球墨铸铁球化率的热分析研究

采用热分析法对球墨铸铁球化率进行研究.在生产现场利用热分析仪记录球墨铸铁凝固冷却曲线,获取冷却曲线上的特征温度值,使用温度特征值和图像分析软件对不同试样的球化率进行分析.研究表明:共晶过冷温度TEU、共晶最高温度TER以及共晶回升温度△T (△T=TER-TEU)与球化级别之间有密切关系,即TEU的降低预示着球墨铸铁球化率和球状石墨数量的提高;球墨铸铁球化率随△T的降低而提高;热分析试样的球化率可由特征温度值组合表达为:y=4376.36118-3.73055TEU-4.21075△T.     

球墨铸铁的球化质量无损检测技术的研究

论述了用无损检测技术判断球墨铸铁球化级别的基本原理 ,即球化级别与声速的关系 ,给出了球化级别与声速的关系的数学模型。文中提供了测量声速的原理和实验装置。实例证明用无损检测技术对球墨铸铁球化级别可以快速无损检测 ,而且该方法独特有效 ,能够准确判断出球化级别     

ER110S-1焊丝拉拔过程中退火工艺及机理探讨

用差热分析法确定了ER110S-1焊丝的相变点,通过扫描电镜观察分析了断口的形貌特征。进行多种再结晶退火和等温球化退火,用金相显微镜观察金相组织,测定维氏硬度和晶粒度,从而确定最佳球化退火工艺。研究表明:ER110S-1焊丝最佳球化退火工艺为660℃保温12 h,随炉冷至380℃空冷;ER110S-1焊丝进行再结晶退火的球化效果优于等温球化退火;ER110S-1焊丝预拉拔产生的塑性变形可以促进再结晶退火的球化率。     

基于超声波的球铁球化率快速检测系统

球墨铸铁的球化率与超声波纵波在其内部传播速度的大小存在着一定的对应关系,根据上述原理,利用压电晶片、任意波形信号发生器、数字示波器、计算机等构建了球墨铸铁球化率超声波检测系统,并采用Lab VIEW编写了相应的软件程序,实现被测球铁件长度和超声波传播速度的自动计算。通过与金相观察法球化率检测结果比对的方法,建立了超声波传播速度和球化率间的具体关系表,并证实了声速与球化率间确实存在很好的相关性。试验结果表明,利用建立的关系,可以通过该系统测得超声波声速,并据此快速求得球铁件的球化率,且准确率大于95%,具有很好的重复性。     

超声无损评价离心球铁管质量的研究

本文在简要介绍了材料无损评价离心球铁管检测与评价的基础上，对超声波声速与球铁管的球化率、超声波衰减系数与球铁管的力学性能之间的相关性进行了实验研究。结果表明，声速与球化率之间较好地符合线性关系，衰减系数与抗拉强度及延伸率均有明显的相关性，二者均可用于离心球铁管的无损评价。     

超声波检测球铁球化率方法的研究与应用

介绍了超声波检测球化率的基本原理以及超声波声速与石墨形态关系,分析出球墨铸铁声速的影响因素是球化率、石墨大小和基体组织,通过数据统计以及回归分析得出球化等级与声速之间的关系:1级声速5 680~5 820 m/s、2级声速5 620~5 680 m/s、3级声速5 560~5 620 m/s、4级声速5 500~5 560 m/s、5级声速5 440~5 500 m/s、6级声速小于5 440 m/s。在不同时间分别对其中15个铸件进行了3次检测,结果显示,声速法测定球化率与金相法测定的球化率相吻合。     

球墨铸铁球化率超声波检测系统设计及实验验证

利用超声波在介质中的传播速度与其杨氏弹性模量的紧密联系,提出利用超声波批量检测球墨铸铁球化率的方法。通过任意波形发生器、示波器、压电晶片和计算机等设计了球墨铸铁球化率检测系统,通过LabVIEW软件编写程序,自动得到超声波传播速度和球墨铸铁球化率之间的关系。结果表明,与金相观察法得到的结果相比,检测准确率达到95%。     

