Melting and precision casting of Ti-6Al-4V alloy by use of electron beam furnace

For melting and casting of Ti-6Al-4V alloy by use of an electron beam furnace, key technologies have been developed: measurement and control of temperature, amount, and chemical composition of molten pool. Temperature in the molten pool was measurred by applying three devices; a thermocouple, a two color pyrometer and the rate of vaporization from the molten pool. Temperature measured by an optical pyrometer without influence of plasma by shifting the wave lengths of the light for the optical pyrometry from those of plasma evolved above the molten pool was in a good accordance with that estimated from the vaporization rate. By combining temperatures measured by three methods, the temperature gradient in the molten pool was estimated to be a level of 100 K/cm. In order to derive an empirical equation for the depth of molten pool of various metals, the depth of the molten pool was determined for Ti, Ti-6Al-4V alloy, solar grade Si, low carbon steel, and stainless steel by chemical etching of vertical cross section of an ingot melted and solidified in a skull crucible. Chemical compositions of Ti-6Al-4V alloy melt before casting was adjusted by adding an aluminum block into the pool before pouring, which compensated vaporization loss of Al from the pool surface under high vacuum. Since, a key to settle Al content in the specified range is the yield and distribution of Al in every castparts, influences of operating variables on the yield have been studied by paying attention to rapid temperature change observed immediately after addition of aluminum. Formerly Graduate School of Iron and Steel Technology Pohang University of Science and Technology San 31 Hyoja-dong, Nam-gu, Pohang 790-784, Korea     

Simulation of mold filling and solidification during centrifugal precision casting of Ti−6Al−4V alloy

A two-dimensional simulation model for melt flow and solidification in centrifugal precision casting has been developed based on experimental results on melt flow in a precision casting tree for Ti-6A1-4V alloy castparts. The amount of liquid alloy is intentionally adjusted to be less than that required for complete filling and is poured under a centrifugal force. The melt flows into mold cavities keeping contact with the vertical inside walls of the cavity in the anti-rotation side, and solidifies directionally by accumulating a solidified layer from the far end of the cavity to the gate according to the gradient of centrifugal force. The model reproduces melt flow observed in casting trials and directional solidification during centrifugal casting. In addition, it has been confirmed that the centrifugal force imposed on the melt enhances removal of defects caused by entrapment of gas bubbles or by solidification shrinkage and improves mechanical properties of the castparts. Formerly Graduate School of Iron and Steel Technology Pohang University of Science and Technology San 31 Hyoja-dong, Namku, Pohang 790-784, Korea     

The high-quality precision casting of titanium alloys

A technique for the high-quality precision casting of titanium alloys has been developed that consists of the instantaneous dissociation of oxide at the metal-mold interface, followed by the rapid absorption and diffusion of the dissociated oxygen into the subsurface of the cast parts during solidification and cooling. In centrifugal casting trials using less molten alloy than required to completely fill the mold, the results suggest that the melt flowing in the mold cavities maintains contact with the vertical inside walls and directionally solidifies from the far end of the cavity to the gate, corresponding to the gradient in the centrifugal force on the horizontal plane. This force enhances the removal of defects, such as entrapped gas bubbles and solidification shrinkage. The results have enabled the development of a two-dimensional model to simulate melt flow during centrifugal casting. Author’s Note: Unless otherwise indicated, compositions are given in weight percent. Ken-ichiro Suzuki earned his Ph.D. at Tohoku University, Faculty of Engineering. He is currently a visiting professor at the Graduate School of Iron and Steel Technology at Pohang University of Science and Technology.     

Application of Technology for The Benefit of Less-Developed Countries

Comments on the UN Conference on the Application of Science and Technology for the Benefit of the Less Developed Nations. Also included are summaries of papers on resource development and the establishment of a steel industry in a developing economy.     

北京地区大气腐蚀及其与城市污染因素的灰色关联分析

利用灰色关联分析方法对北京地区大气腐蚀与污染物的关系进行了分析.将北京地区4个地点的A3钢、铜、铝1年和2年的大气腐蚀数据作为母函数序列，对应地点的6种污染因素在夏季及冬季的平均值作为子函数序列进行斜率关联度分析，得到污染物与北京大气腐蚀的关联顺序，与北京大气腐蚀关系最密切的污染物是夏季的SO2，其次为冬季的SO2以及冬季的微粉尘.      

