Phase Transformations in Cast Superaustenitic Stainless Steels

The goal of this investigation was to study phase transformations in cast superaustenitic stainless steels. Experiments were performed to determine the phase transformation behavior for alloys CN3MN and CK3MCuN. Samples were taken from keel bars that were heat treated between 1160 and 1230 °C and then isothermally held for times ranging from 1 min to 2040 h at temperatures in the range of 700-900 °C. The resulting microstructures were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy and wavelength dispersive spectroscopy. The microstructures, composed primarily of sigma- and Laves-phases within a purely austenitic matrix, showed relatively slow transformation kinetics, with transformation not completed even after the longest anneals. SEM and TEM analysis of superaustenitic samples reveal that precipitation takes place initially on grain boundaries and proceeds intragranularly. The results of these SEM and TEM investigations, along with volume fractions and number densities as a function of time and temperature, will be presented and discussed.     

奥氏体等温转变铸铁研究的新进展

综述了奥氏体等温转交铸铁的最新研究成果。阐述了球墨铸铁奥氏体等温转变的最新理论及高碳奥氏体的稳定性,论述了化学成分及形变对奥氏体等温转变过程的影响,概述了奥氏体等温转变灰铸铁、蠕墨铸铁及可锻铸铁的热处理工艺特点、性能及其应用。     

孕育处理对高铬白口铸铁中碳化物形态的影响

对高铬白口铸铁进行了孕育处理,探讨了高铬白口铸铁组织中碳化物形态的变化特征。研究结果表明：通过孕育处理,高铬白口铸铁中的一次碳化物形貌有明显改善,碳化物形貌为棒状,组织得到明显细化,表明该处理方法对高铬白口铸铁组织具有一定程度的改性作用。     

As 在铸铁中的行为

As在铸铁中是有害元素,影响铸铁的凝固结晶和固态相变,因而影响铸铁的显微组织、力学性能和铸件缺陷.对As的基本特性,As在铸铁中的行为以及避免As对铸铁产生有害作用的方法进行了系统的介绍.     

铸铁力学性能预测的研究

研究了铸铁力学性能预测技术，在华铸CAE(intecast)计算所得数据的基础上，采用人工神经网络模型对抗拉强度和布氏硬度进行预测，从而建立工艺参数、化学成分与力学性能的关系，根据预测结果改善铸造工艺，最终达到优化铸造工艺、缩短实验周期的日的。’     

含硼白口铸铁的研究进展

综述了硼对白口铸铁显微组织、力学性能和耐磨性的影响规律,着重介绍了硼系白口铸铁、含硼高铬铸铁和含硼低合金白口铸铁的组织和性能,分析了硼提高白口铸铁力学性能和耐磨性的原因,提出了扩大含硼白口铸铁应用值得重视的问题.     

正确认识Ti在钢铁中的作用

通过介绍Ti的物理化学性质及其化合物的性能特点,说明Ti在不同钢种中的作用和含量范围;适量的Ti在铸铁中具有脱氧去气、防止氮气孔产生以及促进D型石墨产生等作用.详细阐述了钛对铸铁的影响,有助于铸造企业在铸件生产中正确认识Ti的作用.     

氮在铸铁中的作用及含氮高强度灰铸铁铸铁中的微量元素讲座之二

介绍氮在灰铸铁中的作用及含氮灰铸铁材料。其中包括氮在灰铸铁中溶解的热力学和动力学问题,氮对灰铸铁相变温度的影响,氮在灰铸铁中的分布,氮对灰铸铁组织和性能的影响,以及含氮高强度灰铸铁的生产。     

Inoculated Slightly Hypereutectic Gray Cast Irons

The current experimental investigation in this article was designed to characterize the structure of mold (M) and ladle (L) inoculated, low-S (0.025 wt.% S), low-Al (0.003 wt.% Al), slightly hypereutectic (CE = 4.4-4.5 wt.%) electric melted gray irons, typical for high performance thin-wall castings. It describes the effect of a Ca, Al, Zr-FeSi inoculant addition of 0-0.25 wt.% on structure characteristics, and compares to similar treatments with hypoeutectic irons (3.5-3.6 wt.% CE, 0.025 wt.% S, and 0.003 wt.% Al). A complex structure including primary graphite, austenite dendrites, and eutectic cells is obtained in hypereutectic irons, as the result of nonequilibrium solidification following the concept of a coexisting region. Dendrites appear to be distributed between eutectic cells at higher eutectic undercooling, while in inoculated irons and for lower undercooling, the eutectic cells are “reinforced” by eutectic austenite dendrites. A Zr, Ca, Al-FeSi alloy appears to be an effective inoculant in low S, low Al, gray cast irons, especially for a late inoculation technique, with beneficial effects on both graphite and austenite phases. First, inoculation influenced the nucleation of graphite/eutectic cell, and then their characteristics. A further role of these active elements directly contributed to form nucleation sites for austenite, as complex (Mn,X)S particles.     