射频等离子体制备球形钨粉的研究

通过射频等离子体球化处理工艺,以不规则形状钨粉为原料,制备了球形钨粉,并研究了加料速率和粉末粒度对粉末球化率的影响。采用扫描电子显微镜、X射线衍射和激光粒度分析仪对球化处理前后粉末的形貌、物相和粒度分布进行了测试和分析。结果表明：粒度在5.5~26.5 μm范围的不规则形状钨粉,经等离子球化处理后得到表面光滑、分散性好、球化率可达100%的球形钨粉。球化处理后,粉末的粒度略微增大。随加料速率的增加,钨粉的球化率降低。随着钨粉球化率的提高,粉末的松装密度和流动性得到显著改善。松装密度由6.80 g/cm3 提高到11.5 g/cm3,粉末流动性由14.12 s/50 g提高为6.95 s/50 g     

铸件球化率测定仪的研制与应用

为了确保球墨铸铁产品质量，研制了球化率测定仪，以替代进口仪器。测量采用发射和接收探头，经过标定，球化率仪中的计算机就可计算出被测零件的声速及厚度。用该仪器进行现场检测并通过金相试验对比，试验证明，用球化率测定仪比用测厚仪和探伤仪测得的声速值要精确，而且操作简单，可实现全过程自动控制。通过大量数据统计给出了声速控制范围。     

提高箱体球化率的实践

为了解决箱体凝固过程出现球化级别低问题,对影响球化率的原因进行分析,对箱体铸造工艺、合金熔炼工艺、球化处理和孕育工艺进行了完善,最终解决了箱体球化级别低的难题,箱体球化率普遍达到了85%以上,箱体生产取得了较好的经济效益。     

Effect of nodularity on mechanical properties and fracture of ferritic spheroidal graphite iron

Ferritic spheroidal graphite irons with nodularity from 72% to 96% were prepared. The relationship between the nodularity and the mechanical properties of the ferritic spheroidal graphite iron was investigated. The effect of nodularity on the mechanical properties and tensile fracture of the cast iron were studied. Results showed that the tensile strength Rm, yield strength R_(p0.2), elongation to failure A_5, and impact energy KV_2 of the cast iron had a good linear relationship with its nodularity. Nodularity and annealing treatment would obviously affect the fracture characteristics of ferritic spheroidal graphite iron. The annealed ferritic spheroidal graphite iron with 93% nodularity showed a completely ductile rupture. With the decrease of nodularity from 93% to 72%, the cleavage fracture area ratio increased gradually from 0% to 8.3%. Compared with as-cast ferritic spheroidal graphite iron, annealing treatment reduced the cleavage fracture area of the ferritic spheroidal graphite iron.     

氧电势法炉前快速测定球、蠕化率的研究

为发展一种简便、精确、可靠的炉前快速检测球、蠕化率的方法,综合研究了氧浓差电池的基本原理和变质铁水的溶氧特性,找到了过去通过氧活度测报球化率不准确的原因,同时发现了球化率与氧电势之间有较严格的对应关系,由此发展了氧电势法,并介绍了该法的实施和精确度分析结果。     

铸铁基体及石墨形状超声波无损伤检验探讨

利用超声波（速度和强度）来测试铸铁中不同的石墨形状参数、基体结构及与此相关的机械性能。结果表明，石墨形状参数和超声波速度有着明显的对应关系，但是基体与超声波之间的影响则不明显。随着石墨形状参数的增加，超声波的幅值也随之变化，发现铁素体、珠光体、正火马氏体和贝氏体有相同的特性，但是基体中较大数量的正火马氏体或珠光体都会导致超声波幅值的增大。     

Development of thermal simulation system for heavy section ductile iron solidification

A new reliable thermal simulation system for studying solidification of heavy section ductile iron has been developed using computer feedback control and artificial intelligent methods. Results of idle test indicate that the temperature in the system responses exactly to the inputted control data and the temperature control error is less than ± 0.5 %. It is convenient to simulate solidification of heavy section ductile iron using this new system. Results of thermal simulation experiments show that the differences in nodularity and number of graphite nodule per unit area in the thermal simulation specimen and the actual heavy section block is less than 5 % and 10 %, respectively.     

