率。     

球墨铸铁铸件的补缩工艺

通过分析和总结在生产实践过程中球墨铸铁铸件产生缩孔缩松缺陷以及成功解决办法,对球铁铸件凝固收缩理论提出理解和看法:铸件的补缩及缺陷产生取决于压力,由于球铁的凝固特性使石墨化膨胀和凝固收缩分离.薄壁件截面凝固差异不明显,石墨化膨胀压力无法有效利用,厚大件的截面凝固的差异大,容易实现石墨化膨胀压力的利用.铸造补缩工艺的设计原则就是提供并保持这样的压力,对薄壁要强调外部压力补缩,厚壁则充分利用石墨化膨胀压力自补缩.     

生铁选用对灰铸铁缸体质量的影响

介绍采用球铁生铁代替铸造生铁生产灰铸铁缸体的优点:(1)球铁生铁的石墨形态与铸件要求的石墨形态相近,可以避免生铁遗传性引起的粗大过共晶石墨;(2)可以避免缸体缸筒壁上黑斑缺陷的产生;(3)w(P)量较低,避免了w(P)量过高引起的铸件裂纹。指出选择球铁生铁既要确保成分,又要考虑成本。     

基于凝固过程数值模拟的水轮机下环件微裂纹成因分析

针对某重型设备公司铸造的下环铸件出现的类似微裂纹的铸造缺陷,采用数值模拟方法,从凝固过程热应力角度对缺陷产生的原因进行了分析.利用ANSYS软件计算了下环件凝固过程中的三维应力场.根据热裂形成机理,提出了适当的热裂倾向性预测方法,重点考察了铸件凝固过程中准固相区的受力情况,从而确定热裂倾向性严重的区域.模拟结果与铸件中实际的缺陷分布状况相吻合.分析了缺陷产生的原因,提出了工艺优化措施.     

ASK开发了防止厚断面球铁件中碎块状石墨的金属插块

问：碎块状石墨一直是我们大断面球墨铸铁件的问题。我们常常在铸件最后凝固区域看见这种缺陷。在冒口去除以后,我们时常在铸件冒口截面上看到不同颜色,进一步研究往往发现这些区域的微观组织中是碎块状石墨。有时,我们在加工时或者在超声检测时发现碎块状石墨。曾有建议试一试加入少量的锑以消除碎块状石墨。关于使用锑你们有什么想法？     

国外文摘

1.非合金球铁慢速凝固时碎块状石墨的形成及防止《Fonderie Fondeur Aujourd'hui》〔法〕,1985,Vol.46,P14～23在实验室以模拟厚铸件的凝固(凝固时间约为90分钟)做了约40个试验。结果表明,在原铁水纯净时,附加过量的 FeSiMg 和含碱土金属的孕育剂或附加稀土元素(如0.02%),会产生碎块状石墨。加入微量锑(如0.02%)有助于消除这种缺陷。最后,阐述了防止这种缺陷的各种方法。参202.含 Al3.5%的球墨铸铁的金相《Fonderie     

界面热阻对铸件凝固过程温度场的影响

采用直接差分法求解热传导方程,对T型铸件凝固过程中的温度场进行模拟,研究了界面热阻对温度场分布和凝固速率的影响。结果表明:在铸件凝固过程中,随着铸件/铸型热阻的减小和铸件/空气热阻的增加,整个铸件从冒口位置和侧面同时向内部区域凝固;随着铸型/空气热阻的减小,热量传输迅速,凝固过程加快。在实际工艺设计中,减小冒口位置附近的凝固速率,增加拐角区域和侧面凝固速率,使得冒口、拐角处和侧面凝固趋于同步,从而减少各类缺陷的形成,提高铸件的力学性能。     

球墨铸铁的收缩模型与应用

根据球墨铸铁的石墨析出特点和离异共晶的凝固方式，构造了球铁件冷却凝固时的体积变化模型：①液态收缩，②初期石墨化膨胀，③过冷液体的收缩，④共晶膨胀，⑤二次收缩。根据这一模型分析了铸件产生缩孔缺陷的原因，并应用这种原理改进工艺，消除了铸件的缩孔。     

