Cu-Ni-Sn合金体系油船内底板用耐蚀钢研究

利用扫描电镜（SEM）、电化学、光电子能谱（XPS）、激光原位、透射电镜（TEM）等方法研究了Cu-Ni-Sn体系船体钢在强酸性氯离子环境下的腐蚀行为。结果表明,采用Cu-Ni-Sn的耐蚀合金设计可以显著提高船体钢在强酸性氯离子环境下的耐蚀性,并满足IMO标准的要求;Cu是提高钢耐蚀性的有效元素,其主要机理为其以再沉积颗粒（100～500 nm）的方式在钢的表面富集,降低了钢的溶解速度并抑制点蚀的形核;随着钢中Sn含量的增加,钢的耐蚀性进一步提高,Sn在钢的表面形成了致密的SnO2腐蚀产物保护膜,有效阻止了基体与腐蚀介质的相互作用,进一步抑制了钢的腐蚀。     

A time-dependent corrosion wastage model for seawater ballast tank structures of ships

For assessment of time-dependent reliability or risk of aging ship structures, it is essential to have a mathematical model which provides the statistical characteristics (mean, variance, distribution) of corrosion wastage as a function of time (i.e., ship age). The aim of the present work is to develop such a model for low alloy carbon steel plates used for the structure of seawater ballast tanks in ships. Measurement data of structural wastage due to corrosion for such ship steel plates is collected and the statistical characteristics of corrosion loss and rate are quantified by statistical analysis in terms of ship age. The results and insights developed in the present study will be useful for predicting the wastage of corrosion in seawater ballast tank structures of ships. They will also be useful for designing corrosion tolerant structures subjected to the seawater environment.     

An improved cutting force and surface topography prediction model in end milling

During the milling operation, the cutting forces will induce vibration on the cutting tool, the workpiece, and the fixtures, which will affect the surface integrity of the final part and consequently the product's quality. In this paper, a generic and improved model is introduced to simultaneously predict the conventional cutting forces along with 3D surface topography during side milling operation. The model incorporates the effects of tool runout, tool deflection, system dynamics, flank face wear, and the tool tilting on the surface roughness. An improved technique to calculate the instantaneous chip thickness is also presented. The model predictions on cutting forces and surface roughness and topography agreed well with experimental results.     

A mathematical model for prediction of time from corrosion initiation to corrosion cracking in RC structures

Prediction of time from corrosion initiation to corrosion cracking is a crucial factor in evaluating concrete structures' durability and integrity deteriorated by reinforcement corrosion. This paper presents a mathematical model to predict the time from corrosion initiation to corrosion cracking. A dynamic corrosion rate model based on Bulter–Volmer kinetics and a rust expansion model based on Faraday's law are developed. An analytical model is developed to demonstrate the mechanical consequences of rust buildup around the rebar. The time to corrosion cracking is found to be a function of surrounding concrete material properties, chemical composition of rust, ratio of concrete cover thickness to rebar diameter, and corrosion current density. Comparisons with available experimental results are conducted to show the accuracy and reliability of the present model. Further parametric analysis is carried out to show the influences of various parameters included in the model on the time to corrosion cracking.     

Accelerated corrosion of ship's bottom plate

Abstract

A serious case of accelerated corrosion, resulting in deep pitting and perforations on the internal surface of a ship's bottom plate, was recently brought to our notice. During the relatively short period of less than 2 years, an 8 mm mild steel plate suffered three perforations of O·5 cm, 0·8 cm and 1·0 cm diameter. This necessitated dry docking and the renewal of a section of the ship's bottom plate.     

稀硫酸储罐底部结构的优化设计

针对储存酸性介质的平底储罐底部结构与土建基础之间合理的配置关系,从减少建设成本角度出发,介绍储罐底板结构型式以及土建基础之间的优化设计.     

An improved thermal model for machine tool bearings

Thermal model for machine tool spindle is of great importance to machine tool design. Traditionally, the thermal contact resistance between solid joints and the change of the heat generation power with the bearing temperature are often ignored when thermal characteristics of a machine tool spindle are analyzed. This has caused inaccuracies in the thermal model. With the heat source models and the heat transfer models from Bossmanns and Tu [Journal of Manufacturing Science and Engineering 123 (2001) 495–501, International Journal of Machine Tools & Manufacture 39 (1995) 1345–1366], a model including the thermal contact resistance at solid joints based on a fractal model and the change of the heat generation power, viz. the amount of the heat generation per second, with the bearing temperature increases is developed. The complete thermal model is used to simulate the temperature distribution in grinding machine housing with a conventional spindle bearing. Compared with experiment, it is shown that the completed model is much more accurate than the traditional model which ignores the two important factors above. The thermal expansion of the housing system is analyzed.     