热分析法在铸造生产中的应用

着重介绍了热分析法在测墨铸铁球化级别、铸铁力学性能预测以及铝硅合金变质处理效果检测等方面的应用情况,指出了目前存在的问题及其发展趋势。     

Modelling and simulation of local mechanical properties of high silicon solution-strengthened ferritic compacted graphite iron

This study focuses on the modelling and simulation of local mechanical properties of compacted graphite iron cast at different section thicknesses and three different levels of silicon, ranging from about 3.6% up to 4.6%. The relationship between tensile properties and microstructure is investigated using microstructural analysis and statistical evaluation. Models are generated using response surface methodology, which reveal that silicon level and nodularity mainly affect tensile strength and 0.2% offset yield strength, while Young′s modulus is primarily affected by nodularity. Increase in Si content improves both the yield and tensile strength, while reduces elongation to failure. Furthermore, mechanical properties enhance substantially in thinner section due to the high nodularity. The obtained models have been implemented into a casting process simulation, which enables prediction of local mechanical properties of castings with complex geometries. Very good agreement is observed between the measured and predicted microstructures and mechanical properties, particularly for thinner sections.     

50%～30%中、低蠕化率铸铁的性能及应用

综述了灰铁、蠕铁和球铁中的石墨形态与其力学性能及热力学性能的关系。铸铁材料的实际性能是随着蠕化率或球化率的变化而变化,也就是随着球状、团状、团絮状、蠕虫状石墨的数量比例变化而变化的;中、低蠕化率(蠕化率50%～30%,即球化率50%～70%)铸铁处于由蠕铁向球铁变化的中、后段,具有优于球铁的铸造性能、致密性、导热性、减震性和切削加工性能,同时具有优于高蠕化率蠕铁的常温和高温力学性能。指出中、低蠕化率铸铁适用于需要较高强度和冷热疲劳性能的场合。     

Effects of nodularity on thermal conductivity of cast iron

Abstract

The thermal transport properties of five predominately pearlitic grades of grey, compacted graphite and spheroidal graphite iron have been investigated by the laser flash technique. Samples have been taken from cylinders cast in controlled thermal environments designed to produce three dissimilar cooling rates. Digital image analysis has been utilised in order to characterise the different graphite morphologies. The results indicated linear relationships between the thermal transport properties and the roundness of the graphite and the nodularity for compacted graphite and spheroidal graphite iron. A pronounced decrease in the thermal conductivity occurred when the lamellar graphite structure was transformed into compacted graphite. The thermal conductivity of compacted and spheroidal graphite iron has been recalculated with good accuracy over a temperature range of 25–500°C by means of regression analysis.     

On the thermal conductivity of CGI and SGI cast irons

The thermal conductivity of Compacted Graphite Iron (CGI) and spheroidal graphite iron (SGI) was established in the temperature range from room temperature up to 500 °C using the experimental thermal diffusivity, density and specific heat values. The influence of nodularity, graphite amount, silicon content and temperature on the thermal conductivity of fully ferritic high-silicon cast irons was investigated. It was found that the CGI materials showed higher thermal conductivity than the SGI materials. The thermal conductivity tended to increase with increasing temperature until it reached a maximum followed by a subsequent decrease as temperature was increased up to 500 °C. Conventional models were applied to estimate thermal conductivity and the predictive accuracy of each model was evaluated. The thermal conductivity could be estimated by the Helsing model. The Maxwell model, Bruggeman model and Hashin–Shtrikman model were also in fair agreement using the thermal conductivity value of graphite parallel to the basal planes in graphite.