灰铁轴承衬体铸造工艺模拟与优化

利用ViewCast软件对灰铁轴承衬体充型和凝固过程进行了分析,通过凝固过程金属分布模拟了缩孔(松)产生的位置。采用挂砂外冷铁配合冒口使用对原方案进行了优化,最终消除了铸件中的缩孔(松)缺陷。再次模拟结果表明,改进方案合理可行,实现了平稳逐层充型和顺序凝固,从而有效地改善了铸件质量。     

基于AnyCasting大型薄壁鞍座铸造工艺优化

针对大型薄壁铸件鞍座铸造过程中易产生缩松、缩孔缺陷等问题,基于AnyCasting模拟软件对鞍座的充型和凝固过程进行了模拟。根据模拟结果分析缩松、缩孔缺陷的位置分布,发现铸件内部有缩松、缩孔现象产生,并通过实际浇注试验对比缺陷位置以验证模拟结果的可信性。采用在热节位置添加内冷铁的改进方案,结果表明,原缺陷产生位置在凝固过程中优先凝固,消除了缩松、缩孔缺陷,为类似薄壁铸件实际生产提供相应指导。     

离心球铁管承口部气孔缺陷分析

分析了离心球铁管承口针孔及其成因。结果表明，来自树脂粘结剂中的Ｎ２，Ｈ２等气体是导致针孔的主要气体。氧化夹杂物作为气泡生核的核心，并使之生长。若铸件凝固速度等于气泡逸出速度，针孔生成。     

工艺因素对干砂消失模铸铝件针孔影响的研究

系统研究了各工艺因素对干砂消失模铸铝件密度的影响。结果表明 ,涂层厚度与聚苯乙烯模样厚度增加 ,铸铝件密度下降、针孔增加。为减少铸铝件的针孔 ,铝合金消失模铸造应有适当高的浇注温度和合适的直浇道高度及面积 ,并尽量采用空心直浇道。充型过程中施加一定的真空度有利于减少针孔 ,但真空度太高则会促使铝液产生紊流 ,反而增加铸铝件的针孔 ,降低其密度。     

铸铁件针孔缺陷产生的原因与防止方法

介绍了灰铸铁和球墨铸铁件针孔缺陷的形成机理以及铁液化学成分、铸型材料、铸件壁厚、浇注温度、充型速度和熔炼工艺等因素对针孔形成的影响情况。根据球铁件形成针孔的特点,提出了防止措施,并列举了消除铸铁件针孔缺陷的成功实例。     

铝合金挤压材“麻面”缺陷产生机制的研究

“麻面”是影响铝合金挤压材表面质量的主要缺陷之一。研究了铝合金挤压材,特别是铝型材在挤压过程中出现的“麻面”缺陷产生的机制、规律及影响因素。结果表明,“麻面”缺陷的产生与合金的本性、挤压工艺参数、模子工作带的表面状况、工作带的形状,特别是模孔出口直径及工作带出口方向的圆角大有关。提出了预防或消除这一缺陷的主要措施。     

Mechanism of pinhole generation during welding of flake graphite cast iron and effects of composition of base metal

Abstract

The mechanism of pinhole generation during welding flake graphite cast iron is examined. As a result, the oxidisation progresses inwardly along the interface between matrix and flake graphite, and then oxides such as SiO₂ and MnO are generated. The oxidisation progresses through the graphite in the surface of the nearby eutectic cell. When oxidised cast iron is welded, oxides are deoxidised by the graphite and carbon monoxide gas is generated. The carbon monoxide gas comes up to the surface of the welding bead, but sometimes does not reach the surface and it becomes solidified from the top because the cooling rate at welding is very fast. This is how pinholes are generated.

Also the effect of components of flake graphite cast irons on the pinhole generation is investigated. The number of pinholes increases with the increase in C, Si, Mn, Ni or Cu. Conversely, when the elements of P, S, Cr, Mo and Mg increase, it becomes difficult to generate pinholes.     