铸铁成分的光谱仪器测定方法

简单介绍了使用光谱仪分析铸铁成分的光学原理和常用光谱仪的配置及其适用情况;详细阐述了光谱仪标准曲线的制定方法和常见问题的解决办法;指出:用好光谱仪的关键在标准曲线的制定,但日常标准化工作也不容忽视.     

碲对灰铸铁性能的影响

碲涂料常被用于解决缸体和缸盖铸件的渗漏问题，但研究发现，碲对铸铁的石墨形态和基体组织有影响，因而会影响铸铁的力学性能。当碲的加入量较少时，会阻碍石墨的生长，使石墨变细、变短，发生弯曲，引起不规则的团块状石墨出现．石墨数量增多，导致铁素体量增多。当碲的加入量相对较多时，碲会与MnS形成共生物富集在共晶团前沿，使铁液产生成分过冷，使其按介稳定系进行凝固，导致铸铁形成白口组织。因此，生产过程中应严格控制碲涂料的质量。     

加铬铸铁的生产

介绍了加铬铸铁生产中加铬的作用、合适的加入量、加入方式和注意事项等。     

Nb在灰铸铁中的存在形态

用附带能谱的扫描电镜研究了Nb在灰铸铁中的存在形态,结果显示：少量Nb以原子形式固溶于基体,绝大多数Nb形成富Nb相镶嵌在基体上面;富Nb相形态丰富,有块状（包括方块状和三角形）、不规则形状（包括X型、Y型）以及条棒状;在富Nb相形成过程中,TiN可能作为异质核心,因而对富Nb相的形成起了促进作用。     

Saturated Fractional Design of Experiments: Toughness and Graphite Phase Optimizing in Nihard Cast Irons

The aim of the present research is to identify the manufacturing factors that exert an active influence on the graphite phase formation in mottled Nihard cast irons constituting the roll shells of duplex work rolls processed by the double pour method during centrifugal casting. The studied rolls, referred to as alloy indefinite chill, were processed at industrial scale and had a core consisting of spheroidal graphite cast iron with a matrix of ferrite and pearlite. An additional aim of this study was to evaluate the effect and extent of these factors on the dynamic toughness response of the roll shell material. The research methodology employed consisted of the application of a saturated design of experiments with seven factors, eight experiments, and resolution III. The measured responses for graphite were: the volume fraction, count number per unit area, and morphology, determined by quantitative metallography. Impact testing was characterized by Charpy tests on U-notched specimens at 350 °C. The manufacturing factors studied were: the final weight percent of silicon, sulfur, and manganese; the liquidus and the casting temperatures; and, finally, inoculation with SiCaMn and A-type FeSi (with Zr). The statistical experimental method conducted allowed us to confirm the significance of factors such as the %Si, the liquidus temperature and inoculation with SiCaMn on the precipitation of graphite in a white cast iron such as the Nihard irons used in the roll shell, in agreement with the precipitation of graphite in gray cast irons widely reported in the literature. It was also shown that the development of lamellar graphite shapes were favored by an increase in the total equivalent carbon and also by the increase in the amount of A-type FeSi added. Furthermore, the impact toughness was shown to improve with the increase in both the %Si and the liquidus temperature.     

铸铁用浅色涂料的研究

通过试验,优选出两种铝钒土浅色涂料,并在实际应用中获得了良好效果。     

日本在含球状碳化物铸铁方面的研究进展

由于碳化物球状化可以从根本上改善抗磨铸件的脆性、耐磨性和加工性,介绍了日本在含球状碳化物铸铁方面所取得的研究成果和经验;并着重分析了含球状碳化物的耐蚀铸铁、白口铸铁、高锰铸铁和低膨胀铸铁的化学成分、显微组织、主要性能和球状化工艺。