The Recovery of Elastic Properties at 35 °C in TRIP 700 Steel Following Deformation

The influence of plastic deformation on the elastic properties that determine the magnitude of springback following forming was investigated using dynamic modulus analysis. For this study, the elastic modulus of TRIP 700 steel was measured continuously at 35 °C and a loading frequency of 1.0 Hz for 1000 min following deformation by cold rolling to varying levels up to 27%. The elastic modulus increased at an exponentially decaying rate during these experiments and with a magnitude that increased with pre-strain. These observations are consistent with the hypothesis that deformation creates microstructural defects that contribute compliance when the stress state changes and that these defects are removed by annealing at this low temperature. This article was presented at Materials Science & Technology 2006, Innovations in Metal Forming symposium held in Cincinnati, OH, October 15-19, 2006.     

川威微合金钢中宽带的开发

介绍了川威钒钛冶金科技开发有限公司开发X52微合金中宽带的工艺流程、化学成分、生产工艺,以及成品组织与性能,其特点是Nb、Ti微合金元素的含量较其他厂家的少近一半。     

短小厂房内兼容棒材和不锈钢高线的设计改造

针对郑州永通特钢公司在长度仅185m的厂房内原有1条轴承钢棒材生产线的基础上欲再增加1条不锈钢高线的情况,北京科技大学轧钢研究所对其进行了设计改造,本文分析了其技术难点,采用了吐丝机与散冷辊道垂直布置,以及导管加侧活套的方案。生产实践证明,该工艺合理可行,为其他厂家提供了可供借鉴的模式     

Cement-matrix structural nanocomposites

This paper reviews cement-matrix structural nanocomposites, including those with particulate and fibrous reinforcements. Silica fume is valuable for improving numerous mechanical properties, in addition to enhancing the freeze-thaw durability, the vibration damping capacity, the abrasion resistance, the bond strength with steel rebars, the chemical attack resistance and the corrosion resistance of steel rebars. Furthermore, silica fume decreases the alkali-silica reactivity, the drying shrinkage, permeability, creep rate and thermal expansion. On the other hand, carbon nanofiber is not attractive, as it fails to compete with conventional discontinuous carbon fiber as a reinforcement. This article is based on a presentation made in the “First International Symposium on Nanostructured Materials: Structural Applications,” jointly organized by the Korean Institute of Metals and Materials and the Center for Nanostructured Materials Technology, held at Korea Institute of Science and Technology, Seoul, Korea on October 30–31, 2003.     

The Effect of Adhesion and Tensile Properties on the Formability of Laminated Steels

Laminated steel has been implemented in vehicle structures by several automotive manufacturers to reduce in-cabin noise. This study provides an understanding of how the adhesion between the steel skin and the viscoelastic polymer core affects laminate formability. Material properties, including peel strength, shear strength, and tensile strength were determined. The presence of the viscoelastic core was found to slightly reduce tensile properties of the laminate compared to the skin sheet. Forming limit diagrams were also determined. These indicated that the viscoelastic core properties can significantly affect formability of laminated steel compared to that of solid steel sheet. In general, the formability of laminated steel was found to be similar to or less than that of the much thinner skin sheet material, which indicates that its formability should be less than that of solid steel of the same gauge. This article was presented at Materials Science & Technology 2007, Automotive and Ground Vehicles symposium held September 16-20, 2007, in Detroit, MI.     

高速线材控冷段温度及性能预报系统

北京科技大学与重庆钢铁股份有限公司联合开发了高速线材控冷段温度及性能预报系统。该系统采用隐式有限差分方法计算生产过程中温度的演变及最终产品的各项性能。由于该模型藕合了钢种连续冷却转变曲线,可预测相变热及相变区间,因而为新钢种开发及现有生产工艺的优化提供了依据。     

Study of Intrusion Bending for Steel Tubes with Thin Wall Thickness

In regard to light-weight structural members for automobiles, attention to hydroforming has been increasing. Intrusion-bending method is well suited to the preliminary bending of hydroformed structural members of automobiles, because straight tubes can be bent into three-dimensional forms by this new method. However, in the case of tubes with a thin wall thickness, wrinkling remains a problem. In this report, application of intrusion bending method to tubes with extremely low ratios of wall thickness to outer diameter (from 1.2 to 1.9%), and whose steel grades are SSPDX, SAFC440R, and SAFC590T was investigated. A summary of this study is as follows. Effects of steel grades and wall thickness ratios on wrinkle formation, eccentricity, and ovality are studied. Relationships between wrinkle generation and gyro movement are investigated. This article was presented at Materials Science & Technology 2007, Automotive and Ground Vehicles symposium held September 16-20, 2007, in Detroit, MI.     