Influence of inclusion and grain boundary on corrosion behaviour of low alloy steel in cargo oil tank bottom plate environment

Corrosion behaviours of low alloy steels with various alloying element contents were studied in simulated corrosion environment (pH?=?0·85, 10% NaCl solution) of cargo oil tank (COT) bottom plate corrosion environment. Corrosion rate was measured, and the surface morphology of test steels was characterised using scanning electron microscope (SEM). The electrochemical results were investigated using polarisation curves and electrochemical impedance spectroscopy (EIS). The corrosion behaviour of inclusion was investigated using in situ SEM images and energy disperse spectroscopy (EDS) analysis. The effect of misorientation distribution on corrosion resistance of steel was evaluated using electron backscattered diffraction microscopy. The results showed that MnS dissolved into the simulated COT corrosion solution before steel matrix, whereas TiO₂ would not be dissolved. A 10–20 μm area was formed as a circular cathode around inclusion centre. The corrosion was inclined to occur in the place where curvature radius of inclusion is small. An increase in the proportion of low energy grain boundaries was conducive to the improvement of corrosion resistance especially in the early stages of corrosion.     

底喷式淬火槽结构的优化设计

为改善底喷式淬火槽的冷却均匀性,从入水口方向和变径方面对淬火槽结构进行优化,研究了不同淬火槽结构对淬火冷却的影响。结果表明,在相同边界条件下,入水口方向改为切向后,钢管两侧流速有了显著提高,可有效提高淬火槽的冷却能力;采用过流截面逐渐收缩的变截面淬火槽,钢管轴向及内、外壁面的冷却均匀性均优于等直径淬火槽。     

硫酸贮罐的焊接变形控制与底板结构改进

我公司需制作 ８ ｍ×６．４ ｍ立式浓硫酸贮罐,参照某镍业公司的图纸设计制作,通过采取控制焊接变形与改进底板结构等措施,使结构厚度比原图纸设计降低了 ２５％,获得满意的使用效果。１底板结构变形原因分析 贮罐结构如图 １所示,材质为 Ｑ２３５－Ａ,底板焊接时,焊缝的纵向收缩和横向收缩很容易引起波浪变形,焊后引起最大的变形就是焊接壁板与底板连接的双面角焊缝,它的焊后收缩力很大,如果不能比较自由地收缩,就会引起较大的变形。２焊接变形的控制２．１底板增设一道收缩焊缝 底板由心板和边环板组成,在距离底板边缘４００…     

A corrosion prediction method for weathering steels

Japanese Specification for Highway Bridges [Japan Road Association: Specification for Highway Bridges—I & II, 2002.3] has been revised in 2002, which clearly states that degradation of bridge members, including those of weathering steels, to occur in prolonged period of time must be taken into account at the design stage to realize long term structural durability. To cope with the revised paradigm, SABI chemistry committee in Japan Society of Corrosion Engineers has proposed durable state concept [SABI Chemistry Committee of Japan Society of Corrosion Engineers, in: Proc. 132nd Symposium for Corrosion and Protection, 2001.6.25, p. 3], which is defined as a condition in which corrosion rate of steel is slow enough not to form thick rust [H. Kihira, K. Shiotani, H. Miyuki, T. Nakayama, M. Takemura, Y. Watanabe, Doboku Gakkai Ronbun-shu (J. Japan Soc. Civil Engineers) No. 745/I-65, 2003.10, pp.77-87]. Since corrosiveness of atmosphere differs by location, a corrosion prediction method for both conventional and advanced weathering steels [H. Kihira, A. Usami, K. Tanabe, M. Ito, G. Shigesato, Y. Tomita, T. Kusunoki, T. Tsuzuki, S. Ito, T. Murata, in: Electrochemical Society Proceedings, vol. 99-26, 2000, pp. 127-136] is needed to ensure structural durability for future. Thus, versatile computational scheme for it has been derived through mathematical modeling based upon the durable state concept.     