Corrosion of stainless steel coated with TiN, (TiAl)N and CrN in aqueous environments

The corrosion behaviour of TiN, (TiAl)N and CrN coated on 304 stainless steel by physical vapour deposition was examined in borate solution (pH 9.0) and in 0.5 M NaCl solution. The study was performed by using open circuit potential, potentiodynamic polarization and cyclic polarization techniques, complemented with XRD and laser microscopy. The measurements were also performed on the uncoated substrate for comparison. Nitrided coatings significantly improve the corrosion performance of the steel; however, they are prone to corrosive attack as a consequence of the presence of microstructure defects such as pinholes and pores. Galvanic corrosion between the coatings and the substrate result in significant attack of the substrate, allowed by the penetration of small pinholes into the substrate. In borate solution, (TiAl)N possesses the highest corrosion resistance. However, CrN possessed the highest corrosion resistance in NaCl solution.     

Surface morphology and impurity distribution of electron beam recrystallized silicon films on low cost substrates for solar cell absorber

A line shaped electron beam recrystallised polycrystalline silicon film on the low cost substrate was investigated for the use of the solar cell absorber. The applied EB energy density strongly influences the surface morphology of the film system. Lower EB energy density results in droplet morphology and the rougher SiO2 capping layer due to the low fluidity. With the energy increasing, thecapping layer becomes smooth and continuous and less and small pinholes form in the silicon film. Tungstendisilicide (WSi2) is formed at the interface tungsten/silicon but also at the grain boundaries of the silicon. Because of the fast melting and cooling of the silicon film, the eutectic of silicon and tungstendisilicide mainly forms at the grain boundary of the primary silicon dendrites. The SEM-EDX analysis shows that there are no chlorine and hydrogen in the area surrounding a pinhole after recrystallization because of outgassing during the solidification.     

电弧离子镀方法制备的Ti/TiN多层膜的结构与耐腐蚀性能

采用电弧离子镀技术,通过周期性变换环境气氛,在7075Al合金上制备了Ti/TiN多层膜,并研究调制周期对多层膜的结构组成和腐蚀性能的影响。结果表明:多层膜与铝合金衬底界面结合较好,基本没有孔洞等缺陷。多层膜具有明显的层状特征,层间界面清晰。多层膜中TiN与单层中TiN薄膜有着相同的晶体结构,并存在(111)择优取向,每个调制周期内的TiN层都呈柱状生长。随着调制周期变小,多层膜阳极极化曲线的腐蚀电位增加,交流阻抗谱的阻抗值增大,容抗弧的半径也增大,即膜层的耐腐蚀性增加。多层膜调制周期的减小使得薄膜中含有的层界面增多,而贯穿至衬底表面的针孔等缺陷的数量将减少,这样,腐蚀性介质经过针孔等缺陷与衬底接触的机会变少,这将使薄膜的抗腐蚀能力得到改善。     

Using active thermography to inspect pin-hole defects in anti-reflective coating with k-mean clustering

The study here demonstrates the capability of thermography to detect and characterize pinhole defects in a visually transparent anti-reflection (AR) film. The diameter of the pin-holes varies from 0.03 mm to 4 mm. Each inspected area was unevenly heated for 65 s. Thermal images were processed by the following steps: de-trend processing, primary edge detection based on Sobel approximation, and further edge separation based on k-means clustering. Then, the diameter of pinholes was directly measured from binary images. The proposed image processing enables thermography to detect 86 of 90 inspected areas correctly in position.     

卧式加工中心整机防护控制功能开发与应用

为加工中心配置整机防护,通过PLC程序对安全门进行动作控制,同时通过检测开关辨认安全门的状态,判断加工区域存在人员的可能性,在程序中进行安全互锁的处理,尽量避免安全事故的发生。在满足生产和维修需要的前提之下,更好地保障操作者的安全,提高加工中心的实用性。