Metallurgical problems in the welding process of selected construction steels

Selected problems with the weldability of higher-strength steels, high-strength steels and martensitic copper-precipitation-hardened stainless steels, which were solved by the Physical Metallurgy and Powder Metallurgy Department at the AGH University of Science and Technology, are presented in the article. It was pointed out that the formation of M-A islands in welded structures results from too-slow cooling after the welding process, and is the reason why the welds and the heat affected zones (HAZs) have such a low impact. Testing of copper-based precipitation hardening of martensitic stainless steel demonstrated that fractures occurring in the HAZ were of the hot fracture type, and result from the steel's surface having been enriched with copper.     

全液压矫直机工艺数据采集分析管理系统

太原重工与太原科技大学联合研制的四重式全液压可逆十一辊矫直机,其二级控制系统包含了自动化站、主操作站、监控站、工程师站、服务器集群的分布式计算机控制系统;全线二级系统与回火炉操作台的PC机相连,采集板厚、板宽、材料编号等实时板材数据。在过程计算机工程师站中设置数据库,针对不同材质、温度、板型、板宽和板厚,建立工艺模型,计算出矫正压力、矫正次数及所需压下量的理论数据,再经过试验,计算出矫直机线性弹跳、非线性机架变形、总结出所需压下量的经验数据,两者结合生成矫直机压下量工艺数据。实践证明:该系统运行良好,安全可靠。     

0412-1961

用ZrO_2固体电解质组成氧浓差电池:(-)Re,In,In_2O_3     

0412-1961

本文讨论了空位对间隙原子和代位式原子扩散的影响及它们之间的相互作用:在间隙合金中,由于复合体的存在,间隙原子与空位在扩散过程中将通过复合体的形成与分解反应而相互关联;在     

Cyclic softening properties of 30Cr2MoV steel at elevated temperatures

Low cycle fatigue tests for 30Cr2MoV steel are done at both room and elevated temperatures and their softening properties are investigated. Based on the experimental results, a quantitative relationship between hardness and remaining life is established, allowing prediction of the remaining life of metals. A modified Mason-Coffin equation including the aging effect is also derived. Both the experimental and theoretical results show that it is useful to be able to predict the remaining life of a steam turbine rotor through the measurement of hardness. This article based on a presentation made in the symposium “The 4th International Conference on Fracture and Strength of Solid”, held at POSTECH, Pohang, Korea, August 16–18 under the auspices of Far East and Ocean Fracture Society (FEOFS),et al.     

Corrosion inhibition of gatifloxacin on mild steel in 3% HCL solution北大核心CSCD

The inhibition effect of gatifloxacin on the corrosion of mild steel in 3%HCl solution was investigated by means of mass loss measurements and electrochemical measurements. The surface morphology of the steel after corrosion was studied by scanning electron microscope (SEM). The results demonstrated that the highest inhibition efficiency of gatifloxacin reached 95.6% for a dose of gatifloxacin 700 mg/L. Gatifloxacin acted as a mixed-type inhibitor, the cathodic and anodic processes of corrosion were suppressed. Thermodynamic parameters were acquired from data of weight loss at different experimental temperatures, which suggested that the adsorption of gatifloxacin on metal surface obeyed Langmuir adsorption isotherm model. The adsorption processes were exothermic, and belong to chemisorption and physisorption. The entropy of adsorption processes increased. © 2016, Corrosion Science and Protection Technology. All rights reserved.     

国家大学科技园创新体系建构

国家大学科技园包括作为前提和条件的创新导引系统，作为动力的创新激励系统和作为背景的创新环境支撑系统、作为创新源头的人才支撑系统。创新人才向创业人才的升华，导引系统向激励系统的延展，使国家大学科技园充满活力。     

Transformations,Structure and Properties of Steel 22Kh2G2S2MF Under Continuous Cooling

Metal Science and Heat Treatment - Transformations of structure in structural steel 22Kh2G2S2MF under continuous cooling are studied by the methods of dilatometric analysis and optical microscopy....