15万m3大型钢制储油罐底板焊接

15万m^3双盘浮顶油罐底板焊接质量及变形控制是保证储罐整体施工质量的关键环节，采用合理的焊接工艺和技术，可有效地避免应力集中，提高施工焊接质量，确保储罐建成投入使用后的安全运行。针对15万m^3双盘浮顶油罐底板的特点，介绍了经实践证明合理、有效的储罐底板焊接工艺和技术。     

Morphological characteristics and geometric prediction model of pits in complex corrosion environment

For aircraft serving in coastal environments, the aluminum alloy skin is exposed to high temperature, humidity, and salt environment for a long time. Pitting and exfoliation will affect its normal service life. In this article, static salt spray experiments and electrochemical tests were carried out on 2198-T8 Al–Li alloy in nine different corrosive environments. The effects of salt concentration, temperature, and humidity on the corrosion behavior were analyzed and compared. The relationship between corrosion environment parameters and pits was established. The results show that, under the same corrosion environment, the length, width, and depth of the pits all follow the log-normal distribution; compared with the salt concentration and humidity, the increase in temperature has the most obvious promotion on the corrosion rate. Based on the frequency statistics of pit size and electrochemical test results, the pit morphology was simplified to a semiellipsoid geometric model, and the pit size in different corrosive environments was predicted. The predicted size data all fall within the 1.5-fold dispersion region.     

高压水除鳞蓄势罐内壁腐蚀原因及其防腐

介绍了宽厚板轧机高压水除鳞蓄势罐的工作原理,分析了蓄势罐内部腐蚀原因,通过采用高压水射流清洗技术和环氧树脂涂层7000AR防腐处理,保证了蓄势罐内部至少5~10年的防腐有效年限,有效解决了罐体内壁腐蚀严重的问题。     

An improved finite-element model for electromagnetic analysis in aluminum cells

This article presents the use of an improved finite-element model to calculate the static electromagnetic field for an aluminum reduction cell. Consisting of three solid cells and their surrounding bus bars, the model can evaluate the non-uniformity of the current distribution in the inside conductors and bus bar system and couple the current into the sequential magnetic analysis through a conversion routine. Voltage potential distribution in the molten aluminum was investigated based on one industrial 320 kA aluminum cell with two designed bus bar arrangements. Characteristics of magnetic components’ distributions were also given.     

An enhanced analytical model for residual stress prediction in machining

The predictions of residual stresses are most critical on the machined aerospace components for the safety of the aircraft. In this paper, an enhanced analytic elasto-plastic model is presented using the superposition of thermal and mechanical stresses on the workpiece, followed by a relaxation procedure. Theoretical residual stress predictions are verified experimentally with X-ray diffraction measurements on the high strength engineering material of Waspaloy that is used critical parts such as in aircraft jet engines. With the enhanced analytical model, accurate residual stress results are achieved, while the computational time compared to equivalent FEM models is decreased from days to seconds.     

Technical note Stress corrosion cracking of ammonia receiver tank

Abstract

A 900 t/day capacity installation, used for recycling of ammonia to a urea plant, with two ammonia streams and four receiver tanks, failed after 3 years in service. The vessels were of the cylindrical bullet type, made of SA 516 grade 70 carbon steel. Of the four receiver tanks, only one suffered stress corrosion cracking, caused by incomplete mixing of the 0·2% water required by the process parameters. The vessel was operated at ambient temperature and a pressure of 1·765 x 10⁶ Pa; the design pressure of the vessel was 2·256 × 10⁶ Pa.     

An improved prediction of stability lobes using nonlinear thin wall dynamics

With manufactured sections getting much thinner due to weight requirements, there is the vital need for more accurate prediction of stable cutting conditions in machining. The tools used in machining vary in shapes and design hence a more robust model is required to include these varieties. This paper first presents improvements to the well known stability model, by considering the nonlinearity of the cutting force coefficients, and axial immersion angle and their dependency on the axial depth of cut. Secondly, a finite element (FE) and Fourier transform approach to including the nonlinearity of the workpiece dynamics in thin wall machining when predicting stable region is presented. The model and approach are validated extensively using experimental results and a very good agreement has been achieved.     

The prediction of corrosion by statistical analysis of corrosion profiles

The corrosion of carbon manganese steel in CO₂-acidified sea water has been assessed by a statistical analysis of corrosion profiles. The total population of depth data was multi-modal and could not be fitted to any well known statistical models. However the deepest pits in the profile followed a type I extreme value distribution. The time dependence of the extreme value distribution parameters has been determined and used to predict the rate of penetration of steel components under pitting conditions.